Thin‐Film Infrared Spectroscopy of Acetonitrile

Acetonitrile and [D₃]acetonitrile in the vicinal region of a planar AgX fiber contain linear dipole–dipole linked oligomers as shown by 1) comparison of infrared band intensity ratios in the gaseous and condensed phases and 2) remarkable plots of absorbance (C? N stretch) versus time during evaporation from an AgX planar fiber element. The plots (CH₃CN 2252 cm^?1, CD₃CN 2262 cm^?1) reveal the presence of octamers, hexamers, tetramers, and dimers along with some heptamer, trimer, and monomer structures. A novel isotope effect arises from the somewhat smaller size of the CD₃CN resulting in an increase in the CN band intensity. The organized oligomers may be termed pseudocrystals and are the main components responsible for absorption intensity in the infrared spectrum of acetonitrile, on the AgX planar fiber or in an IR cell.     

CuO/Ce-Zr-La-O催化剂的表征及CO氧化活性

采用柠檬酸溶胶-凝胶法制备的Ce-Zr-La-O固溶体为载体，制备CuO／Ce-Zr-La-O催化剂，用XRD，Raman，TPR等实验技术对Ce-Zr-La-O固溶体及CuO／Ce-Zr-La-O的物相、Redox性能进行了表征。实验结果表明，Ce0.7Cr0.3-yLayO固溶体的还原性能与La含量有关，适量的La能促进固溶体的氧化还原。CuO的负载量为6％时，CuO／Ce0．7Zr0.15La0.15O的活性最高，高分散且与载体相互作用的CuO是CO氧化活性相。     

Synthesis,Liquid‐Crystalline Properties,and Supramolecular Nanostructures of Dendronized Poly(isocyanide)s and Their Precursors

A series of novel dendronized π‐conjugated poly(isocyanide)s were synthesized successfully by using a Pd? Pt μ‐ethynediyl dinuclear complex ([ClPt{P(C₂H₅)₃}₂C?CPt{P(C₂H₅)₃}₂Cl]) as the initiator. The polymerizations of the dendronized monomers follow first‐order kinetics, indicating that living polymerization takes place. The obtained polymers exhibit narrow polydispersities in the range of 1.03–1.20. Thermal properties of the poly(isocyanide)s as well as their isocyanide monomers and precursors with formamido (HCONH‐) moieties as apexes were investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide‐angle X‐ray diffraction (WAXD). Both the peripheries and the apex groups of the dendrons affect the formation of supramolecular column and/or cubic phases of the precursors and monomers. The formamido precursor forms a liquid‐crystalline phase due to intermolecular hydrogen bonding. The isocyanide monomer lacks this hydrogen‐bonding ability and does not display an organized mesophase. All of the rigid poly(isocyanide)s with the monodendrons exhibit columnar liquid‐crystalline phases. Interestingly, cylindrical structures of a poly(isocyanide) were directly visualized by using transmission electron microscopy (TEM).     

Predicting the shape and structure of face-centered cubic gold nanocrystals smaller than 3 nm.

Although a number of computational studies have examined the relative stability of icosahedral and decahedral gold clusters from 1 to 3 nm in size, few studies have focussed on the variety of face-centered cubic (fcc) nanoparticles in this size regime. In most cases small fcc gold particles are assumed to adopt the truncated octahedral shape, but in light of the fact that the shape and structure of gold nanoparticles is known to vary, the relative stability of fcc polyhedra may change with size. Presented here are results of first-principles calculations investigating the preferred shape of gold particles less than 3 nm in size. Our results indicate that the equilibrium shape of fcc gold nanoparticles less than 1 nm is the cuboctahedron, but this shape rapidly becomes energetically unstable with respect to the truncated octahedron, octahedron and truncated cube shapes as the size increases.     

DNA codes for nanoscience

The nanometer scale is a special place where all sciences meet and develop a particularly strong interdisciplinarity. While biology is a source of inspiration for nanoscientists, chemistry has a central role in turning inspirations and methods from biological systems to nanotechnological use. DNA is the biological molecule by which nanoscience and nanotechnology is mostly fascinated. Nature uses DNA not only as a repository of the genetic information, but also as a controller of the expression of the genes it contains. Thus, there are codes embedded in the DNA sequence that serve to control recognition processes on the atomic scale, such as the base pairing, and others that control processes taking place on the nanoscale. From the chemical point of view, DNA is the supramolecular building block with the highest informational content. Nanoscience has therefore the opportunity of using DNA molecules to increase the level of complexity and efficiency in self-assembling and self-directing processes.     

