锌-镉还原-盐酸萘乙二胺分光光度法测定大气中NO2

1 引言 NO2是一种关键的大气化学组分,参与了多种重要的大气化学过程,如OH自由基、HO2自由基及有机过氧自由基RO2之间的光化学循环,光化学氧化剂及酸雨的形成等,对大气环境有重要影响.     

甲烷光化学反应体系中有机过氧化物的产生

10 1 32 5Pa ,2 98K ,O2 N2 气氛下 ,采用长光路Fourier变换红外光谱 (FT IR)仪跟踪反应进程 ,高压液相色谱 (HPLC)仪测定反应产物中有机过氧化物的方法研究了氯原子引发的甲烷光化学反应 .实验结果证实反应产物中有过氧化氢(H2 O2 ) ,甲基过氧化氢 (CH3 OOH ,MHP)和过氧甲醚 (CH3 O2 CH3 ) ,并发现还存在羟甲基过氧化氢 (HOCH2 OOH ,HMHP)和一未知有机过氧化物 .HMHP的发现为过氧甲基CH3 OO·自身复合产生Criegee中间体CH2 OO的途径提供了实验证据 .模拟实验显示甲烷光化学氧化产生有机过氧化物的机制比以往认为的要更为复杂 .甲烷的光化学氧化可能是大气对流层有机过氧化物的重要来源     

电化学法合成荧光碳纳米粒子及性能表征

介绍了一种通过电化学氧化-还原循环的方法的制备碳纳米粒子并对其相关性质进行了表征.透射电镜结果表明,制备的纳米粒子粒径大小分布在(2.5±0.3)nm区间,而且其晶格间距为0.33nm左右,完全符合石墨的晶体特征.荧光光谱显示,该粒子在456nm具有稳定的可见光发射,其荧光量子效率达到了0.11.此外还考察了纳米碳颗粒的电化学发光性质,结果表明,该粒子在电化学发光检测方面具有潜在的应用价值.     

Criegee中间体气相反应热力学的G2理论计算

Criegee intermediate is believed to play an important role in the atmospheric chemistry. Because of its short life and the difficulty in experimental study, we carried out ah initio calculations on the thermochemistry of the Criegee involving reactions in this study. Thermochemistry data of reaction enthalpies and Gibbs free energies for four different stable structures of the Criegee intermediates (singlet CH2OO ①1 A1 in C2v, triplet CH2OO ②3B1 in C2v, singlet CH2OO ③1A' in Cs and triplet CH2OO ④ in C1 symmetry) involved in some of the gas-phase reactions were calculated at the standard Gaussian-2 [G2(MP2) and G2] and a modified G2, G2(fu1)[10],levels of theory. Relative energies among those Criegees and formic acid were compared. Chemical reactions include the formation of Criegees, re-arrangement from Criegee to formic acid, dissociations (producing CH2(3B1)+O2, CH2(1A1)+O2, CO2+H2, CO2+2H, CO+H2O, OH+HCO) and the reactions between Criegee and NO/H2O. Standard equilibrium constants for some reactions were investigated and may be obtained for all of the rest reactions involved in this study by the standard Gibbs free energies. It is shown that the formation of Criegee ①-④ by ethylene and ozone, the re-arrangement from any Criegee to formic acid, the dissociation in producing CO2+O2and CO+H2O and the reactions between any Criegee and NO/H2O are all favourable thermodynamicaly. The dissociation in forming CO2+2H and OH+HCO is less favourable. While the dissociation in forming carbene (either in 3B1 or 1A1 state) is not allowed by ΔrGm? values. Standard enthalpies of formation at 298 K for the four Criegees were predicted at the G2(ful) level of theory. Each value is the average value from ten of the above reactions and they are -4.3, 74.8,98.9 and 244.6 kJ mol-1 at the G2(ful) level for Criegee ① to Criegee ④, respectively. In addition, tile standard enthalpy of formation at 298 K for HOCH2OOH is further predicted to be -315.6 kJ mol-1 at the G2(MP2) level.