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Item type:Publication, Access status: without files , Individual CdS-covered aerographite microtubes for room temperature VOC sensing with high selectivity(2019-09); ; ; ; The synthesis of new nanomaterials with a large surface-to-volume ratio is of high interest for sensing applications, and especially for gas sensors with high performances. In this work, a thin layer of CdS is deposited onto tubular graphitic/aerographite microstructures using RF magnetron sputtering for further integration into sensing devices using a FIB/SEM system. The quality of the deposited layers as well as microstructural features were analyzed by transmission electron microscopy and energy dispersive X-ray spectroscopy. The gas sensing measurements at room temperature demonstrated the excellent sensing properties towards vapors of volatile organic compounds (VOCs), such as ethanol, acetone, 2-propanol and n- butanol. The superior properties were attributed to the nanometer thickness (20–30 nm)and high surface-to-volume ratio of CdS thin layers as a result of the tubular structure of wrinkled Aerographite (AG). This causes a big number of gas sensitive potential barriers between particles, resulting in a high sensor response. This makes mesoporous graphitic/aerographite microtubes ideal construction blocks for the formation of hybrid materials and for their use in gas sensing applications. The presented strategy can be also applied to other materials with high performance gas sensing properties.Publicationtype: Journal Article190 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Improving gas sensing by CdTe decoration of individual Aerographite microtubes(2019-02-08); ; ; ; Novel gas sensors have been realized by decorating clusters of tubular Aerographite with CdTe using magnetron sputtering techniques. Subsequently, individual microtubes were separated and electrically contacted on a SiO2/Si substrate with pre-patterned electrodes. Cathodoluminescence, electron microscopy and electrical characterization prove the successful formation of a polycrystalline CdTe thin film on Aerographite enabling an excellent gas response to ammonia. Furthermore, the dynamical response to ammonia exposure has been investigated, highlighting the quick response and recovery times of the sensor, which is highly beneficial for extremely short on/off cycles. Therefore, this gas sensor reveals a large potential for cheap, highly selective, reliable and low-power gas sensors, which are especially important for hazardous gases such as ammonia.Publicationtype: Journal Article180 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Individual hollow and mesoporous aero-graphitic microtube based devices for gas sensing applications(American Institute of Physics (AIP), 2017-06-27); ; ; ; In this work, individual hollow and mesoporous graphitic microtubes were integrated into electronic devices using a FIB/SEM system and were investigated as gas and vapor sensors by applying different bias voltages (in the range of 10 mV-1 V). By increasing the bias voltage, a slight current enhancement is observed, which is mainly attributed to the self-heating effect. A different behavior of ammonia NH3 vapor sensing by increasing the applied bias voltage for hollow and mesoporous microtubes with diameters down to 300 nm is reported. In the case of the hollow microtube, an increase in the response was observed, while a reverse effect has been noticed for the mesoporous microtube. It might be explained on the basis of the higher specific surface area (SSA) of the mesoporous microtube compared to the hollow one. Thus, at room temperature when the surface chemical reaction rate (k) prevails on the gas diffusion rate (DK) the structures with a larger SSA possess a higher response. By increasing the bias voltage, i.e., the overall temperature of the structure, DK becomes a limiting step in the gas response. Therefore, at higher bias voltages the larger pores will facilitate an enhanced gas diffusion, i.e., a higher gas response. The present study demonstrates the importance of the material porosity towards gas sensing applications.Publicationtype: Journal Article91 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Nanomechanics of individual aerographite tetrapods(Nature Publishing Group, 2017-04-12); ; ; ; Carbon-based three-dimensional aerographite networks, built from interconnected hollow tubular tetrapods of multilayer graphene, are ultra-lightweight materials recently discovered and ideal for advanced multifunctional applications. In order to predict the bulk mechanical behaviour of networks it is very important to understand the mechanics of their individual building blocks. Here we characterize the mechanical response of single aerographite tetrapods via in situ scanning electron and atomic force microscopy measurements. To understand the acquired results, which show that the overall behaviour of the tetrapod is governed by the buckling of the central joint, a mechanical nonlinear model was developed, introducing the concept of the buckling hinge. Finite element method simulations elucidate the governing buckling phenomena. The results are then generalized for tetrapods of different size-scales and shapes. These basic findings will permit better understanding of the mechanical response of the related networks and the design of similar aerogels based on graphene and other two-dimensional materials.Publicationtype: Journal ArticleScopus© Citations 30 425 515 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Low powered, tunable and ultra-light aerographite sensor for climate relevant gas monitoring(Royal Society of Chemistry (RSC), 2016-09-27); ; ; ; Increasing atmospheric CO2 gas pollution and emergence of new types of green energy sources require continuous environmental monitoring. In this context, fast, efficient, light, robust, and reliable gas sensors that can work at room temperature are in high demand. We report on a low-powered type of ultra-light sensor, based on a 3-D-microtube network from a 2-D graphene/nanographite, called aerographite, and a method to tune the nanosensor’s selectivity by a simple variation of the applied bias voltage. Adequate selectivity to CO2 and ultra-fast sensing of H2 by applying 1 V and 5 V, respectively, is obtained. At ultra-low applied bias voltages (1–100 mV) only very low power consumption (z3.6 nW for 1 mV) is needed. This is most important, as it can be run by energy harvesting methods. The presented results are of the highest interest in terms of low-cost production of ultra-light and ultra-low-power consumption gas sensors for environmental monitoring of greenhouse gases and their simplicity from the technological/engineering points of view.Publicationtype: Journal ArticleScopus© Citations 49 388 420