Development of hierarchical copper sulfide-carbon nanotube (CuS-CNT) composites and utilization of their superior carrier mobility in efficient charge transport towards photodegradation of Rhodamine B under visible light.

In this work, the synthesis of visible light sensitive copper sulfide (CuS) nanoparticles and their composites with carbon nanotubes (T-CuS) via a solvothermal technique is reported. The synthesized nanoparticles (NPs) and their composites were significantly characterized by powder X-ray diffraction (PXRD), scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, photoluminescence (PL) spectroscopy and thermogravimetric analysis (TGA). The effect of carbon nanotubes (CNTs) on the crystallinity, microstructures, photo-absorption, photo-excitation, thermal stability and surface area of CuS was investigated. The current-voltage (I vs. V) characteristics of both CuS and T-CuS based Schottky diodes were measured to determine the charge transport parameters like photosensitivity, conductivity, mobility of charge carriers, and transit time. The photocatalytic performance of bare CuS and T-CuS in the decomposition of Rhodamine B dye was studied using a solar simulator. The T-CuS composite showed higher photocatalytic activity (94%) compared to bare CuS (58%). The significance of charge carrier mobility in transferring photo-induced charges (holes and electrons) through complex networks of composites and facilitating the photodegradation process is explained. Finally, the reactive species responsible for the Rhodamine B degradation were also identified.

Effect of Higher Carrier Mobility of the Reduced Graphene Oxide-Zinc Telluride Nanocomposite on Efficient Charge Transfer Facility and the Photodecomposition of Rhodamine B.

The synthesis of solar-light-responsive zinc telluride (ZnTe) nanoparticles and their composite with reduced graphene oxide (rGO-ZnTe) via a simple hydrothermal reaction is reported. The synthesized nanostructures were comprehensively characterized by a combination of X-ray diffraction and photoelectron spectroscopy, electron microscopy, UV-vis spectroscopy, photoluminescence spectroscopy and thermogravimetric analysis. The effects of graphene oxide on the crystallinity, microstructure, photo-excitation, light absorption, surface area and thermal stability of ZnTe were studied. The current-voltage (I-V) characteristics for both as-synthesized ZnTe and rGO-ZnTe composite-based Schottky devices were measured to estimate the charge transport parameters such as dc conductivity, photosensitivity, carrier's mobility and lifetime. The photocatalytic performance of both the materials in the degradation of an azo dye (Rhodamine B) was subsequently investigated using simulated solar light. The rGO-ZnTe composite exhibited a higher photocatalytic activity (66%) as compared to the as-synthesized ZnTe (23%), essentially due to the synergy between rGO sheets and ZnTe nanoparticles. The role of the carrier's mobility in the transportation of photo-induced charges (electrons and holes) through the complex network of the composite materials and thus facilitating the photo-degradation process is explained. In the end, the responsible reactive species for the decomposition of Rhodamine B was also interpreted.

Anthracene-Based Fluorophore and Its Re(I) Complexes: Investigation of Electrical Properties and Schottky Diode Behavior.

A novel fluorophore (HL) [1-((E)-(quinolin-8-ylimino)methyl)anthracen-2-ol] using a suitably designed anthrol and quinoline derivative was synthesized and well characterized. Then, two Re(I) complexes with the fac-[Re(CO)3] + moiety were prepared with the ligand under different reaction conditions. Both the complexes [Re(L)(CO)3] (1) and [Re(HL)(CO)3Cl] (2) absorbed in the visible region. Steady-state fluorescence measurements and time-correlated single-photon count experiments were performed to elucidate the nature of the excited state. The ground- and excited-state geometries were theoretically investigated using density functional theory (DFT) calculations. The electrical properties of the ligand and the complexes have been explored with the help of a sandwich-structured thin-film device of an Al/sample/indium tin oxide (ITO) configuration at room temperature. The thermionic emission (TE) theory was adopted for the extraction of Schottky diode parameters such as ideality factor, barrier height, and series resistance. Further, the space-charge-limited current (SCLC) theory was employed for a better understanding of the charge transport phenomenon.

Phytochemical composition analysis and evaluation of in vitro medicinal properties and cytotoxicity of five wild weeds: A comparative study.

