Low-temperature H-1 NMR spectroscopy was used to study states of water bound to phosphoric and phosphonic acids (phosporus oxyacids, POA) alone or adsorbed onto nanosilica OX-50 (specific surface area S-BET = 52 m(2)/g) or A-300 (S-BET = 297 m(2)/g). Concentrated solutions or weakly hydrated solid POA or dried silica/POA powders placed in CCl4 medium are characterized by different temperature dependences of the chemical shift of the proton resonance (delta H) because of partial dissociation of PO-H bonds strongly affected by water amounts and temperature. NMR cryoporometry results show that both small water clusters and nanodomains are present at the interfaces of hydrated solid POA and silica/POA powders. Quantum chemical calculations of the H-1 NMR spectra demonstrate the influence of POA/water cluster structure and dissociation of the PO-H bonds on the delta(H) values. (C) 2011 Elsevier Inc. All rights reserved.