Wientjes Emilie, Renger Jan, Cogdell Richard, van Hulst Niek F
ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels, Barcelona, Spain.
Laboratory of Biophysics, Wageningen University , 6703 HA Wageningen, The Netherlands.
J Phys Chem Lett. 2016 May 5;7(9):1604-9. doi: 10.1021/acs.jpclett.6b00491. Epub 2016 Apr 18.
Nanoantennas are well-known for their effective role in fluorescence enhancement, both in excitation and emission. Enhancements of 3-4 orders of magnitude have been reported. Yet in practice, the photon emission is limited by saturation due to the time that a molecule spends in singlet and especially triplet excited states. The maximal photon stream restricts the attainable enhancement. Furthermore, the total number of photons emitted is limited by photobleaching. The limited brightness and observation time are a drawback for applications, especially in biology. Here we challenge this photon limit, showing that nanoantennas can actually increase both saturation intensity and photostability. So far, this limit-shifting role of nanoantennas has hardly been explored. Specifically, we demonstrate that single light-harvesting complexes, under saturating excitation conditions, show over a 50-fold antenna-enhanced photon emission stream, with 10-fold more total photons, up to 10(8) detected photons, before photobleaching. This work shows yet another facet of the great potential of nanoantennas in the world of single-molecule biology.
纳米天线因其在荧光增强（包括激发和发射）方面的有效作用而闻名。据报道，荧光增强可达3至4个数量级。然而在实际应用中，由于分子处于单重态尤其是三重态激发态的时间，光子发射受到饱和的限制。最大光子流限制了可实现的增强效果。此外，发射的光子总数受到光漂白的限制。有限的亮度和观察时间对于应用来说是一个缺点，尤其是在生物学领域。在此，我们挑战这一光子限制，表明纳米天线实际上可以提高饱和强度和光稳定性。到目前为止，纳米天线的这种限移作用几乎未被探索。具体而言，我们证明，在饱和激发条件下，单个光捕获复合物显示出超过50倍的天线增强光子发射流，总光子数多10倍，在光漂白前可检测到多达10⁸个光子。这项工作展示了纳米天线在单分子生物学领域巨大潜力的又一个方面。
