Electrochemical Determination of 4-Bromophenoxyacetic Acid Based on CeO2/eGr Composite

The determination of plant growth regulators is of great importance for the quality monitoring of crops. In this work, 4-bromophenoxyacetic acid (4-BPA), one of the phenoxyacetic acids, was detected via the electrochemical method for the first time. A CeO₂-decorated electrochemical exfoliated graphene (eGr) composite (CeO₂/eGr) was constructed as the sensor for sensitive detection of 4-BPA due to the synergistic effect of the excellent catalytic active sites of CeO₂ and good electron transference of the eGr. The developed CeO₂/eGr sensor displayed a good linearity in a wide range from 0.3 to 150 μmol/L and the lowest detection limit of 0.06 μmol/L for 4-BPA detection. Electrochemical oxidation of 4-BPA follows a mix-controlled process on the CeO₂/eGr electrode, which involves 2e in the transference process. This developed CeO₂/eGr sensor has excellent repeatability with a relative standard deviation (RSD) of 2.35% in 10 continuous measurements. Moreover, the practical application of the sensor for 4-BPA detection in apple juice has recoveries in the range of 90–108%. This proposed CeO₂/eGr sensor has great potential for detecting plant growth regulators in the agricultural industry.

In vitro comparison of physical, chemical, and mechanical properties of graphene nanoplatelet added Angelus mineral trioxide aggregate to pure Angelus mineral trioxide aggregate and calcium hydroxide

It is important to cover the pulp surface with a biocompatible material that is physically, mechanically, and chemically adequate. Graphene has the potential to form hard tissue, but at high doses, it shows toxic effects. It can be added to biocompatible materials at low doses to enhance their hard tissue forming potential. The aim of this study was to compare the physical, chemical, and mechanical properties of graphene nanoplatelet (GNP) added Angelus mineral trioxide aggregate (A-MTA) to pure A-MTA and calcium hydroxide. Homogeneous mixtures (created by adding +0.1 weight[wt]% and 0.3 wt% GNP to A-MTA), pure A-MTA, and Dycal were used. Three disc-shaped samples of each material were prepared using Teflon mold. Scanning electron microscope-energy dispersive X-ray (SEM-EDX), particle size, microhardness, and Fourier transform infrared spectroscopy (FTIR) analysis of the materials were performed in vitro. Data were analyzed using Kruskal-Wallis test followed by Conover test (p < .001). A-MTA and GNP added samples showed similar peaks in FTIR analysis. In the EDX analysis, the amount of carbon was observed with a higher increase at A-MTA + 0.3 wt% GNP than A-MTA + 0.1 wt% GNP. In the SEM image, hollow structure and particle size decreased as the amount of GNP increased; particle size was smaller at A-MTA + 0.3 wt% GNP than A-MTA + 0.1 wt% GNP (p < .001). A-MTA + 0.3 wt% GNP showed the highest microhardness while Dycal showed the lowest microhardness. The addition of GNP, a material with high potential for forming hard tissue, to the structure of capping materials can also positively contribute to the microhardness of the capping materials.

Mesoporous Carbon and Ceria Nanoparticles Composite Modified Electrode for the Simultaneous Determination of Hydroquinone and Catechol

In this work, a novel material that was based on mesoporous carbon and ceria nanoparticles composite (MC–CeNPs) was synthesized, and a modified electrode was fabricated. When compared with a bare glass electrode, the modified electrode exhibited enhanced electrocatalytic activity towards the simultaneous determination of hydroquinone (HQ) and catechol (CC), which is attributed to the large specific area and fast electron transfer ability of MC–CeNPs. Additionally, it exhibited linear response ranges in the concentrations of 0.5–500 µM and 0.4–320 µM for HQ and CC, with detection limits (S/N = 3) of 0.24 µM and 0.13 µM, respectively. This method also displayed good stability and reproducibility. Furthermore, the modified electrode was applied to the simultaneous determination of HQ and CC in tap and lake water samples, and it exhibited satisfactory recovery levels of 98.5–103.2% and 98–103.4% for HQ and CC, respectively. All of these results indicate that a MC–CeNPs modified electrode could be a candidate for the determination of HQ and CC.