Posts

Showing posts with the label materials

Smart concrete using nano particles

Image
Nano concrete Addition of nano particles gives significant improvement to concrete than conventional concrete. Addition of nano particles improves the bulk properties of materials by controlling or manipulating at the atomic scale due to nanoscale attack by alkali silicate reaction. It is possible to obtain thinner final products and faster setting time besides lower levels of environmental contamination. Nano concrete is a concrete made with Portland cement particles that are less than 500nm as a cementing agent as against normally used cement particle which range in size from a few nano-meters to a maximum of about100 micro meters. The benefits are cessation of contamination caused by micro silica solid particles, lower cost per building site, high initial and final compressive and tensile strengths, good workability, cessation of super plasticizing utilization and cessation of silicosis risk of concrete. Nanomaterials used are nano-silica (nano-SiO2), nano-titanium oxide (nano-TiO2)

Semiconductor nanoparticles

Image
A nanoparticle (or nanopowder or nanocluster or nanocrystal) is a microscopic particle with at least one dimension less than 100 nm. Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures. Nanoparticles exhibit a number of special properties relative to bulk material.Nanoparticles of many other materials, including metals, metal oxides; carbides, borides, nitrides, silicon, and other elemental semiconductors are available. Mechanism Their unique physical properties are due to atoms residing on the surface. The excitation of an electron from the valance band to the conduction band creates an electron hole pair. Recombination can happen two ways as radiative and non-radiative leading to radiative recombination to photon and non-radiative recombination to phonon (lattice vibrations). Also the band gap gradually becomes larger because of quantum confinement effects giving rise to discrete energy levels, rath

Graphene in loudspeakers and earphones

Image
Loudspeakers and earphones are used with portable devices such as smart phones, laptops, notebooks and tablets. Inside a speaker a flexible material such as paper or plastic forming a thin diaphragm vibrates and amplifies these vibrations, pumping sound waves into the surrounding air and towards the ears producing different sounds depending on their frequency. Sound device The quality of a loudspeaker depends on how flat its frequency response is – that is, on the ability of the design to deliver a constant sound pressure level from 20 Hz to 20 kHz in the audible range. Presently they employ conventional type of speakers which have limitations in their operation in respect of size, frequency response and power consumption. Graphene loudspeaker Researchers at the University of California at Berkeley have made a graphene loudspeaker that, while of no specific design, is already as good as, or even better than, certain commercial speakers and earphones. graphene loudspeaker have ultralow

Nano gold cluster is a marvellous catalyst

Image
Nanosized gold clusters Nanosized gold clusters is known to catalyze various oxidations, esterifications, and epoxidations. But the basis of the precious metal’s reactivity was not very clear to the scientists. However carbon monoxide oxidation catalyst by gold is well known. In the case of CO oxidation a computational study has found that CO can surprisingly provide a cocatalytic assist to gold nanoclusters during oxidation reactions. The presence of neighboring CO molecules on gold nanoclusters enhances dioxygen oxidation of CO to carbon dioxide. Mechanism This self-oxidation mechanism has now been uncovered by researchers of University of Nebraska and  Xiangtan University of in China. The findings reveals that when CO is bound to certain triangular Au3 active sites on gold nanoclusters in the presence of O2, the CO molecule helps facilitate bond scission in an adjacent OCOO intermediate. The analysis shows that an attack on the intermediate by the Au3-bound CO neighbor would signifi

Nanocellulose from blue-green algae

Image
Nanocellulose from blue-green algae Researchers have reported on producing nanocellulose using the algae. Cellulose Cellulose is an organic compound mainly a polysaccharide consisting of a linear chain of several hundred to over ten thousand β (1→4) linked D-glucose units and is an important structural component of the primary cell wall of green plants, many forms of algae oomycetes and secreted by some species of bacteria as bio films. Cellulose is the most abundant organic polymer on Earth, a material, like plastics, consisting of molecules linked together into long chains. Cellulose makes up tree trunks and branches, corn stalks and cotton fibers, the main component of paper and cardboard and the indigestible material in fruits and vegetables. For example the cellulose content of cotton fiber is 90%, that of wood is 40–50% and that of dried hemp is approximately 45%. Few living organisms can synthesize and secrete cellulose in its native nanostructure form of micro fibrils. Nano cel

