DEVELOPMENT OF AMIDE-BASED MOLECULES FOR ENHANCED ANTIMICROBIAL PROPERTIES

This study is devoted to the synthesis of various ensembles on the basis of graphene oxide nanolayers and dihydropyrimidines and the investigation of their antimicrobial activity. The “building blocks” of ensembles, viz dihydropyrimidines were synthesized by the Biginelli reaction in the presence of low-toxic copper triflate under microwave conditions. The positive side of the reaction is the absence of any additional purification stage, formed after cooling the solution precipitate just washed with a few amount of distilled water. The structures of synthesized compounds were determined by 1H, 13C and dept135 NMR spectroscopy methods. The second component, viz graphene oxide nanolayers, was synthesized by a modified Hummer method. The modification of the method is caused by the increasing of the oxidizing agent (H2SO4+KMnO4) concentration, which allowed to receive purier nanolayers. The structure and morphology of nanolayers were investigated by SEM and XRD methods, according to which it was determined that the thickness of nanolayers is 1 nm. Subsequently, graphene oxide was modified with dihydropyrimidines. The synthesis of ensembles was performed by non-covalent coupling of dihydropyrimidines with graphene oxide nanolayers by sonication. In addition, the antimicrobial activity of ensembles against S. aureus, Ps. aeruginosa and E. coli was performed. Obtained during the analysis results were compared with the activity of pristine antibiotic ampicillin. It was found that the addition of graphene oxide nanolayers to the dihydropyrimidine molecule allowed to improve the antimicrobial activity of dihydropyrimidines

Continuous graphene oxide nanolayer arranged on hydrophilic modified polytetrafluoroethylene substrate to construct high performance proton exchange membranes

Ultrasensitive mushroom-like electrochemical immunosensor for probing the activity of histone acetyltransferase

Graphene oxide (GO) is a carbon-based nanomaterial with high surface area and abundant functional groups, providing various sites for binding and immobilization of growth factor vehicles. This study used GO nanolayer as an anchor for the immobilization of bone morphogenetic protein-2 (BMP-2)-encapsulated bovine serum albumin nanoparticles (NPs) on the hydroxyapatite (HA) and tricalcium phosphate (TCP) scaffolds by electrostatic interaction between the positive charges of the NPs and negative charges of GO. GO nanolayers prevented the rapid degradation of TCP scaffolds. Moreover, GO nanolayers promoted NP adsorption on these scaffolds, and realized BMP-2 sustained release. NPs endowed the scaffold surfaces with a nanostructure similar to that of the extracellular matrix (ECM), improving bone marrow stromal cell (BMSC) attachment. Furthermore, the positive charged NPs and negative charged GO nanolayers constructed a charge-balanced surface on the scaffolds, enhancing BMSC proliferation. The nanostructure, charge balance and BMP-2 sustained release capability synergistically improved BMSC differentiation and bone regeneration. In summary, GO is a potential candidate to modify biomaterial surfaces as an anchor for efficient immobilization of growth factor vehicles. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1311-1323, 2017.

In this paper, graphene oxide (GO) and its functionalization with “Amio Methyl Phosphonic Acid” (AMPA) are synthesized using modified Hummers method. Crystal structure of the compounds is investigated by X-ray diffraction pattern (XRD). Fourier transform infrared spectroscopy (FTIR) clearly shows that the AMPA agent does really enter into the GO. Transmission electron microscope (TEM) images of the compounds reveal that they are in the form of nano-sheets. High resolution TEM (HRTEM) microscope is also used to observe and study the nanoscopic morphology of the structures. In addition, the samples are element-analyzed by energy dispersive X-ray spectroscope (EDS), and X-ray photoelectron spectroscopy (XPS) to get more information. Finally, the functionalization mechanism of GO with AMPA is studied and the mechanisms of “nucleophilic displacement” as well as “condensation reaction” are suggested andare experimentally confirmed. Due to the favorable properties of the synthesized material AMPA-GO, its use was suggested for water treatment and removal of heavy metals such as lead and strontium.

