Multi-layer graphene and graphite nanoflakes were produced through graphite liquid exfoliation using organic solvents. The nanoflakes size distribution was statistically analyzed, with the number of ...measured samples being high enough (from ∼200 to 900) for reliable evaluation of the statistical model. The nanoflakes size data were found to follow a log-normal distribution, with higher fraction of large size flakes as compared to a conventional normal distribution. The same kind of distribution was also obtained for nanoflakes thickness. Based on these findings, the detailed mechanism of the pristine polycrystalline graphite exfoliation in a liquid phase due to formation and collapse of cavitation bubbles was discussed. The high quality of nanoflakes was confirmed by Raman spectroscopy.
Quantum dots (QDs) are small nanometer-sized (<10 nm) pure or composite materials with excellent novel properties, thus making them interesting and emerging candidates for new and exceptional ...applications in biomaterials research fields. As emerging members of QDs, carbon (especially, carbon QDs and graphene QDs) and semiconducting QDs have attracted greater attention owing to their excellent properties, unique size, versatile surface, and biocompatibility with nanotechnology. In this work, a comprehensive overview on the possibilities and achievements in the field of carbon and semiconducting QDs obtained by only microwave (MW)-assisted for biomedical purposes is provided. This specific literature review provides knowledge about MW-assisted synthesis and some selected bioapplication of carbon and semiconducting QDs. Currently, the MW-assisted fabrication of QDs represents a growing research field in nanomaterial research. MW-assisted approach for QD synthesis has been studied in details as this approach has several advantages such as uniform distribution of energy inside the reaction vessel, shorter reaction times, environmentally friendly and energy-saving technique, high reproducibility, and excellent control over experimental parameters. Also, a comprehensive overview is provided in this review, which contains the possibilities and achievements using MW-assisted heating approaches. This article updates the latest synthesis progress as well as applications and also comments all the challenges and perspective in this emerging research area.
•This review article provides knowledge about microwave-assisted synthesis and some selected bio applications.•Microwave-assisted heating is a simple, fast and inexpensive process to produce large quantity of quantum dots.•MW-assisted synthesis approach provides QDs formation in various media.•MW-assisted approach provides uniform distribution of energy, shorter reaction times and high reproducibility.
Defects induced by liquid-phase exfoliation of graphite using sonication were studied. It was shown that localized impact by cavitation shock waves can produce bulk ripplocations and various types of ...dislocations in graphite nanoplatelets. Formation of ripples is more pronounced in large aspect (length/width) ratio platelets or nanobelts. Quasi-periodical ripple systems were observed in many nanobelts after sonication. Mechanism of formation of ripples and dislocations during sonication was proposed. Surprisingly, fast high-temperature processing was found to anneal most of defects. This is consistent with our observations that defects associated with ripplocations are strongly localized and thus can be fast annealed.
The general considerations to design a sensor interface for passive RFID tags are discussed. This way, power and timing constraints imposed by ISO/IEC 15693 and ISO/IEC 14443 standards to HF RFID ...tags are explored. A generic multisensor interface is proposed and a survey analysis on the most suitable analog-to-digital converters for passive RFID sensing applications is reported. The most appropriate converter type and architecture are suggested. At the end, a specific sensor interface for carbon nanotube gas sensors is proposed and a brief discussion about its implemented circuits and preliminary results is made.
The highly conductive composite based on graphite nanobelts/ultra-high-molecular-weight polyethylene (UHMWPE) was developed using hot calendering at temperatures below the polymer melting point. The ...fabricated material exhibits excellent electrical conductivity (up to 40 S cm−1), high efficiency of electromagnetic interference shielding (near 35 dB for 100 μm thick samples) and good mechanical properties (flexibility and mechanical strength). These superior characteristics are the result of synergistic combination involving superior mechanical properties of the polymer, perfect transport characteristics of the filler and the specific method of fabrication allowing for formation of a segregated anisotropic conductive network with a low percolation threshold (0.42 vol %).
Burning Graphene Layer-by-Layer Ermakov, Victor A; Alaferdov, Andrei V; Vaz, Alfredo R ...
