Construction of Ultrathin BiVO4-Au-Cu2O Nanosheets with Multiple Charge Transfer Paths for Effective Visible-Light-Driven Photocatalytic Degradation of Tetracycline.

In this study, unique BiVO4-Au-Cu2O nanosheets (NSs) are well designed and multiple charge transfer paths are consequently constructed. The X-ray photoelectron spectroscopy measurement during a light off-on-off cycle and redox capability tests of the photo-generated charge carriers confirmed the formation of Z-scheme heterojunction, which can facilitate the charge carrier separation and transfer and maintain the original strong redox potentials of the respective component in the heterojunction. The ultrathin 2D structure of the BiVO4 NSs provided sufficient surface area for the photocatalytic reaction. The local surface plasmon resonance (LSPR) effect of the electron mediator, Au NPs, enhanced the light absorption and promoted the excitation of hot electrons. The multiple charge transfer paths effectively promoted the separation and transfer of the charge carrier. The synergism of the abovementioned properties endowed the BiVO4-Au-Cu2O NSs with satisfactory photocatalytic activity in the degradation of tetracycline (Tc) with a removal rate of ≈80% within 30 min under visible light irradiation. The degradation products during the photocatalysis are confirmed by using ultra-high performance liquid chromatography-mass spectrometry and the plausible degradation pathways of Tc are consequently proposed. This work paves a strategy for developing highly efficient visible-light-driven photocatalysts with multiple charge transfer paths for removing organic contaminants in water.

Lateral Flow Assay Biotesting by Utilizing Plasmonic Nanoparticles Made of Inexpensive Metals─Replacing Colloidal Gold.

Nanoparticles (NPs) can be conjugated with diverse biomolecules and employed in biosensing to detect target analytes in biological samples. This proven concept was primarily used during the COVID-19 pandemic with gold-NP-based lateral flow assays (LFAs). Considering the gold price and its worldwide depletion, here we show that novel plasmonic NPs based on inexpensive metals, titanium nitride (TiN) and copper covered with a gold shell (Cu@Au), perform comparable to or even better than gold nanoparticles. After conjugation, these novel nanoparticles provided high figures of merit for LFA testing, such as high signals and specificity and robust naked-eye signal recognition. Since the main cost of Au NPs in commercial testing kits is the colloidal synthesis, our development with the Cu@Au and the laser-ablation-fabricated TiN NPs is exciting, offering potentially inexpensive plasmonic nanomaterials for various bioapplications. Moreover, our machine learning study showed that biodetection with TiN is more accurate than that with Au.

Exploring the Remarkably High Photocatalytic Efficiency of Ultra-Thin Porous Graphitic Carbon Nitride Nanosheets.

Graphitic carbon nitride (g-C3N4) is a metal-free photocatalyst used for visible-driven hydrogen production, CO2 reduction, and organic pollutant degradation. In addition to the most attractive feature of visible photoactivity, its other benefits include thermal and photochemical stability, cost-effectiveness, and simple and easy-scale-up synthesis. However, its performance is still limited due to its low absorption at longer wavelengths in the visible range, and high charge recombination. In addition, the exfoliated nanosheets easily aggregate, causing the reduction in specific surface area, and thus its photoactivity. Herein, we propose the use of ultra-thin porous g-C3N4 nanosheets to overcome these limitations and improve its photocatalytic performance. Through the optimization of a novel multi-step synthetic protocol, based on an initial thermal treatment, the use of nitric acid (HNO3), and an ultrasonication step, we were able to obtain very thin and well-tuned material that yielded exceptional photodegradation performance of methyl orange (MO) under visible light irradiation, without the need for any co-catalyst. About 96% of MO was degraded in as short as 30 min, achieving a normalized apparent reaction rate constant (k) of 1.1 × 10-2 min-1mg-1. This represents the highest k value ever reported using C3N4-based photocatalysts for MO degradation, based on our thorough literature search. Ultrasonication in acid not only prevents agglomeration of g-C3N4 nanosheets but also tunes pore size distribution and plays a key role in this achievement. We also studied their performance in a photocatalytic hydrogen evolution reaction (HER), achieving a production of 1842 µmol h-1 g-1. Through a profound analysis of all the samples' structure, morphology, and optical properties, we provide physical insight into the improved performance of our optimized porous g-C3N4 sample for both photocatalytic reactions. This research may serve as a guide for improving the photocatalytic activity of porous two-dimensional (2D) semiconductors under visible light irradiation.

Lateral Flow Assays Biotesting by Utilizing Plasmonic Nanoparticles Made of Inexpensive Metals - Replacing Colloidal Gold.

