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Acetone is an important biomarker for the diagnosis of diabetes. In this work, the ZnFe2O4/ZnSnO3 nanocomposite was first prepared via a facile two-step hydrothermal method, and then obtained by the subsequent calcination process. The structure, morphology, and composition of the nanocomposite were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunner Emmet Teller (BET), scanning electron microscope (SEM), Transmission Electron Microscopy (TEM) and Fourier transform infrared spectrophotometer (DR-FTIR) techniques, and the gas-sensing performance of the composites were investigated comprehensively. The ZnFe2O4/ZnSnO3 nanocomposite is consisted by the ZnSnO3 cubic and the urchin-like ZnFe2O4. The as-prepared ZnFe2O4/ZnSnO3-0.25 gas sensor shows excellent gas-sensing performance toward acetone, including fast response-recovery time (9 s/16 s to 30 ppm acetone), long-term stability and good humidity resistance at 200°C. The improved gas sensing performance of ZnFe2O4/ZnSnO3-0.25 nanocomposite could be due to its large specific surface area, oxygen vacancy and n-n heterojunction.

In this paper a novel visible light-driven ternary compound photocatalyst (β-NaYF4:Ho3+@TiO2-rGO) was synthesized using a three-step approach. This photocatalyst was characterized using X-ray diffraction, Raman scattering spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy, fluorescence spectrometries, ultraviolet-visible diffuse reflectance spectroscopy, Brunauer–Emmett–Teller surface area measurement, electron spin resonance, three-dimensional fluorescence spectroscopy, and photoelectrochemical properties. Such proposed photocatalyst can absorb 450 nm visible light while emit 290 nm ultraviolet light, so as to realize the visible light-driven photocatalysis of TiO2. In addition, as this tenary compound photocatalyst enjoys effecitve capacity of charge separation, superior durability, and sound adsorb ability of RhB, it can lead to the red shift of wavelength of absorbed light. This novel tenary photocatalyst can reach decomposition rate of RhB as high as 92% after 10 h of irradiation by visible-light Xe lamp. Compared with the blank experiment, the efficiency was significantly improved. Recycle experiments showed that theβ-NaYF4:Ho3+@TiO2-rGOcomposites still presented significant photocatalytic activity after four successive cycles. Finally, we investigated visible-light-responsive photocatalytic mechanism of the β-NaYF4:Ho3+@TiO2-rGO composites. It is of great significance to design an effective solar light-driven photocatalysis in promoting environmental protection.

In this research, a composite material (MWCNT@BiVO4) was prepared using a one step hydrothermal method. The prepared composite material was characterized by energy-dispersive X-ray analysis, X-ray diffraction, scanning electron microscopy, EDS, UV-Vis diffuse-reflectance spectroscopy, electron spin resonance (ESR), X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The scanning electron microscopic images showed that MWCNTs were successfully embedded into BiVO4. MWCNT@BiVO4 showed a strong visible-light absorption capacity, high efficiency for electron–hole separation, and excellent stability. The degradation test of RhB was conducted under visible light irradiation. Compared with BiVO4 (K = −0.05657) and P25 (K = −0.03227), MWCNT@BiVO4 (K = −0.11894) realized the highest removal ratio of Rhodamine B (RhB) under visible light irradiation, therefore, MWCNT@BiVO4 might be promoted to practical applications. The stability of MWCNT@BiVO4 was also verified via recycling and reusing experiments. After 5 cycles, MWCNT@BiVO4 could still maintain the removal rate of RhB at 95.96%. In addition, this paper deduced the growth mechanism of MWCNT@BiVO4 and the degradation mechanism of RhB, proving that MWCNT@BiVO4 can be used in future practices.

Formaldehyde (HCHO) is a harmful gas to human health. Here, the CaFe2O4 nanocubes have been successfully synthesized via one-step hydrothermal method. The characterizations of the CaFe2O4 have been carried out, such as XRD, BET, TEM and XPS, etc. The gas-sensing performance of the CaFe2O4 to HCHO has been investigated. The CaFe2O4 based sensor displays high gas response (16.50), fast response-recovery time (153 s, 54 s), excellent humidity resistance and longtime stability. This unique CaFe2O4 nanocube can be used as a hopeful HCHO gas sensing material.

