Polydopamine Polymer Research Articles

Highly stable scalable production of porous graphene-polydopamine nanocomposites for drug molecule sensing

As atenolol overdosing can lead to severe health complications, the rapid detection of atenolol intake in point-of-care settings is highly desirable. The recent advancement of redox analytical methodologies has facilitated the efficacious quantification of these compounds for drug analysis, but their performance still presents challenges in practical applications. This study addresses these challenges by controlling the electropolymerization of polydopamine (PDA) on highly porous laser-induced graphene (LIG) electrodes with enhanced electrochemical redox activity for the detection of drug molecules such as atenolol, with minimized interference with the other active substances to induce variation of electrochemical behavior. The enhanced sensitivity of atenolol is attributed to the superhydrophilicity and increased number of active surface sites and -NH2 groups in the PDA polymer through a controlled polymerization process. Moreover, the simulation results further reveal that highly sensitive sensing of atenolol molecules relies on optimal adsorption of the atenolol molecule on dopamine or dopaminequinone structural units. The resulting sensors with high repeatability and reproducibility can achieve a low detection limit of 80 μM and a sensitivity of 0.020 ± 0.04 μA/μM within a linear range from 100 to 800 μM. The materials and surface chemistry in the electrode design based on highly porous LIG provide insights into the integration and application of future scalable and cost-effective electrochemical sensors for use in point-of-care or in-field applications.

Halloysite@polydopamine/ZIF-8 Nanocomposites for Efficient Removal of Heavy Metal Ions

In this study, polymeric nanocomposites of zeolitic imidazolate frameworks (ZIFs) were synthesized by assembly of a biomimetic polymer-polydopamine (PDA)onto halloysite nanotubes (HNTs@PDA), followed by the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on the surface of HNTs@PDA. The obtained nanocomposites (HNTs@PDA/ZIF-8) prevented agglomeration of ZIFs and increased the number of active sites derived from PDA. The factors influencing heavy metal ions (Pb2+, Cd2+, Cu2+, and Ni2+) adsorption by HNTs@PDA/ZIF-8 were discussed. The Langmuir model was able to well describe the adsorption, and the maximum adsorption capacity of HNTs@PDA/ZIF-8 was calculated to be 285.00 mg/g for Cu2+, 515.00 mg/g for Pb2+, 185 mg/g for Cd2+ and 112.5 mg/g for Ni2+. Thermodynamic parameters confirmed that the adsorption was exothermic and spontaneous. Moreover, HNTs@PDA/ZIF-8 has good regenerability, which is very important in practical applications. The adsorption mechanism study showed that electrostatic attraction, coordination reactions and ion-exchange were the main mechanisms between the adsorbents and heavy metal ions. Hence, HNTs@PDA/ZIF-8 is a promising candidate for removing heavy metal ions from wastewater.

Exploration of polydopamine capped bimetallic oxide (CuO-NiO) nanoparticles inspired by mussels for enhanced and targeted paclitaxel delivery for synergistic breast cancer therapy

Integration of antitumor drug and metallic nanoparticles in a polymeric nanosystem with effective properties is an emerging and promising tool to improve tumor treatment. Nevertheless, there is still a clinical need for multifunctional nanoparticles (NPs) to be developed for an “all-in-one” platform with specific targeting, less side effects and high therapeutic efficacy. In this research, pH-responsive bimetallic oxide-multifunctional NPs wrapped by polydopamine polymer for simultaneous cancer cell targeting and drug delivery were synthesized based on simple metal nanoparticle-ligand interactions. We explored a unique nanosystem of mussel inspired, polydopamine complexed with copper/nickel oxide NPs (CuO-NiO@PDA NPs). CuO-NiO@PDA NPs were then loaded with anticancer drug paclitaxel (PTX) via electrostatic or π-π stacking interaction and functionalized with folic acid (FA), a tumor-targeting ligand, to form CuO-NiO@PDA-PTX/FA NPs. Results highlight therapeutic potential of CuO-NiO@PDA/FA NPs as paclitaxel delivery nanocarrier in breast cancer therapy with sustained drug release pattern due to their increased stability, biocompatibility and antitumor efficacy. Cell viability was demonstrated in vitro using AO/EB dual staining, and its anticancer potential was confirmed by a reactive oxygen species (ROS) assay and mitochondrial membrane potential staining experiments. Consequently, our designed CuO-NiO@PDA-PTX/FA NPs appear to be promising multipurpose nanocarriers with therapeutic potential for MCF-7 tumor targeting and penetration.

