Nucleotide/Tb coordination polymer nanoparticles as luminescent sensor and scavenger for nitrite ion

Newly emerged metal organic coordination polymers have aroused the great interest in designing tailored functional materials. In this study, multiple functional components, luminescent Tb³⁺ ion, nucleobase and antenna molecule, were integrated in a single material and prepared into a responsive nanoparticle for nitrite. The terbium coordination polymer nanoparticles made of this kind of material have the dual functions of recognition and transduction and obey a preset sensing mechanism without a post-functionalization of common materials. As the result of the tailored, the terbium coordination polymer nanoparticles are highly sensitive and selective to nitrite by means of Dexter energy transfer between Tb³⁺ ion and nitrite, and can be used for the scavenger for nitrite in aqueous solution. The detection limit, dynamic range and removal capacity of U–Tb–OBBA CPNPs for nitrite are 0.3 µM, 0.3–470 µM and 4.44 mg per gram of particles, respectively. Metal organic coordination polymers show an attractive potential in constructing smart sensing materials.     

In situ hydrazine reduced silver colloid synthesis – Enhancing SERS reproducibility

Herein we report a novel strategy for the in situ synthesis of the silver colloids for LoC-SERS applications. Silver nanoparticles are obtained in a segmented flow based glass microfluidic chip by the reduction of silver ions with hydrazine in ammonium hydroxide solution. Citrate ions are used as protecting agents. The synthesized nanoparticles are characterized by UV-VIS spectroscopy, SEM and TEM imaging. The SERS performance of the in situ synthesized nanoparticles is tested by using adenine as a test analyte right after the colloid synthesis. Reproducibility is tested by repeating the measurements three times at independent days applying the same measurement conditions. In comparison with nanoparticles synthesized in a conventional strategy i.e. in a large batch, chip synthesized nanoparticles show a better day-to-day and long-term reproducibility, lower detection limits and broader working ranges. The great advantage offered by the in situ synthesized colloids combined with the already proven potential of LoC-SERS for bioanalytics, raises the possibility of the employment of LoC-SERS as a fast and sensitive analytic tool in a plethora of applications.     

Mechanochemically Induced Conversion of Crystalline Benzamide Polymorphs by Seeding

Benzamide has been known for its polymorphism for almost 200 years. Three polymorphic forms are described. To date, it was only possible to crystallize a metastable form in a mixture together with the thermodynamically most stable form I. A complete transformation of form I into the metastable form III by mechanochemical treatment has been achieved. Catalytic amounts of nicotinamide seeds were used to activate the conversion by mechanochemical seeding. NMR experiments indicated that the nicotinamide molecules were incorporated statistically in the crystal lattice of benzamide form III during the conversion. The transformation pathway was evaluated using in situ powder X‐ray diffraction.     

单臂压缩感知鬼成像的光强扩散函数分析法

为了提高单臂压缩感知鬼成像的成像质量,减少成像系统本身和外部环境的干扰,提出了一种光强扩散函数分析方法.在单臂压缩感知鬼成像原理的基础上分析了成像过程,指出降低成像质量的主要因素是菲涅尔衍射和大气湍流.针对这两个因素,推导并分析了光强度扩散函数的公式,研究透镜的焦距与口径之比和照明光源的波长对鬼成像的影响.仿真结果表明:在单臂压缩感知鬼成像中,使用焦距与尺寸半径之比在2~5范围内的成像投影透镜可以消除衍射效应的影响;短波长光源适用于大气湍流较弱时的成像,长波长光源在大气湍流较强时对干扰有更好的耐受能力.该方法可以有效地提高成像质量并优化成像系统.     

结合NSDTCT和稀疏表示的遥感图像融合

为了提高全色图像与多光谱图像的融合质量,提出一种基于非下采样双树复轮廓波变换和稀疏表示的图像融合算法.对多光谱图像进行亮度-色度-饱和度变换,再对亮度分量和全色图像进行直方图匹配及亮度平滑滤波处理.利用非下采样双树复轮廓波变换处理亮度分量和全色图像,得到对应的高低频系数.对于低频系数,利用稀疏表示进行融合,采用空间频率和l1范数双指标取大的融合规则得到稀疏表示系数;对于高频系数,将改进的拉普拉斯能量和作为脉冲耦合神经网络的外部输入项,提出了改进的脉冲耦合神经网络的融合策略.最后进行非下采样双树复轮廓波逆变换和亮度-色度-饱和度逆变换得到融合结果.实验结果表明,该算法最大限度地保留光谱信息的同时可以提高空间分辨率,视觉效果及客观指标均优于经典的融合算法.     

