Anindita Roy

Morphology Controlled Synthesis of SnS2 Nanomaterial for Promoting Photocatalytic Reduction of Aqueous Cr(VI) under Visible Light

A mild, template free protocol has been demonstrated for SnS2 nanoflake formation at the gram level from SnCl2 and thioacetamide (TAA). The SnS2 nanoflakes congregate to nanoflowers and nanoyarns with variable TAA concentrations. BET measurements reveal that the synthesized nanomaterials are highly porous having very high surface area, and the nanoflower has higher surface area than the nanoyarn. The synthesized nanomaterial finds application for promoting photoreduction of extremely toxic and lethal Cr(VI) under visible light irradiation due to their porous nature. The nanoflowers photocatalyst is proved to be superior to nanoyarn due to the increased surface area and higher pore volume. It was also inferred that increased pH decreased the reaction rate. The present result suggests that the morphology-dependent photoreduction of Cr(VI) by SnS2 nanomaterial under visible light exposure will endorse a new technique for harvesting energy and purification of wastewater.

Mesoporous Gold and Palladium Nanoleaves from Liquid−Liquid Interface: Enhanced Catalytic Activity of the Palladium Analogue toward Hydrazine-Assisted Room-Temperature 4‑Nitrophenol Reduction

The importance of an interfacial reaction to obtain mesoporous leafy nanostructures of gold and palladium has been reported. A new synthetic strategy involving 1,4-dihydropyridine ester (DHPE) as a potential reducing agent performs exceptionally well for the desired morphologies of both the noble metals at room temperature. The DHPE in turn transforms into its oxidized aromatic form. The as-synthesized gold leaves exhibit high surface-enhanced Raman scattering activity with rhodamine 6G (R6G) due to their hyperbranched structure. It is worthwhile that as-synthesized porous architectures of palladium support the room-temperature hydrogenation of 4-nitrophenol (4-NP) by hydrazine hydrate (N2H4·H2O), reported for the first time. Furthermore, MPL exhibits exceptionally good catalytic activity toward electrooxidation of formic acid. Therefore, an aromaticity driven synthetic technique achieves a rationale to design leafy nanostructures of noble metals from the liquid-liquid interface for multifaceted applications.

Au@Pd core–shell nanoparticles-decorated reduced graphene oxide: a highly sensitive and selective platform for electrochemical detection of hydrazine

The tailored fabrication of noble metal-based bimetallic nanoparticles-decorated reduced graphene oxide (rGO) is highly demanding for its use as a clean and recyclable substrate for electrochemical performances. Herein, we have successfully prepared Aucore@Pdshell with an average size of ∼11.5 nm on an rGO support (denoted as GAP) through a surfactant-free one-step synthetic protocol. The use of 2-propanol as a solvent as well as a reducing agent for the precursors demonstrates that the designed process is economically preferable for the scalable synthesis of the desired GAP material. Comparative electrocatalytic efficiency in terms of hydrazine (N2H4) oxidation reveals the optimized noble-metal loading on rGO nanosheets and also the composition to capitalize maximum advantage from the as-synthesized GAP material. The most effective electrocatalyst, GAP3 with optimized constituents, was then applied as a substrate to electrochemically determine N2H4 down to a trace concentration level with high selectivity and sensitivity. The limit of detection (LOD) from GAP3 is calculated to be 0.08 μM with a linear range of 2–40 μM from the chronoamperometric (CA) result at −0.15 V vs. SCE. The novelty of N2H4 detection by the designed substrate becomes evident while all of the related reports are reviewed. This electrochemical sensor was successfully applied further to detect trace-level N2H4 in various real water samples, indicating its promising practical application.

Conductivity, thermal stability, dielectric and morphological characteristics of poly(N-vinylcarbazole) prepared in aqueous suspension

Abstract Suspension polymerization of N -vinylcarbazole in toluene/water solvent induced by FeCl 3 in varying mole ratios with the monomer, yields a polymer with appreciably higher specific conductivity (∼1 × 10 −4 S cm −1 ) than that of a conventionally prepared poly( N -vinylcarbazole) (PNVC). Thermal stability, morphology and dielectric characteristics of suspension-polymerized PNVC have also been studied.

A facile synthesis of 1D nano structured selenium and Au decorated nano selenium: catalysts for the clock reaction

Elemental selenium nanowires (Se NWs) are obtained from the easily available, less-toxic, low-cost reagents sodium selenite and ethylenediamine (en) through a modified hydrothermal reaction (MHT). The reaction supports the habitual growth of selenium nanowires and the amine molecules act as a reducing agent. Then, an interesting galvanic exchange reaction deposits Au nanoparticles on the as-synthesized Se evolving an Au decorated composite material. But a similar galvanic exchange produces Ag2Se because of the lower diffusion activation energy of Ag. Selenium nanowires, even as metalloids, have been found to catalyze the reduction of methylene blue (MB) using NaBH4 as a reducing agent. The blue colour of MB vanishes due to the formation of leucomethylene blue (LMB). On shaking the reaction mixture, the blue colour reappears by aerial oxidation. This oscillation of reversible colour change is taken as a clock reaction. The reversible reaction is monitored by a UV-visible spectrophotometer with respect to the absorbance of MB at λmax = 663 nm. Common reducing agents such as hydrazine hydrate, ammonium thiocyanate and glucose do not show this stunning phenomenon. Sodium borohydride fails to assist the reduction process in the presence of bulk selenium. The reduction process proceeds through two steps. Initially, the rate is slower due to an ‘induction period’ and then it becomes facile. A higher catalyst dose reduces the time lag, i.e., the induction period. The Se NWs performed well for about 30–50 cycles for a clock reaction set up. Finally, the composite materials have been found to exhibit a faster clock reaction cycle in comparison to neat Se NWs.

