Manipulating Molecules for Controlling the Conductance

Nongjian Tao, a researcher at the Biodesign Institute at Arizona State University, has demonstrated a smart way of controlling electrical conductance of a single molecule, by exploiting the molecule's mechanical properties. This type of control could lead to a design of ultra-tiny electrical gadgets. It also renders a platform to perform myriad useful tasks from biological and chemical sensing to improving telecommunications and computer memory. The main challenge with this kind of device is that unconventional effects of the quantum world dominate the device behavior.

 In the current research, Tao examines the electromechanical properties of single molecules sandwiched between conducting electrodes. When a voltage is applied, a resulting flow of current can be measured. A particular type of molecule, known as pentaphenylene, was used and its electrical conductance examined.

Scientist was able to vary the conductance simply by changing the orientation of the molecule with respect to the electrode surfaces. Specifically, the molecule's tilt angle was altered, with conductance rising as the distance separating the electrodes decreased, and reaching a maximum when the molecule was poised between the electrodes at 90 degrees.

The reason for the dramatic fluctuation in conductance is due to the pi orbitals of the electrons making up the molecules, and their interaction with electron orbitals in the attached electrodes. Tao opined that pi orbitals may be thought of as electron clouds, projecting perpendicularly from either side of the plane of the molecule. When the tilt angle of a molecule trapped between two electrodes is altered, these pi orbitals can come in contact and blend with electron orbitals contained in the gold electrode. This process is known as lateral coupling. This lateral coupling of orbitals has the effect of increasing conductance.

In the case of the pentaphenylene molecule, the lateral coupling effect was pronounced, with conductance levels increasing up to 10 times as the lateral coupling of orbitals came into greater play. In contrast, the tetraphenyl molecule used as a control for the experiments did not exhibit lateral coupling and conductance values remained constant, regardless of the tilt angle applied to the molecule. Molecules can now be designed to either exploit or minimize lateral coupling effects of orbitals, thereby permitting the fine-tuning of conductance properties, based on an application's specific requirements.

A further self-check on the conductance results was carried out by scientists using a modulation method. Here, the molecule's position was jiggled in 3 spatial directions and the conductance values observed. Only when these rapid perturbations specifically changed the tilt angle of the molecule relative to the electrode were conductance values altered, indicating that lateral coupling of electron orbitals was indeed responsible for the effect. Tao also suggests that this modulation technique may be broadly applied as a new method for evaluating conductance changes in molecular-scale systems.

Nanosilver

Nanosilver is not a new discovery by nanotechnologists - it has been used in various products for over a hundred years,. The antimicrobial effects of minute silver particles, which were then known as "colloidal silver", were known from the earliest days of its use.

As early as the 19th century, minute silver particles were used, for example in antibacterial water filters.

Numerous nanomaterials are currently at the focus of public attention. In particular silver nanoparticles are being investigated in detail, both by scientists as well as by the regulatory authorities. The assumption behind this interest is that they are dealing with a completely new substance. However, nanosilver is by no means the discovery of the 21st century. Silver particles with diameters of seven to nine nm were mentioned as early as 1889. They were used in medications or as biocides to prevent the growth of bacteria on surfaces, for example in antibacterial water filters or in algaecides for swimming pools.

The nanoparticles were known as colloidal silver in those days, but now - extremely small particles of silver. The only new aspect is the use today of the prefix nano. "However," according to Bernd Nowack, "nano does not mean something new, and nor does it mean something that is harmful." When colloidal silver" became available on the market in large quantities in the 1920s it was the topic of numerous studies and subject to appropriate regulation by the authorities. Even in those days the significance of the discovery of nanoparticles and how they worked was realized. But that does not mean that the possible side-effects of nanoparticles on humans and the environment should be played down or ignored. It is important to characterize in exact detail the material properties of nanosilver and not just to use without verifying.

The term nanoparticle is understood to refer to particles whose dimensions are less than 100 nm. Because of their minute size nanoparticles have different properties than those of larger particles of the same material. For example, for a given volume nanoparticles have a much greater surface area, so they are frequently much more reactive than the bulk material. In addition, even in small quantities nanosilver produces more silver ions than solid silver. These silver ions are toxic to bacteria. Whether or not nanosilver represents a risk to humans and the environment is currently the subject of a great deal of investigation.

