Oxide Sponge Research Articles

Laccase immobilized on reduced graphene oxide sponges for simultaneous adsorption and enzymatic degradation of endocrine disrupting chemicals.

The presence of endocrine disrupting chemicals (EDCs) in water can impart detrimental effects on public health by mimicking the behaviors of natural hormones and their associated receptors in human body. Studies have demonstrated that ligninolytic enzymes such as laccase can degrade various phenolic compounds, including a broad range of EDCs. In this study, the technique of covalent immobilization of laccase through carbodiimide coupling chemistry on highly adsorptive reduced graphene oxide (rGO) sponges was utilized to effectively remove two representative EDCs; namely, bisphenol A (BPA) and triclosan (TCS) from water. The bio-functionalized adsorbent (rGO-LA) showed a significant improvement in removing BPA (87 % after 24 h) compared to pristine rGO sponge, (~40 % after 24 h). The removal efficiency of both adsorbents for TCS was as high as 84 %, with faster kinetics being observed for rGO-LA. Further investigation using gas-chromatography-mass spectroscopy revealed that the bio-functionalization not only improved the removal efficiency of the adsorbent, but also facilitated the adsorption of the metabolites generated during the biodegradation of BPA and TCS. When temperature was increased to 40 °C, the removal efficiency and kinetics of rGO-LA sponges were improved significantly for BPA (83 % removal in 4 h) and TCS (73 % removal after 4 h). The study highlights the synergy of enzymatic degradation and adsorption, with enhanced performance observed at elevated temperatures, offering a promising solution for effective EDCs mitigation in water treatment, while also ensuring comprehensive contaminant removal by adsorbing the generated metabolites.

Transport and separation behaviors of crosslinked GO/PVA sponge with high porosity

Separation materials (technology) with high efficiency and high precision is a goal that researchers are relentlessly pursuing. Here, crosslinked graphene oxide and polyvinyl alcohol (GO/PVA) sponges with high porosity are reported, which were constructed by crosslinking a dilute solution of GO/PVA. The structure and transport characteristics of the sponges were investigated. It was found that it took 150 days for 30 mg/L methylene blue (MB) to diffuse from the side of crosslinked GO/PVA sponge (10 mm thickness) to the other side (breakthrough) even though the porosity of sponge was up to 92.9 %, while it needed only 2 days in PVA sponge and 13 days for methyl orange (MO) in the sponge. Hence, the transport and separation behaviors of more substances were explored and it is found that not only a precise separation of more than 99 % was achieved for MB/MO (similar molecular weight) mixed solution due to the extremely wide difference of transport rate, but also a water permeability of (4.3 × 105 L·m−2·h−1·Mpa-1) was reached under 10 cm height of water column pressure (0.01 bar), which is three orders of magnitude higher than that of nanofiltration membrane. The extremely high selectivity and efficiency to MB are attributed to the structural features of the sponge, i.e., the fully dispersed GO nanosheets and their crosslinking structure with PVA. Thus, the adsorption amount, adsorption rate, and adsorption strength to MB were greatly improved due to a synergistic effect of GO and PVA, and the highly efficient, precise, and rapid separation of MB was realized. In addition, the structural characteristics of the sponges favor the slow transport of many substances, which will extend their applications to the controlled release field.

Enhanced physiochemical, antibacterial, and hemostatic performance of collagen-quaternized chitosan-graphene oxide sponges for promoting infectious wound healing

Bacteria-infected wound healing has attracted widespread attention in biomedical engineering. Wound dressing is a potential strategy for repairing infectious wounds. However, the development of wound dressing with appropriate physiochemical, antibacterial, and hemostatic properties, remains challenging. Hence, there is a motivation to develop new synthetic dressings to improve bacteria-infected wound healing. Here, we fabricate a biocompatible sponge through the covalent crosslinking of collagen (Col), quaternized chitosan (QCS), and graphene oxide (GO). The resulting Col-QCS-GO sponge shows an elastic modulus of 1.93-fold higher than Col sponge due to enhanced crosslinking degree by GO incorporation. Moreover, the fabricated Col-QCS-GO sponge shows favorable porosity (84.30 ± 3.12 %), water absorption/retention (2658.0 ± 113.4 %/1114.0 ± 65.7 %), and hemostasis capacities (blood loss <50.0 mg). Furthermore, the antibacterial property of the Col-QCS-GO sponge under near-infrared (NIR) irradiation is significantly enhanced (the inhibition rates are 99.9 % for S. aureus and 99.9 % for E. coli) due to the inherent antibacterial properties of QCS and the photothermal antibacterial capabilities of GO. Finally, the Col-QCS-GO+NIR sponge exhibits the lowest percentage of wound area (9.05 ± 1.42 %) at day 14 compared to the control group (31.61 ± 1.76 %). This study provides new insights for developing innovative sponges for bacteria-infected wound healing.

