Nanotechnology, shortened to "nanotech", is the study of the control of matter on an atomic and molecular scale. Generally nanotechnology deals with structures of the size 100 nanometers or smaller, and involves developing materials or devices within that size. Nanotechnology is very diverse, ranging from extensions of conventional device physics, to completely new approaches based upon molecular self-assembly, to developing new materials with dimensions on the nanoscale, even to speculation on whether we can directly control matter on the atomic scale.

There has been much debate on the future of implications of nanotechnology. Nanotechnology has the potential to create many new materials and devices with wide-ranging applications, such as in medicine, cosmetic, electronics, and energy production. On the other hand, nanotechnology raises many of the same issues as with any introduction of new technology, including concerns about the toxicity and environmental impact of nanomaterials, and their potential effects on global economics, as well as speculation about various doomsday scenarios.
These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.
The first use of the concepts in "nanotechnology" (but pre-dating use of that name) was in "There's Plenty of Room at the Bottom," a talk given by physicist Richard Feynman at an American Physical Society meeting at Caltech on December 29, 1959. Feynman described a process by which the ability to manipulate individual atoms and molecules might be developed, using one set of precise tools to build and operate another proportionally smaller set, and so on down to the needed scale. In the course of this, he noted, scaling issues would arise from the changing magnitude of various physical phenomena: gravity would become less important, surface tension and Van der Waals attraction would become more important, etc. This basic idea appears plausible, and exponential assembly enhances it with parallelism to produce a useful quantity of end products. The term "nanotechnology" was defined by Tokyo Science University Professor Norio Taniguchi in a 1974 paper as follows: "Nanotechnology" mainly consists of the processing of, separation, consolidation, and deformation of materials by one atom or by one molecule." In the 1980s the basic idea of this definition was explored in much more depth by Dr. K. Eric Drexler, who promoted the technological significance of nano-scale phenomena and devices through speeches and the books Engines of Creation: The Coming Era of Nanotechnology (1986) and Nanosystems: Molecular Machinery, Manufacturing, and Computation, and so the term acquired its current sense. Engines of Creation: The Coming Era of Nanotechnology is considered the first book on the topic of nanotechnology. Nanotechnology and nanoscience got started in the early 1980s with two major developments; the birth of cluster science and the invention of the scanning tunneling microscope (STM). This development led to the discovery of fullerenes in 1985 and carbon nanotubes a few years later. In another development, the synthesis and properties of semiconductor nanocrystals was studied; this led to a fast increasing number of metal and metal oxide nanoparticles and quantum dots. The atomic force microscope was invented six years after the STM was invented. In 2000, the United States National Nanotechnology Initiative was founded to coordinate Federal nanotechnology research and development.
Fundamental concepts

One nanometer (nm) is one billionth, or 10-9 of a meter. By comparison, typical carbon-carbon bond lengths, 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.
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. Or another way of putting it: a nanometer is the amount a man's beard grows in the time it takes him to raise the razor to his face.



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. In the "top-down" approach, nano-objects are constructed from larger entities without atomic-level control.
Areas of physics such as nanoelectronics, nanomechanics and nanophotonics have been evolved during the last decades to provide a basic scientific foundation of nanotechnology.
The nanogold

Generally, gold nanoparticles are produced in a liquid ("liquid chemical methods") by reduction of chloroauric acid (H[AuCl4]), although more advanced and precise methods do exist. After dissolving H[AuCl4], the solution is rapidly stirred while a reducing agent is added. This causes Au3+ ions to be reduced to neutral gold atoms. As more and more of these gold atoms form, the solution becomes supersaturated, and gold gradually starts to precipitate in the form of sub-nanometer particles. The rest of the gold atoms that form stick to the existing particles, and, if the solution is stirred vigorously enough, the particles will be fairly uniform in size.
To prevent the particles from aggregating, some sort of stabilizing agent that sticks to the nanoparticle surface is usually added. They can be functionalized with various organic ligands to create organic-inorganic hybrids with advanced functionality. It can also be synthesised by laser ablation.

