银/金纳米线阵列表面增强拉曼基底的制备及对孔雀石绿的高灵敏度检测

利用种子介导的软模板生长方法制备了金纳米线(Au NWs)阵列, 通过调节生长温度控制Au NWs阵列的形貌, 最后在经硼氢化钠(NaBH₄)清洗过的Au NWs阵列上化学沉积银纳米颗粒(Ag NPs), 制得银/金纳米线(Ag/Au NWs)阵列作为表面增强拉曼散射(SERS)基底. 选用罗丹明6G(R6G)作为拉曼探针分子测定了Ag/Au NWs阵列的SERS性能. 结果表明, Ag/Au NWs阵列作为SERS基底具有高灵敏度、 优异的信号均匀性和良好的稳定性. 使用Ag/Au NWs阵列对孔雀石绿(MG)检测的检出限可低至1×10^-8 mol/L, 线性范围为 1×10^-8~1×10^-4 mol/L. NaBH₄可以在不影响SERS性能的情况下去除Ag/Au NWs阵列上吸附的分子, 使得 SERS基底可以重复使用. 使用Ag/Au NWs阵列对湖水中的MG进行检测, 得到了可靠的回收率, 证明Ag/Au NWs 阵列在检测环境水体中的孔雀石绿上具有应用潜力.     

Fluorescent molecular probes for the detection of chemical warfare agents and their mimics

Owing to their direct toxic effects on human beings, animals, and plants, chemical warfare agents (CWAs) and their mimics have become widespread in chemical warfare and agriculture. The considerable concerns about their entry into biological systems and the residues in environment stimulate the development of rapid and sensitive methods for the detection and analysis of this family of compounds. In the progress of sensitive, selective, and fast responsive detection, fluorescent molecular probes have been widely used in the detection of CWAs in recent years. Here the recent reports on the design of fluorescent molecular probes and their advantages in the detection of CWAs were reviewed. Furthermore, the extensive interests accelerate the development of novel fluorescent molecular probes and detection techniques in this field.     

Fabrication of organosilane-modified electrodes for metal ion detection at the molecular level

Organosilane-modified (island-type) electrodes of 5 and 10 microm were fabricated and used to detect trace amounts of metal ions using atomic force microscopy. The smaller electrode had a lower limit of detection due to the enhancement in electron tunneling through metal ions that are adsorbed between the conductive-tip (mobile) and the surface (fixed) electrode. To simulate the detection of metal ions at concentrations below 10(-3) mM, a sectional adsorption mechanism is proposed, which satisfactorily explains the adsorption of Cu(II) and Hg(II) to the amine and thiol moieties of the 5 microm-sized electrode.     

表面增强拉曼散射强度与金纳米粒子粒径关系

表面增强拉曼散射（SurfaceenhancedRamanscattering,简称SERS）的增强机理主要分为两类’‘－‘’：电磁增强和化学增强．通常SERS活性表面的获得需要粗糙化．MOSkovitS最先提出,可将粗糙化的SERS活性表面模型化为平整金属基底上排列的金属胶体粒子“’．这样的模型与实际体系比较符合,同时给理论处理提供了便利．在这一模型基础之上,人们提出了一系列SERS电磁增强的理论计算方法’‘－“．在这些理论计算中,大多包含有SERS强度与粒径关系的结果．粒径对SERS强度的影响体现在两方面：1）SERS与粗糙度有关,粒径可视为粗…     

山莓状Au-树脂微球的制备及SERS性能

采用抗坏血酸在室温下液相还原AuCl₄^--阴离子交换树脂微球, 同时实现Au微柱的形成及在树脂表面的阵列型组装, 低成本高通量地得到山莓状Au-树脂微球; 以苯硫酚为探针考察了山莓状Au-树脂微球用作表面增强拉曼散射(SERS)活性基底的性能, 结果表明, Au-树脂微球具有良好的Raman增强效应(增强因子EF达到10⁸～10⁹量级), 且有很高的重现性和稳定性, Raman信号强度和EF的相对标准偏差(RSD)为(35±5)%.     

适用于针尖增强拉曼技术的Au针尖的研制

采用针尖增强拉曼光谱技术(TERS)研究了刻蚀电位对Au针尖刻蚀效果的影响, 初步探讨了刻蚀过程的机理. 通过监控刻蚀过程中的振荡电流-时间曲线并与扫描电镜得到的结果比较, 发现可以直接利用电流-时间曲线简单地判断刻蚀后针尖的可能形状, 而无需再借助扫描电镜进行表征. 这不但提高了实验效率, 而且还可以避免针尖在转移和电镜表征过程中可能引入的污染. 研究结果表明, 在体积比为1:1的发烟盐酸和无水乙醇的刻蚀液中, 于2.2 V的电压下, 结合电化学方法控制终点可以得到形状对称尖锐的针尖. 这种针尖不但适合于TERS研究, 而且可用作STM针尖和微纳电极并用于其它针尖增强光学技术.     