Exploring recyclable alginate-enhanced GCN-LDO sponge for U(VI) and Cd(II) removal: Insights from batch and column studies

Developing effective water treatment materials, particularly through proven adsorption methods, is crucial for removing heavy metal contaminants. This study synthesizes a cost-effective three-dimensional material encapsulating graphitic carbon nitride-layered double oxide (GCN-LDO) in sodium alginate (SA) through the freeze-drying method. The material is applied to remove uranium (U(VI)) and cadmium (Cd(II)) in real water systems. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analyses conclusively verified the elemental composition and successful encapsulation of GCN-LDO within the SA matrix. Removal effectiveness was tested under various conditions, including adsorbent dose, ionic strength, contact time, temperature, different initial pollutant concentrations, and the impact of co-existing ions. The adsorption of U(VI) and Cd(II) conformed to the pseudo-second-order (PSO) kinetic model, signifying a chemical interaction between the sodium alginate-graphitic carbon nitride-layered double oxide (SA-GCN-LDO) sponge and the metal ions. The Langmuir isotherm indicated monolayer, homogeneous adsorption for U(VI) and Cd(II) with capacities of 158.25 and 165.00 mg/g. SA-GCN-LDO recyclability was found in up to seven adsorption cycles with a removal efficacy of 70%. The temperature effect study depicts the exothermic nature of the U(VI) and Cd(II) ion removal process. Various mechanisms involved in U(VI) and Cd(II) removal were proposed. Further, continuous fixed bed column studies were performed, and Thomas and the Yoon-Nelson model were studied. These insights from this investigation contribute to advancing our knowledge of the material's performance within the context of U(VI) and Cd(II) adsorption, paving the way for optimized and sustainable water treatment solutions.

Compressible and Elastic Reduced Graphene Oxide Sponge for Stable and Dendrite-Free Lithium Metal Anodes.

Dendritic Li deposition, an unstable solid-electrolyte interphase (SEI), and a nearly infinite relative volume change during cycling are three major obstacles to the practical application of Li metal batteries. Herein, we introduce a compressible and elastic reduced graphene oxide sponge (rGO-S) to simultaneously eliminate Li dendrite growth, stabilize the SEI, and accommodate the volume change. The volume change is contained by compressing and expanding the rGO-S anode, which effectively releases the Li plating-induced stress during cycling. The smooth and dense Li metal is deposited on rGO-S without dendrites, which preserves the SEI, reduces consumption of the electrolyte, and prevents the formation of Li debris. The half-cells employing rGO-S show a steady and high Coulombic efficiency. The Li@rGO-S symmetric cells demonstrate excellent cycling stability over 1200 cycles with a low overpotential. When paired with LiFePO4 (LFP), the Li@rGO-S||LFP full cells exhibit a high specific capacity (150.3 mAh g-1 at 1C), superior rate performance, and good capacity retention.

High-performance flexible solid-state asymmetric supercapacitor with NiCo2S4 as a cathode and a MXene-reduced graphene oxide sponge as an anode

Ti3C2 MXenes have revealed immense potential in energy storage systems.

