Functionalization of nitrogen-doped graphene quantum dot: A sustainable carbon-based catalyst for the production of cyclic carbonate from epoxide and CO2.

A series of organic compounds were successfully immobilized on an N-doped graphene quantum dot (N-GQD) to prepare a multifunctional organocatalyst for coupling reaction between CO2 and propylene oxide (PO). The simultaneous presence of halide ions in conjunction with acidic- and basic-functional groups on the surface of the nanoparticles makes them highly active for the production of propylene carbonate (PC). The effects of variables such as catalyst loading, reaction temperature, and structure of substituents are discussed. The proposed catalysts were characterized by different techniques, including Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy/energy dispersive X-ray microanalysis (FESEM/EDX), thermogravimetric analysis (TGA), elemental analysis, atomic force microscopy (AFM), and ultraviolet-visible (UV-Vis) spectroscopy. Under optimal reaction conditions, 3-bromopropionic acid (BPA) immobilized on N-GQD showed a remarkable activity, affording the highest yield of 98% at 140°C and 106 Pa without any co-catalyst or solvent. These new metal-free catalysts have the advantage of easy separation and reuse several times. Based on the experimental data, a plausible reaction mechanism is suggested, where the hydrogen bonding donors and halogen ion can activate the epoxide, and amine functional groups play a vital role in CO2 adsorption.

Glucosamine-conjugated graphene quantum dots as versatile and pH-sensitive nanocarriers for enhanced delivery of curcumin targeting to breast cancer.

Applying multifunctional nanocarriers, comprising specifically traceable and tumor targeting moieties, has significantly increased in cancer theranostics. Herein, a novel targeted, trackable, and pH-responsive drug delivery system was fabricated based on glucosamine (GlcN) conjugated graphene quantum dots (GQDs) loaded by hydrophobic anticancer agent, curcumin (Cur), to evaluate its targeting and cytotoxicity potential against breast cancer cells with overexpression of GlcN receptors. The biocompatible photoluminescent GQDs were synthesized from graphene oxide through the green and facile oxidizing method. The structural and spectral characterizations of the as-prepared GQDs and Cur/GlcN-GQDs were investigated. The GQDs sizes were within 20-30 nm and showed less than ten layers. A pH-sensitive and sustained release behavior was also observed for the Cur loaded nanocarrier with a total release of 37% at pH 5.5 and 17% at pH 7.4 after 150 h. In vitro cellular uptake studies through fluorescence microscopy and flow cytometry exhibited stronger fluorescence for the targeted nanocarrier against MCF-7 cells compared to the non-targeted one, owing to higher cellular internalization via GlcN receptor-mediated endocytosis. Furthermore, the MTT assay results demonstrated the nontoxicity of the bare nanocarrier with the cell viability of above 94% even at concentrations as high as 50 µg·ml-1, while the Cur/GlcN-GQDs exhibited much more cytotoxicity against MCF-7 cells compared to Cur/GQDs. It is reasonable to conclude that this advanced multifunctional nano-assembly offers superior potential for breast cancer cell-targeted delivery.

A functionalized nano-structured cellulosic sorbent aerogel for oil spill cleanup: Synthesis and characterization.

A new synthesis strategy was adopted to convert cellulose to a biodegradable sorbent with properties of very high oil absorption and retention capacities, excellent oil-water selectivity, good mechanical strength and recycling ability. The sorbent in form of a hydrophobic/oleophilic nano-structured aerogel was prepared through functionalizing cotton cellulose with low surface energy moieties followed by dissolving and chemically cross-linking the product in an organic medium (DMSO), and freeze-drying. High absorption capacities of 40.7, 57.1, and 47.3 g/g were achieved for three different light crude oils at 25 °C which is comparable with most synthetic oil sorbents. Washburn's model was utilized to describe the wicking dynamics and fluid flow through the pores and to evaluate the effects of all important factors on the sorption process. Via comparing the experimental data with the predictions made by the model, it was revealed that unlike other cellulose-based oil sorbents reported in the literature, the swelling of fibrous network in the synthesized aerogel plays an important role in the absorption process besides the capillary pressure, resulting in a very good oil retention capacity and at the same time lowering the absorption rate, especially for viscose organic liquids.

