Developing green and efficient technologies for surface modification of magnetic nanoparticles (MNPs) is of crucial importance for their biomedical and environmental applications. This study reports, for the first time, a novel strategy by integrating metal-free photoinduced electron transfer–atom transfer radical polymerization (PET-ATRP) with the bioinspired polydopamine (PDA) chemistry for controlled architecture of functional polymer brushes from MNPs. Conformal PDA encapsulation layers were initially generated on the surfaces of MNPs, which served as the protective shells while providing an ideal platform for tethering 2-bromo-2-phenylacetic acid (BPA), a highly efficient initiator. Metal-free PET-ATRP technique was then employed for controlled architecture of poly(glycidyl methacrylate) (PGMA) brushes from the core–shell MNPs by using diverse organic dyes as photoredox catalysts. Impacts of light sources (including UV and visible lights), photoredox catalysts, and polymerization time on the composition and morphology of the PGMA brushes were investigated. Moreover, the versatility of the PGMA-functionalized core–shell MNPs was demonstrated by covalent attachment of ethylenediamine (EDA), a model functional molecule, which afforded the MNPs with improved hydrophilicity, dispersibility, and superior binding ability to uranyl ions. The green methodology by integrating metal-free PET-ATRP with facile PDA chemistry would provide better opportunities for surface modification of MNPs and miscellaneous nanomaterials for biomedical and electronic applications.Keywords: core−shell structure; magnetic nanoparticles; photoinduced atom transfer radical polymerization; polydopamine; surface-initiated polymerization;

Developing facile and robust technologies for effective enrichment of uranium from seawater is of great significance for resource sustainability and environmental safety. By exploiting mussel-inspired polydopamine (PDA) chemistry, diverse types of PDA-functionalized sorbents including magnetic nanoparticle (MNP), ordered mesoporous carbon (OMC), and glass fiber carpet (GFC) were synthesized. The PDA functional layers with abundant catechol and amine/imine groups provided an excellent platform for binding to uranium. Due to the distinctive structure of PDA, the sorbents exhibited multistage kinetics which was simultaneously controlled by chemisorption and intralayer diffusion. Applying the diverse PDA-modified sorbents for enrichment of low concentration (parts per billion) uranium in laboratory-prepared solutions and unpurified seawater was fully evaluated under different scenarios: that is, by batch adsorption for MNP and OMC and by selective filtration for GFC. Moreover, high-resolution X-ray photoelectron spectroscopic and extended X-ray absorption fine structure studies were performed for probing the underlying coordination mechanism between PDA and U(VI). The catechol hydroxyls of PDA were identified as the main bidentate ligands to coordinate U(VI) at the equatorial plane. This study assessed the potential of versatile PDA chemistry for development of efficient uranium sorbents and provided new insights into the interaction mechanism between PDA and uranium.

Mesoporous silica/polymer hybrids with well-preserved mesoporosity were prepared by integrating the initiators for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) technique with the bio-inspired polydopamine (PDA) chemistry. By manipulating the auto-oxidative polymerization of dopamine, uniform PDA layers were deposited on the surfaces and pore walls of ordered mesoporous silicas (OMSs), thereby promoting the immobilization of ATRP initiators. Poly(glycidyl methacrylate) (PGMA) brushes were then grown from the OMSs by using the ICAR ATRP technique. The evolution of the mesoporous silica/polymer hybrids during synthesis, in terms of morphology, structure, surface and porous properties, was detailed. And, parameters influencing the controlled growth of polymer chains in the ICAR ATRP system were studied. Taking advantage of the abundant epoxy groups in the PGMA platform, post-functionalization of the mesoporous silica/polymer hybrids by the covalent attachment of macrocyclic ligands for the adsorptive separation of lithium isotopes was realized. Adsorption behavior of the functionalized hybrids toward lithium ions was fully investigated, highlighting the good selectivity, and effects of temperature, solvent and counter ions. The ability for lithium isotope separation was evaluated. A higher separation factor could be obtained in systems with softer counter anions and lower polarity solvents. More importantly, due to the versatility of the ICAR ATRP technique, combined with the non-surface specific PDA chemistry, the methodology established in this work would provide new opportunities for the preparation of advanced organic–inorganic porous hybrids for broadened applications.

