resumo
The anomalous properties of water are increasingly understood in terms of its structural fluctuations between high-density (HD) and low-density (LD) domains. However, the temperature at which these fluctuations vanish upon heating (the crossover temperature, T c) and the fraction of LD domains under ambient conditions remain debated, particularly near interfaces. Here, we demonstrate that the surface charge density of colloidal upconverting nanoparticles (UCNPs) plays a key role in controlling T c within the hydration layer, i.e., the water molecules forming the interfacial layer directly interacting with the nanoparticle surface. By combining the reanalysis of existing data with new experiments on compositionally similar UCNPs bearing different surface functionalizations, we demonstrate that T c increases systematically with surface charge density. This trend holds regardless of particle size, surface chemistry, or pH. These results clarify previous conflicting findings and establish surface charge as a major factor governing the transition between LD and HD domains in hydration water. Beyond nanotechnology, these insights provide a framework for understanding how hydration water modulates biological processes, including protein stability and unfolding, where hydration shell dynamics play a determining role.
palavras-chave
LIQUID-WATER; HYDRATION SHELL; DYNAMICS; PROTEINS; BEHAVIOR; STATES; CELL
categoria
Chemistry; Science & Technology - Other Topics; Materials Science; Physics
autores
Raposo, RS; Brites, CDS; Carlos, LD
nossos autores
Carlos Brites
Professor associado
Luís Carlos
Professor Catedrático
Ramon S. Raposo Filho
Estudante de doutoramentoProjectos
Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
agradecimentos
This work was developed within the scope of the project CICECO - Aveiro Institute of Materials, UID/50011/2025 and LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020) and The Shape of Water: Part II - Unveiling the Hidden Architecture 2023.18028.ICDT, financed by national funds through the FCT/MCTES (PIDDAC). R.S.R.F. acknowledges the financial support from FCT through the Portuguese research grant 2024/01558/BD.