Preparation and Investigation of High Surface Area Aerogels from Crosslinked Polypropylenes.

Polypropylene-based aerogels with high surface area have been developed for the first time. By chemical crosslinking of polypropylene with oligomeric capped-end amino compounds, followed by dissolution, thermally induced phase separation, and the supercritical CO2 drying process or freeze-drying method, the aerogels exhibit high specific surface areas up to 200 m2/g. Moreover, the silica-cage multi-amino compound was utilized in a similar vein for forming hybrid polypropylene aerogels. According to the SEM, the developed polypropylene-based aerogels exhibit highly porous morphology with micro-nanoscale structural features that can be controlled by processing conditions. Our simple and inexpensive synthetic strategy results in a low-cost, chemically resistant, and highly porous material that can be tailored according to end-use applications.

Flexible Hybrid and Single-Component Aerogels: Synthesis, Characterization, and Applications.

The inherent disadvantages of traditional nonflexible aerogels, such as high fragility and moisture sensitivity, severely restrict their applications. To address these issues, different techniques have been used to incorporate the flexibility in aerogel materials; hence, the term "flexible aerogels" was introduced. In the case of introducing flexibility, the organic part is induced with the inorganic part (flexible hybrid aerogels). Additionally, some more modern research is also available in the fabrication of hybrid flexible aerogels (based on organic-organic), the combination of two organic polymers. Moreover, a new type (single-component flexible aerogels) are quite a new category composed of only single materials; this category is very limited, charming to make the flexible aerogels pure from single polymers. The present review is composed of modern techniques and studies available to fabricate hybrid and single-component flexible aerogels. Their synthesis, factors affecting their parameters, and limitations associated with them are explained deeply. Moreover, a comparative analysis of drying methods and their effectiveness in the development of structures are described in detail. The further sections explain their properties and characterization methods. Eventually, their applications in a variety of multifunctional fields are covered. This article will support to introduce the roadmap pointing to a future direction in the production of the single-component flexible aerogel materials and their applications.

Host-Guest Interaction-Based Supramolecular Self-Assemblies for H2O2 Upregulation Augmented Chemiluminescence Resonance Energy Transfer-Induced Cancer Therapy.

Given that light is hard to reach deep tumor tissue, how to enhance photodynamic therapy (PDT) efficacy is a big challenge. Herein, we proposed the supramolecular polymer self-assemblies (HACP) with bis[2,4,5-trichloro-6 (pentyloxycar-bonyl) phenyl] oxalate as the cargos (HACP@CPPO) to realize the chemiluminescence resonance energy transfer (CRET)-induced generation of 1O2 in situ. HACP was prepared by cinnamaldehyde-modified hyaluronic acid (HA-CA) and ß-cyclodextrin-modified protoporphyrin IX (ß-CD-PPIX) via host-guest interactions. The CA moiety could elevate H2O2 levels for the enhanced production of chemical energy and macrocyclic CD could enhance the stacking distance of PPIX for enhanced 1O2 yield. Thus, HACP@CPPO exhibited excellent antitumor performance without light irradiation.

Enhanced Cd(II) immobilization in sediment with zero-valent iron induced by hydrogenotrophic denitrification.

In this study, an integrated system of Fe0 and hydrogenotrophic microbes mediated by nitrate (nitrate-mediated bio-Fe0, NMB-Fe0) was established to remediate Cd(II)-contaminated sediment. Solid phase characterization confirmed that aqueous Cd(II) (Cd(II)aq) was successfully immobilized and enriched on iron surface due to promoted iron corrosion driven by hydrogenotrophic denitrification and subsequent greater biomineral production such as magnetite, lepidocrocite and green rust. Compared to a Cd(II)aq removal of 21.1% in overlying water of the nitrate-mediated Fe0 (NM-Fe0) system, the NMB-Fe0 system obtained a much higher Cd(II)aq removal of 83.1% after 7 d remediation. The leaching test and sequential extraction results also showed that the leachability of Cd(II) decreased by 75.9% while the residual fraction of Cd(II) increased by 185.7% in comparison with untreated sediment. Besides, the Cd(II)aq removal raised with the increase of nitrate concentration and Fe0 dosage, further revealing the promotion effect of nitrate on Cd(II) removal by bio-Fe0. This study highlighted the involvement of bio-denitrification in the remediation of Cd(II)-contaminated sediment by Fe0 and provided a new insight to enhance its reactivity and applicability for Cd(II) immobilization.

Boosting the Ion Mobility in Solid Polymer Electrolytes Using Hollow Polymer Nanospheres as an Additive.

