Electrophoretic deposition of photocatalytic materials

Recent development and applications of electrodeposition biocoatings on medical titanium for bone repair

Bioactive coatings play a crucial role in enhancing the osseointegration of titanium implants for bone repair. Electrodeposition offers a versatile and efficient technique to deposit uniform coatings onto titanium surfaces, endowing implants with antibacterial properties, controlled drug release, enhanced osteoblast adhesion, and even smart responsiveness. This review summarizes the recent advancements in bioactive coatings for titanium implants used in bone repair, focusing on various electrodeposition strategies based on material-structure synergy. Firstly, it outlines different titanium implant materials and bioactive coating materials suitable for bone repair. Then, it introduces various electrodeposition methods, including electrophoretic deposition, anodization, micro-arc oxidation, electrochemical etching, electrochemical polymerization, and electrochemical deposition, discussing their applications in antibacterial, osteogenic, drug delivery, and smart responsiveness. Finally, it discusses the challenges encountered in the electrodeposition of coatings for titanium implants in bone repair and potential solutions.

Au/Ag@ZnS yolk-shell photocatalysts enhanced with noble metals and hyaluronic acid for efficient hydrogen production in rheumatoid arthritis therapy

Rheumatoid arthritis, characterized by the abnormal proliferation of synovial cells and extensive macrophage infiltration, is a chronic inflammatory disease. Molecular hydrogen, known for its antioxidant properties, has shown promise in eliminating reactive oxygen species. However, the low solubility and bioavailability of hydrogen limit the effectiveness of this therapy. To overcome these issues, we developed a novel yolk-shell heterostructure, H-AAZS (Au/Ag@ZnS modified hyaluronic acid), utilizing a hydrothermal cation exchange process. Through ion doping, semiconductor hybridization, and Schottky barriers in H-AAZS, photocatalysis for hydrogen generation has been successfully implemented using 660 nm laser irradiation. Additionally, the H-AAZS demonstrate the capacity for mild photothermal therapy, inducing apoptosis in synovial cells with Au's hot electrons with 660 nm laser irradiation. This strategy not only improves the abnormal proliferation of synovial cells but also avoids the exacerbation of inflammation caused by thermal stimulation. Both in vitro and in vivo experiments validate the synergistic effects of hydrogen production mediated anti-inflammatory responses, macrophage polarization and photothermal therapy. Therefore, this work represents a significant advancement as it ingeniously harnesses photocatalysis to modulate the synovial microenvironment while mitigating the side effects associated with photothermal therapy. This nanocrystal provides new and valuable insights into the potential treatment of Rheumatoid arthritis.

Multiparticle Synergistic Electrophoretic Deposition Strategy for High-Efficiency and High-Resolution Displays

Colloidal nanoparticles offer unique photoelectric properties, making them promising for functional applications. Multiparticle systems exhibit synergistic effects on the functional properties of their individual components. However, precisely controlled assembly of multiparticles to form patterned building blocks for solid-state devices remains challenging. Here, we demonstrate a versatile multiparticle synergistic electrophoretic deposition (EPD) strategy to achieve controlled assembly, high-efficiency, and high-resolution patterns. Through elaborate surface design and charge regulation of nanoparticles, we achieve precise control over the particle distribution (gradient or homogeneous structure) in multiparticle films using the EPD technique. The multiparticle system integrates silicon oxide and titanium oxide nanoparticles, synergistically enhancing the emission efficiency of quantum dots to a high level in the field. Furthermore, we demonstrate the superiority of our strategy to integrate multiparticle into large-area full-color display panels with a high resolution over 1000 pixels per inch. The results suggest great potential for developing multiparticle systems and expanding diverse functional applications.

