Our group explores charge and energy transfer dynamics in
hybrids incorporating 0D, 1D and 2D nanomaterials
with optical microscopy methods like time-resolved
micro-photoluminescence imaging and spectroscopy. We use self-assembly methods to connect various nanocomponents
to obtain hybrids with controlled optical behavior. Some of our past work is briefly described
1. Charge/Energy Transfer in Hybrid Nanomaterials including Layered Metal
characterization of charge transfer and development of self-assembly methods to
control such process in hybrids containing inorganic nanocrystals like quantum
dots is an important research topic in our group. We use self-assembly methods to create quantum dot-based hybrid nanomaterials
with controlled behavior, in particular charge transfer, energy transfer and plasmon-assisted
emission. Through self-assembly we regulate molecular parameters
such as intercomponent distance, bandgap or nanoparticle size which in turn
controls the magnitude of a given light-induced processes.
Some examples highlighting our published work in this field are shown below.
We developed a surface-based self-assembly method to produce donor-bridge-acceptor
with varying bridge length and varying Qdot core size (bandgap) that exhibit
transfer (ET) rate. With excellent, size-dependent light absorption properties
conferred by the incorporated Qdots, these dimeric hybrids are promising power generating nanounits for molecular electronics.
related articles in Angew.Chem.Intl.Ed.2011 and in
In collaboration with Prof. Mathew Maye's group at Syracuse, we produced a series of Qdot/conjugated polymer hybrids
with tunable hole transfer rate by using
core/shell Qdots with varying shell thickness and connecting the components by
electrostatic binding. (ACS-Nano2012,
In collaboration with Dr. Oleg Gang (CFN-BNL), we demonstrated control of
photoluminescence in plasmonic Qdot heterodimers and core shell nanoclusters composed of Qdots linked with
gold nanoparticles by DNA. (ChemComm 2010,
2. Hybrid Nanomaterials for Biosensing
We developed biosensors based on Qdot/chaperonin protein
hybrids with controlled nanocrystal:protein stoichiometry (1:1)
and with multiple binding sites allowing detection of target molecules with high
(nanomolar) affinityor biosensing, work reported in
Small 2009. Using water soluble conjugated polyelectrolytes,
we developed label free DNA sensors with sequence specificity (Chem.Mat.2014)
and demonstrated the ability to obtain organic/biological hybrids with
DNA-sequence dependent fluorescence enhancement (Chem.Comm.2014).
3. Structure-Function Relationship in
Conjugated polymers have electronic and optical properties strongly dependent on the polymer chain conformation and
aggregation state. PArt of our past efforts have been focused at understanding
structure/optical property relationship in
such nanomaterials and the development of synthetic or materials processing
routes to control
structure towards improved performance, an area where we have strongly
collaborated with Dr. Hsing Lin Wang's group at LANL (polymer synthesis). Some
examples of published work are below.
2011: we reported a method to fabricate conjugate
polymer based microporous thin films with high transparency and efficient
charge transfer with potential utilization as active substrates for transparent
PVs. These thin film showed structural regularity over large areas consist of
hexagons with sizes 3-5μm, with most polymer material concentrated in the
2010: we showed that polymer/solvent interactions can be employed
to control the polymer chain conformation in the case of a non-ionic conjugated
polymer. Depending on the polarity of the solvent, we found the polymer to
exhibit extended, coiled, and collapsed chain conformations in solutions, which
lead to distinct morphology and optical properties in solid films.
Applied Materials and Interfaces 2011: we reported the
synthesis and characterization of a series of
water-soluble conjugated polymers with varying side chain length (repeat units) with
side-chain-dependent conformation and solvent-dependent photoluminescence
properties. This study found that an increase in EG repeat units induced changes in chain packing,
affecting polymer crystallinity which evolved from semicrystalline to liquid
crystalline to completely amorphous.
we reported a temperature-dependent time resolved spectroscopic study that help us untangle
the role of polymer chain conformation and aggregation state in defining the thermochromic properties of a PPV derivative.