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• A joint learning model for superpixel-based fuzzy sparse subspace clustering is established. • A four-level alteration iterative algorithm for superpixel-based image segmentation is proposed. • A centroid shift strategy suitable for image contents is used to generate superpixels. • Experimental results indicate that the proposed algorithm has very good performance. Sparse subspace clustering (SSC) is an important image segmentation method that constructs a self-representation coefficient matrix to represent the relationships between pixels, and then uses spectral clustering to achieve clustering. Compared with other unsupervised segmentation algorithms, SSC has good segmentation performance. However, SSC has a high computational complexity when processing large-sized image. To improve computational efficiency, many researchers have proposed superpixel-based SSC algorithms, which process superpixels instead of pixels and improve efficiency through preprocessing. Due to the sensitivity of superpixel generation to noise, superpixel-based SSC algorithms still have poor robustness. Additionally, preprocessing increases the complexity of the algorithm. To address these issues, this paper proposes a robust superpixel-based fuzzy sparse subspace clustering algorithm. This algorithm combines fuzzy sparse subspace clustering with superpixel generation, and it constructs a unified optimization learning framework through fuzzy C-multiple-means clustering to improve segmentation performance and reduce complexity. Additionally, this paper introduces additional features of superpixel in sparse subspace clustering to further enhance the segmentation performance of the algorithm. Experiment results indicate that the proposed algorithm not only outperforms existing state-of-the-art robust segmentation algorithms independent of superpixels, but also is superior to the latest superpixel-based segmentation algorithms. [ABSTRACT FROM AUTHOR]

In recent years, several superpixel-segmentation methods have been developed to efficiently segment noisy images. However, these methods still face challenges such as high computational complexity and poor adaptability. Therefore, this paper develops a novel superpixel-based robust segmentation model including two modules: superpixel generation and superpixel-based image segmentation. In the superpixel generation module, a fuzzy factor containing local spatial information of pixels is introduced into fuzzy possibilistic clustering algorithm with local search. In the superpixel-based segmentation module, a superpixel-based fuzzy C-means algorithm with local spatial information of superpixels is proposed, which nonlinearly combines the membership of superpixels with the membership of their neighboring superpixels. The experimental results demonstrate that the proposed method outperforms existing state-of-the-art segmentation algorithms in terms of evaluation indexes and visual effects. [ABSTRACT FROM AUTHOR]

Hybrid piezo/triboelectric nanogenerators (H‐P/TENGs) are developed to compensate the drawbacks of a single nanogenerator by synergizing high triboelectric output voltage and piezoelectric output current in continuous contact‐separation cycles. In particular, piezoelectric zinc oxide (ZnO) has been widely used due to its excellent orientation along the c‐axis and tunable growth structures. Herein, various growth structures of ZnO, unoriented, oriented, and hierarchical structures, are incorporated in H‐P/TENGs, enhancing their power densities from 6 to 17 times. Particularly, oriented ZnO nanorod/PVA (ZnR) achieves a maximum power density of 15.9 W m−2 (≈17‐fold increment compared to pristine PVA). The highly oriented ZnO growth along the c‐axis enables large deformation upon a vertical compression, subsequently generating a large piezoelectric polarization. Moreover, the enhancement mechanism via piezoelectric polarization is elucidated using a modified overlapped electron cloud model supported with Kelvin probe force microscopy measurements. The polarization of ZnO nanocomposites enlarges the difference in the highest electron energies (ΔE) between the two triboelectric layers, driving more electrons to transfer during contact electrification, thereby enriching their surface charge densities. This study highlights the significance of growth structure control in maximizing the piezoelectric responses of ZnO, consequently improving the output performances of H‐P/TENGs. [ABSTRACT FROM AUTHOR]

Undersea optical communication (UOC) has been considered as the most potential next‐generation underwater wireless communication technology for ocean exploration. Photodetector is the essential component in UOC system, however, the harsh undersea environment like light attenuation and seawater corrosivity restricts the applications of conventional photodetectors. Herein, a novel natural‐electrolyte self‐powered photoelectrochemical (PEC) photodetector based on core‐shell structured Cu@GaN nanowires (NWs) network is demonstrated and direct utilization of seawater. High quality GaN shell is encapsulated on the Cu NWs network through Ga‐coating and high temperature nitridation processes. A Schottky junction along radial direction has formed at the Cu/GaN interface due to the outward diffusion of Cu into the GaN layer. Such a structure provides narrowed band detection on blue light as well as efficient carrier separation. A self‐powered undersea PEC photodetector is designed with a mini‐pipes connected device chamber, which allows direct indrawing of seawater and blue channel light communication (458 nm). This photodetector works stably for UOC in both shallow and deep‐sea conditions in Pacific Ocean area. It shows a high responsivity up to 5.04 mA W−1 and rapid response time of 0.68 ms. This photodetector can be easily integrated to marine equipment without waterproof packaging for the future energy‐saving UOC. [ABSTRACT FROM AUTHOR]

