## 1 Introduction
Cobalt oxide (Co\({}_{3}\)O\({}_{4}\)) is a significant p-type semiconductor with a band gap of 3.95-2.13 eV that comprises a spinel structure with tetrahedral sites (8a) occupied by Co\({}^{2+}\) ions and octahedral sites (16d) by Co\({}^{3+}\) ions [38], which makes it highly stable and anti-ferromagnetic [39]. Therefore, Co\({}_{3}\)O\({}_{4}\)-NPs have vast applications, including lithium-ion batteries, electrochromic devices, magneto-resistive devices, sensors for different organic and inorganic substrates, pigments and dyes, supercapacitors, and selective solar absorbers [40; 41]. Recently, [PERSON] et al. reported a facile approach to prepare mesoporous octahedral Co\({}_{3}\)O\({}_{4}\) NPs with a very narrow size distribution as an eco-friendly catalyst for the photo-degradation of toxic dyes under visible light [42]. Immobilization of the metal oxide particles on the surface of a natural polymer, such as chitosan (CS), is one of the ways to prevent aggregation, increase their catalytic efficiency, and improve their biocompatibility properties. The hydroxyl and amino groups on the surface of CS can adsorb the dye molecules, which facilitates the photocatalytic degradation reaction [43; 44]. Utilizing plants and microorganisms to synthesize NPs is a promising alternative method for producing functional materials, thanks to their diverse structures and energy storage capacity. Specifically, the use of fruit extracts that are abundant in reducing agents has recently garnered attention due to their functional versatility and accessibility [28]. Phytochemicals, including primary and secondary metabolites such as antioxidants, flavonoids, catechins, flavones, isoflav, anthocyanins, isothicyanates, carotenoids, and polyphenols, play a crucial role in reduction [45]. These compounds possess strong reducing properties that enable them to facilitate the conversion of metal ions into nanoparticles [46; 47; 48]. Additionally, these metabolites serve as capping agents to thwart potential NPs aggregation throughout the reaction process [49]. Various chemical and physical methods have been described for the synthesis of metal oxide NPs [50]. Therefore, the process of making Co\({}_{3}\)O\({}_{4}\) NPs involves several common chemical and physical techniques, including the sol-gel method, sonochemical techniques, co-precipitation, wet polymerization, thermal decomposition, micro-emulsion, hydrothermal method, and spray pyrolysis [51]. However, these methods necessitate toxic and expensive chemicals, high temperatures, and priccy and complicated equipment; they also produce hazardous by-products that adversely affect the environment and are energy-intensive [52; 53]. Therefore, they demand the development of clean, sustainable, and environmentally friendly synthesis methods [54; 55]. The synthesis of NPs using plants and microorganisms is a promising alternative for making Co\({}_{3}\)O\({}_{4}\) NPs because of their structural diversity and capacity for energy storage [56]. Due to diverse chemical quantities and mixtures in different plant extracts, the features of the produced NPs differed depending on the source of the plant [57; 58]. Successful green synthesis of Co\({}_{3}\)O\({}_{4}\) NPs has been reported using a variety of plant components, including leaves, stems, roots, seeds, latex, fruits, interior plant parts, peels, and shells. [PERSON] et al. synthesized eco-friendly Co\({}_{3}\)O\({}_{4}\) NPs using the aqueous extract of P. dactylifera L seeds to evaluate the antimicrobial and photocatalytic activity [59]. According to [PERSON] et al., Calotropis Procera latex was used to manufacture Co\({}_{3}\)O\({}_{4}\) NPs [60]. Punica granatum peel extract was utilized by [PERSON] et al. to create Co\({}_{3}\)O\({}_{4}\) NPs from cobalt nitrate hexahydrate [61].