Graphene-based materials for antenna applications

The demand of emerging transparent and flexible wireless electronic devices is ever‐increasing for Internet of Things (IoT) scenarios, like noninvasive healthcare, real‐time wearable electronics, etc. However, as an essential part of the IoT wireless communicational devices, radio frequency (RF) antennas are still hampered by poor‐flexibility, low‐conductivity, and weak‐transparency. Here, based on the unique electronic and optical properties of graphene, a method to obtain these appealing features concurrently through promoting synergistic effect between two‐dimensional (2D) and one‐dimensional (1D) materials is studied. It is found that this method could not only successfully maintain transparency and flexibility, but also greatly enhance the overall performance of the antenna. The fabricated antenna exhibits a 75% light transmittance, from 5.6 to 12.8 GHz ultrawide bandwidth and outstanding durability and stability. Moreover, a transparent and flexible radio frequency identification (RFID) tag is also designed and demonstrated with a remarkable reading distance. These findings show that the method by promoting synergistic effect of hybrid materials has great potential in the design of next generation novel and high‐performance wireless electronics.

Stable-jetting water-based graphene oxide (GO) and graphene (GR) inks without any surfactant or stabilizer are prepared from an unstable-jetting water-based starting solvent, with many thermal bubble inkjet satellite drops, by simply increasing the material concentration. The concentration-dependent thermal bubble inkjet droplet generation process is studied in detail. To overcome the low concentration properties of water-based thermal bubble inkjet inks, the substrate temperature is tuned below 60 °C to achieve high-quality print lines. Due to the difference in hydrophilicity and hydrophobicity of the 2D materials, the printed GO lines show a different forming mechanism from that of the GR lines. The printed GO lines are reduced by thermal annealing and by ascorbic acid, respectively. The reduced GO lines exhibit electrical conductivity of the same order of magnitude as that of the GR lines.

Nowadays, the internet of things (IOT) has attracted the attention of the researchers. As a key technology of the Internet of Things, RFID (Radio Frequency Identification) has also attracted the interest of industry and academia. One of the most important issues for the applications of the IOT based on RFID is security. In order to promote the development of IOT based on RFID, first of all, we briefly introduce the IOT system components and work process based on RFID, and then we deeply analyze the security threats in the IOT based on RFID, by the means of these analysis we discuss the current countermeasures for the security threats of RFID. Aiming at the RFID system, the corresponding technologies are raised such as Tag killing, Tag sleeping and blocker Tag; and the authentication based on HASH is the main method aiming at the communication process.

Recent research indicates that graphene oxide (GO) nanosheets can be used to regulate ice formation by controlling critical ice nucleus growth in water at supercooling temperatures. In addition, the study of ice formation mechanisms regulated by GO nanosheets, a good model system for antifreeze proteins (AFPs), will shed light on how AFPs regulate ice formation in nature. In this work, time-resolved small-angle x-ray scattering (TR-SAXS) and quasi-elastic neutron scattering (QENS) experiments were carried out to investigate the structural and dynamical mechanisms of ice formation regulated by GO nanosheets. Strikingly, a transient intermediate state was observed in TR-SAXS experiments that only exists in the aqueous dispersions with a larger GO size (11 nm). This serves as evidence that the size of GO is critical for regulating ice formation. Elastic neutron scattering results indicate that ice is formed in all samples and thermal hysteresis occurs in GO aqueous dispersions in both H2O and D2O. The structural and dynamics information about water molecules in GO, extracted from QENS, reveals different dynamical behaviors of water molecules in GO aqueous dispersions when approaching the ice formation temperature.

We present a comparative experimental and molecular dynamics (MD) simulation study to elucidate the role of oxygen functionalization on aqueous dispersibility of graphene oxide (GO). Our experimental results indicated better aqueous dispersibility of hydroxyl-rich GO due to distribution of hydroxyl groups on GO basal plane, covering more GO surface area than the edge carboxyl groups. Photoluminescence and UV absorbance results indicated that hydroxyl-rich GO consists of maximum number of well-exfoliated GO layers, which leads to the formation of more stable GO dispersions. Further, MD simulations and thermodynamic calculations clearly indicated that the potential of mean force is most repulsive for hydroxyl-modified GO sheets, in comparison to epoxy- and carboxyl-modified GO sheets. An increase in the number of hydrogen bonds between GO and water molecules was observed with increased functionalization. The present experimental study, underpinned by MD simulations, suggests that concentration, distribution, and chemical nature of individual oxygen functional groups present on GO surface determine the strength and nature of interfacial interactions between GO and water, which in turn decides the stability of aqueous GO dispersions. Thus, our results provide a mechanistic insight into the stability of GO dispersions and a guide for controlling GO aqueous dispersibility by custom functionalization.

