Cool coatings have become superior passive cooling technologies for urban surfaces and areas, developed with materials with high solar reflection in the NIR region, which can reduce the energy consumption required for building cooling and improves the thermal comfort of urban living. As temperatures rise, it is essential that buildings’ energy codes and local planning include cooling-oriented design strategies, including passive and nature-based solutions, which may reduce cooling needs and prevent heat islands in expanding urban areas. In 2021, total cooling energy demand rose by more than 6.5% globally, with growth in Asia Pacific and Europe hovering around 8–9%. A report on “Space cooling” published by the International Energy Agency estimated that the number of air conditioners worldwide has doubled since 2000, reaching over 2.2 billion units in 2021. Furthermore, as the planet warms, electricity consumption has increased due to spending on cooling equipment. It has been reported that urban areas experience higher temperatures due to the Urban Heat Island effect than rural areas. The pigments exhibit high near-infrared solar reflectance (with R% ≥ 60%), with an enhancement of nearly 20% for the pigment-containing neodymium when applied in white paint, indicating that the prepared compounds have the potential to be energy-saving color pigments for coatings.Ĭurrent urban development is a global issue as it triggers the formation of heat islands and increases CO 2 pollution. Colorimetric measurements obtained by the CIEL*a*b* method show values correlated to blue pigments attributed to Co 2+ ions in tetrahedral sites. The structural characterization showed that the pigments present the Gahnite crystalline phase. The wettability of the coatings containing the synthesized pigments was also evaluated. The pigments were characterized by XRD, SEM, XPS, UV-Vis, NIR diffuse reflectance spectroscopy, and CIE-1976 L*a*b* color measurements.

Within this perspective, the current study reports on the synthesis of blue pigments of ZnAl 2O 4:M (M = Co 2+ and Co 2+/Nd 3+) using recycled metallic aluminum (discarded can seal) with reflective properties of Near-infrared radiation. Developing strategies for the green synthesis of novel materials, such as pigments for protection from solar radiation, is a fundamental research subject in material science to mitigate the heat island effect.

Pigments 3 synth