Diatom-Inspired TiO2-PANi-Decorated Bilayer Photothermal Foam for Solar-Driven Clean Water Generation

Near-infrared smart responsive orthopedic implants with synergistic antimicrobial and bone integration-promoting properties

Background

The decline in antibiotic use has made the treatment of post-implant infections increasingly challenging, especially the problem of bacterial invasion caused by inadequate tissue fusion with the implant in the early stages of the implant. Developing multiple methods to reduce bacterial infections through synergies will be superior to a single model of antimicrobial means.

Methods

The composite coating composed of titanium phosphate (TiP)/copper oxide nanoparticles (CuO)/nano-hydroxyapatite (n-HA) named TiP-ua was used to kill Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) under near infrared (NIR) irradiation by means of photothermal therapy (PTT) and photodynamic therapy (PDT) synergism.

Results

The TiP-ua composite coating can reach about 60 °C and produce a certain amount of reactive oxygen species after 15 min irradiation with 980 nm near infrared light with 0.9 W/cm2 power. Under the NIR irradiation of 0.9 W/cm2 power for 10 min, the composite coating can achieve about 90% killing effect on S. aureus and more than 90% killing effect on E. coli. In terms of mouse pre-osteoblasts (MC3T3-E1), TiP-ua showed more superiority in promoting osteogenic differentiation ability. In the mouse infection model, it also showed good antibacterial effect, and could significantly reduce the expression of inflammatory factors and accelerate wound healing. In the bone defect model, the intervention significantly accelerated the regeneration of neobone tissue and enhanced osseointegration capacity.

Conclusions

The experimental results show that TiP-ua coating not only has good photothermal conversion ability, but also has good biosafety, which can accelerate the regeneration and repair of bone tissue around the implant, including accelerating the osteogenic differentiation of cells, and reduce the activity of bacteria to effectively reduce the inflammatory response.

The translational potential of this article

The collaborative antibacterial and bone repair coating in this study has a simple preparation process, high repeatability, high biosafety and positive effect on bone tissue repair, and has great clinical application potential in orthopedics and dental implants.

Multifunctional Super-Hydrophilic MXene/Biomass Composite Aerogel Evaporator for Efficient Solar-Driven Desalination and Wastewater Treatment

Solar-driven interfacial evaporation is recognized as a sustainable and effective strategy for desalination to mitigate the freshwater scarcity issue. Nevertheless, the challenges of oil contamination, salt accumulation, and poor long-term stability of the solar desalination process limit its applications. Herein, a 3D biomass-based multifunctional solar aerogel evaporator is developed for water production with fabricated chitosan/lignin (CSL) aerogel as the skeleton, encapsulated with carbonized lignin (CL) particles and Ti3C2TiX (MXene) nanosheets as light-absorbing materials. Benefitting from its super-hydrophilic wettability, interconnected macropore structure, and high broadband light absorption (ca. 95.50%), the prepared CSL-C@MXene-20 mg evaporator exhibited a high and stable water evaporation flux of 2.351 kg m-2 h-1 with an energy conversion efficiency of 88.22% under 1 Sun (1 kW m-2) illumination. The CSL-C@MXene-20 mg evaporator performed excellent salt tolerance and long-term solar vapor generation in a 3.5 wt.% NaCl solution. Also, its super-hydrophilicity and oleophobicity resulted in superior salt resistance and anti-fouling performance in high salinity brine (20 wt.% NaCl) and oily wastewater. This work offers new insight into the manufacture of porous and eco-friendly biomass-based photothermal aerogels for advanced solar-powered seawater desalination and wastewater purification.

