Gold based Nanocages and Nanoboxes: Effective Catalysts for Redox Reaction

Scientists from Korea in collaboration with scientist at washington University, Missouri recently evaluated the catalytic properties of Au-based nanostructures (including nanocages, nanoboxes, and solid nanoparticles) using a model reaction based on the reduction of p-nitrophenol by NaBH₄

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It is well-known that the catalytic activity of a nanoparticle is strongly dependent on its size. Typically, a smaller nanoparticle tends to show a higher catalytic activity as it has a much greater surface-to-volume ratio.However, smaller nanoparticles may not be better candidates for catalyzing all types of reactions. A good example for explaining this exception can be found in a redox reaction. As the catalytic particles become increasingly smaller, the oxidation and reduction half reactions might need to occur on different particles due to the reduction in surface area. In this case, a good “electrical” connection between the particles will play an important role as the electrons have to be transported from the site of oxidation to the site of reduction. The redox reaction will be unable to proceed if the catalytic particles are separated from each other by an insulating medium.It has been argued that this kind of problem can be solved by switching from solid nanoparticles to nanocages or nanoboxes with hollow interiors and ultrathin walls. For a Au-based nanocage of 50 nm in edge length and 5 nm in wall thickness, it should be able to provide a sufficiently large surface area (at least, equivalent to a 50 nm solid particle) to accommodate both the oxidation and reduction half reactions while the ultrathin wall is still able to provide a high activity equivalent to a 5 nm solid particle due to a good electrical connection across the entire surface of the wall. For a model reaction based on the reduction of p-nitrophenol by sodium borohydride (NaBH₄), The experimental data reported indicate that both wall thickness and porosity of the Au-based hollow nanostructures play an important role in enhancing the catalytic activity. The kinetic data in their report (published in Nano letters) indicate that the Au-based nanocages are catalytically more active than both the nanoboxes and nanoparticles probably due to their extremely thin but electrically continuous walls, the high content of Au, and the accessibility of both inner and outer surfaces through the pores in the walls.

In summary, the good intrinsic electrical connection across the entire surface of a Au nanocage makes it a much better catalyst than small Au solid nanoparticles for a redox reaction. In addition, a typical compensation effect was observed in this catalytic system, which can be explained by the assumption of kinetic regime switching. Given the high abundance of Au element relative to other noble metals like Pt and Pd as well as the easiness in controlling the porosity and morphology, the Au-based nanocages might be able to find widespread use as catalysts in a number of industrial applications.

India's ambitious 'Solar Mission'

India's prime minister Manmohan Singh has approved a US$19 billion plan to make the country a global leader in solar energy over the next three decades. The ambitious project would see a massive expansion in installed solar capacity, and aims to reduce the price of electricity generated from solar energy to match that from fossil fuels by 2030.

The 'solar mission' was first mooted as part of India's national action plan on climate change, announced in June 2008. According to a draft mission document whose targets were approved on 3 August, installed solar capacity would be hiked from its current 5 MW to 20 GW by 2020, 100 GW by 2030 and 200 GW by 2050 — more than the current 150 GW power generation capacity of all India's coal, gas and nuclear plants.

Officials say the plan shows that the country is serious about its intention to stem global warming, ahead of the UN climate change conference in Copenhagen in December.

A detailed road map has been drawn up to 2020. By then, according to the mission document, solar lighting will be available for 20 million households and 42 million tonnes of CO₂ emissions will be saved annually by the switch to solar energy. The government plans to create a solar fund with initial investment of $1.1 billion and build it up by taxing fossil fuels and the power generated from them — 0.1 cents for every kWh produced. By 2030, it hopes to reduce the cost of electricity from photovoltaic cells to around 10 cents per kWh, matching the price of electricity derived from conventional fuels.

The plan will be pushed forward by a mixture of other policy and regulatory measures. Those include making it mandatory for existing thermal power plants to generate at least 5% of their capacity from solar power, and for government buildings to install photovoltaic panels on rooftops. Producers connected to the grid will be able to sell their excess solar electricity to utilities; solar-power projects get a 10-year tax holiday; and other 'carrots' for the industry include the duty-free import of raw materials and priority bank loans.

