NiO photocathodes were fabricated by alkaline etching-anodizing nickel foil in an organic-based electrolyte. The resulting films have a highly macroporous surface structure due to rapid dissolution of the oxide layer as it is formed during the anodization process. We are able to control the films' surface structures by varying the anodization duration and voltage. With an onset potential of +0.53 V versus the reversible hydrogen electrode (RHE), the photocurrent efficiency of the NiO electrodes showed dependencies on their surface roughness factor, which determines the extent of semiconductor-electrolyte interface and the associated quality of the NiO surface sites. A maximum incident photon-to-current conversion efficiency (IPCE(max)) of 22% was obtained from NiO film with a roughness factor of 8.4. Adding an Al2O3 blocking layer minimizes surface charge recombination on the NiO and hence increased the IPCE(max) to 28%. The NiO/Al2O3 films were extremely stable during photoelectrochemical water splitting tests lasting up to 20 h, continuously producing hydrogen and oxygen in the stoichiometric 2:1 ratio. The NiO/Al2O3 and NiO films fabricated using the alkaline anodization process produced 12 and 6 times as much hydrogen, respectively, as those fabricated using commercial NiO nanoparticles.

This work presents a thorough guide to procedures for absolute electrochemiluminescence (ECL) quantum efficiency (ΦECL) measurements, which if employed effectively should raise the research impact of ECL studies for any luminophore. Absolute measurements are not currently employed in ECL research. Instead, ECL efficiencies have been determined relative to Ru­(bpy)3 2+ under similar conditions, regardless of whether the conditions are favorable for Ru­(bpy)3 2+ emissions or not. In fact, the most cited Ru­(bpy)3 2+ ΦECL is from the pioneering work by the Bard research group in 1973 by means of a rotating ring-disk electrode revolving at 52 rotations per second measured with a silicon photodiode. Our presented technique uses a common disk electrode, spectrometer, and photomultiplier tube to measure the ΦECL. The more common light detection hardware and electrodes combined with an in-depth calculation walkthrough will provide ECL researchers the necessary tools to implement ΦECL measurement procedures in their own laboratories. Following a facile instrument setup and calculation, a systematic study of Ru­(bpy)3 2+ ΦECL finds comparable results to those performed by Bard and co-workers.

In this work, using a photon-counting device, we outline our physical strategy to determine absolute electrochemiluminescence (or electrogenerated chemiluminescence, ECL) quantum efficiencies of coreactant systems in comparison with those in annihilation pathways. This absolute method addresses many of the issues with existing relative ECL efficiency measurements, including inconsistencies stemming from nonstandardized experimental conditions and incompatible luminophore systems. The absolute efficiency of the Ru­(bpy)3 2+/tri-n-propylamine (TPrA) ECL coreactant system taken as an example was found to be 10.0 ± 1.1% for the first time using 10 Hz potential stepping at a TPrA concentration of 10 mM, which quantifies a 3-fold enhancement in efficiency compared to that in the annihilation pathway. Our physical and analytical technique is anticipated to be an immediate and impactful methodology in the expanding field of ECL research.

The interactions between SbF6 – and metal nanoclusters are of significance for customizing clusters from both structure and property aspects; however, the whole-segment monitoring of this customization remains challenging. In this work, by controlling the amount of introduced SbF6 – anions, the step-by-step nanocluster evolutions from [Pt1Ag28(S-Adm)18(PPh3)4]Cl2 (Pt1Ag28–Cl) to [Pt1Ag28(S-Adm)18(PPh3)4](SbF6)2 (Pt1Ag28–SbF6) and then to [Pt1Ag30Cl1(S-Adm)18(PPh3)3](SbF6)3 (Pt1Ag30–SbF6) have been mapped out with X-ray crystallography, with which atomic-level SbF6 – counterion effects in reconstructing and rearranging nanoclusters are determined. The structure-dependent optical properties, including optical absorption, photoluminescence, and electrochemiluminescence (ECL), of these nanoclusters are then explored. Notably, the Pt1Ag30–SbF6 nanocluster was ultrabright with a high phosphorescence quantum yield of 85% in N2-purged solutions, while Pt1Ag28 nanoclusters were fluorescent with weaker emission intensities. Furthermore, Pt1Ag30–SbF6 displayed superior ECL efficiency over Pt1Ag28–SbF6, which was rationalized by its increased effectively exposed reactive facets. Both Pt1Ag30–SbF6 and Pt1Ag28–SbF6 demonstrated unprecedented high absolute ECL quantum efficiencies at sub-micromolar concentrations. This work is of great significance for revealing the SbF6 – counterion effects on the control of both structures and luminescent properties.

Mechanisms of emissions, especially electrochemiluminescence (ECL), for graphene quantum dots (GQDs) are poorly understood, which makes near-infrared (NIR)-emitting GQDs difficult to create. To explore this poorly understood NIR ECL, two GQDs, nitrogen-doped GQDs (GQD-1) and nitrogenand sulfur-doped ones (GQD-2), were prepared by a simple onestep solvothermal reaction with similar core structures but different surface states. The GQDs were analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and highresolution transmission electron microscopy. Photoluminescence results, with a comparable quantum efficiency of 13% to strong luminophores in aqueous media, suggested a mechanism that the emission mainly depends on the core structure while slightly adjusted by the heteroatom doping. ECL of GQD-2 dispersed in aqueous media with K 2 S 2 O 8 as the coreactant was measured by means of ECL−voltage curves and ECL spectroscopy, demonstrating strong NIR emissions between 680 and 870 nm, with a high ECL efficiency of 13% relative to that of the Ru(bpy) 3 2+ /K 2 S 2 O 8 system. Interestingly, ECL is generated by surface excited states emitting light at a much longer wavelength in the NIR region. The easily prepared GQD-2 has several advantages such as low cost and quite strong NIR-ECL in aqueous media, with which wide applications in biodetection are anticipated.