GO-based Materials Research Articles

Graphene oxide with different oxygen content produced from natural and synthetic graphite sources for methylene blue sorption

Graphene oxide (GO) is of great interest due to its unique structure and properties and potential applications, including water purification. In this work, we report the synthesis of GO samples with different oxidation degree from two different sources of graphite using Hummers method. Natural flake graphite with a high degree of crystallinity, and synthetic fine powder graphite were used. All produced materials were characterized by CHNS analysis, X-Ray Diffractive analysis (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It was shown that the oxidation process for natural and synthetic graphite sources proceeds in different ways. The factors, affecting for the structure and properties of GO are the degree of crystallinity and the lateral size of the graphite flakes. The sorption activity of underoxidized, normally oxidized and overoxidized GO was compared toward the methylene blue (MB) dye in aqueous solution. The most efficient sorption was registered for GO produced from synthetic graphite with the use of 2.0 and 4.5 wt. eq. KMnO4. The sorbents removed 94 % and 100 % of MB from the solution, respectively, in approximately 10 min. Our results reveal that the structure and sorption properties of GO can be tuned by varying the oxidation degree as well as the graphite source, which may open the way to new developments in the GO-based materials applications.

Mechanically flexible graphene oxide network for highly-sensitive and ultra-long fire warning

Graphene oxide (GO)-based intelligent fire alarm sensor (FAS) has recently been a sought-after research topic in fire prevention fields. However, it remains a challenge to facilely construct GO-based composite that simultaneously possess mechanical flexibility, excellent flame resistance, highly-sensitive temperature-responsive behavior, rapid fire response and ultra-long fire alarming durability. Here, a nacre-like ternary hybrid paper is conveniently obtained by integrating GO with hexachlorophosphazene-based multi‑hydroxyl molecule (HHACP) and tannic acid (TA) via a facile and eco-friendly water evaporation-induced self-assembly method. The resultant composite paper (TA-GO/HHACP) exhibits mechanically flexible property with tensile strength of 103.7 MPa and toughness of 1.51 MJ/m3, comparable to 2.52 and 5.39 times higher than those of pure GO paper. Further, the TA-GO/HHACP paper displays excellent nonflammability and high-temperature resistance that can withstand continuous butane flame attack (∼ 1200 °C), resulting in ultra-long sustained alarming period of > 1600 s under an open fire. More importantly, benefiting from its rapid electrical resistance reduction capability, such TA-GO/HHACP paper demonstrates ultra-fast fire-triggered response time of ∼ 0.6 s, and ultra-sensitive early fire alarm responses to abnormal high temperatures during pre-combustion process, e.g., ∼ 1 s at 250 °C and ∼ 19 s at 200 °C, respectively, outperforming the best reported GO‑based FAS counterparts. This work provides an inventive paradigm to develop high-performance GO-based intelligent materials with reliable and sensitive early fire-warning function.

Recent Progress Using Graphene Oxide and Its Composites for Supercapacitor Applications: A Review

Supercapacitors are prospective energy storage devices for electronic devices due to their high power density, rapid charging and discharging, and extended cycle life. Materials with limited conductivity could have low charge-transfer ions, low rate capability, and low cycle stability, resulting in poor electrochemical performance. Enhancement of the device’s functionality can be achieved by controlling and designing the electrode materials. Graphene oxide (GO) has emerged as a promising material for the fabrication of supercapacitor devices on account of its remarkable physiochemical characteristics. The mechanical strength, surface area, and conductivity of GO are all quite excellent. These characteristics make it a promising material for use as electrodes, as they allow for the rapid storage and release of charges. To enhance the overall electrochemical performance, including conductivity, specific capacitance (Cs), cyclic stability, and capacitance retention, researchers concentrated their efforts on composite materials containing GO. Therefore, this review discusses the structural, morphological, and surface area characteristics of GO in composites with metal oxides, metal sulfides, metal chalcogenides, layered double hydroxides, metal–organic frameworks, and MXene for supercapacitor application. Furthermore, the organic and bacterial functionalization of GO is discussed. The electrochemical properties of GO and its composite structures are discussed according to the performance of three- and two-electrode systems. Finally, this review compares the performance of several composite types of GO to identify which is ideal. The development of these composite devices holds potential for use in energy storage applications. Because GO-modified materials embrace both electric double-layer capacitive and pseudocapacitive mechanisms, they often perform better than pristine by offering increased surface area, conductivity, and high rate capability. Additionally, the density functional theory (DFT) of GO-based electrode materials with geometrical structures and their characteristics for supercapacitors are addressed.