Influence of various titanium-containing additives on the modification efficiency of aluminum–silicon eutectic alloy

This study investigates the impact of titanium addition to the eutectic silumin AK12 melt, considering various methods of addition. The research results encompass the sole introduction of titanium (at a calculated amount of 0.1 wt.%) through different forms/methods, such as the Al–4%Ti ligature, TiO2 oxide, K2TiF6 salt, and Ti sponge. Additionally, the study explores the combined addition of titanium and a standard flux (comprising 62.5 % NaCl + 12.5 % KCl + 25 % NaF). The research involved qualitative and quantitative analyses of macro- and microstructures, spectral analysis data, and mechanical properties (tensile strength and relative elongation) of the alloys. The findings highlight that titanium has a positive influence on the structure of eutectic silumin, with the most effective results achieved when combined with the standard flux. However, the efficiency of silumin modification with titanium varies depending on the method of addition. Specifically, the introduction of titanium in the form of K2TiF6 fluoride salt, Al–4%Ti ligature, and titanium sponge positively affected macro grain refinement, reduced the spacing between the secondary dendrite arms of the solid solution (α-Al), and enhanced the dispersion of eutectic silicon. The most promising approach for complex silumin modification involves the joint introduction of titanium-containing substances and a sodium salt-based flux. This combination has a multifaceted impact on the silumin structure, leading to the simultaneous modification of various structural components in aluminum–silicon alloys. Depending on the type of titanium-containing substance, when processed alongside flux, the alloy achieves a relative elongation ranging from 9.7 % to 11.1 %, exceeding the same parameter for the unmodified alloy by more than 4 times and surpassing the sodium-modified alloy's relative elongation by 17–37 %. Furthermore, the ultimate strength reaches levels of 171–193 MPa, representing a 22–38 % improvement compared to the unmodified alloy and a 7–21 % increase compared to the sodium-modified alloy.

Investigation on spilled oil absorption ability of graphene oxide coated melamine sponge

In this 21stcentury due to rise in population there is a great demand for the energy rise in domestic and industrial sector most of our energy demand is meet through fossil fuels. The fossil fuels are non-renewable energy sources such as coal, crude oil and natural gas. The crude oil and other petroleum products are available in large quantities under the ocean. These crude oil is extracted by drilling under the deep ocean through oilrigs and transported the oil and natural gas through container ships. There is a lot of chance for the accidents to occur during transporting oil and the spillage of crude oil causes serious environmental pollution. To reduce the damage to marine ecosystem caused due to oil spill Fabrication of cost-effective and robust hydrophobic and oileophilic sponge for easy clean-up of oil spills is a highly desired way. Here we developed a novel porous melamine sponge coated with reduced graphene oxide. The reduced graphene oxide is synthesized via modified hummer’s method. The sponge is fabricated by using dip coating method. The prepared graphene oxide sponge has to be characterized by scanning electron microscope. The dip coating process increases the absorption capacity of the prepared graphene oxide sponge and the absorption capacity of RGOMS has been tested by using motor oil, pump oil, gasoline, and diesel.

MXene-reduced graphene oxide sponge-based solar evaporators with integrated water-thermal management by anisotropic design

The main issue limiting the performance of the solar evaporators is that water-thermal management is difficult to coordinate. Herein, we achieve integrated water-thermal management by designing hierarchical MXene-reduced graphene oxide sponges with anisotropic thermal conductivity and axial-directional water conveyance channels. The reduced graphene oxide acts as the sponge framework and carbon source for in situ synthesis of MXenes on the surface. The axial-oriented framework supports the structure and provides fast water transmission channels to the air-water interface. Meanwhile, the MXene nanosheets are vertically aligned on the framework surface, making the radial thermal conductivity of the sponges much greater than the axial one, which suppresses heat loss in the axial direction. The material exhibits an evaporation rate of 2.35 kg m−2 h−1 under one sunlight and maintains 85 % energy efficiency under weak sunlight (0.5-sun). Furthermore, the sponge shows a long working life with 96 % evaporation rate retention after a 30-day-sustained operation.

