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Nanotechnology and Prime Materials

Nanotechnology from Different Angle

As we have seen in previous lectures thenano materials are either made of nanostructure (nanowires, nanotubes, nanoparticles..), or covered by nanostructures, or contain nanostructures. As the size of materials reduces to the level of nanoscales, their properties changes including sensitivities. Lack of proper knowledge about nano materials raises concerns about the health and safety

issues.

).


Many toxicological researchers are most concernabout two types of materials: 1) materials contain carbon base nanostructures

(nanotubes, nanosphere…),2) those contain metal, metal-oxideNanoparticles ( like titanium diode, zinc oxide, among many others

Nanotechnology and Prime materials

• Metals:• Iron, needle shape particles with diameters on

the order of 30-100 nm are produced. Widely used in magnetic recording for analog and digital date. Iron-palladium, and Iron-platinum (strong magnetization) alloys are used for ground-water decontamination, and magnetic storage media respectively. Drug delivery and medical imaging


• Aluminum, powders with size range of 10-100 nm, using plasma reactor. In a few thousandths of second a rod of solid material with a massive pulse of electrical energy, heating it to 50,000 C, followed by rapid cooling of the gas, the speed of cooling controls the size of the nano-particles. It is used for optical applications like scratch-resistant coatings for plastic lenses, biomedical applications, fuel cells, and solar energy applications.


• Nickel, powders are valued for their high conductivity and high melting point. Particles with sizes of 100-500 nm are produced using CVD, wet-chemical processes and gas-phase reduction. Multilayer ceramic capacitors have become the major application for these nanoparticles.


• Silver, known for its excellent conductivity and antimicrobial effects. Particles with sizes range of 10-90 nm have been used as an ingredient in a biocide (a chemical substance killing living organisms), in transparent conductive inks and paste,…

• Most recently, it is shown that silver nanoparticles inactivate HIV and herpes viruses.


• Antimicrobial agent for the treatment of wounds.

• Embedded in plastic food storages to kill bacteria from old stored food.

• Destroying odors caused by microorganisms in the form of microbes that can’t live around silver ions

• To make filters from silver nanowires to kill bacteria in drinking water


• Copper, nanoparticles are synthesized using thermal reduction or sonochemical(using ultrasound) methods. superior ability to conduct heat and electricity.

• Using nanowires to fabricate transparent conductive polymers


• Gold, nanoparticles are easier to produce compare to other metals (due to the chemical stability). Colloidal gold has been used in medical applications; in a wide array of catalytic applications, e.g. for low-temperature oxidation processes, and production of other nanoparticles; optical and electrical applications, as components for various probes, sensors, and optical devices, drug delivery…

• Nano particles with size of 5 nano can be used as a catalyst, for purifying air.

• Changing light energy to heat energy.

• One of the best materials to induce localized surface plasmonic resonance (LSPR). Applications were discussed before.

• Gold nanowires has many applications including as components in sensors, (gas, bio.) as we discussed before.


• Mixed Oxides:• Iron Oxide, nanoparticles of ferric oxide are

translucent to visible light but opaque to UV, application in ultra thin transparent coatings with enhanced UV-blocking capabilities. Magnetic properties of magnetite are used to improve various electromagnetic media for storage, like magnetic tapes, computer hard drives, and advance magnets.


• Aluminum Oxide, Nanosized powders of alumina, has a lower melting point, increased light absorption, improved dispersion in both aqueous and inorganic solvents. Are used to polish semiconductor wafers, in advance ceramics, and advance composite materials, for coating light bulbs and fluorescent tubes for uniform emission of light, clear coating to increase hardness, scratch and abrasion resistance, as a performance filler in tires, as a surface fiction agent, coating of high quality inkjet papers.


• Titanium Dioxide, the largest-volume inorganic pigment produced in the world, is widely used in surface coating, paper and plastic applications, as a filler and whitening agent. UV light blocking, additive to sunscreens, cosmetics, varnishes for the preservation of wood, textile fibers, and packaging films. Catalytic, photo-catalytic, self-sanitizing, self-cleaning capabilities. In photoelectrochemical solar cells, thermal coating, corrosion protection. As a component in various polymer composites to yield a product with a tunable refractive index and improved mechanical properties for photonics and electrical applications. Optical communication components (light scattering is significantly reduced).


