General statement of the problem of substance analysis by the products of photochemical reactions

The aim of this study was to formulate the problem and develop a formal procedure for structure determination and substance quantification by the products of its photochemical reaction. This problem appears in studies of rapid photochemical processes, when the lifetime of the initial substance is shorter than the time to the moment of its registration (ecology, toxic substances, etc.). Algorithms of solving corresponding inverse problems are considered, and procedure including several steps is proposed. It includes the determination of the composition and concentrations of mixture components by the spectra of a test substance using the theory of molecular spectra; the recovery of the quantitative composition of the initial substance by the structural formulae of the products of a chemical reaction; and the determination of the initial concentrations of substances and the kinetics of the process on the basis of the developed theory of chemical transformations using information on the reactants and their concentrations. The application of the proposed approach is demonstrated on examples.     

Photochemical conversion and storage of solar energy

The possibilities for the photochemical storage of solar energy are examined from the standpoint of maximum efficiency and mechanism. Loss factors are considered for a general endergonic photochemical reaction and it is concluded that a realistic maximum solar energy storage efficiency for any photochemical system is 15–16%. The natural process of photochemical solar energy storage, namely, photosynthesis, is analyzed and it is found that the maximum solar energy storage efficiency of photosynthesis is 9.5 ± 0.8%. Kinetic and thermodynamic limitations on a photochemical energy storage process are identified and it is shown that the desirable production of hydrogen and oxygen from water probably cannot be sensitized with visible light if only one photochemical step is employed. However, by analogy with the mechanism of photosynthesis, two photochemical reactions operating in series permit a full utilization of the photochemically active part of the solar spectrum. A possible scheme is described and analyzed as to its possibilities and potential difficulties. Finally, some practical considerations are presented not only for the photochemical production of hydrogen but also for solid state photovoltaic devices.     

Umwandlung und Speicherung von Sonnenenergie

The use of sunlight as a renewable source of energy must increase in future. The potential methods of transformation and storage are on a different level of state of the art. The present article reviews the various approaches. Focus is on transformation and storage of sunlight as chemical energy by photocatalytic processes. Photosynthesis of green plants represents both example and prototype. Research interest and endeavor in artificial photosynthesis, in particular for photocatalytic splitting of water and photochemical transformation of carbon dioxide, have increased enormously. Silicon‐based photovoltaic has achieved industrial ripeness and broad application in everyday life.     

Photochemical and Electrochemical Carbon Dioxide Utilization with Organic Compounds

In the last few years, photochemical and electrochemical CO₂ transformations have attracted increasing attention in response to topical interest in renewable energy and green chemistry. The present minireview offers an overview about the current approaches for the photochemical and electrochemical carbon dioxide fixation with organic compounds. Valuable products, including carboxylic acids and heterocyclic compounds, are accessible through carboxylation and carboxylative cyclization, respectively. In photochemical and electrochemical processes, photo‐ or electro‐induced radical ions or other high‐energy organic compounds are considered as key intermediates to react with CO₂. Besides, activation of CO₂ to produce radical anion has also been reported.     

A new form of analytical chemistry: distinguishing the molecular structure of photo-induced states from ground-states

This paper introduces a new analytical technique from the field of crystallography, and the optoelectronics motivation that underpins this effort. The essence of the photocrystallography technique is explained in the context of a four-dimensional (space-time) structural probe, and the four technically distinct time-windows of enquiry are presented. This features the complementary needs of laboratory, synchrotron and Free-electron laser based X-ray diffraction experiments. The different scales of atomic resolution required for the technique to be able to probe various photochemical phenomena are described. Sample requirements for photocrystallography experiments are also considered. The paper concludes by forecasting the prospective fortune of this new analytical technique to respond to major current challenges in the photovoltaic, optical data storage, and non-linear optics industries.     

