Graphene based multifunctional superbots

A versatile graphene coated glass microswimmer displayed directed motions under the influence of applied electric field, chemical potential gradient and external magnetic field. The directed chemical locomotion took place from the region of lower to higher pH with speed ∼13 body lengths per second due to asymmetric catalytic decomposition of dilute hydrogen peroxide across the motor surface. The negative surface potential of graphene coated motor developed an electrical double layer in an alkaline medium which in turn engendered electrophoretic mobility towards anode when the external electrostatic field was applied. Inclusion of sparsely populated ferromagnetic iron nanoparticles on the surface of the motor offered the magnetic remote control on the motion. The coupled in situ and external controls enabled the motor to develop complex motions in diverse open and confined environments. For example, the motor could approach, pick-up, tow, and release a heavy cargo inside microchannel. Remarkably, the motor (∼67 μg) could successfully drive out a ∼1000 times heavier payload (∼0.67 mg) displaying the ability to overcome the drag force of ∼2619 pN with the help of coupled in situ and remote guidance.     

Graphene based ballistic rectifiers

Despite having the longest mean-free-path of carriers in all electronic materials, it has been virtually impossible to demonstrate graphene ballistic devices due to the rather diffusive and hence random scattering of carriers from the edges. Hence we show that this may not be true in the nonlinear transport regime in a nanodevice called ballistic rectifier. In contrast to a conventional transistor, the ballistic rectifier does not necessarily require a sizable bandgap. Here, we not only demonstrate rectifying effect at room temperature but also indicate that the carrier scattering from graphene edges in the nonlinear regime may be more specularly than previous discovered in the linear regime.     

Kanamycin A-derived cationic lipids as vectors for gene transfection

Cationic lipids nowadays constitute a promising alternative to recombinant viruses for gene transfer. We have recently explored the transfection potential of a new class of lipids based upon the use of aminoglycosides as cationic polar headgroups. The encouraging results obtained with a first cholesterol derivative of kanamycin A prompted us to investigate this family of vectors further, by modulating the constituent structural units of the cationic lipid. For this study, we have investigated the transfection properties of a series of new derivatives based on a kanamycin A scaffold. The results primarily confirm that aminoglycoside-based lipids are efficient vectors for gene transfection both in vitro and in vivo (mouse airways). Furthermore, a combination of transfection and physicochemical data revealed that some modifications of the constitutive subunits of kanamycin A-based vectors were associated with substantial changes in their transfection properties.     

基于石墨烯的生物传感器的研究进展

综述了石墨烯在生物传感器方面的研究进展,最后展望了基于石墨烯的生物传感器的发展前景。     

基于PatentStrategies的石墨烯探测器专利技术分析

石墨烯以其优异的光电性能,广泛应用于传感器、信息及能源等领域。基于PatentStrategies专利分析系统,对全球和中国石墨烯探测器专利技术进行专利授权、布局、技术来源、竞争力、IPC分类等角度的分析,在挖掘该研究领域核心专利的基础上,进一步分析石墨烯探测器领域的核心专利情况。该分析可为石墨烯探测器研发人员提供重要参考。     

ROS-sensitive selenium-containing cationic brush polymer with potent gene transfection efficiency and biocompatibility

Smart gene delivery vectors are gaining increasing attention in gene therapy, owing to their low cytotoxicity and intrinsic responsiveness. Our previously fabricated novel cationic brush polymer, comprising C Se bonds and tertiary amine EGIn-g-PDMAEMA, shows potential for gene transfection. In this study, its high efficiency for siRNA/pDNA transfection and low cytotoxicity in reactive oxygen species (ROS)-rich microenvironments is substantiated in vitro. Its superior binding capacity with siRNA/pDNA is confirmed by agarose gel electrophoresis assay. The threshold weight ratios for siRNA/pDNA migration delay are 15 and 3 (polymer-to-nucleic acid, w/w), respectively. Fluorescence microscopy and ribonucleotide reductase regulatory subunit M2 gene silencing essay verify the biodegradability and responsive control release of nucleic acids under hydrogen peroxide stimulation in Huh-7 cells. Compared with the gold standard, polyethylenimine 25 kDa, the target polymer displays superior transfection efficiency in ROS-rich tumor cells under serum-free conditions. Furthermore, the vector–nucleic acid complexes exhibit over 90% cell viability at a high concentration of 12 μg mL⁻¹ and good colloidal stability in phosphate-buffered saline (PBS) and 10% fetal bovine serum-PBS for 24 h. The efficient control release and expression of nucleic acids in ROS environments and reduced cytotoxicity highlight the superiority of EGIn-g-PDMAEMA as a gene delivery platform for tumor gene therapy.     

