Heavy metal-free visible-to-UV photon upconversion with over 20% efficiency sensitized by a ketocoumarin derivative

Efficient triplet-triplet annihilation-based photon upconversion (TTA-UC) from visible to UV light without using heavy metals is still a challenging task. Here we achieve a record-high TTA-UC efficiency of 20.3% among 100% maximum by employing a ketocoumarin derivative as a triplet sensitizer, which shows strong visible absorption, weak UV absorption, and efficient intersystem crossing.

The Function of Flavonoids in the Diurnal Rhythm under Rapidly Changing UV Conditions—A Model Study on Okra

Flavonoids are favored compounds in plant responses to UV exposure and act in UV absorption and antioxidant activity. Here, it was investigated, with okra as a model species, how fast plants can react to changing UV conditions and to what extent these reactions take place. Okra (Abelmoschus esculentus) plants were exposed to either full or nearly no UV radiation. The diurnal rhythm of the plants was driven by the UV radiation and showed up to a 50% increase of the flavonoid content (measured optically in the +UV plants). This was reflected only in the trends in UV-absorption and antioxidant activity of the extracts but not in the soluble flavonoid glycosides and hydroxycinnamic acid derivatives. In a second experiment, a transfer from a −UV to a +UV condition at 9:00 CDT showed the immediate start of the diurnal rhythm, while this did not occur if the transfer occurred later in the day; these plants only started a diurnal rhythm the following day. After an adaptation period of seven days, clear differences between the +UV and -UV plants could be found in all parameters, whereas plants transferred to the opposite UV condition settle between the +UV and -UV plants in all parameters. Broadly, it can be seen that the flavonoid contents and associated functions in the plant are subject to considerable changes within one day and within several days due to the UV conditions and that this can have a considerable impact on the quality of plant foods.

Effect of Magnetic Fields on UV Absorption and Evaporation of Water

We investigated the effects of unipolar magnetic fields (N or S polarity) on the physical properties of deionized water. Long-term experiments revealed significant pole-dependent changes in water absorption in the UV range (180 – 350 nm). In the case of water in open vessels, the order of absorption values was C-N-S. That is, control (C) water absorbed the most, N-pole-influenced water absorbed less, and S pole the least. The differences in absorption between N and S waters were substantial. In the case of closed vessels, the differences in absorption spectra substantially diminished, and the arrangement of the absorption values became C-S-N (highest to lowest). A correlation between UV absorption values and evaporation rates was also found. The relative order of evaporation rates, C-N-S (highest to lowest), was the same as the order of the absorption values, also C-N-S. The differences in UV absorption spectra of the N- and S-treated waters persisted for several months after removing the magnets. Hence, the effects of magnetic fields were long term. The interaction of magnetic fields with water is of interest not only from a physical sciences perspective, but also in the context of the significant applications in medicine and biology.

Tetraphenylethene-Embedded Pillar[5]arene and [15]Paracyclophane: Distorted Cavities and Host–Guest Binding Properties

Two aggregation-induced emission (AIE) macrocycles (DMP[5]-TPE and PCP[5]-TPE) were prepared by embedding Tetraphenylethene (TPE) unit into the skeletons of Dimethoxypillar[5]arene (DMP[5]) and [15]Paracyclophane ([15]PCP) at meso position, respectively. In crystal, the PCP[5]-TPE showed a distorted cavity, and the incubation of hexane inside the DMP[5]-TPE cavity caused a distinct change in the molecular conformation compared to PCP[5]-TPE. There was no complexation between PCP[5]-TPE and 1,4-dicyanobutane (DCB). UV absorption experiments showed the distorted cavity of DMP[5]-TPE hindered association with DCB.

UV Absorption Spectroscopy for the Diffusion of Plasma-Generated Reactive Species through a Skin Model

Skin applications of non-thermal atmospheric pressure plasma (NTAPP) have been at-tracting attention from medical and cosmetic aspects. The reactive species generated from plasma sources have been known to play important roles in the skin. For proper applications, it is essential to know how they diffuse into the skin. In this study, the penetration of active species from NTAPP through a skin model was analyzed by UV absorption spectroscopy. The diffusions of hydrogen peroxide, nitrite, and nitrate were quantified through curve fitting. We utilized an agarose gel to mimic epidermis and dermis layers, and we used a lipid film or a pig skin sample to mimic the stratum corneum (SC). The diffusion characteristics of reactive species through this skin model and the limitations of this method were discussed