Electroplated core–shell nanowire network electrodes for highly efficient organic light-emitting diodes

In this study, we performed metal (Ag, Ni, Cu, or Pd) electroplating of core–shell metallic Ag nanowire (AgNW) networks intended for use as the anode electrode in organic light-emitting diodes (OLEDs) to modify the work function (WF) and conductivity of the AgNW networks. This low-cost and facile electroplating method enabled the precise deposition of metal onto the AgNW surface and at the nanowire (NW) junctions. AgNWs coated onto a transparent glass substrate were immersed in four different metal electroplating baths: those containing AgNO3 for Ag electroplating, NiSO4 for Ni electroplating, Cu2P2O7 for Cu electroplating, and PdCl2 for Pd electroplating. The solvated metal ions (Ag+, Ni2+, Cu2+, and Pd2+) in the respective electroplating baths were reduced to the corresponding metals on the AgNW surface in the galvanostatic mode under a constant electric current achieved by linear sweep voltammetry via an external circuit between the AgNW networks (cathode) and a Pt mesh (anode). The amount of electroplated metal was systematically controlled by varying the electroplating time. Scanning electron microscopy images showed that the four different metals (shells) were successfully electroplated on the AgNWs (core), and the nanosize-controlled electroplating process produced metal NWs with varying diameters, conductivities, optical transmittances, and WFs. The metal-electroplated AgNWs were successfully employed as the anode electrodes of the OLEDs. This facile and low-cost method of metal electroplating of AgNWs to increase their WFs and conductivities is a promising development for the fabrication of next-generation OLEDs.

Effect of Solvents on Fe–Lignin Precursors for Production Graphene-Based Nanostructures

Kraft lignin was catalytically graphitized to graphene-based nanostructures at high temperature under non-oxidative atmospheres. To obtain the best catalytic performance, a uniform catalyst–lignin mixture must be made by bonding transitional metal (M) ions to oxygen (O), sulfur (S) or nitrogen (N)-containing functional groups in kraft lignin. One of the strategies is to dissolve or disperse kraft lignin in a suitable solvent, whereby the polymer chains in the condensed lignin molecules will be detangled and stretched out while the functional groups are solvated, and when mixing lignin solution with catalyst metal solution, the solvated metal ions in an aqueous solution can diffuse and migrate onto lignin chains to form M-O, M-S, or M-N bonds during the mixing process. Therefore, solvent effects are important in preparing M–lignin mixture for production of graphene-based nanostructures. Fe–lignin precursors were prepared by dissolving lignin with different solvents, including water, methanol, acetone, and tetrahydrofuran (THF). Solvent effects on the catalytic performance, size and morphology of graphene-based nanostructures were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), and nitrogen sorption measurements. The sizes, morphologies, and catalytic properties of the products obtained from Fe–lignin precursors are greatly influenced by the solvents used. It was found that Fe–lignin (THF) had the highest iron dispersion and the smallest iron particle size. Furthermore, Fe–lignin (THF) exhibited the best catalytic performance for graphitization of kraft lignin while the graphitization degree decreased in the order: Fe–lignin(THF) > Fe–lignin(Acetone) > Fe–lignin(methanol) > Fe–lignin(water).

On the relationship between the structural and volumetric properties of solvated metal ions inO-donor solvents using new structural data in amide solvents

The relationship between the structural and volumetric properties of ions in solvents with different physico-chemical properties has been studied for 19 cations and six anions in six solvents.