微波电场对甘油水溶液体系中氢键的影响

通过分子动力学模拟考察微波电场对不同水含量甘油溶液中氢键的影响。研究发现：甘油含量高时,甘油分子在溶液中以较大的团簇结构存在,水分子以较小的团簇结构或游离状态存在,电场作用下,大的甘油分子团簇变成较小的团簇并且变得更加有序;随着电场强度继续增加,甘油分子整体结构变化不大,但是团簇结构边缘甘油分子氢键断裂,变成游离状态。对于水分子而言,其较小的团簇结构在电场作用下被打开,团簇结构消失,水分子在电场方向上整齐排布,且电场强度继续增大,其结构变化不大,同样个别水分子氢键断裂变成游离状态。因此,甘油浓度高时,水分子间氢键数减少,甘油分子氢键数先增大后略微减少;甘油浓度低时,水分子氢键数先增大后略有减少,甘油分子间氢键减少。     

微波电场对甘油水溶液体系中氢键的影响

通过分子动力学模拟考察微波电场对不同水含量甘油溶液中氢键的影响。研究发现:甘油含量高时,甘油分子在溶液中以较大的团簇结构存在,水分子以较小的团簇结构或游离状态存在,电场作用下,大的甘油分子团簇变成较小的团簇并且变得更加有序;随着电场强度继续增加,甘油分子整体结构变化不大,但是团簇结构边缘甘油分子氢键断裂,变成游离状态。对于水分子而言,其较小的团簇结构在电场作用下被打开,团簇结构消失,水分子在电场方向上整齐排布,且电场强度继续增大,其结构变化不大,同样个别水分子氢键断裂变成游离状态。因此,甘油浓度高时,水分子间氢键数减少,甘油分子氢键数先增大后略微减少;甘油浓度低时,水分子氢键数先增大后略有减少,甘油分子间氢键减少。     

添加剂对罗丹明B和吖啶黄在SDS溶液中能量转移的影响

罗丹明B(RB)和吖啶黄(AY)在十二烷基硫酸钠(SDS)水溶液中浓度小于临界胶团浓度时,就能发生有效的能量转移,能够反映出SDS形成预胶团的聚集状况。非离子表面活性剂Tween 60,使两种染料分子之间的能量转移受到抑制,分析表明,加入Tween 60后聚集体变小,由于Tween 60的极性头基较大,所以其预胶团结构较紧密,不利于能量转移的发生。在溶液中加入无机盐NaCl和Na2SO4后,虽然聚集体变小,但体系中染料分子仍可以发生有效的能量转移,表明体系中预胶团内部结构较疏松,而且盐的浓度越高,能量转移效率越低,加入无机盐种类不同,能量转移效率也不同,说明无机盐的种类对聚集体的形态有一定影响。     

抑制剂溶剂及滴加体积对酪氨酸酶荧光淬灭的影响

本文研究了溶解抑制剂的溶剂种类与滴加体积对酪氨酸酶荧光淬灭的影响。发现滴加抑制剂会降低体系中酪氨酸酶的浓度,有些溶剂本身也会直接导致酶荧光的淬灭。当每次滴加1μL,滴加20次对酪氨酸酶的荧光没有影响;随着溶剂含量的增加,丙酮及乙酸对酪氨酸酶荧光有明显的淬灭作用,甲醇、石油醚、乙酸乙酯则没有明显的影响。因此,在研究抑制剂与酪氨酸酶作用机制时可用甲醇、石油醚、乙酸乙酯溶解水溶性较差的抑制剂。     

SEBS分子链在不同溶剂中的荧光特性

利用荧光光谱法对SEBS分子链在不同溶剂中的荧光特性进行了分析。研究表明,室温下,SEBS在四氢呋喃和环己烷中的荧光发射波长为380 nm,且为本征荧光;而在甲苯溶液中的发射波长为375 nm,相对于本征荧光蓝移动了5 nm。在共振散色光谱中,3种体系的共振光强度都是随着溶液浓度的增大呈线性增加,但甲苯溶液体系共振散色光强度的变化较缓慢。造成这些现象的原因在于四氢呋喃和环己烷分子中没有苯环结构,不具备荧光发射的条件,因而SEBS在这两种溶剂中具有本征荧光效应;而甲苯和SEBS都具有苯环结构,相邻的苯环间通过π电子的相互重叠形成T型结构的二聚体,导致了荧光强度的减弱和共振散色光强度变化较缓慢。     