Integration of a Bismuth-Based Tris-Mononuclear Complex with 2D Functional Materials for Highly Efficient and Durable Aqueous Electrocatalytic Hydrogen Evolution.

The eminence of transitioning from traditional fossil fuel-based energy resources to renewable and sustainable energy sources is most evidently crucial. The potential of hydrogen as an alternative energy source has specifically focuses the electrocatalytic water splitting (EWS) as a promising technique for generating hydrogen. Development of efficient electrocatalysts to facilitate the EWS process while rationalizing the limitations of noble metal catalysts like platinum has become one of the daunting tasks. Consequently, porous functional materials such as metal complexes (MCs) and graphene oxide (GO) can act as potential catalysts for EWS. Therefore, a composite of GO and a mononuclear bismuth metal complex is synthesized through in situ facile synthesis, which is further utilized as an efficient electrocatalyst for the hydrogen evolution reaction (HER). Several potential electrocatalytic MC@GO composite (BMGO-3,5,7) materials were prepared with compositional variation of GO (3, 5, and 7 wt %). The experimental results demonstrate that the BMGO5 composite exhibits excellent HER activity with a low overpotential value of 105 mV at 10 mA cm-2 and a low Tafel slope of 44 mV dec-1 in 1 M KOH solution. Furthermore, a comprehensive investigation on the potentiality of the BMC-GO composite for hydrogen evolution from river water splitting was performed in order to address the issue of freshwater depletion. Inclusion of a mononuclear MC for facile synthesis of functional GO-based efficient electrocatalyst material is very scanty in the literature. This unique approach could assist future research endeavors toward designing efficient electrocatalysts for sustainable renewable energy generation. This is one of the first of its kind, where mononuclear MCs were utilized to develop GO-based functional composite materials for efficient electrocatalysis toward sustainable renewable energy generation.

Theoretical and Experimental Analysis of Hydroxyl and Epoxy Group Effects on Graphene Oxide Properties.

In this study, we analyzed the impact of hydroxyl and epoxy groups on the properties of graphene oxide (GO) for the adsorption of methylene blue (MB) dye from water, addressing the urgent need for effective water purification methods due to industrial pollution. Employing a dual approach, we integrated experimental techniques with theoretical modeling via density functional theory (DFT) to examine the atomic structure of GO and its adsorption capabilities. The methodology encompasses a series of experiments to evaluate the performance of GO in MB dye adsorption under different conditions, including differences in pH, dye concentration, reaction temperature, and contact time, providing a comprehensive view of its effectiveness. Theoretical DFT calculations provide insights into how hydroxyl and epoxy modifications alter the electronic properties of GO, improving adsorption efficiency. The results demonstrate a significant improvement in the dye adsorption capacity of GO, attributed to the interaction between the functional groups and MB molecules. This study not only confirms the potential of GO as a superior adsorbent for water treatment, but also contributes to the optimization of GO-based materials for environmental remediation, highlighting the synergy between experimental observations and theoretical predictions in advances in materials science to improve sustainability.

