MoSe₂ Nanosheets with Tuneable Optical Properties for Broadband Visible Light Photodetection

Abstract

Full exploitation of two-dimensional (2D) semiconducting MoSe2, an exciting 2D transition-metal dichalcogenide, in optoelectronics is hampered because of dearth of scalable production methods. Here, a redox-mediated green route growth of ultrathin MoSe2 nanosheets and nanocrystals is reported. At solvothermal condition, molybdenum acetate [(CH3COO–)2Mo2+]2 at (+II) oxidation state is employed as the molybdenum source for the first time to grow 2D MoSe2 of 2H phase. Edible olive oil acts as a solvent as well as a ligand to block the growth in the Z direction, leading to the formation of 2D MoSe2. The bottom-up solution-processed method differs distinctly from other available synthesis methods in terms of the 2D MoSe2 nanosheet growth of the semiconducting phase (2H) without using any template or any external reducing agent. Evolution of MoSe2 nanosheets is systematically studied by X-ray diffraction and Raman spectroscopy with the variation of the reaction temperature and the reaction time. Prolonged sonication and gradient centrifugations enable in obtaining MoSe2 nanocrystals of different sizes. Tuneable optical properties and temperature-dependent emissions of MoSe2 nanocrystals and nanosheets are studied by UV–visible and photoluminescence spectroscopies. Finally, we have fabricated a photoconductive device which shows broadband visible light detection, demonstrating the potential use of bottom-up solution-processed semiconducting MoSe2 in broadband photodetection applications.

Colloidal Continuous Injection Synthesis of Fluorescent MoX2 (X = S, Se) Nanosheets as a First Step Toward Photonic Applications

“…As a result, we found that for MoS 2 Δ 0 = 76 ± 2 meV and Δ LO = 210 ± 24 meV, while for MoSe 2 , Δ 0 = 38.6 ± 0.2 meV and Δ LO = 39.7 ± 0.9 meV. Literature reports values of Δ 0 between 52 and 66 meV for MoS 2 (4 meV in hBN-encapsulated MoS 2 ) and 1.5–4.3 meV for MoSe 2 and values of Δ LO between 42.6 and 86 meV for MoS 2 and 11.2–15.6 meV for MoSe 2 . ,− This suggests that our colloidal TMD nanosheets can still be further improved; however, our MoSe 2 monolayer already exhibits a substantially narrower emission linewidth than the MoS 2 monolayer, suggesting that the latter might be more suitable for further application in optoelectronic or photonic devices. − …”

Tuning the photocatalytic/electrocatalytic properties of MoS2/MoSe2 heterostructures by varying the weight ratios for enhanced wastewater treatment and hydrogen production

“…The lower energy PL emission can be ascribed to the transition between quantized energy levels and the other peak is might be due to defect state mediated transition. 27,28 The PL intensity of all the composites prepared was lower than the pure MoSe 2 which indicates that the photocatalytic activity of the composites is higher as compared to individual components because of the higher separation efficiency of the photo-induced charges in the composites. 004), ( 006), ( 102), ( 111), ( 105), ( 201), ( 110), ( 103), ( 200) and (203) (hkl) planes respectively (JCPDS le no 77-1715) and intensity of these peaks increases as the amount of MoSe 2 in the composite increases.…”

Construction of an electrochemical pH sensor using one-pot synthesis of a molybdenum diselenide/nitrogen doped graphene oxide screen-printed electrode

“…The peaks at 235 and 281 cm −1 are related to the out-of-plane A 1g and in-plane E 2g 1 vibrational modes of MoSe 2 , respectively. 22 The peak at 195 cm −1 is attributed to the E 1g mode, which is forbidden in backscattering but appears due to the resonance effect. The peak at 336 cm −1 is connected to the 2-phonon frequency of the B 2g branch at the M point.…”