Adsorption of graphene oxide/chitosan porous materials for metal ions

Porous graphene oxide/chitosan（PGOC） materials were prepared by a unidirectional freeze-drying method.Their porous structure,mechanical property and adsorption for metal ions were investigated.The results show that the incorporation of graphene oxide（GO） significantly increased the compressive strength of the PGOC materials.The saturated adsorption capacity of Pb²⁺ increased about 31%,up to 99 mg/g when 5 wt%GO was incorporated These biodegradable,nontoxic,efficient PGOC materials will be a potential adsorbent for metal ions in aqueous solution.     

Broad spectrum antibacterial zinc oxide-reduced graphene oxide nanocomposite for water depollution

Antimicrobial-resistance (AMR) is a global health challenge arising from the evolution of bacteria, viruses, fungi, and parasites, such that pathogenic microorganisms no longer respond to classical therapies. AMR and the rise of so-called ‘superbugs’ requires innovative nanomaterials and biostatic strategies. Here we report a broad spectrum, antimicrobial nanomaterial integrating light-responsive ZnO nanoparticles (NP) and reduced graphene oxide (rGO) into a heterojunction semiconductor nanocomposite for water depollution. Simultaneous chemical reduction of Zn sulphate and GO sheets yields a low concentration (0.5 mol%) of 10 nm ZnO nanoparticles decorating fragmented rGO nanosheets, with a total surface area of 12 m²/g and optical band gap of 1.6 eV. Antimicrobial performance of the ZnO-rGO nanocomposite was evaluated against methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli 0157:H7 and Salmonella typhimurium bacteria, which are prevalent in contaminated aquatic systems; antimicrobial efficacy against these organisms was 96%, 97%, and 73%, respectively, for a loading of 2 mg/mL, evidencing a strong synergy compared with pure ZnO or rGO components. ZnO-rGO was also an effective photocatalyst for the aqueous degradation of Malachite Green dye, suggesting that its mode of antibacterial action reflects the production of reactive oxygen species under ambient illumination.     

Optimizing the mechanical and surface topography of hydroxyapatite/Gd2O3/graphene oxide nanocomposites for medical applications

A ternary nanocomposite (TNC) was fabricated for introducing multifunctional properties for various biomedical applications. The nanocomposites consist of hydroxyapatite (HAP) combined with/without graphene oxide (GO) and gadolinium oxide (Gd₂O₃). The lattice constants of HAP were around 9.4285 and 6.7476 Å, while for Gd₂O₃ was around 10.8441 Å. The morphological investigation detected the nanosheets of GO, and nanorods of HAP/Gd₂O₃ with length of 27 nm. Moreover, the topological study based on a field emission scanning electron microscope (FESEM) showed that HAP/GO had average roughness (R_a) of 4.8 nm, and the root mean square value (R_q) with a value of 7 nm. Furthermore, the average pore size reached 7.99 nm for the NC of HAP/GO. In addition, the cumulative surface area using the density functional theory (DFT) method was calculated at around 44.61 m²/g for TNC. The cell viability in vitro of osteoblast cell line improved from 95.6 ± 0.6% to 96.7 ± 0.5% which indicates the biocompatibility of the implants to be used in biomedical applications.     

Synthesis of multifunctional fluorescent magnetic graphene oxide hybrid materials

Fluorescent magnetic graphene oxide hybrid materials have been fabricated by a multistep method. X-ray diffraction, transmission and scanning electron microscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, vibration sample magnetometry, and energy dispersive spectroscopy were used to characterize the resulting material. The results showed that the materials have a saturation magnetization value of 22.0 emu/g at room temperature and exhibit a symmetrical and narrow emission peak at 544 nm. The resultant materials are able to carry an anti-cancer drug, 5-fluorouracil, with a load capacity of 0.24 mg/mg.     