Ho 3+ single-doped YF 3 nanoparticles were successfully synthesized by a hydrothermal method. Ultraviolet upconversion luminescence around 288 nm was observed clearly in YF 3 :Ho 3+ nanoparticles under excitation at 450 nm. The structure, composition and upconversion emission properties of the as-prepared products were characterized by X-ray crystallography, scanning electron spectrophotometry, energy-dispersive X-ray analysis, and fluorescence spectrophotometry. Hydrothermal temperature had a significant influence on the size and morphology of YF 3 :Ho 3+ nanoparticles, but the molar ratio of Y 3+ /Ho 3+ had little effect on these characteristics. Upconversion emission spectra demonstrated that the upconversion luminescence properties of the synthesized products were closely related to hydrothermal temperature and the molar ratio of Y 3+ /Ho 3+ . The YF 3 :Ho 3+ @TiO 2 photocatalyst was prepared via a sol-gel process and gave higher photocatalytic activity in degraded Rhodamine B (RhB) than did P25 under Xe lamp irradiation.

A β-NaYF4:Ho3+@TiO2 core–shell microcrystal photocatalyst was synthesized using a hydrothermal method followed by hydrolysis of tetra-n-butyl titanate (TBOT), with polyvinylpyrrolidone K-30 (PVP) as the coupling agent. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, fluorescence and Raman spectrometry, ultraviolet-visible diffuse reflectance spectroscopy, and electron spin resonance were used to characterize the photocatalyst. It was found that the core's hexagonal phase NaYF4:Ho3+ microcrystals were evenly coated by a TiO2 shell and that the average β-NaYF4:Ho3+ microcrystal length was roughly 9 μm with a diameter of about 3.8 μm. After doping which caused a slight increase, the average thickness of the TiO2 shells was about 50 nm. Because Ho3+-single-doped β-NaYF4:Ho3+@TiO2 displays strong visible absorption peaks at 450, 537, and 642 nm, we chose 450, 532, and 633 nm to be the excitation wavelengths. We found ultraviolet emission bands at 290 nm (5D4 → 5I8) and 389 nm (3K7/5G4 → 5I8). Also, the energy transfer from β-NaYF4:Ho3+ to anatase TiO2 was confirmed. Rhodamine B (RhB) was used as a model pollutant to investigate the photocatalytic activity of β-NaYF4:Ho3+@TiO2 microcrystals under Xe lamp (500 W) irradiation. This investigation showed an advanced visible-light-driven catalyst, with about 67% of the RhB decomposed after 10 h. Compared with the blank experiment, the efficiency was obviously improved. Recycling experiments showed that the β-NaYF4:Ho3+@TiO2 composite still presented significant photocatalytic activity after four successive cycles. Finally, we investigated the β-NaYF4:Ho3+ upconversion (UC) mechanism and the β-NaYF4:Ho3+@TiO2 core–shell microcrystal visible-light-responsive photocatalytic mechanism. Understanding the visible-light-responsive photocatalytic mechanism will help to improve the structural design and functionality of this new type of catalytic material.

In order to realize high efficiency visible-light absorption and electron–hole separation of bismuth vanadate (BVO), we synthesized carbon-doped BVO (C-BVO) with high visible-light absorption behavior. We used polyvinylpyrrolidone K-30 as a template and L-cysteine as the carbon source in a one-step hydrothermal synthesis method, and then obtained the carbon-doped BVO@multi-walled carbon nanotubes (C-BVO@MWCNT) by a two-step method. The carbon nanotubes were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, specific surface area, electron spin resonance, and transient photocurrent responses. The XRD analysis confirmed that all photocatalysts were in the same crystal form with a single monoclinic scheelite structure. Combining this with the other characterization results, we showed that the carbon element was successfully doped in BVO and the resulting C-BVO was successfully coupled with multi-walled carbon nanotubes. The removal ratio of rhodamine B by C-BVO@MWCNT was much higher than those by BVO and C-BVO under visible-light irradiation. Recycling experiments verified the stability of C-BVO@MWCNT, which was proved to offer excellent adsorption, strong visible-light absorption behavior, and high electron–hole separation efficiency. Such properties are expected to be useful in practical applications.

