The red long-lasting luminescence properties of the ZnGa2O4:Cr3+ spinel material are shown to be much improved when germanium or tin is substituted to the nominal composition. The resulting Zn1+x Ga2–2x (Ge/Sn) x O4 (0 ≤ x ≤ 0.5) spinel solid solutions synthesized here by a classic solid state method have been structurally characterized by X-ray and neutron powder diffraction refinements coupled to 71Ga solid state NMR studies. In contrast to ZnGa2O4:Cr3+ for which long lasting luminescence properties have been reported to arise from tetrahedral positively charged defects resulting from the spinel inversion, our results show that a different mechanism occurs complementary for Zn1+x Ga2–2x (Ge/Sn) x O4. Here, the great enhancement of the brightness and decay time of the long lasting luminescence properties is directly driven by the substitution mechanism which creates distorted octahedral sites surrounded by octahedral Ge and Sn positive substitutional defects which likely act as new efficient traps.

Bi2ZnTiO6, a lead-free analogue of PbTiO3, has been prepared by high-pressure solid-state synthesis methods. Structural analysis reveals that the tetragonal distortion (c/a ratio = 1.21) of Bi2ZnTiO6 is the largest reported for any d0 B site Pb or Bi based perovskite. Significant cation displacements result in a point-charge calculated polarization of 150 μC cm-2.

Tetrahedral units can transport oxide anions via interstitial or vacancy defects owing to their great deformation and rotation flexibility. Compared with interstitial defects, vacancy-mediated oxide-ion conduction in tetrahedra-based structures is more difficult and occurs rarely. The isolated tetrahedral anion Scheelite structure has showed the advantage of conducting oxygen interstitials but oxygen vacancies can hardly be introduced into Scheelite to promote the oxide ion migration. Here we demonstrate that oxygen vacancies can be stabilized in the BiVO4 Scheelite structure through Sr2+ for Bi3+ substitution, leading to corner-sharing V2O7 tetrahedral dimers, and migrate via a cooperative mechanism involving V2O7-dimer breaking and reforming assisted by synergic rotation and deformation of neighboring VO4 tetrahedra. This finding reveals the ability of Scheelite structure to transport oxide ion through vacancies or interstitials, emphasizing the possibility to develop oxide-ion conductors with parallel vacancy and interstitial doping strategies within the same tetrahedra-based structure type.

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Transparent crystalline yttrium aluminum garnet (YAG; Y3Al5O12) is a dominant host material used in phosphors, scintillators, and solid state lasers. However, YAG single crystals and transparent ceramics face several technological limitations including complex, time-consuming, and costly synthetic approaches. Here we report facile elaboration of transparent YAG-based ceramics by pressureless nano-crystallization of Y2O3–Al2O3 bulk glasses. The resulting ceramics present a nanostructuration composed of YAG nanocrystals (77 wt%) separated by small Al2O3 crystalline domains (23 wt%). The hardness of these YAG-Al2O3 nanoceramics is 10% higher than that of YAG single crystals. When doped by Ce3+, the YAG-Al2O3 ceramics show a 87.5% quantum efficiency. The combination of these mechanical and optical properties, coupled with their simple, economical, and innovative preparation method, could drive the development of technologically relevant materials with potential applications in wide optical fields such as scintillators, lenses, gem stones, and phosphor converters in high-power white-light LED and laser diode.

Water-soluble monodisperse superparamagnetic Fe3O4 nanocrystals decorated with two distinct functional groups are prepared in a single-step procedure by injecting iron precursors into a refluxing aqueous solution of a polymer ligand, trithiol-terminated poly(methacrylic acid) (PMAA-PTTM), bearing both carboxylate and thiol functionalities. The ratio of carboxylic acid groups in the polymer-protecting ligand to the iron precursors plays a key role in determining the particle size and particle size distribution. The surface functionalities of the ligands allow post-synthesis modification of the materials to produce water-soluble fluorescent magnetic nanocrystals.

Highly sensitive and specific discrimination of brain tumor margins from the surrounding parenchyma remains a formidable challenge. Limited by the short of photostable probes with deep tissue penetration and high efficiency of crossing the blood-brain-barrier (BBB), the development of fluorescence-guided surgery (FGS) of brain tumors was markedly constrained. Herein, we report the capability of the strong second near-infrared-IIb (NIR IIb, 1500−1700 nm) fluorescence from Er-based lanthanide nanoparticles in imaging-guided surgery of orthotopic glioma. We designed an energy-cascaded Er 3+ -Ce 3+ -A 3+ (A = Yb, Ho, Tm) system and prepared a series of NaErF 4 :Ce@NaAF 4 @NaLuF 4 down-conversion nanoparticles (DCNPs) for optimizing the influence of NaAF 4 interlayer and Ce 3+ dopants. We modified the optimal NaErF 4 :2.5 %Ce@NaYbF 4 (0.9 nm)@NaLuF 4 DCNPs with Dye-brush polymer (Dye-BP) to facilitate 4 I 13/2 → 4 I 15/2 transition, which leads to an impressive 675-fold enhancement of 1525 nm fluorescence in aqueous solution under 808 nm excitation due to the excellent energy-cascaded downconversion (ECD), in comparison with that of NaErF 4 nanoparticles. We further modified these highly bright nanoparticles with tumor-targeting angiopep-2 peptide, and efficiently delivered them to the glioma by using the focused ultrasound sonication (FUS) to temporarily open the BBB. We obtained the highest tumorto-background ratio (TBR = 12.5) ever reported in the targeted NIR IIb fluorescence imaging of small orthotopic glioma (size < 3 mm, depth> 3 mm) through intact skull and scalp, which was drastically improved to ∼150 after cardiac perfusion and craniotomy to ensure the precise resection of tumor. More importantly, the size of glioma measured from the width of fluorescence profile is very close to that from T 2 -weighted MRI images. Our work provides the insights into engineering NIR IIb fluorescence of lanthanide nanoparticles, and demonstrates the great potential of NIR IIb fluorescence imaging-guided surgery of tumor.

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