Ultrafast nonlinear spectroscopy
Ultrafast nonlinear spectroscopy
Tailored synthesis of molecular complexes with controlled photophysical & photochemical properties
Ultrafast 2-D IR spectroscopy
Spectroscopy with submolecular resolution using inelastic STM
Theoretical Chemical Physics
Non-linear optical (CARS) microscopy
Time-domain study of chemical reactions photochemical properties
Interfacial & Bioanalytical Chemistry (IBAC) photochemical properties
Surface-Enhanced Raman Spectroscopy
Condensed Matter Physics
Time-resolved scannning tunneling microscopy, Single molecule Raman Spectroscopy, Ultrafast electron dynamics in plasmonic materials
Ultrafast nonlinear spectroscopy, multidimensional infrared spectroscopy and nonlinear microscopy.
My research is focused on improving the reliability image force microscopy and spectroscopy by investigating methods of near field excitation with pulled optical fibers, as well as extending these measurements to the time resolved domain.
Development of nonlinear ultrafast laser induced scanning tunneling microscopy and TERS/SERS microscopy/spectroscopy on Au/Ag nano dumbbell and nano-crescent model systems.
Ultrafast spectroscopy and light-matter interactions in plasmonic nanoparticles. Focusing on single molecule SERS/TERS in different nanoparticle geometries and development of ambient light induced fs-STM microscopy.
Study ultrafast dynamics in the single molecule level at space-time-frequency domain with using tunable femtosecond laser coupled UHV-LT-STM.
I am studying the interactions of light with metal nanoparticles by simulation and experiment, and developing optical methods to trap, manipulate and assemble plasmonic nanostructures.
Studying single molecular chemistry by scanning tunneling microscope.
To design highly efficient catalysts for energy production and environment protection, it is critical to understand fundamentals of chemical bonds, through manipulating molecules with different approaches in extreme conditions. In conjunction with experimental efforts, we performed systematic density functional calculations to study the adsorption site, vibration frequencies and electronic properties of small molecules on metal surfaces. Theoretical results are imperative for the understanding of experimental results, providing unambiguous links between experimental spectroscopic features to the changes of individual chemical bonds.
I study the ultrafast nonlinear optical processes of nano-structured materials and work to extend this to the single molecule regime through the measurement of light-induced changes in the attractive force between a cantilevered atomic force microscope tip and the polarizable medium.
Femtosecond Light-Molecule Interaction with a Tunable Wavelength Femtosecond Laser Coupled STM
Theory and method development as it relates to light/matter interactions. Primarily concerned with the response of molecules coupled to plasmonic nanoparticles.
My research is focused on the characterization and application of gold and silver plasmonic nanocrescents. The localized surface plasmon resonances (LSPR) of these structures have been shown to be polarization dependent, leading to selective excitation of unique resonance modes, and maintain nanoscale resonance behavior into microscale dimensions, resulting in resonance frequencies over a visible to infrared frequency range. We are working with the Ge and Potma groups to integrate nanocrescent substrates into surface enhanced sum frequency vibrational spectroscopy.
My current research efforts are focused on using a low-temperature ultra-high vacuum Scanning Tunneling Microscope (STM) coupled to a femtosecond laser and CCD camera to explore the electronic states, charge transfer, light emission and absorption, plasmon resonance and catalysis enhancement of single molecules and nanostructures with sub-Angstrom spatial resolution. Presently we are investigating the spatial dependence of plasmon-enhanced catalysis in the vicinity of gold nanoparticles.
My research involves exploring different plasmonic substrate systems for use in the new technique of surface-enhanced femtosecond stimulated Raman spectroscopy. Our aim to to watch chemical reactions on the femtosecond timescale of nuclear motion by combining the plasmonic enhancements provided by surface- and tip-enhanced Raman spectroscopy with the time resolution of ultrafast spectroscopies.
We are exploring a novel imaging scheme, based on vibrationally resonant sum frequency generation (VR-SFG). The microscope provides us with unprecedented resolution and imaging speed, together with chemical selectivity and phase sensitivity. We have been using this technique to study collagen assemblies in animal tissues and various crystaline structures.
Developing theoretical models to explain Jahn-Teller systems
Studying optically induced force (Image force, Raman force, Plasmonic force, etc) microscopy and spectroscopy by combining atomic force microscope with optical microscope. Key words: optical gradient forces (plasmonic force, image force, Raman force), near-field optics, nonlinear optics, AFM
I am currently utilizing ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) to solve challenging chemical problems that require pushing the limits of space and time. UHV-TERS allows pristine samples to be prepared and studied with Ångstrom-scale topographical resolution, nanometer spectroscopic resolution, sensitivity down to a single-molecule, and currently I am working towards incorporating picosecond temporal resolution.
I am investigating the development of a gold nanocrescent/alumina substrate for surface enhanced spectroscopy investigations of catalytically-active triphenylphosphine-stabilized gold nanoclusters.
I study plasmon dynamics on STM tips via grating coupling of femtosecond laser pulses in an effort to produce coherent field emission of electrons at the tip apex for future applications in time resolution of tunneling measurements at the single molecule level.
Research and development of a Radio Frequency Scanning Tunneling Microscope(RF-STM) with the capability to detect photon induced tunneling current for the purposes of combining femtosecond temporal resolution and sub-angstrom spatial resolution.
Pursuing understanding and videography of chemistry at very fine limits of space and time through the combination of ultrafast spectroscopy and scanning probe microscopy. Studying the interactions between ultrashort pulses and sharp metal tips in terms of plasmon dynamics, field enhancement, and ultrafast electron emission.
I propose to explore the rectifying abilities of DBDT for implementation in solar energy technology. Major characterization methods include STM and AFM experiments.
My primary research is in fabricating and analyzing solution-processed polymeric and small-molecule solar cells. I am specifically interested in understanding and controlling the relationship between processing conditions and the resulting heterojunction morphology and electrical properties of the device.
Single Molecule Vibrational Spectroscopy
Time Resolved Four Wave Mixing Spectroscopy (CARS, Transient Grating) with Visible Femtosecond Pulses. Current systems of interest include: Bulk Magnesium Porphyrin, Silicon Naphthalocyanine in solution, Plasmon Propagation along thin film gold using four wave mixing to create an optically controlled grating to couple a third beam to Surface Plasmon Polaritons.
Research specializing in femtosecond laser coupled STM, STM induced photon emission, single molecule spectroscopy / microscopy.