A colorimetric sensor array for identification of toxic gases below permissible exposure limits

Abstract

A colorimetric sensor array has been developed for the rapid and sensitive detection of 20 toxic industrial chemicals (TICs) at their PELs (permissible exposure limits). The color changes in an array of chemically responsive nanoporous pigments provide facile identification of the TICs with an error rate below 0.7%.Chemists have no equivalent of the physicists' radiation badge: there is no readily available general purpose method to easily measure the low levels of personal exposure that workers may receive to the diverse range of volatile TICs used in laboratories, manufacturing facilities, or general storage areas. 1,2 There are numerous conventional methods 2 for the detection of gas phase hazardous chemicals, including GC/MS, 3 IMS, 4 electronic nose technologies, 5 and of course colorimetric detectors tailored to specific single analytes. 2 Most such detection technologies, however, suffer from severe limitations: GC/MS is expensive and non-portable; IMS has limited chemical specificity; and electronic nose technologies have restricted selectivity, sensitivity, and resistance to environmental interference (e.g., humidity).In recent years, we have developed a rather different optoelectronic technique using colorimetric sensor arrays made from chemically responsive dyes. This array approach 6,7 is based on strong dye-analyte interactions and differs from other electronic nose technologies that generally rely on the weaker and less specific intermolecular interactions (i.e., van der Waals and physical adsorption). The chemically responsive dyes in our colorimetric array include (1) metal ion containing dyes (e.g., metalloporphyrins) that respond to Lewis basicity, (2) pH indicators that respond to Brønsted acidity/basicity, (3) vapochromic/solvatochromic dyes that respond to local polarity, and (4) metal salt redox indicators (see ESI, † Fig. S1).We have very recently improved our array methodology by the use of chemically responsive nanoporous pigments created from the immobilization of dyes in organically modified siloxanes (ormosils). 8, 9 Porous sol-gel glasses provide excellent matrices for colorants due to high surface area, relative inertness in both gases and liquids, good stability over a wide range of pH, and optical transparency. In addition, the physical and chemical properties of the matrix (e.g., hydrophobicity, porosity) can be easily modified by changing the sol-gel formulations. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptThe use of nanoporous pigments significantly improves the stability and shelf-life of the colorimetric sensor arrays and permits direct printing onto non-permeable polymer surfaces. 9,10 Additionally, we observe that the porous matrix serves as a preconcentrator thereby improving the overall sensitivity. 10 We report here the application of colorimetric sensor arrays to the identification and semiquantitative analysis of toxic industrial chemicals at their PELs and demonstrate limits of recognition below 5% of the PELs. We chose 20 repre...

An ultrasensitive method of real time pH monitoring with complementary metal oxide semiconductor image sensor

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Classification of Mineral Waters Based on Digital Images Acquired by Smartphones

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Colorimetric sensing of anions in water using ratiometric indicator-displacement assay

“…In this paper, we have significantly improved our colorimetric IDA methodology by the combination of array technologies and pattern-recognition methods. Sensor array technologies [34,35] have been broadly applied for the determination of toxic industrial gases [36][37][38][39], heavy metal cations [40][41][42], nucleic acid and biomolecules [43,44], diols [45], and even for diagnostics [46]. Array-based cross-reactive fluorescence sensor for multianion detection in water has also been developed recently [22,23].…”