Mussel-inspired polydopamine (PDA) chemistry was employed for the surface modification of ordered mesoporous carbons (OMCs), improving the hydrophilicity, binding ability toward uranium ions, as well as enriching chemical reactivity for diverse postfunctionalization by either surface grafting or surface-initiated polymerization. Uniform PDA coating was deposited on the surface of CMK-3 type OMCs via self-polymerization of dopamine under mild conditions. Surface properties and morphology of the PDA-coated CMK-3 can be tailored by adjusting the dopamine concentration and coating time, without compromising the meso-structural regularity and the accessibility of the mesopores. Due to high density of −NH groups (4.7 μmol/m2 or 2.8 group/nm2) and −OH groups (9.3 μmol/m2 or 5.6 group/nm2) of the PDA coating, the modified CMK-3 showed improved hydrophilicity and superior adsorption ability toward uranyl ions (93.6 mg/g) in aqueous solution. Moreover, with the introduction of α-bromoisobutyryl bromide (BiBB) initiator to the PDA-coated CMK-3, we demonstrated for the first time that activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) can be conducted for controlled growth of polymer brushes from the surface of OMCs. Thus, PDA chemistry paves a new way for surface modification of OMCs to create a versatile, multifunctional nanoplatform, capable of further modifications toward various applications, such as environmental decontamination, catalysis, and other areas.

This study presents an effective and facile strategy by integrating surface-initiated single electron transfer living radical polymerization (SET-LRP) with mussel-inspired polydopamine (PDA) chemistry for controlled building of a novel class of core–shell magnetic nanoparticles (MNPs) for highly-efficient uranium enrichment. The strategy initially involves the deposition of a PDA encapsulation layer by spontaneous self-polymerization on the Fe3O4 core, which serves as a safety shell and provides an enabling platform for anchoring of 2-bromoisobutyryl bromide (BiBB) to form macro-initiators. Dense polyacrylonitrile (PAN) brushes are grown from the BiBB-attached PDA shell via SET-LRP using Cu(0)/Me6TREN as a catalytic/ligand system, followed by conversion to amidoxime (AO) functionalized polymer brushes. The core–shell Fe3O4@PDA@PAO MNPs exhibit favorable superparamagnetic characteristics and a fast response within 6 s under an applied magnetic field. Due to the strong binding ability of AO ligands, Fe3O4@PDA@PAO shows a remarkable adsorption capacity (qe = 162.5 mg g−1) toward uranyl ions under optimal pH conditions. A study on the adsorption kinetics suggests that the adsorption process might conform to the pseudo-second-order model. We conclude that the Fe3O4@PDA@PAO MNPs have the potential for effective enrichment and magnetic separation of uranium, and the integrative synthetic strategy combining the SET-LRP technique and PDA chemistry would bring extensive opportunities for versatile surface modification of nanomaterials for more demanding applications.

Surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) integrated with mussel-inspired polydopamine (PDA) chemistry was, for the first time, employed for controlled grafting of poly(glycidyl methacrylate) (PGMA) brushes from carbon nanotubes (CNTs). The strategy initially involved deposition of a PDA layer by spontaneous self-polymerization, which is a benign and nonsurface specific way for anchoring 2-bromoisobutyryl bromide to form initiators on the CNTs. Dense and uniform PGMA brushes were then grown via ARGET ATRP using low concentration of Cu catalyst in different solvents. With abundant highly reactive epoxy groups, the PGMA-grafted CNTs could serve as a versatile platform for further modification or functionalization. Ethylenediamine ligands were facilely introduced, imparting the functionalized CNTs with record-high adsorption ability toward uranium ions among CNTs composites. The integrated strategy combining surface-initiated ARGET ATRP technique and PDA chemistry would provide new opportunities for surface engineering of nanomaterials for advanced applications.

