Green and Chemical Syntheses of CdO NPs: A Comparative Study for Yield Attributes, Biological Characteristics, and Toxicity Concerns

Abstract

Metallic nanoparticles (NPs) have enormous applications due to their remarkable physical and chemical properties. The synthesis of NPs has been a matter of concern because chemical methods are toxic. On the contrary, biological methods are considered eco-friendly. To compare the toxicity and the environment-friendly nature of the synthesis methodologies, cadmium NPs were synthesized through chemical (Ch) (co-precipitation) and biological (plant extracts as reducing agent) methods. Cadmium nitrate was reduced with NaOH, while in the biological method, the Cd ions were reduced by Artemisia scoparia (As) and Cannabis sativa (Cs) extracts. X-ray diffraction (XRD) analysis confirmed the pure single-phase cubic structure of green and chemically synthesized CdO NPs except As-CdO NPs that were crystalline cum amorphous in nature. The size of nanoparticles was 84 nm (Cs-CdO NPs) and 42.2 nm (Ch-CdO NPs). The scanning electron microscope (SEM) images exhibited an irregular disklike morphology of nanoparticles that agglomerated more in the case of green synthesis. The antioxidant and antimicrobial potential of NPs revealed that chemically synthesized NPs have better antimicrobial capability, while the antioxidative activities were better for green-synthesized NPs. However, the low yield, high ion disassociation, and waste (unreacted metal) production in the green synthesis of CdO NPs increase the risk of contamination to biosphere. Both types of NPs did not affect the seed germination of Dodonaea viscosa. However, chemically synthesized NPs were less toxic on plant morphological response. The study concludes that the chemically synthesized CdO NPs have better morphology, significant antimicrobial activity, and less toxicity to plant species compared to green-synthesized NPs. Moreover, during the green synthesis, unreacted metals are drained, which causes contamination to the ecosystem.

Antioxidants: Classification, Natural Sources, Activity/Capacity Measurements, and Usefulness for the Synthesis of Nanoparticles

“…Plant extracts contain diverse compounds, which can be utilized as potent reducing agents, stabilizing agents, and precursor molecules for NPs formation [ 375 , 376 ]. In order to prepare the extracts, both the biomass of the whole plant and selected parts such as leaves, fruit, seeds, and above-ground parts can be used.…”

Interactive Effect of Light and CdO Nanoparticles on Dodonaea viscosa Morphological, Antioxidant, and Phytochemical Properties

“…CdO NPs were synthesized using green and chemical chemistry under the same conditions and using the same procedure. 22 Both methodologies resulted in formation of brown NPs. SEM disclosed clear and distinct images of green and chemically synthesized CdO NPs ( Figure 1 A,D) with the size range 10–30 nm.…”

“…(A–C) SEM, XRD, and FTIR analysis of chemically synthesized CdO NPs. (D–F) SEM, XRD, and FTIR analysis of green synthesized NPs (borrowed from Nasrullah et al 22 ).…”

“…CdO NPs synthesized through the coprecipitation method and green chemistry were used in this study as previously reported. 22 In short, for chemical synthesis, 50 mL of 0.5 M Cd (NO 3 ) 2 ·4H 2 O was reacted with 50 mL of NaOH (0.5 M). However, for green synthesis, 50 mL of the extract of Artemisia scoparia (30 g DW/150 mL) was reacted with 0.5 M Cd(NO 3 ) 2 ·4H 2 O.…”

“…CdO NPs synthesized through the coprecipitation method and green chemistry were used in this study as previously reported . In short, for chemical synthesis, 50 mL of 0.5 M Cd (NO 3 ) 2 ·4H 2 O was reacted with 50 mL of NaOH (0.5 M).…”