Injectable, self-healing and degradable dynamic hydrogels with tunable mechanical properties and stability by thermal-induced micellization.

Dynamic hydrogels possessing injectable, degradable and self-healing abilities have attracted considerable attention in the biomedical field in recent years, but it is difficult to tune the mechanical properties and stability of conventional dynamic hydrogels. In this work, we synthesized ABA-triblock copolymers via RAFT polymerization, where the A block consisted of thermo-sensitive poly(N-isopropylacrylamide-co-diacetone acrylamide) and the B block was hydrophilic poly(acrylamide). Subsequently, dynamic hydrogels were obtained based on the acylhydrazone bonds between the triblock copolymers and adipic acid dihydrazide (ADH). The obtained hydrogels exhibited injectable and self-healable abilities. In response to the thermal-induced micellization of their temperature-responsive blocks, the mechanical strength of the hydrogels not only increased, but also they exhibited high stability even at pH 2.0. Moreover, the hydrogel in the stable state could be degraded by the fracture of its trithiocarbonate groups. In addition, the hydrogels exhibited good cytocompatibility and controlled release behavior for doxorubicin (DOX). Considering these attractive tunable properties, these dynamic hydrogels show various potential applications in the biomedical field, such as drug carriers and cell or tissue engineering scaffolds.

Photocatalytic Performance of the MOF-Coating Layer on SPR-Excited Ag Nanowires.

The photoactive metal-organic frameworks (MOFs) were controllably coated on the surface plasmon resonance-excited Ag nanowires in a layer manner to adjust the photocatalytic activity. The influence of the thickness of the MOF coating layer on the photocatalytic activity was investigated. A thicker MOF coating layer not only facilitated the photogenerated electron-hole separation efficiency but also provided a larger Brunauer-Emmett-Teller surface area, thus enhancing the photocatalytic activity. This work provided a new way to adjust the photocatalytic activity of the photoactive MOF.

Progressive Increasing of Pt Nanoparticles with Multiple-Layered Manner inside Metal-Organic Frameworks for Enhanced Catalytic Activity.

Single-layered, double-layered, and triple-layered Pt nanoparticles with a well-defined arrangement were encapsulated inside metal-organic frameworks (MOFs) to investigate the catalytic performance influenced by the progressive increasing of Pt nanoparticles inside MOFs; the results show that the catalytic activity of the Pt-MOF hybrid catalysts increases progressively with the progressive increasing of the Pt nanoparticles inside MOFs. Progressive increasing of Pt nanoparticles with a multiple-layered manner inside MOFs provides a new route for designing well-organized hybrid catalysts of noble metal nanoparticles and MOFs with enhanced catalytic activity.

Inserting Pt Nanoparticles at the Designated Location inside Metal-Organic Frameworks for Promoted Catalytic Performance.

Metal-organic frameworks (MOFs)-supported noble metal nanoparticles (NMNPs) catalysts attract increasing attention due to their high durability and efficiency in catalytic reactions. In this work, Pt nanoparticles are inserted at the designated location inside MIL-100(Fe) to investigate the location-effect of NMNPs inside MOFs on the catalytic reaction. The comparison test on the reduction of p-nitrophenol suggests that the location of the Pt nanoparticles inside MIL-100(Fe) largely influences the catalytic performance and the Pt nanoparticles inside MIL-100(Fe) locate closer to the outer surface of the MIL-100(Fe), providing higher catalytic efficiency. Possible reasons are concluded as the location of the Pt nanoparticles inside MIL-100(Fe) dominates the reactants transport pathway and the loading amount of Pt nanoparticles.

Controlling crystal growth of MIL-100(Fe) on Ag nanowire surface for optimizing catalytic performance.

Ag/MIL-100(Fe) core/sheath nanowire with controllable thickness of the MIL-100(Fe) sheath was prepared by controlling the crystal growth of MIL-100(Fe) on the Ag nanowire surface. The evolution of the MIL-100(Fe) sheath monitored by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermogravimetric analyses (TGA), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FT-IR), and N2 adsorption-desorption analysis indicates that the thickness of the MIL-100(Fe) sheath increases with the increasing number of crystal growth cycles of MIL-100(Fe) on the Ag nanowire surface. Catalytic reaction over Ag/MIL-100(Fe) core/sheath nanowire suggests that the thickness of the MIL-100(Fe) sheath largely influences the catalytic performance and it is quite important to control the crystal growth of MIL-100(Fe) on the Ag nanowire surface for optimizing catalytic performance.

