Search Results (15)

The direct discharge of cationic surfactants into environmental matrices has exponentially increased due to their wide application in many products. These compounds and their degraded products disrupt microbial dynamics, hinder plant survival, and affect human health. Therefore, there is an urgent need to develop electroanalytical assessment techniques for their identification, determination, and monitoring. In our study, ZnO-PANI nanocomposites were electrodeposited on a glassy carbon electrode (GCE), followed by the immobilization of laccase enzymes and the electrodeposition of polypyrrole (PPy), to form a biosensor that was used for the detection of CTAB. A UV-Vis analysis showed bands corresponding to the π-π* transition of benzenoid and quinoid rings, π-polaron band transition and n-π*polaronic transitions associated with the extended coil chain conformation of PANI, and the presence and interaction of ZnO with PANI and type 3 copper in the laccase enzymes. The FTIR analysis exhibited peaks corresponding to N-H and C-N stretches and bends for amine, C=C stretches for conjugated alkenes, and a C-H bend for aromatic compounds. A high-resolution scanning electron microscopy (HRSEM) analysis proved that PANI and ZnO-PANI were deposited as fibres with hairy topography resulting from covalent bonding with the laccase enzymes. The modified electrode (PPy-6/GCE) was used as a platform for the detection of CTAB with three linear ranges of 0.5–100 µM, 200–500 µM, and 700–1900 µM. The sensor displayed a high sensitivity of 0.935 μA μM⁻¹ cm⁻², a detection limit of 0.0116 µM, and acceptable recoveries of 95.02% and 87.84% for tap water and wastewater, respectively. Full article

The planar morphology of the backbone significantly contributes to the subtle optoelectronic features of π-conjugated polymers. On the other hand, the atomistic tuning of an otherwise identical π-backbone could also impact optoelectronic properties systematically. In this manuscript, we compare a series of 3,4-cycloalkylchalcogenophenes by tuning them atomistically using group-16 elements. Additionally, the effect of systematically extending these building blocks in the form of oligomers and polymers is studied. The size of the 3,4-substitution affected the morphology of the oligomers. In addition, the heteroatoms contributed to a further alteration in their geometry and resultant optoelectronic properties. The chalcogenophenes, containing smaller 3,4-cycloalkanes, resulted in lower bandgap oligomers or polymers compared to those with larger 3,4-cycloalkanes. Natural bonding orbital (NBO) calculations were performed to understand the disparity alongside the contour maps of frontier molecular orbitals (FMO). Full article

In this work, an oxidized g-C₃N₄ film was successfully synthesized using a two-step acid treatment and electrophoretic deposition method. The delocalized π-system of the oxidized g-C₃N₄ film was extended via an annealing treatment. We investigated the influence of hydrogen bonding reversibility and the oxidation treatment of g-C₃N₄ on the photoelectrochemical property and photocathodic protection for 304 stainless steel (304 SS). The resulting oxidized g-C₃N₄ photoelectrode with an extended π-system presents a remarkably enhanced photogenerated electron transfer capability from the photoelectrode to 304 SS (photoinduced OCP negative shift of −0.55 V_AgCl) compared with oxidized g-C₃N₄ and protonated g-C₃N₄. The oxidation of g-C₃N₄ facilitates the formation of a porous structure and the introduction of abundant oxygen functional groups, which could promote the effective separation and transport of photogenerated electron–hole pairs. The hydrogen bonding reversibility contributes to the extension of the delocalized π-conjugation system, which could enhance light absorption efficiency. Meanwhile, the annealing treatment is beneficial for prolonging the lifetime of photoelectrons, which could reduce the recombination rate of charge carriers. In addition, to understand how the oxidation treatment and annealing treatment affect the charge transfer behavior, the electronic band structure was investigated, and we found that the oxidized g-C₃N₄ film with an extended π-system possesses a more negative conduction band position, which could reduce the energy barrier of the photogenerated electron transfer. Full article

The synthesis of ladder-type 9,9′-bifluorenylidene-based conjugated polymer is reported. Unlike the typical synthetic strategy, the new designed ladder-type conjugated polymer is achieved via tandem Suzuki polymerization/Heck cyclization reaction in one-pot. In the preparation process, Suzuki polymerization reaction occurred first and then the intramolecular Heck cyclization followed smoothly under the same catalyst Pd(PPh₃)₄. The model reaction proved that the introduction of iodine (I) for this tandem reaction can effectively control the sequential bond-forming process and inhibit the additional competitive side reactions. Thus, small-molecule model compounds could be obtained in high yields. The successes of the synthesized small molecule and polymer compounds indicate that the Pd-catalyzed tandem reaction may be an effective strategy for improving extended π-conjugated materials. Full article

