Evolution of structure and functional groups in the functionalization of graphene oxide with L-cysteine

Room-temperature assembled 3D macro-porous Ti3C2Tx/RGO hybrid hydrogel and the application as the self-standing electrode for sodium-ion storage

Assembling two-dimensional (2D) MXene nanosheets into monolithic three-dimensional (3D) structures is an efficient pathway to transfer the nanoscale properties to practical applications. Nevertheless, the majority of the preparation schemes described in the literature are carried out at relatively high temperatures, which inevitably leads to the notorious high-temperature oxidation issue of MXenes. Preparing MXene-based hydrogels at lower temperatures or even room temperature is of great research importance. In this study, we report a novel and efficient room-temperature gelation method for fabricating 3D macro-porous Ti3C2Tx MXene/reduced graphene oxide (RGO) hybrid hydrogels, using anhydrous sodium sulfide (Na2S) as the primary reducing agent and l-cysteine as the auxiliary crosslinker. This room-temperature preparation technique successfully prevents the oxidation issue of MXenes and generates porous aerogels with excellent structural robustness after freeze-drying. As the self-standing anode for sodium-ion storage, the optimized 3D Ti3C2Tx MXene/RGO electrode possesses a specific capacity of 152 mAh/g at 0.1 A/g and good cycling stability with no significant capacity degradation after 500 cycles, which is significantly higher than that of the vacuum-filtered MXene film. This work demonstrates a straightforward room-temperature gelation method for constructing 3D MXene-based hydrogels to avoid the oxidation of MXenes, and casts new insight on the mechanism of the graphene oxide (GO)-assisted gelation.

Highly selective adsorption of Hg (II) from aqueous solution by three-dimensional porous N-doped starch-based carbon

For the first time, N-doped carbon materials with 3D porous-layered skeleton structure was synthesized through a one-step co-pyrolysis method, which was fabricated by co-pyrolysis of natural corn starch and melamine using metal catalysts (Ni (II) and Mn (II)). The 3D-NC possessed a heterogeneously meso-macroporous surface with a hierarchically connected sheet structure inside. Batch adsorption experiments suggested that highly selective adsorption of Hg (II) by the 3D-NC could be completed within 90 min and had maximum adsorption capacities as high as 403.24 mg/g at 293 K, pH = 5. The adsorption mechanism for Hg (II) was carefully evaluated and followed the physical adsorption, electrostatic attraction, chelation, and ion exchange. Besides, thermodynamic study demonstrated that the Hg (II) adsorption procedure was spontaneous, endothermic, and randomness. More importantly, the 3D-NC could be regenerated and recovered well after adsorption-desorption cycles, showing a promising prospect in the remediation of Hg (II)-contaminated wastewater.

Attapulgite as a skeleton for the fabrication of magnetic structural-functional materials with a superhydrophobic shell

Fabrication of structural-functional materials endowed with unique features from attapulgite, and which may be provided a well structural platform for diversified applications, such as adsorbent for organic pollutants, the superhydrophobic coating and water/oil separation.

Inhibitory effect of edible natural compounds with di- and tri-carboxyl moiety on endogenous protease inducing disassembly and degradation of myofibrils from grass carp (Ctenopharyngodon idella)

Inhibition of endogenous protease is a rapid and feasible approach to control the proteolysis proceeding of post mortem fish flesh. In the present study, the in vitro inhibitory effects of common edible di- and tri-carboxylic acids and salts on endogenous proteolytic activities as well as myofibrillar disassembly and degradation mediated by crude enzyme of grass carp muscle were investigated. The results showed that among the compounds tested, maleic acid, fumaric acid, tartaric acid and malic acid were the most effective inhibitor for cathepsin B, L and calpain, with IC₅₀ ranging from 7.76 to 30.13 mM, from 32.38 to 65.12 mM, from 1.06 to 6.76 mM, respectively. Also, relatively lower Ki (ranging from 1.04 to 43.21 mM) of these compounds were found towards cathepsin B, L and calpain. Incubation of myofibrillar protein with crude enzyme in the presence of di- and tri-carboxylic compounds could remarkably suppress the dissociation and degradation of myosin heavy chain (MHC), and ameliorate the loss of heat shock protein (HSP) in myofibrils, with tartaric acid and fumaric acid proved more effective than other compounds, possibly implicating their application as potential and efficient inhibitors for quality control of fish muscle products.

