Synthesis and utilization of LaVO₄:Eu³⁺ nanoparticles as fluorescent near‐field optical sensors

Abstract

We report the use of fluorescent La1‐xEuxVO4 (0.1 ≤ x ≤ 0.3) nanoparticles as near‐field optical sensors. A single particle was glued at the end of a sharp atomic force microscope tip and scanned on the surface of a test sample made of sub‐micron sized holes in a thin silver film. Illumination of the sample was performed at λ = 532 nm in a transmission configuration. The light transmitted through the apertures induced the fluorescence of europium ions. The collection of the fluorescence light as a function of the tip position above the surface allowed to map the near‐field distribution in the vicinity of the holes, at different heights above the surface showing the beam divergence in free space above the sample. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis and Investigation of La,Ca ‐Doped EuVO4 Nanoparticles with Enhanced Excitation by Near Violet Light

“…[25][26][27] The 320 nm band in vanadate compounds is usually connected with 1 A 1 ! 1 T 2 transitions in the VO 4 3anions. [28][29][30][31][32] The additional wide excitation band near 370-390 nm is related with influence of the Ca 2þ impurities as this band was not observed nor for the EuVO 4 neither for the Ca-free La 1Àx Eu x VO 4 samples ( Figure 5, curve 5, [12,30] ).…”

“…We must also mention about a great amount of the oxygen vacancies those can be formed in the REVO 4 crystal lattice doped with the Ca 2þ cations. [15] The Ca 2þ cations those replace 4 3groups. It is well known that excitation bands of vanadate compounds in the 270-350 nm spectral range are caused by 1 A 1 !…”

“…We have to note that all of the studied compositions show the CIE values more closer to standard coordinates (x ¼ 0.63, y ¼ 036) than some reported formerly similar LaVO 4 :Eu compounds. [36] The calculated correlated color temperatures (CCT) of the investigated compounds are varied from 990 K for the EuVO 4 Figure 7). Therefore, the Cadoping could also be applied for warming of the emission colors of the Eu-activated REVO 4 phosphors.…”

“…Rare earth (RE) ion-doped vanadate compounds have attracted considerable attention in recent years due to their important features and wide use in various fields of science and technology. [1][2][3][4] In particular, the most extensively studied samples are europium (EuVO 4 ) and lanthanum (LaVO 4 ) vanadates because of their advantages such as excellent luminescent properties, chemical stability and non-toxicity. [5][6][7][8] Previous investigations have shown that partial replacements of the RE cations with iso-and heterovalent ions in the REVO 4 compounds lead to various changes of their physical and chemical characteristics.…”

“…[1][2][3][4] In particular, the most extensively studied samples are europium (EuVO 4 ) and lanthanum (LaVO 4 ) vanadates because of their advantages such as excellent luminescent properties, chemical stability and non-toxicity. [5][6][7][8] Previous investigations have shown that partial replacements of the RE cations with iso-and heterovalent ions in the REVO 4 compounds lead to various changes of their physical and chemical characteristics. [5,[9][10][11][12] In particular, replacement of the RE cations with alkaline earth (AE) cations (Ca 2þ , Sr 2þ , Ba 2þ ) in the RE vanadate nanoparticles causes increase of luminescent intensity [13][14][15][16] and arising of additional excitation band in violet spectral range of light.…”