Detection of Dopamine in Human Fluids Using N-Doped Carbon Dots

Abstract

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.

One-Pot Hydrothermal Synthesis of Carbon Dots as Fluorescent Probes for the Determination of Mercuric and Hypochlorite Ions

“…Figure 4 shows a gradually decreasing fluorescence intensity of the NSCDs at 440 nm with the increasing addition of Hg 2+ or ClO − ions. The fluorescence quenching efficiency of the NSCDs was evaluated through fitting the Stern−Volmer equation [ 33 , 34 ]: F 0 /F = 1 + K sv [Q] where F 0 and F are the fluorescence intensity of the NSCDs at 440 nm in the absence and presence of the analytes (Hg 2+ or ClO − ions), respectively; K sv is the Stern−Volmer constant; and Q is the concentration of the analytes. It was found ( Figure 4 b) that the proposed method showed a good linear relationship with Hg 2+ concentration in the range of 0.7 μM to 15 μM, and a linear regression coefficient (R 2 = 0.9847) and K sv value of 5.46 × 10 4 M –1 was obtained.…”

“…Figure 4 shows a gradually decreasing fluorescence intensity of the NSCDs at 440 nm with the increasing addition of Hg 2+ or ClO − ions. The fluorescence quenching efficiency of the NSCDs was evaluated through fitting the Stern−Volmer equation [33,34]:…”

Nitrene formation is the first step of the thermal and photochemical decomposition reactions of organic azides

“…50 The labelling convention for the electronic states is based on their energetic ordering (S 0 , S 1 ,…; T 0 , T 1 ,…), where 0 denotes the lowest energy state in each spin state (singlet, S, or triplet, T). Construction of the potential energy curves (PECs) has been done with a linear interpolation method [51][52][53][54][55] using the full space of non-redundant internal coordinates, which are built as follows. First, a common set of 3N-6 internal coordinates is defined for the target geometries, the reactants (R1) and the products R2).…”

Nanomaterials-Based Biosensors for COVID-19 Detection—A Review

“…Work has also been done on electrochemical and electrochemiluminescence sensor. Louleb et al used N-CDs for dopamine detection in human fluids (serum and urine) [59]. Hydrogen bonding between the dopamine -NH 3+ moiety and the surface ligands of the N-CDs caused quenching in the fluorescence of the N-CDs, the extent of which was measured and used to determine the concentration of dopamine.…”