卤化银乳剂颗粒上不对称菁染料J-聚体荧光的研究

光谱增感机理的研究是感光科学中的一个重要课题Gilman^[1]和Kuhn等^[2]曾经提出光谱增感的电子转移和能量传递理论。随着现代谱学手段的出现,为人们了解光谱增感的初始过程提供了条件。近年来,电子转移的机理已被广泛接受,并用来解释与光谱增感有关的各种现象。但在ns~ps范围内的光谱增感动力学方面的研究还不多见。Dahne认为光谱增感不仅决定于染料与卤化银的能级关系,而且是由动力学控制的^[3],激发态染料向卤化银导带注人电子的电子转移过程与辐射及其他无辐射去活过程是竞争的^[4]我们通过对两种不对称的苯并咪哇唾碳著染料在AgBrI乳剂颗粒上吸附形成的J一聚体的荧光性质的研究,以求深人了解光谱增感的电子转移机理及其动力学过程,无疑是有重要意义的。     

Meso-Chloro-Substituted Indodicarbocyanines: Aggregate Behavior,Electrochemical Properties,Crystal Structure and Photographic Performance

The correlation of photographic performance of meso-chloro-substituted indocarbocyanine dyes having different substituent groups with their electrochemical properties and aggregation behavior in solutions and crystals and on emulsion grains was investigated. The experimental results indicate that the dyes form easily H-rather than J-aggregates no matter what they arc on AgBrI emulsions or in solutions and crystals. All the lowest vacant electronic energy level of the dyes, E_LV, are much lower than the energy of conduction band of AgBrI (E_CB)(-3.23 ev), so it is very easy for the dyes to trap electrons from the surface of silver halide, leading to strong desensitization by the electron-trapping process. The desensitization by the dyes depends fundamentally on their amount and structure, especially on the nature of substituents.     

纳米科技的发展对卤化银技术进步的影响

纳米科技和纳米材料在过去的十几年得到了迅速的发展,并将继续发展并渗透到各个领域,给世界和人类生活带来不可估量的影响.“纳米技术”真的是一个新的概念 ?事实上,某些材料的制备和使用早已经涉及了这个长度范围.卤化银照相技术就是“老”的纳米技术之一.在早期,从事卤化银照相的人们凭经验和有限的能力控制材料的某些结构在纳米级范畴.随着纳米科学的发展,纳米技术在卤化银照相领域的使用走过了从无意识到有目的的过程,促进了照相科学的发展.本论文将结合卤化银技术在 21世纪的发展趋势,从三个方面 (在纳米级研究卤化银照相、卤化银微晶上的纳米结构、纳米卤化银微粒)探讨纳米科学对卤化银技术进步的影响.     

Green Biosynthesis of Silver Nanoparticles Using ‘Polygonum Hydropiper’ and Study its Catalytic Degradation of Methylene Blue

The green synthesis of silver nanoparticles with the small size and high stability paved the way to improve and protect the environment by decreasing the use of toxic chemicals and eliminating biological risks in biomedical applications. Plant mediated synthesis of silver nanoparticles is gaining more importance owing its simplicity, rapid rate of synthesis of nanoparticles and eco-friendliness. In this study, focus on biosynthesis of silver nanoparticles using Polygonum hydropiper extract and its catalytic degradation of hazardous dye, methylene blue has been highlighted. The rapid reduction of silver (Ag) ions was monitored using UV-Visible spectrophotometer and showed formation of silver nanoparticles within less than one hour with maximum absorption of silver nanoparticles at 430 nm. The major functional groups present in the synthesis responsible for the formation of silver nanoparticles. It was identified by using Fourier Transform Infrared spectrophotometer (FTIR). Field Electron Scanning Microscope (FESEM) was used to characterise the nanoparticles synthesized using P.hydropiper. The morphology of silver nanoparticles was predominantly spherical and aggregated into irregular structure with average diameter of 60 nm. In addition, this report emphasizes the effect of the silver nanoparticles on the degradation rate of hazardous dyes by sodium borohydride (NaBH₄). The efficiency of silver nanoparticles as a promising candidate for the catalysis of organic dyes by NaBH₄ through the electron transfer process is established in the present study.     

