Electronic Conductivity of Semiconductor Nanoparticle Monolayers at the Air|Water Interface

Abstract

The electronic conductivity of PbS and CdTe nanoparticle monolayers was examined voltammetrically by using interdigitated array (IDA) electrodes at the air|water interface. Their band gap energies were estimated from the I-V responses and were very consistent with results obtained from optical measurements as well as solution electrochemistry. For CdTe nanoparticles, the I-V responses were analogous to those of a molecular diode with reproducible voltammetric behavior after repeated potential cycling. Interestingly, there appeared to be indications of particle surface trap states in the voltammetric responses that correlated with spectroscopic measurements. In addition, the band gap of the nanoparticle monolayers could be manipulated by the interparticle interactions, red shifting with decreasing interparticle separation. In contrast, the electroactive nature of the PbS particles led to the decomposition of the nanoparticles and hence deposition onto the electrode surface. The resulting voltammetric responses evolved from those typical of the faradaic reactions to a rectifying feature of much larger current scales, which finally became linear (ohmic) because of shorting between neighboring IDA fingers. In these studies, it was found that photoexcitation played an important role in regulating the current responses, providing a mechanistic basis on which to manipulate the electronic/electrical properties of semiconductor nanomaterials. The conductivity of the final interfinger deposits was about 2 orders of magnitude smaller than that for pure metallic lead, indicating some surface contamination and/or less than perfect crystalline structure.

Photoconductivity of Langmuir−Blodgett Monolayers of Silicon Nanoparticles

“…The overall behaviors are very similar to those observed with other monolayer-protected nanoparticles. 31,32,35,36 First, the takeoff area (A TO ) can be identified to be ca. 135 cm 2 .…”

Chemical manipulations of nanoscale electron transfers

“…In FETS, the electron transfer between the source and drain electrodes can be regulated by the gate potentials; similarly, in nanoparticle surface ensembles, the charge transfer in aqueous media between the nanoparticle molecules (source) and the electrodes (drain) can be manipulated by electrolyte ions (gate). Further control of nanoscale electron transfers can be achieved by, for instance, magnetic [59] and photochemical interactions [60]. In these studies, the nanoparticle electronic energy can be varied by a mechanism independent of electrochemical control, providing a deeper insight into nanoscale charge transport dynamics.…”

Facile synthesis and application of highly luminescent CdTe quantum dots with an electrogenerated precursor

“…These cathodic peaks can be attributed to the reduction of Cd elements, CdTe and CdS phase, and atomic Te in the QDs. 12 The oxidation peaks resulted from the oxidation of the reduced state of Cd and the injection of holes in the 1S h quantum-confined orbital of the CdTe core, 13 respectively.…”