This research focuses on the development of a non-invasive/minimally invasive optogenetic technique. The study delves into how visible (VIS) and near-infrared (NIR) light interacts with ex vivo mouse head tissues, highlighting the advantages of the NIR-II biological window for deeper tissue penetration and reduced light absorption and scattering. Our computer simulations and experimental results demonstrated that over 12% of initial light irradiation passes through 1 mm tissue (skin and skull), reaching the brain cortex, potentially enabling minimally invasive neural activation. Moreover, this work reveals the nonlinear optical properties of genetically engineered truncated monomeric and dimeric bacterial phytochromes, demonstrating their photoconversion efficiency of up to 73% in the NIR-II range and potential for optogenetics. This discovery opens new avenues in advanced neurostimulation and biomedical research by enhancing tissue penetration and minimizing invasiveness.
Current medicine might be greatly enhanced by the ability to in vivo control and monitor neurons using opsins/phytochromes expressed in neural cells. The fundamental challenge with non-invasive neural cell activity regulation is a high absorption of visible light into biological tissues. This drawback could be mitigated by the photoconversion of phytochromes in spectral ranges with higher tissue transparency. In this study, we first demonstrated two-photon Pr→Pfr conversion of monomeric phytochrome at 1.2 μm wavelength. We did a comparison of linear and nonlinear conversion of truncated DrBphP bacterial phytochromes. This work provides a structured understanding of the optical properties of the dimer and monomer of phytochrome as well as their potential for use in optogenetics.
KEYWORDS: Crystals, Ultrafast phenomena, System on a chip, Picosecond phenomena, Photovoltaics, Organic materials, Organic electronics, Near infrared, Crystallography, Americium
Singlet fission (SF), which allows one singlet state to be converted to 2 triplets, is one of the most perspective phenomena that may facilitate overcoming of the Shockley-Quiser limit in organic and hybrid photovoltaics.
Rubrene, mobility champion of organic electronics, is one of the most popular SF materials. Yet, despite its popularity, SF fundamentals in Rubrene remain strongly debated in the literature due to both experimental and computational limitations.
In this work we applied sub-10 fs transient absorption spectroscopy (TAS) to fully disentangle SF mechanism in low-defects high-quality Rubrene single crystals. We found that on 0.2 ps – 6 ns timescale, SF may be treated as 2 components process with half of the singlets to be converted into triplets at 10ps. Fascinatingly, at early times (<0.2 ps) we found additional component to be involved, which may be associated with hybrid state facilitating coherent SF. Based on our experimental findings, we have built a complete model of singlet fission in crystalline rubrene, which may help to resolve current debates on SF in the literature.
KEYWORDS: Excitons, Organic semiconductors, Solar energy, Absorption, Organic photovoltaics, Energy efficiency, Laser systems engineering, Spectroscopes, Data acquisition
Here, using single-material OPV device and laser system with sub-10fs time resolution, we track in time the formation of localised excitonic states. For this we employ a combination of pump-probe (PP) spectroscopy, sensitive to concentration of excited states, and pump-push-photocurrent (PPPC) technique, sensitive to the state localisation. Combining both methods to monitor charge dynamics at real operation condition allows to separate and track the evolution of strongly bound and spontaneously dissociating excited states. Our data show that PP and PPPC measurement do not follow the same trend, and the discrepancy between the states probed by PP and PPPC indicates that excitons acquire localised character within first 50fs after formation. Results may be useful for a new realisation of efficient donor-acceptor OPV design.
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