Biologically inspired reinforcement using polydopamine of polymer bound composites

Interfacial strength plays a critical role in the mechanical properties of a composite system. In this work, a proven mock high explosive (HE), 5-iodo-2’-deoxyuridine (IDOX) was coated by the adhesive promoting polymer polydopamine (PDA), then formulated with an Estane binder system to form an improved HE mock composite. An extensive comparison study of mechanical properties was performed to determine the effects, if any, of PDA on the composite system. To aid in interpretation of the mechanical test data, neutron reflectometry experiments were performed to determine the thickness and structure of the as deposited PDA films. The mechanical performance of PDA-treated IDOX was then compared to untreated specimens by compression testing in the Brazilian disk geometry. The results strongly suggested that the structure of PDA consists of two layers: one low in density caused by polymer agglomerates attaching to the substrate during polymerization, and the second high in density caused by controlled linear deposition of polydopamine. The mechanical testing showed that PDA greatly increased the stiffness and yield strength of IDOX based mocks without causing any disruption to the underlying crystal system.

Fabrication of polydopamine nanoparticles-based electrochemical sensor for geometry-sensitive detection of chloramphenicol

Chloramphenicol (CAP), a broad-spectrum antibiotic, and the residues in food have profound effect on human’s health, making the detection of antibiotic residues a pressing need. Herein, we synthesized and compared two different geometries of polydopamine polymer, amorphous polydopamine (pDA) and polydopamine nanoparticles (pDA-NPs), for the establishment of a metal-free, green electrochemical sensor for the sensing of CAP. The intrinsic reducing ability of polydopamine was exploited because the catechol group can act on the nitro group of CAP. However, only the geometry of pDA-NPs enabled the sensitive detection of CAP, while the amorphous pDA was no match for the performance. The detection discrepancy may be ascribed to the geometry differences, where pDA-NPs were more likely in a curvature structure while amorphous pDA polymer in a linear structure. Computational method also justified that the curvature structure let to a favorable arrangement toward the sensing of CAP, where more electrons are easier to transfer from the dopamine to the closest oxygen atom of CAP as compared to linear form. The pDA-NPs-based electrochemical sensor presented high sensitivity with a detection limit of 2.57 nM, as well as excellent selectivity in discriminating CAP against the co-existence of other antibiotic and interfering species. Reproducibility was also validated by showing the sensing consistency with which the sensor for three measurements and up to 14-day storage, with CV of 3.4 % and 5.5 %, respectively. A recovery rate from 87 % to 104 % was obtained from a real milk sample spiked with CAP, showing great promise of the developed electrochemical sensor as a facile monitoring tool for CAP in reality.

In-Situ Surface Modification of ITO Substrate via Bio-Inspired Mussel Chemistry for Organic Memory Devices.

The development of organic memory devices, regarding factors such as structure construction, principle exploration, and material design, has become a powerful supplement to traditional silicon-based information storage. The in-situ growth of materials on substrate surfaces can achieve closer bonding between materials and electrodes. Bio-inspired by mussel chemistry, polydopamine (PDA) was self-assembled on a flexible substrate as a connecting layer, and 2-bromoiso-butyryl bromide (BiBB) was utilized as an initiator for the polymerization of an iridium complex via surface-initiated atom-transfer radical polymerization (SI-ATRP). A device with the structure of Al/PDA-PPy3Ir/ITO was constructed after the deposition of aluminum. The device exhibited a nonvolatile rewritable memory characteristic with a turn-on voltage of -1.0 V and an ON/OFF current ratio of 6.3 × 103. In addition, the memory performance of the Al/PDA-PPy3Ir/ITO device remained stable at bending states due to the intrinsic flexibility of the active layer, which can be expanded into the establishment of flexible memory devices. Spectroscopy and electrochemical characterization suggested that the resistive memory properties of the device stemmed from charge transfer between PDA and iridium polymer in the active layer (PDA-PPy3Ir) under an applied voltage.

