A Pitaya-Inspired Modular Cylindrical MOF-Based Capsule Design for Pesticide Signal Probes

Excessive use of pesticides has brought about serious environmental risks worldwide that pose significant harm for human health. Herein, a series of metal-organic framework (MOF)-based gel capsules with a pitaya-like core-shell structure are constructed through a green polymerization strategy for pesticide detection and removal, namely ZIF-8/M-dbia/SA (M = Zn, Cd). Significantly, the ZIF-8/Zn-dbia/SA capsule exhibits sensitive detection of alachlor, a representative pre-emergence acetanilide pesticide, with a satisfactory detection limit of 0.23 μM. In addition, the MOF-based gel capsules can be extended to a universal visual platform for the noninvasive detection of pesticide residues with various MOFs, such as Eu-MOF, Tb-MOF, and Cu-MOF, and participating dye. Similar to pitaya, the ordered porous structure of MOF in ZIF-8/Zn-dbia/SA capsules offers cavity and open sites for removing pesticide from water with the maximum adsorption amount q_max of 61.1 mg·g^-1 toward alachlor in a Langmuir model. Thereby, this work presents the universality of gel capsule self-assembly technologies, including the well-preserved visible fluorescence area and porosity of the different structurally diverse MOFs, offering an ideal strategy for water decontamination and food safety control fields.

Removal of Chloroacetanilide Herbicides from Water Using Heterogeneous Photocatalysis with TiO2/UV-A

Chloroacetanilide herbicides are widely used in the agricultural sector throughout the world. Because of their poor biodegradability, high water solubility, and long persistence, chloroacetanilide herbicides have a high potential to contaminate water, and conventional water treatment processes do not ensure sufficient removal. Therefore, heterogeneous photocatalysis using TiO2/UV-A was investigated for the degradation of alachlor, acetochlor, and metolachlor from water. Two commercially available TiO2 (P25 and AV-01) were used as photocatalysts. Different experimental setups were also tested. In addition, the toxicity of single herbicides and mixtures of their photocatalytic degradation products to the freshwater alga Chlorella kessleri was investigated via a growth inhibition test. The maximum removal efficiency for alachlor, acetochlor, and metolachlor was 97.5%, 93.1%, and 98.2%, respectively. No significant differences in the removal efficiency of chloroacetanilide herbicides were observed for the photocatalysts used. Although the concentrations of all herbicides during photocatalysis decreased, the toxicity of the resulting mixtures of degradation products increased or remained the same, indicating the formation of toxic degradation products.

Enhanced photocatalytic activity of glyphosate over a combination strategy of GQDs/TNAs heterojunction composites

A photocatalytic process was used to effectively remove glyphosate, an emerging pollutant and contaminant, through advanced oxidation. For this purpose, a feasible combination strategy of two-step anodisation and electrodeposition methods were proposed to fabricate graphene quantum dots (GQDs) supported titanium dioxide nanotube arrays (TNAs). The resultant GQDs/TNAs heterojunction composite exhibited significant degradation reactivity and circulation stability for glyphosate due to its excellent photo-generated electron and hole separation ability. After the introduction of GQDs into TNAs, the photodegradation efficiency of glyphosate increased from 69.5% to 94.7% within 60 min under UV-Vis light irradiation (λ = 320-780 nm). By analysing the intermediate products and through the evolvement of heteroatoms during glyphosate photodegradation, alanine and serine were discovered for the first time, and a detailed degradation mechanism of glyphosate was proposed. This study indicates that GQDs/TNAs heterojunction composite can almost completely degrade the glyphosate into inorganics under the appropriate conditions.

TiO2 nanotube arrays sensitized by copper (II) porphyrins with efficient interfacial charge transfer for the photocatalytic degradation of 4-nitrophenol

In this paper, photocatalysts based on TiO₂ nanotubes (TNTs) and TiO₂ nanotube arrays (TNTAs) sensitized by Cu(II) meso-tetrakis(N-ethylpyridinium-4-yl) porphyrin (CuTEPyP) were synthesized and their structures were characterized by various analytical methods. The photocatalytic activities of both composites were then investigated through degradation of 4-nitrophenol (4-NP) in aqueous solutions under visible light irradiation. It was found that CuTEPyP/TNTAs could eliminate 95% 4-NP within 4 h, which was considerably higher than the yield obtained with CuTEPyP/TNTs (56%) under the same conditions. Compared to CuTEPyP/TNTs, the improved photocatalytic activity of CuTEPyP/TNTAs can be ascribed to increased light absorption, high separation rate of photo-generated charge pairs, and efficient charge transfer. A plausible photocatalytic degradation mechanism involving hydroxyl radicals, superoxide radical anions and singlet oxygen species was also proposed. This work presents an efficient paradigm for eliminating 4-NP under visible light irradiation.

Nonstoichiometric titanium dioxide nanotubes with enhanced catalytical activity under visible light

The catalytic activity of nanotubular titanium dioxide films formed during the oxidation of acetone to carbon dioxide under the action of visible light with a wavelength of 450 nm was found to be approximately 2 times higher compared to standard titanium dioxide (Degussa P25). The nanotubular films were grown by the anodization of titanium foil using an original technique. Diffuse reflectance spectra of the films are attributed to enhanced activity in the visible spectrum by the nonstoichiometry of titanium dioxide near the interface between the nanotubular film and the titanium foil substrate.

Conjugated hybrid films based on a new polyoxotitanate monomer

Electropolymerisation of the novel polyoxotitanate (POT) hexamer [Ti(μ₃-O)(OⁱPr)(TA)]₆ (TA = thiophene-3-acetate) with 3,4-ethylenedioxythiophene (EDOT) gives films of hybrid conjugated copolymer, Poly-(EDOT-POT)s, the morphologies of which are, uniquely, influenced by the electropolymerisation potential.