Plasmonic metasurfaces are a promising route for flat panel display applications due to their full color gamut and high spatial resolution. However, this plasmonic coloration cannot be readily tuned and requires expensive lithographic techniques. Here, we present scalable electrically driven color-changing metasurfaces constructed using a bottom-up solution process that controls the crucial plasmonic gaps and fills them with an active medium. Electrochromic nanoparticles are coated onto a metallic mirror, providing the smallest-area active plasmonic pixels to date. These nanopixels show strong scattering colors and are electrically tunable across >100-nm wavelength ranges. Their bistable behavior (with persistence times exceeding hundreds of seconds) and ultralow energy consumption (9 fJ per pixel) offer vivid, uniform, nonfading color that can be tuned at high refresh rates (>50 Hz) and optical contrast (>50%). These dynamics scale from the single nanoparticle level to multicentimeter scale films in subwavelength thickness devices, which are a hundredfold thinner than current displays.

The study of proton-coupled electron transfer reactions is of great current interest. In this work, the catechol redox process was studied voltammetrically in the pH range from 1.0 to 14.0 using a glassy carbon electrode. Analysis of the peak potentials and currents together with Tafel analysis allowed the inference of the likely transition states and electrode reaction mechanism. Modification of the glassy carbon electrode surface with sparse coverages of alumina particles was shown to lead to strong apparent catalysis of the catechol redox process at low pH. A possible mechanism for this is proposed.

Immobilised first-row transition metal complexes are potential low-cost electrocatalysts for selective CO2 conversion to produce renewable fuels. Mechanistic understanding of their function is vital for the development of next-generation catalysts, though poor surface sensitivity of many techniques makes this challenging. Here, a nickel bis(terpyridine) complex is introduced as a CO2 reduction electrocatalyst in a unique electrode geometry, sandwiched by thiol anchoring moieties between two gold surfaces.Gap-plasmon-assisted surface-enhanced Raman scattering spectroscopy coupled with density functional theory calculations reveals the nature of the anchoring group plays a pivotal role in the catalytic mechanism by eliminating ligand loss. Our in-situ spectro-electrochemical measurement enables the detection of as few as 8 molecules undergoing redox transformations in the individual plasmonic hot-spots, together with the calibration of electrical fields via vibrational Stark effects. This advance allows rapid exploration of non-resonant redox reactions at the few-molecule level and provides scope for future mechanistic studies of single-molecules.

Plasmonic metafilms have been widely utilized to generate vivid colors, but making them both active and flexible simultaneously remains a great challenge. Here flexible active plasmonic metafilms constructed by printing electrochromic nanoparticles onto ultrathin metal films (<15 nm) are presented, offering low‐power electricallydriven color switching. In conjunction with commercially available printing techniques, such flexible devices can be patterned using lithography‐free approaches, opening up potential for fullyprinted electrochromic devices. Directional optical effects and dynamics show perceived upward and downward colorations can differ, arising from the dissimilar plasmonic mode excitation between nanoparticles and ultrathin metal films.

Transient bonds between molecules and metal surfaces underpin catalysis, bio/molecular sensing, molecular electronics, and electrochemistry. Techniques aiming to characterize these bonds often yield conflicting conclusions, while single-molecule probes are scarce. A promising prospect confines light inside metal nanogaps to elicit in operando vibrational signatures through surface-enhanced Raman scattering. Here, we show through analysis of more than a million spectra that light irradiation of only a few microwatts on molecules at gold facets is sufficient to overcome the metallic bonds between individual gold atoms and pull them out to form coordination complexes. Depending on the molecule, these light-extracted adatoms persist for minutes under ambient conditions. Tracking their power-dependent formation and decay suggests that tightly trapped light transiently reduces energy barriers at the metal surface. This opens intriguing prospects for photocatalysis and controllable low-energy quantum devices such as single-atom optical switches.

Graphene nanoplatelets (GNPs) are 'tagged' with 1-(biphen-4-yl)ferrocene. Chronoamperometry is then utilised to observe single particle impacts when GNPs suspended in solution collide with a carbon fibre micro wire electrode held at an oxidising potential, resulting in current/time transient "spikes". The impacts are associated with two types of charge transfer: Faradaic due to oxidation of the 'tag' and capacitative due to disruption of the double layer. Analysis of the spikes suggests approximate monolayer coverage of 1-(biphen-4-yl)ferrocene on the GNP surfaces, with a surface coverage of (2.2 ± 0.3) × 10(-10) mol cm(-2). In contrast non-derivatised ferrocene does not exhibit any significant adsorption on the GNP material.

Particle impacts are used to quantify the adsorption of catechol on single alumina particles. In these experiments particles suspended in solution impact a microelectrode held at a suitable potential for the oxidation or reduction of the adsorbed species and the resulting current/time transients "spikes" associated with individual impacts measured. Using theory for charge diffusion over the surface of a sphere, the individual impact spikes arising from the electro-oxidation of adsorbed catechol can be modelled to derive the diffusion coefficient of charge transfer over the surface of alumina as (2.5 ± 0.5) × 10-6 cm 2 s-1. The coverage of catechol on the surface of alumina is found to be (5.9 ± 1.9) × 10-10 mol cm-2 .

The mediated reduction of oxygen via the reduced form of methyl viologen is studied voltammetrically. The investigation is facilitated through the use of a boron-doped diamond electrode, allowing the catalytic response to be clearly delineated from that of the direct oxygen reduction process at the electrode surface. From simulation a high homogeneous electron transfer rate (6 × 10(9) M(-1) s(-1)) is found for the one-electron reduction of oxygen to superoxide. This value is in close agreement with that found using non-electrochemical methods and is significantly higher than the values previously reported in electrochemical studies. In the latter case it is demonstrated that the underestimation of the electron transfer rate arises due to oversimplification of the reaction mechanism.