The Key Role of Intrinsic Lifetime Dynamics from Upconverting Nanosystems in Multiemission Particle Velocimetry

Abstract

Evaluation of particle dynamics at the nano‐ and microscale poses a challenge to the development of novel velocimetry techniques. Established optical methods implement external or internal calibrations of the emission profiles by varying the particle velocity and are limited to specific experimental conditions. The proposed multiemission particle velocimetry approach aims to introduce a new concept for a luminescent probe, which guarantees accurate velocity measurements at the microscale, independent of the particle concentration or experimental setup, and without need for calibration. The simplicity of these analyses relies on the intrinsic luminescence dynamics of core–shell upconverting nanoparticles. Upon excitation with a focused near‐infrared pulsed laser, the nanoparticle emits photons at different wavelengths. The time interval between emissions from different excited states is independent of the local environment or particle velocity. The velocity of the particles is calculated by measuring the distance between the maxima of two different emissions and dividing it by the known difference in luminescence lifetimes. This method is demonstrated using simple digital imaging of nanoparticles flowing in 75–150 µm diameter capillaries. Using this novel approach typically results in a relative standard deviation of the experimental velocities of 5% or lower without any calibration.

Janus Micromotors for Photophoretic Motion and Photon Upconversion Applications Using a Single Near-Infrared Wavelength

“…Tracking using upconversion emissions enables qualitative characterization of the photophoretic motion of the micromotors, demonstrating, for the first-time, detection of the micromotors using upconversion and providing a new strategy to study their movement. Additionally, tracking the upconverted emissions in static and dynamic states allows for spatiotemporal detection for on-demand applications, such as particle velocimetry, 81 detecting particles in living cells, 82 environmental pollution monitoring, 83 and security inks. 84 Finally, as a proof-of-concept for ROS generation, curcumin was used to degrade rhodamine B (RhB), a model organic pollutant.…”

Responsive Regulation of Energy Transfer in Lanthanide‐Doped Nanomaterials Dispersed in Chiral Nematic Structure

“…Tripositive lanthanide ions (Ln 3+ ) are critical resources due to their unique luminescent properties, including characteristic sharp emission bands, tunable visible-near infrared emission DOI: 10.1002/advs.202303235 wavelengths, large excitation-emission shifts, long lifetimes, and excellent photostability. [1] These properties boost applications of Ln 3+ -based materials from lighting to deep-tissue imaging, biosensing, [2] velocity sensing, [3] nanothermometry, [4] molecular structural change sensing, [5] and stress sensing, [6] where energy transfer (ET) involving Ln 3+ plays a key role. ET refers to the phenomenon where energy from an excited donor is nonradiatively transferred to an acceptor via a certain interaction mechanism.…”