Graphene oxide (GO) forms persistent dispersions in aqueous solutions up to concentrations of 0.2 mg mL(-1). Addition of methylene blue (MB) to these aqueous dispersion of GO gives rise to the observation in optical spectroscopy of new absorption bands that are indicative of the formation of MB/GO conjugates. Four new absorption maxima have been characterized, and their intensity varies depending on the relative concentration of MB with respect to GO. Two of these bands appearing at 677 and 757 nm correspond to individual MB molecules adsorbed on neutral or acid sites of GO, respectively. Two other bands at 615 and 580 nm are attributable to adsorbed MB molecules showing interaction with other neighbor dye molecules at incomplete (615 nm) or complete (580 nm) surface coverage. Complete coverage of GO surface by MB causes the formation of a precipitate and the separation of the MB/GO conjugate. EDS mapping of carbon and sulfur atoms of MB/GO conjugate indicates the homogeneous distribution of MB molecules coating GO sheets. A simple and reliable protocol for surface area measurement and determination of the level of aggregation for GO dispersions in water has been proposed by determining the amount of MB that leads to the maximum intensity of the 580 nm band and precipitation of the MB/GO conjugate. Specific surface area as high as 736.6 m(2) g(-1) in the range of the theoretical value for GO has been experimentally measured for diluted GO solutions, but aggregation levels of 15% were estimated for GO concentration of 50 μg mL(-1).

Graphene materials, used as electrocatalyst support in green hydrogen production, contribute to increasing the efficiency and robustness of various systems. However, the preparation of a hybrid catalyst containing graphene materials from industrial wastes is still a challenge due to the heterogeneity of the waste. We report the synthesis of 3D electrodes using graphene oxides (GOs) from industrial waste (IW) prepared by immersion onto Toray carbon paper as a 3D support onto GO suspensions and electrodepositing NiFe layered double hydroxides (LDHs). Standard graphite was also used as the reference. The morphology of the two hybrid electrodes was determined by SEM, HRTEM, XPS. Although very similar in both, the sample containing graphene from IW (higher Csp3 hybridization in the graphene layer) has a NiFe phase with less crystallinity and larger presence of Fe2+ ions. These electrodes exhibited similar activity and stability as electrocatalysts of the oxygen evolution reaction (OER), demonstrating the proactive effect of the graphene into the 3D electrode even when this is prepared from heterogeneous industrial waste. Moreover, the defective graphenic structure of the waste GO enhances the reaction kinetics and improves the electron transfer rate, possibly due to the small differences in the electrodeposited NiFe LDH structure.

Evaluation of design alternatives of End-Of-Life products using internet of things

It is broadly observed that graphene oxide (GO) films appear transparent with a thickness of about several nanometers, whereas they appear dark brown or almost black with thickness of more than 1 μm. The basic color mechanism of GO film on a sub-micrometer scale, however, is not well understood. This study reports on GO pseudo-1D photonic crystals (p1D-PhCs) exhibiting tunable structural colors in the visible wavelength range owing to its 1D Bragg nanostructures. Striking structural colors of GO p1D-PhCs could be tuned by simply changing either the volume or concentration of the aqueous GO dispersion during vacuum filtration. Moreover, the quantitative relationship between thickness and reflection wavelength of GO p1D-PhCs has been revealed, thereby providing a theoretical basis to rationally design structural colors of GO p1D-PhCs. The spectral response of GO p1D-PhCs to humidity is also obtained clearly showing the wavelength shift of GO p1D-PhCs at differently relative humidity values and thus encouraging the integration of structural color printing and the humidity-responsive property of GO p1D-PhCs to develop a visible and fast-responsive anti-counterfeiting label. The results pave the way for a variety of potential applications of GO in optics, structural color printing, sensing, and anti-counterfeiting.

One key technique in Internet of Things(IoT) is localization, which has been an indispensable context for most of the applications in IoT. In this paper, we introduce an indoor location detecting platform based on the passive RFID (Radio Frequency Identification) technology. The major advantage of our platform is that it can be adopted to meet different detection granularity requirement based on the flexible RFID antenna design. Second, the only thing for a user to carry with is a tiny RFID tag on his/her shoes which is light weight and no charging power problems. Thirdly it will be shown that our design is easy to be augmented into normal artifacts in an unobtrusive way for the indoor environment. Two versions of the RFID-based location detection systems are introduced. One is called U-tile (Ubiquitous tile), in which passive RFID reader is embedded into the tiles. Another improved version is called Indoor-tracer, which adopts anti-collision RFID and more light weight comparing with the previous version U-tile so that it can embedded into various artifacts like bags and drawers. The performances of both two prototype systems were evaluated and the mutual-aware applications for remote family based on IoT were developed by using the platform.

