چكيده به لاتين
A novel method has recently emerged in the field of graphene synthesis through direct laser engraving on a polymer substrate (LIG). Unlike previous methods, it is highly economical and scalable, making it suitable for converting both natural and synthetic polymers into graphene. In this thesis, an electrochemical sensor based on LIG for measuring tyrosine and uric acid on a paper substrate was developed. Initially, a graphene structure was formed on a cellulose substrate using a CO2 laser, resulting in a flexible biosensor element. Electrochemical tests, including differential pulse voltammetry and cyclic voltammetry, were conducted to assess its electrochemical behavior, ability to measure tyrosine and uric acid, selectivity, and reproducibility. The results showed that the electron transfer constant of this sensor is with sensitivity and detection limits for uric acid measurement and for tyrosine, Compared to existing paper LIG sensors in the literature, it performs better, and in some features, it is superior or equal to similar sensors on artificial substrates like polyimide.
Additionally, in this thesis, molecular dynamics simulations of LIG formation from cellulose and lignin, abundant biopolymers in nature, were conducted using LAMMPS software and ReaxFF potential. The simulation results were compared with experimental results and showed good agreement. The presence of 5-membered and 6-membered rings in the LIG structure obtained from molecular dynamics simulations, as well as the formation of a hierarchical and porous graphene foam structure, were confirmed by characterization tests including SEM, FT-IR and Raman spectroscopy. Furthermore, the properties and features of LIG obtained from molecular dynamics simulations were studied. The thermal properties of LIG on cellulose and lignin substrates, such as heat transfer coefficient and vibrational density of states (VDOS), were examined using two atomic potentials, Airebo and optimized Tersoff (opt-Tersoff), as well as its diffusion properties like diffusion coefficient (D) and mean square displacement (MSD) using ReaxFF potential at different temperatures and dimensions.