Preparation of a Ti0.7W0.3O2/TiO2 nanocomposite interfacial photocatalyst and its photocatalytic degradation of phenol pollutants in wastewater.

A Ti0.7W0.3O2/TiO2 nanocomposite interfacial photocatalyst was designed and prepared for the photocatalytic degradation of phenol pollutants in wastewater. The detailed properties of the Ti0.7W0.3O2/TiO2 nanocomposite interface (NCI) were analyzed by XRD, SEM, EDX, DRS, UPS and XPS technologies, showing that anatase TiO2 nanospheres (NSs) were uniformly dispersed on the surface of rutile Ti0.7W0.3O2 nanoparticles (NPs) and formed the nanocomposite interface. The DRS and UPS results of 5 wt% Ti0.7W0.3O2/TiO2 NCI indicated a greatly broadened light response range with a wavelength shorter than 527 nm and a shorter band gap energy of 2.37 eV. The conduction band of TiO2 NSs, Ti0.7W0.3O2 NPs and 5 wt% Ti0.7W0.3O2/TiO2 NCI were measured based on the results of the valence band and band gap energy obtained via XPS and DRS, and then the energy level diagram of Ti0.7W0.3O2/TiO2 NCI was proposed. The photocatalytic degradation of phenol at Ti0.7W0.3O2/TiO2 NCI with different loading ratios of Ti0.7W0.3O2 NPs was investigated under optimum conditions (i.e., pH of 4.5, catalyst dosage of 0.45 g L-1 and phenol initial concentration of 95 ppm) under the illumination of ultraviolet visible light. Also, 5 wt% Ti0.7W0.3O2/TiO2 NCI exhibited the highest photocatalytic activity, with the initial rate constant (k) calculated as 0.09111 min-1. After recycling six times, Ti0.7W0.3O2/TiO2 NCI showed good stability and recyclability. The involvement of superoxide radicals in the initial reaction at Ti0.7W0.3O2/TiO2 NCI was evidenced by the use of a terephthalic acid (TA) fluorescent probe. Besides, UV-Vis spectroscopy, UHPLC-MS and GC-MS technologies were used to analyze the main intermediates in the photocatalytic degradation of phenol. The probable photocatalytic degradation mechanism of phenol at Ti0.7W0.3O2/TiO2 NCI was also proposed.

Encapsulating Pt Nanoparticles through Transforming Fe3O4 into MIL-100(Fe) for Well-Defined Fe3O4@Pt@MIL-100(Fe) Core-Shell Heterostructures with Promoting Catalytic Activity.

Metal-organic framework (MOF)-based magnetic Pt catalyst Fe3O4@Pt@MIL-100(Fe) core-shell heterostructures were prepared through transforming Fe3O4 into MIL-100(Fe) in benzene-1,3,5-tricarboxylic acid solution along with encapsulating the Pt nanoparticles successively adsorbed onto the surface of the Fe3O4 nanosphere and the continuously forming surfaces of the growing MIL-100(Fe) crystals. This method circumvented the obstacles, controlling the formation of metal nanoparticles (MNPs) inside MOFs or regulating growth of MOFs around the MNPs, for preparing an MNP-MOF composite catalyst. The obtained well-defined Fe3O4@Pt@MIL-100(Fe) core-shell heterostructure was shown promoting catalytic activity on the reduction of 4-nitrophenol due to the synergistic effect between the Pt nanoparticles and the MIL-100(Fe) shell and recycling convenience due to the rapid separation of the Fe3O4 core under an external magnetic field.

Macroporous monoliths with pH-induced switchable wettability for recyclable oil separation and recovery.

