In this work, oxidation processes are correlated with the current−voltage characteristics of few-layer black phosphorus obtained by liquid-phase exfoliation. Black phosphorous (BP), a room-temperature p-type semiconductor, exhibits an anomalous switching behavior between 373 and 448 K. The anomalous increase in electrical resistance is explained using a combined spectroscopic and DFT approach. The activation energy for thermally activated electrical conductance was calculated from the current−voltage characteristics and correlated with the oxidation processes. The activation energy for thermally activated electrical conductance in the dangling oxide BP phase was found to be 79.7 meV, ∼ 40 times lower than that in the interstitial counterpart. First-principles calculations reveal electronic differences between dangling and interstitial oxides, and electrical resistance measurements reveal a Schottky-to-ohmic contact formation related to the differences in the calculated work function of dangling and interstitial oxides. We propose that this phenomenon can be exploited as a fast, economical method for the evaluation of the oxidation processes in few-layer BP.

Black phosphorus‐based 2D materials have yet to demonstrate their full application potential because of the well‐known sensitivity of phosphorene to spontaneous oxidation under ambient conditions. It is hypothesized that this unfavorable process can be prevented by drop‐casting hexagonal boron nitride (h‐BN) nanosheets on phosphorene. Here, both materials are prepared by sonication‐assisted liquid‐phase exfoliation of bulk materials and characterized by transmission electron microscopy and Raman spectroscopy. Raman spectroscopy is also utilized for the real‐time monitoring of phosphorene oxidation by calculating the A1g/A2g intensity ratio. This value drops below 0.5 (corresponding to complete oxidation) within 100 min for pristine phosphorene layers in the air. However, it remains constant above 0.6 (indicating no oxidation) when phosphorene covered by h‐BN sheets is left in the air. Moreover, deploying h‐BN sheets at midterm during the ambient oxidation reaction is able to halt the process and maintain a steady 0.5 < A1g/A2g < 0.6 Raman intensity ratio. The experimental results are successfully interpreted within the developed theoretical framework by the charge distribution of h‐BN, which keeps O2 molecules from interacting with its surface, and the fact that the first O2 molecules in contact react with the edges of h‐BN, thus creating a barrier for subsequently arriving O2 molecules.

L-Cysteinate-intercalated CaAl-layered double hydroxide (LDH) was prepared by the co-precipitation method producing highly crystalline hydrocalumite phase with a well-pillared interlayer gallery. The obtained materials were characterized by X-ray diffractometry, IR as well as Raman spectroscopies. By performing interlamellar oxidation reactions with peracetic acid as oxidant, oxidation of cysteinate to cystinate in aqueous and cysteinate sulfenic acid in acetonic suspensions occurred. The oxidations could be performed under mild conditions, at room temperature, under neutral pH and in air. It has been shown that the transformation pathways are due to the presence of the layered structure, that is, the confined space of the LDH behaved as molecular reactor.

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