Liquid Phase Deposition Method Research Articles

In Situ Construction of a Hydrophobic Honeycomb-like Structured ZnMoO4 Coating Applied for Enhancing Zinc Anode Performance.

Aqueous zinc-ion batteries (AZIBs) suffer from sharp cycling deterioration due to serious interfacial side reactions and corrosion problems on the zinc anode. Herein, an efficacious approach to construct hydrophobic ZnMoO4 coatings on Zn (denoted as Zn@ZMO) is proposed to mitigate direct contact between the zinc anode and electrolyte and enhance its cycle life. The hydrophobic ZnMoO4 layer (contact angle = 128°) with a honeycomb-like structure is prepared by an in situ liquid phase deposition method. The as-prepared ZnMoO4 coating exhibits persistent corrosion protection for Zn through 30 days of immersion in a 2 M ZnSO4 electrolyte, indicating excellent stability of the ZnMoO4 layer and ensuring its available application in AZIBs. Unique microchannels in this kind of honeycomb-like structured coating favor Zn2+ ion diffusion and ease of ion transport, especially at high current cycling. Its robust surface exclusion can effectively counter other side reactions induced by water, simultaneously. As a result, the Zn@ZMO symmetrical cell shows a remarkable cycle lifespan exceeding 2700 h at 1 mA cm-2/1 mA h cm-2, surpassing that of the bare zinc cell by more than 100 folds. At a current density of 5 A g-1, the Zn@ZMO//V2O5 cell can still achieve a specific capacity of 167.0 mA h g-1 after 500 cycles with a capacity retention rate of 88%, which demonstrates its long-term cycling stability.

Band Gap Engineering of MoxW1-xS2 Alloy Monolayers with Wafer-Scale Uniformity.

Modulating the band gap of two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors is critical for their application in a wider spectral range. Alloying has been demonstrated as an effective method for regulating the band gap of 2D TMDC semiconductors. The fabrication of large-area 2D TMDC alloy films with centimeter-scale uniformity is fundamental to the application of integrated devices. Herein, we report a liquid-phase precursor one-step chemical vapor deposition (CVD) method for fabricating a MoxW1-xS2 alloy monolayer with a large size and an adjustable band gap. Good crystalline quality and high uniformity on a wafer scale enable the continuous adjustment of its band gap in the range of 1.8-2.0 eV. Density functional theory calculations provided a deep understanding of the Raman-active vibration modes of the MoxW1-xS2 alloy monolayer and the change in the conductivity of the alloy with photon energy. The synthesis of large-area MoxW1-xS2 alloy monolayers is a critical step toward the application of 2D layered semiconductors in practical optoelectronic devices.

Enhancement of biohydrogen production by photo-fermentation of corn stover via visible light catalyzed titanium dioxide/activated carbon fiber

In this study, titanium dioxide/activated carbon fiber (TiO2/ACF) was synthesized by liquid-phase deposition method and the effect of TiO2/ACF on the performance of photo-fermentation biohydrogen production (PFHP) from corn stover under visible light catalysis was discussed. Results show the maximum cumulative hydrogen yield (CHY) obtained under the optimal conditions was 74.0 ± 1.3 mL/g TS with TiO2/ACF addition of 100 mg/L, which was twice that without TiO2/ACF addition (36.9 ± 1.0 mL/g TS). Initial pH value had the most significant effect on CHY. The addition of TiO2/ACF promoted the metabolic pathway of nitrogenase to reduce H+ produced by consuming acetic acid and butyric acid to hydrogen, and also shortened the photo-fermentation period. By scanning electron microscopy and X-ray diffraction analysis, the morphology and phase structure of TiO2/ACF after PFHP did not change significantly. This study laid the foundation for the reuse of TiO2 and its practical application in PFHP.

Surface-Enhanced Raman Scattering in Silver-Coated Suspended-Core Fiber.

