Transformation of K(2)Sb(8)Q(13) and KSb(5)Q(8) Bulk Crystals to Sb(2)Q(3) (Q = S, Se) Nanofibers by Acid-Base Solution Chemistry

Abstract

The ability to manipulate crystal structures using kineticcontrolis of broad interest because it enables the design of materials withstructures, compositions, and morphologies that may otherwise be unattainable.Herein, we report the low-temperature structural transformation ofbulk inorganic crystals driven by hard-soft acid-base(HSAB) chemistry. We show that the three-dimensional framework K(2)Sb(8)Q(13) and layered KSb(5)Q(8) (Q = S, Se, and Se/S solid solutions) compounds transformto one-dimensional Sb(2)Q(3) nano/microfibers inN(2)H(4)& BULL;H2O solution by releasingQ(2-) and K+ ions. At 100 & DEG;C and ambientpressure, a transformation process takes place that leads to significantstructural changes in the materials, including the formation and breakageof covalent bonds between Sb and Q. Despite the insolubility of thestarting crystals in N2H4 & BULL;H2O under the given conditions, the mechanism of this transformationcan be rationalized by applying the HSAB principle. By adjusting factorssuch as the reactants' acid/base properties, temperature, andpressure, the process can be controlled, allowing for the achievementof a wide range of optical band gaps (ranging from 1.14 to 1.59 eV)while maintaining the solid solution nature of the anion sublatticein the Sb(2)Q(3) nanofibers.