An autonomous solar-energy authority will be created to execute the mission, but the existing solar-energy centre near New Delhi will be upgraded into an 'apex research institute' to coordinate solar-research centres across the country and promote foreign collaboration. The mission document recommends introducing solar-energy courses to the Indian Institutes of Technology, and creating a fellowship programme to train 100 Indian scientists a year in world-class institution

Developing Complex Patterns on Surface

Researchers at Worcester Polytechnic Institute, Worcester, Massachusetts have recently published an interesting report in Langmuir. They have develop a method for developing complex nanopatterns on surfaces by combining self-assembly, photolabile protecting groups, and multilayered films. An o-nitrobenzyl protecting group has been incorporated into molecular level films utilizing thiol-gold interactions. When the o-nitrobenzyl group is cleaved by ultraviolet light, a carboxylic acid terminated layer remains on the surface and is available for activation and further functionalization through amide bond formation. Using this method, multilayered films have been constructed and characterized by contact angle goniometry, cyclic voltammetry, grazing incidence infrared spectroscopy, and X-ray photoelectron spectroscopy measurements. Complex surface patterns can be achieved by creating a surface array using a photomask and then further fictionalizing the irradiated area through covalent coupling. Fluorophores were attached to the deprotected regions, providing visual evidence of surface patterning using fluorescence microscopy. Their approach is universal to bind moieties containing free amine groups at defined regions across a surface, allowing for the development of films with complex chemical and physicochemical properties.

Figure. Fluorescence microscopy images of surfaces patterned with 100 μm squares (top) and 100 μm lines separated by 150 μm spaces (bottom), images on the left are of rhodamine 110 (green) and images on the right are cresyl violet 670 (red). Inset: reduced scale images of the photomasks used to pattern the surfaces.

Biomedical Imaging of Cells using Quantum Dots

A joint research team, working at the National Institute of Standards and Technology (NIST) and the National Institute of Allergy and Infectious Diseases (NIAID), has discovered a method of using nanoparticles to illuminate the cellular interior to reveal these slow processes. Nanoparticles, thousands of times smaller than a cell, have a variety of applications. One type of nanoparticle called a quantum dot glows when exposed to light. These semiconductor particles can be coated with organic materials, which are tailored to be attracted to specific proteins within the part of a cell a scientist wishes to examine.

These quantum dots last longer than most of the organic dyes and fluorescent proteins that we previously used to illuminate the interiors of cells. They also have the advantage of monitoring changes in cellular processes while most high-resolution techniques like electron microscopy only provide images of cellular processes frozen at one moment. Using quantum dots, cellular processes involving the dynamic motions of proteins can be elucidated.

In the recent study, the research team focused primarily on characterizing quantum dot properties, contrasting them with other imaging techniques. In one example, they employed quantum dots designed to target a specific type of human red blood cell protein that forms part of a network structure in the cell's inner membrane. When these proteins cluster together in a healthy cell, the network provides mechanical flexibility to the cell so it can squeeze through narrow capillaries and other tight spaces. But when the cell gets infected with the malaria parasite, the structure of the network protein changes.

Since the clustering mechanism is not well understood, it was examined with the dots. Researchers believed that if they could develop a technique to visualize the clustering, they could learn something about the progress of a malaria infection, which has several distinct developmental stage.

fig : Human red blood cells, in which membrane proteins are targeted and labeled with quantum dots, reveal the clustering behavior of the proteins. The number of purple features, which indicate the nuclei of malaria parasites, increases as malaria development progresses. The NIST logo at bottom was made by a photo lithography technique on a thin film of quantum dots, taking advantage of the property that clustered dots exhibit increased photoluminescence. (White bars: 1 micrometer; red: 10 micrometer)

The team's efforts revealed that as the membrane proteins bunch up, the quantum dots attached to them are induced to cluster themselves and glow more brightly, permitting scientists to watch as the clustering of proteins progresses. More broadly, the team found that when quantum dots attach themselves to other nanomaterials, the dots' optical properties change in unique ways in each case. They also found evidence that quantum dot optical properties are altered as the nanoscale environment changes, offering greater possibility of using quantum dots to sense the local biochemical environment inside cells. about the progress of a malaria infection, which has several distinct developmental stages.