Aggregation of graphene oxide upon the stripping of oxidized debris: An experimental and molecular dynamics simulation study

The most recent structural study of graphene oxide (GO) indicates that the oxidized debris (ODs) adhered to as-prepared GO will strip in certain aquatic settings. The impact of ODs stripping on the characteristics of GO has been widely reported, but its effects on GO aggregation have received less attention. Here, the influence of OD stripping on the GO aggregation property was identified, and the aggregation of as-prepared GO and GO upon OD stripping was compared. Upon ODs stripping, the pKa values of GO shifted from 3.91, 6.25, and 9.84 to 4.54, 6.65, and 10.21, respectively. Further analysis indicated the removal of ODs reduced the net negative charge and improved the hydrophobicity of GO, hence promoting the aggregation of GO. The acceleration of GO-Ca2+-OD aggregate formation was facilitated by the collective effects of ODs stripping, functional group deprotonation, double layer compression, OD bridging, and charge neutralization. The metal ions and stripped ODs attach to GO edges and link GO, which perform like bridges and contribute to further aggregation. In general, the existence of ODs adds complexity to the constructions and characteristics of GO, and it is important to take this into account while evaluating the aggregation characteristic of GO-based materials.

Identifying the Stripping of Oxide Debris from Graphene Oxide: Evidence from Experimental Analysis and Molecular Simulation.

In this study, characteristics of oxidation debris (OD) and its stripping mechanism from graphene oxide (GO) were explored. The results demonstrated that OD contains three components, namely, protein-, fulvic acid-, and humic acid-like substances; among these, protein-like substances with lower molecular weight and higher hydrophilicity were most liable to be stripped from GO and were the primary components stripped from GO at pH < 10, whereas humic acid- and fulvic acid-like substances were stripped from GO at pH > 10. During the stripping of OD, hydrogen bonds from carboxyl and carbonyl were the first to break, followed by hydrogen bonds from epoxy. Subsequently, π-π interactions were broken, and hydrogen bond interactions induced by hydroxyl groups were the hardest to break. After the stripping of OD, the recombination of OD on GO was observed, and regions containing relatively fewer oxygen-containing functional groups were favorable binding sites for the readsorbed OD. The stripping and recombination of OD on GO resulted in an uneven GO surface, which should be considered during the development of GO-based environmental materials and the evaluation of their environmental behavior.

Magnetic field-responsive graphene oxide photonic liquids.

Modifying the environment around particles (e.g., introducing a secondary phase or external field) can affect the way they interact and assemble, thereby giving control over the physical properties of a dynamic system. Here, graphene oxide (GO) photonic liquids that respond to a magnetic field are demonstrated for the first time. Magnetic nanoparticles are used to provide a continuous magnetizable liquid environment around the GO liquid crystalline domains. In response to a magnetic field, the alignment of magnetic nanoparticles, coupled with the diamagnetic property of GO nanosheets, drives the reorientation and alignment of the nanosheets, enabling switchable photonic properties using a permanent magnet. This phenomenon is anticipated to be extendable to other relevant photonic systems of shape-anisotropic nanoparticles and may open up opportunities for developing GO-based optical materials and devices.

Separation of the heme protein cytochrome C using a 3D structured graphene oxide bionanocomposite as an adsorbent.

Proteins are of great importance for medicine and the pharmaceutical and food industries. However, proteins need to be purified prior to their application. This work investigated the application of a hydrogel bionanocomposite based on agar and graphene oxide (GO) for capturing cytochrome C (Cyto C) heme protein by adsorption from aqueous solutions with other proteins. Although applications of GO-based materials in adsorption are widely studied, the focus on semi-continuous processes remains limited. Adsorption experiments were carried out in batch and fixed bed columns. The effect of pH and ionic strength on adsorption was investigated, and there is evidence that electrostatic interactions between Cyto C and the nanocomposite were favoured at pH = 7; the adsorption capacity decreased as NaCl and KCl concentrations increased, ascribed to the weak electrostatic interaction between the protein and GO active sites in the bionanocomposite. All adsorption isotherm models (Langmuir, Freundlich, Sips) used gave suitable adjustments to the equilibrium experimental data and the kinetic models applied. The maximum adsorption capacity predicted by the Langmuir isotherm was ∼400 mgCytoC gadsorbent,dry-1, and the adsorption thermodynamics indicated a physisorption process. Tests were performed to evaluate the co-adsorption in batch, and the composite was effective in adsorbing Cyto C in solution with bovine serum albumin (BSA) and L-phenylalanine. Fixed bed tests were performed, and although protein adsorption onto nanoparticles can be challenging, the Cyto C adsorbed could be successfully recovered after desorption. Overall, the GO-based hydrogel was an effective method for cytochrome C adsorption, exhibiting a notorious potential for applications in protein separation processes.

