Promoting NIR‐Driven Luminescence Activity of Calcium zinc galliumate via Energy Transfer from Mn4+ to Ho3+ for Second Biological Window

NIR luminescent materials are widely available for biological applications, and the NIR emitting of Ho³⁺ ions has received widespread attention in the second biological window. The NIR emitting of Ho³⁺ ion sensitized by Mn⁴⁺ has achieved in Ca₁₄Zn₆Ga_9.88O₃₅ : Mn⁴⁺,Ho³⁺ upon UV-vis light excited, and the energy transfer from Mn⁴⁺ to Ho³⁺ ions is mainly dominated by dipole-dipole interaction. The sample displays NIR emitting spectra ranging from 1100 to 1300 nm with two emission centers including Mn⁵⁺ and Ho³⁺ emission, respectively, which holds promising potential for applications in the second biological window.

Abstract

NIR luminescent materials are widely available for biological applications, and the NIR emitting of Ho³⁺ ions has received widespread attention in the second biological window. In this work, Ca₁₄Zn₆Ga₁₀O₃₅ : Mn⁴⁺,Ho³⁺ luminescent materials were synthesized using a high temperature solid state method. Optical properties and energy transfer mechanisms have studied in detail. Upon UV-vis light excitation, the Mn single doped Ca₁₄Zn₆Ga₁₀O₃₅ phosphors exhibit deep red and NIR emission centered at 712 and 1151 nm assigned to Mn⁴⁺ and Mn⁵⁺, respectively. Another stronger NIR emitting peaked at 1195 nm occurs when the Ho³⁺ ion is co-doped into Ca₁₄Zn₆Ga₁₀O₃₅ : Mn⁴⁺. The energy transfer from Mn⁴⁺ to Ho³⁺ ion is performed through a resonant type by a dipole-dipole interaction mechanism. In addition, the thermal stability of Ca₁₄Zn₆Ga₁₀O₃₅ : Mn⁴⁺,Ho³⁺ phosphor has been investigated, and the NIR emission of Ho³⁺ ion maintains more than half the strength at 423 K. The findings indicate that the as-prepared Ca₁₄Zn₆Ga₁₀O₃₅ : Mn⁴⁺,Ho³⁺ luminescent materials hold promise for potential applications in the second biological window.

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