Quantum Dot Transfer from the Organic Phase to Acrylic Monomers for the Controlled Integration of Single-Photon Sources by Photopolymerization

Abstract

This paper reports on a new strategy for obtaining homogeneous dispersion of grafted quantum dots (QDs) in a photopolymer matrix and their use for the integration of single-photon sources by two-photon polymerization (TPP) with nanoscale precision. The method is based on phase transfer of QDs from organic solvents to an acrylic matrix. The detailed protocol is described, and the corresponding mechanism is investigated and revealed. The phase transfer is done by ligand exchange through the introduction of mono-2-(methacryloyloxy) ethyl succinate (MES) that replaces oleic acid (OA). Infrared (IR) measurements show the replacement of OA on the QD surface by MES after ligand exchange. This allows QDs to move from the hexane phase to the pentaerythritol triacrylate (PETA) phase. The QDs that are homogeneously dispersed in the photopolymer without any clusterization do not show any significant broadening in their photoluminescence spectra even after more than 3 years. The ability of the hybrid photopolymer to create micro- and nanostructures by two-photon polymerization is demonstrated. The homogeneity of emission from 2D and 3D microstructures is confirmed by confocal photoluminescence microscopy. The fabrication and integration of a single-photon source in a spatially controlled manner by TPP is achieved and confirmed by auto-correlation measurements.

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“…Different ligands can introduce different surface defects, charge transfer properties, and band-gap widths, which alter the fluorescence performance of QDs. − In addition to MPA, we used glutathione (GSH), dihydrolipoic acid (DHLA), and l -cysteine ( l -Cys)three other ligandsfor the surface modification of DMSN for the in situ growth of QDs. As shown in Figure c, the TEM images of UQSN show that this strategy is also applicable to other common ligands.…”

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“…While QDs exhibit remarkable attributes such as strong color purity, tunability, and long fluorescence lifetime, disadvantages exist due to concerns about cytotoxicity, thermochemical instability-induced QD degradation, and the tendency for QDs to aggregate and precipitate in solvents. These issues present suboptimal conditions for their application in photoresist formulation. − In contrast to QDs, a broad spectrum of commercially available organic dyes boasts biocompatibility and is commonly employed in biomedical applications, offering high solubility in organic solvents. , Nevertheless, prevalent drawbacks of most organic dyes used in the optical context involve issues of photostability and photobleaching. , Within the realm of organic dyes, perylene dyes derived from polycyclic aromatic hydrocarbons stand out due to their exceptional photostability, robust fluorescence output, thermal resilience, and resistance to environmental factors. − Notably, the integration of perylene dye-doped photoresists into the domain of TPL-based 3D micro/nanofabrication has not been explored.…”