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A versatile "Spray-n-Sense" sprayable nanofiber technology for on-site chemical detection is demonstrated. Driven by compressed gas, the "Sprayn-Sense" nanofibers, as the name suggests, can be directly sprayed onto any kind or shape of surfaces, while the embedded chemical reporter enables simple colorimetric/fluorometric detection. Herein, nanofibers are sprayed on several surfaces including cardboard, glass, plastic, and rubber. The sensing capabilities of the "Spray-n-Sense" nanofibers are established through the detection of three different analytes including two metal ions (Fe 2+ and Fe 3+ using 1,10-phenanthroline and curcumin as chromogenic reporters, respectively) and ammonia (using rhodamine-B as a fluorogenic reporter) in aqueous media. Additional to being highly portable, the "Spray-n-Sense" nanofibers show impressive sensor characteristics with a sub-ppm lower limit of detection (LLOD) for Fe 2+ and a wide linear working range. Whereas, the LLOD of 6.2 and 32 ppm is achieved for Fe 3+ ions and ammonia, respectively. A custom-designed smartphone application enables quantitative analysis for reliable on-site sensing. The selectivity and specificity are imparted by the embedded reporter, and thus allow analyte detection in complex real-life samples and simultaneous detection of multiple chemical species through co-doping. The "Spray-n-Sense" nanofibers also allow for the detection of target analytes in solid samples.

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