Fig. 1. (a) Preparation process of hydrogel dosimeter; (b) dose-response principle of hydrogel dosimeter; (c) the linear relationship between absorbed dose and absorbance of hydrogel dosimeter with different degrees of modification was fitted (sodium nitrate 0.5 mol/L,sodium formate 2.5×10^-3 mol/L,dose rate 1.4 Gy/min); (d) SEM image of hydrogel dosimeter with 64% acrylic acid content (color online)

Fig. 2. Digital images of the color change of hydrogel dosimeter with different concentrations of sodium nitrate at different doses (color online)

Fig. 3. (a-e) UV spectra of dosimeters with different sodium nitrate concentrations (0.1 mol/L,0.3 mol/L,0.5 mol/L,0.7 mol/L,and 1 mol/L) at 0-42 Gy (sodium formate 5×10^-3 mol/L,acrylic acid content 53%,dose rate 1.4 Gy/min); the effect of sodium nitrate concentration on (f) linear relationship,(g) absorbance,and (h) slope (color online)

Fig. 4. Digital images of color changes of nitrate-based composite hydrogel dosimeters with different concentrations of sodium formate at different doses (color online)

Fig. 5. (a-e) UV spectra of dosimeters with different sodium formate concentrations (0 mol/L,1×10^-3 mol/L,2.5×10^-3 mol/L,5×10^-3 mol/L,5×10^-2 mol/L) at 0-42 Gy (sodium nitrate 0.5×10^-3 mol/L,acrylic acid content 53%,dose rate 1.4 Gy/min); the effect of sodium formate concentration on (f) linear relationship,(g) absorbance,and (h) slope (color online)

Fig. 6. (a) Puncture experiment of hydrogel dosimeter (needle diameter 1mm); (b) effect of different acrylic acid content on Young's modulus; (c) compressive strength of hydrogel dosimeter with different degrees of modification; (d) time stability of hydrogel dosimeter; (e) dose-response of hydrogel dosimeter at different dose rates (sodium nitrate 0.5×10^-3 mol/L,sodium formate 2.5×10^-3 mol/L,acrylic acid content 53%,dose rates 0.7 Gy/min,1.4 Gy/min,2.1 Gy/min,respectively); (f) application example of hydrogel dosimeter (color online)