Efficient Photothermal Sensor Based on Coral‐Like Hollow Gold Nanospheres for the Sensitive Detection of Sulfonamides

Abstract Gold nanoparticles (AuNPs), universally regarded as colorimetric signal reporters, are widely employed in lateral flow immunoassays (LFIAs). However, it is difficult for AuNPs‐LFIA to achieve a wide range and sensitive detection. Herein, novel coral‐like hollow gold nanospheres (CHGNPs) are synthesized. The growth of gold nanospheres can be regulated to obtain a multibranched and hollow construction. The obtained CHGNPs possess intense broadband absorption across the visible to near‐infrared region, exhibiting a high molar extinction coefficient of 14.65 × 10 11 M −1 cm −1 and a photothermal conversion efficiency of 79.75%. Thus, the photothermal/colorimetric dual‐readout LFIA is developed based on CHGNPs (CHGNPs‐PT‐LFIA and CHGNPs‐CM‐LFIA) to effectively improve the detection sensitivity and broaden the detection range in regard to sulfonamides (SAs). The limits of detection of the CHGNPs‐PT‐LFIA and CHGNPs‐CM‐LFIA reached 1.9 and 2.8 pg mL −1 for the quantitative detection of sulfaquinoxaline, respectively, which are 6.3‐fold and 4.3‐fold lower than that of the AuNPs‐LFIA. Meanwhile, the CHGNPs‐PT‐LFIA broadened the detection range to three orders of magnitude, which ranged from 2.5 to 5000 pg mL −1 . The synthesized photothermal CHGNPs have been proven effective in improving the performance of the LFIA and provide a potential option for the construction of sensing platforms.