Tiny Magnetic Switch Discovered by Controlling Single Molecule at Room Temperature

A Kiel research group headed by the chemist, Professor Rainer Herges, has succeeded for the first time in directly controlling the magnetic state of a single molecule at room temperature. The switchable molecule could be used both in the construction of tiny electromagnetic storage units and in the medical imaging.

The researchers developed a molecular machine constructed in a similar way to a record player. The molecule consists of a nickel ion surrounded by a pigment ring and a nitrogen atom which hovers above the ring like the tone arm on a record player. When this molecule is irradiated with blue-green light, the nitrogen atom is placed exactly vertically to the nickel ion like a needle. This causes the nickel ion to become magnetic, because the pairing of two electrons is cancelled out. The counter effect is blue-violet light. The nitrogen atom is raised, the electrons form a pair and the nickel ion is no longer magnetic. One can repeat this switching of the magnetic state over 10,000 times by varied irradiation with the two different wavelengths of light, without wearing out the molecular machine or encountering side reactions.

The switch which has been discovered, with its diameter of only 1.2 nanometres, could be used as a tiny magnetic reservoir in molecular electronics. Most of all, hard disk manufacturers may be interested in this, as a higher storage capacity can be achieved by reducing the size of the magnetic particles on the surface of the disks. Professor Herges also believes the use of the magnetic switch in the medical field is feasible. The record player molecule can be used intravenously as a contrast agent in MRT (magnetic resonance tomography) in order to search for tumors or constricted blood vessels. Initial tests in the University Medical Center Schleswig-Holstein's neuroradiology department were successful.

As the signal-to-noise ratio is improved by the switching process, a smaller amount of the contrast agent is required than for the magnetic salts currently being used. In addition, the molecular machine could also serve as a basis for developing new contrast agents to depict such features as temperature, pH value or even certain biochemical markers in the body in a three-dimensional form. Using contrast agents such as these, it could be possible to localize centers of inflammation, detect tumors and visualize many metabolic processes.

Some Cool Ideas of Nanotechnology

http://www.coolbusinessideas.com/archives/category/nanotechnology/

Touchscreens: Made of Carbon Nanotubes

Touchscreens are not a new thing in this rapidly paced technological world. But what it lacks is its viability as far as the price is concerned. In the upcoming Nano Tech Fair 2011 which is scheduled to take place February 16-18, researchers at Fraunhofer are presenting touchscreens that contain carbon nanotubes.

The versatile nature of touchscreen make it a celebrity in the modern technology. Just touching it slightly with the tips of the fingers is enough. One can effortlessly write, navigate, open menu windows or rotate images on touchscreens. Within fractions of a second one touch is translated into control commands that a computer understands. At first glance, this technology borders on the miraculous, but in real life this mystery just is a wafer-thin electrode under the glass surface of the display made of indium-tin-oxide (ITO). This material is nothing short of ideal for use in touchscreens because it is excellent at conducting slight currents and lets the colours of the display pass through unhampered. But, the problem is: indium is not abundant in nature.

Therefore, private industry is very interested in alternatives to ITO that are similarly efficient. The researchers at Fraunhofer have succeeded at coming up with a new material for electrodes that is on the same level as ITO and on top of it is much cheaper. Its main components are carbon nanotubes and low-cost polymers. This new electrode foil is composed of two layers. One is the carrier, a thin foil made of inexpensive polyethylenterephthalate (PET) used for making plastic bottles. Then a mixture of carbon-nanotubes and electrically conducting polymers is added that is applied to the PET as a solution and forms a thin film when it dries.

In comparison to ITO, these combinations of plastics have not been particularly durable because humidity, pressure or UV light put a strain on the polymers. The layers became brittle and broke down. Only carbon nanotubes have made them stable. The carbon nanotubes harden on the PET to create a network where the electrically conducting polymers can be firmly anchored. That means that this layer is durable in the long run. Ivica Kolaric, project manager from Fraunhofer Institute for Manufacturing Engineering and Automation, admits that the electrical resistance of our layer is somewhat greater than that of the ITO, but it's easily enough for an application in electrical systems. Its merits are more than convincing: carbon is not only low-cost and available all over the world. It is also a renewable resource that can be yielded from organic matter such as wood.

