Cetylpyridinium Chloride Activated Trinitrotoluene Explosive Lights Up Robust and Ultrahigh Surface‐Enhanced Resonance Raman Scattering in a Silver Sol

Surface‐enhanced resonance Raman scattering (SERRS) is not realized for most molecules of interest. Here, we developed a new SERRS platform for the fast and sensitive detection of 2,4,6‐trinitrotoluene (TNT), a molecule with low Raman cross section. A cationic surfactant, cetylpyridinium chloride (CPC) was modified on the surface of silver sols (CP‐capped Ag). CPC not only acts as the surface‐seeking species to trap sulfite‐sulfonated TNT, but also undergoes complexation with it, resulting in the presence of two charge‐transfer bands at 467 and 530 nm, respectively. This chromophore absorbs the visible light that matches with the incident laser and plasmon resonance of Ag sols by the use of a 532.06 nm laser, and offered large resonance Raman enhancement. This SERRS platform evidenced a fast and accurate detection of TNT with a detection limit of 5×10^?11 M under a low laser power (200 μW) and a short integration time (3 s). The CP‐capped Ag also provides remarkable sensitivity and reliable repeatability. This study provides a facile and reliable method for TNT detection and a viable idea for the SERS detection of various non‐resonant molecules.     

多孔氧化铝模板催化制备定向碳纳米管阵列

在不加过渡金属做催化剂的前提下,利用化学气相沉积法在二次阳极氧化法制得的多孔氧化铝模板中制备沉积了定取向碳纳米管阵列。考察了不同沉积温度以及退火处理对沉积结果的影响。温度达到600℃以上时,能得到开口的、定取向的多壁碳纳米管阵列；当沉积温度降至550℃左右时,沉积结果中存在碳纳米管、纳米纤维以及类似于弯曲的竹节状的结构；温度继续降低至500℃以下时,不能得到碳纳米管或碳纳米纤维；从实验结果中可以得出,在氧化铝模板中沉积碳纳米管过程中氧化铝起到了催化乙炔裂解以及催化沉积的碳石墨化成碳纳米管两种作用。另外,退火处理虽然能够提高沉积的碳纳米管的石墨化程度,但是也可能会引入新的缺陷。     

Metastable state nanoparticle-enhanced Raman spectroscopy for highly sensitive detection

Metastable state silver nanoparticle surface-enhanced Raman scattering has been experimentally and theoretically demonstrated; the signal is two to three orders of magnitude higher than that for the traditional method. Ultrasensitive surface-enhanced Raman scattering signals of illicit drug cocaine and organophosphate pesticide methyl-parathion were observed.     

基于两维扫描高场不对称离子迁移谱技术检测挥发酚

要采用自制高场不对称波形离子迁移谱(FAIMS)仪对苯酚、2-甲酚、3-甲酚、4-甲酚以及2,4-二氯酚进行检测,通过结合补偿电压以及射频高压的二维扫描优化了对检测物的分辨.射频高场强度为1.6×104 V/cm时,2-甲酚与4-甲酚有最佳分辨效果,其余物质在高场强度大于1.8×104 V/cm时可以得到最佳分辨.研究...     

Structure and spectroscopic properties of organoclays doped by multiwall carbon nanotubes

A method to modify a montmorillonite (MMT) clay mineral (CM) surface by surfactant (SA) cations with simultaneous doping by multiwall carbon nanotubes (MWNT) has been proposed. The structure and spectroscopic properties of composites based on MMT from two deposits (Cherkassy and Pyzhevsk, Ukraine) that differ in the inorganic impurity contents and cation-exchange capacities (CEC) have been investigated. Cetyltrimethylammonium bromide (CTAB) was used as the SA. According to x-ray diffraction analysis, CTA⁺ cations intercalated into MMT interplanar spaces expand them significantly whereas MWNTs do not affect the MMT galleries due to the much larger sizes of the former. Studies of the composite materials by IR spectroscopy revealed the mutual influence of the components appearing as the ordering of near-surface layers in the aluminosilicate framework and a change in the modifier methylene chain conformation at the interphase boundary. The majority of CTAB (~90%) is shown to be located inside the MMT galleries, the packing arrangement of which depends on the CEC value and affects the interplanar distances in MMT. The alkyl chains of the CTA⁺ cations on the outer surface of the MMT plates are sorbed by nanotubes, thus providing contact between the organoclay and MWNT surfaces.     

土壤中砷元素的激光诱导击穿光谱测量分析

利用Nd:YAG脉冲激光器作为光源,在实验室自然大气环境下诱导产生国家标准土壤的激光等离子体,选取砷的228.8nm特征谱线作为分析线,测量并分析了砷元素的激光诱导击穿光谱特性。在相同含量和积分时间条件下,调节延迟时间,获取了砷元素的时间演化特性。确定砷元素的最佳延迟时间为1μs,积分时间为2μs。测定不同含量下,砷的特征谱线强度,给出砷元素的定标曲线,并计算得到砷元素的检测限为45mg/kg。     

The forgotten sons: Warehousing systems for brick-and-mortar retail chains

Warehouses are an inevitable component in any supply chain and a vividly investigated object of research. Much attention, however, is absorbed by warehousing systems dedicated to the special needs of online retailers in the business-to-consumer segment. Due to the ever increasing sales volumes of e-commerce this focus seems self-evident, but a much larger fraction of retail sales are still realized by traditional brick-and-mortar stores. The special needs of warehouses servicing these stores are focused in this paper. While e-commerce warehouses face low-volume-high-mix picking orders, because private households tend to order just a few pieces per order from a large assortment, distribution centers of retail chains rather have to process high-volume-low-mix orders. We elaborate the basic requirements within both business segments and identify suited warehousing systems for brick-and-mortar stores (e.g., fully-automated case picking). The setup of each identified warehousing system is described, elementary decision problems are discussed, and the existing literature is surveyed. Furthermore, we identify future research needs.     

原位获取新鲜Ag及其SERS活性研究

以立方的AgCl纳米结构作为前躯体, 利用共聚焦拉曼光谱仪的光源原位辐射获取新鲜Ag, 并同步用于对巯基吡啶(4-Mpy )分子的SERS检测。结果表明: 随着辐射时间的增加, 4-Mpy 分子的SERS信号强度增加并趋于最大值。结合信号强度和AgCl表面形貌及其化学组分的演变, 给出了一种可能的机理解释。     

Hamiltonian Reduction of Quantum Systems Controlled by Pulses

We explores Hamiltonian reduction in pulse-controlled finite-dimensional quantum systems with near-degenerate eigenstates. A quantum system with a non-degenerate ground state and several near-degenerate excited states is controlled by a short pulse, and the objective is to maximize the collective population on all excited states when we treat all of them as one level. Two cases of the systems are shown to be equivalent to effective two-level systems. When the pulse is weak, simple relations between the original systems and the reduced systems are obtained. When the pulse is strong, these relations are still available for pulseswith only one frequency under the first-order approximation.