Solid polymer electrolytes (SPEs) possess improved thermal and mechanical stability as safe energy storage devices. However, their low ion mobilities and poor electrochemical stabilities still hinder the wide industrial application of SPEs. Herein, we introduce an SPE design that provides an enormous number of electrochemically stable pathways and space for lithium-ion transport, blending polymer (polydopamine) hollow nanospheres with an inactive inorganic template into a poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) based SPE. Hollow silica acts as a template for polydopamine processing a large contact area with the polymer electrolyte, and the interface between the polymer electrolyte and hollow composite fillers provides amounts of ion transport channels. In addition, theoretical calculations reveal a strong adsorption between polydopamine and TFSI-, which suppresses the TFSI- motion and meanwhile facilitates the selective Li+ transport. The hollow polydopamine can serve as a versatile platform for anion trapping and has large compatible and stable depression for a well-defined ion transfer interface layer, forming a three-in-one nanocomposite for the enhancement of ionic conductivity with no sacrifice of the mechanical properties. Experimental data confirmed the high mobility of ions within the composite electrolyte with an ionic conductivity of 0.189 mS cm-1 in comparison to the SPE without additives (0.105 mS cm-1) at 60 °C. The mobility of the Li+ increases after adding the polymer-coated inorganic additives, associated with a noticeable enlargement of the electrochemical window. Furthermore, an all-solid-state Li/LiFePO4 battery with a hollow polydopamine nanoparticle-polymer composite electrolyte shows long life, high reversible capacity (134.9 mAh g-1), and high capacity retention (97.2%) after 205 cycles at 0.2 C.

Enhanced bacterial inactivation by activated carbon modified with nano-sized silver oxides: Performance and mechanism.

In this study, nano-sized silver oxides were loaded on activated carbon (nAg2O/AC) through a facile impregnation-calcination method for enhanced bacterial inactivation from drinking water, in which Escherichia coli (E. coli) was used as target bacteria. XRD and SEM characterization confirmed that nano-sized Ag2O particles (50-200 nm) were successfully prepared and uniformly distributed on the surfaces and pores of AC. Due to the structural reducing groups of AC, surface-bound Ag(I) was partially converted to Ag in the nAg2O matrix and the resulted Ag could sterilize E. coli directly. More importantly, surface-bound Ag could catalyze O2 and H2O to generate reactive oxygen species (ROS) for oxidation sterilization, thus significantly enhanced the inactivation efficiency from 0.8 log10 CFU/mL (nAg2O control) and 0.2 log10 CFU/mL (AC control) to 6.0 log10 CFU/mL in the nAg2O/AC system. The inactivation process was highly pH-dependent, and neutral pH was favorable for sterilization. A sterilization efficiency of 5.2 log10 CFU/mL could still be achieved after 5 running cycles, indicating stable sterilization performance of nAg2O/AC. In addition, the nAg2O/AC also exhibited excellent renewability since a sterilization efficiency of 5.8 log10 CFU/mL was obtained after nAg2O being stripped and reloaded on the AC. These results demonstrated that nAg2O-modified AC is an efficient material for sterilization in water treatment.

A facile modification of cation exchange resin by nano-sized goethite for enhanced Cr(VI) removal from water.

A novel macroporous strong acidic cation exchange resin (D001) modified by nano-sized goethite (nFeOOH@D001) was fabricated by using a facile ethanol dispersion and impregnation method, and its efficiency for Cr(VI) removal was tested thereafter. Due to the dispersing effect of ethanol, FeOOH particles of 20-150 nm were coated on the D001 surfaces. The nFeOOH@D001 obtained a Cr(VI) removal efficiency and capacity of 80.2% and 7.4 mg/g respectively, 5 times and 8 times higher than that of the pristine D001. The Cr(VI) removal by nFeOOH@D001 followed the pseudo second-order kinetics and the Langmuir adsorption model. Column experiments also demonstrated that the nFeOOH@D001 exhibited a much better ability to remove Cr(VI) as compared to the D001. Additionally, the nFeOOH@D001 showed a potential for reusability and renewability. The adsorbed nFeOOH@D001 could be easily desorbed by 0.1 M acetic acid and a reuse efficiency of 92.7% could be maintained after 4 desorption-adsorption cycles. The used nFeOOH@D001 could be eluted by 0.1 M HCl to remove nFeOOH, and the renewed D001 could be recoated by nFeOOH and achieved a regeneration rate of 97.8% for Cr(VI) removal. The above results indicated that nano-sized goethite modification is a promising method to endow D001 with the ability to remove Cr(VI) from water.

