Hierarchical porous zeolitic imidazolate frameworks (ZIF-8) and ZnO@N-doped carbon for selective adsorption and photocatalytic degradation of organic pollutants

Ultra-stable metal-organic framework-derived carbon nanocontainers with defect-induced pore enlargement for anti-corrosive epoxy coatings

Zeolitic imidazolate frameworks-8 (ZIF-8) have recently gained attention as nanocontainers for encapsulating corrosion inhibitors. However, two main challenges remain unsolved, casting doubt on their suitability as nanocontainers. The first challenge is their instability in acidic and basic environments, leading to structural decomposition and the second challenge is their mass diffusion limitation caused by micropore dominance and a small aperture size of 0.34-0.42 nm, limiting the efficient adsorption of corrosion inhibitors. To address both challenges, in this work, ZIF-8 nanostructures were transformed into nitrogen-doped ZIF-derived carbon-based nanocontainers (CZIF) via carbonization. This transformation not only stabilized the structure but also produced larger pore sizes (micro and mesopores), due to defects formed during carbonization. Benzotriazole (BTA) corrosion inhibitors were then encapsulated in CZIF structures to produce CZIF-BTA. Electrochemical impedance spectroscopy (EIS) demonstrated that the saline solution containing CZIF-BTA extract reduced the corrosion rate of steel by 50 % compared to a blank solution. The scratched epoxy (EP) coating containing 0.2 wt% of CZIF-BTA revealed an active inhibition performance with ∼100 % enhancement in the total resistance value compared to blank EP. Finally, the coating showed superior barrier properties with the impedance at the lowest frequency value of ∼2 × 1010 Ω cm2 after 71 days of immersion.

Sulfonated-polypyrene aniline/polyaniline composite fortified with Cu-GQD@ZIF8 as an electrochemical enzymatic urea biosensor

The determination of urea concentration is essential for human health owing to its crucial role in the ability to metabolize nitrogen-containing substances. This study developed new electrochemical enzymatic detection systems via the synergistic effect of the superior features of novel electropolymerizable pyranine-aniline (PA, 4), polyaniline (PANI) compounds, graphene quantum dots (GQDs) and zeolitic imidazolate framework-8 (ZIF8). The novel compound 4 was characterized via1H-NMR, 13C-NMR, FTIR, and MALDI-TOF mass spectroscopies. Furthermore, Cu-GQD@ZIF8 hybrid materials containing GQD and integrated electroactive Cu metal were prepared in this study. The surface morphology of the prepared Cu-GQD@ZIF8 hybrid material was investigated through microscopic methods such as SEM and TEM, and chemical characterizations were performed using FTIR, XPS, XRD, and TGA analyses. After the characterization of the novel materials, the urease (Urs) enzyme was bound to the new modified electrode surface. Next, the enzymatic biosensor properties of the Urs/Cu-GQD@ZIF8/PANI/PA/GCE sensor electrode for urea detection via reduction of PANI were investigated by DPV and CV techniques. The LOD and LOQ values of the presented sensor were calculated to be 0.77 μM and 2.31 μM, respectively, in the linear range of 1.0-80.0 μM, based on DPV measurements. The presented biosensor system determined the amount of urea in an artificial serum sample, and its accuracy was confirmed via the recovery test and GC-MS analysis.

Cationic lignin as an efficient and sustainable homogenous catalyst for aqueous Knoevenagel condensation reactions

Knoevenagel condensation is a chemical reaction between aldehydes and active methylene-containing compounds in the presence of heterogeneous, basic homogenous organic or inorganic catalysts and solvent or neat systems. Herein, we introduced a new strategy for this synthesis by using the aqueous solution of cationic kraft lignin (CKL) as a catalyst. The CKL was synthesized through the reaction of kraft lignin (KL) with glycidyltrimethylammonium chloride (GTMAC) in a basic medium. The optimal reaction conditions for the Knoevenagel reaction were 5% catalyst load (weight of catalyst to the weight of benzaldehyde), water as the solvent, and at room temperature, which generated the products with a yield of 97%, illustrating that the CKL was an effective homogenous and green catalyst. The results confirmed that the increase in CKL charge density improved the product yield. The water-insoluble products were easily separated by filtration, and the filtrate containing the catalysts was reused effectively for 5 cycles without a significant decrease in the production yield, which would confirm the advantages of this catalyst for this reaction system. The CKL catalyst exhibited biodegradability comparable to KL. This paper discusses a novel method for Knoevenagel condensation reactions for different aldehydes in a green system utilizing a sustainable, biodegradable catalyst at room temperature and in an aqueous system.