• Zinc Oxide, larger UV blocking capability, and very transparent for visible light, make them invisible when they added to other materials like cosmetics, sunscreens and antifungal foot powders. Used in ceramics, and rubber processing (increase elasticity, toughness, abrasion resistance). Nanowires are used in UV nanolasers,…


• In addition to the oxides mentioned above, nanoparticle versions of other compounds, such as antimony, chromium, germanium, vanadium, tungsten, are being developed and their possible uses are being explored.


• Advance Composites: nano-composites are formed when nanometer-sized particles of useful additives are blended with a polymer.

• Advance Ceramics: ceramics in general, are inorganic, nonmetallic materials that are consolidated at high temperatures, usually starting as powder particles and ending as solid, usable forms. A typical ceramic contains complex crystals structures based on the various oxides and may involve covalent and ionic bonding.

• …and of course carbon based nanostructures


• Techniques used to produce nano-particles:

• Plasma-arc• CVD• Electrodeposition• Sol-gel • Mechanical crushing• Use of naturally occurring nano-materials.


No matter which way you turn, nanotechnology seems poised to impact our lives to some degree over the coming years. As materials, structures, and devices are engineered in the nanometer size range, unique properties emerge that can potentially be exploited in many ways. The technology associated with manipulation at the nanoscale—nanotechnology—is underpinning research and development into new materials, medical diagnostics and therapeutics, energy management, sensors, biological interfaces, and electronics with properties that have the potential to revolutionize our society.


• First-generation nanotechnology products are commercially available now, and increasing global investment in nanotechnology suggests we are only at the beginning of what some have called "the next industrial revolution.” However, as with previous industrial revolutions, the potential societal and economic promise of nanotechnology needs to be tempered by possible negative implications.


• The need to proactively develop responsible nanotechnology has been highlighted in a number of high profile reports and articles recently and is central to the many governments strategic plan for developing and implementing the technology. Nowhere will this be more important over the next few years than in workplaces where new materials, devices, and products are being manufactured.


• Nanotechnology is based on the unique properties manifest in nanometer-scale structures, and it is expected that resulting products will in turn present unique health and safety issues. The significance of these issues is not yet clear. What is becoming apparent, however, is that the successful development of nanotechnology relies on proactively understanding and addressing the potential risk to human health and safety. As occupational health researchers and professionals, this is the challenge to face today as society stands on the brink of the nanotechnology revolution.


• Unlike incidental particles, very little is known about engineered nanoparticles and how they interact with cells or human organisms. There are only few papers written on the environmental and health impacts of these particles; however, there is a wealth of knowledge on incidental nanoparticles and how these particles interact with biological organisms. Questions remain whether the engineered nanoparticles will act as a bulk solid or a molecular system


• There is very little available information regarding the hazards and risks posed by materials employed in nanotechnologies. Based on the results of a number of reviews, there is a short information note to advise those working in the area of nanotechnologies of the most appropriate approach to control exposure with the current degree of scientific uncertainty, companies should take a precautionary approach when dealing with nanomaterials. In practical terms, this will mean that steps should be taken to contain material and reduce exposure as far as possible.


• Could the same properties that make the tiny particles so effective also turn them into efficient troublemakers inside the human body? It's one of the most intriguing aspects of nanotechnology: Commonplace materials assume unpredictable and incredible characteristics at the molecular level. Tiny rolled-up "nanotubes" of carbon graphite suddenly turn super strong and highly conductive, inert materials become highly reactive, and particles that once emitted red light appear blue on the nanoscale.


• As more and more nano-based consumer products arrive, scientists are beginning to worry that these unpredictable particles are holding back a few surprises -- ones that could harm human health or the environment. Researchers have conducted only a handful of studies on the health implications of nanotechnology.


• We absolutely know how these materials behave when they are larger. But when we engineer something that small, it changes all the fundamentals. Some are so new we don't even have adequate testing methods.

•Nobody is saying here it's a minor threat or a major threat -- we just don't know.


• In the range of nano scale, thousands of different types of particles exist, some possibly dangerous but many others completely harmless.

• We're looking at a whole batch of nano-materials. You can't go classify all nano-materials as bad or all as good."


