Engineered two-dimensional nanomaterials: an emerging paradigm for water purification and monitoring

Adsorption behavior of different cresols on bismuthene: a DFT study

Phenolic compounds present in wastewater were utilized for first-principle calculations based on DFT to observe adsorption effects. Results indicate that bismuthene exhibits different adsorption characteristics for different compounds. Following the adsorption process, the aromatic ring remains in the same plane, while CH3 and OH groups move upward, causing slight changes in the molecules' overall position. The calculated results show that bisphenol A has the least atomic distance (4.00 Å) from the bismuthene surface and the highest adsorption energy value (12.8509 eV), indicating the stability and smoothness of the adsorption process. The electronic properties results reveal that phenolic compounds exhibit overlapping peaks at a distance from the Fermi level, describing the stability of the adsorption system. Additionally, the charge transfer results mirror the adsorption energy calculation results, showing that the bisphenol A adsorption system accepts a greater amount of (-0.116e) charge from the bismuthene surface, demonstrating a strong adsorption effect.

Recent Progress on Synthesis and Properties of Black Phosphorus and Phosphorene As New-Age Nanomaterials for Water Decontamination

Concerted efforts have been made in recent years to find solutions to water and wastewater treatment challenges and eliminate the difficulties associated with treatment methods. Various techniques are used to ensure the recycling and reuse of water resources. Owing to their excellent chemical, physical, and biological properties, nanomaterials play an important role when integrated into water/wastewater treatment technologies. Black phosphorus (BP) is a potential nanomaterial candidate for water and wastewater treatment, especially its monolayer 2D derivative called phosphorene. Phosphorene offers relative adjustability in its direct bandgap, high charge carrier mobility, and improved in-plane anisotropy compared to the most extensively studied 2D nanomaterials. In this study, we examined the physical and chemical characteristics and synthetic processes of BP and phosphorene. We provide an overview of the latest advancements in the main applications of BP and phosphorene in water/wastewater treatment, which are categorized as photocatalytic, adsorption, and membrane filtration processes. Additionally, we explore the existing difficulties in the integration of BP and phosphorene into water/wastewater treatment technologies and prospects for future research in this field. In summary, this review highlights the ongoing necessity for significant research efforts on the integration of BP and phosphorene in water and wastewater applications.

Potential application of bismuth oxyiodide (BiOI) when it meets light

Bismuth oxyiodide (BiOI) is a kind of typical two-dimensional (2D) material that has been increasingly developed alongside other 2D materials such as graphene, MXenes, and transition-metal dichalcogenide. However, its potential applications have not been widely whispered compared to those of other 2D materials. Using its distinctive properties, BiOI can be used for various applications, especially when it meets sunlight and other light-related electromagnetic waves. In this present review, we discuss the developments of BiOI and challenges in the applications for photodetector and light-assisted sensors, photovoltaic devices, optoelectronic logic devices, as well as photocatalysts. We start the discussion with a basic understanding and development of BiOI, crystal structure, and its properties. The synthesis and further development, such as green synthesis and its challenges in the synthesis-suited industry, as well as device integration, are also explained together with a plausible strategy to enhance the feasibility of BiOI for those various applications. We believe that the provided discussion and perspectives will not only promote BiOI to be one of the highly considered 2D materials but can also assist recent graduates in any materials science discipline and inform the senior scientists and industrial-based stakeholders of the latest advances in bismuth oxide and mixed-anion compounds.

Polycaprolactone/polyacrylic acid/graphene oxide composite nanofibers as a highly efficient sorbent to remove lead toxic metal from drinking water and apple juice

Due to the characteristics of electrospun nanofibers (NFs), they are considered a suitable substrate for the adsorption and removal of heavy metals. Electrospun nanofibers are prepared based on optimized polycaprolactone (PCL, 12 wt%) and polyacrylic acid (PAA, 1 wt%) polymers loaded with graphene oxide nanoparticles (GO NPs, 1 wt%). The morphological, molecular interactions, crystallinity, thermal, hydrophobicity, and biocompatibility properties of NFs are characterized by spectroscopy (scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis), contact angle, and MTT tests. Finally, the adsorption efficacy of NFs to remove lead (Pb2+) from water and apple juice samples was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). The average diameter for PCL, PCL/PAA, and PCL/PAA/GO NFs was 137, 500, and 216 nm, respectively. Additionally, the contact angle for PCL, PCL/PAA, and PCL/PAA/GO NFs was obtained at 74.32º, 91.98º, and 94.59º, respectively. The cytotoxicity test has shown non-toxicity for fabricated NFs against the HUVEC endothelial cell line by more than 80% survival during 72 h. Under optimum conditions including pH (= 6), temperature (25 °C), Pb concentration (25 to 50 mg/L), and time (15 to 30 min), the adsorption efficiency was generally between 80 and 97%. The adsorption isotherm model of PCL/PAA/GO NFs in the adsorption of lead metal follows the Langmuir model, and the reaction kinetics follow the pseudo-second-order. PCL/PA/GO NFs have shown adsorption of over 80% in four consecutive cycles. The adsorption efficacy of NFs to remove Pb in apple juice has reached 76%. It is appropriate and useful to use these nanofibers as a high-efficiency adsorbent in water and food systems based on an analysis of their adsorption properties and how well they work.

