Kinetics and spectroscopic characterization of silica nanoparticles formed while etching quartz in hydrofluoric acid

The kinetic regularities of the silica nanoparticles formed during the quartz etching in hydrofluoric acid were explored for the first time. The main drivers for nanoparticle formation, as well as for the etching reaction of quartz, are the concentration of hydrofluoric acid and the ratio of the solid surface area to the liquid volume. Kinetic factors combined with nanoparticle interaction and agglomeration lead to kinetic changes of their concentrations. The proportion of nanoparticles in the weight balance with the dissolved solids decreases significantly and remains in the 0.03% range during quartz etching. XPS analysis of nanoparticles identified elements of Si, O, and F in chemical states such as Si-O, Si-Ox, SiO2, and F-Si. FT-IR reflection also identified the stretching and bending vibration peaks of the Si-O-Si and O-H. The wide fluorescence peak with a maximum at similar to 633-650 nm matches the spectrums of known non-bridging oxygen centers =Si-O center dot. The UV absorption band with maximum in the range of 195-197 nm, detected for nanoparticle samples in liquid, belongs to the silica E' defect centers Si.= In some spots of the deposited nanoparticles Raman peaks are recorded, which is typical for crystal forms of silica. Using AFM, 3D images of nanoparticles deposited on silicon or glass wafers reveal the grain size range of the particles and the feedback between the morphology of the deposited layers and the surface hydrophilicity. The high stability of the quartz etching nanoparticles in hydrofluoric acid explained their structural specificity because they have a surface fluorinated layer consisting of Si-F bonds around the silica grains. The lack of known molybdate-reactive silica inspection methods for the analysis of etching nanoparticles is disclosed. On the basis of the experimental data, new approaches are proposed for the cleaning of quartz parts from particles and for operative inspection of cleanliness.Silica, nanoparticles, etching, quartz, fluorescence, FT-IR, XPS, NP-ICP-MS.