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The plasmonic resonance of noble metal nanoparticles (NPs) can be exploited to enhance the photoresponse of wide band gap oxides in view of several solar energy applications. Here, we demonstrate single-step synthesis of plasmonic Au nanoparticles integrated in TiO 2 hierarchical nanoporous layers through a vapor phase pulsed laser co-deposition approach. Specifically, we report the fabrication and characterization of Au NPs-decorated TiO 2 forest-like systems with tunable porosity and density as well as the morphological/structural evolution as a function of Au content and we discuss the corresponding optical properties. The effect of post-deposition thermal treatment has been investigated as well in order to control TiO 2 crystallization and Au NPs nucleation and growth. Optical analyses show the onset of characteristic plasmonic resonance of Au NPs with the increase of film absorption in the visible range. Preliminary tests of photodegradation of methyl orange dye indicate that the integration of Au NPs leads to a significant increase of the catalytic activity of nanoporous TiO 2 . Our results suggest the potentiality of this approach for the synthesis and the integration of metallic NPs within wide band gap semiconductors, while paving the way toward novel plasmonic-based devices. [ABSTRACT FROM AUTHOR]

The synthesis and the optical response of gold nanoparticles (NPs) and thin nanostructured films grown by pulsed laser deposition (PLD) are here studied. Different PLD process parameters – including background gas pressure and the number of laser shots as well as post-deposition annealing treatments – have been varied to control the growth of Au NPs and films, thus tuning the surface plasmon characteristics. The mechanisms of NPs and film growth have been explored performing a morphological characterization by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), and the correlation with the optical behavior is investigated. We show that the size distribution and the morphology of the as deposited Au NPs depend on growth mechanisms which are controlled by tuning the deposition process, while the optical behavior is strongly affected by the average size and surface density of NPs or by the length of percolated Au domains. Furthermore, nucleation in gas phase has been reported at high (1000 Pa Ar) background pressures, enabling independent control of NP size and coverage, contrary to surface driven NP growth by diffusion and aggregation on substrate. [ABSTRACT FROM AUTHOR]

Nanostructured TiO 2 films with hierarchical morphology were synthesized by Pulsed Laser Deposition (PLD) and tested as photoanodes for photoelectrochemical water splitting. The tuning of their photoresponse was addressed by employing oxygen-poor conditions both during the growth and the post-deposition annealing of the material: depositions were performed in different Ar/O 2 background gas mixtures from both TiO 2 and Ti targets, while thermal treatments, after standard air annealing for crystallization, were performed in a Ar/H 2 mixture. By testing the double-annealed photoanodes in a three-electrode cell with solar simulator illumination, clear trends with optimal synthesis conditions for each target material appeared; for these conditions, also the effect of vacuum annealing was studied. The morphological, structural and optical properties were investigated by SEM, Raman spectroscopy and UV-visible-IR spectroscopy. From these observations, it emerged that the films deposited in the presence of oxygen do not show substantial differences in their morphology/structure, on the contrary of pure Ar-deposited films; thus, the trends in photoresponse can be related to differences in the defect concentration of the material, induced by depositions in the different Ar/O 2 atmospheres and by annealing in Ar/H 2 mixture or vacuum. In particular, the reported results suggest that some degree of oxygen shortage in the deposition process leads to a better photoelectrochemical performance, and a combination between improved charge transport and surface hydrogenation/reduction effect, leading to enhanced photoresponse, is suggested. This work elucidates the possibility of an accurate tuning of the material photoactivity by control of the deposition and annealing conditions. [ABSTRACT FROM AUTHOR]

Hierarchical titanium oxide nanostructures were synthesized by Pulsed Laser Deposition (PLD) and investigated as photoanodes for photoelectrochemical water splitting. An explorative combined approach to enhance TiO 2 performance was based, on the one hand, on the employment of hydrogenation treatments with the aim of improving quantum efficiency and extending light absorption to the visible range; on the other hand, on the optimization of morphology and structure, to increase light harvesting and charge separation/transport. This approach was pursued by depositing at a fixed background pressure with variable oxygen content (to control the growth morphology and structure) and by annealing in a Ar/H 2 mixture (in substitution of or in combination with air annealing), in order to induce crystallization to the anatase structure and reduction/hydrogenation of the material. Morphology, structure and optical properties were investigated by SEM, Raman spectroscopy, X-ray diffraction and UV–visible-IR spectroscopy. An optical absorption tail towards the visible range appeared after Ar/H 2 annealing, without any significant modification of the nanoscale structure after the different thermal treatments. Photocurrent measurements under solar simulator illumination showed a noteworthy increase of photoresponse for Ar/O 2 -deposited samples with air annealing followed by Ar/H 2 annealing. These findings can be ascribed to the combination between an improved charge transport of TiO 2 deposited in low-O 2 atmosphere and a hydrogenation effect on the nanostructures surface layers, leading to improved quantum efficiency. [ABSTRACT FROM AUTHOR]

