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Gadolinium oxyhydride GdHO is a photochromic material that darkens under illumination and bleaches back by thermal relaxation. As an inorganic photochromic material that can be easily deposited by magnetron sputtering, GdHO has very interesting potential applications as a functional material, specially for smart glazing applications. However, the underlying reasons behind the photochromic mechanism - which can be instrumental for the correct optimisation of GdHO for different applications - are not completely understood. In this paper, we rely on the well-established magnetic properties of Gd3+ to shed light on this matter. GdHO thin films present paramagnetic behaviour similar to other Gd3+ compounds such as Gd2O3. Illumination of the films result in a reversible increase of the Curie-Weiss temperature pointing to Ruderman-Kittel-Kasuya-Yosida RKKY interactions, which is consistent with the resistivity decrease observed in the photodarkened films.

I ett forskningsprojekt som kommer avslutas vid årsskiftet har framtidens multifunktionella glasytor för solceller utvecklats. Antireflektiva, UV-skyddande, fotokatalytiska och lättrengörliga glasytor är egenskaperna som glasytorna kommer att få. Forskningsidén baseras på tidigare kunskap ifrån forskning vid RISE, Uppsala universitet och KTH och förväntas leda till effektiva solceller med längre livslängd.

We report on a one-step, on-chip fabrication process of high-quality nanoporous p-type NiO thin films for gas sensing application. Highly nanoporous and polycrystalline NiO thin films were fabricated and deposited onto alumina substrates employing advanced gas deposition (AGD) technique. AGD-fabricated NiO films were further decorated with gold (AuNP) and copper (CuNP) nanoparticles, respectively. The nano-sensors array thus fabricated were integrated into a purpose-built hybrid senor unit that allows for in-situ conditioning and gas sensing measurement of volatile gases. The results revealed that the relative sensor responses of pure NiO towards CO gas exposures (reducing gas), were higher than the corresponding NP decorated NiO films. In contrast, AuNP decorated NiO sensors exhibited relatively higher sensor response towards oxidizing gases, NO2, than CuNP decorated and pure NiO based nano-sensors. It is noted that the relative sensor response changes are mainly governed by the high porosity of the as-fabricated NiO films and the corresponding grain-grain Schottky barriers. Limits of detection (LOD) was estimated to be 1.5 ppm for CO and 400 ppb for NO2 for pure and AuNP decorated NiO based sensors, respectively. The results are promising for further development of nanoporous p-type metal oxide sensors for specific volatile biomarkers detection, for example, in exhaled breath analysis for disease diagnosis.

We report results of the current-voltage characteristics and low-frequency noise in Au nanoparticle (AuNP)-decorated graphene-Si Schottky barrier diodes. Measurements were conducted in ambient air with addition of either of two organic vapors, tetrahydrofuran [(CH2)(4)O; THF] and chloroform (CHCl3), as also during yellow light illumination (592 nm), close to the measured particle plasmon polariton frequency of the Au nanoparticle layer. We observed a shift of the DC characteristics at forward voltages (forward resistance region) when tetrahydrofuran vapor was admitted (in a Au-decorated graphene-Si Schottky diode), and a tiny shift under yellow irradiation when chloroform was added (in not decorated graphene-Si Schottky diode). Significantly larger difference in the low-frequency noise was observed for the two gases during yellow light irradiation, compared with no illumination. The noise intensity was suppressed by AuNPs when compared with noise in graphene-Si Schottky diode without an AuNP layer. We conclude that flicker noise generated in the investigated Au-decorated Schottky diodes can be utilized for gas detection.

