Silver Nanoparticle-Enabled Photothermal Nanofibrous Membrane for Light-Driven Membrane Distillation

Accessible Tetrathiafulvalene Moieties in a 3D Covalent Organic Framework for Enhanced Near-Infrared Photo-Thermal Conversion and Photo-Electrical Response

Redox-active tetrathiafulvalene (TTF)-based covalent organic frameworks (COFs) exhibit distinctive electrochemical and photoelectrical properties, but their prevalent two-dimensional (2D) structure with densely packed TTF moieties limits the accessibility of redox center and constrains their potential applications. To overcome this challenge, an 8-connected TTF linker (TTF-8CHO) is designed as a new building block for the construction of three-dimensional (3D) COFs. This approach led to the successful synthesis of a 3D COF with the bcu topology, designated as TTF-8CHO-COF. In comparison to its 2D counterpart employing a 4-connected TTF linker, the 3D COF design enhances access to redox sites, facilitating controlled oxidation by I2 or Au3+ to tune physical properties. When irradiated with a 0.7 W cm-2 808 nm laser, the oxidized 3D COF samples (I X - ${\mathrm{I}}_{\mathrm{X}}^{-}$ @TTF-8CHO-COF and Au NPs@TTF-8CHO-COF) demonstrated rapid temperature increases of 239.3 and 146.1 °C, respectively, which surpassed those of pristine 3D COF (65.6 °C) and the 2D COF counterpart (6.4 °C increment after I2 treatment). Furthermore, the oxidation of the 3D COF heightened its photoelectrical responsiveness under 808 nm laser irradiation. This augmentation in photothermal and photoelectrical response can be attributed to the higher concentration of TTF·+ radicals generated through the oxidation of well-exposed TTF moieties.

A practical green synthesis method of Ag NPs using rosy periwinkle plant leaves for solar panel coating

Coated silver nanoparticles (Ag NPs) are currently receiving interest because of their numerous uses in various fields of electronics, antimicrobials, manufacturing sectors, optical science, and pharmaceuticals. Among others, it gained significant attention in the power electronic system. The goal of the proposed study is to use a cost-effective coating material for solar panels; to accomplish this, silver nanoparticles were synthesized from the leaves of the Rosy Periwinkle plants. Green synthesis and characterization, such as Ultraviolet Visible Spectrometer (UV-Vis) analysis, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and Fourier Transform Infrared Spectroscopy (FTIR), were carried out after the silver nanoparticles have been collected prior coating. As a consequence, the effectiveness is determined based on the conductivity test, and the resulting Ag NPs are then applied to the c-si layer of the solar panel. Additionally, a modelling and experimental analysis are performed in this study to ascertain the suggested framework's ability to measure energy before and after coating panels with Ag NPs. Specifically, the Voltage Current (VI) and Power Voltage (PV) characteristics were validated in this study for analyzing the effectiveness and the obtained results revealed that the coating of green synthesized Ag NPs generated 2 % more power than the reference solar panel under the same conditions. Further, hardware testing and simulation were both used to confirm the outcomes and effectiveness of the suggested method. The open circuit voltage (Voc), short circuit current (Isc), maximum peak voltage (Vmp), maximum peak current (Imp), and efficiency are taken into account when assessing how well the suggested system performs at tracking. Moreover, the current density characteristics were evaluated with respect to various irradiation conditions for both the typical solar as well as Ag NPs coated panels. From the observation, it is noted that the efficiency level of coated panel was improved up to 19.20 %, 18 %, and 17.20 % for the irradiations of 200 W/m2, 500 W/m2, and 1000 W/m2 respectively.

Electrospun Nanofiber Materials for Photothermal Interfacial Evaporation

Photothermal interfacial evaporation with low cost and environmental friendliness has attracted much attention. However, there are still many problems with this technology, such as heat loss and salt accumulation. Due to their different structures and adjustable chemical composition, electrospun nanofiber materials generally exhibit some unique properties that provide new approaches to address the aforementioned issues. In this review, the rational design principles for improving the total efficiency of solar evaporation are described for thermal/water management systems and salt-resistance strategies. And we review the state-of-the-art advancements in photothermal evaporation based on nanofiber materials and discuss their derivative applications in desalination, water purification, and power generation. Finally, we highlight key challenges and opportunities in both fundamental research and practical applications to inform further developments in the field of interfacial evaporation.

