Modularization of Regional Electronic Structure over Defect-Rich CeO2 Rods for Enhancing Photogenerated Charge Transfer and CO2 Activation.

Oxygen vacancy (OV) engineering has been widely applied in different types of metal oxide-based photocatalytic reactions. Our study has shown that the redistributed OVs resulting from voids in CeO2 rods lead to significant differences in the band structure in space. The flat energy band within the highly crystallized bulk region hinders the recombination of photogenerated carrier pairs during the transfer process. The downward curved energy band in the surface region enhances the activation of the absorbents. Therefore, the localization of the band structure through crystal structure regionalization renders V-CeO2 capable of achieving efficient utilization of photogenerated carriers. Practically, the V-CeO2 rod shows a remarkable turnover number of 190.58 µmol g-1 h-1 in CO2 photoreduction, which is ∼9.4 times higher than that of D-CeO2 (20.46 µmol g-1 h-1). The designed modularization structure in our work is expected to provide important inspiration and guidance in coordinating the kinetic behavior of carriers in OV defect-rich photocatalysts.

Flexocatalysis Enhances Tumor Photodynamic Therapy.

Photodynamic therapy (PDT) is long-standing suffered from elevated tumor interstitial fluid pressure (TIFP) and prevalent hypoxic microenvironment within the solid malignancies. Herein, sound-activated flexocatalysis is developed to overcome the dilemma of PDT through both enhancing tumor penetration of photosensitizers by reducing TIFP and establishing an oxygen-rich microenvironment. In detail, a Schottky junction is constructed by flexocatalyst MoSe2 nanoflowers and Pt. Subsequently, the Schottky junction is loaded with the photosensitizer indocyanine green (ICG) and encapsulated within tumor cytomembrane to constitute a bionic-flexocatalytic nanomedicine (MPI@M). After targeting the tumor, MPI@M orchestrates flexocatalytic water splitting in tumor interstitial fluid under acoustic stimulation to lower TIFP, which boosted the tumor penetration of ICG. Concurrently, the oxygen released from the flexocatalytic water splitting overcomes the limitation of hypoxia against PDT. Furthermore, superfluous singlet oxygen generated by PDT can induce mitochondrial dysfunction for further tumor cell apoptosis. After 60 min of flexocatalysis, both the 30% decrease of TIFP and the relieved tumor hypoxia are observed, significantly promoting the therapeutic effect of PDT. Consequently, MoSe2/Pt junction nanoflowers, with the excellent flexocatalytic performance, hold significant potential for future applications in biocatalytic cancer therapies.

Harvesting the Vibration Energy of BiFeO3 Nanosheets for Hydrogen Evolution.

In this study, mechanical vibration is used for hydrogen generation and decomposition of dye molecules, with the help of BiFeO3 (BFO) square nanosheets. A high hydrogen production rate of ≈124.1 µmol g-1 is achieved under mechanical vibration (100 W) for 1 h at the resonant frequency of the BFO nanosheets. The decomposition ratio of Rhodamine B dye reaches up to ≈94.1 % after mechanical vibration of the BFO catalyst for 50 min. The vibration-induced catalysis of the BFO square nanosheets may be attributed to the piezocatalytic properties of BFO and the high specific surface area of the nanosheets. The uncompensated piezoelectric charges on the surfaces of BFO nanosheets induced by mechanical vibration result in a built-in electric field across the nanosheets. Unlike a photocatalyst for water splitting, which requires a proper band edge position for hydrogen evolution, such a requirement is not needed in piezocatalytic water splitting, where the band tilting under the induced piezoelectric field will make the conduction band of BFO more negative than the H2 /H2 O redox potential (0 V) for hydrogen generation.

Modulating Smart Mechanoluminescent Phosphors for Multistimuli Responsive Optical Wood.