Harnessing Synchronous Photothermal and Photocatalytic Effects of Substoichiometric MoO3-x Nanoparticle-Decorated Membranes for Clean Water Generation

Solar-driven interfacial evaporation provides a promising pathway for sustainable freshwater and energy generation. However, developing highly efficient photothermal and photocatalytic nanomaterials is challenging. Herein, substoichiometric molybdenum oxide (MoO3-x) nanoparticles are synthesized via step-by-step reduction treatment of l-cysteine under mild conditions for simultaneous photothermal conversion and photocatalytic reactions. The MoO3-x nanoparticles of low reduction degree are decorated on hydrophilic cotton cloth to prepare a MCML evaporator toward rapid water production, pollutant degradation, as well as electricity generation. The obtained MCML evaporator has a strong local light-to-heat effect, which can be attributed to excellent photothermal conversion via the local surface plasmon resonance effect in MoO3-x nanoparticles and the low heat loss of the evaporator. Meanwhile, the rich surface area of MoO3-x nanoparticles and the localized photothermal effect together effectively accelerate the photocatalytic degradation reaction of the antibiotic tetracycline. With the benefit of these advantages, the MCML evaporator attains a superior evaporation rate of 4.14 kg m-2 h-1, admirable conversion efficiency of 90.7%, and adequate degradation efficiency of 96.2% under 1 sun irradiation. Furthermore, after being rationally assembled with a thermoelectric module, the hybrid device can be employed to generate 1.0 W m-2 of electric power density. This work presents an effective complementary strategy for freshwater production and sewage treatment as well as electricity generation in remote and off-grid regions.

Antibacterial Nanocellulose-TiO2/Polyester Fabric for the Recyclable Photocatalytic Degradation of Dyes

In this paper, we report an antibacterial, recyclable nanocellulose-titanium dioxide/polyester nonwoven fabric (NC-TiO2/PET) composite for the highly efficient photocatalytic degradation of dyes. The NC-TiO2 was loaded onto the surface of flexible PET nonwoven fabric through a simple swelling and dipping method. The NC-TiO2 in the particle size range of ~10 nm were uniformly attached to the surface of the PET fibers. The NC-TiO2/PET composite has the ability to achieve the stable photocatalytic degradation of dyes and presents antibacterial properties. The degradation rates to methylene blue (MB) and acid red (AR) of the NC-TiO2/PET composite reached 90.02% and 91.14%, respectively, and the inhibition rate of Escherichia coli was >95%. After several rounds of cyclic testing, the photocatalytic performance, antibacterial performance, and mechanical stability of the NC-TiO2/PET composite remained robust.

Bifunctional Solar Evaporator with Co/N-Doped Graphene Oxide for Synergistic Steam Generation and Organic Pollutant Degradation

Solar-driven interfacial steam generation (SISG) is a promising technology for alleviating freshwater shortage. However, when the SISG technology is applied to wastewater treatment, the contaminant would be enriched in residual bulk water. Herein, a dual-functional evaporator was constructed via tactfully decorating Co/N-doped graphene oxide (GO) on melamine foam (MF), which can simultaneously achieve efficient vapor production and source water purification. N-doped carbon nanotubes (NCNTs) endowed evaporators with powerful light absorption and water transport performance, guaranteeing an evaporation rate of 2.02 kg m-2 h-1 under 1 sun irradiation. Meanwhile, the catalytic activity of the carbon layer was adjusted by the N dopant and embedded Co particles, providing abundant active sites to activate peroxymonosulfate (PMS). When treating the solution containing sulfamethoxazole (SMX), no SMX residues were detected in the remaining bulk water (up to 100% SMX degradation efficiency within 60 min), demonstrating that reactive oxygen species (ROS) were generated to attack SMX in the source water. The bifunctional evaporator successfully combined SISG and advanced oxidation processes (AOPs), providing an ingenious strategy for solving the problem of wastewater enrichment during SISG.

Achieving fast interfacial solar vapor generation and aqueous acid purification using Ti3C2Tx MXene/PANI non-woven fabrics

Acid rain is a worldwide problem because of the emission of acidic gases into the atmosphere, leading to the acidification of first-order streams and aggravation of fresh water shortage. Therefore, it is of great importance to develop an environmentally friendly method for removing acid from water. Herein, an advanced technology that can achieve aqueous acid purification using solar energy is realized with Ti₃C₂T_x MXene/polyaniline (PANI) hybrid non-woven fabrics (MPs) through interfacial solar vapor generation, with PANI acting as an acid absorber through the doping process. Benefiting from the porous structure and crumpled micro-surface of MPs, a high evaporation rate of 2.65 kg m^-2 h^-1 with an efficiency of 93.7% can be achieved under one-sun illumination. Moreover, MPs present an even higher evaporation rate of 2.83 kg m^-2 h^-1 in high concentration aqueous acid and can generate clean water with a pH higher than 6.5. More importantly, thanks to the unique reversible doping process of PANI, when used as an aqueous acid purifier, MPs show good stability and reusability after dedoping. Our work sheds light on an efficient strategy for dealing with aqueous acid and acid rain.

