Luis Velarde

PhD

Luis Velarde.

Luis Velarde

PhD

Luis Velarde

PhD

Research Interests

Physical, materials and analytical chemistry: Nonlinear spectroscopy of interfaces, ultrafast processes at surfaces, molecular devices, biointerfaces and environmental surface chemistry.

Education

  • Postdoctoral Research Associate, Pacific Northwest National Lab, 2010-2013
  • President’s Postdoctoral Fellow, UC Santa Barbara, 2008-2010
  • PhD, University of Arizona, 2008

Specializations

Ultrafast spectroscopy; Interfacial processes; Nonlinear microscopy; Materials chemistry

Research Summary

Our research program focuses on the molecular-level elucidation of dynamic processes and structural characteristics underlying functional interfaces through direct spectral measurements of chemical bonds and molecular interactions at the complex surfaces of nanostructures and porous materials. Our interests include the synthesis of novel materials and the use of nonlinear laser spectroscopy and microscopy to unravel key processes in condensed-phase interfaces as they relate to the discovery of better ways of converting and storing energy as well as to the development of low-cost energy-efficient devices and more powerful and selective chemical sensors.

We integrate recent discoveries in materials and surface science with interface-selective ultrafast nonlinear optical techniques in order to gain detailed quantitative knowledge of the dynamic couplings between the surface electronic states and the molecular degrees of freedom in lower-dimensional and nano-scale environments. We are developing novel ways to provide in-situ measurements of the interfacial properties of organic and organic/inorganic composites by characterizing the surface electronic states, interfacial chemical identity, molecular orientation, binding, and electrochemical environment as they ultimately determine the device efficiency and performance.

Our studies also examine how the energy of an absorbed photon is transferred within different chemical groups of a surface molecule, among neighboring molecules, or to the interface where it can give raise to mobile carriers. Of special interest to our program is the effect that lattice and molecular vibrations, point defects, and adsorbates have in the outcomes of surface chemical reactions and interfacial charge and energy transfer processes.

Selected Recent Publications

  • H. S. AlSalem, S. T. Al-Goul, A. Garcia-Miranda Ferrari, D. A. C. Brownson, L. Velarde, S. P. K. Koehler. Imaging the Reactivity andWidth of Graphene’s Boundary Region. ChemComm., 56, 9612-9615, 2020.
  • M. Raab, J. Becca, J. Heo, C-K Lim, A. Baev, L. Jensen,_ P. N. Prasad, and L. Velarde. Doubly-resonant sum frequency spectroscopy of mixed photochromic isomers on surfaces reveals conformation-specific vibronic effects. J. Chem. Phys., 150, 114704, 2019.
  • S. T. Algoul, S. Sengupta, T. Bui, and L. Velarde. Tuning the Surface Ordering of Self-Assembled Ionic Surfactants on Semiconducting Single-Walled Carbon Nanotubes: Concentration, Tube Diameter, and Counterions. Langmuir, 34, 9279-9288, 2018.
  • D. Elsenbeck, S. K. Das, and L. Velarde. Substrate influence on the interlayer electron–phonon couplings in fullerene fillms probed with doubly-resonant SFG spectroscopy. Phys. Chem. Chem. Phys., 19, 18519-18528, 2017.
  • S. Sengupta, L. Bromley III and L. Velarde. Aggregated States of Chalcogenorhodamine Dyes on Nanocrystalline Titania Revealed by Doubly-Resonant Sum Frequency Spectroscopy. J. Phys. Chem. C, 121, 3424-3436, 2017.
  • H. Kearns, S. Sengupta, I. Ramos Sasselli, L. Bromley III, K. Faulds, T. Tuttle, M. A. Bedics, M. R. Detty, L. Velarde, D. Graham, and W. E. Smith. Elucidation of the Bonding of a Near Infrared Dye to Hollow Gold Nanospheres – A Chalcogen Tripod. Chem. Sci., 7, 5160-5170, 2016.
  • S. K. Das, S. Sengupta, L. Velarde. Interfacial Surfactant Ordering in Thin Films of SDS-Encapsulated Single-Walled Carbon Nanotubes. J. Phys. Chem. Lett., 7, 320-326, 2016.
  • H. F. Wang, L. Velarde, W. Gan and L. Fu. Quantitative Sum-Frequency Generation Vibrational Spectroscopy of Molecular Surfaces and Interfaces: Lineshape, Polarization, and Orientation. Annu. Rev. Phys. Chem., 66, 189, 2015.