Preparation of quaternarized N-halamine-grafted graphene oxide nanocomposites and synergetic antibacterial properties

At present, frequent outbreaks of bacteria and viruses have seriously affected people's normal lives. Therefore, the study of broad-spectrum antibacterial nanocomposites is very promising. However, most antibacterial materials have some disadvantages, such as single bactericidal mechanisms and unrepeatable use. Based on the current situation, a kind of nanocomposite with three structures of graphene oxide (GO), quaternary ammonium salt (QAs) and N-halamine was prepared, which showed synergistic effect to improve antibacterial activity and combined with a variety of sterilization mechanisms. Meanwhile, GO can provide richer ways of sterilization and high specific surface area, which is conducive to the grafting of quaternarized N-halamine. The advantages of physical sterilization of GO, charge adsorption of QAs, reuse of N-halamine and efficient sterilization are fully utilized. The results showed that the quaternarized N-halamine-grafted GO was obtained successfully. GO grafted with quaternarized N-halamine polymer showed strong speedy bactericidal activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (99%). It had good storage and regeneration properties.     

Performance of graphene Oxide/SiO2 Nanocomposite-based: Antibacterial Activity,dye and heavy metal removal

Nanocomposite materials have been successfully applied to remediation of organic and inorganic contaminants from polluted water. The present study investigates the synthesis, characterizations, and adsorptive performances of graphene oxide/SiO₂ nanocomposite-based adsorbent. Graphene oxide/SiO₂ was used for the adsorption of methylene blue (MB) and Cr (VI) ion from wastewater. Furthermore, the antibacterial activity performance of synthesized nanocomposite was studied. The adsorption consideration has been performed by various adsorption parameters in our laboratory. X-ray crystallography (XRD), Scanning electron microscope (SEM), Energy Dispersive X-ray Analysis (EDX) and, thermal gravimetric analysis (TGA) methods were applied in the characterization, morphological structure, crystallinity, and thermal stability of graphene oxide/SiO₂. Maximum capacities of adsorption of graphene oxide/SiO₂-based adsorbent had been evaluated by the Langmuir isotherm model for MB and Cr (VI) ion as 555.50 and 181.81 mg/g, respectively. Generally, adsorption experiments revealed that the performances of graphene oxide/SiO₂ nanocomposite for all adsorbents have been found in the order MB > Cr (VI). Furthermore, antibacterial activity study against gram-positive and gram-negative bacteria showed and proved that graphene oxide/SiO₂ composite showed a remarkable ability to kill bacteria.     

Introduction of CdO nanoparticles into graphene and graphene oxide nanosheets for increasing adsorption capacity of Cr from wastewater collected from petroleum refinery

Graphene and graphene oxide nanocomposites are promising and fascinating types of nanocomposites because of their fast kinetics, unique affinity for heavy metals, and greater specific area. Initially, in this study, a green, cost-effective and facile method was utilized to prepare G, GO, CdO, G-CdO, and CdO-GO nanocomposites by Azadirachta indica and then analyzed using UV–vis spectroscopy, Fourier-transform spectroscopy, Raman, X-ray diffraction and scanning electron microscope. The synthesized nanocomposites were explored for chromium elimination from wastewater collected from a petroleum refinery. CdO-GO, G-CdO nanocomposites showed remarkable adsorption capability of 699 and 430 mg g^?1 which was higher than G (80 mg g^?1), GO (65 mg g^?1), and CdO (400 mg g^?1). Based on the R² (correlation coefficient) values, the kinetic statistics of Cr (VI) onto the G, GO, CdO, G-CdO, and CdO-GO were effectively obeyed by pseudo-second-order than by all other models. The R² values for the five nano-bioadsorbents were extraordinarily high (R² greater than 0.990) which ensured the chemisorption. This study ensured that the adsorptive removal rate of Cr (VI) is still greater than 85 % after repeated five cycles, suggesting that the produced nanomaterials are adsorbents with strong recyclability.     

Synthesis of the polyethylene glycol solid-solid phase change materials with a functionalized graphene oxide for thermal energy storage

Polyethylene glycol (PEG) as a phase change material possesses three obstacles, such as leakage, low thermal conductivity and low thermal stability. A novel solid-solid phase change material (PCM) based on functionalized graphene oxide (GO), Polyethylene glycol (PEG) was prepared, and the three obstacles of PEG as a PCM was solved in one and the same material. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman and Transmission electron microscope (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and thermogravimetric analysis/infrared spectrometry (TG-IR) were used to study the properties of supporting material and composite PCM (CPCM). The results indicated that the PEG was grafted on the surface of the supporting material; Compared with pure PEG, the latent heat of CPCM with 9.6 wt% supporting material decreased only 5.3%, however, the thermal conductivity of CPCM increased 111% and the heat peak release rate of CPCM decreased 33.4%.     

