Table of Contents , homogeneity and particle size. Figure 2 shows the SEM micrograph of NiTiO3 nanoparticles. As can be observed, the NiTiO3 nanoparticles exhibit a homogeneous morphology of spherical shape and the average diameter of the nanoparticles is approximately 38.0 nm. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”? Get the original essay critical such as deformation, crystallite size and structure. Thus, XRD analysis was carried out to study the crystal phases of NiTiO3 nanopowders. Figure 3 shows the XRD spectra of NiTiO3 nanoparticles after heat treatment at 750 °C in air for 2 h, which is the lowest temperature ever reported for the formation of NiTiO3 nanopowders by the sol–gel method. The sharp and intense peaks of nanoparticles at this temperature represent the finely crystalline rhombohedral NiTiO3 phase and all peaks were well coordinated associated with the JCPDS database (file number: 83-0199). The particle size calculated with the Scherrer formula [24] (Eq. 1): D = (0.9λ)/(βcosθ) (1) where λ (0.15418 nm) is the wavelength of the X-rays , β is the full width at half maximum (FWHM) in radians of the X-ray diffraction peak, θ is the diffraction angle, and D is the average particle size. According to Eq. 1, the average particle size of NiTiO3 nanopowders was estimated to be approximately 33.0 nm with a value consistent with the SEM results. Characterization of the modified electrode by EIS In this study, the EIS technique was used to indicate the additional effect of nickel titanate nanoparticles on the modified electrode. The EIS plots of the modified and unmodified electrodes in [Fe(CN)6]3-/4-(Fe2+/Fe3+) as a negatively charged redox probe are shown in Figure 4. The transfer resistance value of electrons (Rct, diameter of the semicircle) depends on the dielectric and insulating characteristics at the electrode/electrolyte interface [25]. The results were approximated by an equivalent circuit. As can be observed, the presence of NiTiO3 nanoparticles on the surface of the carbon paste electrode increases the electron transfer to the surface of the modified electrode. On the other hand, the modified electrode, compared to a bare electrode, had a lower resistance to charge transfer. The surface morphology of bare and modified electrodes was characterized by SEM technique (Figures 5A and B). As shown in Figure 5A, the surface of the pure graphite electrode is not uniform and free from any coating. Figure 5B shows a homogeneous distribution of NiTiO3 nanoparticles on the surface of a modified electrode. Voltammetric studies of the modified electrode The kinetic parameters of NiTiO3/CPE were studied by the cyclic voltammetry (CV) method. Cyclic voltammograms of the modified electrode on Fe2+/Fe3+ probe solution in the range of scan speeds from 10.0 to 70.0 mV s-1 are shown in Fig. 6. It can be seen in Fig. 6(c) for scan rate values ​​greater than 300.0 mV s-1, the anodic potential is directly proportional to the logarithm of the scan rate. Then the rate constant ofelectron transfer (ks, s−1) and the charge transfer coefficient (α) can be calculated by the Laviron equation (equation 2) [26].Log ks = α log (1-α) + ( 1- α) logα – log (RT/nFv) –α (1-α) nαF∆Ep/2.3RT (2) Where v represents different scanning speed values ​​and n is the number of electrons involved in the redox reaction . From these expressions, α can be determined by measuring the variation of the peak potential with respect to the scan rate, and ks can be determined by measuring the ΔEp values. From these results, the values ​​of α and ks were obtained to be 0.32 and 0.14 s-1, respectively. Application of the modified nanostructured sensor in the electrochemical studies of monohydroxybenzoic acid isomers Oxidation of HBO and of PHB on the unmodified and modified electrodes The electrochemical behaviors of OHB and PHB were studied by DPV. Figure 7 shows differential pulse voltammograms of the NiTiO3/CPE and CPE electrodes in BR buffer solution (pH 5.0) containing 50.0 µM PHB and 50.0 µM OHB. As shown in Fig. 7b and c, significant improvement in the voltammetric responses of NiTiO3/CPE compared to bare CPE proves the effect of nickel titanate nanoparticles on the modified electrode. Thus, the modified electrode was used for the simultaneous determination of HBO and PHB with high sensitivity and appropriate detection limit. pH dependence studyThe electrochemical behavior of OHB and PHB to NiTiO3/CPE was studied in the presence of BR buffer with different pH (2.0–9.0). ) by differential pulse voltammetry (DPV). Differential pulse voltammograms of the modified electrode to OHB and PHB were recorded and shown in Figures 1 and 2. 8A and 9A, respectively. As can be seen, the anodic peak potentials of OHB and PHB shift to negative values ​​with increasing pH. Thus, protons participate in the oxidation reaction of OHB and PHB and the acidity of the electrolyte has a significant effect on oxidation. Furthermore, this indicates that the optimal pH of 2.0 can be used for the individual determination of HBO and PHB (Figures 8B and 9B). But when OHB and PHB are determined simultaneously at pH 2.0, they both have only one DPV peak (Fig. 10). Therefore, we used another pH value to separate the peaks of the two isomers. As shown in Figure 11, at pH 5.0, there are two distinct peaks with good sensitivity for two isomers. Therefore, a buffer solution pH = 5.0 was selected for the simultaneous determination of these isomers. Interference Studies The ability of the proposed nanostructured sensor to determine HBO and PHB in the presence of common interfering substances was investigated by the DPV technique. The experiments were performed by analyzing a standard solution containing 50.0 µM of OHB and PHB using an increasing amount of interfering species. The tolerance limit was defined as the concentrations that give an error less than ±5.0% in the peak oxidation current of OHB and PHB [27]. Some common cations and anions such as Na+, K+, NH4+, Ca2+, Mg2+, Cl-, CO32-, NO3- and I- have been studied for their interference with the detection of HBO and PHB. The results demonstrate that these ions have almost no obvious interference with the DPV signals of the targets at the NiTiO3/CPE. Some organic compounds such as gallic acid, uric acid and dopamine were considered to have no influence on HBO and PHB signals with deviations less than 5%. These results were reported in Table 1. The ability to generate a modified electrode with a stable surface was investigated under optimized experimental conditions, using continuous DPV determination of OHB and PHB. Of the.