[Chemical Composition and Characterization of Nitroaromatic Compounds in Urban Areas of Shanghai].

The compositional characteristics, concentration of nitroaromatic compounds(NACs) in PM2.5 in urban Shanghai, and their correlation with gaseous precursors were investigated. A total of 39 winter and 46 summer PM2.5 samples from 2020 to 2021 were collected using a high-flow sampler and analyzed via ultra-performance liquid chromatography coupled with ESI-Orbitrap high-resolution mass spectrometry(UPLC-Orbitrap-HRMS). Quantitative analysis was performed on 12 NACs compounds, combined with backward trajectory meteorological elements, molecular composition, and classification analysis of CHON substances. The results showed that a total of 12 NACs had an average concentration in winter of 17.1 ng·m-3, which was three times higher than that in summer(5.7 ng·m-3), mainly due to air masses in winter coming primarily from the northern part of China with more biomass burning, whereas more air masses in summer came from the cleaner southeastern ocean. 4-Nitrophenol was the most abundant species of NACs in winter, whereas 4-nitrophenol(clean days) and 4-hydroxy-3-nitrobenzoic acid(polluted days) were the most abundant species in summer. Qualitative analysis based on features such as aromatic ring equivalence number(Xc), O/C, and H/C values for the identification and characterization of monocyclic and polycyclic aromatic compounds showed that CHON compounds were mainly aromatic compounds in winter and summer in urban Shanghai. The number and abundance of CHON compounds detected on PM2.5 polluted days were 2 and 1.5 times higher(winter) and 2.5 and 2 times higher(summer) than that on clean days, respectively. Comparing the analysis results of clean and polluted days in winter and summer, it was found that 80% of the CHON compounds with a relative abundance in the top 10 had O/N ≥ 3 and RDBE values between 5 and 8. The results suggest that these highly abundant CHON analogs may have had mononitro- or dinitro-substituted benzene rings. Correlation analysis between gaseous precursors and NACs indicated that oxidative reactive formation of VOCs(benzene, toluene, etc.) from anthropogenic emissions was the main source of NACs in summer. By contrast, it was influenced by a combination of biomass combustion emissions and secondary formation of oxidative NOx from anthropogenic VOCs in winter.

[Characteristics of Nitroaromatic Compounds in PM2.5 in Urban Area of Shanghai].

Nitroaromatic compounds (NACs) are an important class of nitrogen-containing compounds in fine particles. The investigation of characteristics and seasonal variation of NACs in PM2.5 increases our knowledge about nitrogen-containing compounds and contributes to the scientific basis in formulating reduction policies of NOx in urban areas. In this study, we analyzed the chemical composition of PM2.5 samples collected from March 2018 to February 2019 in an urban location in Shanghai. A total of 2439-3695 organic molecular formulas were detected using UPLC-Orbitrap MS. Nine NACs were quantified using an internal standard method. In spring, ρ(NACs) ranged from 3.12 to 16.76 ng·m-3, and the average concentration was 9.31 ng·m-3. In summer, it ranged from 1.05 to 9.70 ng·m-3, and the average value was 4.16 ng·m-3. In autumn, it ranged from 2.87 to 36.27 ng·m-3, and its average was 9.84 ng·m-3. In winter, it ranged from 4.83 to 56.23 ng·m-3, and the average was 22.37 ng·m-3. 4-Nitrophenol accounted for more than 25% of the quantified NACs in different seasons. In summer, the concentration of 5-nitrosalicylic acid accounted for 36%, but it decreased to 19% in winter. NACs in summer mainly originated from secondary formation, as evidenced by their clear correlation with the oxidant level, whereas biomass burning became the main source of NACs in winter.

Environmental stability and cytotoxicity of layered black phosphorus modified with Polyvinylpyrrolidone and Zeolitic Imidazolate Framework-67.

Layered black phosphorus (LBP) is regarded as a promising two-dimensional nanomaterial in various application fields. As bare LBP is unstable in humid environment, many modification methods have been developed recently. However, environmental risks of modified LBP nanomaterials are largely unknown. Herein, by sonication and in-situ surface-confined synthesis, polyvinylpyrrolidone (PVP) coated LBP (LBP/PVP), and zeolitic imidazolate framework-67 (ZIF-67) modified LBP (LBP/PVP-ZIF-67) nanomaterials were synthesized. Environmental stability and toxicity of the modified nanomaterials were compared with bare LBP. Results show that LBP/PVP-ZIF-67 exhibits excellent photothermal performance, and higher potential in electrochemical hydrogen evolution than bare LBP or LBP/PVP. Characteristic visible light absorbance at 593 nm was introduced into the nanomaterial by ZIF-67. LBP/PVP has stability in aqueous environment or cytotoxicity similar to LBP. LBP/PVP-ZIF-67 is completely stable in water within 120 h, in contrast to over 30% degradation of LBP or LBP/PVP. More than 50% of LBP in the LBP/PVP-ZIF-67 can degrade to dissolvable phosphorus in oxygenated water after 17 days, indicating the nanomaterial will not be persistent in the environment. Moreover, modification with ZIF-67 can reduce cytotoxicity of LBP. Therefore, this study develops a safe strategy to modify LBP and provides basic information for ecological risk assessment of LBP based materials.

