The development of intelligent packaging plays a crucial role in determining the spoilage of various foods through highly sensitive, selectable, and fast methods that are irreversible and don't require special tools. The aim of this research was to make colorimetric indicators for use in intelligent packaging by using nanoparticles to determine fish spoilage and banana fruit ripening. First, a colloidal solution of copper and aluminum nanoparticles complex with nitrogen-doped quantum dots was made using the hydrothermal method. Iron nanoparticles were also made using the chemical reduction method. The chemical properties of the solutions were studied when they were exposed to hydrogen sulfide gas from fish spoilage and ethylene gas from bananas ripening. Based on the results obtained, hydrogen sulfide and ethylene gas had the ability to aggregate nanoparticles and precipitate them, change the refractive index and dielectric coefficient, and subsequently change the local surface plasmon resonance spectrum and quench fluorescence. In the second step, the nanoparticle solutions were stabilized on an agar film substrate to make a colorimetric indicator containing nanoparticles. Various physical and chemical properties were investigated. Some of the most important results obtained included resistance to pH changes, migration, eva‎luation of color changes of indicators at different concentrations of hydrogen sulfide and ethylene gas, as well as the selectivity of the indicator containing nanoparticles towards hydrogen sulfide and ethylene gas, and finally the selectivity of these two gases in the presence of other interfering gases. The results of the study showed that the indicator films containing nanoparticles were resistant to pH changes, which provides their use in various types of food. The study of the migration of nanoparticles from the agar bed in two aqueous and oily environments showed that the migration rate was significantly lower in the aqueous environment than in the oily environment. The effect of different concentrations of hydrogen sulfide and ethylene gas on the color change of the indicators was significant, but the response rate of indicators containing different nanoparticles towards these two gases was different. Also, the indicator-containing nanoparticles were able to respond to and identify only hydrogen sulfide gas and ethylene gas among the possible gases resulting from fish spoilage and banana ripening. In the next stage, the color changes of the nanoparticle-containing indicator against fish spoilage at refrigerator temperatures and banana ripening at ambient and refrigerator temperatures were eva‎luated. Finally, Fourier transform infrared spectrum and X-ray photoelectron spectroscopy were eva‎luated. In hydrogen sulfide gas, nanoparticles formed bonds with sulfide groups. In ethylene gas, they formed bonds with carbon and hydrogen. In the last stage, the physical and chemical properties of fish and bananas were examined due to storage. The results of the changes in the physicochemical properties of fish and bananas during storage were consistent with the results of the color change of the indicators containing nanoparticles. Therefore, the designed nanoparticle colorimetric indicators effectively identified the degree of spoilage and ripeness of fish and bananas, achieving the desired color change .

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مهدي كديور , عليرضا علافچيان , هادي الماسي