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.
Highlights
Clinical diagnosis by imaging is expanding due to the development of sensitive and non-invasive techniques such as confocal or fluorescence microscopy, appearing as powerful tools for exploratory analyses of several biological processes and internal structural information of healthy and cancerogenous cells [1,2,3]
Nanospheres of SiO2 —average size of 32 nm—decorated with luminescent Eu3+ -dbm complexes bonded by carboxylic bridges were successfully synthesized by a step-by-step method
As a spectroscopic probe confirmed at least two non-equivalent Eu3+ local sites onto the SiO2 surface composed by Eu3 + bonded to two or three dbm- ligands
Summary
Clinical diagnosis by imaging is expanding due to the development of sensitive and non-invasive techniques such as confocal or fluorescence microscopy, appearing as powerful tools for exploratory analyses of several biological processes and internal structural information of healthy and cancerogenous cells [1,2,3]. Among several biomaterials applied in bioimaging, luminescent biomarkers are widely used as contrast agents for in vivo and in vitro, clinical assays, acting as bio-probes responsible by imaging and clinical information of the cellular environment [4,5]. New strategies towards the development and improvement of the luminescent and structural features of such bio-probes are of large social relevance. Ln3+ or metallic ions in complexes or in inorganic hosts [10,11,12]. Ions in complexes or in inorganic hosts [10,11,12] Each of those materials [9] and Ln
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