Paper-based optical nanosensors - A review

Paper-based analytical devices (PADs) have shown great promise for point-of-care testing and on-site detection of analytes with chemical, biochemical, and environmental importance owing to their low cost, convenience, scalability, portability, and biocompatibility. The World Health Organization stated that sensors should meet the ASSURED criteria (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliver-able). Paper-based optical sensors meet most of these criteria, making them in high demand and applicable in remote areas. Optical PADs outputs are obtained by different means, such as dyes, nanostructures, redox agents, and pH indicators. The outstanding physical and chemical characteristics of nanostructures, their intense signals, and tunable optical properties make them ideal for many sensing platforms, including paper-based ones. This review focuses primarily on paper-based nanosensors using various nanostructures to fabricate and produce optical signals for visualization. We describe the fundamentals and state of the art of PADs and comprehensively explain the following topics: paper types as the substrate of PADs, PAD fabrication approaches, nanostructure stabilization on PADs, signal acquisition, data handling, interpretation of results, sensing mechanisms, and application areas. We also discuss future trends and strategies to enable PADs to reach their full potential and increase their commercialization opportunities.

Automated summary

Paper-based nanosensors using various nanostructures for optical signal visualization are important components of paper-based analytical devices (PADs). They have the potential for point-of-care testing and on-site detection of analytes with chemical, biochemical, and environmental importance due to their low cost, convenience, scalability, portability, and biocompatibility. This review focuses on the fundamentals, state of the art, and future trends of PADs and discusses topics such as paper types, fabrication approaches, nanostructure stabilization, signal acquisition, data handling, sensing mechanisms, and application areas.