A Microorganism Bred TiO2/Au/TiO2 Heterostructure for Whispering Gallery Mode Resonance Assisted Plasmonic Photocatalysis

Biomineralized manganese oxide mediated nitrogen-contained wastewater treatment

In recent years, manganese (Mn) has emerged as an accelerator for nitrogen metabolism. However, the bioactivity of manganese is limited by the restricted contact between microbes and manganese minerals in the solid phase and by the toxicity of manganese to microbes. To enhance the bioactivity of solid-phase manganese, biomineralized manganese oxide (MnOx) modified by Lactobacillus was introduced. Nitrogen removal performance have confirmed the effective role of biomineralized MnOx in accelerating the removal of total inorganic nitrogen (TIN). Metagenomic analysis has confirmed the enhancement of the nitrogen metabolic pathway and microbial extracellular electron transfer (MEET) in biomineralized MnOx treatment group (BIOA group). Additionally, the enrichment of manganese oxidation and denitrification genus indicates a coupling between nitrogen metabolism and manganese metabolism. One point of views is that biomineralized MnOx-mediated nitrogen transformation processes could serve as a substitute for traditional nitrogen removal processes.

Nanozyme-Enhanced Electrochemical Biosensors: Mechanisms and Applications

Nanozymes, as innovative materials, have demonstrated remarkable potential in the field of electrochemical biosensors. This article provides an overview of the mechanisms and extensive practical applications of nanozymes in electrochemical biosensors. First, the definition and characteristics of nanozymes are introduced, emphasizing their significant role in constructing efficient sensors. Subsequently, several common categories of nanozyme materials are delved into, including metal-based, carbon-based, metal-organic framework, and layered double hydroxide nanostructures, discussing their applications in electrochemical biosensors. Regarding their mechanisms, two key roles of nanozymes are particularly focused in electrochemical biosensors: selective enhancement and signal amplification, which crucially support the enhancement of sensor performance. In terms of practical applications, the widespread use of nanozyme-based electrochemical biosensors are showcased in various domains. From detecting biomolecules, pollutants, nucleic acids, proteins, to cells, providing robust means for high-sensitivity detection. Furthermore, insights into the future development of nanozyme-based electrochemical biosensors is provided, encompassing improvements and optimizations of nanozyme materials, innovative sensor design and integration, and the expansion of application fields through interdisciplinary collaboration. In conclusion, this article systematically presents the mechanisms and applications of nanozymes in electrochemical biosensors, offering valuable references and prospects for research and development in this field.

Construction of floatable flower-like plasmonic Bi/BiOCl-loaded hollow kapok fiber photocatalyst for efficient degradation of RhB and antibiotics

The development of low-cost and high-efficiency photocatalysts for the degradation of organic pollutants has been an essential and feasible approach to environmental remediation. However, conventional powder photocatalysts suffer from agglomeration, limited light utilization, and reuse difficulties, which hinder their large-scale practical application. Herein, a floatable flower-like plasmonic Bi/BiOCl-loaded hollow kapok fiber (KF/Bi/BC) photocatalyst was synthesized by a facile solvothermal method. It exhibited excellent photocatalytic degradation of Rhodamine B (RhB), ofloxacin (OFX), and tetracycline (TC) under UV-vis irradiation. The incorporation of metallic Bi not only greatly enhanced the light absorption of BiOCl in the visible region but also served as an effective "electron trap", facilitating the efficient separation and transfer of photogenerated electrons and holes. Furthermore, the remarkable floatability of the catalyst contributed to increased light utilization and facilitated the recycling of the catalyst. This work provided a convenient, effective, and feasible method for the fabrication of floatable photocatalysts with excellent catalytic properties, and has great potential for practical applications.