Nanoparticles (NPs) can be conjugated with diverse biomolecules and employed in biosensing to detect target analytes in biological samples. This proven concept was primarily used during the COVID-19 pandemic with gold NPs-based lateral flow assays (LFAs). Considering the gold price and its worldwide depletion, here we show that novel plasmonic nanoparticles (NPs) based on inexpensive metals, titanium nitride (TiN) and copper covered with a gold shell (Cu@Au), perform comparable or even better than gold nanoparticles. After conjugation, these novel nanoparticles provided high figures of merit for LFA testing, such as high signals and specificity and robust naked-eye signal recognition. To the best of our knowledge, our study represents the 1st application of laser-ablation-fabricated nanoparticles (TiN) in the LFA and dot-blot biotesting. Since the main cost of the Au NPs in commercial testing kits is in the colloidal synthesis, our development with TiN is very exciting, offering potentially very inexpensive plasmonic nanomaterials for various bio-testing applications. Moreover, our machine learning study showed that the bio-detection with TiN is more accurate than that with Au.

Enhanced photocatalysis of metal/covalent organic frameworks by plasmonic nanoparticles and homo/hetero-junctions.

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have garnered attention in photocatalysis due to their unique features including extensive surface area, adjustable pores, and the ability to incorporate various functional groups. However, challenges such as limited visible light absorption and rapid electron-hole recombination often hinder their photocatalytic efficiency. Recent developments have introduced plasmonic nanoparticles (NPs) and junctions to enhance the photocatalytic performance of MOFs/COFs. This paper provides a comprehensive review of recent advancements in MOF/COF-based photocatalysts improved by integration of plasmonic NPs and junctions. We begin by examining the utilization of plasmonic NPs, known for absorbing longer-wavelength light compared to typical MOFs/COFs. These NPs exhibit localized surface plasmon resonance (LSPR) when excited, effectively enhancing the photocatalytic performance of MOFs/COFs. Moreover, we discuss the role of homo/hetero-junctions in facilitating charge separation, further boosting the photocatalytic performance of MOFs/COFs. The mechanisms behind the improved photocatalytic performance of these composites are discussed, along with an assessment of challenges and opportunities in the field, guiding future research directions.

MwdpNet: towards improving the recognition accuracy of tiny targets in high-resolution remote sensing image.

This study aims to develop a deep learning model to improve the accuracy of identifying tiny targets on high resolution remote sensing (HRS) images. We propose a novel multi-level weighted depth perception network, which we refer to as MwdpNet, to better capture feature information of tiny targets in HRS images. In our method, we introduce a new group residual structure, S-Darknet53, as the backbone network of our proposed MwdpNet, and propose a multi-level feature weighted fusion strategy that fully utilizes shallow feature information to improve detection performance, particularly for tiny targets. To fully describe the high-level semantic information of the image, achieving better classification performance, we design a depth perception module (DPModule). Following this step, the channel attention guidance module (CAGM) is proposed to obtain attention feature maps for each scale, enhancing the recall rate of tiny targets and generating candidate regions more efficiently. Finally, we create four datasets of tiny targets and conduct comparative experiments on them. The results demonstrate that the mean Average Precision (mAP) of our proposed MwdpNet on the four datasets achieve 87.0%, 89.2%, 78.3%, and 76.0%, respectively, outperforming nine mainstream object detection algorithms. Our proposed approach provides an effective means and strategy for detecting tiny targets on HRS images.

Design of Furan-Based Acceptors for Organic Photovoltaics.

We explore a series of furan-based non-fullerene acceptors and report their optoelectronic properties, solid-state packing, photodegradation mechanism and application in photovoltaic devices. Incorporating furan building blocks leads to the expected enhanced backbone planarity, reduced band gap and red-shifted absorption of these acceptors. Still, their position in the molecule is critical for stability and device performance. We found that the photodegradation of these acceptors originates from two distinct pathways: electrocyclic photoisomerization and Diels-Alder cycloaddition of singlet oxygen. These mechanisms are of general significance to most non-fullerene acceptors, and the photostability depends strongly on the molecular structure. Placement of furans next to the acceptor termini leads to better photostability, well-balanced hole/electron transport, and significantly improved device performance. Methylfuran as the linker offers the best photostability and power conversion efficiency (>14 %), outperforming all furan-based acceptors reported to date and all indacenodithiophene-based acceptors. Our findings show the possibility of photostable furan-based alternatives to the currently omnipresent thiophene-based photovoltaic materials.

Redox-Bipolar Polyimide Two-Dimensional Covalent Organic Framework Cathodes for Durable Aluminium Batteries.

