Amorphous Cobalt Coordination Nanolayers Incorporated with Silver Nanowires: A New Electrode Material for Supercapacitors

The 2D amorphous cobalt coordination framework/silver nanowires nanocomposites (A‐CoL/Ag NC) are successfully synthesized by one‐step solution agitation at room temperature. The experimental data reveal that the hybrid provides sufficient contact between active materials and electrolyte, and facilitates the transfer of ions/electrons, resulting in high specific capacitance, high output potential, great rate capacity at high current density, and good cycle stability. As supercapacitor electrode materials, the as‐prepared A‐CoL/Ag NC electrode exhibits a great specific capacitance which can reach up to 1467 mF cm^?2 at 1.0 mA cm^?2, and 1060 mF cm^?2 even at 10.0 mA cm^?2. The A‐CoL/Ag NC// activated carbon asymmetric supercapacitor (AC ASC) displays a maximum energy density (110 W h kg^?1 at 760 W kg^?1) and maximum power density (6410 W kg^?1 at 63 W h kg^?1) in 3.0 m KOH. Moreover, the developed solid‐state A‐CoL/Ag NC//AC ASC has a broad operated potential window within 0–1.6 V, long cycle life (95.2% after cycling 7000 cycles), delivering an energy density of 151 W h kg^?1 (at 790 W kg^?1), and a power density of 7972 W kg^?1 (at 70 W h kg^?1). The well‐synthesized nanocomposite provides a novel way to synthesize prominent electrode materials for supercapacitors.     

基于G-四链体模板的银纳米簇共振能量转移比率检测miRNA

以DNA为模板合成的荧光银纳米簇（DNA-Ag NC）是一类性能优秀的发光探针,已被广泛应用于传感与成像领域.目前大多数定量方法都是基于目标物结合带来的直接的银纳米簇发光强度的变化,因此,分析方法的重现性将不可避免地受实验场地或测定条件变化的影响.本工作中,采用以G-四链体为模板的银纳米簇（GQ-Ag NC）与菁染料Cyanine5（Cy5）为能量供-受体对,发展了基于荧光共振能量转移（FRET）机理的miRNA比率测定方法.其中,Cy5标签具有通用性,简化了实际应用中的实验设计,降低了试剂成本.针对miRNA let-7a的方法,检测动态范围为12~300 nmol/L,检测限为6.9 nmol/L,且可以将let-7a与let-7家族中的其他miRNA区分.HepG2细胞的总RNA提取物加标回收结果表明该方法具有应用于临床样本测试的潜力.本研究工作拓展了DNA-Ag NC的应用,并有助于加深在FRET设计中以DNA-Ag NC为供体进行分析应用的进一步理解.     

Chitosan loaded with silver nanoparticles,CS‐AgNPs,using thymus syriacus,wild mint,and rosemary essential oil extracts as reducing and capping agents

The present study describes the green method for the preparation of chitosan loaded with silver nanoparticles (CS‐AgNPs) in the presence of 3 different extracted essential oils. The essential oils play dual roles as reductant and capping agents. The reducing power and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) assay for the 3 essential oils—Thymus syriacus (T), wild mint (M), and rosemary (R)—have been reported. The preparation of CS‐AgNPs was performed by 2 steps. The 3 previously extracted essential oils have been used as reducing and capping agent in the first step, while in the second step, silver nanoparticles were integrated in chitosan. The integration of AgNPs in the structure of chitosan was confirmed by ultraviolet‐visible, Fourier transform infrared spectroscopy, scanning electron microscopy techniques, and energy dispersive X‐ray. Surface plasmon resonance confirmed the formation of CS‐AgNPs with maximum absorbance at λ_max between 405 ‐ 410 and 410 ‐ 430 nm for colloidal and films of CS‐AgNPs, respectively. The intensity of bands at 3408 cm^?1 in the fourier transform infrared spectroscopy measurements was decreased substantially and shifted slightly to lower frequency (?υ = 43 cm^?1). Scanning electron microscopy shows a spherical morphology of AgNPs with size of 62 nm for both colloidal and film samples, and energy dispersive X‐ray analysis shows peaks confirming AgNPs formation.     

