Enhanced photocatalytic activity of zeolite-encapsulated TiO2 clusters by complexation with organic additives and N-doping.

In the literature it was found that titanium oxide clusters of a few metal atoms encapsulated inside the micropores of zeolite Y exhibit large blue shifts in the Ti-O ligand-to-metal charge-transfer band as compared to non-encapsulated bulk titanium dioxide particles. This blue shift of the Ti-O absorption band is believed to have a negative effect on the photocatalytic activity of zeolite-encapsulated TiO2. We report here on circumventing this problem and increasing visible-light absorption by means of a red shift of the absorption band caused by addition of some organic molecular modifiers containing acidic OH groups that can strongly bind with titanol groups TiOH. In the studied series of zeolite-encapsulated TiO2 samples, the red shift of the optical spectrum follows the order: catechol > 4-aminobenzoic acid > benzoic acid. Also N-doping of zeolite-encapsulated TiO2 clusters by thermal treatment with urea leads to a red shift of the TiO2 absorption band that depends on the annealing and hydration conditions. By comparison to the degradation of phenol in aqueous solution, we have demonstrated that these changes in the absorption spectrum on addition of the organic modifier are also reflected in the photocatalytic activity of the samples; a greater increase in photocatalytic activity (about 30%) was observed for the additive catechol.     

Identification of Earth Pigments by Applying Hierarchical Cluster Analysis to Solid State Voltammetry. Application to Severely Damaged Frescoes

Multivariate chemometric methods are applied for identifying earth pigments from square‐wave voltammetric measurements performed at pigment‐modified paraffin‐impregnated graphite electrodes allowing for a separation between hematite‐based earths, French ochres, Spanish ochres, siennas, umbers and green earths. This methodology is applied to the identification of the pigments in samples from the ceiling frescoes of Antonio Palomino (dated 1707) in the vaulted nave of the Sant Joan del Mercat church in Valencia (Spain). These frescoes suffered considerable damage by fire during the Spanish Civil War in 1936, resulting in severe chemical and chromatic alterations. Electrochemical data, supported by scanning electron microscopy/energy dispersive X‐ray microanalysis and Raman spectroscopy, indicate that thermal stress induced the transformation of goethite‐based yellow ochres into hematite and magnetite.     

(ClAlNH)n簇合物的结构与稳定性

用量子化学从头算方法（HF／6－31G）和密度泛函理论（DFT）的B3LYP方法，以6－31G标准基组加一个极化函数，对（ClAlNH)n(n=1-10)簇合物的几何构型，电子结构和红外光谱进行了优化，并讨论了聚合反应（ClAlNH)m→(ClAlNH)n的热力学效应，结果表明，（ClAlNH)n系列簇合物的基态稳定结构为Cs(n=1),D2h(n=2),D3h(n=3),Td(n=4),Cs(n=5),D3d(n=6),Cs(n=7),S4(n=8),D3h(n=9),C2h(n=10,n=2,4,6,8,10等偶数对应的（ClAlNH)n簇化合物的结构比n等于奇数量更稳定。     

嵌入Y型分子筛中钯簇合成与结构的研究

Pd clusters encaged in Y-zeolite (Pd0Y) have been prepared by means of exchanging zeolite HY with [Pd(NH3)4]2+ under microwave radiation. The product formed was deaminized by heating, washed sufficiently with de-ionized water and reduced with hydrogen. The crystal phase diffraction of Pd was not found in the XRD spectrogram of Pd0y. According to polycrystal X-ray diffraction data. Radial Electron Distribution Function (REDF) of Pd0Y was calculated to elucidate the structure of Pd cluster. The results show that the Pd clusters are of the Al type closely packed arrangement. The dimension of them is about 12 Å. They are encaged in the supercage of zeolite Y. Their occupancy on the supercage is as small as 0.06 so that the framework structure of zeolite Y is unchanged. Therefore, the high dispersing Pd cluster aggregating in supercage exhibit strong catalytic effect. The CO-conversion of Pd0Y with Pd 0.72% and 6.13% (in mass fraction) is 67 % and 100 % (in volume fraction) respectively. Evaluation conditions:
mixed gas containing 0.02% CO and air,
space velocity 3000 h-1,
reaction temperature 0 ℃.     

Clustering of nucleosides in the presence of alkali metals: Biologically relevant quartets of guanosine,deoxyguanosine and uridine observed by ESI-MS/MS

