Temperature-dependent Raman spectroscopic study of ferroelastic K_2Sr(MoO_4)

Raman scattering measurements of K_2 Sr（MoO_4）2 were performed in the temperature range of 25–750？C. The Raman spectrum of the low-temperature phase α-K_2 Sr（MoO_4）2 that was obtained by first-principle calculations indicated that the Raman bands in the wavenumber region of 250–500 cm-1 are related to Mo–O bending vibrations in MoO4 tetrahedra,while the Raman bands in the wavenumber region of 650–950 cm-1 are attributed to stretching vibrations of Mo–O bonds.The temperature-dependent Raman spectra reveal that K_2 Sr（MoO_4）2 exhibits two sets of modifications in the Raman spectra at ～ 150？C and ～ 475？C, attributed to structural phase transitions. The large change of the Raman spectra in the temperature range of 150？C to 475？C suggests structural instability of the medium-temperature phase β-K_2 Sr（MoO_4）2.

4-Hydroxy phenyl Retinamide Preferentially Targets FLT3 Mutated Acute Myeloid Leukemia via ROS Induction and NF-κB Inhibition

FMS-like tyrosine kinase 3(FLT3)mutation is strongly associated with poor prognosis in acute myeloid leukemia(AML).Though many FLT3 inhibitors have been developed for clinical application with 34%-56%complete remission rate,patients would develop resistance sooner or later after initial response to tyrosine kinase inhibitors(TKIs),such as gilteritinib.And increasing studies have shown that several resistance related mutations of FLT3 emerged during the AML progression.Thus,further investigation is warranted for these FLT3mu,AML patients to achieve a better treatment outcome.4-Hydroxyphenyl retinamide(4-HPR)has been investigated extensively in animal models and clinical trials as an anticancer/chemopreventive agent and is currently used for protection against cancer development/recurrence,with minimal side effects.In this study,we performed gene-set enrichment analysis and found that down-regulated genes induced by 4-HPR were associated with FLT3-ITD gene sets.CD34+ AML stem/progenitor cells separated from 32 AML samples were treated with 4-HPR.Correlation analysis showed that AML cells with FLT3-ITD genetic alteration were more sensitive to 4-HPR treatment than those without FLT3-ITD.Next,we treated 22 primary AML cells with 4-HPR and found that 4-HPR was more toxic to AML cells with FLT3-ITD.These results indicated that 4-HPR was preferentially cytotoxic to all FLT3-ITD AML cells irrespective of stem/progenitor cells or blast cells.4-HPR-induced reactive oxygen species(ROS)production and NF-kB inhibition might be the reason of 4-HPR selectivity on FLT3 mutated AML cells.

Pressure-Induced Metallization Accompanied by Elongated S–S Dimer in Charge Transfer Insulator NiS2

The insulator-metal transition triggered by pressure in charge transfer insulator NiS2 is investigated by combining high-pressure electrical transport,synchrotron x-ray diffraction and Raman spectroscopy measurements up to40-50 GPa.Upon compression,we show that the metallization firstly appears in the low temperature region at^3.2 GPa and then extends to room temperature at^8.0 GPa.During the insulator-metal transition,the bond length of S-S dimer extracted from the synchrotron x-ray diffraction increases with pressure,which is supported by the observation of abnormal red-shift of the Raman modes between 3.2 and 7.1 GPa.Considering the decreasing bonding-antibonding splitting due to the expansion of S-S dimer,the charge gap between the S-ppπ* band and the upper Hubbard band of Ni-3 d eg state is remarkabl.y decreased.These results consistently indicate that the elongated S-S dimer plays a predominant role in the insulator-metal transition under high pressure,even though the p-d hybridization is enhanced simultaneously,in accordance with a scenario of charge-gap-controlled type.

Pressure-induced enhancement of optoelectronic properties in PtS2

PtS2, which is one of the group-10 transition metal dichalcogenides, attracts increasing attention due to its extraordinary properties under external modulations as predicted by theory, such as tunable bandgap and indirect-to-direct gap transition under strain; however, these properties have not been verified experimentally. Here we report the first experimental exploration of its optoelectronic properties under external pressure. We find that the photocurrent is weakly pressuredependent below 3 GPa but increases significantly in the pressure range of 3 GPa–4 GPa, with a maximum ～ 6 times higher than that at ambient pressure. X-ray diffraction data shows that no structural phase transition can be observed up to26.8 GPa, which indicates a stable lattice structure of PtS2 under high pressure. This is further supported by our Raman measurements with an observation of linear blue-shifts of the two Raman-active modes to 6.4 GPa. The pressure-enhanced photocurrent is related to the indirect-to-direct/quasi-direct bandgap transition under pressure, resembling the gap behavior under compression strain as predicted theoretically.

