photochemical reactions
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Agronomy ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 108
Denis V. Yanykin ◽  
Dmitriy E. Burmistrov ◽  
Alexander V. Simakin ◽  
Julia A. Ermakova ◽  
Sergey V. Gudkov

The influence of light conversion induced by glasses coated with up-converting luminescent nanoparticles on Solanum lycopersicum cultivation was studied. Nanoparticles of Sr0.46Ba0.50Yb0.02Er0.02F2.04 solid solution were used as the up-converting luminophore. These nanoparticles were able to transform IR radiation into visible light (λem = 660 nm with minor peaks at 545 nm and 525 nm). By applying the “variable” chlorophyll fluorescence (ΔF), it was shown that the cultivation of tomatoes under the photoconversion glasses stimulated changes in the rate of plant adaptation to ultraviolet radiation. The restoration time of values of effective quantum yield of photosystem II photochemical reactions and photochemical quenching of chlorophyll fluorescence (reflecting disappearance of imbalance between photosynthetic electron transport and the utilization of NADPH) was reduced from three weeks to three days in the case of control and photoconversion films, respectively. As a result, plants grown under photoconversion glass had an increased leaf number (12.5%), total leaf area (33%), stem length (35%) and chlorophyll content in the leaves (two-fold). It is assumed that an increase in the proportion of red light in the growing spectrum has a positive effect on photosynthetic activity and plant growth.

2021 ◽  
Manvendra Singh ◽  
Bryce Gaskins ◽  
Daniel Johnson ◽  
Christopher Elles ◽  
Zarko Boskovic

We prepared a collection of complex cycloheptatriene-containing azetidine lactones by ap- plying two key photochemical reactions: “aza-Yang” cyclization and Buchner carbene insertion into aromatic rings. While photolysis of phenacyl amines leads to a rapid charge transfer and elimination, we found that a simple protonation of the amine enables the formation of azetidinols as single diastereomers. We provide evidence, through ultrafast spectroscopy, for the electron transfer from free amines in the excited state. Further, we characterize aza-Yang re- action by establishing the dependence of initial reaction rates on rates of photon absorption. Unanticipated change in reactivity in morpholine analogs is explained through interactions with the tosylate anion. Buchner reaction proceeds with slight preference for one diastereomer over the other, and successful reaction requires electron-donating carbene-stabilizing substituents. Overall, sixteen compounds were prepared over seven steps. Guided by an increase in structural complexity, efforts such as this one extend reach of chemists into unexplored chemical space and provide useful quantities of new compounds for studies focused on their properties.

2021 ◽  
Vol 23 (1) ◽  
pp. 267
Alessia Mariano ◽  
Irene Bigioni ◽  
Anna Scotto d’Abusco ◽  
Alessia Baseggio Conrado ◽  
Simonetta Maina ◽  

Pheomelanin is a natural yellow-reddish sulfur-containing pigment derived from tyrosinase-catalyzed oxidation of tyrosine in presence of cysteine. Generally, the formation of melanin pigments is a protective response against the damaging effects of UV radiation in skin. However, pheomelanin, like other photosensitizing substances, can trigger, following exposure to UV radiation, photochemical reactions capable of modifying and damaging cellular components. The photoproperties of this natural pigment have been studied by analyzing pheomelanin effect on oxidation/nitration of tyrosine induced by UVB radiation at different pH values and in presence of iron ions. Photoproperties of pheomelanin can be modulated by various experimental conditions, ranging from the photoprotection to the triggering of potentially damaging photochemical reactions. The study of the photomodification of l-Tyrosine in the presence of the natural pigment pheomelanin has a special relevance, since this tyrosine oxidation/nitration pathway can potentially occur in vivo in tissues exposed to sunlight and play a role in the mechanisms of tissue damage induced by UV radiation.

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Yuanyuan Meng ◽  
Wanlong Sun

China’s rapid urbanisation and industrialisation have led to frequent haze in China in recent years. Although many measures to control haze have been implemented, no significant improvement has been observed, and haze still exists. In this study, we used wavelet transform to investigate the changes in PM2.5 on the time scale, the relationship amongst meteorological factors, and the causes and changes in haze formation and take measures to prevent haze. Results indicated the following: (1) The peak of PM2.5 changes in winter in the past three years primarily occurred in the range from 11:00 to 13:00 and 20:00 to 22:00. (2) Multiple cycles of daily average PM2.5 concentrations existed in 3–5 d, 6–14 d, 6–21 d, and 16–27 d, with a significant oscillation in 6–14 d and stable cycle characteristics. (3) The meteorological factors promoted the formation of haze to a certain extent. When haze occurred, the near-surface wind speed was only 1 m/s, which was not conducive to the spread of pollutants. (4) The formation of haze was affected by the interaction of various factors; the photochemical reactions of NO2 and O3 also exacerbated the formation of pollutants. This study provided a clear direction for the prevention and prediction of haze. Furthermore, the government must take relevant measures to reduce pollutant emissions and ensure the air quality of cities in winter.