Recent advances in photocatalytic nanomaterials for environmental remediation: Strategies, mechanisms, and future directions

Innovative and efficient strategies are urgently needed for wastewater treatment and environmental remediation. The photocatalytic degradation properties of photo-responsive nanomaterials (NMs) have become a prime candidate due to their low negative impact and photo-adjustability. Photocatalytic NMs vary in their degradation of different pollutants depending on the type of synthetic material, excitation light source, and physicochemical properties. Essentially, photocatalytic NMs excited by light produce reactive oxygen species (ROS) or metal ions that can degrade complex structure pollutants. Therefore, this review summarises the recent advances of photocatalytic NMs in the environmental application within the last 3 years, focusing on the development schemes, structural analyses, photocatalytic mechanisms, and the degradation effects of dyes, antibiotics, pesticides, phenolic compounds, metals, hormones, and other contaminants. The limitations and future directions are also explained. This review hopes to provide a possible pathway for the subsequent development of novel and efficient photocatalytic NMs to cope with complex and variable polluted environments.

Metal-organic framework-interfaced ELISA probe enables ultrasensitive detection of extracellular vesicle biomarkers

The enzyme-linked immunosorbent assay (ELISA) remains the prevailing method for quantifying protein biomarkers. Enzymatic signal generation and amplification are key mechanisms that govern its analytical performance. This study reports the synthesis and application of microscale metal-organic framework (MOF)/enzyme composite particles as a novel detection probe to substantially enhance the sensitivity of ELISA. An optimal one-pot approach was established to incorporate a substantial amount of streptavidin-horseradish peroxidase (SA-HRP) either within or on the surface of the metal-azolate framework (MAF-7) microparticles. This approach enables the labeling of a single sandwich antibody-antigen complex with numerous enzymes, which markedly amplifies the enzymatic colorimetric signal generation. Moreover, MAF-7 caging was found to enhance the reactivity of the caged HRP enzyme, further promoting the overall detection sensitivity of ELISA. Compared to other developments that are often associated with more complicated detection modalities, our method is compatible with standard immunoassays and commonly used photometrical signal detection. The implementation of this strategy in the detection of CD147 results in a remarkably low limit of detection of 2.8 fg mL-1, representing a 105-fold improvement compared to that obtained with the standard ELISA. Moreover, the heightened sensitivity of this technique renders it particularly suitable for diagnosing breast cancer, thus presenting a promising tool for the early detection of the disease in clinical settings.

Enhanced visible light photocatalytic activity of octopod Ag3PO4 microcrystals with high index crystal faces

Novel octopod shaped Ag3PO4 microcrystals were successfully fabricated by a simple ion exchange method under the conditions of a hot water bath using [Ag(NH3)2]+ solution and Na2HPO4 solution as the precursors. Meanwhile, sphere and cube shaped Ag3PO4 microcrystals were also prepared followed by changing reaction materials as well as temperature. The surface morphology, microstructure and photocatalytic performance were investigated on the three different shaped crystals respectively. Compared to sphere and cube counterparts, the obtained octopod shaped Ag3PO4 crystals possess 8 symmetric feet with sharp tips and exhibit higher photocatalytic activity and better cycle stability. After further exploring its formation process, UV-vis diffusion reflectance properties as well as photocurrent transient response, it was found that the Ag3PO4 octopod had exposed high index crystal faces, and possessed a narrow band gap as well as high photoexcited transient charge separation efficiency. The results show that the improved photocatalytic activity of octopod shaped Ag3PO4 is mainly due to the synergistic action of the strong light absorption capacity and high carrier separation efficiency. These results highlight the tremendous practical application of octopod Ag3PO4 microcrystals in visible light photocatalysis.

