Fluorescent Properties of a Hybrid Cadmium Sulfide-Dendrimer Nanocomposite and its Quenching with Nitromethane
- 328 Downloads
A fluorescent hybrid cadmium sulphide quantum dots (QDs) dendrimer nanocomposite (DAB-CdS) synthesised in water and stable in aqueous solution is described. The dendrimer, DAB-G5 dendrimer (polypropylenimine tetrahexacontaamine) generation 5, a diaminobutene core with 64 amine terminal primary groups. The maximum of the excitation and emission spectra, Stokes’ shift and the emission full width of half maximum of this nanocomposite are, respectively: 351, 535, 204 and 212 nm. The fluorescence time decay was complex and a four component decay time model originated a good fit (χ = 1.20) with the following lifetimes: τ 1 = 657 ps; τ 2 = 10.0 ns; τ 3 = 59.42 ns; and τ 4 = 265 ns. The fluorescence intensity of the nanocomposite is markedly quenched by the presence of nitromethane with a dynamic Stern-Volmer constant of 25 M−1. The quenching profiles show that about 81% of the CdS QDs are located in the external layer of the dendrimer accessible to the quencher. PARAFAC analysis of the excitation emission matrices (EEM) acquired as function of the nitromethane concentration showed a trilinear data structure with only one linearly independent component describing the quenching which allows robust estimation of the excitation and emission spectra and of the quenching profiles. This water soluble and fluorescent nanocomposite shows a set of favourable properties to its use in sensor applications.
KeywordsDendrimers CdS quantum dots Fluorescence Quenching Nitromethane
The authors would like to thanks the Fundação para a Ciência e Tecnologia (Lisboa, Portugal) under the frame of the Ciência 2007 program. Financial support from Fundação para a Ciência e Tecnologia (Lisboa, Portugal) (FSE-FEDER) (Project PTDC/QUI/71001/2006) and (Project PTDC/QUI/71336/2006) is acknowledged. C.M. Casado and B. Alonso (Departamento de Química Inorgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, Spain) are acknowledged for providing samples of DAB dendrimers.
- 23.Roovers J (2000) Advances in polymer science branched polymers II, vol. 143. Springer-Verlag, BerlinGoogle Scholar
- 24.Vogtle F, Richardt G, Werner N (2009) Dendrimer chemistry. Concepts, synthesis, properties, applications. Wiley-VCH, WeinheimGoogle Scholar
- 30.Lakowicz JR, Gryczynski I, Gryczynski Z, Murphy CJ (1999) Luminescence spectral properties of CdS naoparticles. J Phys Chem 103:7613–7620Google Scholar
- 37.Bouldin KK, Menzel ER, Takatsu M, Murdock RH (2000) Diimide-enhanced fingerprint detection with photoluminescent CdS/dendrimer nanocomposites. J Forensic Science 45:1239–1242Google Scholar
- 39.Harshman RA (1970) Foundations of the PARAFAC procedure: models and conditions for an “explanatory” multi-mode factor analysis. UCLA Working Papers Phonetics 16:1–84Google Scholar
- 42.Olivieri AC, Arancibia JA, Muñoz de la Peña A, Durán-Merás I, Mansilla AE (2004) Second-order advantage achieved with four-way fluorescence excitation-emission-kinetic data processed by parallel factor analysis and trilinear least-squares. Determination of methotrexate and leucovorin in human urine. Anal Chem 76:5657–5666CrossRefPubMedGoogle Scholar
- 45.Lakowicz JR (2006) Principles of fluorescence spectroscopy, 3rd edn. Springer, New YorkGoogle Scholar