Dr Rajiv Desai

THE NANO WORLD

January 8, 2011 by Dr Rajiv Desai

THE NANO WORLD

 

Prologue:

Can you identify what is this?

A group of scientists discovered that placing gold nanoparticles within the leaves of trees causes them to give off a luminous reddish glow. The idea of using trees to replace street lights is an ingenious one – not only would it save on electricity costs and cut carbon dioxide emissions, but it could also greatly reduce light pollution in major cities.

 

The picture speaks louder than the words. Majority people of the world know very little about nanotechnology & nanoparticles but we are ushering in an era of nano-revolution which is going to change our lives for ever. I myself was as ignorant as you on this subject until I decided to welcome the year 2011 with a novelty.

 

Nano (symbol n) is a prefix in the metric system denoting a factor of 10 ^{– 9} or 0.000000001. The prefix is derived from Greek meaning “dwarf”. It is frequently encountered in science and electronics for prefixing units of time, weight and length, such as 30 nanoseconds (ns), 50 nanograms (ng) & 100 nanometers (nm).

 

One nanometer is one billionth of a meter or one millionth of a millimeter or one thousandth of a micrometer. That is, about 1/80,000 of the diameter of a human hair, or ten times the diameter of a hydrogen atom.   

 

1 nanometer = 0.000000001 meter = 0.000001 millimeter = 0.001 micrometer

1000 nanometer = 0.000001 meter = 0.001 millimeter = 1 micrometer

1000000 nanometer = 0.001 meter = 1 millimeter = 1000 micrometer

 

 

A nanometer (nm) is one of the more often used units for very small lengths, and equals ten Angstrom, an internationally recognized non-SI unit of length. It is often associated with the field of nanotechnology and the wavelength of light with visible light falling in the region of 400-700 nm. It is also the most common unit used to describe the manufacturing technology used in the semiconductor industry. To put that scale in another context, the comparative size of a nanometer to a meter is the same as that of a marble to the size of the earth. Inside of your computer are tiny switches that are only 100 nanometers wide. Modern computers have about 100,000,000 switches packed inside, stacked one on top of another. A red blood cell is approximately 7,000 nm wide and a water molecule is almost 0.3 nm across. A hydrogen atom has a diameter of about 0.1 nm but its nucleus is much smaller of about 0.00001 nm. A typical carbon-carbon bond length, or the spacing between these atoms in a molecule, are in the range 0.12–0.15 nm, and a DNA double-helix has a diameter around 2 nm. On the other hand, the smallest cellular life-forms, the bacteria of the genus Mycoplasma, are around 200 nm in length. A light microscope can resolve details down to a limit of 200 nm, an electron microscope down to 0.1 nm and hence particles in the 1 – 100 nanometer range are not visible using a light microscope, but are amenable to electron microscopy or even better atomic force microscopy.

 

This picture shows that the size matters and a mammalian cell which is made up of proteins, nucleic acids, and other small to large molecules is thousand times larger in volume and size compared to a 10 nm nanoparticle and the picture also shows cell membrane incorporating various proteins including a single 10 nm nanoparticle.

 

Introduction:

There are an astonishing 6,000,000,000,000,000,000,000 (6 billion trillion) atoms in just one drop of water! Collectively, groups of atoms fit together in various discrete ways to form molecules. Two hydrogen atoms combine with one oxygen atom to make one water molecule. Everything we see in this world is made up of atoms & molecules. We the humans are made up of carbon, oxygen, hydrogen, nitrogen, phosphorus etc atoms which are arranged in a specific way to make a human cell which is basically a nature’s nano-machine and it is the arrangement of various atoms in us that make us different from each other. Throughout history, variations in the arrangement of atoms have distinguished the cheap from the cherished and the diseased from the healthy. In the same way, all manufactured products are also made from atoms. The properties of these products depend on how its atoms are arranged. If we rearrange carbon atoms in coal, we can make diamond. So the difference between a diamond and a coal is the mere arrangement of carbon atoms. So mere rearrangement of atoms can change the properties of a substance even though chemical composition remains the same. A material such as gold, which is chemically inert at normal scales, can serve as a potent chemical catalyst at nanoscale. So any material or substance when transformed into particles of nanoscale i.e. between 1 to 100 nm, its properties changes and so nanotechnology is a science of particles at nanoscale. At the nanoscale – physical, chemical, optical and electrical properties of materials differ from the properties of matter at either smaller scale such as atoms, or at the larger scales of the “middle world” that we humans inhabit. By harnessing these new properties, researchers have found that they can develop materials, devices and systems that are superior to those in use today.

 

Nanoparticles:

A nanoparticle is a microscopic particle with at least one dimension less than 100 nm. Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures. A bulk material should have constant physical properties regardless of its size, but at the nano-scale, size-dependent properties are often observed. Thus, the properties of materials change as their size approaches the nanoscale and as the percentage of atoms at the surface of a material becomes significant. For bulk materials larger than one micrometer (or micron), the percentage of atoms at the surface is insignificant in relation to the number of atoms in the bulk of the material. A nanoparticle, being on the scale of 1 to 100 billionth of a meter, is still a larger “particle” than a molecule. After all, nanoparticles are typically a collection of molecules. There is no strict dividing line between nanoparticles and non-nanoparticles but novel properties that differentiate nanoparticles from the bulk material typically develop at a critical length scale of under 100nm. It must be emphasized that different nanoparticles of different materials may exhibit different size-related properties that differ significantly from those observed in fine particles or bulk materials and therefore even though size of a nanoparticle is very important for novel properties, the underlying atoms & molecules are also equally important in determining novel properties. Magnetic nanoparticles are a class of nanoparticle which can be manipulated using magnetic field. Such particles commonly consist of magnetic elements such as iron, nickel and cobalt and their chemical compounds. These particles range from 1 to 100 nm in size and may display superparamagnetism. The magnetic nanoparticles have been the focus of much research recently because they possess attractive properties which could see potential use in catalysis, biomedicine, magnetic resonance imaging, magnetic particle imaging, data storage and environmental remediation.

 

Fundamental physics of nanoism:

To better understand how nanotechnology could revolutionize such diverse areas as say, medicine and computing, we need to review a bit of fundamental physics. Two sets of theories relate to this discussion: classical mechanics, which governs the world of our immediate perception (apple falling from tree to hit Newton on the head) and quantum mechanics, which governs the world of atoms and molecules (electrons tunneling through seemingly impenetrable barriers). Given enough information about the initial position of an object and the forces acting upon it, classical mechanics allows one to determine with certainty where that object was at some time in the past and where it will be at some time in the future. This is useful because it allows one to, for example track a baseball from the crack of the bat to where it will drop in center field (at least in theory). Quantum mechanics doesn’t provide such comforting predictability but does a far better job explaining the strange behavior of atoms and molecules and allows us to make (at best) probabilistic assessments of where an electron is and what it might do if we poke it with a light probe. The classical world and the quantum world seem miles apart. I have already proved in my theory of ‘Duality of Existence’ that there is a dual existence of everything in universe and therefore a single frame of logic/rationale/laws cannot explain all phenomena associated with it. Even though classical world and quantum world would seem miles apart, duality of existence bring them close at nanoscale. So as we move along the scale as shown in the figure from the large to the small, the classical rules eventually give way to the quantum rules. The murky, middle ground in between the two domains is the province of nanotechnology. In this transitional regime, a material often exhibits different behavior than it does either in the bulk, where it’s governed by classical mechanics, or as a single atom, where quantum mechanics dominates. Let’s consider the element gold. We’re familiar with gold as a shiny yellow metal that can be worked into a variety of shapes for our adornment. If you cut a piece of gold in half, each of the halves retains the properties of the whole, except that each piece has half the mass and half the volume of the original (When both pieces are summed up, you get the same mass & volume of the original uncut piece). Cut each half in half again and anyone would still recognize the pieces as gold. And so on. You can keep doing this down to a certain size and then the properties of the pieces begin to change. One of these may be the apparent color of the material. When gold is nanoscopic, i.e. clusters of gold atoms measuring 1 nm across, the particles appear red.  And if we change the size of the clusters just a little bit, their color changes yet again. That is only one example of a property that varies with the size of the object. Most of this variability doesn’t begin to manifest until you get to the nanoscopic level. Therefore, if we can control the processes that make a nanoscopic material, then we can control the material’s properties. Chemists have long been able to design materials with useful properties (e.g., polymers); what’s new is the unprecedented degree of control over materials at the molecular level. This may not capture the imagination as much as a tiny machine that precisely assembles materials atom by atom, but it is an extraordinarily interesting and useful phenomenon and that is why nanotechnology is thrilling up such an excitement.

