Selective laser reduction of graphene oxide reveals the chemical origin of fatigue degradation

Laser-induced reduction is widely used to modify graphene oxide, yet the chemical origin of fatigue degradation induced by such processing remains poorly understood. Here, we show that Raman laser irradiation acts not only as a characterization tool but also as a controllable reduction stimulus. Combined Raman and nano-infrared spectroscopy reveal that laser exposure preferentially removes sp³-type oxygen functional groups, particularly epoxide groups, while vacancy-type defects progressively accumulate. Atomic force microscopy-based fatigue experiments further demonstrate that laser-reduced graphene oxide exhibits inferior fatigue resistance compared to oxidized samples. This degradation arises from the combined effects of vacancy accumulation and the loss of epoxide-enabled crack-arresting mechanisms, driving a transition from localized damage to brittle fracture. These findings establish that fatigue reliability in graphene oxide is governed by chemical identity and defect evolution history, rather than defect density alone, highlighting the limitations of single-parameter Raman metrics for predicting mechanical performance in functionalized two-dimensional materials.