Infrared photodetectors based on reduced graphene oxide and graphene nanoribbons

The use of reduced graphene oxide (RGO) and graphene nanoribbons (GNRs) as infrared photodetectors is explored, based on recent results dealing with solar cells, light-emitting devices, photodetectors, and ultrafast lasers. IR detection is demonstrated by both RGO and GNRs in terms of the time-resolved photocurrent and photoresponse. The responsivity of the detectors and their functioning are presented.     

In situ synthesis of thermochemically reduced graphene oxide conducting nanocomposites

Highly conductive reduced graphene oxide (GO) polymer nanocomposites are synthesized by a well-organized in situ thermochemical synthesis technique. The surface functionalization of GO was carried out with aryl diazonium salt including 4-iodoaniline to form phenyl functionalized GO (I-Ph-GO). The thermochemically developed reduced GO (R-I-Ph-GO) has five times higher electrical conductivity (42,000 S/m) than typical reduced GO (R-GO). We also demonstrate a R-I-Ph-GO/polyimide (PI) composites having more than 10(4) times higher conductivity (~1 S/m) compared to a R-GO/PI composites. The electrical resistances of PI composites with R-I-Ph-GO were dramatically dropped under ~3% tensile strain. The R-I-Ph-GO/PI composites with electrically sensitive response caused by mechanical strain are expected to have broad implications for nanoelectromechanical systems.     

Reduced graphene oxide enhanced magnetic nanocomposites for removal of carbamazepine

Ferrite, as a kind of common magnetic adsorbent, always tend to reuniting and lead to the poor performance for removing contaminant in aqueous. Meanwhile, reduced graphene oxide (rGO), a high-efficiency adsorbent used for water treatment, is hydrophobic and easy to stack because of the Van der Waals force, resulting in the low adsorption capacity. Herein, we prepare the magnetic CoFe₂O₄/rGO nanocomposites to solve the reuniting of CoFe₂O₄ and stacking of rGO simultaneously. The rGO nanosheets can improve the dispersion of CoFe₂O₄ nanoparticles. As sorbent, the adsorption behaviors of carbamazepine on the nanocomposites can be fitted well by the Langmuir and pseudo-second-order kinetic models. In addition, the CoFe₂O₄/rGO nanocomposites show enhanced adsorption performance than that of the pure CoFe₂O₄ nanoparticles, and the loading of rGO can affect their adsorption performance. The adsorption of carbamazepine on CoFe₂O₄/rGO is exothermic and mainly controlled by π–π interaction and hydrogen bond interaction. Furthermore, the CoFe₂O₄/rGO can be used to remove other organic pollutants simultaneously. Finally, the nanocomposites can be collected by external magnet, and the regenerated nanocomposites still showed a high adsorption capacity retention (90%) after five cycles.     

Inkjet printed electronics using copper nanoparticle ink

Inkjet printing of electrode using copper nanoparticle ink is presented. Electrode was printed on a flexible glass epoxy composite substrate using drop on demand piezoelectric dispenser and was sintered at 200 °C of low temperature in N₂ gas condition. The printed electrodes were made with various widths and thickness. In order to control the thickness of the printed electrode, number of printing was varied. Resistivity of printed electrode was calculated from the cross-sectional area measured by a profilometer and resistance measured by a digital multimeter. Surface morphology of electrode was analyzed using scanning electron microscope (SEM) and atomic force microscope (AFM). From the study, it was found that 10 times printed electrode has the most stable grain structure and low resistivity of 36.7 nΩ m.     

Melt rheology of nanocomposites based on acrylic copolymer and cellulose whiskers

Nanocomposites based on poly(styrene-co-hexylacrylate) copolymer and cellulose whiskers as the nanosize filler were prepared by in situ miniemulsion polymerization and their melt rheological behaviours were investigated under dynamic shear conditions. The effects of γ-methacryloxypropyl triethoxysilane (MPS) content along with the whisker loading were explored. In the absence of whiskers, a transition from a liquid- to a solid-like behaviour was observed when the polymer was synthesized in the presence of MPS. When cellulose nanofiller was added, the storage modulus G′ and the dynamic viscosities η of the nanocomposites increased monotonically with whisker content and the resulting materials displayed a solid-like behaviour. Above 2 wt.%. loading, a percolated interconnected whisker-whisker network is built up, producing a jump in the storage modulus and strong shear-thinning behaviour of the viscosity. However, as the nanocomposites were prepared in the presence of 3% of MPS, no enhancement nor in the storage modulus nor in the viscosity was observed up to 5 wt.%. of whisker loading. Such a phenomenon was ascribed to inhibition of build-up of the whisker network. The non-linear viscoelastic behaviour of the nanocomposites was also investigated and analysed in terms of the breakdown of different networks, namely the filler-filler and the polymer-filler networks.     

