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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

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.

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 ...

Production and alignment of heterojunction metal oxide semiconductor nanomaterial-based sensing elements for microsensor devices have always posed fabrication challenges since they involve multi-step synthesis processes. Herein, we demonstrate a coaxial electrospinning with an in situ photoreduction process for the fabrication of MEMS-compatible, 1D aligned gold nanoisland (GNI) anchored ZnO-based Heterojunction Nanofibers (HNFs) and their complex plasmon-mediated NO2 gas sensing mechanism has been investigated using operando photoluminescence studies. Evaluation of the gas sensing properties of aligned ZnO-GNI HNFs has exhibited excellent sensor response (196%) with rapid response time towards 500 ppb NO2 gas at reduced operating temperature (200 °C). Operando studies using photoluminescence and electrical measurements ascertained the existence of supplementary active sites in the multicrystalline nanofibers owing to the existence of Au nanograins over aligned ZnO nanofibers (NFs), thereby inducing a spill-over zone and aiding the charge transfer phenomenon. The operando PL studies also revealed the plasmonic effect of metallic Au and the role of zinc interstitial (Zni) defects and oxygen vacancies (V+o), which influence the charge transfer between ZnO and surface anchored Au nanoislands. This study revealed atomistic insights into the structural defects and charge transport properties of metal oxide semiconductor heterojunction materials, and the coaxial integration method of 1D aligned ZnO-GNI HNFs paves the way for unique strategies and the development of suitable MEMS based gas sensors for real-time applications.

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...

A comparative analysis of NO2 gas sensing performances of geometry-controlled Au decorated ZnO heterojunction nanostructures (nanospheres, nanorods, ultra-long nanorods and nanofibers) has been dem...

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, n–n type one dimensional ZnO@In2O3 heterojunction nanowires have been developed and their local electron transport properties during trace-level NO2 gas sensing process have been probed at room-temperature using conducting probe atomic microscopy. Solvothermally synthesized 1D ZnO@In2O3 heterojunction nanowires have been characterized by various spectroscopic and microscopic techniques, which revealed the mesoporous structure indicating their enhanced sensing properties. The dangling bonds and fraction of metal ions to oxygen ions existing on the exposed crystal facets of the heterojunction nanowires have been visualized by employing crystallographic simulations with TEM analysis, which aided in forecasting the nature of surface adsorption of NO2 gas species. In situ electrical characteristics and Scanning Spreading Resistance Microscopic (SSRM) imaging of single ZnO@In2O3 heterojunction nanowires revealed the local charge transport properties in n–n type ZnO@In2O3 heterojunction nanowires. Moreover, the ZnO@In2O3 heterojunction nanowires based sensor exhibited excellent sensitivity (S = 274%), a fast response (4–6 s) and high selectivity towards trace-level concentration (500 ppb) of NO2 gas under ambient conditions with low power consumption. Spatially resolved surface potential (SP) variations in ZnO@In2O3 heterojunction nanowires have been visualized using in situ Scanning Kelvin Probe Force Microscopy (SKPM) under NO2 gas environment at room temperature, which was further correlated with its energy band structure. The work functions of the material evaluated by SKPM reveal considerable changes in the energy band structure owing to the local electron transport between ZnO and In2O3 at the heterojunctions upon exposure to NO2 gas indicating the charge carrier recombination. A plausible mechanism has been proposed based on the experimental evidences. The results suggest that new insights into complex sensing mechanisms deduced from the present investigation on n–n type MOS based heterojunction nanowires under ambient conditions can pave the way for the novel design and development of affordable and superior real-time gas sensors.

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.

We report a one-dimensional titanium dioxide encapsulated with gold heterojunction nanofibers (TiO

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.

