The phase transition through local strain engineering is an exciting avenue for controlling electronic, magnetic properties and catalyst activity of materials but complex phenomenon in nanoscience. Herein, we demonstrate the first combinations of bending strain and 2H/1T phase transition by rolling up MoS sheets for improving catalytic activity in relatively inert basal plane surfaces and promoting electron transfer from the less-conducting 2H MoS sheets to the electrodes. Furthermore, we generate various MoS@Pt nanoparticle hybrids nanomaterials and especially MoS@Pt scrolls containing the coverage of Pt NPs (8.3 wt%) have a high catalytic activity (39 mV per decade). The rolled up MoS@Pt sheets with bending strain (2.4%) provide an intra-layer plane gliding that allows the transversal displacement of an S plane from the 2H to the 1T phases (28%). This unique combination also allows us to maximize the intrinsic HER activity among molybdenum-sulfide based catalysts.
Controlling phase transitions through local strain engineering is an exciting avenue for tailoring the electronic and magnetic properties of materials at the nanoscale. Herein, we demonstrate a tunable semiconducting to metallic phase transition of two-dimensional transition metal dichalcogenides using strain engineering through rolled up MoS sheets (named as MoS scrolls). A phase incorporated structure for MoS nanoscrolls containing the maximum concentration of 1T phase (∼58%) with high thermal stability up to 473 K can be produced by a gliding-rolling process for the S plane. These phase transitions are irreversible by virtue of the van der Waals interaction between the layers of the nanoscrolls, which is relatively stronger than the bending strain. A high concentration of the 1T phase can tune the bandgap through temperature, and also the magnetic property from nonmagnetic to paramagnetic MoS. This study, which is able to control phase transitions by strain engineering in the field of 2D materials, proves an exciting avenue for tailoring the novel functional properties of low-dimensional materials.
Bio-based polycarbonates containing cyclic ketal moieties were designed, and the bio-based diol monomer was synthesized by CQ with glycerol to improve their thermal properties and replace BPA in polymer industry. The molecular structure of the novel bio-based diol monomer 2,2:3,3-bis(4′-hydroxymethylethylenedioxy)-1,7,7-trimethylbicyclo[2.2.1]heptane (abbreviated as CaG) was analyzed by 1 H, 13 C, and 2D-COSY NMR techniques. GPC results show that CaG was reacted successfully and led to the high molecular weights for homopolycarbonate (M w = 18 652) abbreviated as PCaGC and for copolycarbonate (M w = 78 482) as PCaG 20 BPA 80 C. The high thermal stability (T d value above 350°C) and glass transition temperature (T g value from 128 to 151°C) of PCaGCs and PCaG x BPA y Cs were studied by TGA and DSC, respectively. Given the sufficient reactivity and high thermal stability, CaG is a promising renewable building block for applicable polymers.
We report that a high local strain was obtained for multilayer MoS nanoscrolls decorated with noble nanoparticles (Ag and Au NPs) using a rolling process beyond breaking or slipping of MoS. The local strain was estimated through the bending strain in the nanoscrolls and the extent of coverage of Ag and Au NPs decorated on MoS, exhibiting magnified surface-enhanced Raman scattering. TEM images showed that the MoS-Ag and MoS-Au nanoscrolls have a tube-like morphology decorated with NPs on the inner and outer sides of the MoS nanoscrolls. In the Raman spectra, we confirmed the red shift and broadness of the FWHM for nanoscrolls in the eigenvectors of the [Formula: see text] and [Formula: see text] modes. From the Grüneisen parameter γ and the shear deformation potential β, we obtained peak shifts of ∼4.9 cm/% at [Formula: see text] and ∼1.1 cm/% strain at [Formula: see text] for free-standing MoS. According to the obtained relationship of the Raman shift and the induced uniaxial tensile strain, the [Formula: see text] and [Formula: see text] peaks shifted upwards to around -12.8 cm and -2.9 cm, respectively, and can be converted to an induced uniaxial tensile strain of about 2.6% for MoS-Ag nanoscrolls.
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