Mechanoluminescence is a smart light-emitting phenomenon in which applied mechanical energy is directly converted into photon emissions. In particular, mechanoluminescent materials have shown considerable potential for applications in the fields of energy and sensing. This study thoroughly investigates the mechanoluminescence and long afterglow properties of singly doped and codoped Sr2 MgSi2 O7 (SMSO) with varying concentrations of Eu2+ and Dy3+ ions. Subsequently, a comprehensive analysis of its multimode luminescence properties, including photoluminescence, mechanoluminescence, long afterglow, and X-ray-induced luminescence, is conducted. In addition, the density of states mapping is acquired through first-principles calculations, confirming that the enhanced mechanoluminescence properties of SMSO primarily stem from the deep trap introduced by Dy3+ . In contrast to traditional mixing with Polydimethylsiloxane, in this study, the powders are incorporated into optically transparent wood to produce a multiresponse with mechanoluminescence, long afterglow, and X-ray-excited luminescence. This structure is achieved by pretreating natural wood, eliminating lignin, and subsequently modifying the wood to overall modification using various smart phosphors and epoxy resin composites. After natural drying, a multifunctional composite wood structure with diverse luminescence properties is obtained. Owing to its environmental friendliness, sustainability, self-power, and cost-effectiveness, this smart mechanoluminescence wood is anticipated to find extensive applications in construction materials and energy-efficient displays.

Natural MOF-Like Photocatalytic Nanozymes Alleviate Tumor Pressure for Enhanced Nanodrug Penetration.

In oncological nanomedicine, overcoming the dual-phase high interstitial pressure in the tumor microenvironment is pivotal for enhancing the penetration and efficacy of nanotherapeutics. The elevated tumor interstitial solid pressure (TISP) is largely attributed to the overaccumulation of collagen in the extracellular matrix, while the increased tumor interstitial fluid pressure (TIFP) stems from the accumulation of fluid due to the aberrant vascular architecture. In this context, metal-organic frameworks (MOFs) with catalytic efficiency have shown potential in degrading tumor interstitial components, thereby reducing interstitial pressure. However, the potential biotoxicity of the organic components of MOFs limits their clinical translation. To circumvent this, a MOF-like photocatalytic nanozyme, RPC@M, using naturally derived cobalt phytate (CoPA) and resveratrol (Res) is developed. This nanozyme not only facilitates the decomposition of water in the tumor interstitium under photoactivation to reduce TIFP, but also generates an abundance of reactive oxygen species through its peroxidase-like activity to exert cytotoxic effects on tumor cells. Moreover, Res contributes to the reduction of collagen deposition, thereby lowering TISP. The concurrent diminution of both TISP and TIFP by RPC@M leads to enhanced tumor penetration and potent antitumor activity, presenting an innovative approach in constructing tumor therapeutic nanozymes from natural products.

Remarkable Pyro-Catalysis of g-C3N4 Nanosheets for Dye Decoloration under Room-Temperature Cold-Hot Cycle Excitation.

Pyroelectric materials have the ability to convert the environmental cold-hot thermal energy such as day-night temperature alternation into electrical energy. The novel pyro-catalysis technology can be designed and realized on the basis of the product coupling between pyroelectric and electrochemical redox effects, which is helpful for the actual dye decomposition. The organic two-dimensional (2D) graphic carbon nitride (g-C3N4), as an analogue of graphite, has attracted considerable interest in the field of material science; however, its pyroelectric effect has rarely been reported. In this work, the remarkable pyro-catalytic performance was achieved in the 2D organic g-C3N4 nanosheet catalyst materials under the continuous room-temperature cold-hot thermal cycling excitation from 25 °C to 60 °C. The pyro-catalytic RhB dye decoloration efficiency of the 2D organic g-C3N4 can reach ~92.6%. Active species such as the superoxide radicals and hydroxyl radicals are observed as the intermediate products in the pyro-catalysis process of the 2D organic g-C3N4 nanosheets. The pyro-catalysis of the 2D organic g-C3N4 nanosheets provides efficient technology for wastewater treatment applications, utilizing the ambient cold-hot alternation temperature variations in future.

Piezoelectric bimorph cantilever for vibration-producing-hydrogen.

A device composed of a piezoelectric bimorph cantilever and a water electrolysis device was fabricated to realize piezoelectrochemical hydrogen production. The obvious output of the hydrogen and oxygen through application of a mechanical vibration of ~0.07 N and ~46.2 Hz was observed. This method provides a cost-effective, recyclable, environment-friendly and simple way to directly split water for hydrogen fuels by scavenging mechanical waste energy forms such as noise or traffic vibration in the environment.

