Transformation of Fungal Mycelium into Novel Ultrananocrystalline Diamond Nanostructures via Microwave Plasma Pyrolysis

Fungal mycelium has gained increasing interest as an environmentally sustainable potential replacement for a wide range of materials commonly used today in various technologies, including nano-porous scaffolds for biological cell cultivation, wound dressings and medical bandages, biosensors, substitute leather, and construction/insulation materials. The conversion of mycelium and its constituent chitin biomolecular components into carbon-based materials has been demonstrated previously using a Microwave Assisted Pyrolysis (MAP) process, which utilizes microwave (MW) energy to heat the polar water molecules contained in biomass in a controlled environment either directly or via the addition of microwave absorbers, to produce useful carbon allotropes like biochar or activated carbon.<br/>This abstract describes recent research performed by our group to develop a more rapid, efficient, and low-cost improvement to the MAP process, utilizing a plasma-reactor integrated into a commonly available kitchen microwave oven. In this novel Microwave Plasma Pyrolysis (MPP) process, the microwave energy is delivered to a low pressure (&lt;10 Torr) gaseous environment of Ar gas, pumped into a sealed quartz pyrolysis tube mounted inside the microwave oven, containing minimal residual atmospheric N₂ and O₂. When activated the MW power is coupled to the gas and induces the formation of a plasma containing ions (Ar⁺, N⁺, O⁺), neutral atoms (Ar⁰, N⁰, O⁰), and free electrons which act upon the mycelium biomass and induce physical and chemical transformations. The data to be presented reveals that the MPP process converts the mycelium into a “myco-diamond” system containing ultra-nanocrystalline diamond (UNCD) (3-5 nm grain size) in a carbon matrix with macro, micro, and nanoscale features derived from the original specimen. The UNCD structures produced by the MPP process are chemically similar to UNCD coatings previously developed by Auciello’ s group using Microwave Plasma Chemical Vapor Deposition (MPCVD) and Hot Filament Chemical Vapor Deposition (HFCVD) methods. Verification of the MPP-induced transformation of mycelium into UNCD is confirmed via complementary materials analysis techniques including Raman spectroscopy, High Resolution Transmission Electron Microscopy (HRTEM) and X-Ray Diffraction (XRD), yielding data comparable to previously characterized UNCD coatings. Analysis of the myco-diamond surface morphology was performed via Scanning Electron Microscopy (SEM). The MPP process presents a sustainable, scalable and cost-effective method of producing UNCD and carbon-based nanomaterials from readily available or otherwise discarded biomass.