Relating chemical and biological diversity space: a tunable system for efficient gene transfection

Polyethyleneimine (PEI), a well-established nonviral transfection reagent, was combinatorially modified with varying proportions of methyl, benzyl, and n-dodecyl groups to create a library of 435 derivatized polymers. Screening of this library for transfection, DNA binding, and toxicity allows systematic correlation of the biological properties of our polymers to their derivatizations. Combinations of derivatizations bring about a 100-fold variation in transfection efficiency between library members. The best PEI derivatives exhibit increases in transfection efficiency of more than 80-fold over unmodified PEI (up to 28+/-7 % of cells transfected) and rival commercial reagents such as Lipofectamine 2000 (21+/-10 %) and JetPEI (32+/-5.0 %). In addition, we can identify compounds that are specifically tuned for efficient transfection in CHO-K1 over Ishikawa cells and vice versa, demonstrating that the approach can lead to cell-type selectivity of at least one order of magnitude. This work demonstrates that multivalent derivatization of a polymeric framework can create functional diversity substantially greater than the structural diversity of the derivatization building blocks and suggests an approach to a better understanding of the molecular underpinnings of transfection as well as their exploitation.     

Investigation on characterization and transfection of a novel multi‐polyplex gene delivery system

pDNA was condensed by polycationic peptide polylysine (PLL) to form a core, and then encapsulated in biodegradable monomethoxy (poly ethylene glycol)-poly(lactide-co-glycolide)-monomethoxy (poly ethylene glycol) (PELGE) to form core-shell nanoparticles (NPs) as a novel multi-polyplex gene delivery system—PPD(PELGE-PLL-DNA). NPs were prepared by a double emulsification-solvent evaporation technique, using F68 (Pluronic F68, namely Poloxamer 188) as surfactant (not traditional stabilizer PVA), and characterized by morphology, particle size, zeta potential, nuclease, and sonication protection ability, as well as transfection efficiency. Results showed that PPD had a regular spherical shape, with an average diameter of 155 ± 2.97 nm and a zeta potential of −25.6 ± 1.35 mV. PPD could protect plasmid DNA from nuclease degradation and sonication during preparation, while the transfection efficiencies in HepG2 cells and Hela cells were much higher than that of NPs without PLL. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Improved transfection efficiency of chitosan‐DNA complexes employing reverse transfection

The present study was designed to systematically compare the conventional and reverse transfection methodologies for chitosan/DNA complexes using a low molecular weight (MW) chitosan. The hydrodynamic diameter of the complexes, measured by Dynamic Light Scattering (DLS) was found to be ～ 216 nm and TEM investigations showed spherical and compact complexes with an average size of 200 nm. The transfection efficiency of chitosan using the two methodologies was assessed by employing reporter gene coding for green fluorescent protein (GFP) and luciferase. More than 50% of HEK 293 cells were transfected when transfection done using reverse transfection strategy at pH 6.5 with 10% serum for 24 h followed by media replenishment with pH 7.4 with 10% serum for an additional 24 h period. Also, the cytotoxicity of chitosan/DNA complexes was also considerably lower than the commercially available transfection reagent lipofectamine. Our investigation concludes that maximal transgene expression levels could be achieved using reverse transfection where the chitosan/DNA complexes are pre‐incubated on the plate surface followed by plating of cells at pH 6.5 with 10% serum for 24h and media resupplemented with pH 7.4 with 10% serum for an additional 24 h period. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Graphene and Functionalized Graphene Supported Platinum Catalyst for PEMFC

