scholarly journals Nucleating agents based on graphene and graphene oxide for crystallization of the β-form of isotactic polypropylene

2019 ◽  
Vol 55 (4) ◽  
pp. 1436-1450 ◽  
Author(s):  
Jan Broda ◽  
Marcin Baczek ◽  
Janusz Fabia ◽  
Dorota Binias ◽  
Ryszard Fryczkowski
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Isotactic Polypropylene ◽  
Reduced Form ◽  
Pimelic Acid ◽  
Nucleating Agents ◽  
Scanning Calorimetry ◽  
Functionalized Graphene Oxide ◽  
Reduced Graphene ◽  
Carboxylic Groups

Abstract During the investigations, functionalization of graphene oxide synthesized using modified Hummers’ method and its reduced form was performed. Mixtures of graphene oxide and reduced graphene oxide with pimelic acid and calcium hydroxide were prepared for functionalization. During the reaction, the molecules of pimelic acid were attached to the surface of graphene sheets. By forming links between the carboxylic groups of pimelic acid and graphene oxide, the durable connection was achieved. The functionalized graphene oxide and the reduced graphene oxide were used as additives in isotactic polypropylene crystallization. The influence of additives on crystallisation in non-isothermal conditions was examined using polarized optical microscopy and differential scanning calorimetry. The effect of the additives on the polypropylene structure was analysed using wide-angle X-ray scattering. For both functionalized compounds, the nucleating ability towards β-form of polypropylene was detected. Both additives showed the increase in the nucleation rate and promotion of growth of the β-form crystals. Nucleation efficiency similar to other nucleating agents used in the crystallization of the β-form of polypropylene was revealed.

One-step Functionalization of Mildly and Strongly Reduced Graphene Oxide with Maleimide: An Experimental and Theoretical Investigation of the Diels-Alder [4+2] Cycloaddition Reaction

2021 ◽  
Author(s):  
Alfonso Ferretti ◽  
Sourab Sinha ◽  
Luca Sagresti ◽  
Esteban Araya-Hermosilla ◽  
Mirko Prato ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Large Scale ◽  
Cycloaddition Reaction ◽  
Diels Alder ◽  
Reduced Form ◽  
Graphene Nanocomposites ◽  
Exfoliated Graphene ◽  
Reduced Graphene ◽  
One Step

For large-scale graphene applications, such as the production of polymer-graphene nanocomposites, exfoliated graphene oxide (GO) and its reduced form (rGO) are presently considered very suitable starting material, showing enhanced chemical...

scholarly journals Enhancement of Birefringence in Reduced Graphene Oxide Doped Liquid Crystal

Nanomaterials ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 842 ◽  
Author(s):  
Mareddi Bharath Kumar ◽  
Mohammad Awwal Adeshina ◽  
Daekyung Kang ◽  
Youngho Jee ◽  
Taewan Kim ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Liquid Crystal ◽  
Reduced Graphene Oxide ◽  
Photoelectron Spectroscopy ◽  
Transmission Measurement ◽  
Scanning Calorimetry ◽  
Polarized Microscopy ◽  
Electro Optic ◽  
Reduced Graphene ◽  
5Cb Liquid Crystal

We investigated the effect of reduced graphene oxide (rGO) doping on the birefringence of 5CB liquid crystal (LC). The characteristics of the synthesized rGO and LC-rGO composite with different rGO concentrations were analyzed by atomic force microscopy, X-ray photoelectron spectroscopy, white light polarized microscopy, voltage-dependent transmission measurement, and differential scanning calorimetry. We found that doping LC with an appropriate concentration of rGO enhances the birefringence of the LC. This is mainly due to the improved anisotropy of polarizability, which stems from the high shape anisotropy of rGO. However, the aggregation of rGO reduces the birefringence by decreasing the anisotropy of polarizability as well as the order parameter. Our study shows the promising potential of LC-rGO for developing various electro-optic devices that offer improved electro-optic effects.

scholarly journals Tin-Decorated Reduced Graphene Oxide and NaLi0.2Ni0.25Mn0.75O as Electrode Materials for Sodium-Ion Batteries

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1074 ◽  
Author(s):  
Pier Paolo Prosini ◽  
Maria Carewska ◽  
Cinzia Cento ◽  
Gabriele Tarquini ◽  
Fabio Maroni ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Electrode Materials ◽  
Specific Capacity ◽  
Sodium Ion ◽  
Sodium Ion Batteries ◽  
Organic Precursor ◽  
Functionalized Graphene Oxide ◽  
Sodium Metal ◽  
Reduced Graphene

