Light-activated polydopamine coatings for efficient metal recovery from electronic waste

Polydopamine-functionalized capsules: From design to applications

In recent years, polydopamine (PDA)-functionalized capsules have garnered significant interest from researchers in the field of materials, owing to its remarkable properties of adhesion, biocompatibility, photothermal conversion capabilities, chemical reactivity, and so on. At present, numerous studies have reported various structures and morphologies of PDA-functionalized capsules fabricated via diverse strategies, that have found applications across a broad spectrum of disciplines. However, there are few comprehensive and systematic reviews focusing on various preparation strategies of PDA-functionalized capsules with various structures. This paper systematically reviewed the preparation strategies and related applications of PDA-functionalized capsules. These strategies of PDA-functionalized capsules were discussed in detail from four parts including PDA-functionalized capsules based on hollow PDA, mesoporous PDA (MPDA), directly encapsulating emulsion, and surface modification of capsules. Then the review outlined the applications of PDA-functionalized capsules in biomedicine, energy, textiles, and the environment. Furthermore, this review summarized the current research findings on PDA-functionalized capsules and outlines their future development directions. Overall, we aim for this review to inspire researchers and offer valuable guidance for the synthesis and application of advanced PDA-functionalized capsules.

Microscale Metal Patterning on Any Substrate: Exploring the Potential of Poly(dopamine) Films in High Resolution, High Contrast, Conformal Lithography

We have explored the potential of poly(dopamine) (PDA) thin films as versatile, high resolution conformal photoresists, using catalytic photoreduction of silver ions to micropattern the film. The combination of photosensitivity, biocompatibilty, and straightforward deposition under mild conditions into thin (∼45 nm) conformal coatings on nearly any material makes PDA films of interest in lithographic patterning on highly nonplanar geometries as well as on soft and biological materials where standard photoresists cannot be used. PDA and poly(norepinephrine) (PNE) films deposited with a standard autoxidation process were investigated along with PDA film deposited with a fast oxidation (FO) technique. Notably, we find that nonspecific deposition of silver off the lithographic pattern is strongly suppressed in PNE and nearly absent in FO-PDA films, which makes very high contrast lithography possible. We attribute this to a lower ratio of catechol to quinone moieties in these films compared to standard PDA films. PNE and FO-PDA films also exhibit smaller silver grain sizes (<40 nm) than standard PDA films, where grains are up to 200 nm in size. We demonstrate laser-scanning lithography patterns at 1.7 μm spatial resolution near the optical resolution limit of the experiment. Continuous silver films can readily be deposited on PDA, PNE, and FO-PDA with blue (λ = 473 nm) and UV-A (375 nm) light, but not with green (515 nm) light. The UV light at lower intensities deposits silver several times faster than the blue light but also degrades the deposited silver at high light intensities. Silver films deposited in this way reach the percolation threshold at optical doses (at λ = 473 nm) in the range of 10-50 kJ/cm2, and SEM images of the films appear nearly pinhole free at comparable doses.

High-Yield Gold Nanohydrangeas on Three-Dimensional Carbon Nanotube Foams for Surface-Enhanced Raman Scattering Sensors

Recently, carbon nanomaterial-supported plasmonic nanocrystals used as high-performance surface-enhanced Raman scattering (SERS) substrates have attracted increasing attention due to their ultra-high sensitivity of detection. However, most of the work focuses on the design of 2-D planar substrates with traditional plasmonic structures, such as nanoparticles, nanorods, nanowires, and so forth. Here, we report a novel strategy for the preparation of high-yield Au nanohydrangeas on three-dimensional porous polydopamine (PDA)/polyvinyl alcohol (PVA)/carbon nanotube (CNT) foams. The structures and growth mechanisms of these specific Au nanocrystals are systematically investigated. PDA plays the role of both a reducing agent as well as an anchoring site for Au nanohydrangeas' growth. We also show that the ratio of surfactant KBr to the gold precursor (HAuCl4) is key to obtain these structures in a manner of high production. Moreover, the substrate of the CNT foam-Au nanohydrangea hybrid can be employed as SERS sensors and can detect the analytes down to 10-9 M.

Dual photothermal nanocomposites for drug-resistant infectious wound management

Management of antibiotic-resistant bacteria-induced skin infections for rapid healing remains a critical clinical challenge. Photothermal therapy, which uses mediated hyperthermia to combat such problems, has recently been recognised as a promising approach to take. In this study, bacterial cellulose-based photothermal membranes were designed and developed to combat bacterial infections and promote rapid wound healing. Polydopamine was incorporated into gold nanoparticles to produce superior dual-photothermal behaviour. The in vitro antibacterial efficacy of the prepared composite membranes against S. aureus, E. coli and methicillin-resistant Staphylococcus aureus (MRSA) could reach 99% under near-infrared (NIR) irradiation. In addition, the synthesised nanocomposite exhibited good biocompatibility in vitro as demonstrated by a cell survival ratio of >85%. The effectiveness of the composite membranes on wound healing was further investigated in a murine model of MRSA-infected wounds, focusing on the effect of photothermal temperature. According to the detailed therapeutic mechanism study undertaken, the composite membranes cause bacterial killing initially and promote the transition from the inflammatory phase to proliferation by suppressing pro-inflammatory cytokine production, promoting collagen deposition, and stimulating angiogenesis. Considering their remarkable effectiveness and facile fabrication process, it is expected that these novel materials could serve as competitive multifunctional dressings in the management of infectious wounds and accelerate the regeneration of damaged tissues related to abnormal immune responses.

Preparation and catalytic properties of polydopamine-modified polyacrylonitrile fibers functionalized with silver nanoparticles

Fiber-supported catalysts have attracted much attention due to their large specific surface area, high catalytic activity, and good recyclability. Functional polyacrylonitrile fibers were prepared by immersion of polyacrylonitrile fibers at room temperature in an alkaline dopamine (pH = 8.5) aqueous solution which can undergo self-polymerization and reduce silver ions to silver nanoparticles with mild reducibility and adsorption. The surface of the polyacrylonitrile fiber (PAN) was wrapped with a layer of polydopamine (PDA), and silver nanoparticles (Ag NPs) were adsorbed on the surface of PDA, forming an efficient fiber catalyst. The morphology and chemical composition of the catalyst material were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) patterns, and Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The catalytic activity of the nanocomposite was evaluated for the reduction reaction of 4-nitrophenol using sodium borohydride (NaBH₄) at 35 °C with a material molar ratio of 1 : 10 and a fiber loaded catalysis dosage of 40 mg. The liquid phase yield can reach 98% in 30 minutes and can be reused after washing with ethanol. Moreover, the composite material exhibited a good stability up to 10 cycles without a significant loss of its catalytic activity. The results show that the catalyst is easy to recover from the reaction system and has maintained good stability and catalytic activity after many cycles.

Via the help of polydopamine, polyacrylonitrile fiber catalysts functionalized with silver nanoparticles were prepared and employed for the reduction reaction of 4-nitrophenol to 4-aminophenol, with a yield of 98% in 30 minutes, and can be reused for up to 10 cycles.