Flexible OLED Performance Enhancement: The Impact of Ag NWs: Ag NPs Electrode-Integrated MoOX QDs Hole-Injection Layer

The growing interest in organic light-emitting diodes (OLEDs) has largely been attributed to significant performance enhancements achieved with molybdenum trioxide (MoO3). This study aims to achieve the integration of flexible transparent electrodes (FTEs) and hole-injection layers (HILs) through the use of a codoped system comprised of silver nanowires (Ag NWs) and silver nanoparticles (Ag NPs), as well as poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) and molybdenum oxide quantum dots (QDs). The primary objective of this proposed technique is to use a MoO3 QD as part of a flexible electrode, reducing the step of HIL deposition in the traditional device preparation process, thereby simplifying the fabrication of flexible devices. MoO3 was reduced to MoOX, which offered an alternative pathway for hole injection to increase carrier mobility, thereby further enhancing flexible device performance. The luminance of the prepared flexible OLEDs remained at 90% of their original level, even after undergoing 500 bending tests. These findings indicate the fabricated FTEs, integrated into this system with HILs, exhibited excellent optoelectronic performance and high mechanical stability. Moreover, the structure of the flexible device with higher performance was optimized by reducing the HIL deposition process compared to traditional devices.

Recent advances in photothermal nanomaterials for ophthalmic applications

The human eye, with its remarkable resolution of up to 576 million pixels, grants us the ability to perceive the world with astonishing accuracy. Despite this, over 2 billion people globally suffer from visual impairments or blindness, primarily because of the limitations of current ophthalmic treatment technologies. This underscores an urgent need for more advanced therapeutic approaches to effectively halt or even reverse the progression of eye diseases. The rapid advancement of nanotechnology offers promising pathways for the development of novel ophthalmic therapies. Notably, photothermal nanomaterials, particularly well-suited for the transparent tissues of the eye, have emerged as a potential game changer. These materials enable precise and controllable photothermal therapy by effectively manipulating the distribution of the thermal field. Moreover, they extend beyond the conventional boundaries of thermal therapy, achieving unparalleled therapeutic effects through their diverse composite structures and demonstrating enormous potential in promoting retinal drug delivery and photoacoustic imaging. This paper provides a comprehensive summary of the structure-activity relationship between the photothermal properties of these nanomaterials and their innovative therapeutic mechanisms. We review the latest research on photothermal nanomaterial-based treatments for various eye diseases. Additionally, we discuss the current challenges and future perspectives in this field, with a focus on enhancing global visual health.

A Critical Perspective on Photothermal De-Icing

To tackle the formidable challenges posed by extreme cold weather events, significant advancements have been made in developing functional surfaces capable of efficiently removing accreted ice. Nevertheless, many of these surfaces still require external energy input, such as electrical power, which raises concerns regarding their alignment with global sustainability goals. Over the past decade, increasing attention has been directed toward photothermal surface designs that harness solar energy-a resource available on Earth in quantities exceeding the total reserves of coal and oil combined. By converting solar energy into heat, these designs enable the transformation of the interfacial solid-solid contact (ice-substrate) into a liquid-solid contact (water-substrate), significantly reducing interfacial adhesion and facilitating rapid ice removal. This critical perspective begins by emphasizing the advantages of photothermal design over traditional de-icing methods. It then delves into an in-depth analysis of three primary photothermal mechanisms, examining how these principles have expanded the scope of de-icing technologies and contributed to advancements in photothermal surface design. Finally, key fundamental and technical challenges are identified, offering strategic guidelines for future research aimed at enabling practical, real-world applications.

Photo-Stimulated Zn-based Batteries: Progress, Challenges, and Perspectives

Solar energy, as a renewable energy source, dominates the vast majority of human energy, which can be harvested and converted by photovoltaic solar cells. However, the intermittent availability of solar energy restricts the actual utilization circumstances of solar cells. Integrating photo-responsive electrodes into an energy storage device emerges as a dependable and executable strategy, fostering the creation of photo-stimulated batteries that seamlessly amalgamate the process of solar energy collection, conversion, and storage in one system. Endowed by virtues such as cost-effectiveness, facile manufacturing, safety, and environmental friendliness, photo-stimulated Zn-based batteries have attracted considerable attention. The progress report furnishes a brief overview, summarizing various photo-stimulated Zn-based batteries. Their configurations, operational principles, advancements, and the intricate engineering of photoelectrode designs are introduced, respectively. Through rigorous architectural design, photo-stimulated Zn-based batteries exhibit the ability to initiate charging by saving electricity usage, and in certain instances, even without the need for external electrical grids under illumination. Furthermore, the compensation of solar energy can be explored to improve the output electric energy. At last, opportunities and challenges toward photo-stimulated Zn-based batteries in the process of development are proposed and discussed in the hope of expanding their application scenarios and accelerating the commercialization progress.

Advances in Hierarchical Inorganic Nanostructures for Efficient Solar Energy Harvesting Systems

The urgent need to address the global energy and environmental crisis necessitates the development of efficient solar-power harvesting systems. Among the promising candidates, hierarchical inorganic nanostructures stand out due to their exceptional attributes, including a high specific surface area, abundant active sites, and tunable optoelectronic properties. In this comprehensive review, we delve into the fundamental principles underlying various solar energy harvesting technologies, including dye-sensitized solar cells (DSSCs), photocatalytic, photoelectrocatalytic (water splitting), and photothermal (water purification) systems, providing a foundational understanding of their operation. Thereafter, the discussion is focused on recent advancements in the synthesis, design, and development of hierarchical nanostructures composed of diverse inorganic material combinations, tailored for each of these solar energy harvesting systems. We meticulously elaborate on the distinct synthesis methods and conditions employed to fine-tune the morphological features of these hierarchical nanostructures. Furthermore, this review offers profound insights into critical aspects such as electron transfer mechanisms, band gap engineering, the creation of hetero-hybrid structures to optimize interface chemistry through diverse synthesis approaches, and precise adjustments of structural features. Beyond elucidating the scientific fundamentals, this review explores the large-scale applications of the aforementioned solar harvesting systems. Additionally, it addresses the existing challenges and outlines the prospects for achieving heightened solar-energy conversion efficiency.

