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Triethylamine (TEA) exists widely in production and life and is extremely volatile, which seriously endangers human health. It is required to develop high-performance TEA sensors to protect human health. We fabricated Pt-Co3O4/WO3 based on our previous work, and the performance was tested against volatile organic compounds. Compared with the previous work, its operating temperature was greatly reduced from 240 °C to 180 °C. The response value of Pt-Co3O4/WO3 was increased from 1101 to 1532 for 10 ppm TEA with good selectivity. These results show a significant step toward practical use of the Pt-Co3O4/WO3 sensor.

Photocatalytic water splitting is considered to be a feasible method to replace traditional energy. However, most of the catalysts have unsatisfactory performance. In this work, we used a hydrothermal process to grow Ag nanoparticles in situ on g-C3N4 nanosheets, and then a high performance catalyst (Ag–g–C3N4) under visible light was obtained. The Ag nanoparticles obtained by this process are amorphous and exhibit excellent catalytic activity. At the same time, the local plasmon resonance effect of Ag can effectively enhance the absorption intensity of visible light by the catalyst. The hydrogen production rate promote to 1035 μmol g−1 h−1 after loaded 0.6 wt% of Ag under the visible light, which was 313 times higher than that of pure g-C3N4 (3.3 μmol g−1 h−1). This hydrogen production rate is higher than most previously reported catalysts which loaded with Ag or Pt. The excellent activity of Ag-g-C3N4 is benefited from the Ag nanoparticles and special interaction in each other. Through various analysis and characterization methods, it is shown that the synergy between Ag and g-C3N4 can effectively promote the separation of carriers and the transfer of electrons. Our work proves that Ag-g-C3N4 is a promising catalyst to make full use of solar energy.

Trace poisonous and harmful gases in the air have been harming and affecting people's health for a long time. At present, effective and accurate detection of ppb-level harmful gas is still a bottleneck to be overcome. Herein, we report a ppb-level triethylamine (TEA) gas sensor based on p-n heterojunction of Co3O4/WO3, which is prepared with ZIF-67 as the precursor and provides Co3O4deposited tungsten oxide flower-like structure. Due to the introduction of Co3O4and the 3D flower-like structure of WO3, the Co3O4/WO3-2 gas sensor shows excellent gas sensing performance (1101 for 10 ppm at 240 °C), superb selectivity, good long-term stability and linear response for TEA concentration. Moreover, the experimental results indicate that the Co3O4/WO3-2 gas sensor also possesses a good response to 50 ppb TEA, in fact, the theoretical limit of detection is 0.6 ppb. Co3O4not only improves the efficiency of electron separation/transport, but also accelerates the oxidation rate of TEA. This method of synthesizing p-n heterojunction with ZIF as the precursor provides a new idea and method for the preparation of low detection limit gas sensors.

High performance acetone gas sensors were fabricated with molecular imprinted polymers of Ag-LaFeO3 (ALFOMMIPs) and multi walled carbon nanotubes (CNTs) composite using the microwave assisted sol-gel method. The crystalline structure, functional groups, grain size and surface appearance of the synthesized materials were analyzed via different characterization techniques and the gas responses of the samples were examined. The detailed acetone gas sensing tests and analysis revealed that the CNTs and ALFOMIPs nanocomposite (CNT/ALFOMIP) sample possessed a higher response than that of the ALFOMIPs sample. Where 0.75 wt% CNTs were added into the ALFOMIPs (0.75% CNT/ALFOMIP nanocomposite) sensor, an excellent gas sensing performance was exhibited. The response of this sensor was up to 59 for 5 ppm acetone vapors and the response and recovery times were 58 and 33 s at low working temperature of 86 °C, respectively. In addition, it had the best selectivity only to acetone vapors due to the use of the molecular imprinting technique.