Targeting graphene quantum dots to epidermal growth factor receptor for delivery of cisplatin and cellular imaging.

The unique properties of graphene quantum dots (GQDs) which include high loading capacity, excellent physiological stability, strong photoluminescence, biocompatibility, and facile production make them attractive nanomaterials for biomedical applications. In this work, GQDs have been explored as dual-functional targeted drug carriers and cellular bioimaging agents. The GQDs were conjugated to single chain variable fragment of antibody (scFv), which had been engineered with high affinity (B10) to epidermal growth factor receptor (EGFR), via amide covalent linkages (GQDs-scFvB10). The morphology and surface modification of GQDs were characterized by HRTEM, SDS-PAGE, FT-IR, UV-vis and fluorescence spectroscopies. Western blot analysis along with the confocal imaging of EGFR-overexpressing breast cancer cells (MDA-MB-231) demonstrated the targeting functionality of scFvB10 after conjugation to the GQDs, as well as the potential application of GQDs-scFvB10 in targeted bioimaging. The surface of targeted GQDs had a high cisplatin (CDDP) loading capacity of 50% and a pH-dependent release with slower release rate at neutral conditions, which can reduce the commonly observed systemic toxicity of CDDP. The targeted CDDP-loaded nanocarriers ((CDDP)GQDs-scFvB10) exhibited significantly higher toxicity on MDA-MB-231 cells compared to non-targeted ones suggesting their efficient uptake through EGFR. In contrast, cells with saturated EGFR showed lower uptake and cytotoxic effect of (CDDP)GQDs-scFvB10, demonstrating selectivity of the nanocarriers towards EGFR-overexpressing cells. The scFvB10-functionalized GQD is a promising platform for targeted cellular imaging and delivery of CDDP through interactions with EGFRs.

Targeted Delivery of Docetaxel by Use of Transferrin/Poly(allylamine hydrochloride)-functionalized Graphene Oxide Nanocarrier.

The exceptional chemical and physical properties of graphene oxide (GO) make it an attractive nanomaterial for biomedical applications, particularly in drug delivery. In this work we synthesized a novel, GO-based nanocarrier for the delivery of docetaxel (DTX), a potent hydrophobic chemotherapy drug. The GO was functionalized with transferrin (Tf)-poly(allylamine hydrochloride) (PAH), which provided targeted and specific accumulation to extracellular Tf receptors and stabilized GO in physiological solutions. Tf was conjugated to PAH via amide covalent linkages, and Tf-PAH coated the surface of DTX-loaded GO through electrostatic interactions. The morphology and structure of the resulting nanostructure, along with its surface modifications, were verified by use of Fourier transform infrared (FT-IR) and UV-vis spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM). DTX was loaded at a relatively high loading capacity of 37% and released in a pH-dependent and sustained manner under physiological conditions. The targeting efficiency and cytotoxicity of this drug delivery system were evaluated on MCF-7 breast cancer cells. Improved efficacy of targeted DTX-loaded nanocarrier was observed compared to nontargeted carrier and free DTX, especially at high drug concentrations. The Tf-PAH-functionalized GO nanocarrier is a promising candidate for targeted delivery and controlled release of DTX.

Plasma Functionalized Multiwalled Carbon Nanotubes for Immobilization of Candida antarctica Lipase B: Production of Biodiesel from Methanolysis of Rapeseed Oil.

Surface modification of multiwalled carbon nanotubes (MWCNTs) through functionalization could improve the characteristics of these nanomaterials as support for enzymes. Carboxylation of MWCNTs (MWCNT-COOH) has been carried out in this study using the dielectric barrier discharge (DBD) plasma reactor through humidified air. The chemical method was also used for further functionalization of the MWCNT-COOH through which the amidation of the surfaces with either butylamine (MWCNT-BA) or octadecylamine (MWCNT-OA) was performed. By immobilization of Candida antarctica B lipase (CALB) on these nanoparticles, performance of the immobilized enzyme in catalyzing methanolysis of rapeseed oil was evaluated. The CALB loading on the MWCNT-BA and MWCNT-COOH was 20 mg protein/g, while the value for MWCNT-OA was 11 mg protein/g. The yield of biodiesel was determined as percentage of mass of fatty acid methyl ester (FAME) produced per initial mass of the oil, and the yield value for the two of these three supports namely, MWCNT-COOH and MWCNT-BA used for the CALB immobilization was similar at about 92 %, while 86 % was the yield for the reaction catalyzed by the lipase immobilized on MWCNT-OA. Thermal stability of the immobilized CALB and the catalytic ability of the enzyme in the repeated batch experiments have also been determined.