Emerging rechargeable aluminium batteries (RABs) offer a sustainable option for next-generation energy storage technologies with low cost and exemplary safety. However, the development of RABs is restricted by the limited availability of high-performance cathode materials. Herein, we report two polyimide two-dimensional covalent organic frameworks (2D-COFs) cathodes with redox-bipolar capability in RAB. The optimal 2D-COF electrode achieves a high specific capacity of 132 mAh g-1 . Notably, the electrode presents long-term cycling stability (with a negligible ≈0.0007 % capacity decay per cycle), outperforming early reported organic RAB cathodes. 2D-COFs integrate n-type imide and p-type triazine active centres into the periodic porous polymer skeleton. With multiple characterizations, we elucidate the unique Faradaic reaction of the 2D-COF electrode, which involves AlCl2+ and AlCl4 - dual-ions as charge carriers. This work paves the avenue toward novel organic cathodes in RABs.

Plasmonic nanomaterials for solar-driven photocatalysis.

Plasmonic nanomaterials have spurred significant research interest in enhanced solar-driven photocatalysis due to their strong localized surface plasmon resonance (LSPR). As this rapid-developing research area has begun to raise and answer fundamental questions that determine the photocatalytic performance of plasmonic photocatalysts, it is an opportune time to evaluate the advancement and propose future trajectories. We first outline the fundamentals of LSPR, including its excitation, decay, and influencing factors. We then discuss three main enhancement mechanisms and their applicable scenarios for plasmonic photocatalysis. We then critically assess the recent works performed by our groups concerning plasmon-enhanced photocatalytic reactions. By introducing related works from other researchers, we demonstrate our contributions to the advancements of plasmonic photocatalysis. Finally, we discuss the current challenges and suggest future directions in three aspects: material development, mechanism exploration, and application extension. It is anticipated to delineate the state-of-the-art and direct future research in plasmon-enhanced value-added chemical transformations.

Sonophotocatalysis with Photoactive Nanomaterials for Wastewater Treatment and Bacteria Disinfection.

Sonophotocatalysis is described as a combination of two individual processes of photocatalysis and sonocatalysis. It has proven to be highly promising in degrading dissolved contaminants in wastewaters as well as bacteria disinfection applications. It eliminates some of the main disadvantages observed in each individual technique such as high costs, sluggish activity, and prolonged reaction times. The review has accomplished a critical analysis of sonophotocatalytic reaction mechanisms and the effect of the nanostructured catalyst and process modification techniques on the sonophotocatalytic performance. The synergistic effect between the mentioned processes, reactor design, and the electrical energy consumption has been discussed due to their importance when implementing this novel technology in practical applications, such as real industrial or municipal wastewater treatment plants. The utilization of sonophotocatalysis in disinfection and inactivation of bacteria has also been reviewed. In addition, we further suggest improvements to promote this technology from the lab-scale to large-scale applications. We hope this up-to-date review will advance future research in this field and push this technology toward widespread adoption and commercialization.

Imaging Photon-Induced Near-Field Distributions of a Plasmonic, Self-Assembled Vesicle by a Laser-Integrated Electron Microscope.

Plasmonic polymeric nanoassemblies offer valuable opportunities in photoconversion applications. Localized surface plasmon mechanisms behind such nanoassemblies govern their functionalities under light illumination. However, an in-depth investigation at the single nanoparticle (NP) level is still challenging, especially when the buried interface is involved, due to the availability of suitable techniques. Here, we synthesized an anisotropic heterodimer composed of a self-assembled polymer vesicle (THPG) capped with a single gold NP, enabling an 8-fold enhancement in hydrogen generation compared to the nonplasmonic THPG vesicle. We explored the anisotropic heterodimer at the single particle level by employing advanced transmission electron microscopes, including one equipped with a femtosecond pulsed laser, which allows us to visualize the polarization- and frequency-dependent distribution of the enhanced electric near fields at the vicinity of Au cap and Au-polymer interface. These elaborated fundamental findings may guide designing new hybrid nanostructures tailored for plasmon-related applications.

Silver nanoparticle enhanced metal-organic matrix with interface-engineering for efficient photocatalytic hydrogen evolution.