Reduced graphene oxide/carbon nitride composite sponge for interfacial solar water evaporation and wastewater treatment

Interfacial solar-driven steam generation has been proposed as a cost-effective green sustainable technology to alleviate the freshwater crisis. However, the desire to produce clean water from water sources containing organic contaminants is still remains a challenge due to the limitations of the traditional wastewater treatment methods. Here, we constructed a g-C3N4-based composite sponge solar steam generator (rGCPP) by a simple hydrothermal reaction. Benefiting from its low cost and easy preparation, this evaporator can be expected to be a promising candidate for the alleviation of water shortages and water pollution in practical applications. By combination of the solar steam generation and the photocatalysis into the rGCPP-based interfacial solar-driven steam generation system, the resulted rGCPP-based solar steam generator performs outstanding solar absorption of 90.8%, which achieves high evaporation rate of 1.875 kg m-2 h-1 and solar-to-vapor efficiency of 81.07% under 1 sun irradiation. Meanwhile, organic pollutants in the water source can be completely removed by photocatalytic degradation and the degradation rates were measured to be 99.20% for methylene blue and 91.07% for rhodamine B, respectively. Consequently, the as-prepared composite sponge has promising applications in generating clean water and alleviating water pollution.

Nanocomposite-Enhanced Efficient Evaporation System for Solar-Driven Seawater Desalination-An Optimized Design for Clean Water Production

Solar-driven evaporation is a promising technology for desalinating seawater and wastewater without mechanical or electrical energy. The approaches to obtaining fresh water with higher evaporation efficiency are essential to address the water-scarcity issue in remote sensing areas. Herein, we report a highly efficient solar evaporator derived from the nanocomposite of anatase TiO₂/activated carbon (TiO₂/AC), which was coated on washable cotton fabric using the dip-dry technique for solar water evaporation. The ultra-black fabric offers enhanced solar absorption (93.03%), hydrophilic water transport, and an efficient evaporation rate of 1.65 kg/m²h under 1 kW m^-2 or one sun solar intensity. More importantly, the sideways water channels and centralized thermal insulation of the designed TiO₂/AC solar evaporator accumulated photothermal heat at the liquid and air interface along with an enhanced surface temperature of 40.98 °C under one sun. The fabricated solar evaporator desalinated seawater (3.5 wt%) without affecting the evaporation rates, and the collected condensed water met the standard of drinking water set by the World Health Organization (WHO). This approach eventually enabled the engineering design groups to develop the technology pathways as well as optimum conditions for low-cost, scalable, efficient, and sustainable solar-driven steam generators to cope with global water scarcity.

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.

A Composite Fabric with Dual Functions for High-Performance Water Purification

The dilemma of diminishing freshwater resources caused by water pollution has always impacted human life. Solar-driven interfacial evaporation technology has the potential for freshwater production via solar-driven distillation. However, in solar-driven interfacial evaporation technology, it is difficult to overcome the problem of wastewater containing various contaminants. In this work, we propose a bifunctional fabric created by depositing titanium dioxide@carbon black nanoparticles onto cotton fabric (TiO₂@CB/CF). The TiO₂@CB/CF has a coupling effect that includes the photothermal effect of CB and photocatalysis of TiO₂, and it can not only generate clean water but can also purify contaminated water. The resulting bifunctional fabric can achieve an outstanding water evaporation rate of 1.42 kg m^-2 h^-1 and a conversion efficiency of 90.4% in methylene blue (MB) solution under one-sun irradiation. Simultaneously, the TiO₂@CB/CF demonstrates a high photocatalytic degradation of 57% for MB solution after 2 h with light irradiation. It still shows a good photocatalysis effect, even when reused in an MB solution for eight cycles. Furthermore, the TiO₂@CB/CF delivers excellent performance for actual industrial textile dyeing wastewater. This bifunctional fabric has a good application prospect and will provide a novel way to resolve the issue of freshwater scarcity.