Preparation of Ultrathin and Degradable Polymeric Films by Electropolymerization of 3-Amino-l-tyrosine.

Bioderived polymers are one of many current research areas that promise a sustainable future. Due to their unique properties, the bioderived polymer polydopamine has been in the spotlight over the last decades. Its ability to adhere to virtually any surface and its stability over a wide pH range as well as in several organic solvents make it a suitable candidate for various applications like coatings and biosensors. However, strong light absorption over a broad range of wavelengths and high quenching efficiency limit its uses. Therefore, new bioderived polymers with similar features to polydopamine but without fluorescence quenching properties are highly desirable. Herein, the electropolymerization of a bioderived analog of dopamine, 3-amino-l-tyrosine, is demonstrated. The resulting polymer, poly(amino-l-tyrosine), exhibits several characteristics complementary to or even exceeding those of polydopamine and its analog, polynorepinephrine, rendering poly(amino-l-tyrosine) attractive for the development of sensors and photoactive devices. Cyclic voltammetry, spectro-electrochemistry, and electrochemical quartz crystal microbalance measurements are applied to study the electrodeposition of this material, and the resulting films are compared to polydopamine and polynorepinephrine. Impedance spectroscopy reveals increased ion permeability of poly(amino-l-tyrosine) compared to polydopamine and polynorepinephrine. Moreover, the reduced fluorescence quenching of poly(amino-l-tyrosine) supports its use as coating for biosensors and organic semiconductors.

Progress for Co-Incorporation of Polydopamine and Nanoparticles for Improving Membranes Performance.

Incorporating polydopamine has become a viable method for membrane modification due to its universality and versatility. Fillers in their different categories have been confirmed as effective elements to improve the properties of membranes such as hydrophilicity, permeability, mechanical strength, and fouling resistance. Thus, this paper mainly highlights the recent studies that have been carried out using polydopamine and nanomaterial fillers simultaneously in modifying the performance of different membranes such as ultrafiltration, microfiltration, nanofiltration, reverse osmosis, and forward osmosis membranes according to the various modification methods. Graphene oxide nanoparticles have recently attracted a lot of attention among different nanoparticles used with polydopamine, due to their impressive characteristics impacts on enhancing membrane hydrophilicity, mechanical strength, and fouling resistance. Thus, the incorporation techniques of graphene oxide nanoparticles and polydopamine for enhancing membranes have been highlighted in this work. Moreover, different studies carried out on using polydopamine as a nanofiller for optimizing membrane performance have been discussed. Finally, perspectives, and possible paths of further research on mussel-inspired polydopamine and nanoparticles co-incorporation are stated according to the progress made in this field. It is anticipated that this review would provide benefits for the scientific community in designing a new generation of polymeric membranes for the treatment of different feed water and wastewater based on adhesive mussel inspired polydopamine polymer and nanomaterials combinations.

A High-Performance Polyurethane–Polydopamine Polymeric Binder for Silicon Microparticle Anodes in Lithium-Ion Batteries

