Effect of the Photoexcitation Wavelength and Polarization on the Generated Heat by a Nd ‐Doped Microspinner at the Microscale

This work explores the influence of rotation of a heating microparticle ( β-NaLuF4:Nd3+) onits surrounding fluid's thermal distribution. When optically trapped, rotated, and excited using a circularly polarized laser beam, heating is induced via non-radiative relaxations of Nd3+ ions and recorded by luminescent nanothermometers. Surprisingly, rotation results on reduced heat. Here proposed as a result of anisotropic absorption and temporal lag with laser polarization. AbstractThermal control at small scales is critical for studying temperature-dependent biological systems and microfluidic processes. Concerning this, optical trapping provides a contactless method to remotely study microsized heating sources. This work introduces a birefringent luminescent microparticle of NaLuF4:Nd3+ as a local heater in a liquid system. When optically trapped with a circularly polarized laser beam, the microparticle rotates and heating is induced through multiphonon relaxation of the Nd3+ ions. The temperature increment in the surrounding medium is investigated, reaching a maximum heating of ≈5 °C within a 30 µm radius around the static particle under 51 mW laser excitation at 790 nm. Surprisingly, this study reveals that the particle's rotation minimally affects the temperature distribution, contrary to the intuitive expectation of liquid stirring. The influence of the microparticl e rotation on the reduction of heating transfer is analyzed. Numerical simulations confirm that the therma...

Source: Small - April 4, 2024 Category: Nanotechnology Authors: Elisa Ortiz ‐Rivero, Carlos D. González‐Gómez, Raúl A. Rica, Patricia Haro‐González Tags: Research Article Source Type: research