Synthesis and formaldehyde sensing performance of LaFeO3 hollow nanospheres

Metal oxide semiconductors with hollow structure and morphology have attracted considerable attentions because of their promising application on gas sensors. In this paper, LaFeO₃ hollow nanospheres have been prepared by using carbon spheres as templates in combination with calcination. Based on the observation of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and transmission electron microscope (TEM), the structure and morphology of the products were characterized. It has been revealed that as-prepared LaFeO₃ samples have a uniform diameter of around 300 nm and hollow structures with thin shells of about 30 nm consisting of numerous nanocrystals and nanopores. Owing to the hollow and porous structure, large surface area and more surface active sites, the sensor based on LaFeO₃ hollow nanospheres exhibited high response, good selectivity and stability to formaldehyde gas (HCHO). It suggests that the as-prepared LaFeO₃ hollow nanospheres are promising candidates for good performance formaldehyde sensor.     

Pd/BiOCl 高效室温催化甲醛产氢性能研究

利用浸渍-还原法制备Bi OCl纳米片负载的钯纳米颗粒催化剂(Pd/Bi OCl),对室温催化氧化HCHO产氢性能进行了研究,并与纯Pd纳米颗粒催化效果进行了对比.研究结果表明,Pd/Bi OCl催化剂在有效降低贵金属Pd用量情况下(仅为2%wt),仍表现出比纯Pd纳米颗粒更高的催化HCHO产氢的性能.此外,通过进一步优化甲醛浓度、氢氧化钠浓度、氧气浓度和反应温度等参数,Pd/Bi OCl催化氧化HCHO产氢速率最高可达到200 m L/(min*gcatalyst).进一步研究结果表明,Pd/Bi OCl催化HCHO产氢反应的活化能仅为15.2 k J/mol,远低于无催化剂条件下甲醛产氢的活化能65 k J/mol.     

游离和溶胶-凝胶固定化甲醛脱氢酶酶促反应动力学的研究

采用溶胶-凝胶法对甲醛脱氢酶进行固定化,酶的包埋率超过了98％．在pH7附近、37℃下,以游离酶和固定化酶作催化剂,NADH为电子供体,进行了甲酸转化为甲醛的酶促反应．游离和固定化甲醛脱氢酶酶促反应都遵循Michaelis-Menten反应机理,用Dalziel提出的双底物酶促反应动力学方程进行拟合．固定化酶酶促反应速率为游离酶酶促反应速率的50％左右．固定化酶的动力学常数φ和米氏常数K高于游离酶,估计是凝胶基质孔中存在扩散效应所致．     

功能化酸性离子液体催化甲醛与烯烃的Prins缩合反应

研究了以功能化酸性离子液体为催化剂,甲醛与烯烃Prins缩合反应生成1,3-二噁烷及其衍生物,水解得到1,3-二元醇.对不同结构的离子液体、催化剂用量和反应条件进行了考察.结果表明,该体系具有良好的催化性能,反应可在较温和的条件下进行,实现了高活性和高选择性的目标.产物易分离,催化剂重复使用6次,其催化活性基本不变.     

Determination of formaldehyde in frozen fish with formaldehyde dehydrogenase using a flow injection system with an incorporated gel-filtration chromatography column

A flow injection analysis (FIA) system for determination of formaldehyde in frozen fish products is described. The system provides a rapid and selective determination of formaldehyde in aqueous fish extracts by the combination of a deproteinization procedure and a stopped-flow enzymatic approach in a FIA system. The FIA system is furnished with a gel-filtration chromatography column for on-line removal of the proteins from the extract before the enzymatic analysis is performed. Compared with the standard methods for determination of formaldehyde in fish products the present method is much faster and less affected by interferences. The limit of detection for the proposed method is 2.5 mg/l of formaldehyde. The sampling frequency is about 10 determinations per hour.     

Stability of a molybdena-silica catalyst enhanced by water in formaldehyde oxidation

A molybdena-silica catalyst showed rapid deactivation in the oxidation of formaldehyde to carbon oxides. The deactivation was greatly retarded by adding water in the feed. Thus, water coproduced in the partial oxidation of methanol to formaldehyde contributes to the relatively stable activity of the molybdena-silica catalyst in the partial oxidation reaction.     

A tailor designed fluorescent ‘turn-on’ sensor of formaldehyde based on the BODIPY motif

Based on theoretical calculations on the effects of molecular orbital energy levels of amines on the fluorescence properties of the fluorophore, aniline-substituted BODIPY motif (AnB) with quenched fluorescence was developed as a ‘turn-on’ switch for the qualitative and quantitative detection of formaldehyde with the detection limit (LOD) of ca. 165 nM.     

Reactions of Bis(β-Alaninato) Metal(II) Complexes with Formaldehyde and Benzamide: The Crystal Structure of Bis[N-Methyl-N-(N′-Methyl-Benzamido)-β-Alaninato]Copper(II) Monohydrate and Characterization of Bis[N,N-DI(N′-Methylbenzamido)-β-Alaninato]Metal(II) Complexes

The bis[N-methyl-N-(N'-methylbenzamido)-β-alaninato]copper(II), Cu(II)[Me-MeBA]₂, is synthesized by reacting bis(β-alaninato)copper(II) with formaldehyde and benzamide in the presence of a base (NaOH) over the pH range 5.5-8.5. However, the bis[N,N-di (N'-methylbenzamido)-β-alaninato]metal(II) complexes, M(II)[DMeBA]₂ (M = Zn, Ni, Co), are obtained when the respective bis(β-alaninato)metal(II) reacts with formaldehyde and benzamide in the presence of the base in similar pH ranges. Nevertheless, Cu(II)[DMeBA]₂ can be synthesized if the reaction is carried out in the absence of base. The M(II)[DMeBA]₂ complexes are characterized by elemental analysis, IR and UV-Visible spectroscopy and magnetic susceptibility measurements. X-ray crystal structure analysis of Cu(II)[Me-MeBA]₂ suggests that the N'-methylbenzamido substituent of the β-alanine moiety is formed through Mannich aminomethylation, and that the other N-methyl substituent is formed via a Canizzaro-type methylation.     

醛类分子的拉曼光谱研究

应用便携式拉曼光谱仪,采集了四种醛类分子(GnH2nO,n=1,2,3,4)的拉曼光谱,并通过量子化学中密度泛函理论(DFT)对四种醛类分子进行了分子模型构建和理论拉曼光谱模拟计算.通过实验拉曼光谱和DFT模拟计算结果的对比,对四种醛类分子的特征振动峰进行了指认.同时对四种醛类分子的实验光谱进行了分析比较.应用便携式拉...     

皮革中甲醛含量测量不确定度评估

依据GB/T 19941-2005标准,测定了皮革中的甲醛含量,对测量结果的不确定度来源进行了分析和评定,并计算出合成不确定度和有效自由度,最后根据JJF1059规范要求给出了甲醛测量不确定度表达式.