Ligand-Directed Shape Reconfiguration in Inorganic Materials

Polymer elastomers with reversible shape-changing capability have led to significant development of artificial muscles, functional devices, and soft robots. By contrast, reversible shape transformation of inorganic nanoparticles is notoriously challenging due to their relatively rigid lattice structure. Here, the authors demonstrate the synthesis of shape-changing nanoparticles via an asymmetrical surface functionalization process. Various ligands are investigated, revealing the essential role of steric hindrance from the functional groups. By controlling the unbalanced structural hindrance on the surface, the as-prepared clay nanoparticles can transform their shape in a fast, facile, and reversible manner. In addition, such flexible morphology-controlled mechanism provides a platform for developing self-propelled shape-shifting nanocollectors. Owing to the ion-exchanging capability of clay, these self-propelled nanoswimmers (NS) are able to autonomously adsorb rare earth elements with ultralow concentration, indicating the feasibility of using naturally occurring materials for self-powered nanomachine.

Theoretical design of transition metal-doped oxo-triarylmethyl as a disposable platform for adsorption of ibuprofen

Emerging environmental contaminants have become a crucial environmental issue because of the highly toxic effluents emitted by factories. Ibuprofen (IBP), as a typical anti-inflammatory drug, is frequently detected in water sources. Therefore, its removal using various adsorbents has drawn great interest. Herein, the structural, electronic, energetic, and optical properties of pristine oxo-triarylmethyl (oxTAM) and transition metal-doped oxo-triarylmethyl (TM@oxTAM, TM = Sc, Ti, V, Cr, and Mn) for adsorption of the IBU drug were investigated using density functional theory (DFT) calculations implemented in Gaussian and VASP codes. Frontier molecular orbital (FMO), density of states (DOS), and electronic band structure results demonstrated that transition metal-doped oxTAM causes a significant reduction in the energy band gap (Eg) value of pristine oxTAM, with the highest decrease (30.14 %) in the case of Mn@oxTAM. It was found that transition metal doping onto oxTAM leads to an increase in the adsorption energies (1.20-2.64 eV) and charge density between transition metal and IBU. Natural bond orbital (NBO) analysis revealed that charge was effectively transferred from the IBU towards the transition metal, which was further analyzed by charge decomposition analysis (CDA). Furthermore, quantum theory of atoms in molecules (QTAIM), interaction region indicator (IRI), electron localization function (ELF), and radial distribution function (RDF) analyses revealed that the IBU is adsorbed on the Sc@oxTAM surface via covalent interactions, while electrostatic with partially covalent interactions are dominated in other IBU/TM@oxTAM complexes. The results suggest that TM doping on the oxTAM provides a new insight for developing photocatalyst-based covalent organic frameworks (COFs) to remove emerging pollutants in wastewater.

Synthesis of two-dimensional triazine covalent organic frameworks at ambient conditions to detect and remove water pollutants

Synthesis of fully triazine frameworks (C3N3) by metal catalyzed reactions at high temperatures results in carbonized and less-defined structures. Moreover, metal impurities affect the physicochemical, optical and electrical properties of the synthesized frameworks, dramatically. In this work, two-dimensional C3N3 (2DC3N3) has been synthesized by in situ catalyst-free copolymerization of sodium cyanide and cyanuric chloride, as cheap and commercially available precursors, at ambient conditions on gram scale. Reaction between sodium cyanide and cyanuric chloride resulted in electron-poor polyfunctional intermediates, which converted to 2DC3N3 with several hundred micrometers lateral size at ambient conditions upon [2 + 2+2] cyclotrimerization. 2DC3N3 sheets, in bulk and individually, showed strong fluorescence with 63% quantum yield and sensitive to small objects such as dyes and metal ions. The sensitivity of 2DC3N3 emission to foreign objects was used to detect low concentration of water impurities. Due to the high negative surface charge (-37.7 mV) and dispersion in aqueous solutions, they demonstrated a high potential to remove positively charged dyes from water, exemplified by excellent removal efficiency (>99%) for methylene blue. Taking advantage of the straightforward production and strong interactions with dyes and metal ions, 2DC3N3 was integrated in filters and used for the fast detection and efficient removal of water impurities.

Hybrid Data-Driven Discovery of High-Performance Silver Selenide-Based Thermoelectric Composites

Optimizing material compositions often enhances thermoelectric performances. However, the large selection of possible base elements and dopants results in a vast composition design space that is too large to systematically search using solely domain knowledge. To address this challenge, a hybrid data-driven strategy that integrates Bayesian optimization (BO) and Gaussian process regression (GPR) is proposed to optimize the composition of five elements (Ag, Se, S, Cu, and Te) in AgSe-based thermoelectric materials. Data is collected from the literature to provide prior knowledge for the initial GPR model, which is updated by actively collected experimental data during the iteration between BO and experiments. Within seven iterations, the optimized AgSe-based materials prepared using a simple high-throughput ink mixing and blade coating method deliver a high power factor of 2100 µW m-1 K-2 , which is a 75% improvement from the baseline composite (nominal composition of Ag2 Se1 ). The success of this study provides opportunities to generalize the demonstrated active machine learning technique to accelerate the development and optimization of a wide range of material systems with reduced experimental trials.

Low Temperature Chemoresistive Oxygen Sensors Based on Titanium-Containing Ti2CTx and Ti3C2Tx MXenes

The chemoresistive properties of multilayer titanium-containing Ti₂CT_x and Ti₃C₂T_x MXenes, synthesized by etching the corresponding MAX phases with NaF solution in hydrochloric acid, and the composites based on them, obtained by partial oxidation directly in a sensor cell in an air flow at 150 °C, were studied. Significant differences were observed for the initial MXenes, both in microstructure and in the composition of surface functional groups, as well as in gas sensitivity. For single Ti₂CT_x and Ti₃C₂T_x MXenes, significant responses to oxygen and ammonia were observed. For their partial oxidation at a moderate temperature of 150 °C, a high humidity sensitivity (T, RH = 55%) is observed for Ti₂CT_x and a high and selective response to oxygen for Ti₃C₂T_x at 125 °C (RH = 0%). Overall, these titanium-containing MXenes and composites based on them are considered promising as receptor materials for low temperature oxygen sensors.