COCu: A Robust Self-Regenerative Hydrogel with Applicability as Both Hydrated Gel Dressing and Dry Suture for Seamless Tissue Fixation and Repair.

Self-regenerative hydrogels have recently been developed, and represent a special type of self-healing hydrogels with the ability to restore a dehydrated hydrogel with physical damage. In this study, a self-regenerative hydrogel (COCu) based on two chitosan polymers assembled by slow-released Cu2+ is developed. The COCu hydrogel displays an excellent regeneration ability after being dehydrated and fractured. By simple hydration at room temperature, the fragments of the dehydrated gel fuse into one seamless whole, thereby preserving the mechanical properties and functionalities of the original hydrogel. The regeneration process can be conducted repeatedly after different methods of dehydration (natural volatilization, heat drying, lyophilization) and various modes of deconstruction (flakes, powder, lumpy sponge, etc.). Furthermore, the COCu hydrogel provides ultra-stretchability, and it can be stretched into thin (0.01-0.1 mm) filaments, which, when dried (dtCOCu), can be used as suture lines. Moreover, when used as a dry suture, it regenerates into the hydrogel in the presence of the tissue fluid, forming an excellent sealant to immobilize tissues and seamlessly seal wounds. The fast self-regeneration allows for its facile application as both a hydrated gel dressing and dry suture, and offers customized strategies for fixing and repair of different wounds in soft tissues.

One-step removal of harmful algal blooms by dual-functional flocculant based on self-branched chitosan integrated with flotation function.

Harmful algal blooms induce severe environmental problems. It is challenging to remove algae by the current available treatments involving complicate process and costly instruments. Here, we developed a CaO2@PEG-loaded water-soluble self-branched chitosan (CP-SBC) system, which can remove algae from water in one-step without additional instrumentation. This approach utilizes a novel flocculant (self-branched chitosan) integrated with flotation function (induced by CaO2@PEG). CP-SBC exhibited better flocculation performance than commercial flocculants, which is attributed to the enhanced bridging and sweeping effect of branched chitosan. CP-SBC demonstrated outstanding biocompatibility, which was verified by zebrafish test and algae activity test. CaO2@PEG-loaded self-branched chitosan can serve as an "Air flotation system" to spontaneous float the flocs after flocculation by sustainably released O2. Furthermore, CP-SBC can improve water quality through minimizing dissolved oxygen depletion and reducing total phosphorus concentrations.

Transparent floatable magnetic alginate sphere used as photocatalysts carrier for improving photocatalytic efficiency and recycling convenience.

Practical application of powder photocatalysts is far from satisfying due to their low photon utilization, inconvenient recovery and potential environmental risk. In this study, an easily recoverable, environmentally friendly and highly transparent floatable magnetic photocatalyst carrier was prepared based on biopolymer alginate and Fe3O4 particles. Further, three different types of photocatalysts were chosen as model semiconductor photocatalysts and loaded on the shell of the carriers. The freeze process facilitated the formation of internal cavities that enhanced floating ability and transparency of the spheres. Meanwhile, the excellent floating performance offered massive reaction sites for pollutants reacting with photocatalysts, O2 and photons on the air/water interface. Photodegradation results showed all three floatable hybrid photocatalysts exhibited enhanced photocatalytic efficiencies compared to the virgin photocatalysts. In short, the carrier can integrate excellent floating ability, environmental friendliness and full recycling with good stability, and it can greatly improve the photocatalytic efficiency of various powder semiconductor photocatalysts.

Preparation of highly dispersive and antioxidative nano zero-valent iron for the removal of hexavalent chromium.

In this study, carboxymethyl cellulose (CMC) was employed to stabilize zero-valent iron nanoparticles (CMC-nFe0) to improve their dispersity and antioxidation for enhanced hexavalent chromium (Cr(VI)) removal. Scanning electron microscope (SEM) observation revealed that the nFe0 agglomerated in clusters, while the CMC-nFe0 connected as chains and presented higher dispersity. Therefore, compared with 54% of the nFe0, the Cr(VI) removal rate of the CMC-nFe0 increased by 0.8 time, reaching 97%. Besides, the nFe0 precipitated in 1 d and was obviously oxidized within 7 d under anoxic condition, leading to a rapid decease of Cr(VI) removal efficiency from 54% to 3% in 56 d. In contrast, the CMC-nFe0 showed no obvious subsidence and oxidized phenomenon within 14 d, which retained a relatively high Cr(VI) removal efficiency of 63% in 56 d, contributing to effective blockage of dissolved oxygen infiltrating from solution to nFe0 particles in presence of CMC. After reaction, the valence state distribution of Cr between solution and material surface indicated that Cr(VI) reduction was dominant comparing to physical adsorption to particles in the remediation process conducted by CMC-nFe0. In addition, lower initial pH and higher iron dosage facilitated Cr(VI) removal. Those results indicated that the dispersive and antioxidative characteristics of CMC-nFe0 were significantly superior to those of nFe0, and CMC stabilization thereafter can be a promising method to promote Cr(VI) elimination by nFe0.

