Polydopamine-reduced Graphene Oxide Research Articles

A three-components-based disposable electrochemical sensor for the detection of heavy metal ions in water

The development of an efficient sensor based on a novel three-components nanocomposite is presented for the detection of heavy metal ions (Cd2+ and Pb2+) in water. For the preparation of three-components nanocomposite surface, the polydopamine reduced graphene oxide (PyDA/RGO) composite was initially prepared by a one-step polymerization of dopamine (DA) on RGO followed by surface modification of the prepared composite with cysteine (Cys). The formation of three-components nanocomposite surface (i.e., Cys/PyDA/RGO) was initially confirmed through physical characterization techniques, including X-ray diffraction and infrared spectroscopy, whereas scanning electron microscopy revealed the surface morphology after each step of sensor fabrication. The electrochemical properties of the sensing platform were evaluated through electrochemical techniques, including cyclic voltammetry and electrochemical impedance spectroscopy with an external ferri‐−/ferrocyanide redox probe. The prepared three-components nanocomposite on disposable pencil graphite electrode (Cys/PyDA/RGO/PGE) showed an improved charge transfer rate as compared to PyDA/RGO/PGE and bare PGE electrode. Targeted heavy metal ions were detected on the sensor surface using differential pulse voltammetry with greater sensitivity, showing detection limits of 0.77 and 1.13 ppb for Cd+2 and Pb+2 ions in citrate buffer solution, respectively. The sensor demonstrated comparable performance in the tap water samples.

Fabrication of polydopamine/rGO Membranes for Effective Radionuclide Removal.

In this work, a novel polydopamine/reduced graphene oxide (PDA/rGO) nanofiltration membrane was prepared to efficiently and stably remove radioactive strontium ions under an alkaline environment. Through the incorporation of PDA and thermal reduction treatment, not only has the interlayer spacing of graphene oxide (GO) nanosheets been appropriately regulated but also an improved antiswelling property has been achieved. The dosage of GO, reaction time with PDA, mass ratio of PDA to GO, and thermal treatment temperature have been optimized to achieve a high-performance PDA/rGO membrane. The resultant PDA/rGO composite membrane has exhibited excellent long-term stability at pH 11 and maintains a steady strontium rejection of over 90%. Moreover, the separation mechanism of the PDA/rGO membrane has been systematically investigated and determined to be a synergistic effect of charge repulsion and size exclusion. Results have indicated that PDA/rGO could be considered as a promising candidate for the separation of Sr2+ ions from nuclear industry wastewater.

Adhesive, self-healing polydopamine/reduced graphene oxide composite hydrogel for self-powered application

ABSTRACT Graphene-based hydrogels have a broad application prospect in various fields due to their excellent adsorption, electrical conductivity, water retention, flexibility, etc. In this work, polydopamine/reduced graphene oxide (PDA/rGO) composite hydrogel was prepared using water bath heating. The prepared PDA/rGO hydrogel has high swelling ratio, good adhesiveness, and self-healing ability. Furthermore, the generation of electric current was observed when pressure was applied to the PDA/rGO hydrogel filled with NaCl solution, indicating the self-powered property of the hydrogel. The PDA/rGO hydrogel is self-powered because the negative groups on the hydrogel matrix attract cations from the NaCl solution, leaving mobile negative ions in the solution. The pressure-induced flow of liquid in the hydrogel' s nanochannels drives the migration of mobile ions through the channels, generating a net ionic flow. These properties of PDA/rGO hydrogel suggest that the material would be promising for power sources of wearable devices by harvesting ambient mechanical energy.

