MATERIALS SEMINAR
Department of Materials Science & Engineering
Friday, February 21, 2014
2:00 – 3:00 ~ SERF 307
Please join us for refreshments at 1:30 in the lobby outside of 307 SERF
Speaker
Dr. Long Y. Chiang
Department of Chemistry, University of Massachusetts, Lowell, MA
Ultrafast Photoresponsive C70-Light Harvesting Antenna Nanostructures: from
Nonlinear Photonics to Biophotonics
Two C60-(antenna)x analogous compounds C60(>DPAF-C18)(>CPAF-C2M) and tetrad C60(>DPAF-C18)(>CPAF-C2M)2
nanostructures were synthesized and characterized. The structural design was intended to facilitate the ultrafast fs
intramolecular energy-transfer from photoexcited C60[>1(DPAF)*-C18](>CPAF-C2M)1or2 or C60(>DPAF-C18)[>1(CPAF)*C2M]1or2 to the C60> cage moiety upon two-photon pumping at either 780 or 980 nm, respectively. The latter nanostructure
showed approximately equal extinction coefficients of optical absorption over 400‒550 nm that corresponds to near-IR
two-photon based excitation wavelengths at 780‒1100 nm for broadband nonlinear optical (NLO) applications. Aside
from their enhanced two-photon absorption (2PA) activity at 780 nm, ultrafast photoresponses has been demonstrated at
980 nm showing 2PA cross-section (σ2) values of 995‒1100 GM for the hybrid tetrad. Accordingly, 2PA characteristics
of these nanostructures at multiple NIR wavelengths provided support for their suitability in uses as broadband NLO
nanomaterials at 600‒1100 nm that includes the 2PA ability of two antenna, DPAF (700‒850 nm) and CPAF (850‒1100
nm), and the fullerene cage at shorter wavelengths (600‒700 nm).
Photosensitizing drugs operate via the generation of reactive oxygen species (ROS) upon illumination in situ and this
allows non-specific attack. The lack of any demonstrated microbial resistance mechanism toward ROS allows its use
against a wide range of bacteria, viruses, yeasts, and protozoa by killing these pathogens in the infection. Local
administration of the PS into the infected area allows pathogen destruction without undue damage to the surrounding host
tissue. The relentless world-wide increase in multi-antibiotic resistance particularly amongst bacteria, has necessitated the
search for alternative antimicrobial techniques. New hydrophilic fullerenyl photosensitizers (FPS) exhibit high efficiency
in ROS production that leads us to propose their broad-spectrum cytotoxic activity upon illumination against microbial
pathogens and tumor cells regardless of conventional drug-resistance status. In addition, ROS produced by PDT was
shown to kill tumor cells regardless of their responsiveness to traditional chemotherapy drugs or ionizing radiation and
induce no intrinsic resistance upon repeated PDT treatments.
Long Y. Chiang is Professor of Department of Chemistry, University of Massachusetts at Lowell. He received his PhD (1979) in Organic Chemistry
from Cornell University. He is the team leader in a research project from National Institutes of Health, and funded by a four-year, $1.34 million
award. He is editorial board member of Advances in Chemical Science. His research interest include design absorbing emerald green fullerenes for
near-infrared sensing and imaging, filter, and broadband photovoltaic devices; Design of multiphoton absorptive fullerene-fluorene chromophores
for nonlinear photonic sensor protection and optical limiting applications; Design of starburst conductive conjugate-polymer molecular
suprastructures using functionalized C60 as a molecular core for electronic nanodevices.
Contact: Bin Hu – bhu@utk.edu