Fabrication of silver and gold nanoparticles microelectrode by flow deposition technique for lab on a chip application

Abstract

In this research, silver and gold nanoparticles electrodes were fabricated using layer-by-layer technique combining with the flow deposition methods. Pre-designed microfluidic channels were used as templates for the desired electrode. The nanoparticles was alternatively flow with poly(diallyldimethyl amonium chloride) (PDADMAC) through the template. First, the silver nanoparticles were synthesized using either humic acid (HA), poly(4-styrenesulfonic acid-co-maleic acid) (PSS-co-MA) or alginic acid as a stabilizing agent. Sodium citrate was used as stabilizing agent and reducing agent for gold nanoparticles preparation. The multilayer thin film electrode fabricated with the gold nanoparticles using 30 mM sodium citrate as reducing and stabilizing reagents shown the best conductivity. The resistivity of the film was measured using 4 points probe. The resistivity as low as 10-6 ohm.cm was achieved after the deposition of only 6 layers of gold nanoparticles preparing with 30 mM sodium citrate. The thickness and morphology of the flow-printed multilayer microelectrode was characterized by atomic force microscopy (AFM) and field emission scanning electron microscope (FE-SEM). The performance of gold nanoparticles electrodes was then tested using AC current detection of potassium chloride (KCl) solution. The current detection of KCl solution of the ten different gold nanoparticles electrodes revealed good reproducibility with 0.29, 0.13 and 0.28 %RSD for detection of 1, 10 and 100 mM KCl concentrations. Moreover, the performance of an electrode was also tested, which showed a good precision (0.21, 2.18 and 0.08 % RSD for 1, 10 and 100 mM KCl concentrations, respectively). The physical contact test adapted from ASTM D3359 was also performed on the uncoated gold nanoparticles electrode comparing with the gold nanoparticles electrode coated polyelectrolyte multilayers thin films (PEMs). The PEMs coating on gold nanoparticles electrodes could prevent scratching of electrodes and did not affect its detection performace. The detection of carbaryl was investigated as the potential application for the fabricated electrode. First, humic acid was deposited on the PEMs-gold nanoparticles electrodes. When, the carbaryl binding with HA-PEMs-gold nanoparticles electrode, the 7 % drop of current was obtained. Moreover, in this study, the organic solvent resistance substrate was also developed. The poly(methyl methacrylate) (PMMA) and poly(dimethyl siloxane) (PDMS) substrates were coated with either PDADMAC/poly(sodium 4-styrenesulfonate)/(PSS) or chitosan/alginate. %Transmission was used to evaluate the performance of the developed surface of PMMA after dipping to the acetonitrile solution, while the modified PDMS substrate was evaluated by observation of the changing weight under exposing to chloroform vapor. The results showed that the substrate could be protected from organic solvent by simply coating technique as LBL technique