Due to the impact of the new crown epidemic in recent years, disinfectants have played an increasingly important role, so the research and development of new high-efficiency nano-disinfectants are urgent issues. In this study, graphene oxide (GO) was first prepared by the modified Hummer method. Then, the GO/trichloroisocyanuric acid (TCCA) composite was prepared by loading TCCA into GO with the blending method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and atomic force microscopy were used to characterize the composite. The results showed that TCCA was successfully loaded on the surface of GO or intercalated among GO layers. Next, the antibacterial performance of the composite against Escherichia coli and Staphylococcus aureus was tested by the 96-well plate assay. A bactericidal kinetic curve, bacterial inhibition tests, and the mechanism of bacterial inhibition were discussed. The results showed that the minimum inhibitory concentration (MIC) of the GO/TCCA composite (GO:TCCA ratio = 1:50) was 327.5 μg ml−1 against E. coli and 655 μg ml−1 against S. aureus. At the MIC, the inhibition rate of the GO/TCCA composite exceeded 99.46% against E. coli and 99.17% against S. aureus. The bactericidal kinetic curves indicate that the GO/TCCA composite has an excellent bactericidal effect against E. coli and S. aureus.

The development of new antibacterial agents is proposed to solve the problem of drug-resistant bacterial strains caused by antibiotic misuse. The aim of this study was to improve the antibacterial activity by modifying graphene oxide (GO) using ZnO/eugenol and analyzing the interaction computationally. The study was started with GO synthesis using the modified Hummer method, followed by the dispersion of ZnO/eugenol through the mechanochemical method to GO to form GO/ZnO/eugenol composite. The composite was characterized using XRD, FTIR, UV-vis, SEM, and TEM. Results showed that the sonochemical method successfully prepared the GO/ZnO/eugenol composite. This material has better antibacterial E. coli activity than GO, with an inhibition zone of 11.5 mm in diameter, while pure GO showed no inhibition zone. MIC test presented that GO/ZnO/eugenol composite with 25 mg/mL suspension effectively prevented bacterial colony growth, while GO could only inhibit with 50 mg/mL suspension. Additionally, computational analysis through molecular docking suggested that the GO/ZnO/eugenol mechanism of action involves interference with DNA replication by hydrogenously interacting with the active site of DNA gyrase of E. coli bacteria. These findings highlight the potential of GO/ZnO/eugenol as a promising antibacterial agent for combating drug-resistant bacterial strains.

One of the materials that has attracted the attention of nanotechnology researchers today is graphene oxide (GO). GO was first developed by Oxford chemist Benjamin C. Brody in 1859 by processing graphite with a mixture of potassium chlorate and smoky nitric acid. GO, formerly known as graphite acid, is a combination of carbon, oxygen, and hydrogen in variable ratios obtained by refining graphite with strong oxidants and acids to decompose excess metals. The oxidized product is a yellow solid with a C: O ratio between 2.1 and 2.9 that maintains the structure of the graphite layer but at a much larger and irregular distance (Januário et al., 2021). GO is a two-dimensional, monolayer material with a hexagonal and crystalline structure that has oxygen groups on its plates and its high biocompatibility and biodegradability has made it one of the nanomaterial substrates for stabilizing and transporting enzymes. In recent years, researchers have used the substance in both medical and pharmaceutical technologies and industrial applications (Abdelhamid & Hussein, 2021). The use of GO for a glucose sensor was first reported in 2009 (Karki et al., 2020). GO has been used in various fields, including in the manufacture of sensors, due to its outstanding chemical, electrical and optical properties, as well as its high oxygen content. Also as an antimicrobial agent for biomedical applications, as well as nanofillers for membranes was used in wastewater treatment. The future of GO-based membranes for the treatment of water-contaminated water is also presented. GO sheets are used to make materials such as paper, membranes, thin films, and composites. Initially, graphene oxide was considered as a possible intermediate for the production of graphene (Januário et al., 2021). Biochemical and biomedical applications of GO rely heavily on the interactions of biomolecules with it (Zhang et al., 2012). This carbon-based nanoparticle is also used as a drug carrier (Abdelhamid & Hussein, 2021). Chemical vapor deposition and thermal peeling, microchannel peeling of graphite, and direct synthesis and chemical peeling of graphite, are common methods for GO synthesis developed by Brody Stedemiz and Hummer (Ciszewski & Mianowski, 2013). The method chosen in present study for GO synthesis is the modified Hammers method, in which the synthesis duration was shorter and the process was easier. And 0.5 g sodium nitrate were mixed with 23 mL sulfuric acid in a 500 mL flask place in. To synthesize GO, 0.5 g of natural graphite powder and 0.5 g of NaNo3 mixed with 23 ml of sulfuric acid in a 500 mL flask placed in an ice bath (below 20 °C) for 4 hours with stirring. 3 grams of potassium permanganate was added to the flask and the solution was stirred for one hour. The temperature was increased to 35 °C and the solution was stirred for another one hour. 46 mL of distilled water was added slowly and the temperature was increased to 95 °C without boiling for 2 hours. The solution was left to reach the same room temperature. 100 mL distilled water was added and stirred for an hour. 10 mL hydrogen peroxide (0.30%) was added to the solution and stirred for an hour. The solution was centrifuged at 5000 rpm for 7 minutes and the supernatant was removed. 30 mL distilled water and 10 mL HCl (0.37%) was added to the precipitate and the solution was centrifuged. This procedure was carried out for 3 times. The obtained precipitate was evaluated using x-ray diffraction pattern (XRD), scanning electron microscope (SEM) and fourier transform infrared spectroscopy (FTIR) to demonstrate whether the precipitated material was GO nanoparticles. The XRD pattern for GO (Figure 1), SEM image (Figure 2) and The FTIR spectra confirmed the fabrication of GO (Figure 3). We have shown that our modified Hummer method for GO synthesis, is a convenient and cost-effective synthesis of GO nanoparticle.

