Temperature sensing by means of a near-infrared luminescent Ca8NaBi(PO4)6F2:Nd3+ fluorapatite phosphor

Identifier:  imarina:9368062

Handle: https://hdl.handle.net/20.500.11797/imarina9368062

Authors:  Douzi, Abir; Slimi, Sami; Loiko, Pavel; Llamas, Victor; Serres, Josep Maria; Sole, Rosa Maria; Aguilo, Magdalena; Diaz, Francesc; Ben Salem, Ezzedine; Mateos, Xavier

Abstract:
Microrods of calcium sodium bismuth fluorapatite doped with neodymium, denoted as Ca8NaBi1-xNdx(PO4)(6)F-2 (with x ranging from 0 to 0.5), were synthetized using a modified Pechini sol-gel method. The crystalline structure of these phosphors was refined using the Rietveld method and exhibited hexagonal symmetry with space group P6(3)/m-C- 6h(2), where the lattice parameters were a = 9.3855(5) & Aring; and c = 6.8998(6) & Aring; for x = 0.2. The particles morphology was analyzed through SEM, revealing an average length of approximately 1.5 mu m. When excited at 808 nm, the Ca8NaBi(PO4)(6)F-2:0.2Nd(3+) microrods emitted strongly at 872, 957 and 1055 nm, falling within the near-infrared region. These emissions correspond to the F-4(3/2) -> I-4(9/2) (P2), F-4(5/2) -> (4)I11/2(P3), F-4(3/2) -> I-4(11/2)(P1) transitions of Nd3+ ions, respectively, and are situated within the first and second biological windows. The luminescence lifetime of the F-4(3/2) state of Nd3+ was measured to be 294.4 mu s for the sample with the lowest Nd3+ concentration of x = 0.05. In addition, the luminescence intensity ratios P2/P1 and P3/P1 were found to be temperature dependent, potentially making it suitable for luminescent ratiometric thermal sensing. These findings suggest that the synthesized Ca8NaBi(PO4)(6)F-2:Nd3+ microrod thermometers exhibit favorable characteristics in terms of relative sensitivity, temperature uncertainty, and repeatability within the temperature range of 303-403 K.