XPS study of graphene oxide reduction induced by (100) and (111)-oriented Si substrates

Microstructural characterization, mechanical and microbiological properties of acrylic resins added with reduced graphene oxide

To evaluate the microstructural characterization, mechanical properties and antimicrobial activity of acrylic resins incorporated with different concentrations of reduced graphene oxide (rGO). Specimens were made of self-cured and heat-cured acrylic resins for the control group and concentrations of 0.5%, 1%, and 3%. The microstructural characterization was evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDS). For mechanical testing, flexural strength, and Knoop hardness tests were performed. Microbiological evaluations were performed by colony forming units (CFU) analysis, tetrazolium salt reduction (XTT), and SEM images. The modified acrylic resins showed increased mechanical properties at low concentrations (p < 0.05) and with reduced S. mutans (p < 0.05). Reduced graphene oxide interfered with the mechanical performance and microbiological properties of acrylic resins depending on the concentration of rGO, and type of polymerization and microorganism evaluated. The incorporation of graphene compounds into acrylic resins is an alternative to improve the antimicrobial efficacy and performance of the material.

CaO assisted mechanochemical remediation of lindane-contaminated soil

In this study, the planetary ball milling with CaO addition was used to remediate lindane-contaminated soil. Based on Hertzian theory, a mathematical model was proposed to simulate the trajectory of grinding ball and the local energy transfer during a planetary operation at the disk rotation velocities of 150-250 rpm. Besides, the influence of different parameters on lindane removal in soil was investigated, whose results showed that disk rotation velocity and reagent-to-soil ratio had a positive effect, while soil moisture, initial concentration of lindane, and mass of polluted soil demonstrated a negative influence. The mechanochemical method exhibited a higher degradation performance at 3 wt% CaO addition, and a disk rotation velocity of 250 rpm. Active species generated by ball collisions in the presence of CaO, especially superoxide (·O2-) demonstrated a significant role in participating in the lindane conversion. In combination with GCMS and XPS analysis, the proposed model provides insight into mechanochemical remediation process from physical and chemical perspectives, which mainly includes four main steps: mixing, inducing, chemical reaction, and structure destruction.

Clinical potential of plasma-functionalized graphene oxide ultrathin sheets for bone and blood vessel regeneration: Insights from cellular and animal models

Graphene and graphene oxide (GO), due to their unique chemical and physical properties, possess biochemical characteristics that can trigger intercellular signals promoting tissue regeneration. Clinical applications of thin GO-derived sheets have inspired the development of various tissue regeneration and repair approaches. In this study, we demonstrate that ultrathin sheets of plasma-functionalized and reduced GO, with the oxygen content ranging from 3.2 % to 22 % and the nitrogen content from 0 % to 8.3 %, retain their essential mechanical and molecular integrity, and exhibit robust potential for regenerating bone tissue and blood vessels across multiple cellular and animal models. Initially, we observed the growth of blood vessels and bone tissue in vitro using these functionalized GO sheets on human adipose-derived mesenchymal stem cells and umbilical vein endothelial cells. Remarkably, our study indicates a 2.5-fold increase in mineralization and two-fold increase in tubule formation even in media lacking osteogenic and angiogenic supplements. Subsequently, we observed the initiation, conduction, and formation of bone and blood vessels in a rat tibial osteotomy model, evident from a marked 4-fold increase in the volume of low radio-opacity bone tissue and a significant elevation in connectivity density, all without the use of stem cells or growth factors. Finally, we validated these findings in a mouse critical-size calvarial defect model (33 % higher healing rate) and a rat skin lesion model (up to 2.5-fold increase in the number of blood vessels, and 35 % increase in blood vessels diameter). This study elucidates the pro-osteogenic and pro-angiogenic properties of both pristine and plasma-treated GO ultrathin films. These properties suggest their significant potential for clinical applications, and as valuable biomaterials for investigating fundamental aspects of bone and blood vessel regeneration.

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.

