Postdoc, University of Illinois at Urbana-Champaign
Developed a polymer-based colorimetric sensor array for the detection of explosives and biomarkers
Developing a sensitive, rapid and inexpensive sensor for in-situ detection of hazardous analytes has become an urgent need in many aspects, from security screening to food inspection and to health monitoring. The use of colorimetric sensor arrays has proven to be a fast and effective method for liquid or gas analysis where the specificity derives from the pattern of response from sets of cross-reactive and chemoresponsive dyes. Colorimetric sensor arrays have seen successful applications in differentiating diverse families of analytes, ranging from single compounds to composite mixtures, including industrial toxins, foods and beverages, bacteria and fungi. As a continuation of this work, a hand-held reader equipped with a color contact image scanner (CCIS) was integrated with a 40-element colorimetric sensor array to target a broad range of home made explosives (HMEs), including various nitro-compounds and two peroxide-based explosives, triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD). New sensors incorporated include ones that use Fenton reagent (Fe(II) acetate), redox-sensitive dyes (e.g., toluidine and o-dianisidine), transition metal-containing chromogens for nitro-compounds, and optimized Brady’s and Schiff test for ketones. Using multivariate analysis, successful classification results were achieved to group 15 generic explosives into 12 separate groups with the accuracy >99%, as well as 9 variations of TATP and 3 variations of HMTD into 12 separate clusters with the accuracy >96%. Possible applications of the sensor arrays in medical diagnosis were also explored. As an example, I have successfully quantified several biomarkers in the simulated human urine and blood samples, including trimethylamine (TMA), trimethylamine N-oxide (TMAO) and creatinine with relevance to point-of-care evaluation of renal function and diagnosis of a metabolic disease, trimethylaminuria (TMAU). I made use of porous sol-gel formulations to obtain better sensor response to biomolecules and ideal hydrophobicity of the matrices to minimize the dissolution of the dyes during liquid sensing. Detection limits in aqueous phase are ~2 μM for TMA, ~4 μM for TMAO and ~10 μM for creatinine, all of which are well below the diagnostically significant levels. Sensors show great selectivity towards three targeted analytes against other possible interferents (e.g., amino analogues), indicating its promising applications in medical diagnosis.
Abstract: A disposable colorimetric sensor array (CSA) made from printing various chemically responsive dyes was combined with a hand-held device for on-site assessment and monitoring of the freshness of five meat products: beef, chicken, fish, pork, and shrimp. The hand-held device takes advantage of an on-board diaphragm micropump and a commercial 1D CMOS camera (CIS) which enables the real-time collection of colorimetric data. The sensor array shows excellent sensitivity to gaseous analytes, especially amines and sulfides at low ppb levels; excellent discrimination among meat volatiles in terms of meat type and storage time was demonstrated with multiple chemometric approaches including principle component analysis, hierarchical cluster analysis, and support vector machine analysis. This optoelectronic nose proves to be a promising supplement to other available techniques for meat product inspection.
Pub.: 02 Nov '16, Pinned: 14 Jun '17
Abstract: Forensic identification of batches of homemade explosives (HME) poses a difficult analytical challenge. Differentiation among peroxide explosives is reported herein using a colorimetric sensor array and handheld scanner with a field-appropriate sampling protocol. Clear discrimination was demonstrated among twelve peroxide samples prepared from different reagents, with a classification accuracy >98%.
Pub.: 05 Sep '15, Pinned: 14 Jun '17
Abstract: Sensitive detection of trimethylamine both in aqueous and gaseous phases has been accomplished using an inexpensive colorimetric sensor array. Distinctive color change patterns provide facile discrimination over a wide range of concentrations for trimethylamine with >99% accuracy of classification. Calculated limits of detection are well below the diagnostically significant concentration for trimethylaminuria (fish malodor syndrome). The sensor array shows good reversibility after multiple uses and is able to cleanly discriminate trimethylamine from similar amine odorants. Portable sensing of trimethylamine vapors at ppb concentrations is described using a cell phone camera or a hand-held optoelectronic nose. Application of the sensor array in detecting mouth and skin odor as a potential tool for portable diagnosis of trimethylaminuria is also illustrated.
Pub.: 24 May '16, Pinned: 14 Jun '17