A novel light-induced reversible self-assembly (LIRSA) system is based on the reversible photodimerization and photocleavage of coumarin groups on the surface of gold nanoparticles (AuNPs) in THF solution. Facilitated by coumarin groups, light irradiation at 365 nm triggers the stable assembly of monodisperse AuNPs; the resulting self-assembly system can be disassembled back to the disassembled state by a relatively short exposure to benign UV light. The reversible self-assembly cycle can be repeated 4 times. A specific concentration range of coumarin ligand and the THF solvent were identified to be the two predominant factors that contribute to the LIRSA of AuNPs. This is the first successful application of reversible photodimerization based on a coumarin derivative in the field of AuNP LIRSA. This LIRSA system may provide unique opportunities for the photoregulated synthesis of many adjustable nanostructures and devices.

O 7 ) 2 /multi-walled carbon nanotube (MWCNT) composite was fabricated by a solid state reaction and was further used to fabricate a cathode for sodium-ion batteries. The electrochemical behaviors were thoroughly investigated in assembled non-aqueous Na 3.12 Fe 2.44 (P 2 O 7 ) 2 /MWCNT//Na cells, showing higher specific capacity (over 100 mA h g À1 at a rate of 0.15C) and better stable cycle performance than those of the pristine Na 3.12 Fe 2.44 (P 2 O 7 ) 2 -based one. It is noted that with increased charge-discharge cycles, the specific capacity of Na 3.12 Fe 2.44 (P 2 O 7 ) 2 /MWCNT gets close to the theoretical capacity (ca. 117.4 mA h g À1 ). These good performances could be attributed to the incorporated MWCNTs, which improve the conductivity for lower charge transfer resistance and shorten the diffusion length for faster Na + diffusion to access the reaction sites. Through systematic studies of EIS at different states of charge and discharge, it is discovered that R ct decreases with the increase of voltage and reaches a minimum value at redox sites, but R e and D Na + show the opposite trend.Moreover, a full cell test using a carbon black negative electrode also demonstrates good capacity retention up to 50 cycles and a reversible capacity of 145 mA h g À1 with the average operation voltage of 2.8 V.

A 3D railway-like electrode design to tackle the poor conductivity and severe volume expansion in a room temperature Na–S battery.