基于可再生能源的水电解制氢技术（英文）

在全球变暖,污染日益严重的今天,发展可再生清洁能源成为了当务之急.然而可再生能源(风能、太阳能)本身具有间断特性,这就需要寻找一种合适的能量媒介储存能量来保证其能源的稳定输出.当前,我国各地不断出现弃风、弃光和弃水电事件,据国家能源局的公开数据,仅2016年,全国弃风电量497×10~8 kW·h,弃光率仅西部地区就已达20%,弃风弃光日臻凸显[1].从地域方面来看,我国光伏发电呈现东中西部共同发展格局,其中,西部地区主要发展集中式光伏发电,新疆、甘肃、青海、宁夏的累计装机容量均超过5×10~6 k W·h,而中东部地区除集中式光伏发电外,还重点建设分布式光伏发电,江苏、浙江、山东、安徽的分布式光伏装机规模已超过100万千瓦.我国光伏发电集中开发的西北地区也存在严重的弃光问题.根据中国光伏行业协会发布的报告,我国的弃光现象主要集中于西北的新疆、甘肃、青海、宁夏和陕西五省区.据统计,2016年,五省区光伏发电量287.17×10~8 k W·h,弃光电量70.42×10~8 k W·h,弃光率为19.81%,各省区光伏发电并网运行数据如表格所示.可以看出,新疆、甘肃光伏发电运行较为困难,弃光电量绝对值高,弃光率分别达到32.23%和30.45%[2].在新能源体系中,氢能是一种理想的二次能源,与其它能源相比,氢热值高,其能量密度(140 MJ/kg)是固体燃料(50MJ/kg)的两倍多.且燃烧产物为水,是最环保的能源,既能以气、液相的形式存储在高压罐中,也能以固相的形式储存在储氢材料中,如金属氢化物、配位氢化物、多孔材料等.对可再生和可持续能源系统,氢气是一种极好的能量存储介质.氢气作为能源载体的优势在于:(1)氢和电能之间通过电解水技术可实现高效相互转换;(2)压缩的氢气有很高的能量密度;(3)氢气具有成比例放大到电网规模应用的潜力.制氢的方式有很多,包括:化石燃料重整、分解、光解或水解等.全球每年总共需要约40亿吨氢气,95%以上的氢气是通过化石燃料重整来获得,生产过程必然排出CO_2,而电解水技术利用可再生能源获得的电能进行规模产氢,可实现CO_2的零排放,可将具有强烈波动特性的风能、太阳能转换为氢能,更利于储存与运输.所存储的氢气可用于燃料电池发电,或单独用作燃料气体,也可作为化工原料.通过水电解方式获得的氢气纯度较高,可达99.9%以上.     

Reaction pathways and mechanisms of photodegradation of pesticides

The photodegradation of pesticides is reviewed, with particular reference to the studies that describe the mechanisms of the processes involved, the nature of reactive intermediates and final products. Potential use of photochemical processes in advanced oxidation methods for water treatment is also discussed. Processes considered include direct photolysis leading to homolysis or heterolysis of the pesticide, photosensitized photodegradation by singlet oxygen and a variety of metal complexes, photolysis in heterogeneous media and degradation by reaction with intermediates generated by photolytic or radiolytic means.     

UV-Induced Nucleic Acid–Protein Cross-Linking: Manual on Planning of Irradiation Experiments and Calculation of Absorbed Dose and Quantum Yield

We have developed methods of photochemical quantitation of photobiological studies on UV-induced nucleic acid–protein cross-linking. Cases relating to incoherent low-intensity UV sources, laser UV sources and high-intensity laser UV sources are considered. In the case of low-intensity UV radiation the most important point is the correct determination of absorbed dose. The laser UV pulse energy is easily measured and the short-pulse irradiation also has the advantage of "freezing" the conformation of complexes under study. However, the use of high-intensity laser UV irradiation leads to realizations of two-quantum processes both in nucleic acid chromophores–bases and in solvent–water, which complicates singificantly the processing of results. In this paper methods for calculating the absorbed dose and the quantum yield of cross-linking for all above-mentioned cases are given as well as practical advice.     

Utilization of microflow reactors to carry out synthetically useful organic photochemical reactions

This review focuses on recent advances that have been made in conducting synthetically useful organic photochemical reactions by using microflow reactors. Attention is given to the utilization of this technique in the “scale-up” of a variety of photochemical processes including intermolecular photocycloadditions, intramolecular photocycloadditions and photocyclizations, photoadditions, photoreductions, photoisomerizations, photosubstitutions, photooxidations, photorearrangements, and heterogeneous photocatalytic reactions. In many examples, the use of the microflow method is compared to those carried out in batch systems. Finally, advantages and disadvantages of microflow photoreactions along with the possible employment of this approach to scale-up industrial photochemical processes are discussed.     

Liquid chromatography-tandem mass spectrometric analysis and regulatory issues of polar pesticides in natural and treated waters

Pesticides are among the most detected contaminants in the aquatic environment. This is mainly due to their use in agriculture and their physico-chemical properties that enable transportation and a persistent or pseudo-persistent existence in the water media. Several directives and guidelines set maximum levels of pesticides in water in order to protect the human and environmental health. A brief discussion of the existing directives and guidelines concerning pesticides in water is presented, e.g., the new regulatory framework for the Registration, Evaluation and Authorisation of Chemicals (REACH), and the Directive 91/414/EEC concerning the placing of plant protection products on the market. Up-to-date analytical tools to support the REACH program are of prime importance to ensure its complete implementation. Since liquid chromatography (LC) coupled to mass spectrometry (MS) is considered the most appropriate technique for determination of most modern pesticides in environmental waters, the most recent developments and applications in this field are discussed in detail in this review.     

