Outdoor and indoor air pollution is a global environmental concern in modern society. Although many policies and regulations on air quality have been promulgated worldwide over the past decades, airborne pollution still negatively affects health and therefore the life-style of human beings. One of the strategies to challenge this problem might be reducing the amount of airborne pollutant by mineralising them via photoinduced reactions. Photocatalytic oxidation of gaseous pollutants via titanium dioxide is one of the most investigated solar photochemical reactions. In this research work, by means of a green sol-gel procedure, we have coupled titania to graphene (0.5 and 1.0 wt%) aiming to increase the solar photocatalytic activity of the produced hybrid materials. The photocatalytic reactions were assessed by monitoring the removal of nitrogen oxides and two different volatile organic compounds (benzene and isopropanol). Photocatalytic mechanism was investigated by means of EPR spin trapping experiments.Our results highlight the exceptional characteristics of the TiO2/graphene hybrid material (1.0 wt% graphene), and its suitability for multi-purpose applications in the field of environmental remediation. Compared to unmodified titania, the hybrid material with 1.0 wt% graphene shows a clear enhancement in the photocatalytic removal of those hazardous pollutants – corresponding to more than twice the photocatalytic degradation rate. In addition, the same material is highly stable and shows fully recyclability over repeated tests. Hybrid titania-graphene materials could thus be exploited to grant a safer outdoor and indoor environments, having a beneficial impact on public health and thus on the quality of our lives.

Photocatalysis represents an advanced and efficient technology for harnessing light energy. The non-toxicity, affordability, and versatility of this technique render it particularly attractive for hydrogen production via water splitting. Nevertheless, the primary challenge lies in identifying materials capable of efficiently catalyzing the water splitting reaction upon exposure to light. This study presents the influence of the quantity of hematite and graphene on g-C3N4 in the context of hydrogen generation from methanol-water decomposition under UVC irradiation. Pure g-C3N4 exhibits the highest hydrogen generation efficiency. However, adding hematite decreases photocatalytic efficiency, likely due to the formation of a type II heterojunction between α-Fe2O3 and g-C3N4, which reduces the overall reduction capacity of the system. While incorporating graphene into the g-C3N4/α-Fe2O3 system enhances photocatalytic efficiency by improving electron mobility and prolonging the lifetime of photo-generated excitons, the highest yield was achieved with BUF10/GNP0.5. This research offers valuable insights into charge transfer and separation processes for photo-generated excitons within the g-C3N4/α-Fe2O3 and g-C3N4/α-Fe2O3/graphene systems in the context of light-induced hydrogen production.

Solid state light sources irradiating in the UV spectral region are key components in today technologies as they can replace conventional mercury vapor gas-discharge lamps. Ultrathin GaN layers in AlGaN barriers are of great interest for UV-emitting photonic devices, but a detailed understanding of the exciton features of these systems is still lacking. In this work, GaN layers, grown by metal organic chemical vapour deposition, were deeply investigated in AlGaN barriers with different Al amount, in order to correlate excitonic effects with structural features.

Photonics bound states in the continuum (BICs) are peculiar localized states in the continuum of free-space waves, unaffected by far-field radiation loss. Although plasmonic nano-antennas squeeze the optical field to nanoscale volumes, engineering the emergence of quasi-BICs with plasmonic hotspots remains challenging. Here, the origin of symmetry-protected (SP) quasi-BICs in a 2D system of silver-filled dimers, quasi-embedded in a high-index dielectric waveguide, is investigated through the strong coupling between photonic and plasmonic modes. By tailoring the hybridizing plasmonic/photonic fractions, a trade-off is selected at which the quasi-BIC exhibits both high intrinsic Q-factor and strong near-field enhancement because of dimer-gap hotspot activation. Not only radiation loss is damped but in a configuration sustaining a lattice of plasmonic hotspots. This leads to an advantageous small modal volume for enhancing light-matter interaction. The layout of nearly embedded dimers is designed to maximize the spatial overlap between the optical field and the target molecules, enhancing reactive sensing efficiency. The architecture is evaluated for its ability to detect transactive response DNA-binding protein 43. The refractometric sensitivity outperforms current label-free biosensing platforms, reaching the zeptomolar range. The approach highlights the potential of combining plasmonic and dielectric nanomaterials for advanced sensing technologies.

