We investigate interfacial charge transfer and energy transfer in hybrids containing
low dimensional semiconductor nanomaterials like colloidal quantum
dots, 2D TMDCs, perovskite dots for potential application in optoelectronics,
biosensing and photocatalysis. We develop assembly methods to create nanohybrids
with controlled optical and electronic behavior, for example regulated charge transfer,
regulated energy transfer or tunable plasmon-assissted emission.
Some examples highlighting our published work in this field are shown below.
1. Interfacial Charge and Energy Transfer in Low Dimensional Semiconductor Nanomaterials
recent study we assembled quantum dots with layered tin disulfide to obtain
0D-2D hybrids with improved light harvesting properties. We found these
nanomaterials communicate by energy transfer, with the rate of this process
increasing with the increase f tin disulfide layers (ACS
Nano2016). Using this particular 0D-2D hybrid we built field effect transistors
with dramatically increased photocurrent and spectral photoresponse (APL 2016).
We have been successful in detecting and monitoring signals from
individual lead sulfide-cadmium sulfide nanocrystals undergoing
electron transfer with titanium oxide and we have explored blinking of such
nanocrystals to understand interfacial electron transfer in these hybrids.
In this work we patented a surface-based self-assembly method to produce donor-bridge-acceptor Qdot-fullerene dimers
with varying bridge length and varying Qdot core size (bandgap), achieving
transfer (ET) through self-assembly and bandgap engineering.
In collaboration with Prof. Mathew Maye's group at Syracuse University, 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,
3. Biotic-Abiotic Hybrids
Our group is interested in developed biosensors based on
colloidal quantum dots and a chaperonin protein with controlled quantum dot-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).
2. Plasmonic QDs
In these studies done in collaboration with Prof. Gang (CFN-BNL/Columbia U.), we demonstrated
how DNA mediated self-assembly allows the control of
photoluminescence output in plasmonic gold NP-Qdot dimers and gold NP-multiQdots
superstructures (ChemComm 2010,
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
collaborated with Dr.Wang's group at LANL (polymer synthesis). Some
examples of published work are below.
Adv.Funct.Mat. 2016 (Cover): we reported
large area (sub-cm size) breath figures made out of commercial polythiophenes.
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
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.