Disinfection by-products (DBPs) play a significant role in human health. Identification of the precursor of DBPs, which constitutes dissolved organic matter (DOM), can help optimize the processes in a drinking water treatment plant (DWTP). This is very important for obtaining more safe water. In this context, a one-year study was performed in a DWTP. Fluorescence spectra of DOM were quantified for determining DOM composition and properties, and the corresponding DBPs formation was analyzed. Hydrophobic neutral and acidic compounds were found to be the two predominant substances forming DBPs, which also were dominant in the DOM. Coagulation and sedimentation were not effective in DOM elimination. Besides, sand filtration caused organic compounds to increase by 14.8% on average, especially 28.59% for aromatic protein II and 18.7% for soluble microbial product-like compounds, which was due to metabolism by microorganisms present in the filter. Carbonaceous DBPs were elevated from 34.8 μg/L in source water to 42.5 μg/L in effluent, along with organic compounds increasing in filtration, and nitrogenous DBPs were under detection in winter. All DBPs appeared at a high level in summer. Accordingly, enhanced coagulation process and measures that can avoid the release of organic compounds during filtration have been suggested. As the source water was rarely affected by human activities in the study area and owing to the wide use of traditional treatment process, the data of this research can be regarded as environmental background values and the results are considered as a significant reference.

Many studies have focused on the use of BiVO4 as a photocatalyst, but few have investigated the production of free radicals during the photocatalytic process. Following synthesis of flowerlike BiVO4 and characterization by X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM) Scanning electron microscopy (EDX), UV-Vis and XPS, we successfully prepared BiVO4. Then we used electron spin resonance (ESR) to determine the production and degradation of individual active free radicals, including the superoxide radical (·O2-) and the hydroxyl radical (·OH). In the first experiment, we used ESR to detect the signals of free radicals (·O2- and ·OH) under varying oxygen conditions. The results shown that in addition to production by ·O2-, ·OH could also be produced by oxidation of h+ to OH−. In the next experiment, we detected ·OH under varying pH to identify the result of the first experiment, and found that signal intensities increased with increasing pH, indicating the mechanism for ·OH production. Finally, we conducted a trapping experiment to examine free radical degradation mechanisms. We identified ·OH and h+ as the main active free radicals and showed the complete production about ·OH. These results improve current knowledge of free radical production mechanisms, which can be used to enhance the photocatalytic performance of BiVO4.

To achieve an efficient visible-light absorption and degradation of bismuth vanadate (BiVO4), in this paper, a carbon-doped (C-doped) nanosheets monoclinic BiVO4 (m-BiVO4), with thicknesses within 19.86 ± 8.48 nm, was synthesized using polyvinylpyrrolidone K-30 (PVP) as a template and l-carbonic as the carbon source by one-step hydrothermal synthesis method. This C-doped BiVO4 in three-dimensional (3D) hierarchical structure enjoys high visible-light photocatalytic property. The samples were characterized using x-ray diffraction, scanning electron microscope, Raman spectra, energy dispersive spectrometer, transmission electron microscope, x-ray photoelectron spectroscopy, UV–Vis diffused reflectance spectroscopy, specific surface area, electron spin resonance, and transient photocurrent response, photoluminescence spectra, and incident-photon-to-current conversion efficiency, respectively. What is more, we studied the C-doping effect on the band-gap energy of BiVO4 based on First-principles. X-ray diffraction analysis showed that all photocatalysts were in the same single monoclinic scheelite structure. According to the other characterization results, the element C was successfully doped in BiVO4, resulting in the 3D hierarchical structure of C-doped BiVO4 (P-L-BiVO4). We speculated that it could be the directional coalescence mechanism by which the l-cysteine promoted the two-dimensional growth and C-doping process of BiVO4, thus leading to the formation of nanosheets which were then promoted into 3D self-assembly by PVP and the shortening of the band gap. Among all samples, P-L-BiVO4 can make the highest removal ratio of rhodamine B under visible-light irradiation. The stability of P-L-BiVO4 was verified by recycle experiments. It showed that P-L-BiVO4 had strong visible-light absorption behavior and high electron–hole separation efficiency and stability, making a significant advantage in actual situation.

We prepared a unique leaf-like BiVO4-reduced graphene oxide (BiVO4-rGO) composite with prominent adsorption performance and photocatalytic ability by a single-step method. Multiple characterization results showed that the leaf-like BiVO4with average diameter of about 5 um was well dispersed on the reduced graphene oxide sheet, which enhanced the transportation of photogenerated electrons into BiVO4, thereby leading to efficient separation of photogenerated carriers in the coupled graphene-nanocomposite system. The characterization and experiment results also indicated that the outstanding adsorption ability of such composite was closely associated with the rough surface of the leaf-like BiVO4and doped rGO. The surface photocurrent spectroscopy and transient photocurrent density measurement results demonstrated that the doped rGO enhanced separation efficiency and transfer rate of photogenerated charges. As a result, the BiVO4-rGO exhibited higher photocatalytic capacity toward the degradation of rhodamine B dye under visible-light irradiation compared with pure BiVO4and P25.

