Carbon-GO Composites with Preferential Water versus Ethanol Uptake

NaGaSe2: A Water-Loving Multifunctional Non-van der Waals Layered Selenogallate

A missing member of well-known ternary chalcometallates, a sodium selenogallate, NaGaSe₂, has been synthesized by employing a polyselenide flux and stoichiometric reaction. Crystal structure analysis using X-ray diffraction techniques reveals that it contains supertetrahedral adamantane-type Ga₄Se₁₀ secondary building units. These Ga₄Se₁₀ secondary building units are further connected via corners to form two-dimensional (2D) [GaSe₂]_∞^- layers stacked along the c-axis of the unit cell, and the Na ions reside in the interlayer space. The compound has an unusual ability to absorb water molecules from the atmosphere or a nonanhydrous solvent to form distinct hydrated phases, NaGaSe₂·xH₂O (where x can be 1 and 2), with an expanded interlayer space, as verified by X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), desorption, and Fourier transform infrared spectroscopy (FT-IR) studies. The in situ thermodiffractogram indicates the emergence of an anhydrous phase before 300 °C with the decrease of interlayer spacings and reverting to the hydrated phase within a minute of re-exposure to the environment, supporting the reversibility of such a process. Structural transformation induced through water absorption results in an increase of Na ionic conductivity by 2 orders of magnitude compared to that of the pristine anhydrous phase, as verified by impedance spectroscopy. Na ions from NaGaSe₂ can be exchanged in the solid-state route with other alkali and alkaline earth metals in a topotactic or nontopotactic way, leading to 2D isostructural and three-dimensional networks, respectively. Optical band gap measurements show a band gap of ∼3 eV for the hydrated phase, NaGaSe₂·xH₂O, which is in good agreement with the calculated band gap using a density functional theory (DFT)-based method. Sorption studies further confirm the selective absorption of water over MeOH, EtOH, and CH₃CN with a maximum water uptake of 6 molecules/formula unit at a relative pressure, P/P₀, of 0.9.

Electronic structure modulation of multi-walled carbon nanotubes using azo dye for inducing non-radical reaction: Effect of graphitic nitrogen and structural defect

Multiwalled carbon nanotube (MWCNT) have a great potential for advanced oxidation process as a metal free catalyst. However, there catalytic activity is very low and needs to be appropriately tuned. Herein, we demonstrate a novel synthesis method for tuning the defect and surface functionality of MWCNT using azo dyes and the catalytic performance was tested for the degradation of different organic contaminates using PMS as an oxidant. The content, type of heteroatom functional groups, and the defect parameters were optimized by varying the pH and concentration of the organic dye. The quenching effect showed that singlet oxygen (¹O₂) is the primary reactive species generated by graphitic nitrogen, which can be boosted by the degree of graphitic structure disruption in MWCNT. The Linear sweep voltammetry (LSV) also confirmed that extrinsic doping enhanced the non-radical degradation by increasing the direct charge transfer rate from MB to PMS. Moreover, the designed catalyst showed a fast degradation performance with 35.1 kJ/mol activation energy and achieved the highest dye degradation rate and even surpassed some state-of-the-art metal-based and metal-free catalysts. The effect of inorganic anions study has also confirmed its industrial applicability.

Construction of a polyoxometalate-based magnetic composite MOF for the effective adsorption of cationic dyes

Adsorption and separation of dyes are extremely important as they damage the water environment and human health. ZIF-8 has the benefits of large specific surface area, explicit structure and a good confinement effect on POM, which can better facilitate the synergetic effect of POM and ZIF-8. Therefore, ZIF-8 was chosen as the support material to wrap H₃PW₁₂O₄₀. In the present work, magnetic ZIF-8@H₃PW₁₂O₄₀ composites were prepared by a facile impregnation synthesis strategy and applied to the adsorption of cationic dyes with methylene blue (MB) as a representative. Compared with the other three prepared materials, Fe₃O₄@ZIF-8@H₃PW₁₂O₄₀ exhibited the best adsorption performance. The adsorption process conformed to the pseudo-second-order model and the Langmuir model, and the adsorption reaction was spontaneous with the maximum adsorption capacity of up to 431.03 mg g^-1 within 20 min. The electrostatic attraction has been testified to be the major driving force of the adsorption process, and the material can still hold 90% of the max adsorption capacity after 5 cycles, which serve as the foundation for its further applications in the field of adsorption.

Bioinspired Design of Sericin/Chitosan/Ag@MOF/GO Hydrogels for Efficiently Combating Resistant Bacteria, Rapid Hemostasis, and Wound Healing

Due to the spread of drug-resistant bacteria in hospitals, the development of antibacterial dressings has become a strategy to control wound infections caused by bacteria. Here, we reported a green strategy for in situ biomimetic syntheses of silver nanoparticles@organic frameworks/graphene oxide (Ag@MOF-GO) in sericin/chitosan/polyvinyl alcohol hydrogel. Ag@MOF-GO was synthesized in situ from the redox properties of tyrosine residues in silk sericin without additional chemicals, similar to a biomineralization process. The sericin/chitosan/Ag@MOF-GO dressing possessed a high porosity, good water retention, and a swelling ratio. The hemolysis rate of the composite was 3.9% and the cell viability rate was 131.2%, which indicated the hydrogel possessed good biocompatibility. The composite also showed excellent lasting antibacterial properties against drug-sensitive and drug-resistant pathogenic bacteria. The composite possessed excellent hemostatic activity. The coagulation effect of the composite may be related to its effect on the red blood cells and platelets, but it has nothing to do with the activation of coagulation factors. An in vitro cell migration assay confirmed and an in vivo evaluation of mice indicated that the composite could accelerate wound healing and re-epithelialization. In summary, the composite material is an ideal dressing for accelerating hemostasis, preventing bacterial infection, and promoting wound healing.

Deep Eutectic Solvent-Assisted Synthesis of Au Nanostars Supported on Graphene Oxide as an Efficient Substrate for SERS-Based Molecular Sensing

The development of hybrid nanostructures of graphene oxide (GO) and metal nanoparticles (NPs) is of paramount interest for highly flexible surface-enhanced Raman scattering (SERS) substrate-based molecular sensing. In this work, we report a simple and eco-friendly synthesis strategy for the synthesis of a three-dimensional (3D) GO/gold nanostar (3D GO/Au NS) hybrid nanocomposite using deep eutectic solvent (DES) for SERS-based molecular sensing. The 3D GO/Au NS hybrid nanocomposite was obtained by a two-step synthetic process. In the first step, the GO nanosheets of thickness ∼1.25 nm were homogeneously dispersed in choline chloride/urea (molar ratio of 1:2)-derived DES, followed by functionalization of -NH groups using 3-aminopropyltriethoxysilane. Afterward, the presynthesized Au NSs of size ranging between 150-200 nm were then covalently attached on the -NH-functionalized GO nanosheets mediated by DES at 60 °C to obtain 3D GO/Au NS hybrid nanocomposites. Importantly, the SERS substrate fabricated using the 3D GO/Au NS hybrid nanocomposite exhibits highly enhanced SERS activity with an enhancement factor of 1.7 × 10⁵ and high sensitivity for the detection of crystal violet with a concentration up to 10^-11 M. The green synthetic approach presented here can be expected to be promising for the large-scale fabrication of GO-metal NP-based hybrid nanostructures for their potential applications in SERS-based sensing.

Carbon and carbon composites obtained using deep eutectic solvents and aqueous dilutions thereof

Extending the “all-in-one” features of DESs to DES/H₂O binary mixtures.