Preface

This book entitled "Photophysics, Photochemical and Substitution Reactions - Recent Advances" represents a modern branch of science. Photophysics and photochemical reactions are as old as our world. Working on the principle of light-matter interaction, they are present at the crossroads of several disciplines such as chemistry, physics, material science, biology, and medicines. The same is true for substitution reactions as well. To the best of our knowledge, this fantastic combination of topics, substitution reaction clubbed with reactions initiated by photons (i.e., photochemical reactions), appears for the first time in book literature, representing the importance of gross understanding of organic chemistry, materials science, just a few areas to mention. A combined understanding will also help us to expand the development of new molecules, new materials, as well as understanding new photon-initiated processes. The goal of this book is to familiarize both research scholars and postgraduate students with recent advancements in various fields related to reactions initiated by photons and substitution reactions.

This book is broadly divided into three sections: Section I "Photophysics and Application"; SectionII "Photochemical, Photocatalysis and Applications"; and Section III "Substitution Reactions". Each part provides a unique aspect of its headings.

 Section I titled "Photophysics and Applications," contains three chapters and it starts with an in-depth photophysics details of a popular pyran dye and its application in optical sensing. The second chapter deals with another popular and important dye, BODIPY dye. The DNA interaction studies of ferrocenyl ureas and thioureas have been presented in Chapter 3. Section II of this book comprises six chapters under the heading of "Photochemical, Photocatalysis and Applications". This section starts with a very important topic, carbon dioxide reduction on Cu/ TiO2, while the second chapter discusses the recent development of hydrogen evolution reaction. Third chapter of this section discusses the photocatalytic degradation of various organic dyes by using arsenomolybdates, while the fourth describes the visible-light-induced photocatalysis of aldehyde. The potential photocatalysis of metal oxide nanoparticles is presented in fifth chapter. The last chapter in this section deals with the ferrocene unimolecular rectifier. The final section of this book consists of two chapters on substitution reactions. Substitution reactions are a type of reaction where one functional group or ligand is substituted by another. They could be electrophilic or nucleophilic, depending upon whether the reagent is involved. However, whether it is organic or inorganic chemistry, there are two mechanisms of substitution reactions: dissociative or SN1 and associative mechanism or SN2. Many factors such as solvent, ionic strength, concentration, or hardness of metal ions in inorganic reactions could gain great importance on substitution reactions. The special class of organometallic compounds is ferrocenes. This type of compound, including its derivatives, has shown to be bio-applicable. Two chapters in this book bring us the newest research in this field.

Last but not the least, the future of photophysics, photochemical, and substitution reactions, like any other burgeoning field, is more exciting than the past. This is

particularly due to the increase in the number of young researchers and the development of the instrumentations.

We thank all the contributors for their excellent chapters and the publishing process managers of IntechOpen, especially author service manager, Mr. Josip Knapic, for keeping us on our toes to publish this book on time. It has been another extremely nice experience to work with this dynamic publishing house, IntechOpen.
