Deep Learning Enabled SERS Identification of Gaseous Molecules on Flexible Plasmonic MOF Nanowire Films.

Through the capture of a target molecule at the metal surface with a highly confined electromagnetic field induced by surface plasmon, surface enhanced Raman spectroscopy (SERS) emerges as a spectral analysis technology with high sensitivity. However, accurate SERS identification of a gaseous molecule with low density and high velocity is still a challenge due to its difficulty in capture. In this work, a flexible paper-based plasmonic metal-organic framework (MOF) film consisting of Ag nanowires@ZIF-8 (AgNWs@ZIF-8) is fabricated for SERS detection of gaseous molecules. Benefiting from its micronanopores generated by the nanowire network and ZIF-8 shell, the effective capture of the gaseous molecule is achieved, and its SERS spectrum is obtained in this paper-based flexible plasmonic MOF nanowire film. With optimal structure parameters, spectra of gaseous 4-aminothiophenol, 4-mercaptophenol, and dithiohydroquinone demonstrate that this film has good SERS performance, which could maintain obvious Raman signals within 30 days during reproducible detection. To realize SERS identification of gaseous molecules, deep learning is performed based on the SERS spectra of the mixed gaseous analyte obtained in this flexible porous film. The results point out that an artificial neural network algorithm could identify gaseous aldehydes (gaseous biomarker of colorectal cancer) in simulated exhaled breath with high accuracy at 93.7%. The integration of the flexible paper-based film sensors with deep learning offers a promising new approach for noninvasive colorectal cancer screening. Our work explores SERS applications in gaseous analyte detection and has broad potential in clinical medicine, food safety, environmental monitoring, etc.

Investigation of Temperature-Dependent Phonon Anharmonicity and Thermal Transport in SnS Single Crystals.

Tin sulfide has outstanding thermoelectric properties in the b-axis direction of crystallography as a IV-VI group layered compound, which arouses great attention. In this study, temperature-dependent Raman spectroscopy (TDRS) is used to quantify the phonon anharmonicity in SnS crystals from 77 to 475 K, where the three-phonon process dominates in this temperature region. Moreover, integration of the four-phonon process and lattice thermal expansion will better describe the temperature-dependent Raman experimental phenomenon. The good agreement between the calculated and experimental lattice thermal conductivity confirms the three-phonon scattering process is the dominant scattering mechanism at this temperature range. Further, combining the atomic thermal displacement and charge density through density functional theory calculation, the inherently low thermal conductivity of SnS is because of strong lattice anharmonicity, which is brought by the presence of asymmetric chemical bonding resulting from the Sn 5s2 lone pair electrons. These results provide key insights for studying thermal properties of other low-dimensional materials.

Manipulating the surface states of BiVO4 through electrochemical reduction for enhanced PEC water oxidation.

Bismuth vanadate (BiVO4) is a prospective candidate for photoelectrochemical (PEC) water oxidation, but its commercial application is limited due to the serious surface charge recombination. In this work, we propose a novel and effective electrochemical reduction strategy combined with co-catalyst modification to manipulate the surface states of the BiVO4 photoanode. Specifically, an ultrathin amorphous structure is formed on the surface of BiVO4 after electrochemical reduction ascribed to the breaking of the surface metal-O bonds. Photoelectrochemical measurements and first-principles calculation show that the electrochemical reduction treatment can effectively reduce the surface energy, thereby passivating the recombined surface states (r-ss) and increasing the mobility of photogenerated holes. In addition, the FeOOH co-catalyst layer further increases the intermediate surface states (i-ss) of BiVO4, stabilizes the surface structure and enhances its PEC performance. Benefiting from the superior charge transfer efficiency and the excellent water oxidation kinetics, the -0.8/BVO/Fe photoanode achieves 2.02 mA cm-2 photocurrent at 1.23 VRHE (2.4 times that of the original BiVO4); meanwhile, the onset potential shifts 90 mV to the cathode. These results provide a new surface engineering tactic to modify the surface states of semiconductor photoanodes for high-efficiency PEC water oxidation.

Functionalized polymer modified buried interface for enhanced efficiency and stability of perovskite solar cells.

