Search Results (165)

Prolonged ultraviolet (UV) exposure accelerates aging and degradation, while conventional constant-intensity UV simulations do not reflect the variable nature of outdoor radiation. Aging duration and film thickness are both key factors affecting Rubber-Modified Asphalt (RMA), but how their combination influences RMA remains unclear. To address this limitation, this research employed accelerated aging experiments under variable-intensity UV radiation to investigate the performance and aging mechanism of RMA across different aging durations and asphalt film thicknesses. Rheological properties were analyzed through rheological tests, and the UV aging mechanisms of RMA were revealed using FTIR and SEM. The results revealed that crumb rubber improved RMA’s UV aging resistance, including high-temperature performance, fatigue life, and low-temperature cracking resistance. Aging effects were more influenced in RMA with thinner films under prolonged UV exposure. After nine cycles of ultraviolet aging, the rutting resistance, elastic recovery, fatigue life, and low-temperature cracking resistance of RMA with a 1 mm film thickness were 1.33, 1.11, 0.54, and 0.67 times, respectively, those of RMA with a 2 mm film thickness subjected to three UV aging cycles. RMA demonstrated comparable high-temperature performance and elastic recovery under UV aging conditions corresponding to a 1.5 mm film thickness aged for three cycles and a 2.0 mm film thickness aged for six cycles, as well as a 1.0 mm film thickness aged for six cycles and a 1.5 mm film thickness aged for nine cycles. FTIR showed that the increased activity of C=C and C-H under photo-oxidative aging caused a greater impact on the carbonyl groups than the sulfoxide groups. Under high-intensity UV radiation, RMA with thinner films exhibited greater rubber powder detachment, increased surface oxidation, and a substantial widening of cracks. The rubber powder absorbed UV radiation, enhancing the stability of RMA. The maximum crack width of the 1 mm NA was twice that of RMA. These provided insight into the microstructural pattern of cracking resistance degradation caused by aging. This research provides theoretical support for the optimization of the anti-aging performance of RMA. Full article

This study developed cholesteric liquid crystal broadband reflective films using zinc oxide nanoparticles (ZnO NPs) and homotriazine UV-absorbing dye (UV-1577) to enhance infrared shielding. Unlike benzotriazole-based UV absorber UV-327, which suffers from volatility and contamination, UV-1577 exhibits superior compatibility with liquid crystals, higher UV absorption efficiency, and enhanced processing stability due to its larger molecular structure. By synergizing UV-1577 with ZnO NPs, we achieved a gradient UV intensity distribution across the film thickness, inducing a pitch gradient that broadened the reflection bandwidth to 915 nm and surpassing the performance of previous systems using UV-327/ZnO NPs (<900 nm). We conducted a detailed examination of the factors influencing the reflective bandwidth. These included the UV-1577/ZnO NP ratio, the concentrations of the polymerizable monomer (RM257) and chiral dopant (R5011), along with polymerization temperature, UV irradiation intensity, and irradiation time. The resultant films demonstrated efficient ultraviolet shielding via the UV-1577/ZnO NPs collaboration and infrared shielding through the induced pitch gradient. This work presents a scalable strategy for energy-saving smart windows. Full article

Nowadays, nitrate ions and azo dyes are a significant source of water pollution due to their high toxicity, persistence, and potential to be carcinogenic. Both contaminants are the result of anthropogenic sources, such as sewage or industrial wastewater discharge; the first one results also as a consequence of the intensive use of fertilizers. In this work we report the use of a new quaternized pentablock copolymer (PTBr) for the removal of nitrate ions and methyl orange (MO) dye from water by adsorption processes. Morphological, chemical, and thermal properties of the pentablock copolymer were investigated, respectively, by scanning electron microscopy (SEM), Attenuated Total Reflectance Infrared Spectroscopy (ATR-FTIR) (FT-IR), and X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) analyses. Anionic removal ability and adsorption rate in water solutions containing either a single contaminant species or a mix of the two contaminants were studied by UV–VIS absorbance spectroscopy as a function of time and initial concentration. The presence of imidazole groups confers on PTBr a positive charge and a hydrophilic character that are responsible for an effective removal of anions from water. PTBr film reports an adsorption efficiency of 10.15 mg/g for nitrate removal and this value is in line with others reported in the literature. In the case of the simultaneous presence of nitrate and MO, it is found that nitrate ions removal is slightly affected by the presence of the dye, since both contaminants compete for electrostatic interaction with imidazole groups. On the contrary, the dye removal does not show significant change with or without the presence of nitrate ions, probably due to other kinds of interaction that it can establish with the polymer surface (π-π interaction). The adsorption process and the related mechanisms are described using kinetic and isothermal models. Despite a certain reduction in the adsorption efficiency for one of the investigated contaminants, the results confirm the possibility of using the quaternized pentablock copolymer for the co-adsorption of both inorganic and organic anions. Full article