阻光染料对氯化银乳剂光谱增感的影响

增感染料在卤化银微晶上吸附并形成J-聚集体是染料光谱增感和超增感的关键步骤.本文利用紫外-可见吸收光谱研究了增感染料和阻光染料在氯化银微晶上的吸附,并考察了阻光染料对增感染料J-聚集体的形成及乳剂感光性能的影响.结果表明:不同阻光染料在氯化银微晶表面的吸附程度不同,对增感染料J-聚集体形成的影响也有差异.其中,吸附较小的不影响增感染料J-聚集体的形成,而吸附较大的阻碍增感染料J-聚集形成,特别是阻光染料在增感染料之前加入乳剂中时.在氯化银微晶上吸附很小的阻光染料基本不影响增感染料对乳剂的光谱增感,而吸附较强的阻光染料不仅吸收入射光,还抑制或破坏增感染料的光谱增感.因此,在氯化银微晶表面没有吸附的阻光染料才是优良的阻光染料.     

新型中空卤化银颗粒乳剂的制备和性能研究V.中空卤化银T颗粒乳剂的制备和性能研究

８０ 年代以来,许多新型的卤化银微晶已在新开发的各种高质量感光材料中得到应用．近十年来在国内外文献中又出现新型中空卤化银微晶制备方法的报道．本文着重研究一种表面有许多小孔及凹坑的中空卤化银Ｔ颗粒的制备方法和感光性能．由于其独特的孔洞结构,使位错、缺陷增加,填隙银离子浓度增加和电子陷阱增多,潜影形成效率提高,从而达到提高乳剂感光性能的目的．     

卤化银乳剂制备中的新型掺杂剂

本文综述了近年来乳剂制备中常用的新型掺杂剂,较详细地介绍了两种能提高光电子利用效率的掺杂剂,即过渡金属络合物浅电子陷阱掺杂剂和羧酸盐(酯)有机空穴陷阱掺杂剂,总结了掺杂剂的选择原则,并举例说明了掺杂剂对乳剂感光度的影响.     

Donor–acceptor interactions between resonance-excited silver nanoparticles and halide ions in water solutions

Donor–acceptor interactions between silver nanoparticles (NPs), resonance-excited by optical quanta of light, and halide ions are studied in aqueous solutions. It is shown that deactivation of the plasmon excitation of Ag NP proceeds according to the exchange mechanism of electron transfer. Plasmon excitation quenching constants are determined and a correlation between quenching and the donor properties of halide ions is found. The efficiency of electrostatic interaction between resonantly-excited Ag NPs and halide ions is studied, and their dipole moment is determined.

     

Chemical and biological treatment of waste water with a novel silver/ordered mesoporous alumina nanocomposite

One of the serious problems in the present century is chemical and biological pollution of the environment. Nanocomposites are multiphase solid materials that have been used as adsorbent of pollutants such as dyes, pesticides, anions and etc. in the last decades. In this study, a novel nanocomposite including silver nanoparticles and ordered mesoporous alumina (OMA) has been synthesized and used for the removal of dyes pollutants (methyl orange, bromothymol blue and reactive yellow) from aqueous solution. The characterization of synthesized nanocomposite has been performed by TEM, N₂ adsorption/desorption, XRD and energy dispersive X-ray spectroscopy analysis. The adsorption kinetic and equilibrium data have been obtained by UV–vis spectroscopy. The results show that the silver/OMA nanocomposite (Ag/OMA nanocomposite) is good adsorbent for the removal of anionic dyes from aqueous solution, and also this nanocomposite has a biocidal action against both Gram-negative and Gram-positive bacteria.     

新型中空卤化银颗粒乳剂的制备和性能研究 Ⅲ.中空卤化银颗粒乳剂感光性能的研究

本文应用表面显影、Dember效应、化学成熟、光谱增感等方法,对照实心立方体溴化银乳剂研究了中空卤化银微晶的结构与光物理性质及感光性能的关系。实验结果表明:(1)中空卤化银的潜影在孔洞处优先形成;(2)中空卤化银微晶中位错、缺陷较多,其填隙银离子浓度较大,电子陷阱较多;(3)中空颗粒表面反应活性高,感光度高,光谱增感效果好;(4)中空颗粒乳剂其反差较大,最大密度较高;(5)上述结果均可归因于中空卤化银微晶所特有的孔洞结构。     

Biofabrication of silver nanoparticles from various plant extracts: blessing to nanotechnology

ABSTRACT

Nanotechnology is influencing life in many ways. Researchers are developing their interest in biofabrication of silver nanoparticles because of its excellent properties and boundless utilisation in almost every branch of science. Plant extract is used to synthesise silver nanoparticles and reduce silver ion, and act as capping and reducing agent. The phyto-chemicals and metabolites present in the extract help in biogenic reduction of silver ion, forming non-toxic nanoparticles. This review focuses on the green synthesis of nanoparticles from various plants and their parts as an easy and eco-friendly approach.     