A comparative study of α-Ni(OH)2 and Ni nanoparticle supported ZIF-8@reduced graphene oxide-derived nitrogen doped carbon for electrocatalytic ethanol oxidation

Ethanol electrooxidation is an important reaction for fuel cells, however, the major obstacle to ethanol electrocatalysis is the splitting of the carbon-carbon bond to CO2 at lower overpotentials. Herein, a ZIF-8@graphene oxide-derived highly porous nitrogen-doped carbonaceous platform containing zinc oxide was attained for supporting a non-precious Ni-based catalyst. The support was doped with the disordered α-phase Ni(OH)2 NPs and Ni NPs that are converted to Ni(OH)2 through potential cycling in alkaline media. The Ni-based catalysts exhibit high electroactivity owing to the formation of the NiOOH species which has more unpaired d electrons that can bond with the adsorbed species. From CV curves, the EOR onset potential of the α-Ni(OH)2/ZNC@rGO electrode is strongly shifted to negative potential (Eonset = 0.34 V) with a high current density of 8.3 mA cm-2 relative to Ni/ZNC@rGO. The high catalytic activity is related to the large interlayer spacing of α-Ni(OH)2 which facilitates the ion-solvent intercalation. Besides, the porous structure of the NC and the high conductivity of rGO facilitate the kinetic transport of the reactants and electrons. Finally, the catalyst displays a high stability of 92% after 900 cycles relative to the Ni/ZNC@rGO and commercial Pt/C catalysts. Hence, the fabricated α-Ni(OH)2/ZNC@rGO catalyst could be regarded as a potential catalyst for direct EOR in fuel cells.

Synthesis of Metal-Organic Framework-Based ZIF-8@ZIF-67 Nanocomposites for Antibiotic Decomposition and Antibacterial Activities

Toxic antibiotic effluents and antibiotic-resistant bacteria constitute a threat to global health. So, scientists are investigating high-performance materials for antibiotic decomposition and antibacterial activities. In this novel research work, we have successfully designed ZIF-8@ZIF-67 nanocomposites via sol-gel and solvothermal approaches. The ZIF-8@ZIF-67 nanocomposite is characterized by various techniques that exhibit superior surface area enhancement, charge separation, and high light absorption performance. Yet, ZIF-8 has high adsorption rates and active sites, while ZIF-67 has larger pore volume and efficient adsorption and reaction capabilities, demonstrating that the ZIF-8@ZIF-67 nanocomposite outperforms pristine ZIF-8 and ZIF-67. Compared with pristine ZIF-8 and ZIF-67, the most active 6ZIF-67@ZIF-8 nanocomposite showed higher decomposition efficacy for ciprofloxacin (65%), levofloxacin (54%), and ofloxacin (48%). Scavenger experiments confirmed that •OH, •O2-, and h+ are the most active species for the decomposition of ciprofloxacin (CIP), levofloxacin (LF), and ofloxacin (OFX), respectively. In addition, the 6ZIF-67/ZIF-8 nanocomposite suggested its potential applications in Escherichia coli for growth inhibition zone, antibacterial activity, and decreased viability. Moreover, the stability test and decomposition pathway of CIP, LF, and OFX were also proposed. Finally, our study aims to enhance the efficiency and stability of ZIF-8@ZIF-67 nanocomposite and potentially enable its applications in antibiotic decomposition, antibacterial activities, and environmental remediation.

An introductory review on advanced multifunctional materials

This review summarizes the applications of some of the advanced materials. It included the synthesis of several nanoparticles such as metal oxide nanoparticles (e.g., Fe₃O₄, ZnO, ZrOSO₄, MoO_3-x, CuO, AgFeO₂, Co₃O₄, CeO₂, SiO₂, and CuFeO₂); metal hydroxide nanosheets (e.g., Zn₅(OH)₈(NO₃)₂·2H₂O, Zn(OH)(NO₃)·H₂O, and Zn₅(OH)₈(NO₃)₂); metallic nanoparticles (Ag, Au, Pd, and Pt); carbon-based nanomaterials (graphene, graphene oxide (GO), graphitic carbon nitride (g-C₃N₄), and carbon dots (CDs)); biopolymers (cellulose, nanocellulose, TEMPO-oxidized cellulose nanofibers (TOCNFs), and chitosan); organic polymers (e.g. covalent-organic frameworks (COFs)); and hybrid materials (e.g. metal-organic frameworks (MOFs)). Most of these materials were applied in several fields such as environmental-based technologies (e.g., water remediation, air purification, gas storage), energy (production of hydrogen, dimethyl ether, solar cells, and supercapacitors), and biomedical sectors (sensing, biosensing, cancer therapy, and drug delivery). They can be used as efficient adsorbents and catalysts to remove emerging contaminants e.g., inorganic (i.e., heavy metals) and organic (e.g., dyes, antibiotics, pesticides, and oils in water via adsorption. They can be also used as catalysts for catalytic degradation reactions such as redox reactions of pollutants. They can be used as filters for air purification by capturing carbon dioxide (CO₂) and volatile organic compounds (VOCs). They can be used for hydrogen production via water splitting, alcohol oxidation, and hydrolysis of NaBH₄. Nanomedicine for some of these materials was also included being an effective agent as an antibacterial, nanocarrier for drug delivery, and probe for biosensing.

