A series of solution processable semiconducting donor-acceptor (DA) copolymers consisting of either diketopyrrolopyrrole or benzothiadiazole A units and alkoxy- or alkyl-substituted oligothiophene D ...units were synthesized. For all prepared copolymers the measured XPS spectra (C1s, S2p, N1s and O1s) were in a very good agreement with the expected chemical constitution. Spectroscopic studies of the synthesized copolymers showed that their optical band gaps were governed by the presence of the alkoxy substituents whose electron donating properties led to additional gap narrowing yielding semiconductors with band gaps of below 1.3eV in the case of the polymers with the diketopyrrolopyrrole A unit. The same trend was observed with the electrochemical band gaps, whose values were however found to be ca. 0.4eV superior to the corresponding optical band gaps values. Vibrational model was calculated for two of the synthesized copolymers with the goal to unequivocally attribute the observed Raman modes and to support the interpretation of the spectral changes induced by the electrochemical oxidation. It was established that the electrochemical oxidative doping of the copolymer with the benzothiadiazole A unit is limited to the oligothiophene segment in which the charge of the formed polycation is localized. To the contrary, in the case of the polymer with the diketopyrrolopyrrole A segment the charge imposed on the oligothiophene segment delocalizes towards the diketopyrrolopyrrole unit. These findings are in perfect agreement with the UV-vis-NIR spectroelectrochemistry data which show strong localization of electrochemically created charge carriers in the benzothiadiazole - oligothiophene copolymer and their metallic-like delocalization in the diketopyrrolopyrrole one. The latter seems to be very interesting not only as a potential low band gap component of organic photovoltaic cells but also, in the doped state, as electronic conductor of metallic character.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Chalcopyrite-type (Cu–Fe–S2) ternary nanocrystals stabilized by long aliphatic chain ligands could be considered as isolated hard nanoobjects dispersed in a soft network of organic ligands. The main ...attention was paid to the behavior of the particles whose average size was varied in a controllable manner from 3 to 20 nm. Dynamics of the nanoparticles was studied by applying Mössbauer spectroscopy. The fast dynamics could be described by a two-level environment. The deeper level (atomic) was practically the same as for bulk material except for the Debye temperature, but the higher level (particle motion) was described by the classical harmonic oscillator with the spring constant dramatically softening with increasing temperature. Such behavior led to a fast decrease of the fraction detectable by Mössbauer spectroscopy with increasing temperature. The induced internal oscillations within a particle by the surrounding thermal bath additionally contribute to the shift of measured spectra. Slow dynamics was characterized by the thermally driven overdamped harmonic oscillator motions. In addition, the long-range-like diffusion of particles was seen. No significant rotation of particles was found within the accessible temperature range.
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IJS, KILJ, NUK, PNG, UL, UM
Abstract This article establishes the basics of a theoretical model for the constitutive law that describes the skin temperature and thermolysis heat losses undergone by a subject during a session of ...whole-body cryotherapy (WBC). This study focuses on the few minutes during which the human body is subjected to a thermal shock. The relationship between skin temperature and thermolysis heat losses during this period is still unknown and have not yet been studied in the context of the whole human body. The analytical approach here is based on the hypothesis that the skin thermal shock during a WBC session can be thermally modelled by the sum of both radiative and free convective heat transfer functions. The validation of this scientific approach and the derivation of temporal evolution thermal laws, both on skin temperature and dissipated thermal power during the thermal shock open many avenues of large scale studies with the aim of proposing individualized cryotherapy protocols as well as protocols intended for target populations. Furthermore, this study shows quantitatively the substantial imbalance between human metabolism and thermolysis during WBC, the explanation of which remains an open question.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A series of copolymers consisting of alternating thiadiazole and unsubstituted or alkyl disubstituted quaterthiophene units, were synthesized by electropolymerization of ...2,5-bis(2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P1), 2,5-bis(4′-octyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P2), 2,5-bis(3′-octyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P3), 2,5-bis(3-decyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P4). For comparative reasons P3 was also obtained via Suzuki coupling of 2,5-bis(5-bromo-2-thienyl)-1,3,4-thiadiazole and neopentyl ester of 4,4′-dioctyl-2,2′-dithienyl-5,5′-diboronic acid. As evidenced by cyclic voltammetry studies the presence of electron accepting thiadiazole unit in the main polymer chain results in an increase of the reductive doping potential of the studied compounds as compared to polythiophene or poly(alkylthiophene). Electrochemically determined electron affinities values were found in the range from −3.10eV to −3.14eV, showing a negligible effect of the alkyl substituent on this parameter. To the contrary, the oxidation potential of the studied copolymers strongly depended on the presence and the position of the alkyl group. For P3 the electron donating properties of the substituents were particularly pronounced leading to a decrease of its oxidative doping potential by 210mV, as compared to the case of the unsubstituted polymer (P1), and the corresponding drop of the ionization potentials from +5.75eV to +5.54eV. The presence of a characteristic capacitive plateau's following the reductive and oxidative dopings suggests that both redox reactions are true doping reactions and the synthesized polymers can be transformed either in n-type or p-type conductors. For P3 and P4 these findings are additionally corroborated by UV–vis-NIR spectroelectrochemical data which unequivocally show the formation of polaronic/bipolaronic bands upon reductive and oxidative dopings. The analysis of the Raman spectroelectrochemical data obtained for P3, supported by theoretical calculations of the vibrational model, leads to the conclusion that the mechanism of the electrochemical doping in this polymers is the same as in poly(alkylthiophene) homopolymers and involves the transformation of the benzoid-like structure into quinoid one. As judged from the redox properties of the synthesized copolymers, P3 seems to be the most promising candidate for application in such organic electronic devices such as p-channel field effect transistors (FETs), photodiodes (PD) or photovoltaic cells (PC), however its use in air operating n-channel and ambipolar FETs seems to be excluded due to relatively high absolute value of electron affinity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
New push–pull conjugated polymers based on furo3,4-cpyrrole-4,6-dione (FPD) and selenopheno3,4-cpyrrole-4,6-dione (SePD) have been synthesized and compared with their thieno3,4-cpyrrole-4,6-dione ...(TPD) analogues to investigate the effects of the heteroatom on the electrooptical properties. The copolymers were synthesized using either Stille cross-coupling or direct heteroarylation polymerization (DHAP), the latter method giving high molecular weights. Hypsochromic shifts of the band gaps were observed for FPD-based copolymers (sulfur substituted by oxygen) while small bathochromic shift was observed for SePD (sulfur substituted by selenium) when compared to its TPD analogue. These two new classes of conjugated polymers exhibit electrooptical properties that could lead to interesting bulk heterojunction plastic solar cells.
