Yingming Lai

1 Introduction Rare-earth doped nanoparticles (RENPs) have provoked widespread curiosity for their applicability in a plethora of fields, including nanomedicine, bioimaging, security authentication, and sensing.[1] Their popularity is mostly attributed to their diverse photoluminescence properties that span multiple excitation wavelengths and emission possibilities.[2] Of significant interest, many RENPs can be excited by short-wave infrared (SWIR) light (also referred to as near-infrared...

1. Introduction Optical imaging of transient events in their actual time of occurrence exerts compelling scientific significance and practical merits.1 Occurring in two-dimensional (2D) space and at femtosecond (1fs=10−15s) to microsecond (1μs=10−6s) time scales, these transient events reflect many important fundamental mechanisms in biology.2–4 However, many transient phenomena are either nonrepeatable or difficult to reproduce.