A tin-decorated reduced graphene oxide, originally developed for lithium-ion batteries, has been investigated as an anode in sodium-ion batteries. The composite has been synthetized through microwave reduction of poly acrylic acid functionalized graphene oxide and a tin oxide organic precursor. The final product morphology reveals a composite in which Sn and SnO2 nanoparticles are homogenously distributed into the reduced graphene oxide matrix. The XRD confirms the initial simultaneous presence of Sn and SnO2 particles. SnRGO electrodes, prepared using Super-P carbon as conducting additive and Pattex PL50 as aqueous binder, were investigated in a sodium metal cell. The Sn-RGO showed a high irreversible first cycle capacity: only 52% of the first cycle discharge capacity was recovered in the following charge cycle. After three cycles, a stable SEI layer was developed and the cell began to work reversibly: the practical reversible capability of the material was 170 mA·h·g−1. Subsequently, a material of formula NaLi0.2Ni0.25Mn0.75O was synthesized by solid-state chemistry. It was found that the cathode showed a high degree of crystallization with hexagonal P2-structure, space group P63/mmc. The material was electrochemically characterized in sodium cell: the discharge-specific capacity increased with cycling, reaching at the end of the fifth cycle a capacity of 82 mA·h·g−1. After testing as a secondary cathode in a sodium metal cell, NaLi0.2Ni0.25Mn0.75O was coupled with SnRGO anode to form a sodium-ion cell. The electrochemical characterization allowed confirmation that the battery was able to reversibly cycle sodium ions. The cell’s power response was evaluated by discharging the SIB at different rates. At the lower discharge rate, the anode capacity approached the rated value (170 mA·h·g−1). By increasing the discharge current, the capacity decreased but the decline was not so pronounced: the anode discharged about 80% of the rated capacity at 1 C rate and more than 50% at 5 C rate.

Supramolecular structure of polypropylene fibers formed with addition of functionalized graphene oxide

2020 ◽  
Vol 90 (19-20) ◽  
pp. 2322-2335 ◽  
Author(s):  
Jan Broda ◽  
Marcin Baczek ◽  
Janusz Fabia ◽  
Ryszard Fryczkowski
Keyword(s):  
Graphene Oxide ◽  
Polypropylene Fibers ◽  
Pimelic Acid ◽  
Functionalized Graphene ◽  
Fiber Structure ◽  
Scanning Calorimetry ◽  
Functionalized Graphene Oxide ◽  
X Ray ◽  
X Ray Scattering ◽  
Spun Fibers

Pimelic acid and calcium hydroxide were used to attach calcium pimelate to the surface of graphene oxide. The additive was mixed with isotactic polypropylene granulate. Neat polypropylene and polypropylene with functionalized graphene oxide was extruded into fibers under laboratory conditions. The gravity spun fibers containing different concentration of the additive and the fibers taken at various velocities were obtained. Morphology and elemental composition of functionalized graphene oxide were studied by means of scanning electron microscopy and energy dispersive X-ray spectroscopy. The structure of fibers was examined by means of differential scanning calorimetry and wide-angle X-ray scattering. The ability of calcium pimelate supported on the surface of the graphene oxide to nucleate the β-form of polypropylene was revealed. A considerable amount of the β-form crystals was obtained in the gravity spun fibers. In the fibers taken at moderate and higher velocities the β-form disappeared. The structure of the fibers extruded with the additive was similar to the structure of the fibers extruded from neat polypropylene. At moderate velocities, the content of mesophase in the structure was high. At higher velocities, the crystalline structure built only from α-form crystals was obtained. The paper presents a discussion of the changes observed in the fiber structure in connection with polypropylene nucleation.

scholarly journals Partially Reduced Graphene Oxide Modified with Polyacrylonitrile for the Removal of Sm3+ from Water

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 818
Author(s):  
Khadijah Mohammedsaleh Katubi ◽  
Fatimah Mohammed Alzahrani ◽  
Norah Salem Alsaiari ◽  
Abdelfattah Amari ◽  
Faouzi Ben Rebah ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Electron Microscope ◽  
Reduced Graphene Oxide ◽  
Contact Time ◽  
Maximum Adsorption Capacity ◽  
Basic Solution ◽  
Optimum Conditions ◽  
Functionalized Graphene Oxide ◽  
Reduced Graphene ◽  
Partially Reduced Graphene Oxide