Hydrogen has the potential to become a crucial energy storage vector, allowing to maximise the advantages of renewable and sustainable energy sources. Hydrogen is usually stored as compressed hydrogen gas, or liquid hydrogen. However, the former requires high pressure, the latter cryogenic temperatures, being a huge limit to the widespread adoption of these storage methods. Thus, new materials for solid-state hydrogen storage shall be developed. Here we show that a α−MoO3 thin film, grown via atomic layer deposition, is a promising material for reversibly storing hydrogen. We found that hydrogen plasma is a convenient way to hydrogenise − at room temperature and relatively low pressures (500 or 1000 mTorr) − layered monocrystalline α−MoO3 thin films. Hydrogen has been shown to locate itself in the van der Waals gap along the [010] oriented α−MoO3 film. The process has been found to be totally reversible in air. Our essay could be a starting point to a transition from conventional (gas and liquid) to more advantageous solid-state hydrogen storage materials.

Hydrogen is an energy vector capable of storing and supplying large amounts of energy, maximizing the benefits of renewable and sustainable energy sources. Hydrogen is usually stored as compressed hydrogen gas or liquid hydrogen. However, the former requires high pressure and the latter cryogenic temperatures, being a huge limit to the widespread adoption of these storage methods. Thus, new materials for solid-state hydrogen storage shall be developed. Here, we show that an alpha-MoO3 thin film, grown via atomic layer deposition, is a material with potential for reversibly storing hydrogen. We found that hydrogen plasma is a convenient way to hydrogenate - at room temperature and relatively low pressures (200 mTorr) - layered alpha-MoO3 thin films. Density functional theory calculations of stepwise hydrogen insertion into alpha-MoO3 reveal that hydrogen atoms preferentially form covalent bonds with monovalent oxygen atoms located within the van der Waals gaps separating the [010]-oriented layers. The hydrogen absorption process has been found to be totally reversible, with desorption of hydrogen effective at 350 degrees C/4 h under a nitrogen atmosphere, and recoverable after repeated cycles. Furthermore, a nominal 13 nm Al x O y capping layer, grown via atomic layer deposition, has been shown to be efficient in preventing hydrogen release. The volumetric hydrogen storage capacity of 28 kgm-3 achieved in our films is comparable to that of pressurized steel cylinders, highlighting their potential for practical applications. Our essay could be a starting point to a transition from conventional (gas and liquid) to more advantageous solid-state hydrogen storage materials.

Optical Bound States in the Continuum are peculiar localized states within the continuous spectrum that are unaffected by any far-field radiation and intrinsic absorption, therefore possessing infinite mode lifetime and Q-factor. To date they have been widely studied in dielectric structures whereas their exploitation in lossy media, i.e. plasmonic nanostructures, still remains a challenge. Here, we show the emergence of a hybrid BIC state in a 2D system of silver-filled dimers, quasi-embedded in a high-index dielectric waveguide. The hybrid BIC onset is found to be highly dependent on the bare modes' spectral and spatial overlap, but particularly on the plasmonic field's intensity. By tailoring the hybridizing plasmonic/photonic fractions we select an ideal coupling regime for which the mode exhibits both, high Q-factor values and strong near-field enhancement tightly confined in the nanogap and a consequently extremely small modal volume. We demonstrate that this optical layout can be exploited in a proof-of-concept experiment for the detection of TAR DNA-binding protein 43, which outperforms the sensitivity of current label-free biosensing platforms, reaching the zeptomolar range of concentration.