HYPOTHESIS: The effective separation and recovery of oils from water is important for the protections of ecosystems and the environment. Polymeric porous monoliths have been demonstrated as attractive absorbents for oil/water separation. However, the recyclability was mainly realized by squeezing, combustion, or centrifugation, which may restrict in elastic materials, destroy the adsorbates or need special apparatus. Thus it is desirable to developing monoliths with controllable oil absorption and desorption. EXPERIMENTS: A series of "smart" monoliths with pH-induced switchable wettability were fabricated by high internal phase emulsion (HIPE) polymerization and epoxide ring-opening for the incorporation of amine groups. The resultant monoliths and their wettabilities were examined using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), nitrogen adsorption/desorption and contact angle analysis, respectively. The oil separation efficiency and recyclability were evaluated. FINDINGS: The monoliths with macroporous structure can undergo switchable wettability under reversible pH stimulation. As an absorbent, the monoliths not only separated and recovered organic solvents and oils (including crude oil) from aqueous mixtures through a reversible and recyclable absorption and desorption process upon alternating the pH between 7.0 and 1.0, but also continuously expulsed oils from water surfaces in a continuous manner with the aid of external driving pressures. Moreover, the monoliths also allowed the effective separation of surfactant-free and surfactant-stabilized oil-in-water emulsions with high separation efficiency.

Giant Microgels with CO2-Induced On-Off, Selective, and Recyclable Adsorption for Anionic Dyes.

Adsorbents that are capable of controllable pollutants adsorption and release without secondary pollution are attractive in water treatment. Here, we propose eco-friendly CO2 as a trigger to switch the charge states and collapse-expansion transition of giant microgels consisting of hydrophilic acrylamide and hydrophobic 2-(diethylamino)ethyl methacrylate and demonstrated the on-off, selective, and recyclable adsorption of anionic dyes on microgels under CO2 stimulation. Apart from easy-handling separation from the water by a simple filtration process, the maximum adsorption capacity is as high as 821 mg g-1, and the adsorption isotherms and kinetics obeyed Langmuir isotherm and the pseudo-second-order kinetics models, respectively. The anionic dye can also be separated from the mixture solution using CO2-treated microgels. Moreover, a wastewater treatment prototype with microgel-packed column was fabricated. Under continuous flow condition, the dye was removed and recovered by alternative bubbling CO2 and flushing with aqueous alkali (pH 12). Thus, this type of microgels with CO2-induced protonation-deprotonation transition can serve as a cost-effective, environmentally friendly, and efficient adsorbent for water purification applications.

Hydrogel Effects Rapid Biofilm Debridement with ex situ Contact-Kill to Eliminate Multidrug Resistant Bacteria in vivo.

Multidrug resistance and the refractory character of bacterial biofilms are among the most difficult challenges in infection treatment. Current antimicrobial strategies typically are much more effective for prevention of biofilm formation than for eradication of established biofilms; these strategies also leave dead bacteria and endotoxin in the infection site, which impairs healing. We report a novel hydrogel that eradicates biofilm bacteria by non-leaching-based debridement followed by ex situ contact-killing (DESCK) away from the infection site. The debridement effect is likely due to the high water swellability and microporosity of the cross-linked network which is made from polyethylene glycol dimethacrylate tethered with a dangling polyethylenimine (PEI) star copolymer. The large pore size of the hydrogel makes the cationic pore walls highly accessible to bacteria. The hydrogel also degrades in the presence of infection cells, releasing star cationic PEI into the infection site to contact-kill bacteria remaining there. DESCK hydrogel effectively kills (>99.9% reduction) biofilms of methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Pseudomonas aeruginosa (CR-PA) and Acinetobacter baumannii in a murine excisional wound infection model. Silver-based wound dressings (controls) showed almost no killing of CR-PA and MRSA biofilms. This DESCK hydrogel greatly reduces the bioburden and inflammation and promotes wound healing. It has great potential for diverse infection treatment applications.

pH-Switchable and self-healable hydrogels based on ketone type acylhydrazone dynamic covalent bonds.

Stimuli-responsive hydrogels using dynamic covalent bonds (DCBs) as cross-links may exhibit simultaneously the stimuli-responsibility of the physical gels and stability of the chemical gels. We prepared well-defined, ketone-based polymers based on commercially available diacetone acrylamide (DAAM) by a reversible addition-fragmentation chain transfer (RAFT) polymerization technique. The polymers could react with hexanedihydrazide yielding hydrogels. The mechanics, flexible properties and gelator concentration of the hydrogels can be tuned by varying the ratio of DAAM. Gelation time and hydrogel stability were gravely affected by the pH of the surrounding medium. The hydrogels possess self-healing ability without any external stimuli and undergo switchable sol-gel transition by the alternation of pH. In addition, the hydrogels showed pH-responsive controlled release behavior for rhodamine B. These kinds of ketone-type acylhydrazone DCB hydrogels, avoiding the aldehyde component, may ameliorate their biocompatibility and find potential applications in biomedicines, tissue engineering, etc.