Achieving fast interfacial solar vapor generation and aqueous acid purification using Ti3C2Tx MXene/PANI non-woven fabrics

Acid rain is a worldwide problem because of the emission of acidic gases into the atmosphere, leading to the acidification of first-order streams and aggravation of fresh water shortage. Therefore, it is of great importance to develop an environmentally friendly method for removing acid from water. Herein, an advanced technology that can achieve aqueous acid purification using solar energy is realized with Ti₃C₂T_x MXene/polyaniline (PANI) hybrid non-woven fabrics (MPs) through interfacial solar vapor generation, with PANI acting as an acid absorber through the doping process. Benefiting from the porous structure and crumpled micro-surface of MPs, a high evaporation rate of 2.65 kg m^-2 h^-1 with an efficiency of 93.7% can be achieved under one-sun illumination. Moreover, MPs present an even higher evaporation rate of 2.83 kg m^-2 h^-1 in high concentration aqueous acid and can generate clean water with a pH higher than 6.5. More importantly, thanks to the unique reversible doping process of PANI, when used as an aqueous acid purifier, MPs show good stability and reusability after dedoping. Our work sheds light on an efficient strategy for dealing with aqueous acid and acid rain.

Recent advances in emerging application of functional materials in sample pretreatment methods for liquid chromatography-mass spectrometry analysis of plant growth regulators: A mini-review

Plant growth regulators (PGRs) are a class of small molecular compounds, which can remarkably affect the physiological process of plants. The complex plant matrix along with a wide polarity range and unstable chemical properties of PGRs hinder their trace analysis. In order to obtain a reliable and accurate result, a sample pretreatment process must be carried out, including eliminating the interference of the matrix effect and pre-concentrating the analytes. In recent years, the research of functional materials in sample pretreatment has experienced rapid growth. This review comprehensively overviews recent development in functional materials covering one-dimensional materials, two-dimensional materials, and three-dimensional materials applied in the pretreatment of PGRs before liquid chromatography-mass spectrometry (LC-MS) analysis. Besides, the advantages and limitations of the above functionalized enrichment materials are discussed, and their future trends have been prospected. The work could be helpful to bring new insights for researchers engaged in functional materials in sample pretreatment of PGRs based on LC-MS.

Microreactor-based micro/nanomaterials: fabrication, advances, and outlook

Micro/nanomaterials are widely used in optoelectronics, environmental materials, bioimaging, agricultural industries, and drug delivery owing to their marvelous features, such as quantum tunneling, size, surface and boundary, and Coulomb blockade effects. Recently, microreactor technology has opened up broad prospects for green and sustainable chemical synthesis as a powerful tool for process intensification and microscale manipulation. This review focuses on recent progress in the microreactor synthesis of micro/nanomaterials. First, the fabrication and design principles of existing microreactors for producing micro/nanomaterials are summarized and classified. Afterwards, typical examples are shown to demonstrate the fabrication of micro/nanomaterials, including metal nanoparticles, inorganic nonmetallic nanoparticles, organic nanoparticles, Janus particles, and MOFs. Finally, the future research prospects and key issues of microreactor-based micro/nanomaterials are discussed. In short, microreactors provide new ideas and methods for the synthesis of micro/nanomaterials, which have huge potential and inestimable possibilities in large-scale production and scientific research.

MXenes Antibacterial Properties and Applications: A Review and Perspective

The mutations of bacteria due to the excessive use of antibiotics, and generation of antibiotic-resistant bacteria have made the development of new antibacterial compounds a necessity. MXenes have emerged as biocompatible transition metal carbide structures with extensive biomedical applications. This is related to the MXenes' unique combination of properties, including multifarious elemental compositions, 2D-layered structure, large surface area, abundant surface terminations, and excellent photothermal and photoelectronic properties. The focus of this review is the antibacterial application of MXenes, which has attracted the attention of researchers since 2016. A quick overview of the synthesis strategies of MXenes is provided and then summarizes the effect of various factors (including structural properties, optical properties, surface charges, flake size, and dispersibility) on the biocidal activity of MXenes. The main mechanisms for deactivating bacteria by MXenes are discussed in detail including rupturing of the bacterial membrane by sharp edges of MXenes nanoflakes, generating the reactive oxygen species (ROS), and photothermal deactivating of bacteria. Hybridization of MXenes with other organic and inorganic materials can result in materials with improved biocidal activities for different applications such as wound dressings and water purification. Finally, the challenges and perspectives of MXene nanomaterials as biocidal agents are presented.

Two dimensional (2D) materials and biomaterials for water desalination; structure, properties, and recent advances

BACKGROUND

An efficient solution to the global freshwater dilemma is desalination. MXene, Molybdenum Disulfide (MoS₂), Graphene Oxide, Hexagonal Boron Nitride, and Phosphorene are just a few examples of two-dimensional (2D) materials that have shown considerable promise in the development of 2D materials for water desalination. However, other promising materials for desalinating water are biomaterials. The benefits of bio-materials are their wide distribution, lack of toxicity, and superior capacity for water desalination.

METHODS

For the rational use of water and the advancement of sustainable development, it is of the utmost importance to research 2D-dimensional materials and biomaterials that are effective for water desalination. The scientific community has concentrated on wastewater remediation using bio-derived materials, such as nanocellulose, chitosan, bio-char, bark, and activated charcoal generated from plant sources, among the various endeavors to enhance access to clean water. Moreover, the 2D-materials and biomaterials may have ushered in a new age in the production of desalination materials and created a promising future.