Background: Medicinal plants are a source of phytochemicals and they are used for the treatment of several oxidative stress-related or other diseases for their effectiveness, low toxicity and easy availability. Five traditionally used and less characterized herbaceous weeds of West Bengal, India, namely, Heliotropium indicum, Tridax procumbens, Cleome rutidosperma, Commelina benghalensis and Euphorbia hirta, were investigated for the current research study. Methods: Aqueous and 70% ethanolic extracts of the leaves were analyzed for estimation of essential phytochemicals and to evaluate their in vitro antioxidant status, medicinal properties and cytotoxic effects. To the best of our knowledge, several assays and comparative evaluations using these herbs are reported for the first time. For quantitative study, UV-vis spectrophotometry and high-performance liquid chromatography with diode array detector HPLC-DAD techniques were used. Antibacterial properties were investigated using the Kirby-Bauer disc diffusion method. For in vitro anti-lithiatic study, a titration method was used. The cell viability assay was done using peripheral blood mononuclear cells. Results: The aqueous extract exhibits higher content of polyphenols, flavonoids, tannins and inhibition percentage values for free radical scavenging assays, whereas the 70% ethanolic extract exhibits higher content of alkaloids and cardiac glycosides. HPLC-DAD analysis of 70% ethanolic extracts led us to identify 10 predominant phenolic constituents. Euphorbia hirta extracts showed minimum cytotoxicity (cell death ~2.5% and 4% in water and 70% ethanolic extract, respectively ), whereas Cleome rutidosperma and Tridax procumbens' 70% ethanolic extracts showed higher cell death (~13% and 28%, respectively), compared with the control (cell death ~10-12%). Conclusions: The study concluded that of all the medicinal weeds selected for the current study, Euphorbia hirta possesses the highest amount of bioactive compounds and hence exhibits the highest in vitro antioxidant activity and promising in vitro medicinal properties.

Designing of Pb(II)-Based Novel Coordination Polymers (CPs): Structural Elucidation and Optoelectronic Application.

[Pb2(bdc)1.5(aiz)] n (1) and [Pb2(bdc)1.5(aiz)(MeOH)2] n (2) (H2bdc = 1,4-benzene dicarboxylic acid, aiz = (E)-N'-(thiophen-2-ylmethylene)isonicotinohydrazide) have been synthesized, and structural characterization has been established by X-ray analysis and thermogravimetric analysis (TGA). Here, bdc2- links two Pb(II) centers and the aiz ligand binds the metal centers in two different manners: chelating and monodonating. Thus, polymerizations have taken place from the combination of mixed ligand system. Optical band gaps have been studied via UV measurements. Again, the experimental and calculated (from density functional theory (DFT)) band gaps agree well and the semiconducting properties of synthesized polymeric materials have been approved. Thus, optoelectronic and photonic devices can be made by this type of coordination polymers (CPs). The I-V representative curves of 1 (device-A) and 2 (device-B) in both dark and illuminated conditions show that device-A has a higher magnitude of current than device-B. Dark- and photo-conductivity values of device-A are calculated as 2.94 × 10-6 and 6.12 × 10-6 S m-1, respectively, whereas for device-B, the values of dark- and photo-conductivity are 2.92 × 10-7 and 3.66 × 10-7 S m-1, respectively, at room temperature.

Photosensitive Schottky barrier diode behavior of a semiconducting Co(iii)-Na complex with a compartmental Schiff base ligand.

The opto-electronic properties of an X-ray characterized, end-to-end azide bridged cobalt(iii)-sodium complex, [(N3)CoLNa(N3)] n , have been investigated in detail. The complex is found to be a direct semiconductor material as confirmed by determining the band gap of this complex by experimental as well as theoretical studies. The complex has also been used to construct a photosensitive Schottky device. Optical conductivity, calculated from the DFT study, has been used to analyze how the conductivity of the material changes upon illumination. The electrical conductivity and concomitantly, the photoconductivity of the material increase as a consequence of photon absorption.

Positron Annihilation Spectroscopic Investigation on the Origin of Temperature-Dependent Electrical Response in Methylammonium Lead Iodide Perovskite.

Organic-inorganic hybrid perovskite has appeared as one of the leading materials for realizing solution-based high-performing optoelectronic devices. The charge transport properties in this class of material are quite intriguing and still need to be carefully investigated. The temperature-dependent electrical property of methylammonium lead iodide (CH3NH3PbI3) has been investigated by employing positron annihilation spectroscopy (PAS), which unambiguously reveals the gradual formation of open volume defects with the enhancement in temperature. The high-temperature ionic conductivity is due to the generation of both cationic (CH3NH3+) and anionic (I-) vacancies, possibly because of the elimination of methylammonium iodide (CH3NH3I) as identified from the coincidence Doppler broadening (CDB) of the positron annihilation spectroscopy. Further, the evolution of temperature-dependent defect density and corresponding electrical responses has been correlated with the structural phase transitions of CH3NH3PbI3. This is the first ever report of temperature-dependent PAS measurement on hybrid lead halide perovskites to understand the nature and the origin of its electrical characteristics arising due to the variation in temperature.