Stress And Strain Monitoring Via Self-assembled Quantum Dots

Real time and precise monitoring of stress on equipment structure is crusial to its safety and reliability.Researchers found QDs exhibit the obvious fluorescent response under the stress,which makes the possible application in the structural health monitoring.However,the instability of photoluminescence(PL)intensity and disordered distribution of QDs in the matrix restrict the development in structural health monitoring.In this paper,the temperature stability of QDs is investigated based on the core-shell CdSe/ZnS.Compared with disordered distribution of QDs,the self assembled QDs with concentric rings and stripe distributions are formed using the evaporation-induced process.The qualitative stress and strain monitoring based on self assembled QDs are explored.The achieved results are stated as follows:(1)The variation of the PL intensity and wavelength with temperature show negative relationship and positive relationship respectively and QDs exhibit fluorescent recovery under the cyclic temperature when the temperature is below 200?.While in the relative high temperature,the non-recover of QDs structure cause fluorescence quenching which associates with the maximum heating temperature and heating time.(2)The surface patterns of concentric rings and can be constructed via the evaporation of pure chloroform droplets on the surface of PMMA-QDs nanocomposite films.Both the PL intensity(cross-section area)and wavelength(distance between the adjacent rings)increase with the increasing.distance to the ball center.The structure of the self-assembled surface patterns can be regulated via the change of the ball diameter,QDs concentration and film thickness.The evaporation of solvent results in the composite film cracks and self-assembled patterns cracks.The width of the cracks increases with the increasing film thickness and QDs concentration.(3)Using the gradient concentric rings consisting of QDs on the surface of a tensile bar of 304stainless steel,it is found that the distance of adjacent ring increases with the increase of the tensile strain in a certain angle and the slope of force versus the distance increases with the increase of the angle.