Ag/ZrO2-NT/Zr hybrid material: A new platform for SERS measurements

In this paper, we present recent results of our attempts to produce nanoporous zirconia, as well as our investigations of a hybrid material consisting of nanoporous zirconia loaded with Ag-nanoparticles, Ag-n/ZrO₂-NT/Zr, which could be used as an active SERS substrate. The Zr-based hybrid material, as our investigations have shown, is an active and stable substrate in SERS investigations aimed at detecting various organic molecules: mercaptobenzoic acid, pyridine and two different dyes – rodhanine derivatives. The SERS spectra for the probe molecules adsorbed on silver nanoparticles on a ZrO₂-NT/Zr platform display characteristic intensity ratios different from those measured on previously studied nanoporous substrates based on Ti and Al, which ensure a different (alternative) interaction between the investigated adsorbate and adsorbent. In order to characterize our new substrate we used high-resolution SEM and surface analytical techniques: XPS (X-ray photoelectron spectroscopy) and SERS (surface enhanced Raman spectroscopy).     

石墨碳纳米材料光学性质在生化传感领域的应用

石墨碳纳米材料因其特殊的光学性质而受到广泛关注。石墨碳纳米材料最引人注目的光学性质之一是其独特的拉曼性质,作为拉曼探针,石墨碳纳米材料在对于复杂生物样品,极端测试条件和定量拉曼检测方面都有很好的应用;除了拉曼性质以外,单壁碳纳米管(SWNTs)独特的近红外二区(NIR-II,1000-1700 nm)荧光性质,具有穿透深度大、分辨率高的荧光成像特点,在生物活体成像领域也得到了很好的应用。除了光致发光特性,石墨碳纳米材料还具有优异的光热转换效应,同时具有比表面积大的特点,被广泛应用在针对肿瘤的热疗及其它疗法协同治疗当中。除此之外,石墨碳纳米材料还是一种高效的信号传导基底,可以猝灭激发态的染料和光敏剂,利用该类性质设计的生物传感器和纳米药物,显现出高灵敏、高选择性的特点。本文主要结合本课题组的工作,总结和探讨了石墨碳纳米材料作为光学探针、光热材料和信号传递基底在生化传感领域的应用。     

Electrocatalytic Acitivity of rGO/PEDOT : PSS Nanocomposite towards Methanol Oxidation in Alkaline Media

Increasing demand of alternative energy sources leads to the development of new electrocatalytic materials for fuel cells. In present work, we report the synthesis of rGO/PEDOT : PSS (reduced graphene oxide/ Poly (3,4‐ethylenedioxythiophene) : Polystyrene sulfonate) nanocomposite by in‐situ polymerization method using EDOT as precursor and the nanocomposite is used as anode catalyst for methanol oxidation. Structural and chemical characterizations such as XRD, FTIR and Micro‐Raman confirm the formation of the nanocomposite. From TEM image, growth of nanofibrous PEDOT : PSS on rGO nanosheets is observed. Electrochemical characterizations of rGO/PEDOT : PSS/ITO electrode are performed by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry (CA) measurements. Methanol oxidation reactions are performed in 0.5 M NaOH solution. The anodic current of the nanocomposite coated ITO is found be 37.5 mA at 0.59 V due to methanol electro‐oxidation and retentivity of the electrode is 92 % of initial scan after 800 cycles. The chronoamperometric results reveal that the nanocomposite modified electrode exhibits better stability with retention factor of 42.4 % up to 3000 seconds. The rGO/PEDOT : PSS/ITO electrode exhibits enhanced electrocatalytic activity towards methanol oxidation reaction due to larger surface area and excellent conductivity of rGO nanosheet.     

Nanoscale Chemical Imaging Using Tip‐Enhanced Raman Spectroscopy: A Critical Review

Methods for chemical analysis at the nanometer scale are crucial for understanding and characterizing nanostructures of modern materials and biological systems. Tip‐enhanced Raman spectroscopy (TERS) combines the chemical information provided by Raman spectroscopy with the signal enhancement known from surface‐enhanced Raman scattering (SERS) and the high spatial resolution of atomic force microscopy (AFM) or scanning tunneling microscopy (STM). A metallic or metallized tip is illuminated by a focused laser beam and the resulting strongly enhanced electromagnetic field at the tip apex acts as a highly confined light source for Raman spectroscopic measurements. This Review focuses on the prerequisites for the efficient coupling of light to the tip as well as the shortcomings and pitfalls that have to be considered for TERS imaging, a fascinating but still challenging way to look at the nanoworld. Finally, examples from recent publications have been selected to demonstrate the potential of this technique for chemical imaging with a spatial resolution of approximately 10 nm and sensitivity down to the single‐molecule level for applications ranging from materials sciences to life sciences.     

