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��SYNTHESIZES OF SILVER NANOPARTICLES ��

BY : �ELBETHEL HAGOS �SHAHIN AZADIKHAH �ANDY GUAN �JESSE CORREA

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PREVIEW OF OUTLINE

Introduction

APPROACH

Results

Discussion

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INTRODUCTION

  • The main objective of this lab is to synthesize nanoparticles that are relatively monodisperse and to study the characterization of the nanoparticle.
  • Monodispersity of the nanoparticles can be determined by their absorbance spectra
    • Narrower peaks are more monodispersed

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Hypothesis

  • Strong reducing agent such as sodium borohydride may cause the silver nanoparticles to form some larger particles too quickly, making it hard to control the monodispersity and size of the nanoparticles.

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  • It is hypothesized that a weaker reducing agent, such as Thiosulfate, will reduce the silver more slowly in order to improve the accuracy of the size and monodispersity of the silver nanoparticles that are synthesized.

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Sodium Borohydride Vs Sodium Thiosulfate

  • Sodium borohydride is more reactive as a reducing agent than sodium thiosulfate
    • The reduction potential for a hydride is much higher than for thiosulfate

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  • Sodium borohydride carries four hydrides, which means stoichiometrically it has four sources to reduce while Thiosulfate has one

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APPROACH

  • Shahin

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RESULTS: SPECTROSCOPY

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RESULTS: TURBIDITY

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DISCUSSION & CONCLUSION: SEED SYNTHESIS

  • As expected, the seed particle synthesis required more sodium thiosulfate than sodium borohydride to reach the yellow color that indicated the completion of the seed particle synthesis
    • 0.3 mL vs. 3.15 mL
  • This result is likely due to two key factors:
    • Sodium borohydride is more reactive as a reducing agent than sodium thiosulfate
    • Sodium borohydride carries four hydrides, which means stoichiometrically it has four sources to reduce from while thiosulfate has one

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DISCUSSION & CONCLUSION: SPECTRA

  • The sodium thiosulfate did not have a peak for the seed solution
    • Probably not enough seeds were made

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DISCUSSION & CONCLUSION: TURBIDITY

  • The SNPs synthesized with either reagent showed the same turbidity trend
    • The turbidity rises as the size gets larger, then drops drastically for the largest size
  • The turbidity readings for the particles made with thiosulfate are much lower than those made with sodium borohydride

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CONCLUSION

  • In conclusion, sodium thiosulfate did allow for more control over the synthesis of SNPs, but it was not a strong enough reagent to properly synthesize the SNPs
  • Sodium borohydride is much more effective at getting the job done, but creates non-dispersed particles
  • Sodium thiosulfate does make it easier to “control” the synthesis, but only up to a certain point

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Future Directions

  • Try other reducing agents
    • Specifically one with a reduction potential between sodium borohydride and sodium thiosulfate
  • Adjust the concentration of sodium borohydride to account for stoichiometric differences