 

Scientific reasons for novel properties of nanoparticles are discussed as follows:

1)  Nanomaterials have a relatively larger surface area when compared to the same mass of material produced in a larger form. This can make materials more chemically reactive (in some cases materials that are inert in their larger form are reactive when produced in their nanoscale form), and affect their strength or electrical properties. A common feature of all nanomaterials is their large ratio of surface area to volume, which may be orders of magnitude greater than that of macroscopic materials. Cutting a 1-cm cube into 10 raised to 21 cubes (1000000000000000000000) that are each 1 nm size will result in the same volume and mass, but the surface area will be increased by a factor of 10 million. The increase in surface area to volume ratio alters the mechanical, thermal and catalytic properties of materials. Also, it gives the added advantage of using nanomaterials as carriers because their surface can be coated with many molecules.

 

2)  Quantum effects can begin to dominate the behavior of matter at the nanoscale – particularly at the lower end of the scale affecting the optical, electrical and magnetic behavior of materials. This is the “quantum size effect” where the electronic properties of solids are altered with great reductions in particle size. This effect does not come into play by going from macro to micro dimension but becomes dominant only when the nanometer size range is reached at the so called quantum realm.

 

3) Dealing with materials at nano level would make gravity less important while surface tension, van der Waals attraction, surface plasmon resonance in some metal particles and superparamagnetism in magnetic materials would become more significant. Gravity is less important on a nanoscale – even a fly can defy gravity to walk on a ceiling, and an ant can lift what would be a truck to us. At a simulated size of fifty nanometers, gravity counts for nothing. Materials keep their strength, and are just as hard to bend or break, but the weight of an object becomes negligible. It is akin to you lifting an object with 40 million times your mass.

 

One example is sufficient to demonstrate novel properties of particles at nanoscale.

Particles of inorganic semiconducting crystals with nanometer scale dimensions (quantum dots) exhibit size-dependent optical properties. Nanoparticles of semiconductors (quantum dots) were theorized in the 1970s and initially created in the early 1980s. If semiconductor particles are made small enough, quantum effects come into play, which limit the energies at which electrons and holes (the absence of an electron) can exist in the particles. As energy is related to wavelength (or colour), this means that the optical properties of the particle can be finely tuned depending on its size. Thus, particles can be made to emit or absorb specific wavelengths (colours) of light, merely by controlling their size. In other words, the color of a cadmium-selenium (CdSE) quantum dot will vary depending on the quantum dot’s size, even though the chemical composition of the dot has not changed. So chemical composition remains same but optical properties change depending on size of a particle. This is nano effect.

 

Nanotechnology (nanotech) & nanoscience:

Scientists define nanoscience as the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale; and nanotechnologies as the design, characterization, production and application of structures, devices and systems by controlling shape and size at the nanometer scale. Generally nanotechnology deals with structures sized between 1 to 100 nanometer in at least one dimension, and involve developing materials or devices within that size. Quantum mechanical effects are very important at this scale. To put it differently, nanotechnology is the engineering of functional systems at the molecular scale. Several technologies converge with nanotechnologies, the most important being miniaturization of semiconductor structures, driven by progress in microelectronics. Even though nanotechnology was developing the ability to build simple structures on a molecular scale, some researchers were talking about building machines on the scale of molecules, a few nanometers wide – motors, robot arms, and even whole computers, far smaller than a cell and they were accused of science fiction.

 

Two main approaches are used in nanotechnology. In the “bottom-up” approach, materials and devices are built from molecular components which assemble themselves chemically by principles of molecular recognition. This “bottom-up” method of nanoparticle fabrication involves condensation of atoms or molecular entities in a gas phase or in solution. This approach is far more popular in the synthesis of nanoparticles. In the “top-down” approach, nano-objects are constructed from larger entities without atomic-level control. This approach may involve milling or attrition, chemical methods, and volatilization of a solid followed by condensation of the volatilized components.

 

Nano-revolution:

 

Understanding and controlling matter at the nanoscale interests researchers in the sciences, medicine, agriculture, and industry because a material’s properties at the nanoscale can be very different from those at a larger scale. The unique physical, chemical, and biological properties of materials at the nanoscale enable novel applications and functions with the potential to promote enormous societal and economic benefits. Materials reduced to the nanoscale can show different properties compared to what they exhibit on a macro scale, enabling unique applications. For instance, opaque substances become transparent (copper); stable materials turn combustible (aluminum); solids become liquids at room temperature (gold) and insulators turn into conductors (silicon). Nanotechnology may be able to create many new materials and devices with a vast range of applications, such as in medicine, electronics, biomaterials and energy production. Today nanotechnology is featured in those technologies mostly involved in coatings, composites and catalysis. Nanotechnology in its advanced form it will have significant impact on almost all industries and all areas of society. It will offer better built, longer lasting, cleaner, safer, and smarter products for home, for communications, for medicine, for transportation, for agriculture, and for industry in general. Nanotechnology will be dual-use, meaning it will have many commercial uses and it also will have many military uses – making far more powerful weapons and tools of surveillance. Thus it represents not only wonderful benefits for humanity, but also grave risks.

 

Nanoscale molecular machines:

                   

 

                   

 

                                                                          

The above mentioned nano-mechanical device has 15,342 atoms; this parallel-shaft speed reducer gear is one of the largest nanomechanical devices ever modeled in atomic detail.

 

A nanorobot is a tiny machine designed to perform specific tasks repeatedly and with precision at nanoscale dimensions. Nanorobots might function at the atomic or molecular level to build devices, machines or circuits; a process known as molecular manufacturing. Nanorobots might also produce copies of themselves to replace worn-out units; a process known as self-replication. The controller for a nanorobot would be a nanocomputer. A nanocomputer is the logical name for a computer smaller than the microcomputer, having mo­lec­u­lar-sized switching elements and uses single-molecule sliding rods for its logic. Electrical conductors called nanowire would be only one atom thick. A logic gate would require only a few atoms. A data bit could be represented by the presence or absence of a single electron. Nanoporous carbon aerogel and carbon nanotubes are used in making an ultracapacitor used in nanocomputers.

 

The power of nanotechnology can be encapsulated in an apparently simple device called a personal nanofactory that may sit on your desk. Packed with miniature chemical processors, computing, and robotics, it will produce a wide-range of items quickly, cleanly, and inexpensively, building products directly from blueprints. A nanofactory about the size of a washing machine will be able to manufacture almost anything. Fed with simple chemical stocks, this amazing machine breaks down molecules, and then reassembles them into any product you ask for. Packed with nanotechnology and robotics, weighing 200 pounds and standing half as tall as a person, it can produce two tons per day of products.  It costs very little to operate, just the price of materials fed into it. In one hour, $20 worth of chemicals can be converted into 100 pairs of shoes, or 50 shovels, or 200 cell phones, or even a duplicate nanofactory! Impossible? Today it may be impossible but not tomorrow. These nanofactories can produce medical robots, networked computers, networked cameras, untraceable weapons of mass destruction etc. So effects of nanotechnology would be as great as industrial revolution itself. Nanotechnology not only will allow making many high-quality products at very low cost, but it will allow making new nanofactories at the same low cost and at the same rapid speed. This unique (outside of biology) ability to reproduce its own means of production is why nanotech is said to be an exponential technology. It represents a manufacturing system that will be able to make more manufacturing systems – factories that can build factories – rapidly, cheaply, and cleanly. The means of production will be able to reproduce exponentially, so in just a few weeks a few nanofactories conceivably could become billions. It is a revolutionary, transformative, powerful, and potentially dangerous or beneficial technology depending on how we use it.  All these things may happen in 20 to 30 years because of the rapid progress being made in enabling technologies, such as optics, nanolithography, mechanochemistry and 3D prototyping. The US National Science Foundation has predicted that the global market for nanotechnologies will reach $1 trillion or more within 20 years. The research community is actively pursuing hundreds of applications in nanomaterials, nanoelectronics and nanobiotechnology.