The development and characterization of a sustainable carboxymethylcellulose (CMC)-based material hosting Egyptian blue (EB) as a luminophore with emission in both the visible and NIR regions is herein presented and discussed, demonstrating its potential to be applied in a variety of applications, such as bioimaging, sensing, and security marking. Solution casting was used to synthesize the films, with citric acid (CA) as a crosslinking agent. Fully characterization was performed using attenuated total reflection (ATR) and coherent anti-Stokes Raman scattering (CARS) spectroscopy, zeta potential, UV–Vis, and photoluminescence (PL) spectroscopy, and thermal analysis techniques, such as thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results confirm the effective crosslinking of CMC with CA within CMC–EB–CA films with 1.5 and 3% of EB. The introduction of EB retained its usual NIR emission with λ_em max = ~950 nm reaching quantum yield values in the range of 11.2–12.8% while also enabling a stable dispersion within the CMC matrix, as confirmed using CARS imaging and zeta potential. Additionally, the CMC films exhibited the characteristic clustering-triggered emission (CTE) in the blue region at 430 nm with a slight increase in luminescence quantum yield (Φ) from 5.8 to 6.1% after crosslinking with citric acid. Full article

This study examines the intrinsic optical enhancements of carbon fiber-reinforced polymers (CFRPs) achieved through the integration of magnesium oxide (MgO) nanoparticles, as well as Mg/MgO and titanium dioxide (TiO₂) thin films onto carbon fibers. Integration was performed by quasi-continuous electrophoretic deposition (EPD) and physical vapor deposition (PVD), respectively. Employing a customized electrophoretic cell, EPD facilitated uniform MgO nanoparticle deposition onto unsized carbon fibers, ensuring stable nanoparticle dispersion and precise fiber coating. As a result, the fibers exhibited increased ultraviolet (UV) reflectance, largely attributed to the optical properties of the protective MgO layer. In parallel, PVD enabled the deposition of Mg/MgO and TiO₂ thin films with tailored thicknesses, providing precise control over key optical parameters such as reflectivity and interference effects. Mg/MgO coatings demonstrated high UV reflectivity, while TiO₂ layers, with their varying refractive indices, generated vibrant colors in the visible (Vis) range through thickness-dependent light interference. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) assessed the quality, thickness, and uniformity of these thin films, and UV/Vis spectroscopy confirmed the influence of deposition parameters on the resulting optical performance. Post-lamination analyses revealed that both EPD and PVD modifications significantly enhanced UV reflectivity and allowed for customizable color effects. This dual strategy underscores the potential of combining EPD and PVD to develop advanced CFRPs with superior UV resistance, decorative optical features, and improved environmental stability. Full article

Radiative cooling is a passive cooling strategy that dissipates heat externally through the atmospheric window (8–13 μm). This study presents a radiative cooling film with a simple and cost-effective fabrication process. The film was fabricated by mixing SiO₂ hollow microspheres with a UV-curable resin, employing a photopolymerization-induced phase separation method. The resulting gradient refractive index structure enhanced thermal radiation emissivity. At an optimal silica-to-resin mass ratio of 1:1.5 and a film thickness of 1.1 mm, the film achieved a solar reflectivity of 85% and an emissivity of 91% within the atmospheric window. Outdoor experiments conducted in both summer and winter demonstrated stable cooling performance. Under a solar irradiance of 796.9 W/m² (summer), the film reduced surface temperature by 10 °C compared to ambient air and 20 °C compared to an uncoated glass substrate, achieving a radiative cooling power of 76.7 W/m². In winter (solar irradiance of 588.8 W/m²), the film maintained a significant cooling effect, though with reduced efficiency due to lower solar exposure. Furthermore, long-term stability tests over six months showed that the film retained high solar reflectivity and infrared emissivity, indicating good durability. Overall, the developed radiative cooling films demonstrate excellent optical properties, structural stability, and cooling efficiency, making it a promising candidate for real-world radiative cooling applications. Further studies on environmental resilience and optimization under diverse climatic conditions are necessary for broader deployment. Full article

