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Showing posts from January, 2012

Nanotubes to monitor enzyme activity

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Researchers at the University of California have developed a technique to study in detail and monitor the behaviour of the biological molecules particularly protein which is useful for a host of applications in medicine. For investigating biomolecules implicated in various diseases, for developing novel drugs in the future, researchers are studying to understand complex biological molecules as to how they react with their environment.
Proteins activity
The enzyme is a very small molecule of size between 5 and 7 nm and is impossible to 'see' in any kind of optical microscope. Proteins fold along their long chains of amino acids and enzymes, in particular, change shape when they bind to substrates because these shape changes are crucial for how the molecule functions. The behaviour of proteins can be monitored to a certain extent, but there is no real way to track an individual protein over a long period of time.
New technique
The researchers have shown that they are able to observ…

Glass nano metal matrix

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Nanoparticles of metals and semiconductors in glass matrix are commonly formed by homogeneous nucleation in solid state. 'First the desired metal or semiconductor precursors are introduced and homogeneously distributed in the liquid glass melt at high temperatures during glass making, before quenching to room temperature. Then the glass is annealed by heating to a temperature to about the glass transition point and then held for a pre-designed period of time. During annealing, metal or semiconductor precursors are converted to metals and semiconductors. As a result, supersaturated metals or semiconductors form nanoparticles through nucleation and subsequent growth via solid-state diffusion.
Homogeneous glasses are made by dissolving metals, in the form of ions, in the glass melts and then rapidly cooled to room temperature. In such glasses metals remain as ions. Upon reheating to an intermediate temperature, metallic ions are reduced to metallic atoms by certain reduction agents su…

Synthesis of metallic nanoparticles

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Metallic nanoparticles
The term metal nanoparticle is used to describe nano sized metals with dimensions (length, width or thickness) within the size range 1‐100 nm. Metallic nanoparticles display properties that are quite different from those of individual atoms, surfaces or bulk materials. The main characteristics of MNPs are large surface‐area‐to‐volume ratio as compared to the bulk equivalents, large surface energies, existence as a transition between molecular and metallic states providing specific electronic structure (local density of states LDOS), have plasmon excitation, quantum confinement, short range ordering, increased number of kinks, contain a large number of low‐coordination sites such as corners and edges, having a large number of ˝dangling bonds˝ and consequently specific and chemical properties and the ability to store excess electrons.
Their potential applications include, for example, use in biochemistry, in catalysis and as chemical and biological sensors, as syste…

Nanocross

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Metallic nanostructures
Metallic nanostructures excite electrons close to their surface upon incidence of light at a particular frequency. The collective movement of electrons, or resonance, in the metal converts the light energy into heat. The wavelength at which the resonance occurs is strongly dependent on the size and shape of the nanostructures.
Metallic nanocross
Nanocross is a unique cross-shaped nano structure having arms located at an angle. In metallic nanocross spectral tunability can be achieved by changing the cross arm length and the angle between the arms. The degree of rotational symmetry of the nanocross can be varied by adding extra arms, changing the arm angle and shifting the arm intersection point. The symmetry of the particles has a crucial influence on the plasmon coupling to incident radiation. Pronounced dipole, quadrupole, octupole and Fano resonances can be observed in individual cross structures. Furthermore, the nanocross geometry proves to be a useful buildi…

Synthesis of oxide nanoparticles

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The application of nanoparticles in the processes of making commercial products has increased in recent years due to their unique physical and chemical properties. Few such commercially available nanoparticles are TiO2, ZnO and SiO2.
Fabrication of oxide nanoparticles
The most widespread route to fabrication of metal oxide nanoparticles involves the “bottom-up” approach involving the precipitation from aqueous solution from metal salts. Organo metallic species can also be used, but due to their cost and the difficulty in manipulating these compounds, they are used less frequently. An alternative “top-down” approach has been demonstrated for aluminum and iron oxide nanoparticles; however, it is possible that this methodology could be extended to other oxides.
Compared to the synthesis of metallic and non-oxide nanoparticles, the approaches used in the fabrication of oxide nanoparticles are less elaborate and there are less defined general strategies for the achievement of mono sized dist…

Synthesis of nanomaterials

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Synthesis approaches
There are two approaches to the synthesis of nanomaterials and the fabrication of nanostructures: top-down and bottom-up. Attrition or milling is a typical top-down method in making nanoparticles, whereas the colloidal dispersion is a good example of bottom-up approach in the synthesis of nanoparticles. Lithography may be considered as a hybrid approach, since the growth of thin films is bottom-up whereas etching is top-down, while nanolithography and nano manipulation are commonly a bottom-up approach.
Both approaches play very important role in nanotechnology. There are advantages and disadvantages in both approaches. Among others, the biggest problem with top-down approach is the imperfection of the surface structure. It is well known that the conventional top-down techniques such as lithography can cause significant crystallographic damage to the processed and additional defects may be introduced even during the etching steps. For example, nanowires made by lith…

