Recently, the team of Academician Chen Hongyuan from the School of Chemistry and Chemical Engineering in Nanjing University has made important progress in the luminescent probe based on plasma laser system.

The rapid development of modern life sciences and medicine relies to a large extent on the advancement and development of luminescent probes. Over the past few decades, humans have created a range of luminescent materials that have been widely used in basic research, medical diagnostics, and the chemical industry. These luminescent probes include: organic fluorescent dyes, semiconductor quantum dots, fluorescent proteins, up-converting fluorescent materials, bioluminescent molecules and so on.

Using different color luminescent probes, it is possible to observe the coordinated behavior of multiple biomolecules in a biological system, or to simultaneously analyze disease markers of various characteristics. The luminescent behavior of the above luminescent probes is based on spontaneous emission and has a broad emission spectral distribution. This broad-spectrum illuminating feature, physically limits the types of luminescent probes that are simultaneously labeled and detected to only 4-5. If the luminescence behavior of the luminescent probe can be changed from the root of the physical property and its luminescence exhibits a laser-like monochromaticity, it is expected to greatly expand the allowable channel number of life analysis.

However, the two-level plasma laser system has a large distance from actual biological applications. In order to achieve the stimulated radiation amplification of light at the nanometer scale, precise design and regulation of the electronic transition and energy transfer in the gain medium and the cavity must be implemented, so it can reduce the lasing threshold and prolong the lasing time to meet the requirements of actual biological applications.

Inspired by the basic theory of laser, the research team constructed a three-level plasma laser probe for the first time by designing the electronic energy level of the gain medium and utilizing the triplet excited state transition of the electron. Benefiting from the long lifetime of the triplet excited state and the quantum rule of spin forbidden, the excitation ray width of ~3 nm, the luminescence lifetime of ~102 μs and the lasing threshold as low as 1 mJ cm-2 (2 orders of magnitude lower than before)are achieved. And is compatible with conventional biodetection instruments such as confocal microscope and flow cytometry. The establishment of this probe design concept has an important guiding significance for the design, development and application of the next generation new luminescent probes.