Cotton fabric electrodes coated by polydopamine-reduced graphene oxide and polypyrrole for flexible supercapacitors

Cotton fabric electrodes coated by polydopamine-reduced graphene oxide and polypyrrole for flexible supercapacitors

Decellularized extracellular matrix-based 3D nanofibrous scaffolds functionalized with polydopamine-reduced graphene oxide for neural tissue engineering

One of the exciting prospects of using decellularized extracellular matrices (ECM) lies in their biochemical profile of preserved components, many of which are regeneration-permissive. Herein, a decellularized ECM from adipose tissue (adECM) was explored to design a scaffolding strategy for the challenging repair of the neural tissue. Targeting the recreation of the nano-scaled architecture of native ECM, adECM was first processed into nanofibers by electrospinning to produce bidimensional platforms. These were further shaped into three-dimensional (3D) nanofibrous constructs by gas foaming. The conversion into a 3D microenvironment of nanofibrous walls was assisted by blending the adECM with lactide-caprolactone copolymers, wherein tuning the adECM/copolymer ratio along with the amount of caprolactone in the copolymer led to modulating the mechanical properties towards soft, yet structurally stable, 3D constructs. In view of boosting their performance to guide neural stem cell fate, adECM-based platforms were doped with a bioinspired surface modification relying on polydopamine-functionalized reduced graphene oxide (PDA-rGO). These adECM-based 3D constructs revealed a permissive microenvironment for neural stem cells (NSCs) to adhere, grow, and migrate throughout the microporosity, owing to the synergy between the unique biochemical features of the adECM and the nanofibrous architecture. NSC responded differently depending on the adECM-based architecture–nanofibrous bidimensional, or 3D design. The 3D spatial arrangement of the nanofibers – induced by the gas foaming – exhibited a remarkable effect on NSCs’ phenotype determination and neurite formation, thereby reinforcing the critical importance of engineering scaffolds with multiple length-scale architecture. Furthermore, PDA-rGO promoted the differentiation of NSC towards the neuronal lineage. Specifically in 3D, it significantly increases the levels of Tuj1 and MAP2 a/b isoforms, confirming its effectiveness in boosting neuronal differentiation and neuritogenesis.

Photothermal Controlled-Release Immunomodulatory Nanoplatform for Restoring Nerve Structure and Mechanical Nociception in Infectious Diabetic Ulcers.

Infectious diabetic ulcers (IDU) require anti-infection, angiogenesis, and nerve regeneration therapy; however, the latter has received comparatively less research attention than the former two. In particular, there have been few reports on the recovery of mechanical nociception. In this study, a photothermal controlled-release immunomodulatory hydrogel nanoplatform is tailored for the treatment of IDU. Due to a thermal-sensitive interaction between polydopamine-reduced graphene oxide (pGO) and the antibiotic mupirocin, excellent antibacterial efficacy is achieved through customized release kinetics. In addition, Trem2+ macrophages recruited by pGO regulate collagen remodeling and restore skin adnexal structures to alter the fate of scar formation, promote angiogenesis, accompanied by the regeneration of neural networks, which ensures the recovery of mechanical nociception and may prevent the recurrence of IDU at the source. In all, a full-stage strategy from antibacterial, immune regulation, angiogenesis, and neurogenesis to the recovery of mechanical nociception, an indispensable neural function of skin, is introduced to IDU treatment, which opens up an effective and comprehensive therapy for refractory IDU.

Highly self-adhesive, compressible, stretchable, all hydrogel-based supercapacitor for wearable/portable electronics

The increasing popularity of portable/wearable multifunctional electronic devices has highlighted the need for multifunctional power-supply devices. To fulfill this need, we firstly designed a highly self-adhesive and deformable polyacrylamide-based hydrogel electrode. Inspiration by mussels, nanofillers with the design of confined nanospace that formed by the composite of polydopamine-reduced graphene oxide and a compound of cobalt-nickel bimetal oxide and cobalt nitride was involved in the as-prepared hydrogel electrode. This design endows the as-prepared electrode with both the impressive self-adhesive property as well as electrochemical performance. Secondly, a multifunctional all hydrogel-based supercapacitor was assembled by the same as-prepared polyacrylamide hydrogel matrix of electrodes and an electrolyte. The self-adhesive property of both electrode and electrolyte provides a tightly connected interface to ensure structural stability and results in a highly electrical stability during different deformations. Moreover, this multifunctional all hydrogel-based supercapacitor can adhere to the tissue and be used as a functional electronic component as both energy storage and power-supply device. This designed multifunctional supercapacitors can provide insights for further strategies to address energy storage alternatives for portable/wearable electronics.

Electroactive scaffolds of biodegradable polyurethane/polydopamine-functionalized graphene oxide regulating the inflammatory response and revitalizing the axonal growth cone for peripheral nerve regeneration.

