Graphene quantum dot doped viscoelastic lyotropic liquid crystal nanocolloids for antibacterial applications.

Graphene quantum dots (GQDs) are prepared and characterized via X-ray diffraction (XRD), UV-Visible spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL). GQDs are doped (5 mg and 10 mg) in the lyotropic liquid crystalline (LLC) lamellar and hexagonal phases to prepare GQD/LLC nanocolloids. Polarizing optical microscopy and X-ray diffraction measurement reveals that GQDs do not affect the lamellar and hexagonal LLC structures and may organize on their interface. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and GQD/LLC nanocolloids possess shear thinning and frequency dependent liquid viscoelastic behavior. A complex moduli study of LLCs and GQD/LLC nanocolloids is carried out which indicates the gel to viscous transition in LLCs and GQD/LLC nanocolloids as a function of frequency. LLC phases and GQD/LLC nanocolloids are tested for antibacterial activity against Listeria ivanovii. The effect of surfactant concentration, LLC phase geometry and GQD concentration has been studied and discussed. A probable mechanism for the strong antimicrobial activity of LLCs and GQD/LLC nanocolloids is presented considering intermolecular interactions. The viscoelastic behavior and strong antibacterial activity (inhibition zone 49.2 mm) of LLCs and GQD/LLC nanocolloids make them valuable candidates for lubrication, cleaning, cosmetics and pharmaceutical applications.

Synthesis and characterization of gold nanoparticles and graphene oxide for the development of optical fiber biosensors.

Optical fiber technology, in association with the phenomenon of surface plasmon resonance (SPR), has opened a new gateway for quick, easier, and accurate sensing of various chemical, biochemical, and biological parameters. Continuous efforts can be seen in the direction of increasing the sensitivity of the optical fiber biosensors; thus, many hybrid nanostructured optical fiber biosensors composing different nanomaterials, nanomaterial combinations, and different 2D materials have been proposed in the past few decades. This paper discusses the synthesis, characterization, and applications of nanoparticles to the most favorable noble metal for SPR biosensing, i.e., gold. The gold nanoparticles (AuNPs) were prepared by the Turkevich method, and the optical property of AuNPs was characterized using the UV-visible spectrophotometer and transmission electron microscopy (TEM) technique. In addition, the synthesis, characterization, and application of the oxide form the most explored 2D material, i.e., graphene, are also presented in this paper. The graphene oxide was synthesized using an easier and economical method, i.e., a modified Hummer's method, and an evaluation of the characteristics has been done by a UV-visible spectrophotometer and TEM results.