影响一步摄影正象色调与银颗粒大小的几个因素

用透射电子显微镜观察一步摄影正片(明胶介质)的银颗粒,对影响银颗粒大小的因素进行了研究。卤化银负片乳剂中的碘含量,明显地影响卤化银颗粒大小和转印后银颗粒的大小,随着卤化银乳剂中的碘含量减少,卤化银颗粒和银质点簇(即银颗粒)变大,组成银质点簇的银质点数目增多,正象色调由棕向黑转移。不同物理显影核亦显著影响正片银颗粒大小与其色调。     

Quantitative secondary ion mass spectrometry depth profiling of surface layers of cubic silver halide microcrystals

The present article describes depth-profiling studies on populations of cubic silver halide microcrystals (typical size between 400 and 600 nm). These crystals consist of mixed halides (Cl, Br, I) and are characterized by internal halide distributions such as core-shell structures. Determination of the spatial distribution of the different halides in the microcrystals offers valuable information for the optimization of the crystal design of new photographic materials. The first part describes the calibration of the sputtered depth, which is more complicated than in the one-dimensional case of flat surfaces. In a second part, three different quantification methods [halide intensity ratios, XCs₂⁺ detection (X=halide) and the infinite velocity method] are used to determine the mean composition of the surface layer as a function of sputtered depth in the silver halide crystals. Although particles of submicrometer size are obviously not the ideal samples for depth profiling, a good correlation with values obtained by scanning electron microscopy energy dispersive X-ray microanalysis and wavelength dispersive X-ray fluorescence bulk analysis could be achieved.     

Biosynthesis of silver and gold nanoparticles using Sargassum horneri extract as catalyst for industrial dye degradation

This study focuses on the green synthesis of silver and gold nanoparticles using the marine algae extract, Sargassum horneri, as well as the degradation of organic dyes using biosynthesized nanoparticles as catalysts. The phytochemicals of the brown algae Sargassum horneri acted as reducing and capping agents for nanoparticle synthesis. Ultraviolet–visible absorption spectroscopy, dynamic light scattering, high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy were used to characterize the biosynthesized nanoparticles. The green-synthesized SH-AgNPs and SH-AuNPs exhibited high catalytic activity for degradation of organic dyes, such as methylene blue, rhodamine B, and methyl orange. The reduction reactions of dyes are based on pseudo-first-order kinetics.     

Phototropic Glass

Phototropic glass darkens on exposure to light and returns to its original state in the absence of light. The most extensively investigated of these glasses contain grains of silver halide having sizes > 50 Å. A discussion of theoretical principles is followed by a review of the very broad scope of the phenomenon.     

Tuning Phonon Energies in Lanthanide-doped Potassium Lead Halide Nanocrystals for Enhanced Nonlinearity and Upconversion

Optical applications of lanthanide-doped nanoparticles require materials with low phonon energies to minimize nonradiative relaxation and promote nonlinear processes like upconversion. Heavy halide hosts offer low phonon energies but are challenging to synthesize as nanocrystals. Here, we demonstrate the size-controlled synthesis of low-phonon-energy KPb₂X₅ (X=Cl, Br) nanoparticles and the ability to tune nanocrystal phonon energies as low as 128 cm⁻¹. KPb₂Cl₅ nanoparticles are moisture resistant and can be efficiently doped with lighter lanthanides. The low phonon energies of KPb₂X₅ nanoparticles promote upconversion luminescence from higher lanthanide excited states and enable highly nonlinear, avalanche-like emission from KPb₂Cl₅ : Nd³⁺ nanoparticles. The realization of nanoparticles with tunable, ultra-low phonon energies facilitates the discovery of nanomaterials with phonon-dependent properties, precisely engineered for applications in nanoscale imaging, sensing, luminescence thermometry and energy conversion.     

