No abstract

Biosynthesis of nanoparticles using microorganisms has attracted a lot of attention in recent years as this route has the potential to lead to synthesis of monodisperse nanoparticles. Here, we report the intracellular synthesis of stable lead sulfide nanoparticles by a marine yeast, Rhodosporidium diobovatum. The PbS nanoparticles were characterized by UV-visible absorption spectroscopy, X-ray diffraction (XRD) and energy dispersive atomic spectroscopy (EDAX). UV-visible absorption scan revealed a peak at 320 nm, a characteristic of the nanosize range. XRD confirmed the presence of PbS nanoparticles of cubic structure. Crystallite size as determined from transmission electron microscopy was found to be in the range of 2-5 nm. Elemental analysis by EDAX revealed the presence of particles composed of lead and sulfur in a 1:2 ratio indicating that PbS nanoparticles were capped by a sulfur-rich peptide. A quantitative study of lead uptake through atomic absorption spectrometry revealed that 55% of lead in the medium was accumulated in the exponential phase, whereas a further 35% was accumulated in the stationary phase; thus, the overall recovery of PbS nanoparticles was 90%. The lead-exposed yeast displayed a marked increase (280% over the control) in nonprotein thiols in the stationary phase.

The utilization of sustainable natural fibers as green filler/reinforcement material for producing polymeric composites is substantially improved due to increase in the perception of ecological safety and usage of biodegradable and renewable materials toward a green environment. These natural fibers are obtained from various sources and are reinforced in the polymer matrices to produce polymer matrix composites. However, the overall properties of these composites are low when compared to that of the synthetic fiber-based composites due to poor interfacial bonding between the hydrophilic natural fiber and hydrophobic polymers. This deficiency can be addressed by incorporating

Metal-tolerant microorganisms have been exploited in recent years to synthesize nanoparticles due to their potential to offer better size control through peptide binding and compartmentalization. In this paper, we report the intracellular synthesis of silver nanoparticles (SNPs) by the highly silver-tolerant marine bacterium, Idiomarina sp. PR58-8 on exposure to 5 mM silver nitrate. SNPs were characterized by UV-visible spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV-visible absorption scan of a 48 h culture exposed to 5 mM silver nitrate revealed a broad peak at 450 nm indicative of the surface plasmon resonance of SNPs. XRD analysis confirmed the presence of elemental silver and the crystallite size was calculated to be 25 nm using Scherrer formula. The average particle size as per TEM analysis was found to be 26 nm. Metal stress is known to induce the production of non-protein thiols (NP-SHs) which sequester metal ions. In this study, the production of NP-SHs was followed from 6-48 h, wherein it was observed that the NP-SH levels in the silver-exposed culture were consistently higher (261% on an average) than in the unexposed culture.

The objective of this paper is to numerically study the heat transfer and hydrodynamic performance of a graphene-based hybrid nanofluid flowing through a microchannel for electronics cooling applications. Different concentrations of Graphene-Platinum/water hybrid nanofluid were employed as coolants. The thermophysical properties used in this study were considered to be temperature-dependent. The microchannel was modeled as a porous media. The effect of nanoparticle volume concentration on thermal resistance, pressure drop, friction factor and ratio of heat transfer coefficient to pressure drop (Figure of merit) was analyzed and the plots were generated for different Reynolds numbers of the working fluid. The results pointed out that introduction of nanoparticles resulted in the lowering of thermal resistance. However, the pressure drop and friction factor increased. Figure of merit is found to be higher for higher concentrations of hybrid nanofluids compared to base fluid water. On analyzing the results, it was understood that the utilization of Graphene-Platinum/water hybrid nanofluid through microchannels can be highly effective in the laminar region. It also suggests that this graphene based nanofluid has excellent potential as a coolant to remove excess heat from miniature electronic devices.