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One dimensional (1D) nanostructure like nanorods, nanowires, nanotubes and nanofibers have aroused great attention owing to their exceptional properties like high surface-to-volume ratio, excellent electron and thermal transport and also plays as interconnects during fabricating nanoscale devices. In this work, one dimensionally aligned Carbon nanofibers(CFs)@AuNPs-PtNPs/NiNPs-PtNPs have been developed via a single step co-axial electrospinning integrated with in-situ photo-reduction. The carbon nanofibers with in-situ functionalized bimetallic nanoparticles possessed well-defined core-shell structure with carbon nanofibers (CFs) as the core and AuNPs-PtNPs/NiNPs-PtNPs as the surface anchored heterojunctions. Homogeneously distributed AuNPs-PtNPs/Ni NPs-Pt NPs, which are identified as chemical sensitizers, triggers the dissociation of H2 through the spill-over effect, by successive diffusion of these H+ on carbon nanofiber surface, thereby altering the entire surface of the CFs into reaction sites for H2. Aligned core-shell CFs@Ni NPs-PtNPs possessed high sensitivity of 124% (v/v) at room temperature as compared with aligned core-shell CFs@PtNPs NPs (52%) and aligned core-shell CFs@AuNPs-PtNPs (65%), which may be due to the high catalytic adsorption and desorption properties of Ni and Pt towards hydrogen gas. Moreover, co-axially aligned CFs@NiNPs-PtNPs based sensor also demonstrates outstanding selectivity towards hydrogen compared to other gases like ammonia, ethanol, hydrogen sulphide, and acetone with excellent long-term stability. In addition, hydrogen adsorption kinetics of co-axially aligned CFs@NiNPs-PtNPs based sensor was verified theoretically the adsorption rate constant of (0.42) which showed a comparable experimental value (0.38) of adsorption rate constant. The potential suitability of co-axially aligned CFs@NiNPs-PtNPs based sensor towards H2 at room temperature leading towards real time applications also have been demonstrated

Flexible electronic gas sensors working at room temperature have acquired enormous attention in recent years due to their suitability to be integrated into various wearable electronic products. In ...

Herein, we report the formation of well-aligned ultrathin films of polyaniline-functionalized multiwalled carbon nanotubes (PANI@MWCNTs) with a high orientational order over a macroscopic area by L...

Interaction of water on heterogeneous nonwetting interfaces has fascinated researchers' attention for wider applications. Herein, we report the evolution of hierarchical micro-/nanostructures on superhydrophobic pseudoboehmite surfaces created from amorphous Al

Electrospun carbon nanofibers (CNF) with surface-anchored bimetallic gold–platinum nanoislands (CNFs@Au–Pt NIs) have been effectively developed by electrospinning and chemical reduction methods, an...

Herein, porous 1D n–p type ultra-long ZnO@Bi2O3 heterojunction nanorods have been synthesized by a solvothermal method and their complex charge transport characteristics pertaining to NO2 gas sensing properties have been investigated. The porous structure of the ZnO@Bi2O3 heterojunction nanorods assisted in achieving superior sensing properties compared to pristine ZnO nanorods. Temperature-dependent in situ electrical studies of the porous heterojunction nanorods explored the unique electron transport properties under different environments, which revealed the accumulation/depletion of electrons and charge carrier recombination leading to band bending at the metal oxide heterojunctions. The formation of electron depletion layers at n-ZnO/p-Bi2O3 interfaces is believed to increase the adsorption of oxidizing gas, resulting in a fast response time (10–12 s) and 10 times higher sensitivity than that of the ZnO nanorod-based sensor towards 500 ppb NO2. To study the structure–property correlation of the ultra-long ZnO@Bi2O3 heterojunction nanorods-based sensor, a crystallographic model supported by transmission electron microscopy analysis was adopted to understand the NO2 gas adsorption properties on the surface. The crystallographic model helps to visualize the dangling bonds and the ratio of metal to oxygen ions present at the exposed crystal planes. The results suggest that porous, ultralong n–p type ZnO@Bi2O3 heterojunction nanorods could be a promising candidate for a high performance NO2 sensor for real time applications.