Tin Nanocrystals for future battery

Image
Li-Ion Rechargeable Batteries Li-Ion (Lithium-Ion) batteries are the most common rechargeable batteries in portable electronics. Lithium ion batteries have one of the best energy densities, no memory effect,  slow loss of charge when not in use and environmentally safe because there is no free lithium metal, in comparison with other types of rechargeable batteries. Rechargeable lithium ion batteries are the preferred compact light weight storage media of choice to store a large amount of energy in a small space. They provide power for electric cars, electric bicycles, smart phones and laptops. Globally researchers are currently in the process of developing new generation of such batteries with an improved performance. In most lithium ion batteries these days, the plus pole is composed of the transition metal oxides cobalt, nickel, and manganese, the minus pole of graphite. In more powerful lithium ion batteries of the next generation, however, elements such as tin or silicon may well b

Plasmonic nanoparticles

Image
Plasmons are free electrons on the surface of metals that become excited by the input of energy, typically from light. Moving plasmons can transform optical energy into heat.  Plasmonic nanoparticles are particles whose electron density can couple with electromagnetic radiation of wavelengths that are far larger than the particle. This is due to the nature of the dielectric-metal interface between the medium and the particles unlike in a pure metal where there is a maximum limit on what size wavelength can be effectively coupled based on the material size. Plasmonic nanoparticles also exhibit interesting scattering, absorbance, and coupling properties based on their geometries and relative positions. These unique properties have made them a focus of research in many applications including solar cells, spectroscopy, signal enhancement for imaging, and cancer treatment. Plasmonic gold nanoparticles Gold nanoparticles can be used for efficiently converting energy because of their optical

Nanosilicon to produce hydrogen

Image
Nanoparticles of silicon can be made to react instantly with water to produce hydrogen without application of any heat, light or electricity. Hydrogen production Traditional techniques to split water to produce hydrogen include electrolysis, thermolysis and photo catalysis.But bulk silicon abundantly available on earth can react slowly with water to produce hydrogen by releasing two moles of hydrogen gas per mole of silicon without releasing any carbon dioxide. Nanosilicon Silicon nanoparticles due to their high surface to volume ratio can generate hydrogen quickly than bulk silicon due to high reaction rate. Researchers at the University at Buffalo (SUNY) in New York have developed this technique. For example nanoparticles 10 nm in size can produce hydrogen in under a minute which is1000 times faster at producing hydrogen than is bulk silicon and nanoparticles of 100 nm in diameter can produce at 45 minutes. During the hydrogen production reaction, the 10 nm silicon particles reduce i

Nanocups can bend light

Image
Nanoshells, nanoeggs and nanocups.   Nanoshells, consist of a spherical silica core coated with a thin gold shell and can be converted to nanoeggs by offsetting the core within the shell. When the offset of the core is greater than the thickness of the shell layer, the core pierces the shell, resulting in nanocups. Nanoeggs exhibit absorption and scattering spectra with multipolar peaks strongly red shifted relative to those of nanoshells and larger near-field enhancements. Researchers at the Hong Kong University of Science and Technology have developed a nanoegg with a hard cobalt shell surrounding a core of platinum and iron and found that it could safely deliver platinum, a known anticancer agent, to tumor cells. Nanoegg has been found to be seven times more toxic than the anticancer agent cisplatin to cancer cells. Synthesis of cobalt sulfide nanoparticles forms a hollow shell structure in the presence of nanoparticles made of iron and platinum and the resulting structures have

Semiconductor nanocrystals help produce hydrogen fuel

Image
Photosynthesis Photosynthesis is the process of converting solar radiation into green energy to produce sugar, which cellular respiration converts into ATP by the plants, bacteria and some protistans green using green chlorophyll pigment using water and releasing oxygen. Artificial photosynthesis Artificial photosynthesis systems exploiting light-absorbing molecules or chromophores, typically made of organic dyes, to photo chemically split water into hydrogen and oxygen by half-reactions with reduction and oxidation process. But the light-absorbing dyes are damaged due to Sun's rays and the process is inefficient and unstable. Researchers at the University of Rochester, USA have generated hydrogen using nanocrystals, sunlight and a cheap nickel catalyst which can continuously produce fuel without slowing down. Nanocrystals Nanocrystals have fewer defects due to their limited size . nanocrystals have very little interior volume and are virtually all surface and the inner impurities

