Spherical covalent organic framework supported Cu/Ag bimetallic nanoparticles with highly catalytic activity for reduction of 4-nitrophenol

Colorimetry/fluorescence dual-mode detection of Salmonella typhimurium based on a "three-in-one" nanohybrid with high oxidase-like activity for AIEgen

A colorimetry/fluorescence dual-mode assay based on the aptamer-functionalized magnetic covalent organic framework-supported CuO and Au NPs (MCOF-CuO/Au@apt) was developed for Salmonella typhimurium (S. typhimurium) biosensing. The nanohybrid combined three functions in one: good magnetic separation characteristic, excellent oxidase-mimic activity for tetrap-aminophenylethylene (TPE-4A), and target recognition capability. The attachment of MCOF-CuO/Au@apt onto the surface of S. typhimurium resulted in a significant reduction in the oxidase-mimicking activity of the nanohybrid, which could generate dual-signal of colorimetry and fluorescence through the catalytic oxidation of TPE-4A. Based on this, S. typhimurium could be specifically detected in the linear ranges of 102- 106 CFU·mL-1 and 101- 106 CFU·mL-1, with LODs of 7.6 and 2.1 CFU·mL-1, respectively in colorimetry/fluorescence modes. Moreover, the smartphone and linear discrimination analysis-based system could be used for on-site and portable testing. In addition, this platform showed applicability in detecting S. typhimurium in milk, egg liquid and chicken samples.

Incorporation of g-C3N4 nanosheets and CuO nanoparticles on polyester fabric for the dip-catalytic reduction of 4 nitrophenol

In the present work, we present the preparation of a new emerged heterogeneous catalyst (PE/g-C3N4/CuO) by in situ deposition of copper oxide nanoparticles (CuO) over the graphitic carbon nitride (g-C3N4) as the active catalyst and polyester (PE) fabric as the inert support. The synthesized sample (PE/g-C3N4/CuO) "dip catalyst" was studied by using various analytical techniques (Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy and dispersive X-ray spectroscopy (SEM/EDX), and transmission electron microscopy (TEM). The nanocomposite is utilized as heterogeneous catalysts for the 4-nitrophenol reduction in the presence of NaBH4, in aqueous solutions. According to experimental results, PE/g-C3N4/CuO with a surface of 6 cm2 (3 cm × 2 cm) demonstrated the catalyst exhibit excellent catalytic activity with 95% reduction efficiency for only 4 min of reaction and an apparent reaction rate constant (Kapp) of 0.8027 min-1. Further evidence that this catalyst based on prepared PE support can be a good contender for long-lasting chemical catalysis comes from the remarkable stability after 10 repetitions reaction cycles without a noticeably loss in catalytic activity. The novelty of this work consists to fabricate of catalyst based of CuO nanoparticles stabilized with g-C3N4 on the surface of an inert substrate PE, which results in an heterogenous dip-catalyst that can be easily introduced and isolated from the reaction solution with good retention of high catalytic performance in the reduction of 4-nitrophenol.

In Situ Redox Synthesis of Highly Stable Au/Electroactive Polyimide Composite and Its Application on 4-Nitrophenol Reduction

In this study, we developed a series of Au/electroactive polyimide (Au/EPI-5) composite for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using NaBH₄ as a reducing agent at room temperature. The electroactive polyimide (EPI-5) synthesis was performed by chemical imidization of its 4,4'-(4.4'-isopropylidene-diphenoxy) bis (phthalic anhydride) (BSAA) and amino-capped aniline pentamer (ACAP). In addition, prepare different concentrations of Au ions through the in-situ redox reaction of EPI-5 to obtain Au nanoparticles (AuNPs) and anchored on the surface of EPI-5 to form series of Au/EPI-5 composite. Using SEM and HR-TEM confirm the particle size (23-113 nm) of the reduced AuNPs increases with the increase of the concentration. Based on CV studies, the redox capability of as-prepared electroactive materials was found to show an increase trend: 1Au/EPI-5 < 3Au/EPI-5 < 5Au/EPI-5. The series of Au/EPI-5 composites showed good stability and catalytic activity for the reaction of 4-NP to 4-AP. Especially, the 5Au/EPI-5 composite shows the highest catalytic activity when applied for the reduction of 4-NP to 4-AP within 17 min. The rate constant and kinetic activity energy were calculated to be 1.1 × 10^-3 s^-1 and 38.9 kJ/mol, respectively. Following a reusability test repeated 10 times, the 5Au/EPI-5 composite maintained a conversion rate higher than 95%. Finally, this study elaborates the mechanism of the catalytic reduction of 4-NP to 4-AP.

