We have studied manganese doping of zinc selenide core/zinc sulfide shell nanocrystals (NCs) where the impurity phosphor resides primarily in the shell. We have found that a simple two-step synthesis can be used to create these nontoxic materials that display efficient energy transfer from the core to the Mn doped shell. These core/shell NCs retain ample quantum efficiency ( approximately 25%) when solubilized in water, which opens the possibility of using these materials as bioimaging agents. As recent work has shown that nanocrystals can be functionalized with organic dyes to operate as ratiometric chemical sensing agents, we have conjugated the doped NCs with an organic dye to showcase efficient Förster resonant energy transfer from the shell-doped phosphor to the surface-bound dye. This result indicates that doped NCs can be used to develop nontoxic ratiometric sensing/biological imaging agents.
Herein we report our method of water solubilization and subsequent functionalization of a variety of nanoparticle systems with amphiphilic polymers containing build-in "chemical handles". We have used these polymers, which have narrow polydispersity indices, to impart water solubility and chemical sensitivity toward targeted species (here: pH). These material systems have high chemical conjugation efficiencies in aqueous conditions which may be used to create a variety of chemical and biological multifunctional materials.
This work presents mechanics, tests, and finite element analyses of a novel steel dual-core self-centering brace (SCB) with flag-shaped re-centering responses. The axial deformation capacity of the brace is doubled with respect to the SCED brace by serial deformations of two sets of parallel tensioning elements when both braces use the same tensioning elements. The mechanics of the brace is first explained; six tensioning elements and four dual-core SCBs are tested to evaluate their cyclic performance. The braces exhibit excellent performance up to a drift of 2% with a maximum axial force around 1,400 kN. The braces also survive 15 low-cycle fatigue tests at a drift of 1.5%. Tensioning elements fail when the braces are overloaded to 2.5–3% drift. Finite element analysis is conducted to further verify hysteretic responses of the dual-core SCB in cyclic tests. A design procedure for the proposed dual-core SCB is also included in the paper.
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