Record high external quantum efficiency of 20% achieved in fully solution-processed quantum dot light-emitting diodes based on hole-conductive metal oxides

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely used as a hole injection material in quantum dot (QD) light-emitting diodes (QLEDs). However, it degrades the organic materials and electrodes in QLEDs due to its strong hydroscopicity and acidity. Although hole-conductive metal oxides have a great potential to solve this disadvantage, it is still a challenge to achieve efficient and stable QLEDs by using these solution-processed metal oxides. Herein, the state-of-the-art QLEDs fabricated by using hole-conductive MoOx QDs are achieved. The α-phase MoOx QDs exhibit a monodispersed size distribution with clear and regular crystal lattices, corresponding to high-quality nanocrystals. Meanwhile, the MoOx film owns an excellent transmittance, suitable valence band, good morphology and impressive hole-conductivity, demonstrating that the MoOx film could be used as a hole injection layer in QLEDs. Moreover, the rigid and flexible red QLEDs made by MoOx exhibit peak external quantum efficiencies of over 20%, representing a new record for the hole-conductive metal oxide based QLEDs. Most importantly, the MoOx QDs afford their QLEDs with a longer T95 lifetime than these devices made by PEDOT:PSS. As a result, we believe that the MoOx QDs could be used as efficient and stable hole injection materials used in QLEDs.

Recent Advances of Green Electricity Generation: Potential in Solar Interfacial Evaporation System

Solar-driven interfacial evaporation (SDIE) has played a pivotal role in optimizing water-energy utilization, reducing conventional power costs, and mitigating environmental impacts. The increasing emphasis on the synergistic cogeneration of water and green electricity through SDIE is particularly noteworthy. However, there is a gap of existing reviews that have focused on the mechanistic understanding of green power from water-electricity cogeneration (WEC) systems, the structure-activity relationship between efficiency of green energy utilization in WEC and material design in SDIE. Particularly, it lacks a comprehensive discussion to address the challenges faced in these areas along with potential solutions. Therefore, this review aims to comprehensively assess the progress and future perspective of green electricity from WEC systems by investigating the potential expansion of SDIE. First, it provides a comprehensive overview about material rational design, thermal management, and water transportation tunnels in SDIE. Then, it summarizes diverse energy sources utilized in the SDIE process, including steaming generation, photovoltaics, salinity gradient effect, temperature gradient effect, and piezoelectric effect. Subsequently, it explores factors that affect generated green electricity efficiency in WEC. Finally, this review proposes challenges and possible solution in the development of WEC.

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.

Stable polyethylene glycol/biochar composite as a cost-effective photothermal absorber for 24 hours of steam and electricity cogeneration

Seawater desalination powered by solar energy is the most environmentally and economical solution in responding to the global water and energy crisis. However, solar desalination has been negatively impacted by intermittent sun radiation that alternates between day and night. In this study, sugarcane bagasse (SCB) was recycled via the pyrolysis process to biochar as a cost-effective solar absorber. Besides, polyethylene glycol (PEG) as a phase change material was encapsulated in the abundant pore structure of biochar to store the thermal energy for 24 hours of continuous steam generation. The BDB/1.5 PEG evaporator exhibited an evaporation rate of 2.11 kg m-2 h-1 (98.1% efficiency) under 1 sun irradiation. Additionally, the BDB/1.5 PEG evaporator incorporated by the TEC1-12706 module for continuous steam and electricity generation with a power density of 320.41 mW m-2. Moreover, 10 continuous hours of evaporation were applied to the composite demonstrating outstanding stability. The composite exhibited high water purification efficiency through solar desalination due to the abundant functional groups on the biochar surface. Finally, the resulting low-cost and highly efficient PCM-based absorber can be used on a wide scale to produce fresh water and energy.

Hierarchical Tantalum Oxide Composite for Efficient Solar-Driven Water Purification

Applying solar energy to generate drinking water is a clean and low-energy exhaust route to address the issue of water purification. The current challenge with solar vapor generation is constructing nano/micro-hierarchical structures that can convert solar irradiation into exploitable thermal energy with high efficiency. Although various structures and material designs have been reported in recent years, solar vapor conversion can be improved by integrating light harvesting, thermal concentration, and water diffusion. Because of the optimized solar harvesting, enhanced heat capacity, and specified diffusive path endowed by the hierarchical composite structure, amorphous tantalum oxide/carbon-based yolk-shell structures (α-Ta2O5/C YS) for highly efficient solar vapor generation under 1 sun illumination are applied in this study. As a result, the α-Ta2O5/C YS realized a water evaporation rate of 3.54 kg m-2 h-1 with a solar-thermal conversion efficiency of 91% under one sun irradiation (1 kW m-2) with excellent evaporation stability. The collected water from seawater meets the World Health Organization drinking water standard. Importantly, reactive oxygen species enabled by α-Ta2O5 could be produced for water sterilization, exhibiting a facile way for application in various scenarios to acquire drinkable water.

Photothermal Nanomaterials: A Powerful Light-to-Heat Converter

All forms of energy follow the law of conservation of energy, by which they can be neither created nor destroyed. Light-to-heat conversion as a traditional yet constantly evolving means of converting light into thermal energy has been of enduring appeal to researchers and the public. With the continuous development of advanced nanotechnologies, a variety of photothermal nanomaterials have been endowed with excellent light harvesting and photothermal conversion capabilities for exploring fascinating and prospective applications. Herein we review the latest progresses on photothermal nanomaterials, with a focus on their underlying mechanisms as powerful light-to-heat converters. We present an extensive catalogue of nanostructured photothermal materials, including metallic/semiconductor structures, carbon materials, organic polymers, and two-dimensional materials. The proper material selection and rational structural design for improving the photothermal performance are then discussed. We also provide a representative overview of the latest techniques for probing photothermally generated heat at the nanoscale. We finally review the recent significant developments of photothermal applications and give a brief outlook on the current challenges and future directions of photothermal nanomaterials.