The influence of intracellular storage material on bacterial identification by means of Raman spectroscopy

Previous studies dealing with bacterial identification by means of Raman spectroscopy have demonstrated that micro-Raman is a suitable technique for single-cell microbial identification. Raman spectra yield fingerprint-like information about all chemical components within one cell, and combined with multivariate methods, differentiation down to species or even strain level is possible. Many microorganisms may accumulate high amounts of polyhydroxyalkanoates (PHA) as carbon and energy storage materials within the cell and the Raman bands of PHA might impede the identification and differentiation of cells. To date, the identification by means of Raman spectroscopy have never been tested on bacteria which had accumulated PHA. Therefore, the aim of this study is to investigate the effect of intracellular polymer accumulation on the bacterial identification rate. Combining fluorescence imaging and Raman spectroscopy, we identified polyhydroxybutyrate (PHB) as a storage polymer accumulating in the investigated cells. The amount of energy storage material present within the cells was dependent on the physiological status of the microorganisms and strongly influenced the identification results. Bacteria in the stationary phase formed granules of crystalline PHB, which obstructed the Raman spectroscopic identification of bacterial species. The Raman spectra of bacteria in the exponential phase were dominated by signals from the storage material. However, the bands from proteins, lipids, and nucleic acids were not completely obscured by signals from PHB. Cells growing under either oxic or anoxic conditions could also be differentiated, suggesting that changes in Raman spectra can be interpreted as an indicator of different metabolic pathways. Although the presence of PHB induced severe changes in the Raman spectra, our results suggest that Raman spectroscopy can be successfully used for identification as long as the bacteria are not in the stationary phase.     

Conjugated Polymer with Intrinsic Alkyne Units for Synergistically Enhanced Raman Imaging in Living Cells

Development of Raman‐active materials with enhanced and distinctive Raman vibrations in the Raman‐silent region (1800–2800 cm⁻¹) is highly required for specific molecular imaging of living cells with high spatial resolution. Herein, water‐soluble cationic conjugated polymers (CCPs), poly(phenylene ethynylene) (PPE) derivatives, are explored for use as alkyne‐state‐dependent Raman probes for living cell imaging due to synergetic enhancement effect of alkyne vibrations in Raman‐silent region compared to alkyne‐containing small molecules. The enhanced alkyne signals result from the integration of alkyne groups into the rigid backbone and the delocalized π‐conjugated structure. PPE‐based conjugated polymer nanoparticles (CPNs) were also prepared as Raman‐responsive nanomaterials for distinct imaging application. This work opens a new way into the development of conjugated polymer materials for enhanced Raman imaging.     

Fractal characterizations of energetic Si ions irradiated amorphized-Si surfaces

The fractal characterizations of amorphized-silicon (a-Si) surfaces under low-energy ion irradiations are presented. The crystalline Si surfaces have been irradiated with Si ions having different energy of 35, 50, 75, and 100 keV at a fixed fluence of 2 × 10¹⁵ ions-cm⁻². The samples have been characterized by means of using Raman spectroscopy, Channeling-Rutherford backscattering spectrometry (C-RBS), and atomic force microscopy (AFM) techniques. The ion irradiation leads to the amorphization of Si near surface and subsurface region, as confirmed by Raman and C-RBS measurement. The AFM analysis shows that the ion irradiation also leads to the formation of nanodots on the surface and size of the dots increases with increasing of the ion energy. The fractal analysis has been performed using AFM images in order to get the significant evidence about nanodot formations and the correlation inside the surface microstructures. The kinetic roughening and surface smoothening, due to dissipation of kinetic energy of ions through collision cascades of the surface atoms, lead to the formation of dot-like structures.     

Quantitative chemical imaging with multiplex stimulated Raman scattering microscopy

Stimulated Raman scattering (SRS) microscopy is a newly developed label-free chemical imaging technique that overcomes the speed limitation of confocal Raman microscopy while avoiding the nonresonant background problem of coherent anti-Stokes Raman scattering (CARS) microscopy. Previous demonstrations have been limited to single Raman band measurements. We present a novel modulation multiplexing approach that allows real-time detection of multiple species using the fast Fourier transform. We demonstrate the quantitative determination of chemical concentrations in a ternary mixture. Furthermore, two imaging applications are pursued: (1) quantitative determination of oil content as well as pigment and protein concentration in microalgae cultures; and (2) 3D high-resolution imaging of blood, lipids, and protein distribution in ex vivo mouse skin tissue. We believe that quantitative multiplex SRS uniquely combines the advantage of fast label-free imaging with the fingerprinting capability of Raman spectroscopy and enables numerous applications in lipid biology as well as biomedical imaging.     