以共价键相连的卟啉-酞菁化合物分子内能量传递及光诱导电子转移

合成了叶啉与酞菁以共价键连接起来的双发色团分子。测定了它们的吸收光谱,荧光光谱,荧光寿命等。计算了分子内能量传递过程的效率(φ_(EnT))及速率常数(κ_(EnT))。结果表明:在稀溶液中,卟啉与酞菁等克分子混合时,观察不到分子间能量传递过程现象的发生;而双发色团分子的分子内能量传递过程则明显发生了,其效率(φ_(EnT)=13～70％)与速率常数(κ_(EnT)=1.2×10~7～2.0×10~8s~(-1))取决于分子的结构类型。电子转移与能量传递过程与介质性质有关。在极性溶剂中有利于电子转移过程的进行,而不利于能量传递过程;在非极性溶剂中,则有利于能量传递过程的进行,而不利于电子转移。 选择性激发酞菁发色团,观测到了只有电子转移发生的过程,其电子转移效率达到38％。     

(EOXPOYEOX)型嵌段共聚物反胶团形成的影响因素

通过(EOXPOYEOX)型嵌段共聚物有机溶液的水增溶实验研究,探讨了溶剂、聚合物结构、离子强度和温度对增溶水量及临界胶团浓度(CMC)的影响.研究结果表明,正辛醇的加入不仅提高了嵌段共聚物/对二甲苯体系的最大增溶水量(Wo,max),而且也增大了体系的CMC值.lg(1/cmc)随聚合物分子单边EO数X增大而线性递增,表明亲水基EO的内聚能变在胶团化过程中起着重要作用.实验研究范围内,溶液离子强度小于1时,对反胶团的增溶作用有利,一定程度上增大了胶束粒径.反胶团临界浓度的自然对数lnXCMC与温度T成线性关系.胶团化过程是一个自发的放热过程, 并且是一个混乱度降低的熵减过程.     

聚酰胺-胺树形分子荧光性能研究及其在指纹识别领域应用初探

研究了不同温度、浓度、pH值条件下,不同代数、不同端基类型(酯端基和胺端基)的PAMAM(聚酰胺-胺)树形分子的强荧光发射性能.PAMAM树形分子发射强荧光是沿树形结构方向的酰胺基团中的n→π*跃迁和其密实的球状结构共同作用的结果.树形分子的荧光强度在低pH值或者低温条件下大幅度提高,并且在稀溶液中与浓度成线性关系,在高浓度或者高代数条件下逐渐偏离线性关系.本文还对上述规律的内在机理进行了研究:第一,低pH值条件下,PAMAM树形分子内的叔胺基被氢离子质子化,酰胺荧光发射中心和叔胺基团之间的光诱导电子转移作用被抑制,甚至中断,因此荧光强度急剧升高;第二,随着温度升高,PAMAM树形分子的去活作用增强,荧光强度降低;第三,浓度超过临界点浓度后,由于浓度消光作用,PAMAM树形分子的荧光强度不再随浓度增加而线性增强.最后,将PAMAM树形分子水溶液用于锡纸上油印潜指纹的识别,经处理后的指纹在365 nm紫外光的激发下发射出蓝色荧光,潜指纹被成功地清晰识别.     

疏水作用对光化学和光物理过程的影响 Ⅶ.芘基烷基酮的荧光光谱及其在不良溶剂中的簇集

溶剂的极性对芘基烷基酮的单体荧光和激基缔合物荧光有很大影响,在非极性溶剂中单体荧光很弱,随着溶剂极性增大,单体荧光增强,单体荧光和激基缔合物荧光明显红移。利用芘基烷基酮荧光的这些性质研究了长链分子在二甲基亚砜-水(DMSO-H_2O)中的簇集现象。在浓度非常低的情况下,长链芘基烷基酮发射激基缔合物荧光,单体荧光也明显蓝移,表明芘基烷基酮形成了簇集体。长链饱和烷烃和芘基烷基酮发生共簇集,簇集体内的极性比环己烷的极性稍大。     