Micro silicon (Si) has been one of the most promising anode materials for lithium-ion batteries (LIBs) due to high theoretical specific capacity and material sources. Nonetheless, an unavoidable huge volume expansion of Si microparticles (SiMPs) and the uncontrolled growth of the solid–electrolyte interphase (SEI) during the cycling still inhibit its commercialization. Among the strategies to overcome these problems, the design of a polymer binder is more feasible. Herein, a binder derived from two of the most common polymers, polyurethane (PU) and polydopamine (PDA), has been synthesized by a simple heating and mixing method for SiMP anodes in LIBs. In the PU–PDA binder, the synergistic effect of PU and PDA enables it to adapt to the volume expansion of SiMPs and maintain the electrode integrity and provides excellent cycling performance and long cycle life. The SiMP anodes with the PU–PDA binder have a capacity retention above 1000 mA h g–1 after 1000 cycles at a current density of 0.2 C and could deliver a discharging specific capacity of 1399 mA h g–1 at 4 C. Our research provides a safe, simple, and efficient PU–PDA polymer binder for SiMP anodes in the next-generation LIBs.

Dopamine Photochemical Behaviour under UV Irradiation.

To understand the photochemical behaviour of the polydopamine polymer in detail, one would also need to know the behaviour of its building blocks. The electronic absorption, as well as the fluorescence emission and excitation spectra of the dopamine were experimentally and theoretically investigated considering time-resolved fluorescence spectroscopy and first-principles quantum theory methods. The shape of the experimental absorption spectra obtained for different dopamine species with standard, zwitterionic, protonated, and deprotonated geometries was interpreted by considering the advanced equation-of-motion coupled-cluster theory of DLPNO-STEOM. Dynamical properties such as fluorescence lifetimes or quantum yield were also experimentally investigated and compared with theoretically predicted transition rates based on Fermi’s Golden Rule-like equation. The results show that the photochemical behaviour of dopamine is strongly dependent on the concentration of dopamine, whereas in the case of a high concentration, the zwitterionic form significantly affects the shape of the spectrum. On the other hand, the solvent pH is also a determining factor for the absorption, but especially for the fluorescence spectrum, where at lower pH (5.5), the protonated and, at higher pH (8.0), the deprotonated forms influence the shape of the spectra. Quantum yield measurements showed that, besides the radiative deactivation mechanism characterized by a relatively small QY value, non-radiative deactivation channels are very important in the relaxation process of the electronic excited states of different dopamine species.

Multifunctional Photoelectroactive Platform for CO2 Reduction toward C2+ Products─Programmable Selectivity with a Bioinspired Polymer Coating

In recent years, CO2 photo/electroreduction has received great attention due to the urges and concerns to solve problems connected with global warming, for example, reducing the consumption of fossil fuels as energy sources and switching to renewable energy sources. The realization of this technology depends on efficient photo/electrocatalysts with high selectivity for the products. Herein, we report a programmable, bifunctional, scalable, high-performance, and low-cost bioinspired catalyst for photo/electrochemical CO2 reduction (P/EC-R). We synthesized hydroxyapatite (HAP) needle-like nanoparticles coated with a functional polydopamine polymer (HAP/P(DOPA)) and then modified them with copper nanoparticles (HAP/P(DOPA)/Cu NPs). It was expected that HAP and P(DOPA), due to their plentiful functional groups such as hydroxyl (−OH–), oxygen (−O•– and ═O), and amines (−NH2 and −NH−), provide extensive active catalytic sites, participate in the capture, maintenance, and hydrogenation of the CO2 intermediate, and offer a combination of efficient electrical conduction and photoactivity and synergistic effect together with Cu nanoparticles, thus potentially empowering CO2 P/EC-R. Interestingly, varying the polymerization time of the coating layer (P(DOPA)) leads to different product selectivities in both photoelectrochemical and electrochemical reactions. In a shorter polymerization period (2 h), CO (>83%) is the main product, while for 5 and 15 h, C2H6 (>70%) and CH4 (>74%) are the main products, respectively. It is noteworthy to mention that as the applied potential increased (>−1.2 V vs RHE), propanal (C3H6O, FE > 35%) and surprisingly ethyl acetate (C4H8O2, FE > 67%) have been detected. This is the first report on the C4 product.