Experimental Study on the Mechanical Properties, Water Absorption, and Fiber Degradation of Naturally Aged Glass Fiber and Polypropylene Fiber-Reinforced Concrete.

The main objective of this study is to better understand the performance changes of naturally aged glass fiber-reinforced concrete (GFRC) and polypropylene fiber-reinforced concrete (PPFRC), especially the degradation of fibers, which is of great significance for evaluating the durability of structures using these two types of composite materials. The mechanical properties, water absorption, and microstructures of GFRC and PPFRC at a curing age of three years, including their compressive strength, full curves of water absorption, fiber-matrix interaction, and fiber degradation, were systematically studied, and the related properties were compared with those at the curing age of 28 days. The degradation of fibers after freeze-thaw cycles was also studied. The results revealed the following. The water/binder ratio (w/b) affects the rate of increase of the long-term compressive strength of naturally aged concrete. In general, the water absorption of fiber-reinforced concrete (FRC) at the curing age of three years was found to be significantly reduced, but with the increases of w/b and the fiber content to the maximum values, the water absorption of the specimens cured for three years was higher than that of the specimens cured for 28 days. Moreover, with the increase of the curing age, the optimal glass fiber (GF) contents for reducing the water absorption decreased from 1.35% to 0.90% (w/b = 0.30), and from 0.90% to 0.45% (w/b = 0.35), respectively. The GF surface was degraded into continuous pits with diameters of about 200 to 600 nm, and the surface of the pits was attached with spherical granular C-S-H gel products with diameters of about 30 to 44 nm. The freeze-thaw cycles were found to have no significant effect on the pits on the GF surface and the granular C-S-H gel products attached to the pits, but caused a portion of the cement matrix covering the GF to fall off. The interfacial bonding between the polypropylene fiber (PPF) and the cement matrix exhibited almost no change in the PPFRC after three years of curing as compared with that after 28 days of curing. Furthermore, the cement hydration gel on the PPF surface was not significantly damaged by 150 freeze-thaw cycles.

Influence of Different Parameters on the Performance of Alkali-Activated Slag/Fly Ash Composite System.

In order to study the influence law of each parameter on the performance of the alkali-activated composite gelling system, the influence degree was sorted, and the most important parameter affecting each performance was found. The solution of liquid water glass and solid sodium hydroxide was used as the alkaline activator, and the mixing ratio was designed by the orthogonal test method. The effects of four parameters of fly ash content, water glass modulus, water glass solid content, and water-solid ratio on the working performance and mechanical properties of alkali-activated slag-fly ash composite cementation system were discussed. The gelling system was studied by microscopic experiments such as SEM and FTIR. The results show that the solid content of water glass has the greatest influence on the fluidity of the composite cementitious system, and the content of fly ash is the primary factor affecting the setting time of the material. The flexural and compressive strengths at the age of 7 d and 28 d were most affected by the content of fly ash, and the solid content of water glass had the greatest influence on the flexural and compressive strengths at the age of 2 d. From the perspective of microscopic morphology, in the high-strength samples, the fly ash particles and the remaining outer shell are embedded in the gel to form a dense whole. When the amount of silica in the composite gelling system is too high, it will cause the phenomenon of low macroscopic mechanical properties.

High Humidity Response of Sol-Gel-Synthesized BiFeO3 Ferroelectric Film.

In this work, a BiFeO3 film is prepared via a facile sol-gel method, and the effects of the relative humidity (RH) on the BiFeO3 film in terms of capacitance, impedance and current-voltage (I-V) are explored. The capacitance of the BiFeO3 film increased from 25 to 1410 pF with the increase of RH from 30% to 90%. In particular, the impedance varied by more than two orders of magnitude as RH varied between 30% and 90% at 10 Hz, indicating a good hysteresis and response time. The mechanism underlying humidity sensitivity was analyzed by complex impedance spectroscopy. The adsorption of water molecules played key roles at low and high humidity, extending the potential application of ferroelectric BiFeO3 films in humidity-sensitive devices.

