Deformation-induced blueshift in emission spectrum of CdTe quantum dot composites

Abstract

a b s t r a c tPolymer or glass films impregnated with quantum dots (QDs) have potential applications for mesoscale stress/strain sensing in the interior of materials under mechanical loading. One requirement in the development of such nanocomposite sensor materials is the establishment of calibrated relations between shifts in the emission spectrum of QD systems and the input stress/strain on the composites. Here, we use a multiscale computational framework to quantify the strain-dependent blueshift in the emission spectrum of CdTe QDs uniformly distributed in a matrix material under loading of a range of strain triaxiality. The framework, which combines the finite element method, molecular dynamics simulations and the empirical tight-binding method, captures the QD/matrix interactions, possible deformationinduced phase transformations and strain-dependent band structures of the QDs. Calculations reveal that the response of the QDs is strongly dependent on state of input strain. Under hydrostatic compression, the blueshift increases monotonically with strain. Under compression with lateral/axial strain ratios between 0.0 and 0.5, the blueshift initially increases, reaches a peak at an intermediate strain, and subsequently decreases with strain. This trend reflects a competition between increases in the energy levels associated with the conduction and valence bands of the QDs. The deformation-induced blueshift is also found to be dependent on QD orientations. The averaged blueshift over all orientations for the composite under uniaxial strain condition explains the blueshift variation trend observed in laser-driven shock compression experiments. Based on the simulation result, guidelines for developing QD composites as stress/strain sensing materials are discussed.

Effects of Repetitive Pressure on the Photoluminescence of Bare and ZnS-Capped CuInS2 Quantum Dots: Implications for Nanoscale Stress Sensors

“…Quantum dots (QDs) are appealing nanoscale stress/strain sensing materials (SSMs) because of their small size, high photoluminescence (PL) intensity, and tunable band gap governed by the quantum confinement effect. − For example, the potential of QDs applied to detect the pressure induced by explosion, shock, or extreme conditions in experimental biology is enormous due to their GPa-level pressure-sensitive merits. − Moreover, QDs can also be employed for in situ stress/strain detection in highly heterogeneous materials because of their nanometer size . Based on the potential of QDs for stress/strain sensing, the PL responses of QDs related to external pressure under several loading conditions have been studied over the past few years.…”

“…However, the PL often disappears when it is loaded to a critical pressure regime. , Phase transformation is the most possible reason accounting for the disappearance of the PL, and thus, many efforts have been put into the underlying phase transition mechanism of QDs through both experimental − and theoretical methods . In addition, QDs as SSMs under shock compression , and uniaxial compression − have also been investigated recently. In comparison with the PL response in hydrostatic compression, a nonmonotonic dependence between the PL peak shift and external pressure is observed in both shock compression and uniaxial compression experiments due to the axiality of stress states and the crystal orientation of the QDs, ,, which would lead to inaccurate pressure sensing performance.…”

“…In addition, QDs as SSMs under shock compression , and uniaxial compression − have also been investigated recently. In comparison with the PL response in hydrostatic compression, a nonmonotonic dependence between the PL peak shift and external pressure is observed in both shock compression and uniaxial compression experiments due to the axiality of stress states and the crystal orientation of the QDs, ,, which would lead to inaccurate pressure sensing performance.…”

Determination of Trace Phosphoprotein in Food Based on Fluorescent Probe-Triggered Target-Induced Quench by Electrochemiluminescence

“…In addition, TiO 2 can accelerate electron transfer. In recent years, some applications of titanium dioxide in an electrochemiluminescence (ECL) sensor have been reported, such as TiO 2 -CDs, TiO 2 -SnS 2 , and TiO 2 -CdSe . Thus, NH 2 -TiO 2 was applied to the specific recognition platform and as a signal amplifier of the NH 2 -UCNPs in this work.…”