•A facile manufacturing process of new Rb2CO3-decorated In2O3 sensor.•The Rb2CO3/In2O3 composite sensor detecting 100 ppb level NO2 gas at room temperature under visible light illumination.•Propose ...the mechanism for the high sensing performance realized by high rate of electron supply to the receptor.•Good sensing performance of high selectivity, stability, repeatability, linearity, with discussion of the humidity effect.
The Rb2CO3-decorated In2O3 sensor is prepared for detection of NO2 at room temperature under light irradiation. Physical and chemical properties of the materials and structures are thoroughly investigated by various analytical tools of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy, thereby confirming the formation of the Rb2CO3/In2O3 p-n junction at the interface. The Rb2CO3-decoration effect on In2O3 sensor is examined under light irradiation of different wavelengths and intensities. Rb2CO3-decoration exhibits much higher sensing performance than pure In2O3 sensor, and furthermore, the visible light irradiation improves in the response level and sensing kinetics. The sensor detects less than 100 ppb NO2. In addition, the Rb2CO3-decorated In2O3 sensor shows high selectivity, stability, repeatability, and linearity. The ultimate performance of the nanostructured sensor is elucidated by the depletion model of the conduction type gas sensors. The effect of humidity on the sensing performance is also investigated.
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•ZnCo2O4 nanoparticles designed to decorate BiVO4 nanoworms to form n-p heterojunction.•Impressive 4.4 fold increase in the photocurrent density was achieved for ...composite.•Incorporation of ZnCo2O4 accelerates the interfacial kinetics of BiVO4.•Establish correlation between PEC and band structure analysis of the photoelectrodes.•Understanding the surface kinetics of different photoelectrodes was developed.
During the past few decades, photoelectrochemical (PEC) water splitting has attracted significant attention because of the reduced production cost of hydrogen obtained by utilizing solar energy. Significant efforts have been invested by the scientific community to produce stable ternary metal oxide semiconductors, which can enhance the stability and increase the overall production of oxygen. Herein, we present the ternary metal oxide deposition of ZnCo2O4 as a route to obtain a novel photocatalyst layer on BiVO4 to form BiVO4/ZnCo2O4 a novel composite photoanode for PEC water splitting. The structural, topographical, and optical analyses were performed using field emission scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy, and UV–Vis spectroscopy to confirm the structure of the ZnCo2O4 grafted over BiVO4. A remarkable 4.4-fold enhancement of the photocurrent was observed for the BiVO4/ZnCo2O4 composite compared with bare BiVO4 under visible illumination. The optimum loading of ZnCo2O4 over BiVO4 yields unprecedented stable photocurrent density with an apparent cathodic shift of 0.46 V under 1.5 AM simulated light illumination. This is also evidenced by the flat-band potential change through Mott–Schottky analysis, which reveals the formation of p-ZnCo2O4 on n-BiVO4. The improvement in the PEC performance of the composite with respect to bare BiVO4 is ascribed to the formation of thin passivating layer of p-ZnCo2O4 on n-BiVO4 which improves the kinetics of interfacial charge transfer. Based on our study, we have gained an in-depth understanding of the BiVO4/ZnCo2O4 composite as high potential in efficient PEC water splitting devices.
Gas nanosensors with good “3S” (sensitivity, selectivity and stability), ultralow power consumption and low cost are increasingly needed for portable electronic devices. Herein, we demonstrate the ...facile fabrication process of individual, multiple, and networked SnO2 nanowire (NW) sensors, which can be used to detect highly toxic NO2 gas based on the Joule self-heating effect, consuming only few tens of μW of power. Systematic investigation on the gas-sensing properties reveals that the individual NW sensor shows advantages, such as better gas response shorter response–recovery time and lower power consumption over multiple and networked NW sensors. The self-heated individual NW sensor with applying a bias voltage of 25V exhibits a good response to NO2 gas concentrations as low as 1ppm with short response (∼8s) and recovery times (∼25s) and consumes only 35μW of power. In addition, the gas-response of individual NW sensors operated by either self- or external heating was compared to demonstrate the advantages of the development of the sensor concept for practical applications.
