Long-range interfacial electron transfer and electrocatalysis of molecular scale <Emphasis Type="Italic">Prussian</Emphasis> Blue nanoparticles linked to Au(111)-electrode surfaces by different chemical contacting groups

We have explored interfacial electrochemical electron transfer (ET) and electrocatalysis of 5–6 nm Prussian Blue nanoparticles (PBNPs) immobilized on Au(111)-electrode surfaces via molecular wiring with variable-length, and differently functionalized thiol-based self-assembled molecular monolayers (SAMs). The SAMs contain positively (?NH₃ ⁺) or negatively charged (–COO–) terminal group, as well an electrostatically neutral hydrophobic terminal group (–CH₃). The surface microscopic structures of the immobilized PBNPs were characterized by high-resolution atomic force microscopy (AFM) directly in aqueous electrolyte solution under the same conditions as for electrochemical measurements. The PBNPs displayed fast and reversible interfacial ET on all the surfaces, notably in multi-ET steps as reflected in narrow voltammetric peaks. The ET kinetics can be controlled by adjusting the length of the SAM forming linker molecules. The interfacial ET rate constants were found to depend exponentially on the ET distance for distances longer than a few methylene groups in the chain, with decay factors (β) of 0.9, 1.1, and 1.3 per CH₂, for SAMs terminated by ?NH₃ ⁺,–COO–, and–CH₃, respectively. This feature suggests, first that the interfacial ET processes follow a tunneling mechanism, resembling that of metalloproteins in a similar assembly. Secondly, the electronic contact of the SAM terminal groups that anchor non-covalently the PBNP are crucial as reported for other types of molecular junctions. Highly efficient PBNP electrocatalysis of H₂O₂ reduction was also observed for the three linker groups, and the electrocatalytic mechanisms analyzed.     

自极化效应对稀土掺杂聚合物激发和发射光谱的影响

Eu(DBM)3· Phen was synthesized and its structure was characterized by FT-IR and the elementary analysis. Emission and excitation spectra of rare earth complex in solution of methyl methacrylate and in solid matrix of poly(methyl methacrylate) were measured, and the experiments confirmed that an intermolecular solute-solute interaction occurred for rare earth complex in solution and solid matrix, which resulted in self-polarization. Influence of the self-polarization includes two aspects: one is the red-shift in absorption of organic ligands, and another is the symmetric changing of Eu3+ site in the complex. The self-polarization effect also causes a stretching of molecular bonds and shifting of charging distribution on molecules, altering the energy difference between the ground and excited states of the solute. At low concentration, the host matrix has effect on this phenomenon; but above certain concentration the difference in host matrix disappears. The other factors are also discussed impacting fluorescence property of rare earth doped systems.     

天然橡胶-黄腐酸的非均相接枝聚合

腐植酸是一种组份和结构很复杂的天然大分子。利用腐植酸中的自由基进行烯类单体在腐植酸上的接枝聚合反应,已有报道,但尚未见到腐植酸与双烯聚合物反应获得接枝聚合物的报道。巩县风化煤黄腐酸是腐植酸中分子量较小(M_n=1035)的部分,它的结构特点已进行过较详细的表征。本文以这种黄腐酸为原料,在60℃下,以苯为天然橡胶的溶剂,以水为黄腐酸的溶剂,以过氧化苯甲酰为引发剂,聚合得到了天然橡胶与黄腐酸的接枝聚合物,并对接枝聚合物进行了一些表征。     

蛋白蛋分离与纯化过程中高效离子交换色谱柱的再生

高效离子交换色谱法分离和纯化蛋白质时,蛋白质在色谱柱上的不可逆吸附使柱效降低,柱压升高。本文使用2％的胰蛋白酶溶液在37℃下处理TSKgelCM-5PW和TSKgelDEAE-5PW（7×7．5mmI.D.）离子交换色谱柱24h后,柱压显著降低,柱效提高4~13倍,交换容量也得到恢复。离子交换色谱柱的恢复程度和交换容量与处理液的用量有关。     

Ultra high temperature superfluidity in ultracold atomic Fermi gases with mixed dimensionality

It has been an important goal to achieve higher or even room temperature superconductivity,since the discovery of high Tc superconductors in 1986,with a typical maximum transition temperature Tc of around 95 K at ambien pressure[1]or up to 164 K for the Hg-based cuprates under high pressure[2].The typical Tc/TF is only around 0.05 or less,where TF denotes the Fermi temperature.There have been a few other families of superconductors,including the iron-based[3],heavy fermion[4]and organic superconductors[5].Their maximum attainable Tc/TF has not been able to exceed that of the cuprates.Other notable superconductors include the recently discovered H2S with a record high Tc=203 K under an enormous high pressure of 90 GPa[6],and the monolayer FeSe/SrTiO3 superconductors with a gap opening temperature up to 100 K[7].     

Birefringent azopolymer long period fiber gratings induced by 532 nm polarized laser

Based on the photoinduced birefringence in azo materials, the model of the birefringent long period fiber gratings (BLPFGs) has been proposed and the transmission of such birefringent fiber gratings was further simulated by the coupled mode theory. In order to obtain the optimum condition for making birefringent azopolymer optical fiber (APOF) gratings the photoinduced birefringence of azo dye and methyl methacrylate (MMA) copolymers was systematically studied. After photosensitivity study of azo samples, using Teflon technique, azo dye containing single mode polymer optical fiber (POF) was fabricated. Finally, BLPFGs can be fabricated in azopolymer fiber using polarized 532 nm laser. A 120 μm LPFG with a 50% duty cycle has been successfully written within the core of the fiber with 532 nm laser by an amplitude mask method. Under polarized microphotography, the grating was observed when the optical axis was set at 45° with the direction of the first polarizing lens of the polarization microscope.     

