Figure 1.

Contactless method for determining standard reduction potentials (E⁰) of nanoparticles. (a) Comparison of the voltammetry method with our approach for determining reduction potentials of metallic nanoparticles. (b) Equilibrated reaction between gold nanoparticles and a redox couple for determining their E⁰. (c) Redox equilibrium of AuBr₂^–/Au^NP_n and Fe^3+/2+ couple, and the complexation between CTA micelles and AuBr₂^–. (d and e) Time-lapsed UV–vis spectra (arrow indicates the reaction progress) and kinetic trace at plasmon resonance of a typical reaction between 10.9 nm nanoparticles and Fe³⁺. (f) Kinetic trace at the plasmon resonance of the reaction when the CTA⁺ concentration is increased from 0.1 to 1.9 mM.