Since chlorohydrazones are planar molecules, it is in principle possible to distinguish between their E and Z stereoisomers. Chlorohydrazones are known to preferentially assume the Z configuration around the C=N double bond, and their (E, Z) isomerization is almost suppressed at room temperature. The lack, or rather the difficulty, of such an isomerization has been conveniently addressed by the in-depth theoretical study of seven C-methoxycarbonyl-N-aryl chlorohydrazones (aryl = phenyl, 4-chlorophenyl, 4-bromophenyl, 4-iodophenyl, 2-chlorophenyl, 2-bromophenyl, and 2-iodophenyl). DFT ωB97M-D4/cc-pVTZ calculations of these C-methoxycarbonyl-N-aryl chlorohydrazones, supported by the XRD determination of the molecular structure, provided a complete picture of the isomerization processes in the studied compounds. The analysis of the energetics, molecular geometry, and electronic structure (the latter in the framework of the Quantum Theory of Atoms In Molecules) showed that the Z isomers are thermodynamically favored because, within the low-energy planar isomers with extensive π conjugation, the electrostatic interactions between the dipoles of the C–O, C–Cl, and N–H bonds overcome the stabilization induced by the N–H ··· O bond present in the E isomers. We confirmed that the (E, Z) isomerization occurs by the umklapp mechanism, in which the –NHAr moiety rotates in the molecular plane towards a linear C=N–N configuration and then proceeds to the other isomer. The (E, Z) isomerization is very slow at room temperature because the umklapp interconversion has high barriers (≈110 kJ/mol) despite the extended π electron delocalization present in the transition state. Full article

The development of widely applicable methods for the synthesis of C-C-bonded nanostructures on inert and insulating surfaces is a challenging yet rewarding milestone in the field of on-surface synthesis. This would enable studies of nearly unperturbed covalent nanostructures with unique electronic properties as graphene nanoribbons (GNR) and π-conjugated 2D polymers. The prevalent Ullmann-type couplings are almost exclusively carried out on metal surfaces to lower the temperature required for initial dehalogenation well below the desorption threshold. To overcome the necessity for the activation of monomers on the target surface, we employ a recently developed Radical Deposition Source (RaDeS) for the direct deposition of radicals onto inert surfaces for subsequent coupling by addition reactions. The radicals are generated en route by indirect deposition of halogenated precursors through a heated reactive tube, where the dehalogenation reaction proceeds. Here, we use the ditopic 6,11-diiodo-1,2,3,4-tetraphenyltriphenylene (DITTP) precursor that afforded chevron-like GNR on Au(111) via the usual two-staged reaction comprised of monomer-coupling into covalent polymers and subsequent formation of an extended GNR by intramolecular cyclodehydrogenation (CDH). As a model system for inert surfaces, we use Ag(111) passivated with a closed monolayer of chemisorbed iodine that behaves in an inert manner with respect to dehalogenation reactions and facilitates the progressive coupling of radicals into extended covalent structures. We deposit the DITTP-derived biradicals onto both iodine-passivated and pristine Ag(111) surfaces. While on the passivated surface, we directly observe the formation of covalent polymers, on pristine Ag(111) organometallic intermediates emerge instead. This has decisive consequences for the further progression of the reaction: heating the organometallic chain directly on Ag(111) results in complete desorption, whereas the covalent polymer on iodine-passivated Ag(111) can be transformed into the GNR. Yet, the respective CDH proceeds directly on Ag(111) after thermal desorption of the iodine passivation. Accordingly, future work is aimed at the further development of approaches for the complete synthesis of GNR on inert surfaces. Full article

For many years, the research on conjugated polymers (CPs) has been mainly focused on their application in organic electronics. Recent works, however, show that due to the unique optical and photophysical properties of CPs, such as high absorption in UV–Vis or even near-infrared (NIR) region and efficient intra-/intermolecular energy transfer, which can be relatively easily optimized, CPs can be considered as an effective light-activated source of versatile and highly reactive singlet oxygen for medical or catalytic use. The aim of this short review is to present the novel possibilities that lie dormant in those exceptional polymers with the extended system of π-conjugated bonds. Full article