In this study, Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst was prepared via a sol-gel method, and Fe(3)O(4) particles were used as the core of the colloid. Diffraction peaks of Fe(3)O(4) crystals are not found by XRD characterization, indicating that Fe(3)O(4) particles are well encapsulated by SiO(2). FTIR characterization shows that diffraction peaks of Ti-O-Si chemical bonds become obvious when the Fe(3)O(4) loading is more than 0.5%. SEM characterization indicates that agglomeration occurs in the Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst, whereas photocatalysts modified by Fe(3)O(4)/SiO(2) present excellent visible light absorption performance and photocatalytic activity, especially when the Fe(3)O(4) loading is 0.5%. Photocatalytic degradation of glyphosate in soil by these photocatalysts under solar irradiation was investigated. Results show that 0.5% Fe(3)O(4)/SiO(2)/TiO(2) has the best photocatalytic activity. The best moisture content of soil is 30%~50%. Degradation efficiency of glyphosate reaches 89% in 2 h when the dosage of photocatalyst is 0.4 g/100 g (soil), and it increased slowly when more photocatalyst was used. Soil thickness is a very important factor for the photocatalytic rate. The thinner the soil is, the better the glyphosate degradation is. Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm(2) or above 10 mW/cm(2), but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm(2) to 10 mW/cm(2).

In this paper, YF3:Ho3+@TiO2 core-shell nanomaterials were prepared by hydrolysis of tetra-n-butyl titanate (TBOT) using polyvinylpyrrolidone K-30 (PVP) as the coupling agent. Characterization methods including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) under TEM, X-ray photoelectron spectroscopy (XPS), fluorescence spectrometry, ultraviolet-visible diffuse reflectance spectroscopy, and electron spin resonance (ESR) were used to characterize the properties and working mechanism of the prepared photocatalyst material. They indicated that the core phase YF3 nanoparticles were successfully coated with a TiO2 shell and the length of the composite was roughly 100 nm. The Ho3+ single-doped YF3:Ho3+@TiO2 displayed strong visible absorption peaks with wavelengths of 450, 537, and 644 nm, respectively. By selecting these three peaks as excitation wavelengths, we could observe 288 nm (5D4→5I8) ultraviolet emission, which confirmed that there was indeed an energy transfer from YF3:Ho3+ to anatase TiO2. In addition, this paper investigated the influences of different TBOT dosages on photocatalysis performance of the as-prepared photocatalyst material. Results showed that the YF3:Ho3+@TiO2 core-shell nanomaterial was an advanced visible-light-driven catalyst, which decomposed approximately 67% of rhodamine b (RhB) and 34.6% of phenol after 10 h of photocatalysis reaction. Compared with the blank experiment, the photocatalysis efficiency was significantly improved. Finally, the visible-light-responsive photocatalytic mechanism of YF3:Ho3+@TiO2 core-shell materials and the influencing factors of photocatalytic degradation were investigated to study the apparent kinetics, which provides a theoretical basis for improving the structural design and functions of this new type of catalytic material.

Dissolved organic matters (DOM) are critical in the formation of the mutagenic disinfection byproducts (DBPs). In this study, five DOM fractions were isolated and investigated from a contaminated river and a clean reservoir source waters using resin adsorption. The DOM fractions were characterized with excitation-emission matrix, and several typical DBPs formation potentials and the mutagenicity of each DOM fraction were measured. Among these fractions, hydrophobic neutrals (HON), hydrophilic acids (HIA) and hydrophilic bases (HIB) generated the highest carbon-containing DBPs in the river source water, as did HIB and hydrophobic bases (HOB) in reservoir water. Hydrophobic acids (HOA), HON, and HIA were the three most important fractions forming nitrogen-containing DBPs. Following chlorination, the mutagenicity of HON, HIA, HOA and HIB was 1503, 626, 422 and 116 ng 4-NQO/mg DOC in river water, respectively. Only HIA and HOA were mutagenic with 85 and 10 ng 4-NQO/mg DOC in reservoir water, respectively. The soluble microbial products like substances and aromatic proteins contributed significantly to the mutagenicity of river water; whereas the humic acid-like and fulvic acid-like substances were the primary contributors to the mutagenicity of reservoir water.