Ag-modified CuO cavity arrays as a SERS-electrochemical dual signal platform for thiram detection.

Rapid and sensitive determination of pesticide residues in fruits and vegetables is critical for human health and ecosystems. This paper used an Ag-modified CuO sphere-cavity array (CuO@Ag) electrode as a thiram SERS/electrochemical dual readout detection platform. Numerous Raman "hotspots" generated by uniformly distributed silver nanoparticles, charge transfer at the CuO@Ag interface, and the formation of Ag-thiram complexes contribute to the significant enhancement of this SERS substrate, which results in excellent SERS performance with an enhancement factor up to 1.42 × 106. When using SERS as the readout technique, the linear range of the substrate for thiram detection was 0.05-20 nM with a detection limit (LOD) of up to 0.0067 nM. Meanwhile, a correlation between the value of change in current density and thiram concentration was established due to the formation of stable complexes of thiram with Cu2+ generated at specific potentials. The linear range of electrochemical detection was 0.05-20.0 µM, and the detection limit was 0.0167 µM. The newly devised dual-readout sensor offers notable sensitivity and stability. The two signal readout methods complement each other in terms of linear range and detection limit, making it a convenient tool for assessing thiram residue levels in agro-food. At the same time, the combination of commercially available portable equipment makes on-site monitoring possible.

Photocorrosion inhibition of CdS-based catalysts for photocatalytic overall water splitting.

The urgent need for clean and renewable energy drives the exploration of effective strategies to produce hydrogen. Semiconductor-based photocatalytic hydrogen production technology is one of the ideal processes for direct solar energy conversion and storage that has been widely studied. The development of highly efficient photocatalysts is essential for the cost-effective and large-scale production of hydrogen. CdS-based semiconductor photocatalysts have attracted significant attention due to their unique advantages, including strong visible light absorption capacity, suitable band edge levels and excellent electronic charge transfer. However, unlike TiO2 with good photostability, the intrinsic drawback of photocorrosion of CdS-based semiconductors significantly challenges their durable application in photocatalysis. This review focuses on recent advances in material design and strategies for improving the anti-photocorrosion of CdS-based photocatalysts for applications in photocatalytic overall water splitting to produce hydrogen. Moreover, brief prospective development and challenges in the synthesis of anti-corrosion CdS-based photocatalysts are also presented.

Building Oxime-Ni2+ Complex on Polymeric Carbon Nitride: Molecular-Level Design of Highly Efficient Hydrogen Generation Photocatalysts.

We report an effective strategy to in situ construct the oxime-Ni2+ complex unit on polymeric carbon nitride (PCN) as a molecular catalyst for the highly efficient hydrogen evolution reaction (HER). The PCN was functionalized with oxime groups that allowed for immobilizing Ni2+ to form oxime-Ni2+ complex units on the PCN surface with uniform distribution. The electrochemical characterizations reveal that these oxime-Ni2+ units can effectively capture photogenerated electrons from PCN and serve as active catalytic sites for proton reduction. Notably, the oxime-Ni2+ enriched PCN showed even higher activities for photocatalytic hydrogen evolution than the Pt-loaded PCN. This work provides a new way to synthesize low-cost photocatalysts with surface grafting of noble-metal-free molecular HER catalysts for efficient light-driven hydrogen generation.

Drying features of microwave and far-infrared combination drying on white ginseng slices.

In this study microwave and far-infrared combination drying were conducted to investigate the effect of microwave and far-infrared heating mode switching point water content (SW), ginseng slice thickness, and far-infrared drying temperature on drying indicators (surface colour difference, ginsenosides content, and surface shrinkage rate) and drying efficiency (drying time) during the process of drying white ginseng slices. Regarding microwave drying, the microwave drying time cannot exceed 150 s, and the ginseng slice water content cannot be less 50%. For the combination drying, SW, far-infrared drying temperature and slice thickness increased, the colour difference and surface shrinkage rate first decreased and then increased, and the content of ginsenosides first increased and then decreased. In addition, the combination drying showed faster drying rate, higher ginsenosides contents value, colour difference (ΔE) value and lower surface shrinkage rate than single far-infrared drying.

