Unique Three-dimensional Porous Structure Research Articles

Antibacterial polylysine-containing hydrogels for hemostatic and wound healing applications: preparation methods, current advances and future perspectives.

The treatment of various types of wounds such as dermal wounds, multidrug resistant bacteria-infected wounds, and chronic diabetic wounds is one of the critical challenges facing healthcare systems. Delayed wound healing can impose a remarkable burden on patients and health care professionals. In this case, given their unique three-dimensional porous structure, biocompatibility, high hydrophilicity, capability to provide a moist environment while absorbing wound exudate, permeability to both gas and oxygen, and tunable mechanical properties, hydrogels with antibacterial function are one of the most promising candidates for wound healing applications. Polylysine is a cationic polymer with the advantages of inherent antibacterial properties, biodegradability, and biocompatibility. Therefore, its utilization to engineer antibacterial hydrogels for accelerating wound healing is of great interest. In this review, we initially discuss polylysine properties, and then focus on the most recent advances in polylysine-containing hydrogels (since 2016) prepared using various chemical and physical crosslinking methods for hemostasis and wound healing applications. Finally, the challenges and future directions in the engineering of these antibacterial hydrogels for wound healing are discussed.

N, O, P-doped porous carbon with high surface utilization and long cycling life for supercapacitors

The development of miniaturized and lightweight supercapacitors (SCs) becomes a hot research region. Improving the surface area utilization of porous carbon materials can effectively promote the energy density and power density of SCs. This work first constructs three-dimensional porous poly(p-phenylenediamine) hydrogel through adding phytic acid. Thereafter, N, O, P-doped porous carbon (NOPPC) was obtained via simple one-step pyrolysis treatment. The unique three-dimensional porous structure of NOPPC inherited from poly(p-phenylenediamine) hydrogel provides plentiful ion storage space and ion transportation channels. Heteroatom-doped feature endows NOPPC with good wettability and more active surface area. The surface utilization of NOPPC-800 reaches up to 2.56 F m−2, which is better than many carbon materials in literatures. NOPPC-800 can still maintain 135 F g−1 at 20 A g−1. The capacity retention ratio of NOPPC-800 can reach up to 93.4 % after 10000 cycles at 10 A g−1. The quantitative analysis of energy storage mechanism of NOPPC illustrates the synergistic impact of pore structure and doped heteroatoms. These electrochemical results show that NOPPC possesses good practical application value. NOPPC-800//NOPPC-800 supercapacitor shows high energy density and excellent cycle stability. The results show that the balance of heteroatom content, specific surface area and conductivity is the key to obtain promising carbon electrode materials and can be realized via tuning carbonization temperature. This work also demonstrates that rational structure control of carbon precursor is the effective way to promote the capacity of carbon materials.

A self-assembly all-polysaccharide hydrogel for the aquatic heavy metal ions management and utilization

Hydrogels with a unique three-dimensional porous structure are regarded as good adsorbents to treat heavy metal ions-contaminated water. However, the post-treatment of the hydrogels after the wastewater treatment is still a big problem. We herein proposed to use the TEMPO-oxidized cellulose nanofibers (TOCN)/cationic guar gum (CGG) self-assembly hydrogel to adsorb Cu2+ from its contaminated water. The Cu2+-adsorbed hydrogel was demonstrated to be a good stress-sensing material responsive to the loading weight. In addition, the Cu2+-adsorbed hydrogel was transformed into a Cu-doped carbon aerogel after the freeze-drying and carbonization treatments and the resultant carbon aerogel exhibited good and stable electrochemical property. It had an aerial specific capacitance of 3.14 F·cm−2 when the current density was 3 mA·cm−2. Importantly, the existence of copper largely enhanced the electrochemical property of the carbon aerogel since it led to the improvement in conductivity and pseudocapacitance. This work might spur the application of hydrogel in heavy metal ions-contaminated water treatment and provide new ways to convert pollutants into products.

Preparation of phosphoric-modified aloe vera/chitosan aerogels and their efficient adsorption of U(VI).

