Carbon-based sustainable nanomaterials for water treatment: State-of-art and future perspectives

Magnetic chitosan stabilized Cu(II)-tetrazole complex: an effective nanocatalyst for the synthesis of 3-imino-2-phenylisoindolin-1-one derivatives under ultrasound irradiation

In the present research, a recyclable catalyst has been prepared via a simple approach using chitosan as a linear polysaccharide. This paper reports the synthesis of novel copper(II) complex of 5-phenyl-1H-tetrazole immobilized on magnetic chitosan (MCS@PhTet@Cu(II)) as an effective catalyst. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and inductively coupled plasma mass spectrometry (ICP-MS) techniques were applied for the characterization of the catalyst. The catalytic activity of MCS@PhTet@Cu(II) was evaluated in the ultrasound-assisted synthesis of 3-imino-2-phenylisoindolin-1-one derivatives via the reaction between benzoyl chloride and arylcyanamides in ethanol at ambient temperature. Utilizing a wide variety of arylcyanamides under mild conditions, no use of toxic organic solvents, moderate reaction time, high yields along with catalyst excellent reusability and easy separation of the products without any tedious separation techniques, made this method a novel and simple process. The resulting heterogeneous catalyst showed valuable advantages such as easier work-up, better stability, and greater separation ability using an external magnet. The catalyst showed high efficacy and recyclability even after five cycles with no significant loss of its efficacy. The present methodology provides a path for the preparation of structurally diverse heterocyclic compounds, which may exhibit important biological activity.

Nanosponges for Water Treatment: Progress and Challenges

Nanosponges have shown promising capabilities for efficient removal of organic/inorganic pollutants from water based on absorption/adsorption and disinfection processes. The application of nanosponges (especially cyclodextrin-based nanosponges) can be considered a cost-effective strategy with minimal energy and time requirements in comparison to other routinely deployed water treatment modalities. These polymers with unique physicochemical properties, architectures, and highly cross-linked three-dimensional networks need to be further explored for removing pollutants with simultaneous eliminations of microbial contaminants from wastewater. Additionally, the surface functionalization of these nanosponges utilizing magnetic, titanium dioxide, and silver nanomaterials can significantly improve their properties for water remediation purposes, although nanosponges altered with carbon nanotubes and metallic nanomaterials/nanocatalysts for water treatment appliances are barely explored. Notably, crucial factors such as adsorbent type/dosage, contact time, competing ions, adsorption isotherm models, kinetics, thermodynamics, and reaction/experimental conditions (e.g., molar ratios, temperature, and pH) are important aspects affecting the adsorption and removal of pollutants using nanosponges. Furthermore, the nanotoxicity and biosafety of these nanosponge-based systems utilized for water treatment should be comprehensively evaluated. Herein, recent advancements in the design and deployment of nanosponge-based systems for removing organic/inorganic pollutants from water and wastewater are deliberated with an emphasis on challenges and perspectives.

Graphene and graphene oxide with anticancer applications: Challenges and future perspectives

Graphene-based materials have shown immense pertinence for sensing/imaging, gene/drug delivery, cancer therapy/diagnosis, and tissue engineering/regenerative medicine. Indeed, the large surface area, ease of functionalization, high drug loading capacity, and reactive oxygen species induction potentials have rendered graphene- (G-) and graphene oxide (GO)-based (nano)structures promising candidates for cancer therapy applications. Various techniques namely liquid-phase exfoliation, Hummer's method, chemical vapor deposition, chemically reduced GO, mechanical cleavage of graphite, arc discharge of graphite, and thermal fusion have been deployed for the production of G-based materials. Additionally, important criteria such as biocompatibility, bio-toxicity, dispersibility, immunological compatibility, and inflammatory reactions of G-based structures need to be systematically assessed for additional clinical and biomedical appliances. Furthermore, surface properties (e.g., lateral dimension, charge, corona influence, surface structure, and oxygen content), concentration, detection strategies, and cell types are vital for anticancer activities of these structures. Notably, the efficient accumulation of anticancer drugs in tumor targets/tissues, controlled cellular uptake properties, tumor-targeted drug release behavior, and selective toxicity toward the cells are crucial criteria that need to be met for developing future anticancer G-based nanosystems. Herein, important challenges and future perspectives of cancer therapy using G- and GO-based nanosystems have been highlighted, and the recent advancements are deliberated.

Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

Photocatalysis is an advanced technique that transforms solar energy into sustainable fuels and oxidizes pollutants via the aid of semiconductor photocatalysts. The main scientific and technological challenges for effective photocatalysis are the stability, robustness, and efficiency of semiconductor photocatalysts. For practical applications, researchers are trying to develop highly efficient and stable photocatalysts. Since the literature is highly scattered, it is urgent to write a critical review that summarizes the state-of-the-art progress in the design of a variety of semiconductor composite photocatalysts for energy and environmental applications. Herein, a comprehensive review is presented that summarizes an overview, history, mechanism, advantages, and challenges of semiconductor photocatalysis. Further, the recent advancements in the design of heterostructure photocatalysts including alloy quantum dots based composites, carbon based composites including carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and graphene, covalent-organic frameworks based composites, metal based composites including metal carbides, metal halide perovskites, metal nitrides, metal oxides, metal phosphides, and metal sulfides, metal-organic frameworks based composites, plasmonic materials based composites and single atom based composites for CO₂ conversion, H₂ evolution, and pollutants oxidation are discussed elaborately. Finally, perspectives for further improvement in the design of composite materials for efficient photocatalysis are provided.

MXenes in photomedicine: Advances and prospects

MXenes and their related nanocomposites with superior physicochemical properties such as high surface area, ease of synthesis and functionalization, high drug loading capacity, collective therapy potentials, pH-triggered drug release behavior,...

A review on recent advances in the enrichment of glycopeptides and glycoproteins by liquid chromatographic methods: 2016-Present

Among various protein post-translational modifications (PTMs), glycosylation has received special attention due to its immense role in molecular interactions, cellular signal transduction, immune response, etc. Aberration in glycan moieties of a glycoprotein is associated with cancer, diabetes, and bacterial and viral infections. In biofluids (plasma, saliva, urine, milk, etc.), glycoproteins are low in abundance and are masked by the presence of high abundant proteins. Hence, prior to their identification using mass spectrometry methods, liquid chromatography (LC)-based approaches were widely used. A general enrichment strategy involves a protein digestion step, followed by LC-based enrichment and desorption of glycopeptides, and enzymatic excision of the glycans. The focus of this review article is to highlight the articles published since 2016 that dealt with different LC-based approaches for glycopeptide and glycoprotein enrichment. The preparation of stationary phases, their surface activation, and ligand immobilization strategies have been discussed in detail. Finally, the major developments and future trends in the field have been summarized.

Photocatalytic degradation of Eosin B dye in aqueous solution by cadmium oxide nanoparticles

Cadmium oxide (CdO) and potassium (K) doped CdO nanoparticles (NPs) were synthesized by the chemical co-precipitation method and were used as photocatalysts for the degradation of Eosin B dye. The X-ray diffraction results presented that the crystallite size of undoped CdO and K doped CdO NPs were 43.74 and 42.31 nm, respectively. The morphological study and percent composition of synthesized undoped CdO and K doped CdO NPs was done by scanning electron microscope and energy dispersive X-ray analysis. The formation of NPs was confirmed by Fourier transform infrared spectroscopy. The precursor decomposition to CdO after annealing at ∼500 °C was studied by thermogravimetric analysis. The undoped CdO and K doped CdO nanoparticles degraded about 80% and 90% of the dye, respectively, in 140 min. The maximum degradation efficiency of the dye was achieved at a pH of 4, dye initial concentration of 15 ppm, catalyst dose of 20 mg, and a temperature of 45 °C. The degradation efficiency observed for recovered undoped CdO and recovered doped CdO nanoparticles was found to be 63% and 77%, respectively.

