Víctor M. Chapela

Meritorious Autonomous University of Puebla, Ejido Puebla, Baja California, Mexico

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Publications (59)91.82 Total impact

  • Molecules 04/2015; 20(4):5793-5811. DOI:10.3390/molecules20045793 · 2.42 Impact Factor
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    ABSTRACT: The structure of the Schiff base (E)-2-[(2-hydroxybenzylidene)amino]phenylarsonic[(E)-HBAPhAA], synthesized from salicylaldehyde and o-aminophenylarsonic acid in the presence of HCl, was characterized by FTIR, H-1 NMR, EI-MS, UV-Vis spectroscopy, and X-ray crystallography. The crystal belonged to the monoclinic space group P2(1)/c. Two molecules formed a dimer via intermolecular interactions due to the attachment of H atoms to 01, 03 and 04 with 0 H bond distances within reasonable ranges, ca. 0.84(3) angstrom. The structure also showed two intramolecular interactions of 2.634(2) and 3.053(2) angstrom for N-H center dot center dot center dot O hydrogen bonds, which caused the structures to be almost planar. We performed a theoretical analysis using OFT theory at B3LYP/6-31+G(d,p) level to determine the stability of the E and Z conformers. The geometry analysis of the E- and Z-isomers revealed an interconversion energy barrier between E/Z isomers of 22.72 kcal mol(-1). We also theoretically analyzed the keto form of the E-isomer and observed a small energy barrier for the tautomerization of 6.17 kcal moll.
    Journal of Molecular Structure 02/2015; 1081. DOI:10.1016/j.molstruc.2014.10.030 · 1.60 Impact Factor
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    ABSTRACT: The molecular structure and molecular interactions of an [small alpha],[small beta]-unsaturated nitrile, such as the interaction between adjacent molecules of (Z)-3-(4-(diphenylamino)phenyl)-2-(pyridin-2-yl)-acrylonitrile (Z-DPPyACN) throughout the 4-diphenylamino moiety with the phenyl and pyridyl rings, play an important role in the self-assembly behaviors and optical properties of its powder and single-crystal forms. The crystal packing exhibits multiple C-H[small pi] and CHHC edge-to-face interactions that contribute to the supramolecular network between adjacent molecules. The resulting molecular structure resembles a pinwheel which exhibits a strong emission intensity at three different wavelengths. The crystal belongs to the monoclinic space group P21/n, with dimensions a = 12.9551(2), b = 11.29300(15), c = 14.6992(3) A, [small beta] = 115.648(2)[degree] and Z = 4. The single-crystal compound shows three emission maxima at 533, 569, and 607 nm, whereas the powder and the molecules in an aggregated state show maximum emission intensities that are dependent on the nature of the solvent. The Z-DPPyACN dye's optical properties show a Stokes shift caused by the reorganization of the molecule in the excited state, as effected by the solvent polarity. This indicates a large change in the dipole moment of dye molecules upon excitation due to an intramolecular charge transfer interaction. From a theoretical point of view, the molecular geometry, electronic structure, and excitation energies are reported using density functional theory and compared with the experimentally determined one photon absorption and emission spectra.
    CrystEngComm 09/2014; 16(36):-. DOI:10.1039/C4CE00327F · 3.86 Impact Factor
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    ABSTRACT: The effect of the ratio of oxygen to carbon atoms (O/C) on the morphology of carbon nanostructures has been studied by varying the methanol and ethanol ratio in the reaction mixtures. Notable morphological differences in the synthesized carbon nanostructures are observed as a function of the O/C ratio. At a high O/C ratio, i.e., using methanol (O/C = 1), the synthesized carbon nanoshells (CNS) are faceted. Moreover, other faceted nanostructures, such as triangular and hexagonal, are observed in this strong oxidative environment. Decreasing the O/C ratio in the mixture by adding ethanol induces changes in the CNSs morphology; they are less faceted and favor only the growth of single-walled carbon nanotubes mixed with the CNSs. The importance of the O/C ratio is corroborated by replacing ethanol (O/C = 0.5) with polyethylene glycol (O/C = 0.5) in the methanol:ethanol reaction mixture. Finally, at very low O/C ratios, i.e., methanol:octanol mixtures, CNS are obtained and no faceted nanostructures or SWCNT are found. Thus, adjusting the O/C ratio is a method for obtaining high purity samples of CNS. Moreover, the use of the alcohols during the synthetic process is a simple and green method of functionalizing CNS.
