# Fungi-Templated Silver Nanoparticle Composite: Synthesis, Characterization, and Its Applications
## 1 Introduction
Fungal-mycelium-based composite materials pose significant advantages considering their environmental benign nature and the notable functional properties which can be efficiently utilized for several applications. Fungal mycelium consists of a network of microfilaments whose diameter ranges between 2-30 \(\upmu\)m, depending on the species and the environment. The various hyphal colonies interact with each other, forming a network-like structure which efficiently helps in binding various substrates and thereby generating the functional composite materials. Low environmental impact, low cost, and excellent biodegradability are some of the key incentives that enable these composite materials to stand up along with conventional engineered composite materials such as carbon nanotubes, fibres, etc. [18]. The mycelium is found to be a natural polymeric fibrous composite mainly composed of chitin, cellulose, and proteins. Due to the presence of these functionalities in the fungal mycelium, it can readily bind to various substrates via various covalent and non-covalent interactions, thereby forming highly functional composite materials that can be used for varying applications. Moreover, these functional properties can be tuned by changing the substrates that bind to the mycelium. Various dyes released as effluents from industries causes non-aesthetic pollution and eutrophication in aquatic ecosystems. Since the international environmental standards are becoming more stringent, scientists have devoted a significant amount of time and effort to the removal of these hazardous compounds from water bodies. The developed technologies include various physical, chemical, and biological methods which have been applied for the efficient removal of dye compounds from aquatic ecosystems. Among the developed technologies for dye disposal, photocatalysis have exhibited excellent resultsin terms of degradation of dye in various industrial waste water [19]. Methylene blue is an intensely coloured industrially important dye which is used for dying and printing textiles. It is a cationic dye which is found to be carcinogenic, environmentally persistent, mutagenic, and toxic. When released into the external environment, methylene blue poses a great threat to flora and fauna and is known to cause fatal serotonin toxicity in human beings. Therefore, it is highly imperative to eradicate the dye and the associated chemical compounds from the ecosystem. To carry out photocatalytic degradation of an organic dye, the dye is typically mixed with the photocatalyst and exposed to light. The light activates the photocatalyst, causing it to generate highly reactive species such as free radicals, which can break down the organic dye into smaller, less harmful components. This process can be enhanced by adding other substances such as hydrogen peroxide to the reaction mixture, which can help to increase the efficiency of the degradation process. Herein, we report the synthesis of AgNPs using an earlier reported method and the bio-templating of the synthesized AgNPs on the fungal hyphae of _Sclerodium rolfisi_ using a simple and efficient method. This method helped in the development of a 3D fungal hyphae-silver nanoparticle (FH-AgNPs) composite, and this composite was characterized using scanning electron microscopy (SEM), elemental analysis (EDAX), and the X-ray diffraction technique. Additionally, to highlight the application of the synthesized composite, degradation of methylene blue under visible light using the composite as catalyst was carried out. Further, the antibacterial study of the composite was carried out against the bacterium _Escherichia coli_ and _Staphylococcus aureus_. Biogenic AgNPs were prepared economically using a plant extract rich in secondary metabolites that facilitates the stable synthesis. A colloidal suspension of AgNPs was used to synthesize FH-AgNPs. The hybrid stable structure of FH-AgNPs was produced due to the accumulation of NPs on the surface of fungal hyphae.