In Situ Construction of Nitrogen-Doped and Zinc-Confined Microporous Carbon Enabling Efficient Na+-Storage Abilities

Benefiting from the additional active sites for sodium-ion (Na⁺) adsorption and porous architecture for electrolyte accessibility, nitrogen-doped porous carbon has been considered the alternative anode material for Na⁺-storage applications. In this study, nitrogen-doped and zinc-confined microporous carbon (N,Z-MPC) powders are successfully prepared by thermally pyrolyzing the polyhedral ZIF-8 nanoparticles under an argon atmosphere. Following the electrochemical measurements, the N,Z-MPC not only delivers good reversible capacity (423 mAh/g at 0.02 A/g) and comparable rate capability (104 mAh/g at 1.0 A/g) but also achieves a remarkable cyclability (capacity retention: 96.6% after 3000 cycles at 1.0 A/g). Those can be attributed to its intrinsic characteristics: (a) 67% of the disordered structure, (b) 0.38 nm of interplanar distance, (c) a great proportion of sp²-type carbon, (d) abundant microporosity, (e) 16.1% of nitrogen doping, and (f) existence of sodiophilic Zn species, synergistically enhancing the electrochemical performances. Accordingly, the findings observed here support the N,Z-MPC to be a potential anode material enabling exceptional Na⁺-storage abilities.

Acmella oleracea induced nanostructured Ca2Fe2O5 for evaluation of photo catalytic degradation of cardiovascular drugs and bio toxicity

Biosynthesis of nanoparticles is increasingly becoming popular due to the demand for sustainable technologies worldwide. In the present investigation, Acmella oleracea plant extract fuelled combustion technique followed by calcination at 600 °C was adopted to prepare nanocrystalline Ca₂Fe₂O₅. The prepared nano compound was characterised using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Ultra Violet (UV) spectroscopy, Infrared (IR) spectroscopy and its role was assessed for photocatalytic pollutant degradation along with bactericidal action in the concentration range of 1 μg/mL to 320 μg/mL. The photocatalytic degradation efficiency of pollutant drugs Clopidogrel Bisulphate and Asprin used for cardiovascular disorders is around 80% with 10 mg/L photocatalyst. The results showed that the photocatalytic activity increased with rising pH from 4, to 10, along with a significant antibacterial action against Enterococcus faecalis bacteria and a slight cytotoxic effect at high concentrations. The antibacterial property was reinforced by Minimum inhibitory concentrations (MIC) and Minimum bactericidal concentrations (MBC) studies with an average value of 0.103 at 600 nm which was further proved by significant anti-biofilm activeness. Adhesion tests in conjunction with cryogenic-scanning electron microscopy displayed a morphological change through agglomeration that caused an expansion in nano particles from 181 nm to 223.6 nm due to internalization followed by inactivation of bacteria. In addition, the non-toxicity of nano Ca₂Fe₂O₅ was confirmed by subtle cytological changes in microscopic images of Allium Cepa root cells in the concentration range 0.01-100 μg/mL and a slight inhibition in HeLa cell proliferation indicated by IC₅₀ value of 170.94 μg/mL. In total, the current investigation for the first time reveals the application of bio based synthesis of Nano Ca₂Fe₂O₅ to new possibilities in bioremediation namely degrading cardiovascular pharmaceutical pollutants, endodontic antibacterial action and cytological activity.

Dietary Transfer of Zinc Oxide Nanoparticles Induces Locomotive Defects Associated with GABAergic Motor Neuron Damage in Caenorhabditis elegans

The widespread use of zinc oxide nanoparticles (ZnO-NPs) and their release into the environment have raised concerns about the potential toxicity caused by dietary transfer. However, the toxic effects and the mechanisms of dietary transfer of ZnO-NPs have rarely been investigated. We employed the bacteria-feeding nematode Caenorhabditis elegans as the model organism to investigate the neurotoxicity induced by exposure to ZnO-NPs via trophic transfer. Our results showed that ZnO-NPs accumulated in the intestine of C. elegans and also in Escherichia coli OP50 that they ingested. Additionally, impairment of locomotive behaviors, including decreased body bending and head thrashing frequencies, were observed in C. elegans that were fed E. coli pre-treated with ZnO-NPs, which might have occurred because of damage to the D-type GABAergic motor neurons. However, these toxic effects were not apparent in C. elegans that were fed E. coli pre-treated with zinc chloride (ZnCl₂). Therefore, ZnO-NPs particulates, rather than released Zn ions, damage the D-type GABAergic motor neurons and adversely affect the locomotive behaviors of C. elegans via dietary transfer.