• Nanotoxicology was proposed as a new branch of toxicology to address the adverse health effects caused by nanoparticles, mostly by engineered nanoparticles and structures


• People have encountered and ingested nanometer-size particles since the invention of fire -- soot is a good example. So are air pollutants such as smog.


Nanomaterials exposure could happen viaAir, water, food and medical supplies.


• Human skin, lungs, and the gastro-intestinal tract are in constant contact with the environment.

• While the skin is generally an effective barrier to foreign substances, the lungs and gastro-intestinal tract are more vulnerable. These three ways are the most likely points of entry for natural or

• Due to their small size, nanoparticles can translocatefrom these entry portals into the circulatory and lymphatic systems, and ultimately to body tissues and organs. Some nanoparticles, depending on their composition and size, can produce irreversible damage to cells by oxidative stress or/and organelle injury.


• Some of the new concerns center on metal-containing nano-materials such as titanium dioxide and zinc oxide. Compounds like these have always been used as sun blocks -- the thick solid-colored lotions you see on lifeguards' noses -- but once mixed into the lotions at a nano level, they turn translucent. Scientists fear that if the metallic atoms in these lotions get into the body, they'll create free radicals and undergo oxidation reactions, literally pulling cells apart in a fashion similar to the way alcohol consumption and cigarette smoking destroy cells.


• Another worry about special nano-material properties that could cause harm: Scientists are experimenting with brain medications that use nano-materials to more easily target and enter trouble spots (drug delivery). But the easy maneuvering enabled by these tiny particles size could prove a detriment. One study found that, when present in water, carbon structures called buckyballsslipped into the brains of large-mouth bass and killed cells. The study, however, was inconclusive and intended only to open the door for more research.


• Some science interest groups, also contend that while many outstanding questions remain, it's hardly time to sound the warning bells. We don't necessarily believe that there's a need to be alarmist -- we have been exposed to some of the materials for a while. But certainly there's enough novelty and enough new production going on that it's worth evaluating."

As it was for many other new technologies, it will take years before anyone knows for sure.


• Some nano-materials, such as fumed silica, carbon black and titanium dioxide, have been used for years but are just now being labeled “nano”. New nano-materials usually have unique structures, surface characteristics or other novel chemical, physical and/or biological properties.Nano-materials often have no value when considered in isolation but when incorporated into products or processes they “enable” the product to exhibit some new quality or function


• The health and environmental risks from exposure to nano-materials are not yet clearly understood. Many nano-materials are formed from nanometer-scale particles (nanoparticles) that are initially produced as airborne particles or liquid suspensions. Exposure to these materials during manufacturing and use may occur by inhaling them, skin contact or ingesting them. Very little information is currently available on the most important exposure routes, exposure levels and toxicology. The information that does exist comes primarily from the study of ultra-fine particles (typically defined as particles smaller than 100 nanometers in diameter).


• Ultra-fine particles that do not dissolve are more toxic, because smaller particles have a relatively larger surface area. There are strong indications that particle surface area and surface chemistry are primarily responsible for the toxic effects seen in cell cultures and test animals. Research is underway to determine the extent to which ultra-fine particles can penetrate the skin. There is also concern that inhaled nanoparticles may move from the lungs into other organs.


• Workers in nanotechnology-related industries have the potential to be exposed to uniquely engineered materials with novel sizes, shapes and physical and chemical properties at levels far exceeding ambient concentrations. Much research is still needed to understand the impact of these exposures on health and how best to devise appropriate exposure monitoring and control strategies. Until a clearer picture emerges, the limited evidence available would suggest caution when potential exposures to nano-materials may occur


• This new technology has tremendous potential across a number of areas in the economy and promise to improve our lives in different ways. Due to advancements in nanotechnology, its application in areas such as pollution reduction, new methods of energy production, and medical innovation is likely to have a positive effect on our lives in the near future. However, because the technologies are so new, they may have a hazardous impact on our health as well.

• The technology is very complicated and that there are potentially thousands of new substances that can be developed which, like chemicals, can have numerous different attributes. While we can quantify the potential for economic benefit and other benefits to society, presently science does not have the information necessary to quantify the potential for hazards or to develop a method forassessing those hazards.


