Facile, size-controlled deposition of highly dispersed gold nanoparticles on nitrogen carbon nanotubes for hydrogen sensing

Highly dispersed gold nanoparticles (AuNPs) supported on nitrogen-doped multiwalled carbon nanotubes (NCNTs) were synthesized using an electrochemical method. Size of AuNPs and their dispersion profile were tuned in a facile manner by controlling the applied potential and deposition time. The structure of the films was characterized using SEM, HRTEM, XRD and Raman spectroscopy. Electron microscopy revealed that the nanoparticles were deposited homogeneously on the outer surface of the NCNTs in high density. The average dimensions of the AuNPs could be tuned by varying the applied voltage and the duration of the electrochemical process. The XRD patterns confirmed the presence of metallic fcc gold along with disordered graphitic phases. The Raman spectroscopy showed that NCNTs possess 3–5 at.% nitrogen with a heterogeneous distribution profile, which is consistent with nitrogen incorporation in both graphitic and pyridinic moieties within the carbon sp2 network of disordered NCNTs. SERS enhancement was also observed for AuNPs/NCNTs prepared at 10 V/20 min condition. Conductometric gas sensors were developed from the thin films of AuNPs/NCNTs nanocomposites and evaluated towards H2 gas. The sensors were exposed to different concentrations of H2 in synthetic air at room temperature. The highest sensitivity of 75% was measured towards 1% H2 when average size of AuNPs on NCNTs is about 4–6 nm.