Dual nitrogen-sulfur-doping induce microwave absorption and EMI shielding in nanocomposites based on graphene

Graphene-oxide (GO) is one of the most commonly used carbon nanomaterials in advanced applications such as microwave absorption and EMI shielding, due to various advantages such as ease of synthesis and exfoliation, effective doping capability, and superior composite compatibility. In this study, we used the modified Hummer’s method to synthesize GO by exfoliating graphite powder, and a simple hydrothermal approach was employed for elemental doping and GO reduction. As nitrogen–sulfur (N, S) dual-doping precursors, thiourea and l-cysteine amino acids were utilized. The structural features and microporous network structure of GO aerogel foams were investigated. The microwave absorption capabilities of polyethersulfone-based nanocomposite films incorporating the as-produced nitrogen–sulfur enrich reduced GO (NS-rGO) are also explored. According to the physicochemical characterization, the existence of remarkable structural defects with a porous three-dimensional (3D) network was discovered due to heteroatom insertion and hydrothermal doping. Additionally, the dual-doped sample exhibited high Nitrogen and sulfur content of 8.93% and 13.19%, respectively. While NS-rGO possesses a higher conductivity of 174.7[Formula: see text][Formula: see text]S compared to 12.65[Formula: see text][Formula: see text]S for GO. The nanocomposites filled with NS-rGO foams demonstrated a high shielding efficiency (SE) of 45[Formula: see text]dB in the X-band with a filler loading of 0.5[Formula: see text]wt.%. This high SE arises from dopant heteroatoms and the heterogeneous interface, which induce interface polarization, thereby increasing microwave absorption and dielectric constant. It also results from multi-level reflections caused by the 3D porous structures. These findings offer valuable insights into the functionalization of carbon nanostructures and the development of 3D networks in GO-based functional materials, providing further guidance for engineering high-performance electromagnetic interference shielding materials.

Dielectric performance of aluminum cation modified graphene oxide membrane: Influence of Al source

This study demonstrates a facile and effective strategy for modifying the dielectric properties of graphene oxide membranes for applications in advanced energy storage devices. The high dielectric constant and low dielectric loss of graphene oxide (GO) make GO-based materials good dielectric separators for developing thin and flexible devices. Controllable tailoring of the dielectric properties of GO membranes is crucial to advance its applications as a dielectric material. Metal cation modification represents one tailoring strategy, but the effects of cation modification are difficult to compare due to its dependence on the metal cation source and the specific physicochemical conditions. In this study, we explore the dielectric properties of GO membranes modified by the introduction of Al3+ from different chemical sources. The dielectric constant and dielectric loss of an unmodified GO membrane and three Al3+ modified GO (AGO) membranes were measured in the frequency range from 1 Hz to 106 Hz, and the performance of a dielectric capacitor fabricated by sandwiching the GO (AGO) membrane between carbon paper electrodes was evaluated by cyclic voltammetry. Results demonstrate that the three different sources of Al3+ differently impact the dielectric properties of GO membranes and thus the performance of as-fabricated dielectric capacitors. Our results advance the fundamental understanding of how metal cation modification impacts the dielectric properties of GO membranes and demonstrate the possibility of designing membranes with controllable dielectric performance.

The "How" and "Where" behind the Functionalization of Graphene Oxide by Thiol-ene "Click" Chemistry.

