Modares Journal of Biotechnology

Abstract Graphene quantum dots (GQDs) have attracted increasing attention due to their unique properties such as high water solubility, photoluminescence activity, good biocompatibility, physical, chemical and electrical properties which makes them appropriate candidates for use in a variety of bio-applications, sensors and photocatalysts. The objective of this study is synthesis of GQDs and improving their surface properties via chemical modification.
Here, urea and citric acid as carbon precursor were used. Citric acid was self-assembled into graphene framework via hydrothermal method at 160 °C for 4 h. Then, the synthesized GQDs were carbonized and chemically activated by KOH treatment. The surface area and pore structures of GQDs were analyzed by nitrogen adsorption/desorption isotherms. The results showed that the specific surface area of carbonized-activated graphene quantum dots (CA-GQDs) have been increased from 0.06 to 1204.0 m²/g and pore structures have been enhanced significantly. The XRD pattern of GQDs confirmed the basic structure of graphite layer. The TEM images indicated the unique morphology of GQDs and the sizes of GQDs were less than 5 nm. Thus, our applied method is an effective approach in the formation of GQDs with large BET surface area and narrow pore structures which reveals their potential applicability in biomedical field.

Abstract Biosurfactants are surface tension reducing compounds produced by a wide range of microorganisms. These compounds are caused to facilitate the absorption insoluble substrate by microbial cells. The aim of this study was to investigate the effects of nanoparticles of Fe/SDS on the biosurfactant production by Pseudomonas aeruginosa in culture is molasses.
For this purpose were used different concentrations of nanoparticles 1, 500 and 1000 mg/L. As a result the concentration of 1mg /L of Fe/SDS nanoparticles has the best effect on the growth of bacteria and biosurfactant production. This concentration increased 23.21% cell growth and 20.73% biosurfactant production compared with control samples. By increasing the concentration of nanoparticles reduced growth rate and biosurfactant production was observed. This indicates that the nanoparticles having negative effects of higher concentrations.
The results showed that low concentrations of nanoparticles Fe/SDS has positive effects on bacterial biosurfactant production and therefore a good alternative to chemical surfactants for use in the petroleum industry.