近红外光谱分析技术识别奶粉中淀粉掺假的研究

将蒙牛、伊利、完达山三个品牌的奶粉样品掺入不同量的淀粉构成32份实验样品。在跨度近两个月时间内,用JDSU微型近红外光谱仪,分五天重复5次采集这些样品的中波近红外漫反射光谱。采用仿生模式识别（BPR）算法对样品进行掺假识别定性分析,并研究了分析的可靠性与模型的稳健性。以90%作为评价分析结果（样品掺杂的正确识别率 CAR与正确拒识率 CRR）的阈值：将测试结果高于此阈值的所有样品中掺入淀粉的最低含量分别称为样品掺杂的正确识别限与正确拒识限。结果显示：三个品牌奶粉样品分别各自建模时,若用同一天测定的部分光谱数据建立模型,预测该天剩余光谱,样品掺杂的正确识别限与正确拒识限都可以达到0.1%。对于三种品牌奶粉合并后的纯奶粉及其淀粉掺杂样品混合建模时,若用同一天测定的光谱建模与测试,样品掺杂的正确识别限也可以达到0.1%,正确拒识限则为1%;若用不同时间采集的光谱进行交叉测试,正确识别限与正确拒识限都只有5%;若用四天的光谱数据联合建模,测试第五天的数据,正确识别限可以稳定达到1%,正确拒识限可以达到5%。应用两种算法对奶粉中淀粉含量进行定量分析比较,进一步验证了有关定性分析对样品掺杂正确识别限和正确拒识限的可靠性。     

基于表面增强拉曼光谱的苹果毒死蜱残留无损检测方法

对表面增强拉曼光谱(Surface Enhanced Raman Spectroscopy, SERS)技术在苹果毒死蜱残留量无损快速准确检测中的应用进行了研究. 以银溶胶作为表面增强剂, 采用实验室搭建的拉曼光谱系统, 无损地采集苹果样品拉曼光谱. 分别采用二阶导数法(Secondary Derivative Transformation, SD)和极小极大值自适应缩放法(Min-max Signal Adaptive Zooming, MSAZ)扣除所得拉曼光谱的荧光背景以消除样品和环境的干扰, 从而提高检测的准确度. 对获取光谱后的苹果样品采用标准理化方法检测其毒死蜱含量, 在最优条件下, 建立拉曼光谱与15.52～0.064 mg/kg范围内毒死蜱含量的线性关系, 结果表明毒死蜱的两个主要特征峰强度和其浓度呈良好的线性关系, 预测集的相关系数为0.969, 预测均方根误差为1.24 mg/kg. 本研究所开发的方法为果蔬安全品质的无损快速检测提供了一种新思路.     

高效液相色谱-四极杆/静电场轨道阱高分辨质谱测定奶粉中的低聚果糖

建立了高效液相色谱-四极杆/静电场轨道阱高分辨质谱法测定奶粉中低聚果糖的方法。奶粉样品用水溶解,加乙酸锌沉淀蛋白,经离心、0.22 μm粒径的微孔膜过滤后,采用Carbohydrate色谱柱(100 mm×2.1 mm, 2.6 μm)进行分离,以乙腈与0.1%乙酸水溶液为流动相进行梯度洗脱。质谱采用正离子Target-MS/MS模式,在分离窗口为m/z 4.0和碰撞能为30 eV的条件下,提取响应值较高且在待测样品中无干扰的目标子离子的精确质量数,此方法能够很好地排除样品中的基质干扰。在所建立的色谱-质谱条件下,蔗果三糖(GF₂)、蔗果四糖(GF₃)和蔗果五糖(GF₄)能够得到较好的分离,高分辨质谱提取的质量准确度小于5×10^-6(5 ppm),整个分析时间只需10 min。该方法对GF₂和GF₃的检出限可达100 μg/kg,对GF₄的检出限可达55 μg/kg。待测物质采用外标法定量,线性关系良好,相关系数均大于0.998。通过加标验证,在5、10和20 mg/kg 3个加标水平下,奶粉中GF₂、GF₃和GF₄的平均回收率在75.8%~107.3%范围内,相对标准偏差(RSD)在1.6%~8.3%范围内。该方法样品前处理过程简单,只需沉淀蛋白质,通过二级子离子的选择即可排除基质干扰,分析时间短,测定结果准确、可靠,适用于任何奶粉的高通量测定。     