• In most cases, nanoscale systems will alter in physical size upon interaction with an aqueous system. For example, it is very common for many nanostructures to adopt a different chemical form simply through relatively minor interactions; consequently, size is not a constant factor in biological interactions. Furthermore, the surface area can make up a sizeable fraction of these materials, and they can be derived to make many different biomedical systems. By changing surface coatings the nanomaterialtoxicity can almost be completely altered.


• For example, changing the surface features of the materials can change a hydrophobic particle into a hydrophilic one. Hypothetically, surface coats could, for instance, make it possible to eat nanoscale mercury if it has the right surface coating, while it may be dangerous to eat nanoscale table salt if the surface coating was not correct. For this reason, the scientists’ typical view of toxicology, which is driven by the composition of an inorganic particle, may have to be modified for nanoscale materials, because the surface is going to affect different dimensions of environmental and health effects.


• INTERACTIONS WITH BIOLOGICAL SYSTEMS• Chemists and engineers interested in creating

biocompatible nanostructures need to understand their interactions with biological systems. It is suggested that the challenge that nanomaterials pose to environmental health is that they are not one material. It is difficult to generalize about them because, similar to polymers, they represent a very broad class of systems. Many engineered nanomaterials have precisely controlled internal structures, which are structures of perfect solids. Over a third of the atoms in a nanoparticle are at the surface, and these are extremely reactive systems, which in some cases can generate oxygen radicals however, nanoparticles can be tied up very tightly in covalent bonds and wrapped with a polymer.


• Because of the size of nanostructures, it is possible to manipulate the surface interface to allow for interactions with biological systems. With the correct coating particles below 50 nm can translocate into cells relatively easily and are able to interact with channels, enzymes, and other cellular proteins. Those particles above 100 nm, based primarily on size of the particles, have more difficulty. Through the interactions with cellular machinery, there is potential for medical uses, such as drug delivery and cellular imaging.


• While coating or covalently modifying the outer surfaces of nanomaterials eliminates the toxicity of most particles, questions remain about whether under environmental conditions—as opposed to laboratory conditions, the nanomaterials will still be benign. In a recent study, it was demonstrated that if surface-modified C60 materials were irradiated to UVA (i.e., ultraviolet radiation of 320–400 nm in wavelength) for 11 min or UVB (i.e. ultraviolet radiation of 290–320 nm) for 22 min, cytotoxicity returns. Additional research suggests that air exposure and nanoparticle dose are also important for cytotoxiceffects. When cadmium selenide (CdSe) quantum dots in a liver culture model are exposed to air or ultraviolet light, hepatocyte viability decreases as assessed by mitochondrial activity of QD-treated cultures.


• So, while these nanomaterials may be safe under laboratory conditions, a more reliable or maybe environmentally relevant endpoint is to weather these compounds under environmental conditions are safe..


• Fullerenes and other nanomaterials can accumulate in the body, depending on the dosing route. For oral administration, 98 percent of fullerenes are eliminated within 48 hours via feces and urine. The 2 percent that is not eliminated is found throughout the rest of the body. Intravenous dosing is rapidly transported to the liver (73–92 percent), the spleen (up to 2 percent), lung (up to 5 percent), kidney (up to 3 percent), heart (approximately 1 percent), and the brain (approximately 0.84 percent) within 3 hours. After 1 week, 90 percent of intravenously administered fullerenes are still in the body.


• Nanoparticles, including C60, metal QDs, and TiO2 can be redox active (oxide reduction), which may lead to DNA cleavage, oxidative stress, and/or an inflammatory response. For example, C60 fullerenes, if exposed to light, can either make singlet oxygen or be electron donors to make super oxide radicals. The potential dilemma is that not only does the immune system use super oxide radicals to kill foreign toxicants; the super oxide radicals can cause hydroxyl radicals, which can lead to DNA cleavage. The good news is that the body has some ability to prevent the undesired DNA cleavage through super oxide dismutase, part of the antioxidant defense system.


• Toxicity of Carbon Nanotubes• In a recent study, it was tried to investigate the toxicity of

carbon nanotubes, which are approximately 1 nm by 1–5 µm as a singular particle. However, due to strong electrostatic potential, they rarely exist as individual discrete particles and agglomerate into nanoropes.