A 3D porous nitrogen-doped graphene foam with a uniformly grafted platinum electrocatalyst (2–3 nm) (3D-Pt@N-graphene foam) has been developed using a simple hydrothermal synthesis for high performance proton exchange membrane (PEM) fuel cells. Excellent electrocatalytic activity towards the ORR in acidic medium has been exhibited by Pt@N-graphene foam with a favorable 4-electron transfer pathway resulting in the augmentation of active triple phase boundary sites. The positive shift of onset potential (989 mV) and half wave potential (895 mV) with a high limiting current density of 4.675 mA cm−2 exhibited by the 3D-Pt@N-graphene foam was found to be comparatively greater than that of the Pt/C catalyst with high durability. The presence of pyridinic-N and pyrrolic-N species in the highly compressible 3D-Pt@N-graphene foam contributed to the enhancement of the electrocatalytic activity, while graphitic-N improved the electrical conductivity of the material facilitating the electron transport during the ORR process. Compared to the commercial Pt/C electrocatalyst, the 3D-Pt@N-graphene foam based on a membrane electrode assembly exhibited four times higher power density (394 mW cm−2) and current density (1036 mA cm−2) owing to the favorable mass transport due to the hierarchical porous network, high specific surface area, nitrogen doping, uniform distribution of Pt nanoparticles and abundant active sites on the support material. The material demonstrates a new rational design for the fabrication of a highly efficient electrocatalyst assembly for flexible PEMFCs.

Herein, we have successfully developed an integrated strategy to develop antireflective coatings with self-cleaning capabilities based on periodic double-sided photonic γ-AlOOH nanostructures to transmit maximum incident light photons. Interfacial reflections are instinctive and one of the fundamental phenomena occurring at interfaces owing to refractive index mismatch. The eradication of such undesirable light reflection is of significant consideration in many optical devices. A systematic approach was carried out to eradicate surface reflection and enhance optical transmission by tailored γ-AlOOH nanostructures. The γ-AlOOH photonic nanostructures with subwavelength features exhibited a gradient index, which almost eliminated the refractive index mismatch at the interface. Optical transmittance of 97% was achieved in the range of 350-800 nm at normal incidence compared to uncoated glass (89%). A multilayer model approach was adopted to extract the effective refractive index of the coating, which showed a graded index from the top to the bottom surface. Further, to fully comprehend the optics of these nanostructures, the omnidirectional (20-70°) antireflective property has been explored using variable-angle specular reflectance spectroscopy. The hierarchical γ-AlOOH nanostructures exhibited only ∼1.3% reflectance at the lower incident angle in the visible spectra and an average reflectance of ∼7.6% up to an incident angle of 70°. Moreover, the hierarchical nanostructures manifested contact angle (CA) >172° and roll-off angle (RA)

Corona Virus Disease 19 (COVID-19) pandemic has created an alarming situation across the globe. Varieties of diagnostic protocols are being developed for the diagnosis of COVID-19. Many of these diagnostic protocols however, have limitations such as for example unacceptable no of false-positive and false-negative cases, particularly during the early stages of infection. At present, the real-time (quantitative) reverse transcriptase-polymerase chain reaction (RT-PCR) is considered the gold standard for COVID-19 diagnosis. However, RT-PCR based tests are complex, expensive, time consuming and involve pre-processing of samples. A swift, sensitive, inexpensive protocol for mass screening is urgently needed to contain this pandemic. There is urgent need to harness new powerful technologies for accurate detection not only of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) but also combating the emergence of pandemics of new viruses as well. To overcome the current challenges, the authors propose a diagnostic protocol based on surface-enhanced Raman Spectroscopy (SERS) coupled with microfluidic devices containing integrated microchannels functionalized either with vertically aligned Au/Ag coated carbon nanotubes or with disposable electrospun micro/nano-filter membranes. These devices have the potential to successfully trap viruses from diverse biological fluids/secretions including saliva, nasopharyngeal, tear etc. These can thus enrich the viral titre and enable accurate identification of the viruses from their respective Raman signatures. If the device is successfully developed and proven to detect target viruses, it would facilitate rapid screening of symptomatic as well as asymptomatic individuals of COVID-19. This would be a valuable diagnostic tool not only for mass screening of current COVID -19 pandemic but also in viral pandemic outbreaks of future.

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 TiO

Herein, n-n type one dimensional ZnO@In

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.

Defect engineering in n-type undoped metal oxides is a great challenge compared to the often-studied surface oxygen vacancies. The present investigation unravels new insights toward defect chemistry and defect engineering in anatase TiO2 nanoparticles. It is demonstrated that using the rapid cooling process, high concentration of Ti3+ interstitials, and lattice oxygen vacancies can be easily introduced in undoped metal oxides. The structural disorders in anatase TiO2 nanoparticles synthesized under two different argon-annealing processes have been comprehensively investigated using spectroscopy and electron microscopic analysis. Though excess of interstitial Ti3+ ions with one unpaired 3d electron in quenched TiO2 introduces local magnetic moments, they could be antiferromagnetically coupled via lattice Ti4+ ions, which limit the overall magnetic moment of the quenched materials. Lattice contraction was also found to enhance the ferromagnetic coupling between the defect complexes (Ti3+–F+ center) which he...

