Characterization of paper-based substrates in electrochemiluminescence

Electrochemiluminescence (ECL) is a powerful light-emitting technique offering exceptional sensitivity and ultra-low background, critical for precise detection. Its seamless integration with paper-based platforms further enhances portability and cost-efficiency, expanding its applicability across biomedical, environmental, and point-of-care (POC) fields. This study aims to bridge the gap between these two disciplines by exploring the use of paper substrates for the development of low-cost, ready-to-use electrochemiluminescent sensors. Here two types of paper, namely office paper and filter paper, were evaluated and compared to conventional and widely used polyester-based screen-printed electrodes (SPEs). The main goal was to assess their electrochemical behavior, analytical performance, reproducibility and potential for long-term reagent storage. A key innovation of this work is the immobilization of tripropylamine (TPA), the well-known co-reactant for Ru(bpy)₃²⁺ in the classic ECL system, directly onto the electrode surface using a simple drop-casting and drying method. This strategy eliminates the need for manual reagent addition during analysis, simplifies sensor use, and enhances storage stability. Electrochemical characterization confirmed that office paper offers a favorable balance of conductivity and structure, while filter paper's high porosity limited performance. Analytical characterization experiments showed strong linearity for both substrates, with office paper displaying superior signal stability and reproducibility. Overall, this study demonstrates the potential of paper substrates, especially commercial office paper, as sustainable, cost-effective platforms for ECL sensing. The integration of reagent storage, ease of use, and reliable performance highlights their applicability for portable and accessible diagnostics, particularly in resource-limited environments.