Long-gap peripheral nerve injury remains a major challenge in regenerative medicine and results in permanent sensory and motor dysfunction. Nerve guidance scaffolds (NGSs) are known as a promising alternative to autologous nerve grafting. The latter, the current "gold standard" in clinical practice, is frequently constrained by the limited availability of sources and the inevitable damage to the donor area. Given the electrophysiological properties of nerves, electroactive biomaterials are being intensively investigated in nerve tissue engineering. In this study, we engineered a conductive NGS compounded of biodegradable waterborne polyurethane (WPU) and polydopamine-reduced graphene oxide (pGO) for repairing impaired peripheral nerves. The incorporation of pGO at the optimal concentration (3 wt%) promoted in vitro spreading of Schwann cells (SCs) with high expression of the proliferation marker S100 protein. In an in vivo study of sciatic nerve transection injury, WPU/pGO NGSs were found to regulate the immune microenvironment by activating macrophage M2 polarization and upregulate growth-associated protein 43 (GAP43) to facilitate axonal elongation. Histological and motor function analysis demonstrated that WPU/pGO NGSs had a neuroprosthetic effect close to that of an autograft, which significantly promoted the regeneration of myelinated axons, reduced gastrocnemius atrophy, and enhanced hindlimb motor function. These findings together suggested that electroactive WPU/pGO NGSs may represent a safe and effective strategy to manage large nerve defects.

Visible-Light-Driven Antimicrobial Activity and Mechanism of Polydopamine-Reduced Graphene Oxide/BiVO4 Composite.

In this study, a photocatalytic antibacterial composite of polydopamine-reduced graphene oxide (PDA-rGO)/BiVO4 is prepared by a hydrothermal self-polymerization reduction method. Its morphology and physicochemical properties are characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FT-IR), and X-ray diffraction (XRD). The results indicate that BiVO4 particles are evenly distributed on the rGO surface. Escherichia coli (E. coli) MG1655 is selected as the model bacteria, and its antibacterial performance is tested by flat colony counting and the MTT method under light irradiation. PDA-rGO/BiVO4 inhibits the growth of E. coli under both light and dark conditions, and light significantly enhances the bacteriostasis of PDA-rGO/BiVO4. A combination of BiVO4 with PDA-rGO is confirmed by the above characterization methods as improving the photothermal performance under visible light irradiation. The composite possesses enhanced photocatalytic antibacterial activity. Additionally, the photocatalytic antibacterial mechanism is investigated via the morphology changes in the SEM images of MG1655 bacteria, 2′,7′-dichlorofluorescein diacetate (DCFH-DA), the fluorescence detection of the reactive oxygen species (ROS), and gene expression. These results show that PDA-rGO/BiVO4 can produce more ROS and lead to bacterial death. Subsequently, the q-PCR results show that the transmembrane transport of bacteria is blocked and the respiratory chain is inhibited. This study may provide an important strategy for expanding the application of BiVO4 in biomedicine and studying the photocatalytic antibacterial mechanism.

A mechanically robust slippery coating for anti-corrosion, Photothermal deicing, and anti-sticking applications

The preparation of slippery coatings suitable for various environments with good mechanical strength and stability is challenging. Here, we used polydimethylsiloxane (PDMS), epoxy resin (EP), and polydopamine/reduced graphene oxide (PDA/rGO) to prepare mechanically robust slippery coatings with stable water-repellency. Monoglycidyl ether-terminated polydimethylsiloxane and diglycidyl ether-terminated polydimethylsiloxane were covalently grafted into the EP crosslinked skeleton and enriched on the coating surface to form a dense PDMS brushes layer. Since PDMS brushes with high fluidity and low surface energy were firmly grafted onto the EP network, the prepared coating exhibited a sliding angle to water droplets as low as 4° and showed very low sliding angles for different aqueous liquids. The addition of PDA/rGO enhanced the strength of the crosslinked EP network, providing more grafting sites for the PDMS brushes, and effectively reducing phase separation. The wear resistance and corrosion resistance of the coating were also dramatically improved, and the average friction coefficient was only 0.044 during a 5-h tribological test. Furthermore, the slippery coating displayed outstanding photothermal deicing and anti-sticking performances. With its multifunctionality and scalability, the EP/PDMS/rGO coating is promising for practical applications in the field of hydrophobic materials.