This paper investigates the influence of C₂H₂ flow rates on the optical properties, surface roughness, and residual stress of Ti/WC thin films deposited on glass substrates. A range of Ti/WC thin films with varying carbon contents were prepared using the reactive pulsed DC magnetron sputtering technique. The properties of the Ti/WC films can be tuned by adjusting the deposition parameters, among which the acetylene (C₂H₂) flow rate plays a key role in determining the thin film’s microstructure, optical properties, and stress behavior. The optical properties of the thin films were analyzed using UV-visible-NIR spectroscopy and Fourier transform infrared (FTIR) spectroscopy, the surface morphology was analyzed using microscopic interferometry, and the residual stress in the films was measured using a homemade Twyman–Green interferometer. The measurement results show that the average reflectance of Ti/WC films decreases with the increase in the C₂H₂ flow rate, and the measured value changes from 52.24% to 44.56% in the wavelength of 400–800 nm. The infrared reflectance of Ti/WC films in the wavelength of 2.5–25 μm is 81.8% for 10 sccm, 80.8% for 20 sccm, 77.2% for 30 sccm, and 73.6% for 40 sccm. The tensile stress of the Ti/WC films deposited on B270 substrates increases with the increase in the C₂H₂ flow rate, and the stress value changes from 0.361 GPa to 0.405 GPa. The surface roughness of Ti/WC films initially increases and then decreases slightly with the increase in the C₂H₂ flow rate. These results indicate that the C₂H₂ flow ratio significantly affects the reflectance in the visible and infrared bands, surface roughness, and residual stress of the Ti/WC films, which is of great significance for optimizing thin film performance to meet specific application requirements. Full article

TiO₂ films and N-doped TiO₂ films modified with silver (Ag/N-TiO₂) were synthesized using DC magnetron sputtering. By varying the N₂ flow rate and the Ag sputtering power, respectively, the degree of doping and modification was managed. The microstructure, morphology, and properties of the thin film were studied using X-ray diffraction, field emission scanning electron microscopy, UV visible diffuse reflectance spectroscopy, and atomic force microscopy. The results show that TiO₂ in Ag/N-TiO₂ composite has an anatase structure, and the absorption spectrum of (Ag/N-TiO₂) thin film shows a red shift. The best photocatalytic degradation effect regarding the N-TiO₂ films was observed with an N₂ flow rate of 16 sccm (standard cubic per minute). The degradation rate in MO (Methyl orange) pure solution (C₀ = 10 mg/L) can reach 100% in 85 min, and in the MO-Na₂SO₄ mixed solution (C₀ = 10 mg/L, C C_Na2SO4 = 12.5 g/L), it only takes 40 min. Ag/N-TiO₂ films exhibited the highest degradation efficiency at a 5 W sputtering power and 50 s of sputtering time, reaching a 100% degradation rate in MO pure solution that can reach 100% in 50 min, and in the MO-Na₂SO₄ mixed solution, it only takes 36 min. The photocatalytic decomposition of MO was greatly accelerated by the addition of Na₂SO₄, which worked best with a 12.5 g/L concentration. However, when the concentration of Na₂SO₄ is above or below 12.5 g/L, Na₂SO₄ exhibits significant inhibition of photocatalytic degradation. Photocatalytic cycling experiments showed that the photocatalyst still maintained an effective degradation performance after four cycles. The degradation mechanism was analyzed using first-order kinetics and energy band theory. Compared to powder particles, the photocatalyst on the films has high stability and can be recovered 100%. So, photocatalysts on films have great potential for industrial applications. Full article