Although great progress has been made in perovskite solar cells (PCSs), further development of PCSs is hindered by a large number of defects, nonradiative recombination, and mysterious stresses. Here, we propose a new interfacial strategy by introducing a new polymer material named povidone-iodine (PV-I) as a buffer layer. A series of studies indicate that the introduced buffer layer can form a strong chemical interaction with SnO2 and the perovskite, which can not only passivate the defects of the two functional layers but also strengthen the interfacial connection. The reduction of film defects and the enhancement of interface connection are beneficial to the extraction and transport of the carrier. In addition, the introduction of a buffer layer releases the interfacial stress. Ultimately, we achieved attractive efficiency (22.02%, 0.1 cm2) and considerable long-term stability (after aging 500 h, the target device still retains 81% of its original PCE). The excellent performance of the device indicates that this strategy can be used as an effective control method for perovskite solar cells to facilitate their commercialization.

C-H Diselenation and Monoselenation of Electron-Deficient Alkenes via Radical Coupling at Room Temperature.

A new, simple, and metal-free route for the diselenation of maleimides has been first developed employing (bis(trifluoroacetoxy)iodo)benzene (PIFA) at room temperature. The present method is compatible with different functional groups, and various diselenyl maleimides were obtained in moderate to excellent yields. Moreover, this protocol further highlights the unique practical application for the functionalization of biologically relevant molecules and amino acid derivatives. Preliminary mechanism studies suggest that radicals may be involved in this novel transformation. Additionally, this protocol is also applicable for the monoselenation of maleimides by switching the reaction conditions and selenation of other electron-deficient alkenes.

Photocatalysis triggered CVD synthesis of graphene at low temperature.

Conceiving the coupling strategy of photothermal catalysis, in which a CeO2 based photocatalyst facilitates the conversion of CH4 into hydrocarbon species with light irradiation and hydrocarbon species act for the subsequent CVD growth, high quality graphene has been successfully synthesized at 700 °C by photocatalysis triggered CH4-CVD over a Cu substrate.

Organocatalytic Asymmetric Construction of Tetrasubstituted Carbon Stereocenters Bearing Three Heteroatoms via Intramolecular Cyclization of Vinylidene ortho-Quinone Methide with Imidates.

We report herein an organocatalytic asymmetric protocol for the construction of tetrasubstituted carbon stereocenters bearing three heteroatoms. The reaction proceeded via the enantioselective intramolecular cyclization reaction of vinylidene ortho-quinone methide (VQM) with imidates to form pentacyclic heterocycles. The formed tetrasubstituted carbon center was stable under a high temperature and the conditions for further transformations.

A Dual-Ligand Strategy to Regulate the Nucleation and Growth of Lead Chromate Photoanodes for Photoelectrochemical Water Splitting.

Photoelectrochemical (PEC) water splitting for renewable hydrogen production has been regarded as a promising solution to utilize solar energy. However, most photoelectrodes still suffer from poor film quality and poor charge separation properties, mainly owing to the possible formation of detrimental defects including microcracks and grain boundaries. Herein, a molecular coordination engineering strategy is developed by employing acetylacetone (Acac) and poly(ethylene glycol) (PEG) dual ligands to regulate the nucleation and crystal growth of the lead chromate (PbCrO4 ) photoanode, resulting in the formation of a high-quality film with large grain size, well-stitched grain boundaries, and reduced oxygen vacancies defects. With these efforts, the nonradiative charge recombination is efficiently suppressed, leading to the enhancement of its charge separation efficiency from 47% to 90%. After decorating with Co-Pi cocatalyst, the PbCrO4 photoanode achieves a photocurrent density of 3.15 mA cm-2 at 1.23 V (vs RHE under simulated AM1.5G) and an applied bias photon-to-current efficiency (ABPE) of 0.82%. This work provides a new strategy to modulate the nucleation and growth of high-quality photoelectrodes for efficient PEC water splitting.

In-situ micro-Raman study of SnSe single crystals under atmosphere: Effect of laser power and temperature.

