钙离子对卤化银乳剂化学增感和光谱增感的影响

本文通过控制乳剂中一系列不同的钙离子浓度(4.0～80×10^-3mol Ca²⁺/mol AgX),研究了化学增感时间对钙离子浓度的依赖性,测定了相应的感光特性,结果表明,乳剂中的钙离子在不影响最佳感光度的前提下,可有效地抑制灰雾并延缓化学增感过程,延长化学成熟时间。 经感红染料光谱增感后,测定了染料的相对增感倍率,本征及感红光谱感光度,研究了它们对轧剂中钙离子浓度的依赖关系。以卤化银乳剂对染料的吸附,对光的吸收以及Dember效应的实验结果为佐证,说明钙离子在光谱增感的电子转移过程中,起着电子陷阱的作用,从而抑制感红感光度的增感;与此同时,钙离子又抑制染料对本征感光度的减感,这可能是由于钙离子的存在阻碍了染料正空穴对卤化银本征潜影的氧化,从而保护了部分潜影免受染料正空穴的袭击。     

照相光谱增感染料及其组合在溴化银表面的吸附及吸附热测量

本文研究了三个光谱增感染料及其组合在一些溶液中的吸收光谱和吸附态染料的反射光谱,得到25℃在几种溶剂的溴化银分散系中的吸附等温线,并采用精密量热技术测量了微小吸附热效应,得到25±0.01℃染料Ⅰ在溴化银水悬浮液中被吸附的等位摩尔吸附焓△H₂₉₈-(335±2.5)kJ/mol(表面覆盖度θ=0.94)。结合对染料组合的光吸收、吸附以及吸附热等的测试结果,对照相乳剂生产中采用的先加入感绿染料Ⅱ、Ⅲ,后加入感红染料Ⅰ的步序,从吸附角度作了初步的理论探讨。研究结果也表明,精密量热技术与光吸收测量等手段相结合,将有助于在乳剂制备过程中分析研究染料的增感效果。     

立方体溴化银颗粒光谱增感的电子转移超快动力学研究

本文利用皮秒时间分辨条纹相机技术检测了3种染料在立方颗粒溴化银上吸附后形成聚集体的荧光光谱,分析了3种染料在不同染料浓度下对染料聚集体到溴化银导带的超快电子转移过程的影响,进而分析其对增感效率的影响关系,并探讨了增感过程的微观机理.实验结果表明,荧光衰减的动力学曲线与一个双指数函数拟合得相当好,存在一快一慢两个衰减成分,快衰减成分占拟合较大比例,表明其源于与荧光衰减相竞争的从激发态染料聚集体到AgBr导带的电子转移.光致电子转移的速率及增感效率随着染料相对浓度的增加表现出一定的变化趋势,染料浓度增加,增感效率减小.     

MIGRATION OF EXCITATION ENERGY FROM THIONINE TO METHYLENE BLUE IN MICELLES

Abstract— The main absorption bands of thionine (Th⁺) and methylene blue (MB⁺) in aqueous solution lie at 598 nm and 664 nm, respectively. This position permits excitation energy transfer from Th⁺ to MB⁺, but not vice versa. We describe here studies of such transfer between these molecules adsorbed on micelles of sodium lauryl sulfate (SLS), imitating, at least to some extent, the state of pigments in chloroplasts.
The SLS concentration was varied from 3.0 to 11 × 10^-3 M. In the presence of dye, aggregation to micelles, each containing 70–100 detergent molecules, begins at about 3.0 × 10^-3 M SLS. Practically all dye ions are adsorbed on these micelles as soon as their formation begins.
Energy transfer from adsorbed Th⁺ ions to adsorbed MB⁺ ions can be demonstrated by observing the quenching of the fluorescence of thionine and the sensitization of that of methylene blue.
At [Th⁺] = [MB⁺] = 1 × 10^-5 M , the most efficient energy transfer (82 per cent efficiency, as derived from measurements of the quenching of Th⁺ fluorescence, or 90 per cent, as derived from sensitization of MB⁺ fluorescence) is observed at the lowest SLS-concentration (3.0 × 10^-3 M ), when the only micelles present are those formed by aggregation of dye-carrying low molecular complexes of SLS with dye cations. Each micelle carries, under these conditions, 10–14 molecules of the two dyes, and the distance between two closest dye ions is about 16 A. Transfer becomes less efficient as the SLS-concentration increases, causing pigment molecules to distribute themselves among a greater number of micelles.     