The development of economical and green technologies for the effective recovery of palladium has attracted worldwide attention in recent years. Magnetic separation involving the use of functional magnetic nanoparticles (MNPs) with superparamagnetic characteristics holds great promise in this respect. This study presents a novel class of core–shell structured superparamagnetic microspheres decorated with polyazamacrocyclic receptors, which show a highly-selective binding to Pd(II) in HNO3 media. The superparamagnetic microspheres possess a high saturation magnetization (53.8 emu g−1) and high adsorption capacity (qmax ≈ 105.3 μmol g−1), affording efficient enrichment and fast separation (within 13 seconds) of palladium under an applied magnetic field. Adsorptive behavior was fully investigated combined with the corresponding theoretical analysis by using kinetic equations and Langmuir/Freundlich isotherm models. Moreover, the coordination mechanism of the polyazamacrocyclic receptors to Pd(II) was carefully examined based on high resolution X-ray photoelectron spectroscopy (XPS) and FT-IR spectrophotometry. A suggested mechanism involving the synergistic effect of the cyclic amines and carboxyl arms of the polyazamacrocyclic receptors was proposed to describe the coordination manner, while explaining the selectivity to Pd(II) in HNO3 solutions. From a practical perspective, the Pd(II)-enriched microspheres could be readily regenerated for cycle use. We conclude that this kind of polyazamacrocyclic receptor decorated superparamagnetic microsphere is of potential use for the effective recovery of Pd(II) as well as other precious metals.

In this study, a new kind of short-channel SBA-15 mesoporous silica decorated with polyazamacrocyclic ligands was developed, showing selective binding ability to palladium ions based on host–guest interaction. The established synthesis protocol involved the co-condensation synthesis of an SBA-15 precursor with halogen atoms uniformly incorporated in the mesoporous silica matrix, followed by the anchoring of 1,4,7,10-teraazacyclododecane (Cyclen) ligands via post-grafting. Due to the short straight channels and large pore size facilitating the diffusion of the molecules and ions, the mesoporous silicas were found to possess a high density of the functional Cyclen ligands, as well as high adsorption capacity of Pd(II) in HNO3 solutions. The structure and morphology of the Cyclen functionalized mesoporous silicas were fully characterized. And, the adsorption behavior toward Pd(II) was investigated combined with the theoretical interpretation of the experimental data based on typical kinetic equations, isotherm models and thermodynamic equations. Furthermore, the detailed coordination mechanism between the Cyclen ligands and Pd(II) was examined by high resolution X-ray photoelectron spectroscopy (XPS). A suggested mechanism involving the synergistic effect of four cyclic amines in the Cyclen ligands was proposed to describe the coordination to Pd(II) in HNO3 solutions. Overall, this work provides a facile and effective pathway to build polyazamacrocycle ligand decorated mesoporous silicas with short-channels and large pores, which might be potentially used for molecule recognition and selective enrichment of precious metals.

We report a new macromolecular architecture of dual functional block copolymer brushes on commercial thin-film composite (TFC) membranes for integrated “defending” and “attacking” strategies against biofouling. Mussel-inspired catechol chemistry is used for a convenient immobilization of initiator molecules to the membrane surface with the aid of polydopamine (PDA). Zwitterionic polymer brushes with strong hydration capacity and quaternary ammonium salt (QAS) polymer brushes with bactericidal ability are sequentially grafted on TFC membranes via activators regenerated by electron transfer–atom transfer radical polymerization (ARGET-ATRP), an environmentally benign and controlled polymerization method. Measurement of membrane intrinsic transport properties in reverse osmosis experiments shows that the modified TFC membrane maintains the same water permeability and salt selectivity as the pristine TFC membrane. Chemical force microscopy and protein/bacterial adhesion studies are carried out for a comprehensive evaluation of the biofouling resistance and antimicrobial ability, demonstrating low biofouling propensity and excellent bacterial inactivation for the modified TFC membrane. We conclude that this polymer architecture, with complementary “defending” and “attacking” capabilities, can effectively prevent the attachment of biofoulants and formation of biofilms and thereby significantly mitigate biofouling on TFC membranes.Keywords: antifouling; antimicrobial; ARGET-ATRP; block copolymers; thin-film composite (TFC) membranes

