Single Molecule Conductivity in Organic and Biomimetic Molecules:
(Dr. Zhihai Li, Sepideh Afsari, and Ellen Kim)
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.
Nanoscale Dynamics at Liquid/Solid Interfaces:
Properties of Carbon Nanotubes and other Carbon Materials:
(Aashish and Linh Duong)
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)
Nonlinear Optical Studies of Interfaces:
(Shalaka Dewan, Aziz Boulesbaa, Aashish Tuladhar, 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.
Novel Ultra-Broadband IR Laser Sources:
We are developing ultrabroadband IR laser sources providing pulses with bandwidths >1000 cm-1 in the ~1000 - 3000 nm wavelength range. (more information)
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.
We are developing carbon nano-pipettes as electrochemical probes for in-vivo studies of biological systems (e.g. cells).