In this study, the reduced graphene oxide (rGO) using the modified Hummers method from battery waste materials has been successfully carried out. The results obtained were compared with the conventional Hummers method. XRD analysis showed that the characteristic peaks of graphene oxide (GO) were reduced to rGO using both the conventional and modified Hummers methods. The results of the UV‐vis analysis also revealed that the absorption peak of the rGO sample showed a shift toward a longer wavelength, located between 200 and 270 nm, compared to GO. The FTIR results showed that the intensity of all oxygen‐containing functional groups was reduced in rGO (the presence of several spectral peaks and functional groups after reduction), thus confirming the successful reduction of GO using both the modified and conventional Hummers methods. The Raman spectroscopy results showed that the defects in rGO using the modified Hummers method were smaller than those in rGO using the conventional Hummers method. This can be seen from the results of the D‐band and G‐band intensity ratios (ID/IG), which were 1.108 and 1.292 in rGO using the modified and conventional Hummers methods, respectively. SEM analysis shows morphological changes indicating changes in graphite to GO and then to rGO. The EDX results obtained are also reinforced by the increase in carbon elements (84.21% = conventional rGO and 82.80% = modified rGO) and a decrease in oxygen elements in all methods for rGO. These findings suggest that the modified Hummers method, which utilizes environmentally friendly chemicals instead of hazardous ones (convention Hummers method), is a viable approach for converting battery waste into rGO applications. Additionally, the oxygen content produced by the modified Hummers method is higher than that of the conventional Hummers method.

New materials with good antibacterial activity and less toxicity to other species have attracted numerous research interests. Modified Hummers method was used for preparing graphene oxide (GO). Zinc oxide/graphene oxide (ZnO/GO) nanocomposites were synthesized with three different ratios (0.5:1, 1:1, and 2:1) by solution precipitation method. The ZnO/GO nanocomposites were characterized by Fourier transform infrared spectroscopy, X–ray diffraction, Raman spectroscopy, Brunauer–Emmett–Tellerspecific surface area, and transmission electron microscopy image. The characterization results showed that ZnO nanoparticles with a mean size of 12–18 nm were randomly decorated on the surfaces and edges of GO sheets. ZnO/GO 1:1 with a high specific surface area of 65 m2/g was obtained. The antibacterial activity of ZnO, GO, and ZnO/GO was tested against Gram negative bacteria escherichia coli (E. coli) and Gram positive bacteria staphylococcus aureus (S. aureus) using well diffusion method. The test results confirmed that antibacterial activity of ZnO/GO was higher than that of GO and ZnO. Additionally, the ZnO/GO with the ratio of 1:1 is the strongest activity and more active against S. aureus than against E. coli and minimal inhibitory concentration (MIC) value of ZnO/GO 1:1 is 80 µg/mL for S. aureus and 160 µg/mL for E. coli. This novel nanocomposite could be used as a potential material for antimicrobial application.

