Sharif Digital Repository

Chitosan films have a great potential to be used for wound dressing and food-packaging applications if their physicochemical properties including water vapor permeability, optical transparency, and hydrophilicity are tailored to practical demands. To address these points, in this study, chitosan (CS) was combined with polyvinylpyrrolidone (PVP) and graphene oxide (GO) nanosheets (with a thickness of ∼1 nm and lateral dimensions of few micrometers). Flexible and transparent films with a high antibacterial capacity were prepared by solvent casting methods. By controlling the evaporation rate of the utilized solvent (1 vol % acidic acid in deionized water), self-organization of GO in the... 

Abstract: In recent years, temporary skin grafts (TSG) based on natural biopolymers modified with carbon nanostructures have received considerable attention for wound healing. Developments are required to improve physico-mechanical properties of these materials to match to natural skins. Additionally, in-deep pre-clinical examinations are necessary to ensure biological performance and toxicity effect in vivo. In the present work, we show superior acute-wound healing effect of graphene oxide nanosheets embedded in ultrafine biopolymer fibers (60 nm) on adult male rats. Nano-fibrous chitosan-based skin grafts crosslinked by Genepin with physico-mechanical properties close to natural skins were... 

Nanofibrous structures that mimic the native extracellular matrix and promote cell adhesion have attracted considerable interest for biomedical applications. In this study, GO-modified nanofibrous biopolymers (GO) were prepared by electrospinning blended solutions of chitosan (80 vol%), polyvinyl pyrrolidone (15 vol%), polyethylene oxide (5 vol%) containing GO nanosheets (0–2 wt%). It is shown that GO nanosheets significantly change the conductivity and viscosity of highly concentrated chitosan solutions, so that ultrafine and uniform fibers with an average diameter of 60 nm are spinnable. The GO-reinforced nanofibers with controlled pore structure exhibit enhanced elastic modulus and... 

A series of M-doped Pt[sbnd]MgO (M = Pd, Ir, Re, Ru, Rh and Cr) sheet-shaped nano-catalysts were synthesized by the controlled co-precipitation method. The effects of M-doping on both the physicochemical and the chemisorption characteristics of Pt[sbnd]MgO catalysts were examined. The performance of the catalysts for the aqueous phase reforming (APR) of glycerol was also investigated. The APR activity of Pt[sbnd]M[sbnd]MgO catalysts depended on the type of the M dopant used. The APR activity varied in the following order: Rh > Pd > Cr > Ir > undoped ≈ Ru > Re, with the Rh-promoted catalyst having an activity of about one order of magnitude higher than the Re-promoted catalyst at 250 °C. It... 

Cupric oxide (CuO) nanostructures are grown on fluorine doped tin oxide (FTO) coated glass substrate using aqueous solution approach. The concentration of precursor's solution has significant impact on morphology of CuO nanostructure. By varying concentration of precursor, the growth of two different morphologies (oriented nanosheets and nanoleaves) is achieved. X-ray diffraction pattern and X-ray photoelectron spectroscopy reveals formation of pure CuO crystalline phase. Mott-Schottky characteristic confirms the p-type semiconducting nature. Ultrathin structures of nanoleaves lead to higher light trapping and light absorption in visible-NIR region. The nanoleaves film has lower bandgap in... 

AgxPt100−x (x = 0, 25, 50, 75 and 100) nanoparticles were grown on the surface of magnetic graphene oxide nanosheets (Fe3O4@GO) for the first time. The as-prepared nanocomposites were characterized using various techniques such as Fourier transform infrared spectroscopy, powder X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area analysis, vibrating sample magnetometry and thermogravimetric analysis. The Fe3O4@GO-AgxPt100−x catalysts were applied in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol using sodium borohydride (NaBH4). The synthesized nanocomposites... 