Thermal and aqueous stability improvement of graphene oxide enhanced diphenylalanine nanocomposites

Abstract

Nanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to e.g. biosensing, electrochemical, electromechanical or electronic applications.     

Preparation and tribological properties of graphene oxide/nitrile rubber nanocomposites

Graphene oxide (GO)/nitrile rubber (NBR) nanocomposites with various contents of GO were prepared by a solution-mixing method,in this study. The GO sheets were exfoliated from natural fake graphite by an improved Hummers method and could be further dispersed homogeneously in NBR matrix. The thickness and size of the GO sheets were observed by atomic force microscopy and transmission electron microscopy. The tribological properties of the GO/NBR nanocomposites were evaluated on a ring-block MRH-3 wear tester under dry sliding and water-lubricated conditions. The worn surface morphologies of the GO/NBR nanocomposites were observed by a scanning electron microscopy. It was found that under dry sliding, both the friction coefficient (COF) and specific wear rate of the nanocomposites decreased dramatically at first, then increased with increasing GO contents, while under water-lubricated condition, both the COF and specific wear rate of the nanocomposites decreased with increasing GO contents. Finally, the friction and wear mechanisms of the GO/NBR nanocomposites were tentatively proposed.     

Inkjet printed surface enhanced Raman spectroscopy array on cellulose paper

A novel, ultra low-cost surface enhanced Raman spectroscopy (SERS) substrate has been developed by modifying the surface chemistry of cellulose paper and patterning nanoparticle arrays, all with a consumer inkjet printer. Micro/nanofabrication of SERS substrates for on-chip chemical and biomolecular analysis has been under intense investigation. However, the high cost of producing these substrates and the limited shelf life severely limit their use, especially for routine laboratory analysis and for point-of-sample analysis in the field. Paper-based microfluidic biosensing systems have shown great potential as low-cost disposable analysis tools. In this work, this concept is extended to SERS-based detection. Using an inexpensive consumer inkjet printer, cellulose paper substrates are modified to be hydrophobic in the sensing regions. Synthesized silver nanoparticles are printed onto this hydrophobic paper substrate with microscale precision to form sensing arrays. The hydrophobic surface prevents the aqueous sample from spreading throughout the paper and thus concentrates the analyte within the sensing region. A SERS fingerprint signal for Rhodamine 6G dye was observed for samples with as low as 10 femtomoles of analyte in a total sample volume of 1 μL. This extraordinarily simple technique can be used to construct SERS microarrays immediately before sample analysis, enabling ultra low-cost chemical and biomolecular detection in the lab as well as in the field at the point of sample collection.     

Flexible humidity sensor based on light-scribed graphene oxide

Journal of Materials Science: Materials in Electronics - The light scribe (LS) technique has been applied to reduce graphene oxide (LSGO) over a flexible substrate to be used as a humidity sensor....     

Improvement of medical applicability of hydroxyapatite/graphene oxide nanocomposites via additional yttrium oxide nanoparticles

Hydroxyapatite is one of the most studied bioactive materials in the biomedical field. However, Hydroxyapatite’s low mechanical strength and low fracture toughness represent a limitation in its applications as a load-bearing biomaterial. Yttrium oxide and graphene oxide (GO) have previously been shown to enhance these mechanical characterization of hydroxyapatite (HAP) when combined in binary nanocomposites. In this study, a novel ternary nanocomposite hydroxyapatite/yttrium oxide/graphene oxide has been developed and its characteristics have been compared to the nanoparticles and binary nanocomposites of its components. The compositions of the prepared materials have been confirmed. The typical morphologies of the three components of the nanocomposites have been shown by scanning and transmission electron microscopes with HAP nanoparticles. The average roughness has decreased from 11.4 nm in the nanoparticles of the pure HAP to 7.9 nm in the ternary nanocomposite. All prepared nanocomposites have shown an acceptable slight decrease in cell viability with 96.9 ± 3.5% cell viability in the composite. The ternary nanocomposite has also shown a higher antibacterial activity compared to its individual constituents, with a zone of inhibition of 12.9 ± 1.1 mm and 12.5 ± 0.9 mm against E. coli and S. aureus, respectively, compared to no inhibition in the case of pure Hydroxyapatite.     