There are a whole series of implementations for the new technology. This foil is flexible and can be used in a variety of ways. Even with this photovoltaic foils can be made to corrugated roofs or other uneven structures. The researcher has already set up pilot production where the foil can be enhanced for a wide range of applications.

A New Transistor made of Molybdenite: Thinner than Silicon and better than Graphene

In a recent advancement, scientist claimed that molybdenite could be extremely useful in fabricating smaller and more energy efficient electronic chips because of its distinct advantages over traditional silicon or graphene for use in electronics applications.

A discovery made at EPFL's Laboratory of Nanoscale Electronics and Structures (LANES) could play an important role in electronics. It was divulged that researchers can now make transistors that are smaller and more energy efficient. Research carried out in the Laboratory has revealed that molybdenite, or MoS₂, is a very effective semiconductor. This mineral, which is abundant in nature, is often used as an element in steel alloys or as an additive in lubricants. But it had not yet been extensively studied for use in electronics.

Molybdenite is a two-dimensional material, very thin and easy to use in nanotechnology. It has real potential in the fabrication of very small transistors, light-emitting diodes (LEDs) and solar cells.  

When comparing its advantages with silicon, currently the primary component used in electronic and computer chips, , it was seen that it is  less voluminous that silicon, which is a three-dimensional material.

One of molybdenite's advantages is that it is in a 0.65-nanometer-thick sheet of MoS₂, the electrons can move around as easily as in a 2-nanometer-thick sheet of silicon, explains Kis, one of the scientists in LANES. He also commented that it's not currently possible to fabricate a sheet of silicon as thin as a monolayer sheet of MoS₂. Another advantage of molybdenite is that it can be used to make transistors that consume 100,000 times less energy in standby state than traditional silicon transistors. A semi-conductor with a band-gap must be used to turn a transistor on and off, and molybdenite's 1.8 electron-volt gap is ideal for this purpose.

And again if we take the graphene, whose discovery in 2004 earned University of Manchester physicists André Geim and Konstantin Novoselov the 2010 Nobel Prize in Physics, it showed that existence of the band gap in molybdenite also gives it an advantage over graphene. That is why molybdenite considered today by many scientists as the electronics material of the future, as graphene doesn't have a gap, and it is very difficult to artificially reproduce one in the material

Nanocomposites to monitor wind turbine blade structure

Gary D. Seidel, assistant professor of aerospace engineering in the College of Engineering atVirginia Tech developed a carbon nanotube-enhanced composite for structural health monitoring sensors to improve the resiliency of huge wind turbine blades.

Wind turbine blades enjoy a steady wind but can be damaged by gust-induced vibrations. Seidel proposes to create tiny sensor patches that can be selectively placed in key locations where it is anticipated that damage will start. The patches are made of the same base material as the blade but sprinkled with carbon nanotubes, resulting in a nanocomposite sensor which adds negligible weight to the structure.

The submicroscopic carbon nanotubes can be highly conductive, like invisible, extremely lightweight, electrical wires. Placing the highly conducting carbon nanotubes inside a polymer material makes the resulting nanocomposite patch's conductivity sensitive to deformation. As the material is deformed by a stress on the blade, the nanotubes shift, move closer together, and their conductivity jumps – one mechanism behind the phenomenon known as a piezoresistive response. The change in the nanocomposite conductivity sends a signal to the wind turbine control center, allowing the operator to then know which blade is stressed and should be turned off to prevent further damage to that turbine.

Seidel's focus is on assessing the sensing capabilities of the nanocomposite and building multiscale models for use in structural health monitoring software algorithms. His preliminary models have demonstrated that he can create nanocomposites that respond to stresses with conductivity changes.

Based on the mechanism behind the piezoresistive response of our nanocomposites, necessary tools will be created for nanocomposite sensor development and tailoring for the wind turbine blade application.

