A Nanocontact Sensor for Heavy Metal Ion Detection

EPA Grant Number: R829623
Title: A Nanocontact Sensor for Heavy Metal Ion Detection
Investigators: Tao, Nongjian
Institution: Arizona State University - Main Campus
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 2002 through December 31, 2004 (Extended to March 19, 2006)
Project Amount: $375,000
RFA: Exploratory Research: Nanotechnology (2001) RFA Text |  Recipients Lists
Research Category: Nanotechnology , Safer Chemicals


As materials and devices shrink to the nanometer scale, various quantum phenomena become important, which may lead to novel applications, including those that are important to environmental analysis and protection. This project exploits the phenomena of conductance quantization and quantum tunneling to fabricate nanoelectrodes for in situ detection of metal ion pollution. Our goal is to develop a high performance and low-cost sensor for initial on-site screening test of surface and groundwater to provide early warning and prevention of heavy metal ion pollution. The existing analytical techniques usually require preconcentration of samples to detect trace metal ions, which can be time consuming and prone to cross-contamination. Moreover, many of the sensitive techniques, such as inductively coupled plasma-mass spectrometry, are not suitable for on-site monitoring. In contrast, the nanocontact sensor has the potential of detecting even a few metal ions without preconcentration and is particularly suitable for on-site detecting ultratrace level of heavy metal ions, including radioactive elements.


The sensor consists of an array of nanoelectrode pairs on a silicon chip. The nanoelectrodes in each pair are separated with an atomic scale gap, which is achieved with the help of quantum tunneling phenomenon. Electrochemical deposition of even a few metal ions into the gap can bridge the gap and form a nanocontact between the nanoelectrodes, thus triggering a quantum jump in the electrical conductance. The sensor can achieve high specificity by combining several different measurements, such as redox potentials, point-contact spectroscopy and electrochemical potential-modulated conductance changes.

Expected Results:

We anticipate that this project will lead to a prototype nanocontact sensor for detecting heavy metal ion pollution in water. In addition to the unprecedented sensitivity, the sensor will be miniaturized and cost-effective, which should be particularly suitable for initial on-site screening test of polluted samples, thus leading to early warning and prevention of heavy metal ion pollution. The capability to measure and control electrochemical deposition/stripping of a single or a few metal ions to be fully developed in this project may provide opportunities for a better understanding of electroanalytical chemistry of metal ions, and lead to new environmentally benign fabrication methods for nanoelectronics.

Publications and Presentations:

Publications have been submitted on this project: View all 54 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 13 journal articles for this project

Supplemental Keywords:

nanotechnology, scanning tunneling microscopy, atomic force microscopy, electrochemistry, physics, engineering, monitoring and measurement methods., RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, Chemical Engineering, Environmental Chemistry, Monitoring/Modeling, Environmental Monitoring, Chemistry and Materials Science, Engineering, Chemistry, & Physics, Environmental Engineering, monitoring, metal ion pollution, nanotechnology, metal ions, heavy metal ion detection, surface water, nanocontact sensor, scanning tunneling microscopy, measurement, sensor, heavy metals, sensor technology, groundwater

Progress and Final Reports:

  • 2002 Progress Report
  • 2003 Progress Report
  • 2004
  • 2005
  • Final Report