Unique phosphorous doped onion-like carbon nanostructures (P-OLCs) with superior surface properties have been synthesized through a temperature and pressure controlled thermal decomposition method. The substitutional doping of phosphorous in OLCs nanostructures could facilitate the charge transfer during ammonia gas sensing. Presence of polar metaphosphates/phosphonate species in the active sites of highly crystalline P-OLCs due to interstitial doping of oxygen incorporated with substitutionally doped phosphorous atoms significantly enhanced the sensitivity with fast response and recovery characteristics (2.8 s and 4.5 s) towards NH3 at room temperature. Further, ammonia gas adsorption kinetics in OLCs and P-OLCs have been meticulously investigated which revealed the faster adsorption rate in P-OLCs (2.17 x 10-7 Ω-1s-1) compared to pristine OLCs (8.599 x 10-8 Ω-1s-1). This method can widely open up the feasibility to induce enhanced surface activity (phosphorus-containing groups allows the access of oxyge...

Herein, we demonstrate a novel approach for development of TiO2 grafted 2D-TiC nanosheets (TiO2@2D-TiC) based room temperature operable, flexible ethanol gas sensor. The homogeneous distribution, unique composition, and crystalline microstructure of TiO2 nanoparticles grafted 2D-TiC nanosheets have been found to enhance the surface reactivity and efficiency of its transducer–receptor functions. The electron–hole recombination at the TiO2/2D-TiC interfaces offered superior sensor performance with fast response and recovery times. Moreover, TiO2@2D-TiC nanosheets based flexible sensor exhibited high selectivity toward trace-level ethanol gas (10 ppb–60 ppm) with extremely low noise-to-signal ratio and excellent stability. The results suggest that the development of low-cost flexible sensors based on TiO2@2D-TiC nanosheets could be applied for potential applications, such as printed/wearable electronics, biomedical sector and environmental monitoring.

Herein, we report a facile approach for the synthesis of TiO2 nanoparticles tethered on 2D mixed valent vanadium oxide (VOx/TiO2) nanoflakelets using a thermal decomposition assisted hydrothermal method and investigation of its temperature-independent performance enhancement in oxygen-sensing properties. The material was structurally characterized using XRD, TEM, Raman, DSC, and XPS analysis. The presence of mixed valent states, such as V2O5 and VO2 in VOx, and the metastable properties of VO2 have been found to play crucial roles in the temperature-independent electrical conductivity of VOx/TiO2 nanoflakelets. Though pristine VOx exhibited characteristic semiconductor-to-metal transition of monoclinic VO2, pure VOx nanoflakelets exhibited poor sensitivity toward sensing oxygen. VOx/TiO2 nanoflakelets showed a very low temperature coefficient of resistance above 150 °C with improved sensitivity (35 times higher than VOx for 100 ppm) toward oxygen gas. VOx/TiO2 nanoflakelets exhibited much higher response,...

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.

An ultrasensitive and selective chemiresistive sensor interface based on Ag nanocluster integrated polyaniline functionalized multi-walled carbon nanotubes (AgNC@PANI/MWCNTs) has been developed for trace-level detection of NH3 gas at room temperature. AgNC@PANI/MWCNTs was synthesized using surfactant-free, one-pot wet-chemical process, by controlled integration of active Ag sites onto MWCNTs. The structure and morphology of AgNC@PANI/MWCNTs nanocomposite have been extensively studied by various characterization techniques. The gas sensing properties of AgNC@PANI/MWCNTs nanocomposite towards trace-level concentrations NH3 (2-10 ppm), an important biomarker in exhaled human breath, was systematically evaluated. The sensor exhibited dramatic enhancement in the sensor response (26 %), fast response (∼5 s) and recovery (∼4 s) characteristics with good reproducibility and selectivity upon exposure to NH3 gas. The excellent performance of the sensor towards NH3 could be attributed to the rapid electronic sensitization of surface engineered active AgNC sites in the composite in which oxidized AgNC were found to play a critical role. Effect of humidity and the kinetics of the NH3 gas adsorption on nanocomposite were analyzed. The possible interactions between NH3 and AgNC@PANI/MWCNTs nanocomposite were discussed. This investigation can pave the way to novel strategies for designing and fabricating low-cost, high performance NH3 gas sensors for clinical breath analyzer application.

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 %).