酸水解-气相色谱法测定奶粉中的二十二碳六烯酸

建立了盐酸水解,索氏提取总脂肪酸,氢氧化钾甲醇溶液甲酯化,硫酸氢钠处理,气相色谱测定奶粉中二十二碳六烯酸(DHA)含量的方法。采用三因素三水平正交试验对氢氧化钾甲醇溶液甲酯化条件进行了优化,得到最优反应条件为:1 mol/L氢氧化钾在25 ℃反应5 min。甲酯化衍生液经硫酸氢钠处理,在SP-2560气相色谱柱(100 m×0.25 mm×0.20 μ m)上进行55 min程序升温测定DHA含量。DHA在5.0~300 mg/L范围内呈良好线性,相关系数为0.9999。DHA质量浓度为10、50、100 mg/L时目标峰峰面积的相对标准偏差(RSD)分别为3.4%、1.2%和1.1%。方法检出限为2 mg/kg,回收率为90.4%~93.5%。该法用于实际样品的检测,结果令人满意。     

化学增感对苯并三氮唑银的PTG材料感光性能的影响

本文主要研究了传统卤化银照相材料中的增感技术,如硫增感、金增感、硫加金协同增感,对新型的以苯并三氮唑银为银源、水性聚乙烯醇为粘合剂的光敏热成像材料增感是否有效的问题.结果显示,传统化学增感对异位法制备的溴化银为光敏剂的光敏热成像材料具有很好的增感效果,硫加金协同增感的效果要好于单独的硫增感和金增感;传统化学增感对原位法制备的溴化银为光敏剂的光敏热成像材料没有增感效果,反而减感,硫加金减感效果最严重.     

Effect of Graphene Characteristics on Morphology and Performance of Composite Noble Metal-Reduced Graphene Oxide SERS Substrate

Graphene/noble metal substrates for surface enhanced RAMAN scattering (SERS) possess synergistically improved performance, due to the strong chemical enhancement mechanism accounted to graphene and the electromagnetic mechanism raised from the metal nanoparticles. However, only the effect of noble metal nanoparticles characteristics on the SERS performance was studied so far. In attempts to bring a light to the effect of quality of graphene, in this work, two different graphene oxides were selected, slightly oxidized GOS (20%) with low aspect ratio (1000) and highly oxidized (50%) GOG with high aspect ratio (14,000). GO and precursors for noble metal nanoparticles (NP) simultaneous were reduced, resulting in rGO decorated with AgNPs and AuNPs. The graphene characteristics affected the size, shape, and packing of nanoparticles. The oxygen functionalities actuated as nucleation sites for AgNPs, thus GOG was decorated with higher number and smaller size AgNPs than GOS. Oppositely, AuNPs preferred bare graphene surface, thus GOS was covered with smaller size, densely packed nanoparticles, resulting in the best SERS performance. Fluorescein in concentration of 10⁻⁷ M was detected with enhancement factor of 82 × 10⁴. This work demonstrates that selection of graphene is additional tool toward powerful SERS substrates.     

Raman scattering of L‐tryptophan enhanced by surface plasmon of silver nanoparticles: vibrational assignment and structural determination

Vibrational bands of L ‐tryptophan which was adsorbed on Ag nanoparticles (∼10 nm in diameter) have been investigated in the spectral range of 200–1700 cm⁻¹ using surface‐enhanced Raman scattering (SERS) spectroscopy. Compared with the normal Raman scattering (NRS) of L ‐tryptophan in either 0.5 M aqueous solution (NRS‐AS) or solid powder (NRS‐SP), the intensified signals by SERS have made the SERS investigation at a lower molecular concentration (5 × 10⁻⁴ M ) possible. Ab initio calculations at the B3LYP/6‐311G level have been carried out to predict the optimal structure and vibrational wavenumbers for the zwitterionic form of L ‐tryptophan. Facilitated with the theoretical prediction, the observed vibrational modes of L ‐tryptophan in the NRS‐AS, NRS‐SP, and SERS spectra have been analyzed. In the spectroscopic observations, there are no significant changes for the vibrational bands of the indole ring in either NRS‐AS, NRS‐SP, or SERS. In contrast, spectral intensities involving the vibrations of carboxylate and amino groups are weak in NRS‐AS and NRS‐SP, but strong in SERS. The intensity enhancement in the SERS spectrum can reach 10³–10⁴‐fold magnification. On the basis of spectroscopic analysis, the carboxylate and amino groups of L ‐tryptophan are determined to be the preferential terminal groups to attach onto the surfaces of Ag nanoparticles in the SERS measurement. Copyright © 2008 John Wiley & Sons, Ltd.