Concurrent Structural and Electronic Phase Transitions in V_(2)O_(3)Thin Films with Sharp Resistivity Change

The relationship between structural and electronic phase transitions in V_(2)O_(3)thin films is of critical importance for understanding of the mechanism behind metal–insulator transition(MIT)and related technological applications.Despite being extensively studied,there are currently no clear consensus and picture of the relation between structural and electronic phase transitions so far.Using V_(2)O_(3)thin films grown on r-plane Al2O3 substrates,which exhibit abrupt MIT and structural phase transition,we show that the electronic phase transition occurs concurrently with the structural phase transition as revealed by the electrical transport and Raman spectra measurements.Our result provides experimental evidence for clarifying this issue,which could form the basis of theoretical studies as well as technological applications in V_(2)O_(3).

Transforming a Two-Dimensional Layered Insulator into a Semiconductor or a Highly Conductive Metal through Transition Metal Ion Intercalation

Atomically thin two-dimensional(2D) materials are the building bricks for next-generation electronics and optoelectronics, which demand plentiful functional properties in mechanics, transport, magnetism and photoresponse.For electronic devices, not only metals and high-performance semiconductors but also insulators and dielectric materials are highly desirable. Layered structures composed of 2D materials of different properties can be delicately designed as various useful heterojunction or homojunction devices, in which the designs on the same material(namely homojunction) are of special interest because preparation techniques can be greatly simplified and atomically seamless interfaces can be achieved. We demonstrate that the insulating pristine ZnPS_3, a ternary transition-metal phosphorus trichalcogenide, can be transformed into a highly conductive metal and an n-type semiconductor by intercalating Co and Cu atoms, respectively. The field-effect-transistor(FET) devices are prepared via an ultraviolet exposure lithography technique. The Co-ZnPS_3 device exhibits an electrical conductivity of 8 × 10^(4) S/m, which is comparable to the conductivity of graphene. The Cu-ZnPS_3 FET reveals a current ON/OFF ratio of 1-05 and a mobility of 3 × 10^(-2 )cm^(2)·V^(-1)·s^(-1). The realization of an insulator, a typical semiconductor and a metallic state in the same 2D material provides an opportunity to fabricate n-metal homojunctions and other in-plane electronic functional devices.

Lepithiohydimerins A-D:Four Pairs of Neuroprotective Thiohydantoin Dimers Bearing a Disulfide Bond from Maca(Lepidium meyenii Walp.)

Main observation and conclusion An HPLC-UV-guided separation was performed and four pairs of unprecedented macathiohydantoin dimers,lepithiohydimerins A—D(1—4)bearing a rare disulfide bond were isolated from the tubers of Maca.Their structures were unambiguously confirmed by NMR spectroscopic,X-ray crystallographic and electronic circular dichroism(ECD)analyses.At the concentration of 20μmol/L,compounds 2-1,2-2,and 4-1 increased the viability of PC12 cells with the cell viability at(72.06±1.14)%,(72.64±1.49)%,and(70.93±1.22)%,respectively.Furthermore,the serial concentration experiment showed that they can protect PC12 cells in a dose-dependent manner.

Dy_(2-x)Y_xTi_2O_7: phonon vibration and magnetization with dilution

In this paper, the dilution effects of non-magnetic Y ions on spin-ice compound Dy_2Ti_2O_7 by infrared and Raman spectra and magnetization measurements were investigated. An anomalous phonon softening with temperature decreasing is found in both the parent and diluted compounds, and Y doping can relax the softening of phonons except that of the IR mode near 233 cm^-1, indicating a strong phonon–phonon coupling in the spin-ice material.The magnetization measurements reveal that the nonmagnetic impurities do not severely influence the spin-ice rules in the ground state when the level of dilution is not very high. However, a large amount of dilution enhance the disorder and break the spin-ice state because the collective spin-flip clusters are no longer available.

Laser ablation assisted spark induced breakdown spectroscopy and its application

Recently,laser ablation assisted spark induced breakdown spectroscopy(LA-SIBS)has been growing rapidly and continue to be extended to a broad range of materials analysis.Characterized by employ-ing a speifically designed high voltage and pulse discharge cireuit to generate a spark and used to enhance plasma emission produced by laser ablation,allows direct analysis of materials without prior sample preparation.This paper reviews recent development and application of laser ablation assisted spark induced breakdown spectrosoopy for material analysis.Following a summary of fundamentals and instrumentation of the LA-SIBS analytical techmique,the development and applications of laser ablation assisted spark induced breakdown spectroscopy for the analysis of conducting materials and insulating materials is described.