Quick self-grown ternary supramolecules embedded in sodium alginate to fabricate ultralight sponge exhibiting superior flame retardancy.

To mitigate environmental and health risks associated with the use of halogenated flame retardants, effective halogen-free solutions have been extensively explored. In this study, melamine/boric acid/phosphoric acid (MBP)­sodium alginate (SA) sponge was synthesized by treating MBP ternary supramolecules with microwave irradiation via one-pot, facile, and speedy synthesis, obtaining an MBP-SA sponge, a polysaccharide biopolymer. Crosslinking of SA with Ca2+ ion formed an intact network, and this was confirmed using scanning electron microscopy (SEM). Thereafter, the flame retardancy of the as-synthesized SA/MBP sponge was investigated by exposing it to a spirit lamp and a Bunsen burner; the sponge remained intact for up to 540 s and 370 s, respectively, demonstrating the enhanced flame retardancy of MBP supramolecules in the SA/MBP sponge. The limiting oxygen index of the SA/MBP sponge was up to 62 %, demonstrating the self-extinguishing and thermal insulation properties of the as-synthesized sponge. The findings of this study provide insights for developing a new strategy to use SA/MBP sponges for fire protection.

Empowering the flame retardancy and adhesion for various substrates using renewable feedstock.

Developing biobased flame retardant adhesives using a green and simple strategy has recently gained significant attention. Therefore, in this study, we have orange peel waste (OPW) and Acacia gum (AG) phosphorylated at 140 °C to synthesize biomass-derived flame retardant adhesive. OPW is a biomass material readily available in large quantities, which. Has been utilized to produce an eco-friendly, efficient adhesive. Functionalized polysaccharides were used as a binder rather than volatile, poisonous, and unsustainable petroleum-based aldehydes. The P@OPW/AG green adhesive exhibited a higher tensile strength of 11.25 MPa when applied to cotton cloth and demonstrated versatility across various substrates such as glass, cardboard, plastic, wood, and textiles. Additionally, this bio-based robust adhesive displayed remarkable flame-retardant properties. To optimize its flame retardancy, three tests were employed: the spirit lamp flame test, the vertical flammability test (VFT), and the limiting oxygen index (LOI) test. The P@OPW/AG-coated cotton fabric achieved an impressive LOI result of 42 %, while the VFT yielded a char length of only 4 cm. Additionally, during the flame test, P@OPW/AG coated cloth endured more than 845 s of continuous flame illumination. This work offers a sustainable and fire-safe method for creating environmentally friendly high-performance composites using a recyclable bio-based flame-retardant OPW/AG glue.

Microwave-assisted rapid synthesis of nitrogen-enriched amphibious carbon quantum dots for sensitive detection of ROS and multiple other applications.

Carbon quantum dots (CQDs) have gained tremendous attention due to their pertinence in diverse application fields. Herein, we report the application of nitrogen-doped CQDs (N-CQDs) for the sensitive detection of reactive oxygen species (ROS) in vitro. The N-CQDs were synthesized via a rapid, one-pot, cost-effective and environmentally friendly approach, and exhibited amphibious solubility in solvents with a wide range of relative polarities from 1 to 0.4. Spectroscopic and microscopic techniques were used to accomplish the functional, morphological, and optical characterization of these nanoparticles. The as-synthesized luminous N-CQDs reproducibly demonstrated an average size distribution with a diameter of 5-6 nm. Their suitability for multiple other applications, such as metal sensing, confidential information inscription, hosting on cellulose materials with long-standing stability, designing polysaccharide molds flashing bright fluorescence, fingerprint imprinting, and in vitro bioimaging has also been exhibited. The plausible mechanism of peroxide induced fluorescence quenching of CQDs is presented. Treatment of human neuroblastoma cells SH-SY5Y with 1000 µg mL-1 N-CQDs demonstrated excellent (∼100%) cell viability. An empirical relation between fluorescent intensity of N-CQDs as a function of the concentration of oxidants inside single-cells has been established for the first time.

Dual-channel P-type ternary DNTT-graphene barristor.

P-type ternary switch devices are crucial elements for the practical implementation of complementary ternary circuits. This report demonstrates a p-type ternary device showing three distinct electrical output states with controllable threshold voltage values using a dual-channel dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]-thiophene-graphene barristor structure. To obtain transfer characteristics with distinctively separated ternary states, novel structures called contact-resistive and contact-doping layers were developed. The feasibility of a complementary standard ternary inverter design around 1 V was demonstrated using the experimentally calibrated ternary device model.

Waste derived approach towards wealthy fluorescent N-doped graphene quantum dots for cell imaging and H2O2 sensing applications.