Graphene oxide (GO) is a 2D nanomaterial with unique chemistry due to the combination of sp2 hybridization and oxygen functional groups (OFGs) even in single layer. OFGs play a fundamental role in the chemical functionalization of GO to produce GO-based materials for diverse applications. However, traditional strategies that employ epoxides, alcohols, and carboxylic acids suffer of low control and undesirable side reactions, including by-product formation and GO reduction. Thiol-ene "click" reaction offers a promising and versatile chemical approach for the alkene functionalization (-C=C-) of GO, providing orthogonality, stereoselectivity, regioselectivity, and high yields while reducing by-products. This review examines the chemical functionalization of GO via thiol-ene "click" reactions, providing insights into the underlying reaction mechanisms, including the role of radical or base catalysts in triggering the reaction. We discuss the "how" and "where" the reaction takes place on GO, the strategies to avoid unwanted side reactions, such as GO reduction and by-product formation. We anticipate that multi-functionalization of GO via the alkene groups will enhance GO physicochemical properties while preserving its intrinsic chemistry.

Effect of molecular structure on the adsorption behavior of sulfanilamide antibiotics on crumpled graphene balls

Since the 1930s, sulfonamide(SA)-based antibiotics have served as important pharmaceuticals, but their widespread detection in water systems threatens aquatic organisms and human health. Adsorption via graphene, its modified form (graphene oxide, GO), and related nanocomposites is a promising method to remove SAs, owing to the strong and selective surface affinity of graphene/GO with aromatic compounds. However, a deeper understanding of the mechanisms of interaction between the chemical structure of SAs and the GO surface is required to predict the performance of GO-based nanostructured materials to adsorb the individual chemicals making up this large class of pharmaceuticals. In this research, we studied the adsorptive performance of 3D crumpled graphene balls (CGBs) to remove 10 SAs and 13 structural analogs from water. The maximum adsorption capacity qm of SAs on CGB increased with the number of (1) aromatic rings; (2) electron-donating functional groups; (3) hydrogen bonding acceptor sites. Furthermore, the CGB surface displayed a preference for homocyclic relative to heterocyclic aromatic structures. A leading mechanism, π-π electron-donor-acceptor interaction, combined with hydrogen bonding, explains these trends. We developed a multiple linear regression model capable of predicting the qm as a function of SA chemical structure and properties and the oxidation level of CGB. The model predicted the adsorptive behaviors of SAs well with the exception of a chlorinated/fluorinated SA. The insights afforded by these experiments and modeling will aid in tailoring graphene-based adsorbents to remove micropollutants from water and reduce the growing public health threats associated with antibiotic resistance and endocrine-disrupting chemicals.

Modification of Footwear PVC Outsoles into Graphene Oxide-Based PVC (PVC/GO) Soling Composites for the Enhancement of Better Physical Properties

Outsole is a crucial component of a shoe’s bottom that directly contacts the ground. Comfort and durability are the most expected characteristics of outsoles. Various nanocomposites are utilized to increase the thermal stability, light weightiness, microporosity, and durability of polymeric materials. In this research, PVC soling composites were prepared using synthesized graphene oxide (GO) from a modified Hummer method. The goal is to improve physical properties like thermal stability or durability, lightweight, tensile strength, and hardness. The GO content in developed soling composites ranged from 0.1% to 0.4% by the colloidal blending method. FTIR, TGA, XRD, and SEM characterized GO and GO/PVC soling composites. The presence of the functional groups C=C, C-O-C, -C=O, and -OH was confirmed by the FTIR spectra of GO, while oxygen-holding functional groups to the layered structure caused the separation of the interlayer space to grow from 0.34 nm to 0.86 nm, according to GO XRD data. XRD results revealed that the GO layers were uniformly distributed in the polymeric matrix of composites. TGA results exhibited that the percentage of mass loss for GO was 81.96% at 800 °C and for soling composites it decreased continuously with an increase in the content of GO, respectively. SEM analysis revealed that the composites with GO showed a homogeneous composite with significantly porous surface morphology. Proportional improvement of tensile strength and hardness for GO-based soling materials were in an increased proportion and density were in a decreased proportion, making the outsole lightweight and durable. Finally, the results suggest that GO/PVC soling composites can improve the durability, mechanical and thermal stability, light weightiness, and microporosity of PVC soles, while the best performance was found for PVC/GO-0.4% soling composites.

