Size-Dependent Penetration of Nanoparticles in Tumor Spheroids: A Multidimensional and Quantitative Study of Transcellular and Paracellular Pathways.

Tumor penetration of nanoparticles is crucial in nanomedicine, but the mechanisms of tumor penetration are poorly understood. This work presents a multidimensional, quantitative approach to investigate the tissue penetration behavior of nanoparticles, with focuses on the particle size effect on penetration pathways, in an MDA-MB-231 tumor spheroid model using a combination of spectrometry, microscopy, and synchrotron beamline techniques. Quasi-spherical gold nanoparticles of different sizes are synthesized and incubated with 2D and 3D MDA-MB-231 cells and spheroids with or without an energy-dependent cell uptake inhibitor. The distribution and penetration pathways of nanoparticles in spheroids are visualized and quantified by inductively coupled plasma mass spectrometry, two-photon microscopy, and synchrotron X-ray fluorescence microscopy. The results reveal that 15 nm nanoparticles penetrate spheroids mainly through an energy-independent transcellular pathway, while 60 nm nanoparticles penetrate primarily through an energy-dependent transcellular pathway. Meanwhile, 22 nm nanoparticles penetrate through both transcellular and paracellular pathways and they demonstrate the greatest penetration ability in comparison to other two sizes. The multidimensional analytical methodology developed through this work offers a generalizable approach to quantitatively study the tissue penetration of nanoparticles, and the results provide important insights into the designs of nanoparticles with high accumulation at a target site.

Cationic Oxidative Leaching Engineering Modulated In Situ Self-Reconstruction of Nickel Sulfide for Superior Water Oxidation.

Tuning the electroactive surface species of electrocatalysts remains a significant challenge for achieving highly efficient oxygen evolution reactions. Herein, we propose an innovative in situ leaching strategy, modulated by cationic oxidation, to achieve active self-reconstruction of these catalysts. Vanadium is introduced as a cation into Ni3S2 and oxidized under low oxidative potential, leading to subsequent leaching into the electrolyte and triggering self-reconstruction. The structural evolution from V-Ni3S2 to Ni(OH)2 and subsequently to NiOOH is identified by operando Raman as a three-step transition. In contrast, V-free Ni3S2 is unable to bypass the thermodynamically predicted nickel oxysulfide products to transform into active NiOOH. As a result, the self-restructured V-Ni3S2 only needs an ultralow overpotential of 155 mV at 10 mA cm-2, outperforming V-free Ni3S2 and many other advanced catalysts. This work provides new guidelines for manipulating in situ leaching to modulate the self-reconstruction of catalysts.

Electronic-Structure-Modulated Cu,Co-Coanchored N-Doped Nanocarbon as a Difunctional Electrocatalyst for Hydrogen Evolution and Oxygen Reduction Reactions.

To alleviate the problems of environmental pollution and energy crisis, aggressive development of clean and alternative energy technologies, in particular, water splitting, metal-air batteries, and fuel cells involving two key half reactions comprising hydrogen evolution reaction (HER) and oxygen reduction (ORR), is crucial. In this work, an innovative hybrid comprising heterogeneous Cu/Co bimetallic nanoparticles homogeneously dispersed on a nitrogen-doped carbon layer (Cu/Co/NC) was constructed as a bifunctional electrocatalyst toward HER and ORR via a hydrothermal reaction along with post-solid-phase sintering technique. Thanks to the interfacial coupling and electronic synergism between the Cu and Co bimetallic nanoparticles, the Cu/Co/NC catalyst showed improved catalytic ORR activity with a half-wave potential of 0.865 V and an excellent stability of more than 30 h, even compared to 20 wt% Pt/C. The Cu/Co/NC catalyst also exhibited excellent HER catalytic performance with an overpotential of below 149 mV at 10 mA/cm2 and long-term operation for over 30 h.

High-Performance Flexible Graphene Oxide-Based Moisture-Enabled Nanogenerator via Multilayer Heterojunction Engineering and Power Management System.

