Synthesis high specific surface area nanotube g-C3N4 with two-step condensation treatment of melamine to enhance photocatalysis properties

High specific surface area nanotube g-C3N4 was fabricated by a simple two-step condensation method. Photocatalytic activity was evaluated by decomposition of Rhodamine B (Rh B) under visible light. Nanotube g-C3N4 showed 12 times higher photocatalytic activity than bulk g-C3N4. The improvement of photocatalytic activity was mainly due to the higher surface area, the unique morphology and the number of defects

Controlled structure of anatase TiO2 nanoparticles by using organic additives in a microwave process

Synthesis of anatase nanoparticles was carried out in a microwave system. Crystal morphology was controlled by organic additives including PAAc (polyacrylic acid) and PVP (polyvinylpyrrolidone). Modified TiO2 particles were compared to the bare TiO2 anatase structure. The synthesis of materials via the microwave system has great advantages due to the short reaction period and low energy requirement and is therefore an environmentally friendly process compared to the hydrothermal process. The decomposition of acetaldehyde was studied to determine the photocatalytic activity of the modified anatase TiO2 material

Complete oxidation of acetaldehyde over a composite photocatalyst of graphitic carbon nitride and tungsten(VI) oxide under visible-light irradiation

Graphitic carbon nitride (g-C3N4) was prepared by heating melamine and then its specific surface area was enlarged by hydrothermal treatment in aqueous sodium hydroxide solution. The g-C3N4 samples were blended with tungsten(VI) oxide (WO3) using a planetary mill in order to improve photocatalytic activity. The composite photocatalyst with optimized amounts of these contents showed higher photocatalytic activity for decomposition of acetaldehyde under visible-light irradiation than did original samples. From the results, we concluded that the composite photocatalyst utilizes both high oxidation ability of WO3 and high reduction ability of g-C3N4 by Z-scheme charge transfer

Porous cerium dioxide hollow spheres and their photocatalytic performance

Uniform-sized and monodiperse cerium dioxide porous hollow spheres (CeO2-PH) based on the Ostwald ripening process were fabricated by a simple solvothermal method in the absence of any templates. The structure and morphology of CeO2-PH and CeO2-NP (cerium dioxide nanoparticles) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) surface area analysis. The average diameter of face-centered cubic (fcc) phase CeO2-PH was ca. 160 nm with a high specific surface area, and it is composed of small crystal grain particles (ca. 10 nm). Furthermore, CeO2-PH has high activity for the evaluation of acetaldehyde decomposition. Optical, defect, and chemical state properties were characterized by Raman spectra, ultraviolet-visible absorption spectroscopy (UV-vis), and X-ray photoelectron spectroscopy (XPS). The presence of Ce3+ ions narrowed the band gap of CeO2-PH, resulting in the high light harvesting. The large amount of oxygen vacancy defects provided many activity sites on CeO2-PH in the photocatalytic process. The formation scheme and photocatalyic mechanism will be discussed in this paper

Generalized Category Discovery in Semantic Segmentation

This paper explores a novel setting called Generalized Category Discovery in Semantic Segmentation (GCDSS), aiming to segment unlabeled images given prior knowledge from a labeled set of base classes. The unlabeled images contain pixels of the base class or novel class. In contrast to Novel Category Discovery in Semantic Segmentation (NCDSS), there is no prerequisite for prior knowledge mandating the existence of at least one novel class in each unlabeled image. Besides, we broaden the segmentation scope beyond foreground objects to include the entire image. Existing NCDSS methods rely on the aforementioned priors, making them challenging to truly apply in real-world situations. We propose a straightforward yet effective framework that reinterprets the GCDSS challenge as a task of mask classification. Additionally, we construct a baseline method and introduce the Neighborhood Relations-Guided Mask Clustering Algorithm (NeRG-MaskCA) for mask categorization to address the fragmentation in semantic representation. A benchmark dataset, Cityscapes-GCD, derived from the Cityscapes dataset, is established to evaluate the GCDSS framework. Our method demonstrates the feasibility of the GCDSS problem and the potential for discovering and segmenting novel object classes in unlabeled images. We employ the generated pseudo-labels from our approach as ground truth to supervise the training of other models, thereby enabling them with the ability to segment novel classes. It paves the way for further research in generalized category discovery, broadening the horizons of semantic segmentation and its applications. For details, please visit https://github.com/JethroPeng/GCDS

