Laser-induced synthesis of CaMoO₄ nanocolloidal suspension and its optical properties

Pulsed laser ablation in a liquid phase was employed successfully to synthesize a calcium molybdate (CaMoo₄) nanocolloidal suspension. The crystalline phase, particle morphology, particle size distribution, absorbance, optical band-gap and photoluminescence (PL) were examined. Stable colloidal suspensions consisting of well-dispersed CaMoO₄ nanoparticles with a narrow size distribution could be obtained without a surfactant. The optical absorption edge located near 270 nm was blue-shifted by approximately 70 nm compared to that reported for bulk crystals. The estimated optical energy band-gap was 4.7 eV and the PL spectrum was blue-shifted at approximately 430 nm compared to the emission of bulk CaMoO₄ target (525 nm). The observed band-gap widening and blue-shift of PL emission was attributed to the quantum-size effect due to the very small size of the CaMoO₄ nanoparticles prepared by pulsed laser ablation in deionized water.