Femtosecond laser nano-structuring for surface plasmon resonance-based detection of uranium

Surface plasmon resonance (SPR) is a proven technique in sensorics. Wide application of the method is still limited by a necessity of a complex optical equipment using special dispersion elements like a prism or diffraction grating (DG). We have implemented a novel and inexpensive way for fabrication of the DG on a silicon substrate using femtosecond laser ablation (highly regular laser-induced periodic surface structures - HR-LIPSS) technique. The potential of the method has been illustrated for the case of detection of uranium in water. For this purpose, fabricated gratings were coated with thermally evaporated nanofilms of gold and then used as substrates for deposition of nanoparticles of bioinspired polymer polydopamine (PDA) highly selective to uranium under neutral pH. Synergistic combination of the advanced nanofabrication and SPR sensing techniques with advanced PDA ligand allowed preparation of sensing elements with a sub-microgram sensitivity to uranium (∼1.0 × 10−7g/cm2). Even though the results reported here are just a proof of concept, we believe the approach can be expanded to selective detection of various types of analytes (heavy metals, biomolecules, viruses etc.) under different environments (water, air, aerosols) in the future.

Zwitterionic polydopamine modified nanoparticles as an efficient nanoplatform to overcome both the mucus and epithelial barriers

Nanoparticles have opened a new perspective for oral drug delivery. However, nanoparticle transport is strongly hindered by mucus and epithelial barriers before they can enter the systemic circulation. We here establish a Poly(lactic-co-glycolic acid) (PLGA)-based nanoparticle platform with various surface modifications: Poly(ethylene glycol) (PEG), Poly(vinyl alcohol) (PVA) with different molecular weights and degrees of hydrolysis, Pluronic F127 (F127), and Polydopamine (PDA). We then systematically evaluate the mucus penetrability and cellular uptake of these different nanoparticles. Results demonstrate that both the unmodified PLGA and PVA-modified PLGA nanoparticles showed poor mucus penetrating ability as a consequence of strong interactions with the mucin fibers. Moreover, although the PLGA-PEG and PLGA-F127 nanoparticles exhibit relatively satisfactory mucus penetrability, they are not readily taken up by epithelial cells. In contrast, PDA-modified PLGA nanoparticles not only facilitate rapid mucus penetration, but also enhance the cellular uptake both in vitro and in vivo, thanks to the zwitterionic surface property of PLGA-PDA nanoparticles. This study therefore demonstrates the usefulness of zwitterionic modification by PDA polymer in allowing nanocarriers to sequentially penetrate the mucus and epithelial barriers, with significant potential for further application to oral drug delivery.

Application of Polydopamine Functionalized Zinc Oxide for Glucose Biosensor Design.

Zinc oxide (ZnO) nanostructures are widely used in optical sensors and biosensors. Functionalization of these nanostructures with polymers enables optical properties of ZnO to be tailored. Polydopamine (PDA) is a highly biocompatible polymer, which can be used as a versatile coating suitable for application in sensor and biosensor design. In this research, we have grown ZnO-based nanorods on the surface of ITO-modified glass-plated optically transparent electrodes (glass/ITO). Then the deposition of the PDA polymer layer on the surface of ZnO nanorods was performed from an aqueous PDA solution in such a way glass/ITO/ZnO-PDA structure was formed. The ZnO-PDA composite was characterized by SEM, TEM, and FTIR spectroscopy. Then glucose oxidase (GOx) was immobilized using crosslinking by glutaraldehyde on the surface of the ZnO-PDA composite, and glass/ITO/ZnO-PDA/GOx-based biosensing structure was designed. This structure was applied for the photo-electrochemical determination of glucose (Glc) in aqueous solutions. Photo-electrochemical determination of glucose by cyclic voltammetry and amperometry has been performed by glass/ITO/ZnO-PDA/GOx-based biosensor. Here reported modification/functionalization of ZnO nanorods with PDA enhances the photo-electrochemical performance of ZnO nanorods, which is well suited for the design of photo-electrochemical sensors and biosensors.

In situ synthesis of fluorescent polydopamine polymer dots based on Fenton reaction for a multi-sensing platform.

