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Campos B.B.,University of Porto | Abellan C.,University of Castilla - La Mancha | Abellan C.,Regional Institute for Applied Chemistry Research IRICA | Zougagh M.,Regional Institute for Applied Chemistry Research IRICA | And 7 more authors.
Journal of Colloid and Interface Science | Year: 2015

Fluorescent carbon dots (CDs) and its nitrogen doped (N-CDs) nanoparticles have been synthesized from lactose as precursor using a bottom-up hydrothermal methodology. The synthesized nanoparticles have been characterized by elemental analysis, FTIR, Raman, TEM, DLS, XPS, and steady-state and life-time fluorescence. The synthesized carbon nanoparticles, CDs and N-CDs, have a size at about 7.7±2.4 and 50±15nm, respectively, and quantum yields of 8% (CDs) and 11% (N-CDs). These techniques demonstrated the effectiveness of the synthesis procedure and the functionalization of the CDs surface with amine and amide groups in the presence of NH3 in aqueous media. The effect of excitation wavelength and pH on the luminescent properties was studied. Under the optimal conditions, the nitrogen doped nanoparticles can be used as pyridine sensor in aqueous media because they show an enhancement of its fluorescence with a good linear relationship. The analytical method is simple, reproducible and very sensitive for pyridine determination. © 2015 Elsevier Inc.

Moreno V.,University of Castilla - La Mancha | Moreno V.,Regional Institute for Applied Chemistry Research IRICA | Zougagh M.,Regional Institute for Applied Chemistry Research IRICA | Zougagh M.,University of Castilla - La Mancha | And 2 more authors.
Microchimica Acta | Year: 2016

The preparation of magnetic nanoparticles (MNPs) coated with a layer of octadecyl group-modified silica containing multiwalled carbon nanotubes (MWCNTs) is described. Synthesis was accomplished by in-situ high temperature decomposition of the precursors ferric ion, octadecyltrichlorosilane (C18) and MWCNTs in ethylene glycol solvent. Transmission electron microscopy confirmed that the MNPs are encapsulated in the composite silica coating. These MNPs were used for clean-up of maize samples and the preconcentration of zearalenone and its secondary metabolites, namely β-zearalenol, β-zearalanol, α-zearalenol, α-zearalanol, and zearalanone at trace levels, prior to their determination by liquid chromatography-mass spectrometry. A comparative study of analyte adsorption and desorption was conducted with MNPs prepared with and without C18 and showed both solid phases to adsorb the analytes to some extent, but higher recoveries were obtained by using the C18-modified MNPs which therefore was selected for extraction of the mycotoxins. Under the optimum conditions, the MNPs can be re-used 6 times at least without loss of their extraction efficiency. Preconcentration factors are ~25, detection limits range from 0.6 to 1.0 μg mL−1, recoveries from spiked samples from 91.6 to 98.3 %, and relative standard deviations are <3.9 %. © 2015, Springer-Verlag Wien.

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