Kemp elimination in cationic micelles: designed enzyme‐like rates achieved through the addition of long‐chain bases

The Kemp elimination is prototypical reaction used to study proton abstraction from carbon. Several hydrophobic systems are known to accelerate this reaction, including two classes of computationally designed enzymes. However, it is unclear whether these computationally designed enzymes establish specific interactions with their substrates, as natural enzymes do, or if most of the rate acceleration is due to the hydrophobicity of the substrate. We used a simple system composed of cationic micelles and a long chain base (such as lauryl phosphate or lauric acid) to measure the rate acceleration for the Kemp elimination. Remarkably, we found that this simple system can accelerate the reaction by four orders of magnitude, approaching the rates of more complex designed systems. Use of different substrates suggests that the reaction takes place at the interface between the micellar head and water (the Stern layer) with the long‐chain base embedded in the micelle and the substrate in the aqueous solution. Thus, we suggest that significant rate accelerations can be achieved regardless of the precise positioning of substrates. Because natural enzymes use specific interactions to position their substrates, we propose that acceleration of the Kemp elimination is not a suitable benchmark for the success of the design process, and we suggest that more complex reactions should be used. Copyright © 2015 John Wiley & Sons, Ltd.     

磁免疫和荧光免疫传感器的构建及其在检测甲胎蛋白中的应用

甲胎蛋白(AFP)是常见的肝癌肿瘤标志物,在早期诊断方面起到重要作用。分别设计构建了磁免疫和荧光免疫传感器并将其应用于AFP的定量检测。在磁免疫传感器中,采用免疫磁珠代替传统固相载体,实现了目标物的快速分离;利用标记抗体上的辣根过氧化物酶(HRP)催化底物显色,根据底物吸光度值的大小进行定量检测。构建的AFP检测方法的检出限为3.6 ng·mL-1,线性范围为10~80 ng·mL-1。在荧光免疫传感器中,将碲化镉量子点(CdTe QDs)的荧光作为信号输出,并通过同时将多个CdTe QDs连接在纳米硅球表面实现信号放大,通过测量量子点荧光强度实现定量检测。该方法AFP检出限为4.2 ng·mL-1,线性范围为5~150 ng·mL-1。所设计的两种传感器均具有特异性强、灵敏度高的特点,为AFP的检测提供了新的思路和方法。     

Thin-film polycrystalline Si solar cells on foreign substrates: film formation at intermediate temperatures (700–1300 °C)

We give an overview and analysis of research on thin-film polycrystalline Si solar cells on foreign substrates, with layers formed at intermediate temperatures (700–1300 °C), covering substrates, deposition techniques and solar cell processing. The main deposition techniques that have been investigated are solution growth (SG) and chemical vapour deposition (CVD). Insufficient nucleation on foreign substrates is an important problem with SG, which could be solved with appropriate surface preparation techniques and growth conditions. With CVD, continuous layers are achieved routinely, but the electronic quality of the material is usually very low. Solar cell performance appears to be limited by a very large recombination activity of grain boundaries. Improvement can be achieved reducing the grain boundary density and recombination activity, and experimental examples are given. Devices have been demonstrated with efficiencies up to 5.5%. PACS 73.40.Lq; 73.50.Gr; 84.60.It     

LaPO_4∶Ce,Tb纳米荧光粉末的合成及其在指纹无损显现中的应用

采用溶剂热法在水和乙二醇的混合溶剂中合成出了高质量的LaPO_4∶Ce,Tb纳米荧光粉末。然后通过透射电子显微镜(TEM)、粉末X射线衍射(XRD)、荧光光谱(FS)等表征手段分别对稀土纳米荧光粉末的微观形貌、晶体类型、荧光性能进行了表征,合成纳米荧光粉末的形貌为单分散的纳米棒,平均长度为700nm、平均直径为20nm,其晶体结构为单斜LaPO_4晶型,并且在254nm紫外光照射下能够产生较强的绿色荧光。最后将合成的纳米荧光粉末应用于光滑客体表面汗潜指纹的无损显现中,并详细考察了指纹显现的对比度、灵敏度、选择性、背景干扰等指标。实验结果表明,使用LaPO_4∶Ce,Tb纳米荧光粉末显现的指纹在254nm紫外光的激发下能够产生明亮的绿色荧光,指纹乳突纹线部位连贯清晰、细微特征反映明显,指纹与客体之间的对比反差强烈、客体产生的背景干扰较小,因此该显现方法具有较高的对比度、灵敏度和选择性。本显现方法具有操作方法简单、显现效果优良、适用范围广泛等优点。本研究的重要创新之处在于,经LaPO_4∶Ce,Tb纳米荧光粉末显现后的指纹还可以进行后续的DNA提取及检测,这是传统的指纹显现粉末所不能及的。本研究为指纹物证和生物物证这两大物证的同时利用提供了有益参考。     

