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Highly crosslinked poly(dimethylsiloxane) microbeads with uniformly dispersed quantum dot nanocrystals
Shahab Shojaei-Zadeh1, Jeffrey F Morris, Alex Couzis
1Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA. zadeh@rutgers.edu
Journal of Colloid and Interface Science
|August 9, 2011
Summary
This study shows how to prevent quantum dot (QD) aggregation in polymer composites by increasing crosslinking molecules. This method creates uniform QD-embedded microbeads for applications like multiplexed screening.
Area of Science:
- Materials Science
- Nanotechnology
- Polymer Chemistry
Background:
- Uniform dispersion of semiconductor nanocrystals (quantum dots or QDs) in polymer matrices is challenging due to aggregation.
- Nanocrystal aggregation can distort optical properties and limit applications in composite materials.
Purpose of the Study:
- To demonstrate a method for achieving uniform dispersion of QDs within poly(dimethylsiloxane) (PDMS) microbeads.
- To investigate the effect of crosslinking concentration on nanocrystal aggregation in PDMS composites.
- To explore the application of these QD-embedded microbeads in bead-based screening platforms.
Main Methods:
- Fabrication of PDMS microbeads embedded with QDs using microfluidics and flow focusing.
- Polymerization of a prepolymer/crosslinker/nanocrystal mixture with varying crosslinker concentrations.
- Quantification of nanocrystal aggregation by measuring nonradiative resonance energy transfer (RET) between QDs with different emission spectra.
Main Results:
- Increased crosslinker concentration in the PDMS matrix significantly reduced QD aggregation.
- Microbeads fabricated with a higher crosslinker ratio (2:1 prepolymer to crosslinker) showed less RET compared to those with a lower ratio (5:1).
- The emission spectrum of QDs in higher crosslinker concentration composites closely resembled the reference spectrum, indicating minimal aggregation.
Conclusions:
- Increasing the concentration of crosslinking molecules is an effective strategy to prevent nanocrystal aggregation in polymer composites.
- This crosslinking approach enables the creation of uniform QD/polymer composite microbeads with undistorted spectral barcodes for multiplexed screening applications.
- The method provides a general paradigm for fabricating nanoparticle-composite materials with controlled particle dispersion.
