Swelling Effects on the Conductivity of Graphene/PSS/PAH Composites

Graphene/poly-(sodium-4-styrene sulfonate)(PSS)/poly-(allylamine hydrochloride) (PAH) composite is a frequently adopted system for fabricating polyelectrolyte multilayer films. Swelling is the bottleneck limiting its applications, and its effects on the conductivity is still controversial. Herein, we report successful swelling of a graphene/PSS/PAH composite in a vapor atmosphere, and the relation with the mass fraction of water is uncovered. The composite was prepared via a layer-by-layer assembly technique and systematically characterized. The results indicated that the average thickness for each bilayer was about 0.95 nm. The hardness and modulus were 2.5 ± 0.2 and 68 ± 5 GPa, respectively, and both were independent of thickness. The sheet resistance decreased slightly with the prolongation of immersion time, but was distinct from that of the water mass fraction. It reduced from 2.44 × 105 to 2.34 × 105 ohm/sq, and the change accelerated as the water mass fraction rose, especially when it was larger than 5%. This could be attributing to the lubrication effect of the water molecules, which sped up the migration of charged groups in the polyelectrolytes. Moreover, molecular dynamics simulations confirmed that a microphase separation occurred when the fraction reached an extreme value owing to the dominated interaction between PSS and PAH. These results provide support for the structural stability of this composite material and its applications in devices.

Fabrication and Nanoscale Properties of PEDOT:PSS Conducting Polymer Nanospheres

Electrically conducting nanospheres of poly-(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with tailored size were prepared by a solvent displacement technique. To fabricate the nanostructures, dried PEDOT:PSS was dissolved in ethylene glycol (EG) and the solution was precipitated in deionized water. The proposed fabrication route allowed to obtain a water-based dispersion of PEDOT:PSS nanospheres with good optical properties. To determine the physical properties of the nanospheres, we followed a nanoscale approach, using Atomic Force Microscopy. Our nanoscale mechanical and electrical investigations showed that the nanospheres preserved good physical properties, compared to the commercial product. Moreover, the local studies indicated that the confinement imposed by the spherical shape and the treatment with EG lead to a different arrangement of the PSS and PEDOT phases, responsible for the good electrical conductivity of the nanostructures.

Deposition and Characterization of Innovative Bulk Heterojunction Films Based on CuBi2O4 Nanoparticles and Poly(3,4 ethylene dioxythiophene):Poly(4-styrene sulfonate) Matrix

This work presents the deposition and study of the semiconductor behavior of CuBi2O4 nanoparticles (NPs) with an average crystallite size of 24 ± 2 nm embedded in poly(3,4 ethylene dioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) films. The CuBi2O4 NP bandgap was estimated at 1.7 eV, while for the composite film, it was estimated at 2.1 eV, due to PEDOT:PSS and the heterojunction between the polymer and the NPs. The charge transport of the glass/ITO/PEDOT:PSS-CuBi2O4 NP/Ag system was studied under light and dark conditions by means of current–voltage (I–V) characteristic curves. In natural-light conditions, the CuBi2O4 NPs presented electric behavior characterized by three different mechanisms: at low voltages, the behavior follows Ohm’s law; when the voltage increases, charge transport occurs by diffusion between the NP–polymer interfaces; and at higher voltages, it occurs due to the current being dominated by the saturation region. Due to their crystalline structure, their low bandgap in films and the feasibility of integrating them as components in composite films with PEDOT:PSS, CuBi2O4 NPs can be used as parts in optoelectronic devices.

Mechanism of terahertz reflection enhancement on photo-excited MEH-PPV/PEDOT:PSS/Si hybrid structure

The mechanism of enhanced reflection of terahertz wave via photoexcitation of a poly[2-methoxy-5-(2[Formula: see text]-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/poly(3-ethylenedioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) hybrid structure on silicon is reported. The reflectivity and incident angles measured for different samples conform to Brewster’s law. When the sample was excited by a continuous wave 450 nm laser at two randomly selected angles, the reflectivity of sample increased. According to the Fresnel equations, this phenomenon is related to the conductivity and refractive index of the sample. In calculated time-domain spectra excited by the laser at various power densities, the enhanced terahertz reflectivity is attributed to conductivity changes rather than the refractive index.