Yifeng Shi

Metal nanocrystals: Shape, size, compositions, and more

The beautiful transmission electron microscopy (TEM) images are very straightforward and attractive to me when I was a first-year grad school student.   I was told that this is a field that has been set up for almost two decades. Despite the well-developed  protocols , many things still remain mysteries and are waiting for us to explore.     
There is something inside -- Pd-Cu twin cubes/ bipyramids

Have you heard about seed-mediated growth? You can synthesize a small metal nanocrystal as "seed" first, and grow another metal around it. There are so many seed-mediated growth, and here we did a systematic study on growth of copper (Cu) onto a palladium (Pd) nanoplate. We found that the lattice mismatch, capping agent, and number of planar defects in the seeds all play important roles in directing the shape evolution of Cu on the Pd seeds.

check it out here. 
Cleaner surface , better performance--removing surface ligands

Pd cubes are known for their good catalytic activity toward formic acid oxidation. But the ligands adsorbed on the surface (Br-) are not good for the reaction and hard to remove. Here we reported a robust yet simple method to remove the chemisorbed Br- ions to maximize their catalytic activity by giving these nanocubes a "bath" with a little bit of hydrazine. 

check it out here. 
Change from inside out-- hydrazine-induced hydride formation

Continue the story with Pd cube and hydrazine-- here we report a facile method for the transformation of Pd nanocubes into a stable phase made of PdH0.706 by treating them with aqueous hydrazine at different concentrations. The enhanced catalytic performance was confirmed through both experimental and theoretical analysis (thanks to Dr. Roberto Schimmenti, a previous postdoc at Prof. Manos Mavrikaki's group)

check it out here. 
Shape matters--decomposition kinetics of H2O2 on Pd nanocrystals

To people not familiar with this field, one question they ask very often is "why synthesize these nanocrystals in different shapes, do they have real applications?" The answer is yes, and here support-free Pd nanocrystals with different shapes and surface strains are used to elucidate the structure-catalytic property relationship toward H2O2 decomposition. 

check it out here. 

_____________________________________________________________________________________________________________________
I have also co-authored a few review articles introducing different topics in terms of metal nanocrystals, their synthesis and catalytic properties. If you're interested, you can check them out below! 

About one-dimensional metal nanocrystals

About surface capping agent/ligand

About shape-controlled synthesis & catalytic applications of metal nanocrystals

About bi-metallic core-shell nanocrystals

Similar to every other PhD student, I had some projects that did not continue to the very end and didn't ended up as any formal publication, but everything is practice.  Other experience paid me back in different ways other than journal articles, which is pretty cool too :)

Last updated: October 2024