Electrochemistry and Optical Absorbance and Luminescence of Molecule-like Au38 Nanoparticles

Dongil Lee, Robert L. Donkers, Gangli Wang, Amanda S. Harper, Royce W. Murray

Research output: Contribution to journalArticle

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Abstract

This paper describes electrochemical and spectroscopic properties of a well-characterized, synthetically accessible, 1.1 nm diam Au nanoparticle, Au38(PhC2S)24, where PhC2S is phenylethylthiolate. Properties of other Au38 nanoparticles made by exchanging the monolayer ligands with different thiolate ligands are also described. Voltammetry of the Au38 nanoparticles in CH 2Cl2 reveals a 1.62 V energy gap between the first one-electron oxidation and the first reduction. Based on a charging energy correction of ca. 0.29 V, the indicated HOMO-LUMO gap energy is ca. 1.33 eV. At low energies, the optical absorbance spectrum includes peaks at 675 nm (1.84 eV) and 770 nm (1.61 eV) and an absorbance edge at ca. 1.33 eV that gives an optical HOMO-LUMO gap energy that is consistent with the electrochemical estimate. The absorbance at lowest energy is bleached upon electrochemical depletion of the HOMO level. The complete voltammetry contains two separated doublets of oxidation waves, indicating two distinct molecular orbitals, and two reduction steps. The ligand-exchanged nanoparticle Au38(PEG 135S)13(PhC2S)11, where PEG 135S is -SCH2CH2OCH2CH 2OCH3, exhibits a broad (1.77-0.89 eV) near-IR photoluminescence band resolvable into maxima at 902 nm (1.38 eV) and 1025 nm (1.2 eV). Much of the photoluminescence occurs at energies less than the HOMO-LUMO gap energy. A working model of the energy level structure of the Au38 nanoparticle is presented.

Original languageEnglish
Pages (from-to)6193-6199
Number of pages7
JournalJournal of the American Chemical Society
Volume126
Issue number19
DOIs
Publication statusPublished - 2004 May 19

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Electrochemistry
Luminescence
Nanoparticles
Energy gap
Molecules
Ligands
Voltammetry
Polyethylene glycols
Photoluminescence
Oxidation
Molecular orbitals
Electron energy levels
Monolayers
Electrons

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Lee, Dongil ; Donkers, Robert L. ; Wang, Gangli ; Harper, Amanda S. ; Murray, Royce W. / Electrochemistry and Optical Absorbance and Luminescence of Molecule-like Au38 Nanoparticles. In: Journal of the American Chemical Society. 2004 ; Vol. 126, No. 19. pp. 6193-6199.
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Electrochemistry and Optical Absorbance and Luminescence of Molecule-like Au38 Nanoparticles. / Lee, Dongil; Donkers, Robert L.; Wang, Gangli; Harper, Amanda S.; Murray, Royce W.

In: Journal of the American Chemical Society, Vol. 126, No. 19, 19.05.2004, p. 6193-6199.

Research output: Contribution to journalArticle

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T1 - Electrochemistry and Optical Absorbance and Luminescence of Molecule-like Au38 Nanoparticles

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N2 - This paper describes electrochemical and spectroscopic properties of a well-characterized, synthetically accessible, 1.1 nm diam Au nanoparticle, Au38(PhC2S)24, where PhC2S is phenylethylthiolate. Properties of other Au38 nanoparticles made by exchanging the monolayer ligands with different thiolate ligands are also described. Voltammetry of the Au38 nanoparticles in CH 2Cl2 reveals a 1.62 V energy gap between the first one-electron oxidation and the first reduction. Based on a charging energy correction of ca. 0.29 V, the indicated HOMO-LUMO gap energy is ca. 1.33 eV. At low energies, the optical absorbance spectrum includes peaks at 675 nm (1.84 eV) and 770 nm (1.61 eV) and an absorbance edge at ca. 1.33 eV that gives an optical HOMO-LUMO gap energy that is consistent with the electrochemical estimate. The absorbance at lowest energy is bleached upon electrochemical depletion of the HOMO level. The complete voltammetry contains two separated doublets of oxidation waves, indicating two distinct molecular orbitals, and two reduction steps. The ligand-exchanged nanoparticle Au38(PEG 135S)13(PhC2S)11, where PEG 135S is -SCH2CH2OCH2CH 2OCH3, exhibits a broad (1.77-0.89 eV) near-IR photoluminescence band resolvable into maxima at 902 nm (1.38 eV) and 1025 nm (1.2 eV). Much of the photoluminescence occurs at energies less than the HOMO-LUMO gap energy. A working model of the energy level structure of the Au38 nanoparticle is presented.

AB - This paper describes electrochemical and spectroscopic properties of a well-characterized, synthetically accessible, 1.1 nm diam Au nanoparticle, Au38(PhC2S)24, where PhC2S is phenylethylthiolate. Properties of other Au38 nanoparticles made by exchanging the monolayer ligands with different thiolate ligands are also described. Voltammetry of the Au38 nanoparticles in CH 2Cl2 reveals a 1.62 V energy gap between the first one-electron oxidation and the first reduction. Based on a charging energy correction of ca. 0.29 V, the indicated HOMO-LUMO gap energy is ca. 1.33 eV. At low energies, the optical absorbance spectrum includes peaks at 675 nm (1.84 eV) and 770 nm (1.61 eV) and an absorbance edge at ca. 1.33 eV that gives an optical HOMO-LUMO gap energy that is consistent with the electrochemical estimate. The absorbance at lowest energy is bleached upon electrochemical depletion of the HOMO level. The complete voltammetry contains two separated doublets of oxidation waves, indicating two distinct molecular orbitals, and two reduction steps. The ligand-exchanged nanoparticle Au38(PEG 135S)13(PhC2S)11, where PEG 135S is -SCH2CH2OCH2CH 2OCH3, exhibits a broad (1.77-0.89 eV) near-IR photoluminescence band resolvable into maxima at 902 nm (1.38 eV) and 1025 nm (1.2 eV). Much of the photoluminescence occurs at energies less than the HOMO-LUMO gap energy. A working model of the energy level structure of the Au38 nanoparticle is presented.

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