Magnetically steerable iron oxides-manganese dioxide core-shell micromotors for organic and microplastic removals

Microplastics in aquatic systems: An in-depth review of current and potential water treatment processes

Plastic products, despite their undeniable utility in modern life, pose significant environmental challenges, particularly when it comes to recycling. A crucial concern is the pervasive introduction of microplastics (MPs) into aquatic ecosystems, with deleterious effects on marine organisms. This review presents a detailed examination of the methodologies developed for MPs removal in water treatment systems. Initially, investigating the most common types of MPs in wastewater, subsequently presenting methodologies for their precise identification and quantification in aquatic environments. Instruments such as scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, Raman spectroscopy, surface-enhanced Raman spectroscopy, and Raman tweezers stand out as powerful tools for studying MPs. The discussion then transitions to the exploration of both existing and emergent techniques for MPs removal in wastewater treatment plants and drinking water treatment plants. This includes a description of the core mechanisms that drive these techniques, with an emphasis on the latest research developments in MPs degradation. Present MPs removal methodologies, ranging from physical separation to chemical and biological adsorption and degradation, offer varied advantages and constraints. Addressing the MPs contamination problem in its entirety remains a significant challenge. In conclusion, the review offers a succinct overview of each technique and forwards recommendations for future research, highlighting the pressing nature of this environmental dilemma.

Recent advances in targeted drug delivery for the treatment of glioblastoma

Glioblastoma multiforme (GBM) is one of the highly malignant brain tumors characterized by significant morbidity and mortality. Despite the recent advancements in the treatment of GBM, major challenges persist in achieving controlled drug delivery to tumors. The management of GBM poses considerable difficulties primarily due to unresolved issues in the blood-brain barrier (BBB)/blood-brain tumor barrier (BBTB) and GBM microenvironment. These factors limit the uptake of anti-cancer drugs by the tumor, thus limiting the therapeutic options. Current breakthroughs in nanotechnology provide new prospects concerning unconventional drug delivery approaches for GBM treatment. Specifically, swimming nanorobots show great potential in active targeted delivery, owing to their autonomous propulsion and improved navigation capacities across biological barriers, which further facilitate the development of GBM-targeted strategies. This review presents an overview of technological progress in different drug administration methods for GBM. Additionally, the limitations in clinical translation and future research prospects in this field are also discussed. This review aims to provide a comprehensive guideline for researchers and offer perspectives on further development of new drug delivery therapies to combat GBM.

Multi-Stimuli-Responsive Tadpole-like Polymer/Lipid Janus Microrobots for Advanced Smart Material Applications

Microrobots are of significant interest due to their smart transport capabilities, especially for precisely targeted delivery in dynamic environments (blood, cell membranes, tumor interstitial matrixes, blood-brain barrier, mucosa, and other body fluids). To perform a more complex micromanipulation in biological applications, it is highly desirable for microrobots to be stimulated with multiple stimuli rather than a single stimulus. Herein, the biodegradable and biocompatible smart micromotors with a Janus architecture consisting of PrecirolATO 5 and polycaprolactone compartments inspired by the anisotropic geometry of tadpoles and sperms are newly designed. These bioinspired micromotors combine the advantageous properties of polypyrrole nanoparticles (NPs), a high near-infrared light-absorbing agent with high photothermal conversion efficiency, and magnetic NPs, which respond to the magnetic field and exhibit multistimulus-responsive behavior. By combining both fields, we achieved an "on/off" propulsion mechanism that can enable us to overcome complex tasks and limitations in liquid environments and overcome the limitations encountered by single actuation applications. Moreover, the magnetic particles offer other functions such as removing organic pollutants via the Fenton reaction. Janus-structured motors provide a broad perspective not only for biosensing, optical detection, and on-chip separation applications but also for environmental water treatment due to the catalytic activities of multistimulus-responsive micromotors.

Emerging isolation and degradation technology of microplastics and nanoplastics in the environment

Microplastics (MPs, less than 5 mm in size) are widely distributed in surroundings in various forms and ways, and threaten ecosystems security and human health. Its environmental behavior as pollutants carrier and the after-effects exposed to MPs has been extensively exploited; whereas, current knowledge on technologies for the separation and degradation of MPs is relatively limited. It is essential to isolate MPs from surroundings and/or degrade to safe levels. This in-depth review details the origin and distribution of MPs. Provides a comprehensive summary of currently available MPs separation and degradation technologies, and discusses the mechanisms, challenges, and application prospects of these technologies. Comparison of the contribution of various separation methods to the separation of NPs and MPs. Furthermore, the latest research trends and direction in bio-degradation technology are outlooked.

Innovations in chemical degradation technologies for the removal of micro/nano-plastics in water: A comprehensive review

Micro/nanoplastics (M/NPs) in water have raised global concern due to their potential environmental risks. To reestablish a M/NPs free world, enormous attempts have been made toward employing chemical technologies for their removal in water. This review comprehensively summarizes the advances in chemical degradation approaches for M/NPs elimination. It details and discusses promising techniques, including photo-based technologies, Fenton-based reaction, electrochemical oxidation, and novel micro/nanomotors approaches. Subsequently, critical influence factors, such as properties of M/NPs and operating factors, are analyzed in this review specifically. Finally, it concludes by addressing the current challenges and future perspectives in chemical degradation. This review will provide guidance for scientists to further explore novel strategies and develop feasible chemical methods for the improved control and remediation of M/NPs in the future.

Micromotors of MnO2 for the Recovery of Microplastics

Plastics, primarily microplastics, are among the greatest pollutants in aquatic environments. Their removal and/or degradation in these environments are crucial to ensure an optimal future of these ecosystems. In this work, MnO2 particles were synthesized and characterized for the removal of polystyrene microplastics as a model. MnO2 catalyzes the peroxide reaction, resulting in the formation of oxygen bubbles that propel the pollutants to the surface, achieving removal efficiencies of up to 80%. To achieve this, hydrothermal synthesis was employed using various methods. Parameters such as MnO2, pH, microplastics, and H2O2 concentrations were varied to determine the optimal conditions for microplastics recovering. The ideal conditions for a low microplastic concentrations (10 mg L-1) are 0.2 g L-1 MnO2, 1.6% of H2O2 and 0.01 triton as a surfactant. In these conditions, the micromotors can recover approximately 80% of 300 nm sized polystyrene microplastic within 40 min.

Photogenerated outer electric field induced electrophoresis of organic nanocrystals for effective solid-solid photocatalysis

Rapid mass transfer in solid-solid reactions is crucial for catalysis. Although phoretic nanoparticles offer potential for increased collision efficiency between solids, their implementation is hindered by limited interaction ranges. Here, we present a self-driven long-range electrophoresis of organic nanocrystals facilitated by a rationally designed photogenerated outer electric field (OEF) on their surface. Employing perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecular nanocrystals as a model, we demonstrate that a directional OEF with an intensity of 13.6-0.4 kV m-1 across a range of 25-200 μm. This OEF-driven targeted electrophoresis of PTCDA nanocrystals onto the microplastic surface enhances the activity for subsequent decomposition of microplastics (196.8 mg h-1) into CO2 by solid-solid catalysis. As supported by operando characterizations and theoretical calculations, the OEF surrounds PTCDA nanocrystals initially, directing from the electron-rich (0 1 1) to the hole-rich [Formula: see text] surface. Upon surface charge modulation, the direction of OEF changes toward the solid substrate. The OEF-driven electrophoretic effect in organic nanocrystals with anisotropic charge enrichment characteristics indicates potential advancements in realizing effective solid-solid photocatalysis.

