Water-soluble, cyclodextrin-functionalized semiconductor nanocrystals: Preparation and pH-dependent aggregation and emission properties

Using peramino-functionalized β-cyclodextrin molecules for phase.transfer of hydrophobic CdSe multishell nanocrystals into water, we obtained hydrophilic nanoparticles with high quantum yield (up to 50%). At pH > 9, the aqueous solution of these nanocrystals remained stable for several months. The nanoparticles showed a strong influence of the pH of the aqueous solution on the emission of the nanocrystals: the quantum yield varied reversible from ∼10% at pH=6 to ∼50% at pH=14, an effect which according to particle size characterization by dynamic light-scattering and asymmetric flow field-flow fractionation has mainly been attributed to reversible partial aggregation of the hydrophilic nanocrystals at lower pH-values. Additionally, prolonged irradiation in the presence of oxygen led to a strong enhancement of the photoluminescence intensity of the nanocrystals.     

Photophysics of 1-ethynylpyrene-modified RNA base adenine

The photophysical behaviour of a pyrene-modified adenine base is examined. Time-dependent absorption and fluorescence spectroscopy is used to shed light on the fluorescence behavior and the charge transfer between the fluorophore and the nucleobase. The results from TCSPC, fluorescence upconversion and pump-probe absorption spectroscopy are reported, compared and analyzed. This study is a prerequisite for the detailed characterization of RNA dynamics in real time and on a molecular time scale.     

Nanocrystalline BaTiO3, doped with Eu and Cr: Fluorescence spectroscopy and spontaneous ordering effects

The results of optical studies of Cr³⁺ and Eu³⁺ ions doped nanocrystalline ferroelectric BaTiO₃ produced by the sol-gel process (particle size 20-40 nm) are reported. The Cr³⁺ impurity ions ²E-⁴A₂ (R-lines) fluorescence spectra in BaTiO₃ revealed significant differences from that reported in literature for the bulk material. At least three types of Cr³⁺ centers were found in the spectra. The temperature dependence of optical second harmonic generation in nanocrystalline BaTiO₃: Eu³⁺ shows a strong hysteresis in C_4v-O_h ferroelectric phase transition region, which was explained by the ordering effects in the system of electric dipole moments of dipole nanocrystals. The temperature dependencies of radiative lifetime of Eu³⁺⁵D₀ excited level reveal some hysteresis too. The possibility of influence of the ordering in the system of BaTiO₃:Eu³⁺ nanocrystals on the effective index of refraction of the medium and thus on the Eu³⁺⁵D₀ radiative lifetime, due to the local field effects is discussed.     

Spectroscopy and dynamics of the excited singlet and triplet states of 2,3-, 2,4- and 2,5-difluorobenzaldehyde vapors

Emission and absorption spectra have been measured for 2,3-, 2,4- and 2,5-difluorobenzaldehyde vapors at different temperatures. The observed emission consists of the T₁(n, π*) phosphorescence accompanied by the weak S₁(n, π*) delayed fluorescence for all the molecules. The vibrational analyses of the emission spectra based on the results of the DFT calculations indicate that the observed emission originates from only the stable (anti) conformer. It is inferred from the temperature dependence of the phosphorescence intensity that the T₁(n, π*) → T₂(π, π*) internal conversion and/or the reverse T₁(n, π*) → S₁(n, π*) intersystem crossing contribute to the decrease in the phosphorescence intensity upon increasing temperature. The obtained spectroscopic data include the Raman spectrum of 2,3-difluorobenzaldehyde.     

