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Plasmonic nanoclusters (NCs) have been introduced as new fluorescent materials that have low toxicity and do not undergo photo‐bleaching. Several factors including size and type of the NCs, surface chemistry and even solvent affect their luminescence. Despite extensive studies on tuning the fluorescence properties of NCs by manipulation of the above‐mentioned factors, very few researches have been focused on metal enhanced fluorescence (MEF) of them. In this study, the fabrication of silver dendritic nanostructured surfaces (DNSs) with numerous hotspots and unique plasmonic properties were optimized and DNSs were used as the substrates for fluorescence enhancement of NCs. NCs made of gold, silver and copper were synthesized by different stabilizing agents and compared with each other in terms of their MEF characteristics. The results showed that the stabilizing agent, the synthesis method and type of NCs affected their fluorescence enhancement by the DNSs. Copper NCs stabilized by bovine serum albumin (BSA) had the highest rate of fluorescence enhancement, with enhancement factor of 4.8 ± 0.8. Gold NCs synthesized by glutathione (GSH) and bovine serum albumin (BSA) demonstrated 3.9 ± 0.6 and 3.1 ± 0.4 fold fluorescence enhancement, respectively. The possibility of fluorescence enhancement of NCs in the vicinity of plasmonic nano‐structures introduces attractive platforms for sensing purposes. [ABSTRACT FROM AUTHOR]

The water oxidation efficiency of hematite photoanodes is mainly limited by low visible light absorption and short hole diffusion length. Herein, we report on production of nanoporous columnar hematite films modified with Au nanoparticles (NPs) to overcome these drawbacks. The hematite films are prepared by electron beam evaporation. By optimization of deposition conditions including film thickness, annealing and performing the evaporation under oblique angle, an efficient photoelectrochemical (PEC) performance is achieved from the pristine hematite photoanode. Then, Au NPs are infiltrated into the hematite films by a spin coating process. The water oxidation of hematite films is further enhanced after Au modification. The most efficient electrode generates a photocurrent density of 2.7 mA cm−2 at 1.5 V (RHE), showing about two‐fold improvement relative to that of bare hematite. Optical and electrochemical analyses suggest that the improvement after Au modification can be attributed to plasmonic and facilitating surface charge transfer. The contributions of different plasmonic mechanisms to the photocurrent enhancement are qualitatively discussed based on optical characterization and electromagnetic simulations. Electrochemical impedance spectroscopy is carried out to confirm the improvement of surface charge transport by the Au NPs. Our findings show that Au modification is a favorable strategy to improve the PEC performance of hematite photoanodes prepared by PVD methods. Bare efficiency! The production of electron beam evaporated nanoporous columnar hematite films modified with Au nanoparticles to overcome low visible light absorption and short hole diffusion length of hematite is reported. Optical and electrochemical analyses suggest that the improvement after Au modification can be attributed to plasmonic and reducing surface charge recombination effects. The most efficient photoanode shows about two‐fold improvement relative to that of the bare hematite. [ABSTRACT FROM AUTHOR]

The synthesization of Cu2O thin films by electrodeposition for photoelectrochemical water splitting is reported. The synthesized Cu2O samples are annealed at different temperatures between 300 and 500 °C. The XRD analysis and SEM images indicate that the sample without annealing includes Cu2O grains with pyramid shape. With annealing to more than 300 °C, due to the oxidization of the sample, a thin layer of CuO appears on the original Cu2O film and the crystalline signatures of such CuO structure increase with annealing at higher temperatures. The photoelectrochemical measurements indicate that annealing pure Cu2O by more than 300 °C, remarkably increases the photocurrent achieved from this photocathode. The effect is accompanied with considerable improvement of chemical stability of the original Cu2O electrode during water splitting. Such protection effect, which is originated from generation of CuO on the samples, increases with the annealing temperature up to 500 °C. However, the best photocurrent from the Cu2O/CuO composite is obtained from the annealing temperature of about 400 °C. The results of impedance analysis of various annealed samples indicate that annealing at a higher temperature, better charge transfer occurs both at the interface of photocathode/electrolyte and inside the photocathode. [ABSTRACT FROM AUTHOR]

A simple and practical approach is introduced for the deposition of CuI as an inexpensive inorganic hole-transport material (HTM) for the fabrication of low cost perovskite solar cells (PSCs) by gas-solid phase transformation of Cu to CuI. The method provides a uniform and well-controlled CuI layer with large grains and good compactness that prevents the direct connection between the contact electrodes. Solar cells prepared with CuI as the HTM with Au electrodes displays an exceptionally high short-circuit current density of 32 mA cm−2, owing to an interfacial species formed between the perovskite and the Cu resulting in a long wavelength contribution to the incident photon-to-electron conversion efficiency (IPCE), and an overall power conversion efficiency (PCE) of 7.4 %. The growth of crystalline and uniform CuI on a low roughness perovskite layer leads to remarkably high charge extraction in the cells, which originates from the high hole mobility of CuI in addition to a large number of contact points between CuI and the perovskite layer. In addition, the solvent-free method has no damaging side effect on the perovskite layer, which makes it an appropriate method for large scale applications of CuI in perovskite solar cells. [ABSTRACT FROM AUTHOR]