During the last decade, fabrication of high-quality graphene films by chemical vapor deposition (CVD) for nanoelectronics and optoelectronic applications has attracted increasing attention. However, processing of large-area monolayer and defect-free graphene films is still challenging. In this work, we have studied the effect of processing conditions on the self-limited growth of graphene monolayers on copper foils during low pressure CVD both experimentally and theoretically based on thermokinetics and kinetics of Langmuir adsorption. The effect of copper pre-treatment, growth time, and carbon potential of the atmosphere (indicated by the methane-to-hydrogen gas ratio, r) on the quality of... 

In the present work, the effect of graphene oxide (GO) nanosheets on the antibacterial activity of CuO nanowire arrays under visible light irradiation is shown. A combined thermal oxidation/electrophoretic deposition technique was employed to prepare three-dimensional networks of graphene oxide nanosheets hybridized with vertically aligned CuO nanowires. With the help of standard antibacterial assays and X-ray photoelectron spectroscopy, it is shown that the light-activated antibacterial response of the hybrid material against gram-negative Escherichia coli is significantly improved as the oxide functional groups of the GO nanosheets are reduced. In order to explore the physicochemical... 

Weak mechanical possession is one of the limiting factors in application of hydrogels. To modify this inherent disadvantage, different approaches have been studied including synthesizing interpenetrating polymer network (IPN) and nanocomposite hydrogels. So, this study has focused on preparation of a novel full-IPN structure based on anionic monomers of 2-acrylamido-2-methylpropane sulfonic acid/acrylic acid-sodium acrylate via facile solution polymerization technique in an aqueous media with incorporation of graphene oxide (GO) nanosheets. Mechanical performance of materials in the "as-prepared condition" and "swollen state" was characterized via tensile, compression, and rheology tests,... 

Weak mechanical possession is one of the limiting factors in application of hydrogels. To modify this inherent disadvantage, different approaches have been studied including synthesizing interpenetrating polymer network (IPN) and nanocomposite hydrogels. So, this study has focused on preparation of a novel full-IPN structure based on anionic monomers of 2-acrylamido-2-methylpropane sulfonic acid/acrylic acid–sodium acrylate via facile solution polymerization technique in an aqueous media with incorporation of graphene oxide (GO) nanosheets. Mechanical performance of materials in the “as-prepared condition” and “swollen state” was characterized via tensile, compression, and rheology tests,... 

In this study, graphene oxide (GO) was synthesized via modified Hummer's method and exploited as an ideal enzyme immobilization support due to its exclusive chemical and structural features. Then, laccase from genetically modified Aspergillus was covalently immobilized onto GO (nanobiocatalyst). Enzymatic characterization of the nanobiocatalyst exhibited promising results: laccase loading of 156.5 mg g−1 and immobilization yield of 64.6% at laccase concentration of 0.9 mg/ mL. Further employment of various structural characterization techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermo-Gravimetric... 

The development of asymmetric supercapacitors requires the design of electrode construction and the utilization of new electroactive materials. In this regard, an effective strategy is the loading of active materials on an integrated 3D porous graphene-based substrate such as graphene foam (GF). Herein, we successfully designed and fabricated a novel ternary binder-free nanocomposite consisting of polypyrrole, Fe-Co sulfide, and reduced graphene oxide on a nickel foam electrode (PPy/FeCoS-rGO/NF) via a facile, cost-effective, and powerful electrodeposition method for application in high-performance asymmetric supercapacitors. The monolithic 3D porous graphene foam (GF) obtained by the facile... 

The construction of binary and ternary heterojunctions has gathered attention in water remediation applications. Herein, g-C3N4, MIL-101(Fe), and MIL-101(Fe)/g-C3N4 binary composite were synthesized by in-situ growth of MIL-101(Fe) crystals along with the nanosheets of g-C3N4. The materials have been characterized by XRD, FTIR, SEM, EDS, DRS, PL, and BET/BJH. The highest degradation efficiency achieved using MIL-101(Fe)/g-C3N4 nanocomposite was 99.3% while the pristine g-C3N4 degraded only 40% of the pollutants by photocatalyst dosage = 0.005 g, pH = 4.8, and irradiation time = 90 min condition. This enhanced photocatalytic performance might be attributed to improved optical properties and... 