RESULTS

The present review article focuses on and reviews the progress of 2D materials and biomaterials for water desalination. Their properties, surface, and structure, combined with water desalination applications, are highlighted. Further, the practicability and potential future directions of 2D materials and biomaterials are proposed. Thus, the current work provides information and discernments for developing novel 2D materials and biomaterials for wastewater desalination. Moreover, it aims to promote the contribution and advancement of materials for water desalination, fabrication, and industrial production.

Modification of Liquid Separation Membranes Using Multidimensional Nanomaterials: Revealing the Roles of Dimension Based on Classical Titanium Dioxide

Membrane technology has become increasingly popular and important for separation processes in industries, as well as for desalination and wastewater treatment. Over the last decade, the merger of nanotechnology and membrane technology in the development of nanocomposite membranes has emerged as a rapidly expanding research area. The key motivation driving the development of nanocomposite membranes is the pursuit of high-performance liquid separation membranes that can address the bottlenecks of conventionally used polymeric membranes. Nanostructured materials in the form of zero to three-dimensions exhibit unique dimension-dependent morphology and topology that have triggered considerable attention in various fields. While the surface hydrophilicity, antibacterial, and photocatalytic properties of TiO₂ are particularly attractive for liquid separation membranes, the geometry-dependent properties of the nanocomposite membrane can be further fine-tuned by selecting the nanostructures with the right dimension. This review aims to provide an overview and comments on the state-of-the-art modifications of liquid separation membrane using TiO₂ as a classical example of multidimensional nanomaterials. The performances of TiO₂-incorporated nanocomposite membranes are discussed with attention placed on the special features rendered by their structures and dimensions. The innovations and breakthroughs made in the synthesis and modifications of structure-controlled TiO₂ and its composites have enabled fascinating and advantageous properties for the development of high-performance nanocomposite membranes for liquid separation.

Carbon Dots Mediated In Situ Confined Growth of Bi Clusters on g-C3 N4 Nanomeshes for Boosting Plasma-Assisted Photoreduction of CO2

Synthesis of high-efficiency, cost-effective, and stable photocatalysts has long been a priority for sustainable photocatalytic CO₂ reduction reactions (CRR), given its importance in achieving carbon neutrality goals under the new development philosophy. Fundamentally, the sluggish interface charge transportation and poor selectivity of products remain a challenge in the CRR progress. Herein, this work unveils a synergistic effect between high-density monodispersed Bi/carbon dots (CDs) and ultrathin graphite phase carbon nitride (g-C₃ N₄ ) nanomeshes for plasma-assisted photocatalytic CRR. The optimal g-C₃ N₄ /Bi/CDs heterojunction displays a high selectivity of 98% for CO production with a yield up to 22.7 µmol g^-1 without any sacrificial agent. The in situ confined growth of plasmonic Bi clusters favors the production of more hot carriers and improves the conductivity of g-C₃ N₄ . Meanwhile, a built-in electric field driving force modulates the directional injection photogenerated holes from plasmonic Bi clusters and g-C₃ N₄ photosensitive units to adjacent CDs reservoirs, thus promoting the rapid separation and oriented transfer in the CRR process. This work sheds light on the mechanism of plasma-assisted photocatalytic CRR and provides a pathway for designing highly efficient plasma-involved photocatalysts.

Robust and multifunctional natural polyphenolic composites for water remediation

The scarcity of clean water has become a global environmental problem which constrains the development of public health, economy, and sustainability. In recent years, natural polyphenols have drawn increasing interests as promising platforms towards diverse water remediation composites and devices, owing to their abundant and renewable resource in nature, highly active surface chemistry, and multifunctionality. This review aims to summarize the most recent advances and highlights of natural polyphenol-based composite materials (e.g., nanofibers, membranes, particles, and hydrogels) for water remediation, by focusing on their structural and functional features, as well as their diversified applications including membrane filtration, solar distillation, adsorption, advanced oxidation processes, and disinfection. Finally, the future challenges in this field are also prospected. It is anticipated that this review will provide new opportunities towards the future development of natural polyphenols and other kinds of naturally occurring molecules in water purification applications.

Recent trends and advancements in nanoporous membranes for water purification

When it comes to electrocatalysis, the creation of nanodevices, the research of energy and the environment, and diagnostics, nanoporous materials are an asset. Nanoporous membranes, which can be used to filter water, have recently been the subject of new research and are summarized in this review. These membranes are used to remove salts and metallic ions from the water following an analysis of several nanoporous membrane types and production procedures. Demonstrations and discussions of these membrane systems are then conducted. Nanoporous membranes can be used to filter water, according to the conclusions of this study, which will help readers better grasp how they work. As a result, novel water purification nanoporous compounds that are easy to manufacture, inexpensive, and effective will be developed. Merits and demerits of nanoporous membrane for water treatment and its advancements in purification were discussed.

Recent Progress in Fabrication and Application of BN Nanostructures and BN-Based Nanohybrids

Due to its unique physical, chemical, and mechanical properties, such as a low specific density, large specific surface area, excellent thermal stability, oxidation resistance, low friction, good dispersion stability, enhanced adsorbing capacity, large interlayer shear force, and wide bandgap, hexagonal boron nitride (h-BN) nanostructures are of great interest in many fields. These include, but are not limited to, (i) heterogeneous catalysts, (ii) promising nanocarriers for targeted drug delivery to tumor cells and nanoparticles containing therapeutic agents to fight bacterial and fungal infections, (iii) reinforcing phases in metal, ceramics, and polymer matrix composites, (iv) additives to liquid lubricants, (v) substrates for surface enhanced Raman spectroscopy, (vi) agents for boron neutron capture therapy, (vii) water purifiers, (viii) gas and biological sensors, and (ix) quantum dots, single photon emitters, and heterostructures for electronic, plasmonic, optical, optoelectronic, semiconductor, and magnetic devices. All of these areas are developing rapidly. Thus, the goal of this review is to analyze the critical mass of knowledge and the current state-of-the-art in the field of BN-based nanomaterial fabrication and application based on their amazing properties.

