Nanotechnology has gained much attention for its potential application in medical science. Iron oxide nanoparticles have demonstrated a promising effect in various biomedical applications. In particular, magnetite (Fe3O4) nanoparticles are widely applied due to their biocompatibility, high magnetic susceptibility, chemical stability, innocuousness, high saturation magnetisation, and inexpensiveness. Magnetite (Fe3O4) exhibits superparamagnetism as its size shrinks in the single-domain region to around 20 nm, which is an essential property for use in biomedical applications. In this review, the application of magnetite nanoparticles (MNPs) in the biomedical field based on different synthesis approaches and various surface functionalisation materials was discussed. Firstly, a brief introduction on the MNP properties, such as physical, thermal, magnetic, and optical properties, is provided. Considering that the surface chemistry of MNPs plays an important role in the practical implementation of in vitro and in vivo applications, this review then focuses on several predominant synthesis methods and variations in the synthesis parameters of MNPs. The encapsulation of MNPs with organic and inorganic materials is also discussed. Finally, the most common in vivo and in vitro applications in the biomedical world are elucidated. This review aims to deliver concise information to new researchers in this field, guide them in selecting appropriate synthesis techniques for MNPs, and to enhance the surface chemistry of MNPs for their interests.

Room-temperature ferromagnetism in the large and direct bandgap diluted magnetic semiconductor zinc oxide (ZnO) is attributed to the intrinsic defects and p-orbital–p-orbital (p–p) coupling interaction.

Since the first isolation of graphene over a decade ago, research into graphene has exponentially increased due to its excellent electrical, optical, mechanical and chemical properties. Graphene has been shown to enhance the performance of various electronic devices. In addition, graphene can be simply produced through chemical vapor deposition (CVD). Although the synthesis of graphene has been widely researched, especially for CVD growth method, the lack of understanding on various synthetic parameters still limits the fabrication of large-area and defect-free graphene films. This report critically reviews various parameters affecting the quality of CVD-grown graphene to understand the relationship between these parameters and the choice of metal substrates and to provide a point of reference for future studies of large-area, CVD-grown graphene.

Summary Nanogenerators is the growing technology that facilitates self‐powered systems, sensors, and flexible and portable electronics in the thriving era of internet of things (IoT). Since the first invention of the triboelectric nanogenerators (TENGs) in 2012, it has become one of the most important inventions in energy harvesting technologies. In this paper, a brief review on the recent progress of energy harvesting research based on TENGs technology is discussed. Basic working modes of the TENG are discussed in detail and the general procedure to synthesize, measure, and characterize a nanogenerator is presented in a direct structure. The triboelectric material choices are extremely important for TENGs since the triboelectric effects of the materials are fundamental for TENGs. The materials used as triboelectric layers are varied from polymers, metals, and inorganic materials with the commonly used materials are dielectric polymers such as PTFE, PVDF, PDMS, nylon, and Kapton. Recently, two‐dimensional (2D) materials have been widely reported as candidate materials for TENGs. Graphene, the most attractive 2D materials exhibits an excellent electrical property, great flexibility, and a high surface‐to‐volume ratio. Owing to the very low thickness of the atomic unit, a stacking graphene structure can be also made to form a very thin and miniature TENGs device. The major applications of the graphene as active materials for TENGs as a sustainable energy harvester are presented, following which structural designs and materials optimization for output performance improvement of the graphene‐based TENGs are summarized. Finally, the future directions and perspectives of the graphene‐based TENGs are outlined. The graphene‐based TENGs is not only a sustainable micro‐power source for small devices, but also serves as a potential macro‐scale generator of power from blue energy in the future.

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