Charge transport and adsorption kinetics of wet-chemically synthesized CuO nanocuboids have been explored. The growth direction of CuO nanocuboids was found to be (111) plane, which exhibited predominant surface catalytic activity toward the dissociation of H2S and O2. Temperature-dependent adsorption studies revealed the adsorption kinetics of (111) grown p-type CuO nanocuboids toward H2S gas. Adsorption of oxygen (O2) on the CuO (111) surface resulted in the formation of ionosorbed O2¯ species, which increased the hole density and enhanced the surface conductivity of CuO nanocuboids. H2S molecules were found to interact well with CuO (111) surface, donating electrons to the material and reducing the hole-accumulation layer width. Investigation of electrical characteristics of p-type CuO nanocuboids revealed absence of any structural phase transitions under H2S environment. The H2S sensing mechanism was found to be associated with local suppression/expansion of the hole-accumulation layer of p-CuO nanocu...

Novel copper nanoparticles supported on starch micro particles (CuNPs@MS) were prepared successfully and characterized by SEM, EDX, TEM, SAED, TGA, XPS, and XRD analyses. The easily synthesized and thermally stable CuNPs@MS have been applied as a green, degradable, and eco-friendly catalyst in a three component reaction of amines, aldehydes and alkynes for the preparation of diverse propargylamines. The reactions were performed under heterogeneous conditions and the catalyst was successfully recycled for five consecutive runs with a small decrease in activity.

Understanding the origin of magnetic ordering in an undoped semiconductor with native defects is an open question, which is being explored actively in research. In this investigation, the interplay between magnetic ordering and excess induced native defects in undoped anatase TiO2 nanoparticles is explained using an experimental and theoretical approach. It is demonstrated that structurally disordered TiO2 nanoparticles with a high concentration of native defects such as titanium interstitials and oxygen vacancies are synthesized using controlled atmospheric rapid cooling (i.e. quenching) process. The structural disorders in the lattice have been examined using various spectroscopic and microscopic analyses revealed the existence of Ti deficiency in both pristine and quenched TiO2 nanoparticles. A possible origin of magnetic ordering in titanium deficient anatase TiO2 system is elucidated based on first-principle calculations. It was found that the overall magnetic moment of Ti deficient TiO2 system is determined by the distance between Ti interstitials and its neighboring vacancies (i.e. either V Ti or V Os). However, quenched TiO2 nanoparticles possess excess Ti interstitials, Ti and O vacancies and therefore the net magnetic moment of the system is reduced due to anti-ferromagnetically coupled neighboring Tilattice ions.