Nanostructured Integrated Circuits detect Type and Severity of Cancer

The analysis of panels of nucleic acid biomarkers offers valuable diagnostic and prognostic information for cancer management. Scientists at University of Toronto published a recent article in ACSNano where they reported a chip onto which they integrated novel nanostructured microelectrodes and with which direct detection of cancer biomarkers in heterogeneous biological samples—both cell extracts and tumor tissues is possible. Coarse photolithographic microfabrication defines a multiplexed sensing array; bottom-up fabrication of nanostructured microelectrodes then provides sensing elements. They have analyzed a panel of mRNA samples for prostate cancer related gene fusions using the chip. Gene fusions were identified which can correlate with aggressive prostate cancer and distinguished these from fusions associated with slower-progressing forms of the disease.

The multiplexed nanostructured microelectrode integrated circuit reported provides direct, amplification-free, sample-to-answer in under 1 h using the 10 ng of mRNA readily available in biopsy samples. The detection platform described in this research is not only specific, sensitive, and robust, but it is also practical and scalable. The reproducible fabrication method chosen is amenable to the production of probe-modified chips using the same photolithographic technologies in widespread use in consumer electronics microchip fabrication, and only simple, inexpensive instrumentation is needed for readout. Microfluidics are not required for automated analysis, as hybridization can be performed and read out in a single reaction vessel. This system represents an attractive alternative to PCR-based methods that are sensitive but difficult to automate in a clinical setting.

In summary, the new multiplexed electrode platform suggested in the paper is the first to read directly a panel of cancer biomarkers in clinically relevant samples using electronic signals. The array enabling these measurements features microelectrodes that possess controllable and versatile nanotexturing essential for sensitivity. The system combines these nanotextured electrodes with rapid catalytic readout to achieve a long-standing goal: the multiplexed analysis of cancer biomarkers using an inexpensive and practical platform.

Direct Imaging in Real Space and Time with 4D Electron Microscopy

The current methods of detection of nano structures provide insight into the movements but direct real-space and time visualization of modes of oscillations at frequencies pitched in the ultrasonic range (i.e., kilohertz to gigahertz) has not so far been possible.Scientist at Caltech (Ahmed H. Zewail et al), for the first time have reported their observation using four-dimensional (4D) electron microscopy, of the nanomechanical motions of cantilevers.

From the observed oscillations of nanometer displacements as a function of time, for free-standing beams, They were able to measure the frequency of modes of motion and determine Young’s elastic modulus and the force and energy stored during the optomechanical expansions. The motion of the cantilever is triggered by molecular charge redistribution as the material, single-crystal organic semiconductor, switches from the equilibrium to the expanded structure. For these material structures, the expansion is colossal, typically reaching the micrometer scale, the modulus is 2 GPa, the force is 600 μN, and the energy is 200 pJ. These values translate to a large optomechanical efficiency (minimum of 1% and up to 10% or more) and a pressure of nearly 1,500 atm. This has been noted that the observables in the report are real material changes in time, in contrast to those based on changes of optical/contrast intensity or diffraction. The pseudo-one-dimensional molecular material (copper 7,7,8,8-tetracyanoquinodimethane, [Cu(TCNQ)]), which forms single crystals of nanometer and micrometer length scale, has been used as a prototype.Figure show the Atomic scale to macroscale structure of phase I Cu(TCNQ). Shown in the upper panel is the crystal structure as viewed along the a axis (i.e., π stacking axis) and c axis. The unit cell is essentially tetragonal, gray corresponds to carbon, blue corresponds to nitrogen, and yellow corresponds to copper. The lower panel displays a typical selected-area diffraction pattern from Cu(TCNQ) single crystals as viewed down the [011] zone axis along with a micrograph taken in our UEM. The rodlike crystal habit characteristic of phase I Cu(TCNQ) is clearly visible.