Electrospray ionization (ESI) mass spectra of nucleosides, recorded in the presence of alkali metals, display alkali metal ion-bound quartets and other clusters that may have implications for understanding non-covalent interactions in DNA and RNA. The tetramers of guanosine and deoxyguanosine and also their metaclusters (clusters of clusters), cationized by alkali metals, were observed as unusually abundant magic number clusters. The observation of these species in the gas phase parallels previous condensed-phase studies, which show that guanine derivatives can form quartets and metaclusters of quartets in solution in the presence of metal cations. This parallel behavior and also internal evidence suggest that bonding in the guanosine tetramers involves the bases rather than the sugar units. The nucleobases thymine and uracil are known to form magic number pentameric adducts with K+, Cs+ and NH4+ in the gas phase. In sharp contrast, we now show that the nucleosides uridine and deoxythymidine do not form the pentameric clusters characteristic of the corresponding bases. More subtle effects of the sugars are evident in the fact that adenosine and cytidine form numerous higher order clusters with alkali metals, whereas deoxyadenosine and deoxycytidine show no clustering. It is suggested that hydrogen bonding between the bases in the tetramers of dG and rG are the dominant interactions in the clusters, hence changing the ribose group to deoxyribose (and vice versa) generally has little effect. However, the additional hydroxyl group of RNA nucleosides enhances the non-selective formation of higher-order aggregates for adenosine and cytidine and results in the lack of highly stable magic number clusters. Some clusters are the result of aggregation in the course of ionization (ESI) whereas others appear to be intrinsic to the solution being examined.     

钒氧阴离子团簇与小分子碳氢化合物反应的实验和理论研究

为了在分子层次上揭示相关催化反应的机理, 人们对过渡金属氧化物团簇与碳氢化合物分子反应进行了大量研究. 相比于过渡金属氧化物团簇阳离子, 阴离子对一些碳氢化合物的活性弱得多, 因此研究还很少. 在本工作中, 我们通过激光溅射产生钒氧团簇阴离子VxOy, 产生的团簇在接近热碰撞条件下与烷烃(C2H6和C4H10)以及烯烃(C2H4和C3H6) 在一个快速流动反应管中进行反应, 飞行时间质谱用来检测反应前后的团簇分布. 在VxOy与烷烃的反应中, 生成了产物V2O6H-和V4O11H-; 在与烯烃的反应中, 产生了相应的吸附产物V4O11X-(X=C2H4或C3H6). 密度泛函理论计算表明: V2O-6和V4O-11可以活化烷烃(C2H6和C4H10)的C—H键, 也可以与烯烃(C2H4和C3H6)发生3+2环化加成反应形成一个五元环结构(-V-O-C-C-O-), C—H键活化与环加成反应都需经历可以克服的反应能垒. 理论计算与实验观测结果相符合. V2O-6和V4O-11团簇都具有氧原子自由基(O·或O-)的成键特征, 活性O-物种也经常出现在钒氧催化剂表面, 因而本研究在分子水平上, 揭示了表面活性氧物种与碳氢化合物反应的机理.     

固液相变的分子动力学研究Ⅰ─—(KI)_(108)离子簇的熔化和凝固(英)

通过分子动力学模拟，考查并分析了（KI）108离子簇的结构、能量和相变的动力学行为．在加热和冷却过程中，离子簇再现了熔化和凝固现象，而且熔化起始于立方体的其一顶点，熔化的离子簇不是球形的，说明了离子簇的非湿特征．根据结晶的成核速率，讨论了电子衍射实验中观察KI凝固的可能性     

New Hexazirconium Clusters Containing Hydrogen Atoms

Reduction of ZrBr₄ with HSnBu₃ yielded a blue solid. When this blue solid was treated with PMe₃, a hexanuelear cluster [Zr₆Br₁₄H₄( PMe₃)₄] (2) was isolated. Reaction of the blue solid with [PPh₄]Br in CH₂Cl₂ resulted in the formation of a paramagnetic and unstable cluster anion, [Zr₆Br₁₈H₅]^2– (3), which disproportionated to form a new cluster anion, [Zr₆Br₁₈H₅]^3– (4) and some Zr(IV) species. Compounds containing 4 can also be obtained from reaction of the blue solid with Br^– in MeCN. Reduction of ZrCl₄ with HsnBu₃ gave a red–brown solid, and [Zr₆Cl₁₄H₄(AsMe₃)₄] (9) and [Zr₅Cl₁₂H₄(AsMe₃)₅](8) were obtained by reaction of the red–brown solid with AsMe₃. No cluster compounds containing amine ligands were obtained in the reaction of the red–brown solid with amines; only compounds containing the [Zr₆Cl₁₈ H₅]^3– anion and ammonium cations were isolated. Altogether ten products were characterized by single crystal X-ray diffraction and where possible, by ¹H NMR studies.     

铝硫二元团簇的组分及其光解规律

硫与金属元素所形成的二元团簇具有很多重要的特性,已受到人们的普遍重视.用激光-串级飞行时间质谱仪,我们曾研究了硫与过渡金属钽、铁等的二元团簇.最近我们选取主族金属元素铝,研究了铝硫团簇的形成及其光解,实验结果表明,与钽硫或铁硫团簇相比,铝硫团簇无论在其组份构成还是在其光解方面,都表现出鲜明的特有规律性.实验的主要参数如下:溅射用激光为Nd:YAG 二倍频,其输出强度控制在约10~7W·cm~(-2),激光的重复频率10Hz 样品位于激光束的焦点附近,由焦距f=50cm 的透镜调整其聚焦状