A ternary CdS/AgBr/Ag3PO4 nanocomposite: characterization and the kinetics of its photocatalytic activity

Novel portable photoelectrochemical sensor based on CdS/Au/TiO2 nanotube arrays for sensitive, non-invasive, and instantaneous uric acid detection in saliva

Uric acid (UA) monitoring is the most effective method for diagnosis and treatment of gout, hyperuricemia, hypertension, and other diseases. However, challenges remain regarding detection efficiency and rapid on-site detection. Here, we first synthesized a CdS/Au/TiO2-NTAs Z-scheme heterojunction material using a titanium dioxide nanotube array (TiO2-NTAs) as the substrate and modified with gold nanoparticles (Au) and cadmium sulfide particles (CdS). This material achieves bandgap alignment to generate a large number of electron-hole pairs under illumination. Then, using CdS/Au/TiO2-NTAs as the working electrode and molecularly imprinted polymers (MIP) as the recognition unit, we constructed a portable photoelectrochemical (PEC) sensor for non-invasive instant detection of UA concentration in human saliva, which has unique advantages in the field of high-sensitivity PEC instant detection. The portable MIP-PEC sensor achieves a linear range of 0.01-50 μM and a detection limit as low as 5.07 nM (S/N = 3). At the same time, the portable MIP-PEC sensor exhibits excellent sensitivity, specificity as well as stability, and shows no statistically significant difference compared to traditional high-performance liquid chromatography (HPLC) in practical sample detection. Compared to traditional PEC modes, this work demonstrates a novel and universal method for high-sensitivity instant detection in the field of PEC.

A Z-scheme CdS/Ag3PO4 catalyst: Characterization, experimental design and mechanism consideration for methylene blue

Due to the explosive use of Azo dyes in various industries such as textiles, discharging these industrial effluents into the environment critically polluted water supplies. Accordingly, constructing/developing novel binary catalysts to diminish the pollution extent of such effluents before discharging into environment is an excellent issue in environmental chemistry. Here, a binary CdS/ Ag₃PO₄ was constructed, and its boosted photocatalytic activity was proven against methylene blue (MB), as a model dye pollutant. The Wurtzite CdS and Ag₃PO₄ cubic crystal nanoparticles were synthesized and coupled mechanically. The binary sample's lowest photoluminescence (PL) results confirm a higher e/h separation. DRS results confirmed a decreased energy gap for the coupled system. The semiconductors' VB and CV potentials were calculated and used for constructing of Z-scheme mechanism. The photocatalytic activity was followed via an experimental design approach. The model F-value of 89.75 > F_0.05,14,13 = 2.42 and LOF F-value of 6.57 < F_{0.05,10, 3} = 8.79 reveal that the model well processed data. The optimal run conditions were CMB: 5 ppm, Catalyst dose: 1 g/L, pH: 3.25, and irradiation time: 139 min, at which 85% of MB molecules were degraded. Based on the trend of ascorbic acid > isopropanol > formic acid ≈ nitrate obtained for the scavengers' importance in decreasing the photocatalyst activity, superoxide radicals had the highest effect in MB degradation and then ^•OH. The results showed the direct Z-scheme has the main effect on MB degradation by the binary sample.

A core/shell TiO2 magnetized molecularly imprinted photocatalyst (MMIP@TiO2): synthesis and its photodegradation activity towards sulfasalazine

