Preparation of K+ intercalated MnO2-rGO composite for the electrochemical detection of nitroaniline in industrial wastewater

Weakening the Mn-O-Si Interaction via Carbon Intercalation for the Enhanced Catalytic Ozonation of Refractory Pollutants in Environmental Matrices

The strong metal-support interaction (MSI) has been widely attributed to enhanced catalytic activity. However, this attribution might be wrong in catalytic ozonation, since MSI that is too strong might impede the activation of electron-poor ozone molecules. Herein, we reported a strategy to subtly modulate the Mn-O-Si interaction by intercalating the carbon film between the silica support and active manganese oxide. When using MnOx/0.5C/SiO2 with the moderate MSI as a catalyst in the catalytic ozonation of refractory paracetamol (PCM), 91.1 ± 2.4% of PCM was removed within 30 min, about 30% higher than that using the catalyst of MnOx/SiO2 with a strong MSI. Moreover, the reaction rate reached 8.01 × 10-2 min-1, 2.2 and 1.3 times that with MnOx/SiO2 and MnOx/1C/SiO2, respectively. Importantly, further integration of MnOx/0.5C/SiO2 into membrane filtration achieved high rejections of PCM (>94.3%) under various realistic water scenarios during a continuous 12 h operation, demonstrating strong resistance to environmental matrices interference. Experimental and theoretical evidence revealed that the moderate MSI resulted in the high dispersion of active MnOx nanoclusters in the size of 2.3-4.4 nm and promoted the adsorption of ozone over MnOx and its dissociation into surface *O, •OH, •O2-, and 1O2 for decontamination. As a constructive work, this study revealed the significance of MSI in catalytic ozonation and offered a simple regulation method for constructing active interfaces of metal-supported catalysts.

Multi-Sensitive Au NCs/5-FU@Carr-LA Composite Hydrogels for Targeted Multimodal Anti-Tumor Therapy

Multifunctional targeted drug delivery systems have been explored as a novel cancer treatment strategy to overcome limitations of traditional chemotherapy. The combination of photodynamic therapy and chemotherapy has been shown to enhance efficacy, but the phototoxicity of traditional photosensitizers is a challenge. In this study, we prepared a multi-sensitive composite hydrogel containing gold nanoclusters (Au NCs) and the temperature-sensitive antitumor drug 5-fluorourac il (5-FU) using carboxymethyl cellulose (Carr) as a dual-functional template. Au NCs were synthesized using sodium borohydride as a reducing agent and potassium as a promoter. The resulting Au NCs were embedded in the Carr hydrogel, which was then conjugated with lactobionic acid (LA) as a targeting ligand. The resulting Au NCs/5-FU@Carr-LA composite hydrogel was used for synergistic photodynamic therapy (PDT), photothermal therapy (PTT), and chemotherapy. Au NCs/5-FU@Carr-LA releases the drug faster at pH 5.0 due to the acid sensitivity of the Carr polymer chain. In addition, at 50 °C, the release rate of Au NCs/5-FU@Carr-LA is 78.2%, indicating that the higher temperature generated by the photothermal effect is conducive to the degradation of Carr polymer chains. The Carr hydrogel stabilized the Au NCs and acted as a matrix for drug loading, and the LA ligand facilitated targeted delivery to tumor cells. The composite hydrogel exhibited excellent biocompatibility and synergistic antitumor efficacy, as demonstrated by in vitro and in vivo experiments. In addition, the hydrogel had thermal imaging capabilities, making it a promising multifunctional platform for targeted cancer therapy.