 

The Nanotech Age is expected to begin between 2025 and 2050, bringing an end to the current Information Age which began in 1990. Most near term (1-5 years) applications of nanotechnology are in the form of nanomaterials. These include materials such as lighter & stronger nanocomposites, antibacterial nanoparticles, and nanostructured catalysts. Nanodevices and nanoelectronics are farther off, perhaps 5-15 years, and will have applications in medical treatments and diagnostics, faster computers, and in sensors.     

 

Nanomaterials:

Nanomaterials are the materials that can be produced having nanoscale in one dimension (for example, very thin surface coatings), in two dimensions (for example, nanowires and nanotubes) or in all three dimensions (for example, nanoparticles). Nanomaterials generally consist of metal atoms, nonmetal atoms, or a mixture of metal and nonmetal atoms, commonly referred to as metallic, organic, or semiconducting particles, respectively. The surface of nanomaterials is usually coated with polymers or biorecognition molecules for improved biocompatibility and selective targeting of biologic molecules. Graphene has attracted a huge amount of attention in recent years with its extraordinarily high electrical & thermal conductivities, mechanical & chemical properties, and large surface area. In order to meet the various demands for a variety of applications, preparation of desired structures of Graphene sheets with controlled dimension and architecture are of significant importance.

 

There are many types of intentionally produced nanomaterials, and a variety of others are expected to appear in the future. For the purpose of this article, most current nanomaterials could be organized into four types. Carbon based, Metal based, Dendrimers and Composites.

1)  Carbon based: Carbon based materials are composed mostly of carbon, most commonly taking the form of a hollow spheres, ellipsoids, or tubes. Spherical and ellipsoidal carbon nanomaterials are referred to as fullerenes, while cylindrical ones are called nanotubes. These particles have many potential applications, including improved films and coatings, stronger and lighter materials, and applications in electronics.

2)  Metal based: Metal based materials include quantum dots, nanogold, nanosilver and metal oxides, such as titanium dioxide. A quantum dot is a closely packed semiconductor crystal comprised of hundreds or thousands of atoms, and whose size is on the order of a few nanometers to a few hundred nanometers. Changing the size of quantum dots changes their optical properties.

3) Dendrimers: Dendrimers are nanosized polymers built from branched units. The surface of a dendrimer has numerous chain ends, which can be tailored to perform specific chemical functions. This property could also be useful for catalysis. Also, because three-dimensional dendrimers contain interior cavities into which other molecules could be placed, they may be useful for drug delivery.

4)  Composites: Composites combine nanoparticles with other nanoparticles or with larger, bulk-type materials. Nanoparticles, such as nanosized clays are already being added to products ranging from auto parts to packaging materials to enhance mechanical, thermal, barrier and flame-retardant properties.

 

Nanoparticles are produced by a wide range of natural (biogenic) and man-made (anthropogenic) processes. Although the deliberate manufacture of nanoparticles (referred to as ‘manufactured nanoparticles’) is a relatively new human activity, we have been generating them for many years (for example from internal combustion engines) and adding to the natural background. Some of the main biogenic sources of nanoparticles include mineral erosion, atmospheric chemistry processes and evaporation of sea spray. Anthropogenic sources include combustion, mining/quarrying and industrial processes including the deliberate manufacture of engineered nanoparticles.

 

Synthesis of nano materials using biological ingredients can be roughly divided into following three types.

1) Use of microorganisms.

2)  Use of plant extracts or enzymes.

3)  Use of templates like DNA, membranes, viruses and diatoms.

Researchers have created a new recombinant Escherichia coli. for the in vivo biosynthesis of metal nanoparticles. The strategy of employing recombinant E. coli expressing metal binding proteins as a nanoparticle factory is generally applicable to the combinatorial synthesis of diverse nanoparticles having a wide range of characteristics, such as optical, electronic, chemical, and magnetic properties.

Recombinant E. coli cells (colored in background) expressing the metallothionein gene and/or phytochelatin synthase gene accumulate metal nanoparticles (black dots in black-and-white cells) upon incubation with corresponding metal ions.

 

Classification of nano structures:

There are a variety of Nanostructures like nanocomposites, nanowires, nanopowders, nanotubes, fullerenes nanofibers, nanocages, nanocrystallites, nanoneedles, nanofoams, nanomeshes, nanoparticles, nanopillars, thin films, nanorods, nanofabrics, quantum dots etc. The most common way to classify nano structures is by their dimensions.

Dimensional classification:

Dimensions	Criteria	Examples
Zero dimensional (0-D)	The nanostructure has all dimensions in the nanometer range.	Nanoparticles, quantum dots, nanodots
One Dimensional (1-D)	One dimension of the nanostructure is outside the nanometer range.	Nanowires, nanorods, nanotubes
Two Dimensional (2-D)	Two dimensions of the nanostructure are outside the nanometer range.	Coatings, thin-film-multilayers
Three Dimensional (3-D)	Three dimensions of the nanostructure are outside the nanometer range.	Bulk

 

Nano measurements:

Nanometrology is the science of measurement at the nanoscale level. Typical dimensions of nanosystems vary from 10 nm to a few hundred nm and while fabricating such systems, measurement up to 0.1 nm is required. The measurement of length or size, force, mass, electrical and other properties at nanoscale is included in Nanometrology. It is important to measure the physical parameters so as to apply them into engineering of nanosystems and manufacturing them. Various techniques have been developed which can be used for measure or determine the parameters for nanostructures and nanomaterials including X-Ray Diffraction, High Resolution Transmission Electron Microscopy, Atomic Force Microscopy and electron diffraction & emission spectroscope etc.

 

NANO APPLICATIONS:

According to estimates by the United Nations World Resources 2000 report, our world population will expand by 50 percent in the next 50 years, world economic activity will grow by 500 percent and use of global energy and materials will increase by 300 percent. The ramifications of these numbers are staggering, and the development of new ways to respond to burgeoning demands is critical. Many scientists view nanotechnology as the revolutionary technology of the 21st century. Just as plastics were a pervasive and revolutionary product of the 20th century, nanotechnology products are expected to have widespread use and change our lives in myriad ways. Over 800 manufacturer-identified nanotech products are publicly available ranging from air conditioner to sunscreen, with new ones hitting the market at a pace of 3–4 per week.

 

Classification of nano applications can be done according to utility of application or generation of application.

 

Classification of nano applications according to utility of applications:

1)  Energy Storage, Production and Conversion:
a) Novel hydrogen storage systems based on carbon nanotubes and other lightweight nanomaterials.
b) Photovoltaic cells and organic light-emitting devices based on quantum dots.
c) Carbon nanotubes in composite 0.lm coatings for solar cells
d) Nanocatalysts for hydrogen generation.
e) Hybrid protein-polymer biomimetic membranes.

 

2)  Agricultural Productivity Enrichment:
a) Nanoporous zeolites for slow release and efficient dosage of water and fertilizers for plants and of nutrients and drugs for livestock.
b) Nanocapsules for herbicide delivery.
c) Nanosensors for soil quality and for plant health monitoring.
d) Nanomagnets for removal of soil contaminants.

 

3) Water Treatment and Remediation:
a) Nanomembranes for water purification, desalination and detoxification.
b) Nanosensors for the detection of contaminants and pathogens.
c) Nanoporous zeolites, nanoporous polymers and attapulgite clays for water purification.
d) Magnetic nanoparticles for water treatment and remediation.
e) Titanium dioxide nanoparticles for the catalytic degradation of water pollutants.

 

4) Disease Diagnosis and Screening:
a) Nanoliter systems (Lab-on-a-chip)
b) Nanosensor arrays based on carbon nanotubes
c) Quantum dots for disease diagnosis
d) Magnetic nanoparticles as nanosensors
e) Antibody-dendrimer conjugates for diagnosis of HIV-1 and cancer
f) Nanowire and nanobelt nanosensors for disease diagnosis
g) Nanoparticles as medical image enhancers

 

5) Drug Delivery Systems:
 a)Nanocapsules, liposomes, dendrimers, buckyballs, nanobiomagnets and attapulgite clays for slow and sustained drug release systems

 b)  Scientists have tracked the flow of nanoparticles from the lungs to the bloodstream for the first time. The work    could lead to the development of new drug delivery system.