Advances in magnetic materials for microplastic separation and degradation

The widespread use of plastics in modern human society has led to severe environmental pollution with microplastics (MP/MPs). The rising consumption of plastics raises the omnipresence of microplastics in aquatic environments, which carry toxic organic matter, transport toxic chemicals, and spread through the food chain, seriously threatening marine life and human health. In this context, several advanced strategies for separating and degrading MPs from water have been developed recently, and magnetic materials and their nanostructures have emerged as promising materials for targeting, adsorbing, transporting, and degrading MPs. However, a comprehensive review of MP remediation using magnetic materials and their nanostructures is currently lacking. The present work provides a critical review of the recent advances in MP removal/degradation using magnetic materials. The focus is on the comparison and analysis of the MP's removal efficiencies of different magnetic materials, including iron/ferrite nanoparticles, magnetic nanocomposites, and micromotors, aiming to unravel the underlying roles of magnetic materials in different types of MP degradation and present the general strategies for designing them with optimal performance. Finally, the review outlines the forthcoming challenges and perspectives in the development of magnetic nanomaterials for MP remediation.

Helical magnetic micromotors decorated with nickel ferrocyanide for the active and rapid adsorption of radiocesium in water

Separating radioactive cesium from nuclear waste and contaminated environments is critical to mitigate radiological hazards. In response to this need, remote-controllable and Cs-selective micromotor adsorbents have been considered as a promising technology for rapid in-situ cleanup while minimizing secondary waste and radiation exposure to workers. In this study, we demonstrate the active and rapid removal of a radioactive contaminant from water by leveraging the magnetic manipulation capabilities of a helical and magnetic Ni micromotor coated with Cs-selective nickel ferrocyanide (NiFC). The use of polyvinyl alcohol fibers as a template enables the straightforward preparation of the helical wire structure, allowing for precise control over the diameter and pitch of the helix through simple twisting with Ni wires. By harnessing Ni2+ ions eluted from the Ni micromotor in an acid solution, we successfully fabricate NiFC-coated Ni (NiFC/Ni) micromotors that exhibit a selective removal efficiency greater than 98% for 137Cs, even in the presence of high concentrations of competing Na+ ions. Under the influence of an external magnetic field, the NiFC/Ni micromotor demonstrates rapid motion, achieving a pulling motion (100 body lengths per second) through a magnetic gradient and a tumbling motion (46 body lengths per second) induced by a rotating magnetic field. The tumbling motion of the NiFC/Ni micromotor substantially improves the Cs adsorption rate, resulting in a rate that surpasses that achieved under nonmoving conditions by a factor of 21. This improved adsorption rate highlights the considerable potential of magnetically manipulated micromotor self-propulsion for efficient water-pollution treatment.

Photothermal-driven micro/nanomotors: From structural design to potential applications

Micro/nanomotors (MNMs) that accomplish autonomous movement by transforming external energy into mechanical work are attractive cargo delivery vehicles. Among various propulsion mechanisms of MNMs, photothermal propulsion has gained considerable attention because of their unique advantages, such as remote, flexible, accurate, biocompatible, short response time, etc. Moreover, besides as a propulsion source, the light has been extensively investigated as an excitation source in bioimaging, photothermal therapy (PTT), photodynamic therapy (PDT) and so on. Furthermore, the geometric topology and morphology of MNMs have a tremendous impact on improving their performance in motion behavior under NIR light propulsion, environmental suitability and functional versatility. Hence, this review article provides a comprehensive overview of structural design principles and construction strategies of photothermal-driven MNMs, and their emerging nanobiomedical applications. Finally, we further provide an outlook towards prospects and challenges during the development of photothermal-driven MNMs in the future. STATEMENT OF SIGNIFICANCE: Photothermal-driven micro/nanomotors (MNMs) that are regarded as functional cargo delivery tools have gained considerable attention because of unique advantages in propulsion mechanisms, such as remote, flexible, accurate and fully biocompatible light manipulation and extremely short light response time. The geometric topology and morphology of MNMs have a tremendous impact on improving their performance in motion behavior under NIR light propulsion, environmental suitability and functional versatility of MNMs. There are no reports about the review focusing on photothermal-driven MNMs up to now. Herein, we systematically review the latest progress of photothermal-driven MNMs including design principle, fabrication strategy of various MNMs with different structures and nanobiomedical applications. Moreover, the summary and outlook on the development prospects and challenges of photothermal-driven MNMs are proposed, hoping to provide new ideas for the future design of photothermal-driven MNMs with efficient propulsion, multiple functions and high biocompatibility.

3D Motion Manipulation for Micro- and Nanomachines: Progress and Future Directions

In the past decade, micro- and nanomachines (MNMs) have made outstanding achievements in the fields of targeted drug delivery, tumor therapy, microsurgery, biological detection, and environmental monitoring and remediation. Researchers have made significant efforts to accelerate the rapid development of MNMs capable of moving through fluids by means of different energy sources (chemical reactions, ultrasound, light, electricity, magnetism, heat, or their combinations). However, the motion of MNMs is primarily investigated in confined two-dimensional (2D) horizontal setups. Furthermore, three-dimensional (3D) motion control remains challenging, especially for vertical movement and control, significantly limiting its potential applications in cargo transportation, environmental remediation, and biotherapy. Hence, an urgent need is to develop MNMs that can overcome self-gravity and controllably move in 3D spaces. This review delves into the latest progress made in MNMs with 3D motion capabilities under different manipulation approaches, discusses the underlying motion mechanisms, explores potential design concepts inspired by nature for controllable 3D motion in MNMs, and presents the available 3D observation and tracking systems.

Review of emerging contaminants in green stormwater infrastructure: Antibiotic resistance genes, microplastics, tire wear particles, PFAS, and temperature

Green stormwater infrastructure is a growing management approach to capturing, infiltrating, and treating runoff at the source. However, there are several emerging contaminants for which green stormwater infrastructure has not been explicitly designed to mitigate and for which removal mechanisms are not yet well defined. This is an issue, as there is a growing understanding of the impact of emerging contaminants on human and environmental health. This paper presents a review of five emerging contaminants - antibiotic resistance genes, microplastics, tire wear particles, PFAS, and temperature - and seeks to improve our understanding of how green stormwater infrastructure is impacted by and can be designed to mitigate these emerging contaminants. To do so, we present a review of the source and transport of these contaminants to green stormwater infrastructure, specific treatment mechanisms within green infrastructure, and design considerations of green stormwater infrastructure that could lead to their removal. In addition, common removal mechanisms across these contaminants and limitations of green infrastructure for contaminant mitigation are discussed. Finally, we present future research directions that can help to advance the use of green infrastructure as a first line of defense for downstream water bodies against emerging contaminants of concern.

