Optimization of upconversion luminescence excitation mode for deeper in vivo bioimaging without contrast loss or overheating.

Upconversion nanoparticles have attracted considerable attention as luminescent markers for bioimaging and sensing due to their capability to convert near-infrared (NIR) excitation into visible or NIR luminescence. However, the wavelength of about 970 nm is commonly used for the upconversion luminescence excitation, where the strong absorption of water is observed, which can lead to laser-induced overheating effects. One of the strategies for avoiding such laser-induced heating involves shifting the excitation into shorter wavelengths region.

Upconversion microparticles as time-resolved luminescent probes for multiphoton microscopy: desired signal extraction from the streaking effect.

The great interest in upconversion nanoparticles exists due to their high efficiency under multiphoton excitation. However, when these particles are used in scanning microscopy, the upconversion luminescence causes a streaking effect due to the long lifetime. This article describes a method of upconversion microparticle luminescence lifetime determination with help of modified Lucy–Richardson deconvolution of laser scanning microscope (LSM) image obtained under near-IR excitation using nondescanned detectors.