In this paper, the silver-coated large-core suspended-core fiber (LSCF) probe was fabricated by the dynamic chemical liquid phase deposition method for surface-enhanced Raman scattering (SERS) sensing. The 4-mercaptophenylboronic acid (4-MPBA) monolayer was assembled in the LSCF as the recognition monolayer. Taking advantage of the appropriate core size of the LSCF, a custom-made Y-type optical fiber patch cable was utilized to connect the semiconductor laser, Raman spectrometer, and the proposed fiber SERS probe. The SERS signal is propagated in the silver-coated air channels, which can effectively reduce the Raman and fluorescence background of the silica core. Experiments were performed to measure the Raman scattering spectra of the 4-MPBA in the silver-coated LSCF in a non-enhanced and enhanced case. The experiment results showed that the Raman signal strength was enhanced more than 6 times by the surface plasmon resonance compared with the non-enhanced case. The proposed LSCF for SERS sensing technology provides huge research value for the fiber SERS probes in biomedicine and environmental science. The combination of SERS and microstructured optical fibers offers a potential approach for SERS detection.

Modified superhydrophobic magnetic Fe3O4 nanoparticles for removal of microplastics in liquid foods

Microplastics (MPs) stemming from plastic products have attracted wide attention around the world due to their stealth, persistence and potential threat to humans. It is essential to remove MPs by using eco-friendly and effective methods. In this study, to remove MPs, we proposed to prepare Fe3O4 superhydrophobic magnetic adsorbents (Fe3O4@Cn, n = 12, 14, 16, 18) modified by different saturated fatty acids (C12, C14, C16, C18) by liquid phase deposition method. Transmission electron microscope, atomic force microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometry and nitrogen adsorption measurements were applied to characterize the morphology, functional groups, crystalline structures of Fe3O4@Cn as well as its magnetic properties and pore size distribution. It was shown that Fe3O4@Cn exhibited the characteristics of magnetic materials with superhydrophobic properties and thus possessed the ability to separate oil and water. During the removal of MPs in five liquid food systems, Fe3O4@C12 exhibited 92.89 % adsorption efficiency, which was ascribed to the electrostatic and chemical bonding interactions between MPs and Fe3O4@Cn, as suggested by density functional theory (DFT) calculations. In addition, the presence of organic matter in water can decrease the removal efficiency of Fe3O4@Cn due to the competitive adsorption effect. Simulation by Langmuir isotherm model suggested that Fe3O4@C12 displayed the greatest adsorption efficiency for Polystyrene (PS) (809.29 mg/g), which is higher than that of Fe3O4@C14, Fe3O4@C16, and Fe3O4@C18. In addition, Langmuir adsorption isotherm and Gaussian calculations suggested that PS was removed by Fe3O4@C12 through an exothermic reaction controlled by chemisorption. Overall, these results indicated that superhydrophobic magnetic materials prepared in this study show high potential for removing MPs in aqueous systems due to their low costs, good environmental friendliness, and high removal performance.

Study on the catalytic performance of a new double-shell composite energetic material

To improve the pyrolysis of ammonium perchlorate (AP), the effects of P-N junction metal oxides with different coating sequences on thermal decomposition were compared. AP / ZnO / ZnCo2O4 double-shell composite energetic materials and AP / ZnCo2O4 / ZnO double-shell composite energetic materials were manufactured by the liquid phase deposition method. XRD, FT-IR, and TEM characterize the structure of samples. The self-catalytic properties of double-shell composite energetic materials were investigated by differential thermal analysis (DTA). XRD, FT-IR, and TEM results show the formation of a P-N junction. The double-shell composite energetic material was successfully prepared and had a good coating effect. DTA results show the Pyrolytic peak of AP / ZnO / ZnCo2O4 double-shell composite energetic materials has been drowned to 262.85 °C. The decomposition peak of AP / ZnCo2O4 / ZnO double-shell composite energetic material is 272.31 °C, and the difference between the two is obvious. The coating of N-type metal semiconductor material can greatly improve the autocatalytic performance of the material, giving a new idea for designing AP catalysts.

Post-annealing of hematite films: The changes in surface chemistry, lattice dynamics, and photoelectrochemical properties