    Carbon 09/2014; 76:292–300. DOI:10.1016/j.carbon.2014.04.080 · 6.16 Impact Factor
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    ABSTRACT: The properties of aqueous solutions of polyelectrolytes of sodium o- and p-methacryloylaminophenylarsonate (o- and p- MAPHA-Na) with acrylamide (AAD) or sodium methacrylate (MA-Na): poly(sodium o-methacryloylaminophenylarsonate) (poly(o-MAPHA-Na)), poly(sodium o-methacryloylaminophenylarsonate-co-acrylamide) (poly(o-MAPHA-Na-co-AAD)) (26:74), poly(sodium o-methacryloylaminophenylarsonate-co-sodium methacrylate) (poly(o- MAPHA-Na-co-AM-Na) (35:65) and (14:86), and poly(sodium p-methacryloylaminophenylarsonate-co-sodium methacrylate) (poly(p- MAPHA-Na-co-AM-Na)) (34:66) were studied by off-line, multi-angle light scattering, and in-line using size exclusion chromatography coupled with multi-angle light scattering (SEC-MALS) and refractometric (RI) detection. The Mw value corresponding to the homopolymer poly(o-MAPHA-Na) was 1,300,000 g/mol and for the copolymers the Mw and gyration radius values were decreased when the AAD or AM-Na comonomer composition increased. The macromolecular parameters obtained using SEC-MALS were in agreement with the values measured in the off-line mode. Also, SEC-MALS experiments allowed examination of the radius of gyration-Mw relationship in order to determine the polyelectrolyte conformation (ρ) in solution; these values fell between 0.7-0.53, indicating that the polyelectrolytes are random coils at θ-conditions. In addition, the effect of the pH on the macromolecular parameters was evaluated. At pH 4.5, the Mw and gyration radius values corresponding to poly(o-MAPHA-Na) and poly(o-MAPHA-Na-co-AAD) (26/74) remained very close to those measured at pH 7. However, <r g 2 > values for poly(o-MAPHA-Na-co-AM-Na) copolymers at pH 4.5 were less than pH 7, indicating that the presence of AM-Na reduced the size of the copolymer through intermolecular interactions.
    Journal of Polymer Research 08/2014; 21(8). DOI:10.1007/s10965-014-0492-6 · 1.90 Impact Factor
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    ABSTRACT: The novel compound Z-2-phenyl-3-(4-(pyridin-2-yl)phenyl)acrylonitrile (PPyPAN) was synthesized from the condensation reaction between phenylacetonitrile and 4-(pyridin-2-yl)benzaldehyde. This compound crystallizes in two forms: polymorph I (triclinic, P - 1, Z' = 2) and polymorph II (orthorhombic, Pbc2(1), Z' = 2). The molecular structures and optical properties of the two polymorphs have been characterized via H-1 NMR, El, FTIR, UV-Vis spectroscopy, DSC, single-crystal and XRPD. The molecular structure, packing properties, and intermolecular interactions were examined for both polymorphs of PPyPAN in order to interpret the emission properties. A subtle change in the molecular conformation (e.g., a rotation around single C-C bonds) found for both polymorph plays an important role in their solid-state properties. The structure and optical properties of the new structures were well characterized and showed unique features for both polymorphic phases. For phase I, we observed an excitation spectrum with an lambda(ex) at 325-346 nm, which is the maximum excitation or absorption wavelength for the lowest S-0 -> S-1 transition, which is characteristic to the pi-pi* transition, and an emission spectrum with an lambda(max)(em) at 454 nm. For phase II, the excitation spectrum showed an lambda(max)(ex) at 325 nm, whereas the lambda(max)(em) showed a red-shift to 492 nm.