The efficient adsorption of radioactive elements from nuclear wastewater is an important research topic in the environmental field. The unique three-dimensional porous structure of aerogels has great potential in the field of adsorption. Phosphoric-modified aloe vera/chitosan aerogel (CS/AL-AP) was prepared from chitosan, phosphoric acid, and aloe powder by vacuum freeze-drying self-assembly. The maximum adsorption of uranyl ions by CS/AL-AP was found to be 322.34mg/g at pH 6, adsorption time of 120min, solid-to-liquid ratio of 0.125g/L, reaction temperature of 303K, and initial uranyl ion concentration of 50mg/L. The adsorption process is consistent with the Langmuir isotherm model and the quasi-secondary kinetic model, indicating that the adsorption process is monolayer adsorption. The type of adsorption is mainly chemisorption. FTIR and XPS analyses indicate that the adsorption of U(VI) by CS/AL-AP results from the combined action of coordination or chelation of amino, hydroxyl, and carboxyl groups. In addition, CS/AL-AP shows excellent adsorption capacity in the presence of complex co-existing ions. After five adsorption-desorption experiments, the adsorption capacity of CS/AL-AP for uranyl ions remained at a high level. It indicates that CS/AL-AP has good stability and recoverability. The results indicate that CS/AL-AP has excellent potential in the field of uranium removal.

Facile fabrication of biobased porous material via the photocuring technique and a template-assisted approach for oil/water separation

In this study, we developed a facile, low-cost and eco-friendly approach to prepare a sustainable, porous, polymeric sorbent for oil/water separation by using photocurable soybean oil-based urethane methacrylate and inexpensive salt porogen as raw materials. By combining UV curing technology and a salt template-assisted method, a biobased porous sorbent with good hydrophobicity, lipophilicity, and recyclability was prepared. The effects of particle size and content of salt porogen on the density, morphology, porosity and surface wettability of porous sorbent were analyzed and discussed in detail to optimize the preparation conditions. Due to its unique three-dimensional porous structure and large specific surface area, the prepared biobased porous material exhibits the ability of rapid organic solvent absorption and could serve as sorbents that effectively realized the separation of oil/water mixtures. Moreover, all of the key materials are almost low cost and available in large quantities, meaning that this biobased porous material is expected to be used in oil/water separation on a large scale.

Carbonized bamboo parenchyma cells loaded with functional carbon nanotubes for preparation composite phase change materials with superior thermal conductivity and photo-thermal conversion efficiency

Phase change materials (PCMs) are widely used in the field of energy storage management owing to their store and release thermal energy ability through latent heat. However, organic PCMs have the problems of easy leakage, low thermal conductivity and photo-thermal conversion performance, which greatly prevent their practical application. In order to solve these defects, a novel shape stable composite PCMs was prepared by adding polyethylene glycol (PEG) into porous carbonized bamboo parenchyma cells (CPC) containing carbon nanotubes (CNTs). The supporting materials containing CNTs not only had unique three-dimensional porous structure, but also had continuous heat transfer network structure. Compared with pure PEG, the thermal conductivity (TC) of PEG/CPC-CNTs with 0.494 W/m·K was increased by 128%. The prepared composite PCMs had melting and crystallization latent heat with 149.4 J/g and 144.1 J/g. In terms of shape stability, the PEG encapsulation rate by CPC reached 80% which was better than that of untreated PC. Thermo-gravimetric (TG) analysis and thermal cycling experiments showed that PEG/CPC-CNTs had superior physical and chemical stability. More importantly, the matrix material composed of CPC and CNTs made the composite PCMs with a photo-thermal conversion efficiency up to 87.2%. So, PEG/CPC-CNTs composite PCMs with a simple preparation method have great application potential in the field of bamboo or wood based buildings materials such as wood plastic composite, particleboard, floor or roof panels and so on.

Preparation and characterization of multi-network hydrogels based on sodium alginate/krill protein/polyacrylamide—Strength, shape memory, conductivity and biocompatibility