光化学-荧光分析法研究(Ⅷ)——波长扫描-反应速差分析法

提出了波长扫描-光化学反应速差荧光分析同时测定双组分的方法,以核黄素的光分解反应和甲萘醌的光还原反应为例考察了方法的可行性.结果表明,核黄素、甲萘醌浓度分别在(0～1.20)μg/mL和(0～2.70)μg/mL范围内呈良好的线性关系(γ为0.999和0.998).检出限分别为0.22ng/mL和2.6ng/mL(n=11).平均回收率分别为101%、99%.     

Direct Dynamic Evidence of Charge Separation in a Dye-Sensitized Solar Cell Obtained under Operando Conditions by Raman Spectroscopy

Interfaces play an important role in enhancing the energy conversion performance of dye-sensitized solar cells (DSCs). The interface effects have been studied by many techniques, but most of the studies only focused on one part of a DSC, rather than on a complete solar cell. Hence, monitoring the interface evolution of a DSC is still very challenging. Here, in situ/operando resonance Raman (RR) spectroscopic analyses were carried out to monitor the dynamics of the photovoltaic conversion processes in a DSC. We observed the creation of new species (i.e., polyiodide and iodine aggregates) in the photosensitization process. We also obtained molecular-scale dynamic evidence that the bands from the C=C and C=N bonds of 2,2′-bipyridyl (bpy), the S=C=N bonds of the NCS ligand, and photochemical products undergo reasonably strong intensity and frequency changes, which clearly demonstrates that they are involved in charge separation. Furthermore, RR spectroscopy can also be used to quickly evaluate the performance of DSCs.     

Direct Dynamic Evidence of Charge Separation in a Dye‐Sensitized Solar Cell Obtained under Operando Conditions by Raman Spectroscopy

Interfaces play an important role in enhancing the energy conversion performance of dye‐sensitized solar cells (DSCs). The interface effects have been studied by many techniques, but most of the studies only focused on one part of a DSC, rather than on a complete solar cell. Hence, monitoring the interface evolution of a DSC is still very challenging. Here, in situ/operando resonance Raman (RR) spectroscopic analyses were carried out to monitor the dynamics of the photovoltaic conversion processes in a DSC. We observed the creation of new species (i.e., polyiodide and iodine aggregates) in the photosensitization process. We also obtained molecular‐scale dynamic evidence that the bands from the C=C and C=N bonds of 2,2′‐bipyridyl (bpy), the S=C=N bonds of the NCS ligand, and photochemical products undergo reasonably strong intensity and frequency changes, which clearly demonstrates that they are involved in charge separation. Furthermore, RR spectroscopy can also be used to quickly evaluate the performance of DSCs.     

Examination of the photophysical processes of chlorophyll d leading to a clarification of proposed uphill energy transfer processes in cells of Acaryochloris marinas

A comprehensive study of the photophysical properties of chlorophyll (Chl) d in 1:40 acetonitrile-methanol solution is performed over the temperature range 170-295 K. From comparison of absorption and emission spectra, time-dependent density-functional calculations and homologies with those of Chl a, we assign the key features of the absorption and fluorescence spectra. Possible photophysical energy relaxation mechanisms are summarized, and thermal equilibration processes are studied in detail by monitoring the observed emission profiles and quantum yields as a function of excitation energy. In particular, we concentrate on emission subsequent to excitation in the extreme far-red tail of the Qy absorption spectrum, with this emission partitioned into contributions from hot-band absorptions as well as uphill energy transfer processes that occur subsequent to absorption. No unusual photophysical processes are detected for Chl d; it appears that all intramolecular relaxation processes reach thermal equilibration on shorter timescales than the fluorescence lifetime even at 170 K. The results from these studies are used to reinterpret a previous study of photochemical processes observed in intact cells and their acetone extracts of the photosynthetic system of Acaryochloris marina. In the study of Mimuro et al., light absorbed by Chl d at 736 nm is found to give rise to emission by another species, believed to also be Chl d, at 703 nm; this uphill energy transfer process is easily rationalized in terms of the thermal equilibration processes that we deduced for Chl d. However, no evidence is found in the experimental results of Mimuro et al. to support claims that (nonequilibrium) uphill energy transfer is additionally observed to Chl a species that emit at 670-680 nm. This finding is relevant to broader issues concerning the nature of the special pair in photosystem II of A. marina because suggestions that it is comprised of Chl a can only be correct if nonthermal uphill energy transfer processes from Chl d are operative.     