    05/2014; 1078. DOI:10.1016/j.molstruc.2014.04.088
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    ABSTRACT: Two novel ATRP initiator (R-X): 2-bromo-2-methyl-N-(1-phenyl-ethyl)propanamide (I) and 2,2,2-trichloro-N-(1-phenylethyl)acetamide (II) were synthesized and characterized by 1H-NMR, IR, EI. Also, crystal structures of (I) and (II) are reported. Compounds (I) and (II) were used in the ATRP reaction of methyl methacrylate (MMA) and acrylamide (AAD) at 48°C, using CuBr/Me6TREN and ethanol/toluene (60:40) mixture as catalytic complex and solvent, respectively. End-group analysis by 1H-NMR was used to determinate the molecular mass of the polymers synthesized via ATRP. The Mn values for poly(MMA) using (II) were 2333 and 3952 g/mol, which is higher in comparison with the Mn values obatined for (AAD)/(II) and (AAD)/(I) systems indicating that monomers containing ester moiety in their structure, such as acrylates and methacrylates, may be good candidates to polymerize with (II) and CuBr/Me6TREN.
    Macromolecular Symposia 05/2014; 339(1). DOI:10.1002/masy.201300144
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    ABSTRACT: In this review paper, have been investigated three novel crystal structures of three molecules with carbazole substituents as the electron-donor group. These molecules, 2-(phenyl)-3-(N-ethyl-(3'-carbazolyl))acrylonitrile (I), 2-(3''- pyridyl)-3-(N-ethyl-(3'-carbazolyl))acrylonitrile (II), and 2-(4-pyridyl)-3-(N-ethyl-(3´-carbazolyl))acrylonitrile (III) in their structure, possess the electron-donor carbazole moiety, a -CN group attached to the double bond, and a phenyl or a pyridine function at the meta- or para-position. It was revealed with the help of single crystal diffraction X-ray analysis that there exists no difference in the crystal system, because all the compounds were crystallized in monoclinic system with space group P21/c. For determining the effect of the position of the nitrogen atom substitution on the crystal properties, has been analyzed and contrasted the molecular packing in a single crystal with that of other previously reported carbazole derivatives. The double bond bearing N-ethylcarbazole,–CN, phenyl or pyridine groups was observed to impart sufficient polarity in order to show slipped π-stacking aggregation in the solid state, affecting the compounds in the solid state and consequently affecting their fluorescence properties. The substitution at the para position was reported to exhibit more multiple C-H...π interactions as well as an interesting and unexpected short contact distance between adjacent N...N molecules those brought a conformational change resulting in an edge-to-face alignment in the molecules and affecting the best relative photoluminescence efficiency of the sample.
    03/2014; 4(1). DOI:10.2174/1877946803666131213231346
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    ABSTRACT: The structural characterisation of the molecule 1,4-bis[2-cyano-2-(o-pyridyl)ethenyl] benzene obtained through Knoevenagel condensation is reported. The single crystals, as light brown rods, were cultured from a chloroform solution using a slow evaporation method at ambient temperature. The compound crystallised in the monoclinic system belonging to the C2/c space group with a = 26.4556(9) Å, b = 3.73562(10) Å, c = 18.4230(6) Å, β = 109.841(4)° and the asymmetric unit comprising Z = 4. The structure is ordered and the molecules of the title compound exhibited a lattice with water molecules located at sites of inversion and two-fold axial symmetries. Thus, only halves of the molecules are symmetrically independent. The lattice is reported and contrasted with X-ray single-crystal diffraction and theoretical calculations of 1,4-bis(1-cyano-2-phenylethenyl)benzene. By using density functional theory (DFT) and second order Moller-Plesset (MP2) theoretical calculations, the ground state geometry in the whole molecule at the B3LYP/6-31+G(d,p), and MP2/6-31+G(d,p) theory levels, respectively, were optimised. The DFT calculations showed a quasi-planar structure of the molecule, whereas the wave function-based MP2 method afforded a non-planar optimised structure with significant torsion angles between the pyridine and phenyl rings.