Ultra-deep adsorptive desulfurization of a model diesel fuel on regenerable Ni-Cu/γ-Al2O3 at low temperatures in absence of hydrogen.

A model diesel fuel containing 250 ppmw sulfur (as dibenzothiophene) in n-hexadecane was desulfurized at low temperatures in absence of hydrogen, down to about zero ppmwS on a novel adsorbent of well dispersed 3-12 nm Nix-Cu10-x (x=Ni wt%) nanoparticles formed by impregnation on γ-Al2O3 and reduced in H2 at 275 or 450°C. The sorbents were characterized by XRD, TEM-EDX, FESEM-EDS, H2-TPR, TPO, BJH and BET surface area measurement techniques. Effects of various parameters comprising Cu content, reduction and desulfurization temperatures, inhibition by naphthalene, and regeneration of spent sorbents were investigated. As copper is added to nickel: (a) the sorbent reduction temperature shifts to dramatically lower values, (b) sulfur adsorption capacity of the sorbents at lower reduction and desulfurization temperatures is significantly improved, and when 14 wt% Ni5Cu5 sorbent is added to the fuel, the sulfur content reduces from 250 ppmwS to about zero in less than 1 min, (c) loss of adsorption capacity after the regeneration of the spent sorbent reduced at 275°C is significantly diminished, and (d) the selectivity of the sorbents to dibenzothiophene in the presence of naphthalene is improved. A higher reduction temperature tends to agglomerate nickel nanoparticles and reduce the sulfur adsorption capacity.

Asphaltene adsorption onto acidic/basic metal oxide nanoparticles toward in situ upgrading of reservoir oils by nanotechnology.

The effects of surface acidity and basicity of metal oxide nanoparticles on the thermodynamics of asphaltene adsorption were studied. Three different categories of metal oxides/salts with acidic (WO3 and NiO), amphoteric (Fe2O3 and ZrO2), and basic (MgO and CaCO3) surfaces were synthesized, and their textural, structural, and acid-base properties were characterized. Asphaltenes were extracted from a dead oil sample and characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. The acid and base numbers of the asphaltenes were measured. The nanoparticles were added to the asphaltene-toluene solutions, and the amount of adsorbed asphaltene was obtained through centrifugation followed by UV-vis spectroscopy of the supernatant liquid and temperature-programmed oxidation analysis of the precipitated solid. The concentrations of organic acid and base groups in the asphaltenes are 2.75 and 12.34 mg of KOH/g, respectively, indicating that the asphaltenes are more basic in nature. Isotherms of the asphaltene adsorption onto the six metal oxides/salts fit the Langmuir model closely. The asphaltene adsorption capacity of the nanoparticles is 1.23-3.67 mg/m(2) and decreases in the order of NiO > Fe2O3 > WO3 > MgO > CaCO3 > ZrO2, concomitant with the synergetic effects of acidity and the net charge of the surfaces. High-resolution transmission electron microscopy illustrates that the asphaltenes are spread out over the surfaces with no short-range/long-range order. The adsorption of the asphaltenes onto the six samples is exothermic and spontaneous with the Gibbs energy change of -27.80 to -28.79 kJ/mol at 25 °C. The absolute value of the enthalpy change of the adsorption is calculated to be within the range of 5-20 kJ/mol. Acid-base interaction and electrostatic attraction seem to be the dominant forces contributing to the adsorption of the asphaltenes onto the metal oxide/salt surfaces.

Vanadium oxide decorated carbon nanotubes as a promising support of Pt nanoparticles for methanol electro-oxidation reaction.

