Ultrasonic spray pyrolyzed Cr-doped NiO for non-enzymatic photoelectrochemical dopamine sensing

This study presents a non-enzymatic photoelectrochemical (PEC) dopamine (DA) sensor based on chromium-doped nickel oxide (Cr:NiO) thin films synthesized via ultrasonic spray pyrolysis (USP), offering a simple, low-cost, and scalable fabrication route. Cr doping enhances the PEC response to DA by improving interfacial charge-transfer behavior, as supported by electrochemical characterization (CV and chronoamperometry, EIS). The developed sensor exhibits a broad linear detection range from 0.001 mM to 2 mM with a low detection limit of 1 nM. Among all samples, the 4% Cr:NiO electrode provides the highest sensitivity and selectivity toward DA compared with pristine NiO and lower doping levels. USP-prepared Cr:NiO is a favourable earth-abundant photoactive platform for non-enzymatic dopamine sensing. This provides a feasible and materials-engineering-relevant method to utilize dopant-induced defect modulation for the development of advanced PEC sensing techniques.