A highly stable and magnetized citric acid (CA)-functionalized iron oxide aqueous colloidal solution (Fe₃O₄@CA) was synthesized by using a simple and rapid method of one-step co-participation via a chemical reaction between Fe³⁺ and Fe²⁺ in a NaOH solution at 65 °C, followed by CA addition to functionalize the Fe₃O₄ surface in 25 min. The NPs were synthesized at lower temperatures and shortened time compared with conventional methods. Surface functionalization is highly suggested because bare Fe₃O₄ nanoparticles (Fe₃O₄ NPs) are frequently deficient due to their low stability and hydrophilicity. Hence, 19 nm-sized Fe₃O₄ NPs coated with CA (Fe₃O₄@CA) were synthesized, and their microstructure, morphology, and magnetic properties were characterized using X-ray diffraction, transmission electron microscopy, Zeta potential, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. CA successfully modified the Fe₃O₄ surface to obtain a stabilized (homogeneous and well dispersed) aqueous colloidal solution. The Zeta potential value of the as-prepared Fe₃O₄@CA increases from − 31 to − 45 mV. These CA-functionalized NPs with high magnetic saturation (54.8 emu/g) show promising biomedical applications.

Platinum nanoparticles (Pt NPs) have attracted interest in catalysis and biomedical applications due to their unique structural, optical, and catalytic properties. However, the conventional synthesis of Pt NPs using the chemical and physical methods is constrained by the use of harmful and costly chemicals, intricate preparation requirement, and high energy utilization. Hence, this review emphasizes on the green synthesis of Pt NPs using plant extracts as an alternative approach due to its simplicity, convenience, inexpensiveness, easy scalability, low energy requirement, environmental friendliness, and minimum usage of hazardous materials and maximized efficiency of the synthesis process. The underlying complex processes that cover the green synthesis (biosynthesis) of Pt NPs were reviewed. This review affirms the effects of different critical parameters (pH, reaction temperature, reaction time, and biomass dosage) on the size and shape of the synthesized Pt NPs. For instance, the average particle size of Pt NPs was reported to decrease with increasing pH, reaction temperature, and concentration of plant extract.

Gold nanoparticles (AuNPs) are becoming increasingly popular as drug carriers due to their unique properties such as size tenability, multivalency, low toxicity and biocompatibility. AuNPs have physical features that distinguish them from bulk materials, small molecules and other nanoscale particles. Their unique combination of characteristics is just now being fully realized in various biomedical applications. In this review, we focus on the research accomplishments and new opportunities in this field, and we describe the rising developments in the use of monodisperse AuNPs for diagnostic and therapeutic applications. This study addresses the key principles and the most recent published data, focusing on monodisperse AuNP synthesis, surface modifications, and future theranostic applications. Moving forward, we also consider the possible development of functionalized monodisperse AuNPs for theranostic applications based on these efforts. We anticipate that as research advances, flexible AuNPs will become a crucial platform for medical applications.