Sensing Applications of Poly Hydroquinone Gold Nanoparticle Films

Gold nanoparticle (AuNP)–poly(hydroquinone) (polyHQ) films were grown on glass/ITO by electrophoretic deposition (EPD) from 15 nm citrate–AuNP solutions containing hydroquinone (HQ). Holding 1.4 V for 30 min while varying HQ concentration from 0.066–0.242 M (0.11–0.40 g in 15 mL) produced a morphology transition from sparse fractal dendrites (≤0.10 M) to dense, high-aspect “microneedles” (≥0.18 M). The needles arise from destabilization of citrate by HQ oxidation(local pH change), AuNP chain growth, and concurrent electro-polymerization of HQ that welds particles into Au-rich, polyHQ-bound structures. With the increase in EPD deposition time (1→30 min) and HQ concentration, the films become thicker and are more resistant to current flow showing diode like behavior. Scanning electron microscopy (SEM), optical microscopy and digital images revealed distinct anisotropic growth, with needles several microns wide and millimeters in length extending several hundred nanometers to microns from the electrode surface. The presence of HQ was confirmed by FTIR spectroscopy. The AuNP-polyHQ films on Au-Interdigitated electrodes (IDE) showed rapid, reversible conductometric changes due to the swelling of PHQ film and modulation of AuNP percolation pathways to certain vapors namely acetone, ethanol and isopropyl alcohol while being unresponsive to toluene and water under standard atmospheric conditions. The gas sensing was monitored by performing Chronoamperometry and applying positive and negative bias versus air. In the future, we look to monitor the electrochemical detection of dopamine- a neurotransmitter as the films display a surface-confined polyHQ/quinone couple centered at ~0.15–0.25 V vs Ag/AgCl in phosphate-buffered saline.