Layer-by-Layer Assembly of Thin Film Zener Diodes from Conducting Polymers and CdSe Nanoparticles

Abstract

Ultrathin films have been prepared by self-assembling trioctylphosphine oxide, TOPO, capped n-type 20-40 Å diameter CdSe nanoparticles and 1,6-hexadecanethiol, HDT, onto p-doped semiconducting polymers, chemically deposited poly(3-methylthiophene), PMeT (for DeWice A), and electrochemically deposited poly-(pyrrole), Ppy (for DeWice B). The semiconducting polymers have, in turn, been electrochemically layered (for DeWice A) or layer-by-layer chemically assembled (for DeWice B) onto derivatized conducting substrates. The ultrathin films have been characterized by absorption and emission spectroscopy, transmission electron microscopy, scanning force microscopy, X-ray photoelectron spectroscopy, and by electrochemical measurements. By controlling the level of doping into the p-type junction, it was possible to prepare dissymmetrical junctions and observe a rectifying behavior in the forward direction and a Zener breakdown in the reverse direction for Au/PMeT/(HDT/CdSe) 3 , DeWice A, and for Au/MEA/Ppy/(HDT/CdSe) 3 , DeWice B. Additionally, Au/MeA/PAH/CdSe (PAH ) poly(allylamine hydrochloride)), Au/MEA/Ppy/PSS/CdSe (PSS ) polystyrene sulfonate), and Au/MEA/Ppy/R-ZrP/CdSe (R-ZrP ) R zirconium phosphate) films have been prepared and characterized.

High-Resolution Thin-Film Device to Sense Texture by Touch

“…Figure 2A shows the current density J through the film as a function of bias V between the bottom ITO and top Au electrode under a uniform compressive stress s. The uniform stress is applied by placing an optically flat quartz disk on the flexible Au electrode. The nonlinear J-V curve is fit based on a model combining the field-assisted electron tunneling current Ei.e., the Fowler-Nordheim equation (29)(30)(31)^through the nanoparticles and the ionic (leakage) current due to ions in the polyelectrolyte. According to the relation J tunneling 0 Pexp(-aK/V), where, a is the (vertical) interparticle distance, K is a critical field for activated tunneling that depends on the work functions of the particles, and P at constant temperature is proportional to V 2 and the number density of carriers for conduction (29,32).…”

A new specifically designed calix[8]arene for the synthesis of functionalized, nanometric and subnanometric Pd, Pt and Ru nanoparticles

“…In most cases, the solutionphase synthesis of metallic nanoparticles involves the controlled self-condensation of reduced metal centers in the presence of a suitable ligand. This ligand usually acts a stabilizer for the coordinatively unsaturated metal centers, prevents the agglomeration of the nanoparticles and controls the particle's size [8][9][10][11][12][13][14][15][16][17]. The stabilization of nanoparticles by ligands containing multiple anchoring groups is interesting, as it may improve the stability of the ligand shell due to the cooperative binding of all these groups.…”

Modulation of the Work Function in Layer‐by‐Layer Assembly of Metal Nanoparticles and Poly‐L‐lysine on Modified Au Surfaces

“…[11,12] The main driving force for the deposition of the colloidal nanoparticles on the polyelectrolyte film is given by the electrostatic interaction between the fixed charges in the outer layer of the film and the charged groups at the particle surface. One of the key advantages of this approach is the possibility of fabricating hybrid materials that incorporate not only metal and semiconductor nanoparticles, but also conducting polymers, [13] mobile redox species [14] and photoactive dyes. [15] Characterisation of polyelectrolyte/nanoparticle assemblies has been performed by a variety of spectroscopic techniques as well as SEM, AFM, conductivity and electrochemical techniques.…”