Laser Spectroscopy of Biological and Material Interfaces
Our research focuses on molecular structure and
dynamics of surfaces and interfaces. Two complementary
aspects of our research program are (1) development of
new and more powerful surface spectroscopy techniques
with better sensitivity and detection limits, ultrafast time
resolution, and improved molecular-level information
content; and (2) applications of these techniques for
studies of molecular structure, organization, reactivity, and
dynamics in these interesting and complex environments.
Currently, we are focusing on vibrational
spectroscopy (mid-infrared spectral range) because it
provides a wealth of information on the molecular structure
and organization at surfaces and interfaces. To achieve
surface selectivity, we utilize even-order nonlinear optical
processes, such as Sum Frequency Generation (SFG) and
Second Harmonic Generation (SHG), which are symmetry-
forbidden in isotropic bulk media in the electric dipole
approximation.
In addition to the standard frequency-domain spectroscopic measurements that
characterize ensemble averaged structures, we are working on an array of ultrafast
(femtosecond) time-domain techniques, such as SFG-FID (Free Induction Decay) for
complementary studies of the molecular dynamics in real time. Our recent developments include
a mixed Spectrally- and Time-Resolved SFG (STiR-SFG), a novel technique capable of
measuring spectral evolution of
vibrational coherences at surfaces,
and heterodyne-detected SFG (HD-
SFG), a broad-band spectral
interferometry technique capable of
ultrasensitive detection on a few
percent of a monolayer level while
simultaneously providing phase
information on the molecular
vibrations.
We are interested in surfaces and interfaces important in life sciences, nano- and bio-
technology, and material science. Our current projects fall into three categories: 
Structure and dynamics of the hydrogen bonding network at aqueous interfaces, with
the long-range goal of better understanding biomembrane surfaces. H-bonding underlies
most of the important and unique
properties of water in the interfacial
region, in particular 'biological water',
a thin layer adjacent to biointerfaces.
Using surface-selective spectroscopy,
we are systematically investigating
how the ultrafast dynamics of the
aqueous H-bond network is affected
by the chemical functionalities and
electrostatics of interfaces. To this
end, we investigate the ultrafast
vibrational and rotational dynamics of
the water molecules themselves as
well as carefully chosen small probe
molecules at aqueous interfaces.
Molecular organization of monolayer and surface materials. Molecularly ordered
surfaces and thin films are emerging as the base materials for nanoscale devices,
molecular electronics, and biotechnologies. The 'tailored' surface materials under
investigation include: Langmuir-Blodgett monolayers, Self-Assembled Monolayers, polymer
surfaces, and bio-functionalized surfaces used, e.g., for cell adhesion. We study details of
molecular orientation, conformation, packing, dynamics and relaxation, and surface
functionalization chemistry at these surfaces.
Surfaces and interfaces of nanostructures. A common motif in many emerging
nanotechnology applications involves nanostructures covered with chemi- or physisorbed
organic molecules which perform the desired physical, chemical, or biological function. We
apply nonlinear spectroscopy to study organization, conformation, dynamics, and reactivity
of molecules on surfaces of metal and semiconductor nanostructures, e.g. nanoparticles of
different size and shape, and nanoparticle aggregates. In particular, we focus on the new
effects arising when the characteristic size of the nanostructure approaches the molecular
scale. Another aspect of this
project is the exploration of the
enhancement of nonlinear
spectroscopic signals due to local
nanoplasmon effects, with
potential application in sensors
with ultra-low detection limits and
high molecular information
content.
Selected publications
| 1. | Stiopkin, I.V.; Weeraman, C.; Pieniazek, P. A.; Shalhout, F.Y.; Skinner, J.L.; Benderskii, A. V. "Hydrogen bonding at the water surface revealed by isotopic dilution spectroscopy", Nature 474, 192 (2011). |
| 2. | Stiopkin, I. V., Jayathilake, H. D.; Benderskii, A. V. "Temporal Effects on Spectroscopic Line Shapes, Resolution, and Sensitivity of the Broad-Band Sum Frequency Generation" J. Chem. Phys. 132,234503, 1-9 (2010). |
| 3. | Jayathilake, H.D.; Driscoll, J.; Bordenyuk, A. N.; Wu, L.; da Rocha S. R. P.; Verani, C. N.; Benderskii, A. V. "Molecular Order in Langmuir-Blodgett Monolayers of Metal-Ligand Surfactants Probed by Sum Frequency Generation" Langmuir 25, 6880-6886 (2009). |
| 4. | Yatawara, A. K.; Tiruchinapaly, G.; Bordenyuk, A. N.; Andreana, P.R.; Benderskii, A.V. "Carbohydrate Surface Attachment Characterized by Sum Frequency Generation Spectroscopy", Langmuir 25, 1901-1904 (2009). |
| 5. | Palyvoda, O.; Bordenyuk, A. N.; Yatawara, A. K.; McCullen, E; Chen, C.-C.; Benderskii, A. V.; Auner, G. W. "Molecular Organization in SAMs Used for Neuronal Cell Growth" Langmuir, 24, 4097 (2008). |
| 6. | Stiopkin, I. V., Jayathilake, H. D.; Bordenyuk, A. N.; Benderskii, A. V. "Heterodyne-detected Vibrational Sum Frequency Generation Spectroscopy", J. Am. Chem. Soc. 130, 2271 -2275 (2008). |
| 7. | Bordenyuk, A. N.; Weeraman, C.; Yatawara, A. K.; Jayathilake, H. D.; Stiopkin, I. V.; Liu, Y.; Benderskii, A. V. "Vibrational Sum Frequency Generation Spectroscopy of Dodecanethiol on Metal Nanoparticles" J. Phys. Chem. C 111, 8925-8933 (2007). |
| 8. | Weeraman, C.; Yatawara, A. K.; Bordenyuk, A. N.; Benderskii, A. V. "Effect of Nanoscale Geometry on Molecular Conformation: Vibrational Sum-Frequency Generation of Alkanethiols on Gold Nanoparticles" J. Am. Chem. Soc. 128, 14244 - 14245 (2006). |
| 9. | Jayathilake, H. D.; Bordenyuk, A. N.; Weeraman, C.; Zhu, M.; Rosenblatt, C.; Benderskii, A. V. "Rubbing-induced anisotropy of alkyl side chains orientation at polyimide surfaces", J. Chem. Phys. 125, 064706 (2006). |
| 10. | Bordenyuk, A.N.; Jayathilake, H.; Benderskii, A. V. "Coherent Vibrational Quantum Beats as a Probe of Langmuir-Blodgett Monolayers", J. Phys. Chem. B. 10, 15941 - 15949 (2005). Journal Cover Vol. 109, No. 33 (August 25, 2005). |
| 11. | Bordenyuk, A. N.; Benderskii, A. V. "Spectrally- and Time-Resolved Vibrational Surface Spectroscopy: Ultrafast Hydrogen Bonding Dynamics at D2O/CaF2 Interface" J. Chem. Phys. 122, 134713 (2005) (11 pages). Also published in: Virtual Journal of Ultrafast Science (May 2005 issue) and Virtual Journal of Biological Physics Research (April 15, 2005 issue). |