Single crystal of tin selenide (SnSe) was studied by micro-Raman spectroscopy under atmosphere conditions. The effect of varying the incident laser power on the sample up to 2 mW was analyzed. The Raman spectra showed that the number of all vibrational modes have not decreased or increased, but all peaks red-shifted and softened obviously as the laser power increased to the threshold value. The temperature-dependent micro-Raman study of the single crystal was carried out for illustrating thermal effect due to the high incident laser power. A new SnSe2 phase appeared at high temperature without vacuum and become the dominant phase at the surface of the crystal gradually because of oxidation. Detecting few amounts of SnSe2 crystals on the surface of single crystal shows the high sensitivity of Raman spectroscopy. High resolution transmission electron microscopy (HRTEM) was also used to confirm that the newly generated SnSe2 phase is precipitated by SnSe under high temperature oxidation conditions. To study the Raman spectra of low thermal conductivity materials under high temperature and non-vacuum conditions, lower incident laser power should be used to avoid the influence of additional thermal effects.

Revealing the anisotropic phonon behaviours of layered SnS by angle/temperature-dependent Raman spectroscopy.

Tin sulfide (SnS), a IV-VI group layered compound, has attracted much attention because of its excellent thermoelectric properties along the crystallographic b-axis. However, there are few reports on the identification of its in-plane orientation. We observe a strong anisotropy of the in-plane Raman signal in bulk SnS. With the help of ab initio calculations, the vibrational symmetry of each observed Raman mode in the cleaved (00l)-plane is consistent with the experimental values. The angle-resolved polarized Raman spectroscopy, combined with electron backscattered diffraction technology, is utilized to systematically investigate the in-plane anisotropy of the phonon response and then determine the in-plane orientation. Furthermore, the temperature-dependent and laser-power-dependent Raman scattering analyses reveal that the adjacent layers in the SnS crystals show a relatively weak van der Waals interaction. These findings could provide much-needed experimental information for future applications related to the anisotropic transport properties of SnS single crystals.

Phase-Transfer Catalyzed Asymmetric [4 + 1] Annulations for the Synthesis of Chiral 2,2-Disubstituted Tetrahydrothiophenes.

An efficient catalytic asymmetric [4 + 1] reaction, which features the use of simple ß-keto esters as one-carbon nucleophiles and 5-succinimidothio-pent-2-enoates as four-atom bielectrophiles, has been developed in the presence of a bifunctional chiral phase-transfer catalyst. The new annulation provides a distinct protocol to access the functionalized 2-acyl-2-carboxyl tetrahydrothiophenes bearing consecutive quaternary and tertiary carbon stereocenters in high diastereoselectivities and enantioselectivities. Moreover, the prepared products could be readily transformed into the chiral 2-alkyl-2-carboxyl tetrahydrothiophenes via two steps of debenzoylation and alkylation reactions.

A Unified Catalytic Asymmetric (4+1) and (5+1) Annulation Strategy to Access Chiral Spirooxindole-Fused Oxacycles.

A unified catalytic asymmetric (N+1) (N=4, 5) annulation reaction of oxindoles with bifunctional peroxides has been achieved in the presence of a chiral phase-transfer catalyst (PTC). This general strategy utilizes peroxides as unique bielectrophilic four- or five-atom synthons to participate in the C-C and the subsequent umpolung C-O bond-forming reactions with one-carbon unit nucleophiles, thus providing a distinct method to access the valuable chiral spirooxindole-tetrahydrofurans and -tetrahydropyrans with good yields and high enantioselectivities under mild conditions. DFT calculations were performed to rationalize the origin of high enantioselectivity. The gram-scale syntheses and synthetic utility of the resultant products were also demonstrated.

Synthesis of 1,3-Aminoalcohols and Spirocyclic Azetidines via Tandem Hydroxymethylation and Aminomethylation Reaction of ß-Keto Phosphonates with N-Nosyl-O-(2-bromoethyl)hydroxylamine.

An unprecedented tandem α-hydroxymethylation and α-aminomethylation reaction of aromatic cyclic ß-keto phosphonates with N-nosyl-O-(2-bromoethyl)hydroxylamine in the presence of DBU base has been developed, affording a range of 1,3-aminoalcohols in good yields. The resultant products could be flexibly transformed into the spirocyclic and bispirocyclic azetidines via one step of Mitsunobu reaction. Mechanistic study revealed that hydroxylamine in situ generated the formaldehyde and nosylamide, which in turn triggered the sequential Horner-Wadsworth-Emmons, Michael, and aldol reactions.

Structure, phase transition and properties of the one-dimensional antiferromagnet Cu(2,6-dimethylpyrazine)Br2.