Carbon SH-SAW-Based Electronic Nose to Discriminate and Classify Sub-ppm NO2.

In this research, a compact electronic nose (e-nose) based on a shear horizontal surface acoustic wave (SH-SAW) sensor array is proposed for the NO2 detection, classification and discrimination among some of the most relevant surrounding toxic chemicals, such as carbon monoxide (CO), ammonia (NH3), benzene (C6H6) and acetone (C3H6O). Carbon-based nanostructured materials (CBNm), such as mesoporous carbon (MC), reduced graphene oxide (rGO), graphene oxide (GO) and polydopamine/reduced graphene oxide (PDA/rGO) are deposited as a sensitive layer with controlled spray and Langmuir–Blodgett techniques. We show the potential of the mass loading and elastic effects of the CBNm to enhance the detection, the classification and the discrimination of NO2 among different gases by using Machine Learning (ML) techniques (e.g., PCA, LDA and KNN). The small dimensions and low cost make this analytical system a promising candidate for the on-site discrimination of sub-ppm NO2.

Modified graphene oxide nanoplates reinforced 3D printed multifunctional scaffold for bone tissue engineering

Successful regeneration of load-bearing bone defects remains a major challenge in clinical orthopaedics. Designing biologically active 3-dimensional scaffolds possessing physiological responsiveness can potentially overcome current limitations. Here, we have described a novel approach to fabricate scaffolds with modified nanosheets reinforced on mechanically customized thermoplastic polymer-based 3D printed constructs. In this article, we have developed polydopamine-reduced graphene oxide (PD-RGO) reinforced 3D printed PLA scaffold for bone tissue construction. RGO was synthesized by reduction of GO under alkaline conditions using dopamine. 3D printed polylactic acid (PLA) scaffold with defined porosity was doped with PD-RGO. The designed scaffold was studied for its physiochemical properties and human umbilical cord-derived mesenchymal stem cell (hMSC) behaviour within the scaffold. In vitro hMSC studies revealed the influence of fibre direction and nanocoating on directional cell growth and proliferation. The fabricated scaffold showed antioxidant property along with pro-angiogenic and osteoinductive potential. The designed scaffold also successfully prevented the formation of biofilm. In vivo heterotopic implantation of the differentiated hMSC loaded scaffold confirmed the biocompatibility and bio functionality of the scaffold. In summary, the designed nanoplates doped 3D printed scaffold displays stem cell responsive, integrative and pro-regenerative multi functionalities, thereby, exhibiting potential application as bone tissue regeneration treatment alternative.

Endogenous Electric-Field-Coupled Electrospun Short Fiber via Collecting Wound Exudation.

Endogenous electric fields (EF) are the basis of bioelectric signal conduction and the priority signal for damaged tissue regeneration. Tissue exudation directly affects the characteristics of endogenous EF. However, current biomaterials lead to passive repair of defect tissue due to limited management of early wound exudates and inability to actively respond to coupled endogenous EF. Herein, the 3D bionic short-fiber scaffold with the functions of early biofluid collection, response to coupled endogenous EF, is constructed by guiding the short fibers into a 3D network structure and subsequent multifunctional modification. The scaffold exhibits rapid reversible water absorption, reaching maximum after only 30 s. The stable and uniform distribution of polydopamine-reduced graphene oxide endows the scaffold with stable electrical and mechanical performances even after long-term immersion. Due to its unique - bionic structure and tissue affinity, the scaffold further acts as an "electronic skin," which transmits endogenous bioelectricity via absorbing wound exudates, promoting the treatment of diabetic wounds. Furthermore, under the endogenous EF, the cascade release of vascular endothelial growth factor accelerates the healing process. Thus, the versatile scaffold is expected to be an ideal candidate for repairing different defect tissues, especially electrosensitive tissues.