Aqueous Zn-ion batteries (AZIBs) represent a safe and sustainable technology amongst the post-lithium systems, though the poor understanding of the material behaviour at the cathode prevents the full development of efficient AZIBs. ZnMn 2 O 4 (ZMO) has been considered one of the cathode candidates owing to its analogy to the well-established LiMn 2 O 4 cathode for lithium-ion batteries, however its electrochemical mechanism in the presence of Zn ions in aqueous environment is unclear and still debated. In this work, we synthesised nanostructured ZMO thin films by Pulsed Laser Deposition (PLD) and we evaluated, through extensive characterization by microscopic, spectroscopic, and diffraction techniques, how the deposition and annealing conditions affect the film properties. The self-supported nature and the high degree of control down to the nanoscale make a thin film an ideal model system to study the electrochemistry of the material in aqueous solution and to emphasize the impact of the film properties on its electrochemical response. We highlighted the crucial role of the oxygen pressure in the modulation of the film porosity and the combined effect of deposition pressure and annealing temperature to produce a film with tailored properties in terms of morphology, crystallinity, and Zn stoichiometry. A complex redox mechanism involving multiple concurrent reactions and the formation of zinc hydroxide sulphate hydrate (ZHS) was reported, as well as the influence of the film porosity on the voltammetric behaviour of the film at higher scan rate. Our results confirm the intricate electrochemical mechanism of the ZMO material, which does not merely involve the Zn2+ insertion/extraction but also the crucial participation of Mn2+ from the electrolyte, and pave the way for the nanoscale design of engineered ZMO-based electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Compact and nanogranular ZrCu/O films were deposited by pulsed laser deposition and annealed to investigate thermal stability. • Nanogranular films crystallize at 300 °C, while the crystallization of compact films occurs >420 °C. • The Young's modulus and hardness increase with annealing temperatures due crystallization process, reaching 180 and 14 GPa for nanogranular films. • The residual stresses of compact films increase with annealing temperature, while for nanogranular ones they reach a maximum at 420 °C, indicating a complete crystallization. • The evolution of structural/mechanical properties is studied, considering film morphology, local chemistry and free volume. Binary ZrCu nanocomposite amorphous films are synthetized by pulsed laser deposition (PLD) under vacuum (2 × 10−3 Pa) and 10 Pa He pressure, leading to fully amorphous compact and nanogranular morphologies, respectively. Then, post-thermal annealing treatments are carried out to explore thermal stability and crystallization phenomena together with the evolution of mechanical properties. Compact films exhibit larger thermal stability with partial crystallization phenomena starting at 420 °C, still to be completed at 550 °C, while nanogranular films exhibit early-stage crystallization at 300 °C and completed at 485 °C. The microstructural differences are related to a distinct evolution of mechanical properties and residual stress, with compact TFMGs showing the highest values of Young's modulus (157 GPa), hardness (12 GPa), strain rate sensitivity (0.096), and local residual stress (+691 MPa) upon annealing at 550 °C, while nanogranular films reach the maximum values of mechanical properties at 485 °C followed by relaxation at higher temperatures due to complete crystallization. We show that PLD in combination with post-thermal annealing can generate different families of amorphous films with varying nanoscale morphologies, resulting in tunable mechanical properties and thermal stability, which can thus be used for designing novel film configurations for different fields of application. [ABSTRACT FROM AUTHOR]

A functionally graded Al-doped ZnO structure is presented which combines conductivity, visible transparency and light scattering with mechanical flexibility. The nano- and meso-architectures, constituted by a hierarchical, large surface area, mesoporous tree-like structure evolving in a compact layer, are synthesized at room temperature and are fully compatible with plastic substrates. Light trapping capability is demonstrated by showing up to 100% improvement of light absorption of a low bandgap polymer employed as the active layer. [ABSTRACT FROM AUTHOR]