An in situ emulsion polymerization method was used for the synthesis of polyacrylonitrile nanoparticles amino-functionalized partially reduced graphene oxide (PAN-PRGO). After that, hydrolyzed polyacrylonitrile nanoparticles amino-functionalized partially reduced graphene oxide (HPAN-PRGO) nanocomposite was achieved by the modification of nitrile groups of the composite polymer chains to carboxylic groups, aminoethylene diamine, and amidoxime functional groups through partial hydrolysis using a basic solution of sodium hydroxide for 20 min. Different synthesized materials were characterized and compared using well-known techniques including transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FT-IR), Raman spectra, and X-ray diffraction (XRD). The nanocomposite was structured through the interaction between acrylonitrile’s (AN) nitrile groups and amino-functionalized graphene oxide nanosheets’ amino groups to successfully graft polyacrylonitrile over the surface of functionalized nanosheets as approved by characterization techniques. The synthesized composite was examined for the removal of samarium ions (Sm3+) from water. Different experimental conditions including pH, contact time, initial concentration, and adsorbent dose were investigated to determine the optimum conditions for the metal capture from water. The optimum conditions were found to be a contact time of 15 min, pH 6, and 0.01 g of adsorbent dosage. The experimental results found, in a good agreement with the Langmuir isotherm model, the maximum adsorption capacity of Sm3+ uptake was equal to 357 mg/g. A regeneration and reusability study of synthesized composite up to six cycles indicated the ability to use HPAN-PRGO nanocomposite several times for Sm3+ uptake. The obtained results prove that this polymer-based composite is a promising adsorbent for water treatment that must be studied for additional pollutants removal in the future.

scholarly journals Reduced Graphene Oxide (rGO)-Loaded Metal-Oxide Nanofiber Gas Sensors: An Overview

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1352
Author(s):  
Sanjit Manohar Majhi ◽  
Ali Mirzaei ◽  
Hyoun Woo Kim ◽  
Sang Sub Kim
Keyword(s):  
Graphene Oxide ◽  
Metal Oxide ◽  
Metal Oxides ◽  
Reduced Graphene Oxide ◽  
Gas Sensors ◽  
Gas Sensing ◽  
Reduced Form ◽  
Sensing Applications ◽  
Reduced Graphene ◽  
Electrospinning Method

Reduced graphene oxide (rGO) is a reduced form of graphene oxide used extensively in gas sensing applications. On the other hand, in its pristine form, graphene has shortages and is generally utilized in combination with other metal oxides to improve gas sensing capabilities. There are different ways of adding rGO to different metal oxides with various morphologies. This study focuses on rGO-loaded metal oxide nanofiber (NF) synthesized using an electrospinning method. Different amounts of rGO were added to the metal oxide precursors, and after electrospinning, the gas response is enhanced through different sensing mechanisms. This review paper discusses rGO-loaded metal oxide NFs gas sensors.

scholarly journals Comparison of Properties of PVA Nanocomposites Containing Reduced Graphene Oxide and Functionalized Graphene

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 450 ◽  
Author(s):  
Gi Tae Park ◽  
Jin-Hae Chang
Keyword(s):  
Graphene Oxide ◽  
Thermal Properties ◽  
Reduced Graphene Oxide ◽  
Barrier Properties ◽  
Industrial Applications ◽  
Poly Vinyl Alcohol ◽  
Hybrid Films ◽  
Scanning Calorimetry ◽  
Reduced Graphene ◽  
The Matrix

The thermal properties, morphologies, oxygen barrier properties, and electrical conductivities of poly(vinyl alcohol) (PVA) hybrid films containing different nanofillers were compared. For the fabrication of the PVA hybrid films, we used reduced graphene oxide (RGO) synthesized from graphite or functionalized hexadecylamine-graphene sheets (HDA-GS) obtained from HDA and GS as a reinforcing filler. The properties of the PVA hybrid films fabricated by intercalating PVA and the fillers for different filler contents ranging from 3 to 10% w/w were then compared. The dispersions of the graphene fillers in the matrix polymers were examined using wide-angle X-ray diffraction and field emission scanning electron microscopy, and the changes in their thermal properties were observed using differential scanning calorimetry and thermogravimetric analysis. Moreover, we measured the oxygen permeability and electrical conductivity of the films to investigate their industrial applications. In addition, all the physical properties of the PVA composites obtained using the two nanofillers were compared.