In this study, a new bifunctional calixcrown host molecule with superb complexation of cesium (Cs) (distribution ratio D > 45) was synthesized, which was first employed as cross-linker for building a novel class of thermo-responsive poly(N-isopropylacrylamide) microspheres. AFM cross-section analysis revealed a negative shift of lower critical solution temperature (LCST) of the hydrogel microspheres, owing to the calixcrown moieties at the cross-links affecting the balance of hydrogen bonding and hydrophobic association in the 3D polymer network. Due to the host–guest ion recognition, the hydrogel microspheres showed the highest selectivity factors (SFs) so far of Cs over the competing alkali cations (SFCs/K = 20.0, SFCs/Na = 34.0). Moreover, since the thermo-triggered conformation change of polymer network interacting with the calixcrown–Cs complexation, the hydrogel microspheres exhibited a temperature-sensitive ion-binding behavior, which provided a feasible mechanism for controllable release of the bound Cs by tuning the surrounding temperature. Reversible Cs uptake-release cycles were achieved without compromising their complexation property. From a practical perspective, the calixcrown integrated hydrogel microspheres were proven to be able to effectively remove the trace Cs in real seawater (removal rate ∼ 93.5%).

A new kind of silica-based adsorbent with high selectivity and efficient adsorption for palladium ion (Pd(II)) was synthesized in this study. A macrocyclic polyether isomer was modified for incorporation to the silica matrix as a ligand to realize the complexation between Pd(II) and the adsorbent. The adsorption of Pd(II) in HNO3 media was evaluated by both batch and column operations. Influences including acidity, contact time, initial metal concentration and elution conditions were detailed. From a practical viewpoint, the functionalized adsorbent was employed for the recovery of Pd(II) from the simulated high level liquid waste (HLLW) containing a large amount of interferences. Superior selectivity to Pd(II) as well as a recovery rate higher than 90% was obtained. A mechanism concerning the formation of complex ion-pair was proposed for the description of the Pd(II)-binding process. The macrocyclic ligand functionalized silica adsorbent possesses potential for the recovery of the palladium resource in radioactive liquid waste.Graphical abstractA new silica-based adsorbent functionalized with macrocyclic ligand was synthesized. The adsorbent showed high selectivity and efficient adsorption to Pd(II) in HNO3 media. Enrichment of Pd(II) in simulated radioactive waste stream was realized with a recovery rate of high than 90%.Highlights► Novel silica-based adsorbent functionalized with macrocyclic ligand. ► High selectivity and efficient adsorption of Pd(II). ► Pd(II)-recovery rate higher than 90% in simulated radioactive stream.

A series of dicyclohexano-18-crown-6 (DCH18C6) homologues containing different alkyl substituents were synthesized for a comparative study of the extraction ability towards strontium. The synthesis and the structure characterization of the intermediates and the products were detailed. The crown ether homologues were labeled as CX-DCH18C6 (X=3∼7), where the X represents the number of the carbon atoms in the alkyl substituents. The extraction ability of the CX-DCH18C6 samples towards strontium in solvent extraction system was investigated. The substituent effect of the samples was discussed, and the factors affecting the separation such as solvent, acidity and initial metal concentration were examined.

The first example of well-ordered mesoporous organosilica with high selectivity towards Pb(II) based on host–guest interactions was developed. Due to the high functionalization of a specific macrocyclic host, DCH18C6, with easy accessibility, the mesoporous organosilica showed remarkable recognition and efficient adsorption of Pb(II) in a multicomponent system.

A novel kind of organosilica functionalized with dicyclohexano-18-crown-6 (DCH18C6) was synthesized in this study. The DCH18C6 molecule, well known as an excellent complexing agent of strontium, was modified for chemical bonding to the organosilica matrix via a co-condensation approach. 29Si and 13C solid-state NMR, ESEM and N2 adsorption-desorption measurement were employed to characterize the organosilica's structure and surface properties. The functionalized organosilica showed favourable adsorption capacity to the strontium, and the distribution coefficient (Kd) of 114.5 cm3/g could be obtained in 1 mol/L HNO3 solution. This novel functionalized organosilica might be potentially used for the separation of the strontium in radioactive liquid waste.

