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Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging

Published: July 19th, 2016



1Department of Chemistry, Imperial College London, 2Department of Medical Physics and Biomedical Engineering, University College London, 3Department of Chemistry, University College London
* These authors contributed equally

Here we present a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of cadmium selenide quantum dots can be accurately visualized through cross-sectional fluorescence imaging.

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise composition of these materials is essential, especially in the design of surface catalysts, where the surface concentration of the active component determines the activity of the material. Antimicrobial materials which utilize nanoparticles are a particular focus of this technology. Recently swell encapsulation has emerged as a technique for inserting antimicrobial nanoparticles into a host polymer matrix. Swell encapsulation provides the advantage of localizing the incorporation to the external surfaces of materials, which act as the active sites of these materials. However, quantification of this nanoparticle uptake is challenging. Previous studies explore the link between antimicrobial activity and surface concentration of the active component, but this is not directly visualized. Here we show a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of CdSe/ZnS nanoparticles can be accurately visualized through cross-sectional fluorescence imaging. Using this method, we can quantify the uptake of nanoparticles via swell encapsulation and measure the surface concentration of encapsulated particles, which is key in optimizing the activity of functional materials.

The application of nanomaterials has long served as an area of increasing interest for novel technologies.1-3 This has included the growing use of nanoparticles in everyday items, including cosmetics, clothes, packaging and electronics.4-6 A major drive toward using nanoparticles in functional materials stems from their higher reactivity relative to the materials, in addition to the ability to tune properties by variation in particle size.7 One further advantage is the capability to easily form composite materials, introducing crucial properties to the host matrix, such as catalytic functionality, material strengthening and tu....

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1. Preparation of CdSe/ZnS Core/Shell Quantum Dots

  1. Preparation of the trioctylphosphine (TOP)-Se solution
    1. Prepare a 0.5 M solution of selenium in TOP by mixing the appropriate amount of Se into TOP in a Schlenk flask under nitrogen or in a glovebox (8 ml required per reaction, typically 0.4 g dissolved in 10 ml of TOP).
    2. Stir the mixture to dissolve the Se for 1 hr, resulting in a grey solution of the TOP-Se complex.
    3. Ensure the solution is then freeze-pump-tha.......

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The quantum dots exhibited red fluorescence, with a lambda max of approximately 600 nm.22,28 The red emission was due to the confinement of the exciton by the quantum rod whose size dimensions are within the strong confinement regime. Li et al. showed that for quantum rods, the emission shifts to lower energy with an increase in either width or length of the rod. They further showed that the emission mainly determined by the lateral confinement, which plays an importan.......

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Cross-sectional fluorescence imaging allows for direct visualization of nanoparticles during swell encapsulation. The kinetics of encapsulation has been shown, with the drive toward a high nanoparticle surface concentration demonstrated. The extent of nanoparticle incorporation is shown to vary with swell encapsulation time (described in section 2.3), with the total amount of incorporated nanoparticles increasing as this time is extended, with the particle concentration localized at the surface if the polymer samples are.......

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C.R.C. would like to acknowledge the Ramsay Memorial Trust for funding.


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Name Company Catalog Number Comments
Polydimethylsiloxane sheets NuSil - Medical Grade
Oleylamine Sigma Aldrich O7805 Technical Grade
Trioctylphosphine Sigma Aldrich 117854 Technical Grade
Trioctylphosphine oxide Sigma Aldrich 346187 Technical Grade
1-Octadecene Sigma Aldrich O806 Technical Grade
Zinc diethyldithiocarbamate Sigma Aldrich 329703 -
Oleic acid Sigma Aldrich 364525 Technical Grade
Triethylamine Sigma Aldrich 471283 -
Cadmium oxide Alfa Aesar 33235 -
Hexadecylamine Alfa Aesar B22459 Technical Grade
1-Dodecylphosphonic acid Alfa Aesar H26259 -
Selenium powder Acros 19807 -
Chloroform Sigma Aldrich 366919 -
n-Hexane Sigma Aldrich 208752 -
Microscope slides VWR 631-0137 Thickness No. 1

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