For the past decades, the scientific community has attempted to develop photocatalysts to obtain green hydrogen to diversify the current energy vectors, largely based on fossil fuels. In this context, many researchers have focused on modifying well-known photocatalysts such as TiO2 using other transition metals to boost photocatalytic activity in H2 production. However, powdered materials are difficult to reuse after prolonged exposure to liquid media in photocatalytic reactors. In this work, we have taken an alternative approach by developing structured catalysts based on TiO2 thin films and different Cu species. Photoluminescence analysis showed that incorporating Cu species on the TiO2 thin film decreases the e--h+ recombination rate. The photocatalytic activity of the nanostructured thin films is 298 µmol g−1 h−1 which is comparable to the reports described in the literature. Additionally, the thin films have simple and reproducible manufacturing, are easy to handle, are reusable and cost-effective. All these facts, make them a significantly more efficient technology than the counterpart powder materials.

Inkjet printing is a more sustainable and scalable fabrication method than spin coating for producing perovskite solar cells (PSCs). Although spin-coated SnO2 has been intensively studied as an effective electron transport layer (ETL) for PSCs, inkjet-printed SnO(2 )ETLs have not been widely reported. Here, we fabricated inkjet-printed, solution-processed SnOx ETLs for planar PSCs. A champion efficiency of 17.55% was achieved for the cell using a low-temperature processed SnOx ETL. The low-temperature SnOx exhibited an amorphous structure and outperformed high-temperature crystalline SnO2. The improved performance was attributed to enhanced charge extraction and transport and suppressed charge recombination at ETL/perovskite interfaces, which originated from enhanced electrical and optical properties of SnOx, improved perovskite film quality, and well-matched energy level alignment between the SnOx ETL and the perovskite layer. Furthermore, SnOx was doped with Cu. Cu doping increased surface oxygen defects and upshifted energy levels of SnOx, leading to reduced device performance. A tunable hysteresis was observed for PSCs with Cu-doped SnOx ETLs, decreasing at first and turning into inverted hysteresis afterwards with increasing Cu doping level. This tunable hysteresis was related to the interplay between charge/ion accumulation and recombination at ETL/perovskite interfaces in the case of electron extraction barriers.

Magnetization orientation in thin films is intricately influenced by multiple anisotropy components, with the dominant anisotropy serving as a key determinant. This complexity becomes particularly intriguing when considering thin films composed of subnanometer-scale heterogeneous amorphous structures. Our investigation builds upon this foundation, specifically focusing on the Fe-Ni-B-Nb alloy system, known for its moderate glass-forming ability and susceptibility to nanocrystallization. In this study, we present thickness- and temperature-driven spin-reorientation (SRT) transition, attributed to competing magnetic anisotropy energies in thin films featuring a heterogeneous amorphous structure. Thermogravimetric investigations unveiled a unique heterogeneous amorphous structure, a revelation unattainable through conventional structural analysis methods. The observed spontaneous perpendicular magnetization in amorphous films, as evidenced by transcritical hysteresis loops and magnetic stripe domains, is ascribed to the pronounced residual stress arising from the substantial magnetostriction of the alloy system. The temperature-driven SRT is correlated to the order-disorder magnetic transition of the heterogeneous amorphous phase, characterized by a Curie temperature of ∼225 K. This transformative magnetic state of the heterogeneous amorphous matrix limits the exchange interaction among the densely distributed α-Fe nuclei regions, ultimately governing the dynamic magnetic responses with varying temperature. This work provides valuable insights into the dynamic magnetic orientation of thin films, especially those with heterogeneous amorphous structures, contributing to the broader understanding of the underlying mechanisms of magnetization reversals.

