MAP-Fis Research Conference

Mapping the Funnel of Life: Luminescent Nanoprobes as Reporters of Hydration-Water Structural Heterogeneity

2 Oct 2026, 12:30

20m

Anfiteatro de Física, Ed. 6 - 1.02 (School of Sciences, University of Minho)

Contributed Talk (20 minutes) Optics & Photonics (Chair: Michael Belsley, UM)

Speaker

Ramon Raposo Filho (University of Aveiro)

Description

Water’s anomalies stem from fluctuations between low-density (LD) and high-density (HD) local structural motifs, which remain difficult to probe within the hydration layers governing biomolecular and colloidal stability. We demonstrate that luminescent nanoprobes, including upconversion nanoparticles (UCNPs), CdTe quantum dots (QDs), and fluorescent proteins, act as reporters of this structural polymorphism. By monitoring temperature-dependent optical and Brownian observables, we identify a characteristic crossover temperature (Tc) marking the depletion of LD motifs [1].
Our findings establish effective surface charge density (σf) as a unifying descriptor for Tc: higher interfacial electrostatics stabilize LD motifs, causing data from diverse systems to collapse onto a single master curve [2]. This framework is validated through isotopic substitution (D2O and H218O), which perturbs hydrogen-bond dynamics and shifts these structural crossovers [3]. Extending this to high-pressure regimes using diamond anvil cells, we report the first evidence of pressure-induced LD fluctuation suppression. Above 0.1 GPa, the bilinear optical signature of CdTe QDs vanishes, resulting in a strictly linear response. This collapse of structural heterogeneity provides direct support for the "Funnel of Life" scenario, identifying a pressure-dependent boundary for water's anomalies [4]. Together, these results establish luminescent nanoprobes as a powerful toolset for navigating water’s complex metastable landscape.

References
[1] Raposo Filho, R. S., Guo, Y., Maturi, F. E., Brites, C. D., & Carlos, L. D., Acc. Chem. Res., 59(7), 1126-1137 (2026).
[2] Raposo Filho, R. S., Brites, C. D., & Carlos, L. D., J. Phys. Chem. Lett., 16(45), 11683-11689 (2025).
[3] Raposo Filho, R. S., Guo, Y., Brites, C. D., & Carlos, L. D., Optical Materials, 176, 118145 (2026).
[4] Raposo Filho, R. S., Panov, N., Maturi, F., Marin, R., Brites, C. D., Jaque, D., & Carlos, L. D. (unpublished).