The use of microrobotics in biological systems has attracted much attention due to its diverse functionality and controllable motion. Combining magneto-polymer nanocomposite with fluorescent nanoparticles provides new potentials for micro-machining in biomedicine. Due to their contact-free, remote controllable, and biocompatible properties, iron oxide (Fe3O4) nanoparticles have been widely used in magnetic resonance imaging (MRI), cell targeting, and drug delivery, and are considered to be an attractive option in further development of micro- scale systems. The fluorescent properties and high photo-stability of semiconductor nanocrystal quantum dots (QDs) have also shown great potential for bio and quantum applications. This work explores the fabrication and manipulation of bimodel fluorescent-magnetic microstructures on a new photo-patternable composite consisting of colloidal semiconductor nanocrystal QDs (CdSe/CdS), superparamagnetic magnetite nanoparticles (Fe3O4), and a commercial SU-8 photoresist. Using a mask optical lithography technique, we fabricated 2D microstructures of various shapes and demonstrated their strong response to an externally applied magnetic field. Linear, rotational, and spinning movements are presented. Photo-radiation fluorescent checking was used to map the location of the QDs within the microstructures and strong fluorescent emitters were characterized. Combining Fe3O4 nanoparticles, QDs, and SU-8 polymer into a single complex microstructure contributes to a wide range of applications in biomedicine such as biological-labeling, in vivo cargo transportation, and micro-machining, as well as perspectives in quantum technology.
Coupling of a single photon source into photonic structures is highly demanded for implementation of numerous applications in quantum information processing and quantum dot (QD)-based solid-state platforms. In this work, we present a simple strategy for coupling a single semiconductor colloidal nanocrystal (NC) into polymer-based photonic structures. By utilizing low one-photon absorption (LOPA) direct laser writing (DLW) technique, we demonstrate the precise patterning of 2D SU-8 microstructures containing an individual core/shell CdSe/CdS NC. Various shapes of desired structures are fabricated with a single embedded NC while keeping its photon antibunching property as a single photon source. These results open a wide range of perspectives in term of quantum information, tunable emission, and efficient light harvesting by using polymer-based photonic crystal.
The coupling between thick-shell CdSe/CdS colloidal nanocrystals with the hot spots of a semicontinuous gold film is characterized by measuring simultaneously the photoluminescence decay rate and the linear polarization ratio. The absence of correlations between the two quantities is demonstrated. In contrast with the results obtained with continuous gold films, polarization ratios higher than 80% are achieved for the smallest nanocrystals. This ratio decreases quickly when the nanocrystals size is increased.
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