Synthesis of graded CdS1-xSex nanoplatelet alloys and heterostructures from pairs of chalcogenoureas with tailored conversion reactivity.

A mixture of N,N,N'-trisubstituted thiourea and cyclic N,N,N',N'-tetrasubstituted selenourea precursors were used to synthesize three monolayer thick CdS1-xSex nanoplatelets in a single synthetic step. The microstructure of the nanoplatelets could be tuned from homogeneous alloys, to graded alloys to core/crown heterostructures depending on the relative conversion reactivity of the sulfur and selenium precursors. UV-visible absorption and photoluminescence spectroscopy and scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) images demonstrate that the elemental distribution is governed by the relative precursor conversion kinetics. Slow conversion kinetics produced nanoplatelets with larger lateral dimensions, behavior that is characteristic of precursor conversion limited growth kinetics. Across a 10-fold range of reactivity, CdS nanoplatelets have 4× smaller lateral dimensions than CdSe nanoplatelets grown under identical conversion kinetics. The difference in size is consistent with a rate of CdSe growth that is 4× greater than the rate of CdS. The influence of the relative sulfide and selenide growth rates, the duration of the nucleation phase, and the solute composition on the nanoplatelet microstructure are discussed.

A Rationally Designed Complex Replenishes the Transferrin Iron Pool Directly and with High Specificity.

Many forms of anemia are caused or complicated by pathologic restriction of iron (Fe). Chronic inflammation and certain genetic mutations decrease the activity of ferroportin, the only Fe-exporter protein, so that endogenously recycled or nutritionally absorbed Fe cannot be exported to the extracellular Fe carrier protein transferrin for delivery to the bone marrow. Diminished ferroportin activity renders anemia correction challenging as Fe administered intravenously or through nutritional supplementation is trafficked through the ferroportin-transferrin axis. Utilizing judicious application of coordination chemistry principles, we designed an Fe complex (Fe-BBG) with solution thermodynamics and Fe dissociation kinetics optimized to replenish the transferrin-Fe pool rapidly, directly, and with precision. Fe-BBG is unreactive under conditions designed to force redox cycling and production of reactive oxygen species. The BBG ligand has a low affinity for divalent metal ions and does not compete for binding of other endogenously present ions including Cu and Zn. Treatment with Fe-BBG confers anemia correction in a mouse model of iron-refractory iron-deficiency anemia. Repeated exposure to Fe-BBG did not cause adverse clinical chemistry changes or trigger the expression of genes related to oxidative stress or inflammation. Fe-BBG represents the first entry in a promising new class of transferrin-targeted Fe replacement drugs.