# Fungi-Templated Silver Nanoparticle Composite: Synthesis, Characterization, and Its Applications
## 1 Introduction  
The designing and fabrication of bio-templates of microbial origin open up a wide range of applications in nanotechnology, due to the generation of highly functionalized nano/microstructures providing high surface areas [1]. The synthesis of nanomaterials having tuneable and well-defined structures is one of the most promising breakthroughs in this field and furthermore the most challenging part [2]. Therefore, the method of bio-templating offers various advantages in controlling the geometries of nano/microstructures, making an overall increase in the efficiency of the synthesized material [3]. Moreover, bio-templating being a bottom-up method for the generation of nanomaterials aids a low-cost synthesis of these materials, having a versatile and well-defined structure [4]. In the process of bio-templating, a material of choice (e.g., metal nanoparticles) can be deposited on the microbial surface using simple techniques and the nano/microstructures can be obtained in the shape of the template [5]. After the deposition, the template can be partially or completely removed using incineration and thereby engendering the free nano/microstructure [6]. These synthesized micro/nanostructures can be used with or without the microbial association for various applications such as catalysis, chemicaldegradation, sensing, and in medical applications [7; 8]. Since these assemblies are from nature, they always perform exceptionally great when compared to all other assemblies devoid of any biological framework [5; 7; 8; 9]. Furthermore, the binding of metal NPs to the microbial cell wall opens favourable circumstances for the study of the physical and chemical properties of bio-inorganic interfaces [10; 11]. Microorganisms and their structural parts, such as mycelium, hyphae, filament, spores, and flagella, are the most favourable bio-templates due to easy availability, rapid and mass multiplication, simple growth conditions, and a short life cycle [12]. The cell wall of microorganisms contains a wide range of functional groups such as carboxyl, sulphonate, amino, and phosphate groups that help in metal binding and nucleation, thereby forming NPs/microstructures on their surface [13; 14]. Recently, fungal hyphae have been used as bio-templates for the self-organization of noble metal NPs forming metal nano/microstructures [6]. Fungi are generally preferred over other microorganisms because they grow at a very rapid rate and the biomass produced for templating is comparatively large [15]. However, only very few reports are available on organizing metal nanoparticles on fungal hyphae, and therefore, a simple, green, and efficient method should be developed for the same [16]. In most of the earlier reports, the NPs are functionalized before templating, which is again a tedious process. _Sclerotium rofsii_ is a necrotrophic plant pathogen which is known to produce abundant white mycelium on culture. The cells are found to be hyaline, which possess thin cell walls and sparse cross walls. Due to the presence of ample mycelium, _Sclerotium rofsii_ serves as a suitable bio-template for the assembly of metal nanoparticles, thereby generating a microtubule metal nanoparticle composite. The varying structural morphology of the microtubule composite enables the utilization of the same for numerous applications including catalysis, drug storage, and delivery. Silver nanoparticles (AgNPs) are well known for their ability to kill microorganisms. This makes them useful in the production of antimicrobial products, such as clothing, wound dressing, and food packaging. They have also been shown to be effective at killing certain types of bacteria, such as _E. coli_ and _S. aureus_, and viruses, such as the flu virus. In addition to their antimicrobial properties, AgNPs have several other useful properties. They are good conductors of electricity and heat, making them useful in electronic and thermal management applications. They are also highly reflective, making them useful in coating and other optical applications [17].