The ability to detect high explosive compounds is a fundamental step in achieving the goal of creating devices capable of
'sniffing' out explosive devices. To detect high explosive compounds such as 2,4,6-trinitrotoluene (TNT), a molecularly
imprinted polymer (MIP) sensor was developed. This sensor consists of MIP microspheres prepared using methacrylic
acid as the functional monomer in a precipitation polymerization reaction. The MIP microspheres are then combined
with fluorescent semiconductor nanocrystals, or quantum dots, via a simple crosslinking procedure. To study the
sensor's ability to detect nitroaromatic analytes, the fluorescent-labeled MIP particles were exposed to aqueous 2,4-
dinitrotoluene (DNT), a nitroaromatic molecule very similar to TNT. Characterization of the MIP particles shows a
uniform size distribution, with an average diameter of approximately 615 nm. Imaging of the particles also shows that
spherical shapes are being produced by the precipitation polymerization reaction. Preliminary data indicate that the
sensor is capable of detecting nitroaromatic compounds in an aqueous solution. These results illustrate the future
application of the fluorescent-labeled MIP sensor for detecting high explosives, with the potential for use in detecting
vapors from explosive devices and in an array of environmental conditions.
Molecular recognition is an important aspect of any biosensor system. Due to increased stability in a variety of
environmental conditions, molecular imprinted polymer (MIP) technology is an attractive alternative to biological-based
recognition. This is particularly true in the case of improvised explosive device detection, in which the sensor must be
capable of detecting trace amounts of airborne nitroaromatic compounds. In an effort to create a sensor for detection of
explosive devices via nitroaromatic vapor, MIPs have been deployed as a molecular recognition tool in a fluorescence-based
optical biosensor. These devices are easily scalable to a very small size, and are also robust and durable. To
achieve such a sensor scheme, polymer microparticles synthesized using methacrylic acid monomer and imprinted with a
2,4-dinitrotoluene (DNT) template were fabricated. These microparticles were then conjugated with green CdSe/ZnS
quantum dots, creating fluorescent MIP microparticles. When exposed to the DNT template, rebinding occurred
between the DNT and the imprinted sites of the MIP microparticles. This brings the nitroaromatic DNT into close
proximity to the quantum dots, allowing the DNT to accept electrons from the fluorescent species, thereby quenching the
fluorescence of the quantum dot. Results indicate that this novel method for synthesizing fluorescent MIPs and their
integration into an optical biosensor produced observable fluorescence quenching upon exposure to DNT.
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