scholarly journals Photophysical, Thermal and Structural Properties of Thiophene and Benzodithiophene-Based Copolymers Synthesized by Direct Arylation Polycondensation Method

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1151
Author(s):  
Newayemedhin A. Tegegne ◽  
Zelalem Abdissa ◽  
Wendimagegn Mammo
Keyword(s):  
Band Gap ◽  
Decomposition Temperature ◽  
Side Chain ◽  
X Ray Diffraction ◽  
Polar Solvents ◽  
Direct Arylation ◽  
Excitonic State ◽  
X Ray ◽  
Direct Arylation Polycondensation ◽  
Self Aggregation

Three low-band-gap copolymers based on isoindigo acceptor units were designed and successfully synthesized by direct arylation polycondensation method. Two of them were benzodithiophene (BDT)-isoindigo copolymers (PBDTI-OD and PBDTI-DT) with 2-octlydodecyl (OD) and 2-decyltetradecyl (DT) substituted isoindigo units, respectively. Thiophene donor and DT-substituted isoindigo acceptor units were copolymerized to synthesize PTI-DT. The copolymers have a broad absorption range that extends to over 760 nm with a band gap ≈1.5 eV. The photophysical property studies showed that the BDT-based copolymers have non-polar ground states. Their emission exhibited the population of the intramolecular charge transfer (ICT) state in polar solvents and tightly bound excitonic state in non-polar solvents due to self-aggregation. On the contrary, the emission from the thiophene-based copolymers was only from the tightly bound excitonic state. The thermal decomposition temperature of the copolymers was above 380 °C. The X-ray diffraction pattern of the three copolymers showed a halo due to π−π stacking. A second, sharper peak was observed in the BDT-based copolymer with a longer side chain on the isoindigo unit (PBDTI-DT), and the thiophene-based copolymers with PTI-DT, exhibiting a better structural order.

scholarly journals Photophysical, Thermal and Structural Properties of Thiophene and Benzodithiophene-Based Copolymers Synthesized by Direct Arylation Polycondensation Method

2021 ◽  
Author(s):  
Newayemedhin A. Tegegne ◽  
Zelalem Abdissa ◽  
Wendimagegn Mammo
Keyword(s):  
Band Gap ◽  
Decomposition Temperature ◽  
Side Chain ◽  
X Ray Diffraction ◽  
Polar Solvents ◽  
Direct Arylation ◽  
Excitonic State ◽  
X Ray ◽  
Direct Arylation Polycondensation ◽  
Self Aggregation

Three low band gap copolymers based on isoindigo acceptor units were designed and successfully synthesized by direct arylation polycondensation method. Two of them were benzodithiophene(BDT)-isoindigo copolymers (PBDTI-OD and PBDTI-DT) with 2-octlydodecyl(OD) and 2-decyltetradecyl (DT) substituted isoindigo units, respectively. Thiophene donor and DT-substituted isoindigo acceptor units were copolymerized to synthesize PTI-DT. The copolymers have broad absorption range that extends to over 760 nm with a band gap ~ .5 eV. The photophysical property studies showed the BDT based copolymers have non-polar ground states. Their emission exhibited the population of intramolecular charge transfer (ICT) state in polar solvents and tightly bound excitonic state in non-polar solvents due to self-aggregation. On the contrary, the emission from the thiophene based copolymers was only from the tightly bound excitonic state. The thermal decomposition temperature of the copolymers was above 380 oC. The X-ray diffraction pattern of the three copolymers showed a halo due pi-pi stacking. A second sharper peak was observed in the BDT-based copolymer with longer side chain on the isoindigo unit (PBDTI-DT) and the thiophene based copolymers with PTI-DT exhibiting a better structural order.