Herein, we report the synthesis of a highly fluorescent nitrogen doped graphene quantum dots (N-GQDs) from waste precursors such as melamine sponge and arjuna bark via a microwave treatment and its functional and morphological characterization using various spectroscopy techniques such as optical, FTIR, XPS and TEM. The as-prepared aqueous N-GQD (dia. 2-3 nm) was used for the bio-imaging application using breast carcinoma cell line (MDA-MB-231) as a model, and the locations of all cells in the cytoplasm as well as nuclei were observed to stain brightly in blue fluorescent color successfully. In addition to that, the aqueous N-GQD showed fluorescence quenching behavior in the presence of hydrogen peroxide, which was exploited to sense H2O2, a probable toxin generated in the diseased cells. Importantly, the cell cytotoxicity was measured and found to be non-toxic (70% survival) to the MDA-MB-231 cells even at very high concentration (∼1.8 mg/ml) of the synthesized N-GQD. This study revealing excellent biocompatibility and imaging of the model cancer cells, and sensing of H2O2 by fluorescent quenching, indicates potential in-vivo cell culture applications of the prepared fluorescent N-GQD.

Novel approach towards the synthesis of highly efficient flame retardant electrode and oil/organic solvent absorber.

We have developed a facile one pot process to synthesize an ultra-light functionalized spongy graphene (FSG). This is the first approach to use carbon based flame retardant spongy material as an electrode to build completely flame retardant supercapacitor (FRS) also as an oil/organic solvent absorber. The fully FRS concept has created by the compilation of as-prepared FSG with flame retardant separator and electrolyte. As-prepared FSG contained high amount of phosphorus and nitrogen functional groups, which makes it potent flame retardant electrochemical material, to use it as an efficient FR electrode. Flame test of FSG revealed that it doesn't catch fire for ∼1500 s. Also, FSG was able to sustain flame retardancy at a temperature as high as 1500 °C for continuous exposure of ∼300 s. FSG used as an electrode for symmetric capacitor possessing maximum specific capacitance of 494.3 F g-1 at a current density 1 A g-1. Corresponding high energy density and power density values are 55.6 Wh kg-1 and 1799 W kg-1. It shows cycling stability of 86.1% after 5000 cycles at current density of 10 A g-1. The electrochemical property of FSG was also confirmed using three electrode system. Flame retardant FSG material was also used for the absorption and recovery of oil and organic solvents. FSG has high oil and organic solvent sorption capacity in the range of 40-70 g/g, also can be reused for minimum 10 cycles. Such approach has great significance for multifunctional graphene based nanocomposites will open the new window for large-scale applications.

One-Pot Synthesis of Sulfur and Nitrogen Co-Functionalized Graphene Material using Deep Eutectic Solvents for Supercapacitors.

A green approach to the synthesis of sulfur and nitrogen co-functionalized reduced graphene oxide (SN-rGO) is presented; it involves the reduction of graphene oxide (GO) using a deep eutectic solvent (DES) as chemical reducing agent and dopant. For the first time, a DES of choline chloride and sodium sulfide comprising cheap and safe components is introduced, and is both highly effective and reusable as a reducing agent for the production of SN-rGO. The DES is utilized as a solvent as well as reducing agent and dopant to generate SN-rGO. This DES is highly efficient in removing oxygen functionalities from GO and for subsequent sulfur and nitrogen functionalization for high energy-storage efficiency. The reduction ability of this DES is confirmed with five consecutive cycles, which adds to its sustainability and recyclability in the development of energy-storage devices. SN-rGO exhibits a high specific capacitance of 509 F g-1 at 1 A g-1 , which corresponds to high energy and power densities of 57.3 Wh kg-1 and 1804.7 W kg-1 , respectively. This simple and green method for direct reduction of GO with sulfur and nitrogen functionalization on the graphene surface can provide cost-effective bulk production of a nanocarbon template for energy storage applications.

Graphene Oxide Promoted Oxidative Bromination of Anilines and Phenols in Water.

The mildly acidic and oxidative nature of graphene oxide, with its large surface area available for catalytic activity, has been explored in aromatic nuclear bromination chemistry for the first time. The versatile catalytic activity of graphene oxide (GO) has been used to selectively and rapidly brominate anilines and phenols in water. The best results were obtained at ambient temperatures using molecular bromine in a protocol promoted by oxidative bromination catalyzed by GO; these transformations proceeded with 100% atom economy with respect to bromine and high selectivities for the tribromoanilines and -phenols. Reduced graphene oxide (r-GO) was observed to form after the second recycle (third use) of GO. This technique is also effective with N-bromosuccinimide (NBS) as the brominating reagent. In the case of NBS, reactions were instantaneous and the GO displayed excellent recyclability without any loss of activity over several cycles.

Deep Eutectic Solvent Functionalized Graphene Composite as an Extremely High Potency Flame Retardant.