Cerium based UiO-66 MOF as a multipollutant adsorbent for universal water purification

Herein, we demonstrate the use of cerium (Ce)-UiO-66 metal organic framework (MOF) for the removal of a variety of potentially toxic pollutants. The Ce-UiO-66 MOF, with similar framework topologies to Zr-UiO-66, has not been explored for its adsorptive properties in water remediation. The replacement of Zr metal center with Ce yields a MOF that can be synthesized in shorter durations with lesser energy consumptions and with excellent multipollutant adsorption properties. Further, the Ce-UiO-66 MOF was also studied for its adsorption abilities in the binary component system. Interestingly, the adsorbent showed higher adsorption capacities in the presence of other pollutants. Removal studies for other potentially toxic anionic and cationic dyes showed that the Ce-UiO-66 MOF has a wide range of contaminant removal abilities. Investigations of individual adsorption capacities revealed that the Ce-UiO-66 MOF has a maximum adsorption capacity of 793.7 mg/g for congo red (CR), 110 mg/g for methylene blue (MB), 66.1 mg/g for fluoride (F^-), 30 mg/g for Cr⁶⁺ and 485.4 mg/g for the pharmaceutical waste diclofenac sodium (DCF). To imply the practical applications of the Ce-UiO-66 MOF we have also demonstrated an adaptable filter that could separate all the potentially toxic pollutants.

Recent developments in physical, biological, chemical, and hybrid treatment techniques for removing emerging contaminants from wastewater

Emerging contaminants (ECs) in wastewater have recently attracted the attention of researchers as they pose significant risks to human health and wildlife. This paper presents the state-of-art technologies used to remove ECs from wastewater through a comprehensive review. It also highlights the challenges faced by existing EC removal technologies in wastewater treatment plants and provides future research directions. Many treatment technologies like biological, chemical, and physical approaches have been advanced for removing various ECs. However, currently, no individual technology can effectively remove ECs, whereas hybrid systems have often been found to be more efficient. A hybrid technique of ozonation accompanied by activated carbon was found significantly effective in removing some ECs, particularly pharmaceuticals and pesticides. Despite the lack of extensive research, nanotechnology may be a promising approach as nanomaterial incorporated technologies have shown potential in removing different contaminants from wastewater. Nevertheless, most existing technologies are highly energy and resource-intensive as well as costly to maintain and operate. Besides, most proposed advanced treatment technologies are yet to be evaluated for large-scale practicality. Complemented with techno-economic feasibility studies of the treatment techniques, comprehensive research and development are therefore necessary to achieve a full and effective removal of ECs by wastewater treatment plants.

Development of alginate@tin oxide-cobalt oxide nanocomposite based catalyst for the treatment of wastewater

In this study, tin oxide‑cobalt oxide nanocatalyst was prepared by a simple method, which grew in spherical particles with an average diameter of 30 nm. Tin oxide-cobalt oxide was further wrapped in alginate polymer hydrogel (Alg@tin oxide-cobalt oxide), and both materials were utilized as nanocatalysts for the catalytic transformation of different pollutants. Tin oxide-cobalt oxide and Alg@tin oxide-cobalt oxide nanocatalysts were tested for the catalytic reduction of 4-nitrophenol, congo red, methyl orange, methylene blue (MB) and potassium ferricyanide in which sodium borohydride was used as a reducing agent. Tin oxide-cobalt oxide and Alg@tin oxide-cobalt oxide nanocatalysts synergistically reduced MB in shorter time (2.0 and 4.0 min) compared to other dyes. The reduction conditions were optimized by changing different parameters. The rate constants for MB reduction were calculated and found to be 1.5714 min^-1 and 0.6033 min^-1 using tin oxide-cobalt oxide and Alg@tin oxide-cobalt oxide nanocatalysts, respectively. Implementing Alg@tin oxide-cobalt oxide nanocatalyst toward MB reduction in real samples proved its efficacy in sea and well water samples. The catalyst could be easily recovered, recycled and revealed a minimal loss of nanoparticles, which offering a competition and replacement with reputable commercial catalysts.

