Electronic Conductivity of Solid-State, Mixed-Valent, Monolayer-Protected Au Clusters
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- 作者：W. Peter Wuelfing ; Stephen J. Green ; Jeremy J. Pietron ; David E. Cliffel ; and Royce W. Murray
- 刊名：Journal of the American Chemical Society
- 出版年：2000
- 出版时间：November 22, 2000
- 年：2000
- 卷：122
- 期：46
- 页码：11465 - 11472
- 全文大小：107K
- 年卷期：v.122,no.46(November 22, 2000)
- ISSN：1520-5126
文摘
Electronic conductivity, 
EL, in solid-state films of alkanethiolate monolayer protected Au clusters(Au MPCs) occurs by a bimolecular, electron self-exchange reaction, whose rate constant is controlled by (a)the core-to-core tunneling of electronic charge along alkanethiolate chains and (b) the mixed valency of theMPC cores (e.g., a mixture of cores with different electronic charges). The tunneling mechanism is demonstratedby an exponential relation between the electronic conductivity of Au309(Cn)92 MPCs (average composition)and n, the alkanethiolate chainlength, which varies from 4 to 16. The electron tunneling coefficient 
n =1.2/CH2 or, after accounting for alkanethiolate chain interdigitation, dis = 0.8 Å-1. Quantized electrochemicaldouble layer charging of low polydispersity Au140(C6)53 MPCs was used to prepare solutions containing well-defined mixtures of MPC core electronic charges (such as MPC0 mixed with MPC1+). Electronic conductivitiesof mixed-valent, solid-state Au140(C6)53 MPC films cast from such solutions are proportional to the concentrationproduct [MPC0][MPC1+], and give a MPC0/1+ electron self-exchange rate constant of ca. 1010 M-1 s-1.
EL, in solid-state films of alkanethiolate monolayer protected Au clusters(Au MPCs) occurs by a bimolecular, electron self-exchange reaction, whose rate constant is controlled by (a)the core-to-core tunneling of electronic charge along alkanethiolate chains and (b) the mixed valency of theMPC cores (e.g., a mixture of cores with different electronic charges). The tunneling mechanism is demonstratedby an exponential relation between the electronic conductivity of Au309(Cn)92 MPCs (average composition)and n, the alkanethiolate chainlength, which varies from 4 to 16. The electron tunneling coefficient n =1.2/CH2 or, after accounting for alkanethiolate chain interdigitation, dis = 0.8 Å-1. Quantized electrochemicaldouble layer charging of low polydispersity Au140(C6)53 MPCs was used to prepare solutions containing well-defined mixtures of MPC core electronic charges (such as MPC0 mixed with MPC1+). Electronic conductivitiesof mixed-valent, solid-state Au140(C6)53 MPC films cast from such solutions are proportional to the concentrationproduct [MPC0][MPC1+], and give a MPC0/1+ electron self-exchange rate constant of ca. 1010 M-1 s-1.