Semiconductor Nanoplatelets Based Host‐Guest Assembly Structure with High Color Purity for Hue‐Recognizable Lateral Flow Immunoassay

Abstract The hue‐recognition based point‐of‐care diagnosis favorites both human visual perception and imaging analysis with portable terminals. Semiconductor nanoplatelets (NPLs) as an emerging narrow‐emissive fluorophore particularly suit above color‐purity desired diagnosis, but are hindered by their intrinsic hydrophobicity and difficulty in controlled assembly. Here the host‐guest assembling of hydrophobic NPLs are developed within 3D porous space of dendritic templates, and stepwise surface silanization to fabricate silica‐NPLs‐silica structure (SNS). The structure enables high fluorescence of single assembly reaching 246‐fold and 4‐fold brightness of single NPL and commercial europium‐doped polystyrene bead. The strategy is compatible with various colored NPLs (≈540–640 nm emission) and provides stable aqueous colloids with well‐preserved emission. The high brightness and narrow emission of SNS enable both signal amplification and visual/image color discrimination. The hue‐recognizable lateral flow immunoassay for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS‐CoV‐2) nucleocapsid protein reveals an average naked‐eye interpretation accuracy of 92.9% over six concentration levels referring to standard card, accompanied by a quantification linear range of 0.13–200 ng mL −1 and a limit of detection of 0.13 ng mL −1 by smartphone. The diagnostic results for SARS‐CoV‐2 positive clinical samples demonstrate easily distinguishable antigen positive levels based on hue‐gradients, which holds significance for home‐based self‐testing of pathogens.