Electrophoretic Deposition of Chitosan Coatings on the Porous Titanium Substrate

Medicine is looking for solutions to help implant patients recover more smoothly. The porous implants promote osteointegration, thereby providing better stabilization. Introducing porosity into metallic implants enhances their biocompatibility and facilitates osteointegration. The introduction of porosity is also associated with a reduction in Young's modulus, which reduces the risk of tissue outgrowth around the implant. However, the risk of chronic inflammation remains a concern, necessitating the development of coatings to mitigate adverse reactions. An interesting biomaterial for such modifications is chitosan, which has antimicrobial, antifungal, and osteointegration properties. In the present work, a porous titanium biomaterial was obtained by powder metallurgy, and electrophoretic deposition of chitosan coatings was used to modify its surface. This study investigated the influence of ethanol content in the deposition solution on the quality of chitosan coatings. The EPD process facilitates the control of coating thickness and morphology, with higher voltages resulting in thicker coatings and increased pore formation. Ethanol concentration in the solution affects coating quality, with higher concentrations leading to cracking and peeling. Optimal coating conditions (30 min/10 V) yield high-quality coatings, demonstrating excellent cell viability and negligible cytotoxicity. The GIXD and ATR-FTIR analysis confirmed the presence of deposited chitosan coatings on Ti substrates. The microstructure of the chitosan coatings was examined by scanning electron microscopy. Biological tests showed no cytotoxicity of the obtained materials, which allows for further research and the possibility of their use in medicine. In conclusion, EPD offers a viable method for producing chitosan-based coatings with controlled properties for biomedical applications, ensuring enhanced patient outcomes and implant performance.

Interfacial Design of Particulate Photocatalyst Materials for Green Hydrogen Production

Green hydrogen production using particulate photocatalyst materials has attracted much attention in recent years because this process could potentially lead to inexpensive and scalable solar-to-chemical energy conversion systems. Although the development of efficient particulate photocatalysts enabling one-step overall water splitting (OWS) with solar-to-hydrogen efficiencies in excess of 10 % remains challenging, promising photocatalyst candidates exhibiting OWS activity have been demonstrated. This review provides a comprehensive introduction to the solar-to-hydrogen energy conversion process of semiconductor photocatalyst materials and highlights recent advances in photocatalytic OWS via both one-step and two-step photoexcitation processes. The review also covers recent developments in the photocatalytic OWS of SrTiO3, including the establishment of large-scale photocatalytic systems, interfacial design using cocatalysts to enhance water splitting activity, and its photoelectrochemical (PEC) properties at the electrified solid/liquid interface. In addition, there is a special focus on visible-light-absorbing oxynitride and oxysulfide particulate photocatalysts with absorption edges near 600 nm. Methods for photocatalyst preparation and surface modification, as well as PEC properties, are also discussed. The semiconductor properties of particulate photocatalysts obtained from photoelectroanalytical evaluations using particulate photoelectrodes are evaluated. This review is intended to provide guidelines for the future development of particulate photocatalysts capable of efficient and stable OWS.

Nonmonotonic electrophoretic mobility of rodlike polyelectrolytes by multivalent coions in added salt

It is well established that when multivalent counterions or salts are added to a solution of highly charged polyelectrolytes (PEs), correlation effects can cause charge inversion of the PE, leading to electrophoretic mobility (EM) reversal. In this work, we use coarse-grained molecular-dynamics simulations to unravel the less understood effect of coion valency on EM reversal for rigid DNA-like PEs. We find that EM reversal induced by multivalent counterions is suppressed with increasing coion valency in the salt added and eventually vanishes. Further, we find that EM is enhanced at fixed low salt concentrations for salts with monovalent counterions when multivalent coions with increasing valency are introduced. However, increasing the salt concentration causes a crossover that leads to EM reversal which is enhanced by increasing coion valency at high salt concentration. Remarkably, this multivalent coion-induced EM reversal persists even for low values of PE linear charge densities where multivalent counterions alone cannot induce EM reversal. These results facilitate tuning PE-PE interactions and self-assembly with both coion and counterion valencies.

