Complex Assemblies of Soft Matter Laboratory (COMPASS), UMI 3254, CNRS-Solvay-University of Pennsylvania, RIC, Bristol, PA, 19007, USA.
Department of Chemistry and Materials Science, University of Pennsylvania, 231 S. 34th Street, Philadelphia, PA, 19104, USA.
Small. 2020 Feb;16(6):e1903897. doi: 10.1002/smll.201903897. Epub 2020 Jan 21.
There is a crucial need for effective and easily dispersible colloidal microsensors able to detect local pH changes before irreversible damages caused by demineralization, corrosion, or biofilms occur. One class of such microsensors is based on molecular dyes encapsulated or dispersed either in polymer matrices or in liquid systems exhibiting different colors upon pH variations. They are efficient but often rely on sophisticated and costly syntheses, and present significant risks of leakage and photobleaching damages, which is detrimental for mainstream applications. Another approach consists of exploiting the distance-dependent plasmonic properties of metallic nanoparticles. Still, assembling nanoparticles into dispersible colloidal pH-sensitive sensors remains a challenge. Here, it is shown how to combine optically active plasmonic gold nanoparticles and pH-responsive thin shells into "plasmocapsules." Upon pH change, plasmocapsules swell or shrink. Concomitantly, the distance between the gold nanoparticles embedded in the polymeric matrix varies, resulting in an unambiguous color change. Billions of micron-size sensors can thus be easily fabricated. They are nonintrusive, reusable, and sense local pH changes. Each plasmocapsule is an independent reversible microsensor over a large pH range. Finally, their potential use for the detection of bacterial growth is demonstrated, thus proving that plasmocapsules are a new class of sensing materials.
迫切需要能够检测局部 pH 值变化的有效且易于分散的胶体微传感器，以便在脱矿质、腐蚀或生物膜造成不可逆转的损害之前进行检测。此类微传感器的一类基于分子染料，这些染料被封装或分散在聚合物基质中或在液体系统中，在 pH 值变化时显示不同的颜色。它们很有效，但通常依赖于复杂且昂贵的合成，并且存在明显的泄漏和光漂白损坏风险，这不利于主流应用。另一种方法是利用金属纳米粒子的距离相关等离子体特性。然而，将纳米粒子组装成可分散的胶体 pH 敏感传感器仍然是一个挑战。在这里，展示了如何将光学活性等离子体金纳米粒子和 pH 响应的薄壳组合成“等离子体胶囊”。当 pH 值发生变化时，等离子体胶囊会膨胀或收缩。同时，嵌入聚合物基质中的金纳米粒子之间的距离发生变化，导致颜色发生明确的变化。因此，可以轻松地制造数十亿个微米大小的传感器。它们是非侵入性的、可重复使用的，并且可以感知局部 pH 值变化。每个等离子体胶囊在很大的 pH 范围内都是一个独立的可逆微传感器。最后，证明了它们用于检测细菌生长的潜力，从而证明了等离子体胶囊是一类新型的传感材料。
