Time-resolved two-photon excitation fluorescence spectroscopy and microscopy using a high repetition rate streak camera

We present a time-resolved two-photon excitation fluorescence spectroscopy and a simultaneous time- and spectrum- resolved multifocal multiphoton microscopy system that is based on a high repetition rate picosecond streak camera for providing time- and spectrum- resolved measurement and imaging in biomedicine. The performance of the system is tested and characterized by the fluorescence spectrum and lifetime analysis of several standard fluorescent dyes and their mixtures. Spectrum-resolved fluorescence lifetime images of fluorescence beads are obtained. Potential applications of the system include clinical diagnostics and cell biology etc.

组合注入质子导致不对称耦合双量子阱界面混合效应研究

用分子束外延系统 (MBE)生长了GaAs/AlGaAs不对称耦合双量子阱 (ACDQW ) ,采用组合注入质子的方法 ,在同一块衬底上获得了不同注入剂量的GaAs/AlGaAs不对称耦合双量子阱单元 ,没有经过快速热退火的过程 ,在常温下测量了不同注入剂量量子阱单元的显微光荧光谱和光调制反射光谱 ,发现了各区域子带间跃迁能量最大变化范围达到 81meV .由于样品未作高温热退火处理 ,为此由Al组分误差函数模型推导的扩散长度要大大高于扩散系数公式 .耦合量子阱的界面混合效应对于质子注入非常敏感 .

Microwave-assisted in situ synthesis of fluorescent gold nanoclusters with BSA/montmorillonite and application on latent fingermark imaging

A method for in situ preparation of fluorescent gold nanoclusters(Au NCs) with bovine serum albumin/montmorillonite composite powder(Au NC-BSA/MMT) was developed, and the products were used to detect latent fingermarks. In this work, Au NCs were "grown" both inside and on the surface of BSA/MMT clay using one-step reduction of HAu Cl4 by BSA. The as-prepared Au NC-BSA/MMT nanocomposites emit intensive red fluorescence under the excitation of UV-visible light and show stable chemical features and low toxicity. The obtained fluorescent powders were characterized by UV-visible absorption spectroscopy,fluorescence spectroscopy, infrared spectroscopy, transmission electron microscopy/high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction to depict their sizes, structural information and optical features. Given their environmentally friendly preparation, simple operation, low cost, efficient UVvisible radiation-dependent photoluminescence and good affinity with finger residues, the in situ synthesized Au NC-BSA/MMT nanocomposite powders were used as an alternative fluorescent developing reagent for developing latent fingermarks deposited on various object surfaces(such as glass, aluminum foil, painted metal, plastic products and weighing papers) for individual identification. As results, the developed fingermarks with clear patterns and satisfactory level-2(minutiae points) and level-3(sweat pores) ridge details were obtained. Notably, treated prints could be excited by red light and emitted near infrared fluorescence, which was beneficial to avoid background interference and reduce the damage caused by UV light. With the advantages of the simple preparation process and good enhancement performance for latent fingermarks, the proposed method might be used in the preparation of various fluorescent probes for detecting trace evidence in forensic sciences.

Observation of mitochondrial activity based on temporal and spatial pH variations measured by near-field fluorescent ratiometry

A novel method combining dual wavelength fluorescent ratiometry with scanning near-field optical microscopy (SNOM) is proposed and developed to measure the concentration and distribution of protons in the vicinity of biological samples. This method involves immersing mitochondria in a pH-sensitive fluorescent dye solution instead of injecting the dye into the surface of the mitochondrial membrane. It uses a dual emission pH-sensitive dye and SNOM with a thermally pulled and metal-coated optical fiber probe to improve the spatial resolution. The time dependence of the fluorescence intensity ratio (FIR) under acid addition and the response of mitochondria to nutritional supplementation were studied by using this method. Activation of mitochondria and a distance-dependent delay in the FIR response were observed. The results confirmed that mitochondrial activity could be observed by using this method.

Bench-top aqueous two-phase extraction of isolated individual single-walled carbon nanotubes

Isolation and purification of single-walled carbon nanotubes （SWCNTs） are prerequisites for their implementation in various applications. In this work, we present a fast （-5 min）, low-cost, and easily scalable bench-top approach to the extraction of high-quality isolated SWCNTs from bundles and impurities in an aqueous dispersion. The extraction procedure, based on aqueous two-phase （ATP） separation, is widely applicable to any SWCNT source （tested on samples up to 1.7 nm in diameter） and independent of defect density, purity, diameter, and length. The extracted dispersions demonstrate that the removal of large aggregates, small bundles, and impurities is comparable to that by density gradient ultracentrifugation, but without the need for high-end instrumentation. Raman and fluorescence-excitation spectroscopy, single-nanotube fluorescence imaging, atomic force and transmission electron microscopy, and thermogravimetric analysis all confirm the high purity of the isolated SWCNTs. By predispersing the SWCNTs without sonication （only gentle stirring）, full-length, pristine SWCNTs can be isolated （tested up to 20 μm）. Hence, this simple ATP method will find immediate application in the generation of SWCNT materials for all levels of nanotube research and applications, from fundamental studies to high-performance devices.

p-Sulfonatocalix[4]arene-induced amphiphilic aggregation of fluorocarbon surfactant

Sulfonatocalix[4]arene lowers the critical aggregation concentration of fluorocarbon surfactant pronouncedly by a factor of ca.100 to form binary amphiphilic aggregates on the basis of host-guest complexation,which was identified by1H NMR spectroscopy,fluorescence spectroscopy,optical transmittance spectroscopy,dynamic laser scattering,high-resolution transmission electron microscopy,scanning electron microscopy,and surface tension experiments.Moreover,the resulting aggregates can respond to external stimuli,including temperature and inclusion of competitor guest.Therefore,the present system may have potential applications in drug delivery systems.