Nucleation-growth kinetics of the oxidation of silver nanocrystals to silver halide crystals

The electrochemical oxidation of silver nanocrystals to silver halide crystals proceeds by a process of nucleation and growth. The mechanism is confirmed by analyzing chronopotentiograms using a new extension of nucleation theory. The theory makes it possible to derive plots of nucleation-growth currents vs potential, and growth rates vs potential, directly from experimental data. Such plots yield powerful insights into the reaction kinetics. In situ AFM imaging reveals that a few thousand of silver nanocrystals are oxidized to only a few tens of silver halide crystals, without pronounced loss of active material. The mechanism of this remarkable process is described in this paper. In particular, it is shown that the decrease in crystal population proceeds via an oversaturated silver solution, i.e., a process that is mediated by “driven” Ostwald ripening across the electrode surface. At the same time, the low solubility of silver species in bulk solution means that few silver ions escape from the surface. This combination of features explains why the transformation from silver to silver halide is near-stoichiometric yet highly reconstructive.Dedicated to our friend and colleague Professor Dr. Alan Bond on the occasion of his 60th birthday     

Aggregation of sensitizing dyes in solution and their adsorption onto silver halides

The formation of dye dimers and higher aggregates in solution as a function of dye structure and environmental variables are considered. These factors, together with silver halide composition and crystal habit, are also examined in regard to their influence on surface spectra, dye orientation and forces involved in adsorption of dyes at silver halide substrates.     

A novel fluorescence sensor based on covalent immobilization of 3-amino-9-ethylcarbazole by using silver nanoparticles as bridges and carriers

A novel technique of covalent immobilization of indicator dyes in the preparation of fluorescence sensors is developed. Silver nanoparticles are used as bridges and carriers for anchoring indicator dyes. 3-amino-9-ethylcarbazole (AEC) was employed as an example of indicator dyes with terminal amino groups and covalently immobilized onto the outmost surface of a quartz glass slide. First, the glass slide was functionalized by (3-mercaptopropyl) trimethoxysilane (MPS) to form a thiol-terminated self-assembled monolayer, where silver nanoparticles were strongly bound to the surface through covalent bonding. Then, 16-mercaptohexadecanoic acid (MHDA) was self-assembled to bring carboxylic groups onto the surface of silver nanoparticles. A further activation by using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) converted the carboxylic groups into succinimide esters. Finally, the active succinimide esters on the surface of silver nanoparticles were reacted with AEC. Thus, AEC was covalently bound to the glass slide and an AEC-immobilized sensor was obtained. The sensor exhibited very satisfactory reproducibility and reversibility, rapid response and no dye-leaching. Rutin can quench the fluorescence intensity of the sensor and be measured by using the sensor. The linear response of the sensor to rutin covers the range from 2.0 × 10⁻⁶ to 1.5 × 10⁻⁴ mol L⁻¹ with a detection limit of 8.0 × 10⁻⁷ mol L⁻¹. The proposed technique may be feasible to the covalent immobilization of other dyes with primary amino groups.     

Behaviour of Ion Selective Electrodes Based on Silver or Mercuric Sulfide Selenide and Telluride Matrices

Abstract

The analytical behaviour of solid state, ion-selective electrodes based on silver or mercury sulfide, selenide, or telluride matrices was studied. As the active component, the chalcogenides of Cu, Pb, Cd, Zn, Ni, Co, and Bi for the cation electrodes and silver or mercurous halides for the anion electrodes were included. It was found that all possible combinations of matrix compounds are suitable for the preparation of the electrodes, silver being superior to mercury in respect to redox sensitivity. Prepared Ag⁺, Hg²⁺, Pb²⁺, Cu²⁺ and Cd²⁺ electrodes performed well, whereas Zn²⁺, Ni²⁺, Co³⁺ and Bi³⁺ electrodes showed unsatisfactory performances. Anion-selective electrodes constructed from mercuric chalcogenide-mercurous halide were more sensitive than those made from silver chalcogenide-silver halide system. The performance characteristics of all electrodes are described in terms of sensitivities, selectivities, response times, stabilities, reproducibilities, effect of pH and redox potential.