Giant enhancement of two-photon fluorescence induced by resonant double grating waveguide structures

We report a 350-fold enhancement of ultra-short-pulse-excited two-photon fluorescence (TPF) using a resonant double grating waveguide structure (DGWS). These structures show vanishing transmission and maximum reflection under resonance conditions, i.e. specific wavelength, polarisation and angular orientation of the incident light. This guided mode phenomenon is characterised by a large field enhancement inducing an enormous TPF signal of fluorescent molecules at the waveguide surface, as compared to direct non-resonant excitation. We demonstrate that high spectral acceptance for ultra-short pulses with broad spectral bandwidths can be achieved by a specifically designed DGWS, and that neither beam focussing nor high laser power is necessary for TPF excitation. Due to the high enhancement of more than two orders of magnitude, DGWS can be considered as a powerful platform for TPF applications such as biosensing and microarray technology. PACS 42.62.Be; 42.79.Dj; 42.79.Gn     

Thiol‐immobilized silver nanoparticle aggregate films for surface enhanced Raman scattering

We report a novel method for the fabrication of films of silver nanoparticle aggregates that are strongly attached to Si substrates (Thiol‐immobilized silver nanoparticle aggregates or TISNA). The attachment is achieved by chemically modifying the surface of a Si(100) surface in order to provide SH groups covalently linked to the substrate and then aggregating silver nanoparticles on these thiol covered surfaces. The transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) characterization show a high coverage with single nanoparticles or small clusters and a partial coverage with fractal aggregates that provide potential hot spots for surface enhanced Raman scattering (SERS). We have confirmed the SERS activity of these films by adsorbing rhodamine 6G and recording the Raman spectra at several concentrations. By using the silver‐chloride stretching band as an internal standard, the adsorbate bands can be normalized in order to correct for the effects of focusing and aggregate size, which determine the number of SERS active sites in the focal area. This allows a quantitative use of SERS to be done. The adsorption–desorption of rhodamine 6G on TISNA films is reversible. These features make our TISNA films potential candidates for their use in chemical sensors based on the SERS effect. Copyright © 2008 John Wiley & Sons, Ltd.     

Color correction in planar optics configurations

Color correction in planar optics configurations can be achieved by resorting to gradient-index rather than uniform-refractive-index substrates. The basic configuration, principle of correction, and calculated and experimental results are presented. The results reveal that, with an appropriate refractive index distribution along the thickness of the substrates, the color can be corrected over a wavelength range up to 155 nm depending on incidence angles.     

激光陀螺基片散射收集系统的设计与分析

研究了散射测量在激光陀螺用石英基片表面检测中的应用.比较发现,收集物镜比积分球更有利于体散射的消除,更适用于直接检测超光滑石英基片表面的散射测试系统.用ZEMAX设计了散射光收集物镜,使其数值孔径达到了0.4,并完全消除了轴上距离大于1.5 mm的散射点的体散射|为了消除光电倍增管输出本身随时间长漂的问题,设计了特定的散射光收集系统的结构,将散射光和反射光分时打在同一个光电倍增管上.分析发现,这种设置能有效消除光电倍增管输出随时间趋势性漂移的问题,增强了系统长时间的稳定性,有效保障了其工程实用性.     

Gold coated metal nanostructures grown by glancing angle deposition and pulsed electroplating

Nickel based nanostructures are grown by glancing angle deposition (GLAD) on flat and pre-patterned substrates. These fabricated porous thin films were subsequently coated by pulsed electroplating with gold. The morphology and conformity of the gold coating were investigated by scanning electron microscopy and X-ray diffraction. Controlled growth of closed gold layers on the nanostructures could be achieved, while the open-pore structure of the nanosculptured thin films was preserved. Such gold coated nanostructures are a candidate for optical sensing and catalysis applications. The demonstrated method can be applied for numerous material combinations, allowing to provide GLAD thin films with new surface properties.     