3D carbonized grooved straw with efficient evaporation and salt resistance for solar steam generation

Solar steam generation (SSG) is considered an effective solution to the global shortage of freshwater resources. To solve the practical application challenges of SSG in remote outdoor environments where electricity is scarce, it is of great importance to developing new solar evaporators. In this study, a three-dimensional (3D) biochar solar evaporator based on carbonized grooved straw was prepared from agricultural waste corn straw, which had high solar energy conversion efficiency and excellent salt resistance. The existence of grooves increases the surface area to absorb more sunlight and makes the light multilevel reflection improve the evaporation rate. The excellent light absorption, super hydrophilic, and heat shielding properties of 3D carbonized grooved straw resulted in a good evaporation rate (1.57 kg⋅m^-2·h^-1) and energy efficiency (85.9%) under 1 sun irradiation. The 3D grooved biochar solar distiller also demonstrated efficient formation evaporation performance and excellent salt resistance in practical applications in seawater desalination and surface water purification. The 3D grooved biochar solar distiller prepared from agricultural waste has the advantages of being economical and environmentally friendly, with good application prospects.

A flexible, high-efficiency, and low-cost FeS2@CTS hydrogel film for solar interface water evaporation

Solar interfacial water evaporation to obtain pure water has attracted extensive attention in recent years. In this work, based on the excellent optical property of FeS2 and the cross-linking nanostructure of chitosan (CTS), a FeS2@CTS hydrogel composite film for solar interfacial water evaporation was developed by hydrothermal synthesis and the following composite coating technology. The prepared FeS2@CTS presented high solar absorptivity of 95.27% and fast optical response capability. Under the optimized condition, the evaporation rate of pure water reached 3.34 kg m−2 h−1 and the photothermal conversion efficiency was 103.06% under one sun irradiation. In five runs, the evaporation rate of the FeS2@CTS was stable, indicating the excellent cycle stability. Also, in the desalination test, the stable evaporation rate of 1.74 kg m−2 h−1 was obtained in five runs. Due to the simple preparation method, low cost, and outstanding interfacial evaporation property, this FeS2@CTS indicates great potential for the seawater desalination or other photothermal conversion applications.

Advances in Ultra-small Fluorescence Nanoprobes for Detection of Metal Ions, Drugs, Pesticides and Biomarkers

Identification of trace level chemical species (drugs, pesticides, metal ions and biomarkers) plays key role in environmental monitoring. Recently, fluorescence assay has shown significant advances in detecting of trace level drugs, pesticides, metal ions and biomarkers in real samples. Ultra-small nanostructure materials (metal nanoclusters (NCs), quantum dots (QDs) and carbon dots (CDs)) have been integrated with fluorescence spectrometer for sensitive and selective analysis of trace level target analytes in various samples including environmental and biological samples. This review summarizes the properties of metal NCs and ligand chemistry for the fabrication of metal NCs. We also briefly summarized the synthetic routes for the preparation of QDs and CDs. Advances of ultra-small fluorescent nanosensors (NCs, QDs and CDs) for sensing of metal ions, drugs, pesticides and biomarkers in various sample matrices are briefly discussed. Additionally, we discuss the recent challenges and future perspectives of ultra-small materials as fluorescent sensors for assaying of wide variety of target analytes in real samples.

Interface Engineering of a Ti4O7 Nanofibrous Membrane for Efficient Solar-Driven Evaporation

Solar-driven interfacial evaporation provides a feasible and sustainable way to solve the fresh water shortage using abundant solar energy and has recently attracted considerable attention. However, it has been limited by the evaporation rate and solar-heat conversion efficiency of the current materials. Herein, a novel Ti₄O₇ membrane with synergetic photothermal and electrothermal effects was developed using a straightforward in situ approach. Based on interface engineering, the interface between the surface of the membrane and water was hydrophobically modified, and a thermal insulation layer was added to the bottom of the membrane. The optimized self-floating membrane with excellent sunlight absorbability and conductivity achieved a remarkably high evaporation rate of 7.51 kg m^-2 h^-1 with a voltage of 3 V as compensation under one-sun irradiation (1 kW m^-2). Moreover, the bilayered membrane displayed efficient salt ion rejection, and the collected water can meet the World Health Organization (WHO) standard required for potable water.

MoS2 oxidative etching caught in the act: formation of single (MoO3) n molecules

We report the presence of sub-nm MoO x clusters formed on basal planes of the 2H MoS2 crystals during thermal oxidative etching in air at a temperature of 370 °C. Using high resolution non-contact atomic force microscopy (AFM) we provide a histogram of their preferred heights. The AFM results combined with density functional theory (DFT) simulations show remarkably well that the MoO x clusters are predominantly single MoO3 molecules and their dimers at the sulfur vacancies. Additional Raman spectroscopy, and energy and wavelength dispersive X-ray spectroscopies as well as Kelvin probe AFM investigations confirmed the presence of the MoO3/MoO x species covering the MoS2 surface only sparsely. The X-ray absorption near edge spectroscopy data confirm the MoO3 stoichiometry. Taken together, our results show that oxidative etching and removal of Mo atoms at the atomic level follow predominantly via formation of single MoO3 molecules. Such findings confirm the previously only proposed oxidative etching stoichiometry.

Recent Advancements in Photocatalysis Coupling by External Physical Fields

Photocatalysis is one of the most promising green technologies to utilize solar energy for clean energy achievement and environmental governance, such as artificial photosynthesis, water splitting, pollutants degradation, etc. Despite decades of research, the performance of photocatalysis still falls far short of the requirement of 5% solar energy conversion efficiency. Combining photocatalysis with the other physical fields has been proven to be an efficient way around this barrier which can improve the performance of photocatalysis remarkably. This review will focus on the recent advances in photocatalysis coupling by external physical fields, including Thermal-coupled photocatalysis (TCP), Mechanical-coupled photocatalysis (MCP), and Electromagnetism-coupled photocatalysis (ECP). In this paper, coupling mechanisms, materials, and applications of external physical fields are reviewed. Specifically, the promotive effect on photocatalytic activity by the external fields is highlighted. This review will provide a detailed and specific reference for photocatalysis coupling by external physical fields in a deep-going way.