The adsorption and photocatalytic degradation of trimethyl phosphate (TMP) and triethyl phosphate (TEP), two environmentally relevant model pollutants, have been studied on commercial anatase TiO2 and sulfate-terminated anatase TiO2 nanoparticles by means of operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and 2D correlation spectroscopy (2D COS). It is concluded that both TMP and TEP adsorb dissociatively on anatase TiO2, while on the sulfate-terminated anatase TiO2, TMP and TEP adsorb associatively. Upon UV illumination, TMP and TEP are completely oxidized on sulfate-terminated anatase TiO2, as evidenced by the evolution of the IR bands characteristic for water and carbon dioxide. In contrast, on anatase TiO2, UV illumination leads to the formation of stable surface-coordinated carboxylate products, which impedes complete oxidation. 2D COS analysis suggests that parallel reaction pathways occur during oxidation under UV illumination, viz. methoxide/ethoxide (ads) -> carboxylates (ads) and methoxide/ethoxide (ads) -> aldehydes (ads) -> carboxylates (ads). A parallel reaction occurs on sulfated TiO2 that yields CO2 and H2O by direct radical reactions with the methoxide groups with little, or no, formation of surface-coordinated intermediates. Sulfated TiO2 favor the formation of aldehyde intermediates, with reaction rates 10 times and 30 times faster for TMP and TEM, respectively, compared with commercial anatase TiO2. About 37% (33%) and 32% (24%) of TMP (TEP) were degraded on sulfated-terminated TiO2 and pure TiO2, respectively, after the first 9 min of UV illumination. We show that the sulfate-functionalization of TiO2 has two main functions. First, it prevents the formation of strongly bonded bridging carboxylates, thereby alleviating deactivation. Second, it promotes full oxidation of the organic side-chains into carbon dioxide and water. Improved electron-hole separation by the electrophilic S(VI) in combination with the bl

Reactive High Power Impulse Magnetron Sputtering (HiPIMS) of TiO2 thin films was carried out to investigate the influence of ion parameters and the deposition temperature on the film crystallinity and photocatalytic performance. In order to limit unintentional substrate heating, a deposition setup with long target-to-substrate distance was used. Different HiPIMS pulse configurations, deposition temperatures and substrate bias were evaluated. TiO2 films prepared by pulsed dc magnetron sputtering were used as reference. Films deposited at room temperature were all found to be X-ray amorphous, and a minimum temperature of 200 degrees C was needed for film crystallization irrespective of the mode of operation. This is attributed to the relatively long target-to -substrate distance of 180 mm used in this work. The growth of a specific polymorph was shown to be depen-dent on the operation mode, where a high oxygen partial pressure was ideal for anatase formation. The pho-todegradation rates were, as expected, found to be highest for crystalline samples, where single-and mixed-phase films yielded similar rates. Furthermore, the photodegradation rates of HiPIMS films deposited without substrate heating could be enhanced up to 3 times as compared to the corresponding pulsed dc reference film. The ion assistance in HiPIMS is also beneficial at moderate temperatures, here 200 degrees C, where an improved crystallinity as compared to pdcMS, was observed.

In photovoltaics, the cover glass module has hitherto not yet been fully optimized for its purpose. Instead quite conventional architectural glass is used. In a recent review of the state-of-the-art on UV down converting dopants [1], a way forward to improve cover glasses was presented. Some of these possibilities, and others are covered in the present paper. We present possibilities to add several functionalities, instead of using dopants in the glass composition, including omnidirectional antireflection, dynamic solar control, and self-cleaning. Omni-directional anti-reflective coatings, were made by colloidal lithography templating methods on iron free glass, realizing nanopillar structures with dimensions /2 exploiting Mie scattering for wide angle light collection (Fig. 1). Yttrium oxyhydride (YHO) coatings were deposited on the nanopillar structures using magnetron sputtering methods [2]. The YHO film blocks UV light and photo-darkens upon solar light absorption and reverts to its transparent state in dark in reproducible manner [2]. In addition, the YHO film also becomes hydrophobic upon photo-darkening, acting as a self-cleaning layer. The fabricated coatings were compared with bare glass substrates. The results reveal suppressed reflectance, with acceptable anti-reflective properties up to about 50 degrees. Solar light modulation of a thin 100 nm YHO coating is below 10% thus having high transmittance throughput while allowing for solar cell life-time saving by removal of excess irradiance. Finally, the surface energy of the YHO coated glass structures are presented, demonstrating synergetic chemical and structural (the Lotus effect), showing promising self-cleaning properties. In conclusion, we show possibilities to combine photonic and chromogenic principles with suitable surface chemistry to achieve high-performance cover glass for solar energy application. ., Funding: Energimyndigheten P2022-00859, Transparenta multifunktionella tunnfilmer på lågjärnglas för solcellsapplikationer, Semi-transparent solcells- och fotokromt smart fönster

