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Background: There is a paucity of knowledge about the effects of COronaVIrus Disease-19 (COVID-19) on long-term frailty development or progression over time. Aim: This study aims to assess transitions in frailty status in older adults who survived hospitalization for COVID-19. Methods: This is a longitudinal panel study. A multidisciplinary outpatient follow-up service was established since summer 2020, for the evaluation of individuals discharged alive, after hospitalization due to COVID-19. Frailty status was assessed in-hospital and at follow-up using the clinical frailty scale (CFS). Main patients’ characteristics, including health, functional, cognitive, and psychological status were collected. Results: A total of 177 patients aged 65 years and older were evaluated until June 2022. They were predominantly male, with a median age of 70 (Q1–Q3 67–75) years and a median body mass index of 27.5 (Q1–Q3 24.9–30.6) kg/m2 at hospital admission. The median follow-up time was 6.3 (Q1–Q3 3.7–10.9) months. Sixty-one patients (34.5%) scored worse at CFS follow-up compared to hospital admission, and twenty-two patients (12.4%) became frail. Discussion and conclusion: This study shows that one out of three older patients previously hospitalized for COVID-19 had an unfavorable transition in CFS score during a median follow-up of nearly 6 months. Specific interventions to prevent frailty development or progression should be considered for patients at risk. Further studies are required to confirm our findings.

Highly porous nanocrystalline TiO2 films were sensitized with ZnS semiconductor nanocrystals by using a three-step facile strategy. The TiO2 matrices were firstly impregnated with the zinc bis(benzyl)thiol precursor that, unlike many other metal chalcogenides, is easily dispersible in the most common organic solvents. In the second step of the adopted synthetic strategy, the TiO2 impregnated with zinc thiolate was annealed at 250 °C in order to induce nucleation and growth of ZnS nanocrystals inside the porous matrices as well as on the film surface. A final cleavage in dichloromethane allowed us to remove all residual organic reagents and products. The size of the ZnS nanocrystals can be tuned by variation of the annealing time as shown by X-ray diffraction measurements, without changing the crystallographic phase structure (zincblende structure). Scanning electron microscopy analysis showed a random spatial dispersion of the ZnS nanocrystals and no remarkable aggregation was observed. The sensor device based on TiO2-ZnS nanocomposite was able to detect NO2 gas at 270 °C down to 1 ppm with negligible response towards reducing gases (CO, CH4). Compared to bare TiO2 film, the TiO2-ZnS nanocomposite shows higher sensitivity and lower recovery time towards an oxidant NO2 gas.

Polycrystalline, close-packed, homogeneous nanostructured ceria thin films were prepared by sol–gel process via dip-coating technique on soda-lime glass and (100)-oriented Si substrates. To produce the films, a sol was prepared using, as precursor, a home made cerium sec-butoxide dissolved in secondary butanol. The chemical composition, the microstructural/morphological characteristics and the optical properties of the coatings were investigated in detail. The experimental results clearly demonstrate that the ceria films are nanocrystalline (CeO2, cubic phase $$ {\text{Fm}}\bar{3}{\text{m}} $$ ) with an average grain size of about 2–3 nm for the samples grown on glass and of about 4–5 nm for the samples grown on silicon. The analyses of ceria layers grown on silicon show that the ceria coatings are free from organic residues and that a Si-oxide layer is formed at the film/substrate interface. The optical results evidence a red shift of the energy gap of about 0.5 eV that can be ascribed to conversion of relevant Ce4+ sites to Ce3+ sites and a consequent creation of oxygen vacancy at the surface of the ceria grains.

Efficient solar energy conversion is strongly related to the development of new materials with enhanced functional properties. In this context, a wide variety of inorganic, organic, or hybrid nanostructured materials have been investigated. In particular, in hybrid organic–inorganic nanocomposites are combined the convenient properties of organic polymers, such as easy manipulation and mechanical flexibility, and the unique size-dependent properties of nanocrystals (NCs). However, applications of hybrid nanocomposites in photovoltaic devices require a homogeneous and highly dense dispersion of NCs in polymer in order to guarantee not only an efficient charge separation, but also an efficient transport of the carriers to the electrodes without recombination. In previous works, we demonstrated that cadmium thiolate complexes are suitable precursors for the in situ synthesis of nanocrystalline CdS. Here, we show that the soluble [Cd(SBz)2]2·(1-methyl imidazole) complex can be efficiently annealed in a conjugated polymer obtaining a nanocomposite with a regular and compact network of NCs. The proposed synthetic strategies require annealing temperatures well below 200 °C and short time for the thermal treatment, i.e., less than 30 min. We also show that the same complex can be used to synthesize CdS NCs in mesoporous TiO2. The adsorption of cadmium thiolate molecule in TiO2 matrix can be obtained by using chemical bath deposition technique and subsequent thermal annealing. The use of NCs, quantum dots, as sensitizers of TiO2 matrices represents a very promising alternative to common dye-sensitized solar cells and an interesting solution for heterogeneous photocatalysis.

