Optical transparent and electrical conducting materials with broadband transmission are important for many applications in optoelectronic, telecommunications, and military devices. However, studies of broadband transparent conductors and their controlled modulation are scarce. In this study, we report that reversible transmittance modulation has been achieved with sandwiched nanocarbon thin films (containing carbon nanotubes (CNTs) and reduced graphene oxide (rGO)) via electrochemical alkali-ion intercalation/deintercalation. The transmittance modulation covers a broad range from the visible (450 nm) to the infrared (5 μm), which can be achieved only by rGO rather than pristine graphene films. The large broadband transmittance modulation is understood with DFT calculations, which suggest a decrease in interband transitions in the visible range as well as a reduced reflection in the IR range upon intercalation. We find that a larger interlayer distance in few-layer rGO results in a significant increase in transparency in the infrared region of the spectrum, in agreement with experimental results. Furthermore, a reduced plasma frequency in rGO compared to few-layer graphene is also important to understand the experimental results for broadband transparency in rGO. The broadband transmittance modulation of the CNT/rGO/CNT systems can potentially lead to electrochromic and thermal camouflage applications.
Magnetron sputtered CuO thin films with hierarchical structure and large specific surface were prepared, and their electrochemical properties and reaction characteristics as the Li-ion storage electrodes were investigated. The nanostructured CuO thin film showed a high capacity, good cycling stability and excellent rate performance, exhibited the discharge capacities of 703 mAh/g at 100 mA/g and 465 mAh/g at 1000 mA/g even after 100 electrochemical cycles. Transmission electron microscopy was applied to investigate the phase evolution of CuO thin film after being electrochemically induced at various stages in the 3 rd lithiation-delithiation cycle. An intermediate phase of Cu 4 O 3 , besides Cu and Cu 2 O products, was identified in CuO electrode during the electrochemical process. The investigation of phase evolution revealed that the CuO active materials were partially reduced to Cu 4 O 3 , followed by being reduced to Cu 2 O and Cu during the discharge process; while, the reversible electrochemical reactions Cu→Cu 2 O→Cu 4 O 3 →CuO took place in the charge process.
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