We report the crystal structure and properties of the one-dimensional S = 1/2 antiferromagnet Cu(2,6-dimethylpyrazine)Br2 with strong intra-chain exchange. At room temperature, its linear spin chains are formed by Cu2+ ions via the non-bonding Br⋯Br contacts. Interestingly, a phase transition from Pmmn to P21/n structure occurs at T S ≈ 248 K below which the [CuBr2] n spin chains become non-linear and the magnetic susceptibility abruptly increases, reflecting the weakening of antiferromagnetic exchange strength. This result evidences the Goodenough-Kanamori rules which claim that a linear super-exchange pathway produces stronger antiferromagnetic coupling. From magnetic susceptibility measurements we find the average intra-chain exchange strength is J/k B ≈ -88.18 K in the low temperature phase. Both magnetic and specific measurements show the absence of magnetic ordering down to 2 K, implying the excellent magnetic one-dimensionality of Cu(2,6-dimethylpyrazine)Br2. We also performed ultra-violet (UV) absorption and photoluminescence measurements which give a semiconducting band gap Δ ≈ 2.79 eV which is consistent with theoretical calculations.

Dynamic Epitaxial Crystallization of SnSe2 on the Oxidized SnSe Surface and Its Atomistic Mechanisms.

Surface oxidation of SnSe sharply reduces its thermoelectric properties though the bulk single-crystalline materials of SnSe claim the record high zT values. Investigation on the oxidation behaviors of SnSe together with the subsequent phase transition and element migration is fundamentally important to maintaining the ultrahigh zT values, with a potential for further improvement. In this work, we disclose the dynamic epitaxial crystallization of SnSe2 on the amorphous surface of partially oxidized SnSe crystals and the corresponding atomistic mechanisms via transmission electron microscopy (TEM). It is revealed that the thermally annealed amorphous surface crystallized to SnO2 and SnSe2 in the outermost and secondary layers, respectively, forming distinctive SnSe/SnSe2/SnO2 multilayer heterostructures with specific orientation relationships between the two selenides. By means of in situ scanning TEM (STEM), the dynamic epitaxial crystallization process of SnSe2 was revealed when the oxidized SnSe surface was subjected to electron beam irradiation. Through the atomic-scale characterization and modeling analysis, we find that the exposed dangling Se diatoms on the SnSe surface serve as nucleation sites for lateral epitaxial crystallization of SnSe2. The same valence and similar coordination configuration of Se atoms in these two phases are supposed to facilitate the sharing of Se atoms, with lattice distortions in the SnSe2/SnSe interface. These findings are valuable for understanding the surface oxidation behavior of SnSe and revealing the interface structures of SnSe2/SnSe heterojunctions and also offering new routes for SnSe-related multilayer or heterostructure system design.

Organocatalytic Enantioselective γ-Elimination: Applications in the Preparation of Chiral Peroxides and Epoxides.

An organocatalyzed enantioselective γ-elimination process has been achieved and applied in the kinetic resolution of peroxides to access chiral peroxides and epoxides. The reaction provided a pathway for the preparation of two useful synthetic and biologically important structural motifs through a single-step reaction. A range of substrates has been resolved with a selectivity factor up to 63. The obtained enantioenriched peroxides and epoxides allowed a series of transformations with retained optical purities.

A highly [001]-textured Sb2Se3 photocathode for efficient photoelectrochemical water reduction.

Anisotropic Sb2Se3 is an emerging earth-abundant photocathode for photoelectrochemical water splitting. However, controlling the growth of the Sb2Se3 film with optimal [001] crystallographic orientation is still the most challenging issue. Here, we successfully synthesized [001]-oriented Sb2Se3via a reliable and facile method. The [001]-oriented Sb2Se3 film could provide an excellent carrier-migration efficiency. Consequently, we achieved a record-high photocurrent density of -20.2 mA cm-2 at 0 VRHE and a very high half-cell solar-to-hydrogen efficiency of 1.36% under 1-sun simulated solar illumination in a TiO2/[001]-Sb2Se3 photocathode. This work provides an effective strategy and important guidelines for rationally designing optoelectronic devices based on the [001]-oriented Sb2Se3 film.

Consideration of Age Is Necessary for Increasing the Accuracy of the AJCC TNM Staging System of Pancreatic Neuroendocrine Tumors.

