Cooperative ligand fields enriched luminescence of AgGd(MoO₄)₂:Er³⁺/Yb³⁺@mSi core–shell upconversion nanoplates for optical thermometry and biomedical applications

Over past decades, evolutions in health care and breakthroughs in medicine have remarkably enriched the quality of life. Recently, it was realized that multifunctional nanoparticles offer an efficient means of addressing many challenges faced by those developing various biomedical applications. Herein, we report large-pore mesoporous silica (LPMS) coated AgGd(MoO₄)₂:2Er³⁺/10Yb³⁺ (AGM:Er³⁺/Yb³⁺@mSi) upconversion nanoplates for the first time. After coating AGM:Er³⁺/Yb³⁺ nanoplates with LPMS shell, the specific surface area increased from 17.19 to 128.25 m²/g. Under 980 nm laser excitation, upconversion emission intensity was enhanced 2.71-fold due to the existence of cooperative ligand fields at the interface of AGM nanoplate and LPMS shell. Based on the luminescence intensity ratio of thermally combined excited states of Er³⁺ ions (²H_11/2/⁴S_3/2), the temperature sensing performance of AGM:Er³⁺/Yb³⁺@mSi core–shell nanoplates was estimated to be ∼ 0.0152 K⁻¹ at 473 k. Cytocompatibility studies revealed the non-toxic natures of AGM:Er³⁺/Yb³⁺ and AGM:Er³⁺/Yb³⁺@mSi core–shell nanoplates, and in vitro fluorescence studies confirmed their internalization and wide distribution in HeLa cells. Furthermore, drug loading and releasing efficiencies suggested their potential use as multifunctional materials for detecting and targeting cancer and cancer-associated molecules.