A new nanocomposite film constructed of poly-l-cysteine/zinc oxide nanoparticles–electrospun copper oxide nanofibers (PLC/ZnO-NPs–CuO-NFs) was prepared on the surface of the graphite electrode (GE). ...The novel electrode was successfully applied for the simultaneous determination of guanine (G) and adenine (A), two of the most important components of DNA and RNA. The PLC/ZnO-NPs–CuO-NFs/GE enhanced the anodic peak currents of the purine bases conspicuously and could determine them sensitively and separately in 0.1 M phosphate buffer solution at the physiological pH (7.0). The synthesized nanofibers, nanoparticles and nanocomposite were characterized by different methods such as Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). Under the optimum operating conditions, linear calibration curves were obtained in the range of 0.05–6.78 and 0.01–3.87 μM with a detection limit of 12.48 and 1.25 nM for G and A, respectively. The proposed method was applied to quantify A and G in three different DNA samples with satisfactory results. In addition, damage to human blood double-stranded DNA (dsDNA) and DNA purine bases (liberated in previously hydrolyzed human blood dsDNA) caused by UV-C and UV-B were evaluated. The results demonstrated that the proposed biosensing platform not only provides a novel and sensitive approach to detecting DNA damage, but also can be used for simultaneous determination of purine bases and major products of DNA oxidative damage.
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•In this article, a novel interface was prepared by electropolymerization method.•The PLC/ZnO-NPs–CuO-NFs/GE enhanced the peak currents of G and A conspicuously.•The presence of CuO-NFs and ZnO-NPs together causes the increase of the electroactive surface.•The proposed method was applied to quantify G and A in three different DNA samples.•Damage to dsDNA and DNA purine bases caused by UV-C and UV-B were evaluated.
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•The monitoring of synthetic colorants in foods is very important due to their potential toxicity.•A sensitive sensor was fabricated by electropolymerization of MIP in the presence of ...SY onto an f–MWCNTs/GCE.•The MIP/f–MWCNTs/GCE was suitable for determination of SY in foods without the need of laborious pretreatments.•The MIP/f–MWCNTs/GCE showed higher selectivity for determination of SY than the bare GCE.
The monitoring of synthetic colorants in foods is very important due to their potential toxicity and pathogenicity. Therefore, we proposed a new and facile electrochemical method for the determination of sunset yellow (SY) in food samples. A highly sensitive and selective electrochemical sensor was fabricated by electropolymerization of molecularly imprinted polymer (MIP) in the presence of SY onto a functionalized multi-walled carbon nanotubes/glassy carbon electrode (f-MWCNTs/GCE) using cyclic voltammetry (CV). Scanning electron microscopy and CV were employed to characterize the fabricated sensor. The experimental parameters, such as supporting electrolyte and its pH, the monomer concentration, the number of cycles for the electropolymerization and the scan rate for the sensor preparation were optimized. The MIP sensor exhibited an excellent recognition capacity toward SY compared with other structurally similar molecules. Under the optimum operating conditions, the current response of the MIP sensor was linear to SY concentrations in the range from 0.05 to 100μM, with the detection limit of 5.0nM. Finally, the proposed electrode was successfully applied to determine SY in several food samples.
Piperazine-stabilized on nano magnetic-Fe
3
O
4
@SiO
2
-sulfuric acid (Fe
3
O
4
@SiO
2
-SO
3
-
Piperazine
+
-MNPs) was synthesized and evaluated as an efficient catalyst for the one-pot synthesis of ...benzimidazolo-quinazolinone derivatives under solvent-free conditions. The prepared reagent was characterized by FT-IR spectroscopy, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, and energy-dispersive X-ray spectroscopy. In addition to the mild conditions, this method provides other important advantages, including simple work-up procedure, environmental friendliness, short reaction times, high yields of the products, solvent-free conditions, and use of a reusable catalyst.
In this work, silica-coated magnetic nanoparticles were used as seed particles in the production of molecularly imprinted polymer (MIP) shells by copolymerization of ethylene glycol dimethacrylate ...with methacrylic acid in the presence of sunset yellow (SY) and an appropriate porogenic solvent. Thereafter, the MIP sensor was designed by covering a layer of core-shell MIP nanoparticles on a graphite-modified glassy carbon electrode (Gr/GCE). The results indicated that the MIP sensor could remarkably increase the peak current of SY and exhibited an excellent recognition capacity toward it compared with other structurally similar molecules. The detection limit of 5.5 nmol/L and two linear calibration ranges of 0.0085–1 and 1–30 μmol/L were obtained for SY determination. The proposed sensor was successfully applied for the determination of SY in several food samples without complex sample pretreatment.
A new, simple, and low-cost voltammetric sensor was designed by covering a layer of graphene oxide/chitosan (GO–Cs) nanocomposite on a glassy carbon electrode (GCE). The synthesized GO nanosheets and ...GO–Cs nanocomposite were characterized by different techniques such as Fourier transform infrared spectroscopy (FT–IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The electrochemical behavior of rutin at the modified electrode was investigated, and the results demonstrated that the GO–Cs nanocomposite film could remarkably increase the redox peak current of rutin. The effects of supporting electrolyte, pH, accumulation parameters, and interference on the response of rutin were studied. Using differential pulse voltammetry (DPV) under optimized conditions, the analytical curve was linear in rutin concentration range from 0.9 to 90 μmol/L with a detection limit of 0.56 μmol/L. The GO–Cs/GCE exhibited good selectivity and sensitivity for the determination of rutin content in real samples with satisfactory results.
