Capping agent promoted oxidation of gold nanoparticles: cetyl trimethylammonium bromide

Abstract

Capping agents, key for nanoparticle stability, may hugely influence chemical behaviour. We show that differently capped gold nanoparticles, with either citrate or cetyl trimethylammonium bromide (CTAB) capping agents, show qualitatively different electron transfer properties. Specifically through cyclic voltammetry and nanoimpact studies the CTAB promoted dissolution of gold nanoparticles is shown, highlighting the active role which capping agents can play in charge transfer.

Continuous Electrochemical Detection of Gold Nanoparticles in Flow

“…In turn, the presence of chloride or bromide elicited much smaller currents. Indeed, chloride , and bromide , , , ions rather facilitate electrodissolution of gold by complex formation than are oxidized in the presence of gold (AuNPs). The stability of the gold complexes (SO 3 2− > I − > SCN − > Br − > Cl − ) can also affect the shape of the recorded current‐voltage curves and magnitude of current signal.…”

“…It allows an increase of amperometric signal, but also eliminates a memory‐effect caused by irreversible adsorption earlier seen with carbon nanoparticles . We also tested the electrooxidation of AuNPs in acidic solutions containing more difficult to oxidize chloride and bromide ions accelerating gold dissolution , , . Furthermore, we demonstrate that our approach enables a continuous and selective electrochemical AuNPs detection in a wide concentration range in Flow Injection Analysis (FIA) system.…”

“…Although the electrochemical studies of AuNPs films were extensive , , there are only few examples of electrochemical research of AuNPs suspensions . On the basis of earlier studies one can conclude that the electrochemical analysis of gold nanoparticles suspensions can be based on either their electrodissolution or electrocatalytic behaviour .…”

“…In particular, this methodology is employed in industry for gold recovery from ores and secondary sources or in the fabrication of microelectronic, and optoelectronic components . Recently, the anodic behavior of gold has been explored for electrochemical detection of Au nanoparticles in quiescent conditions . It is based on electrochemical oxidation of gold in the acidic medium in the presence of complexing Cl − or Br − anions.…”

“…These ions facilitate AuNPs electrodissolution via formation of complex anions: AuCl 2 − and AuCl 4 − or AuBr 2 − and AuBr 4 − . When the electrode is held at a sufficiently high potential, AuNPs contacting the electrode surface undergo complete electrodissolution . The evaluated charge provides the variety of information about impacting nanoparticles e. g. their concentration, size distribution and the state of aggregation.…”