A Facile Sol–Gel Strategy for the Synthesis of Rod‐Shaped Nanocrystalline High‐Surface‐Area Lanthanum Phosphate Powders and Nanocoatings

Abstract

Synthesis of rod‐shaped nanocrystalline lanthanum phosphate with an average length of 40 nm even after calcination at 400 °C has been realized through a room‐temperature aqueous sol–gel process. The sol is characterized by particle‐size, zeta‐potential, and viscosity measurements. Gelation of the sol is induced by ammonia. The lanthanum phosphate phase‐formation process is followed by thermal, Fourier‐transform IR, and X‐ray diffraction analysis. Transmission electron microscopy shows that the sol and gel particles have a rod‐shaped morphology and comparable particle sizes. Using the Scherrer equation a crystallite size of 11 nm is obtained for the gel powder calcined at 400 °C and Brunauer–Emmett–Teller (BET) nitrogen‐adsorption analysis showed a high specific surface area of 100 m2 g–1. Ammonia temperature‐programmed desorption measurements show that the density of Lewis acid sites is four times higher than ever reported in the case of lanthanum phosphates. The catalytic activity of the above sample is demonstrated by using it as a Lewis‐acid catalyst in an acetal‐formation reaction with a very good yield of 85 %. The sol is used to develop nanocoatings on a glass surface and the morphology of the coatings is investigated using atomic force microscopy and scanning electron microscopy. The microstructure of the coating confirmed the rod‐shaped nature of the sol particles. The coating was uniform with a thickness of about 55 nm.

Microwave‐assisted Hydrothermal Synthesis of Single‐crystal Nanorods of Rhabdophane‐type Sr‐doped LaPO4·nH2O

“…31,32 Some of these previous studies have shown evidences that the nanowires/nanorods retained their morphology after calcination at 400°C-1000°C, 19,20,22,25,27 indicating that these nanowires/nanorods have high thermal stability; in this way, nanorods have been synthesized having 5-50 nm in diameter and 40 nm to several micrometers in length, and whose SSA varies from 7 to 127 m 2 /g. The preparation of nanorods of rhabdophane-type Sr-doped LaPO 4 ÁnH 2 O is less demonstrated, and indeed does not appear to be works reporting the synthesis of rhabdophane phase exclusively.…”

Synthesis of Monodisperse Lanthanum Hydroxide Nanoparticles and Nanorods by Sonochemical Method

“…Among the lanthanides, lanthanum has been extensively examined for its unique properties [9][10][11][12][13][14]. And lanthanum have been synthesized in various compositions such as La(OH) 3 [15], LaF 3 [16], La 2 (CO 3 ) 3 [17], LaPO 4 [18][19][20], LaBO 3 [21], LaOF [22], La 2 Sn 2 O 7 [23], La 2 O 3 [24] nanoparticles.…”

Ultrasonic mediated synthesis of monodispersed lanthanum hydroxide nanorods for possible bioimplant application

“…Microwave heating induces dipole rotation or ion migration which decreases the reaction time and controls nucleation [43,44]. Ultrasonication helps in uniform particle formation and also prevents aggregation [17,45]. Further, dialysis against water helps in removal of excess of dissolved salts from the solution and also prevents aggregation on aging.…”

“…They are also used as components of optoelectronic materials, upconversion materials and fluorescent agents in biological imaging [11][12][13][14][15]. A wide range of preparation techniques have been developed for lanthanum based nanoparticles including non-aqueous [16], sol-gel [17,18], solvothermal [19], hydrothermal [20], sonochemical [8,9], microwave-assisted [21,22], etc. A common feature of several of these synthesis techniques is the use of toxic stabilising agents that makes them unsuitable for biomedical use.…”