Highly porous nanocrystalline films of TiO 2 sensitized with semiconductor nanocrystals (NCs) are very promising for photovoltaic applications, NCs being more versatile and efficient than organic dyes as sensitizer. In this framework, the visible light absorption of TiO 2 can be improved by the superposition of CdS NC absorption band, that is tunable between 2.5 and 5.2 eV. Here, we report on a novel in situ approach for the synthesis of CdS NCs in mesoporous sol-gel TiO 2 anatase films by using as starting reagent for CdS, [Cd(SBz) 2 ]MI, where MI represents 1-methylimidazole. The precursor has been adsorbed into the TiO 2 pores and then decomposed at 480 °C, the procedure being studied for TiO 2 films with different porosity. The matrices have been investigated by atomic force microscopy. X-ray diffraction measurements on TiO 2 matrix and on the corresponding CdS/TiO 2 nanocomposite material revealed a variation of the NCs size of both TiO 2 and CdS as a function of the matrix porosity. The optical properties of the TiO 2 and CdS/TiO 2 have been studied by UV-Vis transmission spectroscopy. CdS/TiO 2 nanocomposites, having higher absorption efficiency with respect to TiO 2 , are suitable as building blocks for 3rd generation solar cell design.

Homogeneous, erbium-modified, non-porous silica glasses containing about 2.4% of ions compared with Si atoms have been prepared by sol–gel process. To limit the loss of the rare earth cations in the liquids, improve the uniformity of ion incorporation and to immobilize the cations in the silica matrix, an amino functionalised silane was used. It was found to be very effective also to allow foamless sintering. Structural evolution and chemical composition of the samples during the preparation process have been monitored by Fourier-Transform Infrared and Near-IR dispersion spectroscopy. The loss of the cations in the syneresis liquid and the surface area of the samples heat treated at different temperature have been evaluated. The erbium transition 4I15/2 versus 4I13/2, related electro-luminescence at 1.54 μm, was evident in gels heat treated at 1000 °C.

The investigation of the surface and interface of a multilayer coating is a key factor for producing high quality optical device. In this work, we present a non-destructive technique as X-ray reflectivity to study deeply the chemical and structural quality of the multilayer. XPS depth profile analysis and AFM images have been used to evaluate the chemical intermixing and the surface roughness in order to verify the X-ray results.

In this work, we propose a new method for the determination of the optical parameters of an inhomogeneous thin optical film deposited on a substrate of finite thickness. The method can be applied successfully, if the following hyphotheses are satisfied: the film exhibits small optical inhomogeneities throughout the thickness (less than 5%), smooth refractive index profiles, weak absorption (extinction coefficient ≤ 0.02) and negligible diffuse light scattering. Useful formulae are derived describing the effects of refractive-index inhomogeneity and absorption not only on the transmittance and reflectance extrema but also for any other wavelength value. This allows us to calculate the refractive index inhomogeneity and to subtract its contribution from the measured transmittance and reflectance curves starting from approximate refraction index and film thickness values. In this way, it is possible to obtain the transmittance and reflectance spectra of a homogeneous film whose optical parameters are the mean values of those of the inhomogeneous film. These new transmittance and reflectance curves can be easily processed with any computer program for the determination of the optical parameters and film thickness based on the homogeneous thin film optical model.

SiO2 films have been deposited by ion-beam sputtering techniques either without assistance or with Ar-ion assistance and the role of the substrate temperature during the deposition process on the film damage threshold by laser light at the wavelength of 308 nm (XeCl) has been investigated. The photoacoustic probe beam deflection technique has been used to determine damage thresholds and it is shown that this technique provides valuable information on the mechanisms leading to laser damage. It has been found that the samples deposited by the Ar-ion beam sputtering technique are characterized by higher damage thresholds at lower temperatures of the substrate than the SiO2 films deposited without ion assistance.