Sodium alginate/krill protein/polyacrylamide (SA/AKP/PAM) hydrogel with “covalent bond―ion complex―hydrogen bond” multi-network structure was prepared by covalent cross-linking and complexion ion crosslinking using SA, AKP, and acrylamide (AM) as raw materials. The effects of ion species (Fe3+, Ba2+, Sr2+, Ca2+, and Zn2+) on the structure, morphology, and properties of multi-network hydrogels were studied in detail. The results showed that the mechanical strength of ionic cross-linked hydrogels increased significantly. The compressive strength of Fe3+ cross-linked hydrogels was 5.56 MPa, 16.13 times that of non-ionic crosslinked hydrogels. The results of ionic conductivity measurements showed that hydrogels had significant ionic conductivity and were sensitive to external forces. Interestingly, the hydrogel can be used as a capacitive pen in mobile phone writing, painting and dialing numbers. Moreover, ionic cross-linked hydrogels had a unique three-dimensional porous structure with gradient distribution, excellent shape memory effect, and good biocompatibility. Fe3+, Ba2+, Sr2+, and Ca2+ cross-linked hydrogels were nontoxic and conducive to the adhesion and growth of Schwann cells. These excellent properties of ionic cross-linked SA/AKP/PAM hydrogels have broad applications prospects in flexible electronic devices, sensors, soft electronic skins, and tissue engineering.

Achieving reversible precipitation-decomposition of reactive Li2S towards high-areal-capacity lithium-sulfur batteries with a wide-temperature range

Facilitating polysulfide conversion by electrocatalysis is a promising strategy to suppress shuttle effect in lithium-sulfur (Li-S) batteries, yet the active sites in electrocatalysts are gradually passivated by continuous formation of Li2S passivation layer over cycling, making it challenging to achieve steady conversion of sulfur species. Herein, a strategy of reactive Li2S collaborated with dual-directional Fe3C electrocatalyst is proposed to achieve fast and continuous conversion of sulfur species for drastically boosting the performance of Li-S batteries. During the reduction process, reactive Li2S with unique three-dimensional porous structure is precipitated on Fe3C surface, which not only shortens ion/electron diffusion path but also exposes and retains more active sites in Fe3C. While for the following oxidation process, Fe3C also promotes the decomposition of reactive Li2S to refresh electrocatalyst surface. Therefore, the high catalytic activity of Fe3C is well retained during the entire electrochemical process, as verified by comprehensive experimental and theoretical calculation results. Eventually, Fe3C enables stable operation of high-areal-capacity Li-S batteries (> 6.0 mAh cm−2) under a wide-temperature range (-10 to 40 °C). Our strategy of coupling reactive Li2S with a bidirectional electrocatalyst provides a new avenue for developing high-energy and wide-temperature Li-S batteries.

Carbonized wood loaded with carbon dots for preparation long-term shape-stabilized composite phase change materials with superior thermal energy conversion capacity

The leakage issue, low thermal conductivity and low photo-thermal conversion capacity of organic phase change material (PCMs) greatly limits their practical utilization. Herein, a novel shape-stabilized composite PCMs with enhanced thermal conductivity and superior photo-thermal conversion efficiency was fabricated by incorporating polyethylene glycol (PEG) into porous carbonized wood loaded with carbon dots (CDs). The CDs-contained supporting material was not only characterized by unique three-dimensional porous structure, but also beneficial to prevent the leakage of melted PEG during the phase change process. The underlying reason was that extra hydrogen-bonding interaction between CDs and PEG can be readily formed in addition to surface tension, capillary action. Thus, the constructed PCMs outperformed the one without CDs incorporation in terms of shape-stabilized performance. Further, the CDs-contained PCMs exhibited high thermal conductivity (0.449 W/m K), which was comparable to the PCMs using carbonized wood as single supporting material, but showing 117% higher than that of pristine PEG. More importantly, this novel supporting material fabricated by integrating carbonized wood and CDs also imparted the resultant PCMs with high photo-thermal conversion efficiency (84.4%), latent heat (112.4 J/g), thermal reliability and thermal stability, thus demonstrating great potential utilization in constructing solar water heating systems.

Direct laser writing of copper-graphene composites for flexible electronics

Copper-graphene composites have potential applications in flexible electronics due to their unique three-dimensional porous structure, high specific surface area, high electrical conductivity and electrochemical properties. Here, a simple room temperature fabrication method for conductive copper-graphene composites on different substrates, such as glass and polycarbonate, using direct laser writing process without pre-synthesis of copper nanomaterials and graphene flakes is presented. This process uses copper ion precursor and laser to generate copper nanoparticles and in-situ join them to form a network structure. Meanwhile, graphene also can be synthesized and coated on copper networks. The as-prepared copper-graphene composites are highly conductive and electrochemically active for thin conductive film and electrodes of supercapacitor. The composite film has a sheet resistance of 0.57Ω sq−1 and the capacitance of as-written copper-graphene all-solid-state flexible micro-supercapacitor is 13.2mF cm−2 at a current density of 0.5mA cm−2. This simple and low temperature process for composite structures will enable the rapid fabrication of flexible devices with low cost.