Nanomaterial-enabled photothermal-based solar water disinfection processes: Fundamentals, recent advances, and mechanisms

The pathogenic microorganisms in water pose a great threat to human health. Photothermal and photothermocatalytic disinfection using nanomaterials (NPs) has offered a promising and effective strategy to address the challenges in solar water disinfection (SODIS), especially in the point-of-use operations. This review aims at providing comprehensive and state-of-the-art knowledge of photothermal-based disinfection by NPs. The fundamentals and principles of photothermal-based disinfection were first introduced. Then, recent advances in developing photothermal/photothermocatalytic catalysts were systematically summarized. The light-to-heat conversion and disinfection performance of a large variety of photothermal materials were presented. Given the complicated mechanisms of photothermal-based disinfection, the attacks from reactive oxygen species and heat, the destruction of bacterial cells, and the antibacterial effects of released metal ions were highlighted. Finally, future challenges and opportunities associated with the development of cost-effective photothermal/photothermocatalytic disinfection systems were outlined. This review will provide guidance in designing future NPs and inspire more research efforts from environmental nano-communities to move towards practical water disinfection operations.

Narrow-Bandgap LaMO3 (M = Ni, Co) nanomaterials for efficient interfacial solar steam generation

Photothermal water evaporation provides a pathway towards a promising solution to global freshwater scarcity. Synergistic integration of functions in a material in diverse directions is a key strategy for designing multifunctional materials. Lanthanum-based perovskite complex oxides LaMO₃ (M = Ni and Co) have narrow band gaps with a high absorption coefficient. These functionalities have not been appropriately explored for photothermal energy conversion. Here, we synthesized nanostructured metallic LaNiO₃ and semiconducting LaCoO₃ and used them to design interfacial solar steam generators. Effective light absorption capability over the entire solar spectrum of these materials leads to a photothermal efficiency of the order of 83% for both materials. Using a cone-shaped 3D interfacial steam generator with a LaNiO₃ absorber, we achieved an evaporation rate of 2.3 kg m^-2 h^-1, corresponding to solar vapor generation efficiency of over 95%. To the best of our knowledge, this evaporation rate is higher than any oxide-based interfacial solar steam generator reported so far. Furthermore, we have also shown an effective way of using such evaporators for long-term seawater desalination.

Coupling solar-driven photothermal effect into photocatalysis for sustainable water treatment

Effectively harnessing renewable and inexhaustible solar radiation for energy conversion has attracted significant research interest in the past decade. Solar thermal conversion, as a ubiquitous phenomenon, can be implemented to evaporate water and concurrently boost photocatalytic performance for addressing freshwater scarcity and energy crisis. Most recently, solar water evaporation accompanied by photocatalytic degradation, sterilization, and hydrogen production has been proposed as a promising avenue to endow new vitality into the field of clean water and energy production. Driven by the advances of rationally designed solar-powered functional materials, a large variety of photothermal-coupled photocatalysis technologies have been exploited. In this context, it is imperative to summarize the recent progress and discuss the challenges in this multidisciplinary field. Herein, we overview photothermal materials based on various fundamental principles and highlight emerging applications in the areas of solar water evaporation, water purification, and solar-driven energy production. Furthermore, the challenges and perspectives toward both fundamental research and practical applications are also proposed. It is envisioned that this review can provide insightful suggestions to further advance the development of integrated solar thermal driven water evaporation and photocatalytic systems to fulfill concurrent energy conversion and environmental applications.

Recent Progress of Sub-Nanometric Materials in Photothermal Energy Conversion

Sub-nanometric materials (SNMs) are an attractive scope in recent years due to their atomic-level size and unique properties. Among various performances of SNMs, photothermal energy conversion is one of the most important ones because it can efficiently utilize the light energy. Herein, the SNMs with photothermal energy conversion behaviors and their applications are reviewed. First, a hydrothermal/solvothermal method for the synthesis of SNMs is systematically discussed, including the LaMer pathway and the cluster-nuclei coassembly pathway. Based on this synthetic strategy, many kinds of SNMs with different morphologies are successfully prepared, such as nanorings, nanowires, nanosheets, and nanobelts. These SNMs exhibit excellent photothermal performance under the laser or solar irradiation according to their different light absorption ranges. These enhanced absorption performances of SNMs are induced by the mechanism of plasmonic localized heating or nonradiative relaxation. Finally, the applications of the photothermal SNMs are illustrated. The SNMs with photothermal behaviors can be widely applied in the fields of solar vapor generation, biomedicine, and light-responsive composites construction. It is hoped that this review can provide new viewpoints and profound understanding to the SNMs in photothermal energy conversion.

Metal-free functionalized carbonized cotton for efficient solar steam generation and wastewater treatment

Water desalination via solar steam generation is one of the most important technologies to address the increasingly pressing global water scarcity. Materials for solar photothermal energy conversion are highly sought after for their cost savings, environmental friendliness and broad utility in many applications including domestic water heating and solar-driven desalination. Herein, we report the successful development of metal-free, low weight and cost effective functionalized carbonized cotton (CC) fibers for efficient solar water desalination and wastewater treatment. The CC fibers with nearly full solar spectrum absorption, efficient photo-thermal conversion and low-cost could provide excellent alternatives to the high-cost plasmonic-based materials for solar water desalination. We also report on a novel and simple device to mitigate the issues associated with conductive heat loss by utilizing the economically viable carbonized cotton materials as an irradiation surface placed on a low-density polyethylene foam that floats on the surface of seawater. The CC solar steam generation device exhibits average water evaporation rates of 0.9, 6.4 and 10.9 kg m^-2 h^-1 with impressive solar-to-vapor efficiencies of 59.2, 88.7 and 94.9% under 1, 5 and 8 sun illumination, respectively. Moreover, the device displays excellent durability showing stable evaporation rates over 10 steam generation cycles under 5 sun of solar intensity. Furthermore, the applicability of the CC device for the removal of organic dyes from contaminated water through solar steam generation is also demonstrated. The low-cost, simple design, high solar thermal evaporation efficiency, excellent stability and long-term durability make this CC device a perfect candidate for applications in seawater desalination and wastewater treatment by solar steam generation.