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IJS, KILJ, NUK, PNG, UL, UM
A series of alkyl- or alkylphenyl-1,4,5,8-naphthalenetetracarboxylic-1,4:5,8-bisimides together with the comparative series of the corresponding 3,4,9,10-perylenetetracarboxylic-3,4:9,10-bisimides ...have been synthesized and characterized by cyclic voltammetry. The naphthalene bisimides family shows a clear dependence of its first reduction potential – corresponding to the LUMO level – on the nature of the N-substituent. Naphthalene bisimides containing alkylphenyl groups undergo the first 1e reduction at potentials of
ca. 100
mV higher than those with alkyl groups (
ca. −900
mV
vs ca. −1000
mV with respect to Fc/Fc
+ couple). No effect of the nature of the substituent is observed for the corresponding perylene bisimide series. Due to their improved solution processibility the synthesized organic semiconductors can be used for the fabrication of all organic, flexible n-channel field effect transistors (OFETs) through spin coating and printing techniques, without the necessity of the use of vacuum deposition techniques. The best of the fabricated transistors, operating in air show the charge carriers mobility of 4
×
10
−2
cm
2/(V
s) and the ON/OFF ratio equal to 4.5
×
10
5.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Two types of polythiophene—single-wall carbon nanotubes (SWCNTs) composites are comparatively studied. Composites of the first type consisted of nonmodified SWCNTs and nonmodified regioregular ...poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene) (P3OT) or poly(dioctylterthiophenes) (PDOTT). Composites of the second type (molecular composites) were obtained by grafting carboxylic acid functionalized poly(alkylthiophene)s on amine functionalized SWCNTs. In AFM images of the composites of nonfunctionalized components, individual carbon nanotubes can be easily distinguished, which are well dispersed in the polymer matrix showing fibrilar morphology. Cyclic voltammetry and Raman spectroelectrochemical experiments unequivocally show that all characteristic redox and spectroscopic features of both SWCTs and the polymer are retained in the composite material. Moreover the percolating network of SWCTs facilitates the electrochemical doping of the polymeric component. These new, solution processible materials are good candidates for printable contact electrodes in organic electronics. Molecular composites obtained by grafting show a different morphology. It is characterized by a network of fibers of diameters ranging from few dozens to few hundreds nm. Individual composite components cannot be distinguished which is an obvious consequence of the grafting reaction. Combined voltammetric and Raman spectroelectrochemical studies show that the grafting reaction lowers the electrochemical activity of the polymer component and the resulting maximum doping level is, in this case, lower than that found in composites of nonmodified components.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We have elaborated a new preparation method of ternary AgInS2 and alloyed quaternary AgInS2–ZnS nanocrystals which consisted of two consecutive injections of sulfur (S dissolved in oleylamine, OLA) ...and silver (AgNO3 or Ag2CO3 dissolved in dichlorobenzene, DCB) precursors into a mixture of indium(iii) chloride, zinc stearate and 1-dodecanethiol (DDT) dissolved in 1-octadecene (ODE). Under these conditions, nucleation of cubic In2S3 seeds took place followed by the growth of orthorhombic AgInS2 or alloyed AgInS2–ZnS cubic phases to yield heterodimer type nanocrystals. In both types of nanocrystals clearly separated photoluminescence peaks could be observed, confirming their heterogenic nature. The first one at 430 nm originated from the luminescence of the In2S3 phase. The second one was ascribed to the presence of a ternary Ag–In–S or quaternary Ag–In–Zn–S phase and its position, within the spectroscopic range from 515 nm to 710 nm, strongly dependent on the nanocrystal composition. The registered two-dimensional excitation–emission topographical maps clearly indicated that the observed emissions in two different spectral regions were related to the excitation in the same spectral range (300–400 nm); however their photoluminescence mechanisms were distinctly different. The photoluminescence lifetime of ∼3 ns measured for the emission at shorter wavelengths was typical of the simple mechanism of exciton radiative recombination in the In2S3 phase. The significantly longer lifetime of the longer wavelength emission (∼26 μs) seemed to clearly indicate that in this case the photoluminescence mechanism was more complex, involving exciton trap states whose positions depended on the composition of the ternary (or quaternary) phase.
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