Graphene materials preparation methods have dramatic influence upon their capacitance

Graphene related materials are widely expected to play a major role as materials for the construction of supercapacitors. We demonstrate here that graphene oxides prepared by various well-established methods exhibit dramatically different capacitances. We exfoliated graphite oxide sonographically to graphene oxide (GO) and we reduced GO by chemical or electrochemical means to chemically reduced graphene oxide (CRGO) and electrochemically reduced graphene oxide (ERGO); in addition, graphite oxide was thermally exfoliated leading to thermally reduced graphene oxide (TRGO). We found clear dependence of weight specific capacitance upon amount of oxygen containing groups presented on the surface of these graphenes. GO exhibits the lowest and TRGO the highest values of weight specific capacitance.     

Electrochemiluminescence resonance energy transfer between graphene quantum dots and graphene oxide for sensitive protein kinase activity and inhibitor sensing

Herein, a novel electrochemiluminescence resonance energy transfer (ECL-RET) biosensor using graphene quantum dots (GQDs) as donor and graphene oxide (GO) as acceptor for monitoring the activity of protein kinase was presented for the first time. Anti-phosphoserine antibody conjugated graphene oxide (Ab-GO) nonocomposite could be captured onto the phosphorylated peptide/GQDs modified electrode surface through antibody–antigen interaction in the presence of casein kinase II (CK2) and adenosine 5′-triphosphate (ATP), resulting in ECL from the GQDs quenching by closely contacting GO. This ECL quenching degree was positively correlated with CK2 activity. Therefore, on the basis of ECL-RET between GQDs and GO, the activity of protein kinase can be detected sensitively. This biosensor can also be used for quantitative analysis CK2 activity in serum samples and qualitative screening kinase inhibition, indicating the potential application of the developed method in biochemical fundamental research and clinical diagnosis.     

Covalent functionalization of graphene oxide by 9-(4-aminophenyl)acridine and its derivatives

Graphene/acridine(G-Acr) hybrid structures were synthesized through covalent functionalization of graphene oxide with 9-(4- aminophenyl)acridine(APA) and its derivatives.The G-Acr hybrids were characterized by Fourier transform infrared spectroscopy, ultraviolet-visible spectrophotometry,thermal gravimetric analysis and Raman spectroscopy.X-ray photoelectron spectroscopy confirms that the binding energies of APA and its derivatives shifted to higher values,revealing pronounced charge transfer at the interface of graphene and organic molecules.     

Robust curcumin-mustard oil emulsions for pro to anti-oxidant modulation of graphene oxide

The compositional flexibility of emulsions, via surfactant and additive choice, has been the major reason for their recognition as tuneable delivery sources for a variety of drugs. In particular, the kinetically stable nanoemulsions (NE) are preferred to minimize the toxicity extents of several poorly hydrophobic drugs through variation in their delivered extents. Inspired by these specialties, we have optimized our curcumin (curc) loaded sodium dodecylsulpahte (SDS) and dodecyl trimethylammonium bromide (DTAB) stabilized mustard oil microemulsions (ME) which catalyzed the pro-oxidant (with ethanol only) to antioxidant graphene oxide (GO) structural expression. The GO was synthesized using wet chemical approach, using ubiquitous graphite flakes as raw material. GO was loaded into 1:1 mixtures of (separately made) SDS and DTAB curc loaded formulations (CLFs). Henceforth, the resultant formulation contained 60% (1:1 SDS and DTAB) CLF mixture and ethanol dispersed GO (@ 1 mg/mL) as the other component. Compared to an insignificant (~47%) free state (while being dispersed in ethanol) DPPH free radical scavenging, the GO dispersed in CLFs enabled (62.47–100.96)% increments in DPPH scavenging, with 94.45% as maximum neutralization extent. The (493.57–3154.95)% particle size increments and (40.64–92.70)% PDI decrements for GO supplemented formulation over SDS and DTAB CLF mixtures, have inferred a wider curc distribution, through the larger GO surface area (SA) and its augmented oxygen enhanced chemical controls. In support, the physicochemical variations, characterized by (1.77–21.23)% γ decrements, (63.56–98.08%) and (68.90–163.22)% η and σ increments, have complemented the dispersion enhancing GO activities. Considering the bioactive nature of curc, these observations predict a prevalence of native curc structure or its enhanced non-covalent interaction controls with GO. Edible nature of mustard oil alongwith frequent inclusion of SDS and DTAB in routine gadgets, propel our formulations as robust media for attaining desired structural activities of functionalized GO derivatives.     