Fenton-like Cerium Metal–Organic Frameworks (Ce-MOFs) for Catalytic Oxidation of Olefins, Alcohol, and Dyes Degradation

A metal–organic framework (MOF) of cerium (Ce) ions and 4,4′,4′′-nitrilotribenzoic acid linker was synthesized via a hydrothermal method. Ce-MOF consists of a Lewis acid moiety, i.e. Ce3+ and triphenylamine cores. It showed Fenton-like properties with excellent catalytic oxidation activity for olefins, primary/secondary alcohols, and water pollutants e.g., organic dyes. It displayed high oxidation conversion of cinnamyl alcohol and styrene of 100% and 53%, respectively. It offered good selectivity towards styrene oxide and benzaldehyde (i.e. 75% and 100%, respectively). It was applied for the oxidative degradation of dyes e.g. rhodamine B (RhB), methyl blue (MeB), Congo red (CR), and direct blue (DB) using hydrogen peroxide (H2O2) as an oxidant. It exhibited high efficiency in the oxidative degradation of these water pollutants. The mechanistic study of oxidation involves the formation of radical hydroxyl (•OH) species. This study revealed the possibility of enhancing the oxidative catalytic performance, including oxidative degradation of organic pollutants, by employing advanced oxidation processes (AOPs) using Ce-MOF. The catalyst is recyclable five times without significantly decreasing of the material’s catalytic performance.

MoSe2-modified ZIF-8 novel nanocomposite for photocatalytic remediation of textile dye and antibiotic-contaminated wastewater

COVID-19-led antibiotic waste generated from hospitals and health centres may cause serious health issues and significantly impact the environment. In the coming decades, antibiotic resistance will be one of the most significant threats to global human health. Photocatalytic water remediation is an effective and promising environmental solution that can be utilized to address this issue, to convert antibiotic waste into non-toxic products by utilizing renewable and abundant solar energy. In the present study, a novel nanocomposite of zeolitic imidazolate frameworks (ZIF-8) and molybdenum diselenide (MoSe₂) was efficiently synthesized by the solvothermal method for the complete degradation of the antibiotics and textile waste from water. The morphology, crystallinity and band gap of the samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and UV-visible spectroscopy. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) provide the binding information of the sample. The photocatalytic activity was tested for degradation of the antibiotics (tetracycline hydrochloride (TC) and metronidazole (MNZ)) used in COVID-19 treatment and textile dye (malachite green). Time-resolved photoluminescence spectroscopy confirmed the enhanced charge separation in the MoSe₂@ZIF-8 nanocomposite with an average lifetime of 4.72 ns as compared to pristine samples. The nanocomposite showed ~ 100% removal efficiency with rate constants of 63 × 10^-3, 49 × 10^-3 and 42 × 10^-3 min^-1 for TC, MNZ and malachite green, respectively. The photocatalytic degradation of TC was carried out under different pH conditions (4, 7 and 9), and the degradation mechanism was explained on the basis of zeta potential measurements and active species trapping experiment. The by-products of the photocatalytic treatment of TC antibiotics were tested using liquid chromatography-mass spectroscopy (LC-MS), and they were found to be non-toxic for aquatic and human life. The regeneration property of the nanocomposite was confirmed by FESEM with regeneration efficiency of 88.7% in the 4th cycle. Thus, MoSe₂@ZIF-8-based photocatalysts have potential application in water remediation, especially in making the antibiotic waste less toxic.