Photothermal Surface Heating Membrane Distillation Using 3D-Printed Ti3C2Tx MXene-Based Nanocomposite Spacers

To address the growing global need for freshwater, it has become essential to use nonpotable saline water. Solar membrane distillation is a potential desalination method that does not need conventional electricity and may cut water production costs. In this study, we develop a photothermal surface heating membrane distillation using a new class of photothermal spacers constructed with Ti₃C₂T_x MXene-based nanocomposites. In contrast to traditional membrane distillation, which utilizes energy-intensive bulk feed heating, solar-powered surface heating membrane distillation removes the external thermal energy input requirements, hence reducing operating costs significantly. In particular, three-dimensional (3D)-printing technology was used to fabricate the functional spacer, which allowed the design and materials to be fine-tuned per the needs of the process. Under solar illumination, the printed spacer can exhibit a localized photothermal conversion-driven heating effect near the surface of distillation membranes, which generates vapor pressure strong enough to operate distillation across membranes. Importantly, a two-dimensional Ti₃C₂T_x MXene with outstanding photothermal conversion efficiency and stability in hypersaline ionic solutions was incorporated into the 3D-printed spacers as the crucial nanofiller for imparting a local heating effect of feed. The fabricated nanocomposite spacers showed superior photothermal heating response under sunlight with an average permeate flux and energy conversion efficiency of 0.49 kg·m^-2·h^-1 and 30.6%, respectively. An enhancement in both photothermal efficiency and permeate flux was noticed as the amount of MXene nanosheets increased in the 3D-printed spacers. This study demonstrates the feasibility of using 3D-printed photothermal spacers for high-performance and sustainable surface heating membrane distillation, providing a promising avenue for further improvement with other photothermal nanofillers or spacer modifications.

Engineered multi-scale roughness of carbon nanofiller-embedded 3D printed spacers for membrane distillation

Membrane distillation (MD) transfers heat and mass simultaneously through a hydrophobic membrane. Hence, it is sensitive to both concentration and temperature polarisation (CP and TP) effects. In this study, we fabricated feed spacers to improve MD efficiency by alleviating the polarisation effects. First, a 3D printed spacer design was optimised to show superior performance amongst the others tested. Then, to further enhance spacer performance, we incorporated highly thermally stable carbon nanofillers, including carbon nanotubes (CNT) and graphene, in the fabrication of filaments for 3D printing. All the fabricated spacers had a degree of engineered multi-scale roughness, which was relatively high compared to that of the polylactic acid (PLA) spacer (control). The use of nanomaterial-incorporated spacers increased the mean permeate flux significantly compared to the PLA spacer (27.1 L/m²h (LMH)): a 43% and 75% increase when using the 1% graphene-incorporated spacer (38.9 LMH) and 2% CNT incorporated spacer (47.5 LMH), respectively. This could be attributed to the locally enhanced turbulence owing to the multi-scale roughness formed on the spacer, which further increased the vaporisation rate through the membrane. Interestingly, only the CNT-embedded spacer markedly reduced the ion permeation through the membrane, which may be due to the effective reduction of CP. This further decreased with increasing CNT concentration, confirming that the CNT spacer can simultaneously reduce the CP and TP effects in the MD process. Finally, we successfully proved that the multi-scale roughness of the spacer surface induces micromixing near the membrane walls, which can improve the MD performance via computational fluid dynamics.