Improving MCM‐41 as a Nitrosamines Trap through a One‐Pot Synthesis

Copper oxide was incorporated into MCM‐41 by a one‐pot synthesis under acidic conditions to prepare a new mesoporous nitrosamines trap for protection of the environment. The resulting composites were characterized by XRD, N₂ adsorption–desorption, and H₂ temperature‐programmed reduction techniques, and their adsorption capabilities were assessed in the gaseous adsorption of N‐nitrosopyrrolidine (NPYR). The adsorption isotherms were consistent with the Freundlich equation. The copper salt was deposited onto MCM‐41 during the evaporation stage and was fixed on the host in the calcination process that followed. MCM‐41 was able to capture NPYR in air below 373 K but not at 453 K. Loading of copper oxide on MCM‐41 greatly improved its adsorption capability at elevated temperatures. The influence of the incorporation of copper into MCM‐41 samples and the adsorption behavior of these samples are discussed in detail.     

MO(M=Cu和Ni)/TiO2/-Al2O3催化剂在CO+O2反应中的活性

采用X射线衍射(XRD),程序升温还原(TPR)等表征手段考察了TiO2改性对CuO(或NiO)在γ-Al2O3表面上分散以及还原性能的影响,同时检测了这些改性的催化剂在CO+O2反应中的活性.结果表明:TiO2的改性使得CuO和NiO在γ-Al2O3载体上的分散复杂化,产生了多种状态的氧化铜(氧化镍)物种.当负载量低于其在γ-Al2O3上的分散容量(0.56 mmol Ti4+/100 m2γ-Al2O3)时,TiO2的加入主要是抑制了CuO和NiO在γ-Al2O3载体上的分散;而当负载量远大于其分散容量时,出现了CuO和NiO在晶相TiO2(锐钛矿)上的分散.无论其负载量如何,TiO2的加入促进了CuO的还原.因此,在250℃的CO+O2反应中,改性的催化剂中具有更多的活性位,因而显示出更高的活性;相反,TiO2的改性则抑制了NiO的还原.因此,在350℃的CO+O2反应中,可还原的氧化镍的量明显少于未经改性的催化剂,导致改性催化剂的活性降低.     

Nanotechnology with soft materials.

Nature exploits self-organization of soft materials in many ways, to produce cell membranes, biopolymer fibers and viruses, to name just three. Mankind is now able to design materials at the nanoscale, whether through atom-by-atom or molecule-by-molecule methods (top-down) or through self-organization (bottom-up). The latter method encompasses soft nanotechnology. Self-organization of soft materials can be exploited to create a panoply of nanostructures for diverse applications. The richness of structures results from the weak ordering because of noncovalent interactions. Thus, thermal energy is important as it enables transitions between phases with differing degrees of order. The power of self-organization may be harnessed most usefully in a number of nanotechnology applications, which include the preparation of nanoparticles, the templating of nanostructures, nanomotor design, the exploitation of biomineralization, and the development of functionalized delivery vectors.     

Templateless assembly of molecularly aligned conductive polymer nanowires: a new approach for oriented nanostructures

Although oriented carbon nanotubes, oriented nanowires of metals, semiconductors and oxides have attracted wide attention, there have been few reports on oriented polymer nanostructures such as nanowires. In this paper we report the assembly of large arrays of oriented nanowires containing molecularly aligned conducting polymers (polyaniline) without using a porous membrane template to support the polymer. The uniform oriented nanowires were prepared through controlled nucleation and growth during a stepwise electrochemical deposition process in which a large number of nuclei were first deposited on the substrate using a large current density. After the initial nucleation, the current density was reduced stepwise in order to grow the oriented nanowires from the nucleation sites created in the first step. The usefulness of these new polymer structures is demonstrated with a chemical sensor device for H(2)O(2), the detection of which is widely investigated for biosensors. Finally, we demonstrated that controlled nucleation and growth is a general approach and has potential for growing oriented nanostructures of other materials.     

加料方式对CuO/ZnO/Al2O3系催化剂前驱体性质的影响

用XRD、TG-DTG、TPR技术研究了不同加料方式对CuO/ZnO/Al2O3系催化剂前驱体物相组成及其结晶情况的影响，用加压微反装置考察了催化剂合成甲醇反应活性。结果表明, 加料方式对Cu2+形成的中间化合物的物相组成及结晶度影响显著,对Zn2+及Al3+的沉淀物相的影响很小。不同加料方式对催化剂前驱体物相组成及催化剂性能的影响主要是形成的初始前驱体中Cu的物相及结晶度不同。正加法主要形成Cu2(OH)3NO3,并流法主要形成无定形Cu2CO3(OH)2,后者与Zn5(CO3)2(OH)6相互作用转化为(Cu,Zn)2CO3(OH)2和（Cu,Zn）5(CO3)2(OH)6，由它们分解形成的CuO-ZnO固溶体是合成甲醇反应的活性相。并流法能最大程度的形成CuO-ZnO固溶体，有利于CuO粒子的细化，其催化活性较好。