Real-time PCR detection of telomerase activity using specific molecular beacon probes

Telomerase is a potentially important biomarker and a prognostic indicator of cancer. Several techniques for assessing telomerase activity, including the telomeric repeat amplification protocol (TRAP) and its modified versions, have been developed. Of these methods, real-time quantitative TRAP (RTQ-TRAP) is considered the most promising. In this work, a novel RTQ-TRAP method is developed in which a telomeric repeats-specific molecular beacon is used. The use of the molecular beacon can improve the specificity of the RTQ-TRAP assay, making the method suitable for studying the overall processivity results and the turnover rate of telomerase. In addition, the real-time, closed-tube protocol used obviates the need for post-amplification procedures, reduces the risk of carryover contamination, and supports high throughput. Its performance in synthetic telomerase products and cell extracts suggests that the developed molecular beacon assay can further enhance the clinical utility of telomerase activity as a biomarker/indicator in cancer diagnosis and prognosis. The method also provides a novel approach to the specific detection of some particular gene sequences to which sequence-specific fluorogenic probes cannot be applied directly. Figure Real-time PCR detection of telomerase activity using specific molecular beacon probes Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Fabrication of large-area ordered and reproducible nanostructures for SERS biosensor application

We propose a large-area SERS device with efficient fluorescence quenching capability. The substrate is based on anodic porous alumina templates with various pore size and wall thickness as small as 15 and 36 nm, respectively. The nano-patterned SERS substrate, with excellent control and reproducibility of plasmon-polaritons generation, shows very efficient enhanced Raman signal in the presence of intrinsically fluorescent molecules such as cresyl violet, rhodamine, and green fluorescent protein. This work demonstrates that, when the nanostructures are properly designed and fabricated, Raman and fluorescence spectroscopy can be used in combination in order to obtain complementary molecular informations. Theoretical simulation shows excellent agreement with the experimental findings. The enhancement factor is found to be 10(3)-10(4), with respect to flat gold surface when the molecules are supposed to be closely packed, with considerable fluorescence suppression, showing a promising disposable biosensor.     

Crystallinity engineering of Au nanoparticles on graphene for in situ SERS monitoring of Fenton-like reaction

Fabrication of multifunctional nanoplatform to in situ monitor Fenton reaction is of vital importance to probe the underlying reaction process and design high-performance catalyst.Herein,a hybrid catalyst comprising of single-crystalline Au nanoparticles（SC Au NPs） on reduced graphene oxide（RGO） sheet was prepared,which not only exhibited an excellent ¹ O₂ mediated Fenton-like catalytic activity in promoting rhodamine 6 G（R6 G） degradation by activating H₂ O_...     

Enhancement factor averaging and the photostability of probes in SERS vibrational pumping

The technique of temperature dependent vibrational pumping in surface enhanced Raman scattering (SERS) has been recently demonstrated as a promising new tool to estimate SERS cross-sections. In this paper we expand on the previous developments and study several details around the implementation and physics of the vibrational pumping technique in SERS. Here we concentrate on two specific aspects related to: (i) the different averaging properties (over the distribution of enhancements) of the Stokes and anti-Stokes signals in the pumping regime; and (ii) the role of the finite photostability of the probes. The fact that the anti-Stokes signal is averaged differently from the Stokes counterpart leads to some unique phenomena in Raman spectroscopy that can only be observed under the conditions of vibrational pumping in SERS.     

Synthesis of SERS active nanoparticles for detection of biomolecules

Surface Enhanced Raman Scattering (SERS) can be used to detect specific DNA sequences by methods based on hybridisation of oligonucleotide functionalized nanoparticles to complementary DNA sequences. The problem, which has to be overcome to use this technique is that DNA is not strongly SERS active. This is due to the lack of a visible chromophore and presence of the highly negatively charged phosphate backbone, which prevents the electrostatic interaction with the metal surface necessary for the enhancement. To obtain SERS active DNA a label containing a surface seeking group, to allow adsorption of DNA on a metal surface, and a chromophore has to be attached to the DNA strand. Here we report the synthesis of three linkers containing a Raman tag [the following fluorophores were used for this purpose due to the fluorescence quenching ability of metallic nanoparticles: fluorescein, 6-aminofluorescein and tetramethylrhodamine (TAMRA)], surface complexing group (cyclic disulphide—thioctic acid) and a chemical functionality for attachment of DNA (carboxyl group). Each of the linkers also contain poly(ethylene glycol) (PEG) (3 mer), which reduces non-specific adsorption of molecules to the surface of the nanoparticles and provides colloidal stability. The synthesized linkers were used to functionalize gold citrate (18 and 50 nm), silver citrate (40 nm) and silver EDTA (35 nm) nanoparticles. All of the conjugates exhibit high stability, gave good SERS responses at laser excitation frequencies of 514 and 633 nm and could be conjugated to amino-modified oligonucleotides in the presence of the commonly used (N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide hydrochloride—EDC·HCl with N-hydroxysulfosuccinimide or 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride—DMT MM, which has not been used for bioconjugate preparation previously. This approach is less time consuming and less expensive than previously used protocols and does not require the formation of a mixed layer of oligonucleotides and Raman reporter on the metal surface. Additionally the presence of a reactive functionality within the linker structure makes it possible to conjugate the linker to other biomolecules of interest such as proteins.     

