The formation of polyethyleneimine–trimethoxymethylsilane organic–inorganic hybrid particles

•Hybrid particles were made with polyethyleneimine (PEI) and trimethoxymethylsilane (TMOMS).•The effects of PEI concentration and different anions were studied.•PEI is present at the surface of the silica hybrid particles made with TMOMS.•Multivalent anions produced larger particles than monovalent anions.•PEI aggregates with multivalent anions followed by silica growth.

Polyethyleneimine–silica (PEI–silica) organic–inorganic hybrid particles were formed in the presence of multivalent anions, using trimethoxymethylsilane as the silica source. Here we present new understanding on the difference in particle formation when multi- and monovalent anions were used as well as providing clear evidence that anions other than phosphate may be used to produce PEI–silica particles, unlike the phosphorylated peptides involved in silication in nature. We also show that PEI–silica particle size increases with ionic strength when monovalent anions were used, but that the diameter is not ionic strength dependent with the use of multivalent anions. Furthermore, our results suggest that PEI–silica particle production involves the formation of polyethyleneimine aggregates with multivalent anions due to electrostatic interactions, producing sites from which silica particles can grow. In addition, for the first time zeta potential measurement data show the surface charge of the PEI–silica particles, giving evidence of the presence of the polyethyleneimine at the surface of the particles, without the need of an additional surface modification step. The superior understanding of silica particle growth in order to control the parameters needed to refine and improve the production of silica particles made using less toxic reagents is of great significance in silica particle fabrication and processing. In addition, the potential application of the polyethyleneimine on the silica particle surface is of great benefit since hybrid organic–inorganic silica particles have several applications from carbon dioxide capture to drug delivery in many fields of science, engineering and medicine.

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