Plasmonic Phenomena in Membrane Distillation

Water scarcity raises important concerns with respect to human sustainability and the preservation of important ecosystem functions. To satisfy water requirements, seawater desalination represents one of the most sustainable solutions. In recent decades, membrane distillation has emerged as a promising thermal desalination process that may help to overcome the drawbacks of traditional desalination processes. Nevertheless, in membrane distillation, the temperature at the feed membrane interface is significantly lower than that of the bulk feed water, due to the latent heat flux associated with water evaporation. This phenomenon, known as temperature polarization, in membrane distillation is a crucial issue that could be responsible for a decay of about 50% in the initial transmembrane water flux. The use of plasmonic nanostructures, acting as thermal hotspots in the conventional membranes, may improve the performance of membrane distillation units by reducing or eliminating the temperature polarization problem. Furthermore, an efficient conversion of light into heat offers new opportunities for the use of solar energy in membrane distillation. This work summarizes recent developments in the field of plasmonic-enhanced solar evaporation with a particular focus on solar-driven membrane distillation applications and its potential prospects.

Purifying water with silver nanoparticles (AgNPs)-incorporated membranes: Recent advancements and critical challenges

In the face of the growing global water crisis, membrane technology is a promising means of purifying water and wastewater. Silver nanoparticles (AgNPs) have been widely used to improve membrane performance, for antibiofouling, and to aid in photocatalytic degradation, thermal response, and electro-conductivity. However, several critical issues such as short antimicrobial periods, trade-off effects and silver inactivation seriously restrict the engineering application of AgNPs-incorporated membranes. In addition, there is controversy around the use of AgNPs given the toxic preparation process and environmental/biological risks. Hence, it is of great significance to summarize and analyze the recent developments and critical challenges in the use of AgNPs-incorporated membranes in water and wastewater treatment, and to propose potential solutions. We reviewed the different properties and functions of AgNPs and their corresponding applications in AgNPs-incorporated membranes. Recently, multifunctional, novel AgNP-incorporated membranes combined with other functional materials have been developed with high-performance. We further clarified the synergistic mechanisms between AgNPs and these novel nanomaterials and/or polymers, and elucidated their functions and roles in membrane separation. Finally, the critical challenges of AgNPs-incorporated membranes and the proposed solutions were outlined: i) Prolonging the antimicrobial cycle through long-term and controlled AgNPs release; ii) Overcoming the trade-off effect and organic fouling of the AgNPs-incorporated membranes; iii) Preparation of sustainable AgNPs-incorporated membranes; iv) Addressing biotoxicity induced by AgNPs; and v) Deactivation of AgNPs-incorporated membrane. Overall, this review provides a comprehensive discussion of the advancements and challenges of AgNPs-incorporated membranes and guides the development of more robust, multi-functional and sustainable AgNPs-incorporated membranes.

NiSe and CoSe Topological Nodal-Line Semimetals: A Sustainable Platform for Efficient Thermoplasmonics and Solar-Driven Photothermal Membrane Distillation

The control of heat at the nanoscale via the excitation of localized surface plasmons in nanoparticles (NPs) irradiated with light holds great potential in several fields (cancer therapy, catalysis, desalination). To date, most thermoplasmonic applications are based on Ag and Au NPs, whose cost of raw materials inevitably limits the scalability for industrial applications requiring large amounts of photothermal NPs, as in the case of desalination plants. On the other hand, alternative nanomaterials proposed so far exhibit severe restrictions associated with the insufficient photothermal efficacy in the visible, the poor chemical stability, and the challenging scalability. Here, it is demonstrated the outstanding potential of NiSe and CoSe topological nodal-line semimetals for thermoplasmonics. The anisotropic dielectric properties of NiSe and CoSe activate additional plasmonic resonances. Specifically, NiSe and CoSe NPs support multiple localized surface plasmons in the optical range, resulting in a broadband matching with sunlight radiation spectrum. Finally, it is validated the proposed NiSe and CoSe-based thermoplasmonic platform by implementing solar-driven membrane distillation by adopting NiSe and CoSe nanofillers embedded in a polymeric membrane for seawater desalination. Remarkably, replacing Ag with NiSe and CoSe for solar membrane distillation increases the transmembrane flux by 330% and 690%, respectively. Correspondingly, costs of raw materials are also reduced by 24 and 11 times, respectively. The results pave the way for the advent of NiSe and CoSe for efficient and sustainable thermoplasmonics and related applications exploiting sunlight within the paradigm of the circular blue economy.

