In Situ Observation of Directed Nanoparticle Aggregation During the Synthesis of Ordered Nanoporous Metal in Soft Templates
- Univ. of California, Davis, CA (United States)
- Sandia National Lab. (SNL-CA), Livermore, CA (United States)
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Univ. of California, Davis, CA (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
The prevalent approach to developing new nanomaterials is a trial-and-error process of iteratively altering synthesis procedures and then characterizing the resulting nanostructures. This is fundamentally limited in that the growth processes that occur during synthesis can be inferred only from the final synthetic structure. Directly observing real-time nanomaterial growth provides unprecedented insight into the relationship between synthesis conditions and product evolution and facilitates a mechanistic approach to nanomaterial development. Here, we use in situ liquid-stage scanning transmission electron microscopy to observe the growth of mesoporous palladium in a solvated block copolymer (BCP) template under various synthesis conditions, and we ultimately determined a refined synthesis procedure that yields extended structures with ordered pores. We found that after sufficient drying time of the casting solvent (tetrahydrofuran, THF), the BCP assembles into a rigid, cylindrical micelle array with a high degree of short-range order but poor long-range order. Upon slowing the THF evaporation rate using a solvent-vapor anneal step, the long-range order was greatly improved. The electron beam induces nucleation of small particles in the aqueous phase around the micelles. The small particles then flocculate and grow into denser structures that surround, but do not overgrow, the micelles, forming an ordered mesoporous structure. The microscope observations revealed that pore disorder can be addressed prior to metal reduction and is not invariably induced by the Pd growth process itself, allowing for more rapid optimization of the synthetic method.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1158478
- Report Number(s):
- PNNL-SA-102164; 47296
- Journal Information:
- Chemistry of Materials, Vol. 26, Issue 3; ISSN 0897-4756
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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