Emerging Two-Dimensional-Based Nanostructured Catalysts: Applications in Sustainable Organic Transformations.

The extension of green and sustainable materials in the preparation of heterogeneous catalysts for organic transformations has increased over the past few decades. Because of their unique and intriguing physical and chemical properties, two-dimensional (2D) nanostructured materials have attracted widespread attention and have been used in a variety of applications, such as catalysis, electronics, and energy storage. A promising pathway to enhance the performance of 2D nanomaterials is their coupling with other functional materials to form heterogeneous or hybrid structures. Herein, we discuss the use of 2D-based nanostructured catalysts for enhancing organic transformations and highlight selected examples to demonstrate the synthesis, advantages, challenges, efficiency, and reusability of the introduced heterogeneous catalysts for cross-coupling and reduction reactions.

Magnetite Metal-Organic Frameworks: Applications in Environmental Remediation of Heavy Metals, Organic Contaminants, and Other Pollutants.

Due to the increasing environmental pollution caused by human activities, environmental remediation has become an important subject for humans and environmental safety. The quest for beneficial pathways to remove organic and inorganic contaminants has been the theme of considerable investigations in the past decade. The easy and quick separation made magnetic solid-phase extraction (MSPE) a popular method for the removal of different pollutants from the environment. Metal-organic frameworks (MOFs) are a class of porous materials best known for their ultrahigh porosity. Moreover, these materials can be easily modified with useful ligands and form various composites with varying characteristics, thus rendering them an ideal candidate as adsorbing agents for MSPE. Herein, research on MSPE, encompassing MOFs as sorbents and Fe3O4 as a magnetic component, is surveyed for environmental applications. Initially, assorted pollutants and their threats to human and environmental safety are introduced with a brief introduction to MOFs and MSPE. Subsequently, the deployment of magnetic MOFs (MMOFs) as sorbents for the removal of various organic and inorganic pollutants from the environment is deliberated, encompassing the outlooks and perspectives of this field.

Structural and optical characterizations of Ce3+ -doped YSO phosphors via the addition of TEOS.

In this work, Y2 O3 phosphors were synthesized utilizing facile sol-gel, combustion, and solid-state techniques. The tested synthesis processes provided various particle sizes from nano to submicron. To synthesize YSO:Ce3+ via a sol-gel method, tetraethylorthosilicate (TEOS) was used as the precursor for SiO2 . Crystal structure, microstructure, and optical behaviour of the synthesized nanostructured phosphors were studied using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform-infrared (FT-IR) spectrometry, and photoluminescence (PL) analyses. FT-IR analysis showed that hydrolysis of TEOS gave rise to the generation of Si-O-Si asymmetrical stretching vibrations. Addition of specific amounts of TEOS resulted in the formation of Y2 SiO5 /Y2 Si2 O7 phosphors with different crystal structures. Upon excitation of the phosphors under 354 nm radiation, there were two strong emission peaks at 395.6 and 424.1 nm, attributed respectively to 5d-2 F5/2 and 5d-2 F7/2 electron transitions of Ce3+ . It was concluded that the most intense PL characteristics belonged to the combination of Y4.67 (SiO4 )3 O, Y2 Si2 O7 , and Y2 SiO5 phosphors.

Recent Advances in the Aptamer-Based Electrochemical Biosensors for Detecting Aflatoxin B1 and Its Pertinent Metabolite Aflatoxin M1.

The notable toxicological impacts of aflatoxin B1 (AFB1) and its main metabolite, aflatoxin M1 (AFM1), on human being health make the evaluation of food quality highly significant. Due to the toxicity of those metabolites-even very low content in foodstuffs-it is crucial to design a sensitive and reliable procedure for their detection. Electrochemical aptamer-based biosensors are considered the most encouraging option, based on multi-placed analysis, rapid response, high sensitivity and specificity. The present review specifically emphasizes the potential utilization of the electrochemical aptasensors for determining the AFM1 and AFB1 with different electrodes.

Recent Advances in the Electrochemical Sensing of Venlafaxine: An Antidepressant Drug and Environmental Contaminant.

Venlafaxine (VEN), as one of the popular anti-depressants, is widely utilized for the treatment of major depressive disorder, panic disorder, as well as anxiety. This drug influences the chemicals in the brain, which may result in imbalance in depressed individuals. However, venlafaxine and its metabolites are contaminants in water. They have exerted an adverse influence on living organisms through their migration and transformation in various forms of adsorption, photolysis, hydrolysis, and biodegradation followed by the formation of various active compounds in the environment. Hence, it is crucial to determine VEN with low concentrations in high sensitivity, specificity, and reproducibility. Some analytical techniques have been practically designed to quantify VEN. However, electroanalytical procedures have been of interest due to the superior advantages in comparison to conventional techniques, because such methods feature rapidity, simplicity, sensitivity, and affordability. Therefore, this mini-review aims to present the electrochemical determination of VEN with diverse electrodes, such as carbon paste electrodes, glassy carbon electrodes, mercury-based electrodes, screen-printed electrodes, pencil graphite electrodes, and ion-selective electrodes.

