PPh3催化Mannich反应机理的密度泛函研究

通过密度泛函理论研究了PPh3催化苯胺、苯甲醛和乙酰乙酸乙酯三组分Mannich反应的机理.计算结果表明该机理主要分3个步骤进行:PPh3催化乙酰乙酸乙酯发生酮式-烯醇式互变异构得到烯醇;烯醇辅助苯胺和苯甲醛缩合并脱水生成亚胺;亚胺和烯醇通过加成反应生成β-氨基羰基化合物.通过详细的机理研究,发现烯醇从亚胺的背面进攻其亲电C原子的过渡态的相对能量更低,容易得到反式的产物,对实验观察到的非对映选择性进行了合理的解释.     

不同Pt-SnO_2制备工艺对乙醇燃料电池性能的影响

本文在石墨烯改性碳纤维的基础上,通过添加聚偏氟乙烯(PVDF)造孔、浸渍法、水热法等制备出不同的Pt-SnO_2/改性碳纤维阳极催化剂。以扫描电镜、X射线衍射仪、拉曼光谱图、电催化性能、单电池发电性能等手段对其结构和性能进行表征。结果表明,添加PVDF造孔后的催化剂催化性能最好,峰电流密度可达137.33mA/cm,其电阻也明显降低;当制备成单电池时,最高功率密度达22.89mW/cm~2。     

Analysis of each branch current of serial solar cells by using an equivalent circuit model

In this paper,based on the equivalent single diode circuit model of the solar cell,an equivalent circuit diagram for two serial solar cells is drawn.Its equations of current and voltage are derived from Kirchhoff’s current and voltage law.First,parameters are obtained from the I–V(current–voltage)curves for typical monocrystalline silicon solar cells(125 mm×125 mm).Then,by regarding photo-generated current,shunt resistance,serial resistance of the first solar cell,and resistance load as the variables.The properties of shunt currents(Ish1and Ish2),diode currents(ID1and ID2),and load current(IL)for the whole two serial solar cells are numerically analyzed in these four cases for the first time,and the corresponding physical explanations are made.We find that these parameters have different influences on the internal currents of solar cells.Our results will provide a reference for developing higher efficiency solar cell module and contribute to the better understanding of the reason of efficiency loss of solar cell module.     

产漆酶真菌筛选、鉴定及酶促去除苯酚的条件优化

以愈创木酚为底物,从自然环境中成功筛选到一株高产漆酶的粗毛革孔菌(Coriolopsis gallica)NCULAC F1。对其漆酶诱导表达条件进行探究,结果表明,9种芳香化合物对NCULAC F1表达漆酶均无显著诱导作用(P>0.05);而硫酸铜具有显著诱导作用(P<0.05),且硫酸铜与2,6-二甲基苯酚具有显著的协同诱导作用(P<0.05);最佳协同诱导条件下,摇瓶发酵5 d漆酶活力达11.29 U·mL-1,比未添加任何诱导剂的对照组显著提高了138.69%(P<0.05)。提取纯化漆酶,进一步探究漆酶对苯酚的去除效果,结果表明,酶促去除苯酚的过程遵循Michaelis-Menten动力学模型,R2为0.984 3,km为52.45 mg·L-1,Vmax为181.82 mg·L-1·h-1;最佳催化条件为温度70℃,pH 6.0,加酶量5 U·mL-1,介体2’2-联氨-双(3-乙基苯并噻唑啉-6-磺酸)二胺盐(ABTS)浓度0.6 mmol·L-1,在此条件下,10 min内苯酚去除率达100%。研究结果为粗毛革孔菌漆酶的高效生产和在酚类污染物控制方面的应用提供了理论参考。     

初始条件对喷雾火焰着火影响的大涡模拟研究

本文基于LES-LEM模拟方法开展了不同环境温度、压力条件下正庚烷喷雾火焰的大涡模拟研究。首先,通过与ECN喷雾燃烧基础数据库(Engine Combustion Network,ECN)中的实验结果进行对比,发现LE-LEM方法预测的着火延迟期和火焰浮升长度与实验值非常符合。因此,基于此分析了不同发动机工况下喷雾燃烧的着火和燃烧过程。结果显示高温火核首先出现在浓混合气区域,同时,喷雾火焰中同时存在预混和非预混燃烧。计算结果显示燃烧能够使喷雾火焰加速向下游发展,但高环境压力又能抑制喷雾火焰向下游运动。     

Discrete Charge Storage Nonvolatile Memory Based on Si Nanocrystals with Nitridation Treatment

A nonvolatile memory device with nitrided Si nanocrystals embedded in a floating gate was fabricated. The uniform Si nanocrystals with high density （3× 10^11 cm^-2 ） were deposited on ultra-thin tunnel oxide layer （- 3 nm） and followed by a nitridation treatment in ammonia to form a thin silicon nitride layer on the surface of nanocrystals. A memory window of 2.4 V was obtained and it would be larger than 1.3 V after ten years from the extrapolated retention data. The results can be explained by the nitrogen passivation of the surface traps of Si nanoerystals, which slows the charge loss rate.     

不同Pt-SnO2制备工艺对乙醇燃料电池性能影响

本文在石墨烯改性碳纤维的基础上,通过添加聚偏氟乙烯(PVDF)造孔、浸渍法、水热法制备出不同的Pt-SnO2/改性碳纤维阳极催化剂。以扫描电镜(SEM)、X射线衍射仪(XRD)、拉曼光谱图、电催化性能、单电池发电性能等手段来表征和测试,结果表明添加PVDF造孔后催化剂催化性能最好,峰电流密度可达137.33mA.cm-2,其电阻也明显减少,当制备成单电池时也具有最高功率密度,为22.89 mW.cm-2。     

分子环境变化对振动退相时间影响的实验研究

物质分子振动退相时间测量是一种非标记无损分子检测方法, 用超连续谱时间分辨相干反斯托克斯拉曼散射方法可同时获得分子振动谱和退相时间. 实验以苯甲腈和甲醇为样品, 研究当分子环境变化时, 其主要振动谱的振动退相时间变化情况. 将苯甲腈与无水乙醇混合, 测量了苯甲腈分子1017, 2247和3085 cm^-1三个典型分子振动的退相时间随环境变化的规律, 并得到了变化后的振动退相时间. 测量了甲醇分子2851, 2960 cm^-1两个相邻分子振动的退相时间随环境的变化情况, 给出实验变化规律. 这种方法具有检测分子所处环境变化和分子相互作用的能力, 在生命科学、分子生物学和材料科学等研究领域中具有重要的应用前景.     

Simultaneous measurements of global vibrational spectra and dephasing times of molecular vibrational modes by broadband time-resolved coherent anti-Stokes Raman scattering spectrography

In broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy with supercontinuum (SC), the simultaneously detectable spectral coverage is limited by the spectral continuity and the simultaneity of various spectral components of SC in an enough bandwidth. By numerical simulations, the optimal experimental conditions for improving the SC are obtained. The broadband time-resolved CARS spectrography based on the SC with required temporal and spectral distributions is realised. The global molecular vibrational spectrum with well suppressed nonresonant background noise can be obtained in a single measurement. At the same time, the measurements of dephasing times of various molecular vibrational modes can be conveniently achieved from intensities of a sequence of time-resolved CARS signals. It will be more helpful to provide a complete picture of molecular vibrations, and to exhibit a potential to understand not only both the solvent dynamics and the solute-solvent interactions, but also the mechanisms of chemical reactions in the fields of biology, chemistry and material science.