Photoelectrochemical processes in polymer-tethered CdSe nanocrystals

R. Clayton Shallcross, Gemma D. D'Ambruoso, Jeffrey Pyun, Neal R. Armstrong

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

We demonstrate the electrochemical capture of CdSe semiconductor nanocrystals (NCs), with thiophene-terminated carboxylic acid capping ligands, at the surfaces of electrodeposited poly(thiophene) films (i) poly((diethyl)propylenedixoythiophene), P(Et)2ProDOT; (ii) poly(propylenedioxythiophene), PProDOT; and (iii) poly(ethylenedioxythiophene), PEDOT, coupled with the exploration of their photoelectrochemical properties. Host polymer films were created using a kinetically controlled electrodeposition protocol on activated indium-tin oxide electrodes (ITO), producing conformai films that facilitate high rates of electron transfer. ProDOT-terminated, ligand-capped CdSe-NCs were captured at the outer surface of the host polymer films using a unique pulse-potential step electrodeposition protocol, providing for nearly closepacked monolayers of the NCs at the host polymer/solution interface. These polymer-confined CdSe NCs were used as sensitizers in the photoelectrochemical reduction of methyl viologen (MV+2). High internal quantum efficiencies (IQEs) are estimated for photoelectrochemical sensitized MV+2 reduction using CdSe NCs ranging from 3.1 to 7.0 nm diameters. Cathodic photocurrent at high MV+2 concentrations are limited by the rate of hole-capture by the host polymer from photoexcited NCs. The rate of this hole-capture process is determined by (a) the onset potential for reductive dedoping of the host polymer film; (b) the concentration ratio of neutral to oxidized forms of the host polymer ([P(n)]/[P(ox)]); and (c) the NC diameter, which controls its valence band energy, EVB. These relationships are consistent with control of photoinduced electron transfer by Marcus-like excess free energy relationships. Our electrochemical assembly methods provide an enabling route to the capture of functional NCs in conducting polymer hosts in both photoelectrochemical and photovoltaic energy conversion systems.

Original languageEnglish (US)
Pages (from-to)2622-2632
Number of pages11
JournalJournal of the American Chemical Society
Volume132
Issue number8
DOIs
StatePublished - Feb 24 2010

ASJC Scopus subject areas

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

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