Graphene-Thickness-Dependent Graphene-Enhanced Raman Scattering

Graphene-enhanced Raman scattering (GERS), enhancing Raman signals on graphene surface, is an excellent approach to investigate the properties of graphene via the Raman enhancement effect. In the present study, we studied the graphene-thickness dependent GERS in detail. First, by keeping molecule density on few-layer graphene using vacuum thermal deposition method, GERS enhancement was found to be the same for all graphene layers (one to six layers). While adsorbing probe molecules by solution soaking, the GERS enhancing factor was different on monolayer and bilayer graphene. By soaking in low concentration solutions, the GERS intensity on bilayer graphene was stronger than that on monolayer graphene, whereas by soaking under high concentration solutions, the GERS intensity difference was much less for that on monolayer and on bilayer. Molecule density, molecular configuration, and GERS enhancing factor are further discussed for molecules on monolayer and bilayer graphene. It was finally concluded that the abnormal graphene-thickness dependence of GERS between monolayer and bilayer graphene was attributed to the different enhancement for GERS on monolayer and bilayer graphene. Monolayer and bilayer graphene have different electronic structure and then doping effect of probe molecules, which shifts the Fermi level of graphenes differently. As a result, monolayer and bilayer graphene have different energy band matching with the probe molecules, yielding different chemical enhancement

Enhanced SERS Stability of R6G Molecules with Monolayer Graphene

In this work, we used monolayer graphene, either underneath or on top of the R6G molecules, to enhance the stability and reproducibility of surface enhanced Raman spectroscopy (SERS). The time evolution of characteristic peaks of the organic molecules was monitored using Raman spectroscopy under continuous light irradiation to quantitatively characterize the photostability. Graphene underneath the organic molecules inhibits the substrate-induced fluctuations; and graphene on top of the organic molecules encapsulates and isolates them from ambient oxygen, greatly enhancing the photostability. Our results showed that the average lifespan of R6G molecules with graphene encapsulation can be increased by about 6-fold under high laser power density (3.67 × 10⁶ W/cm²) and is less dependent on the power density of light irradiation

Image_1_SOX13 is a novel prognostic biomarker and associates with immune infiltration in breast cancer.tif

BackgroundThe transcription factor, SOX13 is part of the SOX family. SOX proteins are crucial in the progression of many cancers, and some correlate with carcinogenesis. Nonetheless, the biological and clinical implications of SOX13 in human breast cancer (BC) remain rarely known.MethodsWe evaluated the survival and expression data of SOX13 in BC patients via the UNLCAL, GEPIA, TIMER, and Kaplan-Meier plotter databases. Immunohistochemistry (IHC) was used to verify clinical specimens. The gene alteration rates of SOX13 were acquired on the online web cBioportal. With the aid of the TCGA data, the association between SOX13 mRNA expression and copy number alterations (CNA) and methylation was determined. LinkedOmics was used to identify the genes that co-expressed with SOX13 and the regulators. Immune infiltration and tumor microenvironment evaluations were assessed by ImmuCellAI and TIMER2.0 databases. SOX13 correlated drug resistance analysis was performed using the GDSC2 database.ResultsHigher SOX13 expression was discovered in BC tissues in comparison to normal tissues. Moreover, increased gene mutation and amplification of SOX13 were found in BC. Patients with increased SOX13 expression levels showed worse overall survival (OS). Cox analysis showed that SOX13 independently served as a prognostic indicator for poor survival in BC. Further, the expression of SOX13 was also confirmed to be correlated with tumor microenvironment and diverse infiltration of immune cells. In terms of drug sensitivity analysis, we found higher expression level of SOX13 predicts a high IC50 value for most of 198 drugs which predicts drug resistance.ConclusionThe present findings demonstrated that high expression of SOX13 negatively relates to prognosis and SOX13 plays an important role in cancer immunity. Therefore, SOX13 may potentially be adopted as a biomarker for predicting BC prognosis and infiltration of immune cells.</p

Forest plot of WMDs for the comparison between dental age using Demirjian’s method and chronological age among boys (A) and girls (B).

