ABSTRACT
A plasmonic molecular electronic device, consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires bridging an ultramicroelectrode and an indium tin oxide (ITO) substrate covered by gold nanoparticles (Au NPs), has been developed. Light irradiation of this device has a dramatic impact on its conductance. Polymer strands, maintained electrochemically in their oxidized, conducting state, reversibly switch to their insulating state upon irradiation by visible-wavelength light, resulting in a sharp decrease in the conductance. The high-conductance state is restored when the light is turned off. Switching depends on the wavelength and the intensity of the incident light. It is due to reversible reduction of the nanosized region of PEDOT nanowires in contact with a gold NP and is attributed to plasmon-induced hot-electron injection into the PEDOT. The high/low conductance ratio can be as great as 1000, and switching requires low light intensity (220 W/m2). These results could open the way to the design of a new family of optoelectronic switches.
ABSTRACT
Molecular plasmonics uses and explores molecule-plasmon interactions on metal nanostructures for spectroscopic, nanophotonic, and nanoelectronic devices. This review focuses on tailored surfaces/assemblies for molecular plasmonics and describes active molecular plasmonic devices in which functional molecules and polymers change their structural, electrical, and/or optical properties in response to external stimuli and that can dynamically tune the plasmonic properties. We also explore an emerging research field combining molecular plasmonics and molecular electronics.
ABSTRACT
Polypyrrole (PPy) films were electrodeposited from a pyrrole/sodium salicylate solution in water, through two-dimensional (2-D) polystyrene (PS) templates self-assembled on various oxidizable metals, after which the template was removed by dissolution in tetrahydrofuran (THF). The resulting PPy films were analyzed by scanning electron microscopy and atomic force microscopy. Two-dimensional PPy honeycomb structures are obtained on copper or mild steel by using PS spheres of various sizes. The morphology of these structures was controlled electrochemically, as an increase in the polymerization charge does not disturb the PPy honeycomb arrangement, leading instead to the formation of deeper pores accompanied by a change in their diameter. The hydrophobicity of the reduced micro-structured PPy surface is much greater than that of a bulk PPy film generated on the same metal. Reversible electro-switching of the wettability was obtained with marked variation of the apparent contact angle upon PPy oxido-reduction, and an important effect of film micro-structuration upon the wettability range.
ABSTRACT
Electrochemical grafting of a water-insoluble diazonium salt in aqueous media onto an electrode surface was achieved by host-guest complexation. 1-(2-Bisthienyl)-4-aminobenzene (BTAB) was solubilized in a water/beta-cyclodextrin solution (beta-CD). The corresponding diazonium salt was generated in situ then electroreduced. This process leads to the attachment of bithiophene or short oligothiophene groups to the electrode surface. The modified surfaces were analyzed by cyclic voltammetry (CV), scanning electrochemical microscopy (SECM), X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRRAS), and atomic force microscopy (AFM). The electrochemical investigations show that the water-based modified surface is similar to one generated in acetonitrile without beta-CD. Thus, the attached organic layer behaves like an electrochemical switch (above some threshold potential, a soluble external probe is oxidized, but the oxidized form cannot be reduced). The modified surfaces consist of grafted bisthienylbenzene (BTB) and cyclodextrins that can be removed from the surface. This procedure may be considered as a new means of creating a surface made of submicrometric holes in an organic semiconducting layer.
ABSTRACT
Monodisperse ruthenium nanoparticles functionalized by electroactive oligothiophenes have been prepared and characterized. Using TEM, UV-visible and FTIR we established that the organization of these nanoparticles into nanospheres can be directly controlled via modulation of the pi-pi interaction between the organic components adsorbed on the surface. This finding also shows that the self-assembled nanoheterostructures may be switched from monodisperse nanoparticles to ordered nanospheres by tuning the pH.