scholarly journals Catalase-like properties of multilayer graphene oxides and their modified forms

Surface ◽  
2020 ◽  
Vol 12(27) ◽  
pp. 251-262
Author(s):  
K. V. Voitko ◽  
◽  
O. M. Bakalinska ◽  
Yu. V. Goshovska ◽  
Yu. I. Sementsov ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Graphene Oxide ◽  
Functional Groups ◽  
Catalytic Reaction ◽  
Active Sites ◽  
Aqueous Media ◽  
Reaction Medium ◽  
Multilayer Graphene ◽  
Graphene Oxides ◽  
Modified Forms

The catalytic system, that mimets catalase enzyme such as “multilayer graphene oxide /peroxide molecule” in aqueous media was investigated. The main factors that influence on catalyst’s effectiveness were determining. The catalytic activity of as-synthesized multilayered graphene oxides, and their modified forms (oxidized and nitrogen doped) were investigated in the decomposition of hydrogen peroxides at room temperature and physiological pHs by measuring the volume of released gases. A phosphate buffer with a pH of 5 to 8 was chosen as the reaction medium. The original and modified samples were characterized using XPS, TPD-MS, Boehm titration analyses. The effect of surface chemistry on the catalytic reaction proceeding has been studied. It was found that catalysis on the graphene plane is determined by the presence of heteroatoms in their structure. The catalytic process takes place in the kinetic zone over the entire accessible surface of the samples. The active sites of the catalysts contain a large amount of both nitrogen and oxygen-containing functional groups. In addition, the surface of graphene oxide is hydrophilic, which enhances the catalytic reaction in an aqueous medium. It has been established that the rate of hydrogen peroxide decomposition by reduced graphene oxide samples is lower than for samples modified with oxygen and nitrogen. The catalase-like activity of graphene increases in alkaline pH up to 7.8. Studies have shown that samples of multilayer graphenes with a high content of functional groups can be an alternative to the catalase enzyme as a catalyst for the decomposition of hydrogen peroxide in physiological solutions.

scholarly journals Characteristics of Graphene Oxide Films Reduced by Using an Atmospheric Plasma System

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 802 ◽  
Author(s):  
Chii-Rong Yang ◽  
Shih-Feng Tseng ◽  
Yu-Ting Chen
Keyword(s):  
Graphene Oxide ◽  
Sheet Resistance ◽  
Functional Groups ◽  
Pyrolytic Graphite ◽  
Chemical Oxidation ◽  
Atmospheric Plasma ◽  
Graphene Oxides ◽  
Plasma Irradiation ◽  
Before And After ◽  
Bond Peak

The chemical oxidation method can be used to mass-produce graphene oxides (GOs) from highly oriented pyrolytic graphite. However, numerous oxygen-containing functional groups (hydroxyl, epoxy, carbonyl, etc.) exist in typical GO surfaces, resulting in serious electrical losses. Hence, GO must be processed into reduced graphene oxide (rGO) by the removal of most of the oxygen-containing functional groups. This research concentrates on the reduction efficiency of GO films that are manufactured using atmospheric-pressure and continuous plasma irradiation. Before and after sessions of plasma irradiation with various irradiation times, shelters, and working distances, the surface, physical, and electrical characteristics of homemade GO and rGO films are measured and analyzed. Experimental results showed that the sheet resistance values of rGO films with silicon or quartz shelters were markedly lower than those of GO films because the rGO films were mostly deprived of oxygen-containing functional groups. The lowest sheet resistance value and the largest carbon-to-oxygen ratio of typical rGO films were approximately 90 Ω/sq and 1.522, respectively. The intensity of the C–O bond peak in typical rGO films was significantly lower than that in GO films. Moreover, the intensity of the C–C bond peak in typical rGO films was considerably higher than that in GO films.

scholarly journals Isotherm and Kinetic Modeling of Strontium Adsorption on Graphene Oxide

