Xiaoxue Lian’s research while affiliated with Civil Aviation University of China and other places

Phosphoric acid-activated biochar has been proven to be a promising adsorbent for pollutant removal in an aqueous solution. It is urgent to understand how surface adsorption and intra-particle diffusion synergistically contribute to the adsorption kinetic process of dyes. In this work, we prepared a series of PPC adsorbents (PPCs) from red-pulp pomelo peel under different pyrolysis temperatures (150–350 °C), which have a broad specific surface area range from 3.065 m^2/g to 1274.577 m^2/g. The active sites on the surface of PPCs have shown specific change laws of decreasing hydroxyl groups and increasing phosphate ester groups occurring as the pyrolysis temperature rises. Both reaction models (PFO and PSO models) and diffusion models (intra-particle diffusion models) have been applied to simulate the adsorption experimental data to verify the hypothesis deduced from the Elovich model. PPC-300 exhibits the highest adsorption capacity of MB (423 mg/g) under given conditions. Due to its large quantities of active sites on the external and internal surfaces (1274.577 m^2/g), a fast adsorption equilibrium can be achieved within 60 min (with an initial MB concentration of 100 ppm). PPC-300 and PPC-350 also exhibit an intra-particle-diffusion-controlled adsorption kinetic process with a low initial MB concentration (100 ppm) or at the very beginning and final stage of adsorption with a high initial MB concentration (300 ppm) at 40 °C, considering that the diffusion is likely hindered by adsorbate molecules through internal pore channels at the middle stage of adsorption in these cases.

The g-C3N4 nanosheets were synthesized by a multistage program calcination with different heating rate, which was an easy, low-cost, and quick method. The morphology and structure of samples were characterized by various techniques. The performance evaluation of the samples was tested by degrading Rhodamine B, Methylene Blue, Tetracycline Hydrochloride and P-Nitrophenol in visible light. The results show that the photodegradation properties of TP-g-C3N4 prepared by multistage program calcination are the best than others. In particular, the degradation rate of TP-g-C3N4 to Rhodamine B reached 99.6% in just 4 min. TP-g-C3N4 catalyst has excellent stability and recycling performance. According to free radical capture experiments, •O2⁻ may be the main active species for pollutant degradation. The possible photocatalytic degradation mechanism was also discussed. Due to the high specific surface area and a narrow band gap, the TP-g-C3N4 becomes a promising photocatalyst.

Metal oxide semiconductor-based sensors are widely used in medicine, industry, agriculture and environmental protection. In this paper, a series of different molar ratios of Sm were doped into SnO2 nanoparticles through a coprecipitation route. The as-obtained Sm/SnO2 nanocomposites were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscope. The results indicated that Sm doping reduced the size of SnO2 nanoparticles and an Sm-O-Sn bond formed on the surface of Sm/SnO2 nanocomposites. The gas-sensing examination of the Sm/SnO2 nanocomposite-based sensor was assessed, and the results displayed that the fabricated sensor with a 4% molar ratio of Sm-decorated SnO2 exhibited a high response (138.9) and outstanding selectivity towards ethanol gas at 160 °C, and the limit of detection was as low as 100 ppb, implying a potential application in trace gas detection. Finally, the enhancement response of the Sm-doped SnO2 nanocomposites was discussed.

Cu-doped TiO 2 having a brookite phase and showing enhanced visible light photocatalytic activity was synthesized using a mild solvothermal method. The as-prepared samples were characterized by various techniques, such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy. Photocatalytic activity of Cu-doped brookite TiO 2 nanoparticles was evaluated by photodegradation of methylene blue under visible light irradiation. The X-ray diffraction analysis showed that the crystallite size of Cu-doped brookite TiO 2 samples decreased with the increase of Cu concentration in the samples. The UV-Vis diffuse reflectance spectroscopy analysis of the Cu-doped TiO 2 samples showed a shift to lower energy levels in the band gap compared with that of bare phase brookite TiO 2 . Cu doped brookite TiO 2 can obviously improve its visible light photocatalytic activity because of Cu ions acting as electron acceptors and inhibiting electron-hole recombination. The brookite TiO 2 sample with 7.0 wt.% Cu showed the highest photocatalytic activity and the corresponding degradation rate of MB (10 mg/L) reached to 87 % after visible light illumination for 120 min, much higher than that of bare brookite TiO 2 prepared under the same conditions (78 %).

