Novel Gd(OH)3, GdOOH and Gd2O3 Nanorods: Microwave-Assisted Hydrothermal Synthesis and Optical Properties

Abstract

We present a study of the controlled synthesis and optical properties of single-crystals Gd(OH) 3 , GdOOH and Gd 2 O 3 nanorods. In this work, Gd(OH) 3 nanorods were synthesized by a simple and fast microwave-assisted hydrothermal method. This process combined with the thermal decomposition oxidation of Gd(OH) 3 nanorods as precursors enabled the preparation of single-crystalline GdOOH and Gd 2 O 3 structures with well-defined morphology at low temperatures. The crystal structure dependence on the optical properties was investigated. We observed a green shift effect on the photoluminescence (PL) emission spectra from Gd(OH) 3 to Gd 2 O 3 nanorods, which can be attributed to different types of surface defects, as well as intrinsic properties that contribute significantly to the modified PL behavior.

An overview into advantages and applications of conventional and unconventional hydro(solvo)thermal approaches for novel advanced materials design

“…Therefore, microwave-assisted hydro(solvo)thermal synthesis offers significant advantages compared to traditional methods, including the following: (i) a rapid heating rate for the desired reaction temperature, (ii) uniform distribution of temperature, (iii) improved crystallization kinetics, as well as, (iv) extremely short reaction times [89,95,96,106,123,[162][163][164][165][166][167][168][204][205][206]. In addition, it is widely recognized that rapid microwave heating can suppress the formation of by products [197].…”

“…The uniqueness of the dielectric heating mechanism causes the specific (thermal) effects of microwaves not being possible to reach by conventional heating. Undoubtedly, the use of microwaveassisted heating contributes to an increase in crystallization kinetics, in orders of magnitude, thereby improving material productivity and favoring the obtainment of more complex structures [86,[119][120][121][122][123][124][125]. Also, is well established that the use of microwave energy substantially impacts the physicochemical properties of these advanced materials [126][127][128].…”

Synthesis of Gd2O3 Nanoparticles and Their Photocatalytic Activity for Degradation of Azo Dyes

“…The absorbance peak of the Gd 2 O 3 nanoparticles was observed at 228 nm in UV-vis spectroscopy [27]. The optical bandgap energy (E g ) was estimated by the method proposed by Tauc [17]. The optical band gap of Gd 2 O 3 is determined by the following equation:…”

“…They are used in a wide range of applications, such as fluorescent materials, high-resolution X-ray medical imaging, ultraviolet (UV) detectors, catalysts, and dopants [11][12][13][14][15][16]. Owing to its high chemical stability, UV absorption, and active photon-to-electron conversion, gadolinium oxide (Gd 2 O 3 ) is widely used as an n-type semiconductor photocatalyst [12,17,18].…”

“…The •OH radicals generated in water under UV irradiation are responsible for the degradation of azo dyes [19]. The unique 4f orbitals/electrons of rare earth compounds have magnetic, electrical, optical, phosphorus, and catalytic properties [17,24].…”