Recently, there has been a surge of interest in nanogenerators within the scientific community because their immense potential for extracting energy from the surrounding environment. A promising approach involves utilizing ambient moisture as an energy source for portable devices. In this study, moisture-enabled nanogenerators (MENGs) are devised by integrating heterojunctions of graphene oxide (GO) and reduced graphene oxide (rGO). Benefiting from the unique structure, a larger ion concentration gradient is achieved as well as a lower resistance, which leads to enhanced electricity generation. The resulting MENG generates a desirable open-circuit voltage of 0.76 V and a short-circuit current density of 73 µA cm-2 with a maximum power density of 15.8 µW cm-2 . Notably, the designed device exhibits a high voltage retention of more than 90% after 3000 bending cycles, suggesting a high potential for flexible applications. Moreover, a large-scale integrated MENG array is developed by incorporating flexible printed circuit technology and connecting it to a power management system. This integrated system can provide ample energy to operate an electronic ink display and drive a heart rate sensor for health monitoring. The outcomes of this research present a novel framework for advancing next-generation self-powered flexible devices, thereby demonstrating significant promise for future wearable electronics.

Highly Selective Metal-Free Electrochemical Production of Hydrogen Peroxide on Functionalized Vertical Graphene Edges.

Electrochemical generation of hydrogen peroxide (H2 O2 ) is an attractive alternative to the energy-intensive anthraquinone oxidation process. Metal-free carbon-based materials such as graphene show great promise as efficient electrocatalysts in alkaline media. In particular, the graphene edges possess superior electrochemical properties than the basal plane. However, identification and enhancement of the catalytically active sites at the edges remain challenging. Furthermore, control of surface wettability to enhance gas diffusion and promote the performance in bulk electrolysis is largely unexplored. Here, a metal-free edge-rich vertical graphene catalyst is synthesized and exhibits a superior performance for H2 O2 production, with a high onset potential (0.8 V versus reversible hydrogen electrode (RHE) at 0.1 mA cm-2 ) and 100% Faradaic efficiency at various potentials. By tailoring the oxygen-containing functional groups using various techniques of electrochemical oxidation, thermal annealing and oxygen plasma post-treatment, the edge-bound in-plane ether-type (COC) groups are revealed to account for the superior catalytic performance. To manipulate the surface wettability, a simple vacuum-based method is developed to effectively induce material hydrophobicity by accelerating hydrocarbon adsorption. The increased hydrophobicity greatly enhances gas transfer without compromising the Faradaic efficiency, enabling a H2 O2 productivity of 1767 mmol gcatalyst -1 h-1 at 0.4 V versus RHE.

Recent Development of Moisture-Enabled-Electric Nanogenerators.

Power generation by converting energy from the ambient environment has been considered a promising strategy for developing decentralized electrification systems to complement the electricity supply for daily use. Wet gases, such as water evaporation or moisture in the atmosphere, can be utilized as a tremendous source of electricity by emerging power generation devices, that is, moisture-enabled-electric nanogenerators (MEENGs). As a promising technology, MEENGs provided a novel manner to generate electricity by harvesting energy from moisture, originating from the interactions between water molecules and hydrophilic functional groups. Though the remarkable progress of MEENGs has been achieved, a systematic review in this specific area is urgently needed to summarize previous works and provide sharp points to further develop low-cost and high-performing MEENGs through overcoming current limitations. Herein, the working mechanisms of MEENGs reported so far are comprehensively compared. Subsequently, a systematic summary of the materials selection and fabrication methods for currently reported MEENG construction is presented. Then, the improvement strategies and development directions of MEENG are provided. At last, the demonstrations of the applications assembled with MEENGs are extracted. This work aims to pave the way for the further MEENGs to break through the performance limitations and promote the popularization of future micron electronic self-powered equipment.

Interface thermodynamic state-induced high-performance memristors.