Effect of successive recycling and reuse of acid liquor for the synthesis of graphene oxides with higher oxygen-to-carbon ratios

Graphene has recently drawn exponential attention due to its surprising physicochemical properties and diversified field of applications. Although graphene oxides (GOs), itself is an exclusive material, it is also an intermediate product for the production of reduced graphene oxides (rGOs), graphene and their derivatives, which are other more superficial materials. In this study, GOs with higher oxygen to carbon ratios were synthesized following the Tour method, where the excess feed acid liquor (FAL) of mixed concentrated sulfuric and orthophosphoric acids at a ratio of 90:10 was recovered from the reaction slurries by applying the centrifugation technique. About 80-90 % of the FAL was recycled and reused as feed for the subsequent batches. The changes in the properties of FAL for the five consecutive recycling and reuse were studied. The properties of recycled FALs were investigated by measuring density, moisture content, pH, and ion concentration. The consecutive recycling of FALs tends to increase the moisture content about 0.5% in each recycles. Ion-chromatography (IC) was used to measure the variation in SO42- and PO43- ions in the FALs. The H2SO4 reacts with KMnO4 and crystalized out from the recovered FAL faster than the phosphoric acid. So, sulfuric acid content in the makeover FALs must be greater than primary FAL. The product GOs were characterized using FT-IR, FT-Raman, UVVis, STA, SEM, XPS, Zeta-potential, and particle size analyzers. The variation of the properties of GOs with the changes in the reaction parameters such as temperature and time were investigated and correlated with the product yield. It was observed that the effect of temperature on the reaction rate was found to be negatively and positive with the reaction time. The oxygen-to-carbon atomic ratio from XPS analysis was found 66.7%, which supported the increase in product yields 66.9% in the experimental results. The effect of acid concentration, reaction temperature, and time on the GOs properties were satisfactory, correlated, and easily controllable with the reaction conditions. A higher extent of oxidation and enhanced product yields 65-70% were observed at 60-70 °C and 14-18 h. A mixture of nano- and macro-molecular GOs was obtained, and their compositions were easily controllable and separable by controlling the reaction conditions. A correlation was made among the properties of synthesized GOs, FAL, and recycled FAL and reaction conditions.

Graphene loaded into dental polymers as reinforcement of mechanical properties: A systematic review

Graphene compounds are incorporated into polymers in order to improve their mechanical properties and in dentistry this modification favors the clinical performance of these materials. The aim of this review was to evaluate graphene compounds, their concentrations, and their effect on mechanical properties as flexural, tensile, and compressive strength and hardness of polymethylmethacrylate (PMMA) and polyether-ether-ketone (PEEK) for dental application. The search was carried out in two steps in PubMed/Medline, Embase, Scopus, and Web of Science databases. The eligibility criteria included studies that incorporated pure graphene compounds into dental polymers and evaluated their mechanical properties. Were found 4984 results, of which 11 articles were included in this review. Graphene compounds: graphene oxide (GO), reduced graphene oxide (rGO), and graphene nanoplatelets (GNP) were incorporated into PMMA and PEEK, in concentrations ranging from 0.1 to 10 wt%. Concentrations lower than 0.75 wt% of GO in PMMA and 1 wt% of GNP in PEEK resulted in increased flexural, tensile, compression strength, and hardness of these polymers. It was concluded that the incorporation of graphene compounds in low concentrations increases dental polymers' mechanical properties.

Osseointegration, antimicrobial capacity and cytotoxicity of implant materials coated with graphene compounds: A systematic review

