Electrochemistry and Electrogenerated Chemiluminescence from Silicon Nanocrystal Quantum Dots
Zhifeng Ding,1
Bernadette M. Quinn,1
Santosh K. Haram,1
Lindsay E. Pell,2
Brian A. Korgel,2*
Allen J. Bard1*
Reversible electrochemical injection of discrete
numbers of electrons into sterically stabilized silicon nanocrystals
(NCs) (~2 to 4 nanometers in diameter) was observed by differential pulse voltammetry (DPV) in
N,N'-dimethylformamide and acetonitrile. The
electrochemical gap between the onset of electron injection and hole
injection--related to the highest occupied and lowest unoccupied
molecular orbitals--grew with decreasing nanocrystal size, and
the DPV peak potentials above the onset for electron injection roughly
correspond to expected Coulomb blockade or quantized double-layer
charging energies. Electron transfer reactions between positively and
negatively charged nanocrystals (or between charged nanocrystals and
molecular redox-active coreactants) occurred that led to electron and
hole annihilation, producing visible light. The electrogenerated
chemiluminescence spectra exhibited a peak maximum at 640 nanometers, a
significant red shift from the photoluminescence maximum (420 nanometers) of the same silicon NC solution. These results demonstrate
that the chemical stability of silicon NCs could enable their use as
redox-active macromolecular species with the combined optical and
charging properties of semiconductor quantum dots.
1 Department of Chemistry and Biochemistry,
2 Department of Chemical Engineering, Center for
Nano- and Molecular Science and Technology, Texas Materials Institute,
The University of Texas at Austin, Austin, TX 78712, USA.
*
To whom correspondence should be addressed. E-mail:
ajbard{at}mail.utexas.edu (A.J.B.); korgel{at}mail.che.utexas.edu
(B.A.K.).
