Size separation of graphene oxide using preparative free‐flow electrophoresis

Graphene oxide nanosheets often bear a wide size distribution. However, it is critical to have nanosheets with narrow size distribution for their unique size‐dependent physiochemical properties, and nanosheets with a narrow size distribution are the cornerstones for application. Therefore, efficient separation methods of graphene nanosheets have been given considerable attention in many scientific areas recently. Free‐flow electrophoresis is extensively used in the separation and purification of biological molecules with continuous flow separation. The charged graphene oxide nanosheets to some extent are very close in size to biological molecules and share similarity in motion behavior in an electric field. Thus, in the present work, we present a new and simple means to separate graphene oxide nanosheets into more mono‐dispersed size groups by using the free‐flow electrophoresis technique. By optimizing the separation conditions, we were able to obtain graphene oxide sheets with narrow size distribution. The separated samples were characterized by atomic force microscopy, and the size measurements were made by using the software “Image Pro Plus.” In addition, a brief discussion is also given into the theoretic background of the separation of graphene oxide according to the size by the technique of preparative free‐flow electrophoresis.     

姜黄素类似物的合成及其清除自由基的研究

姜黄素(见图1)为中药姜黄的主要成分,是一种黄色色素。研究报道姜黄素具有抗氧化、抗炎、抗病毒、抗癌等生物活性[1-4]。本文通过芳香醛和环己酮催化缩合反应合成了一系列姜黄素类似物(见图2),研究了它们抗自由基的活性。图1姜黄素的化学结构F ig.1 Chem ical structure of cur     

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.     

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.     

Polarised infrared microspectroscopy of edge-oriented graphene oxide papers

We have performed FTIR transmission microspectroscopy on graphene oxide papers oriented with the nominal lattice planes parallel to the infrared optical axis. By polarising the IR light for samples of this geometry, spectral contributions of oriented oxide species are isolated from broad convoluted bands. Analysing the data alongside previous works, including experiments where samples were perturbed by reduction, dehydration and deuteration, we tabulate the most likely assignments for the observed spectral bands.     

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.     

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.     

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.     

Photovoltaic properties of graphene oxide sheets beaded with ZnO nanoparticles

A hybrid material of graphene oxide (GO) sheets beaded with ZnO nanoparticles was prepared. The material extends over a few hundred square nanometers, in which the ZnO nanoparticles (average diameter (∼5 nm)) are dispersed evenly on the GO sheet. Both the surface photovoltage or surface photocurrent intensity for the material are much stronger than for pure ZnO nanoparticles, meaning that the free charge carriers can effectively be transferred from ZnO nanoparticles to GO sheets, which can serve as a probe to monitor the electron transfer from excited ZnO to GO. Anchoring ZnO nanoparticles on two dimensional carbon nanostructures such as GO can pave a way towards the design of ordered nanostructure assemblies that can harvest light energy efficiently.     

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.     

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.     

Photo-induced Janus effect of graphene oxide films

The effect of UV irradiation on the wettability of GO films, as well as the possibility of making a film with different properties of its surface, the Janus film, has been studied. The O/C ratio changes from 0.32 to 0.26 after 6 ​h of UV irradiation. The contact angle of water droplet wetting on an unirradiated surface is θ ​≈ ​35°. The contact angle reaches more than 95° on the irradiated surface, which means that a hydrophobic surface on a film can be obtained. The origin of amphiphilic properties of the GO film are associated with the photochemical reduction of GO.     

耦合氧化石墨烯的N掺杂Bi_2O_2CO_3微球光催化性能增强机制(英文)

光催化作为一种环境友好技术,在解决环境污染和能源匮乏问题方面展现出巨大应用潜力.TiO_2因其化学稳定性、无毒和低成本被广泛应用于能源转换和污染物降解等领域,但其快速的电子-空穴复合与低太阳能利用率等限制了其在光催化中的潜在应用.因此,寻找新的有优越可见光活性的催化剂是一个挑战.最近,(BiO)_2CO_3因其独特的形貌、化学稳定性和较高的催化效率成为有前景的光催化剂.然而,(BiO)_2CO_3较大的带隙限制了对太阳光的利用,快速的电子-空穴复合阻碍了光催化性能的提高.因此,提高(BiO)_2CO_3的光催化效率是当务之急.近期研究表明,通过与氧化石墨烯杂交提高载流子的分离能力,可有效增强光催化性能.基于此,我们设计并合成了一种氮掺杂的(BiO)_2CO_3与氧化石墨烯(GO)耦合的新型光催化剂(N-BOC-GO).首先,通过一步水热法合成了N-BOC-GO微球.N-BOC-GO光催化剂对NO可见光光催化去除性能达到62%.采用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-Vis)和光致发光光谱(PL)等表征手段研究了N-BOC-GO的光催化性能增强机制.从N-BOC-GO的XRD谱中没有发现GO的衍射峰,说明加入的GO分散度高;N-BOC-GO中的BOC晶格参数没有发生变化,说明GO没有进入BOC晶格,但加入GO增强了N-BOC的结晶度.XPS结果表明,与N-BOC相比,N-BOC-GO的峰位置发生了明显位移,表明N-BOC和GO之间存在强相互作用.此外,FT-IR和拉曼光谱证明了在复合物中存在GO.SEM表明,N-BOC规则地团聚成微球,且微球被固定在有褶皱的GO片上.这说明GO与N-BOC的作用是静电作用或物理作用,在光激发过程中有利于N-BOC微球上的电子转移到GO片上.UV-Vis图谱中,N-BOC-GO表现出明显增强的可见光吸收,说明加入GO会明显提高N-BOC的吸收能力.此外,3D分层结构会通过SSR效应提高光吸收.从PL图可以发现,N-BOC-GO的电子-空穴复合明显下降,说明GO可以转移电子从而提高光催化性能.结合前面的分析,我们提出了N-BOC-GO光催化剂3D分层结构的形成和性能增强机制.在水热过程中,通过分子间相互作用使N-BOC自组装成块,随后在表面能最小化的作用下转化成3D微球.加入GO后,N-BOC和GO通过物理吸附使得N-BOC微球均匀分散在GO上,最后N-BOC-GO的形貌类似于玫瑰花和其叶子的组合.在可见光照射下,N-BOC产生电子-空穴对,电子从N-BOC表面转移到GO表面,表明GO可作为电子的收集者和传递者以有效分离电子-空穴对,延长载流子寿命.N-BOC价带上的空穴可以直接氧化NO或产生?OH氧化NO.此外,由于GO独特的特征,光催化反应发生在N-BOC催化剂表面和GO片上,从而提高了反应空间位点.故引入GO于N-BOC体系中可有效分离光生载流子和提高反应活性位点,从而显著提高可见光催化性能.     

