Reversible H2 gas sensing at room temperature has been highly desirable given the booming of the Internet of Things (IoT), zero-emission vehicles, and fuel cell technologies. Conventional metal ...oxide-based semiconducting gas sensors have been considered as suitable candidates given their low-cost, high sensitivity, and long stability. However, the dominant sensing mechanism is based on the chemisorption of gas molecules which requires elevated temperatures to activate the catalytic reaction of target gas molecules with chemisorbed O, leaving the drawbacks of high-power consumption and poor selectivity. In this work, we introduce an alternative candidate of cobalt oxysulfide derived from the calcination of self-assembled cobalt sulfide micro-cages. It is found that the majority of S atoms are replaced by O in cobalt oxysulfide, transforming the crystal structure to tetragonal coordination and slightly expanding the optical bandgap energy. The H2 gas sensing performances of cobalt oxysulfide are fully reversible at room temperature, demonstrating peculiar p-type gas responses with a magnitude of 15% for 1% H2 and a high degree of selectivity over CH4, NO2, and CO2. Such excellent performances are possibly ascribed to the physisorption dominating the gas–matter interaction. This work demonstrates the great potentials of transition metal oxysulfide compounds for room-temperature fully reversible gas sensing.
Few rare‐earth (RE) atoms incorporated in lattice greatly tunned the optical, electrical, magnetic, and catalytic performance of doped crystal through the peculiar atomic electron structure of RE. ...The dimensionality scale‐down of RE oxides can further promote their unique traits and broaden their applications. The UV photodetection performance of (111) oriented CeO2 thin film is limited by the existence of grain boundaries, defects, and strains. Consequently, single‐crystal 2D CeO2 is promising for photodetection as it lacks of grain boundaries and defects. However, the synthesis of large‐sized high‐quality 2D CeO2 with lateral dimensions over 100 µm is challenging. In this work, a 3.9 nm thick CeO2 single crystal with 120 µm lateral size is synthesized over a sapphire substrate through a salt‐assisted chemical vapor deposition method, in which an intermediate insulating CeAlO3 layer is formed between the substrate and 2D CeO2 to enhance the crystal lattice matching and therefore facilitates the large area growth. The photodetector based on 2D CeO2 exhibits a photo response from 395 to 532 nm, possibly ascribed to a micro‐strain narrowed bandgap induced at the heterointerface. The photoresponsivity reaches 43.6 A W−1 while the detectivity reaches 7.58 × 1011 Jones under the 395 nm laser irradiation. Besides, the sub‐ms switching kinetics is achieved without gating bias, which is significantly improved over other reported RE oxides‐based photodetectors. This work demonstrates the possibility of the synthesis of large‐size high‐quality 2D RE oxides and their strong potential in high‐performance optoelectronic devices.
A 3.9 nm‐thick CeO2 single crystal with 120 µm lateral size is synthesized over sapphire substrate through salt‐assisted chemical vapor deposition method. The photoresponsitivity reaches 43.6 A W−1 while the detectivity reaches 7.58 × 1011 Jones under the 395 nm laser irradiation. This work demonstrates the possibility of synthesis of large‐size high‐quality 2D rare‐earth oxides and their strong potential in high‐performance optoelectronic devices.
TiO2-decorated ZnO nanorod arrays directly grown on zinc foil are fabricated by a two-step approach combining hydrothermal oxidation and a sol-gel process for dye-sensitized solar cells (DSSCs) ...applications. Its dye absorption and light harvesting are increased by decoration with a TiO2 particle layer, resulting in enhancement of the photocurrent density. In addition, the open-circuit voltage (VOC) of the DSSCs is improved by suppressing interfacial carrier recombination. As a result, the conversion efficiency ( eta ) of the TiO2-decorated ZnO photoanode is increased by a factor of 1.78 compared with that of the bare ZnO. The electrochemical impedance spectroscopy (EIS) analysis shows that depositing TiO2 particles on the surface of the ZnO nanorod arrays can effectively extend electron lifetime and decrease electron recombination rate.
