Synthesis Of Upconversion LaF₃Nanop Articles And Self-Assembled Into CNCS

Upconversion nanomaterial doped with lanthanide ions exhibit a unique luminescent properties, it has the ability to convert near infrared long-wavelength excitation radiation into shorter visible wavelengths. The luminescence features of lanthanide ions include high luminescence quantum yield, narrow bandwidth, long-lived emission, large Stokes shifts and ligand-dependent luminescence sensitization, which have received startling interest because of the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices,(bio-) analytical sensors, bioimaging set-ups and solar cells. Clustering nanoparticles into secondary structures to form so-called colloidal nanoparticle clusters (CNCs) not only allows the combination of properties of individual nanoparticles but also takes advantage of the interactions between neighboring nanoparticles which can result in new properties. They have many potential technological applications, which may include catalysis, energy storage and conversion, magnetic separation, multimode imaging, chemical detection, and drug loading and release. As a promising upconversion luminescent host matrix, LaF3has recently attracted considerable attention. LaF3has very low vibrational energy due to the high ionicity of the La3+to fluorine bond; therefore its non-radiative loss is suppressed and a high quantum efficiency of the desired luminescence could be obtained. By organizing LaF3nanoparticles self-assembled into colloidal nanoparticle clusters, upconversion luminescence is enhanced, and the CNCs represent novel mesoporous structures. It holds great promise for the development of advanced materials with novel integrated functions.A facile and productive method has been developed to synthesize uniform LaF3nanocrystals with controllable shapes, including polyhedrons, nanorods and nanoplates. By tuning the amount of NaOH and ligands (oleic acid and octadecylamine), we can finely tailor the shapes and sizes of LaF3nanocrystals. Three prepared LaF3nanostructures were well characterized, followed by a series of control experiments to propose a mechanism for the shape control. Based on the success in materials synthesis, controlled patterning of LaF3nanoplates on substrates has also been achieved. After Yb/Er or Yb/Tm was co-doped in these LaF3nanostructures, they could serve as nanoparticulate host matrices to give strong upconversion luminescence, showing great potential in biomedical applications considering their small sizes and well-defined shapes.Significant advances in colloidal synthesis made in the past two decades have enabled the preparation of high quality nanoparticles with well-controlled sizes, shapes, and compositions. It has recently been realized that such nanoparticles can be utilized as’artificial atoms’ for building new materials which not only combine the size-and shape-dependent properties of individual nanoparticles but also create new collective properties by taking advantage of their electromagnetic interactions.Colloidal nanoparticles clusters (CNCs) of LaF3nanoplates are developed with an emulsion method. Owing to its highly anisotropic shape, these nanoplates can be assembled into spherical particles with various assembly patterns. Investigation on the formation mechanism suggests that both surface-adsorbed surfactants on LaF3nanoplates and surfactants of the emulsion play important roles in directing the assembly patterns of these nanoplates. After doped with lanthanide ions, LaF3:Yb,Er/Tm CNCs after assembly can show enhanced upconversion fluorescence than their counterparts in a free-standing form. Through loading fluorescent dyes in the mesoporous pore of these LaF3CNCs, one can finely tune their upconversion emissions through the FRET process.