Recent advances on zinc- and/or sulfur-containing mechanoluminescent materials and their spectroscopic properties toward diverse applications

Recently, the longing for new lighting sources and their applications has accelerated the rapid development and exploration of new luminescent materials. In the past years, mechanically-stimulated zinc- and/or sulfur-containing mechanoluminescent materials (ZS-MLMs, hereafter), as an important class of luminescent materials and the most frequently-reported MLMs, have played a crucial role in this process due to their remarkable advantages such as rapid force-converted luminescence response, flexible selectivity of the ML-related emissions and colors, highly sensitive force-responsive luminescence, repeated ML intensity and desirable structural stability in a variety of harsh environments, etc. These make ZS-MLMs typically suitable for use as optically detective and/or sensitive tools in the absence of external light or electrical stimuli. In this review, the recent advances on ZS-MLMs are disclosed, with a special focus on their synthesis, characterization techniques, classification and spectroscopic properties toward diverse applications, ranging from anti-counterfeiting, information storage, pressure sensing and visualization, and to biological purposes. Different types of ML-related activators, including twelve rare earth (RE) activators ( e.g. , Ce 3+ , Pr 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Eu 2+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ , and Yb 3+ ), five non-RE activators ( e.g. , Mn 2+ , Bi 3+ , Pb 2+ , Sb 3+ , and Cu +/2+ ), and the strategic combination of these RE and non-RE activators ( e.g. , Bi 3+ -Mn 2+ , Nd 3+ -Mn 2+ , Ln 3+ -Mn 2+ (Ln = Pr, Ho, Er, Tb, Dy, Eu, Sm, Yb, Tm), Tb 3+ -Eu 3+ , Tb 3+ -Mn 2+ , Nd 3+ -Bi 3+ , Er 3+ -Mn 2+ , Er 3+ -Yb 3+ , and Cu 2+ -Mn 2+ ), as well as the synergistic arrangements of these RE or non-RE ions with other non-RE luminescent ions like Li + , Al 3+ and Ag + , have been involved. These are the reason why ZS-MLMs can generate the ML widely covering the UV, visible, and NIR spectral regions. Moreover, to better understand the intrinsic nature and working principle behind the ML in ZS-MLMs, the structure-activity relationship between the ZS-related crystal structure and the ML behavior, along with their mechanisms have been also elucidated with several representative examples of ZS-MLMs. Finally, we discuss some informative perspectives and future challenges of MLMs to push the discovery of new MLMs with better ML properties toward more new advanced applications, not just limited to ZS-MLMs.