The experimental development of thin films that exhibit higher room -temperature low -field magnetoelectric (ME) sensing without compromising reliable electrical energy storage capabilities is rare. Here, an improved ferroelectric polarization, ME coupling and energy storage performance of polymer -based nanocomposites, which find applications in portable high -power dielectric capacitors, are studied. Multiferroic nanofiller-based three-phase flexible nanocomposites, polyvinylidene fluoride (PVDF)-(Ba 0.7 Ca 0.3 )TiO 3 -(Co 0.6 Zn 0.4 )Fe 2 O 4 , were fabricated using compression molding to enhance polarization which is pivotal for applications. PVDF with a high beta -phase content (92.4 %), switchable ferroelectric behavior and higher breakdown strength (510 kV/mm) was obtained under optimized process conditions (500 MPa at 165 degrees C). The fabrication assisted alteration of intermolecular chain distance results in a tensile strain (1.42 %) of beta -crystallites corresponding to an internal stress of -21 MPa. The progressive increase of nanofiller content has led to enhanced polarization (11 mu C/cm 2 ), soft ferromagnetic properties, and enhanced ME coupling of 59 mV/cm-Oe due to switchable magnetostriction ( lambda 11 = -18 ppm and d lambda 11 /d = -22 x 10 -9 Oe -1 ) at lower saturation field of 1.2 kOe. The ME sensitivity was found to be more than two -folds enhanced compared to solution -cast films making them prospective self -biased flexible devices for wearable electronics. Simultaneously, enhanced change of magnetization (19.6 %) under electric field was obtained. Detailed energy storage characteristics confirm that the nanofiller inclusion up to 7.12 vol% effectively improved the recoverable energy storage density (21.2 J/cm 3 ) with an efficiency of 67 %. The experimental and simulation results corroborate a significantly improved breakdown strength of 617 kV/mm with reliable performance. Thus, careful processing provides viable polymer dielectrics with beneficial storage characteristics.

Heavy pnictogen chalcohalides are often referred to as lead-free, perovskite-inspired materials. Despite theoretical predictions, incontrovertible experimental demonstrations of heavy pnictogen chalcohalides adopting a perovskite structure are lacking. Here we report our attempts to prepare CsBiSCl2 adopting a perovskite structure as colloidal nanocrystals. Synthesis of nanoscale materials can indeed rely on fast, non-equilibrium reactions and on large, eventually thermodynamically favorable surface energies, leading to the possibility of stabilizing kinetically-trapped or metastable phases. However, we obtained no CsBiSCl2, but a mixture of nanocrystals of secondary phases, namely Cs3BiCl6 submicrometric polyhedra, Bi2S3 nanoscopic rods, and Cs3Bi2Cl9 nanoscopic dots, whose low polydispersity enabled an effective separation via size/shape selective precipitation. This work confirms that heavy pnictogen chalcohalides are hardly prone to adopt a perovskite structure. Nevertheless, chemistry at the nanoscale offers multiple possibilities to overcoming phase segregation and pursuing the synthesis of prospective mixed anion compounds.

The photocatalytic properties of TiO2 are primarily determined by its crystallinity and crystalline phase ratios. To improve the photocatalytic properties of TiO2, greater control over the formation of crystalline and amorphous phases during synthesis is therefore required. In this study, we demonstrate how the addition of minute amounts of three organic compounds (isopropanol, acetone and acetic acid) during hydrothermal treatment affects the amorphous and crystalline phase ratios: the addition of isopropanol or acetone accelerates the phase transition from anatase and brookite to rutile, whereas the addition of acetic acid inhibits the transformation of anatase to rutile, increasing the content of amorphous phase compared to samples where no organic compound was added. We show that the combination of the organic compound added, along with the duration of the hydrothermal treatment, can be used to tailor the phase composition of TiO2, so as to obtain either: i) TiO2 with a high content of both rutile and amorphous phase, ii) TiO2 with a high rutile content and iii) TiO2 with different ratios of all four phases, when the duration of synthesis is short (2-4 h). The materials synthesized exhibited high photocatalytic activity (in most cases higher than P25), which is attributed to the beneficial phase composition and high specific surface area.

The ultrawide-bandgap AlGaN alloy system shows great potential for advancing the next generation of UV optoelectronic devices.

Industrialisation has led to unprecedented levels of outdoor air pollution, posing a significant health risk to human beings. Consequently, there is an urgent need to replace fossil fuels with sustainable energy sources, thereby mitigating these risks and providing a safer outdoor and indoor environment. Titanium dioxide is a versatile transition metal oxide with applications ranging from energy conversion to environmental remediation. However, it faces limitations, particularly in its absorption spectrum and charge separation efficiency, and enhancing these properties remains a significant challenge. In this research work, we have decorated the surface of TiO2 hybridising it with noble-metal and/or noble-metal oxides (Ag and/or CuxO) to improve the photocatalytic performances (monitoring the removal of nitrogen oxides and benzene, and hydrogen generation from water splitting) under simulated solar-light irradiation. Our results showed that titania modified with an Ag:Cu molar ratio equal to 1:1, not only exhibited the most promising performance in terms of nitrogen oxides and benzene removal, it was the optimum amount for the light-induced generation of hydrogen from water splitting.