This research deals with tracking changes in the surface chemistry and lattice dynamics of α-Fe2O3 (hematite) thin films upon post-annealing and its correlation with the photoelectrochemical (PEC) properties. The hematite thin films were prepared by the electric field-assisted liquid phase deposition (EA-LPD) method. The as-prepared thin films were heated at three different heating rates: 10, 22, and 80 ℃/min to 350 ℃; and kept for 15 min and then quenched in the air. The structural characterizations showed that the post-annealing process induces oxygen vacancies and the formation of hydroxyl groups on the surface. The extent of the changes in the surface chemistry strongly depends on the heating rate. Such changes in the surface chemistry possess a synergic effect on the PEC properties. Here the post-annealed photoanodes with an 80 ℃/min heating rate showed significantly improved PEC activity and exhibited a maximum photocurrent density ⁓ 0.73 mA.cm−2 at 1.23 V vs. RHE, 2.5 times higher than that for pristine sample. The lattice dynamics investigations suggested that the as-prepared photoanodes are composed of α-FeOOH. Upon post-annealing, α-FeOOH was partially converted into a proto-hematite intermediate phase. The longitudinal optical (LO) modes for the post-annealed samples enhanced as an indicator for the development of lattice disorder, as the results of induced oxygen vacancy defects and hydroxyl groups on the surface.

Surface-Modified TiO2@SiO2 Nanocomposites for Enhanced Dispersibility and Optical Performance to Apply in the Printing Process as a Pigment.

The grafted modification TiO2@SiO2 composite was fabricated by a liquid-phase deposition method with Na2SiO3 and a grafting reaction with a silane coupling agent. First, the TiO2@SiO2 composite was prepared, and the effect of deposition rate and silica content on the morphology, particle size, dispersibility, and pigmentary property of TiO2@SiO2 composites was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and ζ-potential. The islandlike TiO2@SiO2 composite had a good particle size and printing performance compared with the dense TiO2@SiO2 composite. The presence of Si was confirmed by EDX elemental analysis and XPS, and a peak at 980 cm-1 belonging to Si-O was observed in the FTIR spectrum, confirming the presence of SiO2 anchored at TiO2 surfaces via Si-O-Ti bonds. Then, the islandlike TiO2@SiO2 composite was modified by grafting with a silane coupling agent. The effect of the silane coupling agent on the hydrophobicity and dispersibility was investigated. The peaks at 2919 and 2846 cm-1 belong to CH2 in the FTIR spectrum, and Si-C in the XPS confirmed the grafting of silane coupling agent to the TiO2@SiO2 composite. The grafted modification of the islandlike TiO2@SiO2 composite using 3-triethoxysilylpropylamine endowed it with weather durability, dispersibility, and good printing performance.

Synthesis of two-dimensional CeO2-δ-GQD composites and their structural and optical properties

The present study reports on the synthesis of two-dimensional (2D) ceria and graphene quantum dots (CeO2-δ-GQD) composites and their functional properties. Composites were prepared by a simple liquid phase deposition (LPD) method followed by a thermal treatment in air at 250 and 400 °C. The structural and optical properties of composites were investigated by X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), High-Resolution Transmission Electron Microscopy (HR-TEM), Raman spectroscopy, Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), UV-Vis and photoluminescence (PL). The composites consist of crystalline CeO2-δ regions of about 1.8–2.9 nm in size, coexisting with highly disordered GQDs areas. The CeO2-δ-GQD composites experience gradual dehydration and oxidation of carbon processes during thermal treatment, influencing the CeO2 crystal size, Ce3+/Ce4+ ratio, and O vacancies presence. These effects allow for the control of some of the composite functional properties. Specifically, the CeO2-GQD250 composites exhibit a low recombination rate of charge carriers due to the synergistic interaction between the components and low presence of Ce3+. In contrast, the CeO2-GQD400 composites show a high Eg of 3.8 eV (Eg ∼3.2 eV for CeO2NPs) associated with a CeO2 quantum size effect and extremely low fraction of GQDs.

De-Ammonium Ba0.18V2O4.95/NH4V4O10 Film Electrodes as High-Performance Cathode Materials for Magnesium-Ion Batteries

Magnesium-ion batteries (MIBs) have been pushed into the research boom in the post-lithium-ion batteries era due to their low cost, no dendrite hazard, and high capacity. However, finding suitable cathode materials to improve the slow kinetics of Mg2+ is an ongoing challenge. In this work, Ba0.18V2O4.95/NH4V4O10 film electrodes were grown in one step on indium tin oxide (ITO) conductive glass using a low-temperature liquid-phase deposition method. Temperature was used as the probe condition, and it was concluded that the films annealed at 400 °C had suitable crystallinity and de-ammonium lattice space. At lower current density, with 0.5 M Mg(ClO4)2/PC as the electrolyte, it exhibited an initial discharge capacity of 130.99 mA h m-2 at 210 mA m-2 and 106.52% capacity retention after 100 cycles. In addition, it exhibited excellent electrochemical performance in long-term cycling (92.98% capacity retention after 300 cycles at 600 mA m-2). According to the results of ex situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM), the removal of NH4+ created more lattice space, assisting Ba0.18V2O4.95 to increase the transfer channels of Mg2+, providing more active sites to promote diffusion kinetics (the average DMg2+ was 2.07 × 10-12 cm2 s-1) and specific capacity. Therefore, these film electrodes for scalable Mg2+ storage are promising MIB cathode candidates that exhibit good performance advantages in storage applications.

