Recent Advances in Nanostructured Materials for Application as Gas Sensors.

Many different industries, including the pharmaceutical, medical engineering, clinical diagnostic, public safety, and food monitoring industries, use gas sensors. The inherent qualities of nanomaterials, such as their capacity to chemically or physically adsorb gas, and their great ratio of surface to volume make them excellent candidates for use in gas sensing technology. Additionally, the nanomaterial-based gas sensors have excellent selectivity, reproducibility, durability, and cost-effectiveness. This Review article offers a summary of the research on gas sensor devices based on nanomaterials of various sizes. The numerous nanomaterial-based gas sensors, their manufacturing procedures and sensing mechanisms, and most recent advancements are all covered in detail. In addition, evaluations and comparisons of the key characteristics of gas sensing systems made from various dimensional nanomaterials were done.

Room temperature synthesis of highly hemocompatible hydroxyapatite, study of their physical properties and spectroscopic correlation of particle size.

Needle shaped nanoparticles of hydroxyapatite (HA) have been synthesized at room temperature using orthophosphoric acid as the source of (PO4)3- ions, while calcium chloride, the calcium source, is suitably complexed with citric acid/tartaric acid/acetic acid. The presence of ligands inhibits the growth along [001] and [100] directions of the crystal and thus, helps in formation of needle shaped nanoparticles. The chemical compositions of the samples have been established through AAS and FTIR spectroscopy, while the crystallinity has been assessed through XRD and by the spectral changes in the υ1 and υ3 frequencies of the phosphate group in the respective FTIR spectra. The particle sizes of the samples have been determined from line broadening studies and correlations have been established between the curve fitted percentage area of FTIR and full width half height (FWHH) of the XRD peaks. TEM studies revealed the particle to be needle-shaped with a length and diameter in the range of 20-65 nm and 4-11 nm respectively. Changes in the surface charge of the water dispersed HA samples have been determined at different pH and the isoelectric point for the samples have been found in the range of 3.1-3.4. Finally, the morphology, surface area and hemocompatibility characteristics of the HA samples, prepared by using different complexing agents, have been compared.

Microwave-assisted synthesis of WS2 nanowires through tetrathiotungstate precursors.

Tungsten disulfide (WS2) nanowires have been synthesized through a microwave-assisted chemical route that uses tungstic acid, elemental sulfur and monoethanolamine as starting reagents for obtaining a precursor solution of tetrathiotungstate ions. Acidification of the precursor solution yields amorphous precipitates, which lead to the formation of nanowires of WS2 with thickness of about 5-10 nm when heated at 750 °C under argon atmosphere for 1.5 h. Phase and the microstructure of the prepared powders have been investigated through x-ray powder diffraction and high-resolution transmission electron microscopy, respectively. Optical absorption of the WS2 powders reveals a red shift of the exciton bands compared to bulk WS2.