The combination of the ability to absorb most of the solar radiation and simultaneously suppress infrared re-radiation allows selective solar absorbers (SSAs) to maximize solar energy to heat conversion, which is critical to several advanced applications. The intrinsic spectral selective materials are rare in nature and only a few demonstrated complete solar absorption. Typically, intrinsic materials exhibit high performances when integrated into complex multilayered solar absorber systems due to their limited spectral selectivity and solar absorption. In this study, we propose CoSb_x (2 < x < 3) as a new exceptionally efficient SSA. Here we demonstrate that the low bandgap nature of CoSb_x endows broadband solar absorption (0.96) over the solar spectral range and simultaneous low emissivity (0.18) in the mid-infrared region, resulting in a remarkable intrinsic spectral solar selectivity of 5.3. Under 1 sun illumination, the heat concentrates on the surface of the CoSb_x thin film, and an impressive temperature of 101.7 °C is reached, demonstrating the highest value among reported intrinsic SSAs. Furthermore, the CoSb_x was tested for solar water evaporation achieving an evaporation rate of 1.4 kg m⁻² h⁻¹. This study could expand the use of narrow bandgap semiconductors as efficient intrinsic SSAs with high surface temperatures in solar applications.

Nanocrystalline calcium carbonate (CaCO₃) and amorphous CaCO₃ (ACC) are materials of increasing technological interest. Nowadays, they are mainly synthetically produced by wet reactions using CaCO₃ reagents in the presence of stabilizers. However, it has recently been discovered that ACC can be produced by ball milling calcite. Calcite and/or aragonite are the mineral phases of mollusk shells, which are formed from ACC precursors. Here, we investigated the possibility to convert, on a potentially industrial scale, the biogenic CaCO₃ (bCC) from waste mollusk seashells into nanocrystalline CaCO₃ and ACC. Waste seashells from the aquaculture species, namely oysters (Crassostrea gigas, low-Mg calcite), scallops (Pecten jacobaeus, medium-Mg calcite), and clams (Chamelea gallina, aragonite) were used. The ball milling process was carried out by using different dispersing solvents and potential ACC stabilizers. Structural, morphological, and spectroscopic characterization techniques were used. The results showed that the mechanochemical process produced a reduction of the crystalline domain sizes and formation of ACC domains, which coexisted in microsized aggregates. Interestingly, bCC behaved differently from the geogenic CaCO₃ (gCC), and upon long milling times (24 h), the ACC reconverted into crystalline phases. The aging in diverse environments of mechanochemically treated bCC produced a mixture of calcite and aragonite in a species-specific mass ratio, while the ACC from gCC converted only into calcite. In conclusion, this research showed that bCC can produce nanocrystalline CaCO₃ and ACC composites or mixtures having species-specific features. These materials can enlarge the already wide fields of applications of CaCO₃, which span from medical to material science.

Thin‐film solar cells based on wide‐bandgap antimony sulfide (Sb ₂ S ₃ ) offer new possibilities for semitransparent building‐integrated photovoltaics. In this report, impurity‐free Sb ₂ S ₃ thin films are prepared by radio frequency magnetron sputtering. The optimized opaque devices obtain a high power conversion efficiency (PCE) of 4.6%. A detailed characterization is conducted to investigate the impact of annealing conditions on the morphology, crystal structure, composition, and optoelectronic properties of Sb ₂ S ₃ thin films, which are relevant to photovoltaic performance. Moreover, semitransparent solar cells are fabricated using highly compact Sb ₂ S ₃ films with thicknesses of 40, 60, and 80 nm. Using a superstrate device structure (FTO/TiO ₂ /Sb ₂ S ₃ /P3HT‐PEDOT:PSS/Au (≈10 nm)), these solar cells achieve PCEs of 2.0%, 2.6%, and 3.2%, respectively, while maintaining an average visible transmittance (AVT) of 15.5%, 13.5%, and 10.0%. The AVTs of the semitransparent devices are further enhanced by replacing the ultrathin Au top electrode with indium‐doped tin oxide and using wide bandgap inorganic CuSCN as the hole transport layer instead of P3HT‐PEDOT:PSS. Thus, the AVT improves to 20.5% (PCE: 2.0%) for semitransparent solar cells using 60 nm Sb ₂ S ₃ . This study demonstrates that sputtering is a promising deposition technique for high‐quality ultrathin Sb ₂ S ₃ absorbers for semitransparent photovoltaics.

CuInS₂ quantum dots have emerged in the last years as non‐toxic alternative to traditional Pb and Cd based quantum dots, especially for biological applications. In this work, the hydrothermal synthesis of alloyed Cu‐In‐Zn‐S quantum dots (CIZS) doped with manganese(II) is explored, with different metal ratios (Mn‐CIZSy). The doped quantum dots show the sensitized emission of Mn²⁺ (approximately ms lifetime), together with the emission of the CIZS structure (approximately µs lifetime). The relative contribution of Mn²⁺ emission is highly dependent on the composition of the CIZS hosting structure (In:Cu ratio). In addition to that, it is shown that Mn²⁺ sensitization requires a threshold energy, which suggests the involvement of an intermediate state in the sensitization mechanism. The long‐lived emission intensity decay of Mn²⁺ shows a stable and reversible temperature response in physiological conditions (25–45 °C, pH = 7.4). Mn‐CIZSy quantum dots are thus interesting candidates as biological luminescent temperature probe thanks to their easy synthesis, high colloidal stability, insensitivity to dioxygen quenching and quantitative time‐gated detection.

Interfacial solar desalination using plasmonic metal semiconductors is a valuable process for freshwater production. However, the design of a sustainable and efficient photothermal evaporator is still challenging. In the present research, polyethylene terephthalate waste bottles were upcycled into carbon foam (CF) and further functionalized with CuS nanoflakes as a photothermal layer. Analytical characterizations (X‐ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy, and scanning transmission electron microscopy–high‐angle annular dark field) demonstrated the successful decoration of two‐dimensional Covellite CuS nanoflakes on graphitic CF having microporous channels. UV/vis spectroscopy measurements show enhanced optical absorption with CuS/CF of up to 95% compared to bare CF (72%). The photothermal desalination experiment displayed an improved evaporation rate of 1.90 kg m⁻² h⁻¹ for the CuS–CF compared to 1.58 kg m⁻² h⁻¹ for the bare CF and CuS 1.41 kg m⁻² h¹, reveling the excellent water evaporation efficiency of 91%. The obtained results suggested that the design of CuS‐functionalized CF derived from waste plastic for solar desalination is a useful strategy to produce fresh water from the upcycling of waste materials and a good example of circular economy through the development of engineered composite systems.

Photocatalytic H₂ generation holds promise in the green production of alternative fuels and valuable chemicals. Seeking alternative, cost-effective, stable, and possibly reusable catalysts represents a timeless challenge for scientists working in the field. Herein, commercial RuO₂ nanostructures were found to be a robust, versatile, and competitive catalyst in H₂ photoproduction in several conditions. We employed it in a classic three-component system and compared its activities with those of the widely used platinum nanoparticle catalyst. We observed a hydrogen evolution rate of 0.137 mol h^-1 g^-1 and an apparent quantum efficiency (AQE) of 6.8% in water using EDTA as an electron donor. Moreover, the favorable employment of l-cysteine as the electron source opens possibilities precluded to other noble metal catalyst. The versatility of the system has also been demonstrated in organic media with impressive H₂ production in acetonitrile. The robustness has been proved by the recovery of the catalyst by centrifugation and reusage alternatively in different media.