In summary, researchers have successfully suggested that with 4D electron microscopy it is possible to visualize in real space and time the functional nanomechanical motions of cantilevers. From tomographic tilt series of images, the crystalline beam stands on the substrate as defined by the polar and azimuthal angles. The resonance oscillations of two beams, micro- and nanocantilevers, were observed in situ giving Young’s elastic modulus, the force, and the potential energy stored. The systems studied are unique 1D molecular structures, which provide anisotropic and colossal expansions. The cantilever motions are fundamentally of two types, longitudinal and transverse, and have resonance Q factors that make them persist for up to a millisecond. The function is robust, at least for 10⁷ continuous pulse cycles (10¹¹ oscillations for the recorded frames), with no damage or plasticity. With these imaging methods in real time, and with other variants, it will be now possible to test the various theoretical models involved in MEMS and NEMS.

Ultraflat Graphene

Graphene, a single atomic layer of carbon connected by sp2 hybridized bonds, has attracted intense scientific interest since its recent discovery. Much of the research on graphene has been directed towards exploration of its novel electronic properties, but the structural aspects of this model two-dimensional system are also of great interest and importance.

Detailed electron-diffraction studies of free-standing graphene monolayers indicate the presence of an intrinsic rippling, with 1-nm-high corrugations normal to the surface appearing over a characteristic lateral scale of 10–25 nm. It has been argued that these corrugations are necessary to stabilize the suspended graphene sheets against thermal instabilities present in ideal two-dimensional systems.

Researchers from University of Columbia have recented published a report in Nature,where they report the fabrication and characterization of high-quality ultraflat graphene monolayers by making use of a mica support that provides atomically flat terraces over large areas. Using high-resolution, non-contact mode atomic force microscopy (AFM) to characterize the morphology, They have found that graphene on mica approaches the limit of atomic flatness. The availability of such a flat substance provides insight into questions of thermodynamic stability for this model two-dimensional system and also a reference material with which to determine the role of ripples in the panoply of observed and predicted phenomena.

Their measurements demonstrate unambiguously that intrinsic ripples in graphene, if they do exist, can be strongly suppressed by interfacial van der Waals interactions when this material is supported on an appropriate atomically flat substrate.

One-Dimensional Arrangement of Gold Nanoparticles with Tunable Interparticle Distance

Directed assemblies of nanoparticles are promising building blocks for emerging nanotechnology applications (sensors, nanoelectronics, optoelectronics, catalysis, etc.). Compared with randomly distributed particle layouts, the fabrication of nanoparticle arrays with well-defined position, orientation, and interparticle distance has received considerable attention.

Advances in lithography have enabled the precise and reproducible patterning of features from tens of nanometers over the macroscopic scale. A synergetic combination of colloidal nanostructures with lithographic patterning allows the precise control that is necessary to produce highly integrated nanostructure assemblies on all length scales.

Scientist at Munster, Germany demonstrated a facile approach to the fabrication of 1D single-particle arrays of sub-30-nm Au particles in larger-sized grooves (up to 220 nm in width) with tunable interparticle distances. The main difference compared with previous work is the application of templates with larger feature size than the particle size, thus allowing less technological demand in lithography. 2D single-particle patterning can be achieved by using the same principle. The width of the groove and the thickness of the electric double layer of the Au particles are dominating factors that determine the arrangement of the particles. This strategy provides a versatile means, with less lithographic expenditure for prepatterns, to realize the regular low-dimensional arrangement of Au nanoparticles with tunable interparticle distances, which should result in, for example, alteration of the plasmon resonance and thus be useful to develop concepts for (bio)sensing. This novel assembly method can be applied to other metal, semiconductor, or oxide nanoparticles that can form double charge layers.

This report is recently published in Scientific Journal Small, 2009

Newly Designed highly Fluorescent and Photostable Nanoparticles

Fluorescent nanoparticles (FNPs) have attracted considerable interest for their wide range of emerging applications in live cell imaging, biosensing, and optoelectronic devices. Among currently available FNPs, dye-doped polymer nanoparticles are limited by fluorophore aggregation and self-quenching as well as dye leaching.

A relatively unexplored alternative is the use of FNPs with covalently bound fluorophores. Covalent attachment limits chromophore mobility and disperses the monomers within FNPs which potentially reduces fluorophore aggregation and therefore fluorescence self-quenching, providing a distinct advantage over doping. In the communication in Chem Comm, Scientists at Washington State University, Pullman,WA have developed photostable and biocompatible polymeric nanoparticles with covalently bound perylene dye possessing over 50 times brighter fluorescence as compared to single-dye molecules such as rhodamine 6G.