 

6) Food Processing and Storage:
a) Nanocomposites for coatings used in food packaging
b) Antimicrobial nanoemulsions for applications used in decontamination of food equipment or packaging
c) Nanotechnology-based antigen detecting biosensors for identification of pathogen contamination

 

7)  Air Pollution and Remediation:
a) Titanium dioxide nanoparticle-based photocatalytic degradation of air pollutants in self-cleaning systems.
b) Nanocatalysts for more efficient, cheaper and better-controlled catalytic converters
c) Nanosensors for detection of toxic materials and leaks.
d) Gas separation nanodevices.

 

8) Construction:

a) Nanomolecular structures to make asphalt and concrete more robust to counter water seepage.
b) Heat-resistant nanomaterials to block ultraviolet and infrared radiation.
c) Nanomaterials for cheaper and durable housing, surfaces, coatings, glues, concrete and heat and light exclusion.
d) Self-cleaning surfaces (e.g. windows, mirrors, toilets) with bioactive coatings.

 

9) Health monitoring:  

Nanotubes and nanoparticles for glucose, carbon dioxide, and cholesterol sensors and for in-site monitoring of homeostasis.

 

10) Vector and pest detection and control:

a) Nanosensors for pest detection.
b) Nanoparticles for new pesticides, insecticides and insect repellents.

 

Classification of nano applications according to nano generations:

The first generation is that of passive nanostructures, materials designed to perform one task. The second generation, which we have already entered introduces active nanostructures for multitasking; for example actuators, drug delivery devices, and sensors. The third generation is expected to begin emerging around 2011 and will feature nanosystems with thousands of interacting components. A few years after that, the first integrated nanosystems, functioning much like a mammalian cell with hierarchical systems within systems, are expected to be developed.

 

First generation nanotech applications:

1)   Titanium dioxide in sunscreen, cosmetics and some food products.

 

2)   Carbon allotropes used to produce gecko tape.

 

3)  Silver in food packaging, clothing, disinfectants and household appliances.

 

4)   Zinc oxide in sunscreens and cosmetics, surface coatings, paints and outdoor furniture varnishes; and cerium oxide as a fuel catalyst.

 

5)  The clothing industry has started using embedded nanoparticles to create stain-repellent khakis. This seemingly simple innovation will impact not only khaki-wearers, but dry cleaners, who will find their business declining; detergent makers, who will find less of their product moving off the shelf; and stain-removal makers, who will experience a sharp decrease in customers. So nanotech is already at use in textile products ranging from stain-resistant to anti-wrinkle clothing. If keeping clothes clean isn’t enough, ‘smart clothing’ could monitor your heart rate and other vital signs.

 

6)  Nanocrystals of various metals have been shown to be 100 percent, 200 percent and even as much as 300 percent harder than the same materials in bulk form. Because wear resistance often is dictated by the hardness of a metal, various machine parts made from nanocrystals might last significantly longer than conventional parts.

 

7)  Self-cleaning glass – A special Glass, which uses nanoparticles to make the glass photocatalytic and hydrophilic. The photocatalytic effect means that when UV radiation from light hits the glass, nanoparticles become energized and begin to break down and loosen organic molecules on the glass (in other words, dirt). Hydrophilic means that when water makes contact with the glass, it spreads across the glass evenly, which helps wash the glass clean.

 

8)  Antimicrobial bandages – Scientists have created a process to manufacture antibacterial bandages using nanoparticles of silver. Silver ions block microbes’ cellular respiration. In other words, silver smothers harmful cells.

 

9)  Burns dressing: Scientists have developed a nano-dressing working by releasing antibiotics from nanocapsules triggered by the presence of disease-causing pathogenic bacteria, which will target treatment before the infection takes hold. The dressing will also change colour when the antibiotic is released, alerting healthcare professionals that there is infection in the wound. This is an important step in treating burns patients. Your skin is normally home to billions of ‘friendly’ bacteria, which it needs to stay healthy. The dressing is only triggered by disease-causing bacteria, which produce toxins that break open capsules containing the antibiotics and dye. This means that antibiotics are only released when needed, which reduces the risk of the evolution of new antibiotic-resistant super-bugs such as MRSA.

 

10)   N95 mask can only filter out material greater in size than 0.3 microns, which equal to 300 nanometers. N95 masks are not effective against any particulate, virus, or bacteria smaller than 0.3 microns. A new Nano-mask has been tested down to 27 nanometers or 0.027 microns, good enough to block H1N1 viruses (swine flu) as well as ordinary influenza viruses. This new nano-mask has nanoparticle coating along with chlorine particles to achieve an arrest and eradication of undesirable agents. In other words, biohazardous particulates like H1N1 viruses are not only blocked but destroyed, thanks to the nanoparticle coating. A traditional filter without the nanoparticle coating in N95 mask would turn into a breeding ground for a virus or bacterial agent and may indeed be harmful during swine flu epidemic or other epidemics. 

 

 

 Second generation nanotech applications:

1)   The nanocoatings that reduce friction in the transportation industry.

 

2)  The nanocomposites that make airplanes and cars lighter to reduce fuel consumption.

 

3)  Fluorescent polymer-coated nano-spheres could become part of new biological assays.

 

4)  The conjugation of antibodies and nanoparticles with high affinity & specificity through receptor-ligand recognition modes is of paramount importance in the development of vehicles which can be used for diagnosis, treatment of cancer and various other diseases, application of immunodiagnostic nano-biosensors etc

 

5)   Carbon Nanotubes, Silicon Dioxide Nanoparticles, Silicon Nanoparticles, Copper Nanoparticles, Copper Oxide Nanoparticles, Indium Nanoparticles and many others are either superconductors, electrical conductors or semiconductor particles, or quantum dots with far reaching potential in electronics, high speed computing, telecommunication and space travel.

6)  Advances in carbon nanotube technologies are driving the generation of a new class of materials that cross the biomedical, textiles and electronics industries.

 

7)  Chemical catalysis benefits especially from nanoparticles, due to the extremely large surface to volume ratio. The application potential of nanoparticles in catalysis ranges from fuel cell to catalytic converters and photocatalytic devices. Catalysis is also important for the production of chemicals.

 

8)  Nanofilteration: A strong influence of photochemistry on waste-water treatment, air purification and energy storage devices is to be expected. Mechanical or chemical methods can be used for effective filtration techniques. One important field of application is in ultrafiltration for renal dialysis.

 

9)  Researchers are trying to develop nano-sized concrete (nano-concrete) for construction.

 

10)  The nano-size steel produce stronger steel cables which can be in bridge construction 

 

11)  Titanium dioxide (TiO2) is incorporated as nanoparticles, in sun-block to block UV light and it is added to paints, cements and windows for its sterilizing properties since TiO2 breaks down organic pollutants, volatile organic compounds, and bacterial membranes through powerful catalytic reactions. It can reduce airborne pollutants when applied to outdoor surfaces and gives a self cleaning property to surfaces to which it is applied as it is hydrophilic in nature.

 

12)  Applications of nanotechnology have the potential to change the entire agriculture sector and food industry chain from production to conservation, processing, packaging, transportation, and even waste treatment. Nanoscience concepts and Nanotechnology applications have the potential to redesign the production cycle, restructure processing & conservation processes and redefine the food habits of the people. Nanotechnology in food can be applied for detection in food safety, improving the shelf life of food, diseases in crops and livestock, to timely monitor using sensors what crops need more water and nutrients, deliver the right amount of fertilizer or pesticides and prevent over applying fertilizer and prevent run off and pollutants; to understand how water, fertilizers and pesticides interact with crops and deliver better nutrients creating less waste and protecting the environment; to help in developing supplements to improve nutrient delivery to improve health components in milk may offer some potential solutions to diseases like obesity, type II diabetes and cardiovascular diseases; and to develop biosensors to enable early detection of potentially harmful compounds and pathogenic bacteria in food.

 

 

13)   Light-emitting diodes (LED) use only about 10% of the energy that a typical incandescent or fluorescent light bulb uses and typically last much longer. A special variant of LED called the white LED has been developed using nanotechnology. White LEDs consist of semi-conducting organic layers that are only about 100 nanometers in distance from each other and are placed between two electrodes, which create an anode, and a cathode. When voltage is applied to the system, light is generated when electricity passes through the two organic layers. This is called electroluminescence. The semiconductor properties of the organic layers are what allow for the minimal amount of energy necessary to generate light.