A novel sensor for visual and selective detection of Hg2+ based on functionalized doped quantum dots

In this paper, a novel analytical platform for the visual, sensitive and reliable analysis of mercury ions (Hg²⁺) is fabricated based on functionalized doped quantum dots. We synthesized a new specific nano-material, zinc dithiothreitol combined with graphene quantum dots (ZnNCs-NGQDs), by a simple and convenient method which, as an efficient luminophore, was then applied to construct an electrochemiluminescence (ECL) system for the first time. Under optimized conditions, the ECL sensor showed an excellent response for Hg²⁺ in the linear range of 1.0 mM to 10 pM, with a low detection limit of 3 pM. Moreover, the proposed method demonstrated satisfactory selectivity, stability and acceptable reproducibility for the detection of Hg²⁺. The recovery of tap water and lake water samples ranged from 96% to 105%, indicating the potential applicability of the proposed method for monitoring environmental water samples. Meanwhile, visual attempts for mercury ion detection by using doped quantum dots have also obtained satisfactory results. Importantly, our research revealed a viable method for improving the sensitivity and convenience of target studies in sensing fields derived from functional material design.

Low-cost novel nano-constructed granite composites for removal of hazardous Terasil dye from wastewater

The hazardous dyes on mixing with water resources are affecting many life forms. Granite stone is popular worldwide for decorating floors, making other forms of decorative materials and items. Granite stone powder waste can be obtained free of cost from marble factories as factories spend on the disposal of this waste. In the present study, novel granite stone powder waste composite has been prepared and utilized for the effective removal of Terasil dye. Two types of granite including gray granite and white granite were used in pure, calcinized, and chemically modified forms. Freundlich adsorption isotherm model best explained the adsorption mechanism of dye removal using granite composites as compared to other adsorption isothermal models. Characterization techniques like scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were used for the determination of morphological features and functional groups of granite composites. The obtained results were statistically analyzed using analysis of variance (ANOVA) along with the post hoc Tukey test. An extraordinarily high Terasil dye uptake capacity (more than 400 mg/g) was exhibited by granite composites prepared using sodium metasilicate. The synthesized novel nano-constructed composites provided a viable strategy as compared to the pure granite stone for dye removal from wastewater water.

Absolute film separation of dyes/salts and emulsions with a superhigh water permeance through graded nanofluidic channels

The development of multifunctional films with a high permeability has been of great concern for effective separation of complex aqueous contaminants, especially in the face of zero or near-zero release regulations. Inspired by the natural structure of sandy soils, polydopamine-wrapped/connected polypyrrole sub-micron spheres (PPSM) were closely packed onto a polypyrrole-coated bacterial cellulose (PBC) support, by which a new two-layered PBC/PPSM composite film formed with graded nanofluidic channels. Interestingly, after being soaked in complex water environments of ethanol, acids, bases, heat, cold and high salinity, or else bended/folded for more than 10 times, the structure and performance of this film still stayed the same, validating its high structural stability and flexibility. Even in a high salinity environment over seawater, this PBC/PPSM film exhibits a dye-separation capacity of almost 100% with a surprisingly superhigh water permeance over one thousand L h^-1 m^-2 bar^-1, one or two magnitudes higher than that of the related films reported in the literature. Meanwhile, the ability for effective oil-water-separation was also validated. Besides the superhydrophilicity and underwater superoleophobicity, the synapse-like-structure-induced graded nanofluidic channels are also proposed to play a key role for rendering such an outstandingly comprehensive performance of the film by greatly overcoming fluid resistance and reducing permeation viscosity.

Controlled Synthesis of Perforated Oxide Nanosheets with High Density Nanopores Showing Superior Water Purification Performance

A method for creating genuine nanopores in high area density on monolayer two-dimensional (2D) metallic oxides has been developed. By use of the strong reduction capability of hydroiodic acid, active metal ions, such as Fe^III and Co^III, in 2D oxide nanosheets can be reduced to a divalent charge state (2+). The selective removal of FeO₂ and CoO₂ metal oxide units from the framework can be tuned to produce pores in a range of 1-4 nm. By monitoring of the redox reaction kinetics, the pore area density can be also tuned from ∼0.9 × 10⁴ to ∼3.3 × 10⁵ μm^-2. The universality of this method to produce much smaller pores and higher area density than the previously reported ones has been proven in different oxide nanosheets. To demonstrate their potential applications, ultrasmall metal organic framework particles were grown inside the pores of perforated titania oxide nanosheets. The optimized hybrid film showed ∼100% rejection of methylene blue (MB) from the water. Its water permeance reached 4260 L m^-2 h^-1 bar^-1, which is 1-3 orders of that for reported 2D membranes with good MB rejections.

Zwitterionic Graphene Quantum Dots to Stabilize Pickering Emulsions for Controlled-Release Applications

Graphene quantum dots (GQDs) are a subset of the nanocarbon material family, which promise a wide spectrum of applications. Herein, we describe amphiphilic graphene quantum dots with zwitterionic features (ZGQDs), which are able to stabilize the oil/water interface. ZGQDs were fabricated by modifying GQDs with tertiary amine groups and alkyl groups. Moreover, the blocking and unblocking behavior of ZGQDs at the oil/water interface could be tuned by adjusting pH values in the aqueous phase. It would provide a flexible and adjustable method to manipulate interfacial properties of ZGQDs, which enabled a switchable molecular diffusion through a fluid-fluid interface. ZGQDs have shown well-controlled interfacial behavior under different pH conditions, indicating great potential for applications in controlled molecular diffusion based on nanoparticles demonstrated in this work.