We present VOGAS, a semi-portable instrument performing non-invasive and fast detection of gastric cancer. The VOGAS device analyzes the patients exhaled breath using two gas sensing techniques: infrared spectrometry and different technologies of resistive gas sensors (gold nanoparticles, research developed metal oxides and commercial metal oxides). The combination of these techniques results in a great amount of complementary information in a single breath sample measurement, which can increase the ability of a one-gas sensing technique device to detect gastric diseases. In this work, we describe the VOGAS device in detail.

The ability to control electronic states by utilizing quantum confinement of one of the material components in heterojunctions is a promising approach to perform energy-level matching. In this work, we report the possibility to achieve optimum energy alignment in heterojunctions made from size-controlled quantum dots (Q-dots) of ZnO in combination with three copper oxides: Cu2O, Cu4O3, and CuO. Quantum confinement effects on the ZnO nanoparticles in the diameter range 2.6–7.4 nm showed that the direct optical band gap decreased from 3.99 to 3.41 eV, with a dominating shift occurring in the conduction band (CB) edge, and thus the possibility to obtain close to 0.6 eV CB edge shift by controlling the size of ZnO. The effect was utilized to align the electronic bands in the ZnO Q-dot/copper oxide heterojunctions to allow for charge transfer between the materials and to test the ability to improve the photocatalytic performance for the system, evaluated by the transformation of a dye molecule in water. The catalyst materials were investigated by X-ray diffraction, scanning electron microscopy, ultraviolet–visible (UV–vis), photoluminescence, and Raman spectroscopy. The most promising material combination was found to be the Cu2O copper oxide in combination with an energy aligned ZnO Q-dot system with approximately 7 nm diameter, showing strong synergy effects in good agreement with the energy-level analysis, outperforming the added effect of its individual components, ZnO-Q-dots and Cu2O, by about 140%. The results show that utilization of a heterojunction with controllable energy alignment can provide a drastically improved photocatalytic performance. Apart from increased photocatalytic activity, specific surface states of ZnO are quenched when the heterojunction is created. It is anticipated that the same approach can be utilized in several material combinations with the added benefit of a system with controllable overpotential and thus added specificity for the targe

Most transparent conducting materials are based on Sn:In2O3 (ITO). When applied onto flexible substrates, ITO can be prepared in an oxide-metal-oxide (OMO) configuration, typically ITO/Ag/ITO, where the ductility of the embedded metal layer is intended to reduce the mechanical brittleness and improve the electrical conductivity of the OMO multilayer. Hitherto, the lower limit of the thickness of the Ag layer has been limited by the percolation threshold, which limits the Ag layer to be thicker than similar to 10 nm to avoid agglomeration and to ensure conductivity and structural stability. Metal layers of thicknesses below 10 nm are, however, desirable for obtaining OMO coatings with better optical properties. It is known that agglomeration of the metal layer can, to some extent, be suppressed when substituting Ag by an Ag-Pd-Cu (APC) alloy. APC-based OMO films exhibit excellent optical and electrical properties, but still continuous APC films well below 10 nm thickness cannot be achieved. In this work we demonstrate that controlled oxidation of APC results in smooth, ultrathin APC:O continuous coatings (of thickness similar to 5 nm) on ITO-coated PET substrates. Moderate oxidation yields superficial PdOx formation, which suppresses Ag agglomeration, while still maintaining excellent conductivity. On the other hand, extensive oxidation of APC leads to extensive Pd oxide nucleation deteriorating the conductivity of the film. The ITO/APC:O/ITO films exhibit low resistivity, attributed to a high Hall mobility associated with suppressed agglomeration, good stability in high humidity/temperature environments, superior transmittance in the visible and infrared region, and excellent mechanical bending properties, thus providing new opportunities for fabricating superior transparent conducting coatings on polymer substrates.