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They have successfully prepared polymeric nanoparticles with high fluorescent brightness and excellent photostability by covalently embedding a twisted perylene dye into core–shell type polymeric nanoparticles. The high photostability, quantum yield, and unique steric structure of the perylene monomer, coupled with high monomer concentration and core-shell encapsulation enabled by covalent attachment, are believed to mainly contribute to the remarkable brightness and improved photostability. These facile, ultrabright probes ultimately advance the capability for practical applications in live cell imaging, biosensing and in the development of optoelectronic nanodevices.

Carbon Nanotubes Dramatically Affecting Plant Growth !

For the first time, Scientist at University of Arkansas have reported the effect of penetration of plant seed coats by carbon nanotubes. Their research demonstrate that the exposure of carbon nanotubes to seeds of valuable crops, such as tomatoes, can increase the germination percentage and support and enhance the growth of seedlings.
The germination was found to be dramatically higher for seeds that germinated on medium containing CNTs (10−40 μg/mL) compared to control. Analytical methods indicated that the CNTs are able to penetrate the thick seed coat and support water uptake inside seeds, a process which can affect seed germination and growth of tomato seedlings.The activated process of water uptake could be responsible for the significantly faster germination rates and higher biomass production for the plants that were exposed to carbon nanotubes.
Researchers believe that furthering these findings could result in significant developments of improved plants for the area of energy, by taking advantage of the enhancement in the biomass of the plants when they are exposed to nanosized materials and fertilizers.
An observed positive effect of CNTs on the seed germination could have significant economic importance for agriculture, horticulture, and the energy sector, such as for production of biofuels.
paper can be located at ACS Nano, 2009, 3 (10), pp 3221–3227

Enhanced Hydrogen Adsorptivity of Single-Wall Carbon Nanotube Bundles

Single-wall carbon nanotubes (SWCNTs) are considered to be the most promising material for a new sustainable 1.

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View Full Referencand particularly in hydrogen storage, because SWCNT bundles have both internal and interstitial nanospaces that strongly interact even with supercritical H₂.A SWCNT is essentially an interfacial material, being remarkably different from other solid materials in that all component carbon atoms are exposed to both surfaces, each with different nanoscale curvatures. A SWCNT has a huge geometrical surface area of 2630 m² g⁻¹, the same as graphene.Ordinary SWCNTs associate to form an ordered bundle structure through dispersion interaction, providing interstitial pore spaces surrounded by carbon walls with positive curvature, which have the strongest molecular sites. Therefore, bundled SWCNTs have considerable potential for application to gas storage, the stabilization of unstable molecules, quantum molecular sieving, specific reaction fields, gas sensing, electrochemical energy storage, and so on. In a recent report in Nanoletters, Reseachers from Japan have reported the simple preparation of fullerene (C₆₀)-pillared SWCNT bundles by sonication of SWCNTs in a C₆₀ toluene solution and the consequent enhancement of the supercritical H₂ adsorptivity of the SWCNTs. As C₆₀ molecules have a conjugated π-electron structure similar to that of SWCNTs, the C₆₀-pillared SWCNT system can be regarded as a new nanocarbon.

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The H₂ adsorption amounts on the C₆₀-pillared SWCNT bundles doubly increased, compared with nontreated SWCNT bundles. TEM observation revealed that the C₆₀-pillared SWCNT bundle had expanded hexagonal and distorted tetragonal arrays. These expanded interstitial nanospaces were also substantiated by a new XRD peak corresponding to the interlayer distances of SWCNTs in which C₆₀ molecules were surrounded by three or four SWCNTs.
In summary, these new results indicate a simple and promising tuning route for SWCNT bundle structures, allowing the utilization of interstitial nanopore spaces for various fields, such as electrochemical, adsorption, sensor, and separation technologies.
paper can be found at Nano Lett., 2009, 9 (11), pp 3694–3698

Lead-Sulfide (PbS) Nanowire Pine Trees!