    Chemical Papers- Slovak Academy of Sciences 02/2014; 68(2). DOI:10.2478/s11696-013-0434-5 · 1.19 Impact Factor
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    ABSTRACT: The 1-phenyl-2-(α-pyridyl)ethanol [or 1-phenyl-2-(2-pyridyl)ethanol] compound was obtained from the Knoevenagel condensation reaction between 2-methylpyridine with benzaldehyde without catalyst or solvent. The compound was characterized by IR, 1H-NMR, and by single crystal X-ray diffraction. The X-ray structure clearly revealed that the compound crystallizes in a monoclinic system with centrosymmetric space group, P21/c, with Z′ = 1. The unit cell dimensions are a = 5.2481(3), b = 8.2862(4), c = 23.8498(14) Å, and β = 96.761(5)°. The crystal structure showed the formation of one intermolecular hydrogen bond O–H···N between the oxygen atom of the O–H and the nitrogen atom of the pyridine group of the adjacent molecule. The crystallography data gave evidence that the intermediate compound is a new stable 1-phenyl-2-(2-pyridyl)ethanol intermediate which presents an interesting relationship between stability and hydrogen bonds formation in the structure for obtaining similar compounds that have been proposed in the literature. Also, it is shown that it is just before the dehydration process which yields the trans double bond of the 1-phenyl-2-(2-pyridyl)ethene.
    Research on Chemical Intermediates 06/2013; 41(6). DOI:10.1007/s11164-013-1471-y · 1.54 Impact Factor
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    ABSTRACT: Knoevenagel condensation of phenylacetonitrile with 4-diphenylaminophenylacetonitrile in the presence of piperidine was carried out to obtain a novel conjugated compound. In addition to the expected compound 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitrile (I), the 3-((4-diphenylamino)phenyl)-2,4-diphenylpentanedinitrile (II) was also obtained with a good yield. Compound II was obtained as a result of the Michael addition of phenylacetonitrile with 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitrile (I). Conversely, when the same reaction was performed in the presence of KOH as catalyst, only the α,β-unsaturated nitrile (I) was afforded with a 92 % yield. The structures were confirmed with IR, EI-MS and NMR spectroscopy. Single crystals I and II were formed and their structures were determined by X-ray single-crystal diffraction analysis. Crystal I belongs to the monoclinic system with space group P21/n having unit cell parameters of a = 16.8589(5) Å, b = 6.68223(17) Å, c = 19.8289(7) Å, β = 111.133(4)○ and Z = 4. Crystal II belongs to the same monoclinic system with space group P21/c, having unit cell parameters of a = 10.8597(4) Å, b = 24.7533(10) Å, c = 9.7832(4) Å, β = 91.297(3)○ and Z = 4. In addition to the structural data analysis, some theoretical calculations that reveal the nature of relevant structure-property relationships are also reported.
    Chemical Papers- Slovak Academy of Sciences 05/2013; 68(5). DOI:10.2478/s11696-013-0503-9 · 1.19 Impact Factor
  • María Judith Percino, Víctor Manuel Chapela
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    ABSTRACT: The chapter talks about conducting polymers. The doping process is an effective method to produce conducting polymers. Doping allows electrons to flow due to the formation of conduction bands. Electric current is produced when the electrons are moving along the polymer chains. This chapter elaborates on an understanding of the mechanisms of charge storage and charge transfer, the structures and characterization techniques of conducting polymers, and some potential applications for conducting polymers. It also presents some examples of conjugated conducting polymers, including polyacetylene, polypyrrole, polyaniline, and polythiopene.