Calculating potentials of mean force and diffusion coefficients from nonequilibrium processes without Jarzynski's equality

In general, the direct application of the Jarzynski equality (JE) to reconstruct potentials of mean force (PMFs) from a small number of nonequilibrium unidirectional steered molecular-dynamics (SMD) paths is hindered by the lack of sampling of extremely rare paths with negative dissipative work. Such trajectories that transiently violate the second law of thermodynamics are crucial for the validity of JE. As a solution to this daunting problem, we propose a simple and efficient method, referred to as the FR method, for calculating simultaneously both the PMF U(z) and the corresponding diffusion coefficient D(z) along a reaction coordinate z for a classical many-particle system by employing a small number of fast SMD pullings in both forward (F) and time reverse (R) directions, without invoking JE. By employing Crooks [Phys. Rev. E 61, 2361 (2000)] transient fluctuation theorem (that is more general than JE) and the stiff-spring approximation, we show that (i) the mean dissipative work W(d) in the F and R pullings is the same, (ii) both U(z) and W(d) can be expressed in terms of the easily calculable mean work of the F and R processes, and (iii) D(z) can be expressed in terms of the slope of W(d). To test its viability, the FR method is applied to determine U(z) and D(z) of single-file water molecules in single-walled carbon nanotubes (SWNTs). The obtained U(z) is found to be in very good agreement with the results from other PMF calculation methods, e.g., umbrella sampling. Finally, U(z) and D(z) are used as input in a stochastic model, based on the Fokker-Planck equation, for describing water transport through SWNTs on a mesoscopic time scale that in general is inaccessible to MD simulations.     

Random fiber laser of POSS solution-filled hollow optical fiber by end pumping

Random fiber laser is obtained by end pumping a hollow optical fiber (HOF) filled with a dispersive solution of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles and laser dye pyrromethene 597 (PM597) in carbon disulfide (CS₂), in which the concentration is 1.5×10^?2 M for PM597 and 18.5 wt% for POSS, respectively. It is found that the pump light at the one end of the liquid core optical fiber (LCOF) can pass the whole length of LCOF because the POSS nanoparticles were dispersed in CS₂ at a molecular level (1–3 nm) with high stability and without sedimentation. Above the threshold pump energy (～0.81 mJ) the random fiber laser appears coherent and resonant feedback multimode lasing in the weakly scattering system. For the LCOF containing PM597 with the same concentration and no POSS nanoparticles, there occurs only ASE that can be observed under the same experimental condition.     

Effect on the fluorescence branching ratio of different synergistic ligands in neodymium complex doped PMMA

A series of neodymium complexes Nd(TTA)₃L_x (where TTA = α-thenoyltrifluoroacetonato, L_x (x = 1–5) = H₂O, triophenylphosphine oxide (Tppo), 2,2-bipyridine (Bipy), 1,10-phenanthroline (Phen) and 2- (N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine (Dpbt) were synthesized and incorporated in poly(methyl methacrylate). Their absorption spectra were measured and analyzed using Judd–Ofelt theory. Near-infrared luminescent spectra were studied and the radiative properties have been stimulated. Laser parameters such as effective bandwidths (Δλ_eff), stimulated emission cross-sections (σ_e), and gain bandwidth (σ_g) had also been calculated and compared with other systems. The effect on the fluorescence branching ratio (β) in the ⁴F_3/2→⁴I_11/2 transition of different synergistic ligands had been investigated and the relation between β and Judd–Ofelt parameter Ω₂, Ω₄, Ω₆ was discussed. In conclusion, among the five neodymium complexes, Nd(TTA)₃Dpbt has the largest Ω₂ parameter (33.72 × 10^? 20 cm²), stimulated emission cross-sections, which is found promising to be a candidate for laser materials in further application.     

Graphene Nanoplatelets: Electrochemical Properties and Applications for Oxidation of Endocrine‐Disrupting Chemicals

In most graphene‐based electrochemical applications, graphene nanoplatelets (GNPs) have been applied. Now, for the first time, electrochemical properties of GNPs, namely, its electrochemical activity, potential window, and double‐layer capacitance, have been investigated. These properties are compared with those of carbon nanotubes (CNTs). GNP‐ and CNT‐coated electrodes were then applied for electrochemical oxidation of endocrine‐disrupting chemicals. The GNP‐coated electrode was characterized by atomic force microscopy and electrochemical techniques. Compared with the CNT‐coated electrode, higher peak current for the oxidation of 4‐nonylphenol is achieved on the GNP‐coated electrode, together with lower capacitive current. Electrochemical oxidation of 2,4‐dichlorophenol, bisphenol A, and octylphenol in the absence or presence of 4‐nonylphenol was studied on the GNP‐coated electrode. The results suggest that GNPs have better electrochemical performance than CNTs and are thus more promising for electrochemical applications, for example, electrochemical detection and removal of endocrine‐disrupting chemicals.