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In the contemporary social environment, social crisis events occur frequently with significant impacts. Effective management of these events requires comprehensive group intention mining, which encompasses intention detection and intention attribution. Knowledge graph inference facilitates the detection of group intention in crisis events. This is supported by the construction of crisis knowledge graphs, which organize crisis elements and inter-element relations into structured semantic information. This paper provides a comprehensive overview of the research about knowledge graph in social crisis management, focusing on three key areas: knowledge graph construction and inference, knowledge graph-based interpretable crisis attribution, and risk management. Specifically, the interpretable semantics in crisis knowledge graphs enables attribution of intention. To illustrate the significance of knowledge graphs in group intention mining, the COVID-19 and China–US game events are selected as two case studies. Finally, the paper proposes future research directions to solve the limitations of existing knowledge graph-related methods in social crises. [ABSTRACT FROM AUTHOR]

Materials with multiple nonlinear-optical responses have been investigated widely in recent years. Here, we report a hybrid system with both giant multiphoton absorption (MPA) and efficient third harmonic generation (THG) excited by near-infrared femtosecond laser pulses. The hybrid material consists of both CsPbBr3 quantum dots and metal–organic framework microparticles. The two-, three-, four-, and five-photon absorption cross-sections of the hybrid material are three orders of magnitude greater than those of CsPbBr3 micro-crystals. The effective χ(3) values are three orders of magnitude greater than those of α-quartz. Our findings demonstrate a new avenue to realize photo-stable, high-order MPA, and THG in microparticles synthesized using a cost-effective method. [ABSTRACT FROM AUTHOR]

The electron-phonon (e-ph) interaction in lead halide perovskites (LHPs) plays a role in a variety of physical phenomena. Unveiling how the local lattice distortion responds to charge carriers is a critical step toward understanding the e-ph interaction in LHPs. Herein, we advance a fundamental understanding of the e-ph interaction in LHPs from the perspective of stereochemical activity of 6s 2 lone-pair electrons on the Pb 2+ cation. We demonstrate a model system based on three LHPs with distinctive lone-pair activities for studying the structure-property relationships. By tuning the A-cation chemistry, we synthesized single-crystal CsPbBr 3 , (MA 0.13 EA 0.87 )PbBr 3 (MA + = methylammonium; EA + = ethylammonium), and (MHy)PbBr 3 (MHy + = methylhydrazinium), which exhibit stereo-inactive, dynamic stereo-active, and static stereo-active lone pairs, respectively. This gives rise to distinctive local lattice distortions and low-frequency vibrational modes. We find that the e-ph interaction leads to a blue shift of the band gap as temperature increases in the structure with the dynamic stereo-active lone pair but to a red shift in the structure with the static stereo-active lone pair. Furthermore, analyses of the temperature-dependent low-energy photoluminescence tails reveal that the strength of the e-ph interaction increases with increasing lone-pair activity, leading to a transition from a large polaron to a small polaron, which has significant influence on the emission spectra and charge carrier dynamics. Our results highlight the role of the lone-pair activity in controlling the band gap, phonon, and polaronic effect in LHPs and provide guidelines for optimizing the optoelectronic properties, especially for tin-based and germanium-based halide perovskites, where stereo-active lone pairs are more prominent than their lead counterparts.