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.@en

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+:4I13/2 → 4I13/2) varies with temperature increase, as well as Yb3+ emission at 980 nm and Ho3+ emission at 1150 nm (Yb3+:2F5/2 → 2F7/2; 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.@en