Recent Advances in Electrochemical Sensors and Biosensors for Detecting Bisphenol A.

In recent years, several studies have focused on environmental pollutants. Bisphenol A (BPA) is one prominent industrial raw material, and its extensive utilization and release into the environment constitute an environmental hazard. BPA is considered as to be an endocrine disruptor which mimics hormones, and has a direct relationship to the development and growth of animal and human reproductive systems. Moreover, intensive exposure to the compound is related to prostate and breast cancer, infertility, obesity, and diabetes. Hence, accurate and reliable determination techniques are crucial for preventing human exposure to BPA. Experts in the field have published general electrochemical procedures for detecting BPA. The present timely review critically evaluates diverse chemically modified electrodes using various substances that have been reported in numerous studies in the recent decade for use in electrochemical sensors and biosensors to detect BPA. Additionally, the essential contributions of these substances for the design of electrochemical sensors are presented. It has been predicted that chemically modified electrode-based sensing systems will be possible options for the monitoring of detrimental pollutants.

Point-of-Use Rapid Detection of SARS-CoV-2: Nanotechnology-Enabled Solutions for the COVID-19 Pandemic.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the COVID-19 pandemic that has been spreading around the world since December 2019. More than 10 million affected cases and more than half a million deaths have been reported so far, while no vaccine is yet available as a treatment. Considering the global healthcare urgency, several techniques, including whole genome sequencing and computed tomography imaging have been employed for diagnosing infected people. Considerable efforts are also directed at detecting and preventing different modes of community transmission. Among them is the rapid detection of virus presence on different surfaces with which people may come in contact. Detection based on non-contact optical techniques is very helpful in managing the spread of the virus, and to aid in the disinfection of surfaces. Nanomaterial-based methods are proven suitable for rapid detection. Given the immense need for science led innovative solutions, this manuscript critically reviews recent literature to specifically illustrate nano-engineered effective and rapid solutions. In addition, all the different techniques are critically analyzed, compared, and contrasted to identify the most promising methods. Moreover, promising research ideas for high accuracy of detection in trace concentrations, via color change and light-sensitive nanostructures, to assist fingerprint techniques (to identify the virus at the contact surface of the gas and solid phase) are also presented.

A general strategy for site-directed enzyme immobilization by using NiO nanoparticle decorated mesoporous silica.

Mesoporous materials have recently gained much attention owing to their large surface area, narrow pore size distribution, and superior pore structure. These materials have been demonstrated as excellent solid supports for immobilization of a variety of proteins and enzymes for their potential applications as biocatalysts in the chemical and pharmaceutical industries. However, the lack of efficient and reproducible methods for immobilization has limited the activity and recyclability of these biocatalysts. Furthermore, the biocatalysts are usually not robust owing to their rapid denaturation in bulk solvents. To solve these problems, we designed a novel hybrid material system, mesoporous silica immobilized with NiO nanoparticles (SBA-NiO), wherein enzyme immobilization is directed to specific sites on the pore surface of the material. This yielded the biocatalytic species with higher activity than free enzyme in solution. These biocatalytic species are recyclable with minimal loss of activity after several cycles, demonstrating an advantage over free enzymes.

Magnetic boron nitride adorned with Pd nanoparticles: an efficient catalyst for the reduction of nitroarenes in aqueous media.

Hexagonal boron nitride (h-BN) is an excellent support material for nanocatalysts due to its two-dimensional (2D) architectural morphology and physicochemical stability. In this study, a chemically stable, recoverable, eco-friendly, and magnetic h-BN/Pd/Fe2O3 catalyst was prepared by a one-step calcination process, in which Pd and Fe2O3 nanoparticles (NPs) were uniformly decorated on the surface of h-BN via a typical adsorption-reduction procedure. In detail, nanosized magnetic (Pd/Fe2O3) NPs were derived from a Prussian blue analogue prototype, a well-known porous metal-organic framework, and then further surface-engineered to produce magnetic BN nanoplate-supported Pd nanocatalysts. The structural and morphological features of h-BN/Pd/Fe2O3 were investigated by spectroscopic and microscopic characterization techniques. Moreover, the h-BN nanosheets endow it with stability and appropriate chemical anchoring sites which solve the problems of inefficient reaction rate and high consumption caused by the inevitable agglomeration of precious metal NPs. Under mild reaction conditions, the developed nanostructured h-BN/Pd/Fe2O3 as the catalyst shows high yield and efficient reusability in reducing nitroarenes into the corresponding anilines using sodium borohydride (NaBH4) as a reductant.