Plasmonic Gold Nanoparticles Stain Hydrogels for the Portable and High-Throughput Monitoring of Mercury Ions

The hybrid of l-cysteine and agarose can reduce HAuCl₄ and support the rapid growth of plasmonic gold nanoparticles (Au NPs) in the hydrogel phase. The l-cysteine-doped agarose hydrogel (C-AGH) not only offers the substrate the capacity to reduce Au(III) ions but also stabilizes and precisely modulates the in situ grown Au NPs with high repeatability, easy operation, and anti-interference performance. Herein, before the incubation of HAuCl₄, the improved hydrogel is preincubated in the aqueous solution containing mercury ions, and the cysteine can specifically conjugate with mercury via the thiol groups. Subsequently, the responsive allochroic bands from dark blue to red can be identified in the solid hydrogel after the incubation of HAuCl₄, which is attributed to the formation of regulated Au-Hg nanoamalgams. As a proof-of-concept, toxic Hg²⁺ ions are exploited as targets for constructing novel sensing assays based on the improved C-AGH protocol. Based on naked-eye recognition, Hg²⁺ could be rapidly and simply measured. Additionally, the high-throughput and trace analysis with a low limit of detection (3.7 nM) is performed using a microplate reader. On the basis of the filtering technique and remodeling of hydrogels, C-AGH working as the filtering membrane can even achieve the integration of enrichment and measurement with enhanced sensitivity. Significantly, the strategy of using an allochroic hydrogel with the staining of Au NPs can promote the rapid and primary assessment of water quality in environmental analysis.

Size-Dependent Cytotoxic and Molecular Study of the Use of Gold Nanoparticles against Liver Cancer Cells

The size of nanomaterials influences physicochemical parameters, and variations in the size of nanomaterials can have a significant effect on their biological activities in cells. Due to the potential applicability of nanoparticles (NPs), the current work was designed to carry out a size-dependent study of gold nanoparticles (GNPs) in different dimensions, synthesized via a colloidal solution process. Three dissimilar-sized GNPs, GNPs-1 (10–15 nm), GNPs-2 (20–30 nm), and GNPs-3 (45 nm), were prepared and characterized via transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), hydrodynamic size, zeta potential, and UV-visible spectroscopy, and applied against liver cancer (HepG2) cells. Various concentrations of GNPs (1, 2, 5, 10, 50, and 100 µg/mL) were applied against the HepG2 cancer cells to assess the percentage of cell viability via MTT and NRU assays; reactive oxygen species (ROS) generation was also used. ROS generation was increased by 194%, 164%, and 153% for GNPs-1, GNPs-2, and GNPs-3, respectively, in the HepG2 cells. The quantitative polymerase chain reaction (qPCR) data for the HepG2 cells showed up-regulation in gene expression of apoptotic genes (Bax, p53, and caspase-3) when exposed to the different-sized GNPs, and defined their respective roles. Based on the results, it was concluded that GNPs of different sizes have the potential to induce cancer cell death.

Glutathione modulated fluorescence quenching of sulfur quantum dots by Cu2O nanoparticles for sensitive assay

Sulfur quantum dots (S-dots) show great potential for applications in various field, due to their favorable biocompatibility, high stability, and antibacterial properties. However, the use of S-dots in chemical sensing is limited by the lack of functional groups on the surface. In this work, a fluorescence glutathione (GSH) assay is developed based on the GSH modulated quenching effect of Cu₂O nanoparticles (NP) on S-dots. The fluorescence of S-dots is effectively quenched after forming complex with Cu₂O NP through a static quenching effect (SQE). Introducing of GSH can trigger the decomposition of Cu₂O NP into GSH-Cu(I) complex, which leads to the weaken of SQE and the partial recover of the fluorescence. The intensity of recovered fluorescence shows a positive correlation with the concentration of GSH in the concentration range of 20 to 500 μM. The fluorescence GSH assay shows excellent selectivity and robustness towards various interferences and high concentration salt, which endow the successful detection of GSH in human blood sample. The presented results provide a new door for the design of fluorescence assays, which also provides a platform for the applications in nanomedicine and environmental science.

Phenolic compounds degradation: Insight into the role and evidence of oxygen vacancy defects engineering on nanomaterials

Oxygen vacancy as a typical point defect has incited substantial interest in photocatalysis due to its profound impact on optical absorption response and facile isolation of photocarriers. The presence of oxygen vacancy can introduce the midgap defect states, which promote extended absorption in the visible region. The redistribution of electron density at the surface can stimulate the adsorption and activation kinetics of adsorbates, manifesting optimal photocatalytic performance. Despite such alluring outcomes, the ambiguity in understanding the precise location, appropriate concentration, and oxygen vacancy role is still a long-standing task. The present review article comprehensively outlines the identification of oxygen vacancy defects at bulk or on the surface and its ultimate effect on the photocatalytic degradation of phenolic compounds. Particular emphasis has been drawn to summarize the critical influence of oxygen vacancy on different factors such as crystal structure, bandgap energy, electronic structure, and charge carrier mobility by integrating experimental results and theoretical calculations. We have also explored the reaction pathways and the intermediate chemistry of phenol photodegradation by analyzing the molecular activation (O₂, H₂O, and sulphate activation) through oxygen vacancy defects. Finally, the review concludes with the various challenges and future perspectives, aiming to provide a firm base for further progressions towards photocatalysis.

