A Highly Sensitive Luminescent Upconversion Nanosensor for Turn-On Detection of As3.

A luminescent nanoprobe (NP), MnO2-modified Er3+/Yb3+-codoped Ag2MoO4 upconversion nanoparticles (UCNPs; cod-AMO-3/MnO2), was constructed for rapid, sensitive, and selective "turn-on" detection of trace As3+. Herein, two kinds of luminescent NPs were developed based on luminescence resonance energy transfer (LRET) between cod-AMO-3 as the energy donor and MnO2 as the energy acceptor. By using MnO2 as the matrix in cod-AMO-3/MnO2 fluorometric assay, the upconversion luminescence (UCL) intensity (IUCL) of the cod-AMO-3 probe was quenched significantly through LRET, illustrating MnO2 as an efficient quencher for UCL. With the addition of As3+, a stable bidentate binuclear (BB) corner-sharing bridged complex (As5+-MnO2) was probably formed, which alters the surface of the upconversion NP, leading to gradual separation between UCNPs and MnO2 and subsequent recovery of IUCL. Interestingly, it possessed superior sensitivity, reaction kinetics, and also high selectivity toward As3+ in aqueous solution. Our optimized cod-AMO-3/MnO2 nanocomposite (NComp) demonstrated a linear range of 0-150 ppb and an ultrasensitive detection limit of 0.028 ppb for As3+, which is extremely below the regulatory level, signifying the promising practical usage of this system. To the best of our knowledge, such a surface-modified Ln3+-codoped Ag-based nanosensor being applied for As3+ detection probably has not been reported yet, and it is rather unexplored. In a nutshell, the ability to monitor the As3+ concentration may enable the rational design of a convenient platform for a diverse range of environmental monitoring applications.

Tetraphenylporphyrin Decorated Bi2MoO6 Nanocomposite: Its Twin Affinity of Oxygen Reduction Reaction and Electrochemical Detection of 4-Nitrophenol.

A selective electrode for oxygen reduction reaction (ORR) and electrocatalytic reduction of 4-nitrophenol (p-NP) was fabricated on a glassy carbon electrode using organic-inorganic Bi2MoO6/H2TPP nanocomposites with different weight percentages of tetraphenylporphyrin, synthesized by the solvothermal process. Materials thus synthesized were characterized through UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analysis. The electrocatalytic performance of the modified electrode toward ORR in the 0.1 M KOH solution, the onset potential Eonset (0.942 V), E1/2 (0.704 V) vs RHE, Jd (-5.545 mA cm-2), and n = 4 physicochemical parameters were well appreciable. It exhibits good catalytic activity toward ORR through a four-electron pathway with excellent stability and high active site density, and thus, the in situ Porphy-decorated metal oxide system facilitates the electron transport process. High selectivity and efficacy for the oxygen reduction reaction (ORR) are a significant measure for several energy-converting applications. The decorated electrode, glassy carbon electrode (GCE)/Bi2MoO6/3 wt % Porphy, serves as an electrochemical sensor that exhibited good sensitivity (0.4683 µAµM-1 cm-2), good reproducibility, a low detection limit (0.0940 µM), and long-term stability in the aqueous phase without any appreciable effect in the presence of some common organic and inorganic interferences for the detection of p-NP in a linear concentration range of 0.5-350 µM. Therefore, the material performs as an effective electrode for both the ORR and the electrocatalytic reduction of p-NP with real matrix samples at room conditions.

One pot solvent assisted syntheses of Ag3SbS3 nanocrystals and exploring their phase dependent electrochemical behavior toward oxygen reduction reaction and visible light induced methanol oxidation reaction.