Capillary column coated with graphene oxide as stationary phase for gas chromatography

The graphene oxide (GO) is carbon based material that has high surface area, high adsorption ability, and is stable at high temperature. In this work, the GO phase was prepared and used for gas chromatographic separation. GO nanosheets were covalently bonded onto the inner surface of fused silica capillary column using 3-aminopropyldiethoxymethyl silane as cross-linking agent. The prepared GO nanosheets were characterized with TEM and the GO coating was characterized with SEM. As a high performance stationary phase, GO provides not only a high surface area to increase the phase ratio but also rich functional groups for the formation of hydrophobicity, hydrogen bonding, and π–π electrostatic stacking interactions with volatile aromatic or unsaturated organic compounds. Thus, mixtures of a wide range of organic compounds including alcohols and aromatic compounds were well separated and an efficiency of 1990 theoretical plates per meter for anisole was obtained on GO coated 1.0 m × 200 μm i.d. fused silica capillary column. The experimental results demonstrate that GO coated capillary columns are promising for gas chromatographic separation.     

Controlling wrinkles and assembly patterns in dried graphene oxide films using lyotropic graphene oxide liquid crystals

We fabricated graphene oxide (GO) films on glass substrates by blade coating a lyotropic GO liquid crystal dispersion. Substrate temperature and blading speed were precisely controlled to manipulate the surface morphologies of GO films. The temperature and blade speed influenced the drying rate of film and the amount GO dispersion supplied. By controlling these parameters, film-thickness modulation and three types of surface wrinkle patterns were selectively achieved. We also plotted the wrinkle patterns diagram as functions of the film fabrication conditions. The films exhibited different optical anisotropies depending on wrinkle patterns. GO films with controlled wrinkles can be used as electrodes for supercapacitor applications owing to the large surface areas.     

Functionalized graphene oxide for the fabrication of paraoxon biosensors

There is an increasing need to develop biosensors for the detection of harmful pesticide residues in food and water. Here, we report on a versatile strategy to synthesize functionalized graphene oxide nanomaterials with abundant affinity groups that can capture histidine (His)-tagged acetylcholinesterase (AChE) for the fabrication of paraoxon biosensors. Initially, exfoliated graphene oxide (GO) was functionalized by a diazonium reaction to introduce abundant carboxyl groups. Then, N_α,N_α-bis(carboxymethyl)-l-lysine hydrate (NTA-NH₂) and Ni²⁺ were anchored onto the GO based materials step by step. AChE was immobilized on the functionalized graphene oxide (FGO) through the specific binding between Ni-NTA and His-tag. A low anodic oxidation potential was observed due to an enhanced electrocatalytic activity and a large surface area brought about by the use of FGO. Furthermore, a sensitivity of 2.23 μA mM⁻¹ to the acetylthiocholine chloride (ATChCl) substrate was found for our composite covered electrodes. The electrodes also showed a wide linear response range from 10 μM to 1 mM (R² = 0.996), with an estimated detection limit of 3 μM based on an S/N = 3. The stable chelation between Ni-NTA and His-tagged AChE endowed our electrodes with great short-term and long-term stability. In addition, a linear correlation was found between paraoxon concentration and the inhibition response of the electrodes to paraoxon, with a detection limit of 6.5 × 10⁻¹⁰ M. This versatile strategy provides a platform to fabricate graphene oxide based nanomaterials for biosensor applications.     