Recent advancements of spinel ferrite based binary nanocomposite photocatalysts in wastewater treatment

A lot of studies on spinel ferrites (MFe2O4, M = divalent metal ion) and their binary nanocomposites as photocatalysts in the decontamination of wastewater have been performed, because MFe2O4 nanoparticles are relatively stable, biocompatible and low-cost efficient photocatalyst. The separation of MFe2O4 photocatalyst is easy owing to its excellent magnetic behavior. With this background, the recent developments on photocatalytic performances of MFe2O4 based binary nanocomposites were comprehensively reviewed. Especially, a focus on MFe2O4/metal oxides, MFe2O4/carbon based materials, MFe2O4/polymers, MFe2O4/metal nanoparticles and MFe2O4/other compounds for the photocatalytic degradation of dyes, emerging contaminants and inorganic pollutants has been thoroughly given. The advantages of MFe2O4 based nanocomposites as photocatalysts were also discussed. In addition, the possible pathway of active free radical generation by these photocatalysts under visible and ultraviolet irradiation has been explained. A comparison of photocatalytic activities of MFe2O4 based binary nanocomposites with recent reports has been carried out. This review concludes that MFe2O4 based binary nanocomposites have potential capacity in water purification technology. Nevertheless, their practical utilization in water treatment plants still needs to be further studied.

Toxicity and remediation of pharmaceuticals and pesticides using metal oxides and carbon nanomaterials

The worldwide development of agriculture and industry has resulted in contamination of water bodies by pharmaceuticals, pesticides and other xenobiotics. Even at trace levels of few micrograms per liter in waters, these contaminants induce public health and environmental issues, thus calling for efficient removal methods such as adsorption. Recent adsorption techniques for wastewater treatment involve metal oxide compounds, e.g. Fe2O3, ZnO, Al2O3 and ZnO-MgO, and carbon-based materials such as graphene oxide, activated carbon, carbon nanotubes, and carbon/graphene quantum dots. Here, the small size of metal oxides and the presence various functional groups has allowed higher adsorption efficiencies. Moreover, carbon-based adsorbents exhibit unique properties such as high surface area, high porosity, easy functionalization, low price, and high surface reactivity. Here we review the cytotoxic effects of pharmaceutical drugs and pesticides in terms of human risk and ecotoxicology. We also present remediation techniques involving adsorption on metal oxides and carbon-based materials.

Carbon nanotubes mitigate copper-oxide nanoparticles-induced inhibition to acidogenic metabolism of Propionibacterium acidipropionici by regulating carbon source utilization

This study demonstrated that multi-walled carbon nanotubes (MWCNTs) could mitigate copper oxide nanoparticles (CuO NPs)-induced inhibition to acidogenic metabolism of propionic acid bacteria (i.e., Propionibacterium acidipropionici) by regulating carbon source utilization. CuO NPs severely inhibited the growth of P. acidipropionici, damaged its cell membrane, and down-regulated gene expressions and enzyme activities involved in acidogenic metabolism, thereby decreasing propionate production. However, although MWCNTs had a slightly negative impact on the growth and cell membrane, the gene expressions and catalytic activities were enhanced (glycolysis and pyruvate metabolism), resulting in the improved propionate production. Additionally, the gene expressions and catalytic activities of key enzymes (e.g., tpiA, pgk, PK, OTTAC, etc.) related to acidogenic metabolism were also enhanced by the co-existence of both nanomaterials, thereby promoting propionate production towards P. acidipropionici. This work demonstrated that the presence of MWCNTs could affect the inhibition of CuO NPs to fermentation processes via regulating carbon source utilization.

