Square-Facet Nanobar MOF-Derived Co3O4@Co/N-doped CNT Core-Shell-based Nanocomposites as Cathode Materials for High-Performance Supercapacitor Studies

The binary as well as ternary nanocomposites of the square-facet nanobar Co-MOF-derived Co₃O₄@Co/N-CNTs (N-CNTs: nitrogen-doped carbon nanotubes) with Ag NPs and rGO have been synthesized via an easy wet chemical route, and their supercapacitor behavior was then studied. At a controlled pH of the precursor solution, square-facet nanobars of Co-MOF were first synthesized by the solvothermal method and then pyrolyzed under a controlled nitrogen atmosphere to get a core-shell system of Co₃O₄@Co/N-CNTs. In the second step, different compositions of Co₃O₄@Co/N-CNT core-shell structures were formed by an ex-situ method with Ag NPs and rGO moieties. Among several bare, binary, and ternary compositions tested in 6 M aqueous KOH electrolyte, a ternary nanocomposite having a 7.0:1.5:1.5 stoichiometric ratio of Co₃O₄@Co/N-CNT, Ag NPs, and rGO, respectively, reported the highest specific capacitance (3393.8 F g^-1 at 5 mV s^-1). The optimized nanocomposite showed the energy density, power density, and Coulombic efficiency of 74.1 W h.kg^-1, 443.7 W.kg^-1, and 101.3%, respectively, with excellent electrochemical stability. After testing an asymmetrical supercapacitor with a Co₃O₄@Co/N-CNT/Ag NPs/rGO/nickel foam cathode and an activated carbon/nickel foam anode, it showed 4.9 W h.kg^-1 of energy density and 5000.0 W.kg^-1 of power density.

Silver nanoparticles decorated reduced graphene oxide: Eco-friendly synthesis, characterization, biological activities and embryo toxicity studies

This study was aimed on the eco-friendly synthesis of silver nanoparticles (AgNPs), reduced graphene oxide (rGO) and AgNPs decorated rGO (rGO/AgNPs) nanocomposite and appraisal of their bioactivities and toxicity. As-prepared nanomaterials were established through high resolution X-ray diffraction (HR-XRD), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-Vis. spectroscopy and Fourier transform infrared spectroscopy (FT-IR). In this study, leaves extract, graphene oxide (GO) and rGO did not show antibacterial and anticancer activities; no significant embryo toxicity was recorded. On the other hand, AgNPs displayed good antibacterial and anticancer activities; however, higher toxic effects were observed even at the lowest test concentration (0.7 μg/ml). In case of rGO/AgNPs nanocomposite, significant antibacterial activity together with low cytotoxicity was noticed. Interestingly, the embryo toxicity of AgNPs was significantly reduced by rGO, implying the biocompatible nature of as-synthesized nanocomposite. Taken together, these results clearly suggest that rGO/AgNPs nano hybrid composite could be developed as the promising biomaterial for future biomedical applications.

Macrocycle-Functionalized RGO for Gas Sensors for BTX Detection Using a Double Transduction Mode

To fabricate mass and resistive sensors based on reduced graphene oxide (RGO), we investigated the functionalization of RGO by tetra tert-butyl phthalocyanine (PcH2tBu), which possesses a macroring and tert-butyl peripheral groups. Herein, we present the gas sensor responses of the functionalized RGO toward benzene, toluene, and xylene (BTX) vapors. The RGO was obtained by the reduction of graphene oxide (GO) using citrate as a reducing agent, while the functionalization was achieved non-covalently by simply using ultrasonic and heating treatment. The sensor devices based on both QCM (quartz crystal microbalance) and resistive transducers were used simultaneously to understand the reactivity. Both the GO and the RGO showed less sensitivity to BTX vapors, while the RGO/PcH2tBu presented enhanced sensor responses. These results show that the p-network plays a very important role in targeting BTX vapors. The resistive response analysis allowed us to state that the RGO is a p-type semiconductor and that the interaction is governed by charge transfer, while the QCM response profiles allowed use to determine the differences between the BTX vapors. Among BTX, benzene shows the weakest sensitivity and a reactivity in the higher concentration range (>600 ppm). The toluene and xylene showed linear responses in the range of 100–600 ppm.

