Photophysical and photochemical processes of riboflavin (vitamin B2) by means of the transient absorption spectra in aqueous solution

Using time-resolved techniques of 337 and 248 nm laser flash photolysis, the photo physical and photochemical processes of riboflavin (RF, vitamin B₂) were studied in detail in aqueous solution. The excited triplet state of riboflavin (³RF^*) was produced with 337 nm laser, while under 248 nm irradiation, both³RF^* and hydrated electron (e_aq) formed from photoionization could be detected. Photobiological implications have been inferred on the basis of reactivity of³RF^* including energy transfer, electron transfer and hydrogen abstraction. The RF^·+ was generated by oxidation of SO₄ ^·-radical with the aim of confirming the results of photolysis.     

The Effect of Cyclodextrins on the Photochemical Stability of 7-Amino-4-methylcoumarin in Aqueous Solution

The effect of -, - and -cyclodextrin onthe photochemical stability of 7-amino-4-methylcoumarin (C120)was studied. Using spectroscopic techniques (UV/Vis absorption spectroscopy, fluorescence, fluorescence anisotropy and circular dichroism) combined with HPLC/MS and MS analysis it was demonstrated that addition of -cyclodextrin to the aqueoussolution of C120 markedly inhibits the photodegradation of that dye. This results from theformation of an inclusion complex between C120 and -cyclodextrin.     

Elemental Analyses Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) of Geological Samples Fused with Li2B4O7 and Calibrated Without Matrix-Matched Standards

 Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used as a complementary technique to X-ray fluorescence (XRF), for multi-element analysis of geological samples fused with lithium-tetraborate Li₂B₄O₇). Different calibration strategies using external non-matrix matched reference materials were investigated. Various internal standards were tested, including the use of Li from the flux, and the use of the naturally occurring internal standards, Si or Ca. The use of a naturally occurring standard is not as efficient as this required a prior analysis of the samples using XRF. The obtained values for the analysis of geological reference materials were compared with consensus literature values, and satisfactory agreement was found. Laser pits, which were formed, had a diameter of 80 μm and 3–5 replicates on each fused disc were measured. The reproducibility of the method was better than 10% for concentrations above 1 μg/g and better than 15% for lower concentrations. The use of Li as the internal standard offers the possibility of multi-element determinations in geological samples, which have an unknown composition when the laser ablation analysis is carried out. However, using the calculated stoichiometric composition of the lithium-tetraborate for the calculation of the Li concentration leads to a constant deviation from the recommended values. Therefore, it was necessary to determine the Li concentration within each sample batch using at least one lithium tetraborate fused geological reference material. This resulting Li concentration in the beads was then used for all subsequent samples in a run. Limits of detection, reproducibility, deviation from reference values indicate the potential of LA-ICP-MS for such bulk analysis without matrix matched calibration standards.     

高效液相色谱法分析生物样品中的敌鼠

 研究用阴离子交换、氰基及硅胶柱固相萃取技术分离提取血、尿、肝及肾中的敌鼠。以香豆素作内标 ,用高效液相色谱 二极管阵列检测器方法进行分离鉴定。色谱条件 :分析柱为HypersilBDSC18(5 μm ,15 0mm× 4 6mmi.d .) ,保护柱为PhenomenexODS(4mm× 3 0mmi.d .) ;流动相 :A为 0 5 %离子对A水溶液 ,B为 0 5 %离子对A甲醇溶液 ,以梯度淋洗程序分离 ;检测波长为 2 86nm。当敌鼠的质量浓度在 1mg/L～ 10 0mg/L范围时 ,其浓度同其峰面积与内标物的峰面积之比有良好的线性关系 (r=0 9999) ,最小检出限量为 5ng(按S/N =3计 )。     

微柱分离中的激光诱导荧光检测

 激光诱导荧光检测 (LIFD)以其高的灵敏度和选择性而被广泛应用于微柱分离技术中。以检测池为轴线 ,概述了激光诱导荧光检测系统新进展及其应用。引用了 5 2篇文献     

激光等离子体诱导聚甲基硅氧烷的结构重组

将脉冲激光束在惰性气氛中溅射石墨产生的等离子体,与一维链状聚甲基硅氧烷的蒸气束流反应,在产物中通过真空升华和重结晶分离出了两种单晶,经X射线衍射测定为具有(CH3SiO1.5)n(n=8,10)组成的硅氧烷,它们均具有多面体的三维笼状构型。通过色-质联用还检测到其它硅氧烷化合物,其中某些产物已表征为二维多环的构型,反应结果表明,经由激光等离子体的碰撞和能量传递,反应物的链状结构发生解离和进一步反应,经结构重组形成了多种不同组成和构型的产物。     

Direct Toner Printing: A Versatile Technology for Easy Fabrication of Flexible Miniaturized Electrodes