Manganese oxide-functionalized graphene sponge electrodes for electrochemical chlorine-free disinfection of tap water

Low-cost reduced graphene oxide sponges functionalized with manganese oxide were used as electrodes for the disinfection of Escherichia coli in water. Manganese oxide was doped with amino groups (MnxOyNH2) to strengthen the bond with the graphene coating and improve the electrochemical stability of the sponge. The Mn II and Mn III incorporated into the graphene coating favored the formation of oxygen vacancies and enhanced the electric and catalytic properties of the anode. Electrooxidation of real tap water at 29 A/m−2 resulted in 2.2 log removal of E. coli. After storing the treated samples for 18 h at 25 and 37 °C, the removal of E. coli increased to 3.3 and 4.6 log, respectively, demonstrating the irreparable damage to the bacterial cells via low-voltage electroporation, and the key role of storage temperature in their further inactivation. The energy consumption of the system treating real low conductivity tap water was 1.2–1.6 kWh m−3. Finally, experiments with intermittent current suggest the contribution of the pseudo-capacitance of the graphene sponge to electrochemical disinfection during the OFF periods. This study demonstrates the feasibility of manganese oxide-functionalized graphene sponges for the chlorine-free disinfection of water.

Chitosan/poly (ethylene oxide) nanofiber sponge with dual-responsive drug release and excellent antibacterial property

An ideal wound dressing can absorb wound exudate in time, and has the advantages of moisture permeability, oxygen permeability, rapid hemostatic performance, antibacterial and low-toxic, which are the key to wound healing. However, traditional wound dressings exist structural and functional defects, especially in controlling bleeding and active wound protection. Herein, a novel three-dimensional chitosan/ poly (ethylene oxide) sponge dressing (3D CS/PEO sponge-ZPC) consists of CS/PEO nanofiber sponge (carrier unit), Zn metal-organic framework grown in-situ (Zn-MOF, drug loading unit and antibacterial unit), curcumin (CUR, antibacterial unit), and poly[(N-isopropylacrylamide)-co-(methacrylic acid)] (P(NIPAM-co-MAA), ‘gatekeepers’ unit) to promote the wound healing by absorb exudate in time, accelerate hemostasis and inhibit bacteria growth. Due to the unique structure of the as-prepared 3D CS/PEO sponge-ZPC was endowed with smart stimuli-responsive drug release mode, rapid hemostatic performance and strong antibacterial property. The result of CUR release showed smart “ON-OFF” drug release mode. Antibacterial results verified strong antibacterial property up to 99.9 %. Hemolysis test showed that hemolysis ratio of 3D CS/PEO sponge-ZPC met the acceptable standard. The rapid hemostatic property was demonstrated by hemostatic test. High wound healing effect was confirmed in vivo. These results provide an important research basis for the design of new smart dressing.

Electrochemical Decalcification-Exfoliation of Two-Dimensional Siligene, SixGey: Material Characterization and Perspectives for Lithium-Ion Storage.

A two-dimensional (2D) silicene-germanene alloy, siligene (SixGey), a single-phase material, has attracted increased attention due to its two-elemental low-buckled composition and unique physics and chemistry. This 2D material has the potential to address the challenges caused by low electrical conductivity and the environmental instability of corresponding monolayers. Yet, the siligene structure was studied in theory, demonstrating the material's great electrochemical potential for energy storage applications. The synthesis of free-standing siligene remains challenging and therefore hinders the research and its application. Herein we demonstrate nonaqueous electrochemical exfoliation of a few-layer siligene from a Ca1.0Si1.0Ge1.0 Zintl phase precursor. The procedure was conducted in an oxygen-free environment applying a -3.8 V potential. The obtained siligene exhibits a high quality, high uniformity, and excellent crystallinity; the individual flake is within the micrometer lateral size. The 2D SixGey was further explored as an anode material for lithium-ion storage. Two types of anode have been fabricated and integrated into lithium-ion battery cells, namely, (1) siligene-graphene oxide sponges and (2) siligene-multiwalled carbon nanotubes. The as-fabricated batteries both with/without siligene exhibit similar behavior; however there is an increase in the electrochemical characteristics of SiGe-integrated batteries by 10%. The corresponding batteries exhibit a 1145.0 mAh·g-1 specific capacity at 0.1 A·g-1. The SiGe-integrated batteries demonstrate a very low polarization, confirmed by their good stability after 50 working cycles and a decrease in the solid electrolyte interphase level that occurs after the first discharge/charge cycle. We anticipate the growing potential of emerging two-component 2D materials and their great promise for energy storage and beyond.

