In situ XAFS experiments using a microfluidic cell: application to initial growth of CdSe nanocrystals

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• In situ studies of nanoparticle formation are crucial for understanding material properties.
• Conventional optical techniques have limitations in characterizing early-stage nanoparticle growth.
• Synchrotron-based X-ray absorption spectroscopy offers advanced analytical capabilities.

Purpose of the Study:

• To design and evaluate a compact fluorescence XAFS apparatus with a microfluidic cell for in situ nanoparticle analysis.
• To investigate the nucleation and initial growth of Cadmium Selenide (CdSe) nanoparticles.
• To correlate XAFS data with UV-vis spectra for accurate size and density estimation.

Main Methods:

• Development of a compact fluorescence X-ray Absorption Fine Structure (XAFS) apparatus.
• Utilized a microfluidic cell for controlled in situ sample delivery and reaction.
• Performed time-resolved XAFS experiments by precise control of reactor coordinates.
• Analyzed Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) data.
• Interpreted Se K-XANES spectra using multi-scattering calculations.

Main Results:

• Demonstrated the capability of the apparatus for in situ studies of nanoparticle formation.
• Successfully monitored nucleation and initial growth of CdSe nanoparticles.
• Obtained reliable estimations of particle size and density during early growth stages.
• Established bond formation kinetics consistent with EXAFS data through spectral analysis.

Conclusions:

• The developed compact fluorescence XAFS apparatus with a microfluidic cell is effective for in situ nanoparticle studies.
• This technique provides insights into nanoparticle formation inaccessible to conventional optical methods.
• The study successfully characterized CdSe nanoparticle growth kinetics at the nanoscale.