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Long Chiang

Long Chiang, Ph.D. Professor


Design and synthesis of near-infrared absorbing emerald green fullerenes for near-infrared sensing and imaging, near-infrared filter, and broadband photovoltaic devices:  Emerald green fullerenes (EF) are a new class of multifunctionalized C60 derivatives exhibiting long wavelength optical absorption and named according to their intrinsic green color of the material. Structurally, a double-triphenylene interconnected all-trans 18-trannulene moiety was proposed to be responsible for the green color. Electrochemical characteristics of EF-6MC2 in solution substantiated the high multielectron accepting capability of EF compounds that may allow their uses as the acceptors in optoelectronic and photovoltaic applications.

Design and synthesis of multiphoton absorptive fullerene-fluorene chromophores for nonlinear photonic sensor protection and optical limiting applications:  A series of fullerenyl chromophore dyads and triads were synthesized by attachment of two hindered groups on C9 of fluorene ring increases highly on its solubility and makes direct intermolecular stacking contact of fullerene cages and diphenylaminofluorene rings more difficult. We propose the mechanism of keto-enol isomerization between strained cyclopropyl ring moiety and the carbonyl group for extending the p-conjugation length toward the C60 cage, resulting in enhancing electronic interactions, the molecular polarization, and thus multi-photon absorption cross-sections. Based on transient absorption data from femtosecond pump-probe experiments at 800 nm and nanosecond laser flash photolysis at 355 nm confirmed unambiguously the occurrence of two-photon excitation processes in benzene and a subsequent efficient energy transfer from the two-photon pumped donor moiety to the C60 cage moiety.

Design and synthesis of hydrophilic molecular self-assembly of fullerene-derived nanospheres as biologically active free radiacal scavenging agents, PDT drugs and antibacterial agents:  Several water-soluble C60 derivatives were developed specifically as free-radical scavengers in biological system against reactive oxygen species (ROS)-induced diseases.  High efficiency of FC4S as a biophotonic compound in photodynamic therapy (PDT) against tumor and cancer cells, as shown in our recent in vitro and in vivo studies established its platform in conjunction with the use of antibodies and peptides for targeting for potential therapeutic uses.  One limitation of current PDT treatments is its tissue penetration depth of light when the conventional laser irradiation at 630-700 nm is applied.  Combination of fullerenic PDT efficacy and two-photon absorptive moieties will allow us to design the corresponding hydrophilic C60-donor conjugate molecules for photonic utilities.  Optical absorption of C60-donor materials in the near-IR region may provide fundamental insights on the design of two-photon based PDT sensitizers in a better tissue penetration depth.

Design and synthesis of starburst conductive conjugate-polymer molecular suprastructures using functionalized C60 as a molecular core for electronic nanodevices:  Conductive polymer conjugates with hexamethanofullerene malonate, pentamethano-fullerene malonates, and novel hexanitro[60]fullerene were synthesized. Utilization of hexanitro[60]fullerene as a precursor in the synthesis of hexaaminated C60 derivatives becomes a versatile method toward the preparation of starburst C60-derived conductive polymers.  The strategy involves anchoring various conductive polymer arms onto a C60 cage as a molecular core.  Using this synthetic approach, C60-derived, hyper-structured conductive oligoaniline molecules, such as hexa(hexadecaanilino)C60 and dodeca (hexadecaanilino) hexamethanofullerene hexa-malonate, were synthesized.  Molecular C60 and its derivatives are electronegative compounds.  Direct chemical bonding of electron-donating oligoanilines, with a well-defined chain length, on a fullerene cage forms macromolecules in a starburst A-Dn array.  Photoinduced intramolecular electron-transfer consecutively from hexadecaaniline arms of starburst molecules to the C60 core was found to be highly efficient, making these materials applicable in the design of molecular electronic nanodevices.