Bi2O3 modified TiO2 nanotube arrays and their application towards unsymmetrical dimethylhydrazine degradation in wastewater by electroassisted photocatalysis

In the present research, the preparation process parameters of TiO₂ nanotube arrays (TNAs) prepared by anodic oxidation were systematically studied by the orthogonal experimental method for the first time. Herein, the parameters of nine factors were optimized; the optimal parameters were: the electrolyte was a 0.2 mol L^-1 NaF solution with 3% vol H₂O at pH 7, the anodic oxidation voltage was 40 V, the electrode spacing was 4 cm and the reaction was carried out for 60 minutes. The physicochemical properties of the materials were characterized by SEM, XRD, EDS, UV-vis, and PL spectroscopy. By electrodeposition of Bi₂O₃ modified TNAs, the degradation rate of unsymmetrical dimethylhydrazine (UDMH) wastewater on the TNAs-10 was 89.14% within 10 h, which was 2.69 times that on pure TNAs. A bias potential of +0.3 V (vs. open circuit potential) was applied to the modified TNAs-10. The degradation rate of UDMH was significantly enhanced on the TNAs-10 (bias) process as compared to the TNAs-10 process. The degradation rate of UDMH wastewater on TNAs-10 (bias) exhibited an exponential distribution. UDMH and its toxic by-products FDMH, NDMA were completely degraded after 8 h.

Kinetics study of anodic electrophoretic deposition for polytetrafluoroethylene (PTFE) coatings on AZ31 magnesium alloy

Electrophoretic deposition (EPD) coating has become a hot topic due to its simple experiment, wide application, and wide material range. In this study, the PTFE coating was successfully prepared by electrophoretic deposition through the systematic study of electrophoretic deposition kinetics. In particular, in the dispersion system with ethanol as solvent, Nafion and NaOH were simultaneously added as additives to obtain a beneficial synergistic effect on PTFE electrophoretic deposition. And the best additive scheme is: when the concentration of PTFE was 6 g·L− 1 and the deposition time was increased to 20 min, adding 0.10 g·L− 1 Nafion and 0.10 mM NaOH simultaneously. Compared with the scheme with Nafion being only additive, the addition of NaOH can improve the deposition rate from 0.16 mg·cm− 2 to 0.98 mg·cm− 2, and the deposition rate increases by about 6 times. According to electrophoretic deposition kinetics, there is an obvious critical transition time between linear and parabolic regions in the preparation of the coating. Prolonging the arrival of critical transition time is beneficial to effectively achieve stable growth of the coating in a longer time. It is found that a more ideal additive can not only increase the deposition rate of coating, but also significantly accelerate the arrival of critical transition time. Meanwhile, the deposition voltage also has an important influence on the critical transition time. Increasing the voltage can improve the deposition speed but shorten the critical transition time. Therefore, the application of deposition voltage needs to strike a balance between deposition rate and critical time point. The optimal deposition conditions proposed in this work are: deposition voltage 60 V, deposition time 20 min, additive 0.10 g·L− 1 Nafion and 0.10 mM NaOH.

Photoreactive Coating Material as an Effective and Durable Antimicrobial Composite in Reducing Bacterial Load on Surfaces in Livestock

Titanium dioxide (TiO2) is a well-known photocatalytic compound that can be used to effectively reduce the presence of pathogens in human and animal hospitals via ROS release. The aim of this study was to investigate the efficacy of a polymer-based composite layer containing TiO2 and zinc oxide (ZnO) against Escherichia coli (E. coli) of animal origin. We showed that the photocatalyst coating caused a significant (p < 0.001) reduction in pathogen numbers compared to the control with an average reduction of 94% over 30 min. We used six light sources of different wattages (4 W, 7 W, 9 W, 12 W, 18 W, 36 W) at six distances (35 cm, 100 cm, 150 cm, 200 cm, 250 cm, 300 cm). Samples (n = 2160) were taken in the 36 settings and showed no significant difference in efficacy between light intensity and distance. We also investigated the influence of organic contaminant that resulted in lower activity as well as the effect of a water jet and a high-pressure device on the antibacterial activity. We found that the latter completely removed the coating from the surface, which significantly (p < 0.0001) reduced its antibacterial potential. As a conclusion, light intensity and distance does not reduce the efficacy of the polymer, but the presence of organic contaminants does.