Motion of magnetic motors across liquid-liquid interface

HYPOTHESIS

In a number of applications related to chemical engineering and drug delivery, magnetic nanoparticles should move through a liquid-liquid interface in the presence of surfactant molecules. However, due to the action of capillary forces, this is not always possible. The mechanism of particle motion through the interface essentially depends on the intensity of the Marangoni flow, which is induced on the interface during its deformation.

EXPERIMENTS

In this paper we study the motion of nanoparticles Fe3O4 through the water-tridecane interface under the action of a nonuniform magnetic field when using different surfactants.

FINDINGS

If the linear size of the magnetic motor turns out to be less than a certain critical value, then it is not able to move between phases due to the action of capillary forces on the interface. Depending on the type and concentration of the surfactant used, various mechanisms for the motor motion through the liquid-liquid interface can be carried out. In one of them, a liquid phase is transferred through the interface along with a movable motor, while in the other, it is not.

Micro/nanorobots for remediation of water resources and aquatic life

Nowadays, global water scarcity is becoming a pressing issue, and the discharge of various pollutants leads to the biological pollution of water bodies, which further leads to the poisoning of living organisms. Consequently, traditional water treatment methods are proving inadequate in addressing the growing demands of various industries. As an effective and eco-friendly water treatment method, micro/nanorobots is making significant advancements. Based on researches conducted between 2019 and 2023 in the field of water pollution using micro/nanorobots, this paper comprehensively reviews the development of micro/nanorobots in water pollution control from multiple perspectives, including propulsion methods, decontamination mechanisms, experimental techniques, and water monitoring. Furthermore, this paper highlights current challenges and provides insights into the future development of the industry, providing guidance on biological water pollution control.

Eliminating waste with waste: transforming spent coffee grounds into microrobots for water treatment

Water pollutants such as oil spills, industrial dyes, and microplastics threaten public health and aquatic ecosystems. There are considerable challenges in removing water contaminants using traditional methods. Several studies have been conducted in recent years to develop effective water purification materials. Despite this, the mass production of most materials is extremely challenging because they involve multiple intricate steps and sophisticated equipment. Herein, we report the facile synthesis of spent coffee ground (SCG)-derived magnetic microrobots, which we dub "CoffeeBots", to remove oil, organic dyes, and microplastic pollution from contaminated seawater. In order to meet eco-friendly, high-yield and low-cost requirements, iron oxide nanoparticles (IONPs) were deposited on biodegradable SCGs using green chemistry. The IONPs on CoffeeBots facilitate magnetic navigation and recycling, microswarm assembly, and ease of retrieval after water remediation tasks. CoffeeBots' intrinsic surface hydrophobicity enables efficient on-the-fly capture and removal of oil droplets and microplastics from contaminated water with remote magnetic guidance. CoffeeBots were also functionalized with ascorbic acid (AA@CoffeeBots) to remove methylene blue (MB) dye contaminants from polluted seawater. SCGs and AA act as bioadsorbent and reducing agent, respectively, for MB dye removal whereas magnetic propulsion enhances mixing and accelerates MB decolorization. These CoffeeBots can be recycled numerous times for removing oil spills, organic dyes, and microplastics from the seawater. CoffeeBots hold considerable potential as sustainable, recyclable, and low-cost remediation agents for water treatment in the near future.

Magnetically locked Janus particle clusters with orientation-dependent motion in AC electric fields

Active particles, or micromotors, locally dissipate energy to drive locomotion at small length scales. The type of trajectory is generally fixed and dictated by the geometry and composition of the particle, which can be challenging to tune using conventional fabrication procedures. Here, we report a simple, bottom-up method to magnetically assemble gold-coated polystyrene Janus particles into "locked" clusters that display diverse trajectories when stimulated by AC electric fields. The orientation of particles within each cluster gives rise to distinct modes of locomotion, including translational, rotational, trochoidal, helical, and orbital. We model this system using a simplified rigid beads model and demonstrate qualitative agreement between the predicted and experimentally observed cluster trajectories. Overall, this system provides a facile means to scalably create micromotors with a range of well-defined motions from discrete building blocks.

Superhydrophobic cotton fabrics for effective removal of high-density polyethylene and polypropylene microplastics: Insights from surface and colloidal analysis

HYPOTHESIS

The use of superhydrophobic materials to remove particulate pollutants such as microplastics is still in its infancy. In a previous study, we investigated the effectiveness of three different types of superhydrophobic materials - coatings, powdered materials, and meshes - for removing microplastics. In this study, we will explain the removal process by considering microplastics as colloids and taking into account their wetting properties as well as those of a superhydrophobic surface. The process will be explained through the interactions of electrostatic forces, van der Waals forces, and the DLVO theory.

EXPERIMENTS

In order to replicate and verify the previous experimental findings on the removal of microplastics using superhydrophobic surfaces, we have modified non-woven cotton fabrics with polydimethylsiloxane. We then proceeded to remove high-density polyethylene and polypropylene microplastics from water by introducing oil at the microplastics-water interface, and we determined the removal efficiency of the modified cotton fabrics.

FINDINGS

After achieving a superhydrophobic non-woven cotton fabric (159 ± 1°), we confirmed its effectiveness in removing high-density polyethylene and polypropylene microplastics from water with a removal efficiency of 99%. Our findings suggest that the binding energy of microplastics increases and the Hamaker constant becomes positive when they are present in oil instead of water, leading to their aggregation. As a result, electrostatic interactions become negligible in the organic phase, and van der Waals interactions become more important. The use of the DLVO theory allowed us to confirm that solid pollutants can be easily removed from the oil using superhydrophobic materials.

Microplastics in facial cleanser: extraction, identification, potential toxicity, and continuous-flow removal using agricultural waste-based biochar

Microplastic (MP) is an emerging contaminant of concern due to its ubiquitous quantity in the environment, small size, and potential toxicity due to strong affinity towards other contaminants. In this work, MP particles (5-300 μm) were extracted from a commercial facial cleanser and determined to be irregular polyethylene (PE) microbeads based on characterization with field emission scanning electron microscopy (FESEM) and Raman spectroscopy. The potential of extracted MP acting as toxic pollutants' vector was analyzed via adsorption of methylene blue and methyl orange dye where significant dye uptake was observed. Synthetic wastewater containing the extracted MP was subjected to a continuous-flow column study using palm kernel shell and coconut shell biochar as the filter/adsorbent media. The prepared biochar was characterized via proximate and ultimate analysis, FESEM, contact angle measurement, atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy to investigate the role of the biochar properties in MP removal. MP removal performance was determined by measuring the turbidity and weighing the dry mass of particles remaining in the effluent following treatment. Promising results were obtained from the study with highest removal of MP (96.65%) attained through palm kernel shell biochar with particle size of 0.6-1.18 mm and continuous-flow column size of 20 mm.