<p>Forest plot of WMDs for the comparison between dental age using Demirjian’s method and chronological age among boys (A) and girls (B).</p

Table_1_SOX13 is a novel prognostic biomarker and associates with immune infiltration in breast cancer.docx

BackgroundThe transcription factor, SOX13 is part of the SOX family. SOX proteins are crucial in the progression of many cancers, and some correlate with carcinogenesis. Nonetheless, the biological and clinical implications of SOX13 in human breast cancer (BC) remain rarely known.MethodsWe evaluated the survival and expression data of SOX13 in BC patients via the UNLCAL, GEPIA, TIMER, and Kaplan-Meier plotter databases. Immunohistochemistry (IHC) was used to verify clinical specimens. The gene alteration rates of SOX13 were acquired on the online web cBioportal. With the aid of the TCGA data, the association between SOX13 mRNA expression and copy number alterations (CNA) and methylation was determined. LinkedOmics was used to identify the genes that co-expressed with SOX13 and the regulators. Immune infiltration and tumor microenvironment evaluations were assessed by ImmuCellAI and TIMER2.0 databases. SOX13 correlated drug resistance analysis was performed using the GDSC2 database.ResultsHigher SOX13 expression was discovered in BC tissues in comparison to normal tissues. Moreover, increased gene mutation and amplification of SOX13 were found in BC. Patients with increased SOX13 expression levels showed worse overall survival (OS). Cox analysis showed that SOX13 independently served as a prognostic indicator for poor survival in BC. Further, the expression of SOX13 was also confirmed to be correlated with tumor microenvironment and diverse infiltration of immune cells. In terms of drug sensitivity analysis, we found higher expression level of SOX13 predicts a high IC50 value for most of 198 drugs which predicts drug resistance.ConclusionThe present findings demonstrated that high expression of SOX13 negatively relates to prognosis and SOX13 plays an important role in cancer immunity. Therefore, SOX13 may potentially be adopted as a biomarker for predicting BC prognosis and infiltration of immune cells.</p

Chiral Structure Determination of Aligned Single-Walled Carbon Nanotubes on Graphite Surface

Chiral structure determination of single-walled carbon nanotube (SWNT), including its handedness and chiral index (<i>n</i>,<i>m</i>), has been regarded as an intractable issue for both fundamental research and practical application. For a given SWNT, the <i>n</i> and <i>m</i> values can be conveniently deduced if an arbitrary two of its three crucial structural parameters, that is, diameter <i>d</i>, chiral angle θ, and electron transition energy <i>E</i>_<i>ii</i>, are obtained. Here, we have demonstrated a novel approach to derive the (<i>n</i>,<i>m</i>) indices from the θ, <i>d</i>, and <i>E</i>_<i>ii</i> of SWNTs. Handedness and θ were quickly measured based on the chirality-dependent alignment of SWNTs on graphite surface. By combining their measured <i>d</i> and <i>E</i>_<i>ii</i>, (<i>n</i>,<i>m</i>) indices of SWNTs can be independently and uniquely identified from the (θ,<i>d</i>) or (θ,<i>E</i>_<i>ii</i>) plots, respectively. This approach offers intense practical merits of high-efficiency, low-cost, and simplicity

Growth of MoS_{2(1–<i>x</i>)}Se_2<i>x</i> (<i>x</i> = 0.41–1.00) Monolayer Alloys with Controlled Morphology by Physical Vapor Deposition

Transition-metal dichalcogenide (TMD) monolayer alloys are a branch of two-dimensional (2D) materials which can have large-range band gap tuning as the composition changes. Synthesis of 2D TMD monolayer alloys with controlled composition as well as controlled domain size and edge structure is of great challenge. In the present work, we report growth of MoS_{2(1–<i>x</i>)}Se_2<i>x</i> monolayer alloys (<i>x</i> = 0.41–1.00) with controlled morphology and large domain size using physical vapor deposition (PVD). MoS_{2(1–<i>x</i>)}Se_2<i>x</i> monolayer alloys with different edge orientations (Mo-zigzag and S/Se-zigzag edge orientations) have been obtained by controlling the deposition temperature. Large domain size of MoS_{2(1–<i>x</i>)}Se_2<i>x</i> monolayer alloys (<i>x</i> = 0.41–1.00) up to 20 μm have been obtained by tuning the temperature gradient in the deposition zone. Together with previously obtained MoS_{2(1–<i>x</i>)}Se_2<i>x</i> monolayer alloys (<i>x</i> = 0–0.40), the band gap photoluminescence (PL) is continuously tuned from 1.86 eV (<i>i.e.</i>, 665 nm, reached at <i>x</i> = 0.00) to 1.55 eV (<i>i.e.</i>, 800 nm, reached at <i>x</i> = 1.00). Additionally, Raman peak splitting was observed in MoS_{2(1–<i>x</i>)}Se_2<i>x</i> monolayer alloys. This work provides a way to synthesize MoS_{2(1–<i>x</i>)}Se_2<i>x</i> monolayer alloys with different edge orientations, which could be benefit to controlled growth of other 2D materials