Nanodots Derived from Layered Materials: Synthesis and Applications

Layered 2D materials, such as graphene, transition metal dichalcogenides, transition metal oxides, black phosphorus, graphitic carbon nitride, hexagonal boron nitride, and MXenes, have attracted intensive attention over the past decades owing to their unique properties and wide applications in electronics, catalysis, energy storage, biomedicine, etc. Further reducing the lateral size of layered 2D materials down to less than 10 nm allows for preparing a new class of nanostructures, namely, nanodots derived from layered materials. Nanodots derived from layered materials not only can exhibit the intriguing properties of nanodots due to the size confinement originating from the ultrasmall size, but also can inherit some unique properties of ultrathin layered 2D materials, making them promising candidates in a wide range of applications, especially in biomedicine and catalysis. Here, a comprehensive summary on the materials categories, advantages, synthesis methods, and potential applications of these nanodots derived from layered materials is provided. Finally, personal insights about the challenges and future directions in this promising research field are also given.

Naturally Abundant Green Moss for Highly Efficient Solar Thermal Generation of Clean Water

Water and energy scarcity are the challenges for humankind in the coming years. Sun is the largest source of energy available on the planet. Also, brackish seawater covers more than 70% of the surface of the planet. Therefore, combining these two valuable natural resources represents an appealing solution to overcome the problem of sweet water shortage. To achieve this goal, the missing link is to develop appropriate photothermal materials with efficient light-to-heat-to-vapor generation. In this work, green moss is introduced as a natural, eco-friendly, abundant, superhydrophilic, fast water transporter, salt rejector, and highly efficient solar collector material. Green moss, owing to its open-microgrooves, can supply adequate water to the evaporation surface, while its open capillary channels can reject the precipitated salt, allowing its reusability. The green moss solar steam generator demonstrated an outstanding solar evaporation rate of 2.61 kg m^-2 h^-1 under 1 sun illumination, which is much higher than other reported natural and chemically modified biomasses under otherwise similar conditions. Interestingly, upon chemical modification of the green moss surface, it is possible to increase its solar evaporation rate to >3 kg m^-2 h^-1. Using the moss to purify and desalinate brackish water, it was demonstrated that it has the ability to decrease salinity below the WHO standards for drinkable water.

Synthesis of a Co-Sn Alloy-Deposited PTFE Film for Enhanced Solar-Driven Water Evaporation via a Super-Absorbent Polymer-Based "Water Pump" Design

Solar-driven water evaporation is a promising solution to water pollution, the energy crisis, and water shortages. However, the approach in which the photothermal film is in direct contact with bulk water for water evaporation may lead to a large amount of heat loss, thereby reducing the light-to-heat conversion efficiency (η) of the photothermal film. Here, a highly efficient solar-driven water evaporation system was developed using a Co-Sn alloy-deposited Teflon (PTFE) film (Co-Sn alloy@PTFE) and super-absorbent polymers (SAPs) supported with a floating foam substrate. The Co-Sn alloy with full-spectrum (200-2500 nm) absorption characteristics is devoted to high light-to-heat conversion, while the porous PTFE with high mechanical performance can support the Co-Sn alloy. We used density functional theory to prove that the Co-Sn alloy had a strong adhesive force with PTFE without surfactants due to the high adsorption energy between the (101) crystal plane of the Co-Sn alloy and the hydroxyl group on the PTFE film. Importantly, via the SAP-based "water pump" design, we improved the η of the Co-Sn alloy@PTFE film to 89%, mainly because the SAP not only effectively performed water transportation but also markedly reduced the heat loss of the Co-Sn alloy@PTFE film. Our work highlights the strong potential of Co-Sn alloy@PTFE-based light-to-heat conversion systems for realizing highly effective solar energy-driven water evaporation.

High efficiency solar desalination and dye retention of plasmonic/reduced graphene oxide based copper oxide nanocomposites

Water desalination via solar-driven interfacial evaporation is one of the most essential technologies to limit the problem of global freshwater scarcity. Searching for a highly efficient, stable, eco-friendly, and cost-effective solar-absorber material that can collect the full solar spectrum is critically important for solar steam generation. This study reports the development of a new solar thermal evaporation system based on plasmonic copper oxide/reduced graphene oxide (rGO). The silver nanoparticles in the composite exhibit a very strong solar absorption. Also, rGO and CuO nanoparticles offer excellent thermal absorptivity. Polyurethane was used as the support and as a thermal insulator. Moreover, filter paper was used for fast water delivery to the surface of the solar absorber. Ag/CuO-rGO nanocomposite is manifested to be one of the most efficient solar-absorbers reported to date for solar desalination which exhibits an average 2.6 kg m-2 h-1 evaporation rate with solar thermal efficiency up to 92.5% under 1 sun irradiation. Furthermore, the composite has excellent stability and durability as it displays stable evaporation rates for more than 10 repeated cycles in use, with no significant decrease in the activity. Besides, the successful removal of various organic dyes from contaminated water is also revealed, resulting in the production of clean condensed freshwater. Finally, this work commences a new avenue of synthesizing cost-effective thermal absorbers based on metal oxides.

Magnetically Driven 3D Cellulose Film for Improved Energy Efficiency in Solar Evaporation

The architecture of cellulose nanomaterials is definitized by random deposition and cannot change in response to shifting application requirements. Herein, we present a magnetic field-controlled cellulose film derived from wood that exhibits great magnetic properties and reliable tunability enabled by incorporated Fe₃O₄ nanoparticles and cellulose nanofibers (CNF) with a large length-diameter ratio. Fe₃O₄ nanoparticles are dispersed in suspensions of CNF so as to enhance the magnetic response. The plane magnetic CNF can be processed to form a three-dimensional (3D) flower-like structure along the magnetic induction line after applying an external magnet. Inspired by the fluidic transport in natural flowers, a bilayer structure was created using the 3D flower-like film as the solar energy receiver and natural wood as the water pathway in a solar-derived evaporation system. Compared with a planar cellulose film decorated with Fe₃O₄, the 3D structure design can greatly improve the evaporation rate from 1.19 to 1.39 kg m^-2 h^-1 and the efficiency from 76.9 to 90.6% under 1 sun. Finite element molding further reveals that the 3D structural top layer is beneficial for the formation of a gradient temperature profile and the improvement of the energy efficiency through the reduction of thermal radiation. The magnetically controlled fabrication represents a promising strategy for designing cellulose nanomaterials with a complicated structure and controllable topography, which has a wide spectrum of applications in energy storage devices and water treatment.

