The goal of this experiment was to use citrate stabilized gold nanoparticles as color indicators for the existence of melamine in unknown solutions of milk, then use UV/Vis spectra to quantify the results. The purpose of this lab was met successfully. The color change of gold nanoparticle solution was an effective method to predict the presence of melamine. For instance, when 1 ml of AuNPs was added to 1 mL of 50 ppm melamine solution in sample C1, the color changed from wine red to light purple, which indicates that aggregation of the nanoparticles took place. Due to the presence of three amine groups in each melamine molecule, three Au nanoparticles are joined together forming a larger crystal. Thus, this aggregation happened due to the existence
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The R2 value is equal to 0.8356, and this indicates a very strong correlation between the concentration of melamine and the absorbance ratio. Hence, melamine indeed causes Au nanoparticles to aggregate and causes their Plasmon peaks to shift and the absorbance ratio to change consequently. Plasmon peaks shift to longer wavelengths indicate the nanoparticles are larger in size. This shift can be seen from the trend in absorbance in table 3; the absorbance at 520 nm decreases with the increase of melamine concentration, while it increases at 640 nm with the increase of melamine concentration. For instance, the absorbance at 520 nm for 0 ppm concertation in sample C5 is 0.57, while it is 0.38 in sample C4 with 200 ppm. Also, the absorbance is 0 at 640 nm for sample C5, but it increases to 0.43 in sample C4 at the same wavelength. This proves that the peaks have shifted from shorter to the longer wavelengths (~600 nm) as melamine concentration was increase, and that is due to an increased aggregation phenomena. Hence, the absorption ratio (640/520 nm) increased as the concentration of melamine was increased, indicating a larger absorption at the longer wavelength due to the shift in the Plasmon peaks of the gold …show more content…
Using the obtained linear relationship from graph 1, it was concluded that the unknown concentration of melamine in sample A is 41.70 ppm, and 17.17 ppm in sample B. Therefore, milk A had much higher concentration of melamine than milk B (about two times and a half higher in concentration. Another indicator of the presence of melamine in the milk samples was the color change from wine red to pale red/pink when AuNPs were added (Table 1). Pink crystals are larger than red crystals, and that indicates that aggregation of gold nanoparticles had taken place due to the presence of melamine as explained before. The concentration of melamine in both milk samples falls between 0 ppm and 50 ppm, which is the first standard prepared, with milk sample A having a higher melamine concentration than B. However, the FDA standards only allows 1 ppm concentration of melamine in milk and dairy products, so both milk samples do not comply with the limits and regulation of FDA. This has serious health effects for people, especially children, who consume these types of milk products, due to their accumulation in the body that lead to several kidney and bladder
The R2 value is equal to 0.8356, and this indicates a very strong correlation between the concentration of melamine and the absorbance ratio. Hence, melamine indeed causes Au nanoparticles to aggregate and causes their Plasmon peaks to shift and the absorbance ratio to change consequently. Plasmon peaks shift to longer wavelengths indicate the nanoparticles are larger in size. This shift can be seen from the trend in absorbance in table 3; the absorbance at 520 nm decreases with the increase of melamine concentration, while it increases at 640 nm with the increase of melamine concentration. For instance, the absorbance at 520 nm for 0 ppm concertation in sample C5 is 0.57, while it is 0.38 in sample C4 with 200 ppm. Also, the absorbance is 0 at 640 nm for sample C5, but it increases to 0.43 in sample C4 at the same wavelength. This proves that the peaks have shifted from shorter to the longer wavelengths (~600 nm) as melamine concentration was increase, and that is due to an increased aggregation phenomena. Hence, the absorption ratio (640/520 nm) increased as the concentration of melamine was increased, indicating a larger absorption at the longer wavelength due to the shift in the Plasmon peaks of the gold …show more content…
Using the obtained linear relationship from graph 1, it was concluded that the unknown concentration of melamine in sample A is 41.70 ppm, and 17.17 ppm in sample B. Therefore, milk A had much higher concentration of melamine than milk B (about two times and a half higher in concentration. Another indicator of the presence of melamine in the milk samples was the color change from wine red to pale red/pink when AuNPs were added (Table 1). Pink crystals are larger than red crystals, and that indicates that aggregation of gold nanoparticles had taken place due to the presence of melamine as explained before. The concentration of melamine in both milk samples falls between 0 ppm and 50 ppm, which is the first standard prepared, with milk sample A having a higher melamine concentration than B. However, the FDA standards only allows 1 ppm concentration of melamine in milk and dairy products, so both milk samples do not comply with the limits and regulation of FDA. This has serious health effects for people, especially children, who consume these types of milk products, due to their accumulation in the body that lead to several kidney and bladder