Assembly of Ultra-Thin NiO Layer Over Zn1-x Cdx S for Stable Visible-Light Photocatalytic Overall Water Splitting.

Photocatalytic splitting of water into hydrogen and oxygen by using visible light is considered to be a clean, green, and renewable route for solar energy conversion and storage. Although the Zn1-x Cdx S catalysts show comparatively higher activity for photocatalytic hydrogen generation under visible-light irradiation, they suffer from serious photocorrosion during the photocatalytic reaction. The deposition of a protective layer over the Zn1-x Cdx S catalysts is believed to be an effective way to inhibit photocorrosion. However, only a few materials exhibit satisfactory catalytic properties for hydrogen evolution as well as a good protection ability. In this work, a new Zn1-x Cdx S photocatalyst was developed for water splitting under visible-light illumination by assembling an ultrathin NiO layer over Zn0.8 Cd0.2 S through an in situ photodeposition method. The as-prepared NiO/Zn0.8 Cd0.2 S showed significantly higher activity for overall water splitting compared with Pt/Zn0.8 Cd0.2 S under the same conditions without photocorrosion. An apparent quantum efficiency of 0.66 % was achieved for hydrogen evolution at 430 nm with an accomplished multicycle stability for up to 12 h without any significant decay. The strong electronic coupling between the NiO layer and Zn1-x Cdx S also promoted efficient charge separation and migration.

What is the transfer mechanism of photogenerated carriers for the nanocomposite photocatalyst Ag3PO4/g-C3N4, band-band transfer or a direct Z-scheme?

The separation mechanisms of photoexcited carriers for composite photocatalysts are a hot point in the photocatalytic field. In this paper, the Ag3PO4/g-C3N4 nanocomposites with different main parts (Ag3PO4 or g-C3N4) were synthesized using a facile in situ precipitation method. The photocatalysts were characterized by X-ray powder diffraction, UV-vis diffuse reflection spectroscopy, transmission electron microscopy and Brunauer-Emmett-Teller methods. The photocatalytic performance was evaluated by the degradation of methylene blue under visible light irradiation. When the main part of the Ag3PO4/g-C3N4 photocatalyst is Ag3PO4, the transfer mechanism of photogenerated electron-hole takes generic band-band transfer, and the photocatalytic activity is decreased. However, when the primary part of the Ag3PO4/g-C3N4 photocatalyst is g-C3N4, the migration of photogenerated electron-hole exhibits a typical Z-scheme mechanism, and the photocatalytic activity is increased greatly. The separation mechanisms of photogenerated carriers were investigated by the electron spin resonance technology, the photoluminescence technique and the determination of reactive species in the photocatalytic reactions. It is hoped that this work could render guided information for design and application of Z-scheme photocatalysts with excellent photocatalytic performance.

Drying characteristics and quality of red ginseng using far-infrared rays.

BACKGROUND: The current typical drying methods for red ginseng are sun drying and hot-air drying. The purpose of this study was to investigate drying characteristics of red ginseng by using far-infrared drying. METHODS: The far-infrared drying tests on red ginseng were conducted at two drying stages: (1) high temperature for 24 h drying and (2) low temperature drying until the final moisture content was 13 ± 0.5% (wet basis). The high temperature drying stage included three drying chamber temperature conditions of 60°C, 65°C, and 70°C. The low temperature drying stage was conducted at temperatures of 45°C and 50°C. Drying characteristics were analyzed based on factors such as drying rate, color changes, energy consumption, and saponin content. The results were compared with those of the hot-air and sun drying methods. RESULTS: The results revealed that increases in drying temperature caused a decrease in drying time and energy consumption for far-infrared drying. The saponin content decreased under all drying conditions after drying, the highest value (11.34 mg/g) was observed at drying conditions of 60∼50°C. The sun drying condition showed the lowest color difference value when compared with far-infrared and hot-air drying. CONCLUSION: The far-infrared drying showed a faster drying rate, higher saponin content, lower color difference value, and a decrease in energy consumption than seen in hot-air drying.