Highly Efficient Nitrogen-Fixing Microbial Hydrogel Device for Sustainable Solar Hydrogen Production

Conversion of sunlight and organic carbon substrates to sustainable energy sources through microbial metabolism has great potential for the renewable energy industry. Despite recent progress in microbial photosynthesis, the development of microbial platforms that warrant efficient and scalable fuel production remains in its infancy. Efficient transfer and retrieval of gaseous reactants and products to and from microbes are particular hurdles. Here, inspired by water lily leaves floating on water, a microbial device designed to operate at the air-water interface and facilitate concomitant supply of gaseous reactants, smooth capture of gaseous products, and efficient sunlight delivery is presented. The floatable device carrying Rhodopseudomonas parapalustris, of which nitrogen fixation activity is first determined through this study, exhibits a hydrogen production rate of 104 mmol h-1  m-2 , which is 53 times higher than that of a conventional device placed at a depth of 2 cm in the medium. Furthermore, a scaled-up device with an area of 144 cm2 generates hydrogen at a high rate of 1.52 L h-1  m-2 . Efficient nitrogen fixation and hydrogen generation, low fabrication cost, and mechanical durability corroborate the potential of the floatable microbial device toward practical and sustainable solar energy conversion.

Rational Construction of MOF-Derived Porous ZnTiO3/TiO2 Heterostructured Photocatalysts with Remarkable Photocatalytic Performance

TiO2 has been widely used in photodegradation of pollutants, but it suffers from inferior photocatalytic performance under solar light illumination. Thus, novel porous ZnTiO3/TiO2 heterostructured photocatalysts are constructed by hydrothermal and carbonization techniques using ZIF-8 as a sacrificial template. After coating with TiO2, ZIF-8 nanocubes are selectively etched and subsequently coprecipitated with Ti ions during the hydrothermal process. Thereafter, the pores generated from carbonized ZIF-8 provide a large specific surface area and abundant active reaction sites for photocatalysis after annealing, producing stable ZnTiO3/TiO2 nanocomposites. Thus, porous ZnTiO3/TiO2 heterostructured photocatalysts exhibit excellent photocatalytic performance under solar light irradiation due to the boosted electron-hole separation/transfer. The kinetic constant of ZnTiO3/TiO2 nanocomposites (4.66 × 10-1 min-1) is almost 100 and 3.7 times higher than that of self-degradation (4.69 × 10-3 min-1) and TiO2 (1.27 × 10-1 min-1), respectively. This facile strategy provides a deep insight into synthesizing heterostructured photocatalysts with high efficiency in the field of environmental remediation.

Facet-engineered TiO2 drives photocatalytic activity and stability of supported noble metal clusters during H2 evolution

Metal clusters supported on TiO2 are widely used in many photocatalytic applications, including pollution control and production of solar fuels. Besides high photoactivity, stability during the photoreaction is another essential quality of high-performance photocatalysts, however systematic studies on this attribute are absent for metal clusters supported on TiO2. Here we have studied, both experimentally and with first-principles simulation methods, the stability of Pt, Pd and Au clusters prepared by ball milling on nanoshaped anatase nanoparticles preferentially exposing {001} (plates) and {101} (bipyramids) facets during the photogeneration of hydrogen. It is found that Pt/TiO2 exhibits superior stability than Pd/TiO2 and Au/TiO2, and that {001} facet-based photocatalysts always are more stable than their {101} analogous regardless of the considered metal species. The loss of stability associated with cluster sintering, which is facilitated by the transfer of photoexcited carriers from the metal species to the neighbouring Ti and O atoms, most significantly and detrimentally affects the H2-evolution photoactivity.

Synergistic effect of double Schottky potential well and oxygen vacancy for enhanced plasmonic photocatalytic U(VI) reduction

Plasmonic photocatalysis is an effective strategy to solve radioactive uranium hazards in wastewater. A plasmonic photocatalyst Bi/Bi₂O_3-x@COFs was synthesized by in-situ growth of covalent organic frameworks (COFs) on Bi/Bi₂O_3-x surface for the U(VI) adsorption and plasmonic photoreduction in rare earth tailings wastewater. The presence of oxygen vacancy in Bi/Bi₂O_3-x and Schottky potential well formed by Bi and Bi₂O_3-x interface increased the number of free electrons, which induced localized surface plasmon resonance (LSPR) and enhanced the light absorption performance of composites. In addition, oxygen vacancy improved the Fermi level of Bi/Bi₂O_3-x, leading to another potential well between Bi₂O_3-x and COFs interface. The electron transport direction was reversed, thus increasing the electron density of COFs layer. COFs was an N-type semiconductor with specific binding U(VI) groups and suitable band structure, which could be used as an active reaction site. Bi/Bi₂O_3-x@COFs had 1411.5 mg g^-1 removal capacity and high separation coefficient for U(VI) due to the synergistic action of photogenerated electrons and hot electrons. Moreover, the removal rate of uranium from rare earth tailings wastewater by regenerated Bi/Bi₂O_3-x@COFs was over 93.9%. The scheme of introducing LSPR and Schottky potential well provides another way to improve the photocatalytic effect.

