Facile One-Step Synthesis and Enhanced Optical Nonlinearity of Graphene-γMnS

Abstract

Graphene-γMnS were prepared by facile one-step hydrothermal method. Structures and properties of samples were explored by characterization, and nonlinear optical (NLO) enhancement of nanocomposites (NCs) was fully studied. Nanoparticles and NCs were tested at 532 nm by a Z-scan technique. With γMnS attached in G layers, NLO susceptibility of graphene-γMnS was greatly improved under single-pulse laser irradiation compared with G and γMnS. The nonlinearity enhanced was attributed to local field effect and charge transfer between γMnS and graphene layers. And NLO property enhancement was restricted by non-radiative defects in graphene-γMnS. Exploring the mechanism of nonlinearity enhancement was significant for fabrication of NLO devices. However, the optical nonlinearity decreased first and then increased with further increased addition of GO, because the dispersion of γMnS attached on graphene surface might make density of sp 2 fragment and defects changed. Graphene-γMnS exhibited excellent and tunable NLO performance, illustrating that NCs materials have potential applications in NLO devices. Nanomaterials 2019, 9, 1654 2 of 16 and graphene [12][13][14]. However, there are few reports about NLO performance of graphene-γMnS. In fact, we have previously studied αMnS/rGO without thoroughly investigating the nonlinearity of graphene-γMnS and the mechanism of NLO performance enhanced of NCs [15]. It is necessary to explore NLO responses of graphene-γMnS and its mechanism of enhanced nonlinearity.In this study, graphene-γMnS was synthesized by facile one-step hydrothermal method, and mechanism of NLO enhancement was discussed. Nonlinearity of NCs was controlled by changing amount of GO added, and samples were tested at 532 nm by picosecond (PS) laser pulse. We want to explore whether graphene-γMnS had potential applications in optical communication, optical limiter, and all-optical switch. Experiments Synthesis of Graphene Oxide ( GO) and Graphene-γMnSGO was prepared by improved Hummer method [16]. Firstly, graphite powder was oxidized to GO by KMnO 4 and 98% H 2 SO 4 . Then, a solution was mixed with H 2 O 2 and the mixture was washed several times with deionized water to remove impurities. Finally, products were dried at 45 • C for 48 h in vacuum drying oven. Improved Hammer method increased generation efficiency and oxidation degree of GO. Furthermore, this method could effectively prevent generation of toxic gases which caused harm to human body. High efficiency, high quality, and no toxicity in GO synthesis were important for large-scale production of GO.Graphene-γMnS was prepared by facile one-step hydrothermal method. The synthesis process of NCs was shown in Figure 1. Firstly, GO was dispersed in ethylene glycol. Secondly, TAA and MnCl 2 ·4H 2 O were added to GO suspension. After half-an-hour stirring, the solution was transferred to Teflon-lined stainless-steel autoclave and reacted at 170 • C for 6 h. The reaction temperature in our previous study was 190 • C and product was different [15]. Then, products wer...

Tunable Nonlinear Optical Property of MnS Nanoparticles with Different Size and Crystal Form

“…In our previous study, NLO response of αMnS/rGO and γMnS/rGO was investigated. And results showed that nonlinearity of graphene composites was enhanced and the reason for NLO enhancement was surface defects and synergistic effect, including local field theory and charge transfer [18,23]. In this study, NLO absorption and refraction of αMnS with different size and γMnS were measured by Z-scan technique using single Gaussian beam.…”

“…αMnS nanoparticles obtained after treatment [18]. The volume of nanoparticles decreased as the synthesis time increased and size range was 40 nm to 200 nm [23]. This might be due to high temperature and high pressure in stainless-steel reactor.…”

“…Figure 1 showed that sharpness of the diffraction peak of αMnS-14 was higher than that of αMnS-6 and αMnS-10, indicating that the crystallinity of αMnS-14 was the highest. Due to different crystal form, the peaks of γMnS were located at 26 • , 28 • , 29 • , 46 • , 50 • , and 53 • , corresponding to (100), (002), (101), (110), (103), and (112) [23]. For γMnS, sharpness of diffraction peak was lower than αMnS, demonstrating that γMnS exhibited lower crystallinity.…”

“…MnS was prepared by the facile one-step hydrothermal method [18,23]. This method is easy to operate, has high production efficiency, and can produce specific crystal forms of MnS or other semiconductor materials by changing temperature, synthesis time, kinds of solvent, and sulfur source.…”

“…In the previous study, we synthesized different crystal form MnS nanoparticles and their graphene composites [18,23]. We discussed the relationship between synthesis time of composites and NLO property, and the relationship between graphene addition of composites and NLO property.…”