In this study, graphene oxide (GO) was synthesized from graphite using modified Hummers method. According to other methods known in the literature, modified Hummers method; it is simpler and less costly in terms of process steps. In addition, it is safer and environmentally friendly than the Hummers method. Reduced Graphene Oxide (RGO) was obtained by reduction of graphene oxides (GO) synthesized by modified Hummers method. It is understood from the obtained results that GO is synthesized successfully from graphite powder by modified Hummers method and RGO is obtained successfully by reduction of graphene oxides (GO).

The thermal exfoliation and reduction of graphite oxide (GO) is the most commonly used strategy for large-scale preparation of graphene, and the oxidation degree of GO would influence the chemical structure of prepared graphene, thereby affecting its final physical and chemical properties. In addition to serving as the precursor for synthesizing graphene, GO also possesses great potential for various important applications owing to its abundant oxygen-containing groups and hybrid electronic structure. Therefore, systematically studying the influencing factors on the oxidation degree of GO and clarifying the effect of oxidation degree on the corresponding graphene is particularly important. Herein, we have studied the effect of the lateral size of the original graphite on the oxidation degree of GO in order to control the oxidation degree of GO. GOs with different degrees of oxidation were synthesized using a modified Hummers method. The results of X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and Raman spectroscopy revealed that decreased lateral size of the original graphite would lead to increased oxidation degree of GO. Furthermore, the interlayer spacing of the GO samples achieved 0.9–1.0 nm, which indicated that the modified Hummers method could make well oxidized graphite. The corresponding reduced graphite oxide (rGO) was also prepared by low-temperature exfoliation of GO at 140 °C under ambient atmosphere. It was found that a larger lateral size of GO resulted in rGO with fewer oxygen-containing functional groups, but a smaller lateral size of graphite possessed a higher exfoliation degree with a larger specific surface area. More importantly, the relationship between binding energy (EB) of photoelectron of C atom in oxygen-containing groups and the number of oxygen-containing groups in GO and rGO samples was analyzed theoretically.

Over the span of years, improvements over various synthesis methods of graphene are constantly pursued to provide safer and more effective alternatives. Though the extraction of graphene through Hummers method is one of the oldest techniques yet it is one of the most suitable methods for the formation of bulk graphene. Graphene can be obtained in the form of reduced Graphite oxide, sometimes also referred as Graphene oxide. The effectiveness of this oxidation process can be evaluated by the magnitude of carbon/oxygen ratio of the obtained graphene. Here, graphene oxide (GO) was prepared by oxidizing the purified natural flake graphite (NFG) by a modified Hummers method. The attempts have been made to synthesize GO having few layers by using a modified Hummers method where the amount of NaNO3 has been decreased, and the amount of KMnO4 is increased. The reaction has been performed in a 9:1 (by volume) mixture of H2SO4/H3PO4. This modification is successful in increasing the reaction yield and reducing the toxic gas evolution while using a varied proportion of KMnO4 and H2SO4 as those required by Hummers method. A new component of K2S2O8 has been introduced to the reaction system to maintain the pH value. Reduced graphene oxide (rGO) was thereafter extracted by thermal modification of GO. Here, GO has been used as a precursor for graphene synthesis by thermal reduction processes. The results of FTIR and Raman spectroscopy analysis show that the NFG when oxidized by strong oxidants like KMnO4 and NaNO3, introduced oxygen atoms into the graphite layers and formed bonds like C=O, C-H, COOH and C-O-C with the carbon atoms in the graphite layers. The structure and morphology of both GO and rGO were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy, Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Synthesis and functionalization of graphene oxide (GO) for salty water desalination as adsorbent

Nanomaterials show great opportunities in the development of electronics, biosensors, chemical and industrial applications. In this article, we are reporting the cytotoxicity and antibacterial characteristics of graphene-oxide (GO) nanosheets toward selected human pathogens. GO is prepared by using modified Hummers method. The prepared GO is characterized using X-ray diffraction, Raman analysis and transmission electron microscopy. Our studies confirmed the antimicrobial activity of GO against various human pathogens. The cytotoxicity effects of GO nanosheets are investigated using MTT assay which confirms that GO nanosheets are non-toxic and eco-friendly. These results ensure that GO nanosheets can be a potential antibacterial agent in the biological, health related industry development and applications.