    Handbook of Polymer Synthesis, Characterization, and Processing, 02/2013: pages 535-557; , ISBN: 9780470630327
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    ABSTRACT: A combined theoretical and experimental study on the structure, infrared, UV-Vis and 1H NMR data of trans-2-(m-cyanostyryl)pyridine, trans-2-[3-methyl-(m-cyanostyryl)]pyridine and trans-4-(m-cyanostyryl)pyridine is presented. The synthesis was carried out with an efficient Knoevenagel condensation using green chemistry conditions. Theoretical geometry optimizations and their IR spectra were carried out using the Density Functional Theory (DFT) in both gas and solution phases. For theoretical UV-Vis and 1H NMR spectra, the Time-Dependent DFT (TD-DFT) and the Gauge-Including Atomic Orbital (GIAO) methods were used, respectively. The theoretical characterization matched the experimental measurements, showing a good correlation. The effect of cyano- and methyl- substituents, as well as of the N-atom position in the pyridine ring on the UV-Vis, IR and NMR spectra, was evaluated. The UV-Vis results showed no significant effect due to electron-withdrawing cyano- and electron-donating methyl-substituents. The N-atom position, however, caused a slight change in the maximum absorption wavelengths. The IR normal modes were assigned for the cyano- and methyl-groups. 1H NMR spectra showed the typical doublet signals due to protons in the trans position of a double bond. The theoretical characterization was visibly useful to assign accurately the signals in IR and 1H NMR spectra, as well as to identify the most probable conformation that could be present in the formation of the styrylpyridine-like compounds.
    International Journal of Molecular Sciences 02/2013; 14(2):4005-29. DOI:10.3390/ijms14024005 · 2.34 Impact Factor
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    ABSTRACT: Four (dimethylamino)arylacrylonitrile derivatives in the solid state are presented. The compounds were characterized by single crystal X-ray diffraction to investigate the effects of substituents on the resulting crystals lattices and to examine the effects of the factors controlling their solid state on photochemical behavior. The molecules included 2-(phenyl)-3-(4-dimethylaminophenyl)acrylonitrile (I) 2-(2′-pyridyl)-3-(4-dimethylaminophenyl)-acrylonitrile (II), 2-(3′-pyridyl)-3-(4-dimethyl-aminophenyl)acrylonitrile (III) and 2-(3′-pyridyl)-3-(4-dimethylaminophenyl)acrylonitrile (IV). The dimethyl-, CN groups and the position of nitrogen atom in the pyridyl groups affected the nature of the molecular packing and consequently their fluorescence properties. The lattice of each compound is compared with acrylonitriles previously reported and the effect of substitution on the crystal properties with the strongest emission in solid state is examined. Based on analyses of molecular packing in the single crystals, the differences in the fluorescence could be attributed to aggregates that showed non-classical herringbone packing with π–π overlap between neighbor molecules. Also the crystal structure studies showed that the N atom position is located anti to the CN group, giving a more planar geometry. This N-dimethyl substituent for I–IV appears to be general for more planar ground-state geometry about the nitrogen atom and consistent with an “amino conjugation effect” to obtain sufficient quinoid structures.
    Journal of Molecular Structure 02/2013; 1034:238–248. DOI:10.1016/j.molstruc.2012.10.025 · 1.60 Impact Factor
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    ABSTRACT: This study examined absorption properties of 2-styrylpyridine, trans-2-(m-cyanostyryl)pyridine, trans-2-[3-methyl-(m-cyanostyryl)]pyridine, and trans-4-(m-cyanostyryl)pyridine compounds based on theoretical UV/Vis spectra, with comparisons between time-dependent density functional theory (TD-DFT) using B3LYP, PBE0, and LC-ωPBE functionals. Basis sets 6-31G(d), 6-31G(d,p), 6-31+G(d,p), and 6-311+G(d,p) were tested to compare molecular orbital energy values, gap energies, and maxima absorption wavelengths. UV/Vis spectra were calculated from fully optimized geometry in B3LYP/6-311+G(d,p) in gas phase and using the IEFPCM model. B3LYP/6-311+G(d,p) provided the most stable form, a planar structure with parameters close to 2-styrylpyridine X-ray data. Isomeric structures were evaluated by full geometry optimization using the same theory level. Similar energetic values were found: ∼4.5 kJ mol(-1) for 2-styrylpyridine and ∼1 kJ mol(-1) for derivative compound isomers. The 2-styrylpyridine isomeric structure differed at the pyridine group N-atom position; structures considered for the other compounds had the cyano group attached to the phenyl ring m-position equivalent. The energy difference was almost negligible between m-cyano-substituted molecules, but high energy barriers existed for cyano-substituted phenyl ring torsion. TD-DFT appeared to be robust and accurate approach. The B3LYP functional with the 6-31G(d) basis set produced the most reliable λ(max) values, with mean errors of 0.5 and 12 nm respect to experimental values, in gas and solution, respectively. The present data describes effects on the λ(max) changes in the UV/Vis absorption spectra of the electron acceptor cyano substituent on the phenyl ring, the electron donor methyl substituent, and the N-atom position on the electron acceptor pyridine ring, causing slight changes respect to the 2-styrylpyridine title compound.