Scientists at University of Wisconsin−Madison have recently reported lead sulfide (PbS) nanowires with morphologies resembling “pine trees” synthesized via chemical vapor deposition (CVD) and reestablished the screw dislocation nanowire growth mechanism.
In contrast to previous PbS nanowire growth via CVD reactions with or without intentional metal catalysts, this tree morphology is formed by a combination of screw dislocation-driven nanowire growth that produced long and twisted “trunk” nanowires and a simultaneous self-catalytic vapor-liquid-solid (VLS) mechanism that resulted in epitaxial “branch” nanowires. Lead particles generated in situ are suggested to be a self-catalyst to enable VLS growth of the branches that grow epitaxially off the trunk.
The optimum conditions for synthesizing PbS nanowire pine trees have been investigated in this research with detailed studies of morphology changes under various hydrogen, temperature, pressure, and substrate conditions. The successful growth of nanowires driven by screw dislocations requires two basic ingredients: the creation (seeding) of dislocations and a suitably low supersaturation condition for promoting dislocation-driven growth over layer-by-layer growth and other growth modes.
The ability to control the formation of hierarchical nanostructures with increasing structural complexity, as seen in these pine tree nanowires, can potentially empower increasing functionalities and enhance applications such as solar energy conversion and 3-D nanoelectronics.
This paper can be found at J. Am. Chem. Soc., 2009, 131 (45), pp 16461–16471

True Nature of Gold's Bonding

The research, led by a Lai Sheng Wang of Brown University in collaboration with Jun Li of China's Tsinghua University, provides new insight into bonding interactions involving heavier metals and could lead to a better understanding of the recently discovered catalytic properties of gold.

Evidence has confirmed earlier computational studies showing that the Au–C bonds in Au(CN)2– have significant covalent character, in contrast to the ionic behavior of gold's lighter homologs copper and silver.

The researchers used gas-phase photoelectron spectroscopy along with theoretical calculations to probe the electronic structure and determine the electron density in M(CN)2– for M = Cu, Ag, or Au. They found that the molecular orbitals of the complexes are similar but that the electronic structures are strikingly different, ranging from copper with mostly ionic character to gold with multiple-bond covalent character.The results indicate that hybridization of s and d orbitals and an increase in electron affinity drive gold to form covalent bonds. Those properties lead to the high stability of Au(CN)2–, which has been used since ancient times to extract and process gold.

Fig: Electron localization functions show the increasing probability of finding bonding electron pairs between metals and CN–ligands; Cu(CN)2– is mostly ionic, whereas Au(CN)2– is mostly covalent.

paper can be found at J. Am. Chem. Soc. 2009, 131, 16368

Environment-sensitive stabilisation of silver nanoparticles in aqueous solutions

Scientists from Netherlands have recently reported on the formation of silver containing composite nanoparticles (CNPs) consisting of silver nanoparticles (Ag-NPs), poly(N-methyl-2-vinyl pyridinium iodide)-block-poly(ethylene oxide), P2MVP₃₈-b-PEO₂₁₁ and poly(acrylic acid)-block-poly(isopropyl acrylamide), PAA₅₅-b-PNIPAAm₈₈. Both the Ag-NPs and the CNPs from spontaneously upon mixing of the double hydrophilic block copolymers in the presence of silver ions; that is, without the addition of a reducing agent such as NaBH₄. Paper demonstrate the possibilities to achieve control over the size of the Ag-NPs, the size and shape of the CNPs, and the location of the Ag-NPs within the CNPs. Ag-NPs were found to colocalise with the polyelectrolyte blocks within the CNPs. Temperature could be used to trigger a structural transition from a core–shell structure at T = 25 °C to a core–shell–corona structure at T = 60 °C , translocating the Ag-NPs from the micellar core in the former into the micellar shell in the latter. The most uniform and well-defined CNPs were obtained by premixing Ag⁺ and P2MVP₃₈-b-PEO₂₁₁ at room temperature prior to addition of this solution to a solution of PAA₅₅-b-PNIPAAm₈₈ at T = 25 °C (sample H). It has been shown that the colloidal stability of the CNPs is dependent on the ionic strength of the solution: Ag-NP release from the CNPs can easily be triggered by addition of a simple salt, such as NaNO₃.

