Laboratories of Nano-Bioengineering (LNBE) and Hybrid Photonic Nanomaterials (LPNM) debut in the top-rated ACS Photonics: New method to measure fluorescent nanocrystals' two-photon absorption efficiency

The prestigious international journal ACS Photonics has published the study Determination of the single-exciton two-photon absorption cross-sections of semiconductor nanocrystals through the measurement of saturation of their two-photon-excited photoluminescence by Victor Krivenkov, Pavel Samokhvalov, Darya Dyagileva, and Igor Nabiev of the cluster of international laboratories of Nano-Bioengineering (LNBE) and Hybrid Photonic Nanomaterials (LPNM), NRNU MEPhI, and Alexander Karaulov of the Sechenov First Moscow State Medical University. The study deals with the estimation of the efficiency of two-photon light absorption by samples of fluorescent semiconductor nanocrystals with unknown concentrations, which is a challenging issue in a number of their practical applications.

Nanocrystal fluorescence induced by nonlinear absorption of two excitation photons at a time is increasingly widely used in imaging and detection of biological targets because it allows the excitation with infrared light instead of visible one. Nanocrystals are the best choice as fluorophores in these applications because they are capable of two-photon absorption varying for nanocrystals of different sizes, shapes, and compositions. The traditional methods of measuring the efficiency of two-photon absorption (two-photon absorption cross section) for emitting single-exciton states may be inaccurate in the case of large nanocrystals, as well as samples with unknown concentrations or low optical densities.

The authors solve this problem by analyzing the fluorescence signal saturation process with the use of their own theoretical model which takes into account incomplete relaxation of the fluorophores between laser pulses. Experiments have shown that the new method yields excellent results for samples with unknown concentrations of nanocrystals and samples with ultralow optical densities.

The results of the study extend the applications of fluorescent detection and imaging of biological objects with the use of two-photon excitation in the infrared spectral region and offer new possibilities in designing nonlinear optical photodetectors.

ACS Photonics is an interdisciplinary journal published by the American Chemical Society. The journal publishes empirical research and theoretical articles and reviews on various basic and applied aspects of photonics. ACS Photonics, first published as recently as 2014, soon became atop-rated journal. Since 2015, it has always been included in the first quartile of the SCImago journal ranking (SJR) in four categories: Atomic and Molecular Physics, and Optics; Biotechnology; Electrical and Electronic Engineering; and Electronic, Optical and Magnetic Materials. The published article is an LNBE and LPNM's debut in this journal.


Victor A. Krivenkov, Ph.D., research fellow (

Maria G. Korenkova, director of public relations, LNBE (

Alexandra V. Razgulina, engineer, LPNM (

Laboratory of Nano-Bioengineering ( and

Laboratory of Hybrid Photonic Nanomaterials (

National Research Nuclear University MEPhI,
31 Kashirskoe shosse, 115409 Moscow, Russian Federation

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