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2780
Author(s):  
Abdulrahman Abu-Nada ◽  
Ahmed Abdala ◽  
Gordon McKay
Keyword(s):  
Graphene Oxide ◽  
Aqueous Solutions ◽  
Functional Groups ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Nitrogen Adsorption ◽  
Order Kinetic ◽  
X Ray ◽  
Oxygen Functional Groups ◽  
Bet Analysis

In this study, graphene oxide (GO) was synthesized using Hummers method. The synthesized GO was characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) nitrogen adsorption. The analyses confirmed the presence of oxygen functional groups (C=O and C-O-C) on the GO surface. These oxygen functional groups act as active sites in the adsorption Sr (II). The BET analysis revealed the surface area of GO of 232 m2/g with a pore volume of 0.40 cm3/g. The synthesized GO was used as an adsorbent for removing Sr (II) from aqueous solutions. The adsorption equilibrium and kinetic results were consistent with the Langmuir isotherm model and the pseudo-second-order kinetic model. A maximum strontium adsorption capacity of 131.4 mg/g was achieved. The results show that the GO has an excellent adsorption capability for removing Sr (II) from aqueous solutions and potential use in wastewater treatment applications.

Ultrafast H2-Selective Nanoporous Multilayer Graphene Membrane Prepared by Confined Thermal Annealing

2021 ◽  
Author(s):  
Jeong Pil Kim ◽  
Eunji Choi ◽  
Junhyeok Kang ◽  
Seung Eun Choi ◽  
Yunkyu Choi ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
High Pressure ◽  
Graphene Oxide ◽  
Functional Groups ◽  
Thermal Annealing ◽  
Multilayer Graphene ◽  
Graphene Membrane ◽  
Oxygen Functional Groups ◽  
Co2 Selectivity

H2 selective dense pores are generated in graphene oxide (GO) layer by thermal-decomposition of oxygen-functional groups under high pressure. The nanoporous GO membrane shows H2/CO2 selectivity of 12.1 and H2...

Hydrogel-Assisted Delivery of Lipophilic Molecules into Aqueous Milieu for Transdermal Medication Capitalized on Environment-Specific, Regioselective Adsorption of Graphene Oxides

2021 ◽  
Author(s):  
Chongling Cheng ◽  
Wei Bai ◽  
Tonghe Zhu ◽  
Wei Zang ◽  
Sihao Chen ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Aqueous Media ◽  
Graphene Oxides ◽  
Composite Hydrogels ◽  
Assisted Delivery

Graphene oxide (GO) – laden agarose composite hydrogels (GOACHs) were utilized to deliver lipophilic molecules from organic to aqueous media without alteration of the lipophilic nature of the molecules and...

Comparison and Characterization of Two Preparation Methods of Graphene Oxide

2014 ◽  
Vol 989-994 ◽  
pp. 125-129
Author(s):  
Hong Bo Liu ◽  
Wu Ying Zhang ◽  
Feng Lin ◽  
Hong Da Cao
Keyword(s):  
Thermal Expansion ◽  
Graphene Oxide ◽  
Functional Groups ◽  
X Ray Diffraction ◽  
Graphene Oxides ◽  
Ultrasonic Dispersion ◽  
Preparation Methods ◽  
Graphene Nanocomposites ◽  
Infrared Spectrometer ◽  
The Difference

The graphene oxides were prepared form graphite by thermal expansion and ultrasonic dispersion. The structure of graphene oxides was characterized by Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectra. The difference of structure of graphene oxides by two preparation methods was compared. The measurement of FTIR and XRD showed the graphite was completely oxidized. The graphene oxide prepared by thermal expansion would lose large number of active functional groups, such as hydroxyl, carboxyl group, et al. However, the graphene oxide prepared by ultrasonic dispersion can retain these active functional groups. These active functional groups will be benefit to chemically modify the graphene oxides and prepare the polymer/graphene nanocomposites.