In the present work, a study of the structural defects in HfO₂ thin films deposited by dip-coating on p-type silicon substrates treated under different conditions, such as air-annealing, ultraviolet irradiation, and simultaneous annealing–UV irradiation, is presented. HfO₂ thin films were analyzed by grazing incidence X-ray diffraction, Raman spectroscopy, optical fluorescence, atomic force microscopy, and UV-Vis diffuse reflectance. Films treated at 200 °C and 350 °C present peaks corresponding to monoclinic HfO₂. After UV treatment, the films became amorphous. The combination of annealing at 350 °C with UV treatment does not lead to crystalline peaks, suggesting that UV treatment causes extensive structural damage. Fluorescence spectroscopy and UV-Vis spectroscopy suggest that films present oxygen vacancies as their main structural defects. A reduction in oxygen vacancies after the second thermal treatment was observed, but in contrast, after UV irradiation, fluorescence spectroscopy indicated that more defects are created within the mobility gap, irrespective of the simultaneous annealing at 350 °C. An electronic band diagram was proposed assigning the observed fluorescence bands and optical transitions, which, in turn, explain the electrical properties of the films. The results suggest that the electronic structure of HfO₂ films can be tailored with a careful choice of thermal annealing conditions along with the controlled creation of defects using UV irradiation, which could open the way to multiple applications of the materials either in microelectronics, optoelectronics, as well as in photocatalytic/electrocatalytic applications such as photodegradation and hydrogen generation. Full article

Thin films (TFs) of TiO₂ and ZrO₂ were prepared and characterized to evaluate their structural and optical (SO) properties and, later, to test their efficiency for the photocatalytic degradation (PD) of methylene blue (MB) in aqueous solution. The X-ray diffraction patterns showed that the TiO₂ TFs had an anatase crystalline structure, unlike the ZrO₂ TFs, which showed a tetragonal crystalline structure that was verified by Raman spectroscopy. The band gap (BG) energies, as calculated from UV-Vis spectroscopy and diffuse reflectance spectroscopy, corresponded to 3.2 and 3.7 eV for the TiO₂ and ZrO₂ TFs, respectively. SEM examination of the obtained materials was also carried out to assess the surface morphology and topography. The comparative study of the FTIR spectra of the TiO₂ and ZrO₂ TFs successfully confirmed the composition of the two-metal oxide TFs. The electrical properties of the films were studied by conductivity measurements. The two films also showed a similar thickness of about 200 nm and a substantially different photocatalytic performance for the discoloration of MB in aqueous solution. The corresponding rate constants, as obtained from a pseudo-first-order kinetic model, revealed that TiO₂ films promote color removal of the model dye solution almost 20 times faster than the rate observed for ZrO₂ modified glass substrates. We suggest that this difference may be related to the hydrophilic character of the two films under study, which may affect the charge carrier injection process and, therefore, the overall photocatalytic performance. Full article

The utilization of self-healing polymers is a promising way of solving problems associated with the wear and tear of polymer products, such as those caused by mechanical stress or environmental factors. In this study, a series of novel self-healing, high-strength copolymers of acrylamide, acrylic acid, and novel acrylic complexes of 4′-phenyl-2,2′:6′,2″-terpyridine [Co(II), Ni(II), and Cu(II)] was prepared. A systematic study of the composition and properties of the obtained polymers was carried out using a variety of physicochemical techniques (elemental analysis, gel permeation chromatography (GPC), attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FT-IR), ultraviolet-visible spectroscopy (UV-vis), small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), confocal laser scanning microscopy (CLSM), and tensile testing). All metallopolymer samples exhibit autonomous intrinsic healing along with maintaining high tensile strength values (for some samples, the initial tensile strength exceeded 100 MPa). The best values of healing efficiency are possessed by metallopolymers with a nickel complex (up to 83%), which is most likely due to the highest lability of the metal–heteroatom coordination bonds. The example of this system shows the ability to re-heal with negligible deterioration of the mechanical properties. The possibility of tuning the mechanical properties of self-healing films through the use of different metal ions has been demonstrated. Full article

