Program Highlights

High-Sensitivity Detector for Molecular Sensing using Magnetic Particles

S.-H. Liou, D. J. Sellmyer, R. Skomski, and R. Y. Lai
Nebraska MRSEC

The detection of noxious gases or bio-agents is important for various environmental and security needs. High sensitivity, sufficient selectivity and molecular recognition are key characteristics for such sensing. Nebraska MRSEC researchers have developed a scheme for molecular sensing using magnetic tracer particles and a microcantilever torsional magnetometer. An example of using this system with a detection process is illustrated in the Figure below. The feasibility of this technique is demonstrated with regard to successful chemical reactions and the magnetic moment sensitivity of about 7.2 x 10^-11 emu, which corresponds to the magnetic moment of a single Fe particle of 400 nm is diameter. (Damien Le Roy et al., J. Appl. Phys., 109, 07E532, 2011).

These programs are supported by the National Science Foundation, Division of Materials Research, Materials Research Science and Engineering Program, Grant 0820521.

Detection principle using trinitrotoluene (TNT) molecules: (a) the functionalization of the cantilevers with TNT molecules (zero magnetization).  (b) The TNT-analog molecules conjugated with magnetic tracer particles that occupy the TNT receptors (maximum magnetization), and (c) the exposure to TNT that triggers desorption of the magnetic particles from the cantilever surface. A steplike decrease of the magnetization proportional to the TNT concentration is then recorded.