Noble-metal-free Fe3O4/Co3S4 nanosheets with oxygen vacancies as an efficient electrocatalyst for highly sensitive electrochemical detection of As(III).

The electrochemical method for highly sensitive determination of arsenic(III) in real water samples with noble-metal-free nanomaterials is still a difficult but significant task. Here, an electrochemical sensor driven by noble-metal-free layered porous Fe3O4/Co3S4 nanosheets was successfully employed for As(III) analysis, which was prepared via a facile two-step method involves a hydrothermal treatment and a subsequent sulfurization process. As expected, the electrochemical detection of As(III) in 0.1 M HAc-NaAc (pH 6.0) by square wave anodic stripping voltammetry (SWASV) with a considerable sensitivity of 4.359 µA/µg·L-1 was obtained, which is better than the commonly used noble metals modified electrodes. Experimental and characterization results elucidate the enhancement of As(III) electrochemical performance could be attributed to its nano-porous structure, the presence of oxygen vacancies and strong synergetic coupling effects between Fe3O4 and Co3S4 species. Besides, the Fe3O4/Co3S4 modified screen printed carbon electrode (Fe3O4/Co3S4-SPCE) shows remarkable stability and repeatability, valuable anti-interference ability and could be used for detection in real water samples. Consequently, the results confirm that as-prepared porous Fe3O4/Co3S4 nanosheets is identified as a promising modifier to detect As(III) in real sample analysis.

[The Latest Research Progress of Coupling between BiOX and Semiconductor Photocatalyst].

The heterojunction was formed between two kinds of coupling semiconductors , which improved the charge separation efficiency of system, widened the spectral response range of catalysts and improved photocatalytic propertirs of catalysts. The process of preparation of semiconductors coupling was easily affected by preparation methods and reaction temperature and so on, which would cause the changes in crystal structure and surface properties of coupling semiconductors, thus photocatalytic quantum efficiency of coupling semiconductors was increased. In this article, the following three aspects were mainly discussed. (1) About the coupled system of halogen bismuth oxide and oxide, because generaling BiOX with the semiconductor material compound, the efficient heterojunction structure could be formed, photocatalytic performances of the photocatalytic degradation of pollutants were improved. (2) About the coupled system of AgX and BiOX, compared with the pure AgI or BiOI, composite photocatalytic materials of AgI/BiOI had higher photocatalytic reactivity in visible light. (3) About the coupled system of halogen bismuth oxide and other compounds, after Bi2S3 coupled with BiOX, photoproduction electronic migrated in the two kinds of catalysts, the separation efficiency of electrons and holes was improved, and photocatalytic performances of coupling compound were improved. In addition, in recent years, the latest research progress of the preparation method, the influencing factors of the photocatalytic performance and improving the utilization efficiency of visible light of semiconductors coupling at home and abroad was reviewed in this paper. Finally, the main problems and the future striving direction in semiconductors coupling were presented.

[A Study on Preparation and Photocatalytic Activity of Mn-BiOCl].

Using Bi2O3 and MnC2 x 4H2O as raw materials, with HCl as solvent, photocatalysts of Mn-BiOCl with different molar ratio of Mn and Bi were prepared by a hydrolysis method. The obtained samples were characterized by XRD, HRTEM, TEM, UV-Vis DRS and SPS. The UV light photocatalytic activity of Mn-BiOCl was evaluated by using methyl orange as model compounds of photocatalytic reaction. The active species in the degradation process of methyl orange were studied. The results show that the Mn content of Mn-BiOCl photocatalysts has an important effect on the catalytic activity. When the molar ratio of Mn and Bi is 0.25%, the as-prepared Mn-BiOCl photocatalyst has the highest catalytic activity toward the degradation of methyl orange. Photocatalytic degradation rate of methyl orange can reach 95.1%.

[Study on synthesis and matching degree of energy level of terbium complexes using o-fluoro-benzoic acid as ligand].

