MWCNT-Au/Pt-modified screen-printed electrode for electrochemical detection of secondary metabolites in Ganoderma-infected oil palms

Abstract

Ganoderma boninense infection affects nearly half of Indonesia's palm oil plantations, which leads to severe economic losses. Conventional detection methods like PCR are limited by cost and complexity, while electrochemical detection offers a promising alternative by targeting plant-derived metabolites. This study focuses on developing a low-cost, custom fabricated screen-printed electrode (SPE) modified with MWCNTs and Au/Pt nanoparticles to enable practical, scalable early detection of G. boninense in oil palm plantations using various electrochemical techniques. The SPE was fabricated using conductive carbon ink on sticker paper and modified with MWCNT-Au/Pt nanocomposites to enhance performance. Pt nanoparticles (2.5, 5, and 10 mM) were synthesized hydrothermally, while Au (5 mM) was prepared via citrate reduction. The nanocomposites were formed by sonication and applied via drop-casting. Characterization was performed using UV-vis, FTIR, XPS, SEM, contact angle, four-point probe, CV, and EIS. Electrochemical detection of phytol, quinoline, and stigmasterol was conducted using DPV and chronoamperometry in phosphate buffer saline. The results indicate that surface modification enhances conductivity and hydrophilicity, improving the charge transfer process in electrochemical detection. The best combination for SPE modification was the 3 : 1 ratio and 5 mM Pt concentration. The best detection results using DPV were achieved for phytol, quinoline, and stigmasterol, with respective R² and LOD of 0.98 and 2.85 mM, 0.95 and 2.36 µM, and 0.98 and 1.36 µM. Repeated testing on the SPE demonstrated good stability, despite being designed as a disposable test kit. Further, the SPEs demonstrate low detection limits and high sensitivity, highlighting their potential for early diagnosis and rapid screening of Ganoderma-infected oil palm trees as an accessible alternative for disease prevention.