Receptor-based detection of microplastics and nanoplastics: Current and future

Plastic pollution is an emerging environmental concern, gaining significant attention worldwide. They are classified into microplastics (MP; defined from 1 μm to 5 mm) and smaller nanoplastics (NP; <1 μm). NPs may pose higher ecological risks than MPs. Various microscopic and spectroscopic techniques have been used to detect MPs, and the same methods have occasionally been used for NPs. However, they are not based on receptors, which provide high specificity in most biosensing applications. Receptor-based micro/nanoplastics (MNP) detection can provide high specificity, distinguishing MNPs from the environmental samples and, more importantly, identifying the plastic types. It can also offer a low limit of detection (LOD) required for environmental screening. Such receptors are expected to detect NPs specifically at the molecular level. This review categorizes the receptors into cells, proteins, peptides, fluorescent dyes, polymers, and micro/nanostructures. Detection techniques used with these receptors are also summarized and categorized. There is plenty of room for future research to test for broader classes of environmental samples and many plastic types, to lower the LOD, and to apply the current techniques for NPs. Portable and handheld MNP detection should also be demonstrated for field use since the current demonstrations primarily utilized laboratory instruments. Detection on microfluidic platforms will also be crucial in miniaturizing and automating the assay and, eventually, collecting an extensive database to support machine learning-based classification of MNP types.

Microplastic remediation technologies in water and wastewater treatment processes: Current status and future perspectives

Microplastics (MPs) are a type of contaminants produced during the use and disposal of plastic products, which are ubiquitous in our lives. With the high specific surface area and strong hydrophobicity, MPs can adsorb various hazardous microorganisms and chemical contaminants from the environment, causing irreversible damage to our humans. It is reported that the MPs have been detected in infant feces and human blood. Therefore, the presence of MPs has posed a significant threat to human health. It is critically essential to develop efficient, scalable and environmentally-friendly methods to remove MPs. Herein, recent advances in the MPs remediation technologies in water and wastewater treatment processes are overviewed. Several approaches, including membrane filtration, adsorption, chemically induced coagulation-flocculation-sedimentation, bioremediation, and advanced oxidation processes are systematically documented. The characteristics, mechanisms, advantages, and disadvantages of these methods are well discussed and highlighted. Finally, the current challenges and future trends of these methods are proposed, with the aim of facilitating the remediation of MPs in water and wastewater treatment processes in a more efficient, scalable, and environmentally-friendly way.

Plastic waste management for sustainable environment: techniques and approaches

Excessive exploitation, negligence, non-degradable nature, and physical and chemical properties of plastic waste have resulted in a massive pollution load into the environment. Consequently, plastic entres the food chain and can cause serious health issues in aquatic animals and humans. The present review summarizes currently reported techniques and approaches for the removal of plastic waste. Many techniques, such as adsorption, coagulation, photocatalysis, and microbial degradation, and approaches like reduction, reuse and recycling are potentially in trend and differ from each other in their efficiency and interaction mechanism. Moreover, substantial advantages and challenges associated with these techniques and approaches are highlighted to develop an understanding of the selection of possible ways for a sustainable future. Nevertheless, in addition to the reduction of plastic waste from the ecosystem, many alternative opportunities have also been explored to cash plastic waste. These fields include the synthesis of adsorbents for the removal of pollutants from aqueous and gaseous stream, their utility in clothing, waste to energy and fuel and in construction (road making). Substantial evidence can be observed in the reduction of plastic pollution from various ecosystems. In addition, it is important to develop an understanding of factors that need to be emphasized while considering alternative approaches and opportunities to cash plastic waste (like adsorbent, clothing, waste to energy and fuel). The thrust of this review is to provide readers with a comprehensive overview of the development status of techniques and approaches to overcome the global issue of plastic pollution and the outlook on the exploitation of this waste as resources.

Innovations in the Development of Promising Adsorbents for the Remediation of Microplastics and Nanoplastics - A Critical Review

Microplastics and nanoplastics are being assumed as emerging toxic pollutants owing to their unique persistent physicochemical attributes, chemical stability, and nonbiodegradable nature. Owing to their possible toxicological impacts (not only on aquatic biota but also on humans), scientific communities are developing innovative technologies to remove microplastics and nanoplastics from polluted waters. Various technologies, including adsorption, coagulation, photocatalysis, bioremediation, and filtration, have been developed and employed to eliminate microplastics and nanoplastics. Recently, adsorption technology has been getting great interest in capturing microplastics and nanoplastics and achieving excellent removal performance. Therefore, this review is designed to discuss recent innovations in developing promising adsorbents for the remediation of microplastics and nanoplastics from wastewater and natural water. The developed adsorbents have been classified into four main classes: sponge/aerogel-based, metal-based, biochar-based, and other developed adsorbents, and their performance efficiencies have been critically examined. Further, the influence of various pertinent factors, including adsorbents' characteristics, microplastics/nanoplastics' characteristics, solution pH, reaction temperature, natural organic matter, and co-existing/interfering ions on the removal performance of advanced adsorbents, have been critically assessed. Importantly, the particle application of the developed adsorbents in removing microplastics and nanoplastics from natural water has been elucidated. In addition, barriers to market penetration of the developed adsorbents are briefly discussed to help experts transfer adsorption-based technology from laboratory-scale to commercial applications. Finally, the current knowledge gaps and future recommendations are highlighted to assist scientific communal for improving adsorption-based technologies to battle against microplastics and nanoplastics pollution.

Smart micro- and nanorobots for water purification

Less than 1% of Earth's freshwater reserves is accessible. Industrialization, population growth and climate change are further exacerbating clean water shortage. Current water-remediation treatments fail to remove most pollutants completely or release toxic by-products into the environment. The use of self-propelled programmable micro- and nanoscale synthetic robots is a promising alternative way to improve water monitoring and remediation by overcoming diffusion-limited reactions and promoting interactions with target pollutants, including nano- and microplastics, persistent organic pollutants, heavy metals, oils and pathogenic microorganisms. This Review introduces the evolution of passive micro- and nanomaterials through active micro- and nanomotors and into advanced intelligent micro- and nanorobots in terms of motion ability, multifunctionality, adaptive response, swarming and mutual communication. After describing removal and degradation strategies, we present the most relevant improvements in water treatment, highlighting the design aspects necessary to improve remediation efficiency for specific contaminants. Finally, open challenges and future directions are discussed for the real-world application of smart micro- and nanorobots.