Purpose: Currently, of the two most common staging systems of pancreatic neuroendocrine tumors (pNETs) one is from the European Neuroendocrine Tumor Society (ENETS) and the other is from the American Joint Committee on Cancer (AJCC). However, there are imperfections in both these staging systems. Patients and methods: Patients were selected retrospectively from the Surveillance Epidemiology and End Results (SEER) database (2004 to 2013). The effect of age on the hazard ratio (HR) was evaluated using restricted cubic splines. The discriminatory power of the staging systems was determined using the concordance index (C-index). Results: A total of 3,034 patients with pNETs were included in the final analyses. The risk of death increased slowly along with age for patients under 60 years of age, but the risk of death rose sharply for those over 60 years of age, forming a mirrored L-shaped survival curve. In the current AJCC tumor-node-metastasis (TNM) staging system, no statistical significance was observed between stages IA and IB (p = 0.105). Patients with stage IIB even had longer OS than patients with IIA, although there was no statistical significance (p = 0.574). The proportion of stage III patients was small (2.7%). In the proposed aTNM staging system, significant survival differences could be observed among stage I, IIA, and IIB (p < 0.001) and the proportion of stage III rose from 2.7 to 25.7%. Conclusion: Our findings suggest that age has a critical influence on the survival of patients with pNETs. Age should be considered as a factor in future staging systems of pNETs.

Feasibility and application of single-hole video-assisted thoracoscope in pulmonary peripheral tumors.

The feasibility and clinical application of single-hole video-assisted thoracoscope in pulmonary peripheral tumors was examined. From March, 2011 to March, 2015, we retrospectively analyzed the clinical data obtained from 32 patients with pulmonary peripheral tumor that received single-hole thoracoscopic surgery. We completed the surgery via a 1.5-cm incision on the seventh or eighth rib in midaxillary line as the observation hole, and a 4.0-5.0-cm incision in the lateral margin of pectoralis major in the fourth or fifth rib in midaxillary line as the operation hole. All the patients had completed the tumor-reductive surgery under single-hole thoracoscope successfully. None required second operation hole or needed a transfer to thoracotomy. Operation time was 40-100 min with an average of 65.78±15.87 min. Intraoperative blood loss was 20-100 ml, with an average of 47.19±26.91 ml. Post-operative chest drainage time was 3-6 days, with an average of 4.22±0.87 days. Hospitalization time after operation was 5-7 days, with an average hospitalization time of 5.97±0.82 days. No patient received a second surgery for pulmonary leak or bleeding and no patient had any complication. All the cases recovered without any problem. In conclusion, for patients with pulmonary peripheral tumor, single-hole video-assisted thoracoscope could further reduce their surgical trauma. The operation was safe and feasible and worthy of wide application.

Depleting ABCE1 expression induces apoptosis and inhibits the ability of proliferation and migration of human esophageal carcinoma cells.

OBJECTIVE: This study aims to explore the clinical characteristics of ABCE1 in esophageal cancers and its roles in the proliferation, invasiveness, migration and apoptosis of the esophageal carcinoma Eca109 cell line. METHODS: The expression of ABCE1 and its target protein-RNase L, were first studied in tumor tissues of esophageal carcinoma and adjacent non-tumor tissues. The siRNA green fluorescent protein (GFP) expression vector of ABCE1 was prepared and transfected into the esophageal carcinoma Eca109 cells, then the fluorescence microscope was used to study the transfection efficiency. The MTT assay, cell invasion, the transwell and scratch assay were used to study cell proliferation and migration activity; the apoptosis rate was tested by flow cytometry. Western blot and RT-PCR assay were adopted to measure their silencing efficacy. RESULTS: ABCE1 expression is low in the adjacent non-tumor tissues while the expression is high in the esophageal carcinoma; the expression is reversely proportional to the differentiation degrees. The expression of RNase L was in contrary to ABCE1. After transfected with ABCE1-siRNA, the proliferation, invasiveness and migration capabilities of cells decreased significantly whilst the apoptosis rate enhanced greatly (P<0.01). Meanwhile, the expression of ABCE1 in Eca109 cells was blocked (P<0.01) while the expression of RNase L increased significantly (P<0.01). CONCLUSION: ABCE1 is closely connected with the pathogenesis and development of esophageal carcinoma, which act through the cellular pathways of 2-5A/RNase L.