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In this study, the changes in the amylose content, crystalline structure, Fourier transform infrared (FTIR) properties, pasting properties, and rheological properties of potato starch were explored after radio frequency (RF) treatment at different polar plate spacings (90, 100, 110, 120, and 130 mm). The appropriate RF parameters for 3D printing of potato starch gels were determined. The results revealed that under low plate spacing, the content of amylose decreased and the crystalline form of starch transformed from B-type to C-type. We found that the starch gel with RF treatment at a plate spacing of 90 mm had the best morphology in terms of transparent line uniformity and high retention rate. To sum up, we can conclude that RF treatment at low polar plate spacings is an effective method for preparing 3D printed starch gels.

Accurate water content detection is crucial for optimizing chemical reactions, ensuring product quality in pharmaceutical manufacturing, and maintaining food safety. In this study, nitrogen and sulfur co-doped graphene quantum dots (R-GQDs) were synthesized via a one-step hydrothermal method using o-phenylenediamine as the carbon source. The synthesis conditions, including reaction time, temperature, o-phenylenediamine concentration, and H2SO4/water ratio, were optimized using the Box-Behnken response surface methodology. The R-GQDs exhibited excellent fluorescence stability and distinct solvent-dependent characteristics, alongside a broad linear detection range and high sensitivity, making them highly suitable for dual-mode water content detection (colorimetric and fluorescent). To enhance the accuracy of visual detection, R-GQDs were incorporated into portable test strips with smartphone-assisted analysis, compensating for the human eye's limitations in distinguishing subtle color changes. The sensor's practical utility was validated through spiked recovery experiments in food samples, and the R-GQDs demonstrated good biocompatibility for in vivo imaging in shrimp. These findings highlight a novel strategy for developing portable, real-time water content sensors with potential applications in both portable detection systems and biological imaging. [ABSTRACT FROM AUTHOR]