Xylene is a volatile organic compound which is harmful to the human health and requires precise detection. The detection of xylene by an oxide semiconductor gas sensor is an important research direction. In this work, Co3O4 decorated flower-like SnO2 nanorods (SnO2/Co3O4 NRs) were synthesized by simple and effective two-step method. The SnO2/Co3O4 NRs show high xylene response (Rg/Ra = 47.8 for 100 ppm) and selectivity at the operating temperature of 280°C, and exhibit high stability in continuous testing. The resulting SnO2/Co3O4 NRs nanocomposites show superior sensing performance towards xylene in comparison with pure SnO2 nanorods. The remarkable enhancement in the gas-sensing properties of SnO2/Co3O4 NRs are attributed to larger specific surface area and the formation of p-n heterojunction between Co3O4 and SnO2. These results demonstrate that particular nanostructures and synergistic effect of SnO2 and Co3O4 enable gas sensors to selectively detect xylene.

To address the urgent issues of hazardous gas detection and the prevention of environmental pollution, various functional materials for gas sensing and catalytic reduction have been studied. Specifically, the p-type perovskite LaFeO3 has been studied widely because of its promising physicochemical properties. However, there remains several problems to develop a controllable synthesis of LaFeO3-based p-n heterojunctions. In this work, α-Fe2O3 was further compounded with LaFeO3 to form a porous and hollow α-Fe2O3/LaFeO3 heterojunction to improve its gas-sensing performance and photocatalytic efficiency via a microwave-assisted hydrothermal method. While evaluated as sensors of acetone gas, the optimized sample exhibits excellent performance, including a high response (48.3), excellent selectivity, good reversibility, fast response, and recovery ability. Furthermore, it is an efficient catalyst for the degradation of methylene blue. This can be attributed to the enhancement effect of its larger specific surface area, fast diffusion, enhanced surface activities, and p-n heterojunction. Additionally, this work provides a rapid and rational synthesis strategy to produce metal oxides with both enhanced gas-sensing performance and improved photocatalytic properties.

Silver-doped LaFeO3 molecularly imprinted polymers (SLMIPs) were synthesized by a sol-gel method combined with molecularly imprinted technology as precursors. The precursors were then used to prepare SLMIPs cage (SLM-cage) and SLMIPs core-shell (SLM-core-shell) structures by using a carbon sphere as the template and hydrothermal synthesis, respectively. The structures, morphologies, and surface areas of these materials were determined, as well as their gas-sensing properties and related mechanisms. The SLM-cage and SLM-core-shell samples exhibited good responses to methanol gas, with excellent selectivity. The response and optimum working temperature were 16.98 °C and 215 °C, 33.7 °C and 195 °C, respectively, with corresponding response and recovery times of 45 and 50 s (SLM-cage) and 42 and 57 s (SLM-core-shell) for 5 ppm methanol gas. Notably, the SLM-cage and SLM-core-shell samples exhibited lower responses (≤5 and ≤7, respectively) to other gases, including ethanol, ammonia, benzene, acetone, and toluene. Thus, these materials show potential as practical methanol detectors.

In order to explore the similarity, difference, and tendency of binary copper-based chalcogenides, the crystal structure, electronic structure, and optical properties of eight compounds of Cu2Q and CuQ (Q = O, S, Se, and Te) have been calculated by density functional theory with HSE06 method. According to the calculated results, the electronic structure and optical properties of Cu2Q and CuQ present certain similarities and tendencies, with the increase of atomic number of Q elements: the interactions between Cu–Q, Cu–Cu, and Q–Q are gradually enhancing; the value of band gap is gradually decreasing, due to the down-shifting of Cu–4p states; the covalent feature of Cu atoms is gradually strengthening, while their ionic feature is gradually weakening; the absorption coefficient in the visible-light region is also increasing. On the other hand, some differences can be found, owing to the different crystal structure and component, for example: CuO presents the characteristics of multi-band gap, which is very favorable to absorb infrared-light; the electron transfer in CuQ is stronger than that in Cu2Q; the absorption peaks and intensity are very strong in the ultraviolet-light region and infrared-light region. The findings in the present work will help to understand the underlying physical mechanism of binary copper-based chalcogenides, and available to design novel copper-based chalcogenides photo-electronics materials and devices.

