Photoelectrochemical sensor based on Fe-g-C3N4/modified halloysite nanotube (MHNT) composite electrode for highly selective and stable detection of dopamine

A dual modification strategy combining MHNT tubular structure and Fe doping is proposed. • MHNT tubular structure offers high surface area and effective charge transport channels. • Fe doping introduces impurity levels to tailor the band structure of g-C 3 N. • Photoelectrode material maintains stable photoelectrochemical response after one-year ambient storage. Dopamine (DA), a key neurotransmitter in the central nervous system, exhibits concentration abnormalities that are closely associated with various neurological disorders. Thus, its accurate and stable detection in biological samples is crucial for early diagnosis. In this study, using melamine as a precursor, hydrochloric acid-modified halloysite nanotubes (MHNT) as a porous support material, and FeCl 3 ·6H 2 O as an iron source, an Fe-doped graphitic carbon nitride/halloysite nanotube (Fe-g-C 3 N 4 /MHNT) composite photoelectrode material was successfully synthesized via a hydrothermal dispersion combined with high-temperature calcination method. A photoelectrochemical sensor was subsequently constructed for dopamine detection. Fe doping effectively modulated the band structure of g-C 3 N 4 , broadening the visible light absorption range and suppressing the recombination of photogenerated charge carriers. Meanwhile, the tubular structure of MHNT provided a high specific surface area and efficient charge transport pathways. Under optimized conditions, the sensor exhibited good linearity in the concentration ranges of 10–200 μM and 200–2300 μM, with a sensitivity of 0.527 μA·μM −1 ·cm −2 and a detection limit as low as 0.28 μM (S/N = 3). Moreover, the sensor demonstrated excellent selectivity for dopamine in the presence of interfering substances in simulated body fluid. Notably, after one year of storage at room temperature, the sensor retained a stable linear photocurrent response with a detection limit of only 0.39 μM (S/N = 3), indicating outstanding long-term storage stability. This work effectively overcomes the intrinsic drawbacks of g-C 3 N 4 , including insufficient active sites and rapid charge carrier recombination, through the synergistic strategy of MHNT incorporation and Fe doping, providing a viable pathway for the development of highly selective and stable photoelectrochemical sensors. Download: Download high-res image (201KB) Download: Download full-size image