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Biosynthesis of Silver Nanoparticles by Sundried Aleurites Moluccana Leaf and Yeast Pichia Pastoris

Author: Egesa Dan
Tutor: Li Qingbiao
School: Xiamen University
Course: Chemical Engineering
Keywords: Biosynthesis Nanoparticles Silver Candlenut Pichia pastoris
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 35
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Abstract


Due to the nature of the nano-silver and its particle size, particle size distribution and morphology are closely related, and how to control the particle size and morphology of the nano-silver has aroused extensive attention of researchers. This study selected two types of biomass - Stone chestnut leaves and Pichia yeast powder as a reducing agent to prepare the nano-silver, reaction time, temperature, stirring speed, biomass / silver ion ratio and the pH conditions of nano the influence of the particle size and morphology of the silver and UV - visible spectrophotometer (UV-Vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) analysis method to characterize the formation of nano-silver. Candlenut leaves as a reducing agent, the average particle size of the nanocrystalline silver in the 80 ° C is about 31.1nm, when the temperature rises to 100 ° C, the average particle size decreases the synthesis of nano-silver for 13.2nm. Increasing the stirring speed such that the UV - visible absorption peak position occurred blue shift, the peak intensity of the nano silver, when the stirring speed is increased from 10rpm to 30nm, there is a slight decrease in the average particle diameter of the obtained nano-silver (26.3 nm → 25.5nm). Increasing the concentration of stone chestnut leaf will make UV - visible absorption peak of the peak intensity, peak position blue shift, indicating that the obtained nano silver particle size gradually decreased with increasing stone chestnut leaf concentration small. In addition, we found that the pH values ??for the particle size of the nano-silver also has a great influence when the pH of the solution is gradually increased when the (→ 9 → 12), the particle size of the obtained nano-silver is gradually reduced (11.9nm → 11.3nm → 8.7nm). The Pichia yeast powder as a reductant, the present study selected as a silver precursor of silver nitrate and silver ammonia, compare the difference between the two, the study found that using silver ammonia as the precursor, the reduction rate than with the silver nitrate when the fast. Using silver nitrate as a precursor, when pH ≤ 4, the solution does not generate nano silver; When pH gt; 4, with the increase of the pH value, the obtained nano-particle size gradually decreases. The silver ammonia as a precursor, pH ≤ 4, the solution in the same nano-silver generation, with the increase of pH value (5 → 12), nano silver UV - visible absorption peak gradually blue shift (423nm → 418nm ), indicating that the particle diameter of the silver nano gradually decreases. With the stirring speed is increased and the temperature increased, the silver nano UV - visible absorption peak intensity is gradually increased, but the peak position is not changed, indicating little influence of the stirring rate and temperature on the particle size of the silver nano. The silver ion concentration constant, the obtained average particle diameter of the Ag nanoparticles slightly increases with increasing amount of powder Pichia (11.98nm → 12.97nm). Biomass concentration, increasing the concentration of silver nitrate, the obtained nano silver UV - visible absorption peak intensity increases significantly wider FWHM solution nano silver reunion.

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