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Chemical deposition of Cuprous Oxide nanocrystals

Affiliation:

This work was done In courtesy of Mariano D. Susman, Depts. of Materials and Interfaces Weizmann Institute of Science, Rehovot Israel

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Abstract:

  • The value of airSEM technology in material science is the ability to image samples at any state, including natural (in air) or wet conditions.
  • In particular, the open B-Nano architecture may allow the researcher to follow dynamic processes at the nanoscale, as crystal formation and growth processes, in real time and at the sample environments which the experiment might require, and are not compatible with regular SEM or TEM.
  • In this work we present cuprous oxide (Cu2O) nanocrystals (NCs) prepared by an electroless (chemical) deposition (ELD) method. The particles have different sizes and shapes which were controlled by the deposition time and the solution composition. [reference: Susman, M. D.; Feldman, Y.; Vaskevich, A.; Rubinstein, I. “Chemical Deposition of Cu2O Nanocrystals with Precise Morphology Control”, ACS  Nano 2014, 8, 162–174.]
  • The open B-Nano architecture may allow us to trigger and follow chemical changes continuously, and to follow their dynamics. 

 

Objective:

  1. The first objective of this work was to verify the airSEM imaging ability on cuprous oxide (Cu2O) NCs in air compared to conventional SEM and TEM, at high vacuum.
  2. The second objective was to follow ex-situ the growth of single crystals by exposing pre-grown NCs to the electroless growth solution. Particles were imaged before and after growth under the airSEM at the exact same location, in air.
  3. The third objective is to develop suitable measurement conditions to follow crystal growth in-situ, under wet conditions (in course).

 

Challenges:

  • Imaging nanometric sized particles can be challenging compared to conventional SEM.
  • Following the growth of a single particle requires exact alignment and timing.

 

Methods:

  • For initial imaging comparison the Cu2O NCs were imaged using both Surface and STEM detection modes under the airSEM microscope, and by regular TEM and SEM microscopies.
  • In order to follow the crystal growth ex-situ, the slide supporting the NCs was positioned in a cell able to hold and flow the different growth and rinsing media.

 

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Fig1:  The sample is positioned in the cell under the optical microscope and the ROI is chosen:

 

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Fig2:  The sample is moved under the airSEM

 

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Fig3:  The cell is filled with the ELD solution and the growth progress is started

The cell is rinsed to stop the reaction, and the sample is imaged again

 

Results:

 

Cuprous oxide NCs on glass:

Cuprous oxide nanocrystals

Cuprous oxide NCs on ITO:

Cuprous oxide nanocrystals

Cuprous oxide NCs on TEM grids:

 

airSTEM Image Vs. TEM

 

  • The airSEM and airSTEM NC images are very similar to the conventional SEM and TEM images and contain the same information with a shorter, simpler and faster sample preparation.
  • Changes in NC size could be observed ex-situ using the airSEM, under appropriate experimental conditions. Crystals grow in size and their edges become sharper

 

airSEM advantage:

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The ability to manipulate a chemical process while imaging is a unique advantage of airSEM. 

 

Reference:

Susman, M. D.; Feldman, Y.; Vaskevich, A.; Rubinstein, I. “Chemical Deposition of Cu2O Nanocrystals with Precise Morphology Control”, ACS Nano 2014, 8, 162–174.