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Title: Direct in Situ Determination of the Mechanisms Controlling Nanoparticle Nucleation and Growth

Abstract

Although nanocrystal morphology is controllable using conventional colloidal synthesis, multiple characterization techniques are typically needed to determine key properties like the nucleation rate, induction time, growth rate, and the resulting morphology. Recently, researchers have demonstrated growth of nanocrystals by in situ electron beam reduction, offering direct observations of single nanocrystals and eliminating the need for multiple characterization techniques; however, they found nanocrystal morphologies consistent with two different growth mechanisms for the same electron beam parameters. Here we show that the electron beam current plays a role analogous to the concentration of reducing agent in conventional synthesis, by controlling the growth mechanism and final morphology of silver nanocrystals grown via in situ electron beam reduction. We demonstrate that low beam currents encourage reaction limited growth that yield nanocrystals with faceted structures, while higher beam currents encourage diffusion limited growth that yield spherical nanocrystals. By isolating these two growth regimes, we demonstrate a new level of control over nanocrystal morphology, regulated by the fundamental growth mechanism. We find that the induction threshold dose for nucleation is independent of the beam current used for imaging, but is a function of the interaction volume size. Our results indicate that in situ electron microscopy datamore » can be interpreted by classical models, by allowing simultaneous measurement of nucleation induction times, growth rates, and evolution of nanocrystal morphology. The results suggest that systematic dose experiments should be performed for all future in situ liquid studies to confirm the exact mechanisms underlying observations of nucleation and growth.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1054470
Report Number(s):
PNNL-SA-87715
47296
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
ACS Nano, 6(10):8599–8610
Additional Journal Information:
Journal Name: ACS Nano, 6(10):8599–8610
Country of Publication:
United States
Language:
English
Subject:
In situ fluid; STEM; nanoparticle growth; silver nanoparticles; in situ electron microscopy; Classical nucleation theory; Environmental Molecular Sciences Laboratory

Citation Formats

Woehl, Taylor J., Evans, James E., Arslan, Ilke, Ristenpart, William D., and Browning, Nigel D. Direct in Situ Determination of the Mechanisms Controlling Nanoparticle Nucleation and Growth. United States: N. p., 2012. Web. doi:10.1021/nn303371y.
Woehl, Taylor J., Evans, James E., Arslan, Ilke, Ristenpart, William D., & Browning, Nigel D. Direct in Situ Determination of the Mechanisms Controlling Nanoparticle Nucleation and Growth. United States. doi:10.1021/nn303371y.
Woehl, Taylor J., Evans, James E., Arslan, Ilke, Ristenpart, William D., and Browning, Nigel D. Tue . "Direct in Situ Determination of the Mechanisms Controlling Nanoparticle Nucleation and Growth". United States. doi:10.1021/nn303371y.
@article{osti_1054470,
title = {Direct in Situ Determination of the Mechanisms Controlling Nanoparticle Nucleation and Growth},
author = {Woehl, Taylor J. and Evans, James E. and Arslan, Ilke and Ristenpart, William D. and Browning, Nigel D.},
abstractNote = {Although nanocrystal morphology is controllable using conventional colloidal synthesis, multiple characterization techniques are typically needed to determine key properties like the nucleation rate, induction time, growth rate, and the resulting morphology. Recently, researchers have demonstrated growth of nanocrystals by in situ electron beam reduction, offering direct observations of single nanocrystals and eliminating the need for multiple characterization techniques; however, they found nanocrystal morphologies consistent with two different growth mechanisms for the same electron beam parameters. Here we show that the electron beam current plays a role analogous to the concentration of reducing agent in conventional synthesis, by controlling the growth mechanism and final morphology of silver nanocrystals grown via in situ electron beam reduction. We demonstrate that low beam currents encourage reaction limited growth that yield nanocrystals with faceted structures, while higher beam currents encourage diffusion limited growth that yield spherical nanocrystals. By isolating these two growth regimes, we demonstrate a new level of control over nanocrystal morphology, regulated by the fundamental growth mechanism. We find that the induction threshold dose for nucleation is independent of the beam current used for imaging, but is a function of the interaction volume size. Our results indicate that in situ electron microscopy data can be interpreted by classical models, by allowing simultaneous measurement of nucleation induction times, growth rates, and evolution of nanocrystal morphology. The results suggest that systematic dose experiments should be performed for all future in situ liquid studies to confirm the exact mechanisms underlying observations of nucleation and growth.},
doi = {10.1021/nn303371y},
journal = {ACS Nano, 6(10):8599–8610},
number = ,
volume = ,
place = {United States},
year = {2012},
month = {10}
}