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.

Pt-grafted, hierarchical mesoporous carbon nanofibers (Pt/MPCNFs) electrocatalysts have been developed using electrospinning for high-performance PEM fuel cells. The morphological analysis of Pt/MPCNFs revealed uniformly dispersed Pt nanoparticles (2–3 nm) strongly grafted onto the hierarchical nanochannels of mesoporous carbon nanofibers (MPCNFs). Pyridinic and pyrrolic nitrogen species formed in the sp2 graphitic structure during the carbonization process of the MPCNFs have been found to play a major role in augmentation of the triple phase boundaries in the catalyst support materials. Pt/MPCNFs exhibited outstanding electrocatalytic performance towards the oxygen reduction reaction (ORR) with a positively shifted onset potential (54 mV), half-wave potential (78 mV) and high limiting current density (4.75 mA cm−2 at 0.4 V) compared to state-of-the-art Pt/C electrocatalysts in acidic medium and they exhibited superior long-term stability (89.8% retention after 30 000 s and less change in activity after 10 000 potential sweeps). Pt/MPCNFs as a cathode catalyst yielded a maximum power density of 428.6 mW cm−2 during single cell testing, which is 2.08 times higher than a commercial Pt/C electrocatalyst. The electrochemical performance evaluation clearly implied that the unique combination of ultrathin nanofibers with a three-dimensional mesoporous structure, high electrical conductivity, enhanced specific surface area, homogeneous dispersion of Pt nanocatalysts and the presence of optimal nitrogen doping offers superior electrocatalytic activity via a favorable four-electron pathway and long-term operating stability during repeated cycles. Performance analysis in a single PEM fuel cell shows twice the power density (428 mW cm−2) with Pt/MPCNFs compared to commercial electrocatalyst membranes due to the effective enhancement in the triple phase boundaries, indicating that Pt/MPCNFs are potential candidates for high-performance, durable PEMFCs.

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.

A controlled synthetic strategy is established for the development of TiO2@Au heterojunction nanorods using a facile wet-chemical method for the detection of NO2 gas under atmospheric pressure conditions. Structural studies reveal the existence of metastable anatase phase along with thermodynamically stable rutile phase with high degree of crystallinity. The structural analysis divulges the uniform surface anchoring of Au nanoclusters onto mono-dispersed TiO2 nanorods introducing interfacial metal–semiconductor heterojunctions. TiO2@Au heterojunction nanorods exhibited excellent sensor performance towards trace level exposure of NO2 gas. Owing to the interfacial electron transfer process at the heterojunction the optimum operating temperature of TiO2@Au heterojunction nanorods determined to be 250 °C, which is much less as compared to pristine TiO2 gas sensors (400 °C). Sensor response was found to be linear for the trace level concentration range of 0.5–5 ppm with lowest detection limit as 500 ppb. The TiO2@Au heterojunction nanorods exhibited higher sensitivity at atmospheric pressure conditions compared to vacuum conditions because of the changes in surface O2 adsorption properties of the heterojunction material at different oxygen partial pressure and existence of mixed phases in TiO2 nanorods. The superior gas sensor performance of the material under atmospheric pressure conditions point towards their potential for real-time applications.

This work demonstrates the development of Ag@polyaniline/multi-walled carbon nanotube nanocomposite-based sensor strips and a suitable integrated electronic read-out system for the measurement of trace-level concentrations of ammonia (NH3). The sensor is optimized under various operating conditions and the resulting sensor exhibited an enhanced response (32% for 2 ppm) with excellent selectivity. Stable performance was observed towards NH3 in the presence of high concentrations of CO2 (>40 000 ppm), simulated and real breath samples. A suitable electronic sensor read-out system has also been designed and developed based on multi-scale resistance-to-voltage conversion architecture, processed by a 32-bit microcontroller which is operatable over a wide range of sensor resistance (1 kΩ to 200 MΩ). As a proof of concept, integration of gas-sensing strips with the electronic read-out system was tested with various levels of NH3 ( 2 ppm as critical and 2 ppm as threshold), which is important for clinical breath analyzer applications. The developed prototype device can be readily incorporated into a portable, low-cost and non-invasive point-of-care breath NH3 detection unit for portable pre-diagnostic breath analyzer applications.

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 %).

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.

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.