Growth, structural effects, and non-linear and spectroscopic properties of nanocomposites based on α-NiSO4·6H2O single crystals with TiO2 nanoparticles or sols

Nanocomposites based on nickel sulfate hexahydrate α-NiSO4·6H2O (NSH) with titanium (IV) oxide introduced in the form of nanoparticles (Hombifine N: anatase; Degussa P25: 85 % anatase + 15 % rutile; η-phase: 86 % η - phase + 14 % anatase, NSH:Ti(1)) or sols (NSH:Ti(2)) are synthesized for the first time. X-ray diffraction study reveals a single-phase nature of samples, the full occupancy of all crystallographic sites in the NSH:Ti(1) structures, and the presence of Ti4+ ions in interstitial sites near the vacant Ni site in the NSH:Ti(2) structures. A crystallization of the nanosized η-phase of the composition TiO2-x × mH2O directly in the NSH:Ti(1) crystalline matrix with the formation of TiO2 with the rutile structure, facilitated by the structural-geometric correspondence of 2D projections of NSH and rutile, is observed for the first time. The presence of TiO2 in the interblock space of NSH:Ti(1) crystals affects the unit cell parameters due to the induced stresses, which is practically not described in the literature. The intensity of SHG signals of NSH:Ti varies depending on both the prehistory of TiO2 samples and the crystal state, single-crystal or powdered, of the object under study: the highest values were observed for the NSH:Ti(2) powder with the lowest content of titanium ions. The UV–VIS study reveals similar absorption and transmission bands, but with little difference in band width and intensity, for NSH, NSH:Ti(1) and NSH:Ti(2), which can be perspective for UV filters operating in the solar-blind range. •Nanocomposites based on NiSO4·6H2O with TiO2 nanoparticles or sols are synthesized.•The presence of Ti4+ ions in interstitial sites near the vacant Ni site is found.•Rutile structure with Ti4+ octahedra is formed in the interblock space of NSH.•Intensity of SHG signals varies depending on prehistory of TiO2 samples.•NSH:Ti possesses promising spectroscopic properties for solar-blind UV filters.