Carbon nanotube yarn, muscle and transparent sheets

Image
Carbon nanotubes Carbon nanotubes (CNTs) have high strength and modulus, high electrical and thermal conductivities, are stable at relatively high and low temperatures. Individual nanotubes can be 100 times stronger than steel. To effectively exploit the exceptional properties of individual nanotube’s in various applications, continuous pure CNT yarns and high CNT content composite yarns need to be fabricated. MWCNTs reinforced PAN fibers and CNT/cellulosic continuous bamboo yarns can be used to manufacture CNTs filled multifunctional products by electro spinning. This process can give significant improvements of the mechanical, thermal and electrical properties of the yarn by incorporation of CNT into the nanofibers. SWCNT fibers can also be manufactured from liquid crystal solutions to get continuous neat CNT fibers. Making CNT yarn A continuous CNT fiber yarn using multiple threads of high purity double walled carbon nanotubes can be fabricated in a horizontal CVD gas flow reactor w

3D- DNA nanostructures

Image
Folding the DNA DNA nanotechnology which is like paper folding was developed around 30 years back. In 2006, Paul Rothemund of the California Institute of Technology demonstrated folding long strands of DNA into a wide range of predetermined shapes. The resulting nanostructures can be used as scaffolding or as miniature circuit boards for precisely assembling components such as carbon nanotubes and nanowires. But to make DNA  structure of several folds, several hundred "staples" must be added to the regions surrounding the single DNA strands, and for making new nanostructures a new set of staples are requires. Moreover, the DNA structures tend to arrange themselves randomly onto a substrate surface making it difficult to integrate them into electronic circuits subsequently. DNA brick To overcome the above difficulty researchers at Harvard University in the US have developed a technique to make highly complex 3D nanostructures by assembling together synthetic DNA "bricks&q

Nano coating for multiple colours

Image
Optical coatings A vast majority of scientific and industrial optics have a thin-layer coating to avoid ghost images, back reflections, safety hazard or destroying expensive equipments. But by having a thin-film coating critical properties can be introduced in the optics which uses them. Conventional dielectric optical coatings, which are a key component of almost every optical device, are typically made of layers of transparent material with each layer being at least a quarter wavelength of light in thickness. Nano coating Researchers at Harvard University have made an optical coating which can change colour when its thickness is varied by less than 20 nm thick. By changing the thickness the colour of metal surfaces could be customized to the required one. The new ultrathin optical coatings is nanometre-thick, and nearly opaque, highly light-absorbing dielectric materials, such as semiconductors. By adding a 7 nm layer of germanium to the surface of a gold sample its colour can be cha

Gold nanoparticles for chemo sensors

Image
Chemosensor Chemosensor is a sensory receptor that transduces a chemical signal into an action potential. In more general terms, a chemosensor detects certain chemical stimuli in the environment. Chemosensors are finding increased use in fields as diverse as biology, medical analysis, and environmental monitoring. Gold nanoparticles Nanoparticles are versatile materials and find applications in different areas going from industry, to bio-analysis, and catalysis. Gold nanoparticles exhibit excellent catalytic activity due to their relative high surface area-to-volume ratio, and their interface-dominated properties, which significantly differ from their bulk. They have been used extensively for the design and fabrication of electro catalysts and as an enhancing component of catalytic activity or selectivity. For electro catalytic applications techniques like anchoring by electrostatic interaction, covalent linkage, electrochemical deposition, etc.  are used. Such modified interfaces beha

Nano grapheme, silicon based flexible transparent memory

Image
Memory Devices Computers and many electronic gadgets usually rely on stored information which is mainly data which can be used to direct circuit actions. The digital information is stored in memory devices. The long-term nanotechnology prospects for memory devices include carbon-nanotube-based memory, molecular electronics and memristors based on resistive materials such as TiO2. Transparent memory Transparent electronic memory has an advantage in that it would be useful in integrated transparent electronics, but achieving such a transparency produces limits in material composition and hinders processing and device performance. Here we present a route to fabricate highly transparent memory using SiOx as the active material and indium tin oxide or graphene as the electrodes. The two-terminal, non-volatile resistive memory can also be configured in crossbar arrays on glass or flexible transparent platforms. The filamentary conduction in silicon channels generated in situ in the SiOx main

