Polydopamine Graphene Oxide Research Articles

Polyvinylidene fluoride-based loose nanofiltration membrane with graphene oxide intercalation for efficient small organic molecules desalination

Graphene oxide (GO) loose nanofiltration (LNF) membranes show immense potential for the desalination of small organic molecules. However, it remains a significant challenge to compare the performance of GO LNF membranes prepared via different doping methods and study the mechanisms that influence the separation abilities of the membranes. In this study, LNF membranes prepared via three GO doping methods were examined for flux, retention rate, and the separation performance of small organic molecules and inorganic salts. The membranes coated with dopamine (DA) and GO, and subsequently formed polydopamine (PDA)–GO intercalation, showed the best results. A novel LNF membrane material (PVDF/PDA–GO–TFN; PVDF: polyvinylidene fluoride, TFN: thin-film nanocomposite) was developed to enhance the separation performance of small organic molecules and inorganic salts while improving membrane surface stabilization and anti-fouling performance and reducing the “trade-off” effect. The optimal conditions for PDA–GO intercalation and the best combination for interfacial polymerization (IP) were also determined. The intercalation structure was identified via scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, atomic force microscopy, and Fourier-transform infrared spectroscopy. Furthermore, the separation mechanism of the membrane was determined to be based on the Donnan and steric hindrance effects, according to the correlation analysis of the membrane surface electrical properties (zeta potential), hydrophilicity (contact angle), and pore properties. The PVDF/PDA–GO–TFN LNF membrane displayed a maximum water permeance of 10.45 L/(m2·h·bar), with an 88 % rejection of PEG2000 and a 6.83 % rejection of Na2SO4. Moreover, the membrane exhibited excellent anti-fouling performance and long-term stability, with a mean flux recovery rate of 99.06 % after four cycles of filtration and backwashing tests using small organic molecules and inorganic salt solutions. The inorganic salt retention rate was analyzed using SPSS software, and the results indicated excellent membrane stability. In summary, the preparation of PVDF/PDA–GO–TFN membrane materials provides a novel approach for fabricating LNF membranes that can effectively separate small organic molecules and inorganic salts.

Fabrication of polydopamine/graphene oxide composite membranes for effective radionuclide removal

As the energy consumption surges in the past few decades, the utilization of reliable and cost-effective energy resources with minimum greenhouse gas emission is highly desirable, for which nuclear energy has gained intensive attention. The proper treatment of radioactive process water yet remains challenging, but is of vital importance due to its significant threats to environment and public health. In this work, a polydopamine/graphene oxide (PDA/GO) membrane was developed for radionuclide-contaminated water treatment. By the incorporation of PDA, the interlayer spacing of the GO membrane is regulated, as well as an improved anti-swelling property is achieved. At optimal preparation conditions, the PDA/GO has exhibited a high rejection of 99.9 % towards thorium ions with a satisfying water flux of 5.0 L·m−2h−1. Moreover, the influence of solution pH and thorium concentration on the membrane separation performance is studied. Results have indicated that the PDA/GO membrane presents a new promise for the treatment of radionuclide-contaminated water.

Polydopamine in‐situ polymerized on graphene oxide for nitrile butadiene rubber with high strength, elasticity and aging resistance

AbstractThe elasticity and aging resistance of nitrile butadiene rubber (NBR) will be reduced by reinforced filler. Herein, we report that polydopamine (PDA) polymerized in situ on graphene oxide (GO) to obtain polydopamine‐graphene oxide (PDA‐GO) nanofiller for simultaneously improving strength, elasticity and thermal oxidative aging‐resistant performance of NBR. The structure, composition and morphology of PDA‐GO and NBR composites were characterized. The effect of PDA‐GO on the performance of NBR was investigated. Results show that PDA microspheres improved the dispersion of GO in matrix. With incorporation 3 phr of PDA‐GO, the tensile strength of NBR raised from 3.8 to 9.2 MPa. It is satisfactory that the elasticity is also improved significantly. PDA‐GO/NBR composite equips better thermal oxidative stability and aging resistance. The tensile strength of 3 phr‐PDA‐GO/NBR after aging is even 3.4 MPa higher than that of unfilled NBR before aging. Our work proposes an insight for the manufacture of rubber composites with high strength, elasticity and aging resistance.Highlights GO modified by PDA is prepared via an in‐situ polymerization process. In situ polymerized PDA microspheres greatly promotes the dispersion of GO in NBR matrix. NBR filled with PDA‐GO shows a superior strength and elasticity simultaneously. PDA‐GO endows NBR with prominent performance in aging resistance.

