Namrata Saha

Enhanced photocatalytic performance of morphologically tuned Bi2S3 NPs in the degradation of organic pollutants under visible light irradiation

Here in, morphologically tuned Bi2S3 NPs were successfully synthesized from a single-source precursor complex [Bi(ACDA)3] [HACDA=2-aminocyclopentene-1-dithiocarboxylic acid] by decomposing in various solvents using a simple solvothermal method. The as-obtained products were characterized by XRD, TEM, UV-vis spectroscopy and BET surface area measurements. Structural analyses revealed that the as-prepared Bi2S3 NPs can be tuned to different morphologies by varying various solvents and surfactants. The interplay of factors that influenced the size and morphology of the nanomaterials has been studied. Moreover, mastery over the morphology of nanoparticles enables control of their properties and enhancement of their usefulness for a given application. These materials emerged as a highly active visible light-driven photocatalyst towards degradation of methylene blue dye and the efficiencies are dependent on size and surface area of the NPs. In addition, photocatalytic degradation of highly toxic dichlorodiphenyltrichloroethane was studied using synthesized Bi2S3 NPs as catalyst and the rate of degradation has been found to be much better compared to that exhibited by commercial WO3. We believe that this new synthesis approach can be extended to the synthesis of other metal sulfide nanostructures and open new opportunities for device applications.

Enhanced photocatalytic activity of Eu-doped Bi2S3 nanoflowers for degradation of organic pollutants under visible light illumination

Europium (Eu)-doped Bi2S3 nanoparticles (NPs) with different Eu contents were successfully synthesized by solvothermal decomposition of the precursor complexes Bi(ACDA)3 and [Eu(ACDA)3·H2O] [ACDA = 2-aminocyclopentene-1-dithiocarboxylic acid] in ethylenediamine (EN). The precursors were characterized by usual techniques such as UV-vis and FT-IR spectroscopy, and CHN and TGA analyses. The prepared nanomaterials were characterized by XRD, EDX, SEM and TEM analyses. The XRD results demonstrate that the particles were highly crystallized. The TEM images ascertain the NPs to be of flower-like structure consisting of ultrathin nanoplates with an average diameter of 9–10 nm. Photocatalytic efficiency of the Eu-doped Bi2S3 NPs was evaluated by monitoring the degradation of methylene blue (MB) in aqueous solution under visible light. It was observed that the rate of photocatalytic degradation of MB increases with an increase in the amount of the dopant ion. In addition, the photocatalytic degradation of various toxic organic pollutants such as phenol, p-cresol, 4-chlorophenol, 4-tert-butylphenol, 2,5-dimethylphenol and 2,6-di-tert-butyl-p-cresol was carried out with doped NPs in visible light. Under identical conditions, the degradation rate of 4-chlorophenol is higher than the corresponding phenol, p-cresol and 4-tert-butylphenol. Finally, the mechanism of the degradation pathway for phenol and the substituted phenols is discussed.

Morphological tuning of Eu2O2S nanoparticles, manifestation of peroxidase-like activity and glucose assay use

Eu2O2S nanoparticles have been synthesized by solvothermal decomposition of the precursor complex [NHEt3]+[Eu(acda)4]−, wherein acda− is the anion of 2-aminocyclopentene-1-dithiocarboxylic acid. Oleylamine alone or in combination with surface active agents, such as trioctylphosphine or oleic acid, at 280 °C produced nanoparticles of three different morphologies, namely, ultrathin nanoplates, nanospheres and short rods. The optical band energy of the nanoparticles has been found to be 4.57(8) eV. Eu2O2S particles exhibit strong photoluminescence at room temperature with a quantum yield of about 4% upon excitation at 285 nm. All three forms display peroxidase-like activity towards the oxidation of 3,3′,5,5′-tetramethylbenzidine in the presence of H2O2 and follow a Michaelis–Menten enzymatic pathway. The mechanistic investigation reveals that the Eu3+/Eu2+ redox couple plays a crucial role behind this catalytic process. Catalytic efficiency of the nanoparticles decreases in the order plates > spheres > rod-like particles. Based on peroxidase activity, selective detection and estimation of glucose in the presence of related carbohydrates has been carried out.

