Bilayer stabilized Ln³⁺-doped CaMoO₄ nanocrystals with high luminescence quantum efficiency and photocatalytic properties

Abstract

In this article, we discuss the microwave synthesis of sodium dodecyl sulphate (SDS) stabilized Ln(3+)-doped CaMoO4 nanocrystals (Ln(3+) = Eu(3+), Er(3+)/Yb(3+)). The nanocrystals are quite monodispersed with an average size close to 100 nm. FTIR and TGA analyses suggest strong binding of the SDS molecules to the CaMoO4 nanocrystals surface. The high dispersibility of the nanocrystals in water implies that SDS stabilizes the nanocrystals as a bilayer structure. The SDS coating also assists in the easy dispersion of the nanocrystals in toluene without any additional surface chemistry. The Eu(3+) ions doped in the CaMoO4 nanocrystals display very strong red luminescence with a quantum yield close to 40%. Under 980 nm excitation, Er(3+)/Yb(3+)-doped CaMoO4 nanocrystals display Er(3+) emissions at 550 and 650 nm. In addition, interestingly, a NIR peak at around 833 nm is observed, which occurred via a three photon process. Furthermore, the CaMoO4 nanocrystals exhibit photocatalytic activity which is studied through the degradation of Rhodamine B (RhB) dye in neutral conditions. The RhB dye is significantly degraded by ~80% under UV illumination within 4 h and the rate of degradation is comparable to that observed for well known ZnO nanoparticles. The high luminescence quantum efficiency and strong photocatalytic activity of the Ln(3+)-doped CaMoO4 nanocrystals make them a potential material for dual applications such as bio-imaging and photocatalysis.

Revealing the substitution mechanism in Eu3+:CaMoO4and Eu3+,Na+:CaMoO4phosphors

“…Photoluminescence properties of CaMoO4:Eu 3+ have been extensively studied in bulk samples, 5,6,7,8 microparticles 3,9,10,11 and different types of nanoparticles. 12,13,14,15 However, very little attention has been paid to the substitution mechanism and crystal structure of Eu 3+ :CaMoO4 phosphors. In our recent paper on the photoluminescence of peanut-like CaMoO4:1%Eu 3+ architectures, we found that the unit cell parameters of the Eu 3+ -doped sample were slightly higher than those of the undoped material, in spite of the smaller ionic radius of Eu 3+ compared with Ca 2+ in eight-fold coordination.…”

Morphology control of uniform CaMoO4microarchitectures and development of white light emitting phosphors by Ln doping (Ln = Dy3+, Eu3+)

“…17 The potential applications of this kind of phosphors encompass biomedicine, 18 lighting, 10,13 and catalysis. 19 Up to now, several methods have been reported for the synthesis of CaMoO 4 microarchitectures with different shapes 20-27 . However, most of these methods conducted to particles with heterogeneous size and/or a certain degree of agglomeration, except in the case of the persimmon-like (2 µm) 20 particles obtained in a microwave reactor without temperature control and the spherical particles hydrothermally synthesized in the absence (5-6 µm) 22 or the presence (2 µm) 23 of a capping polymer (poly(diallyldimethyl-ammonium chloride).…”

Strong UV Emission from Colloidal Eu2+‐Doped BaSO4 Nanoparticles: A Material for Enhancing the Photocatalytic Activity of Carbon Dots

“…This is also confirmed from the excitation spectrum which displays a broad absorption (shown in Figure S5). Moreover, the lifetime of this peak is around 30 μs which is much lower than that observed for the 4 f –4 f transition of Eu 3+ ions . However, we emphasize that the observed 30 μs lifetime for Eu 2+ is longer than observed in other matrices like Eu 2+ ‐doped GaN/SiO 2 nanocomposites, Eu 2+ ‐doped Ba 2 Si 5 N 8 , Eu 2+ ‐doped Na 2‐x Al 2‐x Si x O 4 (x=0.55), etc ,.…”