Nanostructure and nanoindentation study of pulse electric-current sintered TiB2-SiC-Cf composite.

A carbon-fiber (Cf) doped TiB2-SiC composite was prepared and investigated to determine its densification behavior, micro/nanostructural properties, and mechanical characteristics. TiB2-25 vol% SiC-2 wt% Cf was prepared at 40 MPa and 1800 °C for 7 min using the pulsed electric-current sintering technique, and a relative density of 98.5% was realized. The as-sintered composite was characterized using advanced techniques, e.g., X-ray diffractometry, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, field-emission electron probe micro-analysis, and nanoindentation. The Cf additive could remove the surface oxide layers from the TiB2 and SiC domains, thus transforming them into TiB2 and SiC. According to micro/nanostructural studies, Cf could not retain its initial structure and was eventually converted into graphite nanosheets. In addition, the prepared composite was examined using the nanoindentation technique, and the following results were obtained for the calculated hardness, elastic modulus, and stiffness values: TiB2 > SiC > TiB2/SiC interface.

Recent catalytic applications of MXene-based layered nanomaterials.

The urgent issues related to the catalytic processes and energy applications have accelerated the development of hybrid and smart materials. MXenes are a new family of atomic layered nanostructured materials that require considerable research. Tailorable morphologies, strong electrical conductivity, great chemical stability, large surface-to-volume ratios, tunable structures, among others are some significant characteristics that make MXenes appropriate for various electrochemical reactions, including dry reforming of methane, hydrogen evolution reaction, methanol oxidation reaction, sulfur reduction reaction, Suzuki-Miyaura coupling reaction, water-gas shift reaction, and so forth. MXenes, on the other hand, have a fundamental drawback of agglomeration, as well as poor long-term recyclability and stability. One possibility for overcoming the restrictions is the fusion of nanosheets or nanoparticles with MXenes. Herein, the relevant literature on the synthesis, catalytic stability and reusability, and applications of several MXene-based nanocatalysts are deliberated including the merits and cons of the newer MXene-based catalysts.

Integration of plasmonic AgPd alloy nanoparticles with single-layer graphitic carbon nitride as Mott-Schottky junction toward photo-promoted H2 evolution.

Plasmonic AgPd alloy nanoparticles (AgPdNPs) decorated on single-layer carbon nitride (AgPdNPs/SLCN) for the designing of the Mott-Schottky junction were constructed with the ultrasonically assisted hydrothermal method and used toward photo evolution H2 from formic acid (FA) at near room temperature (30 °C). The Pd atom contains active sites that are synergistically boosted by the localized surface plasmon resonance (LSPR) effect of Ag atoms, leading to considerably enhanced photocatalytic properties. The photoactive AgPdNPs/SLCN obtained supreme catalytic activity to produce 50 mL of gas (H2 + CO2) with the initial turnover frequency of 224 h-1 under light irradiation. The catalyst showed stable catalytic performance during successive cycles.

Modified chitosan-zeolite supported Pd nanoparticles: A reusable catalyst for the synthesis of 5-substituted-1H-tetrazoles from aryl halides.

A novel heterogeneous catalyst has been developed using chitosan-zeolite supported Pd nanoparticles (PdNPs@CS-Zeo) and used in an efficient synthesis of 5-substituted-1H-tetrazoles from aryl halides with high yields for relatively short reaction times with an easy work-up procedure. In this method, highly effective and reusable PdNPs@CS-Zeo catalyst was used in the reaction of various aryl iodides/bromides with K4[Fe(CN)6] as a non-toxic cyanide source to catalyze the [2 + 3] cycloaddition of the corresponding aryl nitriles with NaN3 in the sequential one-pot preparation of 5-substituted-1H-tetrazoles. The synthesized PdNPs@CS-Zeo nanocatalyst was characterized using XRD, FTIR, TEM, HRTEM, XPS, Raman, TG-DTG, ICP-OES, BET, and EDS mapping. Additionally, the nanocatalyst could be effectively separated by filtration and reused for multiple times without significant decrease of catalytic activity.

Architecture engineering of nanostructured catalyst via layer-by-layer adornment of multiple nanocatalysts on silica nanorod arrays for hydrogenation of nitroarenes.