The graphene was synthesized by chemical oxidation followed by thermal exfoliation of natural graphite. The functionalized graphene (FG) was prepared by chemical treatment of the synthesized graphene. The as‐synthesized graphene and FG were characterized and used as Pt support materials. The 20 wt.% Pt/G and 20 wt.% Pt/FG catalysts were prepared by precipitation method. The prepared catalysts were characterized for particle size using X‐ray diffraction, surface morphology, electrochemical performance, and stability using cyclic voltammetry. The electrochemical surface area of the FG supported platinum catalyst was found to be more than 45% as compared to the commercial carbon supported platinum catalyst. The stability of the developed catalyst (Pt/G and Pt/FG) was significantly higher than the commercial Pt/C. The membrane electrode assembly was developed using the catalysts and tested in a PEMFC. The maximum power densities of the fuel cell were found to be 314, 426, and 455 mW cm^–2 using Pt/C, Pt/G, and Pt/FG, respectively.     

Graphene nanocomposites based on poly(vinylidene fluoride): Structure and properties

A nanocomposite of Poly(vinylidene fluoride) (PVDF) was prepared with graphene sheets (GSs), which are a novel filler by a solution method. The structure‐properties relationships of PVDF/GSs nanocomposites were studied. The results of differential scanning calorimetry and X‐ray diffraction show that addition of GSs to the PVDF matrix promotes an α phase to β phase transformation of the polymer crystal. The nanocomposites exhibit significant increases in dynamic mechanical properties and thermal stability compared to the neat PVDF. In addition, the incorporation of GSs in PVDF indicated excellent optical transparency at the lowest weight fractions of GSs and modified wettability of PVDF. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Comparative study of a Surface Plasmon Resonance Biosensor based on Metamaterial and Graphene

In this study, a surface plasmon resonance biosensor at near infrared frequency based on a metamaterial is proposed. The proposed biosensor utilizes the properties of plasmons and metamaterial for enhancement of its performance parameters i.e. sensitivity, detection accuracy and quality factor. The thickness of the metamaterial and gold film has been optimized for optimal performance of the proposed biosensor at near infrared wavelengths. Results obtained from the proposed biosensor were compared with existing two-dimensional nanomaterials such as a graphene based biosensor and a conventional surface plasmon resonance biosensor. Finally, it is observed that the performance parameters of the proposed biosensor are very high when compared to existing surface plasmon resonance biosensors.     

石墨烯、氧化石墨烯改性羟基磷灰石制备及研究进展

羟基磷灰石是一种具有优秀的生物相容性以及骨传导性的材料,但因其较差的力学性能,该材料在临床上的应用受到了较大限制。石墨烯、氧化石墨烯作为新兴的材料,因为独特的层状结构而有着不错的力学性能,因此利用石墨烯、氧化石墨烯对羟基磷灰石进行改性从而提升羟基磷灰石的性能是近期研究的热点。这篇综述简要介绍了近年来关于以石墨烯及氧化石墨烯作为支撑材料对羟基磷灰石进行改性的合成方法及所得产物的性能变化,对其主要研究进展,包括制备、性能和特点进行了探究。     

Graphene oxide nanopaint

Nanostructured materials are receiving growing interest in the development of a number of commercial products. In this study, we have developed a multifunctional graphene oxide (GO) nanopaint by incorporating GO sheets in an alkyd resin with suitable non-toxic additives using ball milling. The drying mechanism of the GO nanopaint has been discussed. Intermolecular cross-linking between GO and the lipid chains in the alkyd resin was studied by Fourier transform infra red spectra, Raman spectra, and X-ray photoelectron spectra, respectively. The prepared GO nanopaint exhibited good corrosion-resistant behavior in both acidic and high-salt-content solutions as examined by the immersion and electrochemical corrosion tests. The GO nanopaint coating possesses a corrosion protection efficiency of about 76% in salt water as estimated from the linear polarization studies. The antibacterial property of the GO nanopaint coated surface was studied against three bacterial strains (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa) and the results showed that GO nanopaint inhibited the bacterial growth on its surface. The in situ biofouling tests demonstrated the inhibition of fouling on the GO nanopaint surface.     

