Ultrafast charge transfer at the interfaces between 5,15-donor-acceptor push-pull porphyrins (Por-tBu and Por-OC8) and nanocarbon materials in the form of fullerene (C60) and graphene carboxylate (GC) are investigated using femtosecond (fs) pump-probe spectroscopy with broadband capabilities. The strong photoluminescence (PL) quenching of the porphyrin indicates electron and/or energy transfer from the photoexcited porphyrin to the nanocarbon materials. More interestingly, the Stern-Volmer plots of PL quenching shows linear and nonlinear patterns upon increasing the concentration of GC or C60 in the porphyrin solution, respectively, clearly indicating static and a combination of static and dynamic quenching at the interfaces with these nanocarbon materials. Using femtosecond transient absorption (TA) spectroscopy, ultrafast electron transfer from a singlet-excited porphyrin to the nanocarbon materials is clearly identified by the fast ground state bleach recovery and the formation of cation radical species. Furthermore, a fs-TA study revealed that both porphyrins show very long-lived ground state bleach (GSB) and excited state absorption (ESA), which can be attributed to the triplet-state formation. This work provides new physical insights into the electron transfer process and its driving force in donor-accepter systems that include nanocarbon materials.
This work introduces a novel method for the detection of H2O2 vapor/aerosol of low concentrations, which is mainly applied in the sterilization of equipment in medical industry. Interdigitated electrode (IDE) structures have been fabricated by means of microfabrication techniques. A differential setup of IDEs was prepared, containing an active sensor element (active IDE) and a passive sensor element (passive IDE), where the former was immobilized with an enzymatic membrane of horseradish peroxidase that is selective towards H2O2. Changes in the IDEs’ capacitance values (active sensor element versus passive sensor element) under H2O2 vapor/aerosol atmosphere proved the detection in the concentration range up to 630 ppm with a fast response time (<60 s). The influence of relative humidity was also tested with regard to the sensor signal, showing no cross-sensitivity. The repeatability assessment of the IDE biosensors confirmed their stable capacitive signal in eight subsequent cycles of exposure to H2O2 vapor/aerosol. Room-temperature detection of H2O2 vapor/aerosol with such miniaturized biosensors will allow a future three-dimensional, flexible mapping of aseptic chambers and help to evaluate sterilization assurance in medical industry.
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