Red-Emitting Hybrid Based on Eu3+-dbm Complex Anchored on Silica Nanoparticles Surface by Carboxylic Acid for Biomarker Application

Abstract

Luminescent organic-inorganic hybrids containing lanthanides (Ln3+) have been prominent for applications such as luminescent bio-probes in biological assays. In this sense, a luminescent hybrid based on dense silica (SiO2) nanospheres decorated with Eu3+ β–diketonate complexes using dibenzoylmethane (Hdbm) as a luminescent antenna was developed by using a hierarchical organization in four steps: (i) anchoring of 3-aminopropyltriethoxysilane (APTES) organosilane on the SiO2 surface, (ii) formation of a carboxylic acid ligand, (iii) coordination of Eu3+ to the carboxylate groups and (iv) coordination of dbm− to Eu3+. The hybrid structure was elucidated through the correlation of thermogravimetry, silicon nuclear magnetic resonance and photoluminescence. Results indicate that the carboxylic acid-Eu3+-dbm hybrid was formed on the surface of the particles with no detectable changes on their size or shape after all the four steps (average size of 32 ± 7 nm). A surface charge of −27.8 mV was achieved for the hybrid, assuring a stable suspension in aqueous media. The Eu3+ complex provides intense red luminescence, characteristic of Eu3+5D0→7FJ electronic transitions, with an intrinsic emission quantum yield of 38%, even in an aqueous suspension. Therefore, the correlation of luminescence, structure, particle morphology and fluorescence microscopy images make the hybrid promising for application in bioimaging.

1,3-Diketone Calix[4]arene Derivatives—A New Type of Versatile Ligands for Metal Complexes and Nanoparticles

“…The covalent functionalization of 1,3-diketonate lanthanide complexes onto silica surface is also well documented as the route for their embedding onto SNs [ 93 , 94 ]. However, search for facile and easy synthetic route for safe conversion of 1,3-diketonate lanthanide complexes into nanoparticulate form is still challenging task.…”

Revisiting carboxylic group functionalization of silica sol–gel materials

“…Santos et al performed the chloroacetic substitution reaction in water which might be questionable as H 2 O competes as a nucleophile. 101 2.3.3 Alcoholysis for introducing COOH groups. Based on the nucleophilicity of the Si-O À group, Gates' lab has tackled a very interesting approach for introducing carboxylic acid functions on silica surfaces based on the alcoholysis of a bifunctional alcohol-acid with a long hydrocarbon chain such as 12-hydroxydodecanoic acid (12-HDA) in propylene carbonate, a green solvent (Scheme 6).…”

“…Santos et al performed the chloroacetic substitution reaction in water which might be questionable as H 2 O competes as a nucleophile. 101…”

Stable Fluorescence of Eu3+ Complex Nanostructures Beneath a Protein Skin for Potential Biometric Recognition

“…Fluorescent materials based on lanthanide (Ln 3+ ) complexes [ 4 , 5 , 6 , 7 ] exhibit sharp emission peaks and high fluorescence intensity compared with traditional fluorescent organic molecules. The advantages of distinctive emission spectra and photostability of Ln 3+ fluorescence nanomaterials make them suitable for biological applications [ 7 ], with the background of the widely investigated luminescence properties of Ln 3+ complexes [ 8 , 9 ].…”

“…Fluorescent materials based on lanthanide (Ln 3+ ) complexes [ 4 , 5 , 6 , 7 ] exhibit sharp emission peaks and high fluorescence intensity compared with traditional fluorescent organic molecules. The advantages of distinctive emission spectra and photostability of Ln 3+ fluorescence nanomaterials make them suitable for biological applications [ 7 ], with the background of the widely investigated luminescence properties of Ln 3+ complexes [ 8 , 9 ]. The emission intensity of Ln 3+ complexes can be increased by the complexation of small organic conjugate molecules [ 10 , 11 ] through the antenna effect, and the emission intensity can be adjusted by varying ligands [ 12 ].…”