 

14)  Nanotechnology offers the potential of novel nanomaterials for the treatment of surface water, groundwater and wastewater contaminated by toxic metal ions, organic and inorganic solutes and microorganisms by the use of electrospun nanofibers & nanobiocides, nanofilteration and electrospinning.

 

15)  The nanotechnology gives the possibility to replace expensive platinum coated electrodes in hydrogen fuel cells with nitrogen-doped carbon nanotubes, being not only cheaper but even more effective (give four times more electric density) in running an environment friendly green-car which does not use fossil-fuel. Also, the use of a lubricant based on spherical inorganic nanoparticles reduces the friction and wear in engines, thus making them live longer and being more efficient.

 

16)   Nanotechnology can enable sensors to detect very small amounts of chemical vapors.  Because of the small size of nanotubes, nanowires, or nanoparticles, a few gas molecules are sufficient to change the electrical properties of the sensing elements. This allows the detection of a very low concentration of chemical vapors.

 

17)  During standard drilling and refining, oil companies are forced to leave behind as much as two barrels for every barrel of oil they produce, but nanotechnology could revolutionize the oil industry by saving this lost oil.

 

18)  Scientists have created a chip that can decode your DNA in a matter of minutes, at a fraction of the cost of current commercial techniques. In the study, the researchers showed that it is possible to propel a DNA strand at high speed through a tiny 50 nanometre (nm) hole or nanopore cut in a silicon chip, using an electrical charge. As the strand emerges from the back of the chip, its coding sequence is read by an electrode junction. This 2 nm gap between two wires supports an electrical current that interacts with the distinct electrical signal from each base code. A computer can then interpret the base code’s signal to construct the genome sequence. Compared with current technology, this device could lead to much cheaper sequencing of human genome in just a few dollars, compared with $1 million to sequence an entire human genome in 2007.

 

19)  In near future, a new mobile diagnostics platform will be guaranteeing fast and low-cost infection diagnostics even while the patient is being transported to the hospital which consists of a plastic card that is inserted in an analysis unit that is smaller than a notebook. This system provides findings in less than one hour to enable the doctor to prescribe the life-saving therapy. This is based on magnetic particles that dock onto the cells to be studied in a blood sample and run through the system fully automatically with magnetic force. The nanoparticles transport the pathogen DNA into the detection chamber where a new type of magnetoresistive biochip can identify pathogens and antibiotics resistances. At the end of the process, the diagnosis is made with magnetic sensors. Platform technology is not only suited for sepsis tests but also for other molecular biological issues ranging from genetic predisposition right down to cancer diagnostics.

 

20)   Nano-rubber: Silicone rubber only retains its viscoelasticity between –55 °C and 300 °C, but the new nano-rubber is highly stable over a broad temperature range due to the energy dissipated as the individual nanotubes zip and unzip at the points of contact. The carbon nanotubes themselves are also very heat resistant between 2000 °C and 3000 °C so an even broader temperature range might be possible for this rubber. This rubber can recover its shape after being repeatedly deformed and has excellent fatigue resistance. This material may find use in space vehicles, wrinkle-free textiles or viscoelastic shoe insoles that reduce mechanical shocks, cold interstellar space or inside a high-temperature vacuum furnace.

 

21)  Researchers have overcome a fundamental obstacle in developing breath-analysis technology to rapidly diagnose patients by detecting chemical compounds called “biomarkers” in a person’s breath in real time. The researchers demonstrated their approach is capable of rapidly detecting biomarkers in the parts per billion to parts per million range, at least 100 times better than previous breath-analysis technologies. Researchers used a template made of micron-size polymer particles and coated them with much smaller metal oxide nanoparticles. Using nanoparticle-coated microparticles instead of a flat surface allows researchers to increase the porosity of the sensor films.

 

22)  Researchers are developing a novel contraceptive, an antiviral gel containing trillions of nanoparticles that will target both HIV & sperm and deliver a bee venom toxin ‘melittin’ that will incapacitate them. Since melittin can annihilate any cell, the trick is to target the melittin to those specific cells intended for destruction (cancer, HIV and sperm) without causing collateral damage to other cells in the body. This nano-vaginal gel affords both contraception & HIV protection. This nano-vaginal gel will be of tremendous help to women in developing nations to prevent unwanted pregnancy and prevent HIV.

 

  

 Third generation nanotech applications:

1)   The medical nanorobot is expected to become the ultimate tool of nanomedicine. So-called nanorobots might serve as programmable antibodies. As disease-causing bacteria and viruses mutate in their endless attempts to get around medical treatments, nanorobots could be reprogrammed to selectively seek out and destroy them. Other nanorobots might be programmed to single out and kill cancer cells.

 

2)    The respirocyte measures about 1 micron in diameter and just floats along in the bloodstream. It is a spherical nanorobot made of 18 billion atoms. Respirocytes mimic the action of the natural hemoglobin-filled red blood cells. But a respirocyte can deliver 236 times more oxygen per unit volume than a natural red cell. The injection of a 5 ml dose of 50% respirocyte aqueous suspension into the bloodstream can exactly replace the entire O₂ and CO₂ carrying capacity of the patient’s entire 5 liter of blood. If you added 1 liter of respirocytes into your bloodstream, you could then hold your breath for nearly 4 hours while sitting quietly at the bottom of a swimming pool. Once a therapeutic purpose is completed, it is desirable to extract artificial devices from circulation by a specialized centrifugation apparatus.

 

3)   Computers can potentially be 10¹² times smaller and use 10⁶ times less power than they do today. It will one day be possible to store at least 2 million terabytes of data in a cubic millimeter of space with molecular nanotechnology.

 

4)  Researchers are developing a multifunctional endoscope-like device for intracellular probing at the single-organelle level, without any recordable disturbance to the metabolism of the cell.

 

Fourth generation nanotech application – Molecular nanotechnology (MNT):

Two concepts associated with molecular nanotechnology are positional assembly and self-replication. Positional assembly deals with the mechanics of moving molecular pieces into their proper relational places and keeping them there. Molecular robots are devices that do the positional assembly. Self-replication deals with the problem of multiplying the positional arrangements in some automatic way, both in building the manufacturing device and in building the manufactured product.  Mature “molecular manufacturing” or “molecular nanotechnology” will enable us to manifest our dreams. We are nearing the ability to build molecules out of atoms mechanochemically, and to use these molecular building blocks to construct virtually any substance or device we can conceive of. The concept of nanofactory is a classical example of MNT (vide supra). This most powerful technology of all will radically transform and extend the capabilities of practically every area of human endeavor by exploring the ultimate limits of fabrication. Molecular Nanotechnology (MNT) will produce effectively no waste and not involve in any cutting, grinding, sanding, melting, forging, or herding of large numbers of unruly atoms. MNT will make exactly what it is expected to make – no more, no less – and therefore no pollution. NASA applications of molecular nanotechnology include computer applications, launch vehicle improvements, and active materials.

 

Some of the applications discussed here are speculative to say the least. However, they do not appear to violate the laws of physics. Something similar to these applications at these performance levels should be feasible if we can gain complete control of the three-dimensional structure of materials, processes and devices at the atomic scale. Also, the applications list published here is not exclusive but a mere tip of the iceberg.

 

Nanomedicine:

Nanomedicine is a well-defined application of nanotechnology in the areas of healthcare, disease diagnosis & treatment. In fact nanomedicine is a part of nanobiotechnology.

 

Nanobiotechnology:

Nanobiotechnology, an integration of physical sciences, molecular engineering, biology, chemistry and biotechnology holds considerable promise of advances in pharmaceuticals and healthcare. An increasing use of nanobiotechnology by the pharmaceutical and biotechnology industries is anticipated.