Turning Toxic Nanomaterials into a Safe and Bioactive Nanocarrier for Co-delivery of DOX/pCRISPR

Hybrid bioactive inorganic-organic carbon-based nanocomposites of reduced graphene oxide (rGO) nanosheets enlarged with multi-walled carbon nanotubes (MWCNTs) were decorated to provide a suitable space for in situ growth of CoNi₂S₄ and green-synthesized ZnO nanoparticles. The ensuing nanocarrier supplied π-π interactions between the DOX drug and a stabilizing agent derived from leaf extracts on the surface of ZnO nanoparticles and hydrogen bonds; gene delivery of (p)CRISPR was also facilitated by chitosan and alginate renewable macromolecules. Also, these polymers can inhibit the potential interactions between the inorganic parts and cellular membranes to reduce the potential cytotoxicity. Nanocomposite/nanocarrier analyses and sustained DOX delivery (cytotoxicity analyses on HEK-293, PC12, HepG2, and HeLa cell lines after 24, 48, and 72 h) were indicative of an acceptable cell viability of up to 91.4 and 78.8% after 48 at low and high concentrations of 0.1 and 10 μg/mL, respectively. The MTT results indicate that by addition of DOX to the nanostructures, the relative cell viability increased after 72 h of treatment; since the inorganic compartments, specifically CoNi₂S₄, are toxic, this is a promising route to increase the bioavailability of the nanocarrier before reaching the targeted cells. Nanosystems were tagged with (p)CRISPR for co-transfer of the drug/genes, where confocal laser scanning microscopy (CLSM) pictures of the 4',6-diamidino-2-phenylindole (DAPI) were indicative of appropriate localization of DOX into the nanostructure with effective cell and drug delivery at varied pH. Also, the intrinsic toxicity of CoNi₂S₄ does not affect the morphology of the cells, which is a breakthrough. Furthermore, the CLSM images of the HEK-293 and HeLa cell displayed effective transport of (p)CRISPR into the cells with an enhanced green fluorescent protein (EGFP) of up to 8.3% for the HEK-293 cell line and 21.4% for the HeLa cell line, a record. Additionally, the specific morphology of the nanosystems before and after the drug/gene transport events, via images by TEM and FESEM, revealed an intact morphology for these biopolymers and their complete degradation after long-time usage.

Recyclable magnetite-silver heterodimer nanocomposites with durable antibacterial performance

There is a significant need for magnetite-silver nanocomposites that exhibit durable and recyclable antimicrobial activity. In this study, magnetic iron oxide nanoparticles (Fe₃O₄ NPs) coated with ethylenediamine-modified chitosan/polyacrylic acid copolymeric layer (Fe₃O₄@ECS/PAA) were fabricated. Subsequently, directly deposited silver (Ag) NPs procedure was carried out to form the antibacterial heterodimers of Fe₃O₄@ECS/PAA-Ag NPs. The composition and morphology of the resultant nanostructures were confirmed by FT-IR, XRD, TEM and TGA. The overall length of the heterodimers was approximately 45 nm, in which the mean diameter of Fe₃O₄@ECS/PAA NPs reached up to 35 nm, and that of Ag NPs was around 15 nm. The mass fraction of silver NPs in the nanocomposites was about 63.1%. The obtained Fe₃O₄@ECS/PAA NPs exhibited good colloidal stability, and excellent response to additional magnetic field, making the NPs easy to recover after antibacterial tests. In particular, the Fe₃O₄@ECS/PAA-Ag NPs retained nearly 100% biocidal efficiency (10⁶–10⁷ CFU/mg nanoparticles) for both Gram-negative bacteria E. coli and Gram-positive bacteria S. aureus throughout ten cycles without washing with any solvents or water, exhibiting potent and durable antibacterial activity.

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Recyclable dual functional antibacterial heterodimer nanocomposites were fabricated.

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The nanostructures realized the combination of antibacterial ability and recyclable function.

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Biocidal efficiency retained nearly 100% throughout ten cycles.

Inactivation of E. coli by nano-Cu/MWCNTs combined with hydrogen peroxide

This paper aims at the study on the antibacterial activity of nCu-MWCNTs combined with H₂O₂ against gram-negative bacteria Escherichia coli (E. coli). The antibacterial ability of nCu-MWCNTs/H₂O₂ was evaluated by traditional surface plating method, fluorescence and SEM imaging, and the effects of variables (contacting time, dose of nCu-MWCNTs and dose of H₂O₂) were investigated. By comparing with other five processes including H₂O₂, MWCNTs, nCu-MWCNTs, MWCNTs/H₂O₂ and nCu/H₂O₂, nCu-MWCNTs and H₂O₂ was proved to have superlative antimicrobial effectiveness against E. coli. The role of nano-Cu, MWCNTs and H₂O₂ in the antimicrobial activity of nCu-MWCNTs/H₂O₂ was clarified. The release of copper ions and formation of hydroxyl radicals (OH) both contributed the antibacterial ability of nCu-MWCNTs/H₂O₂ system. And MWCNTs as the support might be able to promote the electron transfer in nCu-MWCNTs for copper ion release.