Energy Band Gap Studies of CdS Nanomaterials

2008 ◽  
Vol 3 ◽  
pp. 97-102 ◽  
Author(s):  
Dinu Patidar ◽  
K.S. Rathore ◽  
N.S. Saxena ◽  
Kananbala Sharma ◽  
T.P. Sharma
Keyword(s):  
Optical Absorption ◽  
Band Gap ◽  
Energy Band ◽  
Chemical Method ◽  
Optical Absorption Spectroscopy ◽  
Cds Nanoparticles ◽  
X Ray Diffraction ◽  
Energy Band Gap ◽  
X Ray ◽  
Simple Chemical

The CdS nanoparticles of different sizes are synthesized by a simple chemical method. Here, CdS nanoparticles are grown through the reaction of solution of different concentration of CdCl2 with H2S. X-ray diffraction pattern confirms nano nature of CdS and has been used to determine the size of particle. Optical absorption spectroscopy is used to measure the energy band gap of these nanomaterials by using Tauc relation. Energy band gap ranging between 3.12 eV to 2.47 eV have been obtained for the samples containing the nanoparticles in the range of 2.3 to 6.0 nm size. A correlation between the band gap and size of the nanoparticles is also established.

Liquid crystalline polyureas with oligo(ethylene glycol) sequences

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Shahram Mehdipour-Ataei ◽  
Leila Akbarian-Feizi
Keyword(s):  
Liquid Crystalline ◽  
Spectroscopic Method ◽  
Polymerization Reaction ◽  
X Ray Diffraction ◽  
Subsequent Reaction ◽  
Scanning Calorimetry ◽  
Polar Solvents ◽  
X Ray ◽  
H Nmr ◽  
Ft Ir

AbstractA diamine monomer containing ester, amide and ether functional groups was prepared and its polymerization reaction with different diisocyanates to give main chain poly(ester amide ether urea)s was investigated. The monomer was synthesized via reaction of terephthaloyl chloride with 4-hydroxybenzoic acid and subsequent reaction of the resulted diacid with 1,8-diamino-3,6-dioxaoctane. The polymers were characterized by FT-IR and 1H-NMR spectroscopic method and elemental analysis. The resulting polymers exhibited excellent solubility in polar solvents. Crystallinity of the resulted polymers was evaluated by wide-angle X-ray diffraction (WXRD) method, and they exhibited semi-crystalline patterns. The glass transition temperatures (Tg) of the polymers determined by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were in the range of 88-112 °C. The temperatures for 10% weight loss (T10) from their thermogravimetric analysis (TGA) curves were found to be in the range of 297-312 °C in air. Also the prepared polyureas showed liquid crystalline character.

Enhanced visible-active photocatalytic behaviors observed in Mn-doped BiFeO3

2018 ◽  
Vol 32 (17) ◽  
pp. 1850185 ◽  
Author(s):  
Yun-Hui Si ◽  
Yu Xia ◽  
Ya-Yun Li ◽  
Shao-Ke Shang ◽  
Xin-Bo Xiong ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Band Gap ◽  
Diffuse Reflectance Spectroscopy ◽  
X Ray Diffraction ◽  
Electron Hole ◽  
X Ray ◽  
Mn Doped ◽  
Hole Recombination ◽  
Narrow Band Gap Semiconductors

A series of BiFeO3 and BiFe[Formula: see text]Mn[Formula: see text]O3 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) were synthesized by a hydrothermal method. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS) and UV–Vis diffuse reflectance spectroscopy, and their photocatalytic activity was studied by photocatalytic degradation of methylene blue in aqueous solution under visible light irradiation. The band gap of BiFeO3 was significantly decreased from 2.26 eV to 1.90 eV with the doping of Mn. Furthermore, the 6% Mn-doped BiFeO3 photocatalyst exhibited the best activity with a degradation rate of 94% after irradiation for 100 min. The enhanced photocatalytic activity with Mn doping could be attributed to the enhanced optical absorption, increment of surface reactive sites and reduction of electron–hole recombination. Our results may be conducive to design more efficient photocatalysts responsive to visible light among narrow band gap semiconductors.

Are mesoionic compounds aromatic?