So colloidal gold, also known as "nanogold", is a suspension (or colloid) of sub-micrometer-sized particles of gold in a fluid - usually water. The liquid is usually either an intense red color (for particles less than 100 nm), or a dirty yellowish color (for larger particles).The nanoparticles themselves can come in a variety of shapes. Spheres, rods, cubes, and caps are some of the more frequently observed ones.
Known since ancient times, the synthesis of colloidal gold was originally used as a method of staining glass. Modern scientific evaluation of colloidal gold did not begin until Michael Faraday's work of the 1850s. Due to the unique optical, electronic, and molecular-recognition properties of gold nanoparticles, they are the subject of substantial research, with applications in a wide variety of areas, and the synthesis of novel [peacock term] materials with unique properties. [peacock term]

Pioneered by J. Turkevich et al. in 1951 and refined by G. Frens in 1970s, this recipe is the simplest one available. Generally, it is used to produce modestly monodisperse spherical gold nanoparticles suspended in water of around 10-20 nm in diameter. Larger particles can be produced, but this comes at the cost of mono dispersity and shape.
Take 5.0×10?6 mol of HAuCl4, dissolve it in 19 ml of deionized water (the result should be a faintly yellowish solution).
Heat it until it boils.
Continue the heating and, while stirring vigorously, add 1 ml of 0.5% sodium citrate solution; keep stirring for the next 30 minutes.
The color of the solution will gradually change from faint yellowish to clear to gray to purple to deep purple, until settling on wine-red.
Add water to the solution as necessary to bring the volume back up to 20 ml (to account for evaporation).
The sodium citrate first acts as a reducing agent. Later the negatively-charged citrate ions are adsorbed onto the gold nanoparticles, introducing the surface charge that repels the particles and prevents them from aggregating.
Recently, the evolution of the spherical gold nanoparticles in the Turkevich reaction has been elucidated. Interestingly, extensive networks of gold nanowires are formed as a transient intermediate. These gold nanowires are responsible for the dark appearance of the reaction solution before it turns ruby-red.
To produce larger particles, less sodium citrate should be added (possibly down to 0.05%, after which there simply would not be enough to reduce all the gold). The reduction in the amount of sodium citrate will reduce the amount of the citrate ions available for stabilizing the particles, and this will cause the small particles to aggregate into bigger ones (until the total surface area of all particles becomes small enough to be covered by the existing citrate ions).

Brust et al. method

This method was discovered by Brust and Schiffrin in early 1990s, and can be used to produce gold nanoparticles in organic liquids that are normally not miscible with water (like toluene).
Dissolve 9.0×10-4 mol of HAuCl4 (about 0.3 g) in 30 ml of water.
Dissolve 4.0×10-3 mol of tetraoctylammonium bromide (TOAB) (about 2.187 g) in 80 ml of toluene.
Add the HAuCl4 solution to the TOAB and stir vigorously for about 10- minutes. The color of the aqueous phase should become clear, and the color of the organic phase (the toluene) should become orange.
While stirring vigorously, add (preferably dropwise, but really doesn't matter) sodium borohydride.(NaBH4); the colour should change from orange to white to purple to eventually reddish, although the latter colors will be poorly discernible, since the solution will be quite concentrated and thus will look very dark.

Keep stirring the solution for up to 24 hours to ensure monodispersity (especially if NaBH4 was not added dropwise; otherwise just an hour or two is enough).
Separate the organic phase, wash it once with dilute H2SO4 (sulfuric acid) to neutralize it, and several times with distilled water.
Here, the gold nanoparticles will be around 5-6 nm. NaBH4 is the reducing agent, and TOAB is both the phase transfer catalyst and the stabilizing agent.
It is important to note that TOAB does not bind to the gold nanoparticles particularly strongly, so the solution will aggregate gradually over the course of approximately two weeks. To prevent this, one can add a stronger binding agent, like a thiol (in particular, alkanethiols), which will bind to gold covalently, producing a near-permanent solution. Alkanethiol protected gold nanoparticles can be precipitated and then redissolved. Some of the phase transfer agent may remain bound to the purified nanoparticles, this may affect physical properties such as solubility. In order to remove as much of this agent as possible the nanoparticles must be further purified by soxhlet extraction.

