Journal
NANO LETTERS
Volume 15, Issue 1, Pages 51-55Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl503782s
Keywords
Charge state; work function; gold nanoparticle; Kelvin probe force microscopy; chemical sensing
Categories
Funding
- NSF [DMR-1104260]
- University of California, Davis
- University of California, Berkeley
- University of Texas at Dallas [CHE-1300180]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1300180] Funding Source: National Science Foundation
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Electrostatic interactions at the nanoscale can lead to novel properties and functionalities that bulk materials and devices do not have. Here we used Kelvin probe force microscopy (KPFM) to study the work function (WF) of gold nanoparticles (NPs) deposited on a Si wafer covered by a monolayer of alkyl chains, which provide a tunnel junction. We find that the WF of Au NPs is size-dependent and deviates strongly from that of the bulk Au. We attribute the WF change to the charging of the NPs, which is a consequence of the difference in WF between Au and the substrate. For an NP with 10 nm diameter charged with similar to 5 electrons, the WF is found to be only similar to 3.6 eV. A classical electrostatic model is derived that explains the observations in a quantitative way. We also demonstrate that the WF and charge state of Au NPs are influenced by chemical changes of the underlying substrate. Therefore, Au NPs could be used for chemical and biological sensing, whose environmentally sensitive charge state can be read out by work function measurements.
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