Direct consideration for both, the catalytically active species and the host materials provides highly efficient strategies for the architecture design of nanostructured catalysts. The conventional wet chemical methods have limitations in achieving such unique layer-by-layer design possessing one body framework with many catalyst parts. Herein, an innovative physical method is presented that allows the well-regulated architecture design for an array of functional nanocatalysts as exemplified by layer-by-layer adornment of Pd nanoparticles (NPs) on the highly arrayed silica nanorods. This spatially confined catalyst exhibits excellent efficiency for the hydrogenation of nitroarenes and widely deployed Suzuki cross-coupling reactions; their facile separation from the reaction mixtures is easily accomplished due to the monolithic structure. The generality of this method for the introduction of other metal source has also been demonstrated with Au NPs. This pioneering effort highlights the feasibility of physically controlled architecture design of nanostructured catalysts which may stimulate further studies in the general domain of the heterogeneous catalytic transformations.

Facile synthesis of Cu NPs@Fe3O4-lignosulfonate: Study of catalytic and antibacterial/antioxidant activities.

Environmental pollution is one of the important concerns for human health. There are different types of pollutants and techniques to eliminate them from the environment. We hereby report an efficient method for the remediation of environmental contaminants through the catalytic reduction of the selected pollutants. A green method has been developed for the immobilization of copper nanoparticles on magnetic lignosulfonate (Cu NPs@Fe3O4-LS) using the aqueous extract of Filago arvensis L. as a non-toxic reducing and stabilizing agent. The characterization of the prepared Cu NPs@Fe3O4-LS was achieved by vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD), scanning TEM (STEM), thermogravimetry-differential thermal analysis (TG/DTA), fast Fourier transform (FFT), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron (XPS) analyses. The synthesized Cu NPs@Fe3O4-LS was applied as a magnetic and green catalyst in the reduction of congo red (CR), 4-nitrophenol (4-NP), and methylene blue (MB). The progress of the reduction reactions was monitored by UV-Vis spectroscopy. Finally, the biological properties of Cu NPs@Fe3O4-LS were investigated. The prepared catalyst demonstrated excellent catalytic efficiency in the reduction of CR, 4-NP, and MB in the presence of sodium borohydride (NaBH4) as the reducing agent. The appropriate magnetism of Cu NPs@Fe3O4-LS made its recovery very simple. The advantages of this process include a simple reaction set-up, high and catalytic antibacterial/antioxidant activities, short reaction time, environmentally friendliness, high stability, and easy separation of the catalyst. In addition, the prepared Cu NPs@Fe3O4-LS could be reused for four cycles with no significant decline in performance.

Microstructural and nanoindentation study of TaN incorporated ZrB2 and ZrB2-SiC ceramics.

This study assessed the sinterability and microstructure of ZrB2-SiC-TaN and ZrB2-TaN ceramics. Spark plasma sintering at 2000 °C and 30 MPa for 5 min produced both ceramics. The relative density of ZrB2 ceramic containing TaN was 95.3%; the addition of SiC increased this value to 98.1%. SiC's contribution to the elimination of ZrB2 surface oxides was the primary factor in the advancement of densification. The in situ formation of hexagonal boron nitride at the interface of TaN and ZrB2 was confirmed by high-resolution transmission electron microscopy, field emission-electron probe microanalyzer, X-ray diffractometry, and field emission scanning electron microscopy. Moreover, the in situ graphite might be produced as a byproduct of the SiC-SiO2 process, hence boosting the reduction of oxide compounds in the ternary system. The SiC compound had the highest hardness (29 ± 3 GPa), while the ZrB2/TaN interface exhibited the greatest values of elastic modulus (473 ± 26 GPa) and stiffness (0.76 ± 0.13 mN/nm).

Pd nanoparticles loaded on modified chitosan-Unye bentonite microcapsules: A reusable nanocatalyst for Sonogashira coupling reaction.

This work investigates the preparation of a catalytic complex of palladium nanoparticles supported on novel Schiff base modified chitosan-Unye bentonite microcapsules (Pd NPs@CS-UN). The complex has been characterized by FT-IR, EDS, XRD, TEM, HRTEM, Raman, ICP-OES and elemental mapping analyses. Pd NPs@CS-UN was used as a catalyst for Sonogashira coupling reactions between aryl halides and acetylenes, employing K2CO3 as the base and EtOH as a green solvent under aerobic conditions in which it showed high efficacy. Pd NPs@CS-UN was regenerated by filtration after the completion of the reaction. This catalytic process has many advantages including simple methodology, high yields, and easy work-up. The catalytic performance does not notably change even after five consecutive runs.