Abstract
In
2
O
3
nanostructure sensors were fabricated by arc-discharging a source composed of a graphite tube containing indium. The NO gas sensing properties, as well as the morphology, structure, ...and electrical properties, were examined at room temperature under UV light illumination. In particular, the response and recovery kinetics of the sensor at room temperature under various UV light intensities were studied. The maximum response signal was observed at an intermediate UV light intensity, which could be corroborated by a nano-size effect based on the conduction model of a resistive chemical nano sensor. The mechanism for the enhanced adsorption/desorption kinetics for NO in an air environment under UV light irradiation is discussed in detail. Furthermore, the general requirements of the sensor, including the stability, repeatability, and selectivity, are discussed.
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•The rational synthesis of homogeneously surface embedded cobalt clusters: g-C3N4 system.•The cobalt clusters are successfully stabilized via NH2-bpy moieties.•Resulted photocatalyst ...was effective for the CO2 reduction under sunlight irradiation.•Achieved very high rate of conversion (CO2 to CO) and apparent quantum yield (3.2% at 420 nm).•A new one-step strategy to prepare metal clusters embedded photocatalysts.
Metal clusters catalyst embedded in semiconductors is the key factor for an efficient photocatalyst toward photocatalytic CO2 reduction. However, developing a simple method to synthesize such photocatalyst with these features has remained challenging. Herein, a rational one-step synthesis of cobalt clusters embedded in g-C3N4 layers is developed for an enhanced photocatalytic CO2 reduction. The tiny cobalt clusters are embedded into the g-C3N4 structure and stabilized through the interaction with NH2-bpy moieties. Besides, the ligands of cobalt complex can copolymerize with urea during the synthesis owing to the presence of amino groups, thus providing a direct electron transfer between carbon nitride and cobalt clusters, which act as the light harvester and active reduction site, respectively. Consequently, a volcano relationship between the CO generation rate and the cobalt clusters incorporated into the carbon nitride matrix was found. Under optimized conditions, representative C3N4-0.5CoOx exhibits the very high CO generation rate of 2.6 μmol.h−1. Its apparent quantum yield of 3.2% at 420 nm and 1.0% at 460 nm, which is one of the highest values reported so far. The finding offers new opportunities for designing metal clusters catalysts toward photocatalytic CO2 reduction based on the judicious use of the metal complex.
Nanocomposite structures, where the Fe, Fe
O
, or Ni
O
nanoparticles with thin carbon layers are distributed among a single-wall carbon nanotube (SWCNT) network, are architectured using the co-arc ...discharge method. A synergistic effect between the nanoparticles and SWCNT is achieved with the composite structures, leading to the enhanced sensing response in ammonia detection. Thorough studies about the correlation between the electric properties and sensing performance confirm the independent operation of the receptor and transducer in the sensor structure by nanoparticles and SWCNT, respectively. Nanoparticles with a large specific surface area provide adsorption sites for the NH
gas molecules, whereas hole carriers are supplied by the SWCNT to complete the chemisorption process. A new chemo-resistive sensor concept and its operating mechanism is proposed in our work. Furthermore, the separated receptor and transducer sensor scheme allows us more freedom in the design of sensor materials and structures, thereby enabling the design of high-performance gas sensors.
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•Hydrothermal fabrication of F-surface-modified Sn-doped hematite photoanode.•Obtain the highest photocurrent among the hematite based photoanodes.•F-surface-modification improving ...the surface reaction and charge injection.•The uniform Sn-doping to enhance the charge transport efficiency.