Highly Stretchable and Transparent Ionic Conductor with Novel Hydrophobicity and Extreme-Temperature Tolerance.

Highly stretchable and transparent ionic conducting materials have enabled new concepts of electronic devices denoted as iontronics, with a distinguishable working mechanism and performances from the conventional electronics. However, the existing ionic conducting materials can hardly bear the humidity and temperature change of our daily life, which has greatly hindered the development and real-world application of iontronics. Herein, we design an ion gel possessing unique traits of hydrophobicity, humidity insensitivity, wide working temperature range (exceeding 100°C, and the range covered our daily life temperature), high conductivity (10-3~10-5 S/cm), extensive stretchability, and high transparency, which is among the best-performing ionic conductors ever developed for flexible iontronics. Several ion gel-based iontronics have been demonstrated, including large-deformation sensors, electroluminescent devices, and ionic cables, which can serve for a long time under harsh conditions. The designed material opens new potential for the real-world application progress of iontronics.

ß-Cyclodextrin-modified hyaluronic acid-based supramolecular self-assemblies for pH- and esterase- dual-responsive drug delivery.

Although some drug-based supramolecular systems have been constructed to overcome multidrug resistance and enhance the bioavailability of chemical drugs, strengthening the specific stimuli-responsive and active targeting ability of these systems is still a major challenge. In this paper, the synthesis and self-assembly behaviour of supramolecular self-assemblies with active targeting ß-cyclodextrin-modified hyaluronic acid (HA-CD) and drug-drug conjugates (curcumin-oxoplatin, Cur-Pt) as building moieties were carefully investigated. Notably, the curcumin was chosen not only as the chemical anti-cancer drug, but also acted as the guest molecule which could be included into CD cavity to form host-guest interaction-based supramolecular assemblies. The obtained self-assemblies exhibited pH- and esterase-responsive drug release behaviours. Furthermore, basic cell experiments were performed to prove their effective cellular toxicity based on A549 cells and PC3 cells with high expression of CD44 receptor but they showed no toxicity to normal LO-2 cells with low expression of CD44 receptor, which suggests their potential application in the targeted drug release field.

Nitrate mediated biotic zero valent iron corrosion for enhanced Cd(II) removal.

In this study, nitrate mediated biotic zero-valent iron (Fe0) corrosion was employed to enhance cadmium (Cd) removal from groundwater. In comparison with a 17.5% Cd(II) removal treated with abiotic Fe0, a 3.9 times higher Cd(II) removal of 86.2% was recorded in the nitrate-mediated biotic Fe0 system. Solids phase characterization confirmed that biogenic minerals such as green rust and iron sulfide could be formed in the nitrate-amended biotic Fe0 system, offering large amount of adsorption sites for Cd(II) removal. The decrease of nitrate concentration and the competition with cathodic hydrogen for biological nitrate reduction by extra organic substance such as sodium acetate both showed significant inhibition on Cd(II) removal, further proving that hydrogenotrophic denitrification was the main mechanism for enhanced Cd(II) removal. Besides, a relatively high Cd(II) removal efficiency was observed over a pH range of 5-8, and it increased with declining pH values. These results demonstrated that the bio-amended iron corrosion technology coupled Fe0-assisted H2 production with hydrogenotrophic denitrification exhibited excellent Cd(II) removal capacity, which enabled this technology a promising potential for Cd(II)-contaminated groundwater treatment and an alternative strategy for Cd(II) and nitrate co-contaminated groundwater remediation.

Ionic liquid assisted electrochemical coating zinc nanoparticles on carbon cloth as lithium dendrite suppressing host.

