Potassium has its unique advantages over lithium or sodium as a charge carrier in rechargeable batteries. However, progresses in K-ion battery (KIB) chemistry have so far been hindered by lacking suitable electrode materials to host the relatively large K ions compared to its Li and Na counterparts. Herein, molybdenum disulfide (MoS ) "roses" grown on reduced graphene oxide sheets (MoS @rGO) are synthesized via a two-step solvothermal route. The as-synthesized MoS @rGO composite, with expanded interlayer spacing of MoS , chemically bonded between MoS and rGO, and a unique nano-architecture, displays the one of the best electrochemical performances to date as an anode material for nonaqueous KIBs. More importantly, a combined K storage mechanism of intercalation and conversion reaction is also revealed. The findings presented indicate the enormous potential of layered metal dichalcogenides as advanced electrode materials for high-performance KIBs and also provide new insights and understanding of K storage mechanism.
not limited to solar energy harvesting, thin film transistors, light emitting diodes, sensors, optical limiters, and wearable devices. [1] Materials with enhanced optical limiting properties are of great demand in protecting various optical devices from laser radiations. A good optical limiter is a material which allows the optical radiation to pass through at low fluences but clamps the transmitted intensity as the incident laser fluence increases. This property of materials can be useful to fabricate devices for pulse shaping, [2] passive mode locking, [3] and eye protection against powerful lasers. [4] Typically, optical limiting happens in materials is due to reverse saturable absorption or excited state absorption. When a material is illuminated with a laser beam, it can absorb the laser light even when the incident laser energy is lower than the band gap of the material by two-photon absorption (2PA). However, in a direct band gap material in which the incident laser energy is higher than the band gap, the appreciable linear absorption induces free carrier absorption. [5] In the bulk form, most of the 2D dichalcogenides are indirect-band gap materials with conduction band minimum and valence band maximum located at Q and Γ points, respectively. [6] In the monolayer regime, the dichalcogenides The advancement in high power lasers has urged the requisite of efficient optical limiting materials for both eye and sensor protection. The discovery of atomically thin 2D transition metal dichacogenides with distinctive properties has paved the way for a variety of applications including optical limiting. Until recently, the optical limiting effect exhibited by 2D materials is inferior to the benchmark materials fullerene (C 60 ) and graphene. This article reports the optical limiting activity of the 2D transition metal dichal cogenide, titanium disulfide (TiS 2 ) nanosheets, using optical and photo acoustic zscan techniques. The 77% nonlinear optical limiting exhibited by the TiS 2 sheets with 73% lineartransmittance is superior to that of any other existing 2D dichalcogenide sheets, graphene, and the benchmark optical limiting material, C 60 . The enhanced nonlinear response is attributed to the concerted effect of 2photon and the induced excited state absorp tions. By using photoacoustic zscan, a unique tool developed to determine the nonlinear optical limiting mechanism in materials, it is found that the optical limiting exhibited by TiS 2 2D sheets and graphene are mainly due to nonlinear absorption rather than scattering effects. These results have opened the door for 2Ddichalcogenidematerialsbased highly efficient optical limiters, especially at low fluences.Since the advent of graphene, 2D materials have gained considerable attention owing to their incredible electrical and optical properties. Current efforts to utilize the unique features of these materials have been focused on their integration into a vast array of electrooptical applications. These include but are [+] Present address:
The "ion-dipole" interaction has been the most widely accepted mechanism for the direct formation of polar phases (β, γ) of poly(vinylidene fluoride) (PVDF), which have been widely used as transducers, actuators, and sensors. However, the type of charged ions is still controversial. In order to throw light upon this issue, two types of charged small organic molecules that are in different physical states (melt or solid) during the crystallization of PVDF were melt-blended with PVDF resin. Results revealed that only the incorporation of positive charged molecules can lead to the formation of polar phases. Additionally, it is interesting to find that during the crystallization of PVDF, molten positively charged molecules resulted in β-phase dominating, while solid positively charged molecules exclusively induced γ-phase. These results lead to the understanding that the induced formation of polar phases of PVDF is due to the "positive ion-CF2 dipole" interaction.
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