Experimental design for optimization of 4-nitrophenol reduction by green synthesized CeO2/g-C3N4/Ag catalyst using response surface methodology

In this study, the enhancement of catalytic activity of ceria when modified with co-catalysts such as graphitic carbon nitride and silver was established. The material was synthesized using phytogenic combustion method, a green alternative to the traditional preparative routes. The catalyst was characterized using XRD, FTIR, SEM, EDX, XPS and TEM techniques. The synergistic effect of the composite CeO₂/g-C₃N₄/Ag was tested for catalytic reduction of 4-nitrophenol in the presence of sodium borohydride. The reaction was carried out at room temperature without any light source or external stirring. The individual and combined effects of four parameters, viz., concentration of 4-NP, amount of catalyst, amount of NaBH₄ and time for the reduction of reduction 4-NP were investigated using Box-Behnken design of response surface methodology (RSM). This statistical model was used to optimize the reaction conditions for maximum reduction of 4-NP. The optimum conditions for the reduction reaction are found to be 0.01 mmol/L 4-NP, 15 mg catalyst, 20 mg NaBH₄ and 13.7 min time interval.     

拟除虫菊酯类农药在NCI源和EI源中的质谱行为

通过分析19种拟除虫菊酯类农药（pyrethroid pesticides, PyPs）在负化学离子源（NCI）和电子轰击离子源（EI）中的碎片离子信息，得出每种农药在不同离子源中的质谱行为差异。在NCI源中，PyPs获得1个热电子，形成负离子后不稳定而发生热裂解，与酯基相连的碳氧键断裂形成菊酯烷酸根离子，再脱去中性分子（如CO₂、HF、HCl、HCF3等）形成各种碎片离子。一般情况下，含卤原子越多的PyPs，其在NCI源的响应越高。在EI源中，PyPs裂解规律为：1） 与羰基相连的碳氧键发生α-断裂脱去1分子CO，得到含环丙烷结构的特征碎片离子；2） 发生六元环的氢原子重排，当含有苄基苯基醚且甲基上有氰基取代基的PyPs，易形成m/z 181、208特征碎片离子，而不含氰基的PyPs易形成m/z 183特征碎片离子。     

提高α-葡萄糖苷酶抑制率的乳酸菌胞外多糖分阶段控温发酵工艺优化

该文在考察不同温度对人源乳酸菌菌体生长、胞外多糖浓度及α-葡萄糖苷酶抑制率影响的基础上,采取分阶段控制温度策略对α-葡萄糖苷酶抑制活性进行优化。结果表明,当第一阶段温度37℃,变温时间50 h,第二阶段温度40℃发酵66 h时α-葡萄糖苷酶抑制率为58.21%。     

基于GUM法和控制图法评定绿茶中三唑磷残留量测定的不确定度

采用气相色谱-串联质谱法（GC-MS/MS）测定绿茶中三唑磷的残留量并进行不确定度评定。依据ISO/IEC Guide 98-3:2008（GUM法）和GB/T 27411-2012《检测实验室中常用不确定度评定方法与表示》（控制图法）对检测结果进行不确定度的分析与量化。结果表明，GUM法和控制图法的评定结果分别为（0.112±0.012）mg/kg，k=2和（0.108±0.018）mg/kg，k=2。GUM法的不确定度主要来源是质量浓度和仪器稳定性，其各自占总不确定度的38.9%和24.7%。控制图法只对检测结果进行统计分析，简单易操作，考察的是检测结果的长期趋势，可在日常检测工作中的内部质量控制应用中得到实施，而GUM法适用于复检样品或客户对不确定度有要求时的评定，计算复杂，但可在短时间内获得不确定度评定结果。     

Synthesis of novel activated carbon-supported trimetallic Pt–Ru–Ni nanoparticles using wood chips as efficient catalysts for the hydrogen generation from NaBH4 and enhanced photodegradation on methylene blue

A novel activated carbon (AC) supported trimetallic Platinum–Ruthenium–Nickel nanoparticles (AC@Pt–Ru–Ni NPs) synthesized as an efficient catalyst for hydrogen production from NaBH₄ and enhanced photodegradation ability on methylene blue (MB) dye is reported. AC, which is used as a support material in nanoparticle synthesis, was produced from wood chips. X-ray diffractometry (XRD), atomic force microscope (AFM), Fourier transform infrared spectrophotometer (FTIR), Transmission Electron Microscope (TEM), and UV–visible spectrophotometer (UV–Vis) are used for nanoparticles characterization. According to XRD analysis, the average crystal particle size was measured to be about 3.44 nm. In TEM analysis, the average particle size was determined as 2.44 nm. The photocatalytic activity of AC@Pt–Ru–Ni NPs was examined against MB azo dye and found to have 97% photocatalytic degradation at 300 min against MB. The catalyst activity of AC@Pt–Ru–Ni NPs in hydrogen production was determined by the methanolysis reaction from NaBH₄. The Turnover of Frequency (TOF), Activation energy (Ea), enthalpy (ΔH), and entropy values (ΔS) values of the hydrogen production reaction were calculated as 1154.04 h⁻¹, 24.29 kJ/mol, 26.83 kJ/mol, −198.76 J/mol.K, respectively. The study successfully achieved the recycling of wood waste, production of hydrogen, and photodegradation against MB dye. In this study, wood wastes were evaluated and it was aimed to be used in AC production and nanocatalyst synthesis. The efficiency of the synthesized AC@PtRuNi nanocatalyst in hydrogen production and its usability for cleaning dyes from wastewater was determined. The obtained results show that AC@PtRuNi nanocatalyst has potential usability both in hydrogen production and in applications for cleaning dyes from wastewater.