Ultrafine SnO2 nanoparticles anchored in the porous corn straw carbon substrate for high-performance Li-ion batteries application

Abstract Ultrafine SnO2 nanoparticles anchored in porous corn straw carbon as an anode material of Li-ion batteries are synthesized via a facile hydrothermal method. The unique three-dimensional porous structure of corn straw carbon provides ideal accommodation for SnO2 (SnO2/P-CSC), and effectively alleviates the free expansion of SnO2 during charging-discharging process. The SnO2/P-CSC composite exhibits a high capacity of 648 mA h g−1 after 100 cycles at 0.2 C. In particular, compared with porous corn straw carbon (P-CSC) and pure SnO2, the capacity of SnO2/P-CSC is 1.6 times of P-CSC and 2.7 times of SnO2 respectively. The high-performances may benefit from the 3D structure of P-CSC and the synergistic effects between the SnO2 and P-CSC. The as-proposed synthetic strategy not only provides a new scalable application for corn straw carbon as a sustainable anode but also solves the serious volume expansion problem of SnO2.

Fabrication and photovoltaic performance of counter electrode of 3D porous carbon composite

Dye-sensitized solar cell (DSSC) has been widely investigated due to its low cost, simple fabrication process, and excellent photoelectric conversion efficiency. Generally, the DSSC is composed of photoanode, electrolyte and counter electrode. At present, platinum (Pt) film delivers the highest photoelectric conversion efficiency in the available counter electrode materials. However, Pt film is very expensive and prepared by relatively complicated and high-cost magnetron sputtering, which seriously hinders the large-scale applications in DSSC. Therefore, it is of highly academic and engineering significance to develop novel counter electrode materials with low cost and high photoelectric conversion efficiency to replace expensive Pt counter electrode. Previous research shows that carbon-based nanomaterials such as graphene and carbon nanotubes ard promising to be used as highly efficient counter electrode materials. However, the high-cost and complicated fabrication process restrict their practical applications in DSSC. To address such issues, here in this work, we present and fabricate a highly efficient and low-cost three-dimensional porous carbon composite, which is constructed by the relatively dense and conductive graphite film as bottom layer (PC layer), and the porous carbon nanoparticle film as top layer (CC layer). Our fabricated DSSC consists of commercial TiO<sub>2</sub> photoanode (m 4 mm×4 mm), and PC, CC, CC/PC composite, or Pt counter electrode with a size of m 8 mm×8 mm. The results show that under illumination (100 mW/cm<sup>2</sup>) provided by a solar simulator, the short circuit current densities (open circuit voltages) of DSSCs with PC, CC, CC/PC, and Pt counter electrodes are 11.45 mA/cm<sup>2</sup> (0.72 V), 11.88 mA/cm<sup>2</sup> (0.73 V), 12.00 mA/cm<sup>2</sup> (0.75 V), and 13.46 mA/cm<sup>2</sup> (0.74 V), respectively. The filling factors of DSSCs with PC, CC, and CC/PC are 56.09%, 59.80%, 65.28%, and 62.69%, respectively; the photoelectric conversion efficiencies of DSSCs with PC, CC, and CC/PC are 4.61%, 5.20%, 5.90%, and 6.26%, respectively. It is noted that compared with CC layer or PC layer counter electrode, the CC/PC counter electrode delivers better photovoltaic performance. Particularly, the filling factor of DSSC with CC/PC (65.28%) is even 4.10% higher than that of DSSC with commercial Pt (62.69%), and the photoelectric conversion efficiency of the CC/PC-based DSSC is as large as 5.90%, which reaches 94.2% of the Pt-based DSSC (6.26%). The excellent performance of DSSC with CC/PC counter electrode is attributed to the unique three-dimensional porous structure, which can not only facilitate the transfer of electrons and ions, but also provide abundant catalytic sites; these synergistic effects greatly enhance the photovoltaic conversion performance of CC/PC-based DSSC.