Scientific reports,
06/2015, Letnik:
5, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Graphene, in single layer or multi-layer forms, holds great promise for future electronics and high-temperature applications. Resistance to oxidation, an important property for high-temperature ...applications, has not yet been extensively investigated. Controlled thinning of multi-layer graphene (MLG), e.g., by plasma or laser processing is another challenge, since the existing methods produce non-uniform thinning or introduce undesirable defects in the basal plane. We report here that heating to extremely high temperatures (exceeding 2000 K) and controllable layer-by-layer burning (thinning) can be achieved by low-power laser processing of suspended high-quality MLG in air in "cold-wall" reactor configuration. In contrast, localized laser heating of supported samples results in non-uniform graphene burning at much higher rates. Fully atomistic molecular dynamics simulations were also performed to reveal details of oxidation mechanisms leading to uniform layer-by-layer graphene gasification. The extraordinary resistance of MLG to oxidation paves the way to novel high-temperature applications as continuum light source or scaffolding material.
The results of an investigation of thin Ni and CoNiMnP films deposited by electroplating over polyurethane-acrylate flexible substrates are presented. To improve magnetic properties of the films, an ...electroplating process was carried out with assistance of a strong magnetic field (3900G). The evaluated film properties were coercivity, remanence, maximum energy product, adherence and film composition. Comparison between the magnetic properties of the samples has shown that Ni and CoNiMnP films are suitable for distinct areas of applications in micro-devices: vibrating diaphragms and micro-magnet machines, respectively.
► Ni and CoNiMnP films were electroplated in presence of magnetic field. ► Magnetic and mechanical properties of films were evaluated. ► Ni films presented higher remanence and stress resistance. ► CoNiMnP films have higher coercivity and maximum energy product.
We report the design and fabrication of microreactors and sensors based on metal nanoparticle-decorated carbon nanotubes. Titanium adhesion layers and gold films were sputtered onto Si/SiO2 ...substrates for obtaining the electrical contacts. The gold layers were electrochemically thickened until 1 μ m and the electrodes were patterned using photolithography and wet chemical etching. Before the dielectrophoretic deposition of the nanotubes, a gap 1 μ m wide and 5 μ m deep was milled in the middle of the metallic line by focused ion beam, allowing the fabrication of sensors based on suspended nanotubes bridging the electrodes. Subsequently, the sputtering technique was used for decorating the nanotubes with metallic nanoparticles. In order to test the as-obtained sensors, microreactors (100 μ L volume) were machined from a single Kovar piece, being equipped with electrical connections and 1/4′′ Swagelok-compatible gas inlet and outlets for controlling the atmosphere in the testing chamber. The sensors, electrically connected to the contact pins by wire-bonding, were tested in the 10−5 to 10−2 W working power interval using oxygen as target gas. The small chamber volume allowed the measurement of fast characteristic times (response/recovery), with the sensors showing good sensitivity.
Determination of regular features of mechanisms underlying interactions of nanostructured materials is one of the most important problems on the way to create the new generation of efficient ...photovoltaic devices. In this paper, we study the luminescent and photoelectric properties of hybrid structures that are formed on the basis of multilayer graphene nanoribbons and semiconductor quantum nanocrystals of the 0D dimension, CdSe/ZnS core/shell quantum dots, and 2D-dimension CdSe nanoplates. It is shown that the multiexponential decay of the exciton luminescence of CdSe nanoplates at room temperature is determined by the occurrence of delayed luminescence, which is caused by the presence of trap states on the surface of nanoplates. It is found that, in dry layers of nanoplates on a dielectric substrate and in the composition of hybrid structures with graphene nanoribbons, the efficiency of delayed exciton luminescence of nanoplates increases. It is shown that the rate of increase in the photoconductivity in hybrid structures based on CdSe nanoplates is an order of magnitude higher than the rate of this process in similar structures based on CdSe/ZnS quantum dots, which indicates the formation of an effective energy/charge transfer channel from nanoplates to graphene nanoribbons.
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