Electrically conducting organic polymers change their conductivity and relative permittivity when exposed to volatile chemicals [1.2]. The changes depend on the frequency, the concentration and the type of the chemical. In particular the frequency dependence could be used for making more selective sensors. A polypyrrole (PPY) film gas sensor was designed and constructed in order to probe it. The low frequency (20 Hz−10 KHz) a.c. response was studied when it was exposed to 200 ppm of four different vapours: methanol, acetone, ethyl acetate and ethanol. Response patterns to each vapour were obtained by varying the measurement frequencies. The pattern for each vapour investigated was very different from the others, and so it has been possible to discriminate between them. The results demonstrate that it is possible to increase the sensor selectivity using the low frequency a.c. response rather than d.c. resistance change. Ageing and temperature dependence of resistance and capacitance are also reported.

Homogeneous nanocomposite silica films uniformly doped with size-selected gold nanoparticles (AuNPs) have been prepared by a combined use of colloidal chemistry and the sol‐gel process. For this purpose, stable thiol-functionalized AuNPs (DDT-AuNPs) were first synthesized by a two-phase aqueous/organic system and, subsequently, dispersed in an acid-catalysed sol‐gel silica solution. The microstructural morphology of the samples was investigated by x-ray diffraction and field emission scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) and UV‐vis optical spectrophotometry were instead employed to investigate the elemental chemical behaviour and the evolution of the surface plasmon resonance (SPR) band of the AuNPs from their synthesis up to the formation of the Au-doped silica films. The results show that the size, shape and crystalline domains of the AuNPs remain unchanged during the entire preparation process, indicating that their aggregation or decomposition was prevented. XPS results show that the DDT-AuNPs lose the capping shells and oxidize themselves when dispersed in acid-catalysed sol‐gel solutions, and that bare AuNPs are embedded in the SiO2 films. A large broadening of the SPR band, observed for systems with DDT-AuNPs, suggests the presence of interface effects which cause a surface electron density lowering. Thiol chain detachment from the AuNPs determines an increase of the SPR peak intensity while the oxidation of the Au surfaces causes a red shift of its position. The latter is no longer observed in doped films, suggesting that no interfacial effects between bare AuNPs and the host medium are present. (Some figures in this article are in colour only in the electronic version)

Nanocrystalline anatase titania thin films were prepared by using two different precursor solutions, a highly acid solution (Sol-1) and a polymer-like solution (Sol-2), via the dip-coating technique on different substrates (-Si wafer, fused silica and soda lime glass). The influence of the two sol-gel titania precursor solutions and of the substrate type on the film morphology, coating porosity, surface roughness, crystalline phases and grain size of the titania films were investigated. Our experimental results clearly indicate that the sol - composition and substrate type remarkably influence the microstructural/morphological properties of the titanium dioxide. They consequently modify the optical response and hydrophilic performances of the samples. The photocatalytic oxidations of the methylene blue in water of the samples grown on the glass substrate were monitored to investigate the influence of the sol-gel precursor solution on the photocatalytic activity of the titania coatings, and the results were put in relation with the hydrophilic and optical properties of the films. The outcome demonstrates that the optical properties and the hydrophilic and photocatalytic performances of nanocrystalline titania can be opportunely tailored tuning the size dimension of the crystalline domain according to the specific coating applications.

Nanostructured titania thin films were prepared under controlled atmospheric conditions by the sol–gel dip-coating technique on glass, fused silica and (1 0 0)-silicon substrates. Two different sol–gel routes were employed by using different precursor solutions, a highly acid solution and a polymer-like solution. The influence of sol composition and of the substrate type on the morphology, coating porosity, surface roughness, crystalline phases and grain size of the titania films were investigated in detail. In addition, the relationship between microstructural/morphological properties and the optical properties (energy gap, refractive index and extinction coefficient) and the hydrophilic performance of the coatings were evaluated. Our experimental results clearly indicate that the sol composition and substrate type remarkably influence the films' morphology and microstructure; moreover, they consequently modify the optical response and hydrophilic performances of the samples, showing that superhydrophilic titania coatings can be obtained opportunely by choosing the composition of the precursor sol–gel solution. Blue shift of the band gap energy and a band structure mutation from indirect to direct were also revealed. The hydrophilic properties and the change in the band gaps transition can be attributed to oxygen vacancies on the surface of the titania nanocrystallites that gives rise to Ti3+ sites and, consequently, to structural changes/defects of the anatase nanoarchitecture. These findings allow us to design and tailor the optical and hydrophilic properties of the titania coatings.