MXene-Coated Membranes for Autonomous Solar-Driven Desalination

Clean water supply in off-grid locations remains a stumbling stone for socio-economic development in remote areas where solar energy is abundant. In this regard, several technologies have already introduced various solutions to the off-grid freshwater predicament; however, most of them are either costly or complex to operate. Nonetheless, photothermal membrane distillation (PMD) has emerged as a promising candidate with great potential to be autonomously driven by solar energy. Instead of using energy-intensive bulk feed heating in conventional MD systems, PMD membranes can directly harvest the incident solar light at the membrane interface as an alternative driving energy resource for the desalination process. Because of its excellent photothermal properties and stability in ionic environments, herein, Ti₃C₂T_x MXene was coated onto commercial polytetrafluoroethylene (PTFE) membranes to allow for a self-heated PMD process. An average water vapor flux of 0.77 kg/m² h with an excellent temporal response under intermitting lighting and a photothermal efficiency of 65.3% were achieved by the PMD membrane under one-sun irradiation for a feed salinity of 0.36 g/L. Naturally, the efficiency of the process decreased with higher feed concentrations due to the reduction of the evaporation rate and the scattering of incident sunlight toward the membrane photothermal surface, especially at rates above 10 g/L. Notably, with such performance, 1 m² of the MXene-coated PMD membrane can fulfill the recommended daily potable water intake for a household, that is, ca. 6 L/day.

Anisotropic Silver Nanomaterials by Photochemical Reactions: Synthesis and Applications

Silver-based nanoparticles have attracted a broad interest due to their outstanding optical and chemical properties and have been studied for applications in many fields. While different synthetic routes have been explored, photochemical synthesis has attracted a special interest for its limited use of chemicals and ease of control over the shape and size of the nanoparticles. This paper reviews the main factors affecting the synthesis of anisotropic silver nanoparticles, such as irradiation wavelength, pH, etc., and the role of specific key molecules, such as citrate. The paper is structured into different sections depending on how the synthesis is initiated; thus, after the introduction, the photochemical conversion reaction starting from nanoparticles, or seeds, obtained chemically, is covered, followed by reactions from nanoparticles obtained by laser ablation by seedless reactions. After that, the applications proposed for anisotropic nanoparticles obtained by the methods discussed in the previous sections are briefly covered and, finally, the conclusions and the author’s perspectives are given.

Solar-Powered Sustainable Water Production: State-of-the-Art Technologies for Sunlight-Energy-Water Nexus

Alternative water resources (seawater, brackish water, atmospheric water, sewage, etc.) can be converted into clean freshwater via high-efficiency, energy-saving, and cost-effective methods to cope with the global water crisis. Herein, we provide a comprehensive and systematic overview of various solar-powered technologies for alternative water utilization (i.e., "sunlight-energy-water nexus"), including solar-thermal interface desalination (STID), solar-thermal membrane desalination (STMD), solar-driven electrochemical desalination (SED), and solar-thermal atmospheric water harvesting (ST-AWH). Three strategies have been proposed for improving the evaporation rate of STID systems above the theoretical limit and designing all-weather or all-day operating STID systems by analyzing the energy transfer of the evaporation and condensation processes caused by solar-thermal conversion. This review also introduces the fundamental principles and current research hotspots of two other solar-driven seawater or brackish water desalination technologies (STMD and SED) in detail. In addition, we also cover ST-AWH and other solar-powered technologies in terms of technology design, materials evolution, device assembly, etc. Finally, we summarize the content of this comprehensive review and discuss the challenges and future outlook of different types of solar-powered alternative water utilization technologies.

Progress of photothermal membrane distillation for decentralized desalination: A review

The conventional membrane distillation (MD) process is accompanied by large energy consumption, low thermal efficiency and inevitable requirements of centralized infrastructures, which impede its practical applications, especially in the offshore and remote off-grid areas. Thanks to the rapid development of efficient photothermal materials over the last decade, a new photothermal membrane distillation (PMD) process has emerged to harness abundant solar energy and localize heating on the membrane-feed water interface via photothermal effects. Driven by the temperature difference across the PMD membrane, water vapor can be generated on the membrane-feed surface, transported through membrane pores and condensed at permeate side to obtain freshwater, thus tackling the challenge of obtaining clean water using green energy. The PMD process avoids heating the entire bulk feed water and feed transportation from heat units to membrane modules, which save substantial amounts of energy. The interfacial localized heating intrinsically mitigates the temperature polarization across the membrane. The latent heat from vapor condensation can be effectively recovered via multi-level PMD configurations. As great efforts have been made to exploit PMD process, it is imperative to review the state-of-the-art progress of PMD and shed light on its future trend. Here, we briefly illustrate PMD mechanisms and membrane requirements, photothermal materials feasible for developing PMD membranes along with their light-to-heat mechanisms. This is followed by reviewing diverse approaches to prepare PMD membranes, which are classified into one-step fabrication and multi-step modification methods. Comprehensive discussion about PMD membrane performance in different configurations and their small pilot-scaled applications are provided. The effects of operational parameters and module designs are discussed in Section 6. Finally, the current challenges and future perspectives of PMD process are emphasized with the aim of providing guidance for future works.

Photothermal Membrane Distillation toward Solar Water Production

Freshwater production is one of the biggest global challenges today. Though desalination can provide a climate-independent source of clean water, the process requires a high energy consumption. Emerging advancement of photothermal nanomaterials and the urgent demand for a green technology transition have reinvigorated the established solar distillation technology. The current development of photothermal vaporization focuses on material innovation and interfacial heating, which largely emphasizes vapor generation efficiency, without considering pragmatic water collection. Moreover, salt accumulation is another critical issue of seawater solar-driven vaporization. The incorporation of photothermal materials into a photothermal membrane distillation (PMD) solar evaporator design harmoniously resolves these issues through combination of renewable energy and efficient interfacial distillation, to achieve the ultimate goal of practical saline water into freshwater conversion. At this juncture, it is imperative to review the recent opportunities and progresses of the PMD system. Here, the fundamental photothermal processes, strategies for efficient evaporator design, evaluation of various criteria for photothermal material incorporation with desired properties, discussions on desalination, water treatment, and energy generation applications are covered. Guidelines in material and system designs to further advance the PMD system that is highly promising in delivering portable water for both large-scale and decentralized systems are provided.

Comb-like structural modification stabilizes polyvinylidene fluoride membranes to realize thermal-regulated sustainable transportation efficiency

Hydrophobic micro-porous membrane such as polyvinylidene fluoride (PVDF) with excellent thermal-/chemical-stability and low surface energy has received extensive attention in industrial water treatment and sustainable energy conversion. However, undesirable contaminants caused by inevitable proteins or microorganisms adhesion may lead to a rapid loss of separation efficiency, which significantly deteriorate their porous structures and eventually limit their practical performance. Herein, we present a scalable approach for fabricating comb-like copolymer modified PVDF membranes (PVDF-PN@AgNPs) that prevent bacteria from proliferating on the surface and temperature-controlled release of adhered contaminants. Comb-like structured copolymers were imparted to a polydopamine (PDA)-treated PVDF membrane by Michael addition reaction, which enabled a covalent binding of comb-like structured copolymers to the membrane. Such unique structural design of grafted copolymer, containing hydrophilic side chain and temperature-responsive chain backbone, stably prevents bacteria adhesion and provides reversible surface wettability. Therefore, the resultant membranes were evaluated to prevent bacterial adhesion, high touch-killing efficiency and temperature-controlled contaminants release (~99% of protein and ~75% of bacteria). Moreover, with the collapse and stretch of grafted copolymer chain backbone, the synthetic membrane further reversibly adjusted inner micro-porous structure and surface wettability, which eventually helped to achieve variable water fluid transport efficiency. This study not only provides a feasible structural design for stably coping with the challenging of antifouling and subsequent contamination adhesion of PVDF membrane, but also potentially answers the significant gap between lab research advances and practical application, particularly in the industrial membrane field.

