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UV Radiation Processes (with Ruben Rivera)
Published in Jiri George Drobny, Radiation Technology for Polymers, 2020
This reaction is based on a stoichiometric reaction of multifunctional olefins (enes) with thiols. The addition reaction can be initiated thermally, photochemically, and by electron beam and radical or ionic mechanism.55 Thiyl radicals can be generated by the reaction of an excited carbonyl compound (usually in its triplet state) with a thiol or via radicals, such as benzoyl radicals from a Type I photoinitiator, reacting with the thiol. The thiyl radicals add to olefins, and this is the basis of the polymerization process.56 The addition of a dithiol to a diolefin yields linear polymer, higher-functionality thiols, and alkenes form cross-linked systems.
Nanobiosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
The aforementioned light-induced carrier generation provides the basis for the combination of the CdSe/ZnS electrode with a NADH-producing enzyme reaction for the light-triggered detection of the corresponding substrate. Schubert et al. (2009) showed that glucose detection is possible with such an electrode system by photocurrent measurements. To prepare the electrodes (Figure 9.12), the quantum dots were first modified with a dithiol, 1,4-benzenedithiol (BDT), C6H6S2, and then immobilized on the gold electrodes (Au-[QD-BDT]). A thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl (-C-SH or R-SH) group (where R represents an alkane, alkene, or other carbon-containing moiety); a dithiol is a compound having two thiol groups. For immobilization of the CdSe/ZnS nanocrystals, their capping ligand, trioctylphosphine oxide (TOPO), C24H51OP, by synthesis was exchanged with BDT. TOPO is a tertiary alkylphosphine that can be used as an extraction or stabilizing agent. The use of a small dithiol provided the possibility of replacement of the original ligand TOPO, in a first step, as well as the strong coupling of the nanocrystals to the gold electrode surface via chemisorption in a second step (Au-[QD-BDT]). The bare gold electrode showed no photocurrent, but, after quantum dot immobilization, a negative photocurrent of approximately 10 nA was observed at an applied potential of +50 mV versus Ag/AgCl, 1 M KCl. The detection of NADH was possible in the range from 20 μM to 2 mM. The detection of glucose, using glucose dehydrogenase, was effectively demonstrated. Glucose detection due to the catalytic production of NADH by the enzyme glucose dehydrogenase (GDH) in solution, performed at CdSe/ZnS quantum-dot-modified gold electrodes with QDs immobilized on gold via the ligand 1,4-benzenedithiol (Au-[QD-BDT]). (Schubert, K. et al., Langmuir, 26, 1395, doi: 10.1021/la902499e, 2009.)
Electrically controllable reflection bandwidth polymer-stabilized cholesteric liquid crystals with low operating voltage
Published in Liquid Crystals, 2022
Hongbo Lu, Qi Wang, Mengmeng Zhu, Peng Huang, Miao Xu, Longzhen Qiu, Jun Zhu
The preferred approach to broaden the reflection bandwidth of CLC films is to introduce a pitch gradient or a non-uniform pitch distribution [6,8,13–18]. Broer et al. have obtained a broadband reflective polariser with pitch gradients by controlling the kinetics of photo-polymerisation [8,19,20]. Mitov et al. on the other hand, proposed introducing a pitch gradient through thermal diffusion of a chiral dopant between the two thin cholesteric films with red and blue colours [6]. Yang et al. synthesised a novel chiral dithiol with high helical twisting power (HTP) and fabricated an ultrawide broadband reflection CLC composite film with non-uniform pitch distribution via thiol-acylate chemistry [21]. However, the reflection bandwidths of these CLC films cannot be adjusted due to their permanent solid structure.
Application of butane-1,4-diyl bis(2-mercaptoacetate) as dithiol prepolymer for preparation of polythiourethane and clay-based nanocomposites
Published in Journal of Sulfur Chemistry, 2022
Amin Pirayesh, Nazanin Qolizade, Saeid Talebi, Mehdi Salami-Kalajahi
Butane-1,4-diyl bis(2-mercaptoacetate) (BBMA) or 1,4-butanediol bis(thioglycolate) as a dithiol compound has been used as a thiol compound in thiol–ene click reactions [26,27] and in the synthesis of epoxy-based vitrimers via the transesterification reaction [28]. Also, it has been used as a chain extender in the synthesis of hyperbranched PTUs [29]. In this work, we have synthesized butane-1,4-diyl bis(2-mercaptoacetate) (BBMA) as a dithiol compound via the esterification of 1,4-butanediol and thioglycolic acid. BBMA as a prepolymer has been reacted with 4,4'-diphenylmethane diisocyanate (MDI) to prepare poly(thiourethane). Moreover, Cloisite 30B (1–5 wt.%) has been used to prepare clay/poly(thiourethane) nanocomposites. Finally, the effect of Cloisite 30B content on structural, thermophysical, and thermal properties of nanocomposites has been investigated.
Nano-sized ZnS functionalized with dioxa-dithio ligands for removal of Pb(II) from aqueous solution
Published in Inorganic and Nano-Metal Chemistry, 2019
Narjes Alamolhodaei, Hossein Eshghi, Hossein Massoudi
Figure 5 shows the FT-IR spectra of S2O2–ZnS which compared with 3,6-dioxa-1,8-octane-dithiol starting material. The broad band in 3370 cm−1 was attributed to the absorbed water molecules. A characteristic medium band of S–H groups at 2556 cm−1 was disappeared and replaced with a weak broad band as the result of reacting with ZnS. Furthermore, other stretching bands of ether group which were observed in 2932, 2863, 1470, and 1113 cm−1 significantly shifted to higher frequency in S2O2–ZnS. Therefore, it can be deduced that 3,6-dioxa-1,8-octane-dithiol grafts on the surface of S2O2–ZnS through the thiol group, leaving the another thiol group on the outer surface of the nano-sized ZnS. Perhaps, some dioxa-dithio macrocyclic crown ethers doped on ZnS surface.