Overcoming the rise in local deposit resistance during electrophoretic deposition via suspension replenishing

Nanomaterials have unique properties, functionalities, and excellent performance, and as a result have gained significant interest across disciplines and industries. However, currently, there is a lack of techniques that can assemble as-synthesized nanomaterials in a scalable manner. Electrophoretic deposition (EPD) is a promising method for the scalable assembly of colloidally stable nanomaterials into thick films and arrays. In EPD, an electric field is used to assemble charged colloidal particles onto an oppositely charged substrate. However, in constant voltage EPD the deposition rate decreases with increasing deposition time, which has been attributed in part to the fact that the electric field in the suspension decreases with time. This decreasing electric field has been attributed to two probable causes, (i) increased resistance of the particle film and/or (ii) the growth of an ion-depletion region at the substrate. Here, to increase EPD yield and scalability we sought to distinguish between these two effects and found that the growth of the ion-depletion region plays the most significant role in the increase of the deposit resistance. Here, we also demonstrate a method to maintain constant deposit resistance in EPD by periodic replenishing of suspension, thereby improving EPD’s scalability.

Attomolar detection of 4-aminothiophenol by SERS using silver nanodendrites decorated with gold nanoparticles

In the present work we report a simple, fast, reproducible and cheap methodology for surface enhanced Raman spectroscopy (SERS) substrate fabrication of silver dendritic nanostructures (prepared by electrodeposition) decorated with gold nanospheres by electrophoretic deposition. This is the first report where a metal dendritic nanostructure has been decorated with another type of metal nanoparticles by this technique. The decorated nanostructures were used directly as SERS substrate using 4-aminothiophenol (4-ATP) as analyte. The objective of the decoration is to create more hot-spots in order to detect the analyte in a lower concentration. Decorated nanodendrites had a detection limit one million times lower than bare silver nanodendrites and all the substrates showed an increase in the Raman intensity at concentrations below 1 nM; because this concentration corresponds to the threshold for the formation of a monolayer resulting in a triple mechanism of intensity increase, namely electric field, chemical factor and hot-spots. 4-ATP was detected in attomolar concentration, which is below 1 ppq, corresponding to an analytical enhancement factor in the order of 10¹⁵.

Chitosan-Based Biomaterial Scaffolds for the Repair of Infected Bone Defects

The treatment of infected bone defects includes infection control and repair of the bone defect. The development of biomaterials with anti-infection and osteogenic ability provides a promising strategy for the repair of infected bone defects. Owing to its antibacterial properties, chitosan (an emerging natural polymer) has been widely studied in bone tissue engineering. Moreover, it has been shown that chitosan promotes the adhesion and proliferation of osteoblast-related cells, and can serve as an ideal carrier for bone-promoting substances. In this review, the specific molecular mechanisms underlying the antibacterial effects of chitosan and its ability to promote bone repair are discussed. Furthermore, the properties of several kinds of functionalized chitosan are analyzed and compared with those of pure chitosan. The latest research on the combination of chitosan with different types of functionalized materials and biomolecules for the treatment of infected bone defects is also summarized. Finally, the current shortcomings of chitosan-based biomaterials for the treatment of infected bone defects and future research directions are discussed. This review provides a theoretical basis and advanced design strategies for the use of chitosan-based biomaterials in the treatment of infected bone defects.

Zeptomolar detection of 4-aminothiophenol by SERS using silver nanodendrites decorated with gold nanoparticles

In the present work, we report a simple, fast, reproducible and cheap methodology for SERS substrate fabrication of silver dendritic nanostructures (prepared by electrodeposition) decorated with gold nanospheres by electrophoretic deposition. This is the first report where a metal dendritic nanostructure has been decorated with another type of metal nanoparticles by this technique. The decorated nanostructures were used directly as SERS substrate using 4-aminothiophenol (4-ATP) as analyte. The objective of the decoration is to create more hot-spots in order to detect the analyte in a lower concentration. Decorated nanodendrites had a detection limit one million times lower than bare silver nanodendrites and all the substrates showed an increase in the Raman intensity at concentrations below 1 nM; because this concentration corresponds to the threshold for the formation of a monolayer resulting in a triple mechanism of intensity increase, namely electric field, chemical factor and hot-spots. 4-ATP was detected in zeptomolar concentration, which is below 1 ppq, corresponding to an analytical enhancement factor in the order of 10¹⁵.