Introduction: Hydrogen is one of the most promising sources of energy for next generation power and transportation sectors.Owing to the inflammable properties of H2 gas, it is highly essential to develop technologies for its rapid detection to ensure safety and leakage detection in various application domains. In this regard, researchers have focused their attention on development of new chemical sensors based on solid electrolytes, metal oxides, polymers and carbon-based gas sensors [1-2]. Among these materials, carbon-based gas sensors have received immense attention owing to their exceptional structural properties, including high electrical conductivity, chemical and thermal stability and high surface area. Especially, carbon nanofibers (CNFs) have earned significant attention due to their notable electrical conductivity and stability with tailor-made one-dimensional structures. But, the sensors made of CNFs are less explored due to selectivity issues. Integration of catalytically active metal nanoparticles onto 1-D carbon nanostructures have been attempted by many groups [3-4]. For sensing hydrogen, expensive Pt catalysts have shown excellent performance. In order to improve the sensitivity at affordable cost, it is proposed that Pt can be used on mesoporous carbon nanofibers (pCNF). Herein, we report development of a novel room-temperature hydrogen sensor based on Pt@pCNF nanohybrids fabricated by electrospinning. Gas sensing properties were systematically investigated towards trace level detection of hydrogen gas which showed enhanced hydrogen sensing properties at room temperature with fast response/recovery time. Synthesis of Pt@pCNF nanohybrids: Carbon nanofibers were fabricated using electrospinning technique. The electrospun PAN fibers collected on copper sheet were subjected to a two-step thermal process to convert into carbon nanofibers by a stabilization (280°C) step followed by carbonization (800°C) in air and N2 atmosphere with a ramping rate of 2°C/min and 3°C/min by holding time of 1hr. Platinum nanoparticles were chemically deposited on functionalized carbon nanofibers via urea assisted ethylene glycol synthesis method. For fabrication of mesoporous carbon nanofibers (pCNF), NaHCO3 nanoparticles were used as pore forming agent during electrospinning process which was thermally decomposed for introduction of mesopores in carbon nanofibers. Results and Discussion: XRD patterns of Pt@CNF and Pt@pCNF confirms the fcc structure, which corresponds to (111), (200), (220) and (222) planes of Platinum (JCPDS card 04-0802). A broad diffraction peak was appeared at 24.7° in CNF@Pt nanohybrids, which is ascribed to the amorphous phase of carbon ((002) plane) in the carbon nanofibers assigned to hexagonal graphite (JCPDS card 41-1487). The Pt formed over the surface of CNFs exhibited evident diffraction peaks, signifying the formation and favorable crystallization of Pt@CNF and Pt@pCNF nanohybrids. Further structural characterization of the monometallic nanoislands was performed using HRTEM analysis. The lattice d-spacing of 0.227 nm corresponds to the (111) crystalline plane of face centered cubic crystal structure of Pt on the surface of Pt@CNF. Porous structure of carbon nanofibers where studied using HRTEM and SEM analysis. These results indicate that homogenous distribution of Pt nanoparticles over CNF and pCNF. Evaluation of Hydrogen gas sensor properties: H2 gas sensing properties of Pt@CNF and Pt@pCNF nanohybrids were evaluated using in-house gas sensor test station at room temperature. The dynamic gas sensing response of Pt@pCNF nanohybrids towards trace level detection of hydrogen from 0.1% to 4% exhibited sensitivity in the range of 6% to 47% at room temperature. Gas sensing response of CNFs with surface anchored platinum nanoparticles is due to high adsorption property of H2 on monometallic active sites. Upon exposure to H2 gas, H2 molecules initially physisorbed on the sensor and later chemisorbed. Due to this process, work function of the platinum is lowered and hence electron transfer occurs from platinum to supporting materials. Hence, the resistance decreases due to the accumulation of electrons which is evident from the gas sensing response of Pt@pCNF upon exposure to reducing gas, like H2. References: Korotcenkov, S. D. Han, and J. R. Stetter, Review of Electrochemical Hydrogen Sensors, Chem. Rev. (2009) 109, 1402–1433,doi: 10.1021/cr800339k. Hübert, L. Boon-Brett, G. Black, U. Banach, Hydrogen sensors – A review, Sensors and Actuators B 157 (2011) 329– 352, doi: 10.1016/j.snb.2011.04.070. Wang, S. Rathi, B. Singh, I. Lee, H. Joh and G. Kim, Alternating Current Dielectrophoresis Optimization of Pt-Decorated Graphene Oxide Nanostructures for Proficient Hydrogen Gas Sensor, ACS Appl. Mater. Interfaces 2015, 7, 13768-13775, doi: 10.1021/acsami.5b01329. Jung, M. Han, and G. S. Lee , Fast-response room temperature hydrogen gas sensors using Pt-coated spin-capable carbon nanotubes, ACS Appl. Mater. Interfaces,2015, doi: 10.1021/am506578j.

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.

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.

In the present study, highly monodispersed polyaniline (PANI) and gold nanoparticles grafted PANI nanospheres (Au@PANI) have been fabricated through a facile wet-chemical synthesis process by in-situ polymerization of aniline. The structural characterization of the PANI and Au@PANI nanospheres were carried out by UV-Vis spectroscopy, FT-IR spectroscopy, and High Resolution Transmission Electron Microscopy (HR-TEM). Stable uniform sized nanospheres of PANI and Au@PANI obtained were found to exhibit superior gas sensor performance towards trace-level concentration of ammonia (NH3) gas in the range of 1-5 ppm. A comparative analysis of the sensor properties of PANI and Au@PANI nanospheres were performed under ambient conditions. Au@PANI nanospheres exhibited enhanced gas sensing performance with high sensitivity (58.2%), rapid response (48 s) and recovery (58 s) characteristics (1 ppm of NH3). The results indicate the potential use of Au@PANI nanospheres for fabrication of efficient NH3 sensors for varied applications.