Interaction of the docetaxel with human serum albumin using optical spectroscopy methods

Docetaxel is a semi-synthetic product derived from the needles of the European yew. It is an antineoplastic agent belonging to the taxoid family. The interaction between docetaxel and human serum albumin (HSA) has been investigated systematically by the fluorescence quenching technique, synchronous fluorescence spectroscopy, ultraviolet (UV)-vis absorption spectroscopy, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) under physiological conditions. Our fluorescence data showed that HSA had only one docetaxel binding site and the binding process was a static quenching procedure. According to the Van’t Hoff equation, the thermodynamic parameters standard enthalpy (ΔH⁰) and standard entropy (ΔS⁰) were calculated to be −41.07 KJ mol⁻¹ and −49.72 J mol⁻¹ K⁻¹. These results suggested that hydrogen bond was the predominant intermolecular force stabling the docetaxel-HSA complex. The data from the CD, FT-IR and UV-vis spectroscopy supported the change in the secondary structure of protein caused by the interaction of docetaxel with HSA.     

荧光检测-高效液相色谱法测定水果、蔬菜中抗蚜威残留量

建立了水果、蔬菜中抗蚜威残留的荧光检测-高效液相色谱法。样品以乙腈提取,固相萃取氨基小柱(LC-NH2)净化,Waterscarbamateanalysis(3.9mm×150mm,4μm),V(甲醇)∶V(水)∶V(乙腈)=16∶68∶16为流动相,柱温30℃,流速为1.5mL/min进行分离,用荧光检测器进行检测,激发波长和发射波长分别为317nm,392nm。回收率在98.5%~105.4%,相对标准偏差为3.0%~4.6%,检出限为0.01mg/kg。     

荧光光谱法研究抗癌药物与DNA的相互作用

荧光探针技术可以用来测定药物-核酸相互作用的强度。通过药物与核酸相互作用,使DNA与探针键合的程度减小,反映在探针荧光光谱的改变,从而可以了解药物和核酸的作用机理。相互作用常数D为DNA 探针中加入药物后探针的荧光强度相对于DNA 探针荧光强度减去纯探针荧光强度的下降百分数。文章利用盐酸小檗碱(Berberine)作为探针,测定几种抗癌药物加入DNA与荧光探针(盐酸小檗碱)混合溶液的荧光谱,探讨它们与DNA的相互作用。并根据相同浓度的不同药物与核酸相互作用的常数D确定作用强弱。     

过硒二苯2,2'-二甲酸与牛血清白蛋白结合反应热力学特征研究

用荧光光谱和紫外．可见吸收光谱法研究了在不同温度下,新合成的过硒二苯2,2’-二甲酸（PSD）对牛血清白蛋白（BSA）作用的荧光猝灭光谱行为。分别用Stem-Volmer方程和Lineweaver-Burk双倒数方程处理试验数据,证实在试验浓度和温度范围内,其荧光猝灭作用更符合静态猝灭作用特征,PSD与BSA可反应并结合形成具有一定结构的复合物,得到了反应的结合常量、结合热力学性质和结合位点等参数;同时探讨了静态猝灭作用的机理和结合力的性质,为了解PSD与BSA的结合方式、在人体内的传输机理和药理作用提供科学依据。     

毛细管电泳-荧光/非接触电导组合型检测器的研制

报道了一种毛细管电泳-荧光／非接触电导组合型检测器。该检测器共用非接触电导检测池,实现了双检测器响应同步。优化了非接触电导检测系统中激发电压信号及其频率;荧光检测是用发光二极管作为激发光源,用光纤收集并传输荧光信号至光电倍增管。用无机金属离子和异硫氰酸荧光素评价该体系,结果表明,该检测器达到了任一单类型检测器性能指标。     

Tb1-xLnxA3(A=对氨基苯甲酸,x=0-0.9)固体配合物的光谱分析和荧光增强

合成了一系列组成为 Tb1-x Lnx A3 (L n=Gd、Y、La,A=对氨基苯甲酸 ,x=0— 0 .9)的固体配合物。利用红外光谱和荧光光谱研究了配合物的结构和荧光性质 ,结果表明 ,掺杂配合物的结构与未掺杂的对氨基苯甲酸铽相似。荧光光谱的结果显示 ,Gd3 对 Tb3 的发光有明显的增敏作用 ,探讨了荧光增敏机理。