Temperature-dependent quantized double layer charging of monolayer-protected gold clusters.

Area of Science:

• Electrochemistry
• Nanomaterials Science
• Physical Chemistry

Background:

• Monolayer-protected gold clusters (MPCs) exhibit unique electronic properties.
• Understanding the electrical double layer (EDL) is crucial for nanoscale charge transfer.
• Differential pulse voltammetry (DPV) is a powerful technique for probing charge states.

Purpose of the Study:

• To investigate the effect of temperature on the voltammetric behavior of hexanethiolate-coated Au140 clusters (C6 MPCs).
• To analyze the temperature dependence of the cluster's capacitance (C(CLU)).
• To explore the relationship between EDL properties and nanoparticle charging.

Main Methods:

• Low-temperature differential pulse voltammetry (DPV) was performed on C6 MPCs in CH2Cl2.
• Quantized double layer (QDL) charging peaks were resolved at temperatures as low as 263 K.
• Capacitance (C(CLU)) was measured from the voltage spacing between charging peaks.

Main Results:

• Up to 13 resolved QDL charging peaks were observed at 263 K, introducing the concept of voltammetric peak capacity.
• The cluster capacitance (C(CLU)) increased by approximately 15% as temperature decreased from 273 K to 210 K.
• An experimental temperature dependence of C(CLU) was determined and discussed in terms of EDL components.

Conclusions:

• The observed temperature dependence of C(CLU) is likely a combination of diffuse and compact double layer effects.
• Regular peak spacing near the potential of zero charge aligns with EDL theory.
• Deviations at higher charge states suggest the influence of the Au140 core's molecular electronic behavior on electron transfer.