5 research outputs found
Cu2Se and Cu Nanocrystals as Local Sources of Copper in Thermally Activated in Situ Cation Exchange
Among the different synthesis approaches to colloidal nanocrystals, a
recently developed toolkit is represented by cation exchange reactions, where the
use of template nanocrystals gives access to materials that would be hardly
attainable via direct synthesis. Besides, postsynthetic treatments, such as thermally
activated solid-state reactions, represent a further flourishing route to promote
finely controlled cation exchange. Here, we report that, upon in situ heating in a
transmission electron microscope, Cu2Se or Cu nanocrystals deposited on an
amorphous solid substrate undergo partial loss of Cu atoms, which are then
engaged in local cation exchange reactions with Cu âacceptorâ phases represented
by rod- and wire-shaped CdSe nanocrystals. This thermal treatment slowly
transforms the initial CdSe nanocrystals into Cu2âxSe nanocrystals, through the
complete sublimation of Cd and the partial sublimation of Se atoms. Both Cu
âdonorâ and âacceptorâ particles were not always in direct contact with each other;
hence, the gradual transfer of Cu species from Cu2Se or metallic Cu to CdSe
nanocrystals was mediated by the substrate and depended on the distance between the donor and acceptor nanostructures.
Differently from what happens in the comparably faster cation exchange reactions performed in liquid solution, this study
shows that slow cation exchange reactions can be performed at the solid state and helps to shed light on the intermediate
steps involved in such reactions
Homogeneous Protein Analysis by Magnetic CoreâShell Nanorod Probes
International audienceStudying protein interactions is of vital importance both to fundamental biology research and to medical applications. Here, we report on the experimental proof of a universally applicable label-free homogeneous platform for rapid protein analysis. It is based on optically detecting changes in the rotational dynamics of magnetically agitated coreâshell nanorods upon their specific interaction with proteins. By adjusting the excitation frequency, we are able to optimize the measurement signal for each analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins (soluble domain of the human epidermal growth factor receptor 2 - sHER2) specifically binding to antibodies (trastuzumab) immobilized on the surface of our nanoprobes and demonstrate direct deduction of their respective sizes. Additionally, we examine the dependence of our measurement signal on the concentration of the analyte protein, and deduce a minimally detectable sHER2 concentration of 440 pM. For our homogeneous measurement platform, good dispersion stability of the applied nanoprobes under physiological conditions is of vital importance. To that end, we support our measurement data by theoretical modeling of the total particleâparticle interaction energies. The successful implementation of our platform offers scope for applications in biomarker-based diagnostics as well as for answering basic biology questions
CoâFe Nanodumbbells: Synthesis, Structure, and Magnetic Properties
International audienceWe report the solution phase synthesis, the structural analysis, and the magnetic properties of hybrid nanostructures combining two magnetic metals. These nano-objects are characterized by a remarkable shape, combining Fe nanocubes on Co nanorods. The topological composition, the orientation relationship, and the growth steps have been studied by advanced electron microscopy techniques, such as HRTEM, electron tomography, and state-of-the-art 3-dimensional elemental mapping by EDX tomography. The soft iron nanocubes behave as easy nucleation centers that induce the magnetization reversal of the entire nanohybrid, leading to a drastic modification of the overall effective magnetic anisotropy