Optical Properties of Lanthanide‐Doped Lamellar Nanohybrids

Abstract

In this article a detailed study of the optical properties of lanthanide doped lamellar nanohybrids synthesized by the "benzyl alcohol route" is presented. The synthetic approach results in the formation of a highly ordered lamellar nanocomposite consisting of yttrium or gadolinium oxide crystalline layers with a confined thickness of about 0.6 nm, separated from each other by organic layers of intercalated benzoate molecules. When the inorganic layers are doped with optically-active lanthanide ions they show outstanding emission properties in the green (Tb(3+)), red (Eu(3+)) and near infrared (Nd(3+)). The local environment of the emitting ions and the energy transfer processes involving the phenyl ring of the benzoate complexes and the lanthanide ions are presented, as well as radiance and lifetime measurements. The radiance values are comparable and in some cases even larger than those of standard phosphors, proving that these nanohybrids can compete, from an emission efficiency point of view, with commercial phosphors. Furthermore, in these nanohybrids it is possible by simply changing the excitation wavelength, to tune the emission colour chromaticity without loosing the radiance.

Lanthanide‐Containing Light‐Emitting Organic–Inorganic Hybrids: A Bet on the Future

“…Other examples of LMCT states are found for lamellar Y-and Gd-based nanohybrids doped with Eu 3þ , Tb 3þ , and Nd 3þ with benzoate molecules located between the layers. [131] As shown in Figure 3, for the case of Eu 3þ doped Y-based nanohybrids, the excitation spectra is mainly composed of a large broad band, peaking at 284 nm and ascribed to the excitation of organic ligands states, and of a shoulder at 260 nm, associated with a LMCT band related to the excitation of an electron from the 2p oxygen orbital to the 4f 6 orbital. The assignment of the LMCT band was performed observing the Eu 3þ excitation spectra of the hybrids calcined at 8008C, in order to obtain the LMCT energy in the respective inorganic compounds.…”

“…[203] For ordered hybrids only two examples have been reported so far, namely Eu 3þ -based lamellar hybrids self-templated through an hydrogen bonding array, with values below 0.01, [135] and Y 2 O 3 :Eu 3þ nanocrystalline structures, 0.16. [131] The advantage of the latter ordered materials, compared to their corresponding inorganic Ln 3þ -doped oxide nanoparticles, is that even though the emission quantum yield is comparable, the emission radiance is often larger than in standard phosphors, with quantum yields of $0.95. [130,132] This can be explained on the basis of the absorption cross-section of the intercalated organic molecules in the nanocrystalline hybrids being much larger than that of the commonly observed LMCT states of pure inorganic phosphors (Fig.…”

“…3) displays a large broad band centered at $250 nm for the Gd 3þ -based sample, showing that this band in the excitation spectra of the Eu 3þ -nanohybrids results from the overlap of the organic-ligands excited states and LMCT ones involving the oxygen atoms of the pure Y 2 O 3 oxide environment. [131] The Eu 3þ sensitization via hybrid-host excited levels is illustrated in the excitation spectra of diureasil hybrids, which display a series of intra-4f 6 lines with low relative intensity and two broad bands. [60] The main large broad band, centered at 340 and 365 nm for the diureasils with shorter and longer polymer chains, respectively, is ascribed to LMCT transitions, and the band at higher wavelengths, 420-540 nm, is originated from the hybrid host intrinsic excited states.…”

Integrative strategies to hybrid lamellar compounds: an integration challenge

“…Benzoate molecules Sol-gel Optical properties Fundamental (Sá Ferreira et al, 2006) ( Lanthanide oxide (Gd, Sm, Nd) Benzoate molecules Sol-gel Optical properties Fundamental (Karmaoui and Ferreira, 2006) Biphenyl molecules Sol-gel Optical properties Tunable the emission chromaticity / POC (Karmaoui and Mafra, 2007) -ZrP n-Alkyl Monoamines Intercalation Enhanced adsorption capacity Fundamental (Alberti et al, 2000) -ZrP Polyaniline Intercalation, in-situ polymerization Electric properties Fundamental (Takei et al, 2006) Cobalt phosphonate Carboxylates Co-precipitation Magnetic properties Fundamental (Yang et al, 2008) * POC: Proof of Concept Fu, et al, 2005) Zirconium phosphite Bis(triphenylphosphine)palladium (II) dichloride complex Co-precipitation Supported catalyst POC (Villemin et al, 1997) Bimetallic Intercalation Non-linear optics POC (Coradin et al, 1996) 5.…”

Nanocrystalline lanthanide-doped Lu3Ga5O12garnets: interesting materials for light-emitting devices

“…As an example, the patterns for the Eu 3+ -and 4 (tetrahedral) and S 6 (octahedral) sites. The lattice parameters for the lanthanide-doped LuGG samples turn out to be slightly larger than the value reported in the literature for LuGG single crystals [29], due to the presence of the doping agents.…”