The use of graphecs excellent mechanical properties. However, it is necessary to evaluate the biological effects of this material. This systematic review aimed to observe and understand through studies the current state of the art regarding osseointegration, antimicrobial capacity, and the cytotoxicity of graphene coating applied to the surface of dental implant materials. Searches in PubMed, Embase, Science Direct, Web of Science, and Google Scholar databases were conducted between June and July 2021 and updated in May 2022 using the keywords: graphene, graphene oxide, dental implants, zirconium, titanium, peek, aluminum, disilicate, methyl-methacrylate, cytotoxicity, osseointegration, and bone regeneration. The criteria included in vivo and in vitro studies that evaluated antimicrobial capacity and/or osseointegration and/or cytotoxicity of dental implant materials coated with graphene compounds. The risk of bias for in vitro studies was assessed by the JBI tool, and for in vivo studies, Syrcle's risk of bias tool for animal studies was used. The database search resulted in 176 articles. Of the 18 articles selected for full reading, 16 remained in this systematic review. The use of graphene compounds as coatings on the surface of implant materials is promising because it promotes osseointegration and has antimicrobial capacity. However, further studies are needed to ensure its cytotoxic potential.

Effect of Ambient Environment on Laser Reduction of Graphene Oxide for Applications in Electrochemical Sensing

Electrochemical sensors play an important role in a variety of applications. With the potential for enhanced performance, much of the focus has been on developing nanomaterials, in particular graphene, for such sensors. Recent work has looked towards laser scribing technology for the reduction of graphene oxide as an easy and cost-effective option for sensor fabrication. This work looks to develop this approach by assessing the quality of sensors produced with the effect of different ambient atmospheres during the laser scribing process. The graphene oxide was reduced using a laser writing system in a range of atmospheres and sensors characterised with Raman spectroscopy, XPS and cyclic voltammetry. Although providing a slightly higher defect density, sensors fabricated under argon and nitrogen atmospheres exhibited the highest average electron transfer rates of approximately 2 × 10-3 cms-1. Issues of sensor reproducibility using this approach are discussed.

Graphene Oxide Sheets Decorated with Octahedral Molybdenum Cluster Complexes for Enhanced Photoinactivation of Staphylococcus aureus

The emergence of multidrug-resistant microbial pathogens poses a significant threat, severely limiting the options for effective antibiotic therapy. This challenge can be overcome through the photoinactivation of pathogenic bacteria using materials generating reactive oxygen species upon exposure to visible light. These species target vital components of living cells, significantly reducing the likelihood of resistance development by the targeted pathogens. In our research, we have developed a nanocomposite material consisting of an aqueous colloidal suspension of graphene oxide sheets adorned with nanoaggregates of octahedral molybdenum cluster complexes. The negative charge of the graphene oxide and the positive charge of the nanoaggregates promoted their electrostatic interaction in aqueous medium and close cohesion between the colloids. Upon illumination with blue light, the colloidal system exerted a potent antibacterial effect against planktonic cultures of Staphylococcus aureus largely surpassing the individual contributions of the components. The underlying mechanism behind this phenomenon lies in the photoinduced electron transfer from the nanoaggregates of the cluster complexes to the graphene oxide sheets, which triggers the generation of reactive oxygen species. Thus, leveraging the unique properties of graphene oxide and light-harvesting octahedral molybdenum cluster complexes can open more effective and resilient antibacterial strategies.

Electrochemical Fine-Tuning of the Chemoresponsiveness of Langmuir-Blodgett Graphene Oxide Films

Graphene oxide has been widely deployed in electrical sensors for monitoring physical, chemical, and biological processes. The presence of abundant oxygen functional groups makes it an ideal substrate for integrating biological functional units to assemblies. However, the introduction of this type of defects on the surface of graphene has a deleterious effect on its electrical properties. Therefore, adjusting the surface chemistry of graphene oxide is of utmost relevance for addressing the immobilization of biomolecules, while preserving its electrochemical integrity. Herein, we describe the direct immobilization of glucose oxidase onto graphene oxide-based electrodes prepared by Langmuir-Blodgett assembly. Electrochemical reduction of graphene oxide allowed to control its surface chemistry and, by this, regulate the nature and density of binding sites for the enzyme and the overall responsiveness of the Langmuir-Blodgett biofilm. X-ray photoelectron spectroscopy, surface plasmon resonance, and electrochemical measurements were used to characterize the compositional and functional features of these biointerfaces. Covalent binding between amine groups on glucose oxidase and epoxy and carbonyl groups on the surface of graphene oxide was successfully used to build up stable and active enzymatic assemblies. This approach constitutes a simple, quick, and efficient route to locally address functional proteins at interfaces without the need for additives or complex modifiers to direct the adsorption process.