Construction of a Z-scheme Ag2MoO4/BiOBr heterojunction for photocatalytically removing organic pollutants

How to facilitate photogenerated-carrier separation is an important step in developing excellent semiconductor photocatalysts for environmental pollutant removal. Herein, Ag₂MoO₄ (AMO) nanoparticles were assembled onto the surface of BiOBr (BOB) nanosheets to construct a highly efficient Z-scheme AMO/BOB heterojunction photocatalyst. Several analytical techniques were used to elucidate the characteristics and photocatalytic mechanism of the AMO/BOB heterojunction. Photodegradation experiments for removing methylene blue under simulated-sunlight irradiation reveal that a 20%AMO/BOB heterojunction exhibits excellent photodegradation activity with η(30 min) = 93.8% and k_app = 0.08638 min^-1, which were greater by 4.5 and 5.6 times in comparison with that of pure BOB and AMO, respectively. Based on the experimental and density functional theory (DFT) calculation results, it is proposed that the Z-scheme carrier transfer/separation mechanism dominates the enhanced photodegradation performance of the composite photocatalysts. Additionally, the potential application of AMO/BOB photocatalysts in degrading various organic pollutants (including organic dyes, antibiotics and other serious organic pollutants) was also investigated.

Adducing Knowledge Capabilities of Instrumental Techniques Through the Exploration of Heterostructures' Modification Methods

The ongoing evolution of technology has facilitated the global research community to rapidly escalate the constant development of novel advancements in science. At the forefront of such achievements in the field of photocatalysis is the utilisation, and in oftentimes, the adaptation of modern instrumentation to understand photo-physical properties of complex heterostructures. For example, coupling in-situ X-ray Raman scattering spectroscopy for real-time degradation of catalytic materials.

ZIF-8 metal organic framework materials as a superb platform for the removal and photocatalytic degradation of organic pollutants: a review

Metal organic frameworks (MOFs) are attracting significant attention for applications including adsorption, chemical sensing, gas separation, photocatalysis, electrocatalysis and catalysis. In particular, zeolitic imidazolate framework 8 (ZIF-8), which is composed of zinc ions and imidazolate ligands, have been applied in different areas of catalysis due to its outstanding structural and textural properties. It possesses a highly porous structure and chemical and thermal stability under varying reaction conditions. When used alone in the reaction medium, the ZIF-8 particles tend to agglomerate, which inhibits their removal efficiency and selectivity. This results in their mediocre reusability and separation from aqueous conditions. Thus, to overcome these drawbacks, several well-designed ZIF-8 structures have emerged by forming composites and heterostructures and doping. This review focuses on the recent advances on the use of ZIF-8 structures (doping, composites, heterostructures, etc.) in the removal and photodegradation of persistent organic pollutants. We focus on the adsorption and photocatalysis of three main organic pollutants (methylene blue, rhodamine B, and malachite green). Finally, the key challenges, prospects and future directions are outlined to give insights into game-changing breakthroughs in this area.

Comparative Study of SnO2 and ZnO Semiconductor Nanoparticles (Synthesized Using Randia echinocarpa) in the Photocatalytic Degradation of Organic Dyes

Symmetry in nanomaterials is essential to know the behavior of their properties. In the present research, the photocatalytic properties of SnO2 and ZnO nanoparticles were compared for the degradation of the cationic dyes Methylene Blue (MB) and Rhodamine B (RB). The nanoparticles were obtained through a green synthesis process assisted by Randia echinocarpa extracts; they were then analyzed through Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) to characterize their structure. Transmission electron microscopy (TEM) was used to identify the morphology and disclose nanoparticle size, and the optical properties were studied through Ultraviolet–visible spectroscopy (UV–Vis). The results show that the synthesized SnO2 and ZnO nanomaterials have quasispherical morphologies with average sizes of 8–12 and 4–6 nm, cassiterite and wurtzite crystal phases, and band gap values of 3.5 and 3.8 eV, respectively. The photocatalytic activity yielded 100% degradation of the MB and RB dyes in 210 and 150 min, respectively. ZnO performed higher photocatalytic degradation of the cationic dyes than SnO2 due to a higher content of Randia echinocarpa extracts remaining after the green synthesis process.

A comparative study of the toxic effect of ZIF-8 and ZIF-L on the colonization and decomposition of shaded outdoor mice carrions by arthropods

Metal–organic frameworks (MOFs) are promising materials for several applications. Thus, they have been intensively reported and commercialized by several international companies. However, little is known about the fate and risk of MOFs to living organisms. Here, the toxic effect of two Zinc (Zn)-based MOFs; zeolitic imidazolate frameworks (ZIF-8) and leaf-like ZIF (ZIF-L), was tested to investigate the impact of the postmortem period of mice carrions and arthropods which found in decomposing carrions. The data analysis revealed an increase in zinc content over time. Toxicology in forensics studies biological materials for the presence of poisons, such as pharmaceuticals. The toxicology report can provide important details about the types of chemicals present in a person and whether the amount of those substances is in line with a therapeutic dose or exceeds a dangerous level. These findings conclude the possible fate and impact after mortality. This study presents the first study of the toxic effect of ZIFs materials using mice carrions and arthropods (Sarcophaga sp. Larvae) via morphological and microscopic studies compared with control, providing important biological information could aid in the environmental impact of the toxic level of MOF materials.