This work summarizes that complex coacervate core micelles can be regarded as a promising candidate for polymer-assisted synthesis and stabilisation of silver nanoparticles. Future work might be directed towards the potential application of such CNPs as environment-sensitive silver quantum dots and as antimicrobial agents in antifouling surface coatings that can be prepared upon exposure of hydrophilic surfaces to a solution of Ag-NP containing CNPs.

paper can be found at Journal of colloid and Interface Science, Vol 339, 2, pp 317-324

Tetrahedral Gold nanocrystal

Scientist at Hongkong have recently grown Elongated tetrahexahedral Au nanocrystals in high yields using a seed-mediated growth method.

Morphological and structural characterizations show that these Au nanocrystals are single-crystalline and enclosed by 24 high-index {037} facets. They are more electrochemically active than octahedral Au nanocrystals that are enclosed by 8 low-index {111} facets. To date, there have been only a few reports of metal nanocrystals that are enclosed exclusively by high-index facets, including trisoctahedral Au nanocrystals enclosed by 24 {122} facets and tetrahexahedral Pt nanocrystals enclosed by 24 {037} facets. These newly designed tetrahexahedral Au nanocrystals will be an important addition to the family of metal nanocrystals that are enclosed exclusively by high-index facets and will also be useful for fundamental catalytic studies on metal nanocrystals.

Research is published in Journal of Americal Chemical Society,2009, 131 (45), pp 16350–16351

Carbon nanotube sponge!

Scientists from China have invented a carbon-based sponge that can soak up organic pollutants, such as oils and solvents, from the surface of water. No water is absorbed and the sponge can then be wrung out and reused, like an ordinary household sponge. Absorbing up to 180 times its own weight in organic matter, the sponge is light and tough and has the potential to dramatically enhance oil spill cleanup.

This newly invented sponges are made from interconnected carbon nanotubes; tiny, strong and hollow cylinders of interconnected carbon atoms. The tubes are 30 - 50 nanometres across and tens to hundreds of micrometers long . The surface of the tubes is naturally hydrophobic (water-hating), therefore no further modification is needed for the sponges to repel water. At the same time, they love to absorb oil on their surface. As the sponges are over 99% porous or empty, they float on water and there is a lot of room for oil to be absorbed, leading to the extremely high capacity for retention for example, 143 times the sponge's weight for diesel oil and 175 for ethylene glycol.

However, potential applications reach beyond oil spill recovery. According to Researchers, the nanotube sponges can be used as filters, membranes, or absorbents to remove bacteria or contaminants from liquid or gas. They could also be used as noise-absorption layers in houses, and soldiers might benefit by using these sponges in impact energy absorbing components while adding little weight. Thermally insulated clothing is also possible.

Large-scale production is currently being investigated.

This research is published in Scientific Journal Advance Materials, 2009.

Paper is available at www.materialsviews.com/matview/display/en/1220/TEXT

Magnetic charge behaving as electric charge for the first time

The research at London Centre for Nanotechnology find prove for the existence of atom-sized magnetic charges called ‘magnetic monopoles’. These monopoles behave and interact just like more familiar electric charges.Research also demonstrates a perfect symmetry between electricity and magnetism – a phenomenon dubbed ‘magnetricity'.

In order to prove experimentally the existence of magnetic current for the first time, the research team mapped Onsager's 1934 theory of the movement of ions in water onto magnetic currents in a material called spin ice. They then tested the theory by applying a magnetic field to a spin ice sample at a very low temperature and observing the process using muon relaxation at ISIS, a technique which acts as a super microscope allowing researchers to understand the world around us at the atomic level.

The experiment allowed the team to detect magnetic charges in the spin ice (Dy2Ti2O7), to measure their currents, and to determine the elementary unit of the magnetic charge in the material. The monopoles they observed arise as disturbances of the magnetic state of the spin ice, and can exist only inside the material.

This research, reported in Nature, was led by Steven Bramwell of the London Centre for Nanotechnology in the UK. Bramwell was a member of a team, led by Tom Fennell of the Laue-Langevin Institute in Grenoble, that reported neutron results in September.