1-Pyrene carboxylic acid functionalized carbon nanotube-gold nanoparticle nanocomposite for electrochemical sensing of dopamine and uric acid

A highly sensitive, selective and cost effective method is described for sensing dopamine (DA) and uric acid (UA). A glassy carbon electrode (GCE) was modified with a nanocomposite consisting of gold nanoparticle-loaded multi-walled carbon nanotube (CNT) modified with 1-pyrene carboxylic acid (PCA). The stable aqueous dispersion of non-covalently functionalized CNT-PCA is an efficient bioprobe for the ultra sensitive and selective detection of dopamine and uric acid in the presence of the potentially interfering agent ascorbic acid (AA). The presence of PCA on the CNT introduces anionic carboxyl groups which repel ascorbate. The presence of the pyrene group augments high electrocatalytic activity towards oxidation of DA and UA, and the gold nanoparticles contribute to the amplification of the signal. The modified GCE gives an excellent peak current with well distinguishable peaks for AA, DA and UA (near -0.08 V, +0.14 V, and +0.22 V vs Ag/AgCl) in differential pulse voltammetry. Chronoamperometric detection of DA (working potential of 0.16 V vs Ag/AgCl) and UA (working potential of 0.3 V vs Ag/AgCl) showed linear ranges of 1 nM-150 mu M (LOD 1 nM) and 1 mu M-240 mu M (LOD 1 mu M) for DA and UA, respectively. The nanoprobe was validated by monitoring the recovery of spiked DA and UA in human blood serum samples which indicated a recovery within +/- 2%.