Correlation between endoscopic resection outcomes and endosonographic findings in gastric tumors with muscularis propria origin.

Endoscopic resection is an effective treatment for subepithelial tumors arising from the muscularis propria layer of the stomach. However, the invasion pattern revealed by the pathological examination of tumor specimens is often not consistent with the findings of preprocedural endoscopic ultrasounds (EUS). We compared the real growing patterns of tumors, as evaluated on histopathological examination, with their EUS images, and analyzed the outcomes of endoscopic resections in relation to the EUS findings. From January 2006 to June 2015, 32 patients underwent endoscopic resection for gastric tumors originating from the muscularis propria at our hospital. We divided the patients into 3 groups according to the location of the tumor as diagnosed using pre procedural EUS: submucosa (group I, n = 5), muscularis propria (group II, n = 14), and tumors extending into the outer cavity (group III, n = 13). Histopathological examination revealed 15 patients with gastrointestinal stromal tumors (GISTs), 14 with leiomyomas, and 3 with schwannomas. Accuracy of EUS in evaluating tumor invasion was 56%. Some tumors in groups I and II was removed by endoscopic submucosal dissection only. Muscular dissection was needed in 10 patients (71%) in group II and 9 patients (69%) in group III. Four patients (31%) in group III were found to have subserosal tumors. The complete resection rate was 88% (23 patients) among patients who underwent endoscopic submucosal dissection and endoscopic muscular dissection, and 67% (4 patients) among patients who underwent endoscopic subserosal dissection (ESSD). The tumor was completely removed in 12 patients (86%) in group II and 10 patients (77%) in group III. EUS accurately predicts the layer of the subepithelial tumor in the stomach; however, the pattern of invasion of surrounding structures is difficult to evaluate using EUS.

Endoscopic subserosal dissection for gastric tumors: 18 cases in a single center.

BACKGROUND: Endoscopic submucosal dissection has technical limitations for the resection of gastric epithelial tumors with severe fibrosis and mixed or exophytic gastric subepithelial tumors (SETs). AIMS: To analyze the safety and effectiveness of endoscopic subserosal dissection (ESSD) for tumors growing in the subserosal space. METHODS: This observation study enrolled 18 patients who were diagnosed with gastric tumors and underwent ESSD at the Presbyterian Medical Center from 2010 to March 2019. RESULTS: A total of 18 patients were treated by ESSD. The mean age of the patients was 61.7 years. The mean length of the long axis of the tumor was 18.0 ± 5.0 mm. The mean operation time was 44 (range 11-167) min. The pathologic diagnosis was leiomyoma in nine cases (50.0%), gastrointestinal stromal tumor in six (33.3%), low-grade adenoma with severe fibrosis in two (11.1%), and schwannoma in one (5.6%). There were three cases of perforation, which were treated conservatively. The complete resection rate was 94%, and local or systemic tumor recurrence was not seen in a mean 70 months of follow-up. CONCLUSION: ESSD can be used for epithelial tumors with severe fibrosis and mixed or exophytic gastric SETs in the lesser curvature, cardia, or fundus that cannot be treated using standard methods.

Bendable BiVO4-Based Photoanodes on a Metal Substrate Realized through Template Engineering for Photoelectrochemical Water Splitting.

Unlike planar photoelectrodes, bendable and malleable photoelectrodes extend their application to mechanical flexibility beyond conventional rigid structures, which have garnered new attention in the field of photoelectrochemical water splitting. A bendable metal (Hastelloy), which has both bendability and compatibility with various oxide layers, allows high-temperature processes for crystallization; therefore it is far superior as a substrate than a conventional flexible polymer. In this study, we fabricate bendable BiVO4 crystalline thin films on the metal substrates by employing template layers (SrRuO3/SrTiO3) to reduce the structural misfits between BiVO4 and the substrate. The crystallinities were verified through X-ray diffraction and transmission electron microscopy, and photocatalytic performances were examined. The crystallinity of BiVO4 was significantly improved by utilizing similar lattice constants and affinities between BiVO4 and the oxide template layers. We also formed a type II heterojunction by adding a WO3 layer which complements the charge separation and charge transfer as a photoanode. The photocurrent densities of tensile-bent BiVO4/WO3 thin films with a bending radius of 10 mm are comparable to those of pristine BiVO4/WO3 thin film in various aqueous electrolytes. Moreover, photostability tests showed that the tensile-bent crystalline photoanodes retained 90% of their initial photocurrent density after 24 h, which proved their exceptional durability. Our work demonstrates that the bendable photoelectrodes with crystallinity hold great potential in terms of device structure for solar-driven water splitting.

Template Engineering of CuBi2 O4 Single-Crystal Thin Film Photocathodes.

To develop strategies for efficient photo-electrochemical water-splitting, it is important to understand the fundamental properties of oxide photoelectrodes by synthesizing and investigating their single-crystal thin films. However, it is challenging to synthesize high-quality single-crystal thin films from copper-based oxide photoelectrodes due to the occurrence of significant defects such as copper or oxygen vacancies and grains. Here, the CuBi2 O4 (CBO) single-crystal thin film photocathode is achieved using a NiO template layer grown on single-crystal SrTiO3 (STO) (001) substrate via pulsed laser deposition. The NiO template layer plays a role as a buffer layer of large lattice mismatch between CBO and STO (001) substrate through domain-matching epitaxy, and forms a type-II band alignment with CBO, which prohibits the transfer of photogenerated electrons toward bottom electrode. The photocurrent densities of the CBO single-crystal thin film photocathode demonstrate -0.4 and -0.7 mA cm-2 at even 0 VRHE with no severe dark current under illumination in a 0.1 m potassium phosphate buffer solution without and with H2 O2 as an electron scavenger, respectively. The successful synthesis of high-quality CBO single-crystal thin film would be a cornerstone for the in-depth understanding of the fundamental properties of CBO toward efficient photo-electrochemical water-splitting.

