title: Magnetic field induced quantum dot brightening in liquid crystal synergized magnetic and semiconducting nanoparticle composite assemblies.
abstract: The design and development of multifunctional composite materials from artificial nano-constituents is one of the most compelling current research areas. This drive to improve over nature and produce 'meta-materials' has met with some success, but results have proven limited with regards to both the demonstration of synergistic functionalities and in the ability to manipulate the material properties post-fabrication and in situ. Here, magnetic nanoparticles (MNPs) and semiconducting quantum dots (QDs) are co-assembled in a nematic liquid crystalline (LC) matrix, forming composite structures in which the emission intensity of the quantum dots is systematically and reversibly controlled with a small applied magnetic field (<100 mT). This magnetic field-driven brightening, ranging between a two- to three-fold peak intensity increase, is a truly cooperative effect: the LC phase transition creates the co-assemblies, the clustering of the MNPs produces LC re-orientation at atypical low external field, and this re-arrangement produces compaction of the clusters, resulting in the detection of increased QD emission. These results demonstrate a synergistic, reversible, and an all-optical process to detect magnetic fields and additionally, as the clusters are self-assembled in a fluid medium, they offer the possibility for these sensors to be used in broad ranging fluid-based applications.
authors.affiliation: Physics, School of Natural Sciences, University of California, 5200 N. Lake Rd, Merced CA 95343, USA. lhirst@ucmerced.edu sghosh@ucmerced.edu.
authors.forename: Jose Jussi
authors.initials: JJ
authors.lastname: Amaral
authors.forename: Jacky
authors.initials: J
authors.lastname: Wan
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Rodarte
authors.forename: Christopher
authors.initials: C
authors.lastname: Ferri
authors.forename: Makiko T
authors.initials: MT
authors.lastname: Quint
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Pandolfi
authors.forename: Michael
authors.initials: M
authors.lastname: Scheibner
authors.forename: Linda S
authors.initials: LS
authors.lastname: Hirst
authors.forename: Sayantani
authors.initials: S
authors.lastname: Ghosh