A crystalline-coil block copolymer with an amphiphilic corona-forming block affords a variety of different 2D structures in different self-assembly media.

Four dinuclear lanthanide complexes [Gd2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (1), [Tb2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (2), [Dy2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (3) and [Eu2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (4) were synthesized by the reaction of appropriate Ln(III) chloride salts and a multidentate ligand, 2,2'-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (H3L) in the presence of pivalic acid. 1-4 are neutral and are held by two monoanionic, [H2L](-) ligands. The two lanthanide ions are doubly bridged to each other via two phenolate oxygen atoms. Both the lanthanide ions are nine coordinated and possess a distorted capped square antiprism geometry. Photophysical studies reveal that Tb(3+) (2) and Dy(3+) (3) complexes display strong ligand-sensitized lanthanide-characteristic emission. The Tb(3+) complex (2) shows a very high overall quantum yield of 76.2% with a lifetime of 1.752 ms. Magnetic studies reveal single-molecule magnet behavior for 3 which shows in its ac susceptibility studies a two-step slow relaxation yielding two effective relaxation energy barriers of ΔE = 8.96 K and 35.51 K.

Zircon-type tetragonal LaVO4 phase is a suitable host for luminescent lanthanide ions but exhibits poor stability and transforms to monazite-type monoclinic phase at elevated temperatures and pressures. Here, we have studied the effect of partial substitution of La3+ with Eu3+ ions on the phase stability of tetragonal LaVO4 using the temperature and pressure induced phase transformation characteristics. Experimentally measured activation energy required for the initiation of phase transformation is found to increase with increasing europium content and suggests dopant induced stabilization of the tetragonal phase. The critical pressure (P c) and critical temperature (T c) required for tetragonal to monoclinic phase transition increase with increasing Eu3+ ions concentration, values being T c = 300, 500, and 600 °C and P c = 2, 4, and 6.5 GPa for compositions x = 0, 0.025, and 0.05, respectively. The simulations based on density functional theory (DFT) support the P c data, and the decrease in the formation energy of tetragonal La1–x Eu x VO4 (x = 0.0625–0.375) vis-à-vis monoclinic phase suggests improvement in its stability with increasing doping concentration. Further, the doped Eu3+ ions act as an optical probe and the observed variation in their luminescent characteristics is related to the structural transformation occurring due to pressure and heat treatment.

Doping of size mismatched aliovalent ions is challenging due to the associated elastic and electronic stress making the thermodynamics unfavorable. Despite such features, its utilization may be viable if such systems can be made metastable by suppressing the kinetics of phase segregation. In light of such a possibility, we utilize sol-gel synthesis for preparing a size mismatched trivalent europium doped MgO (Mg(1-x)Eu(x)O:(x/2)V"(Mg)) system, which can be potentially used in optical applications. It is found that such a doped system can be metastabilized and the extent of metastability can be correlated with critical temperature (Tc) required for phase segregation which decreases with the dopant concentration. For x = 0.005, 0.01, and 0.02, Tc is above 1200 °C, 500-800 °C and less than 500 °C, respectively. As the synthesis temperature is 500 °C, these trends in critical temperatures make it impossible to metastabilize europium in MgO with x > 0.01. Doping is evident from X-ray diffraction data, excitation spectra, high resolution emission spectra, and luminescence lifetimes. A characteristic strong red emission of Eu(3+) has been observed via energy transfer from the MgO matrix to Eu(3+). Density functional theory based simulations suggest stabilization of Eu(3+) in MgO at lower doping concentration through the formation of cation vacancies which is also evident from optical studies. Furthermore, thin films deposited using the e-beam evaporation technique from the Mg(1-x)Eu(x)O:(x/2)V"(Mg) (x = 0.005) system show UV sensitized emission with CIE coordinates (0.26, 0.21).