Pd nanoparticles decorated on Schiff base-modified chitosan/CeO2 as a heterogeneous and retriable nanocatalyst for Heck reactions and remediation of environmental pollutants

In this paper, we have developed a novel, highly active, eco-friendly, and versatile heterogeneous catalyst system in which Pd nanoparticles are decorated on Schiff base-modified chitosan‑cerium oxide particles (Pd@CS-CeO₂). In order to confirm the successful fabrication of Pd@CS-CeO₂, FTIR, XRD, SEM, TEM, BET, TG/DTG, and EDS analyses were performed, and its performance was evaluated as a heterogeneous nanocatalyst in Heck coupling reaction and reduction of nitro compounds. The catalytic tests showed that the desired Heck products were readily produced by Pd@CS-CeO₂ without being contaminated with the aryl iodides, bromides, and chlorides. Moreover, different nitro compounds were efficiently reduced to corresponding amino compounds by Pd@CS-CeO₂ within 95-160 s. Thanks to the heterogeneous nature of Pd@CS-CeO₂ catalyst, it was easily recovered via simple filtration and reused up to 5 successive runs by giving 88 % yield. Due to its good catalytic and reusability performance together with stability/durability, Pd@CS-CeO₂ is promising candidate as a catalyst for various catalytic or organic reactions.

Electrospun Porous Nanofibers: Pore−Forming Mechanisms and Applications for Photocatalytic Degradation of Organic Pollutants in Wastewater

Electrospun porous nanofibers have large specific surface areas and abundant active centers, which can effectively improve the properties of nanofibers. In the field of photocatalysis, electrospun porous nanofibers can increase the contact area of loaded photocatalytic particles with light, shorten the electron transfer path, and improve photocatalytic activity. In this paper, the main pore−forming mechanisms of electrospun porous nanofiber are summarized as breath figures, phase separation (vapor−induced phase separation, non−solvent−induced phase separation, and thermally induced phase separation) and post−processing (selective removal). Then, the application of electrospun porous nanofiber loading photocatalytic particles in the degradation of pollutants (such as organic, inorganic, and bacteria) in water is introduced, and its future development prospected. Although porous structures are beneficial in improving the photocatalytic performance of nanofibers, they reduce their mechanical properties. Therefore, strategies for improving the mechanical properties of electrospun porous nanofibers are also briefly discussed.

Cu-Doped 1D Hydroxyapatite as a Highly Active Catalyst for the Removal of 4-Nitrophenol and Dyes from Water

Metallic copper nanoparticle (Cu NP)-doped 1D hydroxyapatite was synthesized using a simple chemical reduction method. To describe the structure and composition of the Cu/HAP nanocomposites, physicochemical techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma, N₂ adsorption-desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy were used. The TEM scan of the Cu/HAP nanocomposite revealed a rod-like shape with 308 nm length and 117 nm width on average. The catalytic activity of Cu/HAP nanocomposites for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH₄ has been thoroughly investigated. The 0.7% Cu/HAP nanocomposite was shown to have superior catalytic activity than the other nanocomposites, converting 4-NP to 4-AP in ∼1 min with good recyclability. Moreover, this nanocomposite showed excellent catalytic performance in the organic dye reduction such as Congo red and acriflavine hydrochloride dyes. The high dispersion of Cu NPs on HAP support, the high specific surface area, and the small Cu particles contributed to its remarkable catalytic performance.