title: Synthesis-driven, structure-dependent optical behavior in phase-tunable NaYF4:Yb,Er-based motifs and associated heterostructures.
abstract: Understanding the key parameters necessary for generating uniform Er,Yb co-activated NaYF4possessing various selected phases (i.e. cubic or hexagonal) represents an important chemical strategy towards tailoring optical behavior in these systems. Herein, we report on a straightforward hydrothermal synthesis in which the separate effects of reaction temperature, reaction time, and precursor stoichiometry in the absence of any surfactant were independently investigated. Interestingly, the presence and the concentration of NH4OH appear to be the most critical determinants of the phase and morphology. For example, with NH4OH as an additive, we have observed the formation of novel hierarchical nanowire bundles which possess overall lengths of ∼5 μm and widths of ∼1.5 μm but are composed of constituent component sub-units of long, ultrathin (∼5 nm) nanowires. These motifs have yet to be reported as distinctive morphological manifestations of fluoride materials. The optical properties of as-generated structures have also been carefully analyzed. Specifically, we have observed tunable, structure-dependent energy transfer behavior associated with the formation of a unique class of NaYF4-CdSe quantum dot (QD) heterostructures, incorporating zero-dimensional (0D), one-dimensional (1D), and three-dimensional (3D) NaYF4structures. Our results have demonstrated the key roles of the intrinsic morphology-specific physical surface area and porosity as factors in governing the resulting opto-electronic behavior. Specifically, the trend in energy transfer efficiency correlates well with the corresponding QD loading within these heterostructures, thereby implying that the efficiency of FRET appears to be directly affected by the amount of QDs immobilized onto the external surfaces of the underlying fluoride host materials.
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794-3400, USA. Stanislaus.wong@stonybrook.edu sswong@bnl.gov.
authors.forename: Haiqing
authors.initials: H
authors.lastname: Liu
authors.affiliation: Condensed Matter of Physics and Materials Sciences Division, Brookhaven National Laboratory, Building 480, Upton, NY 11973, USA.
authors.forename: Jinkyu
authors.initials: J
authors.lastname: Han
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794-3400, USA. Stanislaus.wong@stonybrook.edu sswong@bnl.gov.
authors.forename: Coray
authors.initials: C
authors.lastname: McBean
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794-3400, USA. Stanislaus.wong@stonybrook.edu sswong@bnl.gov.
authors.forename: Crystal S
authors.initials: CS
authors.lastname: Lewis
authors.affiliation: Materials Science and Engineering Department, State University of New York at Stony Brook, Stony Brook, NY 11794-2275, USA.
authors.forename: Prahlad
authors.initials: P
authors.lastname: Kumar Routh
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Building 735, Upton, NY 11973, USA.
authors.forename: Mircea
authors.initials: M
authors.lastname: Cotlet
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794-3400, USA. Stanislaus.wong@stonybrook.edu sswong@bnl.gov and Condensed Matter of Physics and Materials Sciences Division, Brookhaven National Laboratory, Building 480, Upton, NY 11973, USA.
authors.forename: Stanislaus S
authors.identifier: http://orcid.org/0000-0001-7351-0739
authors.initials: SS
authors.lastname: Wong