Diffusion kinetics and structural properties of chemically strengthened titania-doped soda-lime silicate glasses were studied by depth-resolved X-ray photoelectron spectroscopy, Raman spectroscopy and spectrophotometry. The glasses were ion exchanged, whereby Na+ in the glass was replaced by K+ in a molten salt bath, at four different treatment temperatures between 350 and 500 ?. The alkali diffusion coefficient, DK-Na, and corresponding activation energy were calculated to be between 3.26x10(-12) and 4.47x10 & nbsp;(-11) cm(2)s(-1) and between 101.1 kJmol(-1) and 105.6 kJmol(-1), respectively. DK-Na was observed to decrease as the TiO2 concentration was increased. Raman analysis showed Q3-silicate species with different bond lengths, which was attributed to surface compressive stresses, and increasing Si-O-Si bond angle with increasing ion exchange temperature. Ti3+ ions exist as a minor species in the glasses and its concentration depends on the TiO2 content. Deconvolution of the optical absorption spectra reveals Jahn-Teller compressive distortion of the Ti3+ octahedral coordination.

The catalytic and photon-induced oxidation of NO2 on anatase TiO2 has been studied and compared with the surface nitrate species obtained after adsorption of HNO3. Using a combination of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), density functional theory (DFT), and temperature-programmed desorption (TPD), it is shown that identical products are obtained in all reaction systems but that their formation rates differ significantly. The surface reaction products are identified as combinations of surface–NO3– species, where NO2 bonds to the lattice oxygen, and freely adsorbed NO3– ions. These products can be obtained either by dissociative adsorption of HNO3 or by catalytic/photocatalytic oxidation of NO2, which is facilitated by UV light. A concerted reaction mechanism is unraveled that involves reorientation of bidentate nitrate that pushes out a neighboring protonated lattice oxygen to form a surface–NO3– species and a terminal OH group. The thermal stability of these surface species has been studied by means of TPD and simultaneous in situ DRIFTS measurements that reveal a main desorption peak (m/z = 46) at around 430 °C, which is attributed to concerted nitrate desorption through pentoxide (N2O5) formation. A weaker and broader TPD peak is found at about 185 °C and is attributed to desorption of nitrate species bonded in a compressed configuration. The experimental results can be explained by the changing stability of the identified nitrate products, which depends strongly on the surface chemical environment and the surface coverage. The DFT results show that the stabilization of intermediate NO2 adsorbates and the final nitrate reaction products occurs through a bifunctional charge exchange mechanism that is mediated by the TiO2 crystal. In particular, a stable surface–NO3– and NO3– ion pair configuration has been identified. This mechanism explains both the thermal and photoinduced oxidation of NO2 and their thermal stability an, Title of manuscript version in list of papers for David Langhammer: Adsorption and Catalytic Oxidation of NO2 on Anatase TiO2: A Combined DFT and Operando DRIFT Spectroscopy StudyAuthors of manuscript version in list of papers for David Langhammer: David Langhammer, Lars Österlund

The gas sensing properties of graphene back-gated field-effect transistor (GFET) sensors toward acetonitrile, tetrahydrofuran, and chloroform vapors were investigated with the focus on unfolding possible gas detection mechanisms. The FET configuration of the sensor device enabled gate voltage tuning for enhanced measurements of changes in DC electrical characteristics. Electrical measurements were combined with a fluctuation-enhanced sensing methodology and intermittent UV irradiation. Distinctly different features in 1/f noise spectra for the organic gases measured under UV irradiation and in the dark were observed. The most intense response observed for tetrahydrofuran prompted the decomposition of the DC characteristic, revealing the photoconductive and photogating effect occurring in the graphene channel with the dominance of the latter. Our observations shed light on understanding surface processes at the interface between graphene and volatile organic compounds for graphene-based sensors in ambient conditions that yield enhanced sensitivity and selectivity.