Thiocyanate-capped nanocrystal colloids: Vibrational reporter of surface chemistry and solution-based route to enhanced coupling in nanocrystal solids

Aaron T. Fafarman, Weon Kyu Koh, Benjamin T. Diroll, David K. Kim, Dong Kyun Ko, Soong Ju Oh, Xingchen Ye, Vicky Doan-Nguyen, Michael R. Crump, Danielle C. Reifsnyder, Christopher B. Murray, Cherie R. Kagan

Research output: Contribution to journalArticle

231 Citations (Scopus)

Abstract

Ammonium thiocyanate (NH 4 SCN) is introduced to exchange the long, insulating ligands used in colloidal nanocrystal (NC) synthesis. The short, air-stable, environmentally benign thiocyanate ligand electrostatically stabilizes a variety of semiconductor and metallic NCs in polar solvents, allowing solution-based deposition of NCs into thin-film NC solids. NH 4 SCN is also effective in replacing ligands on NCs after their assembly into the solid state. The spectroscopic properties of this ligand provide unprecedented insight into the chemical and electronic nature of the surface of the NCs. Spectra indicate that the thiocyanate binds to metal sites on the NC surface and is sensitive to atom type and NC surface charge. The short, thiocyanate ligand gives rise to significantly enhanced electronic coupling between NCs as evidenced by large bathochromic shifts in the absorption spectra of CdSe and CdTe NC thin films and by conductivities as high as (2 ± 0.7) × 10 3 ω -1 cm -1 for Au NC thin films deposited from solution. NH 4 SCN treatment of PbTe NC films increases the conductivity by 10 13 , allowing the first Hall measurements of nonsintered NC solids, with Hall effect mobilities of 2.8 ± 0.7 cm 2 /(V·s). Thiocyanate-capped CdSe NC thin films form photodetectors exhibiting sensitive photoconductivity of 10 -5 ω -1 cm -1 under 30 mW/cm 2 of 488 nm illumination with I photo /I dark > 10 3 and form n-channel thin-film transistors with electron mobilities of 1.5 ± 0.7 cm 2 /(V·s), a current modulation of >10 6 , and a subthreshold swing of 0.73 V/decade.

Original languageEnglish
Pages (from-to)15753-15761
Number of pages9
JournalJournal of the American Chemical Society
Volume133
Issue number39
DOIs
Publication statusPublished - 2011 Oct 5
Externally publishedYes

Fingerprint

Colloids
Surface chemistry
Nanoparticles
Nanocrystals
Ligands
Thin films
thiocyanate
Semiconductors
Electron mobility
Photoconductivity
Hall effect
Thin film transistors
Surface charge
Photodetectors
Lighting
Absorption spectra
Metals
Air
Modulation
Electrons

ASJC Scopus subject areas

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

Cite this

Thiocyanate-capped nanocrystal colloids : Vibrational reporter of surface chemistry and solution-based route to enhanced coupling in nanocrystal solids. / Fafarman, Aaron T.; Koh, Weon Kyu; Diroll, Benjamin T.; Kim, David K.; Ko, Dong Kyun; Oh, Soong Ju; Ye, Xingchen; Doan-Nguyen, Vicky; Crump, Michael R.; Reifsnyder, Danielle C.; Murray, Christopher B.; Kagan, Cherie R.

In: Journal of the American Chemical Society, Vol. 133, No. 39, 05.10.2011, p. 15753-15761.

Research output: Contribution to journalArticle

Fafarman, AT, Koh, WK, Diroll, BT, Kim, DK, Ko, DK, Oh, SJ, Ye, X, Doan-Nguyen, V, Crump, MR, Reifsnyder, DC, Murray, CB & Kagan, CR 2011, 'Thiocyanate-capped nanocrystal colloids: Vibrational reporter of surface chemistry and solution-based route to enhanced coupling in nanocrystal solids', Journal of the American Chemical Society, vol. 133, no. 39, pp. 15753-15761. https://doi.org/10.1021/ja206303g
Fafarman, Aaron T. ; Koh, Weon Kyu ; Diroll, Benjamin T. ; Kim, David K. ; Ko, Dong Kyun ; Oh, Soong Ju ; Ye, Xingchen ; Doan-Nguyen, Vicky ; Crump, Michael R. ; Reifsnyder, Danielle C. ; Murray, Christopher B. ; Kagan, Cherie R. / Thiocyanate-capped nanocrystal colloids : Vibrational reporter of surface chemistry and solution-based route to enhanced coupling in nanocrystal solids. In: Journal of the American Chemical Society. 2011 ; Vol. 133, No. 39. pp. 15753-15761.
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AU - Koh, Weon Kyu

AU - Diroll, Benjamin T.

AU - Kim, David K.

AU - Ko, Dong Kyun

AU - Oh, Soong Ju

AU - Ye, Xingchen

AU - Doan-Nguyen, Vicky

AU - Crump, Michael R.

AU - Reifsnyder, Danielle C.

AU - Murray, Christopher B.

AU - Kagan, Cherie R.

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N2 - Ammonium thiocyanate (NH 4 SCN) is introduced to exchange the long, insulating ligands used in colloidal nanocrystal (NC) synthesis. The short, air-stable, environmentally benign thiocyanate ligand electrostatically stabilizes a variety of semiconductor and metallic NCs in polar solvents, allowing solution-based deposition of NCs into thin-film NC solids. NH 4 SCN is also effective in replacing ligands on NCs after their assembly into the solid state. The spectroscopic properties of this ligand provide unprecedented insight into the chemical and electronic nature of the surface of the NCs. Spectra indicate that the thiocyanate binds to metal sites on the NC surface and is sensitive to atom type and NC surface charge. The short, thiocyanate ligand gives rise to significantly enhanced electronic coupling between NCs as evidenced by large bathochromic shifts in the absorption spectra of CdSe and CdTe NC thin films and by conductivities as high as (2 ± 0.7) × 10 3 ω -1 cm -1 for Au NC thin films deposited from solution. NH 4 SCN treatment of PbTe NC films increases the conductivity by 10 13 , allowing the first Hall measurements of nonsintered NC solids, with Hall effect mobilities of 2.8 ± 0.7 cm 2 /(V·s). Thiocyanate-capped CdSe NC thin films form photodetectors exhibiting sensitive photoconductivity of 10 -5 ω -1 cm -1 under 30 mW/cm 2 of 488 nm illumination with I photo /I dark > 10 3 and form n-channel thin-film transistors with electron mobilities of 1.5 ± 0.7 cm 2 /(V·s), a current modulation of >10 6 , and a subthreshold swing of 0.73 V/decade.

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