Facile design of FeCu metal-organic frameworks anchored on layer Ti3C2Tx MXene for high-performance electrochemical sensing of resorcinol

This work reports the rational design of a composite material by growing FeCu-MOF-919 on the surface of layered Ti3C2Tx MXene. The introduction of Ti3C2Tx MXene simultaneously weakens the aggregation of FeCu-MOF-919 and Ti3C2Tx MXene, which increases the electrochemical reaction active site of the composite material and improves the electrochemical activity. Interestingly, the FeCu-MOF-919/Ti3C2Tx based sensors were used to detect resorcinol (RS) with a wide linear range (0.5-152.5 μM), excellent sensitivity (0.23 μA μM-1 cm-2), low limit of detection (LOD = 0.08 μM) and outstanding stability. Meanwhile, the sensor shows high repeatability of 1.07 % RSD, reproducibility of 1.47 % RSD and anti-interference performance. What's more, the sensor can be successfully used to detect RS in tap water with good recoveries (96.25-103.37 %, RSD ≤2.18 %), demonstrating that the FeCu-MOF-919/Ti3C2Tx exhibits significant potential as an advanced sensing apparatus for the surveillance of RS in the natural environment.

Selective identification of p-nitroaniline by bromine-mediated polarization of carbon dots

A fluorometric method based on boron, bromide-codoped carbon dots (BBCNs) was developed for the first time for the highly selective detection of p-nitroaniline (PNA) in wastewater samples. It should be noted that the introduction of bromine greatly increases the molecular polarizability of the probe, which can regulate the energy level matching between the probe and PNA, resulting in the interaction between BBCNs and PNA. In the presence of PNA, the fluorescence of BBCNs is obviously quenched and accompanied by a red shift of the fluorescence band, which might be attributed to the formation of aggregates caused by the polar adsorption of BBCNs and PNA. It is beneficial for constructing a highly selective sensing platform for PNA determination compared to its isomers (o-nitroaniline and m-nitroaniline) through atomic bromine-mediated polarization of the BBCNs. With the help of this mechanism, an excellent linear range of 0.5-300 μM with a low detection limit of 0.24 μM toward PNA was obtained. This work further confirms that there is a significant relationship between the nature of doping elements and the optical and physicochemical properties of fluorescent materials.

Luminescent Cd coordination polymer based on thiazole as a dual-responsive chemosensor for 4-nitroaniline and CrO42- in water

A novel highly fluorescent cadmium metal-organic framework, [Cd (DPTTZ) (OBA)] (IUST-3), synthesized by using two linkers 2, 5-di (pyridine-4-yl) thiazolo [5, 4-d] thiazole (DPTTZ) and 4, 4'-oxybis (benzoic acid) (OBA) simultaneously, which exhibits a two-dimensional framework. The characteristics of this Cd-MOF were investigated by single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, powder X-ray diffraction, and thermogravimetry analysis. The IUST-3 exhibits excellent luminescence property and good stability in water. Luminescent experiments indicate that the IUST-3 has remarkable sensitivity and selectivity for the detection of 4-nitroaniline (4-NA), and CrO₄^2- anion with K_SV = 1.03 × 10⁵ M^-1 (4-NA) and K_SV = 2.93 × 10⁴ M^-1 (CrO₄^2-) and low limit of detection 0.52 µM (4-NA) and 1.37 µM (CrO₄^2-). In addition, the possible fluorescence quenching mechanism was explored in this paper.

Synthesis of Prussian Blue Analogue and Its Catalytic Activity toward Reduction of Environmentally Toxic Nitroaromatic Pollutants