Graphical Abstract
A new voltammetric sensor was designed by covering a layer of graphene oxide/chitosan nanocomposite on a glassy carbon electrode and used for rutin detection
In this research, the headspace solid‐phase microextraction (SPME) coupled with GC flame ionization detector was applied for the determination of some monocyclic aromatic amines in real water and ...urine samples. A sol–gel technique was applied for the preparation of the SPME fibers. Two different sol–gel coatings, (PEG and poly(ethylene glycol) modified with multi‐walled carbon nanotubes PEG/CNTs), were prepared and compared. Extraction efficiency of PEG/CNTs was better than PEG fiber in the same conditions. To obtain maximum extraction efficiency, some parameters such as desorption temperature and time, temperature and time of extraction, salt effect, pH, and stirring speed were investigated and optimized for PEG/CNTs fiber. Under optimized conditions, the LODs (S/N = 3) were in the range of 0.5–50 ng/L and limits of quantification (S/N = 10) were between 1 and 500 ng/L. Repeatability (n = 5) was in the range of 3.2–9.1% and reproducibility (n = 3) was obtained from 5.5 to 12.0%. The method was successfully applied to the analysis of real water and urine samples with recoveries from 63.7 to 97.0%.
In this study, attempts were made to present a sensitive strategy for determining rutin. To reach the goal of the study, a poly(sulfosalicylic acid) film was electropolymerized on a gold electrode, ...which was modified by 2-mercaptobenzothiazole self-assembled monolayer and multi-walled carbon nanotubes (PSSA/CNTs/MBT/Au). The proposed sensor was characterized by different techniques including field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The resulting sensor displayed electrocatalytic activity towards the oxidation of rutin which is attributed to the presence of the PSSA/MWCNTs nanocomposite. Under optimized conditions, the detection limit of 1.8nmolL–1 and two linear calibration ranges of 0.01–0.8 and 0.8–10.0µmolL–1 were obtained for rutin determination at the PSSA/CNTs/MBT/Au electrode. The proposed modified electrode was successfully applied for the determination of rutin in orange, red apple, red onion, strawberry, oat and salvia samples. The obtained results suggest that the proposed electrode has several advantages, such as high stability, repeatability and good reproducibility and it can be used for a sensitive, selective and rapid determination of rutin.
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•A sensitive sensor was fabricated by electropolymerization of PSSA at the surface of MWCNTs/MBT/Au electrode.•The improved electrochemical behavior mainly attributed to the synergistic effect of PSSA and MWCNTs.•The PSSA/CNTs/MBT/Au showed higher selectivity for determination of rutin than the bare GCE.•The PSSA/CNTs/MBT/Au was suitable for determination of rutin in foods without the need of laborious pretreatments.
In this paper, we have studied the electrochemical behavior of indigo carmine (IC) in the presence and absence of mediator molecules. We have used three azo dyes as mediators in our studies and the ...effect of mediator molecules on the electron transfer between the IC solution and the electrode surface was explained from the cyclic voltammograms data. Among these dyes, 4-(4-nitrophenilazo)N-benzyl,N-ethylaniline (NBE) showed good performance as an electron transfer mediator. The NBE/carbon paste was characterized with Fourier transform infrared spectroscopy and scanning electron microscopy methods. The redox peak currents of IC were enhanced significantly compared with those obtained at the unmodified electrode. Some parameters affecting sensor response were optimized and then the calibration curve was plotted. The oxidation peak current was proportional to the concentration of IC from 1 to 100μmolL–1. The detection limit was 0.36μmolL–1. The proposed electrode was successfully applied to the determination of IC in various real samples without complex sample pretreatment.
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•The electrochemical behavior of IC in the presence and absence of mediator molecules was studied.•The results showed that NBE molecules were an effective mediator for the electron transfer.•The redox peak currents of IC were enhanced significantly compared with that obtained at the unmodified electrode.•The proposed electrode was applied to the determination of IC in various real samples without complex sample pretreatment.
A novel chemically modified carbon paste electrode based on an inexpensive Ni(salph) complex, where salph is
N
,
N'
-bis(salicylidene)-4-methyl-
o
-phenylenediimine, was prepared for the simultaneous ...determination of guanine, adenine and thymine. The electrode was characterized by Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, thermogravimetric analysis and cyclic voltammetry. The proposed sensor enhanced the anodic peak currents of the nucleobases and could determine them sensitively in 0.1 M phosphate buffer solution (pH 7.0). Moreover, well-separated voltammetric peaks were obtained for guanine, adenine and thymine present in the analyte mixture. Under the optimum operating conditions, the peak currents for guanine, adenine and thymine increased linearly with the increase in the analyte mixture concentration in the ranges of 0.1 to 80, 0.1 to 50 and 15 to 150 μM, respectively. The detection limits for guanine, adenine and thymine were 0.03, 0.03 and 5 μM, respectively. This new approach has been successfully applied for the detection of the corresponding targets in a DNA sample with acceptable recovery.
