Metal organic frameworks (MOFs) with two dimensional (2D) nanosheets have attracted special attention for supercapacitor application due to their exceptional large surface area and high surface-to-volume atom ratios. However, their electrochemical performance is greatly hindered by their poor electrical conductivity. Herein, we report a 2D nanosheet nickel cobalt based MOF (NiCo-MOF)/reduced graphene oxide heterostructure as an electrode material for supercapacitors. The NiCo-MOF 2D nanosheets are in situ grown on rGO surfaces by simple room temperature precipitation. In such hybrid structure the MOF ultrathin nanosheets provide large surface area with abundant channels for fast mass transport of ions while the rGO conductive and physical support provides rapid electron transport. Thus, using the synergistic advantage of rGO and NiCo-MOF nanosheets an excellent specific capacitance of 1553 F g⁻¹ at a current density of 1 A g⁻¹ is obtained. Additionally, the as synthesized hybrid material showed excellent cycling capacity of 83.6% after 5000 cycles of charge–discharge. Interestingly, the assembled asymmetric device showed an excellent energy density of 44 W h kg⁻¹ at a power density of 3168 W kg⁻¹. The electrochemical performance obtained in this report illustrates hybridization of MOF nanosheets with carbon materials is promising for next generation supercapacitors.

The fabrication of flexible surface-enhanced Raman scattering (SERS) substrates with high sensitivity and signal consistency in a simple and low-cost way have been a crucial and urgent challenge. In this study, we demonstrated a flexible transparent three-dimensional (3D) ordered micro-hemisphere (MHS) array PDMS film with self-assembled Au nanoparticles (NPs) (an Au NP-MHS array film) as a surface-enhanced Raman scattering (SERS) platform for the in situ detection of pesticides in food. According to the finite difference time domain (FDTD) simulation results, the Au NP-MHS array film possesses high-density and ordered “hot spots” to enhance the electromagnetic field (EMF), so that the sensitivity and signal consistency are effectively improved. The optimized Au NP-MHS array film exhibits fascinating SERS sensitivity, with a limitation of crystal violet (CV) reaching 10⁻¹² M as well as excellent consistency (RSD = 4.89% at 10⁻⁸ M). For in situ pesticide detection in fruits, this flexible film was pasted on the surfaces of tomatoes. The carbendazol and parathion were directly detected, and distinctly identified even at a low concentration (10⁻⁸ M). The flexible Au NP-MHS array film could be a potential candidate for the SERS substrate applied in the rapid and true inspection.

In this paper, an improved 4H-SiC U-shaped trench-gate metal-oxide-semiconductor field-effect transistors (UMOSFETs) structure with low on-resistance (Ron) and switching energy loss is proposed. The novel structure features an added n-type region, which reduces on-resistance of the device significantly while maintaining the breakdown voltage (VBR). In addition, the gate of the improved structure is designed as a p-n junction to reduce the switching energy loss. Simulations by Sentaurus TCAD are carried out to reveal the working mechanism of this improved structure. For the static performance, the on-resistance and the figure of merit (FOM = VBR²/Ron) of the optimized structure are improved by 40% and 44%, respectively, as compared to a conventional trench MOSFET without the added n-type region and modified gate. For the dynamic performance, the turn-on time (Ton) and turn-off time (Toff) of the proposed structure are both shorter than that of the conventional structure, bringing a 43% and 30% reduction in turn-on energy loss and total switching energy loss (ESW).

A hybrid structure gas sensor of reduced graphene oxide (RGO) decorated graphene (RGO-Gr) is designed for ultra-low concentration ammonia detection. The resistance value of the RGO-Gr hybrid is the indicator of the ammonia concentration and controlled by effective charge transport from RGO to graphene after ammonia molecule adsorption. In this hybrid material, RGO is the adsorbing layer to catch ammonia molecules and graphene is the conductive layer to effectively enhance charge/electron transport. Compared to a RGO gas sensor, the signal-to-noise ratio (SNR) of the RGO-Gr is increased from 22 to 1008. Meanwhile, the response of the RGO-Gr gas sensor is better than that of either a pristine graphene or RGO gas sensor. It is found that the RGO reduction time is related to the content of functional groups that directly reflect on the gas sensing properties of the sensor. The RGO-Gr gas sensor with 10 min reduction time has the best gas sensing properties in this type of sensor. The highest sensitivity is 2.88% towards 0.5 ppm, and the ammonia gas detection limit is calculated to be 36 ppb.