26 February 2016:
Dr Annemarie Nadort and CNBP researchers Jiangbo Zhao and Ewa Goldys have had a review paper accepted for the high-impact journal Nanoscale.
Title: Lanthanide upconversion luminescence at a nanoscale: fundamentals and optical properties
Authors: Annemarie Nadort, Jiangbo Zhao and Ewa M. Goldys.
Abstract: Upconversion photoluminescence is a nonlinear effect where multiple lower energy excitation photons produce higher energy emission photons. This fundamentally interesting process has many applications in biomedical imaging, light source and display technology, and solar energy harvesting. In this review we discuss the underlying physical principles and their modelling using rate equations. We discuss how the understanding of photophysical processes enabled strategic influence over the optical properties of upconversion especially in rationally designed materials. We subsequently present an overview of recent experimental strategies to control and optimize the optical properties of upconversion nanoparticles, focussing on their emission spectral properties and brightness.
The paper is available online.
25 February 2016:
CNBP researchers have published a paper in the journal Analytical Chemistry titled, “High-contrast visualization of upconversion luminescence in mice using timegating approach.”
Authors: Xianlin Zheng, Xingjun Zhu, Yiqing Lu, Jiangbo Zhao, Wei Feng, Guohua Jia, Fan Wang, Fuyou Li and Dayong Jin.
Abstract: Optical imaging through the near-infrared (NIR) window provides deep penetration of light up to several centimetres into biological tissues. Capable of emitting 800-nm luminescence under 980-nm illumination, the recently-developed upconversion nanoparticles (UCNPs) suggest a promising optical contrast agent for in vivo bioimaging. However, presently they require high-power lasers to excite when applied to small animals, leading to significant scattering background that limits the detection sensitivity as well as detrimental thermal effect. In this work, we show that the time-gating approach implementing pulsed illumination from a NIR diode laser and time-delayed imaging synchronized via an optical chopper offers detection sensitivity more than one order of magnitude higher than the conventional approach using optical band-pass filters (S/N: 47321/6353 vs. 5339/58), when imaging UNCPs injected into Kunming mice. The pulsed laser illumination (70μs ON in 200 μs period) also reduces the overall thermal accumulation to 35% of that under the continuous-wave mode. Technical details are given on setting up the time-gating unit comprising an optical chopper, a pinhole and a microscopy eyepiece. Being generally compatible with any cameras, this provides a convenient and low cost solution to NIR animal imaging using UCNPs as well as other luminescent probes.
The full paper is accessible online.