CoWO4-x -Based Photothermal Membranes for Solar-Driven Water Evaporation and Eutrophic Lake Water Purification

Solar-driven water evaporation has been proven to be a promising and efficient method for the energy crisis and clean water shortage issues. Herein, we strategically design and fabricate a novel nonstoichiometric CoWO_4-x -deposited foam nickel (NF) membrane (CoWO_4-x @NF) that possesses all the desirable optical, thermal, and wetting properties for efficient water evaporation and purification. The broadband absorption of CoWO_4-x nanoparticles (NPs) obtained by hydrogen reduction contributes to light-to-heat conversion, while NF with a three-dimensional porous structure can support CoWO_4-x NPs and ensure the rapid flow of water molecules during the water evaporation process. We systematically explore and compare the outdoor water evaporation performance of the pure water group, NF group, and CoWO_4-x @NF group, and the results show that CoWO_4-x @NF performs well under natural sunlight irradiation (water evaporation: 2.91 kg m^-2). Significantly, under solar irradiation, the remarkable reduction of Cyanophyta and Euglenophyta in lake water is achieved in the CoWO_4-x @NF membrane-administered group, and these two algae are the main factors for eutrophication of the lake water. Our work highlights the great potentials of the CoWO_4-x @NF membrane as a device for realizing outdoor solar energy-driven water evaporation and proposes a new strategy for purifying the eutrophication of the lake water.

Self-Suspended Photothermal Microreactor for Water Desalination and Integrated Volatile Organic Compound Removal

Steam generation and photocatalytic degradation of organic pollutants based on solar light are regarded as two important strategies for addressing the water scarcity issues. The water evaporation efficiency was greatly inhibited by the high cost, low stability, and low efficiencies of solar light absorption and photothermal conversion of photothermal materials. Moreover, volatile organic compounds (VOCs) are easily volatilized and enriched in as-distilled water during the photothermal process. Inspired by the structure of biomass materials in nature, a bifunctional solar light-driven steam generation and VOC removal microreactor was explored by coating commercial TiO₂ (P25) powders on a carbonized biomass waste Flammulina. With the 3D aligned porous carbon architectures, this microreactor exhibited both a high water evaporation rate (37.0 kg m^-2 h^-1) and a high energy conversion efficiency (91.2%) under simulated sunlight irradiation (light intensity = 25.5 kW m^-2). A high VOC removal rate (80.9% in 40 min) was also achieved during the steam generation process via choosing phenol as the probe pollutant molecules. The nature-inspired designing concept and bifunctional microreactor in this study may open up a new strategy for producing clean distilled water from seawater with an efficient removal of VOCs.

Nanoconfined Water-Molecule Channels for High-Yield Solar Vapor Generation under Weaker Sunlight

Solar vapor generation is a promising method to efficiently produce fresh water. However, the insufficient vapor yields under natural daylight restrict its practical applications, and the basic evaporation mechanisms are deficient for reasonable design of evaporator structure. Here, hydrophobic nano-confined water molecule channels (NCWMCs) are demonstrated, which can reduce the vaporization enthalpy for water evaporation and achieve a record vapor generation rate of 1.25 kg m^-2 h^-1 under 0.5 sun irradiation. Molecular dynamics simulations reveal the cluster-evaporation process in the NCWMC system. As a result, the evaporator with NCWMC system can effectively purify seawater and wastewater samples using this environmentally friendly strategy.

Economical Salt-Resistant Superhydrophobic Photothermal Membrane for Highly Efficient and Stable Solar Desalination

Recently, solar-driven interfacial water evaporation has shown great potential in desalination. In a practical application, the inevitable pollution and accumulation of salt that make the evaporation efficient cannot be maintained for a long time. Herein, we report a flexible and economical superhydrophobic photothermal membrane composed of polyvinylpyrrolidone (PVP) and carbon nanotubes (CNTs) with a 1H,1H,2H,2H-perfluorodecyltriethoxysilane modification, with a piece of expanded polystyrene used for support and thermal insulation. The prepared floating evaporation device showed a high energy efficiency of 91.1% and an evaporation rate of 1.41 kg m^-2 h^-1 under one solar irradiation, and neither salt accumulation nor a significant decrease in the evaporation rate of the device was observed after continuous operation for either 40 h or 18 evaporation cycles. In addition, the self-cleaning performance of the membrane enabled its surface to maintain high absorbance for a long time. With the stable and efficient evaporation performance of this device, it provided guidance for the application of efficient and long-term stable solar desalination.

Molybdenum-Suboxide Thin Films as Anode Layers in Planar Lithium Microbatteries

In this paper, we investigate the effects of operational conditions on structural, electronic and electrochemical properties on molybdenum suboxides (MoO3-δ) thin films. The films are prepared using pulsed-laser deposition by varying the deposition temperature (Ts), laser fluence (Φ), the partial oxygen pressure (PO2) and annealing temperature (Ta). We find that three classes of samples are obtained with different degrees of stoichiometric deviation without post-treatment: (i) amorphous MoO3-δ (δ < 0.05) (ii) nearly-stoichiometric samples (δ ≈ 0) and (iii) suboxides MoO3-δ (δ > 0.05). The suboxide films 0.05 ≤ δ ≤ 0.25 deposited on Au/Ti/SiO2/flexible-Si substrates with appropriate processing conditions show high electrochemical performance as an anode layer for lithium planar microbatteries. In the realm of simple synthesis, the MoO3-δ film deposited at 450 °C under oxygen pressure of 13 Pa is a mixture of α-MoO3 and Mo8O23 phases (15:85). The electrochemical test of the 0.15MoO3-0.85Mo8O23 film shows a specific capacity of 484 µAh cm−2 µm−1 after 100 cycles of charge-discharge at a constant current of 0.5 A cm−2 in the potential range 3.0-0.05 V.