溶液中菁染料的状态对其在AgBr表面吸附效应的量热研究

用半导体精密量热计测得25±0.01℃时溴化银从DMF-H₂O溶液中吸附噻碳菁染料(Ⅰ)的吸附热。发现由于溶液中染料聚集状态的不同导致吸附热明显不同,但吸附于溴化银表面的染料的聚集态则基本相同。     

染料增感AgBr乳剂的光电子衰减动力学研究

本工作利用微波吸收薄膜介电谱测量技术,测量了菁染料光谱增感后的AgBr晶体乳剂在脉冲激光曝光后产生的光电子衰减时间特性,分析了不同类型的染料及其增感条件对材料光电子时间特性的影响关系.通过比较增感后的T 颗粒乳剂和立方体乳剂的光电子衰减特性,实验验证了吸附在T 颗粒(111)晶面上的染料比吸附在立方体(100)晶面上的染料更有效、更有助于形成潜影的论据.     

Photoinduced charge carrier dynamics of Zn-porphyrin-TiO2 electrodes: the key role of charge recombination for solar cell performance

Time resolved absorption spectroscopy has been used to study photoinduced electron injection and charge recombination in Zn-porphyrin sensitized nanostructured TiO(2) electrodes. The electron transfer dynamics is correlated to the performance of dye sensitized solar cells based on the same electrodes. We find that the dye/semiconductor binding can be described with a heterogeneous geometry where the Zn-porphyrin molecules are attached to the TiO(2) surface with a distribution of tilt angles. The binding angle determines the porphyrin-semiconductor electron transfer distance and charge transfer occurs through space, rather than through the bridge connecting the porphyrin to the surface. For short sensitization times (1 h), there is a direct correlation between solar cell efficiency and amplitude of the kinetic component due to long-lived conduction band electrons, once variations in light harvesting (surface coverage) have been taken into account. Long sensitization time (12 h) results in decreased solar cell efficiency because of decreased efficiency of electron injection.     

循环伏安法研究光谱增感染料在溴化银上的吸附

用循环伏安法和电子显微镜研究了不同类型的染料在溴化银上的吸附,使用了电沉积在铂上的溴化银电极作为照相乳剂的模型,证明了由于染料电荷的不同,其在AgBr/Br^-表面上的吸附也不同,正性染料被吸附时,形成难溶的表面络合物,和负性染料相作用时,形成易溶的表面络合物,而当AgBr与非菁负性染料作用时,则由于负电排斥而不形成络合物。因此,利用循环伏安法可以判断不同染料的吸附情况。本文还研完了超增感及Riester提出的‘强色增感’中的吸附情况。实验结果表明在AgBr上染料的排列次序取决于其吸附强度。本工作还证明了Reister所提出的‘强色增感剂’的作用机理是可信的。     

掺杂立方AgBr乳剂介电频谱的研究——Ⅲ.硫的影响

本文研究了用1×10^-5mol～1×10^-2mol Na₂S₂O₃/mol AgBr和1×10^-4mol～1×10^-2mol Na₂S/mol AgBr掺杂的立方AgBr乳剂的介电吸收频谱.发现在我们的实验条件下,当Na₂S₂O₃的加入量小于1×10^-4mol/mol AgBr时,Na₂S₂O₃,在AgBr微晶上吸附的影响占主要,样品介电吸收峰的f_max稍向低频方向位移,f_max位移量(△log f_max)的大小与AgBr微晶的表面状况有关.当Na₂S₂O₃的加入量大于1×10^-4mol/mol AgBr时,Na₂S₂O₃对AgBr微晶表面的溶蚀的影响逐渐占优势,使AgBr微晶表面的结构不均匀性增加,同时乳剂的pAg上升,结果样品的f_max逐渐向高频方向移动,介电吸收峰亦相应展宽.Na₂S的加入量小于1×10^-3mol/mol AgBr时,样品的f_max有稍向低频位移的趋势.当将掺Na₂S的样品干燥后在75℃和110℃下放置6小时后,f_max明显向高频方向移动.     

MECHANISM OF CONCENTRATION QUENCHING OF A XANTHENE DYE ENCAPSULATED IN PHOSPHOLIPID VESICLES

Encapsulating a xanthene dye in phospholipid vesicles produces vesicle solutions that contain dye at very high microscopic concentrations, but have a low overall optical density, thereby eliminating reabsorption. Using this system, we have studied the effects of concentration on the fluorescence lifetime of one such dye, sulforhodamine 101. We have observed that the lifetime decreases as a function of encapsulated dye concentration, which is indicative of collisional quenching. The lifetime decreases from 4.5 nsec for sulforhodamine in dilute aqueous solution to 0.69 ns at an encapsulated concentration of 33 m M . The bimolecular rate constant for this event is 2.6 10¹⁰ M ^-1 s^-1, consistent with a diffusion controlled event. However, the quenching constant calculated from changes in intensity is 2.2 10¹¹ M ^-1 s^-1. Thus, collisional quenching is not the predominant mechanism of quenching. The absorption spectra of dye in vesicles indicate an important contribution from static complex formation. Förster distance calculations indicate that energy transfer can also occur to a significant extent, with a predicted efficiency of transfer of 34% at a dye concentration of only 1 m M     

