Spring 2008 Events

March 19, 2008
A History and Evolution of ICP-MS Technology
Steve Shuttleworth, PhD, of Varian Instruments, Inc.
6:00 pm
Since its commercial introduction in the mid 1980's, ICP-MS has evolved from a pure research tool to a routine technique for the trace elemental analysis of a wide range of matrices. This talk will include a history of the technique including a discussion of why early researchers realized a need for a mass spectrometer to be attached to an ICP source. The talk will also chart the evolution of ICP-MS technology from initial designs to a discussion of today's state of the art instruments and how they work. The various methods for interference management including high resolution, dynamic reaction cell (DRC), collision cell and collision reaction interface (CRI) will be discussed. Comparative techniques such as AA and ICP will also be discussed including analytical figures of merit and sample preparation requirements.

Location: Science Center Room 4102
The Graduate Center of the City of New York
365 Fifth Avenue, New York, NY

April 30, 2008
In-situ Fabrication of Conducting Polymer Nanocomposites for Biosensing Applications: Multiple Roles of DNA Functionalized Carbon Nanotubes
Prof. Huixin He, Rutgers University
6:00 pm

Conducting polymers are attractive for sensor applications because their electronic and electrochemical properties are highly sensitive to molecular interactions, which provide excellent signal transduction for molecular detection. Among conducting polymers, polyaniline is unique since it is environmentally stable and easy to fabricate. It has been applied widely in chemical sensors but not as much in biosensors. The reason is that native polyaniline is neither electrochemically active nor conductive in neutral solutions, which is a prerequisite for biosensor applications. It is also limited both in the variety of molecules that can be detected and in the selectivity of the detection. Major breakthroughs in this field were the discoveries of self-doped polyaniline and polyelectrolyte-anion-doped polyaniline, which brought polyaniline into the biosensor field due to the improved redox activity and conductivity in neutral pH solutions. However, compared to the parent polyaniline, the electrochemical activity, conductivity, and the chemical and mechanical stabilities of both self-doped polyaniline and bulky polyelectrolyte-doped polyaniline are greatly reduced due to steric effects.

Here we report that the stability of a self-doped polyaniline, poly(anilineboronic acid) in this work, is greatly improved when it is polymerized in-situ with ss-DNA-wrapped single walled carbon nanotubes (ss-DNA/SWNTs). The conductivity and redox properties of the polyaniline backbone are conserved in neutral solutions (pH = 7.4), and the sensitivity for biomolecular detection is significantly enhanced. We found that the ss-DNA/SWNTs performed multiple roles in the greatly improved properties of the self-doped polyaniline both during and after the polymerization, which makes this work unique compared to previously reported conducting polymer/carbon nanotube composites. First, the ssDNA/SWNTs acted as effective catalytic molecular templates during polymerization of self-doped polyanline so that not only was the polymerization speed increased, but also the quality of the polymer was greatly improved. Second, they functioned as novel active stabilizers after the polymerization, which significantly enhanced the stability of the film. Furthermore, the ss-DNA/SWNTs also acted as conductive polyanionic doping agents and conductive bridges in the resulting polyaniline film, which showed enhanced conductivity and redox activity. Finally, the large surface area of carbon nanotubes greatly increased the density of the functional groups available for sensitive detection of the target analyte.

Using this material, we developed a non-oxidative approach to electrochemically detect neurotransmitter dopamine with extremely high sensitivity. More importantly, since direct oxidation of dopamine on the electrode was not involved in this sensing approach, its related problems were thus avoided. The high sensitivity along with the improved selectivity of this sensing approach may hold great promise for molecular diagnosis of Parkinson's disease. Changing the functional groups along the polyaniline backbone, we developed extremely sensitive approach for detection of trace level neural toxins, which has been used as chemical warfare agents.

Biosketch: Dr. Huixin He received her PhD in Peking University, China in 1997. She joined National University of Singapore as a research associate, working mainly on plastic microfluid channels and micropatterns by soft lithography. In 1999, she came to the United States working with Professor Nongjian Tao, first in Florida International University and then Arizona State University. At this period time, she was mainly working on molecular electronics, including the electronic properties of metallic quantum wires and single chain conducting polymer wires. In 2002, she joined chemistry department, Rutgers University at Newark, as an assistant professor. Her current research interests include conducting polymer nanocomposite, especially in the fundamental study of interaction at interfaces in the composite and exploration of the composite materials for chemical and biosensor applications. She is also actively working on developing nonviral gene delivery system using these nanocomposites and other nanomaterials.

Location: Science Center Room 4102
The Graduate Center of the City of New York
365 Fifth Avenue, New York, NY