User:Sanuja Mohanaraj/Notebook/Experimental Biochemistry 1 Fall 2017/2017/09/05

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NaOH Stock Solution Preparation First, ~0.5mL of the 1M NaOH was added into a 100mL volumetric flask. Next, deionized water was added into the flask to the mark, achieving a final concentration of 5mM. The volumetric flask was then sealed using parafilm, and stored. Au Nanoparticles Solutions Preparation Because the previous solutions did not form any nanoparticles, each solution was remade using different molar ratios, over a different pH range. This time, both the 1M NaOH and 5mM NaOH were also added into each test tube as follows: Au : AA : 5mM NaOH (1) 1 : 1 : 0.5 (2) 1 : 1 : 1 Au : AA : 1M NaOH (3) 1 : 1 : 0.1 (4) 1 : 1 : 1 A total of twelve solutions with varying molar ratios were made, before placing all the prepared solutions into the oven. Calculations 5mM NaOH Solution M1V1=M2V2 (1M NaOH)(V1)=(5mM NaOH)(100mL) V1 = 0.5mL of 1M NaOH NaOH Stock Solution (Titration) [(0.02L Phenylalanine)(0.00025M Phenylalanine)(1M NaOH)] / (0.02L NaOH) = 0.00025M NaOH M1V1=M2V2 (1M NaOH)V1=(0.00025M NaOH)(0.5L NaOH) V1=0.125mL of 1M NaOH added to 500mL volumetric flask Results Figure 3a Figure 3b Figure 3c Figure 3 displays the formation of AuNPs (colloid) from Au:AA:NaOH solutions with varying molar ratios over a pH range of 7-14; whereas, Table 1 describes the molar ratios of Au:AA:NaOH that were used to form the AuNP colloids, in addition to the theoretical pH values of each solution. The three different amino acids used to make the solutions are arginine (Figure 3a), phenylalanine (Figure 3b) and isoleucine (Figure 3c). Test tube 3 of the Au:AA:NaOH solutions with the molar ratio of 1:1:0.1 of each of the three different amino acids, are the solutions that formed AuNPs of the highest concentration. Figure 4a Figure 4b Figure 4c Following that, the absorbance spectra of the Au:AA:NaOH solutions of Test tube 3 of each of the three amino acids are illustrated in Figure 4. The absorbance peaks of the Au:Arg:NaOH solution, the Au:Phen:NaOH solution and the Au:Iso:NaOH solution, are measured at wavelengths of ~450nm, ~350nm and ~550nm, respectively. NaOH Stock Solution Preparation (Titration) To begin preparing the 0.25mM NaOH stock solution, 0.125mL of the 1M NaOH solution was transferred into a 500mL volumetric flask. The flask was then filled with deionized water to the mark, achieving a final concentration of 0.25mM. The flask was then sealed using parafilm and stored. Titrant Standardization After obtaining a clean buret, the buret was rinsed twice with ~10mL of the 0.25mM NaOH solution. The buret was then filled completely with the 0.25mM NaOH solution, and the initial volume was recorded. Next, ~0.5g of KHPhth was added to an Erlenmeyer flask before filling the flask with ~25mL of deionized water, followed by a few drops of phenolphthalein indicator. The solution was then titrated until there was a color change (pink). The standardization was repeated twice more, and the end volumes are recorded each time. The results are as follow: Trial 1 Initial Volume: 42mL End Volume: 13mL Trial 2 Initial Volume: 50mL End Volume: 10.5mL