Two-dimensional (2D) or ultrathin metal sulfides have been emerging candidates in developing high-performance gas sensors given their physisorption-dominated interaction with target gas molecules. ...Their oxysulfide derivatives, as intermediates between oxides and sulfides, were recently demonstrated to have fully reversible responses at room temperature and long-term device stability. In this work, we explored the micro-scale self-assembly of ultrathin nickel oxysulfide through the calcination of nickel sulfide in a controllable air environment. The thermal treatment resulted in the replacement of most S atoms in the Ni-S frameworks by O atoms, leading to the crystal phase transition from original hexagonal to orthorhombic coordination. In addition, the corresponding bandgap was slightly expanded by ~0.15 eV compared to that of pure nickel sulfide. Nickel oxysulfide exhibited a fully reversible response towards H2 at room temperature for concentrations ranging from 0.25% and 1%, without the implementation of external stimuli such as light excitation and voltage biasing. The maximum response factor of ~3.24% was obtained at 1% H2, which is at least one order larger than those of common industrial gases including CH4, CO2, and NO2. Such an impressive response was also highly stable for at least four consecutive cycles. This work further demonstrates the great potential of metal oxysulfides in room-temperature gas sensing.
Metal oxysulfides are an emerging group of sensitive materials for high‐performance NO2 sensing owing to their room‐temperature operation capacity, excellent selectivity of NO2, the ...part‐per‐billion‐leveled limit of detection, as well as high stability against the ambient environment. Here, the room‐temperature NO2 sensing performances of zinc oxysulfide 3D micro‐self‐assembly composed of ultrathin nanoflakes are investigated. The combined hydrothermal–annealing approach is applied to first synthesize zinc sulfide micro‐self‐assembly and then transform it into zinc oxysulfide in a controlled environment. As a result, the majority of S atoms in zinc sulfide are replaced with O atoms, leading to the crystal structure variation from cubic/hexagonal to an orthorhombic configuration. Simultaneously, the corresponding optical bandgap is reduced from ≈3.6 – 3.8 eV to ≈1.92 eV, enabling the visible light harvesting capability. The sensor demonstrates a fully reversible and repeatable sensing response toward 1.26 ppm NO2 gas at room temperature with a response magnitude of ≈2.27 under the 460 nm excitation, a limit of detection (LOD) of 294.8 part‐per‐trillion (ppt), and almost an order of magnitude larger compared to other commonly used gas species. This work demonstrates the great potential of the metal oxysulfide framework for developing next‐generation room‐temperature NO2 gas sensors.
Self‐assembled zinc oxysulfide micro‐balls consist of ultrathin ZnSO4 nanoflakes. Owing to its moderate bandgap (≈1.92 eV) and intrinsically strong light properties, the material is realized in a high‐performance room‐temperature visible‐light‐assisted sensor. Given illumination of a low‐powered blue light (λ = 460 nm), the sensor demonstrates a fully reversible response toward sub‐ppm low‐concentrated NO2 gas with excellent repeatability and selectivity.
► The novel two-dimensional (2-D) Ga-doped In2O3 nanoleaves are synthesized by a simple one-step carbonthermal evaporation method using Cu–Sn alloy as the substrates. ► The nanoleaves protrude ...outward from the Cu–Sn alloy substrate and are tightly connected to the substrate surface, which would result in a good physical and electrical contact for practical application. ► The room-temperature photoluminescence (PL) measurement of this nanoscaled Ga-doped In2O3 transparent conducting oxide (TCO) detected 2 blue peaks located at 432nm and 481nm, respectively, which can be used by Ru-based dye and indicates potential application in dye-sensitized solar cells (DSSCs).
The novel two-dimensional (2-D) Ga-doped In2O3 nanoleaves are synthesized by a simple one-step carbonthermal evaporation method using Cu–Sn alloy as the substrates. Two basic parts construct this leaf-like nanostructure: a long central trunk and two tapered nanoribbons in symmetric distribution in relation to the trunk. The Ga–In–O alloy particles are located at or close to the tips of the central trunks and serve as catalysts for the central trunk growth by the self-catalytic vapor–liquid–solid (VLS) mechanism. And the homoepitaxial growth of tapered nanoribbon on the surface of the central trunk can be explained by vapor–solid (VS) mechanism. The room-temperature photoluminescence (PL) measurement of this nanoscaled Ga-doped In2O3 transparent conducting oxide (TCO) detected two blue peaks located at 432nm and 481nm, respectively, which can be used by Ru-based dye and indicates potential application in dye-sensitized solar cells (DSSCs). The successful preparation of this novel 2-D Ga-doped In2O3 nanoleaves not only enriches the synthesis of TCO materials, but also provides new blocks in future architecture of functional nano-devices.
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•PPy particles make GOM with dye adsorption function for sub-nano dyes removement.•Intercalation of PPy improves the GOM’s stability extremely.•PPy nanoparticles modified GOM ...resulting in 14 times faster water flux.•PPy inhibits the swelling feature of GOM and exhibits improved separation ability.