Hot Carriers and Photothermal Effects of Monolayer MoOx for Promoting Sulfite Oxidase Mimetic Activity

Local surface plasmon resonance (LSPR)-enhanced catalysis has brought a substantial amount of opportunities across various disciplines such as photocatalysis, photodetection, and photothermal therapeutics. Plasmon-induced photothermal and hot carriers effects have also been utilized to activate the enzyme-like reactions. Compared with natural enzymes, the relatively low catalytic performance of nanozymes severely hampered the potential applications in the field of biomedicine. For these issues mentioned above, herein, we demonstrate a highly efficient sulfite oxidase (SuO_x) mimetic performance of plasmonic monolayer MoO_x (ML-MoO_x) upon LSPR excitation. We also established that the considerable photothermal effect and the injection of hot carriers induced by LSPR are responsible for promoting the SuO_x activity of ML-MoO_x. The high transient local temperature on the surface of ML-MoO_x generated by the photothermal effect facilitates to impact the reaction velocity and feed the SuO_x-like activity, while the generation of hot carriers which are suggested as predominant effects catalyzes the oxidation of sulfite to sulfate through significantly decreasing the activation energy for the SuO_x-like reaction. These investigations present a contribution to the basic understanding of plasmon-enhanced enzyme-like reaction and provided an insight into the optimization of the SuO_x mimetic performance of nanomaterials.

A Hydrogenated Metal Oxide with Full Solar Spectrum Absorption for Highly Efficient Photothermal Water Evaporation

Searching for cost-effective photothermal material that can harvest the full solar spectrum is critically important for solar-driven water evaporation. Metal oxides are cheap materials but cannot cover the full solar spectrum. Here we prepared a hydrogenated metal oxide (H_1.68MoO₃) material, in which H-doping causes the insulator-to-metal phase transition of the originally semiconductive MoO₃. It offers a blackbody-like solar absorption of ≥95% over the entire visible-to-near-infrared solar spectrum, owing to its unusual quasi-metallic energy band, and high solar-to-heat conversion rate due to quick relaxation of excited electrons. Using a self-floating H_1.68MoO₃/airlaid paper photothermal film, we achieved a stable and high water vapor generation rate of 1.37 kg m^-2 h^-1, a superb solar-to-vapor efficiency of 84.8% under 1 sun illumination, and daily production of 12.4 L of sanitary water/m² from seawater under natural sunlight. This thus opens a new avenue of designing cost-effective photothermal materials based on metal oxides.

The Rise of 2D Photothermal Materials beyond Graphene for Clean Water Production

Water shortage is one of the most concerning global challenges in the 21st century. Solar-inspired vaporization employing photothermal nanomaterials is considered to be a feasible and green technology for addressing the water challenge by virtue of abundant and clean solar energy. 2D nanomaterials aroused considerable attention in photothermal evaporation-induced water production owing to their large absorption surface, strong absorption in broadband solar spectrum, and efficient photothermal conversion. Herein, the recent progress of 2D nanomaterials-based photothermal evaporation, mainly including emerging Xenes (phosphorene, antimonene, tellurene, and borophene) and binary-enes (MXenes and transition metal dichalcogenides), is reviewed. Then, the optimization strategies for higher evaporation performance are summarized in terms of modulation of the intrinsic photothermal performance of 2D nanomaterials and design of the complete evaporation system. Finally, the challenges and prospective of various kinds of 2D photothermal nanomaterials are discussed in terms of the photothermal performance, stability, environmental influence, and cost. One important principle is that solutions for water challenges should not introduce new environmental and social problems. This Review aims to highlight the role of 2D photothermal nanomaterials in solving water challenges and provides a viable scheme toward the practical use in photothermal materials selection, design, and evaporation systems building.

Ti3C2Tx MXene-derived TiO2/C-QDs as oxidase mimics for the efficient diagnosis of glutathione in human serum

A Ti₃C₂T_x MXene-derived TiO₂/C-QD oxidase mimic was developed and used for the efficient diagnosis of glutathione in human serum.

MoOx Nanoparticle Catalysts for d-Glucose Epimerization and Their Electrical Immobilization in a Continuous Flow Reactor

Activity and immobilization of catalysts in liquid-phase reactions seem not to coexist. We report here the excellent activity of an MoO_x nanoparticle (NP) catalyst for d-glucose epimerization to d-mannose and the electrical immobilization of NPs in a flow reaction. Prior to that, a green and one-pot method to synthesize the MoO_x NPs (3.05 nm) via oxidizing metal Mo by hydrogen peroxide was presented. The NPs overwhelmed the reported catalysts including epimerase for d-glucose epimerization, originating from a strong interaction between the NPs and the reactant that was demonstrated by ex situ and in situ characterizations and theoretical calculations. The electrically charged feature of NPs inspired us to find a convenient way to "immobilize" them inside an activated carbon bed, and thereby, a flow reactor was assembled. The continuous epimerization was run under 24 V for 16 days with an almost unchanged activity, and only 3.2% of total Mo was lost.

