Molecular Origin of Electrical Conductivity in Gold–Polythiophene Hybrid Particle Films

Abstract

Hybrid electronic materials combine inorganic metals and semiconductors with π-conjugated polymers. The orientation of the polymer molecules in relation to the inorganic components is crucial for electrical material properties and device performance, but little is known of the configuration of π-conjugated polymers that bind to inorganic surfaces. Highly curved surfaces are common when using nanoscale components, for example, metal nanocrystal cores covered with conductive polymers. It is important to understand their effect on molecular arrangement. Here, we compare the molecular structures and electrical conductivities of well-defined nanoscale gold spheres and rods with shells of the covalently bound polythiophene PTEBS (poly­[2-(3-thienyl)-ethyloxy-4-butylsulfonate]). We prepared aqueous sinter-free inks from the particles and printed them. The particles formed highly conductive films immediately after drying. Films with spherical metal cores consistently had 40% lower conductivities than films based on nanorods. Raman and X-ray photoelectron spectroscopy revealed differences in the gold–sulfur bonds of PTEBS on rods and spheres. The fractions of bond sulfur groups implied differences in the alignment of PTEBS with the surface. More polymer molecules were bound in an edge-on configuration on spheres than on rods, where almost all polymers aligned “face-on” with the metal surface. This leads to different interface resistances: gold–polythiophene–gold interfaces between rods with π–π-tacked face-on PTEBS apparently foster electron transport along the surface-normal direction, while edge-on PTEBS does not. Molecular confinement thus increases the conductivity of hybrid inks based on highly curved nanostructures.

Large-Scale Synthesis of Hybrid Conductive Polymer–Gold Nanoparticles Using “Sacrificial” Weakly Binding Ligands for Printing Electronics

“…Our experimental conditions lead to isometric NPs, and we suggest that the main role of CTAB in our synthesis is to prevent particle aggregation. Silver in different states has been found on surface gold particles, , both as CTAB–silver bromide complex and as adsorbed AgBr 2– species . Monolayers or submonolayers of Ag(0) on gold nanoparticles have also been reported .…”

Flexible and transparent electrodes imprinted from Au nanowires: stability and ageing

“…46,47 Their molecular configuration depends on the crystallographic orientation and the curvature of the Au surface. 48…”

“…46,47 Their molecular conguration depends on the crystallographic orientation and the curvature of the Au surface. 48 We used the commercial PEDOT:PSS aqueous dispersion Clevios™ P that contains swollen, gel-like PEDOT:PSS particles of diameter d 50 ¼ 80 nm at a PEDOT : PSS weight ratio of 1 : 2.5 and a pH of 1.9 without any additives. 49,50 While its acidity is harmful for AgNWs, 24 it does not etch AuNWs.…”

Metal–Polymer Heterojunction in Colloidal-Phase Plasmonic Catalysis

“…However, to monitor the local temperature change, it is necessary to use sophisticated methods such as, for instance, fluorescent thermometry combined with DNA technology. 38 Note that in our hybrid system, emission from the polymer shell makes possible measurements of the lifetime of excited states (Figure 2d) which in principle is sensitive to the local temperature. Therefore, we postulate that the present system makes it possible to monitor the change of temperature in situ during a photocatalytic process.…”

“…X-ray photoemission spectroscopy (XPS) further confirmed that the metal–polymer interface is maintained through the Au–S–C (S 2p, 160 eV) from thiophene moiety and Au–O bonds (O 1s, 529 eV) from sulfonate terminal groups (Figure b,d). The formation of π–π interactions between the thiophene rings (C 1s, 290.5 eV in Figure c) suggests that the polymer can form organized structures in either face-on or edge-on fashion. , It is reasonable to assume, however, that in the liquid phase, the hydrated polymer extends toward the bulk solution, resulting in a less compact structure. The hydrodynamic diameter of spherical nanoparticles increased by ∼10 nm after displacing native ligands with PTEBS as confirmed by dynamic light scattering analysis (Figure S2).…”