Dual-Single-Atom Tailoring with Bifunctional Integration for High-Performance CO2 Photoreduction

Single-atom photocatalysis has been demonstrated as a novel strategy to promote heterogeneous reactions. There is a diversity of monoatomic metal species with specific functions; however, integrating representative merits into dual-single-atoms and regulating cooperative photocatalysis remain a pressing challenge. For dual-single-atom catalysts, enhanced photocatalytic activity would be realized through integrating bifunctional properties and tuning the synergistic effect. Herein, dual-single-atoms supported on conjugated porous carbon nitride polymer are developed for effective photocatalytic CO₂ reduction, featuring the function of cobalt (Co) and ruthenium (Ru). A series of in situ characterizations and theoretical calculations are conducted for quantitative analysis of structure-performance correlation. It is concluded that the active Co sites facilitate dynamic charge transfer, while the Ru sites promote selective CO₂ surface-bound interaction during CO₂ photoreduction. The combination of atom-specific traits and the synergy between Co and Ru lead to the high photocatalytic CO₂ conversion with corresponding apparent quantum efficiency (AQE) of 2.8% at 385 nm, along with a high turnover number (TON) of more than 200 without addition of any sacrificial agent. This work presents an example of identifying the roles of different single-atom metals and regulating the synergy, where the two metals with unique properties collaborate to further boost the photocatalytic performance.

Two-Dimensional Nanomaterials for the Removal of Pharmaceuticals from Wastewater: A Critical Review

The removal of pharmaceuticals from wastewater is critical due to their considerable risk on ecosystems and human health. Additionally, they are resistant to conventional chemical and biological remediation methods. Two-dimensional nanomaterials are a promising approach to face this challenge due to their combination of high surface areas, high electrical conductivities, and partially optical transparency. This review discusses the state-of-the-art concerning their use as adsorbents, oxidation catalysts or photocatalysts, and electrochemical catalysts for water treatment purposes. The bibliographic search bases upon academic databases including articles published until August 2021. Regarding adsorption, high removal capacities (>200 mg g−1) and short equilibrium times (<30 min) are reported for molybdenum disulfide, metal-organic frameworks, MXenes, and graphene oxide/magnetite nanocomposites, attributed to a strong adsorbate-adsorbent chemical interaction. Concerning photocatalysis, MXenes and carbon nitride heterostructures show enhanced charge carriers separation, favoring the generation of reactive oxygen species to degrade most pharmaceuticals. Peroxymonosulfate activation via pure or photo-assisted catalytic oxidation is promising to completely degrade many compounds in less than 30 min. Future work should be focused on the exploration of greener synthesis methods, regeneration, and recycling at the end-of-life of two-dimensional materials towards their successful large-scale production and application.

Structure and dynamics of nanoconfined water and aqueous solutions

This review is devoted to discussing recent progress on the structure, thermodynamic, reactivity, and dynamics of water and aqueous systems confined within different types of nanopores, synthetic and biological. Currently, this is a branch of water science that has attracted enormous attention of researchers from different fields interested to extend the understanding of the anomalous properties of bulk water to the nanoscopic domain. From a fundamental perspective, the interactions of water and solutes with a confining surface dramatically modify the liquid's structure and, consequently, both its thermodynamical and dynamical behaviors, breaking the validity of the classical thermodynamic and phenomenological description of the transport properties of aqueous systems. Additionally, man-made nanopores and porous materials have emerged as promising solutions to challenging problems such as water purification, biosensing, nanofluidic logic and gating, and energy storage and conversion, while aquaporin, ion channels, and nuclear pore complex nanopores regulate many biological functions such as the conduction of water, the generation of action potentials, and the storage of genetic material. In this work, the more recent experimental and molecular simulations advances in this exciting and rapidly evolving field will be reported and critically discussed.

Printing thermoelectric inks toward next-generation energy and thermal devices

The ability of thermoelectric (TE) materials to convert thermal energy to electricity and vice versa highlights them as a promising candidate for sustainable energy applications. Despite considerable increases in the figure of merit zT of thermoelectric materials in the past two decades, there is still a prominent need to develop scalable synthesis and flexible manufacturing processes to convert high-efficiency materials into high-performance devices. Scalable printing techniques provide a versatile solution to not only fabricate both inorganic and organic TE materials with fine control over the compositions and microstructures, but also manufacture thermoelectric devices with optimized geometric and structural designs that lead to improved efficiency and system-level performances. In this review, we aim to provide a comprehensive framework of printing thermoelectric materials and devices by including recent breakthroughs and relevant discussions on TE materials chemistry, ink formulation, flexible or conformable device design, and processing strategies, with an emphasis on additive manufacturing techniques. In addition, we review recent innovations in the flexible, conformal, and stretchable device architectures and highlight state-of-the-art applications of these TE devices in energy harvesting and thermal management. Perspectives of emerging research opportunities and future directions are also discussed. While this review centers on thermoelectrics, the fundamental ink chemistry and printing processes possess the potential for applications to a broad range of energy, thermal and electronic devices.

Current Potential Therapeutic Approaches against SARS-CoV-2: A Review

The ongoing SARS-CoV-2 pandemic is a serious threat to public health worldwide and, to date, no effective treatment is available. Thus, we herein review the pharmaceutical approaches to SARS-CoV-2 infection treatment. Numerous candidate medicines that can prevent SARS-CoV-2 infection and replication have been proposed. These medicines include inhibitors of serine protease TMPRSS2 and angiotensin converting enzyme 2 (ACE2). The S protein of SARS-CoV-2 binds to the receptor in host cells. ACE2 inhibitors block TMPRSS2 and S protein priming, thus preventing SARS-CoV-2 entry to host cells. Moreover, antiviral medicines (including the nucleotide analogue remdesivir, the HIV protease inhibitors lopinavir and ritonavir, and wide-spectrum antiviral antibiotics arbidol and favipiravir) have been shown to reduce the dissemination of SARS-CoV-2 as well as morbidity and mortality associated with COVID-19.