The application of lithium metal anode with high specific capacity and energy density is limited by the volume expansion and pulverization caused by dendrite growth during cycle process. We propose a composite lithium anode by immersing molten lithium on the flexible three-dimensional (3D) carbon cloth scaffold with the zinc nanoparticles. The lithiophilic zinc nanoparticles layer of framework is synthesized by fast and easy electrochemical deposition from ionic liquid avoiding high temperature, high pressure and toxic reagent. The lithium is infused into the 3D lithiophilic framework, the composite anode is obtained. The steady network structure can confine the lithium and lead to Li dendrite restraining and reducing volume change due to the low interfacial resistance and reduce the effective current density, which induced the homogeneous Li growth. Benefiting from this, the Li infused 3D carbon cloth-Zn symmetric battery exhibits a low stripping/plating overpotential (~30 mV) and can be stable over 900 h at 1 mA cm-2. The Li//LiFePO4 battery delivers higher reversible capacity (140 mAh g-1 at 2 C and 120 mAh g-1 at 5 C) and stable cycling for 1500 and 2000 cycles than bare Li.

Morphology-tunable and pH-responsive supramolecular self-assemblies based on AB2-type host-guest-conjugated amphiphilic molecules for controlled drug delivery.

Although stimuli-responsive supramolecular self-assemblies have been constructed, the controlled drug delivery induced by morphology transitions of these supramolecular self-assemblies on the basis of host-guest-conjugated monomers (HGCMs) are few reported. In this paper, the self-assembly behaviors of AB2-type HGCMs, e.g., ß-cyclodextrin-benzimidazole2 (ß-CD-BM2), were investigated at neutral and acidic pH conditions, respectively. Specifically, ß-CD-BM2 first self-assembled into fan-shaped supramolecular self-assemblies with a hydrodynamic diameter of 163 nm at neutral pH, whereas they were further dissociated into spherical supramolecular self-assemblies with a size of 52 nm under acidic conditions. This morphology transition process was utilized to conduct a two-stage DOX delivery under neutral and acidic pH. Basic cell experiments demonstrated that the drug-loaded ß-CD-BM2-based supramolecular self-assemblies with varied morphology could inhibit cancer cell proliferation, indicating their potential application in the field of drug delivery.

Photo- and pH- Dual-Responsive ß-Cyclodextrin-Based Supramolecular Prodrug Complex Self-Assemblies for Programmed Drug Delivery.

Despite the fact that progress has been made in the application of supramolecular prodrug self-assemblies to enhance the functionality of drug-delivery systems, corresponding research on multi-responsive supramolecular prodrug self-assemblies for programmed drug delivery is still limited. In this paper, the synthesis and self-assembly behavior of supramolecular prodrug complexes (SPCs) with ß-cyclodextrin-acylhydrazone-doxorubicin (ß-CD-hydrazone-DOX) and the targeting of azobenzene-terminated poly[2-(dimethylamino)ethyl methacrylate] (Azo-PDMA-FA) as a building block were investigated. The obtained SPCs could also form self-assemblies on the basis of their amphiphilic nature. Next, SPC-based multi-compartment vesicles and complex micelles, which were confirmed by transmission electron microscopy and dynamic/static light scattering, were obtained with good reversibility under alternative visible light or UV irradiation. Furthermore, three-stage programmed drug-delivery behavior was observed from dual-responsive SPC-based self-assemblies by utilizing UV and pH stimuli. Specifically, the SPCs first self-assembled into multicompartmental vesicles, which was accompanied by a slow release of DOX. Next, UV-light irradiation induced the dissociation of ß-CD/Azo, which led to morphology transition and a slight increase in the rate of release of DOX. Upon transferring the self-assemblies to phosphate-buffer solution (pH 5.0), the release rates increased notably as a result of the broken acylhydrazone bond. Finally, basic cell experiments further demonstrated that the SPC-based self-assemblies could be internalized into cancer cells, which suggests their promise for applications in cancer therapy.

Cross-linked succinyl chitosan as an adsorbent for the removal of Methylene Blue from aqueous solution.

Removal of a basic dye (Methylene Blue) from aqueous solution was investigated using a cross-linked succinyl-chitosan (SCCS) as sorbent. The chemical structures of chitosan and its derivatives were testified by FT-IR. X-ray diffraction, DTG analysis and swelling measurements were conducted to clarify the characteristics of the chemically modified chitosan. The effect of process parameters, such as pH of the initial solution, and concentrations of dyes on the extent of Methylene Blue (MB) adsorption was investigated. The Langmuir isotherm model was used to fit the equilibrium experimental data, giving a maximum sorption capacity of 289.02 mg/g at 298 K. Kinetic studies showed that the kinetic data were well described by the pseudo-second-order kinetic model. Thermodynamic parameters such as enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were determined to be -25.32 kJmol(-1), -6.76 kJmol(-1) and -62.36 Jmol(-1) K(-1), respectively, which leads to a conclusion that the adsorption process is spontaneous and exothermic.