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.     

Adsorption properties and mechanism of sepiolite to graphene oxide in aqueous solution

Graphene oxide (GO) is widely used in various fields such as improving the performance of cement-based materials and making composite materials due to its large specific surface area and abundant oxygen-containing functional groups. However, it has also caused water pollution. To remove GO in aqueous solution, sepiolite (SEP) was used to adsorb it. The effects of pH, adsorbent quality, GO concentration, temperature and adsorption time on the ability of SEP to adsorb GO were investigated. The materials were characterized by SAP and laser particle size analyzer, and the adsorption performance and mechanism of SEP for GO were further analyzed by XRD, FTIR, SEM, TEM, XPS, AFM, and Zeta potential microscopic tests. The results showed that: 1) Under the conditions of temperature 303 K, pH = 3, adsorbent mass 30 mg, and initial concentration of GO 100 mg/L, the adsorption effect was the best, and the adsorption rate reached 94.8 %. 2) The adsorption reached equilibrium at 2160 min, and the adsorption process was more in line with the pseudo-second-order adsorption kinetic equation, and the adsorption behavior was controlled by chemical effects. 3) The adsorption of SEP to GO is more consistent with the Langmuir and Temkin adsorption isotherm model, and the reaction is a spontaneous, endothermic, and entropy-increasing process. Experiments showed that SEP had a strong adsorption capacity for GO, which provides a reference for the treatment of toxic GO in aqueous solution and the realization of water ecological protection.     

改性氧化石墨烯膜的制备及其性能研究

为了改善氧化石墨烯(GO)膜的低渗透性和不稳定性,本文采用过氧化氢对GO进行改性后抽滤成膜,并在不同温度下对膜进行热还原.采用超高性能全自动气体吸附仪、透射电镜、扫描电镜、拉曼光谱仪、接触角、X射线衍射等对材料进行结构和形貌表征.分析不同HGO(H2O2改性GO)负载量和不同温度热还原对膜水通量和截留率的影响.在优化条...     

Shear-induced assembly of graphene oxide particles into stripes near surface

We report the shear-induced assembly of graphene oxide (GO) particles into periodic stripe-like patterns near the surface. These stripe-like patterns, which have an average periodic length of 100–250 μm, are aligned in a wavy manner along the normal to the flow direction. The self-assembled GO structures are investigated at different depths using three different analysis methods, namely, reflective microscopy observations of the photonic-crystalline GO dispersion, polarized optical microscopy, and fluorescence confocal laser scanning microscopy. The surface microstructures observed in reflection mode are different from the shear-induced band structures formed in bulk thermotropic liquid crystals and liquid crystal polymers, in terms of the shape and scale of the stripes. Further, there is also a difference in terms of the dependence of the stripe width on the shear rate. The observations suggest that the stripes are formed because of a competition between the stable surface-field-induced planar alignment of the GO particles near the surface and their relatively unstable shear-induced vertical alignment in the bulk. The findings of this study should advance our understanding of GO assembly under shear stress. Further, the proposed method is a novel one for inducing the assembly of GO particles into microstructures shaped as thread-like stripes.     

An in situ oxidation route to fabricate graphene nanoplate-metal oxide composites

We report our studies on an improved soft chemical route to directly fabricate graphene nanoplate-metal oxide (Ag₂O, Co₃O₄, Cu₂O and ZnO) composites from the in situ oxidation of graphene nanoplates. By virtue of H⁺ from hydrolysis of the metal nitrate aqueous solution and NO₃⁻, only a small amount of functional groups were introduced, acting as anchor sites and consequently forming the graphene nanoplate-metal oxide composites. The main advantages of this approach are that it does not require cumbersome oxidation of graphite in advance and no need to reduce the composites due to the lower oxidation degree. The microstructures of as-obtained metal oxides on graphene nanoplates can be dramatically controlled by changing the reaction parameters, opening up the possibility for processing the optical and electrochemical properties of the graphene-based nanocomposites.