Mg-doped TiO2 nanorods-SrTiO3 heterojunction composites for efficient visible-light photocatalytic degradation of basic yellow 28

In this study, a series of Mg-doped TiO2/SrTiO3 heterojunctions were constructed using SrTiO3 nanoparticles anchored onto the surface of TiO2 nanorod arrays. Titanium dioxide (TiO2) nanorods and SrTiO3 nanoparticles were synthesized using the liquid phase deposition (LPD) and sol-gel methods, respectively. The photocatalytic activity of obtained photocatalysts was investigated towards the degradation of basic yellow 28 (BY28) dye under visible-light irradiation compared to the pristine TiO2 nanorods and SrTiO3 nanoparticles. The obtained samples were carefully characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron (XPS), UV–Vis, and photoluminescence spectroscopy. 1.5 Mg–TiO2/SrTiO3 nanocomposite demonstrated the highest photocatalytic activity and the corresponding apparent rate constants of 0.0255 min−1 which is that is 2.9, 9.4, and 2.3 times higher than TiO2 nanorods, SrTiO3 nanoparticles, and TiO2/SrTiO3 nanocomposite, respectively. This enhanced photocatalytic performance can be attributed to the improved charge transfer, more effective electron-hole separation, and a red-shift in light absorption derived from the Mg doping and coupling effect of TiO2 nanorods and SrTiO3 nanoparticles.

Ca-doped NaV6O15 film electrodes as high-performance cathodes for sodium-ion batteries

The Ca-doped NaV6O15 films have been prepared on indium-doped tin oxide (ITO) conductive glasses using a low-temperature liquid-phase deposition method. The crystal structure, morphology, and structural information of the Ca-doped NaV6O15 films were systematically studied by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. X-ray photoelectron spectroscopy revealed that the Ca-doped NaV6O15 had a lower ratio of V5+/V4+, which was the compensation for doped Ca2+. Electrochemical properties of films were measured by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge tests. The results proved the doped Ca2+ obviously improved electrochemical performance, which exhibited quicker diffusion process, higher specific capacity, and longer lifespan. The Ca-doped NaV6O15 films showed a high discharge capacity of 237.476 mA h m−2 at 1C rate, which was larger than 96.719 mA h m−2 of the pure NaV6O15 films. The capacity retention reached to 84.72 % at 0.5C rate after 100 cycles, the excellent cyclic ability was attributed to the doped Ca2+ with strong electronegativity stabilizing the structure. This work presents a great potential approach that explores high-performance cathodes for sodium-ion batteries.

In situ construction of Co@nitrogen-doped carbon/Ni nanocomposite for broadband electromagnetic wave absorption

The tunable multicomponent synergistic loss mechanism and multiple heterogeneous interfaces of magnetic carbon-based composites have emerged as the efficient electromagnetic wave absorbing (EMWA) materials. Herein, the Ni(OH)2/ZIF-67 precursors were synthesized via the hydrothermal and liquid-phase deposition methods, and then carbonized at different temperature under N2 atmosphere to obtain Co@nitrogen-doped carbon/Ni (Co@NC/Ni) nanocomposites. The metallic components with good dispersion property provided magnetic loss and improved impedance matching. Meanwhile, they also acted as catalysts to induce the formation of graphitized carbon, enhancing the conductive loss. Furthermore, more heterogeneous interfaces and defects were generated inside the sample, which promotes dielectric loss. Therefore, the Co@NC/Ni nanocomposite (carbonized at 600 °C) exhibited excellent EMWA performance with a minimum reflection loss (RL) of −47.10 dB, and the effective absorption bandwidth (RL ≤ −10 dB) can reach 6.84 GHz at 2.5 mm with a filling ratio of 30%. This work provides a heterogeneous interface construction strategy for the future application of high-performance magnetic carbon based EMWA materials.

