3D printed smartphone device with nano-upconversion cellulose paper for soil boron assessment

Agricultural productivity are paramount concerns to ensure food security to ∼ 10 billion by 2050. Ensuring soil health through precise micronutrient monitoring is essential for sustaining global food security.

This study employs NaYF₄: Yb³⁺, Er³⁺ UCNPs that undergoes fluorescence quenching proportionally upon forming boron-curcumin complex. The UCNPs has been characterised using XRD, TEM, and fluorescence, which confirms hexagonal β-NaYF₄ phase, 30 nm size and 540 nm emission, respectively. The formation of boron-curcumin complex has been confirmed with the red shift in the absorbance maxima that match with the UCNPs emission maxima. The platform achieves a detection limit of ∼1 ppm, suitable for agricultural applications. Linear correlation with boron concentration (R² = 0.99), confirms high sensitivity. Interference studies with common soil ions demonstrates the method's selectivity. The method developed have the capacity to measure the boron concentration between 1 and 50 ppm. The fluorescence quantification has been adopted to the smart phone camera imaging by using 3D printed add-on, designed and optimised inhouse.

To our knowledge this is the first smart phone based boron sensor, further it match with the range of soil boron content in diverse agriculture conditions. By integrating the 3D setup with smartphone and nanomaterials cellulose paper imaging, this technology facilitates real-time micronutrient monitoring, supporting precision agriculture. Further the technique is scalable and cost-effective solution for sustainable soil management and industrial adoption.