Energy down-converting LaPO₄ nanoparticles highly dispersed into poly(lactic acid) electrospun fibers: microstructural and optical properties

Electrospinning technique was used to obtain a new class of biopolymer/inorganic nanoparticle hybrid fibers fabricated by using poly(lactic acid) (PLA) as the biopolymer matrix and lanthanum phosphate nanoparticles (LaPO₄) as energy down-converting materials. Before being incorporated and electrospun with the PLA, the LaPO₄ nanostructures obtained from microwave-assisted hydrothermal method were studied to have a depth understanding related to their synthesis parameters, since it is known they adopt different structures and morphologies with the temperature and pH. Highly hydrophobic samples of LaPO₄ nanoparticles in hexagonal and monoclinic phases with mixed morphologies (rods and semi-spherical) were detected in samples calcined at 400 °C while those calcined at 600 °C consisted mainly in monoclinic phase with semi-spherical morphologies. Smallest particles in semi-spherical and orthorhombic morphologies obtained at pH 1 and 11 were detected after processing them through electrospinning technique and distributed uniformly into the PLA. The vibrational analysis suggested that the ester group (RCOOR') in PLA plays a key role in the interaction with the LaPO₄ nanoparticles. These materials can find practical applications in biomedical areas for replacing conventional polymers.