Graphene oxide-based membrane (GOM) has been massively studied in the dye/water separation field, predominately relying on their 1 nm-sized interlayer distance spacing (D-spacing). However, the inefficient removal of sub-nanosized dye molecules and swelling-induced weak long-term stability are currently two key challenges faced by GOM. In this work, we intercalate the soft polymeric polypyrrole (PPy) nanoparticles into GOM to address such gaps. The strong dye adsorption ability of PPy results in the increase of the sub-nanosized MB molecule rejection rate from 60% for GOM to 97% for GO-PPy membrane (GPM) after the initial filtration treatment. Simultaneously, the nanochannels of GPM are partially expanded, leading to an approximately a ~14 times water permeability (21.14 L m-2h−1 bar−1) improvement over GOM (1.56 L m-2h−1 bar−1). More importantly, the strong hydrogen-bond, electrostatic, and π-π interactions between GO and PPy improve the membrane mechanical stability and further reduce the D-spacing, while the enhanced separation ability of nano-sized dye molecules is also exhibited evidenced by the > 99% rejection rates of CV, EBT, CR, and TB. We consider that our strategy could promote the design and development of the high-performance GOM for nanofiltration applications.
Paint layer was stripped from the 2024 aluminium alloy aircraft skin by either 1000 grit sandpaper or laser with 150 ps pulse width while the laser paint stripping (LPS) process was recorded by a ...high-speed camera. The surface and cross-section morphologies, chemical compositions and chemical valences of obtained the paint stripping samples were also characterise. The corrosion resistance was determined by the Potentiodynamic Polarization Curve (PPC). On mechanical paint stripping (MPS) samples, a large amount of scratches remained. Surface roughness increased and the oxide film was removed completely. The trace of the laser scan was observable on the surface of LPS samples. Recrystallisation occurred on the LPS surface and eventually formed arrayed micro and sub-micro structures. The oxide film is mainly composed of Al
2
O
3
with a thickness about 2.10 µm. The corrosion current density of mechanical and LPS samples are 3.66 ×10
−2
mA·cm
−2
and 6.66×10
−5
mA·cm
−2
, respectively. Comparing to MPS which removed all the oxide film and damaged the substrate metal, LPS only damaged the oxide film mildly without damaging metal substrate. The remaining oxide film contributes to a higher corrosion resistance of the LPS sample.
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Efficient separation of solutes by nanofiltration membranes (NMs) is the key to the utilization of wastewater and sustainable economic development. However, the establishment of dense ...and narrow-dispersed artificial tunnels in NMs remains a challenge, leading to impractical water permeability and solutes selectivity for real-world applications. In this work, we construct approximately 1 nm-sized artificial tunnels within the GO-based membranes (GOMs) to balance the water permeation and nanofiltration performances, by intercalating the three-dimensional wrinkled graphene (WG) sheets with surface functional groups manipulated. Such peculiar nanotunneled structure in the WG/GO composite membrane, at the optimized WG/GO ratio of 1:2, is revealed by the selective filtration of large-sized PEG gel particles over sub-nm-sized counterparts, leading to a selective rejection of >1 nm-sized molecules (e.g. CV, CR, and TB) over sub-nm-sized impurities (e.g. NR, MB, NaCl, and Na2SO4) with excellent mechanical stability and anti-fouling property. More importantly, the dense nanotunneled structure enables the composite membrane with an increased water flux of 65.68 L m-2h−1 bar−1, which is ∼48 times enhanced compared to that of pure GOM. Our strategy enables the precise engineering of artificial nanotunnels within compact GOM for high-performance dye/dye separation and dye desalination applications.
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Thiol functionalization of two-dimensional (2D) metal sulfides has been demonstrated as an effective approach to enhance the sensing performances. However, most thiol ...functionalization is realized by multiple-step approaches in liquid medium and depends on the dispersity of 2D materials. Here, we utilize a three-dimensional (3D) In2S3 nano-porous structure that self-assembled from 2D components as the nanoreactor, in which the surface-absorbed thiol molecules from the chemical residues of the nanoreactor are used for the in-situ covalent functionalization. Such functionalization is realized by facile heat the nanoreactor at 100 °C, leading to the recombing sulfur vacancies with thiol-terminated groups. The NO2 sensing performances of such functionalized nanoreactor are investigated at room temperature, in which In2S3-100 exhibits a response magnitude of 21.5 towards 10 ppm NO2 with full reversibility, high selectivity, and excellent repeatability. Such high-performance gas sensors can be attributed to the additional electrons that transferring from the functional group into the host, thus significantly modifying the electronic band structure. This work provides a guideline for the facile in-situ functionalization of metal sulfides and an efficient strategy for the high performances gas sensors without external stimulus.
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