Up to now, some procedures have been developed for the synthesis of LaPO4 salt, in the nanoscale [1], and we report here the preparation of LaPO4 nanoparticles under ultrasonic irradiation by using La(NO3)3.6H2O and NaH2PO4.2H2O in water/ethylene glycol. The morphology and average particle size were studied by SEM-EDX and XRD. The SEM image showed uniformity in morphology of the prepared LaPO4, and the existence of lanthanum, phosphorous, and oxygen atoms were confirmed by SEM-EDX analysis. XRD pattern of sample is in agreement with monoclinic system of the LaPO4 in P21/n space group (JCPDS 32-0493). The average grain size, of 41 nm, was calculated by using Scherrer equation. The synthetic lanthanum phosphate was used as a new heterogeneous and highly useful nano-catalyst for the synthesis of 3-(4-nitrophenyl)-1-phenyl-3-(phenylthio)propan-1-one from the conjugate addition of thiophenol to p-nitrochalcone. The product was characterized by single-crystal X-ray determination, IR, 1HNMR, 13CNMR, elemental analysis and mass spectrometry. The low solubility of LaPO4 salt in water and its high thermal stability make it as a good candidate in catalytic applications. Moreover, due to the presence of PO43–, the La3+ ion is oxophilic enough to form a strong coordinate bond with the oxygen atom in a carbonyl compound. This is a suitable characteristic to activate Cβ in the α,β-unsaturated ketones giving the sufficiently electrophilic property required in the conjugate addition considered in this work.

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