Langmuir monolayers of gold nanoparticles: from ohmic to rectifying charge transfer

Abstract

The lateral electrical/electronic conductivity of alkanethiolate-protected gold nanoparticles was evaluated at the air/water interface by using the Langmuir method. For particles with short protecting monolayers (C4Au and C5Au), the current-voltage profiles exhibited ohmic behaviors with conductivity several orders of magnitude smaller than that of bulk gold. The conductivity is found to decrease exponentially with increasing interparticle spacing. This is interpreted on the basis of electron tunneling/hopping between neighboring particles where the tunneling coefficient (β) is found around 0.5 Å −1 . With longer alkyl protecting layers (C6 and above), the nanoparticle monolayers demonstrated rectifying charge-transfer characters. This transition from ohmic to diode-like responses can be attributable to the nanocomposite structure of the particle molecules, where the chemical nature of the core and the protecting monolayers, along with the interparticle environment and ordering, are found to play an important role in regulating the electrical/electronic properties of the nanoassemblies.

DNA polymorphism sensitive impedimetric detection on gold-nanoislands modified electrodes

“…In fact, as shown in Figure S1, part B, the Nyquist plots obtained in presence of the redox probe indicated a similar and faster charge transfer rate for nanoAu(0%)-GEC and nanoAu(7.5%)-GEC electrodes, which present comparably low charge transfer resistance values. On the other hand, Nyquist plot for nanoAu(25%)-GEC shows an increased charge transfer resistance value, which is consistent with the less ideal electrochemical signal observed in the cyclic voltammetry studies [27,28]. Moreover, the reproducibility of results obtained with nanoAu(25%)-GEC electrode, either for cyclic voltammetry or for impedance was considerably lower than that obtained for nanoAu(7.5%)-GEC.…”

Optically switchable organic field-effect transistors based on photoresponsive gold nanoparticles blended with poly(3-hexylthiophene)

“…In addition, the hydrophobic nature of the alkanethiol SAMs can enhance the crystallinity of the film, which will promote less trapping centers in the P3HT film, yielding a lower hysteresis. The hysteresis observed in the s-AZONPs/ P3HT-and OPE-NP-based devices can also be determined by the mechanism governing the charge transport between the semiconductor and the NPs, which can proceed by either hopping or tunneling transport (33,34). The different nature of the SAM chemisorbed on the AuNPs (alkanethiolated SAM or a fully con- jugated aromatic molecule or AZO) will also influence the tunneling barrier.…”

Discrete charge transfer in nanoparticle solid films

“…The above results 28,29 can be rationalized by the particle monolayer structure, where the phase behavior of the particle Langmuir monolayers has been found to be mainly defined by the particle core size and the chemical structures of the protecting ligands. { Because of the close proximity and electronic interactions between particles, the capacitance evaluated here most probably reflects the capacitive coupling between neighboring particles (C PP ); whereas C MPC (eqn (1)) denotes the molecular capacitance of individual particles with negligible interparticle interactions.…”

“…28 However, for particles protected by longer alkanethiolates, the I-V profiles exhibited a substantial deviation from the linear characteristics. Fig.…”

“…In fact, single electron transfer can now be achieved with monolayers of these particles at controlled interparticle arrangements. For instance, using the Langmuir technique, 28,29 we have studied the electronic conductivity of a series of gold nanoparticles (core diameter 2 nm, with dispersity ,20%) with varied protecting ligands, and observed drastic differences in the I-V profiles with the variation of the structures of the particles and their ensembles. The experimental setup is shown in Scheme 1.…”