The utilization of edge sites in two-dimensional materials including transition-metal dichalcogenides (TMDs) is an effective strategy to realize high-performance gas sensors because of their high catalytic activity. Herein, we demonstrate a facile strategy to synthesize the numerous edge sites of vertically aligned MoS and larger surface area via SiO nanorod (NRs) platforms for highly sensitive NO gas sensor. The SiO NRs encapsulated by MoS film with numerous edge sites and partially vertical-aligned regions synthesized using simple thermolysis process of [(NH)MoS]. Especially, the vertically aligned MoS prepared on 500 nm thick SiO NRs (500MoS) shows approximately 90 times higher gas-sensing response to 50 ppm NO at room temperature than the MoS film prepared on flat SiO, and the theoretical detection limit is as low as ∼2.3 ppb. Additionally, it shows reliable operation with reversible response to NO gas without degradation at an operating temperature of 100 °C. The use of the proposed facile approach to synthesize vertically aligned TMDs using nanostructured platform can be extended for various TMD-based devices including sensors, water splitting catalysts, and batteries.
Electrochemical reduction of carbon
dioxide (CO2) is
a promising method toward carbon recycling. Highly selective bimetallic
catalysts have been extensively demonstrated, while efforts to understand
the compositional and geometrical effects have been limited. Here,
we studied the relationship between the catalytic activity of bimetallic
Cu–Sn catalysts with their composition and geometry through
the fabrication of three-dimensional hierarchical (3D-h) Cu nanostructure
and the solution-based coating of Sn nanoparticles (NPs). As the coating
time of Sn NPs was increased from 1 to 60 s, Sn NPs with a larger
size and a higher surface density were coated onto the 3D-h Cu, thus
the surface atomic ratio of Cu/Sn gradually decreased. This compositional
change in bimetallic Cu–Sn catalysts remarkably shifted the
faradaic efficiency (FE) of carbon monoxide (CO) from 90.0 to 23.4%
at −0.6 VRHE. Moreover, we found that the catalytic
performance increases as the geometric structure becomes complex in
the order of flat, rods, and 3D-h Cu–Sn. The 3D-h Cu–Sn
began to produce CO at a low potential of −0.15 VRHE and showed the maximum FECO of 98.6% at −0.45
VRHE. This study reveals that the synergetic effects of
composition and nanoscale geometry are significant for the CO2 reduction reaction.
A comparison was made between the use of graphene oxide (GO)/poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and reduced graphene oxide (rGO)/PEDOT:PSS as a hole extraction layer (HEL) in organic photovoltaic (OPV) cells. Hydrazine hydrate (HYD) and the thermal method were adopted to change the GO to rGO. The OPV cell with the GO ($2 nm)/PEDOT:PSS HEL exhibits a power conversion efficiency (PCE) as high as 3.53% under 100 mW/cm 2 illumination and air mass conditions, which is higher than that of the OPV cell without the HEL, viz. 1.78%. The device with the PEDOT:PSS/GO HEL shows a similar PCE of 3.48%. However, the PCE of the OPV cell with the rGO/PEDOT:PSS HEL is not high as those of the cells with the HYD-rGO/ PEDOT:PSS and T-rGO/PEDOT:PSS, viz. 3.3 and 3.37%, respectively. The work function of GO was 4.7 eV, but those of HYD-rGO and T-rGO were 4.2 and 4.5 eV, respectively, suggesting that the decrease of the barrier height between GO and active materials is higher than that in rGO case.
Here, this study successfully fabricates few-layer MoS nanosheets from (NH ) MoS and applies them as the hole transport layer as well as the template for highly polarized organic light-emitting diodes (OLEDs). The obtained material consists of polycrystalline MoS nanosheets with thicknesses of 2 nm. The MoS nanosheets are patterned by rubbing/ion-beam treatment. The Raman spectra shows that {poly(9,9-dioctylfluorene-alt-benzothiadiazole), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)]} (F8BT) on patterned MoS exhibits distinctive polarization behavior. It is discovered that patterned MoS not only improves the device efficiency but also changes the polarization behavior of the devices owing to the alignment of F8BT. This work demonstrates a highly efficient polarized OLED with a polarization ratio of 62.5:1 in the emission spectrum (166.7:1 at the peak intensity of 540 nm), which meets the manufacturing requirement. In addition, the use of patterned MoS nanosheets not only tunes the polarization of the OLEDs but also dramatically improves the device performance as compared with that of devices using untreated MoS .
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