Fluorescent polymeric sensors containing boronic acid derivatives for sugars and dopamine detection. Sensing characteristics enhancement by Au NPs

Two boronic acid copolymers were synthesized by free radical polymerization of 3-acrylamidophenylboronic acid/4-vinylphenylboronic acid with N-acryloyl-l-alanine and vinyl acetate to investigate the role of the boronic acids in the fluorescence response mechanism. The structure and the chemical composition of the formed copolymers (COP-1, COP-2) were confirmed by 1HNMR and FTIR spectroscopy. The UV–vis spectrum profiles of the copolymers are similar, meanwhile their emission spectra (λex = 330 nm) are different: COP-1 has two emission bands (386 nm and 500 nm) and COP-2 emits blue fluorescence with a single maximum in its spectrum (385 nm). Both copolymers were tested as fluorescent sensors at physiological pH for detection of diols, namely sugars (glucose, sucrose) and catecholamines (dopamine), COP-1 showing higher efficiency for such compounds. Also, the sensitivity for dopamine (Cmin = 4 × 10−5 M) was higher than for the sugar derivatives (Cmin = 6 × 10−4 M) and the fluorescence quenching of the copolymers mainly occurred through dynamic processes. An enhancement of sensor sensitivity was performed by the in situ photogeneration of gold nanoparticles (Au NPs) in COP-1 solution upon exposure to UV irradiation. The minimal dopamine concentration detected was 4 × 10−6 M, and the value was lower with an order of magnitude compared to COP-1 alone (4 × 10−5 M).