真空中聚苯乙烯交联材料的沿面闪络特性

搭建了真空沿面闪络实验平台,在实验平台上对聚苯乙烯交联材料进行了真空沿面闪络性能测试,探讨了材料的真空沿面闪络电压强度与材料结构、材料内部微量杂质的关系。实验结果表明:随着聚苯乙烯材料交联程度的增加,其真空沿面闪络电压强度先增加后减少;聚苯乙烯交联材料分子链结构对其真空沿面闪络电压强度有重要影响;材料的真空沿面闪络电压强度还与交联材料内部异质分子数量有关系,微量异质结构的分子将导致沿面闪络电压强度的下降。     

GaP低阻欧姆接触层的AES和SIMS分析

本文用AES和SIMS分析讨论了p-GaP与三层金属膜Pd/Zn/Pd形成良好欧姆接触层的性质.     

Novel ions of quaternary ammonium halides in FDMS

Field desorption mass spectrometry exhibited novel ions [ Y-n H+n R ]+and [ Y-nH+nX]+as well as cluster ions [nY+(n-1)X-mH+mR]+and [nY+( n-1)X-mH+mX]+(n,m=0-3; X and Y represent the cation and anion moieties of quaternary ammonium halides),whose formation mechanism was discussed.     

乙烯系单体自由基聚合的阻聚效应——ⅩⅣ.4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶-1-氧自由基低聚物的合成及对丙烯酸阻聚的研究

研究了数均分子量10~3～5×10~3的聚甲基丙烯酸甲酯的制备及其在甲醇镁存在下和2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基(TMHPO·)间的酯交换反应,合成了聚-4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶-1-氧自由基(PMTMPO·)低聚物。同时观察了4-甲基丙烯酰氧基2,2,6,6-四甲基哌啶的调聚反应,同样制得PMTMPO·低聚物。利用IR、EPR和TGA技术对PMTMPO·进行了表征。评价了PMTMPO·对AIBN引发的丙烯酸(AA)自由基聚合的影响,表明PMTMPO·对AA有良好的阻聚功效。     

One Fluorophore-Two Sensing Films: Hydrogen-Bond Directed Formation of a Quadruple Perylene Bisimide Stack

Elaborately designed π-stacked molecular aggregates are significant for modulation of photophysical properties of polycyclic aromatic hydrocarbons (PAHs). Herein, a double hydrogen-bonds trussed di(pyridyl)pyrrole-perylene bisimide (HDPP-PBI) was designed and its dimerization behavior was studied. HDPP-PBI tends to form a quadruple PBI stack with a dimerization constant of ∼5.56×10⁶ M⁻¹. The dimerization was ascribed to synergistic intramolecular double hydrogen-bonds formation and intermolecular π-π stacking. Addition of CF₃COOH, a hydrogen bond blocker, promotes the dimer to monomer transition. Accordingly, two distinct fluorescent films were prepared by drop-casting of the dimerized or the monomeric HDPP-PBI onto a substrate surface. Interestingly, the less-emissive PBI quadruple stack-based film showed a turn on response to acetone vapor, while the highly emissive HDPP-PBI-based film exhibited fluorescence quenching upon exposure to triethylamine vapor. We believe that the discovered synergistic effect in the PBI aggregates would enlighten the design of new PAHs aggregates with defined structures.     

Perylene Bisimide-Cored Supramolecular Coordination Complexes: Interplay between Ensembles,Excited State Processes,and Aggregation Behaviors

Manipulating the optical properties of fluorescent species is challenging owing to complicated and tedious synthetic works. Herein, the photophysical properties of perylene bisimide (PBI) were effectively tuned by varying the geometrical arrangement of PBI moieties within supramolecular coordination complexes (SCCs), where a PBI-based dicycle ( 2 ) and a trigonal prism ( 3 ) were generated via using a typical 90° Pt(II) reagent, cis-(PEt₃)₂Pt(OTf)₂-based coordination-driven self-assembly approach. The ligand, an ortho-tetrapyridiyl-PBI ( 1 ), exhibits a moderate fluorescence quantum yield (∼13 %) and efficient inter-system crossing (ISC). 2 , however, is much more emissive with a fluorescence quantum yield of ∼41 %, and the relevant ISC process is significantly hindered. The fluorescence quantum yield of 3 is merely ∼6 % due to the observed symmetry-breaking charge separation (SB-CS), which turns to triplet state upon charge recombination. Interestingly, 3 could be fully transformed into 2 by simply adding a suitable amount of a 90° Pt(II)-based neutral triangle. Moreover, 2 tends to form discrete dimers both in crystal and solution states, but 3 does not show the property. Therefore, controlling geometrical arrangement of fluorophores through coordination-driven self-assembly could be taken as another effective way to tune their excited state relaxation pathways and construct high-performance optical molecular materials, which generally have to be prepared via organic synthesis.     

