Physicochemical and rheological properties of a transparent asphalt binder modified with Nano-TiO2

Transparent binder is used to substitute conventional black asphalt binder and to provide light-colored pavements, whereas nano-TiO2 has the potential to promote photocatalytic and self-cleaning properties. Together, these materials provide multifunction effects and benefits when the pavement is submitted to high solar irradiation. This paper analyzes the physicochemical and rheological properties of a transparent binder modified with 0.5%, 3.0%, 6.0%, and 10.0% nano-TiO2 and compares it to the transparent base binder and conventional and polymer modified binders (PMB) without nano-TiO2. Their penetration, softening point, dynamic viscosity, master curve, black diagram, Linear Amplitude Sweep (LAS), Multiple Stress Creep Recovery (MSCR), and Fourier Transform Infrared Spectroscopy (FTIR) were obtained. The transparent binders (base and modified) seem to be workable considering their viscosity, and exhibited values between the conventional binder and PMB with respect to rutting resistance, penetration, and softening point. They showed similar behavior to the PMB, demonstrating signs of polymer modification. The addition of TiO2 seemed to reduce fatigue life, except for the 0.5% content. Nevertheless, its addition in high contents increased the rutting resistance. The TiO2 modification seems to have little effect on the chemical functional indices. The best percentage of TiO2 was 0.5%, with respect to fatigue, and 10.0% with respect to permanent deformation.Fundação para a Ciência e a Tecnologia—under the projects for Strategic Funding UIDB/04650/2020 and UIDB/04029/2020, and Nanobased concepts for Innovative and Eco-sustainable constructive material surfaces PTDC/FIS/120412/2010. Furthermore, we would like to thank the Industrial Research Fund (IOF) of the University of Antwerp for funding the PAPPoA project (IOF/SBO/41859/2020). Lastly, the first author would like to acknowledge FCT for the PhD scholarship (SFRH/BD/137421/2018

Plasmonic near-field localization of silver core-shell nanoparticle assemblies via wet chemistry nanogap engineering

Silver nanoparticles are widely used in the field of plasmonics because of their unique optical properties. The wavelength-dependent surface plasmon resonance gives rise to a strongly enhanced electromagnetic field, especially at so-called hot spots located in the nanogap in-between metal nanoparticle assemblies. Therefore, the interparticle distance is a decisive factor in plasmonic applications, such as surface-enhanced Raman spectroscopy (SERS). In this study, the aim is to engineer this interparticle distance for silver nanospheres using a convenient wet-chemical approach and to predict and quantify the corresponding enhancement factor using both theoretical and experimental tools. This was done by building a tunable ultrathin polymer shell around the nanoparticles using the layer-by-layer method, in which the polymer shell acts as the separating interparticle spacer layer. Comparison of different theoretical approaches and corroborating the results with SERS analytical experiments using silver and silver polymer core shell nanoparticle clusters as SERS substrates was also done. Herewith, an approach is provided to estimate the extent of plasmonic near-field enhancement both theoretically as well as experimentally

Modification of a transparent binder for road pavements using TiO2 nanoparticles

Light and heat are relevant factors for road pavements since they promote the aging of the asphalt surfaces [1], and a large amount of heating can intensify the Urban Heat Island (UHI) effect [2]. Contrariwise, the lack of light strongly affects visibility conditions, reducing safety [3]. The conventional black color of asphalt pavements absorbs light and stores a large amount of thermal energy, which can be reduced opting by the application of light-colored pavements using, for example, a transparent binder [3]. Industrial activities and road traffic are the main sources of pollutant emissions, mostly SO2 and NOx, which are hazardous atmospheric pollutants. There are several consequences at different scales caused by these harmful gases, such as intensification of the greenhouse effect, acid rain, and public health problems. With the use of nano-TiO2 into/over asphalt mixtures, and consequently with the functionalization process considering the photocatalytic and self-cleaning properties, road pavements become the ideal places to mitigate environmental pollution due to proximity to the emissions [4]. If a transparent binder modified with nanoparticles of TiO2 is used, pavements will present multifunction effects and benefits when submitted to high solar irradiation. The production at laboratory-scale of such pavements is presented in Figure 1. First, the transparent binder was modified with nano-TiO2 (0, 0.5%, 3.0%, 6.0% and 10.0%). Binder's workability was confirmed. It presented similar behavior as a polymer modified binder. In these binder samples, the addition of high contents of nano-TiO2 increased the rutting resistance, but it seemed to reduce fatigue life, except for the 0.5%. Also, the nano-TiO2 modification had a slight effect on the chemical functional indices. The best percentage of TiO2 was 10.0% considering rutting resistance and 0.5% concerning fatigue life

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements