Red- and green-emitting nano-clay materials doped with Eu and/or Tb.

Trivalent europium (Eu ) and terbium (Tb ) ions are important activator centers used in different host lattices to produce red and green emitting materials. The current work shows the design of new clay minerals to act as host lattices for rare earth (RE) ions. Based on the hectorite structure, nano-chlorohectorites and nano-fluorohectorites were developed by replacing the OH present in the hectorite structure with Cl or F , thus avoiding the luminescence quenching expected due to the OH groups. The produced matrices were characterized through X-ray powder diffraction (XPD), transmission electron microscopy (TEM), FT-IR, Si MAS (magic angle spinning) NMR, nitrogen sorption, thermogravimetry-differential scanning calorimetry (TGA-DSC) and luminescence measurements, indicating all good features expected from a host lattice for RE ions. The nano-clay materials were successfully doped with Eu and/or Tb to yield materials preserving the hectorite crystal structure and showing the related luminescence emissions. Thus, the present work shows that efficient RE luminescence can be obtained from clays without the use of organic 'antenna' molecules.