    Journal of Molecular Modeling 10/2012; DOI:10.1007/s00894-012-1602-1 · 1.87 Impact Factor
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    06/2012; 1(3):96-105. DOI:10.5539/jmsr.v1n3p96
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    ABSTRACT: A novel water-soluble polymer containing phosphorus poly(sodium p-methacryloylaminobenzylphosphonate) was synthesized by free radical polymerization in the presence of K2S2O8 as initiator, in water as solvent at 70°C with a 48 h reaction time. The new monomer used for the polymerization was synthesized by reaction between sodium aminobenzylphosphonate and methacryloyl chloride at 4°C in methanol with a yield of 78.3%. The compounds, monomer and polymer, were characterized by IR, 1H-NMR and potentiometric titrations. The new monomer and polymer reported here are important because they are very water-soluble and contain a versatile ligand, –PO(ONa)2, which could be used in environmental applications. The polymer possibly could be used as a metalchelating polymer or as flocculant.
    Designed Monomers & Polymers 04/2012; 10(3):273-280. DOI:10.1163/156855507780949173 · 0.88 Impact Factor
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    03/2012; 1(2). DOI:10.5539/jmsr.v1n2p181
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    ABSTRACT: We synthesized three novel highly fluorescent compounds, 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, and 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile by Knoevenagel condensation. The first two were synthesized without solvent in the presence of piperidine as a catalyst; the third was synthesized without a catalyst and with N,N-dimethylformamide as a solvent. In solution, the molar absorption coefficients showed absorptions at 380, 378, and 396 nm, respectively; in solid state, absorptions were at 398, 390, and 442 nm, respectively. The fluorescence emission was at 540, 540 and 604 nm, respectively, the 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile showed a red shift in the emission of 64 nm compared to the other two compounds. The fluorescence quantum yield for the compounds in powder form showed values of 0.05, 0.14, and 0.006, respectively; compared with the value measured for the Alq3 reference, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile had a lightly higher value. The third harmonic generation measurement for 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile yielded a χ(3) value of 5.5 × 10−12 esu, similar to that reported for commercial polymers.
    Materials 12/2011; 4(3). DOI:10.3390/ma4030562 · 1.88 Impact Factor
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    ABSTRACT: Nanocrystalline 2,6-distyrylpyridine (2,6-DStP)-doped TiO(2) monoliths were prepared by the sol-gel technique. Different concentrations of the 2,6-DStP doping agent were utilized. Samples were characterized by x-ray diffraction, photoacoustic spectroscopy (optical absorption), and luminescence spectroscopy. As-prepared samples showed amorphous structure and traces of the anatase crystalline phase of TiO(2) after annealing at room temperature. The samples exhibited average particle size from 6 nm to 7.5 nm for molar concentration of 2,6-DStP from 0.0% to 0.03%. The photoacoustic spectra revealed the absorption edge at wavelength around 375 nm (3.38 eV), which is attributed to TiO(2), and a gap shift varying from 1.91 eV, to 2.41 eV, to 1.86 eV with the molar concentration of 2,6-DStP. Photoluminescence spectroscopy showed three different bands around 555 nm, 607 nm, and 779 nm when the samples were excited with 407 nm, 488 nm, and 633 nm laser lines, respectively.
    Journal of Electronic Materials 12/2011; 40(12):2388-2391. DOI:10.1007/s11664-011-1778-7 · 1.68 Impact Factor