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Controlling the thermal switching in upconverting nanoparticles through surface chemistry
Eduardo D Martínez1, Alí F García-Flores2, Albano N Carneiro Neto3
1Instituto de Nanociencia y Nanotecnología (INN), Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (CNEA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. E. Bustillo 9500, R8402AGP, S. C. de Bariloche, Río Negro, Argentina. eduardo.martinez@cab.cnea.gov.ar.
Rare-earth-doped nanoparticles show anomalous thermal modulation of photon upconversion. Surface capping influences water adsorption, affecting optical properties and creating thermal hysteresis loops.
Area of Science:
- Materials Science
- Nanotechnology
- Photonics
Background:
- Photon upconversion in rare-earth-doped nanoparticles is sensitive to thermal effects.
- Adsorbed water molecules act as surface quenchers, influencing upconversion intensity.
- Surface functionalization impacts water adsorption/desorption dynamics and optical properties.
Purpose of the Study:
- Investigate the influence of surface capping on the thermal modulation of upconversion in Yb3+/Er3+ co-doped nanoparticles.
- Characterize the thermal hysteresis and intensity overshoot phenomena.
- Understand the role of surface chemistry in nanoparticle luminescence.
Main Methods:
- Synthesis of small (<25 nm) Yb3+/Er3+ co-doped nanoparticles with varying surface capping molecules.
- Temperature-controlled luminescence measurements.
- Numerical modeling of non-radiative energy transfer from surface defects.
Main Results:
- Upconversion intensity exhibits thermal hysteresis loops dependent on surface hydrophilicity.
- An intensity overshoot is observed after heating cessation, affecting different transitions uniquely.
- Surface chemistry dictates the irreversibility patterns upon thermal cycling.
Conclusions:
- Surface functionalization critically controls thermal hysteresis and luminescence behavior in upconversion nanoparticles (UCNPs).
- The observed phenomena are linked to surface water dynamics and energy transfer mechanisms.
- Findings are crucial for UCNP applications in nanothermometry, bioimaging, and optical encoding.