Facile one-pot synthesis of superhydrophobic reduced graphene oxide-coated polyurethane sponge at the presence of ethanol for oil-water separation

Polyurethane (PU) sponge has attracted significant interest in oil-water separation for its unique three-dimensional porous structure. However, its oil-absorption efficacy is dramatically limited by its poor hydrophobicity. Herein, superhydrophobic reduced graphene oxide-coated polyurethane (RGO@PU) sponge has been facilely fabricated using a one-pot solvothermal method at the presence of ethanol. The formation of RGO-coating layer on the surface of PU sponge is promoted with the assistance of ethanol, because the addition of ethanol decreases the surface tension of aqueous GO solution and improves the wettability of PU sponges. The as-prepared RGO@PU sponge with a superhydrophobic surface (water contact angle of 153°) exhibits a high oil-absorption capacity of more than 37 times of its original mass. A strong recycling absorption capacity (34 g/g) can be observed even after the RGO@PU sponge has experienced 50 oil absorption-desorption cycles. Moreover, our RGO@PU sponges have potential application as a promising absorbent for oil-water separation due to their fast oil-absorption rate (the oil can be removed in 5 s) and high oil-water separation efficiency (∼99%).

Highly Efficient and Rapid Lead(II) Scavenging by the Natural Artemia Cyst Shell with Unique Three-Dimensional Porous Structure and Strong Sorption Affinity

Heavy metal purification of water is a worldwide issue. In this work, we first find that the discarded Artemia cyst shell exhibits a unique three-dimensional porous structure, which can be recycled for efficient toxic Pb(II) removal. The hierarchical skeleton comprised of the macro–meso–micropore confirmation as well as 17 types of amino acid species provides fast ion accessibility and a strong sorption affinity. The results prove that an extremely rapid Pb capture is obtained in less than 2 min, strong adsorption occurs in the presence of high concentration of Ca/Mg/Na ions, and selectivity is far beyond that of the commercial 001x7 (greater than 50 times). More importantly, an efficient application is achieved with a treatment capacity of 9100 kg wastewater/kg sorbent, which is 45 times greater than the performance of commercially activated carbon and ion-exchange resin. The effluent can be dramatically reduced to below 10 μg/L level (WHO). In addition, we can also regenerate the exhausted biomaterial A...

Three-dimensional porous biocarbon wrapped by graphene and polypyrrole composite as electrode materials for supercapacitor

A unique nature derived three-dimensional porous biocarbon, graphene (G), and polypyrrole composite as electrode materials for supercapacitor was successfully fabricated, which utilizes the advantage of the natural porous carbon structure, G and polypyrrole to promote the electrochemical performance of this composite electrode. Firstly, natural loofah and G oxide composite was prepared by direct dip-coating process. Secondly, high-temperature carbonization strategy was used to prepare loofah-based carbons–G (LBCs-G) composite. Thirdly, polypyrrole was directly coated on LBCs–G composite by applying electrochemical deposition method. The unique three-dimensional porous structure incorporated with G and polypyrrole boost the capacitance ascribe to both the electric double-layer capacitance and pseudocapacitance. The results also reveal that there are synergistic effects among the porous structure, G and polypyrrole.

Combined electro-catazone/electro-peroxone process for rapid and effective Rhodamine B degradation

An integral electro-catazone and electro-peroxone (E-cataperoxone) process was developed for quick and effective oxidation of Rhodamine B (RhB) as the model refractory organic pollutant in this study. A mesoflower-structured TiO2-coated porous Titanium gas diffuser (MFT-PTGD) acted as both the anode and the O3 gas diffuser, while carbon polytetrafluoroethylene was used as the cathode. During O3/O2 mixture flowing through the MFT-PTGD, O3 was electrochemically catalyzed simultaneously by the TiO2 mesoflower at the anode (via an electro-catazone reaction) and the in situ generated H2O2 at the cathode (via an electro-peroxone reaction) to achieve a high yield of ·OH. The individual processes show integral effects and significantly enhances the RhB degradation rate and efficacy. Additionally, owing to the unique three-dimensional porous structure and flow-through configuration of the MFT-PTGD anode, the O3 flow-through mode is superior to O3 flow-by mode for the E-cataperoxone oxidation of RhB. These results suggest that the E-cataperoxone process is an effective and promising means of degrading refractory organic pollutants in wastewater.