Sonolysis

Another method for the experimental generation of gold particles is by sonolysis. In one such process based on ultrasound, the reaction of an aqueous solution of HAuCl4 with glucose[citation needed], the reducing agents are hydroxyl radicals and sugar pyrolysis radicals (forming at the interfacial region between the collapsing cavities and the bulk water) and the morphology obtained is that of nanoribbons with width 30 -50 nm and length of several micrometers. These ribbons are very flexible and can bend with angles larger than 90°. When glucose is replaced by cyclodextrin (a glucose oligomer) only spherical gold particles are obtained suggesting that glucose is essential in directing the morphology towards a ribbon.


History

A so-called Elixir of Life, a potion made from gold, was discussed, if not actually manufactured, in ancient times. Colloidal gold has been used since Ancient Roman times to color glass intense shades of yellow, red, or mauve, depending on the concentration of gold. In the 16th century, the alchemist Paracelsus claimed to have created a potion called Aurum Potabile (Latin: potable gold). In the 17th century the glass-colouring process was refined by Andreus Cassius and Johann Kunchel. In 1842, John Herschel invented a photographic process called Chrysotype (from the Greek word for gold) that used colloidal gold to record images on paper. Paracelsus' work is known to have inspired Michael Faraday to prepare the first pure sample of colloidal gold, which he called 'activated gold', in 1857. He used phosphorus to reduce a solution of gold chloride.
For a long time the composition of the Cassius ruby-gold was unclear. Several chemists suspected it to be a gold tin compound, due to its preparation. Faraday was the first to recognize that the color was due to the minute size of the gold particles. In 1898 Richard Adolf Zsigmondy prepared the first coloidal gold in diluted solution.

Current research

Research in 2005 demonstrated that nanogold-coated bacteria can be used for electronic wiring. Bacillus cereus was deposited on a silicon / silicon dioxide wafer lined with gold electrodes. This device was covered with poly(L-lysine). The bacterium's surface has a negative charge, even more so due to the presence of flexible teichoic acid brushes. Poly(L-lysine)-coated nanogold particles carry a positive charge when washed with nitric acid and therefore the particles will only stick to the bacteria and nothing else. The bacteria survive this treatment. When the humidity increases in a sample, the bacterium absorbs water and the resulting membrane expansion can be monitored by measuring the electrical current flowing through the bacteria. The Fowler-Nordheim equation is obeyed when the interbacterial distance is very small.
The reduction of hydrogen tetrachloroaurate by sodium borohydride in the presence of one of the enantiomers of penicillamine results in optical active colloidal gold particles.
Penicillamine anchors to the gold surface by virtue of the thiol group. In this study the particles are fractionated by electrophoresis into three fractions, Au6, Au50 and Au150 as evidenced by Small angle X-ray scattering (SAXS). The D and L isomers have a mirror image relationship in circular dichroism.