Integrating plasmonic nanoparticles into the photoactive metal-organic matrix is highly desirable due to the plasmonic near field enhancement, complementary light absorption, and accelerated separation of photogenerated charge carriers at the junction interface. The construction of a well-defined, intimate interface is vital for efficient charge carrier separation, however, it remains a challenge in synthesis. Here we synthesize a junction bearing intimate interface, composed of plasmonic Ag nanoparticles and matrix with silver node via a facile one-step approach. The plasmonic effect of Ag nanoparticles on the matrix is visualized through electron energy loss mapping. Moreover, charge carrier transfer from the plasmonic nanoparticles to the matrix is verified through ultrafast transient absorption spectroscopy and in-situ photoelectron spectroscopy. The system delivers highly efficient visible-light photocatalytic H2 generation, surpassing most reported metal-organic framework-based photocatalytic systems. This work sheds light on effective electronic and energy bridging between plasmonic nanoparticles and organic semiconductors.

A Janus Au-Polymersome Heterostructure with Near-Field Enhancement Effect for Implant-Associated Infection Phototherapy.

Polymer-inorganic hybrid Janus nanoparticles (PI-JNPs) have attracted extensive attention due to their special structures and functions. However, achieving the synergistic enhancement of photochemical activity between polymer and inorganic moieties in PI-JNPs remains challenging. Herein, the construction of a novel Janus Au-porphyrin polymersome (J-AuPPS) heterostructure by a facile one-step photocatalytic synthesis is reported. The near-field enhancement (NFE) effect between porphyrin polymersome (PPS) and Au nanoparticles in J-AuPPS is achieved to enhance its near-infrared (NIR) light absorption and electric/thermal field intensity at their interface, which improves the energy transfer and energetic charge-carrier generation. Therefore, J-AuPPS shows a higher NIR-activated photothermal conversion efficiency (48.4%) and generates more singlet oxygen compared with non-Janus core-particle Au-PPS nanostructure (28.4%). As a result, J-AuPPS exhibits excellent dual-mode (photothermal/photodynamic) antibacterial and anti-biofilm performance, thereby significantly enhancing the in vivo therapeutic effect in an implant-associated-infection rat model. This work is believed to motivate the rational design of advanced hybrid JNPs with desirable NFE effect and further extend their biological applications.

Enhancing Efficiency of Nonfullerene Organic Solar Cells via Using Polyelectrolyte-Coated Plasmonic Gold Nanorods as Rear Interfacial Modifiers.

Sufficient sunlight absorption and exciton generation are critical for developing efficient nonfullerene organic solar cells (OSCs). In this work, polyelectrolyte polystyrenesulfonate (PSS)-coated plasmonic gold nanorods (GNRs@PSS) were incorporated, for the first time, into the inverted nonfullerene OSCs as rear interfacial modifiers to improve sunlight absorption and charge generation via the near-field plasmonic and backscattering effects. The plasmonic GNRs effectively improved the sunlight absorption and enhanced the charge generation. Meanwhile, the negatively charged PSS shell ensured the uniform dispersion of the GNRs on the surface of the photoactive layer, optimized the interfacial contact, and further promoted the hole transport to the electrode. These concerted synergistic effects augmented the efficiency (10.11%) by nearly 20% relative to the control device (8.47%). Remarkably, the ultrathin (∼2.2 nm) organic layer on the surface of GNRs was closely examined by acquiring the carbon contrast image through energy-filtered transmission electron microscopy (EF-TEM), which clearly confirmed the coating uniformity from the side to end-cap of GNRs. The surface plasmon resonance (SPR) effect of the GNRs@PSS on the surface of the photoactive layer was unprecedentedly mapped by photoinduced force microscopy (PiFM) under the illumination of a tunable wavelength supercontinuum laser mimicking sunlight. Furthermore, investigations into the effect of size, surface coverage, and incorporation location of GNRs@PSS on the performance of OSCs revealed that the appropriate design and incorporation of the plasmonic nanostructures are crucial, otherwise the performance can be decreased, as evidenced in the case of front interface integration.

Highly thermal stable RNase A@PbS/ZnS quantum dots as NIR-IIb image contrast for visualizing temporal changes of microvasculature remodeling in flap.

Surgeons face great challenges in acquiring high-performance imaging because fluorescence probes with desired thermal stability remains rare. Here, hybrid lead sulfide/zinc sulfide quantum dots (PbS/ZnS QDs) nanostructures emitting in the long-wavelength end of the second near-infrared (NIR-IIb) window were synthesized and conjugated with Ribonuclease-A (RNase A). Such formed RNase A@PbS/ZnS QDs exhibited strong NIR IIb fluorescence and thermal stability, as supported by the photoluminescent emission assessment at different temperatures. This will allow the RNase A@PbS/ZnS QDs to provide stable fluorescence signals for long-time intraoperative imaging navigation, despite often happened, undesirable thermal accumulation in vivo. Compared to NIR-IIa fluorescence imaging, NIR-IIb vascular fluorescence imaging achieved larger penetration depth, higher signal/background ratios and nearly zero endogenous tissue autofluorescence. Moreover, these QDs illustrate the reliability during the real-time and long-time precise assessment of flap perfusion by clearly visualizing microvasculature map. These findings contribute to intraoperative imaging navigation with higher precision and lower risk.

