Site-selective deposition of ultra-fine Au nanoparticles on polyaniline nanofibers for H₂O₂ sensing

Ultra-fine and uniform gold nanoparticles (AuNPs, 2 nm) were selectively reduced on polyaniline nanofibers (PANFs) without using protective agents. The water-dispersible PANFs, which acted as the reductant, provided a high surface area to absorb and react with chloroaurate anions (AuCl₄^-). In-situ UV-vis spectra indicated that the imine sites on PANFs formed complexes with AuCl₄^-. The AuNPs were then selectively produced on these sites, resulting in a uniform distribution of AuNPs on PANFs as evidenced by transmission electron microscopy. A possible mechanism for the formation of the AuNPs-PANFs nanocomposite is proposed. The Fourier transform infrared spectroscopy and X-ray diffraction results indicate a strong interaction between AuNPs and PANFs. This strong interaction would accelerate the redox reactions for both PANFs and AuNPs, and enhanced the anodic oxidation of H₂O₂. The nanocomposite electrode of AuNPs-PANFs (3 μg with 45 wt% AuNPs) on a glassy carbon electrode (GCE) exhibited a fast response time (less than 3 s) and a high sensitivity (8.34 mA M^-1) for H₂O₂ sensing. Our findings suggested that the obtained nanocomposite electrode may find interesting applications in biosensors.