Magnetically controlled anisotropic light emission of DNA-functionalized supraparticles

Abstract: In this article, we show the DNA-functionalization of supraparticles, form their network, and manipulate the optical features of these networks by applying a magnetic field. We start with preparing the supraparticles (SPs) of semiconducting InP/ZnSeS/ZnS quantum dots (QDs), plasmonic silver nanoparticles, and superparamagnetic iron oxide nanoparticles. These SPs are prepared by employing azide-functionalized amphiphilic diblock or triblock copolymers as well as by using their combinations. Subsequently, we attached single-stranded DNAs to these SPs by employing copper-free click chemistry. Next, we hybridized DNA-coated QD SPs with the iron oxide SPs and formed a network. By applying a magnetic field, we restructured this network such that the iron oxide SPs are aligned. This led to an anisotropic emission from the QD SPs with a polarization ratio of 1.9. This study presents a proof-of-concept scheme to control the optical features of a self-assembled supraparticle system using an external interaction. We believe that our work will further contribute to the utilization of smart self-assembly techniques in optics and photonics. Impact statement: The self-assembly of the nanoparticles, which lies at the heart of this article, enables achieving unconventional physical responses that cannot be obtained by the individual nanomaterials. Therefore, controlling the self-assembly process can lead to unprecedented control over the mechanical, optical, or electronic features of such novel architectures made of various types of nanoparticles. This smart self-assembly process will undoubtedly enable the realization of novel applications and open new avenues in materials science and engineering. In this article, we employ the self-assembly in two different aspects. First, we self-assembled magnetic, plasmonic, and semiconducting nanoparticles to obtain their supraparticles with the help of various amphiphilic polymers. Next, single-stranded DNA molecules were attached to them for the first time to achieve a precise control over their physical forming a “network of supraparticles of nanoparticles.” As a proof-of concept demonstration, we hybridized DNA-functionalized magnetic supraparticles made of iron oxide nanoparticles and DNA-functionalized light-emitting supraparticles containing InP/ZnSe/ZnS quantum dots. We explored the potential of tailoring the emission characteristics of the emitted light by utilizing an external magnetic field. We observed that under an external magnetic field the hybrid network reshapes; as a result, the polarization of the emitted light can be changed such that polarization anisotropy reaches ~1.9. We believe that our work presented here can initiate advanced-level active polarization control in displays and other light-emitting devices in the future. Considering that LCD-based displays require polarized light to function, the results of this work may serve for realizing efficient polarizer-free displays that rely on the manipulation of the structure under the magnetic field. Graphical abstract: Single-stranded DNA molecules are attached to the supraparticles of semiconductor, metal, and magnetic nanoparticles to tailor optical features of the self-assembled network. An external magnetic field is employed to actively control the polarization of the light emitted by the network of semiconductor and magnetic supraparticles.[Figure not available: see fulltext.]