2021 ◽  
Dianming Wu ◽  
Jingwei Zhang ◽  
Mengdi Wang ◽  
Junling An ◽  
Ruhai Wang ◽  

2021 ◽  
Taotao Liu ◽  
Gaojie Chen ◽  
Jinsheng Chen ◽  
Lingling Xu ◽  
Mengren Li ◽  

Abstract. Peroxyacetyl nitrate (PAN) acting as a typical indicator of photochemical pollution can redistribute NOx and modulate O3 production. Coupled with the observation-based model (OBM) and a generalized additive model (GAM), the intensive observation campaigns were conducted to reveal the pollution characteristics of PAN and its impact on O3, the contributions of influencing factors to PAN formation were also quantified in this paper. The F-values of GAM results reflecting the importance of the influencing factors showed that ultraviolet radiation (UV, F-value = 60.64), Ox (Ox = NO2+O3, 57.65), and air temperature (T, 17.55) were the main contributors in the PAN pollution in spring, while the significant effects of Ox (58.45), total VOCs (TVOCs, 21.63) and T (20.46) were found in autumn. The PAN formation rate in autumn was 1.58 times higher than that in spring, relating to the intense photochemical reaction and meteorological conditions. Without considering the transformation of peroxyacetyl radical (PA) and PAN, acetaldehyde contributed to the dominant production of PA (46 ± 4 %), followed by methylglyoxal (28 ± 3 %) and radical cycling (19 ± 3 %). The PAN formation was highly VOC-sensitive, and sufficient NOx (compared with VOCs abundance) would not be the limited factor for atmospheric photochemistry. PAN could promote or inhibit O3 formation under high or low ROx levels, respectively. The PAN promoting O3 formation mainly occurred during the periods of 11:00–16:00 (local time) when the favorable meteorological conditions (high UV and T) stimulated the photochemical reactions to offer ROx radicals, which accounted for 17 % of the whole monitoring periods in spring and 31 % in autumn. In this study, the formation mechanism of PAN and its effect on ozone were identified, which might be helpful to improve the scientific understanding of photochemical pollution in coastal areas.

Cristian Guerra ◽  
Leandro Ayarde-Henríquez ◽  
Mario Duque-Noreña ◽  
Eduardo Chamorro

2021 ◽  
Vol 12 ◽  
Arturo Alberto Vitale ◽  
Eduardo Alberto Bernatene ◽  
Alicia Beatriz Pomilio

Background: The Fenton reaction is of growing interest due to its primary function in bodily processes and industrial waste disposal. However, the effects of alcohol on this reaction have not been addressed. Therefore, we analyze for the first time the role that catalytic concentrations of alcohols play in the Fenton reaction. Methods: The Fenton reaction was carried out by measuring oxidation-reduction potential and pH monitoring under dark conditions to avoid photochemical reactions. The reaction end point was established using the first derivative of plotting potential versus time. This point was also checked by the dichromate test for hydrogen peroxide detection. Gas-liquid chromatography was used to measure alcohol content. The Fenton reaction of glucose was performed first, and then each alcohol, including ethanol, methanol, iso-propanol, and ter-butanol, was added separately in catalytic amounts, as well as the cyclic ether tetrahydrofuran. The reaction rate constants and the stability constants of each complex formed were measured. Results : Alcohols were shown to inhibit the Fenton reaction by forming iron-alcohol complexes. An iron-tetrahydrofuran complex was also formed. The crucial oxygen role in the functional group of alcohols and ethers is supported by a reaction with tetrahydrofuran. These results also explain the difficulties in the disposal of sugar-enriched alcoholic industrial effluents. Conclusion: Our findings show that alcohols, such as ethanol, methanol, iso-propanol, and ter-butanol at catalytic concentrations, slow down the Fenton reaction due to decreased iron availability by forming iron(II)-alcohol complexes. The method is also useful for calculating stability constants for iron-alcohol and iron-tetrahydrofuran complexes, which are not otherwise easy to assess.

2021 ◽  
Stephanie Jones ◽  
Mohit Singh ◽  
Denis Duft ◽  
Alexei Kiselev ◽  
Thomas Leisner

<p>The impact of atmospheric aerosol on the climate remains poorly understood. Organic aerosol makes up a significant fraction of total aerosol and is prevalent throughout the atmosphere. It can exist as a liquid, semi-solid or amorphous solid. The viscosity of organic aerosol will have an impact on transformations that organic aerosol will undergo during its lifetime such as evaporation and growth, heterogeneous and photochemical reactions as well as the ability to act as an ice nucleating particle.  Therefore, it is of key importance to be able to determine aerosol viscosity over a range of atmospherically relevant conditions in order to better understand the impact of organic aerosol on the climate.</p> <p>Here we report proof of concept viscosity measurements of water droplets levitated in an electrodynamic balance over a range of temperatures. Charged droplets are levitated in a temperature and relative humidity-controlled environment allowing properties over a temperature range of 300 to 220 K to be studied. As the droplets evaporate they reach a point where Coulomb instabilities are induced resulting in droplet oscillations. The relaxation of these oscillations can then be probed to determine the droplet viscosity. Future work will involve determination of the viscosity of different types of organic aerosol over a broad temperature range.</p>

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