Star-Shaped CuS Flat Nanoflakes Reinforced Ni(OH)(2) Nanosheets for Enhanced Capacitance

Enhanced electrochemical capacitance of 2D-nanosheets of Ni (OH)(2) via reinforcement of star-shaped CuS flat nanoflakes synthesized using in-situ hydrothermal root is presented. Microscopic and structural characterization suggest the inclusion of CuS nanoflakes in the films. Reinforced CuS nanoflakes offer high surface area resulting into open-sheet morphologies for Ni(OH)(2)@CuS films; contrasting with the folded sheet structures attained for the neat Ni(OH)(2) films. The remarkably high bulk (10(-3) Scm(-1)) conductivity of CuS enhances the conductivity and enable facile electron transport in the composites. Asymmetric supercapacitors constructed using Ni (OH)(2)@CuS and graphite as the electrodes is noted to show specific capacitances of 642 Fg(-1) at current density of 1 Ag-1, good rate capability and excellent cycling stability (86% capacitance retention at the end of 1000 cycles) relative to the neat Ni(OH)(2) based supercapacitor cells that shows specific capacitance of 142 Fg(-1) at the same current density. The direct contact of Ni(OH)(2) with the conductive CuS nanoflakes and highly porous structures of Ni(OH)(2)@ CuS electrodes doubles the power densities of the Ni(OH)(2)@ CuS supercapacitors than Ni(OH)(2) cells due to the low ion-diffusion resistances for charging by ions from the electrolyte, afforded by the short diffusion pathways in the composites

Plant leaf extracts as photocatalytic activity tailoring agents for BiOCl towards environmental remediation

The inducement of plant leaf extracts for the synthesis of various nanostructures has intrigued researchers across the earth to explore the mechanisms of biologically active compounds present in the plants. Herein, a green modified hydrolysis route has been employed for the synthesis of bismuth oxychloride i.e. BiOCl-N, BiOCl-T and BiOCl-A using plant extracts of Azadirachta indica (Neem), Ocimum sanctum (Tulsi), and Saraca indica (Ashoka), and; simultaneously, without plant extract (BiOCl-C), respectively. The as-prepared samples were examined by several microscopic and spectroscopic techniques which revealed that the biosynthesized BiOCl attained certain favorable features such as hierarchical nano-flower morphology, higher porosity, higher specific surface area and narrower band gap compared to BiOCl-C. The degradation of methyl orange (MO) and bisphenol A (BPA) using biosynthesized BiOCl were improved by 21.5% within 90 min and 18.2% within 600 min under visible light irradiation, respectively. The photocurrent response, electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) studies indicated the effective inhibition of the electron-hole pair recombination and enhanced photocatalytic activity of the biosynthesized BiOCl

Citrate-capped quantum dots of CdSe for the selective photometric detection of silver ions in aqueous solutions

A simple strategy for the synthesis of water soluble, luminescent, citrate-capped CdSe quantum dots (Q-CdSe) and their applications to selective detection of silver ions are described. The steady state photoluminescence (PL) spectra show single, narrow emission band at ca. 554 nm without any contribution from the trap states. The effect of various ions including physiologically important metal ions (viz. K+, Ca2+, Fe3+, Zn2+, Mg2+, Mn2+, Cu2+, Ag+, Pb2+ and Cd2+), on the PL intensity of citrate-capped Q-CdSe has been studied. Among these, selective luminescence quenching with Ag+ ion was found to be predominant. Under the optimum conditions, the response was linear between 1.7 and 18 μM. The quenching constant KSV was found to be ca. 3.4 × 105 M−1. The mechanism of photoluminescence quenching of Q-CdSe by metal ions (Ag+) is also discussed. Based on these studies, the potential use of Q-CdSe as a luminescent probe for the selective detection of silver ion has been proposed

Probing the crystal structure, composition-dependent absolute energy levels, and electrocatalytic properties of silver indium sulfide nanostructures

The absolute electronic energy levels in silver indium sulfide (AIS) nanocrystals (NCs) with varying compositions and crystallographic phases have been determined by using cyclic voltammetry. Different crystallographic phases, that is, metastable cubic, orthorhombic, monoclinic, and a mixture of cubic and orthorhombic AIS NCs, were studied. The band gap values estimated from the cyclic voltammetry measurements match well with the band gap values calculated from the diffuse reflectance spectra measurements. The AIS nanostructures were found to show good electrocatalytic activity towards the hydrogen evolution reaction (HER). Our results clearly establish that the electronic and electrocatalytic properties of AIS NCs are strongly sensitive to the composition and crystal structure of AIS NCs. Monoclinic AIS was found to be the most active HER electrocatalyst, with electrocatalytic activity that is almost comparable to the MoS_2^-based nanostructures reported in the literature, whereas cubic AIS was observed to be the least active of the studied crystallographic phases and compositions. In view of the HER activity and electronic band structure parameters observed herein, we hypothesize that the Fermi energy level of AIS NCs is an important factor that decides the electrocatalytic efficiency of these nanocomposites. The work presented herein, in addition to being the first of its kind regarding the composition and phase-dependence of electrochemical aspects of AIS NCs, also presents a simple solvothermal method for the synthesis of different crystallographic phases with various Ag/In molar ratios

Probing the Mechanism of Fluorescence Quenching of QDs by Co(III)-Complexes: Size of QD and Nature of the Complex Both Dictate Energy and Electron Transfer Processes