Distinguishing between different handedness of circularly polarized light can be a useful additional property in photodetector technology. The integration of this functionality can be obtained either using optical media with chiro-optical response, or by the employment of chiral metamaterials. In this work, 3D chiral metasurfaces composed by a 3D helix array, are integrated onto a micrometer-scale silicon-based transistor and act as optical filter for circularly polarized light. The technological process involving focused electron beam induced deposition for helix manufacturing is carefully studied with respect to its effect on the phototransistor response. The integrated system exhibits a photoresponse which is dependent on the circular polarization, with a promising asymmetry factor in the visible spectral range. The proposed technology can pave the way for novel potential applications in diverse areas such as materials science, bioimaging, and quantum computing. Three-dimensional (3D) chiral metasurface-based phototransistors are miniature detectors that can distinguish between left- and right-circularly polarized light in the visible spectrum. This capability is enabled by a 3D chiral metasurface, composed of ordered nanohelices, which is integrated onto a micrometer-scale phototransistor using focused electron beam induced deposition (FEBID).image

We present narrow-band polarization-sensitive reflectance of GaN/AlGaN heterostructures in the mid-infrared range. Experimental measurements performed at 15° angle of incidence show the excitation of a Berreman mode at the interface between GaN and sapphire substrate. A transfer matrix method for anisotropic layers has been used to analyze the obtained results. The contribution of the two-dimensional electron gas at the interfaces of the heterostructures has been included by proper modelization of an effective thin layer.

Chitosan (Cs) and hydroxyapatite (HA) 3D scaffolds/composites were prepared with a sustainable pro-cess, as HA was obtained using CaCO3 derived from cork, a natural material used as a template agent. The HA@Cs composites were prepared with HA in situ formation in a Cs solution, with a dissolution -precipitation mechanism.Different reaction times were considered, with time of 72 h leading to the best materials (sample CsHA_72). X-ray Diffraction (XRD) analysis confirmed HA formation. The analysis of Cs unit cell pa-rameters showed that, for the unmodified Cs, the cell had larger dimensions and a higher degree of distortion than previously reported in literature; HA incorporation in the CsHA_72 composite led to a further increase in the cell dimensions.The morphology of the scaffolds was studied with Scanning Electron Microscopy (SEM) and a high level of porosity was observed; a statistical comparison was performed between the unmodified Cs and CsHA_72 to determine the pore size, structure, and distribution. This analysis, the first of this kind for this type of composites, showed smaller and more circular pores for the CsHA_72 composite (average diameter of 70 mm vs. 88 mm for unmodified Cs). The overall level of porosity, however, did not change (>77%); likewise, the Young modulus was not affected by HA incorporation (about 11 kPa). Antibacterial tests, performed on Escherichia coli and Staphylococcus aureus, showed that HA presence did not significantly reduce the antimicrobial properties; the composites were particularly effective towards S. aureus, as a >90% the bacterial population reduction was observed for an incubation time of 2 h. HA@Cs also showed excellent biocompatibility and good cell proliferation.The properties of these 3D scaffolds make them suitable for application as biomaterials.(c) 2023 Elsevier Ltd. All rights reserved.

MoS2 is a two-dimensional layered transition metal dichalcogenide with unique electronic and optical properties. The fabrication of ultrathin MoS2 is vitally important, since interlayer interactions in its ultrathin varieties will become thickness-dependent, providing thickness-governed tunability and diverse applications of those properties. Unlike with a number of studies that have reported detailed information on direct bandgap emission from MoS2 monolayers, reliable experimental evidence for thickness-induced evolution or transformation of the indirect bandgap remains scarce. Here, the sulfurization of MoO3 thin films with nominal thicknesses of 30 nm, 5 nm and 3 nm was performed. All sulfurized samples were examined at room temperature with spectroscopic ellipsometry and photoluminescence spectroscopy to obtain information about their dielectric function and edge emission spectra. This investigation unveiled an indirect-to-indirect crossover between the transitions, associated with two different Λ and K valleys of the MoS2 conduction band, by thinning its thickness down to a few layers.

