CTAB Enhanced Room-Temperature Detection of NO2 Based on MoS2-Reduced Graphene Oxide Nanohybrid

A new NO2 nanohybrid of a gas sensor (CTAB-MoS2 /rGO) was constructed for sensitive room-temperature detection of NO2 by 3D molybdenum disulfide (MoS2 ) and reduced graphene oxide (rGO), assisted with hexadecyl trimethyl ammonium bromide (CTAB). In comparison with MoS2 and MoS2 /rGO, the BET and SEM characterization results depicted the three-dimensional structure of the CTAB-MoS2 /rGO nanohybrid, which possessed a larger specific surface area to provide more active reaction sites to boost its gas-sensing performance. Observations of the gas-sensing properties indicated that the CTAB-MoS2 /rGO sensor performed a high response of 45.5% for 17.5 ppm NO2, a remarkable selectivity of NO2, an ultra-low detection limit of 26.55 ppb and long-term stability for a 30-day measurement. In addition, the response obtained for the CTAB-MoS2 /rGO sensor was about two to four times that obtained for the MoS2 /rGO sensor and the MoS2 sensor toward 8 ppm NO2, which correlated with the heterojunction between MoS2 and rGO, and the improvement in surface area and conductivity correlated with the introduction of CTAB and rGO. The excellent performance of the CTAB-MoS2 /rGO sensor further suggested the advantage of CTAB in assisting a reliable detection of trace NO2 and an alternative method for highly efficiently detecting NO2 in the environment

Studies of dopamine oxidation process by atmospheric pressure glow discharge mass spectrometry

An atmospheric pressure glow discharge ionisation source was constructed and utilized to study the dopamine (DA) oxidation process coupling with mass spectrometry. During the DA oxidation process catalysed by polyphenol oxidase (PPO), six cationic intermediates were directly detected by the atmospheric pressure glow discharge mass spectrometry (APGD-MS). Combined with tandem mass spectrometry, the structures of the dopamine o-semiquinone radical (DASQ) and leukodopaminochrome radical (LDAC●) intermediates and structures of the isomers of dopaminochrome (DAC) and 5,6-dihydroxyindole (DHI) were further characterised with the introduction of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and deuterium oxide (D2O) to APGD-MS. Meanwhile, UV–Vis studies confirmed the important role of PPO in catalyzing the DA oxidation reaction. Based on APGD-MS studies, a possible mechanism could be proposed for DA oxidation catalysed by PPO. Furthermore, APGD-MS could provide possibilities for the effective detection and characterisation of short-lived intermediates, even in complicated systems

Development and application of a porous cage carrier method for detecting trace elements in soils by direct current glow discharge mass spectrometry

The accurate and reliable determination of trace elements in soil still remains a big challenge for glow discharge mass spectrometry due to the poor conductive nature of soils. In the present work, a porous cage carrier was developed and used in the analysis of soils. The investigation results suggested that the carrier with a circular cross-sectional area in the range from 20 to 38 mm2, length from 15 to 17 mm and diameter of hole size from 1.5 mm to 2.0 mm could obtain good signals. Then the porous cage carrier method was systematically evaluated by analysing three types of soil reference materials. The discharge process was kept stable for more than 100 minutes, which was much longer than the boric acid method and indium sheet method. The investigations suggested that the internal precision was obtained within 16%, the external precision was better than 20% and the relative error was in the range from 0.7% to 17%. The detection limit of Tb could reach 0.014 μg g−1, which indicated that the new method qualified for the analysis of trace elements in soils. Compared to traditional tablet-pressed methods, the porous cage carrier method was not only convenient for sample preparation, but also showed good stability, reproducibility and better detection limits for trace elements. Furthermore, this method was proved to promote the potential application of GD-MS in the environmental field

Depth-profiling analysis of ZnO layers with three morphologies by direct-current glow discharge mass spectrometry

• The capability of direct-current glow discharge mass spectrometry (dc-GD-MS) was demonstrated for depth-profiling analysis of zinc oxide (ZnO) layers on steel substrates. • ZnO-1/steel fabricated by magnetron sputtering presented superior performance with a high depth resolution of 0.22?µm and a clear interface between the ZnO layer and steel substrate. • The effects of layer morphology, thickness and sputtering rate on depth resolutions were investigated and layer morphology had greater impact on depth resolutions

Carbon Disulfide Cosolvent Electrolytes for High-Performance Lithium Sulfur Batteries

Development of lithium sulfur (Li–S) batteries with high Coulombic efficiency and long cycle stability remains challenging due to the dissolution and shuttle of polysulfides in electrolyte. Here, a novel additive, carbon disulfide (CS₂), to the organic electrolyte is reported to improve the cycling performance of Li–S batteries. The cells with the CS₂-additive electrolyte exhibit high Coulombic efficiency and long cycle stability, showing average Coulombic efficiency >99% and a capacity retention of 88% over the entire 300 cycles. The function of the CS₂ additive is 2-fold: (1) it inhibits the migration of long-chain polysulfides to the anode by forming complexes with polysulfides and (2) it passivates electrode surfaces by inducing the protective coatings on both the anode and the cathode

Studies of dopamine oxidation process by atmospheric pressure glow discharge mass spectrometry

An atmospheric pressure glow discharge ionisation source was constructed and utilized to study the dopamine (DA) oxidation process coupling with mass spectrometry. During the DA oxidation process catalysed by polyphenol oxidase (PPO), six cationic intermediates were directly detected by the atmospheric pressure glow discharge mass spectrometry (APGD-MS). Combined with tandem mass spectrometry, the structures of the dopamine o-semiquinone radical (DASQ) and leukodopaminochrome radical (LDAC?) intermediates and structures of the isomers of dopaminochrome (DAC) and 5,6-dihydroxyindole (DHI) were further characterised with the introduction of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and deuterium oxide (D2O) to APGD-MS. Meanwhile, UV–Vis studies confirmed the important role of PPO in catalyzing the DA oxidation reaction. Based on APGD-MS studies, a possible mechanism could be proposed for DA oxidation catalysed by PPO. Furthermore, APGD-MS could provide possibilities for the effective detection and characterisation of short-lived intermediates, even in complicated systems

The formation of defect-pairs for highly efficient visible-light catalysts

Highly efficient visible-light catalysts are achieved through forming defect-pairs in TiO2 nanocrystals. This study therefore proposes that fine-tuning the chemical scheme consisting of charge-compensated defect-pairs in balanced concentrations is a key missing step for realizing outstanding photocatalytic performance. This research benefits photocatalytic applications and also provides new insight into the significance of defect chemistry for functionalizing materials