Analysis of Cellular Damage Resulting from Exposure of Bacteria to Graphene Oxide and Hybrids Using Fourier Transform Infrared Spectroscopy.

With the increase in antimicrobial resistance, there is an urgent need to find new antimicrobials. Four particulate antimicrobial compounds, graphite (G), graphene oxide (GO), silver-graphene oxide (Ag-GO) and zinc oxide-graphene oxide (ZnO-GO) were tested against Enterococcus faecium, Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. The antimicrobial effects on the cellular ultrastructure were determined using Fourier transform infrared spectroscopy (FTIR), and selected FTIR spectral metrics correlated with cell damage and death arising from exposure to the GO hybrids. Ag-GO caused the most severe damage to the cellular ultrastructure, whilst GO caused intermediate damage. Graphite exposure caused unexpectedly high levels of damage to E. coli, whereas ZnO-GO exposure led to relatively low levels of damage. The Gram-negative bacteria demonstrated a stronger correlation between FTIR metrics, indicated by the perturbation index and the minimal bactericidal concentration (MBC). The blue shift of the combined ester carbonyl and amide I band was stronger for the Gram-negative varieties. FTIR metrics tended to provide a better assessment of cell damage based on correlation with cellular imaging and indicated that damage to the lipopolysaccharide, peptidoglycan and phospholipid bilayers had occurred. Further investigations into the cell damage caused by the GO-based materials will allow the development of this type of carbon-based multimode antimicrobials.

Anti-fouling mechanism of ultrafiltration membranes modified by graphene oxide with different charged groups under simulated seawater conditions

There are positively charged Ca2+ and Mg2+, negatively charged colloids and lots of bacteria in seawater. The different surface potentials of ultrafiltration membranes may lead to different adsorption properties for contaminants in seawater when ultrafiltration membranes were applied to the pretreatment of Reverse Osmosis process. Herein, this work prepared modified ultrafiltration membranes with different surface potentials using three GO-based materials, and investigated the anti-fouling of Ca2+, Mg2+, humic acid, the anti-bacterial adhesion performance and mechanisms of modified ultrafiltration membranes under simulated seawater conditions. Results showed that the modified membranes exhibited enhanced hydrophilicity, anti-fouling performance, antibacterial property and permeability compared with the unmodified polyvinylidene fluoride membrane. Conspicuously, with the highest surface potential among all membranes, quaternized graphene oxide modified ultrafiltration membrane (QGO-M) presented the best anti-fouling property to Ca2+, Mg2+, humic acid and antibacterial property. In particular, the flux recovery rate against the simulated seawater solution containing humic acid and the surface bacteriostatic rate against salt-tolerant bacteria of QGO-M were 95.7% and 97.9%, respectively. The results can provide an important reference for the investigation of modified ultrafiltration membranes suitable for seawater filtration.

Compositing graphene oxide with carbon fibers enables improved dynamical thermomechanical behavior of papers produced at a large scale

This article discusses the morphology and thermomechanical properties of graphene oxide (GO) paper sheets and GO paper composites reinforced with carbon fibers. GO paper was fabricated using GO paste obtained by the condensation of GO aqueous solution synthesized using the Hummers' method. Carbon fibers were implemented to improve the mechanical properties of the pristine GO paper. All the investigated papers were subjected to thermal treatment to check thermo-related morphological and mechanical properties. The results presented in this study allowed for the deeper insight into morphological, structural, and mechanical volume and surface-related properties of pristine GO and GO-based composite materials reinforced with carbon fibers. We showed that there are two important factors that should be taken into consideration for the design and fabrication of GO-based papers. These factors were the concentration of the reinforcing agent and the thermal reduction of the papers. Both factors have influenced the final properties of the resulting GO-based papers. For the first time, it was revealed how the addition of the reinforcing material affects the GO paper thermal expansion coefficient.

