title: Photoreversible fluorescent modulation of nanoparticles via one-step miniemulsion polymerization.
abstract: A nitrobenzoxadiazolyl(NBD)-based fluorescent dye and a photochromic spiropyran derivative are incorporated into polymeric nanoparticles via a one-step miniemulsion polymerization. The diameter of the nanoparticles can be varied from approximately 40 nm to 80 nm by adjusting the polymerization conditions. The prepared nanoparticles exhibit the spectral properties of both NBD dye and spiropyran, indicating that the two chromophores are incorporated into the nanoparticles. The determined amount of NBD and spiropyran in the nanoparticles are about approximately 85-90% of the feed amount, while the determined weight ratios of spiropyran to NBD in nanoparticles are very close to that of feed ratios, suggesting the miniemulsion polymerization is a suitable approach for incorporating multiple chromophores into individual nanoparticles with controlled amounts (content) and ratio. UV and visible light can be applied to modulate the fluorescence emission of NBD dye in nanoparticles. Upon UV irradiation, the spiropyran moieties in nanoparticles are converted to the open-ring (McH form) structure and upon visible-light irradiation they return to the closed-ring (SP form) structure; as a result, the fluorescence of NBD can be reversibly "switched off" and "switched on". Fluorescence resonance energy transfer from the excited NBD dye molecules to the McH form of the spiropyran moieties is the drives the fluorescence modulation. The nanoparticles display fairly good photoreversibility, photostability, and relatively fast photoresponsivity upon alternate UV/Vis irradiation. This class of photoresponsive nanoparticles may find applications in biological fields, such as labeling and imaging, as well as in optical fields, for example, individually light-addressable nanoscale devices.
authors.affiliation: College of Materials Science and Engineering, South China University of Technology, Guangzhou, P. R. China. shzhwu@scut.edu.cn
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Fang
authors.initials: F
authors.lastname: Zeng
authors.forename: Shuizhu
authors.initials: S
authors.lastname: Wu
authors.forename: Junhua
authors.initials: J
authors.lastname: Su
authors.forename: Zhen
authors.initials: Z
authors.lastname: Tong
mesh_terms: D001578:Benzopyrans / Q000737:chemistry; D004655:Emulsions / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry* / Q000528:radiation effects; D009574:Nitro Compounds / Q000737:chemistry; D010316:Particle Size; D014466:Ultraviolet Rays
chemical_list: D001578:Benzopyrans; D004655:Emulsions; D005456:Fluorescent Dyes; D007211:Indoles; D009574:Nitro Compounds; C088184:spiropyran