The above picture is a Schematic illustration of nanotechnology revolutionising biomedical sciences. The integration of nanomaterials with biology has led to the development of diagnostic devices, contrast agents, analytical tools, physical therapy applications, and drug-delivery vehicles. With nanomaterials, the high ratio of surface area to volume permits high surface loading of the therapeutic agent; and in the case of organic nanomaterials, their hollow or porous core allows encapsulation of hundreds of drug molecules into a single carrier particle. This nanobiotechnology is expected to create innovations and play a vital role in various biomedical applications, not only in drug delivery and gene therapy, but also in molecular imaging, biomarkers and biosensors. Target-specific drug therapy and methods for early diagnosis of pathologies are the priority research areas where nanotechnology would play a prominent role. Nanoscale polymer capsules can be designed to break down and release drugs at controlled rates, to allow differential release in certain environments, such as an acid medium, and to promote uptake in tumours versus normal tissues.   Nanoparticulate carriers have been developed as a solution to overcome drug delivery problems like poor solubility, limited chemical stability in vitro & in vivo after administration (i.e. short half-life), poor bioavailability and potentially strong side-effects requiring drug enrichment at the site of action (targeting). Magnetic nanoparticles, bound to a suitable antibody, are used to label specific molecules, structures or microorganisms. Gold nanoparticles tagged with short segments of DNA can be used for detection of genetic sequence in a sample. Researchers are exploring polymer-DNA complexes and liposome-DNA complexes for gene delivery in gene therapy. Calcium phosphate nanoparticles present a unique class of non-viral vectors, which can serve as efficient and alternative DNA carriers for targeted delivery of genes. The synthesis of more effective and biodegradable chemicals for agriculture and the production of implantable detectors could be aided by nanotechnology with minimal quantities of blood. Employing this technology it should also be possible to develop methods that use saliva instead of blood for the detection of illnesses or that can perform complete blood testing within a short period of time. Quantum Dots of a specific colour are believed to be flexible and could offer a cheap and easy way to screen a blood sample for the presence of a number of different viruses at the same time. It could also give physicians a fast diagnosis tool to detect, say, the presence of a particular set of proteins that strongly indicates the onset of myocardial infarction. Nanoparticles have a larger, localized magnetic field as compared with that of larger particles. This larger magnetic field can increase the contrast on imaging (MRI), since more protons interact in a larger field.  The nanosensors are now being applied for simultaneous intracellular measurements of oxygen and glucose. The involvement of nanotechnology in creating a truly bioartificial tissue or organ that can take the place of one that is terminally diseased, such as an eye, ear, heart, or joint has been envisaged. Nanoscale building of cells can be accomplished by their programmed replication. “Tissue engineering” makes use of artificially stimulated cell proliferation by using suitable nanomaterial-based scaffolds and growth factors. For example, bones can be regrown on carbon nanotube scaffolds. Tissue engineering might replace today’s conventional treatments like organ transplants or artificial implants. These new organs could have the necessary DNA encoded to be compatible with the required human body immunological status. Researchers have built a nanomachine out of DNA that can guide the construction of any of several different strands of DNA; the product sequence can be chosen by “programming” the machine with other DNA strands.

 

Nanotechnology applications in anti-cancer management:

Cancer-feeding blood vessels are different than normal ones; they tend to have holes and gaps in the vessel walls that aren’t found in normal blood vessels. If a nanoparticle is created which is too large to pass through normal blood vessel walls, but small enough to pass through cancerous blood vessel holes, then we have a targeted delivery method. Nanomaterials infused into the bloodstream can accumulate in tumors owing to the enhanced permeability and retention effect when the vasculature of immature tumors has pores smaller than 200 nm, permitting extravasation of nanoparticles from blood into tumor tissue. The trick would be to find a compound that would form itself into nanoscale balls and then coat it with toxin to kill a cancer cell.

 

Another way to kill cancer cells is through nanovectors. Multifunctional organic and inorganic nanoparticles, nanowires and nanotubes are known as nanovectors. Nanovectors are found most useful for combined targeted delivery of anticancer drugs with localized killing of cancerous and pre-cancerous cells through thermal ablation and in the development of nanosurgical tools that may be integrated with conventional surgical tools for the treatment of cancerous diseases.

 

The drug-resistant cancer cells can be killed by using synergistic benefit of nanotechnology. Investigators of the Cancer Nanotechnology Platform Partnership at Northeastern University have shown that a different type of polymer nanoparticle can deliver two anticancer agents simultaneously and as a result can kill cancer cells that have become resistant to drug therapy. The researchers have shown that the nanoparticle containing two drugs was far more effective at killing the drug-resistance cancer cells than when the two drugs were co-administered in separate nanoparticles.    

 

Nanoparticles can also be used for both quantitative and qualitative in vitro detection of tumour cells. They enhance the detection process by concentrating and protecting a marker from degradation, in order to render the analysis more sensitive. For example, the fluorescent nanospheres provided a sensitivity of 25 times more than that of the conjugate streptavidin-fluorescein in the detection of human epidermoid carcinoma cells. Contrast agents have been loaded onto nanoparticles for tumour diagnosis purposes. The physico-chemical features (particle size, surface charge, surface coating, and stability) of the nanoparticles allow the redirection and the concentration of the marker at the specific site of interest.

 

Specific anti-cancer nano applications are as follows:  

 

1) Polyethylene glycol-coated gadolinium based iron oxide nanoparticles.

These are used to target cancer cells and detect apoptosis using magnetic resonance imaging techniques. Magnetic fields are also induced to heat the iron oxide nanoparticles to destroy the cancer cells.

 

2) Silicon-and silica-based nano-and micro-particles:

These are injectable nano-vectors, porous, biodegradable, and therapeutic agents encapsulated inside the nanoparticles can deliver drugs to kill cancer cells.

 

3) Nanoshells (metal-based nanoparticles):

The nanoshells consist of a silica core with a surface layer of nanogold. Changing of the optical absorption properties of the nanoshells depend on the thickness of the gold layer. When radiated with near-infrared light, the nanoshells heat up to 55º to 70º C and can destroy cancer cells thermally.

 

4) Fullerene-based derivatives:

These are used as anti-HIV, as well as anti-cancer agents. Both empty and metallo-fullerenes have low cyto-toxicity in vitro and in vivo and can be effectively used for drug design and delivery. The cage-like structure of fullerene is ideal for packing with anti-cancer drugs or even radiological materials to increase treatment efficacy for destroying cancer cells.

 

5) Carbon nanotubes:

To destroy cancer cells, the surface of the nanotubes is modified with proteins for cellular uptake and the nanotubes are heated with near-infrared light. They confine heat and destroy cancer cells. Complete destruction of nanotubes inside the body makes them ideal for handling toxicity problems that may be associated with nanotubes and nanoparticles.

 

6)  Genetic ignition switch:

A new study in mice has shown that a set of genetic instructions encased in a nanoparticle can be used as an “ignition switch” to rev up gene activity that aids cancer detection and treatment. The switch, called a promoter, is a set of chemical letters that interacts with DNA to turn on gene activity.

 

7) Magnetic Nanoparticles:

Picture showing magnetic nanoparticles, in brown, attach themselves to cancer cells, in violet, from the human abdominal cavity. The ovarian cancer cells under study highly express a receptor called EphA2, while the nanoparticles are functionalized with ligands that bind with high affinity to the EphA2 receptor in the ovarian cancer cells. This attraction is how the nanoparticles seek out specific cancer cells. It is possible to apply this same technology to other cancer cells or pathogens by using ligands that bind to receptors expressed specifically by those cells or pathogens.

 

8) Liquid biopsy using Nanotechnology:

Metastasis – the most common cause of cancer-related death in patients with solid tumors – is caused by marauding tumor cells that break off from the primary tumor site and ride in the bloodstream to set up colonies in other parts of the body. These breakaway cancer cells in the peripheral blood are known as circulating tumor cells (CTCs). Detecting and analyzing these cells can provide critical information for managing the spread of cancer and monitoring the effectiveness of therapies. By capturing CTCs, doctors can essentially perform a liquid biopsy by capturing break-away cells floating in the bloodstream. Researchers have invented a groundbreaking method of detecting cancer early; contained on a microchip the size of a business card, the technique uses nanotechnology to sort healthy and cancerous cells in the bloodstream. The experimental device could one day replace needle biopsy as the best way to diagnose cancer. It is so sensitive that it can spot a single cancer cell among hundreds of millions of healthy ones in only several teaspoons of a patient’s blood. Using this technique, oncologists could give a drug today and sample the blood tomorrow to see if the CTCs are gone. The test could transform care for several types of cancer, including breast, prostate, colon, and lung. Initially, doctors want to use it to try to predict what treatments would be best for each patient’s tumor and find out quickly if they are working. 

