Temperature Based Investigation on Structure and Optical Properties of Bi2S3 Nanoflowers by Solvothermal Approach

International audienceA solvothermal process has been employed to synthesis Bi2S3 nanostructures which has a wide spread applications in photodiode, hydrogen storage, high energy batteries, as well as luminescence and catalytic fields. Bismuth nitrate, thiourea and PolyVinyPyrrolidene (PVP), used as the starting materials are dissolved in ethylene glycol for different reaction times. It was found that the temperature plays a key role in determining the shape of the products. The crystalline phase and structure of the Bi2S3 nanostructures were investigated by power X-ray diffraction (XRD). The surface morphology has been analyzed by Scanning electron microscopy (SEM), the optical properties of the Bi2S3 nanoparticles were analyzed using UV-Vis spectroscopy. The functional groups present in the Bi2S3 nanoparticles were characterized by FT-IR spectroscopy. The novel Bi2S3 nanoparticles will be exploited for its application as photocatalyst

Hot electron extraction from CdTe quantum dots via beta carotene molecular energy levels

We report our findings related to hot electron extraction from CdTe quantum dots, and we were able to do this by using beta carotene as an electron acceptor. Transient absorption spectra with two slow recovering negative bleaches at the absorption maximum of the molecule and quantum dot have indicated the slowing down of cooling process and the existence of hot carriers in this hybrid system. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4730623]open1142sciescopu

Rod-Shaped Carbon Aerogel-Assisted CdS Nanocomposite for the Removal of Methylene Blue Dye and Colorless Phenol

A carbon aerogel (CA)-assisted CdS nanocomposite was prepared by hydrothermal process and was investigated as a photocatalyst towards the photodegradation of methylene blue (MB) dye and colorless phenol under visible light irradiation (VLI). CdS have attracted wide attention due to their relatively narrow band gap for the visible light effect and the suitably negative potential of the conduction band (CB) edge for the neutralization of H+ ions. The obtained characterization results suggest that the CA-assisted CdS nanocomposite has enhanced photophysical properties, a more surface area, and the desired morphology at the nm scale. Under optimization, CdS CA 8% shows superior catalytic activity for degradation compared with other samples. The photocatalytic activities of the as-synthesized samples were examined under VLI through the MB and phenol degradation. Compared with pure CA and CdS, the CA (8%)-assisted CdS nanoparticles (NPs) offer significantly enhanced photocatalytic efficiency for MB and phenol. The mechanism of photocatalytic reaction was examined by adding various scavengers, and the results revealed that the holes generated in CA (8%)-assisted CdS NPs have a crucial impact on the visible light photocatalytic process. The improved photocatalytic degradation was due to the strong interaction between the CA and CdS NPs

Systematic investigation of the structure and photophysical properties of CdSe, CdSe/ZnS QDs and their hybrid with beta-carotene

A systematic investigation was conducted to determine the excitation energy dependent emission characteristics of CdSe quantum dot-beta-carotene and CdSe/ZnS core-shell quantum dot-beta-carotene hybrid samples. The emission intensity was recorded at different excitation energies by continuously varying the excitation energy from the band edge value of the QDs to a maximum value. In both the hybrids, the emission intensity increased with an increase of the excitation energy and then a sudden quenching occurred, which is in contrast with the results from bare samples, where the emission intensity showed a decreasing trend at all excitation energies. The quantum yields corresponding to the maximum emission are 47.12% and 69%, for CdSe QD-beta C and CdSe/ZnS core-shell QD-beta C hybrids, respectively. At higher excitation energy, electrons were transferred to the molecule's LUMO level, leaving behind holes in the valance band of the QD, and thus the produced charge separated state became responsible for the PL quenching in the hybrid sample. We have confirmed this charge separated state by lifetime measurements. It is because of this PL quenching behaviour of the hybrids that the nature of the interface band structure was deduced as type I. Furthermore, because of the involvement of higher energy photons in the quenching process, the transferred electrons in the LUMO level of the molecule were known as hot electrons. The present paper discusses the excited state electron dynamics across the interface between the two hybrid materials in detail.open1167sciescopu

Molecular conformation dependent emission behaviour (blue, red and white light emissions) of all-trans-β-carotene-ZnS quantum dot hybrid nanostructures

A novel hybrid material consisting of all-trans-beta-carotene and ZnS quantum dots (QDs) was prepared by two different controlled experiments and their photophysical properties were investigated in detail. Depending upon the preparation method, the beta-carotene molecule had formed either an upright or wrapped conformation around the ZnS QDs and consequently the interaction between these two hybridizing systems was either charge transfer induced or electrostatic in type, respectively. Optical absorption, Raman and FTIR investigations have confirmed the two different conformations of the molecule around the ZnS QDs. Because of the two different conformations and the consequent interactions, different emission colours, such as blue and red wavelengths were obtained from these hybrids. We were also able to obtain white light emission by using cadmium doped ZnS QDs for the hybrid preparation.open111010sciescopu