1.3 μm range effectively cylindrical In0.53Ga0.47As/In0.52Al0.48As quantum wires grown on (2 2 1)A InP substrates by molecular beam epitaxy

Vertically coupled quantum wires (QWRs) have been made by alternately stacking nominally 3.6 nm thick In_0.53Ga_0.47As self-organized QWR layers and 1 nm thick In_0.52Al_0.48As barrier layers on (2 2 1)A-oriented InP substrates by molecular beam epitaxy. The surface of In_0.53Ga_0.47As QWR layers was corrugated at an amplitude of 1.1 nm and period of 27 nm, and lateral confinement potential is induced by their thickness modulation. The wavelength of photoluminescence (PL) from the stacked QWRs at 15 K becomes longer from 1220 to 1327 nm with increasing total number of stacked QWR layers, N_SL, from 1 to 9, while PL full-width at half-maximum is reduced from 22 to 8.6 meV. The PL intensity with the polarization parallel to the wire direction, I, is 1.30 times larger than that with the normal polarization, I, when N_SL=1. The PL intensity ratio, I/I, reaches as large as 4 when N_SL=9, indicating successful control of relative strength between vertical confinement and lateral confinement of carriers. The value of I/I obtained for the stacked QWRs with N_SL=9 is the same value as cylindrical QWRs have. The results indicate that effectively cylindrical QWRs with the best uniformity and 1.3 μm range emission were realized by stacking of self-organized QWR layers.     

Vapor nanobubble-mediated photoporation constitutes a versatile intracellular delivery technology

Vapor nanobubble-mediated photoporation has evolved into a promising physical intracellular delivery technology. When irradiated with short but intense laser pulses, photothermal nanomaterials can generate vapor nanobubbles that, when they collapse, induce transient membrane pores through which exogenous effector molecules can be delivered into the cells. Interestingly, this technique offers high-throughput delivery in various cell types, including hard-to-transfect primary cells. A unique feature among cell transfection technologies is its ability to deliver compounds in spatially defined areas, even with single-cell resolution, through controlled scanning of the laser beam. This is especially useful for targeting specific cells in dense heterogenous samples. Although primarily used for permeabilizing the outer cell membrane, this strategy has been exploited to destabilize endosomal and nuclear membranes as well.     

Bienzyme Electrode Compatible Behavior for Water-Soluble and-Insoluble Substrates

Abstract

A bienzymatic sensing layer containing two enzymes able to work sequentially, choline oxidase (ChOD) and phospholipase D (PLaseD), was used to design an electrochemical biosensor for the detection of either a water-soluble (choline) or insoluble (phosphatidylcholine) substrate. A photocrosslinkable polymer, poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ), was used as host-matrix for enzyme immobilization. Controlled amounts of PVA-SbQ and of the two enzymes were directly coated on a platinum disk, then photopolymerized. The compatibility of working conditions for choline and phosphatidylcholine detection in the presence of Triton X-100 and CaCl₂ was investigated. The effect of the activity ratio PLaseD / ChOD on the sensor performance was determined. The sensitivities to choline and to phosphatidylcholine were 18 mA.1mol^?1 and 0.66 mA.1.mol^?1 respectively, the detection limit being 1.5.10^?8 M for choline and 1.5.10^?6 M for phosphatidylcholine. The linear range extended up to ca. 10^?4 M for choline and ca. 2.10^?5 M for phosphatidylcholine and the response time was close to 30 seconds for choline and ca. 2 min for phosphatidylcholine.     

金刚石晶形显露的化学控制

采用热丝化学气相沉积法（HPCV），研究了N2、O2对金刚石晶形显露的影响。发现微量的氮气的加入（[N2]／[CH4]＜1％）有利于金刚石（100）晶面的显露，且不会降低金刚石晶形的完整性；微量氧的加入有利于金刚石（111）面显露．采用氧辅助控制金刚石膜（111）织构生长，可以使X射线（111）峰摇摆曲线的半宽降到6．2°．氮或氧的加入扩大了织构生长金刚石（100）或（111）膜的基片温度范围．     

喹啉的生物降解动力学

喹啉是一种典型的氮杂环化合物,在化工、医药及农药生产中经常用作溶剂和原材料．喹啉又是一种毒性大、致变性和致癌性强的物质,对人类、水生生物及植物有着很大的危害．因此随着工业废水特别是焦化废水的排放,使喹啉成为水中常见的污染物．喹啉的结构为许多人工合成化合物的基本结构,而人工合成化合物一般不易被自然界中固有的微生物识别,所以多数为难以生物降解的化合物,研究喹啉的生物降解能为研究其他人工合成化合物的生物降解提供有益的启示．人们对喹啉的降解途径进行了有益的探索［１ -３］,对喹啉降解的动力学也进行了研究［…     

Surface-enhanced Raman scattering: realization of localized surface plasmon resonance using unique substrates and methods