 

Nanoscience in complementary & alternative medicine:

A scientific team from IIT-Mumbai demonstrated that homeopathy works on the principle of nanotechnology. The research  published in the journal Homeopathy, states that even when diluted to 1 part in 10 raised to 400 parts, certain homeopathic pills containing naturally occurring metals like gold, copper and iron retain their potency due to formation  of nano-particles of these metals. Prima facie, it appears to be pseudo-science.  In fact, it is quite simple to synthesize stable monometallic nanoparticles by wet chemical method using the reducing capabilities of different sugars which has a bearing on the particle size. Evaporation of the precursor solutions on the solid surface (strong metal–support interaction) leads to the formation of  spherical nanoparticles of approximately 1, 3, 10 and 20 nm sizes for gold, platinum, silver and palladium, respectively. Fructose has been found to be the best suited sugar for the synthesis of smaller particles and remained stable for months together. Since fructose is ubiquitous in nature, various herbal & homeopathic medicines containing metal could have used  fructose in its synthesis and therefore they may possess few metallic nanoparticles.  Suspensions of nanoparticles are possible since the interaction of the particle surface with the solvent is strong enough to overcome density differences, which otherwise usually result in a material either sinking or floating in a liquid. So when further dilution is attempted, these particles will be carried passively to new solution and again remain suspended in a solution so that extreme dilution can still contain such nanoparticles albeit fewer. Now, whether such metallic nanoparticles can cure diseases right from asthma to cancer, is a matter of speculation. In fact, in my view, these metallic nanoparticles of herbal & homeopathic medicine indeed harm human tissues after ingestion due to toxicity of nanoparticles (vide infra).    

 

Nano hazards:

The following attributes of nanoparticles create a number of unknown exposures:

1)   Size of particles: The size of nanoparticles makes them incapable of being measured using normal techniques.

 

2)  Increased reactivity and conductivity: Nanoparticles are more reactive and conductive than particles larger in size because of their extremely small size and large surface area. As such, materials that have been benign in the past may become toxic in nanoparticle form.

 

3)  Routes of exposure: Because of their size, nanoparticles can be inhaled or ingested and may even enter the body through the skin. In addition, they are capable of crossing the blood-brain barrier.

 

The famous 18th century Spanish artist Pablo Picasso, once said, “Every positive value has its price in negative terms” and so the genius of Einstein leads to Hiroshima and that appears to be so true of nanoparticles.

 

 

Due to far-ranging claims that have been made about potential applications of nanotechnology, a number of serious concerns have been raised about what effects these will have on our society if realized, and what action if any is appropriate to mitigate these risks. Once released there is no mechanism for the recall of nanoparticles. Their fate in the environment is unknown. Their capacity for bioaccumulation, bio-excretion, and the health ramifications for humans and other species, remain open questions. One of the new properties of nano-sized particles is their extreme mobility. If they become airborne, nano particles can float for long periods – unlike larger particles – they do not readily settle onto surface and current drinking water filters do not effectively remove nano particles. Insoluble or low solubility nanoparticles are the greatest cause for concern. Several studies have shown that some of them can pass through the various protective barriers of living organisms. The inhaled nanoparticles can end up in the bloodstream after passing through all the respiratory or gastrointestinal protective mechanisms. They are then distributed in the various organs and accumulate at specific sites. They can travel along the olfactory nerves in the nose and penetrate directly into the brain, just as they can pass through cell barriers. Some of these nanoparticles have shown major toxic effects. Another special feature of nanoparticles is that their toxicity seems to be linked to their surface. This is a major difference from the usual situations, in which toxicity is normally linked to a product’s mass. Nanoparticles are so tiny that small quantities (expressed in terms of mass) could have major toxic effects because of their large surface. Several studies have shown much greater toxic effects for the same mass of nanoparticles as compared to the same product with a higher granulometry. The available studies have shown several effects in animals, depending on the type of nanoparticles. Nephrotoxicity, effects on reproduction and genotoxic effects have been identified so far. Some particles cause granulomas, fibrosis and tumoural reactions in the lungs. Thus titanium dioxide, a substance recognized as non-toxic, shows high pulmonary toxicity on the nano-scale. Cytotoxic effects have also been reported. People are concerned about “unknown and long-term side effects” and agree that it is important to know if products “are made with nanotechnology”. The issue with nanotechnology is that here is a technology of the invisible, which is being driven by industrial economics rather than consumer sentiment and it is infiltrating the food chain in a climate of inadequate testing, labeling, regulation and predictability. The ramifications, be they long or short term, are unknown for the consumers, the biosphere, and the environment. Nonetheless, I enlist various nano-hazards as follows.

 

1)   Untraceable weapons of mass destruction, networked cameras for use by the government, and weapons developments fast enough to destabilize arms races.

 

2)   Researchers have discovered that silver nanoparticles used in socks to reduce foot odor are being released in the wash with possible negative consequences as silver nanoparticles are bacteriostatic, which may then destroy beneficial bacteria which are important for breaking down organic matter in waste treatment plants or farms.

 

3)  A study found that lab mice consuming nano-titanium dioxide showed DNA and chromosome damage to a degree “linked to all the big killers of man, namely cancer, heart disease, neurological disease and aging”. Titanium dioxide (TiO2) nanoparticles are found in almost everything today – cosmetics to sunscreen to paint to vitamin to toothpaste to food colorants to personal care products to improve solar cell efficiency.

 

4)  Some forms of carbon nanotubes could be as harmful as asbestos if inhaled in sufficient quantities and may cause mesothelioma.

 

5)  As nanoparticles and nanosensors become more common place in a building construction, a loss of privacy may result from users interacting with increasingly intelligent building components.

 

6)  Nanoparticles are highly catalytic and they are also able to pass through cell membranes in organisms, and their interactions with biological systems are relatively unknown. Smaller nanoparticles evinced increased cytotoxicity. However, free nanoparticles in the environment may rapidly agglomerate and thus leave the nano-regime.

 

7)  When rats breathed in nano-sized materials at a concentration routinely inhaled by factory welders, the tiny particles followed a rapid and efficient pathway from the nasal cavity to several regions of the brain, according to a study in the August 2010 issue of Environmental Health Perspectives. Researchers conclude that despite differences between human and rodent olfactory systems, this pathway is likely to be operative in humans.

 

8)  A recent study showed that polystyrene nanoparticles up to 240nm in size can be transported through a human placenta and may harm the developing brains and reproductive systems of unborn babies following maternal exposure to nanoparticles.

 

9)  According to an article published in the European Respiratory Journal by a group of Chinese researchers, seven young female workers fell seriously ill after working in a paint factory that used nanotechnology. The workers suffered severe and permanent lung damage, and face and arm eruptions. Two of them died, while the other five have not improved after several years.

 

A groundbreaking study was produced recently by researchers at UC Santa Barbara how nanoparticles are able to biomagnify in a simple microbial food chain. The researchers observed that nanoparticles formed from cadmium selenide were entering certain bacteria (called Pseudomonas) and accumulating in them. According to them the cadmium increased in the transfer from bacteria to protozoa and, in the process of increasing concentration, the nanoparticles were substantially intact, with very little degradation. Another study found that caterpillars feeding on tobacco plants grown in solutions containing gold nanoparticles accumulated the nanoparticles at concentrations between 6-12 times higher than those measured in the plants. Biomagnification – the increase in concentration of cadmium & gold as the tracer for nanoparticles from prey into predator – this is the first time it has been reported for nanomaterials in a food chain. These findings represent ‘potentially important’ transfer mechanisms for human health and since humans sit at the top of the food chain, concentrations could be dangerous if biomagnification continued all the way up.The issue is how scientists can prevent any possible negative effects that might pose a threat to humans because nanoparticles are able to biomagnify in living cells.   

 

Green nanotechnology:

Green nanotechnology is the development of clean technologies, “to minimize potential environmental and human health risks associated with the manufacture and use of nanotechnology products, and to encourage replacement of existing products with new nano-products that are more environmentally friendly throughout their lifecycle.”  Evaluation of ‘green’ nanotechnology requires a full life cycle assessment of nanoparticles. Green Nanotechnology has two goals: producing nanomaterials and products without harming the environment or human health, and producing nano-products that provide solutions to environmental problems. As nanotechnology applications and nanomaterials slowly move into mainstream manufacturing, there will have to be an increasing focus on the environmental footprint that the production of various nanomaterials creates.   