Synthesis, characterization and adsorption of cationic dyes by CS/P(AMPS-co-AM) hydrogel initiated by glow-discharge-electrolysis plasma

In this work, a novel chitosan/P(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylic amide) (CS/P(AMPS-co-AM)) hydrogel was successfully prepared by a simple one-step method using glow-discharge-electrolysis plasma (GDEP) initiated copolymerization, in which N,N′-methylenebisacrylamide was used as a cross-linking agent. A copolymerization mechanism of AMPS and AM onto CS initiated by GDEP was proposed. The structure, thermal stability and morphology of CS/P(AMPS-co-AM) hydrogel were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), TG/DTG, and scanning electron microscope (SEM). This hydrogel was employed as an absorbent for the removal of methylene blue (MB) and malachite green (MG) from aqueous solutions. The effects of pH, contact time and equilibrium concentration on the dye adsorption were investigated batchwise. FTIR and XRD indicated that AM and AMPS were grafted onto the CS backbone successfully, forming copolymer. TG/DTG suggested that grafted AMPS and AM onto CS could change the thermal stability of the CS. SEM showed a unique three-dimensional porous structure for the CS/P(AMPS-co-AM) hydrogel. The optimum pH for the removal of cationic dyes was 5.8, and time of adsorption equilibrium was achieved in 90 min. The CS/P(AMPS-co-AM) hydrogel exhibited a very high adsorption potential, and its adsorption capacities calculated based on the Langmuir isotherm for MB and MG were 1,538.5 and 917.4 mg g−1, respectively. The dye adsorption data fitted well to the pseudo-second-order model and Langmuir model at 25 °C with pH 5.8.

Unusual Loading-Dependent Sintering-Resistant Properties of Gold Nanoparticles Supported within Extra-large Mesopores

Unexpected, excellent antisintering property of highly loaded AuNPs is observed when extra-large mesoporous silica EP-FDU-12 (cage size >25 nm) is used as the supports. The average particle size of the entrapped AuNPs after 550 °C calcination approaches 25.6 ± 5.2 nm at the gold loading amount of 5.0 wt %, but it greatly reduces into only 5.6 ± 1.2 nm as the metal loading reaches up to 26.1 wt %. It is demonstrated that the unique three-dimensional porous structure of EP-FDU-12 makes particle-migration difficult to occur and thus prevents direct particle–particle aggregation. This further allows two or more AuNPs to be encapsulated in every extra-large cage at high particle concentrations (10–35 wt %), which enables interparticle interactions via significant overlapping of the diffusion-spheres of AuNPs. As a result, atom-migration via vapor from cage to cage is largely shut off and local vapor-particle equilibrium within each cage is possible, leading to a successful stable AuNPs/mesoporous silica system.

Synthesis and characterization of dextran-methacrylate hydrogels and structural study by SEM.

The objectives of this study were to develop a simple and reproducible method for the preparation of the hydrogel precursor dextran-methacrylate and to conduct a visual observation of the interior structure of the swollen dextran-methacrylate hydrogel with minimum artifacts. A dextran-methacrylate hydrogel precursor was synthesized by reacting dextran with methacrylic anhydride in the presence of triethylamine as a catalyst. The effects of reaction time, temperature, concentration, and catalyst amount were studied to obtain a wide range of degree of substitution (DS) in dextran by methacrylate. The dextran-methacrylate synthesized showed an enhanced solubility in water and common organic solvents. UV irradiation of dextran-methacrylate by a long-wave UV lamp (365 nm) generated a photocrosslinked hydrogel. This dextran-methacrylate hydrogel showed a range of swelling ratio from 67 to 227% and exhibited an increase in swelling ratio with a decrease in methacrylate substitution. The pH of the swelling media did not affect the swelling behavior of the dextran-methacrylate hydrogels at all the degrees of substitution used. Special cryofixation and cryofracturing techniques were used to prepare aqueous swollen dextran-methacrylate hydrogel samples for SEM observation of their surface and interior structures. A unique three-dimensional porous structure was observed in the swollen hydrogel but was absent in the unswollen hydrogel. Different pore sizes and morphologies between the surface and the interior of swollen hydrogels also were observed.