石墨烯及氧化石墨烯增强PE–UHMW复合材料进展

从力学性能、化学稳定性和摩擦学性能3个方面,叙述了石墨烯及氧化石墨烯增强超高分子量聚乙烯(PE–UHMW)复合材料的研究现状。根据PE–UHMW复合材料所表现出来的优异性能可知,新型复合材料拥有优异的力学性能,在不远的将来将会取代目前广泛使用的交联聚乙烯材料,并将获得举足轻重的地位。     

Graphene nanosheets based on controlled exfoliation process for enhanced lithium storage in lithium-ion battery

A facile and rapid approach was used for the fabrication of chemically derived graphene nanosheets based on the reduction of graphite oxide (GO) in tube furnace assembly at different temperatures. The morphologies, microstructures, specific surface areas and other features of GO and graphene nanosheets were characterized. Structure characterization indicates that the platelet thickness of graphene nanosheets obtained at 300 °C was 1.62 nm, which corresponds to an approximately 5 layers stacking of the monoatomic graphene nanosheets. Electrochemical performances of the as-prepared graphene nanosheets were performed, the result of which could prove the above observation that graphene nanosheets (5 layers) obtained at 300 °C actually displayed the most remarkable electrochemical performances: the first discharge and charge capacities of graphene nanosheets were as high as 2137 mAh/g and 994 mAh/g, respectively, and after 100 cycles graphene nanosheets still possessed a high capacity of 478 mAh/g.     

Graphene oxide coupled with gold nanoparticles for localized surface plasmon resonance based gas sensor

An optical gas sensor was prepared by depositing graphene oxide flakes over a monolayer of gold nanoparticles, chemically attached to a functionalized fused silica substrate. The coupling between flakes and nanoparticles lead to optical changes upon exposure to different gases: in particular, we observed a shift of the surface plasmon resonance band in presence of both reducing and oxidizing gases. This effect can be explained in terms of a strong gold–graphene interaction and specifically of electron transfer between the gold nanoparticles and the two-dimensional sheet of the sp²-hybridized carbons of graphene oxide.     

石墨烯对聚苯胺/石墨烯复合电极容量的影响研究

石墨烯因其优异的导电性能和巨大的比表面积而被广泛应用于复合材料的研究。本文借助微晶石英天平采用循环伏安法一步电沉积制备了聚苯胺/石墨烯复合材料,其中所用到的石墨烯分散液是电解剥离法制备的。保持苯胺单体的浓度不变,观察改变石墨烯的含量对聚苯胺/石墨烯复合材料的制备的影响。结果表明,制得的复合材料的比电容高达1166 F/g。当苯胺单体浓度不变时,石墨烯的含量越高,循环伏安结果表明其电容性能也越好。所得的聚苯胺/石墨烯复合材料中石墨烯起到了良好的电子传输作用。     

Binding Graphene Sheets Together Using Silicon: Graphene/Silicon Superlattice

We propose a superlattice consisting of graphene and monolayer thick Si sheets and investigate it using a first-principles density functional theory. The Si layer is found to not only strengthen the interlayer binding between the graphene sheets compared to that in graphite, but also inject electrons into graphene, yet without altering the most unique property of graphene: the Dirac fermion-like electronic structure. The superlattice approach represents a new direction for exploring basic science and applications of graphene-based materials.     

基于石墨烯微片的Fe/C微电解处理机械加工切削废液

采用Fe/C微电解原理,研究了铁/活性炭、铁/石墨烯微片两种不同微电解组合对高浓切削废液COD去除效果的影响,并通过添加锰粉或调节pH等方式对试验效果进行了优化和验证。