Thermal stability of Mg_2Si_(0.4)Sn_(0.6) in inert gases and atomic-layer-deposited Al_2O_3 thin film as a protective coating

Mg_2Si_(1−x)Sn_x solid solutions are promising thermoelectric materials to be applied in vehicle waste-heat recovery. Their thermal stability issue, however, needs to be addressed before the materials can be applied in practical thermoelectric devices. In this work, we studied the crystal structure and chemical composition of Mg_2Si_(1−x)Sn_x in inert gas atmosphere up to 823 K. We found that the sample was oxidized even in high-purity inert gases. Although no obvious structural change has been found in the slightly oxidized sample, carrier concentration decreased significantly since oxidation creates Mg vacancies in the lattice. We demonstrated that an atomic-layer deposited Al_2O_3 coating can effectively protect Mg_2Si_(1−x)Sn_x from oxidation in inert gases and even in air. In addition, this Al_2O_3 thin film also provides in situ protection to the Sb-doped Mg_2Si_(1−x)Sn_x samples during the laser-flash measurement and therefore eliminates the measurement error that occurs in uncoated samples as a result of sample oxidation and graphite exfoliation issues

SnS2 quantum dots: facile synthesis, properties and applications in ultraviolet photodetector

Tin sulfide quantum dots (SnS2 QDs) are n-type wide band gap semiconductor. They exhibit a high optical absorption coefficient and strong photoconductive property in the ultraviolet and visible regions. Therefore, they have been found to have many potential applications, such as gas sensors, resistors, photodetectors, photocatalysts, and solar cells. However, the existing preparation methods for SnS2 QDs are complicated and require a high temperature and high pressure environment; hence they are unsuitable for large-scale industrial production. An effective method for the preparation of monodispersed SnS2 QDs at normal temperature and pressure will be discussed in this paper. The method is facile, green, and low-cost. In this work, the structure, morphology, optical, electrical, and photoelectric properties of SnS2 QDs are studied. The synthesized SnS2 QDs are homogeneous in size and exhibit good photoelectric performance. A photoelectric detector based on the SnS2 QDs is fabricated and its J-V and C-V characteristics are also studied. The detector responds under λ=365 nm light irradiation and reverse bias voltage. Its detectivity approximately stabilizes at 1011 Jones at room temperature. These results show the possible use of SnS2 QDs in photodetectors

Regulation of IFN-γ-mediated PD-L1 expression by MYC in colorectal cancer with wild-type KRAS and TP53 and its clinical implications

Introduction: In the tumor microenvironment, interferon gamma (IFN-γ) secreted by tumor infiltrating lymphocytes can upregulate programmed cell death 1 ligand 1 (PD-L1) expression in many cancers. The present study evaluated the expression of PD-L1 in selected colorectal cancer cell lines with IFN-γ treatment and explored the correlation between programmed cell death 1 ligand 1 expression and KRAS/TP53 mutation status.Methods: The selected colorectal cancer cell lines had known KRAS mutations or TP53 mutations. TCGA data analysis were used to investigate the correlation between overall survival of patient with anti-PD-1/PD-L1 immunotherapy and KRAS/TP53 mutation status. Besides, the correlation between PD-L1 expression and KRAS/TP53 mutation status were also investigated by using TCGA data analysis. In vitro experiments were used to explore the mechanism underlying KRAS- and TP53-related PD-L1 expression.Results: Firstly, TCGA data analysis for gene expression and overall survival and an in vitro study revealed that the wild-type KRAS/TP53 cell lines exhibited hyperresponsiveness to interferon gamma exposure and correlated with better survival in patients receiving anti-PD-1/PD-L1 treatment. Secondly, experimental data revealed that interferon gamma induced the upregulation of programmed cell death 1 ligand 1 mainly through regulating MYC in wild-type KRAS and TP53 colorectal cancers.Discussion: Our findings revealed that the response to anti-PD-1/PD-L1 cancer immunotherapy frequently happened in wild-type KRAS and TP53 colorectal cancers, which were also found to show higher programmed cell death 1 ligand 1 expression. Our results indicate that the wild-type KRAS/TP53 colorectal cancer cell lines may respond better to interferon gamma treatment, which causes increased programmed cell death 1 ligand 1 expression and may be a mechanism underlying the better responses to anti-PD-1/PD-L1 therapies in wild-type KRAS and wild-type TP53 colorectal cancer. Furthermore, the experimental results suggest that interferon gamma regulated programmed cell death 1 ligand 1 expression through the regulation of MYC, which may further affect the response to PD-1/PD-L1 cancer immunotherapy. These results suggest a novel potential treatment strategy for enhancing the efficacy of PD-1/PD-L1 blockade immunotherapy in most colorectal cancer patients

