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Megacities play important roles in countries' politics, economy, culture, etc. Exploring the law of urban expansion of megacities has important reference for sustainable urbanization. Here, the spatiotemporal dynamics of urban expansion were quantified analyzed in 21 Chinese megacities from 2000 to 2020 with quantitative measurement indicators and explored the human-land synergistic relationship used the decoupling model. Results are as follows: (1) China's megacities experienced significant expansion, and urban expansion characterized as rapid initially but slowed down thereafter. (2) Urban expansion in megacities was characterized as having significant spatial differences, and rapidly expanding megacity centers moved from eastern to midwestern China. (3) Urban spatial expansion of megacities was mainly an enclave type in 2000-2010 and marginal type in 2010-2020. (4) The main type of human-land synergistic relationship in megacities were weak decoupling, there is a significant increase in expansive coupling and expansive negative decoupling in 2010-2020; (5) Lastly, human-land synergy relationship in most megacities was uncoordinated based on the per capita urban land area and decoupling type. The findings of this study can deepen the understanding of the characteristics and quality of urbanization evolution, and provides reference for high-quality development planning and decision-making in megacities., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Polydopamine nanoparticles (PDA NPs) are an appealing biomimetic photothermal agent for photothermal antibacterial treatment because of their long-term safety, excellent photostability, accessible manufacturing, and good biodegradability. However, the low photothermal conversion efficiency (PCE) of PDA NPs requires high-power and long-term near-infrared light irradiation, which severely restricts their practical application. In this work, PDA@Cu NPs were fabricated by growing Cu NPs in situ on the surface of PDA and then introduced into a polyelectrolyte hydrogel precursor (cationic polyethyleneimine/anionic pectin, named as CPAP). The formulated photothermal platform possessed a high PCE (55.4%), almost twice as much as pure PDA NPs (30.8%). Moreover, the designed CPAP/PDA@Cu captured and killed some bacteria by electrostatic adsorption, which helped enhance the antibacterial performance. As expected, the formed CPAP/PDA@Cu that combined the advantageous features of PDA@Cu NPs (high PCE) and CPAP matrix (inherent antibacterial activity and preventing NPs aggregation) can efficiently kill bacteria both in vitro and in vivo under the help of near-infrared laser irradiation. Taken together, this study offers a promising strategy for constructing a facile and safe PDA-based photothermal agent for photothermal antibacterial therapy., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 The Authors.)