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Graphene resonant sensors have shown strong competitiveness with respect to sensitivity and size. To advance the applications of graphene resonant sensors, the damage behaviors of graphene harmonic oscillators after thermal annealing and laser irradiation were investigated by morphology analysis and frequency domain vibration characteristics. The interface stress was proven to be the key factor that directly affected the yield of resonators. The resulting phenomenon could be improved by appropriately controlling the annealing temperature and size of resonators, thereby achieving membrane intactness of up to 96.4%. However, micro-cracks were found on the graphene sheets when continuous wave (CW) laser power was more than 4 mW. Moreover, the fluctuating light energy would also cause mechanical fatigue in addition to the photothermal effect, and the threshold damage power for the sinusoidally modulated laser was merely 2 mW. In this way, based on the amplitude-frequency surface morphology of the graphene resonator, the thermal time constant of the order of a few microseconds was confirmed to evaluate the damage of the graphene oscillator in situ and in real time, which could be further extended for those resonators using other 2D materials. [ABSTRACT FROM AUTHOR]

Regarding the dependence of the treatment of removing polymethyl methacrylate (PMMA) from graphene upon the prestress in the film, two typical PMMA removal methods including acetone-vaporing and high-temperature annealing were investigated based on the opto-mechanical behaviors of the developed optical fiber Fabry-Perot (F-P) resonant sensor with a 125-µm diameter and ∼10-layer-thickness graphene diaphragm. The measured resonant responses showed that the F-P sensor via annealing process exhibited the resonant frequency of 481 kHz and quality factor of 1 034 at ∼2 Pa and room temperature, which are respectively 2.5 times and 33 times larger than the acetone-treated sensor. Moreover, the former achieved a high sensitivity of 110.4 kHz/kPa in the tested range of 2 Pa–2.5 kPa, apparently superior to the sensitivity of 16.2 kHz/kPa obtained in the latter. However, the time drift of resonant frequency also mostly tended to occur in the annealed sensor, thereby shedding light on the opto-mechanical characteristics of graphene-based F-P resonant sensors, along with an optimized optical excitation and detection scheme. [ABSTRACT FROM AUTHOR]

As the important electric loss of a graphene resonator, intrinsic current loss has received increasing attention, but the existing research is limited to qualitative analysis and approximate calculation. Based on the microscopic behavior of carriers, we have accurately established the calculation model of induced current loss, which is in good agreement with the existing experimental results. Compared with the previous models, the model in this work can not only fit the inverse V-shaped Q − Vdc curve well but also be compatible with the V-shaped Q − Vdc curve, which is beyond the reach of the previous models. In addition, the calculation results show that selecting the appropriate gate voltage combination when stimulating the graphene resonator can increase the quality factor by nearly 1–2 orders of magnitude. Furthermore, we reasonably explain the importance of DC gate voltage applied in the experiment compared with the case of non-DC gate voltage. This work realizes the accurate calculation of intrinsic current loss and is of great significance for reducing the intrinsic current loss in the practical application of graphene resonators. [ABSTRACT FROM AUTHOR]

Energy‐dense supercapacitors (SCs) based on metal oxides@graphene electrode and ionic liquid (IL) electrolyte hold great promise in sustainable energy system. However, these types of SCs suffer from poor cycling stability, especially at high working voltage. Herein, a porous ferric oxide/graphene (P−Fe2O3/G) electrode has been developed, in which Fe2O3 nanoparticles exhibit abundant and suitable mesoporous channels. This structure ensures the high ionic diffusion kinetics of the IL ions during the repeated charging‐discharging processes, thereby providing the P−Fe2O3/G electrode with outastanding capacitance behavior and cycling performance in IL electrolyte. As a result, an ingenious asymmetric electrode concept has been put forward to fabricate energy‐dense SCs based on this P−Fe2O3/G as negative electrode, carbon dodecahedrons/graphene (CDs/G) as positive electrode and IL electrolyte. Remarkably, the fabricated devices exhibit superior high‐voltage cycling stability with 95 % retention after 20 000 cycles, which are much better than that of most previously reported SCs based on metal oxides/graphene electrode and IL electrolyte. On this basis, a sustainable energy system combining wind harvesting with asymmetric SCs has been established, wherein the asymmetric SCs can be effectively recharged by harvesting sustainable wind power and repeatedly supply power without decline of electrochemical performance. Therefore, this work can provide a promising porous electrode for high performance SCs in sustainable energy system. A kind of unique porous Fe2O3@Graphene (P−Fe2O3/G) hybrid electrode with abundant and suitable mesopores has been put forward and applied for ionic liquids based supercapacitors towards sustainable energy storage for the first time. This porous structure ensures the high ionic diffusion kinetics of the IL ions during the repeated charging‐discharging processes, thereby providing outastanding capacitance behavior and cycling performance in IL electrolyte. As a result, an energy‐dense SCs is fabricated by using this P−Fe2O3/G as negative electrode, carbon dodecahedrons@graphene (CDs/G) as positive electrode and IL electrolyte, exhibiting low resistance, high energy density (98.75 W h/kg), and strong high‐voltage durability (95 % retention after 20 000 cycles in 0 to 3.5 V). Such the durable high‐voltage stability are better than that of previously reported SCs based on metal oxides@graphene electrode and IL electrolytes. On this basis, a sustainable energy system combining wind harvesting with ASCs has beenn constructed, wherein the asymmetric SCs can be effectively recharged by harvesting sustainable wind power and repeatedly supply power without decline of electrochemical performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • ATP modulated nickel nanowires/graphene aerogel was prepared. • Effective absorption bandwidth can be up to 6.8 GHz at 2.5 mm. • Magnetic nickel nanowire is like a thorny rose-like stalk. While bringing convenience to our life, the extensive use of electromagnetic waves also does harm to the environment and human health. It is crucial to develop electromagnetic wave absorption materials (EAMs) which can solve these problems. However, the developed EAMs cannot meet the increasing requirement well. Here, a novel attapulgite modulated thorny nickel nanowires/graphene aerogel was fabricated by a simple one-pot solvothermal method and freeze drying process. Among all synthesized samples, the minimum reflection loss is −47 dB and the widest effective absorption bandwidth is 6.80 GHz, which is the result of great impedance matching and strong attenuation capability. Attapulgite effectively regulates the electromagnetic parameters, and multiple components provide multiple ways to absorb electromagnetic waves. Our results may help to further design cost-effective EAMs which exhibit excellent absorption performance and broaden the application fields of attapulgite clay minerals. [ABSTRACT FROM AUTHOR]