Search

Gold catalysts have been reported to be applied only for the Sonogashira-Hagihara reaction of iodobenzene and phenylacetylene under harsh reaction conditions, while the scope of the reaction has not been expanded for coupling reaction of other aryl halides and alkynes. In this investigation, a cost-effective, Pd-free catalyst based on mesoporous magnesium oxide supported bimetallic AuNi nanoparticles (m-MgO@AuNi) have been synthesized by hydrothermal method and its efficiency has been demonstrated in Sonogashira-Hagihara cross-coupling reaction. The m-MgO@AuNi nanocatalyst was structurally and morphologically characterized using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and the mesoporous structure of MgO has been confirmed through BET analysis. Using this palladium-free catalyst, Sonogashira-Hagihara coupling reaction of aryl iodides and aryl bromides with alkynes have been successfully performed and catalyst was recycled for several times. The results demonstrate that the synergistic effect between Au, Ni and mesoporous MgO support plays key role in enhancement of m-MgO@AuNi catalytic activity in Sonogashira-Hagihara reaction. Iran National Science Foundation (INSF-Grant number of 99023403), Ministerio de Ciencia, Innovación y Universidades (RED2018-102387-T, PID2019-107268GB-100), FEDER, the Generalitat Valenciana (IDIFEDER/2021/013), and the University of Alicante.

PdCu bimetallic nanoparticles with a diameter of about 3 nm are prepared and supported on a polymeric vinylimidazole ligand modified magnesium oxide. This new material is characterized using different analysis such as XRD, XPS, CHNS, TEM, SEM, and EDX-mapping. PdCu supported on MgO (MgO@PdCu) exhibits high catalytic activity in the Sonogashira coupling reaction of aryl iodides, bromides and chlorides with low Pd loading (0.05–0.2 mol%). This catalyst is recovered and recycled for 11 consecutive runs preserving its catalytic activity in the model reaction of iodobenzene with phenylacetylene for at least 8 cycles. Reused catalyst is characterized with TEM, XPS and EDX showing preservation of the catalyst structure. Using hot filtration and PVP poisoning tests, the catalyst shows a heterogeneous behavior for the model reaction. The authors are grateful to Institute for Advanced Studies in Basic Sciences (IASBS) Research Council and Iran National Science Foundation (INSF-Grant number of 95844587) for support of this work. C. Nájera is also thankful to the Spanish Ministerio de Economía y Competitividad (MINECO) (projects CTQ2013-43446-P and CTQ2014-51912-REDC), the Spanish Ministerio de Economía, Industria y Competitividad, Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER, EU) (projects CTQ2016-76782-P and CTQ2016-81797-REDC), the Generalitat Valenciana (PROMETEOII/2014/017) and the University of Alicante for financial support.

We report a facile, one pot solvothermal route to prepare ultrathin molybdenum disulfide supported on nanocarbon hybrid (MoS2@NCHy) network with varied mass loading of MoS2 (20 wt%, 40 wt% and 60 wt%) for catalyzing hydrogen evolution reaction (HER). A large current density of −451 mAcm−2 at an overpotential of −480 mV vs. RHE, proves 40 wt% MoS2@NCHy/GCE nanocomposite as a highly HER active catalytic material. This value was found to be 50 times, 6 times and 2.5 times higher compared to MoS2/GCE (−8 mAcm−2), 20 wt% MoS2@NCHy/GCE (−75 mAcm−2) and 60 wt% MoS2@NCHy/GCE (−180 mAcm−2) respectively. Meanwhile, η10 (overpotential required to attain a current density of −10 mAcm−2) is −186 mV for 40 wt% MoS2@NCHy/GCE, which is much lower to MoS2/GCE (−498 mV), NCHy/GCE (−334 mV), 20 wt% MoS2@NCHy/GCE (−264 mV) and 60 wt% MoS2@NCHy/GCE (−204 mV). The overall activity of the catalyst was manifested by the least overpotential, η10 = −186 mV vs. RHE, Tafel slope of 53 mVdec−1 and exchange current density (j0) of 6.3 × 10−2 mAcm−2. The superior performance of 40 wt% MoS2@NCHy should be attributed to the highly conductive and porous support of three dimensional NCHy architecture as well as the enlarged interlayer spacing of MoS2. This study paves a new paradigm to exploit the synergistic effect of MoS2 and NCHy resulting in strong electronic coupling for enhancement in the HER activity.