Au-HKUST-1 Composite Nanocapsules: Synthesis with a Coordination Replication Strategy and Catalysis on CO Oxidation.

A novel coordination replication of Cu2O redox-template strategy is reported to efficiently fabricate Au-HKUST-1 composite nanocapsule, with a HKUST-1 sandwich shell and an embedded Au nanoparticles layer. The novel synthesis procedure involves forming Au nanoparticles on the surface of Cu2O, transforming partial Cu2O into HKUST-1 shell via coordination replication, and removing the residual Cu2O by acid. The as-prepared Au-HKUST-1 composite nanocapsules displayed high catalytic activity on CO oxidation.

High-Performance Capacitive Deionization Disinfection of Water with Graphene Oxide-graft-Quaternized Chitosan Nanohybrid Electrode Coating.

Water disinfection materials should ideally be broad-spectrum-active, nonleachable, and noncontaminating to the liquid needing sterilization. Herein, we demonstrate a high-performance capacitive deionization disinfection (CDID) electrode made by coating an activated carbon (AC) electrode with cationic nanohybrids of graphene oxide-graft-quaternized chitosan (GO-QC). Our GO-QC/AC CDID electrode can achieve at least 99.9999% killing (i.e., 6 log reduction) of Escherichia coli in water flowing continuously through the CDID cell. Without the GO-QC coating, the AC electrode alone cannot kill the bacteria and adsorbs a much smaller fraction (<82.8 ± 1.8%) of E. coli from the same biocontaminated water. Our CDID process consists of alternating cycles of water disinfection followed by electrode regeneration, each a few minutes duration, so that this water disinfection process can be continuous and it only needs a small electrode voltage (2 V). With a typical brackish water biocontamination (with 10(4) CFU mL(-1) bacteria), the GO-QC/AC electrodes can kill 99.99% of the E. coli in water for 5 h. The disinfecting GO-QC is securely attached on the AC electrode surface, so that it is noncontaminating to water, unlike many other chemicals used today. The GO-QC nanohybrids have excellent intrinsic antimicrobial properties in suspension form. Further, the GO component contributes toward the needed surface conductivity of the CDID electrode. This CDID process offers an economical method toward ultrafast, contaminant-free, and continuous killing of bacteria in biocontaminated water. The proposed strategy introduces a green in situ disinfectant approach for water purification.

CO2-switchable wormlike micelles.

A wormlike micellar system that undergoes a fully reversible, repeatable "sol-gel" transition upon alternative treatment with CO2 and N2 has been developed based on a C18-tailed polyamine surfactant.

Functionalization of multi-walled carbon nanotubes with thermo-responsive azide-terminated poly(N-isopropylacrylamide) via click reactions.

Covalently functionalized multi-walled carbon nanotubes (MWNTs) were prepared by grafting well-defined thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) via click reactions. First, azide-terminated poly(N-isopropylacrylamide) (N3-PNIPAM) was synthesized by reversible addition fragmentation chain-transfer (RAFT) polymerization, and then the N3-PNIPAM moiety was connected onto MWNTs by click chemistry. The products were characterized by means of FT-IR, TGA and TEM. The results show that the modification of MWNTs is very successful and MWNTs functionalized by N3-PNIPAM (MWNTs-PNIPAM) have good solubility and stability in water. TEM images show the functionalized MWNTs are dispersed individually, indicating that the bundles of original MWNTs are separated into individual tubes by surface modification with polymer chains. These MWNTs modified with PNIPAM represent a potential nano-material for preparation of hydrophilic composite materials.

CO(2) -responsive "smart" single-walled carbon nanotubes.

A new type of "smart" single-walled carbon nanotubes is created by wrapping a pyrene-labeled CO(2) -responsive polymer via π-π stacking. The polymer/SWNT hybrids not only undergo a hydrophobic-hydrophilic transition upon CO(2) stimulus of CO(2) in a mixed solvent, but also exhibit switchable dispersion/aggregation states upon the alternate bubbling of CO(2) and N(2) in pure water.

A novel smart polymer responsive to CO2.

An amidine-based polymer was prepared by combination of RAFT polymerization and "click" reaction, and the polymer undergoes a hydrophobic-hydrophilic transition upon the stimulus of CO(2).