The role of available nitrogen in the adsorption of polystyrene nanoplastics on magnetic materials

Several studies have been conducted on nanoplastics (NPs). However, few studies have investigated the complexity of the interactions between NPs and other aqueous pollutants in multi-solute media. In this study, the adsorption of polystyrene nanoplastics (PSNPs) on magnetic materials (MS) in the presence of available nitrogen (AN) was studied. The results demonstrated that the adsorbed amount of PSNPs increased in the presence of ammonium nitrogen (NH₄⁺-N), whereas no significant difference was detected on the adsorbed amount of PSNPs using nitrate nitrogen (NO₃^--N) as a cosolute. The increase in the adsorbed amount of PSNPs was attributed to the formation of an MS-PSNPs-NH₄⁺-N complex. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and zeta potential analyses indicated that the PSNPs with NH₄⁺-N as a cosolute can be bound on the MS surfaces. Moreover, the change in the PSNPs amount adsorbed by MS depends on the valence state, electronegativity of the coexisting ions, and the surface properties and functional groups of PSNPs. Additionally, the ionic strength, dissolved organic matter, solution pH, metal cations and the subsequent release of MS-coated PSNPs and NH₄⁺-N changed considerably in different aquatic systems and artificial nitrating fluids. Among different natural aquatic systems, the PSNPs adsorption on MS was excellent in lake water. The results indicate high potential for the attachment of PSNPs to MS in the presence of AN and further deepen the understanding of removing NPs using magnetic materials in aqueous systems with various coexisting contaminants.

Removing microplastics from aquatic environments: A critical review

As one of the typical emerging contaminants, microplastics exist widely in the environment because of their small size and recalcitrance, which has caused various ecological problems. This paper summarizes current adsorption and removal technologies of microplastics in typical aquatic environments, including natural freshwater, marine, drinking water treatment plants (DWTPs), and wastewater treatment plants (WWTPs), and includes abiotic and biotic degradation technologies as one of the removal technologies. Recently, numerous studies have shown that enrichment technologies have been widely used to remove microplastics in natural freshwater environments, DWTPs, and WWTPs. Efficient removal of microplastics via WWTPs is critical to reduce the release to the natural environment as a key connection point to prevent the transfer of microplastics from society to natural water systems. Photocatalytic technology has outstanding pre-degradation effects on microplastics, and the isolated microbial strains or enriched communities can degrade up to 50% or more of pre-processed microplastics. Thus, more research focusing on microplastic degradation could be carried out by combining physical and chemical pretreatment with subsequent microbial biodegradation. In addition, the current recovery technologies of microplastics are introduced in this review. This is incredibly challenging because of the small size and dispersibility of microplastics, and the related technologies still need further development. This paper will provide theoretical support and advice for preventing and controlling the ecological risks mediated by microplastics in the aquatic environment and share recommendations for future research on the removal and recovery of microplastics in various aquatic environments, including natural aquatic environments, DWTPs, and WWTPs.

Controlled propulsion of micro/nanomotors: operational mechanisms, motion manipulation and potential biomedical applications

Inspired by natural mobile microorganisms, researchers have developed micro/nanomotors (MNMs) that can autonomously move by transducing different kinds of energies into kinetic energy. The rapid development of MNMs has created tremendous opportunities for biomedical fields including diagnostics, therapeutics, and theranostics. Although the great progress has been made in MNM research, at a fundamental level, the accepted propulsion mechanisms are still a controversial matter. In practical applications such as precision nanomedicine, the precise control of the motion, including the speed and directionality, of MNMs is also important, which makes advanced motion manipulation desirable. Very recently, diverse MNMs with different propulsion strategies, morphologies, sizes, porosities and chemical structures have been fabricated and applied for various uses. Herein, we thoroughly summarize the physical principles behind propulsion strategies, as well as the recent advances in motion manipulation methods and relevant biomedical applications of these MNMs. The current challenges in MNM research are also discussed. We hope this review can provide a bird's eye overview of the MNM research and inspire researchers to create novel and more powerful MNMs.

Current status of microplastics and nanoplastics removal methods: Summary, comparison and prospect

In modern society, plastics also play an indispensable role in people's lives due to their various excellent properties. However, when these plastic products are discarded after being used, after being subjected to external influences, they will continue to be worn, damaged and degraded into micro- and nano-scale plastics, which are microplastics and nanoplastics (M/NPs). Although people's attention has been paid to M/NPs at present, the focus is still mainly on the detection and hazard of M/NPs, and how to remove M/NPs is relatively less popular. This review was written in order to draw the attention of more researchers to remove M/NPs. This review first briefly introduces the research background of M/NPs, and also shows the main analytical methods currently used for qualitative and quantitative M/NPs. Then, most of the current literature on the removal of M/NPs was collected, and they were classified, summarized, and introduced according to the classification of physical, physicochemical, and biological methods. The advantages and disadvantages of various methods are summarized, and they are also compared, which can help more researchers choose the appropriate method for research. In addition, the application scenarios of these methods are briefly introduced. Finally, some future research directions are proposed for the current research status of M/NPs removal. It is hoped that this will further promote the development on the method of removing M/NPs.

Magnetic Extraction of Weathered Tire Wear Particles and Polyethylene Microplastics

Magnetic extraction offers a rapid and low-cost solution to microplastic (MP) separation, in which we magnetize the hydrophobic surface of MPs to separate them from complex environmental matrices using magnets. We synthesized a hydrophobic Fe-silane based nanocomposite (Fe@SiO₂/MDOS) to separate MPs from freshwater. Pristine and weathered, polyethylene (PE) and tire wear particles (TWP) of different sizes were used in the study. The weathering of MPs was performed in an accelerated weathering chamber according to ISO 4892-2:2013 standards that mimic natural weathering conditions. The chemical properties and morphology of the Fe@SiO₂/MDOS, PE and TWP were confirmed by Fourier transform infrared spectroscopy and Scanning electron microscopy, respectively. The thermal properties of PE and TWP were evaluated by Thermogravimetric analysis. Using 1.00 mg of Fe@SiO₂/MDOS nanocomposite, 2.00 mg of pristine and weathered PE were extracted from freshwater; whereas, using the same amount of the nanocomposite, 7.92 mg of pristine TWP and 6.87 mg of weathered TWP were extracted. The retrieval of weathered TWP was 13% less than that of pristine TWP, which can be attributed to the increasing hydrophilicity of weathered TWP. The results reveal that the effectiveness of the magnetic separation technique varies among different polymer types and their sizes; the weathering of MPs also influences the magnetic separation efficiency.

Self-driven magnetorobots for recyclable and scalable micro/nanoplastic removal from nonmarine waters

Micro/nanoplastic (MNP) contamination in nonmarine waters has evolved into a notable ecotoxicological threat to the global ecosystem. However, existing strategies for MNP removal are typically limited to chemical flocculation or physical filtering that often fails to decontaminate plastic particulates with ultrasmall sizes or ultralow concentrations. Here, we report a self-driven magnetorobot comprising magnetizable ion-exchange resin sphere that can be used to dynamically remove or separate MNPs from nonmarine waters. As a result of the long-range electrophoretic attraction established by recyclable ion-exchange resin, the magnetorobot shows sustainable removal efficiency of >90% over 100 treatment cycles, with verified broad applicability to varying plastic compositions, sizes, and shapes as well as nonmarine water samples. Our work may facilitate industry-scale MNP removal with affordable cost and minimal secondary pollution and suggests an appealing strategy based on self-propelled micro/nanorobots to sample and assess nanoplastics in aqueous environment.

