Anti-Galvanic Reduction of Silver Ion on Gold and Its Role in Anisotropic Growth of Gold Nanomaterials

The role of silver ions in the seed-mediated growth of gold nanostructures has been investigated. Silver submonolayer or monolayer on specific facet of gold is assumed in previously suggested mechanism owing to underpotential deposition (UPD) of silver by ascorbic acid having weak reducing power. Silver overpotential deposition by ascorbic acid, however, is confirmed by electrochemical stripping voltammetry, whereas submonolayer of silver on gold is spontaneously formed by anti-galvanic reduction in the absence of ascorbic acid. In the presence of cetyl­trimethyl­ammonium bromide (CTAB), silver overpotential deposition by ascorbic acid does not occur, but submonolayer of silver is formed on gold surface. Adsorption of silver and CTAB on gold dramatically hindered the electron transfer by the oxidation of ascorbic acid on gold, which reduces gold ions to metallic gold in seed-mediated growth. These results provide the evidence to the in-depth observation of mechanism in seed-mediated growth where the blocking effect of CTAB/Ag­(submonolayer)/Au for oxidation of reducing agent determine the shape and facet of gold nanomaterials

Subcellular Neural Probes from Single-Crystal Gold Nanowires

Size reduction of neural electrodes is essential for improving the functionality of neuroprosthetic devices, developing potent therapies for neurological and neurodegenerative diseases, and long-term brain–computer interfaces. Typical neural electrodes are micromanufactured devices with dimensions ranging from tens to hundreds of micrometers. Their further miniaturization is necessary to reduce local tissue damage and chronic immunological reactions of the brain. Here we report the neural electrode with subcellular dimensions based on single-crystalline gold nanowires (NWs) with a diameter of ∼100 nm. Unique mechanical and electrical properties of defect-free gold NWs enabled their implantation and recording of single neuron-activities in a live mouse brain despite a ∼50× reduction of the size compared to the closest analogues. Reduction of electrode dimensions enabled recording of neural activity with improved spatial resolution and differentiation of brain activity in response to different social situations for mice. The successful localization of the epileptic seizure center was also achieved using a multielectrode probe as a demonstration of the diagnostics potential of NW electrodes. This study demonstrated the realism of single-neuron recording using subcellular-sized electrodes that may be considered a pivotal point for use in diverse studies of chronic brain diseases

An Alternative Host Material for Long‐Lifespan Blue Organic Light‐Emitting Diodes Using Thermally Activated Delayed Fluorescence

It has been challenging to find stable blue organic light emitting diodes (OLEDs) that rely on thermally activated delayed fluorescence (TADF). Lack of stable host materials well‐fitted to the TADF emitters is one of the critical reasons. The most popular host for blue TADF, bis[2‐(diphenylphosphino)phenyl] ether oxide (DPEPO), leads to unrealistically high maximum external quantum efficiency. DPEPO is however an unstable material and has a poor charge transporting ability, which in turn induces an intrinsic short OLED operating lifespan. Here, an alternative host material is introduced which educes the potential efficiency and device lifespan of given TADF emitters with the appropriateness of replacing the most popular host material, DPEPO, in developing blue TADF emitters. It simultaneously provides much longer device lifespan and higher external quantum efficiency at a practical brightness due to its high material stability and electron‐transport‐type character well‐fitted for hole‐transport‐type TADF emitters

A capacitive touch controller robust to display noise for ultrathin touch screen displays

Capacitive touch screens have become widely adopted in mobile applications. Capacitive touch-screen display modules have conventionally been assembled by bonding two separate modules: 1) a touch-screen module with touch panel glass or film attached to the cover window, and 2) a display module, with a small air gap between them. An important role of the air gap is to decrease capacitive coupling of display noise to the sensors, and it is very effective since permittivity of air is more than 4?? lower than that of glass