Investigation of Oxygen-Induced Quenching of Phosphorescence in Photoexcited Aromatic Molecules by Positron Annihilation Spectroscopy


Book Description

Platinum OctaEthyl Porphyrin (Pt.OEP) is an efficient phosphor under ultraviolet excitation. The phosphorescent triplet state P(T(Sup 1)) is readily quenched by the oxygen O2 molecules. This phenomenon is being utilized as the basis for global air pressure measurements in aerodynamic facilities at various laboratories. The exact mechanism by which O2 molecules quench the P(T(Sup 1) approaches P(S(Sub O)) transitions is still unknown. The diamagnetic singlet states P(S(Sub n)), which feed P(T(Sub 1)) states via intersystem crossings, would presumably not be affected by O2. It must be only the magnetic P(T(Sub 1)) states, which can interact with the paramagnetic O2 molecules, that are affected. However, our positron lifetime and Doppler broadening studies suggest the formation of O2P(S(Sub n)), complexes which can also eventually reduce the population of the P(T(Sub 1)) states (i.e., quench phosphorescence). This reduction is possible because higher triplet states in (Pt.OEP) are admixed with the P(S(Sub 1)), states via spin orbit interactions. The experimental procedures and the results of various measurements are presented in this paper. Singh, Jag J. and Eftekhari, Abe Langley Research Center NASA-TP-3619, NAS 1.60:3619, L-17577 RTOP 274-00-94-04...
















Light-Associated Reactions of Synthetic Polymers


Book Description

This book combines theoretical explanations of the reactions of light and polymeric materials with development of light responsive polymeric materials for various practical applications. Photo associated reactions and light responsive materials have great potential to improve existing industrial processes, including capturing solar energy. This book presents a range of reactions and materials with some of the most exciting current and future applications.




Photoelectrocatalysis


Book Description

Photoelectrocatalysis: Fundamentals and Applications presents an in-depth review of the topic for students and researchersworking on photoelectrocatalysis-related subjects from pure chemistry to materials and environmental chemistry inorder to propose applications and new perspectives. The main advantage of a photoelectrocatalytic process is the mildexperimental conditions under which the reactions are carried out, which are often possible at atmospheric pressure androom temperature using cheap and nontoxic solvents (e.g., water), oxidants (e.g., O2 from the air), catalytic materials (e.g.,TiO2 on Ti layer), and the potential exploitation of solar light. This book presents the fundamentals and the applications of photoelectrocatalysis, such as hydrogen production fromwater splitting, the remediation of harmful compounds, and CO2 reduction. Photoelectrocatalytic reactors and lightsources, in addition to kinetic aspects, are presented along with an exploration of the relationship between photocatalysisand electrocatalysis. In addition, photocorrosion issues and the application of selective photoelectrocatalytic organictransformations, which is now a growing field of research, are also reported. Finally, the advantages/disadvantages andfuture perspectives of photoelectrocatalysis are highlighted through the possibility of working at a pilot/industrial scale inenvironmentally friendly conditions. Presents the fundamentals of photoelectrocatalysis Outlines photoelectrocatalytic green chemistry Reviews photoelectrocatalytic remediation of harmful compounds, hydrogen production, and CO2 reduction Includes photocorrosion, photoelectrocatalytic reactors, and modeling along with kinetic aspects







Supramolecular Amphiphiles


Book Description

An amphiphile is a molecule that contains a hydrophilic part and a hydrophobic part, linked by covalent bonding. Supramolecular amphiphiles (supra-amphiphiles) are amphiphiles linked by non-covalent interactions. As they employ non-covalent interactions, these species demonstrate adaptability and reversibility in conformational transformation, making them one of the most important emerging species in supramolecular chemistry. They have proven important in bridging the gap between molecular architecture and functional assembly. This book is written and edited by the current leaders in the topic and contains a foreword from Professor Jean-Marie Lehn, a father of the supramolecular chemistry field. Bringing together supramolecular chemistry and colloidal and interfacial science, the book provides a detailed and systematic introduction to supramolecular amphiphiles. Chapters explain how to employ non-covalent interactions to fabricate supra-amphiphiles. The book opens with an introduction to the history and development of the field, followed by chapters focussing on each type of interaction, including host-guest interaction, electrostatic interaction, charge-transfer interaction, hydrogen bonding and dynamic covalent bonds. This book will be a valuable resource for students new to this field and experienced researchers wanting to explore the wider context of their work.