Herein, poly (dopamine- Cr3+) nanocubes functionalized reduced graphene oxide ((poly (DAQ-Cr3+) @ rGO)) nanohybrid was proposed for electrochemical determination of flibanserin (FLBN). The poly (DAQ-Cr3+) and poly (DAQ-Cr3+)@ rGO nanohybrids were characterized via different morphological and spectroscopic techniques such as scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The modified electrode exhibited high electro- catalytic activity towards the electrochemical oxidation of FLBN in phosphate buffer solution (PBS, pH 6.0). Using DPV technique, the anodic oxidation peak current (Ipa) was increased with the increase of FLBN concentration in the range of 0.05–25.0 × 10−7 M with LOD of 0.016 × 10−7 M. Moreover, the poly (DAQ-Cr3+) @ rGO/GCE was successfully applied for analysis of FLBN in human plasma and urine samples.

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In this research paper, an innovative electrochemical sensor was suggested for simultaneous voltammetric analysis of azithromycin (AZM) and hydroxychloroquine (HCQ) for the first time. The sensor based on hydrothermal synthesis of vanadium disulfide quantum dots (VS2 QDs) and insertion within 3D N, S graphene aerogel (3D N, S @ GNA) and carbon nanotubes nanaostructure as a new and widely group of carbon nanomaterials. The nanocomposites were characterized morphologically using different techniques. In addition, the nanomaterials were characterized electrochemically using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The proposed electrochemical sensor showed wide dynamic linear ranges of 0.28–30 × 10−8 M and 0.84–22.5 × 10−8 M for analysis of AZM and HCQ, respectively. The limits of detection (LODs) based on signal to noise (S/N) 3:1 were found to be 0.091 × 10−8 M and 0.277 × 10−8 M for AZM and HCQ, respectively. Briefly, the electrochemical sensor had good stability, selectivity, reproducibility and feasibility for simultaneous detection of AZM and HCQ in presence of different interfering species.

Herein, mannitol capped magnetic nanoparticles were fabricated for dispersive micro-solid-phase extraction of sparfloxacin (SPX) and orbifloxacin (ORX) from milk and natural water samples. The synthesized magnetic sorbent is readily dispersed in the water and easily isolated magnetically from the medium after loaded with the cited analytes. The effect of main adsorption experimental parameters were studied and optimized. The small amount of the sorbent (15 mg) is applicable for the preconcentration in a reasonable time (15 min). Additionally, the adsorption characterization fits the pseudo-second order kinetic and Langmuir isotherm model with a high determination coefficient. Magnetic nanoparticles were modified with mannitol polar groups to adsorb polar drugs (SPX and ORX) from complicated matrices via hydrogen bonding and electrostatic interactions. After micro-extraction, SPX and ORX were analyzed using boron-doped carbon quantum dots (B-CQDs) as a fluorescence nanoprobe, as the extracted SPX and ORX favor the fluorescence of B-CQDs via hydrogen bonding and electron donor-acceptor association (charge-transfer complex). The synthesized nanomaterials were characterized by different techniques such as Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), Powder X-ray diffraction (PXRD), Energy-dispersive X-ray spectroscopy (EDS), and UV/Vis spectroscopy. Under the optimum conditions, the fluorimetric method exhibited the increase of fluorescence intensity in the range of 1.5 × 10−9–1.3 × 10−7 M and 1.2 × 10−9–1.1 × 10−7 M with limits of detection (LODs) of 5.0 × 10−10 and 4.0 × 10−10 M for SPX and ORX, respectively. The proposed dispersive micro-solid-phase extraction based fluorimetric method was applied for the determination of SPX and ORX in milk and natural water samples with satisfactory results.