Laccase-mimicking Mn-Cu hybrid nanoflowers for paper-based visual detection of phenolic neurotransmitters and rapid degradation of dyes

Background

Laccase-based biosensors are efficient for detecting phenolic compounds. However, the instability and high cost of laccases have hindered their practical utilization.

Results

In this study, we developed hierarchical manganese dioxide–copper phosphate hybrid nanoflowers (H–Mn–Cu NFs) as excellent laccase-mimicking nanozymes. To synthesize the H–Mn–Cu NFs, manganese dioxide nanoflowers (MnO₂ NFs) were first synthesized by rapidly reducing potassium permanganate using citric acid. The MnO₂ NFs were then functionalized with amine groups, followed by incubation with copper sulfate for three days at room temperature to drive the coordination interaction between the amine moieties and copper ions and to induce anisotropic growth of the petals composed of copper phosphate crystals, consequently yielding H–Mn–Cu NFs. Compared with those of free laccase, at the same mass concentration, H–Mn–Cu NFs exhibited lower K_m (~ 85%) and considerably higher V_max (~ 400%), as well as significantly enhanced stability in the ranges of pH, temperature, ionic strength, and incubation periods evaluated. H–Mn–Cu NFs also catalyzed the decolorization of diverse dyes considerably faster than the free laccase. Based on these advantageous features, a paper microfluidic device incorporating H–Mn–Cu NFs was constructed for the convenient visual detection of phenolic neurotransmitters, including dopamine and epinephrine. The device enabled rapid and sensitive quantification of target neurotransmitters using an image acquired using a smartphone.

Conclusions

These results clearly show that H–Mn–Cu NFs could be potential candidates to replace natural laccases for a wide range of applications in biosensing, environmental protection, and biotechnology.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01560-0.

Enhancement of critical-sized bone defect regeneration using UiO-66 nanomaterial in rabbit femurs

Background

Repair of large-sized bone defects is a challengeable obstacle in orthopedics and evoked the demand for the development of biomaterials that could induce bone repair in such defects. Recently, UiO-66 has emerged as an attractive metal–organic framework (MOF) nanostructure that is incorporated in biomedical applications due to its biocompatibility, porosity, and stability. In addition, its osteogenic properties have earned a great interest as a promising field of research. Thus, the UiO-66 was prepared in this study and assessed for its potential to stimulate and support osteogenesis in vitro and in vivo in a rabbit femoral condyle defect model. The nanomaterial was fabricated and characterized using x-ray diffraction (XRD) and transmission electron microscopy (TEM). Afterward, in vitro cytotoxicity and hemolysis assays were performed to investigate UiO-66 biocompatibility. Furthermore, the material in vitro capability to upregulate osteoblast marker genes was assessed using qPCR. Next, the in vivo new bone formation potential of the UiO-66 nanomaterial was evaluated after induction of bone defects in rabbit femoral condyles. These defects were left empty or filled with UiO-66 nanomaterial and monitored at weeks 4, 8, and 12 after bone defect induction using x-ray, computed tomography (CT), histological examinations, and qPCR analysis of osteocalcin (OC) and osteopontin (OP) expressions.

Results

The designed UiO-66 nanomaterial showed excellent cytocompatibility and hemocompatibility and stimulated the in vitro osteoblast functions. The in vivo osteogenesis was enhanced in the UiO-66 treated group compared to the control group, whereas evidence of healing of the treated bone defects was observed grossly and histologically. Interestingly, UiO-66 implanted defects displayed a significant osteoid tissue and collagen deposition compared to control defects. Moreover, the UiO-66 nanomaterial demonstrated the potential to upregulate OC and OP in vivo.

Conclusions

The UiO-66 nanomaterial implantation possesses a stimulatory impact on the healing process of critical-sized bone defects indicating that UiO-66 is a promising biomaterial for application in bone tissue engineering.