We report a simple and green approach to develop the deep eutectic solvent functionalized graphene derivative as an effective flame retardant. The deep eutectic solvent functionalized graphene oxide (DESGO) was synthesized by introducing nitrogen-supported phosphorus functional groups on the surface of graphene derivative via a deep eutectic solvent, which is prepared by the treatment of monosodium dihydrogen orthophosphate and choline chloride. Subsequently, the resultant DESGO material is characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The as prepared DESGO solution coated cloth piece was sustaining its initial shape and size by releasing a little amount of smoke at the early stage without catching fire for more than 540 s (9 min), whereas the pristine cloth is totally burned out within 10 s, leaving small amounts of black mass. This simple method of directly functionalized deep eutectic solvent on a graphene oxide surface can be a common process for the cost-effective bulk production of a nano carbon template for extremely high potency, nontoxic flame retardant applications.

Graphene-Iodine Nanocomposites: Highly Potent Bacterial Inhibitors that are Bio-compatible with Human Cells.

Graphene-composites, capable of inhibiting bacterial growth which is also bio-compatible with human cells have been highly sought after. Here we report for the first time the preparation of new graphene-iodine nano-composites via electrostatic interactions between positively charged graphene derivatives and triiodide anions. The resulting composites were characterized by X-ray photoemission spectroscopy, UV-spectroscopy, Raman spectroscopy and Scanning electron microscopy. The antibacterial potential of these graphene-iodine composites against Klebsiella pneumonia, Pseudomonas aeruginosa, Proteus mirobilis, Staphylococcus aureus, and E. coli was investigated. In addition, the cytotoxicity of the nanocomposite with human cells [human white blood cells (WBC), HeLa, MDA-MB-231, Fibroblast (primary human keratinocyte) and Keratinocyte (immortalized fibroblast)], was assessed. DGO (Double-oxidizes graphene oxide) was prepared by the additional oxidation of GO (graphene oxide). This generates more oxygen containing functional groups that can readily trap more H(+), thus generating a positively charged surface area under highly acidic conditions. This step allowed bonding with a greater number of anionic triiodides and generated the most potent antibacterial agent among graphene-iodine and as-made povidone-iodine (PVP-I) composites also exhibited nontoxic to human cells culture. Thus, these nano-composites can be used to inhibit the growth of various bacterial species. Importantly, they are also very low-cytotoxic to human cells culture.

Phosphorus-Doped Graphene Oxide Layer as a Highly Efficient Flame Retardant.

A simple and easy process has been developed to efficiently dope phosphorus into a graphene oxide surface. Phosphorus-doped graphene oxide (PGO) is prepared by the treatment of polyphosphoric acid with phosphoric acid followed by addition of a graphene oxide solution while maintaining a pH of around 5 by addition of NaOH solution. The resulting materials are characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The as-made PGO solution-coated cloth exhibits excellent flame retardation properties. The PGO-coated cloth emits some smoke at the beginning without catching fire for more than 120 s and maintains its initial shape with little shrinkage. In contrast, the pristine cloth catches fire within 5 s and is completely burned within 25 s, leaving trace amounts of black residue. The simple technique of direct introduction of phosphorus into the graphene oxide surface to produce phosphorus-doped oxidized carbon nanoplatelets may be a general approach towards the low-cost mass production of PGO for many practical applications, including flame retardation.

Efficient Direct Reduction of Graphene Oxide by Silicon Substrate.

Graphene has been studied for various applications due to its excellent properties. Graphene film fabrication from solutions of graphene oxide (GO) have attracted considerable attention because these procedures are suitable for mass production. GO, however, is an insulator, and therefore a reduction process is required to make the GO film conductive. These reduction procedures require chemical reducing agents or high temperature annealing. Herein, we report a novel direct and simple reduction procedure of GO by silicon, which is the most widely used material in the electronics industry. In this study, we also used silicon nanosheets (SiNSs) as reducing agents for GO. The reducing effect of silicon was confirmed by various characterization methods. Furthermore, the silicon wafer was also used as a reducing template to create a reduced GO (rGO) film on a silicon substrate. By this process, a pure rGO film can be formed without the impurities that normally come from chemical reducing agents. This is an easy and environmentally friendly method to prepare large scale graphene films on Si substrates.

Cancer therapy using ultrahigh hydrophobic drug-loaded graphene derivatives.

