In this work, different lanthanides (Tm³⁺, Er³⁺; Yb³⁺, Ho³⁺, Nd³⁺) were doped into NaYF₄ via a high-temperature coprecipitation method, and followed by SiO₂ coating to improve the water dispersibility, resulting in NaYF₄:Tm³⁺, Er³⁺@NaYF₄@SiO₂ and NaYF₄:Yb³⁺, Ho³⁺@NaYF₄:Nd³⁺@SiO₂ nanoparticles (NPs). The two NPs both exhibited the temperature-dependent second near-infrared (NIR-II) downshifting luminescence over the physiological range. The luminescence ratio of Tm³⁺ emission at 1460 nm to Er³⁺ emission at 1525 nm (Tm³⁺:³H₄ → ³F₄; Er³⁺:⁴I_13/2 → ⁴I_13/2) varies with temperature increase, as well as Yb³⁺ emission at 980 nm and Ho³⁺ emission at 1150 nm (Yb³⁺:²F_5/2 → ²F_7/2; Ho³⁺:⁵I₆ → ⁵I₈). The highest relative sensitivity of NaYF₄:Tm³⁺, Er³⁺@NaYF₄@SiO₂ and NaYF₄:Yb³⁺, Ho³⁺@NaYF₄:Nd³⁺@SiO₂ aqueous suspension is 0.36% K⁻¹ (at 298 K) and 0.76% K⁻¹ (at 343 K), respectively. The biological tests prove the good biocompatibility and low toxicity of the water-soluble NPs. In vitro tissue penetration experiments verify a much better penetration ability of the synthesized NaYF₄:Tm³⁺, Er³⁺@NaYF₄@SiO₂ compared with NaYF₄:Yb³⁺, Ho³⁺@NaYF₄:Nd³⁺@SiO₂ NPs. The excellent physiological luminescent thermometry with favor wave penetration depth provides a promising platform in deep tissue temperature measurement, which is very important in vivo biosensing.

Due to the satisfactory property and high productivity, heat-cured concretes have been widely used in engineering practice. However, heat curing process also brings some drawbacks that are detrimental to the long-term property of this material. To address this issue, lightweight fine aggregate (LWFA) was employed to provide internal curing (IC) for a heat-cured mortar (HCM) blended with fly ash (FA). The influences of LWFA on the interior relative humidity of HCM and the reaction environment and behavior of FA were measured. It was found that IC of LWFA could mitigate the drop of interior humidity and enhance the reaction degrees of cement and FA. This contributed significantly to the microstructure densification of HCM, higher compressive strength and better resistance to chloride ion. The results indicate that LWFA benefits to enhancing the efficiency of FA in a heat curing system and the combination of LWFA and FA contribute to improving the long-term property of HCM.