The decrease in photoluminescence (PL) of four different sized CdSe colloidal quantum dots (donors) has been investigated in the presence of three different Cobalt(III) complexes (acceptors). The steady-state and time-resolved PL (TRPL) spectroscopy have been used to investigate the mechanism of quenching. The complex concentration driven change in lifetimes of QDs and stronger PL quenching than predicted solely by TRPL data indicate that the quenching is neither purely static nor purely dynamic in nature. Further, the absence of any ground state complex absorption feature suggests that the static quenching contribution is due to the close proximity of the QDs fluorophores and deactivating sites of complexes. The dynamic quenching processes like diffusion mediated collisional quenching, Dexter energy transfer, and hole transfer have been methodically ruled out, leaving Forster resonant energy transfer (FRET) and the electron transfer (eT) between the QDs and complexes as the possible mechanisms. The Marcus model of eT has been successfully used to demonstrate the otherwise looking random trends of experimental eT rates. The apparent static contributions have been separated from the total quenching by normalization of steady state PL with TRPL data. Finally, FRET and eT mediated dynamic quenching in conjunction with the donor acceptor proximity driven static quenching was used to explain steady state PL quenching trends

Sustainable Upcycling of Nitrogen-Enriched Polybenzoxazine Thermosets into Nitrogen-Doped Carbon Materials for Contriving High-Performance Supercapacitors

Nitrogen-enriched polybenzoxazine thermosets derived from the ring-opening polymerization of side-chain-type benzoxazine-functionalized polyethylenimine resins (Bz-pei) have been previously reported by our group. In view of the appreciable nitrogen content and significant char yield, these thermosets have been envisioned as enticing carbon precursors and therefore have been sustainably upcycled to nitrogen-doped carbon materials. It is worth mentioning that the sustainable upcycling method should circumscribe energy as well as cost consumption, due to which carbon materials in the present work have been developed under moderate carbonization conditions, without chemical activation treatment. The developed nitrogen-doped carbon materials have been characterized by using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, elemental analysis, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The pore topography has been analyzed using scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis has been performed, while the Brunauer–Emmett–Teller (BET) surface area has been determined using nitrogen adsorption–desorption experiments. A comparison of the results obtained from electrochemical investigations performed in a three-electrode setup shows that carbon material upcycled from the guaiacol-based polybenzoxazine thermoset, exhibiting 6.4% nitrogen doping in the carbon framework (labeled as C-GP81), exhibits an impressive capacitance of 700 F g–1 at 10 A g–1 current density, suggesting excellent efficiency and rate capability of the obtained N-doped carbon-material-based supercapacitor electrodes. Furthermore, the carbon material designated as C-GP81 could deliver a maximum energy density (Ed) of 48 Wh kg–1 at a power density (Pd) of 8400 W kg–1 in a three-electrode configuration. The performance of the crafted supercapacitor device for the present study has surpassed the performance reported for polybenzoxazine-derived carbons. Additionally, the performance of carbon material labeled as C-GP81 has been evaluated for its potential as an active component in the electrodes of a symmetric device

Biofabricated BiOI with enhanced photocatalytic activity under visible light irradiation

In the recent past, there has been a large-scale utilization of plant extracts for the synthesis of various photocatalysts. The biofabrication technology eliminates the usage of harmful chemicals and serves as an eco-friendly approach for environmental remediation. Herein, a comparative analysis between bismuth oxyiodide synthesized via Azadirachta indica (neem) leaf extract (BiOI-G) and without leaf extract (BiOI-C) has been envisaged. The BiOI-G and BiOI-C samples were characterized by spectral and microscopic techniques, which revealed that the Azadirachta indica assisted BiOI-G attained enhanced features over BiOI-C such as narrower band gap, large surface area, porosity, increased absorption range of visible light and effectual splitting of the photogenerated e(-)-h(+) pairs. Benefiting from these enhanced features, BiOI-G degraded methyl orange (MO), rhodamine B (RhB), and benzotriazole (BT) at a significantly higher rate in comparison to BiOI-C. The degradation rate of MO, RhB and BT by BiOI-G was observed to be 1.3, 1.25 and 1.29 times higher in comparison to BiOI-C. Moreover, BiOI-G displayed high stability upto five cycles of the photocatalytic activity, which endow its effectiveness as a highly-efficient green photocatalyst

In situ solid-state synthesis of a AgNi/g-C₃N₄ nanocomposite for enhanced photoelectrochemical and photocatalytic activity

A graphitic carbon nitride (g-C₃N₄) polymer matrix was embedded with AgNi alloy nanoparticles using a simple and direct in situ solid-state heat treatment method to develop a novel AgNi/g-C₃N₄ photocatalyst. The characterization confirms that the AgNi alloy particles are homogeneously distributed throughout the g-C₃N₄ matrix. The catalyst shows excellent photoelectrochemical activity for water splitting with a maximum photocurrent density of 1.2 mA cm⁻², which is the highest reported for doped g-C₃N₄. Furthermore, a detailed experimental study of the photocatalytic degradation of Rhodamine B (RhB) dye using doped g-C₃N₄ showed the highest reported degradation efficiency of approximately 95 % after 90 min. The electronic conductivity increased upon incorporation of AgNi alloy nanoparticles on g-C₃N₄ and the material showed efficient charge carrier separation and transfer characteristics, which are responsible for the enhanced photoelectrochemical and photocatalytic performance under visible light