Herein,
we fabricated nanoparticles of doped carbon dots with nitrogen
(N-CDs) with an ecofriendly and easy approach, yielding spherical
nanoparticles (mean size: 19 nm). N-CDs were further characterized
by high-resolution transmission electron microscopy, X-ray photoelectron
spectroscopy, and fluorescence spectroscopy. In addition, we developed
a fluorometric method for determination of dopamine (DA) in human
fluids at nanomolar concentrations (rapid and highly sensitive). The
quenching effect over the emission of the doped CDs at 438 nm was
the basis of the quantification of DA. A linear trend between 0 and
652 nM was the range of application with a detection limit at 4 nM,
acceptable accuracy (>80%), and precision (relative standard deviation
< 10%), showing a highest selectivity with related analytes. The
obtained sensing method was applied for DA determination in human
fluids (urine and serum samples) with acceptable accuracy. In order
to understand the interaction of DA with the nanoparticles of N-CDs,
we applied density functional theory. The bonding between the −NH3
+ moiety of DA and the corresponding N-CD surface
ligand consists of the formation of hydrogen bonds. It is demonstrated
that the selected geometrical models explain the spectroscopic experiments
performed on such nanoparticles.
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