Colorimetric sensors have a number of advantages, including easy fabrication, rapid quantification, great
sensitivity and selectivity, and naked-eye detection. Using Fe3O4 nanoparticles, we present a simple and effective
nano-sensor array for colorimetric detection of arginine and ascorbic acid. When utilized in biodetection,
however, changes in the chemical or biological surroundings can quickly affect the stability of Fe3O4 NPs. The
surfaces of Fe3O4 nanoparticles were changed with SiO2 and AgNPs(Fe3O4@SiO2@Ag). The toxicity of silver
nanoparticles has also been decreased utilizing green synthesis. A TEM image showed that the AgNPs are cube
shaped with an average size ranging from 10 to 15 nm. The dynamic ranges were linear in the ranges of 30–100
μM and 30–60 μM for ascorbic acid and arginine, respectively. Also, detection limits of 10.37 μM and 2.56 μM
obtained for AA and Arg, respectively. The proposed colorimetric sensor was successfully used to determine
analytes in the urine and serum samples.