DNA Could Lead to Enhanced Electronics

Nanoscience has the potential to play an enormous role in enhancing a range of products, including sensors, photovoltaics and consumer electronics. Scientists in this field have created a multitude of nano scale materials, such as metal nanocrystals, carbon nanotubes and semiconducting nanowires. However, despite their appeal, it has remained an astounding challenge to engineer the orientation and placement of these materials into the desired device architectures that are reproducible in high yields and at low costs.

Jen Cha, a UC San Diego nanoengineering professor, and her team of researchers, have discovered that one way to bridge this gap is to use biomolecules, such as DNA and proteins.

Self-assembled structures are often too small and affordable lithographic patterns are too large. But rationally designed synthetic DNA nanostructures can access length scales between 5 and 100 nanometers and bridge the two systems.

People have created a huge variety of unique and functional nanostructures, but for some intended applications they are worthless unless billions or trillions of individual structures can be placed at the same time, at precise locations. This research can lead researchers to a step closer to solving this very difficult problem.

This work is the first example of how top down lithography can be merged with bottom up self assembly approach to build arrays. That signifies that substrate is patterned by conventional lithography merge it with something that can direct the assembly of even smaller objects, such as those having dimensions between 2 and 20 nanometers. There is a need an intermediate template. For that DNA origami is there which has the ability to bind to something else much smaller and direct their assembly into the desired configuration; there by transistors can be built from carbon nanotubes.

For the last 6years, Cha's research has focused on using biology to engineer the assembly of nanoscale materials for applications in medicine, electronics and energy. One of the limitations of nanoscience is it doesn't allow mass production of products, but Cha's work is focused on trying out how to do that and do it cheaply. Much of her recent work has focused on using DNA to build 2D structures.

Nanobiotechnology Product Market Size

The total market for nanobiotechnology products is $19.3 billion in 2010 and is growing at a compound annual growth rate (CAGR) of 9% to reach a forecast market size of $29.7 billion by 2015.

Medical applications, including drug delivery and microbicides, dominate today’s market, with sales of $19.1 billion in 2010. This market segment is growing at a compound annual growth rate (CAGR) of 8.7%, and is forecast to reach sales of $29 billion by 2015.

In the R&D tools market, DNA sequencing is an emerging growth opportunity for nanotechnologies. This sector is valued at $63 million in 2010 and is expected to increase at a 37% compound annual growth rate (CAGR) to reach $305 million in 2015.

Mass production of non-reflective polymer surfaces (nanofabrication) yields more efficiency in solar energy

A key hurdle in realizing high-efficiency, cost-effective solar energy technology is the low efficiency of current power cells. In order to achieve maximum efficiency when converting solar power into electricity, ideally there is a need for solar panel that can absorb nearly every single photon of light across the entire spectrum of sunlight and irrespective of the sun's position in the sky.

One way to achieve suppression of sunlight's reflection over a broad spectral range is by using nanotextured surfaces that form a graded transition of the refractive index from air to the substrate. Researchers in Finland have now demonstrated a scalable, high-throughput fabrication method for such non-reflecting nanostructured surfaces.

The main advances of this work are in the field of nanofabrication. It was published in a recent paper in Advanced Materials ("Non-Reflecting Silicon and Polymer Surfaces by Plasma Etching and Replication").

The process involves a maskless deep reactive ion etching process that produces nanospikes on a silicon wafer. The process is known as black silicon process. The geometry of the nanospikes i.e. height, width and also the density can be controlled by changing the etching parameters. The main strength of the maskless method is its high throughput.

Different applications require different types of surfaces, and in this study the Finnish team shows that the densest arrays of nanospikes with slightly positively tapered sidewalls had the lowest optical reflectance, while pyramid-shaped nanospikes were ideal for use as templates for polymer replication. Polymer replication techniques are typically high-throughput and low-cost methods which make them very attractive.