Preparation of Porous Hollow SiO2 Spheres by a Modified St?ber Process Using MF Microspheres as Templates

Using the surface charged and acid dissolvable melamine formaldehyde (MF) microspheres as sacrificial hard templates, silica coated MF core?Cshell composite microspheres, denoted as MF@SiO₂, were synthesized via a surfactant-assisted sol?Cgel process by using tetraethyl orthosilicate (TEOS) as silica source. Hollow SiO₂ spheres with mesoporous shells were then obtained after selective removal of the MF cores and the pore directing surfactant by hydrochloric acid etching or calcinations in air. Interesting shrinkage phenomena were observed in both the hollow products derived from hydrochloric acid etching and calcinations. The influence of the ratio of MF sphere to TEOS and the removal method of the MF core on the size of the hollow spheres, the shell thickness and the shell surface roughness have been studied. The composition, the thermal stability, the morphology, the surface area and pore size distribution, the wall thickness and adsorption properties of the hollow spheres derived from hydrochloric acid etching and calcinations were also investigated and compared based on the FTIR, SEM, TEM, TGA, Nitrogen adsorption?Cdesorption and spectrophotometer techniques or measurements.     

Platinum and Palladium Nanotubes Based on Genetically Engineered Elastin–Mimetic Fusion Protein‐Fiber Templates: Synthesis and Application in Lithium‐O2 Batteries

The coupling of proteins with self‐assembly properties and proteins that are capable of recognizing and mineralizing specific inorganic species is a promising strategy for the synthesis of nanoscale materials with controllable morphology and functionality. Herein, GPG‐AG3 protein fibers with both of these properties were constructed and served as templates for the synthesis of Pt and Pd nanotubes. The protein fibers of assembled GPG‐AG3 were more than 10 μm long and had diameters of 20–50 nm. The as‐synthesized Pt and Pd nanotubes were composed of dense layers of ～3–5 nm Pt and Pd nanoparticles. When tested as cathodes in lithium‐O₂ batteries, the porous Pt nanotubes showed low charge potentials of 3.8 V, with round‐trip efficiencies of about 65 % at a current density of 100 mA g^?1.     

新型石墨烯基LED器件：从生长机理到器件特性

III族氮化物因具有禁带宽度大、击穿电压高、电子饱和漂移速度大、稳定性高等优异特性而广泛应用在发光二极管(LED)、激光器以及高频器件中。目前III族氮化物薄膜通常是异质外延生长在蓝宝石衬底表面,但是由于蓝宝石与III族氮化物之间存在较大的晶格失配与热失配,使得外延生长的III族氮化物内部存在较大的应力与较高的位错密度,严重影响了器件性能;与此同时,蓝宝石衬底热导率差,限制了其在大功率器件方面的应用。近年来研究发现,石墨烯作为外延生长缓冲层,能够有效解决蓝宝石衬底与外延III族氮化物薄膜之间由于晶格失配和热失配导致的高应力与高位错密度等问题,进而获得了高品质薄膜,并提升了器件的性能。本文综述了石墨烯/蓝宝石衬底上III族氮化物生长与LED器件构筑的研究现状,着重介绍了本课题组提出的一种新型外延衬底—石墨烯/蓝宝石衬底的特点,阐明了III族氮化物在该新型衬底上的生长机理,总结了其对III族氮化物质量提升的作用,并对其发展前景进行了展望。     

Effect of the social influence on topological properties of user-object bipartite networks

Social influence plays an important role in analyzing online users’ collective behaviors[Salganik et al., Science 311, 854 (2006)]. However, the effect of the socialinfluence from the viewpoint of theoretical model is missing. In this paper, by takinginto account the social influence and users’ preferences, we develop a theoretical modelto analyze the topological properties of user-object bipartite networks, including thedegree distribution, average nearest neighbor degree and the bipartite clusteringcoefficient, as well as topological properties of the original user-object networks andtheir unipartite projections. According to the users’ preferences and the global rankingeffect, we analyze the theoretical results for two benchmark data sets, Amazon andBookcrossing, which are approximately consistent with the empirical results. This worksuggests that this model is feasible to analyze topological properties of bipartitenetworks in terms of the social influence and the users’ preferences.