This study aimed to demonstrate that curcumin (Cur)-containing graphene composites have high anticancer activity. Specifically, graphene-derivatives were used as nanovectors for the delivery of the hydrophobic anticancer drug Cur based on pH dependence. Different Cur-graphene composites were prepared based on polar interactions between Cur and the number of oxygen-containing functional groups of respective starting materials. The degree of drug-loading was found to be increased by increasing the number of oxygen-containing functional groups in graphene-derivatives. We demonstrated a synergistic effect of Cur-graphene composites on cancer cell death (HCT 116) both in vitro and in vivo. As-prepared graphene quantum dot (GQD)-Cur composites contained the highest amount of Cur nano-particles and exhibited the best anticancer activity compared to the other composites including Cur alone at the same dose. This is the first example of synergistic chemotherapy using GQD-Cur composites simultaneous with superficial bioprobes for tumor imaging.

Fast synthesis of high-quality reduced graphene oxide at room temperature under light exposure.

An approach of presenting new reducing reagents, sodium-benzophenone (Na-B) or Na-B in the presence of the hydrazine (Na-B-H) system under light exposure could produce rGOs with/without N-doping at room temperature in both the solution phase and on a solid substrate. Benzophenone activated those solutions acting as a photosensitizer under light. It was assumed that the newly generated radical anions with electrons from Na-B under light can reduce GO to rGO sheets (rGONa-B1). In addition, the Na-B-H system can allow a higher degree of reduction with the doping of nitrogen atoms by the introduction of hydrazine to produce radical anions and electrons with a sodium hydrazide complex, which helps decrease the sheet resistance of the as-made rGONa-B-H2. The excellent properties (very low oxygen content (C/O ∼16.2), and low sheet resistance (∼130 Ω square(-1))) of the rGOs were confirmed by XPS, XRD, IR, Raman spectroscopy, TGA, wettability, and sheet resistance measurements. High-quality rGO films on flexible substrates could be prepared by directly immersing the GO films in these solutions for several minutes.

Highly hydrophilic and insulating fluorinated reduced graphene oxide.

A facile method for the synthesis of highly fluorinated reduced graphene oxide from graphene oxide using BF3-OEt2 solution and alkylthiol/alkylamine on the Gram scale has been described using a detailed mechanism. The maximum fluorination was as high as 38 wt% and the fluorinated reduced graphene oxide produced has great wettability and high insulating properties.

High-quality reduced graphene oxide by a dual-function chemical reduction and healing process.

A new chemical dual-functional reducing agent, thiophene, was used to produce high-quality reduced graphene oxide (rGO) as a result of a chemical reduction of graphene oxide (GO) and the healing of rGO. Thiophene reduced GO by donation of electrons with acceptance of oxygen while it was converted into an intermediate oxidised polymerised thiophene that was eventually transformed into polyhydrocarbon by loss of sulphur atoms. Surprisingly, the polyhydrocarbon template helped to produce good-quality rGOC (chemically reduced) and high-quality rGOCT after thermal treatment. The resulting rGOCT nanosheets did not contain any nitrogen or sulphur impurities, were highly deoxygenated and showed a healing effect. Thus the electrical properties of the as-prepared rGOCT were superior to those of conventional hydrazine-produced rGO that require harsh reaction conditions. Our novel dual reduction and healing method with thiophene could potentially save energy and facilitate the commercial mass production of high-quality graphene.

Highly sensitive and selective gas sensor using hydrophilic and hydrophobic graphenes.

New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor.

Graphene oxide as a recyclable phase transfer catalyst.

We demonstrated a simple and green chemical method to obtain Michael adducts and their derivatives by using GO as a phase transfer catalyst with different kinds of bases in water and dichloromethane, and we also used GO multiple cycles almost without reduction in reaction yields.

Dual functions of highly potent graphene derivative-poly-L-lysine composites to inhibit bacteria and support human cells.

Dual-function poly(L-lysine) (PLL) composites that function as antibacterial agents and promote the growth of human cell culture have been sought by researchers for a long period. In this paper, we report the preparation of new graphene derivative-PLL composites via electrostatic interactions and covalent bonding between graphene derivatives and PLL. The resulting composites were characterized by infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The novel dual function of PLL composites, specifically antibacterial activity and biocompatibility with human cells [human adipose-derived stem cells and non-small-cell lung carcinoma cells (A549)], was carefully investigated. Graphene-DS-PLL composites composed of 4-carboxylic acid benzene diazonium salt (DS) generated more anionic carboxylic acid groups to bind to cationic PLLs, forming the most potent antibacterial agent among PLL and PLL composites with high biocompatibility with human cell culture. This dual functionality can be used to inhibit bacterial growth while enhancing human cell growth.

Highly air-stable phosphorus-doped n-type graphene field-effect transistors.

Phosphorus-doped double-layered graphene field-effect transistors (PDGFETs) show much stronger air-stable n-type behavior than nitrogen-doped double-layered graphene FETs (NDGFETs), even under an oxygen atmosphere, due to strong nucleophilicity, which may lead to real applications for air-stable n-type graphene channels.