Health/Medical Applications

Colloidal gold is also extremely useful in the medical field. Colloidal gold has been successfully used as a therapy for rheumatoid arthritis in rats. In a related study, the implantation of gold beads near arthritic hip joints in dogs has been found to relieve pain.
An in vitro experiment has shown that the combination of microwave radiation and colloidal gold can destroy the beta-amyloid fibrils and plaque which are associated with Alzheimer's disease. The possibilities for numerous similar radiative applications are also currently under exploration.
Gold nanoparticles are being investigated as carriers for drugs such as Paclitaxel. The administration of hydrophobic drugs require encapsulation and it is found that nanosize articles are particularly efficient in evading the reticuloendothelial system.
In cancer research, colloidal gold can be used to target tumors and provide detection using SERS (Surface Enhanced Raman Spectroscopy) in vivo. These gold nanoparticles are surrounded with Raman reporters which provide light emission that is over 200 times brighter than quantum dots. It was found that the Raman reporters were stabilized when the nanoparticles were encapsulated with a thiol-modified polyethylene glycol coat. This allows for compatibility and circulation in vivo. To specifically target tumor cells, the pegylated gold particles are conjugated with an antibody (or an antibody fragment such as scFv), against e.g. Epidermal growth factor receptor, which is sometimes overexpressed in cells of certain cancer types. Using SERS, these pegylated gold nanoparticles can then detect the location of the tumor.
Gold nanorods are being investigated as photothermal agents for in-vivo applications. Gold nanorods are rod shaped gold nanoparticles whose aspect ratios tune the surface plasmon resonance (SPR) band from the visible to near infrared wavelength. The total extinction of light at the SPR is made up of both absorption and scattering. For the smaller axial diameter nanorods (~10 nm), absorption dominates, whereas for the larger axial diameter nanorods (>35 nm), scattering can dominate. Consequently, for in-vivo applications, small diameter gold nanorods are being used as photothermal converters of near infrared light due to their high absorption cross sections.[citation needed] Since near infrared light transmits readily through human skin and tissue, these nanorods can be used as ablation components for cancer, and other targets. When coated with polymers, gold nanorods have been known to circulate in-vivo for greater than 15 hours half life.

A field that has showed fast growth over the past decades is the use of gold nanoparticles in biology, or life sciences. These bioapplications can be classified into four areas: labelling, delivery, heating, and sensing.
For labelling, certain properties of the particles are exploited to generate contrast. For example in transmission electron microscopy, the strong electron absorbing properties of gold nanoparticles make them suitable as a stain for samples with poor contrast, such as tissue samples. Their small size and the possibility of functionalising the particles, for instance with antibodies (immunostaining), mean that they also provide extremely high spatial resolution and specificity in many labelling applications. Similarly, the particles' optical properties - strong absorption, scattering and especially plasmon resonance - make them of value for a large variety of light-based techniques including combined schemes such as photothermal or photo-acoustic imaging. In addition, gold nanoparticles can be radioactively-labelled by neutron activation, which allows for very sensitive detection, and used as an x-ray contrast agent.


Gold nanoparticles have bioapplications in four areas: labelling, delivery, heating, and sensing.

Secondly, gold nanoparticles can serve as carriers for drug and gene delivery. Biologically active molecules adsorbed on the particle surfaces can be guided inside cells and released. DNA delivery, for instance, is the basis for gene therapy.

Thirdly, their strong light absorbing properties makes gold nanoparticles suitable as heat-mediating objects; the absorbed light energy is dissipated into the particles' surroundings, generating an elevated temperature in their vicinity. This effect can be used to open polymer microcapsules, for example, for drug delivery purposes. What's more, appropriately functionalised nanoparticles might bind specifically to certain cells, which might one day find a use in cancer targeting and hyperthermal therapy by heating the particle-loaded tissue in order to destruct the malignant cells. However, for such in vivo applications, the potential cytotoxicity of the nanoparticles might become an issue and should be investigated with care. So far very little is known about the implications for organisms or environmental systems in contact with nanosized materials.
Finally, gold nanoparticles can also be used as sensors. Their optical properties can change upon binding to certain molecules, allowing the detection and quantification of analytes. The absorption spectra of gold nanoparticles change drastically when several particles come close to each other. In the business of colloids aggregation is actually rather annoying but it can be exploited for very sensitive DNA detection, even of a single-base mismatch.

New research into the unique properties of gold nanoparticles should lead to well-established, routinely-used assays for a variety of biological applications.

Another strategy for sensing makes use of fluorescence quenching. Fluorescent molecules that are excited and in close proximity to a gold particle can transfer their energy to the metal, resulting in a non-radiative relaxation of the fluorophore. In several different detection schemes the analyte displaces the fluorescent molecules from the particle surface or changes their conformation, so that the optical emission of those reporter molecules is changed in the presence of the analyte.

Whilst many of the unique optical properties of gold nanoparticles have been exploited in recent applications, there is still plenty of room for new research. This should eventually lead to well-established, routinely-used assays for a variety of biological applications in the near future.

