We report a simple technique for the fabrication of dots-on-spheres (DoS) structures in which conjugated polymer dots (CPdots) are immobilized on the surface of silica spheres via charged interaction. Red-, green-, and blue-emissive conjugated polymers were synthesized and employed to validate the feasibility of an approach to develop a DoS system with emission across the visible range. The robust binding of CPdots to silica particles provides a buffer resistance and good stability to photoirradiation and mechanical agitation. Further bioconjugation of the DoS system is achieved by the introduction of polyarginine and neu antibody that is specific for the HER2 receptor, leading to their successful application to targeted imaging of SKBR-3 breast cancer cells overexpressing HER2. Moreover, DoS with simultaneous multicolor emissions of red, green, and blue can be easily synthesized and used to demonstrate the versatility of this strategy for multicolor cellular imaging based upon a single excitation source. We believe that this hybrid DoS strategy and the easy fabrication of organic polymer nanoparticles with silica substrates will facilitate their effective integration of organic and inorganic materials into versatile applications.
We report the preparation of fluorescent nanospheres based on conjugated polymers, which enables a facile fluorescence color tuning. The fluorescent nanospheres have aldehyde groups on the surface that enable the introduction of a protein ligand, biotin. The intrinsic fluorescence of the nanospheres allows detection of a dye-labeled target protein, streptavidin, via Förster resonance energy transfer. The controlled biofunctionalization of conjugated polymer-based fluorescent nanospheres represents a novel approach with high applicability to sensing of biological molecules.
Electrospun, emission color-tunable nanofibrous sheets were fabricated by multinozzle electrospinning equipped with a secondary electrode for the preparation of white-emissive sheets under a single excitation source, manipulating energy transfer between dyes. By control of the concentration of commercially available red, green, and blue dyes in the matrix polymer [poly(methyl methacrylate)], emission color tuning can be easily accomplished because each dye is located in spatially separated fibers to maintain enough distance to prevent or suppress energy transfer, allowing white-light emission. The application of dye separation for the white-light emission upon excitation with a blue light-emitting-diode lamp is demonstrated, indicative of its potential application for the easy and facile tuning of fluorescence color toward flexible illumination.
A novel chemical warfare agent sensor based on conjugated polymer dots (CPdots) immobilized on the surface of poly(vinyl alcohol) (PVA)–silica nanofibers was prepared with a dots-on-fibers (DoF) hybrid nanostructure via simple electrospinning and subsequent immobilization processes. We synthesized a polyquinoxaline (PQ)-based CP as a highly emissive sensing probe and employed PVA–silica as a host polymer for the elctrospun fibers. It was demonstrated that the CPdots and amine-functionalized electrospun PVA–silica nanofibers interacted via an electrostatic interaction, which was stable under prolonged mechanical force. Because the CPdots were located on the surface of the nanofibers, the highly emissive properties of the CPdots could be maintained and even enhanced, leading to a sensitive turn-off detection protocol for chemical warfare agents. The prepared fluorescent DoF hybrid was quenched in the presence of a chemical warfare agent simulant, due to the electron transfer between the quinoxaline group in the polymer and the organophosphorous simulant. The detection time was almost instantaneous, and a very low limit of detection was observed (∼1.25 × 10–6 M) with selectivity over other organophosphorous compounds. The DoF hybrid nanomaterial can be developed as a rapid, practical, portable, and stable chemical warfare agent-detecting system and, moreover, can find further applications in other sensing systems simply by changing the probe dots immobilized on the surface of nanofibers.
Fluorescent conjugated polymers with various monomer compositions were synthesized via Suzuki coupling polymerization and spherically-shaped conjugated polymer dots (CPdot) with uniform size were prepared via conventional reprecipitation technique. Chemically modified graphene oxide (GO) was prepared to use as a component of sensor platform for protein detection. GO showed an excellent interaction with CPdot on its surface via hydrophobic interaction, which, in turn, induced the quenching of the fluorescence of CPdot. Upon exposure to bovine serum albumin (BSA), the quenched fluorescence was recovered, resulting from the release of CPdot from the complex with GO, as BSA adsorbed preferentially on the GO surface.
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