In situ liquid cell electron microscopy of Ag-Au galvanic replacement reactions

Area of Science:

• Materials Science
• Nanotechnology
• Chemistry

Background:

• Galvanic replacement reactions are crucial for creating complex porous and hollow nanostructures from nanoparticle templates.
• These nanostructures possess unique properties valuable for diverse applications.
• Real-time observation of these transformations using liquid cell electron microscopy (LCEM) is hindered by electron beam-induced radiolysis.

Purpose of the Study:

• To investigate the impact of solution pH on galvanic replacement reactions during LCEM observations.
• To overcome the challenges posed by electron beam radiolysis in observing nanoparticle transformations.
• To enable real-time imaging of the stages of galvanic replacement reactions.

Main Methods:

• Utilized liquid cell electron microscopy (LCEM) for in situ observations.
• Studied the transformation of silver (Ag) nanocubes in gold (Au) salt solutions.
• Manipulated solution pH by adding sulfuric acid (H2SO4) to create neutral and acidic conditions.

Main Results:

• Lowering the pH of aqueous solutions significantly reduced modifications to redox reactions caused by radiolysis.
• Acidic conditions (lower pH) prevented excessive reduction of metal-chloro complexes by aqueous electrons (e_aq^-).
• The galvanic replacement process was slowed down sufficiently for detailed real-time imaging by LCEM.

Conclusions:

• Adjusting solution pH is an effective strategy to control radiolysis effects in LCEM studies of galvanic replacement.
• This pH control allows for the detailed, real-time observation of nanoparticle transformation into hollow and porous nanostructures.
• The findings facilitate a deeper understanding of galvanic replacement mechanisms and the synthesis of advanced nanomaterials.