The Wireless Sensing Detection Of Persistent Organic Pollutants And Pathogens

This dissertation is focused on the theoretics and the applications of the wireless magnetoelastic sensors. Environmental pollution is seriously global problems, especially caused by the pathogens and persistent organic pollutants (POPs). The wireless magnetoelastic technique is based on magnetoelastic principle, the sensor platforms consist of a magnetoelastic sensor and an exciting/a receiving coil. In response to a time varying magnetic field, the magnetoelastic sensor efficiently couples and translates magnetic energy to mechanical energy. The elastic energy mechanically deforms the sensor, causing it mechanically vibrate along its length. When the frequency of the ac field is equal to the mechanical resonance frequency of the sensor, the vibration amplitude is maximum, and the sensor vibrates at its characteristic resonance frequency that shifts in response to change of liquid properties (such as viscosity or density) or mass loading. Since the sensor material is also magnetostrictive, the mechanical oscillation in turn generates magnetic flux that can be remotely detected using a pick-up coil. The sensor is totally passive. No physical connections between the sensor and the detection system are required for signal telemetry, nor does the sensor require any internal power sources. The wireless nature of the magnetoelastic sensor makes it a powerful candidate for in situ and in vivo analysis. With the development of nano-technology, nano-materials due to its small size and large specific surface area and other features have begun to penetrate the field of environment among the detection and analysis. Combination of nano-particle properties and magnetic sensor wireless passive features, it will be a significant and meaningful work to research the detection methods of environmental contaminants. Based on this innovation, in this dissertation, three kinds of magnetoelastic biosensors were developed:(1) The development of wireless magnetoelastic pathogens sensor:Fabricate the wireless magnetoelastic pathogen sensor with Escherichia coli O157:H7 (E. coli) as a target using chitosan-modified magnetic Fe3O4 nanoparticles (CMNPs) as signal-amplifying tags; At suitable pH the CMNPs bind to negatively charged E. coli through electrostatic attraction. The E. coli attached CMNPs are magnetically bound to the surface of the magnetoelastic sensor, resulting in enhanced mass loading on the sensor surface that in turn decreases its resonance frequency allowing quantification of E. coli concentrations; investigate the sensor in response to the change of CMNPs and the effect of glutaraldehyde introduction; The sensor shows a linear response to the logarithmic concentration of E. coli in the range of 10 cells mL-1 to 3.7×108 cells mL-1, with a detection limit (LOD) of 10 cells mL-1; The sensor shows good selectively to bacterial detedction, as small molecules such as albumin bovine and ovalbumin show no interference on the detection.(2) The development of wireless magnetoelastic polycyclic aromatic hydrocarbons (PAHs) sensor:Fabricate the wireless magnetoelastic PAHs sensor with anthracene as the model target using humic acid-modified magnetic Fe3O4 nanoparticles (HMNPs) as signal-amplifying tags; A sandwich-type detection strategy involves the humic acid (HA)/chitosan composite self-assembled on the polyurethane-protected sensor surface and HMNPs, both of which flank the anthracene target in sequence. As the HMNPs-combined anthracene absorbs to the sensor surface, there is an increase in the mass load on the sensor, and consequently a decrease in resonance frequency; investigate the sensor in response to different coatings on the surface of magnetic sensors, different concentrations of HMNPs and pH; obtained the detection linear range and detection limit of six of the US Environmental Protection Agency (EPA) priority monitor PAHs; and investigate the sensor selectivity to PAHs by determining the sensor responses to some representative environmental pollutants; The highest sensitivity was observed in the response to benzo[a]pyrene and anthracene with LODs of 3 nM and 5 nM, respectively; the sensor can be used for detection of PAHs in water, and has the application prospect in enriching PAHs.(3) The development of wireless magnetoelastic benzo[a]pyrene (BaP) sensor: Based on (2), fabricate the wireless magnetoelastic BaP sensor using aminocalix[4]arene-modified gold nanoparticles (aminocalix[4]arene-Au NPs) as signal-amplifying tags; A sandwich-type detection strategy involves the aminocalix[4]arene self-assembled on the Au-protected sensor surface and aminocalix[4]arene-Au NPs, both of which flank the BaP target in sequence. As the aminocalix[4]arene-Au NPs-combined BaP absorbs to the sensor surface, there is an increase in the mass load on the sensor, and consequently a decrease in resonance frequency; investigate the sensor in response to different concentration aminocalix[4]arene-Au NPs, other PAHs and other pollution in water; as aminocalix[4]arene with BaP to form a stable 2:1 inclusion complexes, the sensor shows good selectivity to BaP detection and shows a detection limit of 1×10-11 M. The sensor can be used for detection of BaP in water.