微孔板荧光法对土壤糖酶活性的测定研究

应用荧光共轭物质作为底物,将96微孔板和荧光检测法结合进行稻-麦轮作系统CO₂倍增条件(FACE)下土壤两种糖酶(木聚糖酶和纤维素酶)活性的测定,探讨了微孔板结合荧光法测定糖酶活性的可行性。结果表明,此种方法可以灵敏的检测到土壤稀释液中的糖酶活性,测定结果重现性较好(变异系数最大为4.879%)。与传统的分光光度法相比,是一种准确、快速、简便的土壤糖酶活性测定方法。CO₂倍增条件下土壤木聚糖酶活性高于自然条件,且在小麦的拔节期,抽穗期和成熟期及水稻的抽穗期和成熟期显著高于对照(P<0.05),CO₂浓度升高提高作物的生长代谢水平,进而影响微生物活性造成土壤木聚糖酶活性提高。纤维素酶活性在CO₂倍增条件下未发生显著变化,说明土壤纤维素酶在短时期内对CO₂增加的响应不显著。     

Study on Synthesis and Spectrum of Novel Styryl Cyanine Dyes with a Carbazole Bridged Chain

Based on the frequently-used cyanine dye probe thiazole orange (TO), a novel kind of cyanine dye was designed and synthesized. Carbazole was inserted into the methylidyne structure of TO as a bridge to afford a kind of novel styryl cyanine dye with carbazole bridged chain. The dyes were characterized by HNMR and MS. The spectra of the novel dyes were also studied and the results showed that the fluorescent wavelength of novel carbzole dye shifted red for 100 nm, stock shift increased by 70 nm and the fluorescent intensity enhanced by 70 times compared to that of TO. When the novel dye was labeled by BSA, its fluorescent wavelength changed little and the intensity enhanced. It is indicated that it can be used as an excellent fluorescent probe in biological labeling.     

Screen-printed polymer waveguides for integrated optics

We demonstrate screen printing of polymer waveguides on rigid and flexible substrates. The waveguides are characterized by optical microscopy and propagation losses are determined by cut-back measurements. Furthermore, the efficiency of light coupling using fluorescent molecules within the waveguides is measured with regard to the application feasibility in sensor systems. It is shown that minimum propagation losses of 0.74 dB/cm can be reached with this low-cost printing technique.     

改进电热法测定比热容实验的研究

改进电热法测量比热容方法中使用的物理公式,使实验电路更为精简。在以往比热容测定仪器的基础上进行改良,制作出新的比热容测定装置,并通过实验验证该装置测定物质比热容所能达到的精确度。对实验的数据处理方法进行改进,并验证其精度。     

The Role of Intermolecular Interactions in Solid State Fluorescent Conjugated Polymer Chemosensors

A functionalized fluorescent conjugated polymer, tolylterpyridine poly(p-phenyleneethynylene-thienyleneethynylene (ttp-PPETE), was designed and synthesized to detect trace amounts of toxic transition metal pollutants in ground water. Photophysical studies in tetrahydrofuran (THF) successfully demonstrated this polymer as a selective and sensitive chemosensor for Ni²⁺ and Co²⁺ in aqueous solution. Solid state composites of these chemosensors have now been prepared which can be modified to provide for inexpensive and portable field based chemical detection. A solid composite of ttp-PPETE, blended with poly (methyl methacrylate) shows UV–vis absorption and fluorescence emission spectra which are red- shifted when compared to solution phase spectra, suggesting an increase in conjugation in the solid state. An additional absorption peak, not present in solution, is also observed in the solid state. The presence of this new peak provides evidence of interacting FCP chains in the solid state. Concentration dependent experiments were done on the solid composite showing red-shifted emission peaks accompanied by a significant reduction in the fluorescent quantum yield. These observations are consistent with the formation of aggregated polymer species in the solid state. Intermolecular interactions of this type can be manipulated in the design of sensitive and selective solid state fluorescent conjugated polymer sensors.     

The time-resolved spectrum of a pulsed dye laser

The spectral evolution in a xenon ion-pumped open dye stream laser was measured and analysed in terms of a theoretical spectro-temporal relation previously derived. Sweep occurs in a 200 ns time scale and simultaneous oscillations of several wavelengths can be achieved by varying laser cavity parameters. Experiments were completely reproduced by assuming that the phenomena can be ascribed to the homogeneous broadening of the laser fluorescent band.     