Photoelectrocatalytic activity of silicon nanowires decorated with electroless copper nanoparticles and graphene oxide using a plasma jet for removal of methyl orange under visible light†

Silicon nanowires (Si_NWs) have been studied due to their interesting properties, such as light trapping and catalytic activity for removing organic molecules. In this work, silicon nanowires are decorated with copper (Si_NWs-Cu_NPs), graphene oxide (Si_NWs-GO), and both copper and graphene oxide GO (Si_NWs-Cu_NPs-GO). They were prepared and tested as photoelectrocatalysts to remove the azoic dye methyl orange (MO). The silicon nanowires were synthesized by the MACE process using HF/AgNO₃ solution. The decoration with copper nanoparticles was made by galvanic displacement reaction utilizing a copper sulfate/HF solution, while decoration with GO was achieved using an atmospheric pressure plasma jet system (APPJ). The as-produced nanostructures were then characterized by SEM, XRD, XPS, and Raman spectroscopy. Cu(i) oxide was generated during the decoration with copper. Cu(ii) oxide was produced when Si_NWs–Cu_NPs were exposed to the APPJ. GO was successfully attached on the surface of silicon nanowires and silicon nanowires decorated with copper nanoparticles. The photoelectrocatalytic activity of silicon nanostructures was tested under visible light, leading to an MO removal efficiency of 96% within 175 min with Si_NWs–Cu_NPs-GO, followed by Si_NWs-Cu_NPs, Si_NWs-GO, undecorated Si_NWs, and bulk silicon.

Silicon nanowires (Si_NWs) have been studied due to their interesting properties, such as light trapping and catalytic activity for removing organic molecules.

Piezotronic Effect Induced Schottky Barrier Decrease to Boost the Plasmonic Charge Separation of BaTiO3-Au Heterojunction for the Photocatalytic Selective Oxidation of Aminobenzyl Alcohol

Charge carrier transfer efficiency as a crucial factor determines the performance of heterogeneous photocatalysis. Here, we demonstrate a simple nanohybrid structure of BaTiO₃-Au (BTO-Au) for the efficient selective oxidization of benzyl alcohol to benzaldehyde upon piezotronic effect boosted plasmonic photocharge carrier transfer. With the aid of ultrasonic mechanical vibration, the reaction rate of the photocatalytic organic conversion would be considerably accelerated, which is about 4.2 and 6.2 times higher than those driven by sole visible light irradiation and sole ultrasonication, respectively. Photoelectrochemical tests under ultrasonic stimuli reveal the BTO-Au catalytic system is independent of the light intensity, showing a consistent photocurrent density, over a wide range of incident light brightness. The largely enhanced photocatalytic activity can be ascribed to the synergetic effect of surface plasmonic resonance (SPR)-piezotronic coupling by which a built-in electric field induced by the piezotronic effect significantly favors the oriented mobilization of energetic charge carriers generated by the SPR effect at the heterojunction. Notably, a decrease of the Schottky barrier height of ∼0.3 eV at the BTO-Au interface is verified experimentally, due to the band bending of BTO induced by the piezotronic effect, which can greatly augment the hot electron transfer efficiency. This work highlights the coupling of the piezotronic effect with SPR within the BTO-Au nanostructure as a versatile and promising route for efficient charge transfer in photocatalytic organic conversion.

A study on the role of plasmonic Ti3C2Tx MXene in enhancing photoredox catalysis

Engineering the spatial separation and transfer of photogenerated charge carriers has been one of the most enduring research topics in the field of photocatalysis due to its crucial role in determining the performances of photocatalysts. Herein, as a proof-of-concept, Ti₃C₂T_x MXene is coupled with a typical heterojunction of TiO₂@CdS through a co-assembly strategy to boost electron pumping towards improving the photocatalytic efficiency. In addition to the band alignment-mediated electron transfer in TiO₂@CdS-Ti₃C₂T_x heterojunctions, the plasmon-induced electric field enhancement of Ti₃C₂T_x is found to cooperate with the electron-reservoir role of Ti₃C₂T_x to extract photoinduced electrons. The synergistic dual functions of Ti₃C₂T_x promote multichannel electron transfer in TiO₂@CdS-Ti₃C₂T_x hybrids to improve the photocatalytic efficiency. These results intuitively show that there is a wide scope to manipulate the spatial separation and transfer of photoinduced electrons by cultivating the fertile ground of Ti₃C₂T_x toward boosting the efficiency of solar-to-chemical conversion.