A new class of memristors based on long-range-ordered CeO2 nanocubes with a controlled degree of self-assembly is presented, in which the regularity and range of the nanocubes can be greatly improved with a highly concentrated dispersed surfactant. The magnitudes of the hydrophobicity and surface energy components as functions of surfactant concentration were also investigated. The self-assembled nanostructure was found to demonstrate excellent degradation in device threshold voltage with excellent uniformity in resistive switching parameters, particularly a set voltage distribution of ∼ 0.2 V over 30 successive cycles and a fast response time for writing (0.2 µs) and erasing (1 µs) operations, thus offering great potential for nonvolatile memory applications with high performance at low cost.

Interfacial Solar Evaporation: From Fundamental Research to Applications.

In the last decade, interfacial solar steam generation (ISSG), powered by natural sunlight garnered significant attention due to its great potential for low-cost and environmentally friendly clean water production in alignment with the global decarbonization efforts. This review aims to share the knowledge and engage with a broader readership about the current progress of ISSG technology and the facing challenges to promote further advancements toward practical applications. The first part of this review assesses the current strategies for enhancing the energy efficiency of ISSG systems, including optimizing light absorption, reducing energy losses, harvesting additional energy, and lowering evaporation enthalpy. Subsequently, the current challenges faced by ISSG technologies, notably salt accumulation and bio-fouling issues in practical applications, are elucidated and contemporary methods are discussed to overcome these challenges. In the end, potential applications of ISSG, ranging from initial seawater desalination and industrial wastewater purification to power generation, sterilization, soil remediation, and innovative concept of solar sea farm, are introduced, highlighting the promising potential of ISSG technology in contributing to sustainable and environmentally conscious practices. Based on the review and in-depth understanding of these aspects, the future research focuses are proposed to address potential issues in both fundamental research and practical applications.

Multiscale Structural Design of 2D Nanomaterials-based Flexible Electrodes for Wearable Energy Storage Applications.

2D nanomaterials play a critical role in realizing high-performance flexible electrodes for wearable energy storge devices, owing to their merits of large surface area, high conductivity and high strength. The electrode is a complex system and the performance is determined by multiple and interrelated factors including the intrinsic properties of materials and the structures at different scales from macroscale to atomic scale. Multiscale design strategies have been developed to engineer the structures to exploit full potential and mitigate drawbacks of 2D materials. Analyzing the design strategies and understanding the working mechanisms are essential to facilitate the integration and harvest the synergistic effects. This review summarizes the multiscale design strategies from macroscale down to micro/nano-scale structures and atomic-scale structures for developing 2D nanomaterials-based flexible electrodes. It starts with brief introduction of 2D nanomaterials, followed by analysis of structural design strategies at different scales focusing on the elucidation of structure-property relationship, and ends with the presentation of challenges and future prospects. This review highlights the importance of integrating multiscale design strategies. Finding from this review may deepen the understanding of electrode performance and provide valuable guidelines for designing 2D nanomaterials-based flexible electrodes.

Stabilizing Lead Halide Perovskites via an Organometallic Chemical Bridge for Efficient and Stable Photovoltaics.

Defects around the surface and grain boundaries of perovskite films normally cause severe nonradiative recombination and imbalanced charge carrier transport, further limiting both the efficiency and stability of perovskite solar cells (PSCs). To tackle this critical issue, we propose a chemical bridge strategy to reconstruct the interface using organometallic molecules. The commercially available molecule bis(diphenylphosphino)ferrocene (FcP2), with a unique bridge molecular structure, anchors and chelates Pb atoms by forming strong Pb-P bonds and further passivates both surfaces and grain boundaries. Detailed characterization revealed that bridge molecule FcP2 reconstruction can effectively suppress nonradiative recombination, and the electron delocalization properties of the ferrocene core can further achieve more balanced interfacial carrier transport. The resultant N-i-P PSC device outputs close to 25% efficiency together with one of the best reported operational stabilities, maintaining over 95% of the initial efficiency after 1000 h of continuous operation at the maximum power point under 1-sun illumination.