Herein, mannitol capped magnetic nanoparticles were fabricated for dispersive micro-solid-phase extraction of sparfloxacin (SPX) and orbifloxacin (ORX) from milk and natural water samples. The synthesized magnetic sorbent is readily dispersed in the water and easily isolated magnetically from the medium after loaded with the cited analytes. The effect of main adsorption experimental parameters were studied and optimized. The small amount of the sorbent (15 mg) is applicable for the preconcentration in a reasonable time (15 min). Additionally, the adsorption characterization fits the pseudo-second order kinetic and Langmuir isotherm model with a high determination coefficient. Magnetic nanoparticles were modified with mannitol polar groups to adsorb polar drugs (SPX and ORX) from complicated matrices via hydrogen bonding and electrostatic interactions. After micro-extraction, SPX and ORX were analyzed using boron-doped carbon quantum dots (B-CQDs) as a fluorescence nanoprobe, as the extracted SPX and ORX favor the fluorescence of B-CQDs via hydrogen bonding and electron donor-acceptor association (charge-transfer complex). The synthesized nanomaterials were characterized by different techniques such as Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), Powder X-ray diffraction (PXRD), Energy-dispersive X-ray spectroscopy (EDS), and UV/Vis spectroscopy. Under the optimum conditions, the fluorimetric method exhibited the increase of fluorescence intensity in the range of 1.5 × 10−9–1.3 × 10−7 M and 1.2 × 10−9–1.1 × 10−7 M with limits of detection (LODs) of 5.0 × 10−10 and 4.0 × 10−10 M for SPX and ORX, respectively. The proposed dispersive micro-solid-phase extraction based fluorimetric method was applied for the determination of SPX and ORX in milk and natural water samples with satisfactory results.

In this study, zinc sulfide nanoparticles were loaded on reduced graphene oxide (ZnS NPs/rGO) using simple sonochemical method. The nanocomposite was characterized using different morphological and electrochemical techniques such as TEM, SEM, PXRD, EDX, Raman spectroscopy, FTIR, N2-adsorption–desorption, CV, and EIS. The ZnS NPs/rGO modified glassy carbon electrode (GCE) was used to simultaneously estimate hydroxychloroquine (HCQ) and daclatasvir (DAC) in a binary mixture for the first time. The modified nanocomposite exhibited good catalytic activity towards HCQ and DAC detection. In addition, it showed higher sensitivity, good selectivity and stability; and high reproducibility towards HCQ and DAC analysis. The activity of the modified electrode was noticeably improved due to synergism between ZnS NPs and rGO. Under optimum conditions of DPV measurements, the anodic peak currents (Ipa) were obviously increased with the increase of HCQ and DAC amounts with linear ranges of 5.0–65.0 and 7.0–65.0 nM with LODs of 0.456 and 0.498 nM for HCQ and DAC, respectively. The ZnS NPs/ rGO modified GCE was used to quantify HCQ and DAC in biological fluids with recoveries of 98.7–102.7% and 96.9–104.5% and RSDs of 1.89–3.57% and 1.91–3.70%, respectively.

In this study, zinc sulfide nanoparticles were loaded on reduced graphene oxide (ZnS NPs/rGO) using simple sonochemical method. The nanocomposite was characterized using different morphological and electrochemical techniques such as TEM, SEM, PXRD, EDX, Raman spectroscopy, FTIR, N2-adsorption–desorption, CV, and EIS. The ZnS NPs/rGO modified glassy carbon electrode (GCE) was used to simultaneously estimate hydroxychloroquine (HCQ) and daclatasvir (DAC) in a binary mixture for the first time. The modified nanocomposite exhibited good catalytic activity towards HCQ and DAC detection. In addition, it showed higher sensitivity, good selectivity and stability; and high reproducibility towards HCQ and DAC analysis. The activity of the modified electrode was noticeably improved due to synergism between ZnS NPs and rGO. Under optimum conditions of DPV measurements, the anodic peak currents (Ipa) were obviously increased with the increase of HCQ and DAC amounts with linear ranges of 5.0–65.0 and 7.0–65.0 nM with LODs of 0.456 and 0.498 nM for HCQ and DAC, respectively. The ZnS NPs/ rGO modified GCE was used to quantify HCQ and DAC in biological fluids with recoveries of 98.7–102.7% and 96.9–104.5% and RSDs of 1.89–3.57% and 1.91–3.70%, respectively.

Nitrite (NO2−), an important intermediate in the biological nitrogen cycle, can be considered as a life-threatening marker since it leads to the production of carcinogenic nitrosamines when it reacts with secondary amines in the digestive system, besides being a methemoglobinemia risk factor in the children. Herein, we reported a fluorescence detection method for rapid, selective, and sensitive detection of NO2− in water samples. The method is based on the modification of α-MnO2 nanorods with fluorescein dye (FLR@ α-MnO2 NR) where the former acts as a quencher and the latter acts as a fluorescence reporter. After the addition of NO2− to the FLR@ α-MnO2 NR system, it reduces α-MnO2 NR to soluble Mn2+ and liberates FLR, restoring the fluorescence of FLR (Turn On). The nanoprobe, with λex/λem at 490/518 nm, has a linear range of 0.83–67.0 µM with a limit of detection (LOD) of 0.27 µM, for analysis of NO2−. The proposed method was successfully applied to the determination of NO2− in natural water samples.