An affordable label free immunosensor based on activated carbon synthesized from waste palm kernel shell with the aid of ball milling technology for HSA detection

The generation of activated carbon (AC) from palm kernel shells (PKS), a by-product of the palm oil industry, can be achieved through various processes, including pyrolysis and activation (KOH wet method). The particle size of waste PKS (wPKS) was controlled through ball milling to maximize the surface area of AC-wPKS. The smallest particle size, 189 nm, was achieved after ball milling for 24 h. The electrochemical and morphological properties of AC-wPKS were thoroughly investigated using a combination of cyclic voltammetry, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, Brunauer-Emmett-Teller (BET) analysis, and field emission transmission electron microscopy (FETEM). Oxygen-containing functional groups on AC-wPKS were linked with methylene blue (MB) to develop a label-free immunosensor (antibody-antigen interaction) for human serum albumin (HSA) detection. The analytical performance of the immunosensor, including linearity, reproducibility, storage stability, and selectivity, was examined using differential pulse voltammetry (DPV). The AC-wPKS:MB-modified screen-printed carbon electrode successfully detected HSA in blood serum samples with acceptable recovery rates ranging from 84 ± 1 to 101.2 ± 0.4 %. This study highlights the potential of waste from palm oil production as a sustainable source of graphite-like material, offering not only a novel approach for electrochemical sensing but also an effective waste management strategy.