碳酸镁结晶过程离子团簇与扩散成核机制

理解离子的团簇演化成核机制可以更好地进行结晶过程的调控。基于分子动力学模拟研究了结晶温区、溶质离子浓度等对溶液结晶成核与生长过程的影响,并探讨了溶质离子的团簇演化规律。结果表明,溶质离子的扩散速率与物质结构和分子间作用力有关,并且与成核或晶界生长过程的团簇演化相互影响。在此研究范围内,溶质离子浓度一定（1.71 mol/L）时,388 K体系的成核与生长能力最强,是晶界引导无水碳酸镁生长、干扰镁离子和水分子结合的最佳温度,吸附在晶界的溶质离子分数为28.33%;一定温度下（298 K）,溶质离子浓度为3.99 mol/L时最有利于晶体生长,吸附在晶界的溶质离子分数为32.14%,且该浓度起到了最佳的脱水效果,有利于形成无水碳酸镁。这为获得结晶良好、形貌均匀的无水碳酸镁等工艺技术提供了理论依据和指导。     

One-pot synthesis of fluorescent mesoporous materials for detection of the presence of Be<Superscript>2+</Superscript> ion

A fluorescent mesoporous silica solid (F-MCM-41) has been successfully prepared by one-pot hydrothermal synthesis from TEOS and 2-((3-(triethoxysily)propylimino)methyl)phenol in the presence of CTMABr surfactant, followed by removal of CTMABr in F-MCM-41 from extraction of ethanol solution at 50 °C for 5 h. The fluorescent sample was characterized with X-ray diffraction, nitrogen isotherms, nuclear magnetic resonance (NMR), and fluorescence spectroscopy, and the obtained results show that the sample has ordered hexagonal mesoporous symmetry, uniform pore size, high BET surface area, large pore volume as well as good fluorescent properties. When this sample is used to detect Be²⁺ ions in water, the degree of fluorescence quenching is dependent on the concentration of Be²⁺ solutions ranged from 1 to 20 μg/L.     

Picosecond excimer fluorescence spectroscopy: applications to local motions of polymers and polymerization monitoring

The local motions of α,ω-bis-(1-pyrene)alkanes and pyrene-labelled poly(methyl methacrylate) polymers in solution were characterized by picosecond excimer fluorescence spectroscopy. The experimental results showed that 1,3-bis-(1-pyrene)propane and 1,10-bis-(1-pyrene)decane have similar local motions that bring two pyrene groups together to form excimers. Further, poly(1-pyrenylmethyl methacrylate) and a copolymer of methyl methacrylate and 1-pyrenylmethyl methacrylate in solution were found to have similar local motions that lead to excimer formation. In addition, the viscosity change during the polymerization of methyl methacrylate was monitored by measuring with picosecond fluorimetry the fluorescence lifetime of a trace amount of 1,3-bis-(1-pyrene)propane dissolved in methyl methacrylate.     

Surfactants from glucamines and ω‐epoxy fatty acid esters

The ring‐opening reaction of ω‐epoxy fatty acid methyl esters (9,10‐epoxy decanoic acid methyl ester, 10,11‐epoxy undecanoic acid methyl ester and 13,14‐epoxy tetradecanoic acid methyl ester) with N‐methyl glucamine or glucamine was studied. A new method (in methanol under reflux) leads to products, which are surfactants of linear‐ or γ‐type‐structure, in fair yields and purities. In a following step the ring‐opening products were saponificated by enzymatic catalysis or by conversion with sodium hydroxide leading to amphoteric surfactants. The surface‐active properties of the methyl esters and their corresponding acids or salts were studied at various pH‐values by measurement of surface tension of aqueous solutions and by examination of foaming properties. Depending on the chain length of the used epoxides, the structure of the obtained sugar‐based surfactant and the pH‐values, different surface‐active properties were observed. Several of the achieved products reduce the surface tension of aqueous solution down to 26—40 mN/m. Examination of foaming properties of the latter show rather poor or good foamers, depending on the surfactant used or the pH‐value of the solution.     

The fluorescence resonance energy transfer between dye compounds in micellar media

The fluorescence resonance energy transfer from fluorescein to merocyanine 540 in aqueous sodium dodecyl sulfate, cetyltrimethylammonium bromide and Triton X-100 micellar solutions as well as deionized water was investigated at room temperature using steady-state and time-resolved fluorescence spectroscopy techniques. Fluorescence resonance energy transfer rate constants (k_T), obtained using both Stern–Volmer and Förster theories, were in good agreement. Moreover, energy transfer efficiency values of 0.14, 0.38, 0.77 and 0.85 for deionized water, sodium dodecyl sulfate, TX-100 and cetyltrimethylammonium bromide micellar solution were obtained at the highest acceptor concentration at which fluorescence resonance energy transfer was achieved. The data obtained from steady-state absorption, fluorescence spectral studies and time-resolved lifetime measurements indicated that the fluorescence resonance energy transfer from fluorescein to merocyanine 540 occurred most effectively in aqueous cetyltrimethylammonium bromide micellar solutions.     