Investigation of various synthetic protocols for self-assembled nanomaterials and their role in catalysis: progress and perspectives

Self-assembly is one of the most used strategies in the controlled synthesis and design of well-organized nanomaterials for various applications in diverse realms namely catalysis, sensors, microelectronics, energy storage, and energy conversion. It is quite common to see reports on the synthesis and design of several self-assembled nanomaterials for the application in the catalysis of various chemical, photochemical, and electrochemical reactions and processes. Nevertheless, a combined overview on the synthetic strategies for self-assembled nanomaterials has not been reported in any form in literature. Owing to the current interest shown and the future significance on the self-assembled nanomaterials, it is highly essential to have such an elaborated review on the progress and perspectives of synthesis of self-assembled nanomaterials and their subsequent application to catalysis of various chemical, photochemical, and electrochemical reactions and processes. In this review, we have highlighted various synthetic methodologies used so far for fabricating the self-assembled nanomaterials that includes Langmuir–Blodgett method, layer-by-layer assembly, amphiphilic (artificial and bio) self-assembly, and template-free approach. Nanomaterials derived from the above mentioned methods in various catalysis reactions are also highlighted in detail with an emphasis on confronts and prospects in the field of materials self-assembling and its concomitant application to catalysis.     

Synthesis of seven and higher membered nitrogen containing heterocycles using photochemical irradiation

Photochemical reactions have been applied for the synthesis of complex targets in many examples recently. In many cases, these processes provide access to unique modes of reactivity or offer unrivaled increases in molecular complexity. The key-features of photochemical reactions include increased selectivity, conversion, and yield and are beneficial for industrial and “green” processes. Despite these advantages, however, photochemical reactions in chemical production or R and D processes are rare. Most technical processes are limited to commodity chemicals and have been developed decades ago. The application of photochemical reactions for the synthesis of fine chemicals, natural products, and pharmaceutically active compounds, has become very popular. Photochemical reactions are used for organic synthesis and this review article highlighted the syntheses of heterocycles. Photochemistry is particularly fascinating and afforded an exotic charm due to its unconventional nature. In this review, I have given a clear idea of applicability of photochemical irradiations for the synthesis of a number of seven and higher membered N-heterocycles.     

Photogalvanic and photovoltaic effects in systems based on metal complexes of Schiff bases

The nature of the processes that occur when electrodes modified with complexes [M(Schiff)] (M = Ni, Pd, Pt; Schiff denotes four-dentate Schiff base ligands) are irradiated with visible light for the potential use of these electrodes in photoelectrochemical energy conversion devices is considered. The factors responsible for shifts in the electrode potential upon photoexcitation, i.e., the nature of the metal site, the nature of the substituents in the sensitizer, and the oxygen concentration are discussed. Tentative mechanisms of the photovoltaic effects observed for conventional and semiconductor electrodes modified with [M(Schiff)] complexes are determined.     

Surface-enhanced Raman spectroscopy toward application in plasmonic photocatalysis on metal nanostructures

Among photothermal, photovoltaic and photochemical techniques, photochemistry is superior in energy storage and transportation by converting photons into chemical fuels. Recently plasmonic photocatalysis, based on localized surface plasmon resonance (LSPR) generated from noble metal nanostructures, has attracted much attention. It promotes photochemical reaction efficiency by optimizing the solar spectrum absorption and the surface reaction kinetics. The deeper understanding is in urgent need for the development of novel plasmonic photocatalysts. Surface-enhanced Raman spectroscopy (SERS), which is also originated from the LSPR effect, provides an excellent opportunity to probe and monitor plasmonic photoreactions in situ and in real-time, with a very high surface sensitivity and energy resolution. Here, fundamentals of plasmonic photocatalysis and SERS are first presented based on their connections to the LSPR effect. Following by a validity analysis, latest studies of SERS applied for the plasmon mediated photochemical reaction are reviewed, focusing on the reaction kinetics and mechanism exploration. Finally, limitations of the present study, as well as the future research directions, are briefly analyzed and discussed.     

PHOTOELECTRONIC EFFECTS IN ORGANIC MATERIALS–II. VARIATION OF PHOTOVOLTAGE WITH pH IN CHLOROPHYLL-QUINONE SOLUTIONS

Abstract— The photovoltaic effect in ethanolic solutions of chlorophyll a with benzoquinone or hydroquinone has been measured as a function of pH. In acidic media, stable, fast-rising photovoltaic signals of positive sign are obtained. In neutral and basic media, less stable, slower rising photovoltaic signals of negative sign are found. The results in acid media are explained in terms of a photochemical interaction between chlorophyll and either the benzoquinone or hydroquinone producing protons which can then act as the electrode active agent. In basic media, negatively charged radical species, such as the benzoquinone radical-anion, are considered to be the most likely electrode-active species.