Decoding a Percolation Phase Transition of Water at ∼330 K with a Nanoparticle Ruler

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 phase transitions and anomalous properties of water, which are subtle to observe experimentally. Here, 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) phase becomes percolated below 330 K. Around this critical temperature, we find that the sizes of the LDL clusters to be similar to the nanoparticles, confirming the role of upconversion nanoparticle as a powerful ruler for measuring the extensiveness of the LDL hydrogen-bond network and nanometer-scale spatial changes (20 to 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 modelling water's many anomalous properties and phase transitions.

Exploring Single-Nanoparticle Dynamics at High Temperature by Optical Tweezers

“…The similarity between the temperature dependence of Δv norm (Figure b) and that of the instantaneous Brownian velocity of NaYF 4 :Yb,Er upconversion nanoparticles, measured by some of us in ref , suggests that both trends share the same origin: the anomalous change in the structure of water at these temperatures. The hypothesis of liquid water being described as a mixture of two organizations of hydrogen bonds competing at thermal equilibrium has been proposed to explain this anomalous behavior.…”

“…The bilinear trend was also recently observed through experimental measurements of the instantaneous Brownian velocity of NaYF 4 :Yb,Er upconversion nanoparticles using luminescence nanothermometry. 34 Figure 3c shows the temperature dependence of the position of the second nearestneighbor oxygen−oxygen peak (r 2 ) of the pair distribution function of water. 35,36 r 2 increases with temperature with a clear change at around 320 K, which has been assigned to a singularity in the molecular structure of water at this temperature.…”

Thermochromic Narrow Band Gap Phosphors for Multimodal Optical Thermometry: The Case of Y3+-Stabilized β-Bi2O3:Nd3+

“…21 Moreover, it is worth noting that, theoretically, bismuth-based materials are particularly appealing hosts for effective phosphors due to their high refractive indexes, which directly influences the spontaneous emission probability of the luminescent centers. In recent years, luminescent thermometers were demonstrated to be particularly intriguing to locally probe the intracellular temperature, 22−24 heating effects in microelectronic devices, 25 and also the phase transition temperatures 26,27 and the temperature of catalytic reactions. 28−31 In the field of optical thermometry, by taking advantage of the change with temperature of luminescent parameters such as the emission position, the band shape broadening, the emission intensity, the excited state lifetime, and so forth, many different techniques were adopted as thermal sensors so far.…”

Switching to the brighter lane: pathways to boost the absorption of lanthanide-doped nanoparticles

“…7,8 The small size of LNPs makes them usable in microenvironments (e.g., cells), 9 and more generally for the investigation of phenomena with sub-micrometric accuracy while minimally perturbing the observed system. 10,11 They have also been proposed for the preparation of light harvesting layers for low-energy photons, which would otherwise go unexploited in photovoltaic devices. 12,13 All in all, LNPs deservedly gained a place of respect in the field of nanotechnology alongside their older kin featuring photoluminescence properties: the family of semiconductor nanocrystals.…”