Recent advancements in amorphous materials have opened new avenues for exploring unusual magnetic phenomena at the sub-nanometer scale. We investigate the phenomenon of low-temperature “magnetic hardening” in heterogeneous amorphous Fe–Ni–B–Nb thin films, revealing a complex interplay between microstructure and magnetism. Magnetization hysteresis measurements at cryogenic temperatures show a significant increase in coercivity (HC) below 25 K, challenging the conventional Random Anisotropy Model (RAM) in predicting magnetic responses at cryogenic temperatures. Heterogeneous films demonstrate a distinct behavior in field-cooled and zero-field-cooled temperature-dependent magnetizations at low temperatures, characterized by strong irreversibility. This suggests spin-glass-like features at low temperatures, which are attributed to exchange frustration in disordered interfacial regions. These regions hinder direct exchange coupling between magnetic entities, leading to magnetic hardening. This study enhances the understanding of how microstructural intricacies impact magnetic dynamics in heterogeneous amorphous thin films at cryogenic temperatures.

The phenomenon of exchange bias has been extensively studied within crystalline materials, encompassing a broad spectrum from nanoparticles to thin-film systems. Nonetheless, exchange bias in amorphous alloys has remained a relatively unexplored domain, primarily owing to their inherently uniform disordered atomic structure and lacking grain boundaries. In this study, we present a unique instance of exchange bias observed in Fe-B-Nb amorphous thin films, offering insights into its origins intertwined with the system's spin-glass-like behavior at lower temperatures. The quantification of exchange bias was accomplished through a meticulous analysis of magnetic reversal behaviors in the liquid-helium temperature range, employing a zero-field cooling approach from various initial remanent magnetization states (±MR). At reduced temperatures, the appearance of asymmetric hysteresis, a hallmark of negative exchange bias, undergoes a transformation into symmetric hysteresis loops at elevated temperatures, underscoring the intimate connection between exchange-bias and dynamic magnetic states. Further investigations into the magnetic thermal evolution under varying probe fields reveal the system's transition into a spin-glass-like state at low temperatures. We attribute the origin of this unconventional exchange bias to the intricate exchange interactions within the spin-glass-like regions that manifest at the interfaces among highly disordered Fe-nuclei. The formation of Fe-nuclei agglomerates at the sub-nanometer scale is attributed to the alloy's limited glass-forming ability and the nature of the thin-film fabrication process. We propose that this distinctive form of exchange bias represents a novel characteristic of amorphous thin films.

We report the fabrication and characterization of solution-route CeO2 thin films with a tunable porosity and microstructure. Films were deposited by means of inkjet printing technique using 0.2 M, 0.4 M and 0.6 M concentration inks prepared from Ce(NO3)(3)center dot 6H(2)O precursor. Printing was performed at two different temperatures of 60 degrees C and 300 degrees C to study the variation in structure. Printing parameters were adjusted for the consecutive deposition of layers, resulting in approximate to 140 nm and approximate to 185 nm thick single layers for 60 degrees C and 300 degrees C printing temperatures, respectively. We compared the microstructure of printed films for different concentrations, printing temperatures, solvents and substrates. The formation of the cubic fluorite structure of the printed films was confirmed via XRD characterization. We suggest this technique as an advanced method for high-quality film fabrication with a controlled microstructure and with a minimal waste of materials. Through adjusting printing parameters, both dense and porous films can be produced for use in different applications.

Microstructures, phase transformations and mechanical properties of the Ti-48Al-2Cr-2Nb-xHf (4822-xHf, x = 0, 2, 4, 6 at%) intermetallic alloys were investigated. The alloys were fabricated by vacuum arc remelting followed by hot isostatic pressing and homogenization treatment. The results showed that Hf alloying leads to a significant microstructure refinement in terms of both colony size and inter-lamellar spacing. Homogenization at 1400 degrees C resulted in a fully lamellar (FL) microstructure in 4822 and 2Hf alloys, while nearly lamellar (NL) in 4Hf and 6Hf alloys. Differential thermal analysis (DTA) demonstrated that Hf addition up to 2 at% has a slight contribution to phase transition sequences, but a significant implication to the phase equilibrium of the alloys with further Hf content. Based on the DTA data and annealing at 1450 degrees C, the solvus temperature of the eutectic phases was estimated to be over the range of 1430-1440 degrees C. Although the eutectic phases of Al3Hf2 and TiAl2 formed during solidification of the high-Hf alloys did not undergo any phase transition, both size and volume fraction of the eutectic cells increased due to the solvus of these metastable eutectic phases. The orientation relationship {111}(Tetragonal)//{001}(Orthorhombic) detected between the eutectic phases and their surrounding matrix confirmed the occurrence of (gamma c) (TiAl) -> eutectics (Al3Hf2, TiAl2) phase transformation. Small punch tests results showed that the 2Hf and 4Hf alloys exhibit a higher maximum load (F-m) than the base 4822 alloy due to the solid solution effect of Hf and finer inter-lamellar spacing. Nevertheless, the brittle behavior of the eutectic phases dramatically deteriorated mechanical performance such that the 6Hf alloy possessed the lowest Fm and displacement. The major fracture mode changed from trans-lamellar to inter-lamellar as the Hf content increased from 4 to 6 at%.