Graphene and MOF Assembly: Enhanced Fabrication and Functional Derivative via MOF Amorphization.

The integration of graphene and metal-organic frameworks (MOFs) has numerous implications across various domains, but fabricating such assemblies is often complicated and time-consuming. Herein, a one-step preparation of graphene-MOF assembly is presented by directly impregnating vertical graphene (VG) arrays into the zeolitic imidazolate framework (ZIF) precursors under ambient conditions. This approach can effectively assemble multiple ZIFs, including ZIF-7, ZIF-8, and ZIF-67, resulting in their uniform dispersion on the VG with adjustable sizes and shapes. Hydrogen defects on the VG surface are critical in inducing such high-efficiency ZIF assembly, acting as the reactive sites to interact with the ZIF precursors and facilitate their crystallisation. The versatility of VG-ZIF-67 assembly is further demonstrated by exploring the process of MOF amorphization. Surprisingly, this process leads to an amorphous thin-film coating formed on VG (named VG-IL-amZIF-67), which preserves the short-range molecular bonds of crystalline ZIF-67 while sacrificing the long-range order. Such a unique film-on-graphene architecture maintains the essential characteristics and functionalities of ZIF-67 within a disordered arrangement, making it well-suited for electrocatalysis. In electrochemical oxygen reduction, VG-IL-amZIF-67 exhibits exceptional activity, selectivity, and stability to produce H2O2 in acid media.

High-Performance Optoelectronic Gas Sensing Based on All-Inorganic Mixed-Halide Perovskite Nanocrystals with Halide Engineering.

Gas sensors are of great interest to portable and miniaturized sensing technologies with applications ranging from air quality monitoring to explosive detection and medical diagnostics, but the existing chemiresistive NO2 sensors still suffer from issues such as poor sensitivity, high operating temperature, and slow recovery. Herein, a high-performance NO2 sensors based on all-inorganic perovskite nanocrystals (PNCs) is reported, achieving room temperature operation with ultra-fast response and recovery time. After tailoring the halide composition, superior sensitivity of ≈67 at 8 ppm NO2 is obtained in CsPbI2 Br PNC sensors with a detection level down to 2 ppb, which outperforms other nanomaterial-based NO2 sensors. Furthermore, the remarkable optoelectronic properties of such PNCs enable dual-mode operation, i.e., chemiresistive and chemioptical sensing, presenting a new and versatile platform for advancing high-performance, point-of-care NO2 detection technologies.

Multi-Interface Engineering of MXenes for Self-Powered Wearable Devices.

Self-powered wearable devices with integrated energy supply module and sensitive sensors have significantly blossomed for continuous monitoring of human activity and the surrounding environment in healthcare sectors. The emerging of MXene-based materials has brought research upsurge in the fields of energy and electronics, owing to their excellent electrochemical performance, large surface area, superior mechanical performance, and tunable interfacial properties, where their performance can be further boosted via multi-interface engineering. Herein, a comprehensive review of recent progress in MXenes for self-powered wearable devices is discussed from the aspects of multi-interface engineering. The fundamental properties of MXenes including electronic, mechanical, optical, and thermal characteristics are discussed in detail. Different from previous review works on MXenes, multi-interface engineering of MXenes from termination regulation to surface modification and their impact on the performance of materials and energy storage/conversion devices are summarized. Based on the interfacial manipulation strategies, potential applications of MXene-based self-powered wearable devices are outlined. Finally, proposals and perspectives are provided on the current challenges and future directions in MXene-based self-powered wearable devices.

Enhanced Piezocatalytic Performance of Li-doped BaTiO3 Through a Facile Sonication-Assisted Precipitation Approach.