Chlorophyll sensitized (BiO)2CO3/ CdWO4/rGO nano-hybrid assembly for solar assisted photo-degradation of chlorzoxazone

In the present laboratory scale experiment, we report the fabrication of chlorophyll sensitized (BiO)₂CO₃/CdWO₄/rGO (BCR) photo-catalyst. The green approach has been adopted for boosting the optical activity by chlorophyll as a sensitizer. The functionality, nature and surface compositions of synthesized photo-catalyst have been identified by FTIR, XRD and XPS instrumentation. The internal and surface morphology has been studied using FE-SEM and HR-TEM. The optical activity has been investigated by UV-vis and photoluminescence spectroscopy. The catalytic activity of chlorophyll sensitized BCR have been tested for the photo degradation of Chlorzoxazone (CZX) under simulated visible light for 90 min. The detailed comparison has been studied for the different loading amount of chlorophyll and RGO onto BCR photo-catalyst. The potential of BCR for the photo-degradation of CZX was investigated under various operational parameters such as catalysts dosage, pollutant concentration, effect of pH and ions etc. Approximately, 96.2% of CZX has been degraded over 90 min with the optimum catalyst amount 250 mgL^-1 at pH 7. The ^●OH radical has been identified as major reactive species using radical scavenging experiment. The mineralization of CZX has been evaluated in terms of HR-MS and TOC-COD analysis.

White LED active α-Fe2O3/rGO photocatalytic nanocomposite for an effective degradation of tetracycline and ibuprofen molecules

The formation of phase pure magnetically separable α-Fe₂O₃ and α-Fe₂O₃/rGO nanostructures were achieved through a simple hydrothermal technique. The properties of synthesized materials were investigated through different analytical techniques. The formation of phase pure FO and FO/rGO nanostructures were confirmed by XRD analysis with crystallite size of about ∼42 nm and ∼65 nm, respectively. The morphological analysis reveals the formation of sphere-like nanoparticles with high agglomeration. The UV-DRS analysis clearly shows the enhanced visible-light activity of FO/rGO nanoparticles. The BET analysis revealed the mesoporous property of FO/rGO nanocomposite. The enhancement in the photoinduced charge transfer process is observed after including rGO nanoparticles with FO. The photocatalytic efficiency of nanomaterials was analyzed using tetracycline and ibuprofen as model organic pollutants under white LED irradiation. The enhanced photocatalytic degradation ability of FO/rGO nanocomposite is studied against both tetracycline and ibuprofen molecules.

MFP-FePt-GO Nanocomposites Promote Radiosensitivity of Non-Small Cell Lung Cancer Via Activating Mitochondrial-Mediated Apoptosis and Impairing DNA Damage Repair

Background: Recent advances in nanomedicine provided promising alternatives for tumor treatment to improve the survival and life quality of cancer patients. This study was designed to explore the insight mechanisms of the anti-tumor effects of the novel nanocomposites (NCs) MFP-FePt-GO with non-small cell lung cancer (NSCLC).

Methods: A chemical co-reduction method was applied to the synthesis process of MFP-FePt-GO NCs. The chemical synthesis efficiency and morphology of the NCs were measured with spectroscope and transmission electron microscope. Colony formation assay and cell apoptosis were conducted to assess the radiosensitivity effect of NCs with radiation. Then, we detected cell mitochondrial membrane potential and reactive oxygen species (ROS) level by flow cytometry to further explore the cause of cell death. Immunofluorescence staining and Confocal were carried out to determine the DNA damage repair. A Lewis lung carcinoma animal model was used to measure safety and anti-tumor efficiency in vivo.

