Compared with other energy storage devices, supercapacitors have superior qualities, including a long cycling life, fast charge/discharge processes, and a high safety rating. The practical use of supercapacitor devices is hindered by their low energy density. Here, we briefly review the factors that influence the energy density of supercapacitors. Furthermore, possible pathways for enhancing the energy density via improving capacitance and working voltage are discussed. In particular, we offer our perspective on the most exciting developments regarding high-energy-density supercapacitors, with an emphasis on future trends. We conclude by discussing the various types of supercapacitors and highlight crucial tasks for achieving a high energy density.
The preparation, characterization, and photochromic properties of a mononuclear gold(I) complex (1oo) with two identical DTE-acetylides and a dinuclear gold(I) complex (2ooo) with both DTE-acetylide and DTE-diphosphine are described. Both gold(I) complexes exhibit multistep and multiple photocyclization/cycloreversion reactions. Particularly, four-state and four-color photochromic switch is successfully achieved for the dinuclear gold(I) complex upon irradiation with appropriate wavelengths of light. In contrast, fully ring-closed form is unattained through multiple photocyclization for the two corresponding model organic compounds coupling with the same DTE units as gold(I) complexes but without gold(I)-participation. It is demonstrated that coordination of gold(I) ion to DTE-acetylides exerts indeed a crucial role in achieving stepwise and selective photocyclization and cycloreversion reactions for both gold(I) complexes, in which the coordinated gold(I) atom acts as an effective "barrier" to prohibit intramolecular energy transfer between multi-DTE moieties.
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