g-C3N4/Fe3O4 Nanocomposites as Adsorbents Analyzed by UPLC-MS/MS for Highly Sensitive Simultaneous Determination of 27 Mycotoxins in Maize: Aiming at Increasing Purification Efficiency and Reducing Time

According to known studies, numerous mycotoxins have been found simultaneously in foods and have a certain expansion toxicity, so the simultaneous detection of multiple mycotoxins is absolutely critical. In this article, multifunctional magnetic g-C₃N₄/Fe₃O₄ nanocomposites have been fabricated to employ as modified QuEChERS adsorbents. In addition, they were also used in conjunction with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), an accurate quantitative approach, to analyze 27 mycotoxins in maize. The improved method not only has a powerful adsorption effect on the complex matrix by g-C₃N₄/Fe₃O₄ but also enables magnetic separation from the sample solution. Experiments proved that this method can exhibit good linearity under the appropriate and optimal external environment (r² ≥ 0.9954), high sensitivity (the threshold of detection limit is 0.0004-0.6226 μg kg^-1, and the threshold of quantification limit is 0.0014-2.0753 μg kg^-1), adequate recoveries (77.81-115.21%), and excellent repeatability (with a threshold of intraday precision of 1.5-10.8% and interday precision in the range of 2.9-12.5%). In practice this method has been used to evaluate a variety of mycotoxins in maize specimens, and certain actual outcomes have been achieved.

Simultaneous Gd2O3 clusters decoration and O-doping of g-C3N4 by solvothermal-polycondensation method for reinforced photocatalytic activity towards sulfamerazine

To improve the visible-light photocatalytic activity of graphitic carbon nitrate (g-C₃N₄) for practical application, a Gd₂O₃-cluster decorated O-doping g-C₃N₄ was fabricated via an ethanol assisted solvothermal-polycondensation method. The as-prepared photocatalysts, including bulk g-C₃N₄ (CN), O-doping g-C₃N₄ (HECN) and Gd₂O₃-cluster decorated O-doping g-C₃N₄ (HECN-xGd), were characterized and the paralleled experiments were conducted to evaluate the photocatalytic activity, mineralization capacity and mineralization mechanism, where sulfamerazine (SMR) was employed as the target pollutant. Furthermore, the quenching tests with scavengers were executed to analyze the contributions of the dominant active species, where the O₂^- was identified as a major role, and h⁺ as the minor role in the photodegradation of SMR. Results from the paralleled experiments suggested that the HECN-xGd possesses superior photocatalytic activity to HECN and CN, besides the feasible reusability through five cycles and impressive total organic carbon (TOC) removal about 60%. And the improved photocatalytic activity of HECN-xGd is ascribed mainly to the oxygen doping and Gd₂O₃ decoration. Herein, oxygen doping optimizes the structure of g-C₃N₄ and expands the light absorption range of HECN, and Gd₂O₃ facilitates the reduction of O₂ into O₂^-, and acts as the separator and transporter for the photo-induced charges.

Enhanced photocatalytic reduction for the dechlorination of 2-chlorodibenzo-p-dioxin by high-performance g-C3N4/NiO heterojunction composites under ultraviolet-visible light illumination

Polychlorinated dibenzo-p-dioxins (PCDDs), characterized by their high persistency and bioaccumulation, are widely detected in the environment. In this study, high-performance g-C₃N₄/NiO heterojunctions were fabricated to degrade 2-chlorodibenzo-p-dioxin (2-CDD) under ultraviolet-visible (UV-vis) light illumination. Experiments revealed that the pure g-C₃N₄ and range of g-C₃N₄/NiO heterojunctions were synthesized by the mixing and heating method, and then were characterized by XRD, TEM, XPS and PL etc. The composites exhibited enhanced dechlorination activities under anoxic conditions. After comparison, the g-C₃N₄/NiO (4:6) showed optimal dechlorination performance such that 70.4% of 2-CDD was removed within 8 h and 52.3% of 2-CDD was transformed to dibenzo-p-dioxin (DD), about fourfold higher than the pristine g-C₃N₄. The transformation of 2-CDD was accompanied by the resale of Cl ion, and the additional oxygen was proven to be able to consume electrons and hydrogen ions, thus greatly inhibiting the degradation of PCDD in systems. The g-C₃N₄/NiO (4:6) can be reused at least seven times, and the mechanism was proposed in detail to promote photoinduced electrohole separation and provide active sites. This study extends the use range of g-C₃N₄/NiO heterojunctions and develops a new technology to degrade PCDDs with striking activity and stability.

Mesoporous Graphitic Carbon Nitrides Decorated with Cu Nanoparticles: Efficient Photocatalysts for Degradation of Tartrazine Yellow Dye

A series of mesoporous graphitic carbon nitride (mpg-C₃N₄) materials are synthesized by directly pyrolyzing melamine containing many embedded silica nanoparticles templates, and then etching the silica templates from the carbonized products. The mass ratio of melamine-to-silica templates and the size of the silica nanoparticles are found to dictate whether or not mpg-C₃N₄ with large surface area and high porosity form. The surfaces of the mpg-C₃N₄ materials are then decorated with copper (Cu) nanoparticles, resulting in Cu-decorated mpg-C₃N₄ composite materials that show excellent photocatalytic activity for degradation of tartrazine yellow dye. The materials’ excellent photocatalytic performance is attributed to their high surface area and the synergistic effects created in them by mpg-C₃N₄ and Cu nanoparticles, including the Cu nanoparticles’ greater ability to separate photogenerated charge carriers from mpg-C₃N₄.

Photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin by Pd modified g-C3N4 photocatalysts under UV-vis irradiation: Efficacy, kinetics and mechanism

Polychlorinated dibenzo-p-dioxins (PCDDs), as a group of notorious anthropogenic environmental toxicants, are arguably ubiquitous in nature. In this study, we investigated the photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin (2-CDD) over Pd/g-C₃N₄ catalysts under UV-vis irradiation. The g-C₃N₄ and a series of Pd/g-C₃N₄ catalysts were prepared by thermal polymerization and mechanical mixing-illumination method and characterized by XRD, TEM, BET, SEM and UV-vis DRS analyses. Among all the samples, the Pd/g-C₃N₄ (5 wt%) yielded the optimal dechlorination activity with a total 2-CDD conversion of 54% within 4 h, and 76% of those converted 2-CDD were evolved to dibenzo-p-dioxin (DD). The kinetics of dechlorination could be described as pseudo-first-order decay model (R² > 0.84). Corresponding rate constants (k) increased from 0.052 to 0.17 h^-1 with Pd contents up to 5 wt% and decreased to 0.13 h^-1 with a 10 wt% of Pd. The enhanced activities originated from the surface plasmonic resonance (SPR) effect of Pd nanoparticles and the formation of Schottky barrier between Pd and g-C₃N₄, which extend the spectrum responsive range and suppress the charge recombination of g-C₃N₄. This is the first report on the photocatalytic reductive removal of PCDDs and may provide a new approach for PCDDs pollution control.