Effect of a surface charge on the halfwidth and peak position of cluster plasmons in colloidal metal particles

The optical response of colloidal particles depends on a variety of properties of the cluster, e.g., shape, size, size distribution and particle material. Since particles often are charged, also the surface charge may be a parameter which influences their optical properties. In this paper the effect of a surface charge on optical properties of spherical colloidal particles is studied and its magnitude is estimated by extended computations for silver clusters with surface plasmon in aqueous suspension. Two models are presented and discussed. The first model is based on the electrodynamic solution by Bohren and Hunt (Can. J. Phys. 55, 1930 (1977)), where a surface conductivity _S for a free surface charge yield an additional contribution _S to the dielectric constant of the particle material. In the second model, the surface charge contributes to the number density of free electrons in the cluster. Both models lead to a shift of the cluster plasmon peak, while an increase of the plasmon halfwidth could not be derived. The effect is quite small and limited on very small clusters.PACS 61.46+w 73.20.Mf 78.20.Dj     

DNA荧光探针—荧光素-中性红体系的研究

基于DNA对荧光素(FL)-中性红(NR)分子间荧光能量转移的抑制作用，以荧光素-中性红为荧光探针，考察该探针与DNA的结合反应，建立了准确测定DNA的新方法，在pH＝6.5条件下，hsDNA、ctDNA和smDNA的浓度与荧光素-中性红体系的荧光比值变化量Δ(Fd／Fa)成线性关系，响应线性范围分别为0．25-6．25μg／mL、0．10-5．00μg／mL、0．10-4．00μg／mL，0.025μg/mL和0．023μg／mL；分析测定了DNA合成样品，回收率91．3％-101．4％，相对标准偏差小于4．2％．     

锆—钙—茜素S异多核络合物极谱吸附波的研究

报道了锆－钙－茜素Ｓ异多核络合物的形成及该异多核络合物极谱吸附波测定锆的最佳实验条件，用此法测定了矿石样品中的微量锆，并探讨了该极谱法的性质的电极反应机理，在单扫描示波极谱上用单纯形法和斜率比法测得该体系异多核络合物的组成比为：ｎｚｒ（Ⅳ）：ｎｃａ＾２＋；ｎＡＢＳ＝１：１：４．用分光光度法测定亦得到相同的结论。     

Temperature response of a number of plastic dosimeters for radiation processing

Various plastic dosemeters are employed for dosimetry control of radiation processing within gamma and electron irradiation facilities.

The temperature response of a dosimeter is important when the dose to such a dosimeter is accumulated under varying irradiation temperatures. Such measurements would be significant for proper assessment of the dose for better process control, as well as, performance evaluation of dosimetry systems.

In this work we have developed a high current peltier junction temperature controller system for our Gammacell-220. This system has been designed to regulate the operating temperature of the irradiation chamber in the range of 0 to 80 C this system has been applied to measure the temperature response of the red perspex, a local clear PMMA, Gammex, Gammachrome, and Gafchromic dosimeters. The curves of relative performance or variation of the induced optical densities of the above dosemeters versus the irradiation temperature at fixed dose values are obtained.     

Combined AC‐electrokinetic effects: Theoretical considerations on a three‐axial ellipsoidal model

AC fields induce charges at the structural interfaces of particles or biological cells. The interaction of these charges with the field generates frequency‐dependent forces that are the basis for AC‐electrokinetic effects such as dielectrophoresis (DEP), electrorotation (ROT), electro‐orientation, and electro‐deformation. The effects can be used for the manipulation or dielectric single‐particle spectroscopy. The observation of a particular effect depends on the spatial and temporal field distributions, as well as on the shape and the dielectric and viscoelastic properties of the object. Because the effects are not mutually independent, combined frequency spectra are obtained, for example, discontinuous DEP and ROT spectra with ranges separated by the reorientation of nonspherical objects in the linearly and circularly polarized DEP and ROT fields, respectively. As an example, the AC electrokinetic behavior of a three‐axial ellipsoidal single‐shell model with the geometry of chicken‐red blood cells is considered. The geometric and electric problems were separated using the influential‐radius approach. The obtained finite‐element model can be electrically interpreted by an RC model leading to an expression for the Clausius–Mossotti factor, which permits the derivation of force, torque, and orientation spectra, as well as of equations for the critical frequencies and force plateaus in DEP and of the characteristic frequencies and peak heights in ROT. Expressions for the orientation in linearly and circularly polarized fields, as well as for the reorientation frequencies were also derived. The considerations suggested that the simultaneous registration of various AC‐electrokinetic spectra is a step towards the dielectric fingerprinting of single objects.     