Study on the Mechanical Properties, Wear Resistance and Microstructure of Hybrid Fiber-Reinforced Mortar Containing High Volume of Industrial Solid Waste Mineral Admixture.

The use of a high volume of industrial solid waste mineral admixture and hybrid fiber can greatly reduce the amount of cement in mortar or concrete, improve its performance, ensure the service properties of mortar or concrete, and reuse industrial solid waste to reduce the environmental burden, which has significant research significance. In this paper, the mechanical properties, wear resistance and microstructure of hybrid fiber-reinforced mortar (HFRM) with a high content of industrial solid waste mineral admixture were systematically studied under different water/binder ratios. Mineral admixtures include fly ash, silica fume and granulated blast furnace slag (slag). The total content of hybrid glass fiber (GF) and polypropylene fiber (PPF) was 2% by volume fractions, and six different water/binder ratios ranging from 0.27 to 0.62 were used. The following conclusions were drawn: fibers have a significant negative effect on the properties of mortars with a low water/binder ratio (w/b = 0.27) and high content of mineral admixtures. In general, the effect of adding hybrid fiber on improving the wear resistance of mortar is more obvious. The average residual weight of hybrid fiber-reinforced mortar is the highest after the wear resistance test. Comprehensively considering the compressive strength, flexural strength, wear resistance and microstructure of the mortar samples, G8PP2-0.40 is the optimal mix ratio. At this time, the replacement rates of fly ash, silica fume and slag are: 20%, 5% and 30%, the water/binder ratio is 0.40, and the content of GF and PPF is 1.6% and 0.4%, respectively.

Strong Tribocatalytic Nitrogen Fixation of Graphite Carbon Nitride g-C3N4 through Harvesting Friction Energy.

Mechanical energy derived from friction is a kind of clean energy which is ubiquitous in nature. In this research, two-dimensional graphite carbon nitride (g-C3N4) is successfully applied to the conversion of nitrogen (N2) fixation through collecting the mechanical energy generated from the friction between a g-C3N4 catalyst and a stirring rod. At the stirring speed of 1000 r/min, the tribocatalytic ammonia radical (NH4+) generation rate of g-C3N4 can achieve 100.56 µmol·L-1·g-1·h-1 using methanol as a positive charge scavenger, which is 3.91 times higher than that without any scavengers. Meanwhile, ammonia is not generated without a catalyst or contact between the g-C3N4 catalyst and the stirring rod. The tribocatalytic effect originates from the friction between the g-C3N4 catalyst and the stirring rod which results in the charges transfer crossing the contact interface, then the positive and negative charges remain on the catalyst and the stirring rod respectively, which can further react with the substance dissolved in the reaction solution to achieve the conversion of N2 to ammonia. The effects of number and stirring speed of the rods on the performance of g-C3N4 tribocatalytic N2 fixation are further investigated. This excellent and efficient tribocatalysis can provide a potential avenue towards harvesting the mechanical energy in a natural environment.

In Situ Construction of ZIF-67-Derived Hybrid Tricobalt Tetraoxide@Carbon for Supercapacitor.

The Co3O4 electrode is a very promising material owing to its ultrahigh capacitance. Nevertheless, the electrochemical performance of Co3O4-based supercapacitors is practically confined by the limited active sites and poor conductivity of Co3O4. Herein, we provide a facile synthetic strategy of tightly anchoring Co3O4 nanosheets to a carbon fiber conductive cloth (Co3O4@C) using the zeolitic imidazolate framework-67 (ZIF-67) sacrificial template via in situ impregnation and the pyrolysis method. Benefiting from the enhancement of conductivity and the increase in active sites, the binder-free porous Co3O4@C supercapacitor electrodes possess typical pseudocapacitance characteristics, with an acceptable specific capacitance of ~251 F/g at 1 A/g and long-term cycling stability (90% after cycling 5000 times at 3 A/g). Moreover, the asymmetric and flexible supercapacitor composed of Co3O4@C and activated carbon is further assembled, and it can drive the red LED for 6 min.

