Research

RESEARCH

Single Molecule Conductivity in Organic and Biomimetic Molecules:
(Dr. Zhihai Li, Sepideh Afsari, and Aseem Malhotra)
The conductance of single molecules depends not only on how conductive the molecule is but also on how the molecule connects to the electrodes. Our group has designed a conjugated thiol linker which can improve the conductance of the molecule-electrode junction. We continue to explore this topic by using the STM (scanning tunneling microscopy) break-junction method to study the conductance of single conjugated molecules with conjugated thiol linkers.

Conjugated Thiol Linker for Enhanced Conductivity of Gold-Molecule Contacts (Yufan He)

PNA is an artificial analog of DNA. PNA has neutral backbone may allow more compact SAM growth than for DNA. Metal ions can be introduced into PNA duplexes by replacing the natural bases with metal complexing ligands. We study the self-assembly and charge transfer of PNA using Scanning Probe Microscopy (SPM), Cyclic Voltammetry.

Related Papers

Nanoscale Dynamics at Liquid/Solid Interfaces:
(Dr. Zhihai Li, and Sepideh Afsari)
We use surface charge to control adsorbate-substrate interactions and to tune dynamics at solid-liquid interfaces. We use Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM) to study the resulting phenomena:
- Molecular redox dynamics at electrode-electrolyte interfaces.
- Molecular diffusion and self-assembly.

Related Papers

Previous studies:
- Dynamics of surface reconstruction and lifting of the reconstruction, nanoscale islands decay/growth.
Atomic and Molecular STM/AFM at Liquid/Solid Interfaces (Yufan He, Tao Ye)
- Potential driven phase transition in aromatic Self-assembled Monolayer (SAM) (Kyoungja Seo)
- Read/Write/Erase nanolithography (Kyoungja Seo)

Properties of Carbon Nanotubes and other Carbon Materials:
(Lan Nguyen)
Understanding the interaction between molecules and carbon nanotubes is key to a number of applications. We use NIR, Raman, FTIR, thermogravimetric analysis, TEM, AFM and TPD under vacuum conditions to probe molecular interactions with, and chemical functionality on, carbon materials. Environmental applications include development of solar energy harvesting devices as well as new and better sorbents for pollution control.

Our current interests focus on:
- Identification and quantification of chemical functionalities on the surfaces of carbon materials, including nanotubes
- Photophysical properties of carbon nanotubes
- Carbon nanotube purification methods for the efficient removal of carbon and metallic impurities
- Interactions of simple molecules with carbon surfaces (nanotubes, carbon blacks)

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Nonlinear Optical Studies of Interfaces:
(Shalaka Dewan, Aziz Boulesbaa, Aashish Tuladhar, Asghar Razavi, and Devika Sil)
Second order non-linear optical techniques, e.g. Sum Frequency Generation (SFG) and Second Harmonic Generation (SHG), provide both ultrafast time resolution and interface selectivity. Current projects focus on SFG studies of ultrafast vibrational dynamics at aqueous interfaces, as well as acid-base equilibria at water-mineral surfaces.

Related Papers

Previous studies:
- SHG Spectroscopy & Dynamics of Semiconductor Interfaces (Dora Bodlaki, Vasiliy Fomenko, Julie Fiore, Catherine Faler)
- Nonlinear Optical Spectroscopy of Electrode-Electrolyte Interfaces (Vasiliy Fomenko)

Novel Ultra-Broadband IR Laser Sources:
(Aziz Boulesbaa)
We are developing ultrabroadband IR laser sources providing pulses with bandwidths >1000 cm^-1 in the ~1000 - 3000 nm wavelength range. (more information)

Related Papers

Previous studies:
- Transform-limited Picosecond Infrared OPA (Dora Bodlaki)

Sensors:

- Bio-Sensors
(Aseem Malhotra)
Detection of bio species (cells, proteins, antibodies, ...) by surface immobilization on piezoelectric sensor devices.

- Hydrogen and Humidity Sensors
(Olivier Katz, Uduak Odoeyo and Devika Sil)
In collaboration with ASRD, we are developing surface acoustic wave sensors for NASA applications.

Related Papers

Fluorescence Detection of Surface Functionality:

FLOSS (Fluorescence Labeling of Surface Species) exploits the sensitivity of fluorescence and the specificity of covalent bond formation to identify and quantify low concentrations of surface functionalities. FLOSS can distinguish between COOH, OH and aldehyde groups and detect down to 10¹¹ functional groups/cm2 on surfaces. This sensitivity is well beyond the detection limits of FTIR and XPS.

FLOSS has been applied to understand SAM photoreactivity and is being extended to other materials.

Related Papers

Previous studies:
- Growth, Stability and Photoreactivity of Self Assembled Monlolayers (Tao, Ye, Eric Mc Arthur)

Nanoprobe Studies:

We are developing carbon nano-pipettes as electrochemical probes for in-vivo studies of biological systems (e.g. cells).