Graphene Oxide: Key to Efficient Charge Extraction and Suppression of Polaronic Transport in Hybrids with Poly (3-hexylthiophene) Nanoparticles

Nanoparticles (NPs) of conjugated polymers in intimate contact with sheets of graphene oxide (GO) constitute a promising class of water-dispersible nanohybrid materials of increased interest for the design of sustainable and improved optoelectronic thin-film devices, revealing properties exclusively pre-established upon their liquid-phase synthesis. In this context, we report for the first time the preparation of a P3HT_NPs-GO nanohybrid employing a miniemulsion synthesis approach, whereby GO sheets dispersed in the aqueous phase serve as a surfactant. We show that this process uniquely favors a quinoid-like conformation of the P3HT chains of the resulting NPs well located onto individual GO sheets. The accompanied change in the electronic behavior of these P3HT_NPs, consistently confirmed by the photoluminescence and Raman response of the hybrid in the liquid and solid states, respectively, as well as by the properties of the surface potential of isolated individual P3HT_NPs-GO nano-objects, facilitates unprecedented charge transfer interactions between the two constituents. While the electrochemical performance of nanohybrid films is featured by fast charge transfer processes, compared to those taking place in pure P3HT_NPs films, the loss of electrochromic effects in P3HT_NPs-GO films additionally indicates the unusual suppression of polaronic charge transport processes typically encountered in P3HT. Thus, the established interface interactions in the P3HT_NPs-GO hybrid enable a direct and highly efficient charge extraction channel via GO sheets. These findings are of relevance for the sustainable design of novel high-performance optoelectronic device structures based on water-dispersible conjugated polymer nanoparticles.

Nanoscale Charge Density and Dynamics in Graphene Oxide

Graphene oxide (GO) is widely used as a component in thin film optoelectronic device structures for practical reasons because its electronic and optical properties can be controlled. Progress critically depends on elucidating the nanoscale electronic structure of GO. However, direct experimental access is challenging because of its disordered and nonconductive character. Here, we quantitatively mapped the nanoscopic charge distribution and charge dynamics of an individual GO sheet by using Kelvin probe force microscopy (KPFM). Charge domains are identified, presenting important charge interactions below distances of 20 nm. Charge dynamics with very long relaxation times of at least several hours and a logarithmic decay of the time correlation function are in excellent agreement with Monte Carlo simulations, revealing an universal hopping transport mechanism best described by Efros-Shklovskii's law.

Reaction of an angry consumer

The greatest deterrents to client participation in community mental health are: 1) The attitudes of professionals; 2) The undemocratic structure of patient grievance procedures. The remedy for these deficits is a restructuring of the population and power structure of mental health boards to facilitate meaningful participation by clients.