Selective removal of ultrafine suspended solids during organic pollutant degradation by a MoS2/graphene oxide sponge

Selective removal of ultrafine suspended solids during organic pollutant degradation by a MoS2/graphene oxide sponge

Anti-stacking synthesis of MXene-reduced graphene oxide sponges for aqueous zinc-ion hybrid supercapacitor with improved performance

Two‑dimensional MXenes with an enormous active surface area are considered to be significant cathode materials for Zn‑ion hybrid supercapacitors. However, the nanosheets are easily self-restacked during the assembly into macroscopic porous electrodes, resulting in a significantly reduced effective surface area, hindering their applications in energy storage. Here, MXenes are subtly distributed on the surface of the sponge in a coral-like structure rather than participating in the assembly of the framework, which has suppressed the self-restacking of MXene effectively, improved the hydrophilicity of the sponge, and provided fast diffusion channels for electrolyte ions. Therefore, the MXene-TiC-reduced graphene oxide sponge exhibits excellent electrical conductivity, an enormous specific surface area with abundant accessible electroactive sites, and superior electrochemical performance. The resulting sponge demonstrates an outstanding specific capacity, up to 501 mAh g–1 at 0.2 A g–1, with excellent capacity retention (90%) after 3100 cycles as Zinc-ion hybrid supercapacitor cathodes. Furthermore, it exhibits an elegant gravimetric energy density of 486 mWh g–1 at 415 mW g–1, which has surpassed most leading MXene-based Zn-ion cathodes. This work provides a new synthetic idea for MXene-based macro-composites and paves a new avenue for designing next-generation flexible and portable porous electrodes with high gravimetric and rate performances.

Stacking order reduction in multilayer graphene by inserting nanospacers

Toward macroscopic applications of graphene, it is desirable to preserve the superior properties of single-layer graphene in bulk scale. However, the AB-stacking structure is thermodynamically favored for multilayer graphene and causes strong interlayer interactions, resulting in property degradation. A promising approach to prevent the strong interlayer interaction is the staking order reduction of graphene, where the graphene layers are rotated in-plane to form a randomly stacking structure. In this study, we propose a strategy to effectively decrease the stacking order of multilayer graphene by incorporating nanospacers, cellulose nanofibers, or nano-diamonds (NDs) in the formation process of porous graphene sponges. We conducted an ultrahigh temperature treatment at 1500 °C with ethanol vapor for the reduction and structural repair of graphene oxide sponges with different concentrations of the nanospacers. Raman spectroscopy indicated an obvious increase in the random-stacking fraction of graphene by adding the nanospacers. The x-ray diffraction (XRD) analysis revealed that a small amount of the nanospacers induced a remarkable decrease in ordered graphene crystalline size in the stacking direction. It was also confirmed that a layer-number increase during the thermal treatment was suppressed by the nanospacers. The increase in the random-stacking fraction is attributed to the efficient formation of randomly rotated graphene through the ethanol-mediated structural restoration of relatively thin layers induced by the nanospacers. This stacking-order-reduced graphene with bulk scale is expected to be used in macroscopic applications, such as electrode materials and wearable devices.

CoFe2O4 Hollow Spheres-Decorated Three-Dimensional rGO Sponge for Highly Efficient Electrochemical Charge Storage Devices.

The energy demand, the crisis of fossil fuels, and the increasing popularity of portable and wearable electronics in the global market have triggered the demand to develop high-performance flexible all-solid-state supercapacitors that are capable of delivering high energy at high power density as well as being safely entrenched in those electronics. Herein, we have designed a nanocomposite, 80CFhs-20rGOsp, which exhibits a high specific capacitance (CS) value of 1032 F g–1 at 3 A g–1. Utilizing this nanocomposite as the cathode and reduced graphene oxide sponge (rGOsp) as the anode, a flexible all-solid-state asymmetric device has been fabricated. In this device, poly(vinyl alcohol) (PVA) gel embedded with a mixture of 3 M KOH and 0.1 M K4[Fe(CN)6] was used as an electrolyte cum separator. The fabricated device showed the capability to deliver an energy density of 65.8 W h kg–1 at a power density of 1500 W kg–1 and retained its capability even after various physical deformations. The device also exhibited a long cycle life and retained ∼96% of its CS value after 5000 cycles. Moreover, the fabricated flexible all-solid-state device successfully illuminated light-emitting diodes, which proved its potential use in real-life supercapacitor applications. The obtained results revealed the excellent electrochemical performances of the fabricated device and rendered it a promising candidate in the energy sector.