3D Nanoscale Morphology Characterization of Ternary Organic Solar Cells.

It is highly desired to develop advanced characterization techniques to explore the 3D nanoscale morphology of the complicated blend film of ternary organic solar cells (OSCs). Here, ternary OSCs are constructed by incorporating the nonfullerene acceptor perylenediimide (PDI)-diketopyrrolopyrrole (DPP)-PDI and their morphology is characterized in depth to understand the performance variation. In particular, photoinduced force microscopy (PiFM) coupled with infrared laser spectroscopy is conducted to qualitatively study the distribution of donor and acceptors in the blend film by chemical identification and to quantitatively probe the segmentation of domains and the domain size distribution after PDI-DPP-PDI acceptor incorporation by PiFM imaging and data processing. In addition, the energy-filtered transmission electron microscopy with energy loss spectra is utilized to visualize the nanoscale morphology of ultrathin cross-sections in the configuration of the real ternary device for the first time in the field of photovoltaics. These measurements allow to "view" the surface and cross-sectional morphology and provide strong evidence that the PDI-DPP-PDI acceptor can suppress the aggregation of the fullerene molecules and generate the homogenous morphology with a higher-level of the molecularly mixed phase, which can prevent the charge recombination and stabilize the morphology of photoactive layer.

Solar Energy and Solar Cells.

Thanks to the helpful discussions and strong support provided by the Publisher and Editorial Staff of Nanomaterials, I was appointed as a section Editor-in-Chief of the newly launched section "Solar Energy and Solar Cells" earlier this year (2021) [...].

Synergistic Effect of Dielectric Property and Energy Transfer on Charge Separation in Non-Fullerene-Based Solar Cells.

In non-fullerene-based photovoltaic devices, it is unclear how excitons efficiently dissociate into charge carriers under small driving force. Here, we developed a modified method to estimate dielectric constants of PM6 donor and non-fullerene acceptors. Surprisingly, most non-fullerene acceptors and blend films showed higher dielectric constants. Moreover, they exhibited larger dielectric constants differences at the optical frequency. These results are likely bound to reduced exciton binding energy and bimolecular recombination. Besides, the overlap between the emission spectrum of donor and absorption spectra of non-fullerene acceptors allowed the energy transfer from donor to acceptors. Hence, based on the synergistic effect of dielectric property and energy transfer resulting in efficient charge separation, our finding paves an alternative path to elucidate the physical working mechanism in non-fullerene-based photovoltaic devices.

Bioinspired tough gel sheath for robust and versatile surface functionalization.

Sutures pervade surgeries, but their performance is limited by the mechanical mismatch with tissues and the lack of advanced functionality. Existing modification strategies result in either deterioration of suture's bulk properties or a weak coating susceptible to rupture or delamination. Inspired by tendon endotenon sheath, we report a versatile strategy to functionalize fiber-based devices such as sutures. This strategy seamlessly unites surgical sutures, tough gel sheath, and various functional materials. Robust modification is demonstrated with strong interfacial adhesion (>2000 J m-2). The surface stiffness, friction, and drag of the suture when interfacing with tissues can be markedly reduced, without compromising the tensile strength. Versatile functionalization of the suture for infection prevention, wound monitoring, drug delivery, and near-infrared imaging is then presented. This platform technology is applicable to other fiber-based devices and foreseen to affect broad technological areas ranging from wound management to smart textiles.

Phase-enabled metal-organic framework homojunction for highly selective CO2 photoreduction.

Conversion of clean solar energy to chemical fuels is one of the promising and up-and-coming applications of metal-organic frameworks. However, fast recombination of photogenerated charge carriers in these frameworks remains the most significant limitation for their photocatalytic application. Although the construction of homojunctions is a promising solution, it remains very challenging to synthesize them. Herein, we report a well-defined hierarchical homojunction based on metal-organic frameworks via a facile one-pot synthesis route directed by hollow transition metal nanoparticles. The homojunction is enabled by two concentric stacked nanoplates with slightly different crystal phases. The enhanced charge separation in the homojunction was visualized by in-situ surface photovoltage microscopy. Moreover, the as-prepared nanostacks displayed a visible-light-driven carbon dioxide reduction with very high carbon monooxide selectivity, and excellent stability. Our work provides a powerful platform to synthesize capable metal-organic framework complexes and sheds light on the hierarchical structure-function relationships of metal-organic frameworks.