A Versatile Probe for Caffeine Detection in Real-Life Samples via Excitation-Triggered Alteration in the Sensing Behavior of Fluorescent Organic Nanoaggregates

Excitation triggered alteration in the sensing behavior of fluorescent nanoaggregates was explored in water, considering caffeine as the target analyte. Merely by changing the excitation wavelength, we could specifically excite either the monomeric species or the fluorescent nano aggregates. The monomer showed highly sensitive interaction with caffeine despite poor selectivity, while the strongly associated fluorescent nano aggregates displayed relatively high selectivity with low sensitivity. In addition, the extent of self-aggregation was also found to be influenced by the micropolarity of the local surroundings and the electronics of the core carbazole unit. Furthermore, the present protocol was utilized for the estimation of caffeine in different beverages and biological fluids with reasonably high accuracy. Inexpensive, portable paper strips were designed for a rapid, on-site detection of caffeine without involving sophisticated instruments or trained technicians.