Solution-, melt-, and co-axial electrospinning are well-known methods for producing nano- and microfibers. The electrospinning of colloids (or colloid-electrospinning) is a new field that offers the possibility to elaborate multicompartment nanomaterials. However, the presence of colloids in the electrospinning feed further complicates theoretical predictions in a system that is dependent on chemical, physical, and process parameters. Herein, we give a summary of recent important results and discuss the perspectives of electrospinning of colloids for the synthesis and characterization of multicompartment fibers.

We present a method for the fabrication of ultralight upconverting mats consisting of rigid polymer nanofibers. The mats are prepared by simultaneously electrospinning an aqueous solution of a polymer with pronounced oxygen-barrier properties and functional nanocapsules containing a sensitizer/emitter couple optimized for triplet–triplet annihilation photon upconversion. The optical functionality of the nanocapsules is preserved during the electrospinning process. The nanofibers demonstrate efficient upconversion fluorescence centered at λmax = 550 nm under low intensity excitation with a continuous wave laser (λ = 635 nm, power = 5 mW). The pronounced oxygen-barrier property of the polymer matrix may efficiently prevent the oxygen penetration so upconversion fluorescence is registered in ambient atmosphere. The demonstrated method can be used for the production of upconverting ultralight porous coatings for sensors or upconverting membranes with freely variable thickness for solar cells.

A model system for multicompartment nanofibers was fabricated by colloid electrospinning. The obtained nanostructured material consisted of fluorescent polymer nanoparticles that were synthesized in a miniemulsion and then embedded in fluorescently labeled polymer nanofibers. Because of the absence of contrast between both polymers, the immobilized nanoparticles cannot be reliably identified in the nanofibers via electron microscopy or other techniques. Here, we describe investigations on the hybrid material with two-color STED microscopy to localize the nanoparticles and to quantify their distribution along nanofibers with particle and fiber radii down to 50 nm.

A new top-down approach is proposed to form large amounts of anisometric particles. Multicompartment fibers that present different domains composed of silica nanoparticles and larger polystyrene nanoparticles are fabricated by colloid-electrospinning and are subsequently calcinated and broken. The obtained fibers containing voids are subsequently cut via sonication to yield anisometric particles. It is shown that the majority of the fibers can be broken at the voids.