Results: The novel NCs MFP-FePt-GO designed on a lamellar-structure magnetic graphene oxide and polyethylene glycol drug delivery system was synthesized and functionalized for co-delivery of metronidazole and 5-fluorouracil. While no severe allergies, liver and kidney damage, or drug-related deaths were observed, MFP-FePt-GO NCs promoted radiosensitivity of NSCLC cells both in vivo and in vitro. It improved the effects of radiation via activating intrinsic mitochondrial-mediated apoptosis and impairing DNA damage repair. This NCs also induced a ROS burst, which suppressed the antioxidant protein expression and induced cell apoptosis. Furthermore, MFP-FePt-GO NCs prevented NSCLC cell migration and invasion.

Conclusion: MFP-FePt-GO NCs showed a synergistic anti-tumor effect with radiation to eliminate tumors. With good safety and efficacy, this novel NCs could be a potential radiosensitive agent for NSCLC patients.

Quantum capacitance tuned flexible supercapacitor by UV-ozone treated defect engineered reduced graphene oxide forest

A forest like 3D carbon structure formed by reduced graphene oxide (RGO) was prepared to use as an electrode material for a highly power efficient supercapacitor. To improve the specific energy of the electrode, pore like defects were incorporated on the RGO forests by atomic oxygen etching, during the UV-ozone treatment. The modified surface helps to increase the net capacitance by permitting the electrolyte to the inner core of the active material and improving the minimal quantum capacitance. Density functional theory based first principle studies were carried out to find DOS at the Fermi level of defect induced RGO sheet and hence to validate the effect of quantum capacitance on net capacitance. Specific capacitance of RGO forest was increased by almost 150% after introduction of the defects. The best performing material exhibits 18.87 mF cm^-2 areal capacitance at 2 mA cm^-2 current density which is equivalent to 70 F cm^-3 at 3.7 A cm^-3 current density, and it was used to fabricate the supercapacitor. Two supercapacitors were fabricated, (i) on graphite sheet (non-flexible) and (ii) on scotch tape (flexible). Here PVA-KOH gel soaked filter paper was used as electrolyte-separator. Both the prepared supercapacitors on graphite sheet and scotch tape are able to transfer electrical energy with ultra high specific power (656.25 mW cm^-3 and 164.06 mW cm^-3 respectively) while maintaining moderate energy densities. The first device can withstand its primary capacitance by 90% even after 10 K charge-discharge cycles and the flexible device was able to hold 96% of its capacitance after 1 K bending cycles.

Graphene and its derivatives: Opportunities and challenges in dentistry

The emerging science of graphene-based engineered nanomaterials as either nanomedicines or dental materials in dentistry is growing. Apart from its exceptional mechanical characteristics, electrical conductivity and thermal stability, graphene and its derivatives can be functionalized with several bioactive molecules, allowing them to be incorporated into and improve different scaffolds used in regenerative dentistry. This review presents state of the art graphene-based engineered nanomaterial applications to cells in the dental field, with a particular focus on the control of stem cells of dental origin. The interactions between graphene-based nanomaterials and cells of the immune system, along with the antibacterial activity of graphene nanomaterials are discussed. In the last section, we offer our perspectives on the various applications of graphene and its derivatives in association with titanium dental implants, membranes for bone regeneration, resins, cements and adhesives, as well as tooth-whitening procedures.

Oxidized Laser-Induced Graphene for Efficient Oxygen Electrocatalysis

An efficient metal-free catalyst is presented for oxygen evolution and reduction based on oxidized laser-induced graphene (LIG-O). The oxidation of LIG by O₂ plasma to form LIG-O boosts its performance in the oxygen evolution reaction (OER), exhibiting a low onset potential of 260 mV with a low Tafel slope of 49 mV dec^-1 , as well as an increased activity for the oxygen reduction reaction. Additionally, LIG-O shows unexpectedly high activity in catalyzing Li₂ O₂ decomposition in Li-O₂ batteries. The overpotential upon charging is decreased from 1.01 V in LIG to 0.63 V in LIG-O. The oxygen-containing groups make essential contributions, not only by providing the active sites, but also by facilitating the adsorption of OER intermediates and lowering the activation energy.