Magnetically Driven Muco-Inert Janus Nanovehicles for Enhanced Mucus Penetration and Cellular Uptake

One of the main challenges of transmucosal drug delivery is that of enabling particles and molecules to move across the mucosal barrier of the mucosal epithelial surface. Inspired by nanovehicles and mucus-penetrating nanoparticles, a magnetically driven, mucus-inert Janus-type nanovehicle (Janus-MMSN-pCB) was fabricated by coating the zwitterionic polymer poly(carboxybetaine methacrylate) (pCB) on the mesoporous silica nanorod, which was grown on one side of superparamagnetic Fe3O4 nanoparticle using the sol–gel method. X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and Fourier infrared spectroscopy were used to characterize the structure and morphology of the nanovehicles, proving the success of each synthesis step. The in vitro cell viability assessment of these composites using Calu-3 cell lines indicates that the nanovehicles are biocompatible in nature. Furthermore, the multiparticle tracking, Transwell® system, and cell imaging experimental results demonstrate that both the modification of pCB and the application of a magnetic field effectively accelerated the diffusion of the nanovehicles in the mucus and improved the endocytosis through Calu-3. The favorable cell uptake performance of Janus-MMSN-pCB in mucus systems with/without magnetic driving proves its potential role in the diagnosis, treatment, and imaging of mucosal-related diseases.

Metal Complex/ZnS-Modified Ni Foam as Magnetically Stirrable Photocatalysts: Roles of Redox Mediators and Carrier Dynamics Monitored by Operando Synchrotron X-ray Spectroscopy

Magnetically stirrable photocatalysts binding the ZnS-decorated Ni foam with the metal complex cocatalyst as a redox mediator and light-absorbing composition were investigated. Loading metal complex can improve light absorption, surface hydrophilicity, interfacial charge migration, and H₂ production activity. The variation of the metal valences of the composite photocatalysts in an operando environment (with sacrificial agent solution) with and without light irradiation was investigated by X-ray absorption near-edge structure (XANES) spectra and Fourier-transformed extended X-ray absorption fine structure (EXAFS) spectra to monitor the charge carrier dynamics of photocatalysis and explain how the macrocyclic Cu complex (CuC) acted as a redox mediator better than the Ni complex. The smaller valence difference of copper valence in ZS/CuC for dark and light states revealed that the Cu complex facilitates a reversible electron transfer between the ZnS photocatalyst and H⁺. Loading the Cu complex can improve the separation of photogenerated carriers by the redox couple of complexes, leading to a significantly improved photocatalytic H₂ production activity of 8150 μmol h^-1 g^-1. The reactants can flow through these magnetically stirrable Ni foam-based photocatalysts by magnetic-field-driven stirring, which improves the contact between photocatalysts and the sacrificial agents. The operando synchrotron provides new insights for understanding the roles of redox mediators.

Propulsion, deformation, and confinement response of hollow nanocellulose millimotors

HYPOTHESIS

Micromotor and nanomotor particles are typically made using dense solid particles that can sediment or be trapped in confined flow environments. Creation of much larger motors should be possible if a very low-density system is used with sufficient strength to carry liquid and still experience propulsive motion. Light, dense millimotors should also be able to deform more than dense solid ones in constrictions.

EXPERIMENTS

Millimotors are created from permeable capsules of bacterial cellulose that are coated with catalse-containing metal-organic frameworks, enabling reactive propulsion in aqueous hydrogen peroxide. The motion of the motors is quantified using particle tracking and the deformation is measured using microcapillary compression and flow through confined channels.

FINDINGS

Two different propulsion mechanisms are dominant depending on the motor surface chemistry: oxygen bubbles are expelled from hydrophilic millimotors, driving motion via recoil force and buoyancy. Hydrophobic millimotors remain attached to growing bubbles and move by buoyancy alone. Despite their large size, the low-density capsules compress to pass through contractions that would impede and be blocked by solid motors. The sparse structure but relatively large size of the motors enables them to transport significant volumes of liquid using minimal solid mass as a motor support structure.

Gas generation due to photocatalysis as a method to reduce the resistance force in the process of motors motion at the air-liquid interface

HYPOTHESIS

The problem of the development of miniature motors able to move on the air-liquid interface at low Reynolds numbers is a crucial challenge due to dominating role of viscous force. To solve this problem the chemical generation of gas can be used. Generated gas pushes liquid out from the surfer surface, so the resistance force is reduced.

EXPERIMENTS

Surfer composed of TiO₂ nanoparticles and ferromagnetic cobalt microparticles moves at the interface of an aqueous solution of hydrogen peroxide under the action of magnetic force. After irradiation with UV or visible light, the gas cavern is formed at the surfer surface due to photo-catalytic decomposition of hydrogen peroxide. As a result, the area of surfer contact with liquid is reduced.

FINDINGS

The resistance force acting on the surfer is reduced due to the liquid pushing out from the surfer surface. This effect is strengthened with the increase in the intensity of gas generation. The resistance force is increased when increasing the liquid viscosity or using a surfactant. The proposed method allows control of the velocity of the motors in a rather wide range by changing the gradient of the magnetic field and parameters of light.

Review of Bubble Applications in Microrobotics: Propulsion, Manipulation, and Assembly

In recent years, microbubbles have been widely used in the field of microrobots due to their unique properties. Microbubbles can be easily produced and used as power sources or tools of microrobots, and the bubbles can even serve as microrobots themselves. As a power source, bubbles can propel microrobots to swim in liquid under low-Reynolds-number conditions. As a manipulation tool, microbubbles can act as the micromanipulators of microrobots, allowing them to operate upon particles, cells, and organisms. As a microrobot, microbubbles can operate and assemble complex microparts in two- or three-dimensional spaces. This review provides a comprehensive overview of bubble applications in microrobotics including propulsion, micromanipulation, and microassembly. First, we introduce the diverse bubble generation and control methods. Then, we review and discuss how bubbles can play a role in microrobotics via three functions: propulsion, manipulation, and assembly. Finally, by highlighting the advantages and current challenges of this progress, we discuss the prospects of microbubbles in microrobotics.

Trapping and detecting nanoplastics by MXene-derived oxide microrobots

Nanoplastic pollution, the final product of plastic waste fragmentation in the environment, represents an increasing concern for the scientific community due to the easier diffusion and higher hazard associated with their small sizes. Therefore, there is a pressing demand for effective strategies to quantify and remove nanoplastics in wastewater. This work presents the “on-the-fly” capture of nanoplastics in the three-dimensional (3D) space by multifunctional MXene-derived oxide microrobots and their further detection. A thermal annealing process is used to convert Ti₃C₂T_x MXene into photocatalytic multi-layered TiO₂, followed by the deposition of a Pt layer and the decoration with magnetic γ-Fe₂O₃ nanoparticles. The MXene-derived γ-Fe₂O₃/Pt/TiO₂ microrobots show negative photogravitaxis, resulting in a powerful fuel-free motion with six degrees of freedom under light irradiation. Owing to the unique combination of self-propulsion and programmable Zeta potential, the microrobots can quickly attract and trap nanoplastics on their surface, including the slits between multi-layer stacks, allowing their magnetic collection. Utilized as self-motile preconcentration platforms, they enable nanoplastics’ electrochemical detection using low-cost and portable electrodes. This proof-of-concept study paves the way toward the “on-site” screening of nanoplastics in water and its successive remediation.