A novel approach to investigate vascular wall in 3D: Combined Raman spectroscopy and atomic force microscopy for aorta en face imaging

A novel approach based on the combination of Raman confocal 3D imaging with atomic force microscopy (AFM) for analysis of the murine vessel wall en face is described. The approach is based on subsequent Raman and AFM imaging of the same areas of the sample. This methodology allows for direct correlation of the chemical structure (Raman data) with morphology of the surface (AFM). The sub-cellular structures of the tissue e.g., cell nuclei, heme, or lipid-rich species are visualized and localized by the application of Raman imaging, while AFM complements these data with high-resolution information about the surface topography and size of lipid-rich structures. Overall, the applied approach enables detailed characterization of the inner layer of the vessel wall.     

Recent advances in electron tomography: TEM and HAADF-STEM tomography for materials science and semiconductor applications.

Electron tomography is a well-established technique for three-dimensional structure determination of (almost) amorphous specimens in life sciences applications. With the recent advances in nanotechnology and the semiconductor industry, there is also an increasing need for high-resolution three-dimensional (3D) structural information in physical sciences. In this article, we evaluate the capabilities and limitations of transmission electron microscopy (TEM) and high-angle-annular-dark-field scanning transmission electron microscopy (HAADF-STEM) tomography for the 3D structural characterization of partially crystalline to highly crystalline materials. Our analysis of catalysts, a hydrogen storage material, and different semiconductor devices shows that features with a diameter as small as 1-2 nm can be resolved in three dimensions by electron tomography. For partially crystalline materials with small single crystalline domains, bright-field TEM tomography provides reliable 3D structural information. HAADF-STEM tomography is more versatile and can also be used for high-resolution 3D imaging of highly crystalline materials such as semiconductor devices.     

Elucidation of Biosynthetic Pathways of Natural Products

During the last decade, we have revealed biosynthetic pathways responsible for the formation of important and chemically complex natural products isolated from various organisms through genetic manipulation. Detailed in vivo and in vitro characterizations enabled elucidation of unexpected mechanisms of secondary metabolite biosynthesis. This personal account focuses on our recent efforts in identifying the genes responsible for the biosynthesis of spirotryprostatin, aspoquinolone, Sch 210972, pyranonigrin, fumagillin and pseurotin. We exploit heterologous reconstitution of biosynthetic pathways of interest in our study. In particular, extensive involvement of oxidation reactions is discussed. Heterologous hosts employed here are Saccharomyces cerevisiae, Aspergillus nidulans and A. niger that can also be used to prepare biosynthetic intermediates and product analogs by engineering the biosynthetic pathways using the knowledge obtained by detailed characterizations of the enzymes. (998 char.)     

Optical fibre SERS sensors

Surface-enhanced Raman scattering (SERS) has established itself as an important analytical technique. However, efforts to transfer the technology from the laboratory to the production line, clinic or field have been frustrated by the lack of robust affordable substrates and the complexity of interfacing between sample and spectrometer. Prompted by the success of optical fibre systems for implementing normal Raman scattering spectroscopy in remote locations and biomedical applications, attention has now shifted to the development of SERS-active optical fibres. Other workers have attempted to develop SERS probes with extended interaction lengths and both far-field and near-field SERS imaging techniques for high-resolution chemical mapping of surfaces. This review discusses the development of these technologies and presents the current state of the art. Although recent developments show great promise, some outstanding challenges and opportunities remain to be addressed.     

Raman Imaging: An Impending Approach Towards Cancer Diagnosis

In accordance with the recent studies, Raman spectroscopy is well experimented as a highly sensitive analytical and imaging technique in biomedical research, mainly for various disease diagnosis including cancer. In comparison with other imaging modalities, Raman spectroscopy facilitate numerous assistances owing to its low background signal, immense spatial resolution, high chemical specificity, multiplexing capability, excellent photo stability and non-invasive detection capability. In cancer diagnosis Raman imaging intervened as a promising investigative tool to provide molecular level information to differentiate the cancerous vs non-cancerous cells, tissues and even in body fluids. Anciently, spontaneous Raman scattering is very feeble due to its low signal intensity and long acquisition time but new advanced techniques like coherent Raman scattering (CRS) and surface enhanced Raman scattering (SERS) gradually superseded these issues. So, the present review focuses on the recent developments and applications of Raman spectroscopy-based imaging techniques for cancer diagnosis.     