Bio-inspired nanocomposite coatings on orthodontic archwires with corrosion resistant and antibacterial properties.

The corrosion resistance and antibacterial properties of fixed orthodontic devices are insufficient in the complex oral cavity, which delays tooth movement and causes enamel demineralization. To overcome the challenges, this research constructs a series of polydopamine-graphene oxide (PDA-GO) nanocoatings on representative NiTi archwires via self-assembly. The morphology, chemical structure, and multifunctional properties of coatings showed tunability dependent on the PDA/GO ratio. Optimized PDA-GO coatings with uniform and dense characteristics prolonged the diffusion path for the corrosive medium and reduced Ni dissolution in NiTi alloys. Meanwhile, the applied coatings endowed NiTi alloys with antibacterial activity against Streptococcus mutans due to the surface structures and inherent properties of PDA-GO. In vitro cytotoxicity tests further verified their good biocompatibility. This bio-inspired nanocomposite coating provides a practical reference for modification of dental metal surfaces to better behave in the intraoral environment.

Biomimetic synthesis of polydopamine-graphene oxide/hydroxyapatite for efficient and fast uranium(VI) capture from aqueous solution.

A novel and efficient mesoporous nano-absorbent for U(VI) removal was developed through an environment-friendly route by inducing the biomimetic mineralization of hydroxyapatite (HAP) on the bioinspired surface of polydopamine-graphene oxide (PDA-GO). PDA-GO/HAP exhibited the greatly rapid and efficient U(VI) removal within 2 min, and much higher U(VI) adsorption capacity of 433.07 mg·g-1 than that of GO and PDA-GO. The enhanced adsorption capacity was mainly attributed to the synergistic effect of O-H, -C=N-, and PO43- functional groups and the incorporation of uranyl ions by the formation of a new phase (chernikovite, H2(UO2)2(PO4)2·8H2O). The adsorption process of U(VI) fitted well with pseudo-second-order kinetic and Langmuir isotherm model. Moreover, PDA-GO/HAP showed a high U(VI) adsorption capacity in a broad range of pH values and owned good thermal stability. PDA-GO/HAP with various excellent properties made it a greatly promising adsorbent for extracting uranium. Our work developed a good strategy for constructing fast and efficient uranium-adsorptive biomimetic materials.

Super-hydrophilic nanofiber substrate supported forward osmosis membrane with less polyamide layer defects by polydopamine-graphene oxide modification for high salinity desulfurization wastewater desalination

Super-hydrophilic electrospun nanofiber as the substrate of a thinu film composite forward osmosis (eTFC-FO) membrane can improve the performance of the membrane by mitigating internal concentration polarization (ICP). However, polyamine (PA) layer defects easily formed on super-hydrophilic nanofiber substrate hinders its further performance improvement. To prevent PA from forming deep inside the pores of substrate and alleviate PA defects, polydopamine-graphene oxide (PDA-GO) was introduced to modify the interlayer and PA layer of eTFC-FO membrane. Results showed that PA layer defects can be alleviated by addition of PDA-GO in interlayer or PA layer, and the simultaneous addition of PDA-GO in interlayer and PA layer resulted in the least defective PA layer of the eTFC-FO membrane (eTFC0.5-0.125). Performance evaluation demonstrated that the eTFC0.5-0.125 had a high FO water flux of 54.0 LMH and excellent ion rejections (>98.0%) for desalination of a real high salinity desulfurization wastewater. Besides the PA defects alleviation, nanochannel of PDA-GO for water transport also contributed to the performance improvement, as well as the fast water and salts diffusion by super-hydrophilic nanofiber substrate. Thus, a high performance eTFC-FO membrane was prepared on super-hydrophilic nanofiber substrate and was able to be used for high salinity water desalination.

Enhancing the Efficiency of a Forward Osmosis Membrane with a Polydopamine/Graphene Oxide Layer Prepared Via the Modified Molecular Layer-by-Layer Method.