Nanoplastic water pollution represents an increasing concern. Here, photogravitactic MXene-derived microrobots are programmed to trap nanoplastics in the layered structure and magnetically transfer them to low-cost electrodes for further detection.

Micromachines for Microplastics Treatment

The increasing accumulation of persistent nondegradable microplastics in the marine environment represents a global environmental problem. Among emerging approaches to tackle microplastics are micro- and nanomotors, tiny devices capable of autonomous propulsion powered by chemical fuels or light. These devices are capable of on-the-fly recognition, capture, and decomposition of pollutants. In the past, various micromotors were designed to efficiently remove and degrade soluble organic pollutants. Current effort is given to the rational design and surface functionalization to achieve micromotors capable of capturing, transporting, and releasing microplastics of different shapes and chemical structures. The catalytic micromotors performing photocatalysis and photo-Fenton chemistry hold great promise for the degradation of most common plastics. In this review, we highlight recent progress in the field of micromotors for microplastics treatment. These tiny self-propelled machines are expected to stimulate a quantum leap in environmental remediation.

α-Fe2O3/Reduced Graphene Oxide Composites as Cost-Effective Counter Electrode for Dye-Sensitized Solar Cells

The counter electrode (CE) is an important and vital part of dye-sensitized solar cells (DSSCs). Pt CEs show high-performance in DSSCs using iodide-based electrolytes. However, the high cost of Pt CEs restricts their large-scale application in DSSCs and the development of Pt-free CE is expected. Here, α-Fe2O3/reduced graphene oxide (α-Fe2O3/RGO) composites are prepared as the Pt-free CE materials for DSSCs. A simple hydrothermal technique was used to disseminate the α-Fe2O3 solid nanoparticles uniformly throughout the RGO surface. The presence of the α-Fe2O3 nanoparticles increases the specific surface area of RGO and allows the composites to be porous, which improves the diffusion of liquid electrolyte into the CE material. Then, the electrocatalytic properties of CEs with α-Fe2O3/RGO, α-Fe2O3, RGO, and Pt materials are compared. The α-Fe2O3/RGO CE has a similar electrocatalytic performance to Pt CE, which is superior to those of the pure α-Fe2O3 and RGO CEs. After being fabricated as DSSCs, the current–voltage measurements reveal that the DSSC based on α-Fe2O3/RGO CE has a power conversion efficiency (PCE) of 6.12%, which is 88% that of Pt CE and much higher than that of pure α-Fe2O3 and pure RGO CEs. All the results show that this work describes a promising material for cost-effective, Pt-free CEs for DSSCs.

Simultaneous removal of heavy metals and dyes in water using a MgO-coated Fe3O4 nanocomposite: Role of micro-mixing effect induced by bubble generation

This study focused on the development of a nano-adsorbent for contaminant removal without the use of any external energy. An eco-friendly Fe₃O₄@MgO core-shell nanocomposite was synthesized and tested for the removal of a heavy metal, lead (Pb²⁺) and a dye, rhodamine B (RhB). The addition of H₂O₂ into the system enabled the self-mixing of the aqueous solution containing Fe₃O₄@MgO through the generation of bubbles. This system showed an excellent removal efficiency of 99% in just 15 min for Pb²⁺ and 120 min for RhB, which is far better than the control experiment (without H₂O₂). The cation exchange mechanism dominated in the removal of heavy metals, while the adsorptive removal of dye proceeded through the H-bonding between Mg(OH)₂ and dye molecules. The removal efficiency increased exponentially with the increase of H₂O₂ at the optimal concentration of 5% and it was effective over a wide pH range. Moreover, the performance of the Fe₃O₄@MgO-H₂O₂ system was verified for other heavy metals such as Cd, Ni, Zn, Co, and Cu, demonstrating that the Fe₃O₄@MgO-H₂O₂ system can be widely implemented in the treatment of real water matrices contaminated with heavy metals and organic dyes.

Microplastics and nanoplastics: Recent literature studies and patents on their removal from aqueous environment

The presence of microplastics (MP) and nanoplastics (NP) in the environment poses significant hazards towards microorganisms, humans, animals and plants. This paper is focused on recent literature studies and patents discussing the removal process of these plastic pollutants. Microplastics and nanoplastics can be quantified by counting, weighing, absorbance and turbidity and can be further analyzed using scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, surface-enhanced Raman spectroscopy and Raman tweezers. Mitigation methods reported are categorized depending on the removal characteristics: (i) Filtration and separation method: Filtration and separation, electrospun nanofiber membrane, constructed wetlands; (ii) Capture and surface attachment method: coagulation, flocculation and sedimentation (CFS), electrocoagulation, adsorption, magnetization, micromachines, superhydrophobic materials and microorganism aggregation; and (iii) Degradation method: photocatalytic degradation, microorganism degradation and thermal degradation; where removal efficiency between 58 and 100% were reported. As these methods are significantly distinctive, the parameters which affect the MP/NP removal performance e.g., pH, type of plastics, presence of interfering chemicals or ions, surface charges etc. are also discussed. 42 granted international patents related to microplastics and nanoplastics removal are also reviewed where the majority of these patents are focused on separation or filtration devices. These devices are efficient for microplastics up to 20 μm but may be ineffective for nanoplastics or fibrous plastics. Several patents were found to focus on methods similar to literature studies e.g., magnetization, CFS, biofilm and microorganism aggregation; with the addition of another method: thermal degradation.

Critical review of the characteristics, interactions, and toxicity of micro/nanomaterials pollutants in aquatic environments

A wide range of contaminants of emerging concern such as micro/nanoplastics (MPs/PNPs) and metal-nanoparticles (Me-NPs) from anthropogenic activities have been identified in aquatic environments. The hazardous effects of these micro/nanomaterials as pollutants in organisms and the lack of knowledge about their behavior in aquatic environments have generated growing concern in the scientific community. The nanomaterials have a colloidal-type behavior due to their size range but with differences in their physicochemical properties. This review comprises the behavior of micro/nanomaterials pollutants and the physicochemical interactions between MPs/PNPs and Me-NPs in aquatic environments, and their potential toxicological effects in organisms. Moreover, this article describes the potential use of Me-NPs to remove MPs/PNPs present in the water column due to their photocatalytic and magnetic properties. It also discusses the challenge to determine harmful effects of micro/nanomaterials pollutants in organisms and provides future research directions to improve integrated management strategies to mitigate their environmental impact.

Shape-controlled Mn–Fe PBA derived micromotors for organic pollutant removal

A new strategy is employed to prepare Mn–Fe PBA derived oxide micromotors with excellent motion performances through co-precipitation and heat treatment, which can be used for organic pollutant degradation with recycling and reusing advantages.

