Pocket-sized lab: rapid screening of Fe(III), Na(I), and pyridoxamine via a smartphone-enabled fluorescent PAD

The presented research work demonstrates the development of a naphthalene-armed calix[4]arene-based ICT-CHEF fluorescence sensor p-tert-BuNHC for recognition of Fe(III) and Na(I). The linear concentration range for Fe(III) and Na(I) is 0-110 µM with detection limits of 1.083 μM and 0.433 μM, respectively. Moreover, the complex formation of p-tert-BuNHC with both ions has been confirmed using UV-visible analysis, MALDI-TOF mass spectrometry, FT-IR, and powder X-ray diffraction (PXRD). This fluorescence technique has also been validated for Fe(III) and Na(I) using spinach, table salt, kiwi, and orange as real samples. To make this sensor system more efficient, p-tert-BuNHC:Fe(III) has been utilised as a secondary sensor for the detection of pyridoxamine dihydrochloride (PYD) vitamin possessing a detection limit of 6 µM. The prepared ligand p-tert-BuNHC has also been fabricated in a paper-based analytical device (PAD) to discover Fe(III), Na(I), and PYD via an RGB study using a smartphone.