Antibacterial activity of graphene-based materials

Complications related to infectious diseases have significantly decreased due to the availability and use of a wide variety of antibiotics and antimicrobial agents. However, excessive use of antibiotics and antimicrobial agents over years has increased the number of drug resistant pathogens. Microbial multidrug resistance poses serious risks and consequently research attention has refocused on finding alternatives for antimicrobial treatment. Among the various approaches, the use of engineered nanostructures is currently the most promising strategy to overcome microbial drug resistance by improving the remedial efficiency due to their high surface-to-volume ratio and their intrinsic or chemically incorporated antibacterial activity. Graphene, a two-dimensional ultra-thin nanomaterial, possesses excellent biocompatibility, putting it in the forefront for different applications in biosensing, drug delivery, biomedical device development, diagnostics and therapeutics. Graphene-based nanostructures also hold great promise for combating microbial infections. Yet, several questions remain unanswered such as the mechanism of action with the microbial entities, the importance of size and chemical composition in the inhibition of bacterial proliferation and adhesion, cytotoxicity, and other issues when considering future clinical implementation. This review summarizes the current efforts in the formulation of graphene-based nanocomposites with antimicrobial and antibiofilm activities as new tools to tackle the current challenges in fighting against bacterial targets. Furthermore, the review describes the features of graphene-bacterial interactions, with the hope to shed light on the range of possible mode of actions, serving the goal to develop a better understanding of the antibacterial capabilities of graphene-based nanostructures.

The Antibacterial Applications of Graphene and Its Derivatives

Graphene materials have unique structures and outstanding thermal, optical, mechanical and electronic properties. In the last decade, these materials have attracted substantial interest in the field of nanomaterials, with applications ranging from biosensors to biomedicine. Among these applications, great advances have been made in the field of antibacterial agents. Here, recent advancements in the use of graphene and its derivatives as antibacterial agents are reviewed. Graphene is used in three forms: the pristine form; mixed with other antibacterial agents, such as Ag and chitosan; or with a base material, such as poly (N-vinylcarbazole) (PVK) and poly (lactic acid) (PLA). The main mechanisms proposed to explain the antibacterial behaviors of graphene and its derivatives are the membrane stress hypothesis, the oxidative stress hypothesis, the entrapment hypothesis, the electron transfer hypothesis and the photothermal hypothesis. This review describes contributions to improving these promising materials for antibacterial applications.

Mussel-inspired PEGylated carbon nanotubes: biocompatibility evaluation and drug delivery applications

Carbon nanotubes (CNTs) have been widely examined for biomedical applications. However, surface functionalization of CNTs with polymers is often required to improve their application performance. To obtain these CNT-based polymer nanocomposites, surface-initiated polymerization strategies are generally adopted. However, all of these methods rely on the surface oxidation of CNTs, which is a rather complex and time-consuming procedure, and involves hazardous reagents. In this work, a facile and efficient bio-inspired strategy was developed for surface PEGylation of CNTs via a combination of mussel-inspired chemistry and the Michael addition reaction. The potential biomedical applications of these PEGylated CNTs were evaluated for intracellular delivery of a normally used anticancer drug (Doxorubicin hydrochloride). Two steps were involved in this strategy, which included the surface coating of CNTs with polydopamine (PDA) through self-polymerization of dopamine, and a Michael addition reaction between the PDA-coated CNTs (CNT-PDA) and amino-functionalized polymers, which were obtained by free radical polymerization using poly(ethylene glycol) methyl methacrylate and N-(3-aminopropyl) methacrylamide as monomers. Results suggested that these PEGylated CNTs are well dispersed in aqueous solution and showed improved biocompatibility toward cancer cells. On the other hand, we also demonstrated that DOX can be effectively loaded on these PEGylated CNTs and delivered into cells for cancer treatment. More importantly, this strategy can also be utilized for surface modification of many other materials with different polymers due to the strong and universal adhesion of PDA and designability of polymerization. Therefore, this method should be of great interest for the fabrication of multifunctional nanocomposites for biomedical applications.

Facile synthesis of a biocompatible silver nanoparticle derived tripeptide supramolecular hydrogel for antibacterial wound dressings

Through a mineralization process, Nap-FFC peptides produced transparent silver nanoparticle-based hydrogels (AgNPs@Nap-FFC) for antibacterial wound dressing.

Nickel-oxide multiwall carbon-nanotube/reduced graphene oxide a ternary composite for enzyme-free glucose sensing

We report a solvent-free method of preparation for a NiO–carbon nanotube/graphene ternary composite using nickel formate as a green precursor via a thermal decomposition method.