The development of fluorescent nanosensors has attracted extensive research interest owing to their superior optoelectronic properties. However, current fluorescent nanoprobes generally involve complicated synthesis processes, background signal disturbance, and limited analyte detection. In this work, a facile and time-saving synthetic strategy for the preparation of green emitting polydopamine polymer dots (PDA-PDs) from dopamine via Fenton reaction at room temperature was proposed for the first time. The obtained PDA-PDs possessed excellent luminescence properties, with a long-wavelength emission of 522 nm, a large Stokes shift of 142 nm, and good photostability against ionic strength and UV irradiation. The formation mechanism of fluorescent PDA-PDs is as follows: in the presence of Fe2+ and H2O2, dopamine could rapidly undergo oxidation to its quinone derivatives and further polymerize to synthesize the fluorescent PDA-PDs with the acceleration of hydroxyl radicals produced from the Fenton reaction. Thus, a versatile turn-on fluorescence sensing method was developed for the detection of multi-analytes (including Fe2+, dopamine, H2O2, and glucose) based on monitoring the intrinsic fluorescence signal of the in situ formation of PDA-PDs. This sensing method could be efficiently applied for the detection of Fe2+, dopamine, and glucose in real human serum samples. Moreover, a three-input AND molecular logic gate based on this sensing platform was designed with the fluorescence signal of PDA-PDs as the gate. Finally, the proposed PDA-PDs could have immense broad prospects in nanomaterials and biosensors.

Tribological properties of PDA + PTFE coating in oil-lubricated condition

In this study, the tribological properties of 45 ± 2 μm-thick polytetrafluoroethylene (PTFE) and polydopamine (PDA) + PTFE coatings in oil-lubricated conditions were investigated under a normal load of 10 N and a linear reciprocating speed of 0.1 m/s. Both the PTFE and the PDA + PTFE coatings were deposited using an in-house spray-coating method. The PDA + PTFE coating was five times more durable compared to the PTFE coating in oil-lubricated conditions. Both PTFE and PDA + PTFE coatings showed lower COF in oil-lubricated conditions than in dry conditions. The nanomechanical properties measured by PeakForce Quantitative Nanomechanical (PFQNM) characterization method showed an increase in Young’s modulus and adhesion force for the PDA + PTFE coatings compared to the PTFE coatings. Chemical analysis showed that the cross-linking between PDA and PTFE polymer chains occurred during the high-temperature sintering procedure. The higher adhesion of PDA + PTFE coating to the cast iron substrate and the stronger cohesion due to the cross-linking between PDA and PTFE contributed to the higher durability of the PDA + PTFE composite coatings.

Construction of hierarchical functionalized black phosphorus with polydopamine: A novel strategy for enhancing flame retardancy and mechanical properties of polyvinyl alcohol

As a rising star of two-dimensional (2D) materials, single or few-layer black phosphorus (BP) possess great potential as nanofiller in fabricating polymer nanocomposites, due to its thermodynamic stability, nano-size effect and structural characteristics. Herein, few-layer BP nanosheets were scalable exfoliated via solvent-thermal method, the Lithium ion intercalation was achieved during this procedure. Follow by a polydopamine (PDA) encapsulated BP sandwich nanostructure was developed by oxidation–reduction strategy, which improved the air stability of few-layer BP and its interfacial compatibility with polymer matrix. As could be expected, the PDA encapsulated BP (BP-PDA) can effectively enhance the mechanical properties and flame retardancy of polyvinylalcohol (PVA) nanocomposite films. For instance, the PVA/BP-PDA5.0 nanocomposite film loaded with 5 wt% BP-PDA exhibited 57.2% maximum decrease in peak heat release rate and 47.9% maximum reduction in total heat release. Meanwhile, while the BP-PDA loading achieved 2 wt%, PVA/BP-PDA2.0 nanocomposite film revealed an 81.1% increase in the tensile strength. In particular, onaccountofdual protection of the PDA encapsulation and polymer matrix embedding, the air stability of BP in PVA matrix was significantly improved. As an evidence, the ratio of Ag1/Ag2 in Raman spectra of BP-PDA decreased from the initial 0.72 to 0.62, even after exposed to air for five months, indicating a low level of oxidation. This work provides a novel strategy for scalable exfoliation and functionalization of BP, and enables a wide range of potential applications of BP in polymer nanocomposites.