Effect of Ag and Au nanoparticles on the SERS of 4-aminobenzenethiol assembled on powdered copper

Raman scattering measurements were conducted for 4-aminobenzenethiol (4-ABT) assembled on powdered copper substrates. Initially, very weak Raman peaks were detected, but upon attaching Ag nanoparticles probably via NH2 groups onto 4-ABT/Cu, distinct Raman spectra were observed. Considering the fact that no Raman peak was identified when Ag nanoparticles were adsorbed on 4-aminophenyl-derivatized silane monolayers assembled on silica powders, the Raman spectra observed for Ag@4-ABT/Cu should be surface-enhanced Raman scattering (SERS) spectra, occurring by an electromagnetic coupling of the localized surface plasmon of Ag nanoparticles with the surface plasmon polariton of Cu powders. The extra enhancement factor attainable by the attachment of a single Ag nanoparticle is estimated to be as large as 1.4 x 10(5) in the case when 632.8-nm radiation is used as the excitation source. When Au nanoparticles were attached onto 4-ABT/Cu, at least an order of magnitude weaker Raman spectra were obtained at all excitation wavelengths, however, indicating that the Au-to-Cu coupling should be far less effective than the Ag-to-Cu coupling for the induction of SERS.     

Naphthalimide-based fluorescent off/on probes for the detection of thiols

Herein, we report the design and synthesis of two naphthalimide-based fluorescent probes. These probes provided high on/off signal ratios and exhibited good selectivity towards thiols over other analytes. Thus, they were identified as good sensors for the detection of thiols both in living cells and in rabbit plasma samples.     

Fabrication of a liquid-gated enzyme field effect device for sensitive glucose detection

This study presents fabrication of a liquid-gated enzyme field effect device and its implementation as a glucose biosensor. The device consisted of four electrodes on a glass substrate with a channel functionalized by carboxylated multi-walled carbon nanotubes-polyaniline nanocomposite (MWCNTCOOH/PAn) and glucose oxidase. The resistance of functionalized channel increased with increasing the concentration of glucose when an electric field was applied to the liquid gate. The most effective and stable performance was obtained at the applied electric field of 100 mV. The device resistance, R, exhibited a linear relationship with the logarithm of glucose concentration in the range between 0.005 and 500 mM glucose. The detection limit (S/N = 3) for glucose was about 0.5 μM. Large effective area and good conductivity properties of MWCNTCOOH/PAn nanocomposite were the key features of the fabricated sensitive and stable glucose biosensor.     

金纳米粒子单层膜表面SPR催化反应的原位SERS研究

表面增强拉曼散射（SERS）基底的活性和均匀性是其SERS应用研究的关键,通过气-液两相界面自发组装的方式及控制组装的时间可制备致密性不同的金纳米粒子单层膜（Au MLF）.由于疏松和致密基底表面的LSPR产生的方式和强度不同导致SERS增强效应和均匀性两者无法同时兼顾,通常得到局域表面等离激元共振（SERS）增强性能及表面等离激元共振（SPR）催化性能优异但均匀性欠佳的疏松基底,或SERS增强性能与SPR催化性能中等但均匀性优越的致密基底.研究表明SERS增强效应的提高与粒子密度增加和“热点”活性增加有关,而SPR催化转化率仅与“热点”活性有关.本文以致密的Au MLF为基底,以对巯基苯胺（PATP）和对巯基苯甲酸（MBA）为探针分子系统研究了激光功率对SPR催化反应效率的影响,研究发现激光功率提高可显著提升PATP偶联反应及MBA脱羧反应的转化率.同时发现后者脱羧反应的速率与激光功率平方的倒数成线性关系,为相关表面过程的动力学参数测定提供了新的途径.     

SERRS-based enzymatic probes for the detection of protease activity

Measurement of protease activity, for the first time using SERRS as a detection method, is reported herein. Synthetic introduction of phenylalanine to a benzotriazole azo dye allows the SERRS response to be "switched off" and subsequent exposure to protease restores the SERRS response. The substrates exhibit varying reactivity for a range of proteases and allow for in situ, real-time analysis of protease reactivity. A limit of detection for one protease, Subtilisin carlsberg, was investigated and was established to be 50 ng ml-1.