Highly active spherical amorphous MoS2: facile synthesis and application in photocatalytic degradation of rose bengal dye and hydrogenation of nitroarenes

Herein, we developed a facile method to prepare amorphous spherical MoS2 via a simple solvothermal decomposition of a precursor complex MoO2(acda)2 (Hacda = 2-aminocyclopentene-1-dithiocarboxylic acid) in the presence of triethylenetetramine (TETA) as a solvent at 200 °C in an inert atmosphere. The as-obtained product was characterized by X-ray diffraction analysis (XRD), electron diffraction X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and UV-vis spectroscopic techniques. The transmission electron microscopic study ascertains the amorphous particles to be of spherical structure. The amorphous MoS2 has shown photocatalytic activity for the degradation of rose bengal (RB) dye under visible light illumination. The kinetics of the decomposition process was also investigated and found to show the pseudo-first-order reaction kinetics with rate constants of 5.0 × 10−2 min−1. Furthermore, amorphous MoS2 was found to be highly effective in catalyzing the reduction of a series of nitroarenes to the corresponding anilines by an eco-friendly protocol.

Observation of enhanced photocurrent response in M–CuInS2 (M = Au, Ag) heteronanostructures: phase selective synthesis and application

We report controlled synthesis of CuInS2 in wurtzite and zinc blende phases by solution based thermal decomposition of dual precursors [In(acda)3] (acda = 2-aminocyclopentene-1-dithiocarboxylic acid) and [Cu(PPh3)2(acda)] (PPh3 = triphenylphosphine) in the presence of appropriate surface-active agents. Furthermore, the preparation of M–CuInS2 (M = Au and Ag) heteronanostructures on both the phases has been achieved successfully by hot injection of respective gold and silver precursor solutions into the reaction mixture. The characterization of both pure and hybrid nanostructures was carried out by X-ray diffraction (XRD), UV-vis spectroscopy, energy dispersive X-ray (EDX) study and transmission electron microscopy (TEM). A detailed photovoltaic study has been performed with both pure materials and the twin structures and their photocurrent and photoresponse behavior have been compared. The study reveals that upon loading Au and Ag, the material exhibits high photocurrent efficiency compared to pure CuInS2. An appreciable increase in the light to dark current density ratio confirms that these materials can be used in the fabrication of promising photovoltaic devices.

Solvent assisted and solvent free orientation of growth of nanoscaled lanthanide sulfides: tuning of morphology and manifestation of photocatalytic behavior

A new class of precursor complexes Ln(acda)3(phen), (where Ln = Nd, Sm, Eu, Tb and Yb, acda− is the anion of 2-aminocyclopentene-1-dithiocarboxylic acid and phen stands for 1,10-phenanthroline) have been used to obtain phase pure lanthanide sulfide nanoparticles by solution-based as well as solution-free thermal treatments at inert conditions. During solution-phase thermolysis, long chain alkyl-amine solvents have been used to promote the reaction at much lower temperature (280 °C) than the solid-phase reaction (650 °C). A contrasting growth feature is observed for nano sulfides and consequently the shape of the material is varied from isotropic cube-like morphology to anisotropic short nanofibers according to the variation of surfactants. The study confirmed that the introduction of 1-dodecanethiol as a structure-modifying capping agent along with reacting amine significantly facilitates the anisotropic growth in a preferred direction. These have been characterized by XRD, TEM, FESEM, UV-vis spectroscopy and BET surface area measurements. The optical absorption data indicated a narrow band gap energy ranging from 1.71–1.97 eV for different EuS. The material emerged as a highly active visible light-driven photocatalyst among the lanthanide sulfides towards the degradation of organic dyes. A comparative catalytic study with morphologically different EuS revealed that the degradation rate changes with varying morphology and for all the dyes it strictly follows the decreasing order of sphere-like particles > cube-like particles > nanofibers.

Advanced catalytic performance of amorphous MoS 2 for degradation/reduction of organic pollutants in both individual and simultaneous fashion

A cluster [(S2)2Mo(S2)2Mo(S2)2], has been used to synthesise molybdenum sulfide microparticles (MPs) by solvothermal treatments under inert environment. During synthesis, surfactants i.e. oleylamine and dodecanthiol take part in chief role in shaping the morphology of MPs into ultrathin nano-fibre, and nano-rod. MPs have been characterized by X-ray diffraction analysis, energy dispersive X-ray spectroscopy, transmission electron microscopy and UV-vis spectroscopic techniques. The optical spectral data reveals a simultaneous presence of direct and indirect band gap in both MoS2. The material emerges as an effective catalyst towards the mineralization of different cationic dyes (rhodamine B and methylene blue) and anionic dye (rosebngal). These MPs have also been effectively used for the simultaneous degradations of different dyes in the same reaction mixture which make further highlighted the catalytic performances of MoS2. The above kinetics of the decomposition processes were examined and found to follow the pseudo-first-order reaction model. The plausible mechanism has been explained by comparing the position of conduction band levels of MoS2 (measured by Mott-schotky and toucs plot) and potential value of borohydride. We have also investigated the active species behind the degradation of dyes by using different scavengers. The new catalyst was also effective for the degradation of mixture of dyes to the same extent as it was in case of individual.