Ultrasound-assisted fabrication of dispersed two-dimensional copper/reduced graphene oxide nanosheets nanocomposites

Graphene oxide nanosheets (GOS) were employed as template and hydrazine hydrate was used as reductant for GOS and cupric ion. Highly dispersed two-dimensional (2D) copper/reduced graphene oxide nanosheets (Cu/RGOS) nanocomposites were effectively fabricated by ultrasound-assisted electroless copper plating process. Sandwich-like 2D Cu/RGOS nanocomposites consist of uniform Cu layer on the both side of centric RGOS. The Cu layer with thickness of about 60 nm exhibits almost single-crystalline with (1 1 1) preferred crystalline direction and have tight binding with RGOS. The effect of ultrasound on electroless Cu plating includes: accelerating deposition rate, enhancing interfacial bonding and preventing 2D Cu/RGOS nanocomposites from aggregating.     

Electrical and optical properties of reduced graphene oxide and multi-walled carbon nanotubes based nanocomposites: A comparative study

Graphene and multi-walled carbon nanotubes have attracted interest for a number of potential applications. One of the most actively pursued applications uses graphene and carbon nanotubes as a transparent conducting electrode in solar cells, displays or touch screens. In this work, in situ reduced graphene oxide/Poly (vinyl alcohol) and multi-walled carbon nanotubes/Sodium Dodecyl Sulfate/Poly (vinyl alcohol) composites were prepared by water dispersion and different reduction treatments. Comparative studies were conducted to explore the electrical and optical properties of nanocomposites based on graphene and multi-walled carbon nanotubes. A thermal reduction of graphene oxide was more effective, producing films with sheet resistances as low as 10²–10³ Ω/square with 80% transmittance for 550 nm light. The percolation threshold of the thermally reduced graphene oxide composites (0.35 vol%) was much lower than that of the chemically reduced graphene oxide composites (0.57 vol%), and than that of the carbon nanotubes composites (0.47 vol%). The Seebeck coefficient of graphene oxide films changes from about 40 μV/K to −30 μV/K after an annealing of three hours at 200 °C. The optical absorption of the nanocomposites showed a high absorbance in near UV regions and the photoluminescence enhancement was achieved at 1 wt% graphene loading, while the carbon nanotubes based composite presents a significant emission at 0.7 wt% followed with a photoluminescence quenching at higher fraction of the nanofillers 1.6 wt% TRGO and 1 wt% MWCNTs.     

The effect of Ag loading on supercapacitor performance of graphene based nanocomposites

In the present study, we prepared reduced graphene oxide (rGO) decorated with Ag nanoparticles by a one pot, simultaneous reduction method. The effect of AgNO₃ amount on the chemical, morphological and electrochemical properties of binary rGO-Ag nanocomposite for supercapacitor application was investigated. The chemical and morphological characterization of prepared rGO-Ag nanocomposites was realized with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). For supercapacitor application, electrochemical performance of the nanocomposites was investigated with cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. As a result of their excellent conductivity and spacer role which prevent aggregation of rGO nanosheets and maintain the electroactive surface area, Ag nanoparticles significantly enhance the electrochemical performance of the nanocomposite. The rGO-Ag nanoparticle nanocomposite exhibited a maximum specific capacitance of 34.2?mF?cm^?2 at 0.6?A?cm^?2 current density. The nanocomposite electrode also has excellent rate capability and cycle life. The capacitance retention of rGO-Ag electrode is 98% after 1000 charge-discharge cycle. The results showed that rGO-Ag nanocomposite is a building block for ternary or other multicomponent nanocomposites.     

Thermoelectric behavior of aerogels based on graphene and multi-walled carbon nanotube nanocomposites

In this work, we presented that the Seebeck coefficient and electrical conductivity can be increased simultaneously in aerogels based on graphene and multi-walled carbon nanotube (graphene-MWCNT) nanocomposites, and at the same time the thermal conductivity is depressed due to 3D porous skeleton structure. As a result, graphene-MWCNT aerogels possess ultra-low thermal conductivities (∼0.056 W m⁻¹ K⁻¹) and apparent density (∼24 kg m⁻³), thereafter the figure of merit (ZT) of ∼0.001 is achieved. Although the ZT value is too low for practical application as a thermoelectric (TE) material, the unique structure in this project provides a potential way to overcome the challenge in bulk semiconductors that increasing electrical conductivity generally leads to decreased Seebeck coefficient and enhanced thermal conductivity.     

