Silica Etching without HF in Particle Brushes

People have created hybrid materials for centuries by molecularly blending two different materials. Particle brushes are an emerging type of hybrid material in which polymer brushes are grafted from or onto the surfaces of micro/nanoparticles. Silica is the most prevalent choice of core in particle brushes. Normally, hydrofluoric acid (HF) is used to etch these particles prior to chromatographic analysis of the detached polymer, but HF is particularly hazardous to humans and the environment. Herein we report the use of nonvolatile fluoride instead of HF in the sample pretreatment. We found the effectiveness of aqueous ammonium bifluoride (NH₄HF₂) is comparable to HF etching and extended it to particle brushes with other inorganic cores such as barium titanate. This technique is promising for silica template removal in other nanomaterials. Our findings may inspire future efforts in hazard control by substitution in research protocols.