A huge variety of silver based ternary sulfide semiconductors (SCs) have been considered for the sustainable advancement of renewable energy sources. Herein, we have synthesized two important classes of newly emerging semiconductor nanocrystals (NCs) Ag3SbS3 (SAS), i.e. hexagonal and monoclinic by simply tuning the solvent polarity, of which the second one has been synthesized in a phase pure NC for the first time by the thermal decomposition of silver and antimony based dithiocarbamate (∼N-CS2-M) complexes. Interestingly, these two systems exhibit two different semiconducting (SC) properties and band gaps; hexagonal SAS has a p type (Eg ∼ 1.65 eV) whereas monoclinic SAS has an n type (Eg ∼ 2.1 eV) character. For the first time ever we have designed a reducing working electrode (i.e. cathode) by modifying the rotating disc electrode (RDE) with hexagonal SAS that exhibits excellent electrochemical oxygen reduction reaction (ORR) activity (Eonset = 1.09 V vs. RHE and average number of electron transfer: 3.89) comparable to that of the highly expensive Pt/C (Eonset = 0.88 V vs. RHE and average number of electron transfer: 3.92). Density functional theory (DFT) investigation confirms the corroborations of experimental data with theoretical implications. In addition, the electrode fabricated from monoclinic SAS acts as an efficient photoanode which exhibits higher photoelectrochemical (PEC) methanol oxidation reaction (MOR) activity under illumination in alkaline medium compared to that of standard TiO2 grown on an indium tin oxide (ITO) coated glass slide. On illumination, the relative photocurrent density at the onset potential has been obtained to be 845 which is a very significant experimental output with respect to any other TiO2 or Pt@TiO2 based photocatalysts for this application. The physicochemical stability and reusability of both materials were supported by 50 hours of extended electrochemical chronoamperometric measurements and powder XRD and the TEM analyses after electrocatalysis. This study explores a possible pathway for designing simple and less expensive but catalytically efficient silver based ternary sulfide NC systems for developing an SC material to reduce the energy crisis in the near future.

One Step Synthesis of a Gold/Ordered Mesoporous Carbon Composite Using a Hard Template Method for Electrocatalytic Oxidation of Methanol and Colorimetric Determination of Glutathione.

Ordered mesoporous carbon-supported gold nanoparticles (Au/OMC) have been fabricated in one step through a hard template method using gold nanoparticle-intercalated mesoporous silica (GMS) to explore two different catalytic properties, for example, electrocatalytic oxidation of methanol and colorimetric determination of glutathione (GSH). The catalytically inert but conducting nature of mesoporous carbon (OMC) and promising catalytic activity of gold nanoparticles (AuNPs) has inspired us to synthesize Au/OMC. The as-prepared Au/OMC catalyst was characterized by powder X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis-elemental mapping, and X-ray photoelectron spectroscopy. The characterization results indicate that AuNPs are uniformly distributed on the surface of OMC. The conducting-OMC framework with a high surface area of Au/OMC provides superior transport of electrons through the porous surface of carbon matrix and resulted in its high efficiency and stability as an electrocatalyst for the oxidation of methanol in comparison to CMK-3, SBA-15, and GMS in alkaline medium. The efficiency of Au/OMC toward methanol oxidation in alkaline medium is much higher in comparison to that in acidic medium. The lower value of I f/I b in the acidic medium in comparison to that in the alkaline medium clearly indicates that the oxidation process with Au/OMC as a catalyst is much more superior in alkaline medium with better tolerance toward the accumulation of intermediate CO species on the active surface area. Furthermore, the Au/OMC catalyst is successfully utilized for the detection and quantification of GSH spectrophotometrically with a limit of detection value of 0.604 nM.

Advanced catalytic performance of amorphous MoS2 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 touc's 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.

Single source precursor driven phase selective synthesis of Au-CuGaS2 heteronanostructures: an observation of plasmon enhanced photocurrent efficiency.

The design of new functional metal-semiconductor heteronanostructures with improved photovoltaic efficiencies has drawn significant attention because of their unprecedented properties and potential applications. Herein, we report a phase selective synthesis of ternary CuGaS2 (wurtzite and tetragonal) by simple solution based thermal decomposition of a new binuclear single molecular precursor [Ga(acda)3Cu(PPh3)2]NO3 (acda = 2-aminocyclopentene-1-dithiocarboxylic acid, PPh3 = triphenylphosphine) where the phase selectivity has been achieved easily by changing the combination of surface active agents. Furthermore, we have extended our approach to develop a well-controlled synthetic strategy for the preparation of a Au-CuGaS2 heteronanocomposite with both the phases. A detailed microscopic study reveals that during heterostructure synthesis, an epitaxial junction has been formed at the interface of ternary CuGaS2 and metallic Au. To find out the influence of this epitaxial connectivity on the properties, we have studied the photocurrent and photoresponse behavior of the material and compared them with that of bare CuGaS2. For both the wurtzite and tetragonal phases, the Au-CuGaS2 twin structure exhibits a plasmon enhanced superior charge transport ability and an abruptly high photocurrent density compared to that of pure CuGaS2. Due to efficient charge separation by strong plasmon-exciton coupling at the interface, Au-CuGaS2 can be used as a potential candidate for photoelectrochemical applications.