Photoluminescent Porous Alginate Hybrid Materials Containing Lanthanide Ions
ABSTRACT The photoluminescence features of Eu(3+)-, Tb(3+)-, Tb(3+)/Eu(3+)-alginate aerogel (hydrogel and alcogel) and Eu(3+)-alginate xerogel hybrids were investigated. The Eu(3+)-alginate aerogel and alcogel exhibit the highest (5)D0 quantum efficiencies (9.9 and 8.2%, respectively), while the hydrogel and xerogel have lower values (5.2 and 5.6%, respectively). The Tb(3+)/Eu(3+) hybrids are multiwavelength emitters in which the emission color can be tuned across the chromaticity diagram from the red toward the yellowish-green spectral regions, crossing the white area by selecting the excitation wavelength.
- SourceAvailable from: Luís D Carlos[Show abstract] [Hide abstract]
ABSTRACT: Three different types of photoluminescent hybrid materials containing trivalent lanthanide (Ln(3+) = Eu(3+), Tb(3+)) ions, chitosan, and silica have been prepared with different structural features. The different silica sources lead to diverse microstructures of hybrid materials, with silica being homogeneously dispersed in the chitosan materials (LnChS-H), or forming a core-shell morphology. Postsynthesis treatment is necessary for embedding the luminescent probe. The Ln(3+)-based materials have been investigated by photoluminescence spectroscopy (12-300 K). The chitosan-Eu(3+)-related local environment is maintained in the EuChS-H hybrid material. The emission features of the core-shell materials are characterized by the presence of two Eu(3+) distinct local environments, one associated with the chitosan core and the other with the silica shell.The Journal of Physical Chemistry B 12/2009; 114(1):77-83. DOI:10.1021/jp908563d · 3.30 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The Ce3+, Mn2+-codoped calcium fluorapatite [Ca5(PO4)3F, FAP] nanorods were prepared by a simple hydrothermal method. SEM and TEM images indicate that the FAP:Ce3+,Mn2+ sample consists of nanorods with lengths around 30–70 nm and diameters around 20 nm, respectively. The as-obtained FAPnanorods show an intense bright blue emission (centered at 432 nm, lifetime 7.5 ns) arising from CO2˙− radical impurities in the crystal lattice under UV light irradiation. In addition, codoped with Ce3+ and Mn2+, the as-synthesized FAP:Ce3+,Mn2+ sample shows the tunable luminescence from blue to white to yellow by the variation of excitation UV light. The emission spectra of the as-synthesized FAP:Ce3+,Mn2+ sample show three broad bands, which are associated with the CO2˙− radical impurities (blue emission), Ce3+ ions (ultraviolet emission), and Mn2+ ions (yellow emission), respectively. The coexistence of three broad emissions results in the bright white light directly under suitable excitation wavelength. The combination emissions of impurities and metal activator ions may provide a novel strategy to obtain white light and tunable luminescence.Journal of Materials Chemistry 08/2010; 20(32). DOI:10.1039/c0jm01036g · 7.44 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Aerogels are low density materials which are produced from wet gels, and find a variety of potential uses. The relative importance of shape/geometry and self-association of the starting materials for the production of aerogels is studied herein. Aerogels were produced from microcrystalline cellulose (MCC) and its functionalized analog, carboxymethyl cellulose (CMC). With increasing functionalization, CMC gains the potential for self-association, differentiating itself from MCC. The present study explores the preparation of aerogels from MCC and CMC, comparing performance with and without significant self-association potential, and more broadly evaluating the production of low density structural materials from renewable cellulose. It was observed that the self-association present in CMC substantially increases aerogel mechanical properties when compared those of non-interactive MCC. Aspect ratio is proposed to also be an import parameter in the structure–property relationship for these materials. KeywordsAerogel-Structure-Cellulose-Self associationPolymer Bulletin 12/2010; 65(9):951-960. DOI:10.1007/s00289-010-0306-x · 1.49 Impact Factor