 

Nano weapons:

Leading scientists have acknowledged that nano weapons would “revolutionize warfare.” The molecular nano weapons seem to be the next super weapons after the nuclear weapons. They are molecules converted by their own atoms and by atoms inserted into their atomic systems, transforming molecules into tiny computers, racing through space like submicroscopic viruses, able to find enemy submarines and bombers carrying nuclear weapons and destroy them. Destructive nanomachines could do immense damage to unprotected people and objects. If the wrong people gained the ability to manufacture any desired product, they could rule the world, or cause massive destruction in the attempt. Certain products such as vast surveillance networks, powerful aerospace weapons, and microscopic antipersonnel devices provide special cause for concern. The weapons of MNT will be on such a small scale that they will be invisible, smaller than their biological & chemical counterparts, and more precise because they will be programmable. This means that they can evade defenses and strike predetermined targets much as cruise missiles do, though invisibly. In addition, Nanotechnology could be used to create “miniaturized nuclear weapons” that would have virtually no fallout, and super-efficient bioterrorism. Even worse, with the new technology it becomes useless to strike traditional targets such as weapons and factories because they could be restored overnight by the advanced manufacturing of nanotechnology. Raze a factory one day; it will grow back soon thereafter. So the target will become the ultimate target, the people. Military planners will seek a target that cannot be easily replaced and that is large enough to find and hit, and that only leaves the civilian population. MNT also makes war between states inevitable because by its very nature, it creates a general equality in destructive capacity. As MNT spreads, so does the ability to create powerful and deadly weapons and the ability to rebuild an industrial base in a very short time. So each state becomes more of a threat to its neighbors by making it more deadly due to the nano-weapons and more difficult to defeat due the rebuilding capabilities.

 

Nano laws:

Regulatory bodies in the U.S. as well as in the EU have concluded that nanoparticles form the potential for an entirely new risk and that it is necessary to carry out an extensive analysis of the risk. A truly precautionary approach to regulation could severely impede development in the field of nanotechnology if we require safety studies for each and every nanoscience application because existing regulatory systems have been assessing the safety of nanometer scale molecular arrangements for many years and many substances comprising nanometer scale particles have been in use for decades e.g. Carbon black, Titanium dioxide, Zinc oxide, Bentonite, Aluminum silicate, Iron oxides, Silicon dioxide, Diatomaceous earth, Kaolin, Talc, Montmorillonite, Magnesium oxide, Copper sulphate etc. However, a new law may be required to manage potential risks of nanotechnology. The law would require manufacturers to submit a sustainability plan which would show that the product will not present an unacceptable risk. The political obstacles to passing new legislation are very large and the drawbacks of trying to fit Nanotech under existing laws make the attempt worthwhile.

 

What are the problems faced by the world in 21’st century?

The list is long right from terrorism to poverty and from global warming to disease. However, two problems merit special mentions, namely, water shortage and energy crisis. If these two problems can be solved by nanotechnology, other problems will be consequently solved.

 

Nanotechnology for energy security:

Nano solar cells made of plastic can turn the sun’s power into electrical energy, and they are many times more efficient than present silicon-based solar cells.  Flexible sheets of tiny solar cells made by using nano science applications may be used to harness the sun’s energy and will ultimately provide a cheaper, more efficient source of energy. With nanotechnology, tiny solar cells can be printed onto flexible, very thin light-retaining materials, bypassing the cost of silicon production which is used in traditional solar cells. Thin rolls of highly efficient light-collecting plastics is spread across rooftops or built into building materials known as solar buildings. By integrating applications of nanoscience, “solar farms” may be created which consist of the plastic material with solar cells which can be rolled across deserts to generate energy. The idea is to convert sunlight into electrical energy using integrated nanotechnology for micro & thin-film applications. New ways of making solar cells very cheaply on a very large scale offer us the best hope we have for providing low-carbon energy on a big enough scale to satisfy the needs of a growing world population aspiring to the prosperity we’re used to in the developed world. Nanotech will work on several fronts to greatly increase available power from sustainable generation while lowering the cost per kilowatt-hour (kWh). Through nanotech, solar power may become the top pick for clean and sustainable worldwide power generation. Nanotech is also advancing battery technology to allow much higher capacity, more durable cells to be manufactured less expensively. Nanotechnology could be harnessed to consume extremely low amounts of energy, making it a vital alternative to current methods of supplying power.     

 

Nanotechnology for water security:

Freshwater could become the oil of the 21st century – scarce, expensive and fought over. While over 70 per cent of the Earth’s surface is covered by water, most of it is unusable for human consumption. Technological advances have made desalination and demineralization feasible – albeit expensive – solutions for increasing the world’s supply of freshwater. With population growth and climate change limiting the world’s fresh water stores, there is an urgent need to make the process of desalination more effective and less costly than current methods. So nanotechnology may come to the rescue of humanity. Various nanotech methods are available for desalination of sea water.

1)   Boron nitride nanotubes can be thought of as a hollow cylindrical tube made up of boron and nitrogen atoms. These nanotubes are incredibly small, with diameters less than one-billionth of a meter. Using boron nitride nanotubes and the same operating pressure as current desalination methods, we can achieve 100 percent salt rejection for concentrations twice that of seawater with water flowing four times faster, which means a much faster and more efficient desalination process.

 

2)   One of the most promising applications for carbon nanotube membranes is sea water desalination. These membranes will some day be able to replace conventional membranes and greatly reduce energy use for desalination. In the recent study, the researchers wanted to find out if the membranes with 1.6 nanometer pores reject ions that make up common salts. In fact, the pores did reject the ions and the team was able to understand the rejection mechanism. If water desalination is achieved at lower energy, water supplies from all around the world could significantly grow. That would mean more food for the poor countries and cheaper water all in all for the rest of the world.

 

3)  Researchers have developed a new reverse osmosis (RO) membrane that promises to reduce the cost of seawater desalination and wastewater reclamation. The new membrane uses a uniquely cross-linked matrix of polymers and engineered nanoparticles designed to draw in water ions but repel nearly all contaminants. These new membranes are structured at the nanoscale to create molecular tunnels through which water flows more easily than contaminants.

 

4)  Researchers have now demonstrated a new, efficient and clean desalination process based on the ion concentration polarization (ICP) phenomenon – a fundamental electrochemical transport phenomenon that occurs when an ion current is passed through ion-selective membranes ( nanochannel or nanoporous membrane) for direct desalination of sea water.  The system works at a microscopic scale, using fabrication methods developed for microfluidics devices – similar to the manufacture of microchips, but using materials such as silicone (synthetic rubber). Each individual device would only process minute amounts of water, but a large number of them – the researchers envision an array with 1,600 units fabricated on an 8-inch-diameter wafer – could produce about 15 liters of water per hour, enough to provide drinking water for several people.

 

MNT promises so much that it resembles science fiction, but it matters what kind of science fiction it resembles. For decades, science fiction authors have read about scientific progress, anticipated future developments, and written about them. Examples include visions of Moon landings, nuclear bombs, and the internet. Authors have also written about apparent impossibilities — warp drives, time travel, antigravity, and the like. But we must distinguish between ideas that are fiction because they can never happen and those that are fiction because they have not happened yet — between fantasy and forewarning. Research in MNT is based on established science. It can happen, and in a competitive world, it seems hard to avoid. It resembles science fiction because it warns of enormous consequences, not because it is fantasy. To reject these forewarnings merely because they resemble science fiction would be to reject scientific evidence because it appears to have enormous consequences. This would be an enormous mistake. On the other hand, the concern of the mainstream scientist is the media’s current perception of nanotechnology. The media seems to blur the distinction between what is realistic and what is improbable. Much of the increasingly vocal debate is no longer based on peer-reviewed science. Since possible nano-robots are in the size range of viruses, some suggested that nano-robots can control life processes and overcome all diseases. This would be the most interesting science fiction for the public, as many people are struggling with diseases for which they want miraculous cure.

 

THE MORAL OF THE STORY:

From wound dressing to cancer management, from wrinkle-free clothing to self-cleaning glass, and from desalination of water to harnessing solar energy; nanotechnology has revolutionized our thinking and our life. The next half of the 21’st century belongs to the nano world. We must prepare ourselves to embrace nano world. We must be cautious in distinguishing between fact & fiction about nanotechnology and we must make efforts to mitigate potential nano hazards.

 

Dr. Rajiv Desai. MD.

January 8, 2011