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A macroarray immobilisation of fluorophores on filter papers for sensing metal ions by in-situ reductive amination and carbodiimide coupling is reported herein. Chemometric approaches resulted in a rapid discovery of sensors that can synergistically discriminate up to 12 metal ions with great prediction accuracies. Covalently bound on paper, sensoring scaffolds that were synthesised from the macroarray format can readily be adopted as practical paper-based sensors with great reusability and sensitivity, achieving the limit of detection at low nanomolar level with some repeating spotting. Lastly, the discovered scaffolds were also confirmed to be functional as unbound molecules, thus paving the way for more diverse applications.

A novel fluorescent turn-on cyanide sensor containing indolium salt as the selective CNreceptor was synthesized 2 steps via Sonogashira coupling and Knoevenagel reaction. The compound 2 was developed as a new fluorometric and colorimetric sensor for cyanide with a sensing mechanism through cyanide ion addition to the indolium group. Importantly, the inclusion complexes between compound 2 and α-cyclodrextin, exhibited fluorescent turn-on detection of CNin 100 % aqueous media with the detection limit of 1.3 μM. The turn-on signal is the result of the conversion of the conjugated hemicyanine moiety to cyano-hemicyanine group via the addition of cyanide ion. Using paper sensor strips, a naked eye detection of cyanide is possible down to 4.59 ng.mm -2 . Test strips based on compound 2 can act as a convenient and efficient CNtest kit.