Water scarcity is one of the most critical problems that humans have to face. Working toward solving this problem, we have developed a thin-film composite (TFC) membrane using the modified molecular layer-by-layer (modified mLBL) method to fabricate polyamide (PA) active layers on different substrates. Besides, it has been found that graphene oxide (GO) contains abundant functional groups such as hydroxyl and epoxide groups, which are able to improve both the physical and chemical properties of the forward osmosis (FO) membrane. Thus, we have employed graphene oxide (GO) as the substrate and used the modified mLBL method to prepare active polydopamine/graphene oxide (PDA/GO) layers to enhance the water flux of the forward osmosis (FO) membrane. PDA/GO-coated layers could enhance the hydrophilic nature of the substrate and lower its surface roughness, which would facilitate the formation of the PA layer. Moreover, the PDA/GO coating can be applied to all substrates because of the high degree of adhesion of PDA to different substrates. In this study, the highly hydrophilic poly(vinylidene fluoride) membrane is superior in FO properties, with a water flux of 17.32 LMH and a reverse solute flux of 4.34 gMH. In addition, an excellent performance of 60.15 LMH and 14.88 gMH can be achieved when the pressure-retarded osmosis (PRO) test mode with a draw solution concentration of 2.0 M is used in the test. It shows that the membrane prepared using the novel method showed excellent FO performance, which has high potential in industrial applications such as desalination.

An online dual-enzyme co-immobilized microreactor based on capillary electrophoresis for enzyme kinetics assays and screening of dual-target inhibitors against thrombin and factor Xa

In this study, an online capillary electrophoresis (CE) based dual-enzyme (thrombin and factor Xa) co-immobilized microreactor (THR-FXa IMER) was constructed for studying enzyme kinetics and screening dual-target inhibitors against THR and FXa with the aid of the polydopamine/graphene oxide (PDA/GO) coating. Based on the developed THR-FXa IMER, the Michaelis-Menten constants (Km) of THR and FXa were calculated to be 187.26 and 48.80 μM, respectively. The inhibition constants (Ki) for two known inhibitors, argatroban and rivaroxaban, on THR and FXa were determined to be 14.73 and 0.41 nM, respectively. In addition, after 30 consecutive runs, the enzymes’ activity was remained 98% of the initial immobilized activity for both THR and FXa, which shows that the constructed IMER has good stability and repeatability. Finally, the developed method was successfully applied to screen dual-target inhibitors against THR and FXa from 30 small molecular compounds. Among them, 10 compounds such as salvianolic acid C and epigallocatechin gallate (EGCG) have dual-enzyme inhibitory activity, and 2 compounds named saikosaponin A and oleuropein have single THR inhibitory activity, 5 compounds such as rosemary acid and salvianolic acid B have single FXa inhibitory activity. Finally, the molecular interactions between enzyme and potential inhibitors were further verified via the molecular docking, and a new compound with a theoretically good coagulation inhibition effect was designed by the scaffold hopping study. In summary, the developed THR-FXa IMER is a reliable method for screening THR and/or FXa inhibitors.

Ultrathin and stable graphene oxide film via intercalation polymerization of polydopamine for preparation of digital inkjet printing dye

As a result of distinctive nanopores of two-dimensional material, graphene oxide (GO) has emerged as a new-generation membrane for high performance water separation. However, GO-based composed membrane applied to dye desalting gains less attention. A series of novel ultrathin and stable polydopamine/graphene oxide (PGO) membranes has been successfully fabricated via intercalation polymerization of dopamine using triple vacuum filtration. The polymerized dopamine (PDA) via intercalation polymerization in the interspace between the lamellar layers is used to simultaneously improve the stability of GO film and rapid passage of ions. The high permeation of pure water of as-prepared PGO membranes is investigated through adjusting the thickness (9–126 nm) of modified layers. In addition, the values decrease from 24.2 to 0.65 L m−2 h−1 bar−1 with increasing the layer. With the ultrafast ion transport and dyes rejection under cross-flow condition, the stability PGO membranes show a good capability for desalination dyes and concentration of dye (11.6 times of the initial dye solution).

Thin-film composite membranes comprising ultrathin hydrophilic polydopamine interlayer with graphene oxide for forward osmosis

In this study, a thin-film composite (TFC) membrane with a polysulfone (PSf) support layer comprising an ultrathin polydopamine/graphene oxide (PDA/GO) interlayer was fabricated by phase inversion, self-polymerization, and interfacial polymerization to improve water permeability of the TFC membrane for forward osmosis (FO) application. The surface of the support layer exhibited greater hydrophilicity because of the hydrophilic functional groups of PDA and GO. For longer PDA coating time, the permeability decreased due to pore blocking by PDA and GO. The TFC membrane with the PSf support layer coated with the PDA/GO interlayer showed great improvement of water flux (57.6%) without severe loss of the reverse solute flux under an optimum condition of 1 h of PDA coating time and 0.5 g/L of GO concentration. The results of this study are expected to contribute to the development of TFC FO membranes containing a hydrophilic interlayer to achieve improved membrane performance for water treatment and seawater desalination.

