Er3+-Yb3+: YMoO4@SiO2 core@shell upconversion (UC) nanoparticles (NPs) with its particle size similar to 35 nm and shell thickness similar to 3 nm synthesized via Stober method have explored its thermal stability, particle morphology and optical properties. The optical band gap energy clearly shows the effect of surface coating of silica layer across the surface of core@shell NPs due to increase in the crystallite size. Due to presence of silica layer across the core NPs, the UC emission intensity corresponding to the H-2(11/2), S-4(3/2) -> I-4(15/2) transition has been increased about similar to 10 times in the core@shell NPs than the core NPs. Temperature dependent study using thermally coupled H-2(11/2) -> 4I(15/2) and S-4(3/2) -> I-4(15/2) transitions in the biological temperature range (300-368 K) has been performed. The maximum sensitivity similar to 2.36% K (1) at 368 K, which is similar to 12 times greater than the core NPs of the core@shell UC NPs has been reported. Thermal heat gain by the core@shell NPs within 311-343 K temperature range is suitable for hyperthermia based cancer treatment has been reported. The core@shell NPs show good dispersibility in different biological solvents such as water, methanol and DMSO. Moreover, the core@shell NPs dispersed with biological solvents show good luminescence stability without interactions with solvent molecules which could minimize the thermal effect caused by the 980 nm diode laser excitation. As a consequence, Er3+-Yb3+: YMoO4@ SiO2 core@shell NPs have suitable applications for making optical devices namely upconvertors, LEDs, optical bioprobes, etc. (C) 2017 Elsevier B.V. All rights reserved.