O-chloranil initiated polymerization of pyrrole in presence of N-vinylcarbazole and some properties of the polymer

Abstract The polymerization of a mixture of N-vinylcarbazole (NVC) and pyrrole (PY) by O-chloranil in toluene yields an insoluble black polymer P(PY-NVC) which exhibits properties distinct from PPY or PNVC. The inclusion of either monomer moieties in P(PY-NVC) has been endorsed by IR spectroscopy. Kinetics of PPY-OCA homopolymerization and of PY-NVC-OCA copolymerization have been elucidated. TGA reveals the stability order as PNVC > P(PY-NVC) > PPY. DSC analyses reveal a single inflection for P(PY-NVC) around (198–202 °C) and for PPY and PNVC around 180 and 228 °C respectively. PPY exhibits a high dielectric constant (~ 350) at 10 Hz while P(PY-NVC) or PNVC exhibit values (~ 11) and (~5) respectively—the dielectric constant falling consistently with increasing frequency as does the dielectric loss parameter also—suggesting interfacial polarization. P(PY-NVC) shows maximum d.c. conductivity of 3.5 x 10 −6 ohm −1 cm −1 depending on [PY]/[NVC] mole ratio. For PPY, the conductivity is in the range (10 −3 –10 −5 )ohm −1 cm −1 and the conductivity in all these polymers is dependent on the concentrations of the monomers, O-CA and runs parallel to the trend in conversion.

Facile synthesis of pyridine intercalated ultra-long V2O5 nanowire from commercial V2O5: catalytic applications in selective dye degradation

The synthesis of exclusive ultra-long nanowire (NW) mediated by the inherent intercalative properties of vanadium pentoxide (V2O5) has been reported using a pyridine–nitric acid (Py–HNO3) system. It is worth noting that the introduction of HNO3 in the reaction mixture as an additive with pyridine generates vanadium oxide with only the V(+V) oxidation state, as ascertained from XPS analysis, whereas pyridine itself produces vanadium oxide with V with mixed valences. The method is proved to be an energy efficient, and time and cost effective proposition for the production of an industrially important oxidant without any surfactant or template. Then, the as-produced V2O5 leads to the efficient oxidative degradation of dyes without the use of any extra oxidising agent. It has been shown that the oxidation of the dyes complies with the electrostatically allowed ‘adsorption–oxidation–desorption’ mechanism.

A conductive poly(N-vinylcarbazole)-carbon black composite

Abstract Carbon black initiated poly(N-vinylcarbazole) yields a composit which exhibits a conductivity as high as 1 Ω −1 cm −1 . The value is the highest ever reported for poly(N-vinylcarbazole)-based systems.

Evolution of tubular copper sulfide nanostructures from copper(I)–metal organic precursor: a superior platform for the removal of Hg(II) and Pb(II) ions

A wet-chemical reaction strategy has been adopted for the exclusive production of porous copper sulfide using an aqueous solution of copper chloride (CuCl2·2H2O), which acts as a precursor salt, and thioacetamide (TAA) with prolonged standing at room temperature (∼25 °C). The mixed phase copper(I) sulfide with tubular porous morphology has been derived from rod-shaped, white-colored Cu(I) metal organic complex through an auto degenerative hollowing. The importance of chloride ions for obtaining mixed phase copper sulfide has been proved unequivocally. Porous copper sulfide showed outstanding removal efficiency towards two toxic heavy metal ions, i.e. Hg(II) and Pb(II), which certifies the strong interaction between these metal ions and S2− based on the SHAB (soft hard acid base) principle, and a cation exchange mechanism emerges out at the tubular surface as confirmed by various spectroscopic techniques. The as-synthesized product shows removal capacity of 3096 and 2787 mg g−1 for Hg(II) and Pb(II), respectively. Thus, mixed phase copper(I) sulfide stands to be a highly effective substrate for environmental abatement application.

Micelle confined mechanistic pathway for 4-nitrophenol reduction

The model 4-nitrophenol reduction has been carried out by different groups in presence of metallic or even non-metallic catalyst elaborating different mechanistic aspects. In the present investigation, we have thoroughly studied the hydrogenation of 4-nitrophenol in a completely metal free homogeneous condition. The introduction of a non-fluorescent probe unequivocally generates a fluorescent molecule that indirectly justifies the anion radical stabilization in the micelle. The reduction mechanism under metal-free condition was proposed and the concept of stabilization of anion radical transition state of 4-nitrophenol at the positively charged Stern layer of anionic micelle was established. The plausible reduction mechanism has also enlightened the graphene-like conducting property of Stern layer of the homogeneous micellar system. Furthermore, the confinement effect for catalysis has also been authenticated by supporting experimental evidences. The borrowed concept of catalysis in confinement drives the catalytic study to a new era of catalysis.