Magnetic Mesoporous Silica Nanoparticles Cloaked by Red Blood Cell Membranes: Applications in Cancer Therapy

Targeted drug delivery is an emerging technological strategy that enables nanoparticle systems to be responsive for tumor therapy. Magnetic mesoporous silica nanoparticles (MMSNs) were cloaked with red blood cell membrane (RBC). This integrates long circulation, photosensitizer delivery, and magnetic targeting for cancer therapy. In vivo experiments demonstrate that RBC@MMSNs can avoid immune clearance and achieve magnetic field (MF)‐induced high accumulation in a tumor. When light irradiation is applied, singlet oxygen rapidly generates from hypocrellin B (HB)‐loaded RBC@MMSN and leads to the necrosis of tumor tissue. Such a RBC‐cloaked magnetic nanocarrier effectively integrates immunological adjuvant, photosensitizer delivery, MF‐assisted targeting photodynamic therapy, which provides an innovative strategy for cancer therapy.     

Ultra‐fast liquid chromatography coupled with electrospray ionization time‐of‐flight mass spectrometry for the rapid phenolic profiling of red maple (Acer rubrum) leaves

The red maple (Acer rubrum) species is economically important to North America because of its sap, which is used to produce maple syrup. In addition, various other red maple plant parts, including leaves, were used as a traditional medicine by the Native Americans. Currently, red maple leaves are being used for nutraceutical and cosmetic applications but there are no published analytical methods for comprehensive phytochemical characterization of this material. Herein, a rapid and sensitive method using liquid chromatography with electrospray ionization time‐of‐flight tandem mass spectrometry was developed to characterize the phenolics in a methanol extract of red maple leaves and a proprietary phenolic‐enriched red maple leaves extract (Maplifa™). Time‐of‐flight mass spectrometry and tandem mass spectrometry experiments led to the identification of 106 phenolic compounds in red maples leaves with the vast majority of these compounds also detected in Maplifa™. The compounds included 68 gallotannins, 25 flavonoids, gallic acid, quinic acid, catechin, epicatechin, and nine other gallic acid derivatives among which 11 are potentially new and 75 are being reported from red maple for the first time. The developed method to characterize red maple leaves phenolics is rapid and highly sensitive and could aid in future standardization and quality control of this botanical ingredient.     

导数光谱法络合物稳定常数的测定

本文利用导数光谱法消除体系中共存有关物种干扰,直接测定游离配体浓度。基于此仿照对应溶液法的图解法,我们拟订两个测定络合物稳定常数的新方法。方法简便可靠,试用于La-BPR体系获得了令人满意结果。     

Isophorone-based Fluorescent Dopant for Red Organic Electroluminescence Device

IntroductionOrganiclight emittingdiodes (OLEDs)haveattractedconsiderableattentionsincetheinitialworksbyTangetal.1andFriendetal.2 duetotheirpotentialapplicationsinfull colorflat paneldisplays .3,4 Torealizefull colorap plications ,highperformanceorganicmaterialsemittingthethreeelementalcolorsofred ,greenandbluearerequired .Aftertwodecadesofintensiveresearch ,anumberofgreenandblueemitterswithhighluminousefficiencies ,reason ablecolorpurityandpracticallifetimehavenowbeenreal izedinbothsmallmole…