VO(x)-MWCNTs nanocomposite was prepared via deposition-precipitation method followed by microwave treatment. Platinum nanoparticles were dispersed via polyol process over the nanocomposite support, and thus, prepared electro-catalyst was employed in methanol electro-oxidation reaction. The electro-catalysts were characterized by means of TGA, XRD, EDS, FESEM, TEM, and H(2)-TPR analysis. The electro-catalytic activity and stability of the electrodes toward methanol oxidation reaction in acidic medium were studied by using cyclic voltammetry (CV), CO-stripping, and electrochemical impedance spectroscopy (EIS) techniques. Compared to the Pt/MWCNTs, the Pt/VO(x)-MWCNTs electro-catalyst not only exhibits high electro-catalytic activity, but also shows very good stability during methanol electro-oxidation reaction. In addition, the presence of VO(x) in the composite support dramatically increases the electrochemical active surface area of platinum nanoparticles. The results of electrochemical impedance spectroscopy reveal that formation kinetics of adsorbed hydroxyl group on surface of the electro-catalysts is improved upon vanadium oxide addition to the support. This phenomenon is very helpful to facilitate oxidative removal of adsorbed CO group through bifunctional mechanism on Pt/VO(x)-MWCNTs.

Novel microwave-induced combustion synthesis of SnO2 nanoparticles for selective sensing of CO using tin chloride.

A novel technique of chloride solution combustion synthesis (CSCS) is employed for preparation of SnO2 nanoparticles, using SnCl4 and sorbitol as a novel precursor and a fuel, respectively. Ammonium nitrate is also used as a combustion aid. The solution combustion synthesis is a single-step and simple method for nanoparticles synthesis. However, it commonly uses nitrate precursors. In this study tin chloride is used in CSCS method for the first time, employing ammonium nitrate as a combustion aid. The nanoparticles are characterized by means of XRD, SEM, EDS and BET and applied in sensing of carbon monoxide and methane. The molar ratio of fuel plus oxidant to SnCl4 (psi) and the ratio of fuel-to-oxidant (phi) were varied in the modified CSCS technique. The smallest nanoparticles size, i.e., 3.9 nm with 220 m2 x g(-1) obtained at phi = 1 and psi = 1. The sensor fabricated based on the SnO2 nanoparticles obtained by CSCS method shows 2-3 times higher sensitivity to CO than the one obtained by the conventional sol-gel method. The CSCS sensors show high sensitivity to CO at temperatures lower than 300 degrees C, at which insignificant sensitivity to methane is observed. This makes the sensor selective to CO in presence of methane.

Highly sensitive tin oxide hollow microspheres and nanosheets to ethanol gas prepared by hydrothermal method.

In this study, we synthesized tetragonal-phase SnO2 with a variety of well-crystallized morphologies as solid microspheres, hollow microspheres and mixture of hollow microspheres and nanosheets via the hydrothermal method. The synthesized samples were characterized with XRD, SEM, and BET. SnO2 hollow microsphere structures have been hydrothermally synthesized by using urea and SnCl2 as raw materials. With the addition of cetyltrimethylammonium bromide (CTAB), nanostructures with morphologies of hollow microspheres and nanosheets were obtained. Also, when CTAB was added in the reaction solution without urea, SnO2 microsphere with a solid interior composed of nanoparticles were obtained. A possible formation mechanism of these samples was briefly discussed. The gas sensing properties of sensors based on these samples were investigated. The result revealed that sample with morphology of hollow microsphere and nanosheet calcined at 600 degrees C showed the highest sensitivity to ethanol due to the special morphology and absence of SnO phase.

Fabrication and highly sensitive gas sensors based on h-MoO3/SnO2 hollow nanostructures operated at low temperatures.

Simulated by the synthesis of one dimensional hollow nanostructures with significant sensing, electrical, and optical properties, we have successfully synthesized 1D hollow nanostructures of h-MoO3/SnO2 with well-defined multi-side walls. These hollow nanostructured materials synthesized via a hydrothermal method with SnCl2.2H2O as the precursor and h-MoO3 as the template. SnO2 nanoparticles grew on the surface of h-MoO3 with preferential direction [001]. The morphological change was observed with variation of the growth conditions, such as HNO3, and h-MoO3 concentration. 1D hollow nanostructures of h-MoO3/SnO2 were studied and their growth mechanism was discussed. The result revealed that the existence of h-MoO3 caused to increase the sensor response to ethanol gas and downshift the sensor operating temperature at low temperatures.