Femtosecond Laser Structuring Of Graphene Oxide And Its Wettability Modulation

Graphene has been of great interest to researchers in various fields since its discovery in 2004.However issues such as zero band gap,low absorption rate,and difficulty in large-area high-quality preparation have hindered its development in many fields.In contrast,graphene derivatives(e.g.,graphene oxide,reduced graphene oxide,etc.)have attracted much attention for retaining as well as expanding some of the physical/chemical properties of graphene.The properties of graphene derivatives can be further optimized and enhanced through rational structural design and preparation,so that it can be applied to a wider range of fields.Among many micro and nano processing technologies,femtosecond laser plasmonic lithography(FPL)is an emerging micro and nano processing technology developed in recent years,which shows unique advantages in the preparation of fast,large-area and periodic subwavelength grating structures.In this thesis,the preparation of periodic subwavelength grating structures on the surface of graphene oxide thin film was carried out including further investigations on processing,morphological changes,and the surface wettability regulation.The details are as follows:1.Structured reduced graphene oxide with periodic subwavelength grating structure was successfully prepared using a femtosecond laser micro and nano processing platform based on FPL technology,and the effects of parameters such as femtosecond laser power and scanning speed on its surface morphology were investigated.The results show that the structure depth decreases with increasing laser power(or decreasing laser scanning speed),the structure regularity decreases,and the surface"roughness"increases.The anomalous phenomenon that"the structure depth decreases with increasing laser power(or decreasing laser scanning speed)"is considered to be caused by the combined effect of ablation and sputtering during the femtosecond laser processing.2.The effects of laser parameters and high-temperature annealing on the surface wettability of structured reduced graphene oxide were investigated.The results show that the structured reduced graphene oxide surface wettability can be tuned in the range of 60°(17°-78°)by changing the laser parameters.By introducing a high-temperature annealing process,the modulation range of its surface wettability can be further broadened,thus achieving the modulation of the surface wettability of structured reduced graphene oxide in the range of 110°(17°-127°).3.The structured reduced graphene oxide/TiO₂ composite film was prepared in one step by processing the graphene oxide/titanium precursor composite film using the aforementioned femtosecond laser micro and nano processing platform,and the effect of the introduction of TiO₂ on the surface wettability of the film was investigated.The results show that the introduction of TiO₂ can enhance the hydrophilicity of the film surface,and the preparation of superhydrophilic composite films can be achieved under suitable laser parameters.Meanwhile,the photocatalytic effect of TiO₂ also makes the composite film with recoverable wettability under ultraviolet light irradiation,indicating that the superhydrophilic composite film is expected to be applied to outdoor self-cleaning photothermal or photovoltaic devices in the future.