Showing posts from November, 2012

Nanotree structure by GLAD process

For the morphological control of nanostructures during bottom-up growth several techniques are used. GLAD Glancing angle deposition (GLAD) is a technique that uses a flow of atoms from gas phase to impinge on a substrate surface under an oblique angle. Physical vapor deposition under conditions of obliquely incident flux and limited atom diffusion results in a film with a columnar microstructure. These columns will be oriented toward the vapor source and substrate rotation can be used to sculpt the columns into various morphologies. Glancing angle deposition (GLAD) is an advanced bottom-up nanostructuring technique developed by Michael Brett’s group at the University of Alberta, Canada. GLAD provides precision engineering of nanostructures via control over macroscopic geometry during deposition. Deposition modulation allows for real-time fabrication of previously unachievable hybrid architectures during bottom-up growth. For example, with modulation of deposition rate and substrate ori

Nano coating for multiple colours

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

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