Engineering the Defects and Microstructures in Ferroelectrics for Enhanced/Novel Properties: An Emerging Way to Cope with Energy Crisis and Environmental Pollution.

In the past century, ferroelectrics are well known in electroceramics and microelectronics for their unique ferroelectric, piezoelectric, pyroelectric, and photovoltaic effects. Nowadays, the advances in understanding and tuning of these properties have greatly promoted a broader application potential especially in energy and environmental fields, by harvesting solar, mechanical, and heat energies. For example, high piezoelectricity and high pyroelectricity can be designed by defect or microstructure engineering for piezo- and pyro-catalyst, respectively. Moreover, highly piezoelectric and broadband (UV-Vis-NIR) light-responsive ferroelectrics can be designed via defect engineering, giving rise to a new concept of photoferroelectrics for efficient photocatalysis, piezocatalysis, pyrocatalysis, and related cocatalysis. This article first summarizes the recent developments in ferroelectrics in terms of piezoelectricity, pyroelectricity, and photovoltaic effects based on defect and microstructure engineering. Then, the potential applications in energy generation (i.e., photovoltaic effect, H2 generation, and self-powered multisource energy harvesting and signal sensing) and environmental protection (i.e., photo-piezo-pyro- cocatalytic dye degradation and CO2 reduction) are reviewed. Finally, the outlook and challenges are discussed. This article not only covers an overview of the state-of-art advances of ferroelectrics, but also prospects their applications in coping with energy crisis and environmental pollution.

Study on Electromagnetic Performance of La0.5Sr0.5CoO3/Al2O3 Ceramic with Metal Periodic Structure at X-Band.

A radar absorbing material (RAM) is designed by combining the La0.5Sr0.5CoO3/Al2O3 ceramic and the metal periodic structure. The phase constitution and the microscopic morphology of the La0.5Sr0.5CoO3/Al2O3 ceramic are examined, respectively. The electrical properties and magnetic properties of the La0.5Sr0.5CoO3/Al2O3 ceramic are also measured at the temperature range of 25~500 °C. Based on the experimental and simulation results, the changes in the reflection loss along with the structure parameters of RAM are analyzed at 500 °C. The analytical results show that the absorption property of the RAM increases with the increase in the temperature. When the thickness of the La0.5Sr0.5CoO3/Al2O3 ceramic is 1.5 mm, a reflection loss <−10 dB can be obtained in the frequency range from approximately 8.2 to 16 GHz. More than 90% microwave energy can be consumed in the RAM, which may be applied in the high temperature environment.

Lead-Free Bi0.5Na0.5TiO3 Ferroelectric Nanomaterials for Pyro-Catalytic Dye Pollutant Removal under Cold-Hot Alternation.

In this work, explicitly pyro-catalytic performance is observed in sol-gel-synthesized ferroelectric Bi0.5Na0.5TiO3 lead-free nanomaterials, and its application for dye wastewater purification is also actualized under temperature fluctuations varying from 23 °C to 63 °C. The decomposition ratios of the pyro-catalytic Bi0.5Na0.5TiO3 nanomaterials on Rhodamine B, methyl blue and methyl orange can reach 96.75%, 98.35% and 19.97%, respectively. In the pyro-catalytic process, the probed active species such as hydroxyl radicals, superoxide radicals and holes play an extremely important role in decomposing dye molecules. The ferroelectric Bi0.5Na0.5TiO3 lead-free nanomaterials will have an excellent prospect for dye wastewater purification due to its explicit pyro-catalysis.

Anchoring Platinum Clusters onto Oxygen Vacancy-Modified In2O3 for Ultraefficient, Low-Temperature, Highly Sensitive, and Stable Detection of Formaldehyde.