铱盐在AgBr乳剂中的作用

用(NH₄)₃IrCl₆(Ⅲ)和(NH₄)IrCl₆(Ⅳ)分别对立方体AgBr乳剂颗粒表面和内部进行敏化,用表面显影和内部显影的方法,对铱盐在乳剂颗粒中的作用进行了研究。实验表明,经铱表敏的AgBr乳剂表面感光度增加,而铱内敏的AgBr乳剂表面感光度降低,内部感光度增加;铱内敏并经灰化的乳剂在曝光后能形成直接正像。这是因为经化学灰化的铱内敏乳剂在曝光后,光生电子被乳剂颗粒内部的铱中心捕获而形成内潜影,光空穴则破坏颗粒表面的灰化中心,使其不能显影。因此,我们认为铱在乳剂颗粒内部起着电子陷阱的作用。     

菁染料在TiO2胶体表面光诱导的电子转移

本文用紫外-可见光谱及荧光光谱研究了吸附在TiO₂胶体表面上的染料1,1'-二乙基-3,3'-二磺丁基-5,5'-二氰基咪碳菁与胶体间发生的光诱导电子转移过程。荧光实验表明,菁染料荧光发射强度随着体系中TiO₂胶体浓度的增加而降低,这是由于电子从染料的激发单重态注入到TiO₂的导带所致。通过染料荧光寿命的测定得到光诱导电子转移速率常数K_et约为4×10₈s^-1。     

SPECTRAL SENSITIZATION OF SnO2 THIN FILM ELECTRODE BY THE J-AGGREGATE OF CYANINE DYES IN MONOLAYERS

Arachidic acid monolayers containing 5,6,5',6'-dibenzo-I,I-diethyl-2,2'-cyanine chloride were prepared by the spreading method and deposited on the SnO₂ surface using the Langmuir-Blodgett technique. The SnO₂ : dye assembly prepared in this manner was used as a photoelectrode of the conventional electrochemical cell. A distinct J-band was observed in the action spectra of sensitized anodic and cathodic photocurrents. Effects of calcium arachidate barriers inserted between dye layer and either SnO₂ electrode (inside barrier) or electrolyte solution (outside barrier) on the photocurrent were examined. Although the inside barrier was effective in decreasing both anodic and cathodic photocurrents, the outside barrier did not suppress cathodic photocurrent. The following mechanism involving a molecular exciton of the J-aggregate is proposed for the sensitized photocurrent. The anodic photocurrent is caused by hole trapping by some reducing agent and concomitant injection of the electron from molecular exciton to the conduction band of SnO₂. Extraction of conduction-band electron of SnO₂ by molecular exciton and supplying to some oxidizing agent such as dissolved oxygen are responsible for the cathodic photocurrent.     

PREPARATION AND PHOTOPHYSICAL STUDIES OF PORPHYRIN-C60 DYADS

Abstract Porphyrin-C₆₀ dyads in which the two chromophores are linked by a bicyclic bridge have been synthesized using the Diels-Alder reaction. The porphyin singlet lifetimes of both the zinc (Pz_n-C₆₀) and free base (P-C₆₀) dyads, determined by time-resolved fluorescence measurements, are ≦17 ps in toluene. This substantial quenching is due to singlet-singlet energy transfer to C₆₀ The lifetime of Pzn-¹C₆₀ is -5 ps in toluene, whereas the singlet lifetime of an appropriate C₆₀ model compound is 1.2 ns. This quenching is attributed to electron transfer to yield P_zn^bull;+-C₆₀^bull;-. In toluene, P-¹C₆₀ is unquenched; the lack of electron transfer is due to unfavorable thermodynamics. In this solvent, a transient state with an absorption maximum at 700 ran and a lifetime of-10 μs was detected using transient absorption methods. This state was quenched by oxygen, and is assigned to the C₆₀ triplet. In the more polar benzonitrile, P-¹C₆₀ underoes photoinduced electron transfer to give P^•+-C₆₀^bull;-. The electron transfer rate constant is −2 × 10¹¹ s⁻¹.     

吸附在溴化银颗粒表面上的增感染料的ESR波谱研究

本文用电子顺磁共振技术研究了光照条件下三十八种增感染料与溴化银之间发生的电子转移过程。增感染料和溴化银无论在黑暗处还是在光照下,均不产生ESR信号。当增感染料吸附在溴化银颗粒表面上时,如不加光照,仍看不到ESR信号。只有在光照条件下,才有可能观察到ESR信号,这主要取决于增感染料分子的最高占有能级与溴化银价带的相对位置。若染料分子的最高占有能级比溴化银价带顶部高0.7 eV,就可以观察到ESR信号,反之则观察不到。顺磁性中心是由染料正空穴Dye^©形成的。根据ESR信号的强度可以判断增感染料是否有较强的减感作用。     