Synthesis and Electrochemical Performance of V6O13 Nanosheets Film Cathodes for LIBs

V6O13 thin films were deposited on indium-doped tin oxide (ITO) conductive glass by a concise low-temperature liquid-phase deposition method and through heat treatment. The obtained films were directly used as electrodes without adding any other media. The results indicate that the film annealed at 400 °C exhibited an excellent cycling performance, which remained at 82.7% of capacity after 100 cycles. The film annealed at 400 °C with diffusion coefficients of 6.08 × 10-12 cm2·s-1 (Li+ insertion) and 5.46 × 10-12 cm2·s-1 (Li+ extraction) in the V6O13 film electrode. The high diffusion coefficients could be ascribed to the porous morphology composed of ultrathin nanosheets. Moreover, the film endured phase transitions during electrochemical cycling, the V6O13 partially transformed to Li0.6V1.67O3.67, Li3VO4, and VO2 with the insertion of Li+ into the lattice, and Li0.6V1.67O3.67, Li3VO4, and VO2 partially reversibly transformed backwards to V6O13 with the extraction of Li+ from the lattice. The phase transition can be attributed to the unique structure and morphology with enough active sites and ions diffusion channels during cycles. Such findings reveal a bright idea to prepare high-performance cathode materials for LIBs.

Fabrication of flower-like Ag/lignin composites and application in antibacterial fabrics

The bacterial infection and its transmission pose a great threat to life and health, which leads to the urgent development of efficient and broad-spectrum antibacterial agents. Herein, Ag/lignin layered nanoflower (Ag/EHL-CM-0.05) was synthesized by using biomass lignin as reducing and capping agents and silver nitrate as precursor. The study showed that the size distribution of Ag NPs was uniform distribution and about 20–40 nm. The crystal surface of Ag NPs was Ag (111) surface. The minimum inhibitory concentration of Ag/EHL-CM-0.05 against E. coli and S. aureus was all 7.8 μg/mL, which was the lowest of other Ag/lignin antibacterial materials and reached a level nearly as polycationic antibacterial agents. The antibacterial mechanism suggested that Ag/EHL-CM-0.05 could release OH and Ag+, which could cause bacterial death. Finally, Ag/EHL-CM-0.05 was sprayed onto the viscose fabrics by liquid-phase spray deposition method. It was found that the inhibition zone diameter of modified viscose fabrics against E. coli and S. aureus only dropped about 0.16 cm on average after friction treatment and 0.32 cm on average after washing treatment. This work provides a new idea for the design and synthesize of efficient, broad-spectrum, and bio-compatible antibacterial agents, which has important social, economic, and environmental significance.

Experimental study of the copper-coated hollow fiber surface plasmon resonance sensor

A novel optical fiber surface plasmon resonance (SPR) sensor based on the copper-coated hollow fiber structure was proposed. The simple chemical liquid phase deposition method was developed to coat the thin copper film on the inner surface of the hollow fiber to fabricate the proposed sensor. The performance of the hollow fiber SPR sensors with different copper film thickness were investigated experimentally by measuring the transmission spectra of the sensors filled by sensed liquid media with different refractive indices. Theoretical analysis based on the ray transmission model was also carried out for comparison. The experimental and theoretical results agree well with each other. The factors which affect the sensor performance are discussed. The sensor achieves a maximum sensitivity of 7111 nm/RIU, which is relatively high in the copper film based optical fiber SPR sensors and comparable to the silver-coated hollow fiber sensors. Moreover, the fabrication process of the proposed sensor is much simpler than other copper based optical fiber SPR sensors, which make it more practical. The copper film deposition method presented in this paper is also applicable to the fabrication of some microstructured optical fiber or photonic crystal fiber based sensors with copper film.