Aptamer functionalized magnetic graphene oxide nanocomposites for highly selective capture of histones

The binding coverage of aptamer was an important restricted factor for aptamer‐based affinity enrichment strategy for capturing target molecules. Herein, we designed and prepared aptamer functionalized graphene oxide based nanocomposites (GO/NH₂‐NTA/Fe₃O₄/PEI/Au), and the coverage density of aptamer was high to 33.1 nmol/mg. The high aptamer coverage density was contributed to the large surface area of graphene oxide. The successive modification of Nα,Nα‐Bis(carboxymethyl)‐L‐lysine, magnetic nanoparticles, polyethylenimine, and Au nanoparticles ensured the histone purification with fast speed and high purity. Histones could be captured rapidly and specifically from nucleoproteins by our aptamer based purification strategy, while traditional acid‐extraction could not specifically enrich histones. Compared with traditional acid‐extraction method, rapid and efficient discovery of histones and their post‐translational modifications, such as several kinds of methylation at H3.1K9 and H3.1K27, were achieved confidently. It demonstrated that our aptamer functionalized magnetic graphene oxide nanocomposites have a great potential for histone analysis.     

Self-assembly of graphene oxide nanosheets in t-butanol/water medium under gamma-ray radiation

Graphene oxide (GO) nanosheets dispersed in strong acidic t-butanol/water medium can be reduced and self-assembled into a self-standing graphene hydrogel under γ-ray radiation, providing a facile and economical preparation method for hydroxylalkylated graphene-based aerogel.     

Synthesis of Ferrosoferric Oxide‐graphene Oxide Nanocomposite by Isoelectric Point Method for the Detection of Catechol

Ferrosoferric oxide functionalized graphene oxide nanocomposite with layer by layer structure was synthesized by isoelectric point method in this work. The prepared material was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Then the material was used to modify a glassy carbon electrode to fabricate an electrochemical sensor for the detection of catechol. The electrochemical sensor exhibited excellent electrochemical performance towards the detection of catechol with a linear response in the range of 5–205 μM and a detection limit of 2.32 μM. Furthermore, the electrochemical sensor showed excellent selectivity, stability and repeatability. These results revealed ferrosoferric oxide functionalized graphene oxide nanocomposite has potential applications in the fabrication of electrochemical sensors.     

Fluorescence quenching of graphene oxide combined with the site-specific cleavage of restriction endonuclease for deoxyribonucleic acid demethylase activity assay

We report on the development of a sensitive and selective deoxyribonucleic acid (DNA) demethylase (using MBD2 as an example) activity assay by coupling the fluorescence quenching of graphene oxide (GO) with the site-specific cleavage of HpaII endonuclease to improve the selectivity. This approach was developed by designing a single-stranded probe (P1) that carries a binding region to facilitate the interaction with GO, which induces fluorescence quenching of the labeled fluorophore (FAM, 6-carboxyfluorescein), and a sensing region, which contains a hemi-methylated site of 5′-CmCGG-3′, to specifically recognize the target (T1, a 32-mer DNA from the promoter region of p53 gene) and hybridize with it to form a P1/T1 duplex. After demethylation with MBD2, the duplex can be specifically cleaved using HpaII, which releases the labeled FAM from the GO surface and results in the recovery of fluorescence. However, this cleavage is blocked by the hemi-methylation of this site. Thus, the magnitude of the recovered fluorescence signal is related to the MBD2 activity, which establishes the basis of the DNA demethylase activity assay. This assay can determine as low as ∼(0.05 ± 0.01) ng mL⁻¹ (at a signal/noise of 3) of MBD2 with a linear range of 0.2–300 ng mL⁻¹ and recognize MBD2 from other possibly coexisting proteins and cancer cell extracts. The advantage of this assay is its ability to avoid false signals and no requirement of bisulfite conversion, PCR amplification, radioisotope labeling, or separation.     

氧化石墨烯-石墨烯纳米复合物传感器检测 对乙酰氨基酚和对氨基苯酚

本文通过简单超声法制备了氧化石墨烯-石墨烯(GO-Gr)碳复合材料,通过扫描电镜和电化学方法进行表征。将其修饰在玻碳电极表面,成功构建了用于对乙酰氨基苯酚(APAP)和对氨基苯酚(PAP)检测的电化学传感器。采用差分脉冲伏安法(DPV)测定APAP和PAP,线性检测范围为0.1～70μmol/L和0.3～60μmol/L,检出限为0.02 和0.1μmol/ L。同时,构建的传感器还表现出良好的稳定性和抗干扰能力,可用于实际样品的检测。