Ultrasensitive Biosensing by a Plasmonic Nanolaser with a Record-Low Threshold at Room Temperature

Plasmonic nanolasers are proposed as one of the most promising tools in biosensing due to their high energy density, narrow spectral bandwidth, and feature sizes down to nanometers. However, the high threshold value greatly inhibits the widespread application of nanolasers. Researchers have made many efforts, among which the preparation of low-loss plasmonic nanocavities is the most fundamental approach. Herein, we used UV holographic lithography to prepare optical nanocavities with both a high quality factor (<i>Q</i>-factor) and strong resonance intensity (<i>I</i>), pairing with the LDS 751 dye as the gain material, to construct a plasmonic nanolaser with a record ultralow threshold of 0.49 mW/cm² at room temperature. Thus, we could display the first ultrasensitive DNA sensing of nanolaser in a biological environment by using a commercial laser pointer as the pumping source, achieving an ultralow detection limit of 1.91 nM for the <i>Brucella</i> genetic detection in serum. This work not only provides a universal strategy for constructing ultralow threshold nanolasers but also fully demonstrates the enormous advantages of nanolasers for biosensing.