Electrochemical synthesis of a gold atomic cluster-chitosan nanocomposite film modified gold electrode for ultra-trace determination of mercury.

Gold atomic cluster based nanocomposites are important in the field of energy and sensing applications due to their interesting optical, electronic, chemical and catalytic properties. In the present study a chitosan stabilized gold atomic cluster nanocomposite was synthesised by a simple electrochemical technique based on the anodic dissolution of a gold electrode in the presence of a cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), and a biopolymer, chitosan, on a gold electrode. The gold clusters formed were characterized by DLS, TEM, MALDI-TOF-MS, XPS, fluorescence and cyclic voltammetry. The developed gold atomic cluster-chitosan (AuAC-Chit) nanocomposite modified gold electrode was highly sensitive and selective for the electrochemical detection of Hg(ii) ions. It offers a wider calibration range of 10(-14)-10(-7) M with a limit of detection (LOD) of 0.8 × 10(-14) M and a limit of quantification (LOQ) of 6.6 × 10(-14) M, much below the guideline value of 1 × 10(-8) M stipulated by United States Environmental Protection Agency (USEPA), accompanied by a good precision of 1.06% for 10(-13) M of Hg(ii). The designed sensor is selective to Hg(ii) ions in the presence of other coexisting species.

Ultrasensitive voltammetric determination of catechol at a gold atomic cluster/poly(3,4-ethylenedioxythiophene) nanocomposite electrode.

A novel gold atomic cluster-poly(3,4-ethylenedioxythiophene) (AuAC/PEDOT/Au) nanocomposite modified gold electrode has been designed for the trace level sensing of catechol. The addition of copper(II) enhanced the electro-catalytic oxidation of catechol via the formation of copper(I). The electrochemically synthesized PEDOT/Au and the AuAC/PEDOT/Au hybrid films were characterized by electrochemical and morphological methods. Under optimal conditions the nanocomposite modified electrode offers a wider calibration range of 1 × 10(-4) to 10 µM with a lowest detection limit of 6.3 pM for catechol. Moreover, the developed electrochemical sensor exhibited good selectivity and acceptable reproducibility (1.23% for 1 nM of catechol) and could be used for the routine detection and quantification of catechol in natural water samples. To gain a better understanding of such an excellent sensor performance achieved with this electrode, studies were undertaken to pinpoint electrode kinetics of charge transfer processes.

Mixed monolayer protected gold atom-oxide cluster synthesis and characterization.

Small atomic gold clusters in solution, Au(n), stabilized by cetyl trimethylammonium bromide (CTAB) and cysteine, have been synthesized potentiodynamically in quiescent aqueous solutions. The electrodissolution of gold to gold ions during an anodic scan and subsequent cluster formation during a cathodic scan in underpotential (UPDD) and overpotential dissolution-deposition (OPDD) regions were studied. The experimental potentiodynamic I-E profiles and chronoamperometric i-t transients are fit into reported theoretical models of adsorption and electrocrystallization. The plausible application of clusters/cluster film to cysteine sensing based on fluorescence quenching and square wave stripping voltammetry is demonstrated.