Polymer structure and catalytic activity of ion exchangers

1981 ◽  
Vol 46 (7) ◽  
pp. 1577-1587 ◽  
Author(s):  
Karel Jeřábek
Keyword(s):  
Catalytic Activity ◽  
Ethyl Acetate ◽  
Active Sites ◽  
Crosslinking Agent ◽  
Reaction Medium ◽  
Polymer Structure ◽  
Local Concentration ◽  
Ion Exchangers ◽  
Styrene Divinylbenzene ◽  
Kinetics Of

Catalytic activity of ion exchangers prepared by partial sulphonation of styrene-divinylbenzene copolymers in reesterifications of ethyl acetate by methanol and propanol, hydrolysis of ethyl acetate and in synthesis of bisphenol A has been compared with data on polymer structure of these catalysts and with distribution of the crosslinking agent, divinylbenzene, calculated from literature data on kinetics of copolymerisation of styrene with divinylbenzene. It was found that the polymer structure of ion exchangers influences catalytic activity predominantly by changing the local concentration of acid active sites. The results obtained indicated that the effect of transport phenomena on the rate of catalytic reactions does not depend on the degree of swelling of the ion exchangers in reaction medium but it is mainly dependent on the relative affinity of reaction components to the acid groups or to the polymer skeleton.

scholarly journals Non-Enzymatic Desymmetrization Reactions in Aqueous Media

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 720
Author(s):  
Satomi Niwayama
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Functional Groups ◽  
Organic Compounds ◽  
Recent Progress ◽  
Aqueous Media ◽  
Building Blocks ◽  
Organic Reactions ◽  
Environmentally Benign ◽  
Enzymatic Desymmetrization

Symmetric organic compounds are generally obtained inexpensively, and therefore they can be attractive building blocks for the total synthesis of various pharmaceuticals and natural products. The drawback is that discriminating the identical functional groups in the symmetric compounds is difficult. Water is the most environmentally benign and inexpensive solvent. However, successful organic reactions in water are rather limited due to the hydrophobicity of organic compounds in general. Therefore, desymmetrization reactions in aqueous media are expected to offer versatile strategies for the synthesis of a variety of significant organic compounds. This review focuses on the recent progress of desymmetrization reactions of symmetric organic compounds in aqueous media without utilizing enzymes.

scholarly journals Mechanical Properties of Graphene Oxide Coupled by Multi-Physical Field: Grain Boundaries and Functional Groups

Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 62
Author(s):  
Xu Xu ◽  
Zeping Zhang ◽  
Wenjuan Yao
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
Grain Boundaries ◽  
Functional Groups ◽  
Oxygen Content ◽  
Tensile Fracture ◽  
Hydroxyl Groups ◽  
Molecular Configuration ◽  
Spatial Design ◽  
Out Of Plane

Graphene and graphene oxide (GO) usually have grain boundaries (GBs) in the process of synthesis and preparation. Here, we “attach” GBs into GO, a new molecular configuration i.e., polycrystalline graphene oxide (PGO) is proposed. This paper aims to provide an insight into the stability and mechanical properties of PGO by using the molecular dynamics method. For this purpose, the “bottom-up” multi-structure-spatial design performance of PGO and the physical mechanism associated with the spatial structure in mixed dimensions (combination of sp2 and sp3) were studied. Also, the effect of defect coupling (GBs and functional groups) on the mechanical properties was revealed. Our results demonstrate that the existence of the GBs reduces the mechanical properties of PGO and show an “induction” role during the tensile fracture process. The presence of functional groups converts in-plane sp2 carbon atoms into out-of-plane sp3 hybrid carbons, causing uneven stress distribution. Moreover, the mechanical characteristics of PGO are very sensitive to the oxygen content of functional groups, which decrease with the increase of oxygen content. The weakening degree of epoxy groups is slightly greater than that of hydroxyl groups. Finally, we find that the mechanical properties of PGO will fall to the lowest values due to the defect coupling amplification mechanism when the functional groups are distributed at GBs.

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