A novel gas sensor for the detection of formaldehyde was developed based on molecular imprinting technique (MIT) with formaldehyde as template. The structure of the molecular imprinting nanoparticles (MINs) is of orthogonal perovskite. The MINs with a good dispersion possess high surface-to-volume ratio. The particles are spherical and uniform, and then the MINs are printed onto an alumina tube to form a sensor device. At 92°C, the response to 1 ppm formaldehyde based on the sensor is 8, while the response to the other test gases is less than 3. The response time and recovery time are 40 s and 90 s, respectively.

The vanadium-doped TiO2 nanoparticles were prepared by a sol–gel method with Ti(OBu)4 as a precursor. The powders were characterized by XRD, FT-IR, TEM, XPS and UV–Vis absorption spectrum. The photocatalytic activity of the powders for methyl orange degradation was investigated under a fluorescent lamp. The results show that the doping V presents mainly in the form of V5+, and vanadium doping can restrain the crystal growth and promote the phase transfer from anatase to rutile. Vanadium doping can widen the light absorption range of TiO2, and the absorption threshold wavelength is red shifted from 380 nm to about 650 nm. As a result, the photocatalytic activity of the V–TiO2 nanoparticles is higher than that of P25 under the fluorescent lamp.

The supercells of pure anatase TiO2 and lanthanide-doped anatase TiO2 were calculated by density functional theory with the plane-wave ultrasoft pesudopotentials method. The effects of lanthanide doping on the crystal structure, electronic structure, optical properties and photocatalytic activity were investigated according to the calculation data. The results indicate that lanthanide doping could remarkably improve the photocatalytic activity of TiO2, and the effect of improvement was sensitive to the atomic electronic configuration and ionic radius. Most lanthanide-doped TiO2 simultaneously realized visible-light response and maintained strong redox potentials. The conclusions would have important significance for understanding and further developing TiO2 photocatalysts that are active under visible-light irradiation.

The gas-sensing characteristics of In(2)O(3) and CdO doped nanocrystalline SnO(2) compounds for formaldehyde were investigated in this study. The phases of the resulting materials and the morphologies of the sensing layers were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Indirect-heating sensors using SnO(2)-In(2)O(3)-CdO compounds as sensitive materials were fabricated on an alumina tube with Au electrodes and platinum wires. All measurements were performed at several operating temperatures from 100 to 180 °C. Good gas-sensing responses to formaldehyde have been found for all the prepared samples. It is shown that the sensors exhibited high sensitivity at low operating temperature (133 °C), making them promising candidates for practical detectors for formaldehyde.

We have systematically investigated the modification mechanism of anatase TiO2 doped with nitrogen using the plane-wave ultrasoft pseudopotentials method based on density functional theory. The crystal structure, impurity formation energy, electronic structure and optical properties of TiO2 supercells containing subsitutional nitrogen, interstitial nitrogen or oxygen vacancies were calculated. TiO2 doped with substitutional nitrogen has shallow acceptor states above the valence band. In contrast, TiO2 doped with interstitial nitrogen has isolated impurity states in the middle of the band gap. These impurity energy levels are mainly hybridized by N 2p states with O 2p states and Ti 3d states. TiO2 containing oxygen vacancy has shallow donor states below the conduction band, which consists of Ti 3d states. Except for containing oxygen vacancies, the band gaps of N-doped TiO2 are narrowed in the range 0.03–0.23 eV, and thus their fundamental absorption edges extend to the visible-light region. By nitrogen doping, the octahedral dipole moments in TiO2 increase due to the changes in lattice parameters, bond length and charges on atoms, which is very effective for the separation of photoexcited electron–hole pairs. The calculated results are consistent with the existing experimental data. Based on these results, the effects on the electronic structure and photocatalytic activity of anatase TiO2 doped with nitrogen were analysed and compared in detail, and the mechanism by which anatase TiO2 doped with nitrogen has higher photocatalytic activity than that of pure TiO2 was explained. The conclusions have important significance for understanding and further developing TiO2 photocatalysts that are active under visible-light irradiation.