Browsing by Author "Kichukova D."

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    Exploring the impact of different soft reducers in Reduced Graphene Oxide synthesis
    (2019-01-01) Kichukova D.; Staneva A.; Kovacheva D.; Tzoneva I.
    The most common way for the synthesis of bulk graphene is based on exfoliation of graphite. This method involves oxidation of graphite using highly oxidizing agents and subsequently reducing graphene oxide (GO) to graphene. Reduced graphene oxide (RGO) is prepared from reduction of GO by thermal, chemical or electrical treatments. Different reducing agents are widely used for the chemical reduction. However, many of the commonly used reducing agents are hazardous. To decrease the level of toxicity, ``green`` materials recently were applied. The present study reports the preparation of RGO with the use of mild and nontoxic reducing agents. The obtained materials were characterized by X-Ray powder diffraction, Raman and FTIR spectroscopy, as well as by SEM and TEM electron mycroscopy. The results show that at the conditions choosen for the experiment glycerol, ethylene glycol and citric acid do not reduce GO. The use of succrose, acetic acid and oxalic acid in the rection process resulted in an incomplete reduction of GO, The use of urea, L-ascorbic acid and glycine leaded to the removal of interlayer functional groups in GO where the complete reduction of GO is acheaved in the case of the use of L-ascorbic acid and glycine. The results show that L-ascorbic acid and glycine reduce graphene oxide effectively but, depending on the type of the reducer, the morphological properties of the obtained RGO are different.
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    Facile Synthesized Cu–RGO and Ag–RGO Nanocomposites with Potential Biomedical Applications
    (2022-06-01) Kichukova D.; Spassova I.; Kostadinova A.; Staneva A.; Kovacheva D.
    In the present study, we report on the facile prepared nanocomposites of reduced graphene oxide RGO with Cu and Ag. The synthesis was performed through an environmentally friendly and easy method by simultaneous reduction in solutions containing Cu2+ or Ag+ and graphene oxide (GO) using zinc powder as a reducing agent in aqueous acidic media. The composites are characterized by powder X-ray diffraction, low-temperature nitrogen adsorption, X-ray photoelectron and FTIR and Raman spectroscopies, as well as Scanning and Transmission electron microscopies. The antibacterial activity of the composites was tested for Staphylococcus aureus, Escherichia coli and antifungal activity for Candida albicans. The cytotoxicity of the materials was studied towards two types of eukaryotic cells—MDCK II and A549 cell lines. The composites obtained consist of homogeneously distributed Cu and Ag nanoparticles on the surface of graphene sheets and manifest good antimicrobial activity and high cytotoxicity. The results clearly show that both metal–RGO composites can be successfully used as antimicrobial and anticancer agents.
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    Synthesis of Antibacterial Nanocomposites with Reduced Graphene Oxide and Silver Nanoparticles
    (2021-01-01) Staneva A.; Kichukova D.; Kovacheva D.
    A technological scheme for the production of nanocomposite materials based on silver nanoparticles and graphene has been developed. It involves the preparation of graphene oxide and the subsequent in-situ preparation of both reduced graphene oxide (RGO) and silver nanoparticles in the composites by the addition of AgNO3and reduction using sodium borohydride. The obtained composites were characterized by X-ray diffraction, Raman spectroscopy, and Scanning Electron Microscopy. It has been shown that the silver nanoparticles have an average size of about 35 nm and are evenly dispersed in the composites. According to Raman spectroscopy data, the number of graphene layers is in the range of 1-2 for the developed composites as well as in pure RGO. All composite materials with silver nanoparticles and graphene have antibacterial properties against Staphylococcus aureus and Escherichia coli. As the content of silver nanoparticles in the composites increases, the antibacterial activity against the two studied bacteria increases too. The activity of all samples against Escherichia coli was higher than against Staphylococcus aureus.