An Investigation of a Polydopamine-Graphene Oxide Composite as a Support for an Anode Fuel Cell Catalyst

Home-made graphene oxide (GO) with a high surface area was functionalized by polydopamine (PDA) and was labeled PDA-GO, while GO without PDA was labeled as GO. With different compositions of metals (Pt and/or Pd), the electrodeposition of the metals onto the prepared GO and PDA-GO supports was prepared for the anode electrocatalyst. The electrocatalytic activities of the electrocatalysts (xPtPd/GO and xPtPd/PDA-GO, where x = 1–5) were studied in the oxidation of alcohols (e.g., methanol and ethanol). Morphologies obtained from transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) images showed that the as-prepared GO and PDA-GO supports can accommodate electrodeposited metals loaded on the topmost layer of the support surfaces, although the size of nanoparticles is somewhat different. The electrochemical results indicated that the xPtPd/PDA-GO catalysts offered outstanding oxidation efficiencies. The prepared 5PtPd/PDA-GO catalyst provided enhanced activity and long-time stability in the oxidation reactions. The GO surface modified by the polymer and the other electrodeposited metal catalysts provided a larger number of available active sites, as the PDA offered a greater electric connection between the metal catalysts and the GO support during alcohol oxidation.

Surface functionalization graphene oxide by polydopamine for high affinity of radionuclides

Abstract The utilization of nuclear energy plays an important role in our energy system; however, the leaking of radionuclides has potential threat to human health. In this paper, two-dimensional polydopamine/graphene oxide (PD/GO) composites were synthesized through a simple bio-inspired surface functionalization process by self-polymerization of dopamine monomers on GO surface. To evaluate the adsorption performance of PD/GO composites, the adsorbent was applied to remove uranium(VI) from aqueous solutions. Based on the Langmuir's equation, the maximum adsorption capacity was calculated to be 145.39 mg · g−1 by PD/GO composites, which is higher than that of pure PD (34.21 mg · g−1) and GO (75.71 mg · g−1). The enhanced adsorption capacity was mainly ascribed to the synergistic effect of PD with multifunctional groups and GO with high surface area. The adsorption process fitted well with the Langmuir adsorption isotherm and a pseudo-second order kinetics. Moreover, adsorption and regeneration experiment proved the samples can support long-term use in nuclear waste management. This work provides a convenient and promising materials for the removal of U(VI) from polluted water.

Facile preparation of protein stationary phase based on polydopamine/graphene oxide platform for chip-based open tubular capillary electrochromatography enantioseparation

A novel chip-based enantioselective open-tubular capillary electrochromatography (OT-CEC) was developed employing bovine serum albumin (BSA) conjugated polydopamine–graphene oxide (PDA/GO) nanocomposites (PDA/GO/BSA) as stationary phase. After the poly(dimethylsiloxane) (PDMS) microfluidic chip was filled with a freshly prepared solution containing dopamine and graphene oxide, PDA/GO nanocomposites were formed and deposited on the inner wall of microchannel as permanent coating via the oxidation of dopamine by the oxygen dissolved in the solution. The PDA/GO-coated PDMS microchips not only have the adhesion of PDA that make them easily immobilized in the microchannel, but also have the larger surface and excellent biocompatibility of graphene which can incorporate much more biomolecules and well maintain their biological activity. In addition, incorporation of GO in PDA film can make surface morphology more rough, which is beneficial for enhancing the loading capacity of proteins in the microchannels and increasing sample capacity of OT-CEC columns. BSA was stably immobilized in the PDMS microchannel to fabricate a protein-stationary phase. Compared with the native PDMS microchannels, the modified surfaces exhibited much better wettability, more stable electroosmotic mobility, and less nonspecific adsorption. The efficient separation of chiral amino acids (tryptophan and threonine) and chiral dipeptide demonstrate that the constructed OT-CEC columns own ideal enantioselectivity. The presented strategy using PDA/GO coating as a versatile platform for facile conjugation of proteins may offer new processing strategies to prepare a functional surface designed on microfluidic chips.