Group VI transition metal dichalcogenides (TMDs) are considered to be chemically widely inert, but recent reports point toward an oxidation of monolayered sheets in ambient conditions, due to defects. To date, the degradation of monolayered TMDs is only studied on individual, substrate-supported nanosheets with varying defect type and concentration, strain, and in an inhomogeneous environment. Here, degradation kinetics of WS₂ nanosheet ensembles in the liquid phase are investigated through photoluminescence measurements, which selectively probe the monolayers. Monolayer-enriched WS₂ dispersions are produced with varying lateral sizes in the two common surfactant stabilizers sodium cholate (SC) and sodium dodecyl sulfate (SDS). Well-defined degradation kinetics are observed, which enable the determination of activation energies of the degradation and decouple photoinduced and thermal degradation. The thermal degradation is slower than the photoinduced degradation and requires higher activation energy. Using SC as surfactant, it is sufficiently suppressed. The photoinduced degradation can be widely prevented through chemical passivation achieved through the addition of cysteine which, on the one hand, coordinates to defects on the nanosheets and, on the other hand, stabilizes oxides on the surface, which shield the nanosheets from further degradation.

中文翻译：

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添加剂在抑制液体剥离 WS2 单层降解中的作用

VI 族过渡金属二硫属元素化物 (TMD) 被认为在化学上具有广泛的惰性，但最近的报道指出，由于缺陷，单层板在环境条件下会氧化。迄今为止，单层 TMD 的降解仅在具有不同缺陷类型和浓度、应变以及不均匀环境中的单个基底支撑纳米片上进行研究。在这里，WS ₂纳米片集合体在液相中的降解动力学通过光致发光测量进行研究，该测量选择性地探测单层。单层富集 WS ₂在两种常见的表面活性剂稳定剂胆酸钠 (SC) 和十二烷基硫酸钠 (SDS) 中，产生具有不同横向尺寸的分散体。观察到明确定义的降解动力学，这使得能够确定降解的​​活化能并解耦光诱导和热降解。热降解比光致降解慢，需要更高的活化能。使用SC作为表面活性剂，它被充分抑制。通过添加半胱氨酸实现化学钝化，可以广泛地防止光诱导降解，半胱氨酸一方面与纳米片上的缺陷协调，另一方面稳定表面上的氧化物，从而保护纳米片免于进一步降解。