A Novel Approach to Water Softening Based on Graphene Oxide-Activated Open Cell Foams

This work focuses on exploring a new configuration for the reduction of water hardness based on the surface modification of polyurethane (PU) open cell foams by the deposition of thin graphene oxide (GO) washcoat layers. GO was deposited by the dip–squeeze coating procedure and consolidated by thermal treatment. The final washcoat load was controlled by performing consecutive depositions, after three of which, a GO inventory up to 27 wt% was obtained onto PU foams of 60 pores per inch (PPI). The GO-coated PU foams were assembled into a filter, and the performance of the system was tested by continuously feeding water with hardness in the 190–270 mgCa2+,eq·L−1 range. Remarkable results were demonstrated in terms of total adsorbing capacity, which was evaluated by measuring the outlet total hardness by titration and exhibited values up to 63 mgCa2+,eq·gGO−1 at a specific filtered water volume of 650 mLH2O·gGO−1, outperforming the actual state-of-the-art adsorbing capacity of similar GO-based materials.

Ion-Mediated Self-Assembly of Graphene Oxide and Functionalized Perylene Diimides into Hybrid Materials with Photocatalytic Properties

A novel ion-mediated self-assembly method was applied for integration of graphene oxide (GO), propanoic- and glutaric-substituted perylenes (glu-PDI and PA-PDI), and Zn (OAc)2 into new hybrid materials with photocatalytic properties. The structuring of chromophores through coordination bonding on the GO surface is controlled by the chemistry of the PDI linkers. Four-substituted glu-PDI forms consolidated microporous particles, whereas di-substituted PA-PDI binds with GO into a macroporous gel-like structure. The GO/PDI controls without Zn2+ ions form only non-integrated dispersions. Both hybrids can initiate photodestruction of 1,5-dihydroxynaphtalene (DHN) due to the effective charge separation between the PDI components and GO by generating hydroxyl radicals determined by luminescent probing with terephthalic acid. The reduction mechanism of photodegradation was confirmed by MALDI-TOF spectroscopy. The structure of the hybrids controls the rate of photodegradation process. The glu-PDI-based photocatalyst shows a smaller rate of photoreduction of 3.3 × 10−2 min−1 than that with PA-PDA (4 × 10−2 min−1) due to diffusion limitations. Our results suggest that the ion-mediated synthesis is a useful and rational alternative for the conventional synthesis of GO-based functional hybrid materials through aromatic stacking between the graphene oxide and organic chromophores to produce new affordable and efficient photocatalysts.

Cu/graphene oxide composited coatings for preventing clinical implant bacterial infections: an antibacterial mechanism study

Recently, graphene oxide (GO) based materials have shown great potential in the treatment of implant bacterial infections due to its inherent antibacterial activity. However, the effect of GO-based materials on biological systems particularly the antibacterial mechanisms is still not clear. In this study, GO, NaBH4 treated GO (GO-Y), copper decorated GO (GO-Cu, GO-Cu-GO) composited coatings were prepared on the surface of silicon dioxide (SiO2) substrate by spin-coating and chemical in-situ formation. The growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) on GO-Y, GO-Cu, and GO-Cu-GO were significantly inhibited, especially on GO-Cu and GO-Cu-GO coatings. The implied antibacterial mechanism of GO-Cu-Cu coatings was further studied and discussed. The enhanced antibacterial performance of GO-Cu-GO coatings has significant potential application in preventing clinical implant bacterial infections. Moreover, the systematic study of various antibacterial effects also enriches our knowledge of the possible antibacterial mechanisms of graphene-based materials.