A highly controllable, green, and rapid strategy is demonstrated for fabricating of highly sensitive non-enzymatic glucose sensing platforms. Carbon nanohorns (CNHs) were decorated onto the screen-printed electrodes. Binary nickel-cobalt sulfide (NiCo-S) nanosheets (NSs) were then deposited on CNH-casted electrodes by a facile and scalable method. Following detailed structural characterization and the electrocatalytic activity of the fabricated NiCo-S/CNH electrodes towards electro-oxidation of glucose was examined in detail. The proposed electrodes operated within two distinct linear dynamic ranges of 0.001- 0.330 mM and 0.330 - 4.53 mM with sensitivities of 1842 µA.mM−1.cm−2 and 854... 

Performance enhancement of supercapacitors has been recently discussed. In this paper a novel and facile procedure for functionalization of graphene with some electroactive molecules is presented. The graphene has been functionalized by catechol-based molecules, which are electroactive molecules with electrochemically reversible properties. The functionalized graphene exhibits very effective pseudocapacitor behaviorfor charge storage. For the first time, with the aim of an electrosynthesis procedure, catechol is covalently attached on graphene sheets. This attachment has been investigated by electrochemical, X-ray photoelectron spectroscopy and attenuated total reflectance methods. Catechol... 

Nanomaterials are chemical compounds or substances which are moderately produced and used. Nanomaterials are engineered to reveal novel properties of nanocells that contrast with related non-visible substances, such as expanded consistency, conductivity or synthetic reaction. Topological indexes are quantities related to molecules that capture the harmony of molecular structures and give scientifically related properties, such as: viscosity, boiling point, radius of gravity, and so on. Their demands in genetics, chemistry, physics and nanoscience are infinite. The molecular topology of such compounds would be clarify by the quantitative structure properties relationship (QSPR) and... 

In the present study, three influential parameters including concentration, temperature and specific surface area of graphene nanosheets were investigated, which are the effective parameters on the viscosity and thermal conductivity of aqueous graphene nanosheets (GNP) nanofluids. A mathematical model developed by respond surface methodology (RSM) based on a central composite design (CCD). Also, the significance of the models was tested using the analysis of variance (ANOVA). The optimum results of aqueous GNP nanofluid showed that the concentration has a direct effect on the relative viscosity and thermal conductivity. Furthermore, predicted responses proposed by the Design Expert software... 

Decoding behavioral aspects associated with the water molecules in confined spaces such as an interlayer space of two-dimensional nanosheets is key for the fundamental understanding of water-matter interactions and identifying unexpected phenomena of water molecules in chemistry and physics. Although numerous studies have been conducted on the behavior of water molecules in confined spaces, their reach stops at the properties of the planar ice-like formation, where van der Waals interactions are the predominant interactions and many questions on the confined space such as the possibility of electron exchange and excitation state remain unsettled. We used density functional theory and... 

A high performance asymmetric supercapacitor (ASC)has been fabricated by using nickel oxide-cobalt oxide nanosheets (NiO–CoO NSs), which were directly grown on carbon nanotubes (CNTs)and hydrothermal carbon spheres (HTCs)as positive and negative electrodes, respectively. Both electrode materials are binder-free prepared by using a catalytic chemical vapour deposition (CVD)approach followed by a facile hydrothermal method for cathode and a one-step environmental-friendly route called hydrothermal carbonization for anode. Using NiO–CoO NSs@CNTs and HTCs, which were directly grown on Ni foam, not only leads to a very small equivalent series resistance, but also provides an impressive capacitive... 

High-performance supercapacitors that merit superior power and energy densities, as well as long-term cycle durability are always of great significance as a building block of energy storage devices. Herein, an innovative strategy is developed to design hierarchical and unique porous structures of ternary metal sulfide nano-flake decorated porous hydrothermal carbon microspheres. Hierarchical microspheres of ternary zinc-cobalt sulfide nanosheet (NS) decorated biomass derived hydrothermal carbon spheres (HTCSs) are directly employed as the positive supercapacitor electrodes. In addition, composites of pyrolyzed polyaniline nanotubes (PPNTs) and iron oxide, receiving advantages from highly...