In this research it has been shown that both hot-embossing and UV-embossing of polymer is possible with the PDMS stamp. The use of polymers instead of silicon would be useful in high-volume applications due to lower costs. Nanospike-structured polymeric and silicon surfaces are non-reflective and additionally they can be made ultrahydrophobic and self-cleaning, by coating them with a low-surface energy coating. These kinds of inexpensive, non-reflective and self-cleaning surfaces have many applications, for instance in sensors and solar cells.

Another important issue is the mechanical durability of the nanostructured surfaces. At the moment the nanostructured surfaces damage quite easily but the team is studying ways to make the surfaces more robust.

To do this, first, an elastomeric stamp is produced by casting a PDMS layer on top of the nanospike-structured silicon surface (the original nanospikes were fabricated on full silicon wafers using the black silicon process). The PDMS is thermally cured and peeled off. Then, the PDMS stamp can be used to replicate the original nanospike pattern into other polymers, such as PMMA.

Building 3D Batteries with Coated Nanowires

The researchers at Rice University recently managed to find a way to coat nanowires with PMMA (Poly(methyl methacrylate)) coating that provides good insulation from the counter electrode while still allowing ions to pass easily through.This minimized separation between two electrodes manages to make the battery much more efficient.

In a battery, there are two electrodes separated by a thick barrier. The main objective is to bring everything into close proximity so this electrochemistry becomes much more efficient.

To achieve this, researchers took the concept of 3D batteries and coated millions of nanowires to create the 3D structure from the bottom up. By increasing the height of the nanowires, the amount of energy stored is increased while keeping the lithium ion diffusion distance constant.

The whole process involves the growing of 10-micron-long nanowires through electrodisposition in the pores of an anoidized alumina template. Then PMMA is coated onto the nanowire array, resulting in an even casing from top to bottom. The result of this work is ultimately expected to be batteries for scalable microdevices that possess a greater surface area than thin-film batteries.

10 best inventions in 2010

http://hotnewshome.com/offbeat/10-best-inventions-of-2010.html

Water Pollution and Nanotechnology

Nanotechnology is being used to develop solutions to three very different problems in water quality.

One challenge is the removal of industrial water pollution, such as a cleaning solvent called TCE, from ground water. Nanoparticles can be used to convert the contaminating chemical through a chemical reaction to make it harmless. Studies have shown that this method can be used successfully to reach contaminates dispersed in underground ponds and at much lower cost than methods which require pumping the water out of the ground for treatment.

Another challenge is the removal of salt or metals from water. A deionization method using electrodes composed of nano-sized fibers shows promise for reducing the cost and energy requirements of turning salt water into drinking water.

The third problem concerns the fact that standard filters do not work on virus cells. A filter only a few nanometers in diameter is currently being developed that should be capable of removing virus cells from water.

 

See the following for more about the potential of nanotechnology in removing contaminates from water.

 

Nanotechnology Applications in Water Pollution

 

1. Combining a nanomembrane with solar power to reduce the cost of desalinating seawater

2. Using iron nanoparticles to clean up carbon tetrachloride pollution in ground water

3. Using silver chloride nanowires as a photocatalysis to decompose organic molecules in polluted water.

4. Using an electrified filter composed of silver nanowires, carbon nanotubes and cotton to kill bacteria in water.

5. Nanoparticles that can absorb radioactive particles polluting ground-water

6. Coating iron nanoparticles allow them to neutralize dense, hydrophobic solvents polluting ground-water

7. Using nanowire mats to absorb oil spills

8. Using iron oxide nanoparticles to clean arsenic from water wells.

9. Using gold tipped carbon nanotubes to trap oil drops polluting water.

10. Using antimicrobial nanofibers and activated carbon in a disposable filter as an inexpensive way to clean contaminated water.

11. Researchers at Pacific Northwestern Laboratory have developed a material to remove mercury from groundwater. The material is called SAMMS, which is short for Self-Assembled Monolayers on Mesoporous Supports. This translates taking a ceramic particle whose surface has many nano-size pores and lining the nanopores with molecules that have sulfur atoms on one end, leaving a hole in the center that is lined with sulfur atoms as shown in figure-SAMMS. They line the nanopores with molecules containing sulfur because it bonds to mercury, so mercury atoms bond to the sulfur and are trapped in the nanopores.