Modulating Photophysical Properties of Dye Loaded Gold Nanoparticles Through Plasmon Molecule Coupling

Abstract

Metal nanoparticles (MNPs) exhibiting surface plasmon resonance (SPR) properties newlinecan interact with the oscillating dipoles of organic molecules in a pronounced manner. newlineMolecules which absorb light near to the SPR absorption peak of MNPs can induce changes newlinein the photophysical and electronic properties of MNPs due to plasmon-molecule newlineinteractions. These interactions can also increase or decrease the field incident on the dye newlinemolecule and perturb their electronic transitions. Plasmon-molecule interactions are governed newlineby several factors such as the spectral overlap between the molecular and plasmonic newlineresonance, chemical composition and concentration of the dye molecule, shape and size of newlineMNPs and the distance between MNPs and dye molecule. If the coupling interactions are newlineweak, various surface-enhanced phenomena are known to arise whereas strong coupling often newlineresults in the formation of hybrid plexcitonic states. Irrespective of the strength of the newlinecoupling interactions, the optical properties of the hybrid systems are markedly different from newlinethose of their constituents. newlinePlasmon-molecule coupled systems have incredible potential in materials science and newlinebiology. Several literature reports exemplify their utility as ultrafast switches, bistable newlinedevices, modulators, sensors, photocatalysts and biological imaging agents. A limited number newlineof examples are also known wherein molecule-plasmon interactions have been utilized in newlinexiphotodynamic therapy (PDT) although the mechanistic details of such systems are generally newlineoverlooked. Motivated by these facts, we aim to study systematically the photophysical newlineproperties of a series of nanocomposites with the objective of understanding the underlying newlinemechanism of plasmon-molecule interactions. We chose gold nanoparticles and organoboron newlinecompounds for our investigations because of the low toxicity and tuneable absorption profile newlineof gold nanoparticles and the luminescence features of the dye molecules. newlineChapter 1 focuses on literature review of plasmon-molecule interactions from newline