Magnetic force microscopy (MFM) is a powerful technique for studying magnetic microstructures and nanostructures that relies on force detection by a cantilever with a magnetic tip. The detected magnetic tip interactions are used to reconstruct the magnetic structure of the sample surface. Here, we demonstrate a new method using MFM for probing the spatial profile of an operational nanoscale spintronic device, the spin Hall nano-oscillator (SHNO), which generates high-intensity spin wave auto-oscillations enabling novel microwave applications in magnonics and neuromorphic computing. We developed an MFM system by adding a microwave probe station to allow electrical and microwave characterization up to 40 GHz during the MFM process. SHNOs-based on NiFe/Pt bilayers with a specific design compatible with the developed system-were fabricated and scanned using a Co magnetic force microscopy tip with 10 nm spatial MFM resolution, while a DC current sufficient to induce auto-oscillation flowed. Our results show that this developed method provides a promising path for the characterization and nanoscale magnetic field imaging of operational nano-oscillators.

Photocatalysts for water purification and energy production belong to the class of materials for which there is an urgent need for more environmentally friendly manufacturing. Here we report a high throughput method for inkjet printing of nanostructured photocatalytically active TiO2 films and a detailed analysis of their properties and photocatalytic performance. We show that the inkjet dispersion of TiO2 particles is highly reproducible which leads to a close to linear relation between the number of printed single layers and the thickness of the films. The films here obtained have uniform surfaces and the interfaces with the substrates are free from defects such as grain boundaries, ripples, or discontinuities. This contrasts with films obtained with the traditional doctor blade method. The inkjet printed films have higher photocatalytic performance than the doctor blade films which results in higher catalytic activity per mass of material used. Lifetime tests with wet and dry cycles show that the inkjet films subjected to 10 photocatalytic cycles of 100 minutes each have a loss of performance of only 7 %, while the films made via the doctor blade method have a performance loss of 66 %. These tests revealed additionally that the mechanical stability of the inkjet films is higher than that of the films manufactured via the traditional casting method. This set of results shows that inkjet printing can be an efficient method for the large-scale production of TiO2 photocatalysts. 

Inkjet printing emerged as an alternative deposition method to spin coating in the field of perovskite solar cells (PSCs) with the potential of scalable, low-cost, and no-waste manufacturing. In this study, the materials TiO2, SrTiO3, and SnO2 were inkjet-printed as electron transport layers (ETLs), and the PSC performance based on these ETLs was optimized by adjusting the ink preparation methods and printing processes. For the mesoporous ETLs inkjet-printed from TiO2 and SrTiO3 nanoparticle inks, the selection of solvents for dispersing nanoparticles was found to be important and a cosolvent system is beneficial for the film formation. Meanwhile, to overcome the low current density and severe hysteresis in SrTiO3-based devices, mixed mesoporous SrTiO3/TiO2 ETLs were also investigated. In addition, inkjet-printed SnO2 thin films were fabricated by using a cosolvent system and the effect of the SnO2 ink concentrations on the device performance was investigated. In comparison with PSCs based on TiO2 and SrTiO3 ETLs, the SnO2-based devices offer an optimal power conversion efficiency (PCE) of 17.37% in combination with a low hysteresis. This work expands the range of suitable ETL materials for inkjet-printed PSCs and promotes the commercial applications of inkjet printing techniques in PSC manufacturing.