A novel kind of organosilica functionalized with dicyclohexano-18-crown-6 (DCH18C6) was synthesized in this study. The DCH18C6 molecule, well known as an excellent complexing agent of strontium, was modified for chemical bonding to the organosilica matrix via a co-condensation approach. 29Si and 13C solid-state NMR, ESEM and N2 adsorption-desorption measurement were employed to characterize the organosilica's structure and surface properties. The functionalized organosilica showed favourable adsorption capacity to the strontium, and the distribution coefficient (Kd) of 114.5 cm3/g could be obtained in 1 mol/L HNO3 solution. This novel functionalized organosilica might be potentially used for the separation of the strontium in radioactive liquid waste.

Mesoporous silica/polymer hybrids with well-preserved mesoporosity were prepared by integrating the initiators for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) technique with the bio-inspired polydopamine (PDA) chemistry. By manipulating the auto-oxidative polymerization of dopamine, uniform PDA layers were deposited on the surfaces and pore walls of ordered mesoporous silicas (OMSs), thereby promoting the immobilization of ATRP initiators. Poly(glycidyl methacrylate) (PGMA) brushes were then grown from the OMSs by using the ICAR ATRP technique. The evolution of the mesoporous silica/polymer hybrids during synthesis, in terms of morphology, structure, surface and porous properties, was detailed. And, parameters influencing the controlled growth of polymer chains in the ICAR ATRP system were studied. Taking advantage of the abundant epoxy groups in the PGMA platform, post-functionalization of the mesoporous silica/polymer hybrids by the covalent attachment of macrocyclic ligands for the adsorptive separation of lithium isotopes was realized. Adsorption behavior of the functionalized hybrids toward lithium ions was fully investigated, highlighting the good selectivity, and effects of temperature, solvent and counter ions. The ability for lithium isotope separation was evaluated. A higher separation factor could be obtained in systems with softer counter anions and lower polarity solvents. More importantly, due to the versatility of the ICAR ATRP technique, combined with the non-surface specific PDA chemistry, the methodology established in this work would provide new opportunities for the preparation of advanced organic–inorganic porous hybrids for broadened applications.

The development of economical and green technologies for the effective recovery of palladium has attracted worldwide attention in recent years. Magnetic separation involving the use of functional magnetic nanoparticles (MNPs) with superparamagnetic characteristics holds great promise in this respect. This study presents a novel class of core–shell structured superparamagnetic microspheres decorated with polyazamacrocyclic receptors, which show a highly-selective binding to Pd(II) in HNO3 media. The superparamagnetic microspheres possess a high saturation magnetization (53.8 emu g−1) and high adsorption capacity (qmax ≈ 105.3 μmol g−1), affording efficient enrichment and fast separation (within 13 seconds) of palladium under an applied magnetic field. Adsorptive behavior was fully investigated combined with the corresponding theoretical analysis by using kinetic equations and Langmuir/Freundlich isotherm models. Moreover, the coordination mechanism of the polyazamacrocyclic receptors to Pd(II) was carefully examined based on high resolution X-ray photoelectron spectroscopy (XPS) and FT-IR spectrophotometry. A suggested mechanism involving the synergistic effect of the cyclic amines and carboxyl arms of the polyazamacrocyclic receptors was proposed to describe the coordination manner, while explaining the selectivity to Pd(II) in HNO3 solutions. From a practical perspective, the Pd(II)-enriched microspheres could be readily regenerated for cycle use. We conclude that this kind of polyazamacrocyclic receptor decorated superparamagnetic microsphere is of potential use for the effective recovery of Pd(II) as well as other precious metals.

The first example of well-ordered mesoporous organosilica with high selectivity towards Pb(II) based on host–guest interactions was developed. Due to the high functionalization of a specific macrocyclic host, DCH18C6, with easy accessibility, the mesoporous organosilica showed remarkable recognition and efficient adsorption of Pb(II) in a multicomponent system.