Reliable ratiometric colorimetric monitoring of dopamine in practice based on the catalytic signal amplification of nano CeO2/CuO modified carboxylated chitosan

Abstract

To reliably monitor dopamine (DA), a common neurotransmitter, a kind of nano CeO2/CuO modified carboxylated chitosan nanozyme (CeO2/CuO@CC) was constructed under microwave-assisted conditions. The proposed CeO2/CuO@CC exhibited superior synergistic- enhancement oxidase-like activity, with high specific surface area and superior stability. It could accelerate the oxidization of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxTMB in the air. What’s more, the presence of trace DA could exclusively change the enzyme-like activity of CeO2/CuO@CC, accompanied with visual color changes from blue to colorless. Under the optimized conditions, there expressed double ratiometric linear relationships between lg(A652/A285)/lg(A370/A285) and cDA, with a large linear range between 6.0 × 10−9 and 1.0 × 10−5 M of DA. When applied for visual detection of DA in real samples, the detection limit was low to 2.0 × 10−9 M with RSD % less than 4.14 %. The mechanisms for enhanced oxidase-mimic activity of CeO2/CuO@CC and its selective detection of DA were proposed. This work will offer an insight to design efficient nanozyme for visual detection of bio-analytes in practice.