A screen printed electrode modified with Fe3O4@polypyrrole-Pt core-shell nanoparticles for electrochemical detection of 6-mercaptopurine and 6-thioguanine.

In this paper, Fe3O4@ppy-Pt core-shell nanoparticles (NPs) could be produced and utilized for the development of a novel electrochemical sensor to detect 6-mercaptopurine (6-MP). 6-MP determination was examined by cyclic voltammetry (CV), chronoamperometry (CHA), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV) at Fe3O4@ppy-Pt core-shell NPs modified screen printed electrode (Fe3O4@ppy-Pt/SPE) in phosphate buffered solution (PBS). The outcomes obtained from DPV demonstrated that the Fe3O4@ppy-Pt/SPE proved a linear concentration range among 0.04 and 330.0 µM having a detection limit of 10.0 nM for 6-MP. Also, modified electrode was satisfactorily utilized to detect 6-MP in the presence of 6-thioguanine (6-TG). This sensor showed two separate oxidative peaks at 530 mV for 6-MP and at 730 mV for 6-TG with a peak potential separation of 200 mV which was large enough for simultaneous detection of the two anticancer drugs. In addition, the proposed sensor presented long-term stability, good repeatability, and excellent reproducibility. Finally, the modified electrode demonstrated satisfactory outcomes while used in real samples, proposing the appropriate potential of Fe3O4@ppy-Pt/SPE in the case of clinical diagnosis, biological samples and pharmaceutical compounds analysis.

Comparison of fractal dimensions from nitrogen adsorption data in shale via different models.

The roughness of pore surfaces in shale reservoirs can affect the fluid flow, which makes it necessary to be characterized. Fractal dimension, a key component in fractal geometry, can be used to describe the surface irregularities. In this paper, we evaluated and compared the fractal dimensions of several shale samples with three major fractal models based on nitrogen adsorption isotherms. The results showed that Frenkel-Halsey-Hill (FHH), Neimark, and Wang-Li models all can be applied for fractal dimension characterization of shale samples. From theoretical thermodynamics, these three models should be considered identical based on the FHH equation. However, the experimental data obtained from these samples showed that the fractal dimensions that are derived from the Neimark model and Wang-Li model are the same while a discrepancy was observed with the results from the FHH model. The difference in the fractal dimensions in the experimental data among these three models was attributed to the micropore structures. It was found that as the micropore surface area or the micropore volume increases in the samples, the difference in the fractal dimensions would increase as well. If the number of micropores present in the samples is limited, all three models can become suitable for fractal dimension calculation in shale samples, otherwise, the Neimark or Wang-Li model is preferred.

Natural Polymers Decorated MOF-MXene Nanocarriers for Co-delivery of Doxorubicin/pCRISPR.

A one-pot and facile method with assistance of high gravity was applied for the synthesis of inorganic two-dimensional MOF-5 embedded MXene nanostructures. The innovative inorganic MXene/MOF-5 nanostructure was applied in co-delivery of drug and gene, and to increase its bioavailability and interaction with the pCRISPR, the nanomaterial was coated with alginate and chitosan. The polymer-coated nanosystems were fully characterized, and the sustained DOX delivery and comprehensive cytotoxicity studies were conducted on the HEK-293, PC12, HepG2, and HeLa cell lines, demonstrating acceptable and excellent cell viability at both very low (0.1 µg.mL-1) and high (10 µg·mL-1) concentrations. The chitosan-coated nanocarriers showed superior relative cell viability compared to others, more than 60% on average of relative cell viability in all of the cell lines. Then, alginate-coated nanocarriers ranked at second place on the higher relative cell viability, more than 50% on average for all of the cell lines. Also, MTT results showed a complete dose-dependence, and by increasing the time of treatment from 24 to 72 h, the relative cell viability decreased by a meaningful slope; however, this decrease was optimized by coating the nanocarrier with chitosan and alginate. The nanosystems were also tagged with pCRISPR to analyze the potential application in the co-delivery of drug/gene. CLSM images of the HEK-293 and HeLa cell lines unveiled successful delivery of pCRISPR into the cells, and the enhanced green fluorescent protein (EGFP) reached up to ca. 26% for the HeLa cell line. Also, a considerable drug payload of 35.7% was achieved, which would be because of the interactions between the nanocarrier and the doxorubicin. In this unprecedented report pertaining to the synthesis of MXene assisted by a MOF and high-gravity technique, the methodology and the optimized ensuing MXene/MOF-5 nanosystems can be further developed for the co-delivery of drug/gene in animal models.