Optical Fiber Surface Plasmon Resonance Sensor Based on the Gold-Coated Hollow Fiber Structure for the Detection of Liquid With High Refractive Index

A hollow fiber (HF) surface plasmon resonance (SPR) sensor based on the gold-coated HF structure for the detection of liquid with high refractive index has been presented experimentally for the first time. The designed sensors with different gold layer thicknesses are fabricated by the liquid phase deposition method. The performances of the fabricated sensors, including sensitivity and figure of merit, are analyzed with the measured transmission spectra. The experimental results show that the proposed sensor with a thicker gold layer exhibits the sensitivity and the corresponding figure of merit up to 8945 nm/RIU and 92 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> , respectively, which is much higher than that of the silver-coated HF SPR sensor reported previously. Considering the extraordinary chemical stability and durability of gold, the presented sensor has large potential in biological and chemical applications. Moreover, the chemical method of coating smooth gold film in the hollow core of HF presented in this work is simple and cost-effective. It can be employed easily in the fabrication of other kinds of microstructured optical fiber devices coated with gold film and promote the experimental realization of them.

Thin-film temperature sensors based on LPD-fabricated β-Ga2O3 Schottky diodes

We report the synthesis of wide-bandgap β-Ga2O3 nanocrystalline thin films via the low-cost and non-vacuum-based liquid phase deposition (LPD) method. The morphological evolution of the nanocrystalline β-Ga2O3 grains was investigated as a function of the growth temperature, processing time, and pH value of the precursor solution. We successfully calcined gallium oxide hydroxide GaO(OH) through a 3-h annealing process at 800 °C to convert it into β-Ga2O3. We fabricated horizontal-structured Ni/β-Ga2O3 Schottky diodes and investigated the electrical characteristics pertinent to sensing temperature in the range of 100−800 K. The temperature sensitivity of the Ni/β-Ga2O3 Schottky-junction temperature sensors, defined as the temperature dependence of junction voltage at a fixed bias current of 10 µA, peaked at −2.924 mV/K in the range between 300 and 500 K. At room temperature, we measured a barrier height of 0.915 eV and a Richardson constant of 43.04 ± 0.01 A/cm2 K2 from the Ni/β-Ga2O3 Schottky junctions. These results indicate that the LPD-synthesized β-Ga2O3 material and devices hold promising potential for sensing applications especially at high temperatures.

Photoelectrochemical properties of butane reduced flame‐treated Zr‐doped hematite thin films

AbstractIn this research, Zr‐doped hematite thin films were prepared by a simple and highly scalable liquid phase deposition method, and their photoelectrochemical (PEC) properties were investigated. The samples were post‐heat treated using a butane reduced flame. PEC studies revealed that both Zr‐doping and flame‐treatment enhanced the performance of the hematite photoanodes. The photocurrent densities of the samples were considerably increased upon flame‐treatment, that is, about 3.5 times for a 4% Zr‐doped sample. The highest photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) was obtained, about 0.50 mA cm−2 for the 4% Zr‐doped sample, about five times higher than the undoped sample. The Mott–Schottky measurements revealed that the donor charge carrier density for the 4% Zr‐doped sample was increased fivefold upon flame‐treatment from 2.49 × 1019 to 1.38 × 1020 cm−3. The optical investigations showed that the optical band gap energy values depend on the level of Zr‐doping, and the sample with 4% Zr‐doping showed the lowest band gap energy value, about 1.82 eV. The mechanism behind the effectiveness of the flame‐treatment was investigated and attributed to the oxygen vacancy formation upon flame‐treatment. The formation of oxygen vacancies activates the donor doping, and as a result, the charge carrier density increases. In general, butane reduced flame‐treatment as a simple and effective strategy can be used as a post‐heat treatment to boost the PEC properties of hematite thin films.

Gas sensing performances of commercial carbon fibers functionalized by NiO/SnO2 composite

Commercial carbon fibers (CFs) were functionalized with NiO/SnO2 composite powders via a simple liquid phase deposition method followed by heat treatment and the influences of CFs content on the micro-structure and gas sensing performances of the CFs/NiO/SnO2 gas sensor were investigated. The results indicate that the distinctive one-dimensional CFs overlapped with each other, forming a large number of pores inside the CFs/NiO/SnO2 composite, which increases the effective reaction area between sensitive materials and target gases greatly. The CFs/NiO/SnO2 gas sensor with 0.5 wt% CFs exhibits a good sensitivity, selectivity and excellence response-recovery characteristic to formaldehyde at lower operation temperature of 170 °C. Notably, the detectable concentration of HCHO is as low as 1 ppm, indicating a certain application prospect in formaldehyde detection. And the electronic transmission bridge mechanism is performed to explain the gas sensing mechanism, which plays a certain role in the functional application of CF.