UV-LED curable acrylic films containing phosphate glass powder: effect of the filler loading on the thermal, optical, mechanical and flame retardant properties

In this work, we thoroughly investigate the effects of the incorporation of a phosphate glass micrometric powder on the morphology, as well as on the thermal, optical, mechanical and flame retardant properties of UV-LED curable acrylic films. To this aim, the filler loading was changed within 10 and 50 wt.%. UV-LED initiated curing was selected as a fast and reliable system, as the standard UV-curing process was not suitable because of the presence of the glass powder that decreased the quantum efficiency during the UV exposure, hence preventing the transformation of the liquid system into a solid network. The glass powder slightly increased the glass transition temperature of the acrylic network, hence showing a limited effect on the chain segments mobility; besides, increasing filler loadings were responsible for a progressive decrease of the transparency of films, irrespective of a marginal effect on their refractive index. Conversely, the presence of increasing amounts of phosphate glass improved the thermal and thermo-oxidative stability of the cured products. Besides, phosphate glass was capable of remarkably enhancing the flame retardance of the acrylic network at 50 wt.% loading, which achieved self-extinction in vertical flame spread tests (and was V-0 rated). This formulation, as assessed by forced-combustion tests, also displayed a remarkable decrease of peak of Heat Release Rate and Total Heat Release (by 44 and 33%, respectively) and of Total Smoke Release and Specific Extinction Area (by 53 and 56%, respectively). Further, the filler promoted an increase of the stiffness and surface hardness of the films, at the expense of a decrease in ductility. All these findings may justify the potential use of these composite films as flame retardant coatings for different flammable substrates

Stokes drift for inertial particles transported by water waves

We study the effect of surface gravity waves on the motion of inertial particles in an incompressible fluid. Using the multiple-scale technique, we perform an analytical calculation which allows us to predict the dynamics of such particles; results are shown for both the infinite- and finite-depth regimes. Numerical simulations based on the velocity field resulting from the second-order Stokes theory for the surface elevation have been performed, and an excellent agreement with the analytical predictions is observed. Such an agreement seems to hold even beyond the formal applicability of the theory. We find that the presence of inertia leads to a non-negligible correction to the well-known horizontal Stokes drift; moreover, we find that the vertical velocity is also affected by a drift. The latter result may have some relevant consequences on the rate of sedimentation of particles of finite size. We underline that such a drift would also be observed in the (hypothetical) absence of the gravitational force.Comment: 9 pages, 4 figure

Gold nanostructured surface for the detection of contaminants in water

We will report on the realization of cost-effective SERS probes for portable systems for the detection of contaminants in water reaching sensitivities below 300 part-per-trillion

Effect of Size and Morphology of Different ZnO Nanostructures on the Performance of Dye-Sensitized Solar Cells

In this study, the influence of zinc oxide (ZnO) nanostructures with various morphologies on the performance of dye-sensitized solar cells (DSSCs) was investigated. Photo-electrodes were fabricated incorporating ZnO transport layers of distinct nanoscale morphologies—namely nanoparticles, microballs, spiky microballs, belts, and triangles—and their respective current–voltage characteristics were evaluated. It was observed that the DSSCs employing the triangular ZnO nanostructures, with a side length of approximately 30 nm, achieved the highest power conversion efficiency of 2.62%. This was closely followed by the DSSCs using spherical nanoparticles with an average diameter of approximately 20 nm, yielding an efficiency of 2.54%. In contrast, the efficiencies of DSSCs with microball and spiky microball ZnO nanostructures were significantly lower, measuring 0.31 and 1.79%, respectively. The reduction in efficiency for the microball-based DSSCs is attributed to the formation of micro-cracks within the thin film during the fabrication process. All DSSC configurations maintained a uniform active area of 4 mm2. Remarkably, the highest fill factor of 59.88% was recorded for DSSCs utilizing the triangular ZnO morphology, with the spherical nanoparticles attaining a marginally lower fill factor of 59.38%. This investigation corroborates the hypothesis that reduced particle size in the transport layer correlates with enhanced DSSC performance, which is further amplified when the nanoparticles possess pointed geometries that induce strong electric fields due to elevated charge concentrations

Glass and Glass–Ceramic Photonic Materials for Sensors

Recent developments in sensors are pushing for optimized materials that can increase their usage, bolster their sensitivity and enable new and more efficient transduction mechanisms. We hereby review some of the most relevant applications of glasses and glass-ceramics for photonic sensors considering the recent trends and innovative approaches. This review covers from bulk glasses to thin films and from fiber optics to nanocrystal-based and their applications in sensing

Infrared Nanosecond Laser Texturing of Cu-Doped Bioresorbable Calcium Phosphate Glasses

The surface modification of bioactive glasses significantly impacts their performance for in vivo biomedical applications. An affordable nanosecond pulsed laser surface-modification technique would provide great flexibility in applications such as cell scaffolding and fouling/anti-fouling engineered surfaces. This study reports on an infrared nanosecond laser modification technique we developed and applied to a Cu-doped bioresorbable calcium phosphate glass. With this technique, clean micro-protrusion features could be produced. By tuning the laser parameters such as the laser scan speed and average power, the width and height of the formed protrusions could be controlled. Finally, optimal laser parameters were defined to obtain complex surface textures without significant damage or thermal-stress-induced cracks. These results could provide effective aid for the affordable, fast, and selective surface texturing of metal-doped bioglasses, opening new possibilities in their application in the biological field

High concentration Yb-Er co-doped multi-component phosphate glasses for compact eye-safe optical amplifiers

In recent years, the increasing need of airborne LIght Detection And Ranging (LIDAR) systems for environmental monitoring and surveillance has noticeably boosted the development of compact eye-safe optical amplifiers. In this scenario, multi-component phosphate glasses can be regarded as ideal candidate materials as they can be doped with a large amount of rare-earth (RE) ions without clustering, thus enabling the realization of few-cm long optical amplifier sections featured by high optical gain per unit length. In this work we will report the ongoing activities and the recent results obtained by our research group on the design, processing and characterization of a series of Yb-Er co-doped phosphate glasses to be used as active materials for the core of a waveguide amplifier. The physical, thermo-mechanical, optical and spectroscopic properties of the prepared glasses have been thoroughly investigated