Oxygen Vacancy-Engineered PEGylated MoO3-x Nanoparticles with Superior Sulfite Oxidase Mimetic Activity for Vitamin B1 Detection

Sulfite oxidase (SuO_x ) is a molybdenum-dependent enzyme that catalyzes the oxidation of sulfite to sulfate to maintain the intracellular levels of sulfite at an appropriate low level. The deficiency of SuO_x would cause severe neurological damage and infant diseases, which makes SuO_x of tremendous biomedical importance. Herein, a SuO_x mimic nanozyme of PEGylated (polyethylene glycol)-MoO_3-x nanoparticles (P-MoO_3-x NPs) with abundant oxygen vacancies created by vacancy-engineering is reported. Their level of SuO_x -like activity is 12 times higher than that of bulk-MoO₃ . It is also established that the superior increased enzyme mimetic activity is due to the introduction of the oxygen vacancies acting as catalytic hotspots, which allows better sulfite capture ability. It is found that vitamin B1 (VB1) inhibits the SuO_x mimic activity of P-MoO_3-x NPs through the irreversible cleavage by sulfite and the electrostatic interaction with P-MoO_3-x NPs. A colorimetric platform is developed for the detection of VB1 with high sensitivity (the low detection limit is 0.46 µg mL^-1 ) and good selectivity. These findings pave the way for further investigating the nanozyme which possess intrinsic SuO_x mimicing activity and is thus a promising candidate for biomedical detection.

Photothermal materials for efficient solar powered steam generation

Solar powered steam generation is an emerging area in the field of energy harvest and sustainable technologies. The nano-structured photothermal materials are able to harvest energy from the full solar spectrum and convert it to heat with high efficiency. Moreover, the materials and structures for heat management as well as the mass transportation are also brought to the forefront. Several groups have reported their materials and structures as solutions for high performance devices, a few creatively coupled other physical fields with solar energy to achieve even better results. This paper provides a systematic review on the recent developments in photothermal nanomaterial discovery, material selection, structural design and mass/heat management, as well as their applications in seawater desalination and fresh water production from waste water with free solar energy. It also discusses current technical challenges and likely future developments. This article will help to stimulate novel ideas and new designs for the photothermal materials, towards efficient, low cost practical solar-driven clean water production.

Flexible and Washable CNT-Embedded PAN Nonwoven Fabrics for Solar-Enabled Evaporation and Desalination of Seawater

Nanostructured photothermal membranes hold great potential for solar-driven seawater desalination; however, their pragmatic applications are often limited by substantial salt accumulation. To solve this issue, we have designed and prepared flexible and washable carbon-nanotube-embedded polyacrylonitrile nonwoven fabrics by a simple electrospinning route. The wet fabric exhibits a strong photoabsorption in a wide spectral range (350-2500 nm), and it has a photoabsorption efficiency of 90.8%. When coated onto a polystyrene foam, the fabric shows a high seawater evaporation rate of 1.44 kg m^-2 h^-1 under simulated sunlight irradiation (1.0 kW m^-2). With a high concentration of simulated seawater as the model, the accumulation of solid salts can be clearly observed on the surface of the fabric, resulting in a severe decay of the evaporation rate. These salts can be effortlessly washed away from the fabric through a plain handwashing process. The washing process has a negligible influence on the morphology, photoabsorption, and evaporation performance of the fabric, demonstrating good durability. More importantly, a larger fabric can easily be fabricated, and the combination of washable fabrics with various parallel PS foams can facilitate the construction of large-scale outdoor evaporation devices, conferring the great potential for efficient desalination of seawater under natural sunlight.

Co2.67S4-Based Photothermal Membrane with High Mechanical Properties for Efficient Solar Water Evaporation and Photothermal Antibacterial Applications

The lack of freshwater resources, or the freshwater crisis, is an important issue in the resource field. One potential green and sustainable method to solve this problem is to implement solar energy-driven water evaporation to collect freshwater. Capitalizing on the low cost, high production yield, and simplified fabrication process properties of nonstoichiometric Co_2.67S₄ nanoparticles, we strategically designed and synthesized a Co_2.67S₄-deposited Teflon (PTFE) membrane for realizing efficient solar water evaporation and photothermal antibacterial properties under light irradiation. Compared with previously reported cellulose acetate and poly(vinylidene fluoride) membranes, the PTFE membrane displayed significantly enhanced mechanical properties. Additionally, a Co_2.67S₄-deposited PTFE membrane with a hydrophobic treatment (termed as the Final-PTFE membrane) exhibited excellent durability. The light-to-heat conversion efficiency (η) of water evaporation reached a value of 82% for our as-prepared Final-PTFE membrane under two sun irradiation conditions. Moreover, the antibacterial mechanism observed by scanning electron microscopy was attributed to the thermal effect, which damaged the cell wall of bacteria. Our work highlights the great potentials of the Final-PTFE membrane as a versatile system for implementing solar energy-driven photothermal water evaporation and water purification.

The revival of thermal utilization from the Sun: interfacial solar vapor generation

Since solar energy is the ultimate energy resource and a significant amount of global energy utilization goes through heat, there have been persistent efforts for centuries to develop devices and systems for solar–thermal conversion. Most recently, interfacial solar vapor generation, as an emerging concept of solar–thermal conversion, has gained significant attention for its great potentials in various fields such as desalination, sterilization, catalysis, etc. With the advances of rationally designed materials and structures and photon and thermal management at the nanoscale, interfacial solar vapor generation has demonstrated both thermodynamic and kinetical advantages over conventional strategies. In this review, we aim to illustrate the definition, mechanism and figures of merit of interfacial solar vapor generation, and to summarize the development progress of relevant materials and applications, as well as to provide a prospective view of the future.

Materials and design of nanostructured broadband light absorbers for advanced light-to-heat conversion

Light-to-heat conversion systems have been attracting growing research interest in the last few decades, due to their highly intriguing photothermal properties and their wide applications ranging from biomedical applications to solar energy harvesting to mechanical actuators. In general, because the light-to-heat conversion efficiency depends strongly on the absorbing material, significant efforts have been focused on fabricating broadband light absorbers. However, there are several challenges associated with the design and fabrication of light absorbers, such as minimizing heat loss, and optimizing the broadband light absorption and omnidirectional light absorption. Thus, the rational design of enhanced light absorbers is critical to achieve efficient light absorption over a broad wavelength range. In this paper, we introduce the basic theory of light absorption and heat transfer, then summarize fundamental understanding of representative light-to-heat conversion agents including carbon-based, semiconductor-based and plasmonic metal-based materials and structures, and highlight state-of-the-art structural designs towards the development of broadband light absorbers. In addition, the practical applications of these materials and designs are also discussed.