Monodisperse Silica-Coated Polyvinylpyrrolidone/NaYF4 Nanocrystals with Multicolor Upconversion Fluorescence Emission

摘要

Nanosized fluorescent labeling materials have been widely used for biological studies and clinical applications. Conventional downconversion fluorescent labels require an ultraviolet or blue excitation wavelength.[1], [2] These single-photon fluorescent labels emit one lower-energy photon after absorbing a higher-energy UV or visible photon. Their disadvantages include low light-penetration depth and possible severe photodamage to living organisms. Furthermore, many biological samples show autofluorescence under short-wavelength UV radiation, which decreases the sensitivity of detection. It is desirable to use fluorescent labels that can be excited in the near-infrared (NIR) region.[3] The IR-to-visible upconversion nanocrystal is a good choice.