MMSum: A Dataset for Multimodal Summarization and Thumbnail Generation of Videos

Multimodal summarization with multimodal output (MSMO) has emerged as a promising research direction. Nonetheless, numerous limitations exist within existing public MSMO datasets, including insufficient maintenance, data inaccessibility, limited size, and the absence of proper categorization, which pose significant challenges. To address these challenges and provide a comprehensive dataset for this new direction, we have meticulously curated the \textbf{MMSum} dataset. Our new dataset features (1) Human-validated summaries for both video and textual content, providing superior human instruction and labels for multimodal learning. (2) Comprehensively and meticulously arranged categorization, spanning 17 principal categories and 170 subcategories to encapsulate a diverse array of real-world scenarios. (3) Benchmark tests performed on the proposed dataset to assess various tasks and methods, including \textit{video summarization}, \textit{text summarization}, and \textit{multimodal summarization}. To champion accessibility and collaboration, we will release the \textbf{MMSum} dataset and the data collection tool as fully open-source resources, fostering transparency and accelerating future developments. Our project website can be found at~\url{https://mmsum-dataset.github.io/}Comment: Project website: https://mmsum-dataset.github.io

Dependence of photocatalytic activity on aspect ratio of a brookite TiO2 nanorod and drastic improvement in visible light responsibility of a brookite TiO2 nanorod by site-selective modification of Fe3+ on exposed faces

Exposed crystal face-controlled brookite titanium(IV) oxide (TiO2) nanorods with various aspect ratios were prepared by a hydrothermal process with or without PVA or PVP as an aspect reagent. The nanorod-shaped brookite TiO2 had larger {2 1 0} and smaller {2 1 2} exposed crystal faces, which were assigned by TEM with the SAED technique. Their aspect ratios were greatly influenced by the addition of PVA or PVP as an aspect ratio control reagent to the reaction solution used in the hydrothermal treatment. The photocatalytic activity for decomposition of acetaldehyde increased with increase in the aspect ratio because the surface area ratio of {2 1 0} to {2 1 2} exposed crystal faces, which are attributed to reduction and oxidation sites, respectively, became more optimal. The {2 1 2} exposed crystal faces of surface-controlled brookite TiO2 were site-selectively modified with trivalent iron(III) (Fe3+) ions by utilizing the adsorption property of iron(III)/iron(II) (Fe3+/Fe2+) ions. The brookite TiO2 nanorod with site-selective modification of Fe3+ ions showed much higher photocatalytic activity than that of commercial brookite TiO2 loaded with Fe ions under visible-light irradiation because of the separation of redox sites. In other words, oxidation and reduction proceed over Fe3+ ion-modified {2 1 2} faces of the TiO2 surface and on {2 1 0} faces of the TiO2 surface without modification of Fe3+, respectively

Constructing hydrogen bond based melam/WO3 heterojunction with enhanced visible-light photocatalytic activity

Hydrogen bond based visible-light-response heterojunction photocatalyst Melam/WO3 (MW) has been fabricated for the first time by facile planetary milling treatment. Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric (TG) analysis reveal the formation of hydrogen bonds (NH···O) between melam and WO3. As compared to WO3, the MW not only complete decomposes acetaldehyde, but also shows 10 times and 12 times higher photocatalytic activity for photo-degradation of 2-propanol and photo-generation of H2O2, respectively, under the visible-light irradiation. X-ray photoelectron spectroscopy suggests that the potential difference between N and O (N+H⋯O−) in the heterojunction provides the driving force for the charge transfer from WO3 to melam. Furthermore, hydrogen bonds offer an ultrafast electron pathway for heterojunction. This study demonstrates that hydrogen bond based heterojunction could be a promising approach for developing a new photocatalyst with efficient visible-light photocatalytic activity