Nitroanilines are environmentally toxic pollutants which are released into aquatic systems due to uncontrolled industrialization. Therefore, it is crucial to convert these hazardous nitroanilines into a harmless or beneficial counterpart. In this context, we present the chemical reduction of 4-nitroaniline (4-NA) by NaBH4 utilizing Prussian blue analogue (PBA) as nanocatalyst. PBAs can serve as inexpensive, eco-friendly, and easily fabricated nanocatalysts. PBA cobalt tetracyanonickelate hexacyanochromate (CoTCNi/HCCr) was stoichiometrically prepared by a facile chemical coprecipitation. Chemical, phase, composition, and molecular interactions were investigated by XRD, EDX, XPS, and Raman spectroscopy. Additionally, SEM and TEM micrographs were utilized to visualize the microstructure of the nanomaterial. The findings revealed the synthesized PBA of the cubic phase and their particles in nanosheets. The band gap was estimated from the optical absorption within the UV-vis region to be 3.70 and 4.05 eV. The catalytic performance of PBA for the reduction of 4-NA was monitored by UV-vis spectroscopy. The total reduction time of 4-NA by PBA was achieved within 270 s, and the computed rate constant (k) was 0.0103 s-1. The synthesized PBA nanoparticles have the potential to be used as efficient nanocatalysts for the reduction of different hazardous nitroaromatics.

Enhanced Catalytic Ozonation for Eliminating CH3SH via Stable and Circular Electronic Metal-Support Interactions of Si-O-Mn Bonds with Low Mn Loading

Catalytic ozonation of methyl mercaptan (CH₃SH) can effectively control this unbearable odorous sulfur-containing volatile organic compound (S-VOC). The construction of an electronic metal-support interaction (EMSI) coordination structure to maximize the number of active sites and increase the intrinsic activity of active sites is an effective means to improve catalytic performance. In this work, the abundant Si-OH groups on PSBA-15 (SBA-15 before calcination) were used to anchor Mn to form a Si-O-Mn-based EMSI coordination structure. Detailed characterizations and theoretical simulations reveal that the strong EMSI effect significantly adjusts and stabilizes the electronic structure of Mn 3d states, resulting in an electron-rich center on the Si-O-Mn bond to promote the specific adsorption/activation of ozone (O₃) and an electron-poor center on the (Si-O-)Mn-O bond to adsorb a large amount of CH₃SH accompanied by its own oxidative degradation. In situ Raman and in situ Fourier transform infrared (FTIR) analyses identify that catalytic ozonation over 3.0Mn-PSBA generates atomic oxygen species (AOS/*O) and reactive oxygen species (ROS/^•O₂^-) to achieve efficient decomposition of CH₃SH into CO₂/SO₄^2-. Furthermore, the electrons obtained from CH₃SH in electron-poor centers are transferred to maintain the redox cycle of Mn^2+/3+ → Mn⁴⁺ → Mn^2+/3+ through the internal bond bridge, thus accomplishing the efficient and stable degradation of CH₃SH prolonged to 180 min. Therefore, the rational design of catalysts with abundant active sites and optimized inherent activity via the EMSI effect can provide significant potential to improve catalytic performance and eliminate odorous gases.

Facile synthesis of single-crystalline Fe-doped copper vanadate nanoparticles for the voltammetric monitoring of lethal hazardous fungicide carbendazim

The highly selective and sensitive electrochemical detection of highly toxic fungicide carbendazim (CBZ) by the iron (Fe)-doped copper vanadate (CuVO₄; CuV) is discussed. The Fe-doped copper vanadate (Fe-CuV) is prepared by the simple co-precipitation method followed by an annealing process which produced high crystallinity. The material properties of Fe-CuV are characterized by XRD, Raman spectrometry, XPS analysis, HRTEM, and SAED pattern. The electrochemical characterization of Fe-CuV towards CBZ detection are done by CV and DPV techniques. The Fe-CuV/GCE exhibits good electroanalytical activity towards the electro-oxidation of CBZ at the potential of 0.81 V vs Ag/AgCl. The developed sensor electrode revealed a linear range of 0.01 to 83.1 μM and a limit of detection of about 5 nM. In addition, Fe-CuV/GCE reveals good storage stability (RSD = 2.63%) and reproducibility (RSD = 2.85%) for the electro-oxidation of CBZ. The electrode material was applied to the detection of CBZ in apple juice and soy milk samples, and the results were discussed. Thus, our projected Fe-CuV/GCE can be employed as electrode material in a rapid onsite sensor for the detection and determination of noxious pollutants.