Although the selectivity of TiO₂ for the degradation of target molecules is not enough, it is a broadly employed photocatalyst for the degradation of many pollutants. Molecularly imprinted compounds owing to their extreme recognition specificity have become increasingly popular for preparing selective photocatalysts. In this work, based on molecularly imprinted magnetized TiO₂ (MMIP@TiO₂), a selective photocatalyst was prepared. Via the co-precipitation method, Fe₃O₄ particles were prepared and coated respectively by SiO₂, vinyl end groups, and molecularly imprinted polymers (MIP). The synthesized photocatalyst was characterized by the X-ray diffraction method (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), vibrating sample magnetometry (VSM), high-performance liquid chromatography (HPLC), and photoluminescence analysis (PL). The photocatalyst was then used to degrade the sulfasalazine pharmaceutical pollutant under UV irradiation. An average crystallite size of 9 nm was obtained for the MMIP@TiO₂ sample from the Scherrer formula and 34.5 nm by the Williamson-Hall formula. The results revealed that compared to the non-imprinted counterpart, the molecularly imprinted photocatalyst had significantly higher efficiency and selectivity for the degradation of target molecules. The process was forwarded with 90% efficiency within 10 min. Optimal conditions were 10.0 min irradiation when 25 mL SSZ solution (50 mg/L), 0.07 g/L catalyst dose, and pH 6.0 were applied. The maximum removal efficiency was calculated to be 92%. The external magnetic field quickly removed the photocatalyst from the solution and regenerated it. It was revealed that after each regeneration cycle, the efficiency dropped. Nevertheless, 63% of the preliminary effectiveness remained after four regeneration steps.

Nanocubic copper cobaltite for methyl orange degradation through photocatalytic process

In this study, cubic spinel structured CuCo₂O₄ (Copper cobaltite) nanospheres were fabricated by thermal decomposition method. The visible light degradation of organic contaminant methyl orange (MO) was focused in this study using the synthesized pure CuO, Co₃O₄ and CuCo₂O₄ with different weight ratios of raw materials (90:10, 75:25 and 50:50). It could be well realized that after the characterization techniques, the synthesized CuCo₂O₄ materials resembled cubic spinel structure as confirmed by X-ray diffraction (XRD) investigation. Meanwhile, all the synthesized materials through transmission electron microscopy (TEM) have showed cubic shaped particles and among the CuCo₂O₄ materials, CuCo₂O₄ (50:50) expressed not as much of crystallinity due to the agglomerated nanospheres. On the other hand, well crystalline CuCo₂O₄ (75:25) displayed higher surface area than the other materials when analysed through Brunauer-Emmett-Teller (BET) method. The Fourier transform infra-red (FTIR) spectrum has evinced the formation of CuCo₂O₄ nanostructures. In addition, the cubic spinel structured CuCo₂O₄ provided positive results over visible light irradiation. Finally, the CuCo₂O₄ (75:25) sample has scored high as much of 85% MO degradation compared with others. This sample was progressed with repetitive recycling tests and presented the best photocatalytic degradation efficiency. The upgraded results of CuCo₂O₄ sample have been linked with the developed synergistic effects during the formation of binary metal oxides. Also, the interfacial electron-hole formation leads to the migration and hindering of charge carriers for visible light activity.

A designed experiment for CdS-AgBr photocatalyst toward methylene blue

A boosted photocatalytic activity was observed for the CdS-AgBr nanocomposite in the degradation of methylene blue (MB). The experimental design method based on the response surface methodology (RSM) approach used to study the simultaneous interaction effects between the influencing variables. Analysis of variance (ANOVA) of the results confirmed a significant model for processing the data because an F value of 32.34 for the suggested model was higher than that of the critical value of F_{0.05, 14, 13} = 2.55 at 95% confidence interval. This analysis also showed a non-significant lack of fit (LOF) (as a measure of the randomness of the deviations around the obtained data) because the LOF F value of 8.27 was smaller than that of the critical value of F_{0.05, 10, 3} = 8.79. R² values near to unity were achieved (the multiple correlation coefficients R² (R² = 0.9627), adjusted R² (adj-R² = 0.9226), and predicted R² (pred-R² = 0.7423)). Six center points suggested by the model included the following conditions: pH, 6.1; C_MB, 3.5 mg/L; a dose of the catalyst, 0.68 g/L; and irradiation time, 40.5 min. During the center point runs, the degradation efficiencies were obtained in the range of 38 to 43%. The optimal run included pH, 9; catalyst dosage, 1 g/L; irradiation time, 60 min; and C_MB, 2 mg/L, and the best removal efficiency of 98% was achieved during these conditions.