Ag@ZnO/MWCNT ternary nanocomposite as an active and stable catalyst for the 4-nitrophenol reduction in water

The nitroaromatic compounds, known as organic pollutants, have arising attention due to their carcinogenic character, highly dangerous to human health. In this work, the Ag@ZnO/MWCNT ternary nanocomposite synthesized via conjugation of sonochemical and solvothermal treatments manifests high performance in the reduction of 4-nitrophenol in the aqueous media (TOF value of 246 min^-1μmol metal^-1). The incorporation of MWCNT onto the nanocomposite structure favored the reusing of the catalysts even after eight consecutive catalytic runs without catalysts cleaning nor product removal. Obtained samples were characterized by XRD, TEM, UV-vis, Raman and FTIR spectroscopies. It was found that ultrasonic treatment at relatively moderate conditions leads to functionalization of MWCNT, the appearance of C=C and OH groups and change of electronic properties of Ag@ZnO/MWCNT composite which provide its stable material dispersion in aqueous solution and high catalytic performance in the 4-nitrophenol reduction. This technique may be effectively applied for the functionalization of carbon including materials for their usage in an aqueous media.

Greenness of magnetic nanomaterials in miniaturized extraction techniques: A review

Green analytical chemistry principles should be followed, as much as possible, and particularly during the development of analytical sample preparation methods. In the past few years, outstanding materials such as ionic liquids, metal-organic frameworks, carbonaceous materials, molecularly imprinted materials, and many others, have been introduced in a wide variety of miniaturized techniques in order to reduce the amount of solvents and sorbents required during the analytical sample preparation step while pursuing more efficient extraction methods. Among them, magnetic nanomaterials (MNMs) have gained special attention due to their versatile properties. Mainly, their ability to be separated from the sample matrix using an external magnetic field (thus enormously simplifying the entire process) and their easy combination with other materials, which implies the inclusion of a countless number of different functionalities, highly specific in some cases. Therefore, MNMs can be used as sorbents or as magnetic support for other materials which do not have magnetic properties, the latter permiting their combination with novel materials. The greenness of these magnetic sorbents in miniaturized extractions techniques is generally demonstrated in terms of their ease of separation and amount of sorbent required, while the nature of the material itself is left unnoticed. However, the synthesis of MNMs is not always as green as their applications, and the resulting MNMs are not always as safe as desired. Is the analytical sample preparation field ready for using green magnetic nanomaterials? This review offers an overview, from a green analytical chemistry perspective, of the current state of the use of MNMs as sorbents in microextraction strategies, their preparation, and the analytical performance offered, together with a critical discussion on where efforts should go.

Recent Developments in the Application of Nanomaterials in Agroecosystems

Nanotechnology implies the scientific research, development, and manufacture, along with processing, of materials and structures on a nano scale. Presently, the contamination of metalloids and metals in the soil has gained substantial attention. The consolidation of nanomaterials and plants in ecological management has received considerable research attention because certain nanomaterials could enhance plant seed germination and entire plant growth. Conversely, when the nanomaterial concentration is not properly controlled, toxicity will definitely develop. This paper discusses the role of nanomaterials as: (1) nano-pesticides (for improving the plant resistance against the biotic stress); and (2) nano-fertilizers (for promoting the plant growth by providing vital nutrients). This review analyzes the potential usages of nanomaterials in agroecosystem. In addition, the adverse effects of nanomaterials on soil organisms are discussed. We mostly examine the beneficial effects of nanomaterials such as nano-zerovalent iron, iron oxide, titanium dioxide, nano-hydroxyapatite, carbon nanotubes, and silver- and copper-based nanomaterials. Some nanomaterials can affect the growth, survival, and reproduction of soil organisms. A change from testing/using nanomaterials in plants for developing nanomaterials depending on agricultural requirements would be an important phase in the utilization of nanomaterials in sustainable agriculture. Conversely, the transport as well as ecological toxicity of nanomaterials should be seriously examined for guaranteeing its benign usage in agriculture.