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We report a facile and friendly to the environment method for the preparation of superparamagnetic γ-Fe 2 O 3 /Gd 2 O 3 -chitosan nanocomposite for magnetic hyperthermia application. The nanocomposite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer, Scanning electron microscopy and Energydispersive X-ray spectroscopy (EDAX). In addition, the heating efficiency and biocompatibility with human cells are reported. XRD patterns indicated that the most dominant crystalline phase is γ-Fe 2 O 3 with the presence of chitosan in the coated sample. FT-IR and EDAX confirmed the presence of chitosan on the surface of the nanostructure. Magnetic measurements showed the superparamagnetic behavior with decrease in saturation after coating due to diamagnetic nature of chitosan. This behavior is corroborated by the successfully fitting into Langevin function for paramagnetic materials. The specific absorption rate under an alternating magnetic field is investigated as a function of the concentration and amplitude of the applied magnetic field. A mean heating efficiency of 35 W/g is obtained for concentration of 15 mg/ml at 332 kHz and 170 Oe. It was found that the heating efficiency of the nanocomposite can be tuned by changing parameters such as concentration and amplitude of applied AC magnetic field. Cell viability assay of coated nanocomposite showed low cytotoxic effect on A549 cells line (human alveolar epithelial). In overall, the prepared nanocomposite can be used as potential candidate for magnetic hyperthermia application due to their superparamagnetic nature, heating ability and biocompatibility with human cells.

Graphene, a remarkable material, is ideal for numerous applications due to its thin and lightweight design. The synthesis of high-quality graphene in a cost-effective and environmentally friendly manner continues to be a significant challenge. Chemical reduction is considered the most advantageous method for preparing reduced graphene oxide (rGO). However, this process necessitates the use of toxic and harmful substances, which can have a detrimental effect on the environment and human health. Thus, to accomplish the objective, the green synthesis principle has prompted researchers worldwide to develop a simple method for the green reduction of graphene oxide (GO), which is readily accessible, sustainable, economical, renewable, and environmentally friendly. For example, the use of natural materials such as plants is generally considered safe. Furthermore, plants contain reducing and capping agents. The current review focuses on the discovery and application of rGO synthesis using extracts from different plant parts. The review aims to aid current and future researchers in searching for a novel plant extract that acts as a reductant in the green synthesis of rGO, as well as its potential application in a variety of industries.

A straightforward approach that uses Clinacanthus nutans leaf extract as a bio-reduction agent has been reported to anchor silver nanoparticles onto graphene oxide (rGO-Ag). The nanocomposite was characterized by using ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy, and X-ray diffraction. A qualitative colour transition from yellowish to dark brown confirmed the biosynthesis of rGO-Ag nanocomposite and showed a surface plasmon resonance at 263 nm and 425 nm. Utilizing cyclic voltammetry, the electrochemical characteristics of the rGO-Ag nanocomposite modified screen printed carbon electrodes were examined. The rGO-Ag nanocomposite electrode enhanced anodic current approximately 1.29 times greater compared to silver nanoparticles (AgNPs) and 1.34 times greater compared to graphene oxide (GO). Moreover, rGO-Ag nanocomposites exhibited excellent antibacterial activity against typical Gram-positive (S. aureus) (11.99 ± 0.26 mm) and Gram-negative (E. coli) (11.86 ± 0.29 mm) bacteria. Toxicity was assayed using brine shrimp Artemia salina. The results of hatching and mortality assay demonstrates that AgNPs and rGO-Ag nanocomposite is biocompatible with A. salina at a low dosage (0.001 mg/mL). This work offers a guide for the future synthesis of nanocomposites using green reductants. The as- synthesized nanocomposite shows a promising component for the development of biomedical devices applications.

Magnetite nanoparticle and graphene oxide is a promising nanoparticle that can be used in multitude of field due to their exceptional characteristic. Graphene oxide has a unique 2-D structure, and excellent chemical and physical characteristics while magnetite nanoparticle has its superparamagnetic properties which enable it to be controlled by external magnetic field. Owing to that, any new formulations of magnetic nanoparticle functionalities with graphene oxide have to be taken into consideration. In this research, magnetite nanoparticles were functionalized with graphene oxide using simple emulsion and evaporation method. All the samples were characterized by X-ray diffraction, and Fourier-transform infrared, and Raman spectroscopy. The toxicity of the nanomaterials was tested with cell viability assay (XTT) using A549 cells. The cell viability remains high within 24 h and 72 h of incubation, and when the concentration increases up to 100 µg/mL only a slight decrease of viability was observed.