Photoresponse of polyaniline-functionalized graphene quantum dots

Polyaniline-functionalized graphene quantum dots (PANI-GQD) and pristine graphene quantum dots (GQDs) were utilized for optoelectronic devices. The PANI-GQD based photodetector exhibited higher responsivity which is about an order of magnitude at 405 nm and 7 folds at 532 nm as compared to GQD-based photodetectors. The improved photoresponse is attributed to the enhanced interconnection of GQD by island-like polymer matrices, which facilitate carrier transport within the polymer matrices. The optically tunable current–voltage (I–V) hysteresis of PANI-GQD was also demonstrated. The hysteresis magnifies progressively with light intensity at a scan range of ±1 V. Both GQD and PANI-GQD devices change from positive to negative photocurrent when the bias reaches 4 V. Photogenerated carriers are excited to the trapping states in GQDs with increased bias. The trapped charges interact with charges injected from the electrodes which results in a net decrease of free charge carriers and a negative photocurrent. The photocurrent switching phenomenon in GQD and PANI-GQD devices may open up novel applications in optoelectronics

Thermal stability of Mg_2Si_(0.4)Sn_(0.6) in inert gases and atomic-layer-deposited Al_2O_3 thin film as a protective coating

Mg_2Si_(1−x)Sn_x solid solutions are promising thermoelectric materials to be applied in vehicle waste-heat recovery. Their thermal stability issue, however, needs to be addressed before the materials can be applied in practical thermoelectric devices. In this work, we studied the crystal structure and chemical composition of Mg_2Si_(1−x)Sn_x in inert gas atmosphere up to 823 K. We found that the sample was oxidized even in high-purity inert gases. Although no obvious structural change has been found in the slightly oxidized sample, carrier concentration decreased significantly since oxidation creates Mg vacancies in the lattice. We demonstrated that an atomic-layer deposited Al_2O_3 coating can effectively protect Mg_2Si_(1−x)Sn_x from oxidation in inert gases and even in air. In addition, this Al_2O_3 thin film also provides in situ protection to the Sb-doped Mg_2Si_(1−x)Sn_x samples during the laser-flash measurement and therefore eliminates the measurement error that occurs in uncoated samples as a result of sample oxidation and graphite exfoliation issues

A novel anoikis-related gene prognostic signature and its correlation with the immune microenvironment in colorectal cancer

Background: Anoikis is a type of apoptosis associated with cell detachment. Resistance to anoikis is a focal point of tumor metastasis. This study aimed to explore the relationship among anoikis-related genes (ARGs), immune infiltration, and prognosis in colorectal cancer (CRC).Methods: The transcriptome profile and clinical data on patients with CRC were retrieved from The Cancer Genome Atlas and Gene Expression Omnibus databases. Patients were divided into two clusters based on the expression of ARGs. Differences between the two ARG molecular subtypes were analyzed in terms of prognosis, functional enrichment, gene mutation frequency, and immune cell infiltration. An ARG-related prognostic signature for predicting overall survival in patients with CRC was developed and validated using absolute value convergence and selection operator (LASSO) regression analysis. The correlation between the signature risk score and clinicopathological features, immune cell infiltration, immune typing, and immunotherapy response was analyzed. The risk score combined with clinicopathological characteristics was used to construct a nomogram to assess CRC patients’ prognosis.Results: Overall, 151 ARGs were differentially expressed in CRC. Two ARG subtypes, namely, ARG-high and ARG-low groups, were identified and correlated with CRC prognosis. The gene mutation frequency and immune, stromal, and ESTIMATE scores of the ARG-high group were higher than those of the ARG-low group. Moreover, CD8, natural killer cells, M1 macrophages, human leukocyte antigen (HLA), and immune checkpoint-related genes were significantly increased in the ARG-high group. An optimized 25-gene CRC prognostic signature was successfully constructed, and its prognostic predictive ability was validated. The high-risk score was correlated with T, N, M, and TNM stages. Risk scores were negatively correlated with dendritic cells, eosinophils, and CD4 cells, and significantly positively correlated with regulatory T cells. Patients in the high-risk group were more likely to exhibit immune unresponsiveness. Finally, the nomogram model was constructed and showed good prognostic predictive power.Conclusion: ARGs are associated with clinicopathological features and the prognosis of CRC, and play important roles in the immune microenvironment. Herein, we underpinned the usefulness of ARGs in CRC to develop more effective immunotherapy techniques