abstract
Liquid water, despite its simple molecular structure, remains one of the most fascinating and complex substances. Most notably, many questions continue to exist regarding the phase transitions and anomalous properties of water, which are subtle to observe experimentally. Her; we report a sharp transition in water at 330 K unveiled through experimental measurements of the instantaneous Brownian velocity of NaYF4:Yb/Er upconversion nanoparticles in water. Our experimental investigations, corroborated by molecular dynamics simulations, elucidate a geometrical phase transition where a low-density liquid (LDL) clusters become percolated below 330 K. Around this critical temperature, we find the sizes of the LDL clusters to be similar to those of the nanoparticles, confirming the role of the upconversion nanoparticle as a powerful ruler for measuring the extensiveness of the LDL hydrogen-bond network and nanometer-scale spatial changes (20-100 nm) in liquids. Additionally, a new order parameter that unequivocally classifies water molecules into two local geometric states is introduced, providing a new tool for understanding and modeling water's many anomalous properties and phase transitions.
keywords
LIQUID-LIQUID TRANSITION; THERMAL-CONDUCTIVITY; X-RAY; DENSITY; NANOCRYSTALS; RELAXATION; DYNAMICS; BEHAVIOR; TESTS; ORDER
subject category
Chemistry; Science & Technology - Other Topics; Materials Science; Physics
authors
Brites, CDS; Zhuang, BL; Debasu, ML; Ding, D; Qin, X; Maturi, FE; Lim, WWY; Soh, D; Rocha, J; Yi, ZG; Liu, XG; Carlos, LD
our authors
Projects
Nanoparticles - based 2D thermal bioimaging technologies - NanoTBTech (NanoTBTech)
SusPhotoSolutions - Soluções Fotovoltaicas Sustentáveis (SUSPHOTOSOLUTIONS)
acknowledgements
This work was partially developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement. Financial support from the European Union's Horizon 2020 FET Open programme under Grant Agreement No. 801305 and FCT (PTDC/CTM-NAN/4647/2014 and NANOHEATCONTROL -POCI-01-0145-FEDER-031469 funded by FEDER, through POCI and by national funds, OE, through FCT/MCTES) is also acknowledged. The authors acknowledge JFCBR (University of Aveiro) for his help with the signal denoising procedure. C.D.S.B. thanks SusPhotoSolutions project, CENTRO-01-0145-FEDER-000005, Portugal. X.L. is grateful for the support by the Singapore Ministry of Education (MOE2017-T2-2-110), Agency for Science, Technology and Research (A*STAR) (Grant No. A1883c0011 and A1983c0038), National Research Foundation, Prime Minister's Office, Singapore under the NRF Investigator ship programme (Award No. NRF-NRFI05-2019-0003). D.D. acknowledges support by A*STAR under an AME Young Individual Research Grant (Grant No. A1884c0020). B.Z. acknowledges support by A*STAR under the SERC Career Development Award (Grant No. A1820g0085).