α-MoO3 Crystals with a Multilayer Stack Structure Obtained by Annealing from a Lamellar MoS2/g-C3N4 Nanohybrid

Abstract

Transition metal oxides and chalcogenides have recently attracted great attention as the next generation of 2-D materials due to their unique electronic and optical properties. In this study, a new procedure for the obtaining of highly crystalline α-MoO3 is proposed as an alternative to vapor-phase synthesis. In this approach, a first reaction between molybdate, citrate and thiourea allowed to obtain MoS2, which—upon calcination at a temperature of 650 °C in the presence of g-C3N4—resulted in MoO3 with a definite plate-like shape. The colorless (or greenish) α-MoO3 nanoplates obtained with this procedure featured a multilayer stack structure, with a side-length of 1–2 μm and a thickness of several nanometers viewed along the [010] direction. The nucleation-growth of the crystal can be explained by a two-dimensional layer-by-layer mechanism favored by g-C3N4 lamellar template.

Synthesis of MoO3 by glow discharge in contact with water

“…The thickness of a layer is around 50 nm. This value is higher than that obtained by Martin-Ramoz et al (1 micrometer for 44 layers) [38]. The EDX analysis showed oxygen and molybdenum signals only.…”

Preparation and Properties of 2D Materials

“…However, such conventional preparation methods have faced some critical challenges related to substantial energy, complex equipment, and expert operational skills. Thus, Ramos et al report a new preparation method to obtain highly crystalline α-MoO 3 using vapor-phase synthesis [5]. They obtained highly ordered multilayer α-MoO 3 from molybdate using carbon nitride (g-C 3 N 4 ) with a lamellar template.…”

MoO3 nanowire growth on VO2/WO3 for thermochromic applications

“…In the MoO 3 thin film, the prominent peaks at 820, 860, and 994 cm À1 correspond to the a-MoO 3 crystal phase and M-O stretching modes. [32][33][34] Weaker peaks at 190, 283, 336, and 352 cm À1 are linked to Mo-O bending mode, 35,36 while the 658 cm À1 peak relates to triply coordinated oxygen Mo 3-O stretching. 37 In the WO 3 layer, the monoclinic phase is characterized by peaks at 270 and 326 cm À1 .…”

“…[29][30][31]40,41 In the case of the top MoO 3 thin layer, the most robust peaks observed at 820, 860, and 992 cm À1 correspond to the a-MoO 3 crystal phase and the M-O stretching modes. [32][33][34] Additionally, weaker peaks are detected at 191, 284, 335, and 350 cm À1 , which are attributed to the bending mode of Mo-O, 35,36 while the peak at 658 cm À1 is associated with the triply coordinated oxygen Mo 3 -O stretching. 37 Moving on to the WO 3 layer, the monoclinic phase is identified by peaks at 267 and 327 cm À1 .…”