Differential Surface Capping Effects on the Applications of Simple Amino-Acid-Capped ZnS:Mn Nanoparticles

Water-dispersible ZnS:Mn nanoparticles (NPs) were prepared by capping their surface with simple structured amino acids: l-alanine (Ala), l-glycine (Gly), and l-valine (Val) molecules, which have very similar structures except for the terminal organic functional groups. The detailed characterization works for the prepared colloidal NPs were performed using various spectroscopic methods. In particular, the NPs commonly showed UV/visible absorption peaks around 325 nm and PL emission peaks around 590 nm, corresponding to the wavelength of orange color light. In this study, these amino-acid-capped NPs were applied as optical photosensors in the detection of specific divalent transition metal cations in the same conditions. Consequently, all three NPs showed exclusive fluorescence quenching effects upon the addition of Cu (II) metal ions, whereas their quenching efficiencies were quite different to each other. These experimental results indicated that the Gly-ZnS:Mn NPs (k = 4.09 × 105 M−1) can be the most effective optical photosensor for the detection of Cu2+ ions in water among the three NPs in the same conditions. This study showed that the steric effect of the capping ligand can be one of the key factors affecting the sensor activities of the ZnS:Mn NPs.

Synthesis, characterization and functional evaluation of gold nanoparticles prepared using Dovyalis abyssinica leaf extracts as reducing and surface capping agent

Green synthesis of nanoparticles using plants and microorganisms is biologically safe, cost effective, and environmentally friendly technology. Gold nanoparticles (Au NPs) were synthesized using aqueous extracts of leaves of Dovyalis abyssinica as reducing and surface capping agent and the catalytic activity, antibacterial action and antioxidant potential of the synthesized AU NPs were evaluated. Firstly, HAuCl4 was synthesized in the laboratory from metallic gold and hydrochloric acid using a predesigned method. Secondly, Au NPs was synthesized by mixing HAuCl4 and the plant extract at 45 oC with a digestion time of 1 h. The size of the nanoparticles was modulated by varying the ratio of the plant extract and HAuCl4 with known concentrations. The synthesized Au NPs showed strong absorption around 540 nm which lies in the characteristic absorption region of Au metal nanoparticles (520–580 nm). The X-ray diffraction spectrum of the synthesized Au NPs showed characteristic crystalline structures of gold. The scanning electron spectroscopy images of the synthesized Au NPS revealed the presence of mixed shapes predominantly of irregular shapes and a particle size analyzer displayed an average size of 63.13 nm. The fourier-transform infrared spectrum of Au NPS confirmed the presence of amine, carbonyl and hydroxyl functional groups as surface capping molecules. Although the synthesized Au NPs showed poor bacterial growth inhibition activity on two selected bacteria, it demonstrated excellent free radical scavenging activity against 2, 2-Diphenyl-2-picrylhydrazyl (DPPH) radical and good catalytic activity for degrading bromothymol blue and methyl red compounds. In contrast to the hexane and ethyl acetate extracts, the aqueous fraction was identified as powerful reducing fraction for the synthesis of Au NPs in this experiment.

Late Pleistocene microlithic industries in the Ayodhya hills, Purulia, West Bengal: Insights from geoarchaeological exploration

New evidence from Ayodhya hills, located in the western upland of West Bengal has expanded knowledge of a Late Pleistocene microlithic technology in South Asia spanning 42-25 ka. Continuous exploration for the past two decades has resulted in substantial information on technology, distribution of sites and the colluvial context. It is now clear from surface exploration and excavations that there are localized differences in the formation of the colluvial context. At Mahadebbera and Kana sites which have yielded the OSL dates, the Insitu occurrence of artefacts in the excavated sections confirm their association with a colluvial context. The occurrence of microliths for a prolonged period (25-34 ka) at Mahadebbera indicates that the colluvial deposition must have followed a slower rate during the course of occupation at the site. At Khududih-Chauniya, a site currently being investigated, excavation and surface exploration indicate that the artefacts are mostly scattered over the regolith surface capping the bedrock; much of the colluvial material from the site has been eroded and transported downslope exposing the lithic artifacts over the regolithic badland surface. Added interest to this site ensues from recent finds of Middle Paleolithic cores and a Lower Palaeolithic core from the badland rain gullies. This promises to complement the already published results from the region, which has emerged as an important zone in understanding the behaviour patterns of Anatomically Modern Humans in South Asia.

Can Surface Capping Ligand Probe Cation Exchange in Inorganic Nanoparticles?

Cation exchange by post-synthetic modification of inorganic nanoparticles (NPs) are commonly monitored by probing alterations of NP’s core, and not much is known on surface capping ligand’s ability to probe...

Tailoring Oxygen Evolution Reaction Activity of Metal-Oxide Spinel Nanoparticles via Judiciously Regulating Surface-Capping Polymers

High cost and scarcity of the state-of-the-art noble metal-based catalysts represents one of the critical hurdles to be overcome in electrocatalysis. A promising direction is to utilize transition metal-based nanoparticles...

The Effect of Surface-Capping Oleic Acid on the Optical Properties of Lanthanide-Doped Nanocrystals

The rapid development of nanotechnology has placed higher demand on the synthesis of nanomaterials. Benefiting from its capability to keep nanoparticles away from aggregation, oleic acid (OA) has been routinely...