Even invented and applied initially during the World War II, RFID (Radio Frequency IDentification) technologies [1] have attracted much attention recently. Precisely speaking, RFID technologies have been applied very widely in some proprietary or closed systems, for example, animal control [2], portal control (access badges), etc. in last decades. The main advantages of RFID application are, storing item data in an electronic way even for further update, data access by electromagnetic wave in a wireless manner, and allowing quick multiple accesses to RFID tags. Based on the diverse applications, different spectrum bands are allocated, for example, LF (125 134.2 kHz and 140 148.5 kHz) for animal control, HF (13.56MHz) for electronic ticket, and UHF (868 MHz-928 MHz) for logistics, etc. Most of the frequencies are located in the ISM (Industrial, Scientific and Medical) bands [1]. However, RFID was emphasized again mainly because of the need of supply chain [3]. By proposing a standard for the format of electronic data used for goods items, of which EPC (Electronic Product Code) [4] is an example, the products can be registered at once when they are shipped out from the factories in one country, and be released when they are checked out at the counter of a supermarket in the other country in the world. These products might have been transferred through Customs of many countries and carried by different traffic means. When being through these check points, the related data stored in the tags are updated. This is called “product tracking” and is to be carried out in an “Internet of Thing (IOT)” [5]. This Chapter is to have a review on the technology theme – how to provide low-cost RFID Tags, when RFID technology is to be applied into the logistics area where the RFID tags are supposed to be not re-usable and to be as “zero-cost” as possible. Generally speaking, there are three major parts composing a RFID Tag’s total cost, namely, antenna, chip and assembly for them. The cost of antenna, in addition to the design phase, is mainly dependent on the manufacturing process. Therefore, manufacturing process should be focused if antenna’s cost, then the tag, is concerned. This is the theme of this Chapter. Not like the other antenna applications, for example, wireless LAN or mobile phone, in which antennas need to be compliant to the end products’ appearance by following the market trend. In the tag antenna industry, on the contrary, it does not need to design or modify the tag antenna often. The tag antenna just needs to electrically match the chip used in the beginning of design. It is not necessary for tag providers to prepare a wide product spectrum in the market. Again, not like the mobile phone industry, RFID tag’s players just

Research into graphene supercapacitors is currently undergoing a large increase in growth due to its beneficial chemical and mechanical properties. However, reports on ‘graphene’ supercapacitors use graphene materials produced through various methods. Currently, there has been no investigation into the effect the production method has upon the capacitance of the system, meaning direct comparison of the literature is not possible. In this work we compared several ‘types’ of graphene. These include “pure” graphene samples which include liquid phase exfoliated graphene, graphene nanoribbons, anodically exfoliated electrochemically graphene in aqueous system and cathodically exfoliated electrochemically exfoliated graphene in an organic system. Also included were “modified” graphene samples which included graphene oxide and reduced graphene oxide. It was observed that graphene oxide exhibited the highest specific capacitance of 164 F/g (5-10 times higher) , measured at a current density of 0.5 A/g, due to the oxygen containing functional groups giving an additional pseudocapacitance response as well as preventing restacking of the material. The graphene oxide also showed similar or superior cyclability when compared to the other pure and modified graphene materials. However, due to its intrinsically high resistance the addition of a conductive additive is required to achieve high rate capability. The higher capacitance and less energy demanding processing indicate that graphene oxide may be a better choice for high energy supercapacitor applications than “pure” graphene which will be suitable for high power applications.

Large scale preparation of graphene oxide/cellulose paper with improved mechanical performance and gas barrier properties by conventional papermaking method

Graphene oxide (GO) performs well as a filtration additive in water-based drilling fluids at concentrations as low as 0.2 % (w/w) by carbon content. Standard American Petroleum Institute (API) filtration tests were conducted on pH-adjusted, aqueous dispersions of GO and xanthan gum. It was found that a combination of large-flake GO and powdered GO in a 3:1 ratio performed best in the API tests, allowing an average fluid loss of 6.1 mL over 30 min and leaving a filter cake ~20 μm thick. In comparison, a standard suspension (~12 g/L) of clays and polymers used in the oil industry gave an average fluid loss of 7.2 mL and a filter cake ~280 μm thick. Scanning electron microscopy imaging revealed the extreme pliability of well-exfoliated GO, as the pressure due to filtration crumpled single GO sheets, forcing them to slide through pores with diameters much smaller than the flake's flattened size. GO solutions also exhibited greater shear thinning and higher temperature stability compared to clay-based fluid-loss additives, demonstrating potential for high-temperature well applications.

The Internet of Things (IoT) envisions an ecosystem where smart and interconnected objects can sense surrounding changes, communicate with each other, process information and take active roles in decision making. Optimizing supply chain performance is a primary concern of manufacturing and logistics organizations. Radio Frequency Identification (RFID) is helping organizations to build automated and interconnected smart environment by object identification and tracking, motivating the first step towards an IoT-enabled world. This chapter attempts to understand extant literature studying applications of RFID in implementing the IoT in supply chain management. We categorize extant literature, firstly, based on research methodology and secondly, based on supply chain processes. We find that presently academic activity is around conceptualizing the usability of RFID in the IoT with limited analytical and empirical evidence. Supply chain processes such as demand planning, procurement, retail shelf space management and product returns are prospective areas for interesting future research.