Nanofibers and filaments for enhanced drug delivery

Image
Drug Delivery Drugs are transported from their site of introduction to their molecular site of action after rapid filtration in the kidney and mix in the bloodstream and travel to target cells within tissues. At the tissue or cellular target, the drug must cross the plasma membrane, harsh environment within the cell and the multiple drug resistance mechanisms that pathological cells can develop. But nanomaterials are promising as drug or vaccine carriers to assist in navigating these barriers. Drug delivery vehicles Most of the nanoparticles based drug delivery vehicles are spheres, but cylindrical nanoparticles can survive for a long period in the blood stream to reach their intended target and penetrate the cell wall and deliver therapeutic payload where it is needed. North-western CCNE have developed self-assembling nanofibers that takes care of this requirement. Cylindrical vehicles To create tumor-inhibiting cylinders the researchers immersed peptide amphiphiles made using automa

Nanostructured electron cloak

Image
Invisibility cloaks Invisibility cloaks are used to hide objects from electromagnetic waves and are made from metamaterials.  Metamaterials are artificial structures with special optical properties such as negative refractive indices arranged in such a way that incoming light waves can flow smoothly around the cloak and meet on the other side as if the cloak was not present. Electron cloak Electrons normally travel as waves over a certain distance before scattering destroys their wave phases over coherent transport length and the particles exhibit characteristic wave behaviour, such as amplitude superposition or interference. The principle of Invisibility cloaks can be applied to electrons made of core-shell nanoparticle structures embedded in a host semiconductor that does not disturb the flow of electrons. Researchers of Massachusetts Institute of Technology have developed a method to make an electron cloak, or an object that is invisible to electrons and made of a nanostructure tha

Graphene nanoribbon

Image
Graphene Graphene has no gap between its valence and conduction bands which is essential for electronics applications because it allows a material to switch the flow of electrons on and off. But a band gap can be introduced into graphene by making extremely narrow ribbons. For example, dense arrays of 10 nm wide graphene nanoribbons can have a band gap of about 0.2 eV. Graphene nanoribbons (GNRs), are strips of graphene with ultra-thin width (<50 b="b"> Production By using small molecule precursors, scientists have found a way to precisely build graphene nanoribbons and make them in different shapes. Most routes to make nano-graphene are top-down - starting from a bulk material and breaking it up which has been tricky to make nano-sized ribbons of graphene with a defined structure of a size that would be useful in nanoelectronics. Width controlled GNRs can be produced via graphite nanotomy process shown by Berry group, where sharp diamond knife application on graphite p

Nanodiamonds for magnetic sensors

Image
Nanodiamonds Nanodiamonds are diamond-structured particles measuring less than 10 nanometers in diameter which result as a residue from a TNT or Hexogen explosion in a contained space. Nanodiamonds have excellent mechanical and optical properties, high surface areas and tunable surface structures. Nanodiamonds have a wide range of potential applications in tribology, drug delivery, bio imaging and tissue engineering, for biomedical applications as they are also non-toxic, as protein mimics and also a filler material for nano composites. Nanodiamonds have perfect mechanical performance and widely used in various industries such as spaceflight, aero plane manufacture, information industry, precision machinery, optical instrument, automobile manufacture, chemical plastics and lubricant etc. Measuring magnetic fields Researchers at the University of California, Santa Barbara have developed an electron spin resonance technique involving nanodiamonds and lasers to measure local magnetic fiel

Nanocrystalline alloys

Image
Nanocrystals for ferro electricity Ferro electricity The phenomenon of ferro electricity was discovered in 1921 using Rochelle salt. Barium titanate (BaTiO3) is a ferroelectric material used in making ferro electricity. There are more than 250 materials that exhibit ferroelectric properties, which include;     Lead titanate, Lead zirconate titanate and Lead lanthanum zirconate titanate. Ferroelectric materials have a permanent dipole moment, like their ferromagnetic counterparts. However, in ferroelectrics, the dipole moment is electric and not magnetic and so can be oriented using electric fields rather than magnetic ones to allow electrically digital information to be stored in ferroelectric thin films. Applications of ferroelectric materials Ferroelectric materials are used in making capacitors, non-volatile memory, piezoelectrics for ultrasound imaging and actuators, electro-optic materials for data storage applications, thermistors, switches known as transchargers or transpolarize