Using single-bonded and fused aromatic rings are two methods for extending the π-conjugation in the vertical direction of benzo [1,2-b:4,5-b′] dithiophene (BDT) unit. To investigate which method is more efficient in nonfullerene systems, two novel polymers based on alkylthionaphthyl and alkylthiobiphenyl substituted BDT named PBDTNS-FTAZ and PBDTBPS-FTAZ are designed and synthesized. Two polymers only exhibit small differences in structure, but huge differences in photovoltaic properties. They are studied by blended with 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone)-5,5,11,11-tetrakis(4-hexylphenyl)dithieno [2,3-d’:2,3’-d’]-s-indaceno [1,2-b:5,6-b’] dithiophene (ITIC). The device based on PBDTNS-FTAZ:ITIC showed the best power conversion efficiency (PCE) of 9.63% with the V_oc of 0.87 V, a J_sc of 18.06 mA/cm² and a fill factor of 61.21%, while the PBDTBPS-FTAZ:ITIC only exhibit a maximum PCE of 7.79% with a V_oc of 0.86 V, a J_sc of 16.24 mA/cm² and a relatively low fill factor of 55.92%. Therefore, extending π-conjugation with alkylthionaphthyl is more effective against constructing nonfullerene solar cells. Full article

Core–shell structured TiO₂ is a promising solution to promote the photocatalytic effectiveness in visible light. Compared to metal or semiconductor materials, polymers are rarely used as the core materials for fabricating core–shell TiO₂ materials. A novel core–shell structured polymer@TiO₂ was developed by using phenolic polymer (PP) colloid nanoparticles as the core material. The PP nanoparticles were synthesized by an enzyme-catalyzed polymerization in water. A subsequent sol–gel and hydrothermal reaction was utilized to cover the TiO₂ shell on the surfaces of PP particles. The thickness of the TiO₂ shell was controlled by the amount of TiO₂ precursor. The covalent connection between PP and TiO₂ was established after the hydrothermal reaction. The core–shell structure allowed the absorption spectra of PP@TiO₂ to extend to the visible-light region. Under visible-light irradiation, the core–shell nanosphere displayed enhanced photocatalytic efficiency for rhodamine B degradation and good recycle stability. The interfacial C–O–Ti bonds and the π-conjugated structures in the PP@TiO₂ nanosphere played a key role in the quick transfer of the excited electrons between PP and TiO₂, which greatly improved the photocatalytic efficiency in visible light. Full article

The structure, reactivity, natural bond orbital (NBO), linear and nonlinear optical (NLO) properties of three thiazole azo dyes (A, B and C) were monitored by applying B3LYP, CAM-B3LYP and ωB97XD functionals with 6-311++G** and aug-cc-pvdz basis sets. The geometrical parameters,dipolemoments,HOMO-LUMO(highest occupied molecular orbital,lowest unoccupied molecular orbital) energy gaps, absorption wavelengths and total hyperpolarizabilities were investigated in carbon tetrachloride (CCl4) chloroform (CHCl3), dichloromethane (CH2Cl2) and dimethlysulphoxide (DMSO). The donor methoxyphenyl group deviates from planarity with the thiazole azo moiety by ca. 38◦; while the acceptor dicyanovinyl, indandione and dicyanovinylindanone groups diverge by ca. 6◦. The HOMOs for the three dyes are identical. They spread over the methoxyphenyl donor moiety, the thiazole and benzene rings as π-bonding orbitals. The LUMOs are shaped up by the nature of the acceptor moieties. The LUMOs of the A, B and C dyes extend over the indandione, malononitrile and dicyanovinylindanone acceptor moieties, respectively, as π-antibonding orbitals. The HOMO-LUMO splittings showed that Dye C is much more reactive than dyes A and B. Compared to dyes A and B, Dye C yielded a longer maximum absorption wavelength because of the stabilization of its LUMOs relative to those of the other two. The three dyes show solvatochromism accompanied by significant increases in hyperpolarizability. The enhancement of the total hyperpolarizability of C compared to those of A and B is due to the cumulative action of the long π-conjugation of the indanone ring and the stronger electron-withdrawing ability of the dicyanovinyl moiety that form the dicyanovinylindanone acceptor group. These findings are facilitated by a natural bond orbital (NBO) technique. The very high total hyperpolarizabilities of the three dyes define their potent nonlinear optical (NLO) behaviour. Full article

In our continued efforts in the synthesis of ruthenium(II) polypyridine complexes as potential dyes for use in varied applications, such as the dye-sensitized solar cells (DSSCs), this work particularly describes the synthesis, absorption spectrum, redox behavior and luminescence properties of a new homoleptic ruthenium(II) complex bearing a simple trans-2-methyl-2-butenoic acid functionality as the anchoring ligand on terpyridine moiety. The functionalized terpyridine ligand: 4’-(trans-2-methyl-2-butenoic acid)-terpyridyl (L1) was synthesized by aryl bromide substitution on terpyridine in a basic reaction condition under palladium carbide catalysis. In particular, the photophysical and redox properties of the complex formulated as: bis-4’-(trans-2-methyl-2-butenoic acid)-terpyridyl ruthenium(II) bis-hexafluorophosphate [Ru(L1)₂(PF₆)₂] are significantly better compared to those of [Ru(tpy)₂]²⁺ and compare well with those of the best emitters of Ru(II) polypyridine family containing tridentate ligands. Reasons for the improved photophysical and redox properties of the complex may be attributed partly to the presence of a substituted α,β-unsaturated carboxylic acid moiety leading to increase in the length of π-conjugation bond thereby enhancing the MLCT-MC (Metal-to-ligand-charge transfer-metal centred) energy gap, and to the reduced difference between the minima of the excited and ground states potential energy surfaces. Full article

