A Broadband Near-IR Detector Based on a Large-Area InGaAs Photodiode for Time-Resolved Detection of Singlet Oxygen

Ultrafast pump-probe spectroscopies have proved to be an important tool for the investigation of charge carriers dynamics in perovskite materials providing crucial information on the dynamics of the excited carriers, and fundamental in the development of new devices with tailored photovoltaic properties. Fast transient absorbance spectroscopy on mixed-cation hybrid lead halide perovskite samples was used to investigate how the dimensions and the morphology of the perovskite crystals embedded in the capping (large crystals) and mesoporous (small crystals) layers affect the hot-carrier dynamics in the first hundreds of femtoseconds as a function of the excitation energy. The comparative study between samples with perovskite deposited on substrates with and without the mesoporous layer has shown how the small crystals preserve the temperature of the carriers for a longer period after the excitation than the large crystals. This study showed how the high sensitivity of the time-resolved spectroscopies in discriminating the transient response due to the different morphology of the crystals embedded in the layers of the same sample can be applied in the general characterization of materials to be used in solar cell devices and large area modules, providing further and valuable information for the optimization and enhancement of stability and efficiency in the power conversion of new perovskite-based devices.

Download Full-text

Photophysical Properties of Protoporphyrin IX, Pyropheophorbide-a, and Photofrin® in Different Conditions

Pharmaceuticals ◽

10.3390/ph14020138 ◽

2021 ◽

Vol 14 (2) ◽

pp. 138

Author(s):

Bauyrzhan Myrzakhmetov ◽

Philippe Arnoux ◽

Serge Mordon ◽

Samir Acherar ◽

Irina Tsoy ◽

...

Keyword(s):

Singlet Oxygen ◽

Photophysical Properties ◽

Protoporphyrin Ix ◽

Fluorescence Emission ◽

Solvent Polarity ◽

Visible Absorption ◽

Light Dosimetry ◽

Time Resolved ◽

Pyropheophorbide A ◽

Influence Of Solvent

Photodynamic therapy (PDT) is an innovative treatment of malignant or diseased tissues. The effectiveness of PDT depends on light dosimetry, oxygen availability, and properties of the photosensitizer (PS). Depending on the medium, photophysical properties of the PS can change leading to increase or decrease in fluorescence emission and formation of reactive oxygen species (ROS) especially singlet oxygen (1O2). In this study, the influence of solvent polarity, viscosity, concentration, temperature, and pH medium on the photophysical properties of protoporphyrin IX, pyropheophorbide-a, and Photofrin® were investigated by UV-visible absorption, fluorescence emission, singlet oxygen emission, and time-resolved fluorescence spectroscopies.

Download Full-text

Photoreactivity of Hair Melanin from Different Skin Phototypes—Contribution of Melanin Subunits to the Pigments Photoreactive Properties

International Journal of Molecular Sciences ◽

10.3390/ijms22094465 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4465

Author(s):

Krystian Mokrzynski ◽

Shosuke Ito ◽

Kazumasa Wakamatsu ◽

Theodore G. Camenish ◽

Tadeusz Sarna ◽

...

Keyword(s):

Chemical Composition ◽

Singlet Oxygen ◽

Near Infrared ◽

Paramagnetic Resonance ◽

Time Resolved ◽

W Band ◽

Epr Oximetry ◽

X Band ◽

Hair Samples ◽

Electron Paramagnetic

Photoreactivity of melanin has become a major focus of research due to the postulated involvement of the pigment in UVA-induced melanoma. However, most of the hitherto studies were carried out using synthetic melanin models. Thus, photoreactivity of natural melanins is yet to be systematically analyzed. Here, we examined the photoreactive properties of natural melanins isolated from hair samples obtained from donors of different skin phototypes (I, II, III, and V). X-band and W-band electron paramagnetic resonance (EPR) spectroscopy was used to examine the paramagnetic properties of the pigments. Alkaline hydrogen peroxide degradation and hydroiodic acid hydrolysis were used to determine the chemical composition of the melanins. EPR oximetry and spin trapping were used to examine the oxygen photoconsumption and photo-induced formation of superoxide anion, and time-resolved near infrared phosphorescence was employed to determine the singlet oxygen photogeneration by the melanins. The efficiency of superoxide and singlet oxygen photogeneration was related to the chemical composition of the studied melanins. Melanins from blond and chestnut hair (phototypes II and III) exhibited highest photoreactivity of all examined pigments. Moreover, melanins of these phototypes showed highest quantum efficiency of singlet oxygen photogeneration at 332 nm and 365 nm supporting the postulate of the pigment contribution in UVA-induced melanoma.

Download Full-text