Severe charge recombination and sluggish water oxidation reaction (OER) kinetics significantly limit the practical application of hematite in photoelectrochemical (PEC) water-splitting devices. In this study, fluorine-surface-modified tin-doped hematite (F/Sn:Fe2O3) photoelectrodes have been fabricated by a hydrothermal method incorporated impregnation annealing process. The grown FeOOH nanorods coated with NH4F solution are annealed first at 550 °C in the vacuum to modify the hematite surface and then at 750 °C in argon to promote the diffusion of tin atoms from the fluorine-doped tin oxide (FTO) glass substrate to the hematite structure. The synergistic effect of F-modification and Sn-doping on Fe2O3 electrode considerably enhances its PEC water oxidation performance, resulting in the highest photocurrent density of 3.64 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination. Both effects increase the carrier concentration in the photoelectrode, which improves its transport efficiency. Moreover, the surface-localized F species promote the OER process on the electrode surface and improve the charge separation at the electrode/electrolyte interface by increasing its hole supply rate under the increased electric field. This work may open a new avenue for fabricating novel photoelectrodes with high PEC water splitting efficiency.
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•DWCNTs-Gr hybrid thin film was successfully synthesized by LPCVD method.•A novel structure of DWCNTs-Gr hybrid thin film modified SPE was prepared.•An electrochemical sensor using ...ChOx enzyme for detection of As(V) was developed.•A high sensitive sensor was achieved with low LOD for As(V) detection.
In this work, we demonstrate the preparation of hybrid thin films based on double-walled carbon nanotubes and graphene for electrochemical sensing applications. The hybrid films were synthesized on polycrystalline copper foil by thermal chemical vapor deposition under low pressure. This carbonaceous hybrid film has exhibited high transparency with a transmittance of 94.3 %. The occurrence of this hybrid material on the electrode surface of screen-printed electrodes was found to increase electroactive surface area by 1.4 times, whereas electrochemical current was enhanced by 2.4 times. Such a highly transparent and conductive hybrid film was utilized as a transducing platform of enzymatic electrochemical arsenic(V) sensor. The as-prepared sensor shows the linear detection of arsenic(V) in the range from 1 to 10 ppb, with a limit of detection as low as 0.287 ppb. These findings provide a promising approach to develop new multifunctional electrochemical sensing systems for environmental monitoring and biomedical diagnostics.
Tin sulfide (SnS) is known for its effective gas-detecting ability at low temperatures. However, the development of a portable and flexible SnS sensor is hindered by its high resistance, low ...response, and long recovery time. Like other chalcogenides, the electronic and gas-sensing properties of SnS strongly depend on its surface defects. Therefore, understanding the effects of its surface defects on its electronic and gas-sensing properties is a key factor in developing low-temperature SnS gas sensors. Herein, using thin SnS films annealed at different temperatures, we demonstrate that SnS exhibits n-type semiconducting behavior upon the appearance of S vacancies. Furthermore, the presence of S vacancies imparts the n-type SnS sensor with better sensing performance under UV illumination at room temperature (25 °C) than that of a p-type SnS sensor. These results are thoroughly investigated using various experimental analysis techniques and theoretical calculations using density functional theory. In addition, n-type SnS deposited on a polyimide substrate can be used to fabricate high-stability flexible sensors, which can be further developed for real applications.
•Gas sensing response/recovery kinetics of NO sensing by ZnO with light irradiation and Au catalytic effect at room temperature.•Molecular dynamics consideration for adsorption and desorption to ...explain the detection of ppm level gas concentrations.•The nano-effect in varying thicknesses of ZnO.
ZnO thin-films with precisely controlled thicknesses were fabricated by the atomic layer deposition and their NO gas sensing properties were investigated at different temperatures, and in particular, under light irradiation of various energy and intensity at room temperature with and without Au catalyst. The molecular dynamics of NO and O2 during the response and recovery cycles in relation with the NO sensing performance in air environment was elaborated using the energy diagram modelled for adsorption and desorption kinetics of the gas molecules. The blue light irradiation combined with Au catalytic effect greatly enhanced the NO response rate, but delayed the recovery rate in the air environment via molecular dynamic interference from the environmental oxygen. The optimum condition for NO sensing was obtained for the film thickness, light energy and intensity. Critical issues for the stable sensor operation such as concentration dependence, gas selectivity, and humidity effect were also reported.
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