Determination of U(VI) by differential pulse stripping voltammetry using a polydopamine/reduced graphene oxide nanocomposite modified glassy carbon electrode

A novel mercury-free electrochemical sensor for uranium has been fabricated with two-dimensional polydopamine-reduced graphene oxide (PDA-rGO) composites, which is obtained through a simple self-polymerization of dopamine monomers on GO surface. Morphological characterization displayed that PDA was well coated on the rGO and the PDA-rGO composites exhibited a rougher structure. Furthermore, the introduction of PDA greatly increased the amount of functional groups, and PDA-rGO showed significantly enhanced detection activity for uranium. The influence of several experimental parameters such as pH of supporting electrolyte, accumulation time and PDA-rGO amount on the sensitivity of uranium measurement were studied. Under the best conditions, the PDA-rGO electrode could detect U(VI) concentration from 0.1 to 50 μmol L−1 with a detection limit of 0.05 μmol L−1. Besides, the developed sensor exhibited higher selectivity and stability, suggesting that the proposed uranium sensor has broad application prospects in the determination of trace uranium.

Underwater, Multifunctional Superhydrophobic Sensor for Human Motion Detection.

Superhydrophobic conductive materials have received a great amount of interest due to their wide applications in oil-water separation, electrically driven smart surface, electromagnetic shielding, and body motion detection. Herein, a highly conductive superhydrophobic cotton cloth is prepared by a facile method. A layer of polydopamine/reduced graphene oxide (PDA/rGO) was first coated on the cotton fabric, and then copper nanoparticles were in situ grown on the prepared surface. After further modification with stearic acid (STA), the wettability of the cotton surface changed from superhydrophilic to superhydrophobic (water contact angle (WCA) = 153°). The electrical conductivity of the PDA/rGO/Cu/STA cotton is as high as 6769 S·m-1, while the stearic acid effectively protects Cu NPs from oxidation. As a result, the superhydrophobic PDA/rGO/Cu/STA cotton has shown excellent electrical stability and can be used in detecting human motions in both ambient and underwater conditions. The sensor can recognize human motion from air into water and other underwater activities (e.g., underwater bending, stretching, and ultrasound). This multifunctional cotton device can be used as an ideal sensor for underwater intelligent devices and provides a basis for further research.

Robust magnetic and electromagnetic wave absorption performance of reduced graphene oxide loaded magnetic metal nanoparticle composites

With the increasing demand for microwave absorbing materials, to develop a microwave absorber with a simple synthesis process is of great significance to the field of protection. Herein we have successfully loaded iron-cobalt-nickel oxide (FeCoNiOx) onto the as-prepared polydopamine-reduced graphene oxide (PDA-rGO) through a two-step process. The preparation method has mild reaction conditions without high temperature and pressure compared with the traditional method, which is conducive to large-scale production. Based on effectively combining dielectric loss and magnetic loss mechanism, the obtained material possesses excellent electromagnetic waves absorbing performance with the minimum RL value of −36.28 dB. The results proved that the composites can be endowed with various microwave absorption effects by the adjustion of different component ratios. In addition, the microwave absorption mechanism was dicussed in detail, and we believe that the results of our research have certain guiding significance for preparation of efficient microwave absorbers.

Thermal properties and shape stabilization of epoxidized methoxy polyethylene glycol composite PCMs tailored by polydopamine-functionalized graphene oxide

A series of composite phase change materials (cPCMs) are fabricated through the one-pot method with the epoxidized methoxy polyethylene glycol (EmPEG) as the thermal energy unit and polydopamine-reduced graphene oxide (PDA-rGO) nanosheets as the interfacial enhancement. Structure and thermal properties such as phase change enthalpy, thermal repeatability, and light-to-thermal conversion capacity of EmPEG/PDA-rGO cPCMs with PDA-rGO content varying from 0.5 to 4 wt% have been detailed discussed. A superior stabilization performance of EmPEG/PDA-rGO cPCMs to pristine EmPEG is demonstrated based on the interfacial action from the incorporated PDA-rGO nanosheets. EmPEG/PDA-rGO-3 presents good structure-stabilized behavior after 100 heating-cooling cycles, and no liquid leakage appears up to 105 °C. In the meantime, EmPEG/PDA-rGO-3 illustrates a stable thermal reliability and thermal charging/discharging rate, and the light-to-thermal conversion efficiency reaches 96% under the 100 mW/cm2 irradiation. Thus, the structure-stabilized EmPEG/PDA-rGO cPCMs tuned by the interfacial interaction demonstrates the promising application in the field of the thermal energy storage and solar energy conversion.