照相光谱增感染料在溴化银沉淀表面的吸附及吸附热测量

用离心分离法得到25℃菁染料Ⅱ和Ⅲ分别在几种溶剂的溴化银分散系中的吸附等温线;记录了染料溶液的吸收光谱和吸附态染料的反射光谱。采用精密量热技术得到25±0.01℃溴化银从DMF-水溶液中吸附染料Ⅱ等位摩尔吸附热为-(3.18±0.09)KJ/mol(θ=0.87)。还对从DMF溶液中吸附染料Ⅱ的体系绘制了以单位溴化银表面的吸附热表示的吸附等温线,表明用精密量热技术可以研究染料的吸附过程。     

溴化银晶体光谱敏化光电流的研究和染料增感性能的判据

本文以AgBr晶体和菁染料为对象,对AgBr晶体的光电流进行了研究。实验发现,AgBr晶体经其本征吸收波长的光辐照后,可产生新的诱导吸收带。用诱导吸收带波长范围内的光辐照AgBr晶体,在非本征吸收区可测量到自敏化光电流。若染料吸附在AgBr晶体片上,则其敏化光电流将叠加在自敏化光电流上。增感染料对AgBr晶体的阳极和阴极光电导均有不同程度的敏化作用。本文在实验研究的基础上,提出了对染料增(减)感性能的判据S_D,比现有的一些判据更具有综合性。利用S_D—λ曲线可以较直观地对染料的增(减)感性能做出预测。本文利用S_D判据对一些实用增感染料及其组合作了分析。     

Fast Redox Perturbation of Aqueous Solution by Photoexcitation of Pyranine

Abstract— Intense illumination (60-120 MW/cm²) of an oxygen-free aqueous solution of pyranine (8-hydroxypyrene-l,3,6-tri-sulfonate) by the third harmonic frequency of an Nd-Yag laser (355 nm) drives a two successive-photon oxidative process of the dye. The first photon excites the dye to its first electronic singlet state. The second photon interacts with the excited molecule, ejects an electron to the solution and deactivates the molecule to a ground state of the oxidized dye (φ⁺). The oxidized product, φ⁺, is an intensely colored compound (Λ_max= 445 nm, ε= 43 000 ± 1000 M ⁻¹ cm⁻¹) that reacts with a variety of electron donors like quinols, ascorbate and ferrous compounds. In the absence of added reductant, φ⁺ is stable, having a lifetime of -10 min. In acidic solutions the solvated electrons generated by the photochemical reaction react preferentially with H⁺. In alkaline solution the favored electron acceptor is the ground-state pyranine anion and a radical, φ, of the reduced dye is formed. The reduced product is well distinguished from the oxidized one, having its maximal absorption at 510 nm with e = 25 000 ± 2000 M^-l cm⁻¹. The oxidized radical can be reduced either by φ^- or by other electron donors. The apparent second-order rate constants of these reactions, which vary from 10⁶ up to 10⁹M⁻¹ s⁻¹, are slower than the rates of diffusion-controlled reactions. Thus the redox reactions are limited by an energy barrier for electron transfer within the encounter complex between the reactants.     

REACTIVITY OF ACRIDINE DYE TRIPLET STATES IN ELECTRON TRANSFER REACTIONS

Abstract—Rate constants, k _q , for the reaction of cationic and neutral acridine orange and 10-methylacridine orange triplet states (³AOH ⁺, ³AO, ³MAO⁺) with a series of electron donors have been measured. Two different protolytic forms of the semireduced dye radical are produced by acridine orange triplet quenching at various pH^M values in methanolic solution.
It is found that k ₄ decreases with increasing oxidation potential of the reducing agent for all triplet states in a manner which is expected for electron transfer reactions. The different reactivities of the cationic and neutral triplet forms can, therefore, be attributed to the difference in reduction potentials of these species. The difference in reduction potentials is related to the p K ^M values of triplet state, p K _T^M , and semireduced dye radical, p K ^M_S , by thermodynamic consideration. p K _T^M (³AOH⁺/³AO) is determined to be 11.2. From thisp K _S^M (AOH./AO;) is estimated to be 17–18. This is in striking contrast to the protolytic equilibrium of the semireduced dye radicals found to be pK^F= 4.1. We conclude that the last value represents the second protonation equilibrium (AOH⁺₂./AOH). This conclusion is confirmed by spectroscopic data.     

冠醚对溴化银乳剂的增感作用

近年来,已有将冠醚化合物用于卤化银感光乳剂中的一些报道^[1-4]。为了改善卤化银感光材料的性能,我们将合成的一种新冠醚——N-对甲苯磺酰基-7-氮杂-1,4,10,13-四硫杂环十六烷(NTsTTH)用于卤化银乳剂中,发现它能提高卤化银乳剂的感光度。