Manganese-Based Micro/Nanomotors: Synthesis, Motion, and Applications

As emerging micro/nano-scale devices, micro/nanomotors have been innovatively applied in the environmental and biomedical applications. In this paper, the recent advances of Mn-based micro/nanomotors (Mn-micro/nanomotors) in catalytic oxidation of organic contaminants and the mechanisms in decomposition of H₂ O₂ (e.g., the generation of O₂ bubbles and reactive oxygen species) are reviewed. The intrinsic characteristics and synthetic strategies of Mn-based materials are discussed, aiming to gain comprehensive understandings on the asymmetric design of micro/nanomotors. Mn-micro/nanomotors have many advantages such as flexible structures, biocompatibility, powerful motion, long lifetime, and low-cost as compared to noble-metal micro/nanomotors. These merits fulfil Mn-micro/nanomotors great promises from proof-of-concept studies to realistic applications, including pollutant decomposition, trace detection of heavy metal ions, oil removal, drug delivery, isolation of biological targets, and killing bacteria and cancer cells. The great flexibility in fabrication enables diverse and innovative strategies to address challenges for Mn-micro/nanomotors, including high consumption of H₂ O₂ and non-directional motion. Meanwhile, a perspective of Mn-micro/nanomotors in water remediation by coupling the motors with other Fenton/Fenton-like systems to enhance the catalytic activity and to yield more reactive oxygen species is presented. Directions to the design of on-demand H₂ O₂ -fueled Mn-micro/nanomotors for advanced purification of organic contaminants in aquatic systems are also proposed.

Flexible fabrication of lipophilic-hydrophilic micromotors by off-chip photopolymerization of three-phase immiscible flow induced Janus droplet templates

Self-propelled microparticles are promising for lots of applications ranging from analytical detection to water treatment. Herein, we present an effective approach to fabricate lipophilic-hydrophilic micromotors via the photocuring of three-phase immiscible flow induced droplet templates. In the microfluidic system, two immiscible inner fluids, the lipophilic 1, 6-Hexanediol diacrylate (HDDA), and the hydrophilic poly (ethylene glycol) diacrylate (PEGDA), are simultaneously injected into a theta-shaped cylindrical capillary from two separate inlets, and they are emulsified into Janus drops when encountering the outer immiscible silicone oil. Because of the immiscible feature of droplet templates, off-chip photopolymerization strategy has been used, which can significantly decrease the blocking chance of microdevice. And also, the lipophilic-hydrophilic structure of droplets is convenient for the loading of cargos with different characteristics. More importantly, the size and configuration of droplet templates can be flexibly regulated by changing the flow rates of three different phases. Accordingly, multifunctional micromotors can be fabricated by adding different nanoparticles and materials into the HDDA or PEGDA phase first and then photocuring the droplets. Taking the bubble-propelled micromotors for example, we prepare microswimmers by loading Ag, TiO₂ and Fe₃O₄ nanoparticles into the PEGDA phase. The swimming behaviors of micromotors in H₂O₂ solution are systematically investigated, finding that the proportion of PEGDA phase and the concentration of H₂O₂ both positively affect the moving speed. Furthermore, the applicability of motor particles on water treatment is successfully demonstrated by using neutral red solution as the model pollutant. And the micromotors can be recycled using magnets after the catalytic degradation process. Therefore, this micromotor generation technique and this kind of micromotor can be attractive for many applications.

Functionalizing Ti3C2Tx for enhancing fire resistance and reducing toxic gases of flexible polyurethane foam composites with reinforced mechanical properties

Flexible polyurethane foam (FPUF) is the most used polyurethane, but the highly flammable characteristic limits its widespread usage. In this work, ZIF-8@Ti₃C₂T_xwas synthesized to reduce the heat and toxic gases of FPUF. Flame-retardant FPUF was characterized by cone calorimeter (Cone), thermogravimetric analysis/fourier-transform infrared spectroscopy (TG-FTIR), tensileand compression tests. Compared with pure FPUF, these results showed that the peak of heat release rate (PHRR), total heat release (THR), CO and HCN of FPUF6 decreased by 46%, 69%, 27% and 43.5%, respectively. Moreover, the tensile and compression strength of FPUF6 demonstrated a 52% and 130% increment, respectively. The superior dual metal catalytical charring-forming effect and physical barrier effect of ZIF-8@Ti₃C₂T_x were achieved. In summary, a simple and reliable strategy for preparing flame-retardant FPUF with reinforced mechanical and fire safety properties was provided.

Dual-stimuli-responsive CuS-based micromotors for efficient photo-Fenton degradation of antibiotics

Antibiotics as emerging pollutants in water pose great risks to human health. Due to their persistence in the environment, advanced oxidation processes (AOPs) have been proposed for the degradation of antibiotics. Therefore, developing efficient catalysts for AOPs becomes critical for the removal of antibiotics. Herein, we develop self-propelled CuS-based micromotors (CuS@Fe₃O₄/Pt) as active heterogenous catalysts for efficient photo-Fenton degradation of antibiotics. Combining the merits of conventional heterogenous and homogenous catalysts, the prepared micromotors are easy to recycle and free of secondary pollution risks, while demonstrating high degradation efficiency due to self-induced intensification of mass transfer via autonomous motion and microbubble generation. The H₂O₂ in the Fenton reagents can serve as the fuel for the micromotors to drive their self-propulsion by bubbles generated from catalytic decomposition of H₂O₂ by the platinum layer. The dual-stimuli-responsiveness of the micromotors to magnetic field and light irradiation allows multi-modes of propulsion and guidance in different systems. The efficient photothermal effect of CuS enables the micromotors to achieve collective phototactic motion toward light, whereas magnetic responsiveness facilitates the recovery and collection of the micromotors. The synergistic effect of CuS and Fe₃O₄ NPs in H₂O₂ under visible light irradiation generates a large amount of OH· and ·O₂^- to effectively degrade tetracycline within several minutes. With these advantages, the dual-stimuli-responsive CuS-based micromotors provide a new strategy for enhanced degradation of antibiotics in water purification applications.

Microplastics remediation in aqueous systems: Strategies and technologies

In recent years, the ubiquitous detection and accumulation of microplastics (MPs) in the aquatic environment have raised significant concerns on water security and long-term ecological impacts all around the world. Nevertheless, critical reviews on strategic control and effective remediation of MPs in the aqueous phase are still lacking. In this work, we summarise the origins and types of MPs, and then introduce the methodologies for extraction, identification and quantification. More importantly, we for the first time provide a comprehensive overview of the recent advances in the emerging MPs removal and transformation technologies. Except for biodegradation, this review presents new applications of advanced oxidation processes (AOPs) for MPs degradation and utilisation, including photocatalysis, photoreforming and Fenton-like reactions. Physical or catalytic thermal treatment can transform plastics into value-added nanocarbons or hydrocarbons. These transformation technologies demonstrate great potentials in dealing with MPs. The review will guide researchers to further explore the feasible approaches and develop new strategies for advanced control and remediation of MPs in the future.