In Situ Growth of Nanostructured BiVO4-Bi2O3 Mixed-Phase via Nonequilibrium Deposition Involving Metal Exsolution for Enhanced Photoelectrochemical Water Splitting.

Nonequilibrium deposition is a remarkable method for the in situ growth of unique nanostructures and phases for the functionalization of thin films. We introduce a distinctive structure of a mixed-phase, composed of BiVO4 and ß-Bi2O3, for photoelectrochemical water splitting. The mixed-phase is fabricated via nonequilibrium deposition by adjusted oxygen partial pressure. According to density functional theory calculations, we find that vanadium exsolution can be facilitated by introducing oxygen vacancies, enabling the fabrication of a nanostructured mixed-phase. These unique structures enhance charge migration by increasing the interfacial area and properly aligning the band offset between two crystalline phases. Consequently, the photocurrent density of the nanostructured mixed-phase thin films is about twice that of pristine BiVO4 thin films at 1.23 VRHE. Our work suggests that nonequilibrium deposition provides an innovative route for the structural engineering of photoelectrodes for the understanding of fundamental properties and improving the photocatalytic performance for solar water splitting.

Long-term stabilized high-density CuBi2O4/NiO heterostructure thin film photocathode grown by pulsed laser deposition.

Harvesting sustainable hydrogen through water-splitting requires a durable photoelectrode to achieve high efficiency and long lifetime. Dense, uniform CuBi2O4/NiO thin film photocathodes grown by pulsed laser deposition achieved photocurrent density over 1.5 mA cm-2 at 0.4 VRHE and long-term chronoamperometric stability for over 8 hours.

Direct In Situ Growth of Centimeter-Scale Multi-Heterojunction MoS2/WS2/WSe2 Thin-Film Catalyst for Photo-Electrochemical Hydrogen Evolution.

To date, the in situ fabrication of the large-scale van der Waals multi-heterojunction transition metal dichalcogenides (multi-TMDs) is significantly challenging using conventional deposition methods. In this study, vertically stacked centimeter-scale multi-TMD (MoS2/WS2/WSe2 and MoS2/WSe2) thin films are successfully fabricated via sequential pulsed laser deposition (PLD), which is an in situ growth process. The fabricated MoS2/WS2/WSe2 thin film on p-type silicon (p-Si) substrate is designed to form multistaggered gaps (type-II band structure) with p-Si, and this film exhibits excellent spatial and thickness uniformity, which is verified by Raman spectroscopy. Among various application fields, MoS2/WS2/WSe2 is applied to the thin-film catalyst of a p-Si photocathode, to effectively transfer the photogenerated electrons from p-Si to the electrolyte in the photo-electrochemical (PEC) hydrogen evolution. From a comparison between the PEC performances of the homostructure TMDs (homo-TMDs)/p-Si and multi-TMDs/p-Si, it is demonstrated that the multistaggered gap of multi-TMDs/p-Si improves the PEC performance significantly more than the homo-TMDs/p-Si and bare p-Si by effective charge transfer. The new in situ growth process for the fabrication of multi-TMD thin films offers a novel and innovative method for the application of multi-TMD thin films to various fields.

Enhanced Photocatalytic Performance Depending on Morphology of Bismuth Vanadate Thin Film Synthesized by Pulsed Laser Deposition.

We have fabricated high quality bismuth vanadate (BiVO4) polycrystalline thin films as photoanodes by pulsed laser deposition (PLD) without a postannealing process. The structure of the grown films is the photocatalytically active phase of scheelite-monoclinic BiVO4 which was obtained by X-ray diffraction (XRD) analysis. The change of surface morphology for the BIVO4 thin films depending on growth temperature during synthesis has been observed by scanning electron microscopy (SEM), and its influence on water splitting performance was investigated. The current density of the BiVO4 film grown on a glass substrate covered with fluorine-doped tin oxide (FTO) at 230 °C was as high as 3.0 mA/cm2 at 1.23 V versus the potential of the reversible hydrogen electrode (VRHE) under AM 1.5G illumination, which is the highest value so far in previously reported BiVO4 films grown by physical vapor deposition (PVD) methods. We expect that doping of transition metal or decoration of oxygen evolution catalyst (OEC) in our BiVO4 film might further enhance the performance.

Large enhancement of the photovoltaic effect in ferroelectric complex oxides through bandgap reduction.

Tuning the bandgap in ferroelectric complex oxides is a possible route for improving the photovoltaic activity of materials. Here, we report the realization of this effect in epitaxial thin films of the ferroelectric complex oxide Bi3.25La0.75Ti3O12 (BLT) suitably doped by Fe and Co. Our study shows that Co (BLCT) doping and combined Fe, Co (BLFCT) doping lead to a reduction of the bandgap by more than 1 eV compared to undoped BLT, accompanied by a surprisingly more efficient visible light absorption. Both BLCT and BLFCT films can absorb visible light with a wavelength of up to 500 nm while still exhibiting ferroelectricity, whereas undoped BLT only absorbs UV light with a wavelength of less than 350 nm. Correlated with its bandgap reduction, the BLFCT film shows a photocurrent density enhanced by 25 times compared to that of BLT films. Density functional theory calculations indicate that the bandgap contraction is caused by the formation of new energy states below the conduction bands due to intermixed transition metal dopants (Fe, Co) in BLT. This mechanism of tuning the bandgap by simple doping can be applied to other wide-bandgap complex oxides, thereby enabling their use in solar energy conversion or optoelectronic applications.