Tip-enhanced near-field optical microscopy of carbon nanotubes

We review recent experimental studies on single-walled carbon nanotubes on substrates using tip-enhanced near-field optical microscopy (TENOM). High-resolution optical and topographic imaging with sub 15 nm spatial resolution is shown to provide novel insights into the spectroscopic properties of these nanoscale materials. In the case of semiconducting nanotubes, the simultaneous observation of Raman scattering and photoluminescence (PL) is possible, enabling a direct correlation between vibrational and electronic properties on the nanoscale. So far, applications of TENOM have focused on the spectroscopy of localized phonon modes, local band energy renormalizations induced by charge carrier doping, the environmental sensitivity of nanotube PL, and inter-nanotube energy transfer. At the end of this review we discuss the remaining limitations and challenges in this field. Figure Tip-enhanced Raman scattering and photoluminescence spectroscopy with sub 15 nm spatial resolution provides novel insights into the electronic and vibronic properties of single-walled carbon nanotubes.     

Spatially resolved determination of the structure and composition of diatom cell walls by Raman and FTIR imaging

Vibrational spectroscopic imaging has developed into a versatile tool to study the local composition of various materials. Here, we present for the first time that Raman mapping and Fourier transform infrared imaging are useful tools to study diatom cell walls as is demonstrated for the species Stephanopyxis turris. The unicellular diatoms exhibit intricately micro- and nano-patterned cell walls, which consist of amorphous silica as well as various organic and inorganic constituents, thus making up an extremely interesting inorganic/organic hybrid material. The structure and composition of this material as well as the biochemical and biophysical processes leading to its formation remain to be challenges for ongoing research. Whereas the lateral resolution of Fourier transform infrared imaging is limited to 5 μm by diffraction, Raman maps are shown to be capable of detecting the spatial distribution of the silica as well as an additional inorganic component and the organic material down to 330-nm resolution. Due to the spherical shape of the sample with a radius of 40 μm and the requirement to accurately focus the laser before each Raman measurement within the micrometer range, Raman maps of whole diatom cell walls were registered after an adjustment of the axial position. The results reveal local differences in the cell wall composition of the honeycomb-like structures and the bottom layer.     

利用硫化铋纳米颗粒增强类石墨相氮化碳的光生载流子分离效率和光催化活性（英文）

二氧化钛,氧化锌,磷酸铋等传统的紫外光响应光催化剂虽然具有良好的光催化性能,但是对太阳能利用率很低(紫外光只占太阳光能量的4%左右).近年来,类石墨相氮化碳(g-C3N4)受到了广泛的关注.g-C3N4的带隙约2.7 eV,它只能吸收460nm以下的光,对太阳能的利用率依然比较低.构筑异质结是一种有效的提高光催化活性的方法.BiOCl/g-C3N4,TiO2/g-C3N4, Bi2MoO6/g-C3N4, Al2O3/g-C3N4, Ag3PO4/g-C3N4等异质结光催化剂曾被广泛的报道.硫化铋是属于正交晶系的窄带隙半导体,它的带隙约1.3–1.7 e V.由于其独特的电子结构和光学特性,硫化铋在光催化,光检测器和医药成像等领域有着广泛的应用.另外,硫化铋还具有优异的光热转换性能,在光热癌症治疗领域有显著的效果.微波辅助法,水热法,惰性气体下高温煅烧法等都曾被用来合成g-C3N4/Bi2S3异质结光催化剂.不同的文献也提出了不同的催化机理.如何使用更简单环保的方法来合成g-C3N4/Bi2S3异质结光催化剂?电子和空穴的转移路径是怎样的?本文利用简单的低温方法合成了硫化铋,利用超声法得到了g-C3N4/Bi2S3异质结光催化剂,分析了其微观形貌,结构,并探讨了光催化的反应机理和提高光催化性能的因素.X射线衍射,傅里叶变换红外光谱, X射线光电子能谱和透射电子显微镜的结果表明,硫化铋纳米颗粒被成功地引入到g-C3N4中.使用亚甲基蓝为分子探针研究了所制材料在模拟太阳光下的光催化活性.结果发现, CN-BiS-2表现出最佳的光催化活性,是g-C3N4的2.05倍,是Bi2S3的4.42倍.利用液相色谱二级质谱联用分析了亚甲基蓝的降解路径.硫化铋的引入拓展了复合材料的吸收边,使其向可见光区红移,且在整个可见光区的光吸收能力都有明显的增强.光电流的增强和交流阻抗谱圆弧半径的减小,表明光生载流子的迁移与分离速率得到了增强.自由基捕获试验表明,最主要的活性物种是光生空穴,次之是羟基自由基和超氧自由基.在CN-Bi S-2样品中羟基自由基和超氧自由基的电子顺磁共振信号都比g-C3N4有明显的增强,表明复合样品中能够产生更多的羟基自由基和超氧自由基.基于光电流,交流阻抗,荧光光谱,自由基捕获和电子顺磁共振的结果,我们提出了高能电子由硫化铋转移到g-C3N4,同时空穴由g-C3N4转移到硫化铋的电子空穴转移机制.此外,红外热成像的结果表明, g-C3N4/Bi2S3异质结材料具有更强的光热转换能力,从而有利于加速光生载流子分离.     