Piezocatalysis-induced dye degradation has garnered significant attention as an effective method for addressing wastewater treatment challenges. In our study, we employed a room-temperature sonochemical method to synthesize piezoelectric barium titanate nanoparticles (BaTiO3: BTO) with varying levels of Li doping. This approach not only streamlined the sample preparation process but also significantly reduced the overall time required for synthesis, making it a highly efficient and practical method. One of the key findings was the exceptional performance of the Li-doped BTO nanoparticles. With 20 mg of Li additive, we achieved 90 % removal of Rhodamine B (RhB) dye within a relatively short timeframe of 150 minutes, all while subjecting the sample to ultrasonic vibration. This rapid and efficient dye degradation was further evidenced by the calculated kinetic rate constant, which indicated seven times faster degradation rate compared to pure BTO. The enhanced piezoelectric performance observed in the Li-doped BTO nanoparticles can be attributed to the strategic substitution of Li atoms, which facilitated a more efficient transfer of charge charges at the interface. Overall, our study underscores the potential of piezocatalysis coupled with advanced materials like Li-doped BTO nanoparticles as a viable and promising solution for wastewater treatment, offering both efficiency and environmental sustainability.

One-Step Synthesis of Graphene-Covered Silver Nanowires with Enhanced Stability for Heating and Strain Sensing.

Solution-processed silver nanowire (AgNW) networks have been considered as promising electrode candidates for next-generation electronic devices. However, they suffer from poor thermal and electrical stability and low mechanical properties, hindering their practical applications. In this work, graphene nanosheets are successfully introduced into AgNW via a facile one-step solvothermal process. Benefiting from increased conductive paths, the resultant AgNW/graphene films exhibit high electrical conductivity. More importantly, the interlocking NW morphology can be maintained under high temperature and applied voltage due to suppressed Ag migration, which is enabled by the introduction of graphene. This feature leads to enhanced thermal and electrical stability, making them suitable for use as transparent heaters. Furthermore, the composite films present excellent mechanical performance, and negligible resistance change is observed after 10 000 repeated bending cycles. To demonstrate their feasibility toward sensor applications, sandwiched strain sensors are designed, which can endure larger tensile strains and show higher sensitivity and repeatability compared with pure AgNW-based device. Furthermore, various hand gestures can be easily recognized by the resultant sensors based on unique combinations of sensing response. This work not only provides a low-cost method to realize large-scale synthesis of AgNW/graphene composites but also offers guidance to prepare high-performance electrodes for advanced electronics.

Stabilizing High-Voltage Performance of Nickel-Rich Cathodes via Facile Solvothermally Synthesized Niobium-Doped Strontium Titanate.

Ni-rich layered ternary cathodes are promising candidates thanks to their low toxic Co-content and high energy density (∼800 Wh/kg). However, a critical challenge in developing Ni-rich cathodes is to improve cyclic stability, especially under high voltage (>4.3 V), which directly affects the performance and lifespan of the battery. In this study, niobium-doped strontium titanate (Nb-STO) is successfully synthesized via a facile solvothermal method and used as a surface modification layer onto the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. The results exhibited that the Nb-STO modification significantly improved the cycling stability of the cathode material even under high-voltage (4.5 V) operational conditions. In particular, the best sample in our work could provide a high discharge capacity of ∼190 mAh/g after 100 cycles under 1 C with capacity retention over 84% in the voltage range of 3.0-4.5 V, superior to the pristine NCM811 (∼61%) and pure STO modified STO-811-600 (∼76%) samples under the same conditions. The improved electrochemical performance and stability of NCM811 under high voltage should be attributed to not only preventing the dissolution of the transition metals, further reducing the electrolyte's degradation by the end of charge, but also alleviating the internal resistance growth from uncontrollable cathode-electrolyte interface (CEI) evolution. These findings suggest that the as-synthesized STO with an optimized Nb-doping ratio could be a promising candidate for stabilizing Ni-rich cathode materials to facilitate the widespread commercialization of Ni-rich cathodes in modern LIBs.

Synergistic barium titanate/MXene composite as a high-performance piezo-photocatalyst for efficient dye degradation.