Surface-enhanced Raman scattering (SERS) enhancement and the reproducibility of the SERS signal strongly reflect the quality and nature of the SERS substrates because of diverse localized surface plasmon resonance (LSPR) excitations excited at interstitials or sharp edges. LSPR excitations are the most important ingredients for achieving huge enhancements in the SERS process. In this report, we introduce several gold and silver nanoparticle-based SERS-active substrates developed solely by us and use these substrates to investigate the influence of LSPR excitations on SERS. SERS-active gold substrates were fabricated by immobilizing colloidal gold nanoparticles on glass slides without using any surfactants or electrolytes, whereas most of the SERS-active substrates that use colloidal gold/silver nanoparticles are not free of surfactant. Isolated aggregates, chain-like elongated aggregates and two-dimensional (2D) nanostructures were found to consist mostly of monolayers rather than agglomerations. With reference to correlated LSPR and SERS, combined experiments were carried out on a single platform at the same spatial position. The isolated aggregates mostly show a broadened and shifted SPR peak, whereas a weak blue-shifted peak is observed near 430 nm in addition to broadened peaks centered at 635 and 720 nm in the red spectral region in the chain-like elongated aggregates. In the case of 2D nanostructures, several SPR peaks are observed in diverse frequency regions. The characteristics of LSPR and SERS for the same gold nanoaggregates lead to a good correlation between SPR and SERS images. The elongated gold nanostructures show a higher enhancement of the Raman signal than the the isolated and 2D samples. In the case of SERS-active silver substrates for protein detection, a new approach has been adopted, in contrast to the conventional fabrication method. Colloidal silver nanoparticles are immobilized on the protein functionalized glass slides, and further SERS measurements are carried out based on LSPR excitations. A new strategy for the detection of biomolecules, particularly glutathione, under aqueous conditions is proposed. Finally, supramolecular J-aggregates of ionic dyes incorporated with silver colloidal aggregates are characterized by SERS measurements and correlated to finite-difference time-domain analysis with reference to LSPR excitations. Figure SPR and SERS images for isolated, elongated and two-dimensional gold nanostructures     

Ultrafast plasmon dynamics and evanescent field distribution of reproducible surface-enhanced Raman-scattering substrates

Surface-enhanced Raman scattering (SERS) is a potent tool in bioanalytical science because the technique combines high sensitivity with molecular specificity. However, the widespread and routine use of SERS in quantitative biomedical diagnostics is limited by tight requirements on the reproducibility of the noble metal substrates used. To solve this problem, we recently introduced a novel approach to reproducible SERS substrates. In this contribution, we apply ultrafast time-resolved spectroscopy to investigate the photo-induced collective charge-carrier dynamics in such substrates, which represents the fundamental origin of the SERS mechanism. The ultrafast experiments are accompanied by scanning-near field optical microscopy and SERS experiments to correlate the appearance of plasmon dynamics with the resultant evanescent field distribution and the analytically relevant SERS enhancement. Figure Ultrafast time-resolved differential absorption spectroscopy combined with scanning near-field optical microscopy (left) and atomic force microscopy (right) yields insight into the photoinduced charge-carrier dynamics in innovative reproducible SERS-substrates Dana Cialla and Ronald Siebert contributed equally to this work.     

α-二亚胺钯配合物的合成及催化Suzuki偶联反应

设计合成并表征了3个具有不同骨架结构的α-二亚胺钯配合物,并在有氧条件下催化不同溴代芳烃与芳硼酸的Suzuki偶联反应,重点考察了配合物骨架结构、碱性强度、溶剂极性和不同反应温度对催化反应的影响。结果表明,α-二亚胺类钯配合物能催化Suzuki偶联反应,采用质子溶剂、无机碱,以及较高反应温度都有利于偶联反应的进行,能够高效制备一系列联芳类化合物。     

Metabolism of Halogenated Alkanes by Cytochrome P450 enzymes. Aerobic Oxidation versus Anaerobic Reduction

The cytochromes P450 are a large class of heme‐containing enzymes that catalyze a broad range of chemical reactions in biosystems, mainly through oxygen‐atom transfer to substrates. A relatively unknown reaction catalyzed by the P450s, but very important for human health, is the activation of halogenated substrates, which may lead to toxicity problems. However, its catalytic mechanism is currently unknown and, therefore, we performed a detailed computational study. To gain insight into the metabolism of halogenated compounds by P450 enzymes, we have investigated the oxidative and reductive P450‐mediated activation of tetra‐ and trichloromethane as halogenated models with density functional theory (DFT) methods. We propose an oxidative halosylation mechanism for CCl₄ under aerobic conditions by Compound I of P450, which follows the typical Groves‐type rebound mechanism. By contrast, the metabolism of CHCl₃ occurs preferentially via an initial hydrogen‐atom abstraction rather than halosylation. Kinetic isotope effect studies should, therefore, be able to distinguish the mechanistic pathways of CCl₄ versus CHCl₃. We find a novel mechanism that is different from the well accepted P450 substrate activation mechanisms reported previously. Moreover, the studies highlight the substrate specific activation pathways by P450 enzymes leading to different products. These reactivity differences are rationalized using Marcus theory equations, which reproduce experimental product distributions.