Green synthesis of gold nanoparticles using plant extracts is one of the more promising approaches for obtaining environmentally friendly nanomaterials for biological applications and environmental remediation. In this study, proanthocyanidins-functionalized gold nanoparticles were synthesized via a hydrothermal method. The obtained gold nanoparticles were characterized by ultraviolet and visible spectrophotometry (UV-Vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements. UV-Vis and FTIR results indicated that the obtained products were mainly spherical in shape, and that the phenolic hydroxyl of proanthocyanidins had strong interactions with the gold surface. TEM and XRD determination revealed that the synthesized gold nanoparticles had a highly crystalline structure and good monodispersity. The application of proanthocyanidins-functionalized gold nanoparticles for the removal of dyes and heavy metal ions Ni²⁺, Cu²⁺, Cd²⁺ and Pb²⁺ in an aqueous solution was investigated. The primary results indicate that proanthocyanidins-functionalized gold nanoparticles had high removal rates for the heavy metal ions and dye, which implies that they have potential applications as a new kind of adsorbent for the removal of contaminants in aqueous solution.

The effects of the electroforming polarity on the bipolar resistive switching characteristics in ${\text{SrTiO}}_{3-\delta }$ thin films have been investigated. The conduction mechanisms of high resistance state and low resistance state are Poole–Frenkel emission and tunneling, respectively. The temperature dependences of the resistance at high and low resistance state are both semiconductorlike. The impact of the polarity of the electroforming voltage on the resistive switching mechanism and the distribution of defects was discussed. A simple model describing the combination of bulk and the interface effect was proposed to explain the resistive switching in this material.

Reproducible and reliable bipolar resistive switching was obtained from memory cells. The current–voltage characteristic of the Ag/STO/Pt cells with a positive voltage applied to the Pt electrode and the results of X-ray photoelectron spectroscopy imply that the electrochemical reaction and the diffusion of ions play a critical role in the resistive switching effect. The temperature dependence of the on-state resistance, combined with the time dependence of the on- and off-state resistances under a constant voltage, provides further evidence that the resistive switching mechanism should be ascribed to the formation and dissolution of the metallic Ag nanofilaments.

Electric switching and memory effects were observed on devices composed of a $\mathrm{Rb}{\mathrm{Ag}}_4{\mathrm{I}}_5$ film sandwiched between Ag and Pt electrodes. The $\mathrm{Rb}{\mathrm{Ag}}_4{\mathrm{I}}_5$ films were prepared by pulsed laser deposition and the lateral size of devices was scaled down to $300\mathrm{nm}$ by focused ion beam lithography. The device can be switched between high- and low-resistance states with a ratio of $\sim {10}^3$ by applying voltage with opposite polarities. The read-write cycles could be repeated at $1\mathrm{kHz}$ and for ${10}^4$ times. The switching characters are attributed to the formation or breakdown of Ag filaments in $\mathrm{Rb}{\mathrm{Ag}}_4{\mathrm{I}}_5$ films induced by electrochemical reactions.