To avoid carcinogenicity, formaldehyde gas, currently being only detected at higher operating temperatures, should be selectively detected in time with ppb concentration sensitivity in a room-temperature indoor environment. This is achieved in this work through introducing oxygen vacancies and Pt clusters on the surface of In2O3 to reduce the optimal operating temperature from 120 to 40 °C. Previous studies have shown that only water participates in the competitive adsorption on the sensor surface. Here, we experimentally confirm that the adsorbed water on the fabricated sensor surface is consumed via a chemical reaction due to the strong interaction between the oxygen vacancies and Pt clusters. Therefore, the long-term stability of formaldehyde gas detection is improved. The results of theoretical calculations in this work reveal that the excellent formaldehyde gas detection of Pt/In2O3-x originates from the electron enrichment due to the surface oxygen vacancies and the molecular adsorption and activation ability of Pt clusters on the surface. The developed Pt/In2O3-x sensor has potential use in the ultraefficient, low-temperature, highly sensitive, and stable detection of indoor formaldehyde at an operating temperature as low as room temperature.

Novel mechano-luminescent sensors based on piezoelectric/electroluminescent composites.

A high-sensitivity mechano-luminescent sensor was fabricated on the basis of piezoelectric/electroluminescent composites. The working principle of this mechano-luminescent sensor was elucidated by analyzing the relationship between the piezoelectric-induced charges and the electroluminescent effects. When a stress is applied on the piezoelectric layer, electrical charges will be induced at both the top and bottom sides of the piezoelectric layer. The induced electrical charges will lead to a light output from the electroluminescent layer, thus producing a mechano-luminescence effect. By increasing the vibration strength or frequency applied, the mechano-luminescence output can be obviously enhanced. Mechano-luminescence sensors have potential in smart stress-to-light devices, such as foot-stress-distribution-diagnosis systems and dynamic-load-monitors for bridge hanging cables.

Durability Investigation of Carbon Fiber Reinforced Concrete under Salt-Freeze Coupling Effect.

In order to study the durability behavior of CFRP (carbon fiber reinforced polymer) reinforced concrete, three category specimens (plain, partially reinforced, and fully reinforced) were selected to investigate its performance variation concerning chlorine salt and salt-freeze coupled environment, which included the microscopic examination, the distribution of chloride ion concentration, and the compressive properties. By observing the microscopic of the specimens, the surface and cross-section corrosion deterioration was examined with increasing exposure time, and the physical behavior of CFRP and core concrete were discussed. The chloride ion diffusion test exerted that the chloride ion concentration in plain specimens is at least 200 times higher than that of fully reinforced specimens. Therefore, the effectiveness of CFRP reinforcement will be proved to effectively hinder the penetration of chloride ions into the core section. The formula of the time-dependent effect of concrete diffusivity with salt-freeze coupling effect was presented and its accuracy verified. A time-varying finite element model of chloride ion distribution was established by using ABAQUS software. It can be seen from the axial compression test that the strength loss rate of three categories of specimens was varied when subjected to the corrosion environment. Therefore, it is proved that CFRP reinforcement can effectively reduce the deterioration of the specimen's mechanical properties caused by the exposure environment. The research results can provide technical reference for applying the CFRP strengthened concrete in a severe salt-freeze environment.

Strong piezocatalysis in barium titanate/carbon hybrid nanocomposites for dye wastewater decomposition.

In this work, the strong piezocatalysis is found in the two-step hydrothermally-synthesized barium titanate/carbon hybrid nanocomposites and is used for rhodamine B dye decomposition. As the carbon content increases from 0 to 5 wt%, the catalytic performance of hybrid nanocomposites first increases and then slightly decreases. When the carbon content increases to 2 wt%, the barium titanate/carbon hybrid nanocomposites exhibit the optimal piezocatalytic performance, which have the ~75.5% dye decomposition ratio and the ~0.04901 min-1 reaction rate constant after the 40 min vibration stimulation, while that of the pure barium titanate are 48.4% and 0.01942 min-1, respectively. The improvement of piezocatalytic performance in barium titanate/carbon hybrid nanocomposites can be ascribed to the action of carbon's charge transfer which promotes the effective separation of the piezoelectrically-induced electric charges. After three runs recycle utilization tests, the barium titanate/carbon hybrid nanocomposites still exhibit ~70% decomposition ratio of rhodamine B dye. The strong piezocatalytic performance and the good reusability make the barium titanate/carbon hybrid nanocomposites potential in the field of wastewater treatment through utilizing natural vibration energy in future.