Use of metal-organic frameworks and metal oxides for sensing chemicals using electrical impedance spectroscopy

Inventors

Peterson, Gregory W • Fountain, III, Augustus W • Soliz, Jennifer R • Hauser, Adam J

Assignees

United States Department of the Army • Government of the United States of America

Abstract

Provided are processes for the sensitive detection of the presence of, absence of, and optionally the identity of, one or more chemical agents. The processes use the binding of chemical agents to a metal organic framework or metal oxide/hydroxide electrically connected to a pair of electrodes to detect low levels of chemical in a sample. By exposing the surface of the metal organic framework or the surface of the metal oxide/hydroxide to the chemicals and then measuring changes in impedance magnitude and/or phase shift through electrical impedance spectroscopy, the presence of a chemical agent is readily detected.

Core Innovation

The invention provides processes for the sensitive detection of the presence, absence, and optionally the identity of one or more chemical agents by using electrical impedance spectroscopy (EIS). The processes utilize the binding of chemical agents to a metal organic framework (MOF) or metal oxide/hydroxide electrically connected to a pair of electrodes to detect low levels of chemicals in a sample. Changes in impedance magnitude and phase angle caused by the adsorption or absorption of chemicals onto these materials enable highly sensitive and selective chemical detection.

Current detection methods for explosives or toxic chemicals, including ion mobility mass spectrometry, gas chromatograph mass spectrometry, and Raman spectroscopy, though selective, suffer from shortcomings such as low resolution, side reactions, variation in response, limited detection range, bulky equipment, and requirement of significant training. Colorimetric systems are subjective and lack mechanisms for identification of unknown chemicals. There is therefore a need for improved materials, methods, and devices for field detection of analytes such as explosives.

The invention addresses this need by using surfaces comprising one or more detection agents which are metal organic frameworks, metal oxides, or combinations thereof, that selectively bind target chemical compounds. These surfaces are intermediate to and electrically connected to a pair of electrodes and are subjected to electrical impedance spectroscopy by applying alternating current across a broad frequency range, optionally with applied voltages between 10 millivolts and 10 volts. The interaction of chemicals with these detection agents causes measurable changes in capacitance, impedance magnitude, and phase angle, facilitating fingerprint-specific and highly sensitive detection. The detection agents may include porous media and can be combined with polymers exhibiting dielectric properties. The invention enables reusable and reversible detection surfaces such as interdigitated capacitors suitable for in-field use without bulky equipment.

Claims Coverage

The patent discloses two independent claims encompassing processes for detecting chemicals by using detection agents comprising metal organic frameworks or metal oxides with electrical impedance spectroscopy.

These independent claims cover processes employing specific detection agents comprising metal organic frameworks and metal oxides associated with electrodes, utilizing electrical impedance spectroscopy over defined frequency ranges to detect chemicals, including toxic and explosive substances, through changes in impedance characteristics.

Stated Advantages

Documented Applications