In this work we report on the synthesis and the characterization of CdS nanocrystals (NCs) in mesoporous TiO2 anatase films as a first step towards the production of quantum dot sensitized TiO2 based solar cells. A novel in-situ approach has been devised using a unimolecular precursor, containing both the metal and the non-metal part. A [Cd(SR)2]Ln cadmium thiolate complex, where L represents 1-methylimidazole, has been prepared in order to maximize the adsorption into the TiO2 pores. The thiolate complex absorbed in TiO2 can be decomposed at 500°C in argon atmosphere in order to obtain the final CdS/TiO2 composite material. The optical properties of the final product have been monitored by UV-Vis transmission spectroscopy carried out with non polarized light and at normal incidence with respect to the sample surface. The morphology and porosity of the TiO2 matrix have been investigated by scanning electron microscopy. X-ray diffraction and transmission electron microscopy have been performed in order to study the crystalline structure of the samples and to estimate the TiO2 and CdS NCs size. The proposed synthesis strategy allows us to fabricate tailored band gap CdS/TiO2 composite material, with 10 nm to 100 nm diameter for TiO2 anatase crystallite pores and 3.2 nm average diameter for CdS NCs.

This paper is a work-in progress report on the development of sol-gel coatings for high power laser systems in the near-UV, infrared region. Silica, titania and titania-silica acid catalysed sols were prepared by using tetraethoxysilane and titanium isoproxide as precursors. Single and multi-layer coatings were generated by dipping on fused silica substrates. The single films were heated at 500°C and 900°C after deposition in order to investigate the role of the sintering temperature either on the optical properties and on the film laser-induced damage threshold at 1064 nm (Nd:YAG c.w. laser) and 351 nm (XeF excimer laser). The ageing effects due to the exposure to humidity was investigated by testing the damp heat resistance of the coatings in agreement with the ISO environmental test for optical coatings. The silica coatings have been assessed before and after the damp heat test with regard to their laser-induced-damage resistance, reflectance and transmittance properties. The optical parameters (refractive index and extinction coefficient) have been determined by UV-VIS-NIR spectrometry. A global fit procedure based on the simultaneous characterisation of several samples was used for the evaluation of the optical properties of the materials both as single films and inside multi-layer stacks.

Optical properties of materials inside a multilayer stack may differ from those of single layers. This fact is specially noticeable in the case of sol-gel films obtained by dip coatings. We propose a method to determine the refractive index and thickness of materials inside a multilayer stack, based on the simultaneous characterization of several samples. The procedure increases the reliability of the results and helps in improving quality in optical coating production. ( Summary only available )

Nanostructured gadolinia thin layers with small sized crystalline grains (∅ ≈ 3–13 nm) were successfully prepared by the sol–gel process on fused silica and silicon substrates. The film growth, the chemical composition, the morphology and the microstructure of the films were investigated in detail by thermo-gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and x-ray diffraction. The experimental results clearly show that the morphological and structural properties of the films are not influenced by the substrate properties and the Gd2O3 cubic crystalline phase (symmetry group ) is enhanced when the films are free from organic residuals and decompose to Gd-oxides. FTIR analysis of gadolinia layers grown on silicon suggest that the formation of Gd2O3 grains may favour the diffusion of oxygen through the coatings. The optical spectroscopy measurements evidence a blue shift of the energy gap and suggest a quantum confinement effect in nano-sized Gd2O3. In addition, two absorption features are observed, which can be attributed to a simultaneous presence of direct and indirect electronic transition indicating a modification of the band structure when the grain size changes from very small to larger Gd2O3 grains.

SiO(2) thin films (approximately 100 nm thick) with transmittivity and a laser damage threshold nearly equal to those of bulk material are deposited on silica substrates by the technique of ion-assisted electron-beam evaporation. The influence of film packing density on the laser damage threshold is investigated by the technique of photoacoustic probe beam deflection. It is shown that films with lower packing density may have a higher laser damage threshold and as a consequence better heat dissipation.