Radiative cooling, an emerging technology that reflects sunlight and emits radiation into outer space, has gained much attention due to its energy-efficient nature and broad applicability in buildings, photovoltaic cells, and vehicles. This study focused on fabricating SiO₂-polymethyl methacrylate (PMMA) and TiO₂-SiO₂-PMMA thick films via the blade-coating method. The investigation aimed to improve cooling performance by adding TiO₂ particles to increase the coverage area and utilize the TiO₂ reflectance ability. The characterizations of the emissivity/absorptivity, solar reflectance, and microstructure of the thick films were conducted by using ultraviolet–visible/near-infrared (UV-Vis/NIR) diffuse reflection spectroscopy and scanning electron microscopy, respectively. Experimental results revealed that the maximum temperature drops of approximately 9.4 and 9.8 °C were achieved during the daytime period for SiO₂-PMMA and TiO₂-SiO₂-PMMA thick films. The total solar radiation reflectivity increased from 71.7 to 75.6% for SiO₂-PMMA radiative cooling thick films after adding TiO₂. These findings underscored the potential of TiO₂-SiO₂-PMMA thick films in advancing radiative cooling technology and cooling capabilities across various applications. Full article

In this work, TiO₂ and Anderson-type polyoxometalates (Ni, Co, and Fe) thin-film composites were fabricated. The composites were characterized by FTIR and Raman spectroscopy, diffuse reflectance, and scanning electronic microscopy. The methylene blue (MB) photocatalytic degradation on the composites under UV irradiation was studied. Spectroscopic results verified the modification of TiO₂ thin films. Optical and morphological properties changed after TiO₂ modification. The largest change in the optical band gap was observed for the FePOM/TiO₂ system, which reported a value of 3.05 eV. The POM/TiO₂ systems were more efficient in methylene blue (MB) adsorption than bare TiO₂. Furthermore, the modified films were more efficient than bare TiO₂ during MB photodegradation tests. The NiPOM/TiO₂ and the CoPOM/TiO₂ were the most efficient in the MB adsorption, reaching ~20%. The NiPOM/TiO₂ and the CoPOM/TiO₂ composites were the most efficient in the photodegradation process, reaching ~50% of MB removal. The stability tests indicated that composite films were moderately stable after the three performed reusability cycles. Thus, these results suggest that POM modification of TiO₂ can improve the adsorption and photodegradation capacity of semiconductors. Full article

Titanium dioxide thin films on the inner wall of quartz tubes were prepared in situ by the sol–gel method. Meanwhile, copper and cerium were loaded onto the surface of the titanium dioxide thin films to enhance photocatalytic activity and broaden the range of light absorption. X-ray diffractometer, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray spectrum, N₂ gas adsorption, UV diffuse reflectance spectroscopy, electron paramagnetic resonance, photoluminescene spectroscopy, and so on were used to characterize the structure, morphology, chemical composition, and optical properties of the prepared photocatalyst. Methylene blue (MB) was used as a simulated organic pollutant to study the photocatalytic performance of the photocatalyst, which was a translucent, structurally stable, and reusable high-efficiency photocatalytic catalyst. Under UV lamp irradiation, the MB photodegradation efficiency was 94.5%, which reached 91.2% after multiple cycles. Full article

The present work investigates the physicochemical stability of spray paints when irradiated with artificial solar light (at spectral range 300–800 nm). This research highlights the importance of understanding the materials used in street art and public murals, recognising them as a significant component of contemporary cultural heritage. By examining the stability and degradation of spray paints toward solar light exposure, the study aims to contribute to the preservation of contemporary murals, which reflect current social and cultural narratives. A physicochemical approach was employed for the study of spray paints’ physical and thermal properties, as well as the effect of specific photochemical ageing reactions/processes. The photochemical ageing results were compared with reference (unaged) samples. Specifically, a multi-technique approach was applied using stereo microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurement, colorimetry, glossimetry, differential scanning calorimetry (DSC), UV-Vis spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and pyrolysis-GC/MS (Py-GC/MS). The photodegradation of the spray paints occurred from the first 144 h of solar light irradiation, resulting in changes in morphology, colour, gloss, roughness, and wettability. Regarding photochemical stability, ageing seems to affect the binders more than the synthetic organic pigments and the inorganic fillers. In particular, acrylic binders showed small chemical changes, whereas the alkyd, nitrocellulose, and styrene binders underwent severe chemical modification. The results suggest that simulated daylight irradiation prompts the migration of additives toward the surface of the spray paint films. In addition, the results of the analyses on the white spray paints in comparison with the coloured paints (from the same manufacturer) showed that there seems to be an active distinct photoageing mechanism involving titanium dioxide, but the whole issue needs further investigation. Full article