Tb(2-FBA)3 x 2H2O and Tb(2-FBA)3 phen were synthesized using o-fluoro-benzoic acid (2-FBA) as the first ligand, and 1,10-phenanthroline (phen) as the second ligand. Elemental analysis and IR spectra were employed to characterize the molecular composition of the two kinds of lanthanide complexes. The UV absorption spectra with same concentration show that the second ligand phen of Tb(2-FBA)3 phen absorbs the portion of the UV light instead of the first ligand 2-FBA. Liquid fluorescence spectra with same concentration show that the fluorescence intensity of Tb(2-FBA)3 x 2H2O is higher than that of Tb (2-FBA)3 phen. The analytical results show that the energy level of 2-FBA matches the lowest excited state energy level of Tb3+ (5D4) better than that of phen. The O-H oscillation of the crystal water in Tb(2-FBA)3 x 2H2O will greatly consume the absorbed energy by ligands, and cause the fluorescence intensity of Tb(2-FBA)3 x 2H2O significantly decline. The energy level of triplet state of the first ligand 2-FBA corresponding to the absorption peak 273 nm has poor matching degree with the 5D4 energy level of Tb3+. In this case, the emission intensity of Tb(2-FBA)3 x 2H2O is still stronger than that of Tb(2-FBA)3 phen. It illustrates that the energy level of the triplet state of the first ligand 2-FBA corresponding to 252 nm has much better matching degree with the lowest excited state of 5D4 energy level of Tb3+ than that of phen. It is the only way to compensate for energy loss by thermal vibration of water molecules and low energy transfer efficiency for poor matching degree between the energy level of corresponding to 273 nm of the first ligand 2-FBA and 5D4 energy level of Tb3+. By combining UV absorption spectra with fluorescence spectra of lanthanide complexes to qualitatively analyze energy level of ligands, the contribution of different types of ligands to the fluorescence properties can be preliminarily understood.

[Study on preparations and fluorescent properties of rare earth complex with property of fluorescence sensor].

Europium chloride, 2-thienylformyltrifluoroacetone and sodium silicate were used to synthesize new-style rare earth complex (Eu-TNS). By adding into dichloromethane solution containing Eu-TNS, the fluorescent intensities were enhanced gradually and regularly. High-resolution mass spectrometry was used to detect the formula of Eu-TNS, which belongs to multi-core rare-earth complex. Polarity of solution increasing by adding absolute ethanol will cause Eu-TNS to dissociate, which enhances the fluoresceot intensities of Eu-TNS solution. This rare earth complex Eu-TNS can be employed as fluorescence sensor to detect the content of ethanol in organic solvent.

[Synthesis of SiO2 coated Eu(TTA)3phen and study on its fluorescent property].

New-style fluorescent material of SiO2/Eu(TTA)3 phen was synthesized by the method of dispersing Eu(TTA)3 phen in isopropanol and hydrolyzing TEOS. Fluorescence spectra showed that the emission intensities of SiO2/Eu(TTA)3 phen were much more stronger than that of Eu(TTA)3 phen by more than two times. At the same time, the peak at 617.4 nm became very sharp, which could not be observed for Eu(TTA)3 phen. This indicated that the structure of Eu(TTA)3 phen became more rigid after coated by SiO2. Thus, the emission intensity was enhanced largely. Life-time of SiOz/Eu(TTA)3 phen decreasing just confirmed the rigidity of SiO2/Eu(TTA)3 phen.

[Synthesis and characterization of new lanthanide complexes using pipemidic acid (PPA) and dioxane as ligands].

Eu(PPA)3 dioxane and Tb(PPA)3 dioxane were synthesized by firstly adopting dioxane as second ligand and using pipemidic acid (PPA) as first ligand. In contrast with two kinds of binary lanthanide complexes Eu(PPA)3 and Tb(PPA)3, the photoluminescent intensities of Eu (PPA)3 dioxane and Tb (PPA)3 dioxane are much stronger, especially for that of Tb(PPA)3 dioxane. The enhancement of photoluminescent intensities of Eu(PPA)3 dioxane and Tb(PPA)3 dioxane is because of the replacement of dioxane for water bonded to Eu3+ and Tb3+, by which the energy loss through heat oscillation will be inhibited. The as-synthesized lanthanide complexes were characterized by FT-IR, photoluminescence spectra and photoluminescence lifetime. The lifetime of Eu(PPA)3 dioxane and Tb(PPA) dioxane remarkably changed compared with those of Eu(PPA)3 and Tb(PPA)3. However, there is much difference for the lifetime change of as-synthesized lanthanide complexes formed by Eu3+ and Tb3+, which shows that there is different energy transfer process for the lanthanide complexes formed by Eu3+ and Tb3+. The synthesis of lanthanide complexes using dioxane as second ligand will provide a new method to detect the existence of dioxane.

Synthesis of Galacto-oligosaccharide in Two-phase System.

35 of the total products of galacto-oligosaccharide (GOS) could be obtained from the two-phase system with cyclohexane and ethyl acetate as bulk organic phases and 15% phosphate buffer as aqueous phase. The effects of temperature pH of buffer lactose concentration galactose and glucose and the immobilization of enzyme on the synthesis of GOS were studied. It was found that the reaction temperature and initial lactose concentration didn'thave obvious effects while the addition of glucose and galactose somewhat affected the GOS yield and the GOS yields could reach 64.78% with lactase immobilized on resin D345.