Due to increasing global warming resulting from the greenhouse effect, subsequent environmental impacts and corresponding ecological influences are unavoidable. These problems are becoming more serious with time. Due to rising temperatures, the survival crisis of polar bears is a very often reported issue, because polar bears are encountering shortened seasons for catching prey on their sea-ice habitat. In this work, we report an innovative and facile strategy to save polar bears via prolonging the existence of ice layers based on plasmon-activated water (PAW). PAW with a reduced hydrogen-bonded network can be created by letting bulk deionized (DI) water flow through supported gold nanoparticles (AuNPs) under resonant illumination. Experimental results indicated that the freezing time of PAW was faster than that of DI water. In contrast, the melting time of frozen PAW was slower than that of the frozen DI water. Because the PAW with reduced hydrogen bonds (HBs) is in a high-energy state, it can more easily transform into a stronger HB structure in a low-energy state during cooling when freezing. This is accompanied by the release of more available energy, resulting in more-perfect tetrahedral symmetrical ice. Similar results were observed for solutions with 3 wt% NaCl, which is similar to the salinity of sea water. Moreover, the heat required to melt frozen PAW was ca. 7.6% higher than that of frozen DI water. These interesting phenomena suggest that prolonging the existence of solid ice can be achieved in a PAW-based system. Moreover, a system of AuNP-coated filter paper in DI water or in a DI water solution (3 wt% NaCl) under resonant illumination could work to prolong the presence of solid ice, compared to a system of AuNP-free filter paper. This innovative concept has emerged as a practical strategy to save polar bears and for other related applications.
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