Dead-end membrane distillation with localized interfacial heating for sustainable and energy-efficient desalination

Membrane distillation (MD) has the high potential to circumvent conventional desalination limitations in treating highly saline brines. However, the performance of MD is limited by its low thermal efficiencyand temperature polarization (TP) effect. Consequently, the driving force decreases when heat loss increases.In this study, we propose to minimize TP through localized heating where the thin feed channel was heated uniformly at the membrane-liquid interface without changing the properties of the membrane.This concept was further improved by implementing a new dead-end MD configuration. Investigated for the first time,this configuration eliminated circulation heat losses, which cannot be realized in conventional MD due to a rapid temperature stratification. In addition, the accumulation of foulants on the membrane surface was successfully controlled by intermittent flushing. 3-Dimensional conjugate heat transfer modeling revealedmore uniform heat transfer and temperature gradient across the membrane due to the increased feed water temperature over a larger membrane area. The increase of water vapor flux (45%) and the reduction of heat lossobserved in the new dead-end concept led to a decrease of the specific energy consumption by 57%, corresponding to a gain output ratio increase of about 132 %, compared to a conventional bulk heating, while preserving membrane integrity. A conjugate heat transfer model was deployed in ANSYS-Fluent framework to elucidate on the mechanism of flux enhancement associated with the proposed technique. This study provides a framework for future sustainable MD developmentby maintaining a stable vapor flux while minimizing energy consumption.

Plasmonic Titanium Nitride Nano-enabled Membranes with High Structural Stability for Efficient Photothermal Desalination

Herein, we demonstrate the desalination performance of a solar-driven membrane distillation (MD) process, where upon light illumination, a highly localized heating of plasmonic titanium nitride nanoparticles (TiN NPs) immobilized on a hydrophobic membrane provides the thermal driving force for the MD operation. The engineered TiN photothermal membrane induces vapor generation directly at the feed-membrane interface upon solar irradiation, thereby eliminating the need to heat the entire bulk feed water. The results indicate that the average vapor flux through the TiN photothermal membrane without any auxiliary feed heating was recorded as 1.01 L m^-2 h^-1, which corresponds to the solar-thermal efficiency of 66.7% under 1 sun solar irradiance. The superior performance of the photothermal MD process is attributed to the broadband optical absorption and excellent light-to-heat conversion properties of the plasmonic TiN NP layer, which enabled efficient interfacial water heating at the membrane surface and increased the net driving force for vapor transport. Results also reveal the high mechanical stability of the TiN photothermal coating layer during long-term photothermal MD operations. We believe that the TiN photothermal membranes fabricated using a relatively inexpensive and nontoxic material via the simple technique with high stability and photothermal conversion efficiency will provide a path forward for developing the solar-driven MD applications.

Cellular Structured CNTs@SiO2 Nanofibrous Aerogels with Vertically Aligned Vessels for Salt-Resistant Solar Desalination

The emerging solar desalination technology is considered as one of the most promising strategies to ensure water security. However, with the proceeding of solar desalination, salt crystallization on the surface of solar evaporators caused by increasing salinity of seawater will result in a decrease in the evaporation rate. Thus, it is still challenging to fabricate solar evaporators with superior salt resistance. In this work, elastic ceramic-based nanofibrous aerogels with a cellular architecture are fabricated by the combination of electrospinning and fiber freeze-shaping technologies, which are composed of vertically aligned vessels and porous vessel walls. Under the action of convection and diffusion promoted by this unique cellular architecture, the aerogels exhibit a superior salt-resistance without any salt crystals on the surface of aerogels even in 20% brine and under 6-sun irradiation. Moreover, by virtue of the synergistic effect of the promising structure and light absorbance of carbon nanotubes, aerogels possess a high light absorbance of up to 98% and excellent evaporation performance achieving 1.50 kg m^-2 h^-1 under 1-sun irradiation. This work may provide a fascinating avenue for the desalination of seawater in a salt-resistance and efficient manner.