Piezo-photocatalysis combines photocatalysis and piezoelectric effects to enhance catalytic efficiency by creating an internal electric field in the photocatalyst, improving carrier separation and overall performance. This study presents a high-performance piezo-photocatalyst for efficient dye degradation using a synergistic barium titanate (BTO)-MXene composite. The composite was synthesized via a facile method, combining the unique properties of BTO nanoparticles with the high conductivity of MXene. The structural and morphological analysis confirmed the successful formation of the composite, with well-dispersed BTO nanoparticles on the MXene surface. The piezo-photocatalytic activity of the composite was evaluated using a typical dye solution (Rhodamine B: RhB) under ultraviolet irradiation and mechanical agitation. The results revealed a remarkable enhancement in dye degradation (90 % in 15 min for piezo-photocatalysis) compared to individual stimuli (58.2 % for photocatalysis and 95.8 % in 90 min for piezocatalysis), highlighting the synergistic effects between BTO and MXene. The enhanced catalytic performance was attributed to the efficient charge separation and transfer facilitated by the composite's structure, leading to increased reactive species generation and dye molecule degradation. Furthermore, the composite exhibited excellent stability and reusability, showcasing its potential for practical applications in wastewater treatment. Overall, this work represents a promising strategy for designing high-performance synergistic catalysts, addressing the pressing need for sustainable solutions in environmental remediation.

Introduction to Supercapacitors.

Guest editors Zhaojun Han, Ruopian Fang, Dewei Chu, Da-Wei Wang and Kostya (Ken) Ostrikov, introduce this Nanoscale Advances themed issue on supercapacitors.

Oxygen Defect and Cl--Doped Modulated TiNb2O7 Compound with High Rate Performance in Lithium-Ion Batteries.

TiNb2O7 has attracted extensive attention from lithium-ion battery researchers due to its superior specific capacity and safety. However, its poor ion conductivity and electron conductivity hinder its further development. To improve the ion/electron transport of TiNb2O7, we report that chlorine doping and oxygen vacancy engineering regulate the energy band and crystal structure simultaneously through a simple solid-phase method. NH4Cl was used to realize Cl- doping and oxygen vacancy production. A Rietveld refinement demonstrates an effective substitution of Cl in the O sites of Nb-O octahedra, with an enlarged crystal plane spacing. The oxygen vacancies provide more active sites for lithium intercalation. The diffusion coefficient of Li+ is inceased from 2.39 × 10-14 to 1.50 × 10-13 cm2 s-1, which reveals the positive influence of Cl- doping and oxygen vacancies on the promoted Li+ transport behavior. Charge compensation is introduced by the doping of Cl- and the generation of oxygen vacancies, leading to the formation of Ti3+ and Nb4+ and the adjustment of the electronic structure. DFT calculations reveal that TiNb2O7 with Cl- doping and an O vacancy shows a metallic property with a finite value at the Fermi level, which is conducive to electron transfer in the electrode material. Benefiting from these advantages, the modified TiNb2O7 presents superior rate performance with a commendable capacity of 172.82 mAh g-1 at 50 C. This work provides guidance to design high-performance anode materials for high-rate lithium-ion batteries.

Engineering work functions of cobalt-doped manganese oxide based electrocatalysts for highly efficient oxygen evolution reaction.

The crystalline and electronic structures are two important factors for the design of electrocatalysts. In this work, Co-doped MnO electrocatalysts grown on nickel foam (NF) were prepared by a facile hydrothermal reaction, followed by H2 treatment process. The electrocatalytic performance of MnO was significantly improved after doping with Co and the Co0.1Mn0.9O-NF sample achieved excellent oxygen evolution reaction (OER) performance with low overpotential (370 mV at 10 mA cm-2) and reasonable Tafel slope (85.6 mV dec-1). Significantly, the low work function was obtained in the Co0.1Mn0.9O-NF sample (4.37 eV), which could accelerate the charge transfer process of the OER activity. The excellent OER performance of the Co0.1Mn0.9O-NF sample is also attributed to the rich active sites, which improved electrical conductivity and enlarged electrochemical surface areas.