Hand-Held Mulberry Paper-Based Colorimetric Sensor for Riboflavin via Novel Solubility-Modulated Prussian Blue Analogues

Solubility-modulated Prussian blue analogues (SM-PBAs) were first created by using colloidal silver nanoparticles as an accelerator in the formation process, which greatly improved their solubility compared to previous methods and broadened their applicability for colorimetric purposes. By precisely tuning the synthesized parameters, we achieved a highly efficient and sustainable method for synthesizing SM-PBAs under eco-friendly conditions. Additionally, we can complete this novel synthesis approach in under a minute. The synthesized SM-PBAs were characterized via UV-vis spectrometry, FESEM, EDS, and XPS analyses to confirm their composition and structure. To demonstrate practical utility, these SM-PBAs were employed as novel mulberry paper-based colorimetric sensors for riboflavin detection. Upon exposure to riboflavin, the sensor undergoes an immediate, visually detectable color change from blue to yellow, driven by a redox reaction. Under optimized conditions, the sensor demonstrates a straight-line calibration from 10 to 600 ppm, with a detection limit (3SD/slope) of 1.36 ppm, quantified using ImageJ software. Validation tests in vegetable and supplement samples confirmed the advantages of the sensor, including high selectivity, precision, and accuracy. This synthesis approach offers a solubility-driven green fabrication route and a versatile alternative for riboflavin detection. Furthermore, the fabrication approach is low-cost, scalable, and compatible with roll-to-roll manufacturing, suggesting strong potential for field-deployable applications.