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance

Membrane distillation (MD) is a thermally induced membrane separation process that utilizes vapor pressure variance to permeate the more volatile constituent, typically water as vapor, across a hydrophobic membrane and rejects the less volatile components of the feed. Permeate flux decline, membrane fouling, and wetting are some serious challenges faced in MD operations. Thus, in recent years, various studies have been carried out on the modification of these MD membranes by incorporating nanomaterials to overcome these challenges and significantly improve the performance of these membranes. This review provides a comprehensive evaluation of the incorporation of new generation nanomaterials such as quantum dots, metalloids and metal oxide-based nanoparticles, metal organic frameworks (MOFs), and carbon-based nanomaterials in the MD membrane. The desired characteristics of the membrane for MD operations, such as a higher liquid entry pressure (LEPw), permeability, porosity, hydrophobicity, chemical stability, thermal conductivity, and mechanical strength, have been thoroughly discussed. Additionally, methodologies adopted for the incorporation of nanomaterials in these membranes, including surface grafting, plasma polymerization, interfacial polymerization, dip coating, and the efficacy of these modified membranes in various MD operations along with their applications are addressed. Further, the current challenges in modifying MD membranes using nanomaterials along with prominent future aspects have been systematically elaborated.

PPy nanoneedle based nanoplatform capable of overcoming biological barriers for synergistic chemo-photothermal therapy

The biological barriers in vivo have limited the site-specific bioavailability and impeded therapeutic efficacy. To tackle these issues, nonspherical particles with a shape effect have attracted wide attention to affect the in vivo translocation of a drug delivery system. Herein, we constructed a nanoplatform based on polypyrrole (PPy) nanoneedles by hyaluronic acid (HA) modification and doxorubicin (DOX) loading. The PPy-HA@DOX nanoneedles with high aspect ratios could enhance the extravasation through the fenestrated vasculature of tumors, transport across tumor cell membrane via an endocytosis mechanism or even penetrated the membrane directly, and ultimately enter the nucleus easily via the nuclear pore complex by passive diffusion. With the ability of overcoming biological barriers, the PPy nanoneedle based nanoplatform would deliver drugs into the organelles more effectively. Under near infrared (NIR) laser irradiation, PPy as the photothermal agent could lead to tumor cellular structure damage for photothermal therapy (PTT). Therefore, PPy-HA@DOX developed here would exploit the merits of synergistic combination of chemo-photothermal therapy, which would pave the way toward more effective nanotherapeutics.

Thiol-Affinity Immobilization of Casein-Coated Silver Nanoparticles on Polymeric Membranes for Biofouling Control

Silver nanoparticles (AgNPs) have been widely studied for the control of biofouling on polymeric membranes due to their antimicrobial properties. However, nanoparticle leaching has posed a significant impediment against their widespread use. In this study, a one-step method of chemically embedding AgNPs on cellulose acetate (CA) membranes via their affinity to thiol group chemistry was investigated. The operational efficiency of the membranes was then determined via filtration and biofouling experiments. During filtration study, the average flux values of pure CA membranes was determined to be 11 ± 2 L/(m2·hr) (LMH), while membranes embedded with AgNPs showed significant increases in flux to 18 ± 2 LMH and 25 ± 9 LMH, with increasing amounts of AgNPs added, which is likely due to the NPs acting as pore formers. Leaching studies, performed both in dead-end and crossflow filtration, showed approximately 0.16 mg/L leaching of AgNPs after the first day of filtration, but afterwards the remaining chemically-attached AgNPs did not leach. Over 97% of AgNPs remained on the membranes after seven days of crossflow leaching filtration studies. Serratia marcescens were then used as target microorganisms in biofouling studies. It was observed that membranes embedded with AgNPs effectively suppressed the growth of Serratia marcescens, and specifically, membranes with AgNPs displayed a decrease in microbial growth by 59% and 99% as the amount of AgNP increased.