Pure brookite TiO2 with unique structure and property has demonstrated to be an interesting candidate in photocatalytic applications in recent years. In this study, single-phase brookite TiO2 was controllable synthesized via hydrothermal method using titanium chloride (TiCl4), sodium lactate and urea as starting materials. The structure and morphology of as-synthesized samples were characterized by various techniques, such as X-ray powder diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The band gap value of as-synthesized samples was calculated by ultraviolet–visible (UV–vis) spectroscopy. Experimental results showed that the co-existence of sodium lactate and urea contributed to the formation of single-phase brookite TiO2. The amounts of sodium lactate and urea had significant effects on the structure and morphology of as-synthesized samples. Sodium lactate acted as a key complexant, and the concentration of urea determined the crystalline structure of as-synthesized samples. Single-phase brookite TiO2 was obtained when the amount of sodium lactate and urea was not less than 2.0 mL and 3.0 g, respectively. As the amount of sodium lactate or urea increases, the morphology of as-synthesized brookite TiO2 changes from quasi-spherical structures to rod-like structures. This study might be useful for understanding how the pure structure of brookite TiO2 is formed under given conditions and furtherly overcoming the difficulties of the preparation of pure brookite TiO2 with high purity and large specific surface area, which limits its applications in the field of photocatalysis. Graphic abstract

Stannic oxide nanoparticles with the different Au decorating contents are prepared by a simple hydrothermal method in this paper. The products are characterized by X-ray diffraction (XRD), energy dispersive spectrum (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns reveal that all the products are tetragonal phase of rutile SnO2 crystal structure. The gas-sensing performance of the Au-decorated SnO2 nanoparticles for volatile organic compounds (VOCs) are studied. At its optimal operation temperature of 240 oC, the sensing properties of the Au-decorated SnO2 nanoparticles to n-buthanol gas show a good gas sensing performances as low detection limit (1ppm), good selectivity and good repeatability. The highest sensing response of 6.0 at. % Au-decorated SnO2 nanoparticles (251.23 for 200 ppm to n-buthanol) is over 21 times higher than that of pure SnO2 (11.5). All results prove the potential of using Au-decorated SnO2 for n-buthanol gas detection.

Solvothermal reactions of the 2,5-di(1H-1,2,4-triazol-1-yl)terephthalic acid (H2L), ancillary bridging linkers oxalate, and transitional metal Co(II) cations afford two coordination polymers, namely, [Co(L0.5)2(H2O)]n (1), and [Co2L(ox)H2O]n (2), (L = 2,5-di(1H-1,2,4-triazol-1-yl)terephthalic acid, ox²⁻ = oxalate). Their structures and properties have been determined by single-crystal X-ray diffraction analyses, IR spectra, elemental analyses, thermogravimetric analyses (TGA). Complex 1 exhibits an interesting 3D framework with double helical 2D sheets structure. The host network of complex 2 displays an unusual 3D networks by 1D chains, which are further connected by L²⁻ ligands into dense packing structures. Topology analyses reveal that 1 and 2 can be simplified as a trinodal (4,5,6)-connected topological net with a point symbol of (4² · 6² · 8²)(4⁴ · 6³ · 8³)2(4⁶ · 6⁷ · 8²) for 1, and (4² · 8⁴)(4⁶ · 6⁶ · 8³)(4⁸ · 6²)2 for 2. Besides, magnetic studies indicate both complexes 1 and 2 showing antiferromagnetic properties.

In this work, coryphantha elephantidens-like SnO 2 with porous structures were prepared successfully by a simple hydrothermal route, through adjusting the temperature of hydrotherm. Its morphology was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET). Compared to the regular nanospheres, the coryphantha elephantidens-like SnO 2 nanospheres had obviously higher gas-sensing response, owing to the special structure with large specific surface area (161.16 m ² g ⁻¹ ). It surprised us that the coryphantha elephantidens-like SnO 2 sensor could easily distinguish between ethanol and acetone, whose chemical property were similar. Moreover, it also exhibited wide measurement range, fast response speed (less than 10 s) and good repeatability at a low temperature (180 °C) to ethanol. The desirable specific surface area and pore volume were conducive to molecules adsorption and diffusion, which were believed to be the major cause of the improvement of gas sensing performance.

A series of high-response and fast-response/recovery n-butanol gas sensors was fabricated by adding ZnO to In2O3 in varying molar ratios to form ZnO-In2O3 nanocomposites via a facile co-precipitation hydrothermal method. Morphological characterizations revealed that the shape of pure In2O3 was changed from irregular cubes into irregular nanoparticles, 30–50 nm in size, with the addition of ZnO. Compared with the pure In2O3 gas sensor, the ZnO-In2O3 gas sensor exhibits superior n-butanol sensing performance. With the introduction of ZnO, the response of the sensor to n-butanol was improved from 17 to 99.5 at 180 °C for a [Zn]:[In] molar ratio of 1:1. In addition, the ZnO-In2O3 gas sensors show a reduced optimal working temperature, excellent selectivity to n-butanol, and good repeatability. The response of the ZnO-enhanced In2O3-based sensors showed a strong linear relationship with the n-butanol gas concentration, allowing for the quantitative detection of n-butanol gas.