Boron nitride colloidal solutions, ultralight aerogels and freestanding membranes through one-step exfoliation and functionalization

TLDR

Manufacturing aerogels and membranes from hexagonal boron nitride is difficult because its poor water dispersibility limits exfoliation and colloidal preparation. The study presents a simple, one‑step mechano‑chemical process to exfoliate and functionalize h‑BN into highly water‑dispersible, few‑layer sheets bearing amino groups. This method yields few‑layer, amino‑functionalized h‑BN that can be cryodried into ultralight aerogels and filtered into freestanding membranes. The resulting colloidal solutions reach concentrations up to 30 mg ml⁻¹, remain stable for months, and enable aerogels with a density of 1.4 mg cm⁻³, freestanding membranes, and strong blue‑light emission under UV.

Abstract

Manufacturing of aerogels and membranes from hexagonal boron nitride (h-BN) is much more difficult than from graphene or graphene oxides because of the poor dispersibility of h-BN in water, which limits its exfoliation and preparation of colloidal solutions. Here, a simple, one-step mechano-chemical process to exfoliate and functionalize h-BN into highly water-dispersible, few-layer h-BN containing amino groups is presented. The colloidal solutions of few-layer h-BN can have unprecedentedly high concentrations, up to 30 mg ml(-1), and are stable for up to several months. They can be used to produce ultralight aerogels with a density of 1.4 mg cm(-3), which is ∼1,500 times less than bulk h-BN, and freestanding membranes simply by cryodrying and filtration, respectively. The material shows strong blue light emission under ultraviolet excitation, in both dispersed and dry state.