Synergistic Light-Harvesting and Heat Transfer in Platinum-Confined Gold Nanocages for Sensitive Photothermal Lateral Flow Immunoassay.

Photothermal lateral flow immunoassay (LFIA) is a promising point-of-care testing platform renowned for its high sensitivity and quantitative capability. However, its development is constrained by the limited performance of available photothermal nanotags. Herein, platinum-confined gold nanocages (PANCs) were designed as efficient photothermal nanotags. The mesoporous structure of PANCs enhanced light-harvesting by prolonging the optical path while facilitating heat transfer via their high specific surface area. The confined platinum nanoparticles (PtNPs) played dual roles, including enhancing light-harvesting through plasmonic coupling with the gold framework and serving as nanoscale heat conduits, collectively boosting the photothermal performance. Finite-difference time-domain (FDTD) simulations confirmed that confining PtNPs within the gold framework generated intense plasmonic hotspots and substantially enhanced the local electric field. The synergistic combination of a mesoporous structure and PtNPs endowed PANCs with a high molar extinction coefficient of 1.31 × 1011 M-1 cm-1 and a photothermal conversion efficiency of 71.54%. Subsequently, the LFIA platform based on PANCs was developed for the detection of chlorantraniliprole in apples and chilis. The limit of detection of the PANCs-LFIA was 0.015 ng mL-1, representing a 12.53-fold improvement over conventional AuNPs-LFIA. This study provides valuable insights into the rational design of photothermal nanotags for the development of sensitive LFIA platforms.