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Unformatted text preview: Luminescent Amino-functionalized or Erbium-doped Silica Spheres for Biological Applications F RANCESCO E NRICHI Associazione CIVEN—Coordinamento Interuniversitario Veneto per le Nanotecnologie, Marghera (Venice), Italy This work presents the morphological and optical properties of luminescent silica spheres, dis- cussing applications in bioimaging and biosensing. The spheres are obtained by the hydrolysis and condensation of tetraethylorthosilicate (TEOS) and can be synthesized by following either a basic or an acidic route. Luminescence emission is induced after incorporation of aminopropy- ltriethoxysilane (APTES) during synthesis or by introducing an optically active element, such as erbium, or other rare-earth elements. The luminescence properties of APTES-functionalized silica spheres have been investigated and optimized by varying the annealing temperature. On the other hand, erbium incorporation in silica spheres was also studied and the corresponding Er 3 + lumi- nescence emission at 1.54 μ m was evaluated for intensity and lifetime. The basic pH environment in the synthesis allows good control of the size of the spheres ( ∼ 200 nm in diameter), whereas the acidic route produces a wide dispersion in particle size (200–5000 nm). Both these approaches, however, can be followed to obtain an efficient photoluminescence (PL) emission for the APTES- functionalized silica spheres after 400–600 ◦ C thermal treatment. If Er(NO 3 ) 3 is introduced in the basic solution, a rapid precipitation of Er(OH) 3 occurs, but erbium can be easily and efficiently incorporated in the acid-synthesized spheres, showing high PL intensity at 1.54 μ m with lifetime of 3.9 ms. Finally, I discuss perspectives for the applications of these luminescent silica spheres, in particular as biological markers for bioimaging and biosensing. Key words: silica nanoparticles; erbium; luminescence; biomarkers; bioimaging Introduction Luminescent nanoparticles are becoming more and more important in the field of biosensors and bioimaging, 1 , 2 leading to improvements in sensitivity, selectivity, and multiplexing capacity 3 over conven- tional fluorophores. Key features for their actual use for in vitro and in vivo applications are the intensity of their optical emission, the efficiency of their surface func- tionalization for molecular recognition, and their low toxicity. For all these reasons, silica nanoparticles seem to be an interesting choice 4 because of easy control of their surface ligands and biocompatibility. 5 Moreover, the possibility of having a cheap, fast, and reliable pro- duction process would also be desirable. Silica spheres can be obtained by condensation of tetraethylorthosil- icate (TEOS) by a St¨ober basic route 6 or by an acidic Address for correspondence: Francesco Enrichi, Associazione CIVEN—Coordinamento Interuniversitario Veneto per le Nanotecnolo- gie, via delle Industrie 5, 30175 Marghera (Venice), Italy. Voice: + 39-349- 3206604....
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This note was uploaded on 07/11/2010 for the course SPECTOGRAP 545 taught by Professor Gdf during the Spring '10 term at AIB College of Business.
- Spring '10