Enhanced electricity generation and extracellular electron transfer by polydopamine–reduced graphene oxide (PDA–rGO) modification for high-performance anode in microbial fuel cell

Anode performance is a key factor for power output and long-term stability of microbial fuel cells (MFCs). This is because it considerably influences biofilm growth and extracellular electron transfer (EET). In this study, carbon cloth (CC) was used as the anode substrate, and a hydrophilic, biocompatible, and highly conductive CC–PDA–rGO anode was synthesized by surface modification with polydopamine (PDA) and reduced graphene oxide (rGO) using an easy and facile solvent immersion method. The power density of the MFC with CC–PDA–rGO anode reached 2047 mW·m−2, which was 6.1, 2.2, and 1.9 times greater than those of the CC, CC–PDA, and CC–rGO, respectively. The charge transfer resistance of the MFC prepared with the CC–PDA–rGO anode was ten-fold lower than that of the CC anode. Moreover, the EET was remarkably enhanced on the CC–PDA–rGO anode, and the electroactive biofilm of CC–PDA–rGO anode exhibited the highest cell viability. The CC–PDA–rGO anode achieved the highest cumulative total charge, which suggested that it had the best electron harvesting capacity. The foregoing can be attributed to the introduction of PDA and rGO onto the electrode surface. The PDA possesses superior hydrophilicity and excellent adhesive force for strong interaction with biofilm, whereas the rGO provides abundant electrochemically active sites to facilitate electron transfer from the biofilm to the anode. This work provides an easy and facile surface modification method for the development of high-performance MFC anode materials.

Binding Fe2O3 nanoparticles in polydopamine-reduced graphene as negative electrode materials for high-performance asymmetric supercapacitors

Ternary composite with immobilization of Fe2O3 nanoparticles (NPs) onto porous polydopamine-reduced graphene oxide framework, abbreviated as Fe2O3@PDA-RGO, was fabricated via a simple, scalable and cost-efficient hydrothermal reaction. The as-prepared 3D Fe2O3@PDA-RGO nanocomposite provides a specific surface area of 119.9 m2 g-1 on account of the well-dispersed Fe2O3 NPs (~35 nm) onto the PDA-RGO sheets as spacer. When applied as a special faradic electrode material in negative potential region, Fe2O3@PDA-RGO can offer 169 mA h g-1 (609 F g−1) at 1 A g-1. The fabricated AC//Fe2O3@PDA-RGO asymmetric supercapacitor (ASC) delivers an energy density of 35.8 W h kg-1 (0.94 mW h cm-3) at 800 W kg-1 (21 mW cm-3) and an outstanding cyclic stability (75.7% capacity retention after 10,000 cycles). The good performance of Fe2O3@PDA-RGO in single-electrode and ASC manifests the potential the ternary composite in energy storage devices.

Elucidating the Chemistry behind the Reduction of Graphene Oxide Using a Green Approach with Polydopamine.

A new approach using X-ray photoelectron spectroscopy (XPS) was employed to give insight into the reduction of graphene oxide (GO) using a green approach with polydopamine (PDA). In this approach, the number of carbon atoms bonded to OH and to nitrogen in PDA is considered and compared to the total intensity of the signal resulting from OH groups in polydopamine-reduced graphene oxide (PDA-GO) to show the reduction. For this purpose, GO and PDA-GO with different times of reduction were prepared and characterized by Raman Spectroscopy and XPS. The PDA layer was removed to prepare reduced graphene oxide (RGO) and the effect of all chemical treatments on the thermal and electrical properties of the materials was studied. The results show that the complete reduction of the OH groups in GO occurred after 180 min of reaction. It was also concluded that Raman spectroscopy is not well suited to determine if the reduction and restoration of the sp2 structure occurred. Moreover, a significant change in the thermal stability was not observed with the chemical treatments. Finally, the electrical powder conductivity decreased after reduction with PDA, increasing again after its removal.