从分子碎片到活性位：分子筛催化材料的原位、共振紫外拉曼光谱研究

在过去的近十年中,各种新型原位表征技术和反应器设计被应用于多相催化过程和催化材料的合成研究中,并获得了许多新认识．特别是最近几年,利用原位、共振拉曼光谱技术对分子筛合成关键物种检测、杂原子分子筛催化活性位的研究取得了一系列进展．这些技术的应用使得从分子水平认识复杂的多孔材料成为可能：从合成初期碎片基元检测、碎片相互连接的关键化学键到预组装类微孔结构;从高度隔离过渡金属中心到配位化学键断裂生成活性中间物种,再到完成催化反应循环．这为设计特定功能和结构的催化材料及高选择性的活性中心奠定了坚实的基础．     

A New Strong-Acid Free Route to Produce Xanthan Gum-PANI Composite Scaffold Supporting Bioelectricity

Conductive hybrid xanthan gum (XG)–polyaniline (PANI) biocomposites forming 3D structures able to mimic electrical biological functions are synthesized by a strong-acid free medium. In situ aniline oxidative chemical polymerizations are performed in XG water dispersions to produce stable XG–PANI pseudoplastic fluids. XG–PANI composites with 3D architectures are obtained by subsequent freeze-drying processes. The morphological investigation highlights the formation of porous structures; UV–vis and Raman spectroscopy characterizations assess the chemical structure of the produced composites. I–V measurements evidence electrical conductivity of the samples, while electrochemical analyses point out their capability to respond to electric stimuli with electron and ion exchanges in physiological-like environment. Trial tests on prostate cancer cells evaluate biocompatibility of the XG–PANI composite. Obtained results demonstrate that a strong acid-free route produces an electrically conductive and electrochemically active XG–PANI polymer composite. The investigation of charge transport and transfer, as well as of biocompatibility properties of composite materials produced in aqueous environments, brings new perspective for exploitation of such materials in biomedical applications. In particular, the developed strategy can be used to realize biomaterials working as scaffolds that require electrical stimulations for inducing cell growth and communication or for biosignals monitoring and analysis.     

锂电池电极过程的原位电化学原子力显微镜研究进展

随着人类对能源的使用与存储需求不断增加,高能量密度和高安全性能的二次锂电池体系正在被不断地开发与完善.深入理解充放电过程中锂电池内部电极/电解质界面的电化学过程以及微观反应机理,有利于指导电池材料的优化设计.原位电化学原子力显微镜将原子力显微镜的高分辨表界面分析优势与电化学反应装置相结合,能够在电池运行条件下实现对电极/电解质界面的原位可视化研究,并进一步从纳米尺度上揭示界面结构的演化规律与动力学过程.本文总结了原位电化学原子力显微镜在锂电池电极过程中的最新研究进展,主要包括基于转化型反应的正极过程、固体电解质中间相的动态演化以及固态电池界面演化与失效分析.     

The Interplay of Photophysical Properties in Carbazole Fluorescent Oligomers

The photophysical properties and the organic synthesis using effective palladium‐catalyzed Suzuki coupling reactions from a series of carbazole derivatives are described and the relationships of the donor and acceptor groups are also investigated. The purification of the materials and its applications along with the corresponding photo‐physical characterizations were presented. With the advantages gained from 2D‐COSY spectra, which provide more correlated information between immediate atoms than ¹H‐NMR spectra and a series of further investigations were undertaken including powder X‐ray diffraction analysis, Infrared and Raman spectroscopy, constructing the composition conformation and chemical structure of the materials is more easily to achieve. Additionally, the optimized structure of the minimized energy geometries and spatial distributions of carbazole derivatives was calculated using density functional theory (DFT), new materials can be developed and designed selectively based on the method proposed in this work.