Secondly, gold nanoparticles can serve as carriers for drug and gene delivery. Biologically active molecules adsorbed on the particle surfaces can be guided inside cells and released. DNA delivery, for instance, is the basis for gene therapy.

Introduction of Nanoparticles in practice

Three noble metals, also called precious metals, are currently used in medicine and skincare compositions. These are





Silver         Gold           Platinum

None of these metals are considered essential, and there are no daily requirements. Nanocolloids are the metallic form of these metals finely divided with particle sizes below 10 nanometers (nm). This small size of the metallic form acquires new physical, chemical, and physiological properties when finely divided with particle sizes in the low nanometer range


Increased anti-oxidant properties


    
Nano-Silver            Nano-Gold        Nano-Platinum


   
Increased  anti-bacterial  effect

Nano Silver 

The Antibacterial Properties Of Nano-Silver Colloid

One of the most powerful natural antibiotic substances colloidal silver is useful in the treatment of all sorts of bacteria, fungi and viruses.
It can be used in different type of medical and cosmetic preparations: deodorizing talc powder, antibacterial cream, antyfungy body care compositions, colloid silver soap ect. 
There are no age restrictions in the recommendation of colloidal cosmetic preparations, they can be used for the body hygiene of new born babies as well as for the daily skin care of adults. The medical applications of the product are the ones that support its cosmetic functions too.
The colloidal silver compositions help the people who suffer from acne and eliminates skin rashes, dermatitis and fungi in the case of more severe skin affections.
In the treatment of acne, colloidal compositions is definitely a great way of reducing redness, swelling and the occurrence of infected pimples. The therapeutic action relies on the inhibition colloidal triggers when in contact with bacteria; this mineral supplement disables the breathing functions of the bacteria that suffocates because of lack of oxygen.

Nano Platinum       
                                                                    
Physical Property: Nano Platinum particles surface area with free radical of nano platinum increased about 16 million times than 1mm2 particle

Main effect of Platinum:


Anti-oxidant mechanism of nano platinum:

Application of Nano Platinum

In cosmetic:  Nano platinum has approved as anti-oxidant ingredient by Japanese Health Administration.  Many cosmetic companies are using nano platinum for their products from 2007.

In drinks: Approved as food additive by Japanese

Medical: Heart blood vessel trouble treatment and therapies 

Nano Gold                                                                            
 

In beauty care compositions

Gold nanoparticles are used in a wide range of cosmetic and beauty care applications. Colloid gold is presently included in a large number of anti-aging formulas produced by various manufacturers all over the world. The list of other ingredients used in the composition is incredibly large too, but it remains the most important one when it comes to long-term treatment results.

Colloidal gold cosmetic treatments can be used in association with very efficient collagen-based anti-wrinkle creams that regenerate the age-damaged tissue. Collagen is a protein that is naturally produced by the body but its level drops with age and the system stops producing it. A synergistic action of both colloidal gold and other natural cosmetic treatments should preserve skin condition for a longer period of time
There are two main explanations for the use of colloidal gold as a skin care product: one is the fact that in the colloidal form, gold has some amazing anti-oxidant properties and the other relates to the capacity of this mineral to get electrically connected to the metal ions present in the cellular structure.
Colloidal gold has a certain positive electrical charge that results from the specificity of the manufacturing process. The gold nano-particles in suspension have definitely a different impact at the cellular level than larger particles would; this allows colloidal gold to connect to the cellular structure at the most profound level.
In case there are any broken connections between the cells, colloidal gold helps to their restoration, not to mention the fact that it gives a push to the regular regeneration rhythm. This means that even when tissue deterioration has reached a considerable level, when the expression wrinkles are formed and it seems like there is no turning back, the body suddenly starts to create new cells to replace the old decayed ones.

What is the main properties of Nano Gold in beauty care compositions :


Korean nanotechnology company has recently been assigned with an International Nomenclature Cosmetic Ingredient (INCI) designation for its nano gold material. The assignment was made by the industry body The Cosmetic, Toiletry and Fragrance Association (CTFA).