We reported here three simple, low cost and easy to accomplish strategies for the fabrication of microelectrodes and other conductive patterns using ordinary office laser‐printers. In this work, toner patterns were directly printed onto the flexible substrate, acting as a mask to create the intended conductive design. To highlight the versatility of such technology, toner‐printed patterns were employed in two diverse ways: one in which the patterned toner had the exact design of the electrode and other employing a reverse toner‐printed pattern. The first one was used for the adaptation of the well‐known printed circuit board (PCB) fabrication technique, but using direct toner printing (DTP) in an already conductive flexible substrate. The second was employed for the two remaining strategies: one based on the deposition of conductive film, followed by lift‐off process; and another based on drop‐casting of a conductive ink into the formed toner cavities, followed by thermal cure. As proof‐of‐concept, all three DTP strategies were used for the fabrication of miniaturized gold electrodes in polyimide substrate, and electrochemical performance of each obtained electrode was evaluated by cyclic voltammetry. Insights about DTP technology, alignment issues, advantages, limitations and resolution of each presented approach were provided. Finally, direct toner printing showed to be a simple, affordable and quite promising technology for the fabrication of low cost point‐of‐care electrochemical devices using flexible platforms.     

Improved detection sensitivity of elements in solids via laser postionization in laser desorption time‐of‐flight mass spectrometry

A newly constructed laser desorption (532 nm, 5 ns) and laser postionization (266 nm, 5 ns) time‐of‐flight mass spectrometer (LD‐LPI‐TOFMS) has been applied for improving the detection sensitivity of elements in solid samples. This method affords to acquire the information of the elemental impurities in solid standards as well as limit of detection (LOD) down to 10⁻⁸ g/g for some elements. Neutral atoms of solids are generated by low‐irradiance laser desorption (< 10⁸ W/cm²), followed by high‐irradiance laser postionization (~ 10⁹ W/cm²) of the desorbed atoms, facilitating to decouple the desorption and ionization processes in spatial and temporal domain. This non‐interacting feature overcomes the discrimination between deteriorating spectral resolution at high irradiance (10⁹–10¹¹ W/cm²) and limited detectable elemental species and high LOD at low or medium irradiance (below 10⁹ W/cm²). The utilization of originally “wasted” neutral atoms by laser postionization will help improve atom utilization and instrumental sensitivity. In this work, getting the utmost out of the consumed neutral atoms instead of an increment in sampling amounts is given attention with high priority for achieving high sensitivity and low LOD, which is especially useful on the occasions where very low sample consumption is desired.     

激光刻蚀模板中电沉积特殊结构CIGS薄膜

本文利用激光刻蚀模板,在水溶液中电沉积制备金属铜薄膜,讨论了温度、电流、硫酸铜浓度对薄膜形貌的影响. 采用SEM对制备的铜薄膜进行表征,结果表明在沉积温度为30 ℃,沉积电流为4 A·dm^-2(表观工作电流密度),硫酸铜浓度在20 ~ 50 g·L^-1的水溶液中电沉积可以得到中空馒头状和开口碗状结构的铜薄膜. 利用激光刻蚀模板,在离子液体1-丁基-3-甲基咪唑三氟甲磺酸盐([BMI][TfO]) - 30 Vol%丙醇混合电解质中电沉积CIGS薄膜,研究了沉积电势、沉积时间对薄膜形貌的影响. SEM观察发现,在沉积电势为-1.8 V,沉积时间为1.5 h条件下电沉积可以得到近似柱状的簇状花束样的CIGS薄膜, 电沉积铜后再进一步电沉积CIGS,得到了均匀有序的鼓包柱状结构的Cu/CIGS复合薄膜. 用恒电势方波法对制备的薄膜真实表面积进行测试,计算结果表明,与无模板电沉积制备的CIGS薄膜相比,激光刻蚀模板法制备的Cu/CIGS复合薄膜的表面积提高了约8倍.     

Synthesis and electroluminescent performance of thermally activated delayed fluorescence‐conjugated polymers with simple formylphenyl as pendant acceptor

Formylphenyl has been demonstrated to act as an acceptor to construct thermally activated delayed fluorescence (TADF) emitter, and therefore a series of the TADF‐conjugated polymers with formylphenyl as pendant acceptor and carbazole/acridine as backbone donor are designed and synthesized. All polymers involve the twisted donor/acceptor structural moieties with the sufficiently spatial separation between the highest occupied molecular orbital and the lowest unoccupied molecular orbital as well as a small singlet/triplet splitting, and exhibit the legible TADF features confirmed by theoretical calculation and their transient decay spectra. The solution‐processed organic light‐emitting diodes using neat film of the polymers as emissive layer achieve excellent performance with the maximum external quantum efficiency (EQE) of up to 10.6%, the maximum current efficiency of up to 35.3 cd A⁻¹ and the low turn‐on voltage of 2.7 V. Moreover, the EQE still remains 10.3% at the luminance of 1000 cd m⁻² with the low driving voltage of 4.4 V and extremely small efficiency roll‐off. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1989–1996