Investigation on microwave absorption capacity of nanocomposites based on metal oxides and graphene

Graphene and its nanocomposites were prepared via solution mixing process. Graphene based polymer nanocomposites were prepared by two step process. Firstly, graphene/poly(3-methyl thiophene)(PMT)/BaTiO₃ nanocomposite was prepared by in situ chemical oxidation polymerization technique. In the second step these nanocomposites were dispersed in thermoplastic polyurethane (TPU) matrix by solution blending process. All the four nanocomposites in TPU [30 % modified graphene (P1), 30 % Poly(3-methyl thiophene) (P2), 30 % graphene/PMT/BaTiO₃ (P3) and 15 % graphene/PMT/BaTiO₃ + 15 % Fe₃O₄ (P4)] were analyzed by different analytical techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Microwave absorbing property was measured by Agilent vector network analyzer (ENA E5071C) in the X-band region (8–12 GHz). Microwave absorption result was interpreted with the help of complex permittivity and permeability of the prepared materials. Matching of both dielectric loss and magnetic loss is essential for an effective radar absorbing material (RAM). P1, P2, P3 and P4 showed the maximum return loss of ?14.37, ?9.3, ?30.02 and ?47.59 dB respectively. Thermal stability of the RAMs was determined by the help of thermogravimetric analysis (TGA) instrument. Among the all, P4 showed better thermal property. All results support their use as RAM in different field.     

Analysis of structure characteristics in laminated graphene oxide nanocomposites using molecular dynamics simulation

The characteristics of laminated graphene oxide (LGO) nanocomposite, which are expected to be used for highly functional composites, are known to be related to its microstructure. In this study, we investigate the influences of hydrogen-bonding and cross-linked network structures on the initial stiffness and yield stress, using molecular dynamics simulations. Our results show that each structure increases the mechanical properties, and the combination of these structures strengthens the properties. Moreover, we found that the physical origin of the enhancement is cross-linked networks that generate stretched polymers connecting graphene sheets. Our study concludes by suggesting an appropriate selection of materials for high-performance LGO nanocomposites.     

Preparation and properties of reduced graphene oxide/polyacrylonitrile nanocomposites using polyvinyl phenol

Nanocomposites of polyacrylonitrile (PAN) with reduced graphene oxide (rGO) were prepared using a solution mixing technique employing polyvinyl phenol (PVP) as a compatibilizer. The PVP can facilitate composite formation by interacting with both rGO and PAN via π-π and H-bonding respectively. Various amounts of rGO were used to prepare PAN nanocomposites. The cross-sectional morphology of the composite films shows a uniform dispersion of rGO sheets in the PAN matrix. The Fourier transform infrared (FT-IR) studies revealed that good interaction of the rGO/PVP hybrid with PAN. The wide angle x-ray diffraction (WAXS) study confirms that the rGO sheets were uniformely dispersed as individual sheets in the PAN matrix. Thermogravimetric analysis shows enhanced thermal stability of the composite compared to pure PAN. The tensile strength and elastic modulus of the nanocomposites increased with increasing rGO content. A 102% enhancement in tensile strength and a 62.9% enhancement in elastic modulus were observed in the nanocomposite with 5% rGO.     

丙烯酸功能化纳米氧化石墨烯/丙烯酸酯复合乳液的制备及性能

以烯丙基磺酸钠（ALS）为可聚合乳化剂,采用种子乳液聚合法制备丙烯酸功能化纳米氧化石墨烯（FAGO）/丙烯酸酯复合乳液。通过红外光谱、XRD表征GO、FAGO的结构,通过SEM和TEM观察GO、FAGO、纳米FAGO/丙烯酸酯复合乳液的形貌。结果表明,丙烯酸上的羧基与GO羟基反应生成了酯键;FAGO的边缘发生扭曲变形,局部产生较多褶皱,体系的不规整度显著增加;纳米FAGO/丙烯酸酯乳胶粒子呈规则的球形。纳米粒径电位分析表明,纳米FAGO/丙烯酸酯复合乳液粒径大小均一,分散性良好,随着ALS加入量的增加,纳米FAGO/丙烯酸酯乳胶粒子的粒径逐渐减小,其分散性指数（PDI）先减小后增大,相应的Zeta电位逐渐升高,乳液的黏度逐渐增大,乳胶膜耐水性变差,当ALS用量为0.8wt%时,纳米FAGO/丙烯酸酯复合乳液综合性能最佳。