Recent progress of graphene oxide as a potential vaccine carrier and adjuvant

Vaccine is one of the most effective strategies for preventing and controlling infectious diseases and some noninfectious diseases, especially cancers. Adjuvants and carriers have been appropriately added to the vaccine formulation to improve the immunogenicity of the antigen and induce long-lasting immunity. However, there is an urgent need to develop new all-purpose adjuvants because some adjuvants approved for human use have limited functionality. Graphene oxide (GO), widely employed for the delivery of biomolecules, excels in loading and delivering antigen and shows the potentiality of activating the immune system. However, GO aggregates in biological liquid and induces cell death, and it also exhibits poor biosolubility and biocompatibility. To address these limitations, various surface modification protocols have been employed to integrate aqueous compatible substances with GO to effectively improve its biocompatibility. More importantly, these modifications render functionalized-GO with superior properties as both carriers and adjuvants. Herein, the recent progress of physicochemical properties and surface modification strategies of GO for its application as both carriers and adjuvants is reviewed. STATEMENT OF SIGNIFICANCE: Due to its unique physicochemical properties, graphene oxide is widely employed in medicine for purposes of photothermal treatment of cancer, drug delivery, antibacterial therapy, and medical imaging. Our work describes the surface modification of graphene oxide and for the first time summarizes that functionalized graphene oxide serves as a vaccine carrier and shows significant adjuvant activity in activating cellular and humoral immunity. In the future, it is expected to be introduced into vaccine research to improve the efficacy of vaccines.

L-cysteine reduced/functionalized graphene oxide application as a smart/control release nanocarrier of sustainable cerium ions for epoxy coating anti-corrosion properties improvement

One of the main limitations for large scale mass production of reduced graphene oxide is the application of some toxic and hazardous reducing agents such as hydrazine and borohydride. In this study, the effectiveness of the l-Cys (HSCH₂CH(NH₂)CO₂H) molecules, as a green amino acid in the GO reduction, as well as its active corrosion inhibition capacity were explored. The l-Cys/GO nanosheets were then modified by trivalent-cerium ions to obtain a nanocarrier with excellent controlled release activity. The electrochemical impedance spectroscopy (EIS) and polarization tests were used to measure the smart corrosion inhibition activity of the cerium modified l-Cys/GO nanocarrier in the saline solution and epoxy coating. The results showed that the cerium ions adsorption on the l-Cys/GO nanosheets obeyed a Langmuir isotherm model. The l-Cys/GO sample showed cerium ions adsorption capacity about 66% higher than the unmodified GO nanosheets. Furthermore, the EIS tests results revealed that in the presence of cerium modified l-Cys/GO nanocarriers the improvement in the corrosion resistance of bare steel in the solution phase and coated sample was about 7.5 times (after 24 h) and 950 times (after 40 days) higher than the blank saline solution and the pure epoxy sample, respectively.

Thin Electric Heating Membrane Constructed with a Three-Dimensional Nanofibrillated Cellulose⁻Graphene⁻Graphene Oxide System

Nanofibrillated cellulose (NFC) and graphene oxide (GO) with reinforcing and film-forming properties were employed with graphene to develop a novel and thin electric heating membrane with heat dissipation controllability. A negative charge was found on the surface of GO and NFC in aqueous dispersions, which contributed to the homogeneous distribution of the graphene sheets. The membrane had a good laminated structure with three-dimensional interaction between GO and NFC, with embedded graphene sheets. Conductivity was characterized as a function of the amount of graphene, thus giving control over to the heating power by adjusting the ratio of graphene. Subsequent electric heating tests can remove irregularities on the GO and graphene sheet, improving the laminated structure further. The temperature on the surface of the membrane presented an exponential increasing regularity with time. Under the same power density and time, the stabilized temperature rise of membranes was higher when grammage was higher, which was characterized by the linear function of the power density. Low-grammage membranes (1 and 4 g·m⁻²) also exhibited regular and even stabilized temperature rises. The indicated structure and heating performance of the membrane, as well as the variation induced by Joule heating, would drive its applications.