Photonic Methods to Enhance Fluorescence Correlation Spectroscopy and Single Molecule Fluorescence Detection

Recent advances in nanophotonics open the way for promising applications towards efficient single molecule fluorescence analysis. In this review, we discuss how photonic methods bring innovative solutions for two essential questions: how to detect a single molecule in a highly concentrated solution, and how to enhance the faint optical signal emitted per molecule? The focus is set primarily on the widely used technique of fluorescence correlation spectroscopy (FCS), yet the discussion can be extended to other single molecule detection methods.     

DSC study on the effect of cure reagents on the lignin base epoxy cure reaction

The cure reactions of liquid lignin base epoxy resin (LEPL) with three different curing agents, viz., methylhexahydrophthalic anhydride, maleic anhydride, and 2‐methyl‐4‐methylimidazole (EMI‐2,4), were investigated by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry. Cure kinetics was evaluated using the multiple heating rate Kissinger method. The reactivities of the three curing agents were compared based on kinetics results obtained by DSC. FTIR spectra of these curing systems were also studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

十聚钨酸钠的制备及其光催化降解甲基橙的研究

自制了不同于TiO2的绿色光催化剂十聚钨酸钠(Na4W10O32),通过紫外-可见吸收光谱、红外吸收光谱对制得的产物进行了表征.以紫外灯为光源,研究了Na4W10O32对模拟甲基橙染料废水的光催化脱色性能.实验结果表明,溶液初始pH对Na4W10O32光催化活性有影响,催化剂投加量及甲基橙初始浓度是影响脱色率的重要因素.20mg/L的甲基橙溶液在300W紫外灯辐照下,Na4W10O32质量浓度为0.6 g/L,溶液初始酸度pH=2,光照30 min即可完全脱色.实验利用Na4W10O32光催化降解模拟甲基橙染料废水取得了良好效果,在国内尚未见相关报道,为以后利用多金属氧酸盐光催化降解水中有机污染物的研究提供了参考.     

苯甲醛修饰的聚酰胺胺树状大分子的合成与荧光性能研究

以乙二胺为中心核,丙烯酸甲酯为支化单体,苯甲醛为端基官能团合成了3.0代和4.0代两种聚酰胺胺-苯甲醛树状大分子。对其荧光性能进行了研究,结果表明,溶液中的Fe3+对不同代数聚酰胺胺-苯甲醛树状大分子的荧光具有淬灭效应,并且荧光发射峰出现了红移现象。溶液中的Zn2+对聚酰胺胺-苯甲醛树状大分子的荧光具有增强作用,但是当Zn2+与树状大分子摩尔比持续增加时,其混合溶液的荧光强度却减小。     

Synthesis and solution properties of poly(acrylamide-styrene) block copolymers with high hydrophobic content

Hydrophobically associating block copolymers of polyacrylamide/styrene with a high hydrophobe content were synthesized using micellar copolymerization under various conditions of surfactant and initiator concentrations with the objective of determining the conditions that produce optimum solution properties for enhanced oil recovery. Solubilities, aqueous solution viscosities and interfacial properties with air and oil of the copolymers were investigated. The influence of salt on the solution properties was also studied. Nature of hydrophobic sites and onset of hydrophobic association were studied by measuring the fluorescence of pyrene in polymer solutions. Optimum solution properties were obtained for copolymers synthesized under conditions of high surfactant and initiator concentrations. The copolymers displayed substantial thickening properties at low concentrations with enhanced thickening in the presence of salt. The interfacial tensions of the aqueous solutions with n-decane and air were also reduced. Interfacial properties were slightly sensitive to salt concentration. The copolymer solutions showed shear and temperature thinning behaviors typical of polymer solutions.     

罗丹明B的三维荧光光谱研究

本文利用三维荧光激发-发射光谱研究了罗丹明B的荧光光谱特性。考察了罗丹明B浓度、pH值大小等因素对罗丹明B的荧光光谱影响,给出了其三维荧光光谱图。结果显示,罗丹明B的三维荧光光谱图较二维荧光光谱图能更详细地描述被测组分的性质,为综合考查罗丹明B的结构特征提供了参考。