Nanoporous plasmonic nanostructures based on noble metals have received extensive attention on the high-performance detection of chemical analytes. However, the size of such pores is rarely at the angstrom scale given the limitation of current fabrication methods. This leads to a relatively poor performance in the detection of ions. Here, we demonstrate the formation of angstrom-scale pores in ultra-thin plasmonic ammonium doped molybdenum oxide through crystal nucleation. The molybdenum oxide octahedra assemble into hexagonal rings, in which dopants fill in parts of the rings to stabilize the crystal structure and simultaneously generate a broad plasmon resonance across the visible to near-infrared regions. As a result, the unfilled centers of the rings effectively become angstrom-scale pores. Na⁺ ion sensing capability is investigated by integrating plasmonic ammonium doped molybdenum oxide onto D-shaped optical fibers. The ions are facilely accommodated within the pores and induce a charge re-distribution in the host. This alters the plasmon resonance behavior and modulates the optical output of the fiber transducing platform, through a strong light-matter interaction. The structure is sensitive to a wide concentration range of Na⁺ ions from subnanomolar (sub-nM) to submolar (sub-M) with the limit of detection (LOD) of ~5 fM, and high selectivity in both the aqueous solution and simulated serum conditions, which is a superior sensitivity over other reported optical ion sensors. This work demonstrates the strong potential of angstrom-scale porous plasmonic materials for chemical detection, and the possibility of being integrated with popular optical transducing platforms for practical high-performance sensing.

基于贵金属的纳米多孔等离子体纳米结构在化学分析物的高性能检测方面受到广泛关注。然而，鉴于当前制造方法的限制，此类孔的尺寸很少达到埃级。这导致离子检测的性能相对较差。在这里，我们证明了通过晶体成核在超薄等离子体铵掺杂的氧化钼中形成埃级孔。氧化钼八面体组装成六边形环，其中掺杂剂填充环的部分以稳定晶体结构，同时在可见光到近红外区域产生广泛的等离子体共振。结果，环的未填充中心有效地变成埃级孔。钠⁺通过将等离子体铵掺杂的氧化钼集成到D形光纤上来研究离子传感能力。离子很容易被容纳在孔内并在宿主中引起电荷重新分布。这通过强烈的光-物质相互作用改变了等离子体共振行为并调制了光纤转换平台的光输出。该结构对较宽的 Na ⁺浓度范围敏感离子从亚纳摩尔 (sub-nM) 到亚摩尔 (sub-M)，检测限 (LOD) 约为 5 fM，在水溶液和模拟血清条件下均具有高选择性，比其他报道的光学灵敏度更高离子传感器。这项工作证明了埃级多孔等离子体材料在化学检测方面的强大潜力，以及与流行的光学转换平台集成以实现实用高性能传感的可能性。