Structure–property relationship of luminescent zirconia nanomaterials obtained by sol–gel method

Abstract

Nanocrystalline ZrO 2 materials were prepared by sol-gel method combining different W = [H 2 O]/[ZTB] ratios (ZTB: zirconium tetrabutoxide) with 600, 800, and 1000°C annealing temperatures, yielding diverse phase compositions. A lower post-synthesis annealing temperature (600°C) favored the t-ZrO 2 tetragonal phase while higher temperatures (800 and 1000°C) yielded the monoclinic one (m-ZrO 2 ). Depending on the preparation conditions, mixed structure materials are readily obtained. The luminescence activator in the undoped ZrO 2 is assumed as trivalent titanium and emission bands are assigned to the 3d 1 (e g ) ? 3d 1 (t 2g ) transition. Due to weaker crystal field in m-ZrO 2 form, the Ti 3? emission band is red-shifted from 410 nm in t-ZrO 2 to 500 nm. The luminescence intensity of the t-ZrO 2 form is quenched at higher temperature than that of m-ZrO 2 , indicating higher activation energy and smaller Stokes shift. The undoped ZrO 2 excitation seems to involve photoionization of Ti 3? to Ti IV . Simultaneously, the freed electron is trapped to the oxygen vacancies (F ?? centers) created by Ti 3? /Ti IV charge compensation, so this can be considered as a metalto-host/ligand charge transfer. Since most of the excitation results in immediate emission, the traps are probably very shallow though deeper ones leads to the persistent luminescence from the undoped ZrO 2 .

Unusual blue and red luminescence properties of BaO–ZrO2 nanocrystals

“…The absorption peaks at 287 nm, 305 and 310 nm have already been ascribed to exciton formation in BaO [10]. The bands at 319 nm and 342 nm are ascribed to the inherent Ti 3+ ion in ZrO 2 [17,22]. The excitation spectrum obtained by monitoring the 710 nm emission wavelength presents the same bands listed above (obtained by probing 434 nm emission wavelength), except that the 310 nm band is now dominant.…”

“…The peak at 212.9/214.8 nm is due to the zirconia band to band transition [8,[14][15][16]. The 291.2 nm and 341.6 nm absorption peaks are assigned to the d-d transition states of impurity Ti 3+ ion [17]. However, peaks at wavelength above 341 nm are assigned to BaO absorption, which becomes more prominent after annealing them.…”

“…This ion is known to be a major impurity that serves as primary activator in ZrO 2 [17,[22][23][24][25]. According to [17], the blue emission band is temperature and phase dependent; varying from blue (at low temperature and tetragonal phase of ZrO 2 ) to green (at 800°C and monoclinic phase). However, in this work we did not observe this kind of variation, probably because of the presence of Barium ions which could quench the Ti 3+ emission like it is the case for Fe.…”

SrAl12O19: Fe3+ @3‐aminopropyl triethoxysilane: Ambient aqueous stable near‐infrared persistent luminescent nanocomposites

“…However, as a novel bio‐imaging technique, several flaws have seriously limited the further application of N‐PLNPs. Currently, most conventional N‐PLNPs are synthesized by using a sol‐gel method, which results in large particles . Although hydrothermal method can produce smaller nanoparticles, this process is more complex and still has many uncontrollable factors.…”

“…Currently, most conventional N-PLNPs are synthesized by using a sol-gel method, which results in large particles. 18,19 Although hydrothermal method can produce smaller nanoparticles, this process is more complex and still has many uncontrollable factors. In addition, most of the current researches ignore the aqueous solution stability of N-PLNPs, which will cause problems with poor mobility and sedimentation | 259 KANG et Al. of N-PLNPs in living organisms.…”