Nano oxides

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Nano-oxides are essential materials in nanotechnology as their demand has greatly expanded. The materials are used in a variety of applications including colloid science, environmental remediation, catalysis and photo-catalysis, electronics, medicinal applications, separations, thin films, inks and disinfection. The efficient production of nanoparticles is likely to play a key role in the future of the chemical industry.
ZnO
ZnO, a wide-band gap semiconductor (3.37eV) at room temperature with a large exciton binding energy (60 meV), is a multifunctional material for a variety of practical applications due to its excellent physical and chemical properties. One-dimensional nanostructures of ZnO have attracted great interest because of their unique and fascinating optical, electrical, mechanical and piezoelectric properties together with their wide use in fundamental scientific research and potential technical applications, such as nano-ultraviolet lasers, piezoelectric devices, field emis…

Nanoparticle solution to repair surface

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Researchers at the universities of Massachusetts and Pittsburgh in the US have developed a new technique to repair surfaces using oil-based microcapsules filled with a nanoparticle solution.
Nano capsules
Using a polymer surfactant that stabilizes oil droplets in water, the researchers encapsulated cadmium selenide nanoparticles in nano size thin wall capsules in such a way that the particles could be released when desired. The capsules roll or glide over damaged substrates and selectively deposit their nanoparticle contents into the damaged or cracked regions due to hydrophobic–hydrophobic interactions between a nanoparticle and the cracked surface. The nanoparticles can easily be tracked too because cadmium selenide is fluorescent.
Working
If nanoparticles were held in a certain type of microcapsule, they could probe a surface and release the nanoparticles into certain specific regions of damaged surfaces, where the defective regions possess characteristics that are very different to t…

Nano-ear

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Physicists in Germany have developed a "nano-ear" of detecting sound on microscopic length scales. The technique was discovered in the 1980s and is used routinely in research labs around the world. It is particularly useful for manipulating biological objects, since the optical field used to make the trap is non-destructive.
Working
The researchers suspended gold nanoparticles in a drop of water. They trapped one sphere in a laser beam and then fired rapid pulses of light from a second laser at others a few micrometres away. The pulses heated the nanoparticles, which disturbed the water around them, generating pressure, or sound, waves. The device can optically trap gold nanoparticle and could be used to "listen" to biological micro-organisms as well as investigate the motion and vibrations in tiny machines. When laser light is focused at a point in space gold nanoparticles can be trapped in optical tweezers and an electric dipole moment is induced in the particle a…

Gold NPs and its alloys

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Nanoparticles Metal nanoparticles and alloy nanoparticles have remarkable optical, electronic and catalytic properties and have many different applications in biomedical and material sciences. In biomedicine, gold nanoparticles (AuNPs) are used in several purposes such as leukemia therapy, biomolecular immobilization, biosensor design and used as AuNPs as anti-angiogenesis, anti-malaria and anti-arthritic agents. Silver nanoparticles (AgNPs) are applied as selective coating agent for solar energy absorption, intercalation material for electric batteries, catalysts in chemical reactions and antimicrobial agents.Physical methodsPreparation of nanometals using physical methods such as attrition and pyrolysis supply nanostructures with narrow and controlled size ranges, however, these methods require very expensive equipments and the final yield is low.BiosynthesisMicroorganisms, both unicellular and multicellular, are known to produce inorganic materials often of nanoscale dimensions eit…

Graphene amplifier

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Voltage amplifier
A voltage amplifier device capable of amplifying small alternating voltage signals. The voltage amplifier is the main building block in analogue electronics. Amplification or voltage gain must be larger than 1 if the device is to be called an amplifier.
Graphene
Graphene is an allotrope of carbon, whose structure is one-atom-thick planar sheets and is most easily visualized as an atomic-scale chicken wire made of carbon atoms and their bonds. The crystalline or "flake" form of graphite consists of many graphene sheets stacked together. Graphene differs from most conventional three-dimensional materials. Intrinsic graphene is a semi-metal or zero-gap semiconductor and has remarkably high electron mobility at room temperature.
Graphene exhibits a minimum conductivity which is still unclear. However, rippling of the graphene sheet or ionized impurities in the SiO2 substrate may lead to local puddles of carriers that allow conduction. Graphene has the ideal prope…