Electromagnetic Mechanisms or Chemical Mechanisms? Role of Interfacial Charge Transfer in the Plasmonic Metal/Semiconductor Heterojunction

The plasmonic metal/semiconductor heterojunction provides a unique paradigm for manipulating light to improve the efficiency of plasmonic materials. Previous studies suggest that the improvement originates from the enhanced carrier exchanges between the plasmonic component of the heterojunction and molecules. This viewpoint, known as the chemical mechanism, is reasonable but insufficient, because the construction of the heterojunction will lead to a charge redistribution in the plasmonic component and cause changes in its physical characteristics. Herein, we will try to clarify that these changes are decisive factors in specific applications by investigating the surface-enhanced Raman scattering (SERS) behavior of a typical Ag/TiO₂ heterojunction. We observed significant changes in SERS spectra by modulating the band alignment of the heterojunction in a loop. Identical trends in SERS spectra were observed despite the fact that the charge transfer from the heterojunction to molecules was blocked, suggesting that the major SERS enhancement originates from electromagnetic mechanisms rather than chemical ones.

Multicomponent Composite Membrane with Three-Phase Interface Heterostructure as Photocatalyst for Organic Dye Removal

A multicomponent composite membrane (P-S-T/C) with three-phase interface heterostructure is ingeniously designed. A polydopamine (PDA)-modified conductive carbon fiber cloth (C_FC) is used as the substrate. Activated poly(vinylidene fluoride) (PVDF) with titanium dioxide (TiO₂) and a silicon dioxide (SiO₂) aerogel are electrospun as the top layer. The three-phase interface heterostructure was formed by TiO₂, conductive C_FC, and the SiO₂ aerogel. Its photocatalytic performance is validated by photodegradation of organic dyes in a low-oxygen (O₂) water environment. On combining with the capillary condensation of a bilayer structure, P-S-T/C exhibits excellent removal capability for anionic and cationic dyes. Moreover, P-S-T/C exhibits excellent stability and recyclability under simulated sunlight. The mechanism study indicates that the separated photogenerated carriers diffuse to the composite membrane surface rapidly on the three-phase interface of P-S-T/C. The abundant O₂ adsorbed on the porous SiO₂ aerogel surface acts as an electron (e^-)-trapping agent, which can also decrease the work function of the composite materials. Superoxide radicals (^•O₂ ^-) play a dominant role in the reaction of photodegradation supported by a free radical-trapping experiment. This work paves a way to design a membrane with photocatalytic performance by constructing the interface heterostructure.

UV illumination-enhanced ultrasensitive ammonia gas sensor based on (001)TiO2/MXene heterostructure for food spoilage detection

Ammonia has been used as an important marker to indicate the extent of food spoilage. However, current gas sensors for ammonia suffer from either insufficient sensitivity and selectivity or unsatisfactory levels of automation, impeding their practical application for on-site and real-time monitoring of food quality. To overcome these limitations, we propose here the design of a sensing material by in-situ growing (001)TiO₂ onto a two-dimensional transition-metal carbide (Ti₃C₂T_x, MXene). In this design, TiO₂ with a highly active (001) crystal plane provides efficient photogeneration under UV irradiation, while Ti₃C₂T_x can store holes through Schottky junction formed at the interface with TiO₂, which greatly promotes the separation of electron-hole pairs, thereby enhancing ammonia sensing performance. By further introducing UV light for electron excitation, the (001)TiO₂/Ti₃C₂T_x based sensor shows 34 times higher sensitivity for ammonia (30 ppm) than that of Ti₃C₂T_x. The density functional theory further revealed that the (001) plane of TiO₂ and Ti₃C₂T_x composite configuration exhibited the highest adsorption affinity towards ammonia. Finally, an integrated circuit alarm system including near-field communication and a micro-controller system was designed to detect the decay process of fresh pork, fish, and shrimp. We believe such a sensing technology holds great promise in food quality monitoring.