吡唑林荧光化合物的合成与红外光谱研究

由苯并噻唑基及苯并咪唑基取代的吡唑林类化合物是一类新型荧光化合物。此类荧光化合物可用于多种领域,但一直发展较缓慢。依据Schellhammer经验中化学结构与荧光性关系,在吡唑林的1-位引入了苯并噻唑基或苯并咪唑基,3-位引入苯基衍生物,使其具有荧光性,5-位引入苯基作为助色团,可使荧光谱红移,增加荧光性。作者设计出新型荧光化合物的结构式,新合成了两种苯并咪唑及苯并噻唑吡唑林荧光化合物,用元素分析确定其结构。两种化合物具有较好的荧光性,荧光发射波长处在蓝绿光的范围内。经红外光谱分析,找出由苯并噻唑基或苯并咪唑基取代的吡唑林类化合物具有的典型特征吸收峰,可由此作为基准,推断化合物的结构。两种化合物的合成与光谱分析研究可为吡唑林类荧光化合物的研究开拓新途径。     

Local dimming algorithm and color gamut calibration for RGB LED backlight LCD display

A 32 in RGB LED backlight unit is developed. A local dimming algorithm is designed for the backlight, and grid-noise artifacts in the LC driving signal are successfully removed with consideration of the backlight distribution to provide identical intensity from each LED block. The 32 in RGB LED backlight LCD display has achieved a static display contrast of over 20000:1 and an average power reduction of 30%. We have also obtained the color gamut transformation matrix for transferring a cold cathode fluorescent lamp BLU LCD display gamut system to our RGB LED BLU LCD display gamut system, and extended the color saturation by suppositional color expansion method. As a result, the color has been accurately reproduced in RGB LED BLU LCD display with more richness and more saturation.     

三维多回波流动补偿定量磁化率成像(QSM)方法研究

定量磁化率成像(QSM)利用一般成像技术舍弃的相位信息得到局部磁场变化特性,通过复杂的场到源反演计算,可直接得到定量的磁化率图,它广泛应用于测量血氧饱和度、脑部微出血、铁沉积、组织钙化等方面．然而,梯度磁场中流动会引起相位错误,并且产生显著的流动伪影,最终得到错误的QSM图像．为了矫正流动的影响,该文在3 T磁共振系统上实现了三维多回波流动补偿梯度回波序列,并用该序列采集流动水模和志愿者颅脑数据．流动水模和颅脑数据均显示,流动补偿能够明显矫正相位错误,消除流动伪影．颅脑横断位QSM结果证明,流动补偿序列可以消除血液流动引起的QSM的错误,提高QSM的准确性．     

Electronic Properties of Metallic Nanoclusters on Semiconductor Surfaces: Implications for Nanoelectronic Device Applications

We review current research on the electronic properties of nanoscale metallic islands and clusters deposited on semiconductor substrates. Reported results for a number of nanoscale metal-semiconductor systems are summarized in terms of their fabrication and characterization. In addition to the issues faced in large-area metal-semiconductor systems, nano-systems present unique challenges in both the realization of well-controlled interfaces at the nanoscale and the ability to adequately characterize their electrical properties. Imaging by scanning tunneling microscopy as well as electrical characterization by current-voltage spectroscopy enable the study of the electrical properties of nanoclusters/semiconductor systems at the nanoscale. As an example of the low-resistance interfaces that can be realized, low-resistance nanocontacts consisting of metal nanoclusters deposited on specially designed ohmic contact structures are described. To illustrate a possible path to employing metal/semiconductor nanostructures in nanoelectronic applications, we also describe the fabrication and performance of uniform 2-D arrays of such metallic clusters on semiconductor substrates. Using self-assembly techniques involving conjugated organic tether molecules, arrays of nanoclusters have been formed in both unpatterned and patterned regions on semiconductor surfaces. Imaging and electrical characterization via scanning tunneling microscopy/spectroscopy indicate that high quality local ordering has been achieved within the arrays and that the clusters are electronically coupled to the semiconductor substrate via the low-resistance metal/semiconductor interface.     

磷光材料fac-tris(2-phenylpyridinato-N，C2′)iridium(Ⅲ)对不同荧光材料的敏化作用及发光机制分析

在荧光材料中掺杂合适的磷光敏化剂,可以大大提高荧光有机电致发光器件(OLED)的效率。选择磷光材料知fac-tris(2-phenylpyridinato-N,C^2′)iridium(Ⅲ)(Ir(ppy)3)分别与荧光材料4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl(DCJTB)、5,6,11,12,-tetraphenylnaphthacene(Rubrene)掺杂作为发光层,当掺杂质量比合适时,磷光材料的发光消失,得到了纯正的荧光材料的发光。同时,对磷光材料的敏化作用及发光机制进行了分析,比较了Ir(ppy)3对两种不同荧光材料的敏化作用强弱,发现Ir(ppy)3对荧光材料Rubrene的敏化作用更强。对影响敏化作用的因素进行了分析,推测其原因与磷光材料和荧光材料的相容性质有关。