This study investigates a possible alternative reuse of spent coffee grounds (SCG), the major residue of the brewing process, to manufacture green geopolymeric materials for innovative building applications in energy-saving construction, in line with the European Green Deal towards zero-energy building. Specimens were prepared by a combination of biomass fly ash from the Kraft paper-pulp process, as raw material (70 wt%), and SCG (up to 17.5 %), as filler. The high amount of reused bio-wastes makes the material fit the requirements for the Minimum Environmental Criteria (MEC) certification, in light of the Circular Economy (CE) approach. Sustainability is also boosted by the manufacturing process that completely occurred at ambient conditions (20 degrees C, 65 % RH). Materials engineering performance is eval-uated to predict possible applications in construction and promote an integrated architectural design process to propose a "coffee-house" equipped with an innovative energy structure and envelope. For the scope, different technological solutions are designed and virtual energy modelling is implemented to simulate the performance of a building model in different climatic conditions and estimate the possi-ble real efficacy of the proposed solutions in relation to building efficiency and cost management, as envisaged by the EU 2018/844 on the buildings' energy performance. The major result is that the devel-oped material represents an optimum candidate to substitute traditional construction and building mate-rials with a great manufacturing financial saving, up to 37 % for the 17.5 % SCG, and an energy improvement up to about 19 % per year, leading further saving in the yearly building management.(c) 2023 Elsevier B.V. All rights reserved.

This paper reports the development of green bio-composite mortars, obtained reusing spent coffee ground (SCG), an agri-food residue, in the light of the Circular Economy approach. This process can boost the sustainability in Construction and proposes an alternative to SCG disposal in landfill, potentially dangerous to humans and the environment. For the first time, specimens were produced and compared using different blends of conventional hydraulic binders (ordinary Portland cement and natural hydraulic lime); SCG partially substituted sand (up to 15 wt%, with a 2.5% increment) for the aggregate mix. The manufacturing process was performed at ambient conditions (20 degrees C, 65% RH) resulting highly sustainable, and consisted of simple operative steps reproducible in a real building site. The prepared mixes were fully characterised to assess their technological potentials in construction. Morphology analysis, performed by Scanning Electron Microscopy (SEM), showed SCG addition led to a more compact structure. Considering the functional properties, results widely range on binder blend base, offering various concrete applications; it was observed that with SCG addition, despite a decrease in the bulk density (up to 26%), the mechanical performance still remained suitable for proper masonry applications, ac-cording to the relevant standards (class of resistance M2.5-M10). A light water imbibition increase was registered (about 5%) while a significant decrease of the capillarity index was seen. Moreover, a robust thermal conduc-tivity reduction was observed (up to 72%), making the mortars highly suitable for energy-saving uses in building. Finally, a reduction in the manufacturing cost (up to 8%) was calculated, granting significant financial saving in light of the industrial symbiosis. These encouraging results showed that reusing SCG not only provides numerous benefits to the overall building performance and management but it is also a valid alternative to usual SCG disposal. The high amount of reused bio-waste significantly widens the knowledge of greener and more efficient building sector, making the prepared mortars promising candidates for the Minimum Environmental Criteria certification, in light of the recent EU regulations, and in line with the principles of the Circular Economy.

Heavy pnictogen chalcohalide semiconductors are coming under the spotlight for energy conversion applications. Here we present the colloidal synthesis of phase pure AgBiSCl2 nanocrystals. This quaternary chalcohalide compound features a quasi-two-dimensional crystal structure and a direct band gap, in contrast with the monodimensional structure and the indirect band gap peculiar to the orthorhombic, ternary Bi chalcohalides. Consistently, colloidal AgBiSCl2 nanocrystals exhibit photoinduced luminescence compatible with both band edge excitons and midgap states. This is the first observation of band edge emission in chalcohalide nanomaterials at large, although exciton recombination in our AgBiSCl2 nanocrystals mostly occurs via nonradiative pathways. This work further advances our knowledge on this class of mixed anion semiconductor nanomaterials and provides a contribution to establishing chalcohalides as a reliable alternative to metal chalcogenides and halides.

In this research work, we present a study on time-sequenced plasma-enhanced atomic layer deposition (PE-ALD) processes towards the achievement of high-quality α-MoO3 thin films which are suitable for exfoliation. In particular, a conventional precursor injection method along with a boosted precursor delivery approach are discussed and analysed. In the latter, the proposed gas supply mechanism ensures a large number of deposited Mo atoms per unit of time, which, along with a proper thermal energy, leads to high-quality and oriented orthorhombic α-MoO3 films. The proposed boosted approach is also compared with post growth annealing steps, resulting in more effective achievement of a highly oriented orthorhombic α-MoO3 phase and less time consumption.