1998 ◽  
Vol 76 (6) ◽  
pp. 869-872 ◽  
Author(s):  
Alfredo Mayall Simas ◽  
Joseph Miller ◽  
Petrônio Filgueiras de Athayade Filho
Keyword(s):  
Experimental Evidence ◽  
Key Words ◽  
Dipole Moments ◽  
The Other ◽  
Side Chain ◽  
Theoretical Studies ◽  
X Ray Diffraction ◽  
Ring Plane ◽  
X Ray ◽  
Single Bonds

We have evaluated the experimental evidence relevant to the structure and character of mesoionic compounds, accumulated for more than 100 years and including X-ray diffraction studies. We have also evaluated relevant theoretical studies. All these, including our own extensive work, lead us to conclude that mesoionic compounds are not aromatic. According to our recent definition “mesoionic compounds are planar five-membered heterocyclic betaines with at least one side chain whose α-atom is also in the ring plane and with dipole moments of the order of 5 D. Electrons are delocalized over two regions separated by what are essentially single bonds. One region, which includes the a-atom of the side chain is associated with the HOMO and negative π-charge whereas the other is associated with the LUMO and positive π-charge.” Key words: mesoionic compounds, betaines, aromaticity.

scholarly journals Flexible ZnO photoelectrode for photo electrochemical energy conversion

2021 ◽  
Author(s):  
T. Shiyani ◽  
Indrani Banerjee ◽  
Santosh K. Mahapatra ◽  
Asim K Ray
Keyword(s):  
Band Gap ◽  
Diffraction Pattern ◽  
Absorption Spectra ◽  
Optical Band Gap ◽  
Solar Fuels ◽  
Photoelectrochemical Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
A Value ◽  
Pet Substrate

Abstract Photoelectrochemical properties have been investigated for flexible ZnO/ITO/PET photoelectrodes. ZnO was spin coated on ITO/PET substrate with thickness of about 310 nm. The high crystalline structure of ZnO was studied using x-ray diffraction pattern. A value of 3.4 eV has been estimated for optical band gap from its absorption spectra. The flexible ZnO photoelectrode was demonstrated to generate photoelectrochemical current. Values of 1.022 and 0.714 were found to be for photo switching and photoresponsivity, respectively. ZnO/ITO/PET can be used as a substrate for making flexible hybrid PEC devices to generate solar power and solar fuels.

scholarly journals Effect of Re and Tm-site on morphology structure and optical band gap of ReTmO3 (Re: La, Ce, Nd, Gd, Dy, Y and Tm: Fe, Cr) prepared by sol-gel method

2018 ◽  
Vol 64 (4) ◽  
pp. 381
Author(s):  
Muhammad Tufiq Jamil ◽  
Javed Ahmad ◽  
Syed Hamad Bukhari ◽  
Murtaza Saleem
Keyword(s):  
Band Gap ◽  
Sol Gel ◽  
Xrd Analysis ◽  
Sem Analysis ◽  
X Ray Diffraction ◽  
Orthorhombic Crystal ◽  
X Ray ◽  
Average Grain Size ◽  
Auto Combustion ◽  
Uv Visible

Rare earth nano sized pollycrystalline orthoferrites and orthocromites ReT mO3 (Re = La, Nd, Gd, Dy, Y and T m = Fe, Cr) have been synthesized by sol-gel auto combustion citrate method. The samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and UV-visible spectroscopy. The samples are single phase as confirmed by XRD analysis and correspond to the orthorhombic crystal symmetry with space group pbnm. Debye Scherer formula and Williamson Hall analysis have been used to calculate the average grain size which is consistent with that of determined from SEM analysis and varied between 25-75 nm. The elemental compositions of all samples have been checked by EDX analysis. Different crystallographic parameters are calculated with strong structural correlation among Re and Tm sites. The optical energy band gap has been calculated by using Tauc relation estimated to be in the range of 1.77 - 1.87 eV and 2.77 - 3.14 eV, for ReFeO3 and ReCrO3, respectively.

scholarly journals NMR and X-ray studies of apetalic acid isolated from Calophyllum brasiliense and of its chiral amides

2021 ◽  
Author(s):  
Marie-Rose Van Calsteren ◽  
Ricardo Reyes-Chilpa ◽  
Chistopher K Jankowski ◽  
Fleur Gagnon ◽  
Simón Hernández-Ortega ◽  
...  
Keyword(s):  
Antimycobacterial Activity ◽  
Side Chain ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Rain Forests ◽  
X Ray ◽  
X Ray Crystallography ◽  
Calophyllum Brasiliense ◽  
Derivatives Of

