Biosynthesis Of Silver Nanoparticles By Sundried Aleurites Moluccana Leaf And Yeast Pichia Pastoris

Because the properties of silver nanoparticles depend so closely on their size,size distribution and morphology,controlling the size and shape of silver nanoparticles is of great interest to researchers today.In this study,we focus on the control of size of silver nanoparticles biologically synthesized using aleurites moluccana leaf broth and pichia pastoris,as reducing agents.The effect of reaction temperature,rotate rate,the ratio between biomass concentration to silver ions,and pH on the synthesis process of silver nanoparticles was investigated.The formation of nanoparticles was understood and monitored by UV-Vis spectrometer,transmission electron microscopy(TEM),scanning electron microscopy(SEM),and Fourier transform infrared spectrometer(FTIR).Using A.moluccana leaf broth as reducing agent,when the reaction temperature was fixed at 80℃,the mean particle diameter was 31.1 nm,increase in reaction temperature to 100℃,led to reduction of the mean particle diameter to 13.2 nm.Increasing the rotate rate led to steady reduction in absorbance and a blue shift in the absorbance peak,there was reduction in particle size from 26.3 nm to 25.5 nm with increase in rotate rate from 10 rpm to 30 rpm respectively. While increasing biomass concentration led to increase in absorbance and a blue shift in the position of the spectrum suggesting reduction in particle size.In addition,pH was found to have a great impact on the size of silver nanoparticle.When pH of the biomass solution was increased from 5 to 9 to 12,this led to a reduction in particle size from 11.9 nm to 11.3 nm and to 8.7 nm respectively.Using P.pastoris biomass as reducing agent,silver nitrate and silver amine were used in separate experiments as sources of silver ions.A comparison was made between these two sources of silver ions under similar reaction conditions,when silver amine was used the bioreduction was much faster and the absorbance peak was higher compared to silver nitrate. When silver amine was source of silver ions,in acidic condition at pH 4 and below there was no bioreduction and increase in pH led to reduction in particle size.When silver nitrate was used as source of silver ions,there was also no bioreduction in acidic conditions at pH 4 and below. Increase in pH led to steady increase in absorbance and a blue shift in the position of absorbance peak from 423 nm at pH 5 to 418 nm at pH 12.Increasing the rotate rate and temperature led to a steady increase in the absorbance and there was no shift in position of the absorbance peak. Increasing biomass concentration led to increase in particle size from 11.98 nm to 12.97 nm. Increasing the ratio of silver ions to biomass led to increase in absorbance and broadening of peak hence suggesting aggregation of nanoparticles in solution.