• Following instillation of the carbon nanotubes into the lung of animals, the tissue was analyzed by looking at cell proliferation, histopathology, lung weights, etc. at 24 hours, 1 week, 1 month, and 3 months post instillation. Through this paradigm, the researchers would be able to determine the initial, transient reaction, but also ask whether the toxicity was sustained or progressive.


• Fifteen percent of the animals died within the first 12 hours due to high agglomeration from electrostatic attraction, which essentially coated the airways of these animals. This was not because of the toxicity of the material, but rather because the material coated their airways. Thus, these animals died from suffocation because of the unique properties of carbon nanotubes.


• The animals that survived the first 24 hours post instillation survived through the 3 months. Exposure to carbon nanotubes produced only a transient inflammatory response at 24 hours, but this was acute, with no inflammatory effects seen at 3 months. Since carbon nanotubes are used in the electronics field for diode, transistors, cellular-phone signal amplifier, and ion storage for batteries, particles need to be thought of as having inherent toxicity, and being carriers for organic molecules and metals.


• Researchers, performed exposure assessments of nanotubes in workplaces. The results suggested that the dust was less than 53 µg/m3, which was extremely low. Most of the nanotubes were aggregated into nanoropes, which may not be respirable. Scientists cannot assume that all nanomaterials are the same as their bulk counterparts, which suggests that materials will need to be tested on a case-by-case basis, a process that may be infeasible because of resource constraint. It was suggested that priorities for studying particles based on surface coating, surface charge, and particle aggregation will need to be made.

Biointerphases vol. 2, issue 4 (2007)

In Summary• Toxicological aspects and assessment of nano materials

are just starting.• Insoluble nanoparticles are the greatest cause of

concern. Several studies have shown that some of them can pass through the various protective barriers of the living organisms. The inhaled nanoparticles can end up in the bloodstream after passing through respiratory or gastrointestinal protective mechanism. They the may penetrate nerves and eventually brain.

• Most toxicity is linked nanoparticles large surface area.• Many substance like TiO2 recognized as non-toxic

material becomes toxic on nano scales.

In Summary• Still due to the small number of studies, the short

exposure period, the different composition of the nanoparticles tested, and other factors, the toxicological data remains insufficient.

• Toxic dose is usually measured in mass unit however, in case of nanoparticles due to large numbers and their large surfaces this unit is not appropriate anymore and should be measure in term of numbers and the surface of any given mass.

• Discouraging the aggregation and agglomerate among nanoparticles, usually they are coated by specific chemical which may change the toxicity of the nanostructures.

In Summary

• Current developments in nanotechnology are increasing at such a rapid pace that it is a challenge for any government to stay up-to-date with progress. Nanotechnology has received considerable attention from scientific communities and governments worldwide. The United States, France, Japan, and Canada have centers and government agencies where they make assessments of the potential risks and benefits to human health posed by nanotechnology

In Summary

• Nanotechnology is one of the priorities for the Canadian government. Canada wants to be a world leader in developing and applying twenty-first century technologies such as biotechnology, environmental technology, information and communication technologies, health technologies, and nanotechnology. In order to achieve these goals, the Canadian government invests about $45–50 million a year in nanotechnology. The Canadian government also has realized that it is time to break down barriers between research disciplines and to foster multidisciplinary approach. In this spirit, the government in Canada no longer funds one lab working on one item in isolation and favors a multi-faculty approach, where people with different backgrounds (physicists, biologists, and chemists) can work together on nanotechnology issues.

In Summary

• The Canadian government sees its responsibility in terms of ensuring that their society will be able to interact with new technologies, contribute to them, and manage them as they develop. In order to do so, the Canadian government conducts discussions with many departments and agencies and holds workshops that bring people together and allow them to take leads on different issues. Hopefully, the Canadian government plans to continue this interdepartmental, interdisciplinary approach.

In Summary

• Some basic strategies approached by the government are:

• Encouraging basic research to achieve fundamental knowledge and understanding of nanoscale phenomena and processes.

• Promoting applied research in specific “grand challenge”areas to accelerate transition of scientific discovery into innovative technologies.

• Providing mechanisms to facilitate transfer of technology into commercial applications and to support basic and applied research.

• Establishing research programs to understand the social, ethical, health, and environmental implications of the technology.

In Quebec

• IRSST (“Institute de recherche Robert Sauve en sante et en securite du travail”) supporting researches on Safety and health effects of nanostructures.

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