Biosynthesis of Metal and Metal Oxide Nanoparticles

Abstract

Bioresource‐based green synthesis of nanoparticles has gained significant interest as an emerging technology to reduce the toxicity of nanoparticles commonly associated with conventional chemical synthesis approaches. Studies on green synthesis of metal nanoparticles have been carried out with various biological materials including from bacteria, fungi, and plant extracts. Plant extracts in particular have been extensively used for the synthesis of metal and metal oxide nanoparticles, and this is due to the presence of essential phytochemicals in plant extracts especially from the leaves. Leaf extract contains various types of phytochemicals such as terpenoids, flavonoids, ketones, aldehydes, amides, and carboxylic acids, which play a major role in formulating and enhancing the bioactivity of the nanoparticles. This article discusses flavonoids as an essential phytochemical for the formation of metal and metal oxide nanoparticles and enhancement of their bio‐functionality and compatibility. In addition, bioprocess developments for the synthesis of metal as well as metal oxide nanoparticles from various biological materials are discussed.

Green synthesis and physiochemical characterization of nickel oxide nanoparticles: Interaction studies with Calf thymus DNA

“…On introduction of the plant extract, the active phytochemicals reduced the metal cations into zerovalent ions, which agglomerates into NPs due to lack of interatomic repulsion. The exact method of metal oxide NPs formation is not exactly understood, but it is suggested that they are formed due to oxidation of metal NPs with atmospheric oxygen or decomposition of phytochemicals . Figure (b) is a schematic representation of the formation of NiO NPs from the precursor nickel acetate.…”

“…The exact method of metal oxide NPs formation is not exactly understood, but it is suggested that they are formed due to oxidation of metal NPs with atmospheric oxygen or decomposition of phytochemicals. [11] Fig…”

“…The secondary metabolites mentioned consisted of several bioactive compounds including proteins, sugars, vitamins, and flavonoids . It has been proposed that transition of flavonoids from the enol to the keto form is responsible for this reduction . The exact method of metal oxide NP formation from the metal NPs is not fully understood, but it is believed that they are formed due to oxidation of metal NPs or intermediates with atmospheric oxygen or decomposition of phytochemicals from the plant extract …”

“…[10] It has been proposed that transition of flavonoids from the enol to the keto form is responsible for this reduction. [11] The exact method of metal oxide NP formation from the metal NPs is not fully understood, but it is believed that they are formed due to oxidation of metal NPs or intermediates with atmospheric oxygen or decomposition of phytochemicals from the plant extract. [11] DNA-NP conjugates are excellent candidates for biosensors in which DNA acts as the sensor and the NPs either alone or immobilized onto a stratum that serves as a transducer.…”

“…[11] The exact method of metal oxide NP formation from the metal NPs is not fully understood, but it is believed that they are formed due to oxidation of metal NPs or intermediates with atmospheric oxygen or decomposition of phytochemicals from the plant extract. [11] DNA-NP conjugates are excellent candidates for biosensors in which DNA acts as the sensor and the NPs either alone or immobilized onto a stratum that serves as a transducer. DNA can be conjugated to NPs via different physicochemical forces, from being immobilized onto the NPs chemically via a bivalent linker [12] or being physically bound via electrostatic, van der Waals, or other weak forces.…”