scholarly journals Ultrasensitive bioassaying of HER-2 protein for diagnosis of breast cancer using reduced graphene oxide/chitosan as nanobiocompatible platform

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hassan Nasrollahpour ◽  
Ibrahim Isildak ◽  
Mohammad-Reza Rashidi ◽  
Esmat Alsadat Hashemi ◽  
Abdolhosein Naseri ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Limit Of Detection ◽  
Test Method ◽  
Reduced Graphene ◽  
Relative Standard ◽  
Carboxylic Groups ◽  
Her 2 ◽  
Amine Groups

Abstract Background In this label-free bioassay, an electrochemiluminescence (ECL) immunosensor was developed for the quantification of breast cancer using HER-2 protein as a metastatic biomarker. Method For this purpose, the ECL emitter, [Ru(bpy)3]2+, was embedded into biocompatible chitosan (CS) polymer. The prepared bio-composite offered high ECL reading due to the depletion of human epidermal growth factor receptor 2 (HER-2) protein. Reduced graphene oxide (rGO) was used as substrate to increase signal stability and achieve greater sensitivity. For this, rGO was initially placed electrochemically on the glassy carbon electrode (GCE) surface by cyclic voltammetry (CV) technique. Next, the prepared CS/[Ru(bpy)3]2+ biopolymer solution was coated on a drop of the modified electrode such that the amine groups of CS and the carboxylic groups of rGO could covalently interact. Using EDC/NHS chemistry, monoclonal antibodies (Abs) of HER-2 were linked to CS/[Ru(bpy)3]2+/rGO/GCE via amide bonds between the carboxylic groups of Ab molecules and amine groups of CS. The electrochemical behavior of the electrode was studied using different electrochemical techniques such as electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV) and square wave voltammetry (SWV) and also ECL tests. Results After passing all optimization steps, the lower limit of detection (LLOQ) and linear dynamic range (LDR) of HER-2 protein were practically obtained as 1 fM and 1 fM to 1 nM, individually. Importantly, the within and between laboratory precisions were performed and the suitable relative standard deviations (RSDs) were recorded as 3.1 and 3.5%, respectively. Conclusions As a proof of concept, the designed immunosensor was desirably applied for the quantification of HER-2 protein in breast cancer suffering patients. As a result, the designed ECL-based immunosensor has the capability of being used as a conventional test method in biomedical laboratories for early detection of HER-2 protein in biological fluids. Graphic Abstract

Functionalization and Chemical Linking of Reduced Graphene Oxide or Graphite onto Polyurethane and the Impact on the Tensile Strength and Sheet Resistance of Polymer Composites

2018 ◽  
Vol 26 (2) ◽  
pp. 141-153
Author(s):  
Yong-Chan Chung ◽  
Ho-Sung Kim ◽  
Byoung Chul Chun
Keyword(s):  
Tensile Strength ◽  
Graphene Oxide ◽  
Shape Memory ◽  
Reduced Graphene Oxide ◽  
Sheet Resistance ◽  
Sharp Decrease ◽  
Hydroxyl Groups ◽  
Functionalized Graphene Oxide ◽  
Reduced Graphene ◽  
The Impact

Reduced graphene oxide (RGO) or graphite is functionalized with hydroxyl groups for linking to the sides of polyurethane (PU) chains. Blended PU with RGO or graphite is prepared as a control for comparison. The PU composites are compared with respect to their spectroscopic, thermal, mechanical, shape memory, and sheet resistance properties. Scanning electron microscopy images demonstrate the good distribution of functionalized graphene oxide (FGO) or functionalized graphite (FG) particles on the inner surface of the PU. The linking of FGO or FG onto PU does not significantly affect the thermal behavior or shape memory properties but sharply improves the tensile strength of the PU composites without a noticeable decrease in tensile strain. The shape recovery of PU composites remains at approximately 90%, regardless of the FGO or FG content. The FG-linked PU composites exhibit a sharp decrease in sheet resistance as the FG content increases, whereas the sheet resistance of the FGO-linked PU composites does not decrease with increasing FGO content. The control PU composites with blended RGO or graphite show significant reductions in their sheet resistance. Considering the ease of functionalization of the graphite surface and the significant improvement in tensile strength, linking FG onto PU is advantageous for the development of PU composites with low sheet resistance.

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