Dopant-driven recombination delay and ROS enhancement in nanoporous Cd1-xCuxS heterogeneous photocatalyst for the degradation of DR-23 dye under visible light irradiation

Starch-derived carbon quantum dots: Unveiling structural insights and photocatalytic potential as a bio-sourced metal-free semiconductor

The optical appeal and sustainability of carbon quantum dots (CQDs) have led to these nanoparticles swiftly gaining attention and emerging as a new, multifunctional class of nanomaterials. This work centers on the hydrothermal preparation of CQDs utilizing starch, an abundant and renewable biopolymer, as the precursor. Extensive characterization via spectroscopy and microscopy techniques revealed that the starch-derived CQDs exhibit a spherical nanoscale morphology averaging a ∼ 4 nm diameter, demonstrating a red-orange photoluminescence emission. Diffuse reflectance spectroscopic analysis verified their semiconductor behavior, with an estimated direct band gap of 4.1 eV comparable to conventional semiconductors. The prepared CQDs demonstrated considerable promise as metal-free, semiconductor photocatalysts for degrading aqueous dye pollutants under UV irradiation. High photodegradation efficiencies of 45.11 %, 62.94 %, and 91.21 % were achieved for Acid Blue 21, Reactive Blue 94, and Reactive TB 133 dyes, respectively. Systematic investigations of critical process parameters like pH, CQDs dosage, dye concentration, and contact time provided vital insights into the photocatalytic mechanism. The bio-sourced CQD nanomaterials offer a sustainable pathway for effective environmental remediation.

Molecular surface-dependent light harvesting and photo charge separation in plant-derived carbon quantum dots for visible-light-driven OH radical generation for remediation of aromatic hydrocarbon pollutants and real wastewater

Despite the growing emphasis on eco-friendly nanomaterials as energy harvesters, scientists are actively searching for metal-free photocatalysts to be used in environmental remediation strategies. Developing renewable resource-based carbon quantum dots (CQDs) as the sole photocatalyst to harvest visible light for efficient pollutant degradation is crucial yet challenging, particularly for addressing the escalating issue of water deterioration. Moreover, the photocatalytic decomposition of H2O2 under visible light irradiation remains an arduous task. Based on this, we designed two types of CQDs, C-CQDs (carboxylic-rich) and A-CQDs (amine-rich) with distinct molecular surfaces. Owing to the higher amount of upward band bending induced by amine-rich molecular surface, A-CQDs efficiently harvest the visible light and prevent recombination kinetics resulting in prolonged lifetimes (25 ps), and augmented charge carrier density (35.7 × 1018) of photoexcited charge carriers. A-CQDs enabled rapid visible-light-driven photolysis of H2O2 (k = 0.058 min-1) and produced higher quantity of •OH radicals (0.158 μmol/sec) for the mineralization of petroleum waste, BETX (i.e. Benzene, Ethylbenzene, Toluene and Xylene) (k = 0.017-0.026 min-1) and real textile wastewater (k = 0.026 min-1). To assess comparative toxicities of both remediated and non-remediated real wastewater samples in a time and dose depended manner, Drosophila melanogaster was used as a model organism. The findings unequivocally demonstrate the potential of remediated wastewater for watering urban forestry.

A magnetically reusable Ce-MOF/GO/Fe3O4 composite for effective photocatalytic degradation of chlortetracycline

Herein, we report a novel 1/GO/Fe3O4 photocatalyst, comprising Ce(BTB)(H2O) (MOF-1, H3BTB = 1,3,5-benzenetrisbenzoic acid), graphene oxide (GO), and iron oxide (Fe3O4) for photocatalytic degradation of chlortetracycline (CTC). This design enables the effective transfer of electrons from the MOF to GO, thereby reducing the photoelectron-hole recombination rate. Therefore, the optimized 1/GO/Fe3O4 photocatalyst with H2O2 shows the highest photocatalytic activity toward CTC. The kinetic constant is 5.4 times that in the system of MOF-1 and hydrogen peroxide, which usually acted as efficient electron acceptors to improve the photocatalytic performance of MOFs. More importantly, light absorption is extended from the ultraviolet to the visible region. Furthermore, 1/GO/Fe3O4 can be quickly recycled under an applied magnetic field and displays outstanding stability and reusability. According to the radical trapping experiments and electron paramagnetic resonance results, hydroxyl radicals, superoxide radicals, and holes all contribute to excellent photocatalytic activity. The possible catalytic mechanism of 1/GO/Fe3O4 is tentatively proposed. This work aims to explore the synergistic effect between metal-organic frameworks (MOFs) and GO, and provide a theoretical basis for MOF-based composites to remove antibiotic contaminants in the environment.

Unlocking the Molecular Behavior of Natural Amine-Targeted Carbon Quantum Dots for the Synthesis of Diverse Pharmacophore Scaffolds via an Unusual Nanoaminocatalytic Route

Despite the fact that carbon quantum dots (CQDs) have significant catalytic potential, only emblematic applications that rely on simple acid-base or hydrogen-bonding activation pathways have been reported. In this study, natural amine-targeted CQDs (NAT-CQDs) have been successfully fabricated using a sustainable technique that harnesses a renewable green source. Based on a holistic sustainable assessment, the present approach for the synthesis of NAT-CQDs surpasses previously reported methods in terms of estimated circular and good-manufacturing-practice metrics. A set of spectroscopic and analytical techniques, including FTIR, XPS, conductometric assay, pH titration, 19FNMR, and 13CNMR confirms the presence of the assessable amino-rich groups (0.0083N) at the surface of NAT-CQDs. The occurrence of surface amine groups unlocked the molecular behavior of as-prepared NAT-CQDs and makes them an unprecedented nanoaminocatalytic platform for the synthesis of diverse pharmacophore scaffolds (>40 examples) via a one-pot Knoevenagel/(aza) Michael addition reaction in water at room temperature. The assessable amine group can covalently activate carbonyl groups through nucleophilic iminium activation modes in water and facilitate the ability to build valuable and therapeutic scaffolds on a gram scale. By transferring significant molecular primacy at the frontier of nanoscale materials, NAT-CQDs can thus bridge the gap between the nanoscale and molecular domains. This protocol can also be applied for the preparation of therapeutic anticoagulant drugs, warfarin, and coumachlor. All the reactions exhibited a high atom economy, low E-factor, low process mass intensity (PMI), high reaction mass efficiency (RME), high carbon efficiency (CE), and high catalyst reusability with overall high sustainable values. NAT-CQDs show high recyclability, and the spectral data of reused catalysts indicate that the NAT-CQDs maintained their surface chemistry and electronic properties, suggesting their stability under the tested conditions. This study presents a remarkable instance of NAT-CQDs showcasing covalent catalysis. Expanding on the aforementioned design concept, the utilization of NAT-CQDs' "potential" as distinct colloidal organocatalysts in aqueous environments at the molecular level introduces valuable prospects for aminocatalytic pathways.