Coordination polymer templated engineering of YVO4:Eu submicron crystals and photoluminescence†
Abstract
Submicron-sized cuboidal and octahedral (Y0.95Eu0.05)VO4 crystals were selectively synthesized via hydrothermally reacting sodium vanadate with a (Y0.95Eu0.05)–tartrate coordination polymer (CP) precipitated at room temperature, where the CP compound was analyzed to be an amorphous mass having particle sizes of ∼300 nm and an approximate composition of (Y0.95Eu0.05)2(C4H4O6)3·7.4H2O. A series of well controlled experiments clearly revealed that a stoichiometric amount of VO43− [VO43−/(Y0.95Eu0.05)3+ molar ratio R = 1.0] favors cuboidal crystals (∼300–500 nm), which are formed via tartrate-directed [001] stacking of ∼15 nm thick nanosquares exposed with high energy {001} facets, whereas superfluous VO43− (R = 1.5 and 2.0) promotes the crystallization of octahedral crystals (∼600–800 nm) enclosed by low energy {101} facets. The acting mechanisms of reaction temperature (80–200 °C) and time (1–24 h) in structure and morphology evolution were discussed in detail. The octahedrons were also analyzed to have a ∼60% stronger 619 nm red emission and a larger (5D0 → 7F2)/(5D0 → 7F1) intensity ratio, though both the types of crystals have similar fluorescence lifetimes of ∼0.9 ms for their 619 nm main emissions.