Highly monodispersed, mesoporous ZnO@Au heterojunction micro-spheres have been successfully synthesized using a two-stage facile chemical method and their surface bound NO2 sensing properties were explored. Room temperature Photoluminescence (RTPL) reveal the presence of high degree of oxygen defects and zinc interstitials for the pristine ZnO mesoporous-spheres and a drastic reduction in PL intensity of the ZnO@Au heterojunction mesoporous-spheres pointing towards the utilization of surface defects for the Au cluster growth, facilitating electron transfer process between ZnO and Au. NO2 gas sensor property analysis of the ZnO@Au mesoporous-spheres showed an extraordinary sensitivity and selectivity at a lower operating temperature of 250 °C than pristine ZnO mesoporous-spheres (450 °C). The enhanced sensing behavior of the ZnO@Au heterojunction mesoporous-spheres can be ascribed to the synergetic effect of Au nanoclusters at the heterojunctions which acts as spill-over zone for the physisorption mediated sensing process and the inherent high surface area and surface defects.

The development of hybrid materials with high pseudocapacitance and electrical double layer capacitance is an urge for the fabrication of efficient supercapacitor electrodes. Herein, a highly effective, easily performable, high-yielding, and economical method is demonstrated for the preparation of α -Fe2O3 nanorods incorporated defect-free graphene nanosheets that showed excellent supercapacitor performance. α -Fe2O3/graphene nanocomposite has been synthesized by an interlayer catalytic exfoliation of α -Fe2O3 intercalated graphite which showed high conductivity of 3.1 × 106 S/cm. α -Fe2O3/graphene nanocomposite modified carbon paste electrode exhibited ultrahigh specific capacitance values of 1135 mF/cm2 at a scan rate of 5 mV/s and 815 mF/cm2 at a current density of 0.5 mA/cm2. The fast ionic diffusion with no charge transfer resistance of the electrode material was revealed from the electrochemical impedance spectroscopic analysis. α -Fe2O3/graphene nanocomposite showed 100 folds of increase in the specific capacitance compared to α -Fe2O3 and graphene, suggesting their synergistic effect in the nanocomposite leading to a drastic increase in the specific capacitance. The composite displayed good cyclic stability of 79.9% retention of the initial capacitance after 1500 cycles and 54.9% after 10,000 repeated cycles.

Aquatic contamination from the accumulation of pharmaceuticals has induced severe toxicological impact to the ecological environment, especially from non-steroidal anti-inflammatory drugs (NSAIDs). Real-time monitoring of flutamide, which is a class of NSAIDs, is very significant in environmental protection. In this work, we have synthesized the hexagonal-h boron nitride decorated on bismuth oxide (Bi2O3/h-BN) based nanocomposite for the effective electrochemical detection of flutamide (FTM). The structural and morphological information of the heterostructured Bi2O3/h-BN nanocomposite was analyzed by using a sequence of characterization methods. Voltammetric techniques were used to evaluate the analytical performance of the Bi2O3/h-BN modified screen-printed carbon electrode (SPCE) for the FTM detection. The Bi2O3/h-BN modified SPCE displays a synergetic catalytic effect for the reduction of FTM due to large surface area, numerous active sites, fast charge transfer and abundant defects. The proposed electrochemical sensing platform demonstrates high selectivity, low detection limit (9.0 nM), good linear ranges (0.04–87 μM) and short response time for the detection of FTM. The feasibility of the electrochemical sensor has been proved by the successful application to determine FTM in environmental samples.

Mono-dispersed and small-sized bimetallic copper and palladium nanoparticles were successfully supported on phosphinite functionalized agarose biopolymer. The new material was characterized using various techniques such as solid state UV–vis and FT-IR spectroscopies, SEM, EDX, TGA, HRTEM, SAED, EDX-Map, and nitrogen adsorption–desorption analysis. The heterogeneous and recyclable catalyst has been used in Sonogashira coupling reaction of aryl iodides at room temperature and aryl bromides at 50 °C under low palladium loading conditions (0.05 mol %).