Progress on photocatalytic semiconductor hybrids for bacterial inactivation

Due to its use of green and renewable energy and negligible bacterial resistance, photocatalytic bacterial inactivation is to be considered a promising sterilization process. Herein, we explore the relevant mechanisms of the photoinduced process on the active sites of semiconductors with an emphasis on the active sites of semiconductors, the photoexcited electron transfer, ROS-induced toxicity and interactions between semiconductors and bacteria. Pristine semiconductors such as metal oxides (TiO₂ and ZnO) have been widely reported; however, they suffer some drawbacks such as narrow optical response and high photogenerated carrier recombination. Herein, some typical modification strategies will be discussed including noble metal doping, ion doping, hybrid heterojunctions and dye sensitization. Besides, the biosafety and biocompatibility issues of semiconductor materials are also considered for the evaluation of their potential for further biomedical applications. Furthermore, 2D materials have become promising candidates in recent years due to their wide optical response to NIR light, superior antibacterial activity and favorable biocompatibility. Besides, the current research limitations and challenges are illustrated to introduce the appealing directions and design considerations for the future development of photocatalytic semiconductors for antibacterial applications.

Point-of-care testing of butyrylcholinesterase activity through modulating the photothermal effect of cuprous oxide nanoparticles

Butyrylcholinesterase (BChE) is an important indicator for clinical diagnosis of liver dysfunction, organophosphate toxicity, and poststroke dementia. Point-of-care testing (POCT) of BChE activity is still a challenge, which is a critical requirement for the modern clinical diagnose. A portable photothermal BChE assay is proposed through modulating the photothermal effects of Cu₂O nanoparticles. BChE can catalyze the decomposition of butyrylcholine, producing thiocholine, which further reduce and coordinate with CuO on surface of Cu₂O nanoparticle. This leads to higher efficiency of formation of Cu₉S₈ nanoparticles, through the reaction between Cu₂O nanoparticle and NaHS, together with the promotion of photothermal conversion efficiency from 3.1 to 59.0%, under the excitation of 1064 nm laser radiation. An excellent linear relationship between the temperature change and the logarithm of BChE concentration is obtained in the range 1.0 to 7.5 U/mL, with a limit of detection of 0.076 U/mL. In addition, the portable photothermal assay shows strong detection robustness, which endows the accurate detection of BChE in human serum, together with the screening and quantification of organophosphorus pesticides. Such a simple, sensitive, and robust assay shows great potential for the applications to clinical BChE detection and brings a new horizon for the development of temperature based POCT.

In Silico Identification and Validation of Organic Triazole Based Ligands as Potential Inhibitory Drug Compounds of SARS-CoV-2 Main Protease

The SARS-CoV-2 virus is highly contagious to humans and has caused a pandemic of global proportions. Despite worldwide research efforts, efficient targeted therapies against the virus are still lacking. With the ready availability of the macromolecular structures of coronavirus and its known variants, the search for anti-SARS-CoV-2 therapeutics through in silico analysis has become a highly promising field of research. In this study, we investigate the inhibiting potentialities of triazole-based compounds against the SARS-CoV-2 main protease (Mpro). The SARS-CoV-2 main protease (Mpro) is known to play a prominent role in the processing of polyproteins that are translated from the viral RNA. Compounds were pre-screened from 171 candidates (collected from the DrugBank database). The results showed that four candidates (Bemcentinib, Bisoctrizole, PYIITM, and NIPFC) had high binding affinity values and had the potential to interrupt the main protease (Mpro) activities of the SARS-CoV-2 virus. The pharmacokinetic parameters of these candidates were assessed and through molecular dynamic (MD) simulation their stability, interaction, and conformation were analyzed. In summary, this study identified the most suitable compounds for targeting Mpro, and we recommend using these compounds as potential drug molecules against SARS-CoV-2 after follow up studies.

Advances in the Synthesis and Application of Anti-Fouling Membranes Using Two-Dimensional Nanomaterials

This article provides a comprehensive review of the recent progress in the application of advanced two-dimensional nanomaterials (2DNMs) in membranes fabrication and application for water purification. The membranes fouling, its types, and anti-fouling mechanisms of different 2DNMs containing membrane systems are also discussed. The developments in membrane synthesis and modification using 2DNMs, especially graphene and graphene family materials, carbon nanotubes (CNTs), MXenes, and others are critically reviewed. Further, the application potential of next-generation 2DNMs-based membranes in water/wastewater treatment systems is surveyed. Finally, the current problems and future opportunities of applying 2DNMs for anti-fouling membranes are also debated.

Drawing on Membrane Photocatalysis for Fouling Mitigation

Photocatalysis is an effective and environmentally friendly approach for degrading organic pollutants, particularly in scenarios where sunlight can be utilized as the energy source. Opportunities are emerging to apply materials and methods from photocatalytic pollutant degradation to address the challenge of fouling. Membrane fouling, attributed to organic foulants, is a prevalent problem for all membrane-based technologies and represents a major deleterious impact on membrane performance. Integration of tactics developed in photocatalysis more broadly to membranes reveals new strategies for membrane fouling control-an approach taken by an increasing number of researchers. This review summarizes key developments in photocatalytic materials and methods in water treatment and presents recent progress in the development of processes for photocatalytic alleviation of membrane fouling, including photocatalyst design and modification strategies aimed at enhancing photocatalytic efficiency, as well as different configurations of photocatalysis-membrane systems (PMS). Perspectives on future research and development opportunities for photocatalytic membrane fouling control are also provided.