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Recent upgrading of the nanosecond pulse radiolysis setup and construction of laser flash photolysis setup at the Institute of Nuclear Chemistry and Technology in Warsaw, Poland

Szreder Tomasz

Nukleonika

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2022

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Vol. 67, No. 3

49--64

EN

Modification of pulse radiolysis (PR) setup and construction of a new laser flash photolysis (LFP) setup at the Institute of Nuclear Chemistry and Technology (INCT) is described. Both techniques are dedicated to studying fast reactions in real time by direct observation of transients. Time resolution of the PR setup at INCT was ~11 ns, limited by the duration of the electron pulse. Implementation of a new spectrophotometric detection system resulted in a significant broadening of experimental spectral range with respect to the previous setup. Noticeable reduction of the noise-to-signal ratio was also achieved. The LFP system was built from scratch. Its time resolution was ~6 ns, limited by the duration of a laser pulse. LFP and PR were purposely designed to share the same hardware and software solutions. Therefore, components of the detection systems can be transferred between both setups, signifi cantly lowering the costs and shortening the construction/upgrading time. Opened architecture and improved experimental fl exibility of both techniques were accomplished by implementation of Ethernet transmission control protocol/Internet protocol (TCP/IP) communication core and newly designed software. This is one of the most important enhancements. As a result, new experimental modes are available for both techniques, improving the quality and reducing the time of data collections. In addition, both systems are characterized by relatively high redundancy. Currently, implementation of new equipment into the systems hardly ever requires programming. In contrast to the previous setup, daily adaptations of hardware to experimental requirements are possible and relatively easy to perform.

2

Mercaptoalkoxy-thioxanthones as novel photoinitiators for free radical polymerization – mechanistic study

Ścigalski Franciszek, Obrębowska Agnieszka, Bajorek Agnieszka

Polimery

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2019

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T. 64, nr 3

190--198

EN

Three mercaptoalkoxy-thioxanthones were developed as new photoinitiators for radical polymerization. These compounds can act as either one- or two-component photoinitiating systems. The quenching of the excited triplet states of thioxanthone derivatives by aromatic amines was investigated in dimethyl sulfoxide (DMSO). Based on the mechanism of the intermolecular electron-transfer process, we proposed sequence of reactions leading to the formation of radicals that are capable of initiating the polymerization reaction.

PL

Zsyntetyzowano trzy alkoksypochodne tioksantonu i oceniono możliwość ich zastosowania jako nowych fotoinicjatorów polimeryzacji rodnikowej. Na podstawie wyników badań stwierdzono, że związki te mogą działać zarówno jako jednoskładnikowe układy fotoinicjujące, jak i układy dwuskładnikowe w kompozycji z donorem elektronu. Fotoliza i badania kinetyczne stanów wzbudzonych zsyntetyzowanych pochodnych tioksantonu w obecności amin aromatycznych w środowisku dimetylosulfotlenku (DMSO) pozwoliły na zaproponowanie sekwencji reakcji prowadzących do powstania rodników zdolnych do zainicjowania reakcji polimeryzacji.

3

Free-radical chemistry of thiourea in aqueous solution, induced by OH radical, H atom, a-hydroxyalkyl radicals, photoexcited maleimide, and the solvated electron

Schuchmann M., Schuchmann H., Knolle W., von Sonntag J., Naumov S., Wang W., von Sonntag C.

Nukleonika

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2000

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Vol. 45, nr 1

55-62

EN

Hydroxyl radicals react with thiourea (and its tetramethyl derivative) yielding dimeric radical cations which are characterized by strong absorptions at 400 nm (450 nm). An analysis of the kinetics of the buildup of these absorptions gives evidence for the intermediacy of OH-adducts and the monomeric radical cations. The dimeric radical cations are also generated in the reactions of triplet-excited maleimide with these thioureas. Moreover, in acid solutions even reducing radicals such as the H atom and a-hydroxyalkyl radicals give rise to these intermediates in full yields, albeit displaying different kinetics. Potential mechanistic implications are discussed. The dimeric thiourea radical cations are strong oxidants and readily oxidize the anions of phenol and 2’-deoxyguanosine. The solvated electron gives rise to an intermediate which is rapidly protonated by water (pKa > 11). Quantum-mechanical calculations support the assignment of the 400 nm (450 nm) absorption to the respective dimeric thiourea radical cation.