Preparation of Copolymer-Based Nanoparticles with Broad-Spectrum Antimicrobial Activity.

Polyacrylate and guanidine-based nanoparticles which involve acrylate monomers and glycidyl methacrylate modified oligo-guanidine were prepared by a seeded semi-continuous emulsion polymerization. The results from transmission electron microscope and dynamic light scattering measurements showed that the nanoparticles were spherical in shape and the particle size was in the range of 80⁻130 nm. Antimicrobial experiments were performed with two types of bacteria, Gram-negative (Escherichia coli, ATCC 8739) and Gram-positive (Staphylococcus aureus, ATCC 6538). The as-synthesized cationic nanoparticles exhibited effective antimicrobial activities on Escherichia coli and Staphylococcus aureus with the minimal inhibitory concentrations at 8 µg/mL and 4 µg/mL, respectively. The mechanism of action of the resulted nanoparticles against these bacteria was revealed by the scanning electron microscopic observation. In addition, the films consisting of latex nanoparticles are non-leaching antimicrobial materials with excellent antimicrobial activity, which indicates the polymers could preserve their antimicrobial activity for long-term effectiveness.

[Spectroscopic study on the conformational change of silk fibroin in methanol-water mixtures].

A combinational study of circular dichroism, intrinsic fluorescence of protein and exogenous fluorescence probe of ANS was made to investigate the conformational change of silk fibroin in methanol-water mixtures as well as the mechanism. The spectral results showed that small hydrophobic regions were formed in silk fibroin in methanol-water mixtures at the concentration lower than 30% (V/V) via hydrophobic interaction, which was decreased at higher methanol content due to a structural transition of silk fibroin from random coil to beta-sheet. The conformational change of silk fibroin was found to be of a close relationship with the microstructure of the solvent and to be determined by the interaction between the peptide unit of silk fibroin and the cluster of the mixed solvent. Methanol-water mixture at low concentration had little effect on the solvation of the peptide unit and the conformation of silk fibroin, as a consequence of the fact that the inherent water structure was conserved. The transition from the tetrahedral-like water structure to the chain-like methanol structure, due to the increasing concentration of methanol, induced the conformational change of silk fibroin to eliminate the contact of peptide unit with the solvent molecular.

[Spectroscopy characteristics of various aluminum phosphates in Al2O3-P2O5-H2O system and its high temperature products].

Various aluminum phosphates were prepared with phosphoric acid and aluminum hydroxide under different conditions. IR, XRD, Raman and SEM were used to study the structure difference and their change in heating process and particle morphology of obtained products and aluminum tripolyphosphate. The results show that the spectral characteristic change of phosphate from H2PO4-, PO4(3-), H2P3O10(3-) and PO3- can be seen when P/Al molar ratio = 3 or the condensation temperature is different. The PO symmetric stretching peaks shift to lower wavenumber and the bands widen along with the extent of polymerization. After aluminum tripolyphosphate is heated, the frequencies of stretching vibrational modes depend on the micro-structure units of phosphate and increase with the extent of polymerization. Both Raman and infrared spectra can characterize the pattern of the hydroxyl stretching vibrations. The laminated thickness of reaction product is increases and laminar boundary is vague until the clinker clew is formed.

[Spectral properties and thermal stability of zinc phosphate hydrate].

X-ray, FTIR, and Raman spectra were used to measure the spectral properties of three kinds of zinc phosphate hydrate. Spectral changes with crystalline water were analyzed. The thermal stability of zinc phosphate tetrahydrate was studied by TG-DTA to identify the existent temperature of zinc phosphate hydrate. The results show that the differences in crystalline water among these hydrates results in the variation in both 2theta characteristic values and peaks. The FTIR spectra reflect H--O--H strength information (1 600 cm(-1)) and O--H bond stretching vibrations (3 400-3 500 cm(-1)). Raman spectra show the difference in P--O bond stretching mode at 400-700 cm(-1) and the shape of O--H stretching peak. According to the mass-loss curves, the onset temperature of zinc phosphate tetrahydrate was 95 degrees C. Heating to 145 degrees C was accompanied by the removal of 2H2O and transform into Zn3 (PO4)2 x 2H2O, indicating that Zn3 (PO4)2 x 2H2O was established at this temperature. Zn3 (PO4)2 x H2O can be obtained by heating to 195 degrees C. The third stage of dehydration gave an anhydrous Zn3 (PO4)2 phase.