An optical humidity sensor based on Li 3PO 4 hollow nanospheres

Abstract

Orthorhombic Li 3PO 4 hollow nanospheres and solid particles have been successfully prepared respectively via a simple neutralization reaction between H 3PO 4 and LiOH aqueous solutions, by just changing the adding sequence of H 3PO 4 and LiOH aqueous solutions (with PVP) in dropwise. Transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FESEM) images display Li 3PO 4 hollow nanospheres with average diameters of about 400 nm and wall thickness of about 50 nm which is actually composed of nanoparticles with sizes of 20–50 nm, and Li 3PO 4 solid particles with lengths of 100–500 nm and widths of 100–250 nm. The photoluminescence (PL) properties of the samples reveal that the Li 3PO 4 hollow nanospheres show stronger PL intensity than the Li 3PO 4 solid particles. Furthermore, an adapted photoluminescence-type gas sensor based on Li 3PO 4 hollow nanospheres has been devised and its sensing property to humidity has also been investigated. This novel sensor exhibits good sensitivity, ideal linearity, quick response/recovery, and reliable repeatability in a very wide humidity range at room temperature.