Evaluation of different organic solvents adsorption by porous ammonium-treated graphene and graphene oxide sponges

Evaluation of different organic solvents adsorption by porous ammonium-treated graphene and graphene oxide sponges

Ultra-sensitive, lightweight, and flexible composite sponges for stress sensors based combining of “through-hole” polyimide sponge and “pleated stacked” reduced graphene oxide

For the advantages of light weight, rapid recovery, and high sensitivity, the conductive flexible composite sponges with idiographic spatial structure as a stress sensor has received great attention. However, for small pressure and deformation, it is still challenging to achieve high sensitivity and response. Here, the polyimide (PI) sponge with through-hole structure and special functional groups is successfully fabricated through a clever structural design and is used as substrate of the composite sponges. The new PI sponge effectively induces the fabrication of reduced graphene oxide (RGO) sponge that possessing a pleated stacked structure in the cells only by a hydrothermal route. By controlling the GO dispersion concentration, the maximum electrical conductivity of the composite sponges reaches to 10.68 × 10−4 S/m. The maximum sensitivity of composite sponges arrives at 1.172 kPa−1 and possesses a wide response range from 0 to 1 kPa. Comparing with previous similar works, the maximum sensitivity is improved by 74.9–1231.8%. Meanwhile, composite sponges exhibit excellent cycling stability under different compression rates, and present obvious response to tiny stress or deformation which is as low as 0.09 N and 0.45%. This is of great significance for the application of the conductive composite sponges sensor in tiny stress.

Achieving Super Broadband Electromagnetic Absorption by Optimizing Impedance Match of rGO Sponge Metamaterials

AbstractThe reduced graphene oxide (rGO) sponges exhibit exciting electromagnetic absorption (MA) performance in high‐frequency range. However, it is still a great challenge to realize desirable MA property at low frequency (2–4 GHz) due to the great difficulty in balancing the good interfacial impedance matching and strong dielectric loss. Herein, the MA metamaterials based on rGO sponge with different unit shapes are reported. The relationship between the unit shape and MA performance is explored by experiment and simulation. The results show that frustum pyramid metamaterial exhibits ultrabroad band MA; the qualified absorption (the reflection loss lower than −10 dB) of electromagnetic wave can be achieved at 2.4–40 GHz. The average absorption intensity is −22.9 dB in the band of 2–40 GHz. Moreover, the bandwidth for strong absorption with an absorption rate of 99% (−20 dB) is up to 32 GHz. It is significant that the reflection loss has ignorant change even though the incident angle is increased from 5° to 40°. These are contributed to the excellent impedance matching and strong dielectric loss. These lightweight frustum pyramid metamaterials are very promising in the application for broadband electromagnetic protection.

Chlorine-free electrochemical disinfection using graphene sponge electrodes

Graphene sponge electrodes were employed for chlorine-free inactivation of Escherichia coli from low conductivity water. The nitrogen-doped reduced graphene oxide (NRGO) sponge anode bearing more positive charge achieved complete E. coli inactivation (i.e., 5 log removal) in the anode–cathode configuration at 115 A m−2, versus 2.6 log removal using boron-doped reduced graphene oxide sponge anode. The bacteria were mainly inactivated via electrosorption and electroporation, as confirmed by the scanning electron microscopy. Storage of the electrochemically treated samples revealed further killing of the bacteria due to the damaged cell membranes. When using real tap water, 5.5 log E. coli removal required 5.70 kWh m−3, which was drastically lowered to 1.38 kWh m−3 using intermittent current and thus exploiting the capacitive properties of graphene. The developed graphene sponge anode does not form any chlorine, chlorate, or perchlorate, and holds great promise for efficient electro-disinfection without forming toxic disinfection byproducts.