Recent Advances in Plasmonic Photocatalysis Based on TiO2 and Noble Metal Nanoparticles for Energy Conversion, Environmental Remediation, and Organic Synthesis

Plasmonic photocatalysis has emerged as a prominent and growing field. It enables the efficient use of sunlight as an abundant and renewable energy source to drive a myriad of chemical reactions. For instance, plasmonic photocatalysis in materials comprising TiO₂ and plasmonic nanoparticles (NPs) enables effective charge carrier separation and the tuning of optical response to longer wavelength regions (visible and near infrared). In fact, TiO₂ -based materials and plasmonic effects are at the forefront of heterogeneous photocatalysis, having applications in energy conversion, production of liquid fuels, wastewater treatment, nitrogen fixation, and organic synthesis. This review aims to comprehensively summarize the fundamentals and to provide the guidelines for future work in the field of TiO₂ -based plasmonic photocatalysis comprising the above-mentioned applications. The concepts and state-of-the-art description of important parameters including the formation of Schottky junctions, hot electron generation and transfer, near field electromagnetic enhancement, plasmon resonance energy transfer, scattering, and photothermal heating effects have been covered in this review. Synthetic approaches and the effect of various physicochemical parameters in plasmon-mediated TiO₂ -based materials on performances are discussed. It is envisioned that this review may inspire and provide insights into the rational development of the next generation of TiO₂ -based plasmonic photocatalysts with target performances and enhanced selectivities.

Microcystis@TiO2 Nanoparticles for Photocatalytic Reduction Reactions: Nitrogen Fixation and Hydrogen Evolution

Solar-driven photocatalysis has been known as one of the most potential technologies to tackle the energy shortage and environmental pollution issues. Utilizing bio-pollutants to prepare functional materials has been considered as a green option. Herein, we used Microcystis aeruginosa as a bio-template to fabricate a Microcystis@TiO2 photocatalyst using a calcination method. The as-prepared Microcystis@TiO2 showed prominent ability as well as favorable stability for photocatalytic reduction reactions including hydrogen evolution and nitrogen fixation. Under light illumination, Microcystis@TiO2 calcined at 550 °C exhibited optimal photo-reduced activity among all samples, with the highest hydrogen evolution (1.36 mmol·g−1·h−1) and ammonia generation rates (0.97 mmol·g−1·h−1). This work provides a feasible approach to prepare functional materials from disposed pollutants.

Fabrication of visible-light response cadmium sulfide modified superhydrophobic surface for water resource remediation

Widespread concern has been attached to the frequent occurrence of pollution by oil slicks and water-soluble pollutants in recent years. The semiconductor photocatalysis is applied to sewage treatment owing to the advantages of energy-conserving and environmental protection. However, its application is limited by the defects of not solving oil slicks and the hard recyclability. In this paper, the high specific surface area and rod-shaped CdS were prepared using template and alkali-treated methods. Next, the alkylated SiO₂and alkali-treated CdS were deposited on pure fabric by physical deposition to prepare the multifunctional superhydrophobic fabric. The specific surface area and morphology of alkali-treated CdS were tested by BET specific surface area test and field emission scanning electron microscope. Besides, oil/water separation, water contact angle, and stability test experiments were performed to determine the superhydrophobic performance. Photocatalysis degradation efficiency and cycle degradation stability of multifunctional fabric were characterized by photocatalysis degradation Rh B experiment. Consequently, the alkali-treated CdS displays a high specific surface up to 343 m²g^-1. The multifunctional fabric presents excellent superhydrophobic performance with the water contact angle up to 155°. Meanwhile, the water contact angle of multifunctional fabric is always over 150° under various circumstances (acid-base corrosion, soaking time at 100 °C and frictional numbers), indicating that the multifunctional fabric has excellent superhydrophobic stability. Moreover, the fabric also exhibits outstanding photocatalysis performance (the degradation efficiency is 94% after 3 cycles). Our work provides a feasible method for addressing oil slicks on water surface and degrading water-soluble pollutants with extensive application prospects in water resource remediation.