Breakdown of Raman selection rules by Frohlich interaction in few-layer WS_(2)

The polarization selection rule of Raman scattering is crucial in symmetry analysis of elementary excitations in semiconductors and correlated electron systems.Here we reported the observation of breakdown of Raman selection rules in few-layer WS_(2) by using resonant Raman spectroscopy.When the excitation energy is close to the dark A exciton state,we observed some infrared active modes and backscattering forbidden modes.Importantly,we found that all observed phonon modes follow the same paralleled-polarization behavior.According to the electron-phonon coupling near the band edge in WS_(2),we proposed a theoretical model based on the intraband Frohlich interaction.In this case,the polarization response of the scattering signal is no longer determined by the original Raman tensor of scattered phonons.Instead,it is determined by a new isotropic Raman tensor that generated from this intraband Frohlich interaction between dark A exciton and phonons.We found that this theoretical model is in excellent agreement with the observed results.The breakdown of Raman selection rules can violate the conventional limitations of the optical response and provide an effective method to control the polarization of Raman scattering signals in two-dimensional materials.

Nucleolar protein 6 promotes cell proliferation and acts as a potential novel prognostic marker for hepatocellular carcinoma

Background:Nucleolar protein 6(NOL6)is a nucleolar RNA-associated protein that is highly conserved between species.It has been proved to be associated with the prognosis of liver cancer.However,the underlying mechanism has not been fully established.This study aimed to assess the relationship between NOL6 and liver cancer prognosis.Methods:We constructed anNOL6-short hairpin RNA(shRNA)-expressing lentivirus.Through viral transfection,cell growth assay and fluorescence-activated cell sorting,we evaluated the effect of shRNA-mediatedNOL6 knockdown on the proliferation,colony formation,and apoptosis of hepatocellular carcinoma(HCC)cells.The relationship betweenNOL6 expression and HCC patient survival has been established through bioinformatics analysis.We also explored the downstream molecular regulatory network ofNOL6 in HCC by performing an Ingenuity Pathway Analysis in the database.Results:IncreasedNOL6 expression was detected in HCC cells compared to normal controls;HCC patients with highNOL6 expression had poorer prognoses than those with low expression.NOL6 knockdown inhibited HCC cell proliferation,apoptosis,and colony formation.Also,MAPK8,CEBPA,andFOSL1 were selected as potential downstream genes ofNOL6.Conclusions:NOL6 up-regulates HCC cell proliferation and affects downstream expression of related genes.Moreover,NOL6 is considered to be associated with poor prognosis in HCC patients.

Spectroscopic and electrochemical properties of Cu-dicyandiamide complex

Dicyandiamide(DICY) is a common ligand that exhibits low toxicity but can irritate the skin and eyes and cause methemoglobinemia on long-term exposure. Crystalline Cu-dicyandiamide(Cu-DICY) was obtained via facile synthesis and its molecular structure and theoretical Raman spectra were simulated by using density functional theory(DFT). The results suggested that the Cu^(2+) coordinates with two H_2 O molecules and two different DICY molecules(an imino DICY and an amino DICY). The stability constants of Cu-DICY were calculated, and the electrochemical properties were studied. Two electrochemical redox processes occur in Cu-DICY in an aqueous solution: a reversible reaction with a formal potential of 0.2 V vs.MSE and an irreversible reaction between –0.4 and –1.2 V vs. MSE. The standard rate constant k0 for the reversible reaction was estimated to be 7.6×10^(-3) cm/s. In addition, based on the reversible reaction of Cu-DICY, square wave voltammetry was used to rapidly determine the concentration of Cu(II) and the detection limit was 66.7 μg/L, which satisfies the detection limit requirements for copper in tap water(2 mg/L) as provided by the World Health Organization.