α-Fe2O3 functionalized, less-defective graphene sheets have been synthesized by a cost effective green solvent-assisted ultrasonication induced graphite exfoliation followed by hydrothermal method and its chemiresistive ammonia gas sensing properties have been investigated. The less-defective nature of graphene and the strong interaction of aromatic graphene network with α-Fe2O3 have been revealed from Raman spectroscopic and XPS and Raman spectroscopic analyses. The α-Fe2O3/graphene nanocomposite exhibited outstanding chemiresistive sensing properties towards NH3 gas, which is a toxic industrial pollutant. High sensor response, selectivity and repeatability are offered by the α-Fe2O3/graphene nanohybrid towards NH3 gas at 250 °C. The sensor response was linear in the range of 10–50 ppm with a regression coefficient of 0.95. A plausible sensing mechanism is suggested, indicating the role of both α-Fe2O3 and graphene leading to a synergistic response towards NH3.

Herein we report excellent gas sensor properties of Polyaniline functionalized multiwalled carbon nanotubes (PANI/MWCNTs) based nanocomposite for trace level detection of ammonia (NH3) gas. PANI/MWCNTs nanocomposite was synthesized by in-situ chemical oxidative polymerization of aniline monomer with carboxylated multiwalled carbon nanotubes (C-MWCNTs). The material was structurally characterized by UV–vis Spectroscopy, FT-IR Spectroscopy, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM). Uniform PANI layer with ∼7 nm thickness was formed on the external walls of the MWCNTs. The gas sensor properties of C-MWCNT and PANI/MWCNTs nanocomposite towards NH3 gas exposure at trace level concentrations (2–10 ppm) under ambient conditions were analyzed and their performances were compared. PANI/MWCNT nanocomposite based sensor exhibited excellent enhancement in sensor response and response/recovery characteristics with good reproducibility towards NH3 gas in comparison with C-MWCNT. The response and recovery time of the PANI/MWCNTs nanocomposite based sensor were found to be significantly improved in the order of a few seconds (6 s) towards NH3 gas. The results reveal the potential application of this sensor in monitoring trace level NH3 gas for varied applications.

A rapid synthesis route for hybrid ZnO@Au core–shell nanorods has been realized for ultrasensitive, trace-level NO2 gas sensor applications. ZnO nanorods and hybrid ZnO@Au core–shell nanorods are structurally analyzed using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Optical characterization using UV–visible (UV–vis), photoluminescence (PL) and Raman spectroscopies elucidate alteration in the percentage of defect and charge transport properties of ZnO@Au core–shell nanorods. The study reveals the accumulation of electrons at metal–semiconductor junctions leading to upward band bending for ZnO and thus favors direct electron transfer from ZnO to Au nanoclusters, which mitigates charge carrier recombination process. The operating temperature of ZnO@Au core–shell nanorods based sensor significantly decreased to 150 °C compared to alternate NO2 sensors (300 °C). Moreover, a linear sensor response in the range of 0.5–5 ppm of NO2 concentration was observed with a lowest detection limit of 500 ppb using conventional electrodes. The defects with deep level, observed in ZnO nanorods and hybrid ZnO@Au core–shell nanorods influences local electron density, which in-turn indirectly influence the gas sensing properties. The ZnO@Au core–shell nanorods based sensor exhibited good selectivity toward NO2 and was found to be very stable.

The present investigation is related to synthesis of high surface area lanthanum phosphate by an aqueous sol–gel process involving post gelation treatment by solvent exchange resulting in a soft agglomerated gel. Precursor sol, prepared from lanthanum nitrate through precipitation and peptization had an average particle size of 34 nm. The sol to gel transformation was carried out in presence of ammonia and resulted in a porous gel structure. Washing of the gel with different alcohols led to solvent exchange and subsequent drying resulted in the high surface area lanthanum phosphate. The surface area increased with the increase in boiling point of the alcohol used for washing. A surface area of 140 m 2 /g was obtained for the octanol washed lanthanum phosphate calcined at 400 °C.