High-Responsivity Natural-Electrolyte Undersea Photoelectrochemical Photodetector with Self-Powered Cu@GaN Nanowires Network (Adv. Funct. Keywords: copper nanowires; photodetectors; self-powered devices; underwater optical communication EN copper nanowires photodetectors self-powered devices underwater optical communication 1 1 1 07/21/23 20230718 NES 230718 B Underwater Optical Communication b In article 2302872, Duanjun Cai, Shengli Huang, and co-workers propose a novel type electrolyte-free and self-powered photoelectrochemical photodetector with Cu@GaN nanowires network for undersea optical communication. Copper nanowires, photodetectors, self-powered devices, underwater optical communication. [Extracted from the article]

ZnO/Si nanotrees were coated by Ag 2 S and In 2 S 3 nanoparticles. The built-in electric field of the heterojunctions induced electron-hole pair recombination in the conduction band of ZnO and valence bands of other semiconductors at the interfaces, which reduced charge recombination in the interior of the component semiconductors and improved redox ability. • Heterogeneous nanowire arrays were grown resulting in efficient dye photodegradation. • Introduction of quantum dots yielded a quarter resistance and 31-fold photocurrent. • The samples got efficiency of 62% and 55% in visible and UV light with recyclability. • Z-scheme heterojunctions played a critical role in the high photocatalytic activity. Hierarchical heterogeneous ZnO/Si nanowire arrays grown from metal-induced wet etching process on p-type silicon wafer were obtained and have been strategically sensitized by narrow bandgap semiconductors of In 2 S 3 nanosheets and Ag 2 S quantum dots via successive ionic layer adsorption and reaction technique. The photodegradation of methylene blue as catalyzed by the arrays was conducted under visible light and ultraviolet light. By introducing the coating layers, the specimens were found to achieve absorptivity higher than 94% and yield a quarter of the resistance and 31-fold of the photo-current as compared to the primary nanowire arrays. The photodegradation efficiency was improved from 48.9% to 62.0%, and 43.0% to 55.0%, respectively in visible light and ultraviolet light with an enhanced recyclability. Band structure analysis indicated that the coating brought different Z-scheme heterojunctions for efficient photocatalytic performance, while the function could only work in a given spectral range. These results would be helpful to better realize the photocatalytic mechanisms and meanwhile, could be extended to design heterogeneous semiconductor nanomaterials for their potential applications. [ABSTRACT FROM AUTHOR]

• Ag 2 S-sensitized ZnO/SnO 2 core-shell nanowire arrays were successfully synthesized. • The absorptivity of the sample was larger than 95% in visible and UV range. • The photocurrent response of the sample reached 53.6-fold of the ZnO NW arrays. • The catalytic efficiency got 71.61% and 57.58% respectively in visible and UV range. • Mechanism of the effective photocatalysis was explored. Ag 2 S quantum dots-sensitized ZnO/SnO 2 core-shell nanowire arrays were successfully synthesized layer by layer through hydrothermal growth, atomic layer deposition, and successive ionic layer adsorption and reaction process. By introducing the two-layer semiconductors, the bandgap of ZnO component in the arrays was slightly modulated, while the light absorption was obviously improved with an absorptivity higher than 95% in visible and ultraviolet range. In contrast to the ZnO NW arrays, the photocurrent response of the ZnO/SnO 2 /Ag 2 S NW arrays for the visible light was improved from 0.42 μA to 22.5 μA, and the photodegradation efficiency of methylene blue was increased from 45.24% to 71.61%, and 42.61% to 57.58%, respectively in visible light and ultraviolet light. Band structure analysis indicated that the coating layer brought different staggered gaps and suitable band alignment for efficient photocatalytic performance, which could be extended to design heterogeneous semiconductor nanomaterials for their potential applications. [ABSTRACT FROM AUTHOR]