Stimulus-responsive liquid foams have gained much attention for use in various industrial applications. However, it remains challenging to construct such systems with integrated functionality of easy preparation, high stability, high foaming ability, and rapid on-demand degradation. Herein, by combining the Hofmeister effect and nanotechnology, a promising ultrastable and photoresponsive liquid foam was prepared that had a lifetime of several months and could be destroyed on demand in a few minutes. Specifically, the system was prepared by simply mixing a gelatine solution containing black phosphorus nanosheets (BPNs) and kosmotropic anions in the Hofmeister series with air in one step using only two syringes, and there were no chemical modifications or crosslinking agents required. The kosmotropic anions induced stronger hydrophobic interactions, bundling within molecular chains, and blockage of foam drainage channels, which significantly improved the foaming ability and the lifetime and mechanical properties of the foam. Moreover, rational structure design realized a promising on-demand degradation mechanism via a cascading “light trigger–heat generation–Marangoni flow generation” process occurring on the bubble surfaces. On this basis, the BPNs converted light into thermal energy, which induced Marangoni flow driven by surface tension gradients along the gas‒liquid interfaces, and the bubble film ruptured within seconds upon light illumination. The designed stimulus‒response systems combined stable, fast and repeatable processes without sacrificing the foaming abilities, thus providing a general way to control the stabilities of foams, bubbles and films.

中文翻译：

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利用霍夫迈斯特效应和二维黑磷一步构建光响应智能泡沫：高稳定性和按需降解


刺激响应液体泡沫在各种工业应用中的使用引起了广泛关注。然而，构建具有易于制备、高稳定性、高发泡能力和快速按需降解等综合功能的系统仍然具有挑战性。在此，通过结合霍夫迈斯特效应和纳米技术，制备了一种有前途的超稳定和光响应液体泡沫，其寿命为几个月，并且可以根据需要在几分钟内销毁。具体来说，该系统是通过仅使用两个注射器将含有黑磷纳米片（BPN）和霍夫迈斯特系列亲液阴离子的明胶溶液与空气一步混合来制备的，并且不需要任何化学修饰或交联剂。亲液阴离子诱导更强的疏水相互作用，在分子链内成束，并堵塞泡沫排水通道，从而显着提高泡沫的发泡能力、寿命和机械性能。此外，合理的结构设计通过气泡表面发生的级联“光触发-热量产生-马兰戈尼流产生”过程实现了一种有前景的按需降解机制。在此基础上，BPNs将光转化为热能，沿着气液界面诱导由表面张力梯度驱动的Marangoni流动，并且气泡膜在光照射下几秒钟内破裂。设计的刺激响应系统结合了稳定、快速和可重复的过程，而不牺牲发泡能力，从而提供了控制泡沫、气泡和薄膜稳定性的通用方法。