Bio-inspired superior barrier self-healing coating: Self-assemble of graphene oxide and polydopamine-coated halloysite nanotubes for enhancing corrosion resistance of waterborne epoxy coating

Bio-inspired dopamine have attracted immense scientific interest in the surface modification field due to the high bio-adhesive properties for varies substrate. Herein, the polydopamine (PDA) was used as a novel pH-response gatekeeper to be coated on the BTA-loaded HNTs hybrids (PBH) via conventional polymerization reaction (Tris HCl/pH=8.5), which can be destroyed in an acidic environment resulting in release of BTA. Further, the as prepared PBH were self-assembled with graphene oxide (GO) through π-π* interaction between GO and PDA. The waterborne epoxy coating (WEC) loaded with GO@PBH possessed superior barrier properties owing to the excellent shielding performance of GO nanosheets against the corrosive ions. The dual self-healing effect of GO@PBH based WEC for the carbon steel substrate mainly originated from release of BTA during corrosion process and the formation of complex between catechol of the damaged PDA polymer network and Fe3+. The barrier and self-healing properties of the composite coating were tested by electrochemistry and neutral salt spray test. The results prove that the WEC loaded with GO@PBH hybrids possesses superior barrier properties for the corrosion medium and outstanding self-healing effect as the corrosive ions reached the metal/coating interface.

Mussel chemistry inspired synthesis of Pd/SBA-15 for the efficient reduction of 4-nitrophenol

In this study, N-doped platelet-like metal-loaded Zr/SBA-15 was synthesized and employed for reducing 4-nitrophenol to remove this contaminant from water. Dopamine hydrochloride was used as a novel CN source for the modification of ZrSBA-15. The N doping process occurred readily at a low temperature due to the polymerization of dopamine, which could save energy and simplify the experimental fabrication of catalysts. In addition, polydopamine can immobilize Pd ions in a facile manner and the trapped Pd ions are reduced to Pd nanoparticles due to the reducibility of the polydopamine polymer. The utilization of dopamine allows the catalyst to be obtained in a facile and cost-effective synthetic process, while the production of the CN layer as well as the reduction and immobilization of the Pd ions can occur simultaneously. Characterization of the product showed that the catalyst had a platelet-like structure after decoration with elemental Zr, which enhanced the catalytic reaction compared with the natural fiber-like SBA-15. The optimal Pd loading capacity was determined as ~3.0 wt% and the materials obtained could reduce 4-nitrophenol to 4-aminophenol within 120 s with a conversion ratio above 90%.

Self-Adhesive, Self-Healable, and Triple-Responsive Hydrogel Doped with Polydopamine as an Adsorbent toward Methylene Blue

As a kind of attractive biomaterial, stimuli-responsive hydrogel had been widely used in wound dressings and wearable devices. However, it remained challenging to prepare a hydrogel with both excellent self-adhesion and self-healing performances. Inspired by the adhesion mechanism of mussel, we prepared a self-adhesive, self-healing, and triple-responsive hydrogel by a hybrid system based on tunable composition of polydopamine (PDA) and polymer network composed of poly(N,N-diethylacrylamide-co-acrylic acid). It was found that the resulting hydrogel could be directly adhered to a variety of substrates without the need of external adhesives on account of the existence of enough free catechol groups in the hydrogel. Due to the synergistic effect of PDA nanoparticles and polymer network, hydrogel also showed excellent self-healing property. Moreover, we demonstrated that the triple-responsive hydrogel as an adsorbent could efficiently remove methylene blue, and the maximum adsorption capacity was 305.4 mg/g w...