All spectrophotometric measurements were made using a Thermo Spectronic model Aquamate (New York, USA) spectrophotometer fitted with a standard 10 mm path length quartz cell. A Varian (Melborurne, ...

State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China Center of Materials Science and Optoelectronics Engineering, ...