Catalytic reduction of p-nitrophenol As a model reaction, we selected the reduction of 4-NP by NaBH4 to 4-AP. The reduction was followed with the aqueous solution in a standard quartz cell with a 1cm path length. The reaction process was as follows: 1.5 mL of 0.15 mM 4-NP was mixed with 1.0 mL of 0.02 M NaBH4 in the cell for UV-Vis measurements. Immediately, the colour change was observed from light yellow to deep yellow. 0.5 mL of AuNPs solution was added to the above mixture. The UV-Vis spectra were recorded with a time interval of 1 min in a scanning range of 200-600nm at ambient temperature (25±20C). Antimicrobial activity The agar disc diffusion method was employed for the determination of antimicrobial activity of the papaya leaf extract stabilized gold nanoparticles. The 0.1 ml of 108cfu/ml of different pathogenic bacteria suspension was spread on different plates nourished with LB media. Filter paper …show more content…
Figure.3 shows the FTIR spectra of the papaya leaf extract and papaya leaf extract capped AuNPs. The major absorbance bonds present in the spectrum of papaya leaf extract were at 3245, 2862, 1810, 1679, 1491, 1354,1106 and 790 cm-1 respectively. The broad band observed at 3245 cm-1 could be assigned to stretching vibrations of -OH and –NH2 groups in the papaya leaf extract. The peak at 2862 cm−1 is due to asymmetric stretching vibrations of methylene groups. The peak at 1816 cm−1could is assigned to carbonyl stretching vibrations of carboxylic acids. The band found at 1679 cm−1could be assigned to characteristic asymmetrical stretch of carboxylate group. The symmetrical stretch of carboxylate group can be attributed to the bands present at 1491 and 1354 cm−1. The peaks at 1105 and 789 cm−1were due to the C–O stretching vibrations of polyols, ether and alcoholic