Majid Kazemian Abyaneh

Sulfite reductase‐mediated synthesis of gold nanoparticles capped with phytochelatin

An enzymatic synthesis route to peptide‐capped gold nanoparticles has been developed. Gold nanoparticles were synthesized using α‐NADPH‐dependent sulfite reductase and phytochelatin in vitro. The gold ions were reduced in the presence of the enzyme sulfite reductase, leading to the formation of a stable gold hydrosol of dimensions 7–20 nm and were stabilized by the capping peptide. The nanoparticles were characterized by X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy and UV–visible optical absorption. These studies will help in designing a rational enzymatic strategy for the synthesis of nanomaterials of different chemical compositions, shapes and sizes as well as their separation.

Formation of gold nanoparticles in polymethylmethacrylate by UV irradiation

Gold–polymethylmethacrylate (PMMA) nanocomposites were fabricated with a photoreduction method using UV irradiation. The irradiated samples are compared with unirradiated ones to investigate the mechanism of gold nanoparticle formation and the effect of UV irradiation and polymer matrix on the morphology of the particles. The triangular gold nanoparticles were formed in polymer medium at a specific concentration of gold salt and UV exposure. The particle size decreased when the gold salt to polymer ratio was increased. The samples were analysed using UV–Vis spectroscopy, Fourier transform infrared spectrometry, atomic force microscopy, x-ray diffraction, small angle x-ray scattering and x-ray photoelectron spectroscopy. The interfacial interaction of Au nanoparticles and PMMA polymer has been discussed.

Giant piezoresistive response in zinc?polydimethylsiloxane composites under uniaxial pressure

Investigations on the piezoresistive response of composites containing zinc conductive fillers at different concentrations in polydimethylsiloxane (PDMS) polymer matrix are presented here. The composites remain insulating even at high filler concentrations. The piezoresistive behaviour of the Zn–PDMS composites under uniaxial pressure shows the resistivity changes by approximately seven orders of magnitude around 4 MPa pressure. We find that the piezoresistive behaviour of the Zn–PDMS composites can be explained in the framework of electron tunnelling between the metal particles.

Rapidly switched wettability of titania films deposited by dc magnetron sputtering

Rapid switching (5–15 minutes) in the wettability of titania (TiO2) thin films in the anatase phase has been observed after UV irradiation. The film surface becomes superhydrophilic when exposed to UV radiation. The relationship between wettability, thickness and crystallinity of TiO2 films has been investigated. Amorphous and anatase TiO2 thin films have been deposited by varying the argon to oxygen gas ratio, using the reactive dc magnetron sputtering technique. It was found that the gas ratio primarily affects thickness, crystallinity, morphology and wettability of the films. The highest contact angle that has been reported so far, namely, 170°–176°, has been observed for film thickness varying from 112–500 nm in the case of pristine anatase TiO2 films. On the other hand, amorphous films show a variation in the contact angle from 120° to 140° as the thickness varied from 70 to 145 nm. The deposition is extremely robust and has an ultralow hysteresis in the contact angle. The films exhibit a morphology similar to the lotus leaf and the water hyacinth.