Chemical Vapor Deposition and Raman Spectroscopy of Two-Dimensional Antiferromagnetic FeOCl Crystals

Chemical vapor deposition (CVD) and probing magnetic properties of atomically thin two-dimensional (2D) materials are of great interest for future information devices. Here, we report a CVD growth of 2D FeOCl crystals and a Raman spectroscopic study of the magnetic phase transition. 2D FeOCl crystals with different thicknesses have been grown on mechanically exfoliated h-BN by using KMnO4 and FeCl3 as precursors. Raman scattering has been conducted on the chemically grown FeOCl thin crystals, which can probe the magnetic orderings in various ways, such as quasi-particle scattering, quasi-elastic scattering (QES), magneto-optical effect, and so on. Under an external magnetic field, the Ag phonon modes have shown a linear relationship of B/ρ to B2 (B is the external magnetic field and ρ is the degree of Raman circular polarization), which supports the calculated magnetic point group of m′m′m in FeOCl thin crystals below TN. Other magnetic Raman features, including quasi-elastic scattering and two-magnon scattering, have been observed, which gives information about the magnetic specific heat and magnetic excitations, respectively. At last, temperature-dependent and thickness-dependent Raman spectroscopic measurements have shown a robust paramagnetic–antiferromagnetic (PM–AFM) phase transition in FeOCl thin crystals

Observation of Low-Frequency Combination and Overtone Raman Modes in Misoriented Graphene

Stacking disorder will significantly modify the optical properties and interlayer coupling stretch of few-layer graphene. Here, we report the observation of the Raman breathing modes in the low-frequency range of 100–200 cm^–1 in misoriented few-layer graphene on a SiO₂/Si substrate. Two dominant Raman modes are identified. The one at ∼120 cm^–1 is assigned as the E_g + ZO′ combination mode of the in-plane shear and the out-of-plane interlayer optical phonon breathing modes. Another peak at ∼182 cm^–1 is identified as the overtone mode 2ZO′. The appearance of these Raman modes for different twist angles indicates that stacking disorder in few-layer graphene significantly alters the Raman feature, especially for those combination modes containing the interlayer breathing mode. Further investigation shows that the two Raman vibrational modes (∼120 and ∼182 cm^–1) are strongly coupled to the excitation laser energy, but their frequencies are independent of the number of graphene layers before folding. The present work provides a sensitive way to study the phonon dispersion, electron–phonon interaction, and electronic band structure of misoriented graphene layers

Graphene–Organic Two-Dimensional Charge-Transfer Complexes: Intermolecular Electronic Transitions and Broadband Near-Infrared Photoresponse

Charge-transfer (CT) complexes with unique intermolecular electronic transitions have attracted broad interest and hold great potential in optoelectronic applications. Here, we report a new family of two-dimensional graphene-organic molecule CT complexes. Density functional theory (DFT) calculation has revealed low-energy CT bands in the near-infrared (NIR) region up to 2000 nm for graphene-TCNQ (tetracyanoquinodimethane), graphene-F₄TCNQ (2,3,5,6-Tetrafluoro-tetracyanoquinodimethane) and graphene-TCOQ (tetrachloro-o-benzoquinone) complexes. Raman and electrical measurements have confirmed a partial charge transfer between graphene and the molecules at the ground state. CT excitations have been calculated by DFT and verified by optoelectronic measurements. The graphene–organic CT complexes have shown a broadband photoresponse from the visible to NIR range, attributed to the intermolecular electronic transitions. Further, the photoresponsivity (up to 10³ A/W) suggests a high photoelectrical gain arising from the photogating effect at the graphene/molecule interface. At last, the photoresponse property of the graphene–organic CT complexes can be tuned by electrical gating of graphene