title: Mercury(II) sensing based on the quenching of fluorescence of CdS-dendrimer nanocomposites.
abstract: A chemical sensor for mercury(II) (Hg(II)) was developed based on the quenching of the fluorescence of cadmium sulfide (CdS) quantum dots (QDs) coated with polypropylenimine tetrahexacontaamine dendrimer (DAB) generation 5, CdS-DAB nanocomposites. The synthesis and characterization of CdS-DAB nanocomposites by means of EDXA, SEM and steady state luminescence is described. Macroscopic spherical structures are observed by electronic microscopy and the wavelength for the maximum fluorescence emission occurs at 535 nm (excitation at 351 nm). Stern-Volmer plots show a linear response in the range of 1 x 10(-6) to 1 x 10(-5) M with a quenching constant (K(sv)) of 1.5 x 10(5) M(-1). A parallel factor (PARAFAC) analysis model confirmed that Hg(II) alone provokes quenching of the fluorescence. Cu(II) and Pb(II) also quench the fluorescence of CdS-DAB nanocomposites, with a K(sv) = 1.9 x 10(5) M(-1) and K(sv) = 2.2 x 10(4) M(-1), respectively, and Cd(II), Zn(II), Co(II) and Ni(II) have no effect. Ionic strength, in the range from 1.25 x 10(-3) up to 2 M, provokes a shift in the wavelength of the maximum of the emission spectra, from 482 to 677 nm.
authors.affiliation: Centro de Investigação em Química, Departamento de Química, Faculdade de Ciências da Universidade do Porto, Rua Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: Bruno B
authors.initials: BB
authors.lastname: Campos
authors.forename: Manuel
authors.initials: M
authors.lastname: Algarra
authors.forename: Beatriz
authors.initials: B
authors.lastname: Alonso
authors.forename: Carmen M
authors.initials: CM
authors.lastname: Casado
authors.forename: Joaquim C G
authors.initials: JC
authors.lastname: Esteves da Silva
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D050091:Dendrimers / Q000737:chemistry*; D055664:Electrochemical Techniques; D005453:Fluorescence; D008628:Mercury / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D009994:Osmolar Concentration; D013440:Sulfides / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D050091:Dendrimers; D013440:Sulfides; C034939:cadmium sulfide; D008628:Mercury