Fabrication and characterization of functionalized polyoxometalates

• Main Author: Yu, Lingling.
• Other Authors: School of Materials Science and Engineering
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Materials::Organic/Polymer electronics
• Online Access: http://hdl.handle.net/10356/48863
• Institution: Nanyang Technological University

Polyoxometalates (POMs), a versatile group of metal oxide polyanions which exhibits variety of properties as it has a wide range of sizes and structures that can be tuned to suit the fabrication needs. Organic pyrene dye which has rather long fluorescence as well as long-lived excited state was chosen to be grafted onto POM skeleton through its imido group to study and understand the charge-transfer mechanism in organic functionalized POMs. In this report, a detailed outline of synthesis and the characterization of organic-inorganic charge-transfer hybrid were recorded. The charge-transfer mechanism was analyzed with the time resolved transient absorption spectroscopy. The hybrid shown electronic absorption at 450nm, indicating that there was a strong electronic interaction between the organic pyreneimido group and inorganic hexamolybdate cluster. The overall studies revealed that the strong electronic absorption at the visible region mainly came from the optically allowed π-π* transition of the pyreneimido component (S0 to S2 transition). The charge-transfer process from the excited pyreneimido moiety to the inorganic POM cluster at the time scale of approximately 700fs was observed, which could be ascribed to the internal conversion of singlet excited state from S2 state to S1 state. This result shed light on new route for the design of new charge-transfer hybrid clusters of organic functionalized POMs and serves as crucial guidance for their applications in optical and electrical devices.