Nanostructured TiO2 Sensitized with MoS2 Nanoflowers for Enhanced Photodegradation Efficiency toward Methyl Orange

Nanostructured titanium dioxide (TiO₂) has a potential platform for the removal of organic contaminants, but it has some limitations. To overcome these limitations, we devised a promising strategy in the present work, the heterostructures of TiO₂ sensitized by molybdenum disulfide (MoS₂) nanoflowers synthesized by the mechanochemical route and utilized as an efficient photocatalyst for methyl orange (MO) degradation. The surface of TiO₂ sensitized by MoS₂ was comprehensively characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence spectroscopy (PL), Brunauer-Emmett-Teller (BET) surface area, and thermogravimetric analysis (TGA). From XRD results, the optimized MoS₂-TiO₂ (5.0 wt %) nanocomposite showcases the lowest crystallite size of 14.79 nm than pristine TiO₂ (20 nm). The FT-IR and XPS analyses of the MoS₂-TiO₂ nanocomposite exhibit the strong interaction between MoS₂ and TiO₂. The photocatalytic results show that sensitization of TiO₂ by MoS₂ drastically enhanced the photocatalytic activity of pristine TiO₂. According to the obtained results, the optimal amount of MoS₂ loading was assumed to be 5.0 wt %, which exhibited a 21% increment of MO photodegradation efficiency compared to pristine TiO₂ under UV-vis light. The outline of the overall study describes the superior photocatalytic performance of 5.0 wt % MoS₂-TiO₂ nanocomposite which is ascribed to the delayed recombination by efficient charge transfer, high surface area, and elevated surface oxygen vacancies. The context of the obtained results designates that the sensitization of TiO₂ with MoS₂ is a very efficient nanomaterial for photocatalytic applications.

Structured photocatalytic systems: photocatalytic coatings on low-cost structures for treatment of water contaminated with micropollutants-a short review

The persistence of many micropollutants in water and wastewater is of great concern to the contemporary scientific community. Several types of advanced techniques such as heterogeneous photocatalysis are being used for the degradation of micropollutants in waters from domestic, industrial, and agricultural activities. Thus, structured photocatalytic systems are a great alternative in the development of photocatalytic reactors and continuous water treatment systems, as they present good autonomy during the treatment process. Many aspects such as type and geometry of the catalytic structure to be developed must be carefully chosen for the proper functioning of the system, as well as the best routes by which the photocatalysts will be immobilized. In this sense, this work brings the main photocatalytic coating techniques in low-cost structures for the treatment of water and wastewater contaminated with micropollutants. The methodologies and synthesis parameters that can influence the final result of the coating were highlighted, as well as the ability to reuse photocatalysts and methods for pretreating the structural surface. The dip-coating technique was the most reported among the current works due to its simplicity and, predominantly, the pretreatment techniques of the structure are still cleaning the surface with water, soap, and also some alcohols.

Electrophoretic-deposited Superhydrophobic Coatings

Electrophoretic deposition (EPD) is an excellent surface coating approach widely investigated for applications ranging from solar cells, batteries, electrochemical capacitors, solid oxide fuel cells, sensors, molecular sieves, corrosion-resistant coatings, and biomedical materials. On the other hand, superhydrophobic (SHPC) surfaces have enticed substantial recent research interest owing to their superb surface properties. Here, we provide a comprehensive review of electrophoretic-deposited SHPC coatings. Concise descriptions of EPD and superhydrophobicity are provided first, followed by a brief mentioning of works reported on electrophoretic-deposited SHPC coatings by one-step or two-step processing (§2.1). The next section (§2.2) delivers a comprehensive description of these reports based on the micro/nanoparticles used. Works reported in specific applications such as anti-corrosion, biomedical, and oil-separation are described in §2.3. Future scopes of research also presented.

A review of electrophoretic deposition of metal oxides and its application in solid oxide fuel cells

Because of its cost-effectiveness, good uniformity, fast deposition rate and simplicity, electrophoretic deposition (EPD) has been widely used to deposit various metal oxide films for different applications. As with other coating fabrication processes, the deposition rate and film quality are two crucial criteria to evaluate the effectiveness and suitability of EPD. In this review, we summarize the parameters and discuss the dynamic processes influencing the deposition behavior of ionically charged metal oxide particles. Special focus is also given to the methods to improve the film quality. In addition, the application of EPD in the fabrication of solid oxide fuel cells (SOFCs) is summarized.