A novel upconversion emission material based on Er3+ - Yb3+ - Mo6+ tridoped Hydroxyapatite/Tricalcium phosphate (HA/β-TCP)

Effect of pH on Structure and Green Emission of Er/Yb/Mo Tri-doped Hydroxyapatite

“…This can be explained as follows: i) The intense UC emission of the S1 and S2 samples was due to the presence of the β-TCP phase in the systems (Figure 1), leading to increases the UC emission intensity of the phosphor. This phenomenon has also been observed by Silva et al, [5] that they found the emission intensity of TCP: Eu (obtained at low pH, 5.89) was 20-times higher than HA: Eu (obtained at high pH, 10.28); and ii) At high pH values (10 and 12), the presence of the OH − groups in the HA phase has a luminescence quenching effect [22,24,25], leads to decrease UC emission intensity of the phosphor, which has also been explored in our recent work [26]. These results indicate that the UC emission intensity of the phosphor is not linear dependent on the pH of the solution.…”

“…The green and red emission bands were attributed to the 2 H11/2 → 4 I15/2/ 4 S3/2 → 4 I15/2 and 4 F9/2 → 4 I15/2 transitions of Er 3+ , respectively. The selective enhancement in green UC emission can be explained due to the energy transfer from the highenergy excitation state of the Yb 3+ − MoO 4 2− dimer to the 4 F7/2 level of Er 3+ [24]. It can be seen in the inset of Figure 4, the UC emission intensity of phosphor increased from pH6 to pH8 and reached its maximum value at pH8 then decreased with further increased pH.…”

Impact of Dopants on the Electrical and Optical Properties of Hydroxyapatite

“…Eventually, the best emission intensity was in the range 330 to 430 nm [56]. Erbium-ytterbium (Yb)-molybdenum (Mo) tri-doped HA/β-TCP phosphor prepared by solid-state reaction was examined for intense green upconversion (UC) emission [51]. M5 ((0.5% mol) Er-(10% mol) Yb-(8% mol) Mo tri-doped HA/β-TCP) showed green emission intensity 650 times than that of the M1 (0.5% mol Er-doped HA/β-TCP), M2 ((0.5% mol) Er-(10% mol) Yb co-doped HA/β-TCP) due to energy transfer from 2 F 7/2 , 3 T 2 > state of Yb 3+ − MoO 4 2− dimer to the 4 F 7/2 of Er 3+ ions.…”

“…Further, red emission was weak because of feeble absorption cross-section of 4 I 13/2 and the green emission band can be controlled by the Mo 6+ doping concentrations. It aids to use the material for bioimaging application [51]. N-doped carbon dots/HAp:Eu,Gd (N-CDs/HAp:Eu,Gd) composite were studied [47] and the PL spectra of N-CDs/HAp:Eu,Gd simultaneously revealed the emission from N-CDs and HAp:Eu,Gd on single wavelength excitation.…”

“…Reddy et al observed a strong green emission from Ni 2+ -doped Ca-Li HAp (CLHA) [50]. Erbium-ytterbium-molybdenum tri-doped HA/β-TCP phosphor was synthesized using solid-state reaction by Van et al They demonstrated 650 times higher green emission in the presence of molybdenum [51]. In the case of tri-doped HAp, each dopant generates its energy levels and active centers for recombination leading to different emissions.…”