The charging and aggregation properties of boron nitride nanospheres (BNNSs) were investigated in the presence of electrolytes of different compositions and valences in aqueous suspensions. The influence of mono- and multivalent cations (counterions) and anions (coions) on the colloidal stability of the negatively charged particles was studied over a wide range of salt concentrations. For monovalent ions, similar trends were determined in the stability and charging of the particles irrespective of the salt composition, i.e., no ion-specific effects were observed. Once multivalent counterions were involved, the critical coagulation concentrations (CCCs) decreased with the valence in line with the direct Schulze–Hardy rule. The dependence indicated an intermediate charge density for BNNSs. The influence of the coions on the CCCs was weaker and the destabilization ability followed the inverse Schulze–Hardy rule. The predominant interparticle forces were identified as electrical double-layer repulsion and van der Waals attraction. These findings offer useful information to design stable BNNS dispersions in various applications, where mono- and multivalent electrolytes or their mixtures are present in the samples.

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Boron nitride nanospheres (BNNSs) were functionalized with polyelectrolytes. The effect of the polyelectrolyte dose and ionic strength on the charging and aggregation properties was investigated. At appropriate polyelectrolyte doses, charge neutralization occurred, whereas by increasing the dose, charge reversal was observed. The complete coating of the particles was indicated by a plateau in the ζ-potential values, which do not change significantly beyond the dose corresponding to the onset of such a plateau. The dispersions were highly aggregated around the charge neutralization point, while at lower or higher doses, the particles were stable. The salt-induced aggregation experiments revealed that the polyelectrolyte coatings contribute to the colloidal stability of the particles, namely, the critical coagulation concentrations deviated from the one determined for bare BNNSs. The presence of electrostatic and steric interparticle forces induced by the adsorbed polyelectrolyte chains was assumed. The obtained results confirm that the comprehensive investigation of the colloidal stability of BNNS particles is crucial to design stable or unstable dispersions and that polyelectrolytes are suitable agents for both stabilization and destabilization of BNNS dispersions, depending on the purpose of their application.

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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.