The tropical tree Calophyllum brasiliense (Clusiaceae) grows in the rain forests from Brazil to Mexico. Its leaves, as well as those of other Calophyllum species, are rich sources of chromanone acids, such as apetalic acid, isoapetalic acid, and their derivatives. Apetalic acid has shown significant antimycobacterial activity. The biological activity of apetalic acid has been related to the configuration of three asymmetric centers and the stereochemistry of the molecule; however, the C-19 configuration in the acidic side chain has not been fully resolved. For this reason, the unequivocal determination of the absolute configuration by means of X-ray crystallography in a sample of unique homogeneous apetalic acid stereoisomer was the most important point to start this study. We prepared some chiral amides using the carboxyl group. We determined the C-19 stereochemistry of apetalic acid, and its specific chiral derivatives, using NMR, X-ray diffraction methods, and molecular mechanics. Finally, we observed that steric hindrance in the side chain of apetalic acid leads to restriction of rotation around the pivotal link C-10 and C-19 establishing chiral centers at C2(R), C3(S), and C19(R). We were able to separate derivatives of these two high-rotatory-barrier conformers of apetalic acid by forming diastereoisomeric amides with phenylglycine methyl ester having a chiral center at C-2’. Our results allowed the conclusion of the existence of atropisomerism in the apetalic acid molecule.

Carboxyl graphene reinforced melamine-based polyamide nanocomposites

2021 ◽  
pp. 089270572110514
Author(s):  
Himanshu V Madhad ◽  
Dilip V Vasava
Keyword(s):  
Electron Microscopy ◽  
Decomposition Temperature ◽  
Differential Scanning Calorimetric ◽  
X Ray Diffraction ◽  
One Pot ◽  
X Ray ◽  
Mild Conditions ◽  
Thermal Stability Of ◽  
Infrared Techniques ◽  
Scanning Electron

Over the years, various types of techniques have been used for the synthesis of nanocomposites. In this work, melamine-based polyamide (PA) was synthesized using a one-pot polycondensation method under mild conditions. carboxyl graphene (CG)/PA nanocomposites (CGMPA) were prepared by CG nanofiller loadings of 1, 3, and 5 wt.% via delamination/adsorption approach. The prepared CGMPA nanocomposites were characterized using different analyses, such as Fourier transform infrared techniques (FTIR), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), differential scanning calorimetric (DSC), and thermogravimetric analysis (TGA). The effects of the CG on the thermal properties of the CGMPA nanocomposites were significant. The results showed that the melting temperature (Tm) of neat PA and CGMPA were increased from 378°C to 393°C suggested better dispersion of CG in PA matrix. The decomposition temperature of PA was increased from 451°C to 463°C in CGMPA nanocomposites indicates the better thermal stability of PA matrix by addition of CG.

Rotational Polymorphism of Methyl-Substituted Ammonium Perchlorates

1965 ◽  
Vol 9 ◽  
pp. 170-189 ◽  
Author(s):  
M. Stammler ◽  
R. Bruenner ◽  
W. Schmidt ◽  
D. Orcutt
Keyword(s):  
Phase Transition ◽  
Ammonium Perchlorate ◽  
Room Temperature ◽  
Decomposition Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Techniques ◽  
Cell Dimensions ◽  
Thermal Analysis Techniques ◽  
Space Requirements

AbstractThe thermal transformations which take place in solid methyl-substituted ammonium perchlorates have been studied using high-temperature X-ray diffraction and differential thermal analysis techniques. In the temperature range from 20°C to their decomposition temperature (above 300°C), ammonium perchlorate and tetramethyl ammonium perchlorate undergo only one enantiomorphic phase transition, namely at 240 and 340°C (with decomposition), respectively. This I—II transition is ascribed to the beginning of the free rotation of the ClO4− ions. The rotation of the cations, however, begins below room temperature. If the symmetry of the cation is lowered by having both methyl groups and hydrogens arranged around the nitrogen (as in monomethyl, dimethyl, and trimethyl ammonium perchlorates), there is an additional enantiomorphic phase transition. This I—II transformation is ascribed to the rotation of the cations which have, in the partially substituted ions, two sets of non-equivalent symmetry axes (different moments of inertia). The temperatures of transformation are discussed in terms of the space requirements for rotation. Symmetries and cell dimensions of some modifications were determined.

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