基于压缩感知/重采样的NMR噪声抑制新方法

发展高灵敏检测方法是分析化学的永恒主题之一,提高信号强度和降低噪声水平是增强灵敏度的根本途径.在核磁共振波谱(NMR)分析中,通常采用高磁场强度的谱仪或复杂的脉冲实验方法来提高信号强度,或通过使用超低温探头来降低噪声水平,但这无疑会提高实验成本或增加实验难度.相较而言,利用数据后处理方法辨识和抑制噪声,是更为经济的提高信噪比(SNR)的途径.因此,该文在前期研究中发展的基于统计学中重采样原理的数据后处理方法(NASR)的基础上,通过引入压缩感知(CS)技术,对重采样方法进行了优化改进,所发展的NMR数据处理新方法(CS_NASR)可有效排除主观因素影响,提高处理结果的鲁棒性.     

拉曼除谱原位测量水溶液中蛋白质的酰胺A谱带

蛋白质的酰胺A谱带对蛋白质的酰胺氢键结构很敏感. 然而由于该谱带和水的OH伸缩振动谱带严重重叠,导致在蛋白质水溶液中原位测量酰胺A谱带依旧很困难. 我们提出了一种新的分析方法用于原位测量水溶液中的酰胺A谱带. 这个方法称为拉曼除谱法. 将蛋白质水溶液光谱除以纯水光谱即可获得拉曼除谱. 利用数值模拟从数学上肯定了使用拉曼除谱可以直接获得酰胺A谱带. 我们还通过测量溶菌酶和α-糜蛋白酶的固体和水溶液的拉曼光谱,这些光谱也证实了可以通过拉曼除谱法直接获取酰胺A谱带. 利用拉曼除谱还分析了溶菌酶的热变性过程. 这些研究表明拉曼除谱可以原位地表征水溶液中的蛋白质酰胺A谱带.     

Methodological aspects of in vitro sensing of L-glutamate in acute brain slices

L-Glutamate is a major amino acid neurotransmitter in the central neuronal system of the mammalian brain and plays a vital role in brain development, synaptic plasticity, neurotoxicity, and neuropathological disorders. Despite technical limitations, progress is being made in sensing L-glutamate in vivo and in vitro. Sophisticated microsensors with the necessary spatial and temporal resolution have recently been emerging, which enable us to discern regional distribution, concentration levels, and temporal changes of L-glutamate in acute brain slices. The L-glutamate sensors for in vitro sensing have different structures and sizes, such as glass capillary-based enzyme sensors, polymer-coated enzyme sensors, and patch sensors based on natural sensing probes. The concentration of L-glutamate released in brain slices by chemical stimulation is markedly dependent on neuronal regions, types of stimulation, and sensing methods. Real- and long-time monitoring of L-glutamate in acute hippocampal slices is beginning to shed light on L-glutamate release related to the molecular mechanisms of long-term potentiation. Progress is also being made toward the visualization of L-glutamate release in acute hippocampal slices. The methodological aspects of in vitro sensing of L-glutamate are discussed.     

Smart Poly(styrene)/Carbon Black Conductive Polymer Composites Films for Styrene Vapour Sensing

Conductive Polymer Composites (CPC) can be used to elaborate sensing elements able to detect solvent vapours at very low concentrations (some ppm). Our experiments have shown that combining atactic PS or syndiotactic PS to five carbon black of different specific surfaces, allows obtaining a wide range of electrical resistances and surface morphologies. The CPC films have been elaborated from solutions by spraying and spin coating, the former being more adequate to design sensitive films with tuneable electrical properties. The larger electrical responses were obtained with an initial resistance close to 10⁴ Ω. Our sensors gave a response for very low styrene concentration (some ppm) increasing as a function of vapour concentration.     

In situ scanning probe microscopy and new perspectives in analytical chemistry

The resolution of scanning tunnelling microscopy (STM) and other scanning probe microscopies is unprecedented but the techniques are fraught with limitations as analytical tools. These limitations and their relationship to the physical mechanisms of image contrast are first discussed. Some new options based on in situ STM, which hold prospects for molecular- and mesoscopic-scale analytical chemistry, are then reviewed. They are illustrated by metallic electro-crystallisation and -dissolution, and in situ STM spectroscopy of large redox molecules. The biophysically oriented analytical options of in situ atomic force microscopy, and analytical chemical perspectives for the new microcantilever sensor techniques are also discussed.