In this work, two ligands: 4-(trans-2-Methyl-2-butenoic acid)-2,2'-bipyridine) (L₁) and 5-(trans-2-methyl-2-butenoic acid)-1,10-phenanthroline (L₂), with the corresponding mixed-ligand heteroleptic Ru(II) complex were synthesized and characterized by FT-IR, ¹H-, ¹³C-NMR spectroscopy and elemental analysis. The influence of the mixed functionalized polypyridyl ruthenium(II) complex on the photophysical and electrochemical properties were investigated and compared to individual single-ligand homoleptic complexes. Interestingly, the mixed-ligand complex formulated as [RuL₁L₂(NCS)₂] exhibits broad and intense metal-to-ligand charge transfer (MLCT) absorption with a high molar extinction coefficient (λ_max = 514 nm, ε = 69,700 M⁻¹ cm⁻¹), better than those of individual single-ligand complexes, [Ru(L₁)₂(NCS)₂] and [Ru(L₂)₂(NCS)₂], and a strong photoluminescence intensity ratio in the red region at λ_em = 686 nm. The electrochemical properties of the complex indicated that the redox processes are ligand-based. Full article

In our quest to develop good materials as photosensitizers for photovoltaic dye-sensitized solar cells (DSSCs), cis-dithiocyanato-4-(2,3-dimethylacrylic acid)-2,2'-bipyridyl-4-(9-anthracenyl-(2,3-dimethylacrylic)-2,2'-bipyridyl ruthenium(II) complex, a high molar extinction coefficient charge transfer sensitizer, was designed, synthesized and characterized by spectroscopy and electrochemical techniques. Earlier studies on heteroleptic ruthenium(II) complex analogues containing functionalized oligo-anthracenyl phenanthroline ligands have been reported and documented. Based on a general linear correlation between increase in the length of π-conjugation bond and the molar extinction coefficients, herein, we report the photophysical and electrochemical properties of a Ru(II) bipyridyl complex analogue with a single functionalized anthracenyl unit. Interestingly, the complex shows better broad and intense metal-to ligand charge transfer (MLCT) band absorption with higher molar extinction coefficient (λ_max = 518 nm, e = 44900 M⁻¹cm⁻¹), and appreciable photoluminescence spanning the visible region than those containing higher anthracenyl units. It was shown that molar absorption coefficient of the complexes may not be solely depended on the extended π-conjugation but are reduced by molecular aggregation in the molecules. Full article

Two series of bidentate polypyridine ligands, made of phenanthroline chelating subunits having substituted mono-and di-anthracenyl groups, and 1-methoxy-1-buten-3-yne at the 4 and 7-positions with the corresponding heteroleptic Ru(II) complex have been synthesized and characterized. The complex is formulated as [(Ru(L₁)(L₂)(NCS)₂)], (where L₁ = 4-(9-dianthracenyl-10-(2,3-dimethylacrylic acid)-7-(9-anthracenyl-10-(2,3-dimethylacrylic acid)-1,10-phenanthroline and L₂ = 4,7-bis(1-methoxy-1-buten-3-yne)-1,10-phenanthroline). The Ru(II) complex shows characteristic broad and intense metal-to-ligand charge transfer (MLCT) bands absorption and appreciable photoluminescence spanning the visible region. The ligands and complex were characterized by FT-IR, ¹H, ¹³C NMR spectroscopy, UV-Vis, photoluminescence and elemental analysis (see in supplementary materials). The anchoring groups in both ligands have allowed an extended delocalization of acceptor orbital of the metal-to-ligand charge-transfer (MLCT) excited state. Full article

In an effort to develop new ruthenium(II) complexes, this work describes the design, synthesis and characterization of a ruthenium(II) functionalized phenanthroline complex with extended π-conjugation. The ligand were L₁ (4,7-bis(2,3-dimethylacrylic acid)-1,10-phenanthroline), synthesized by a direct aromatic substitution reaction, and L₂ (4,7-bis(trianthracenyl-2,3-dimethylacrylic acid)-1,10-phenanthroline), which was synthesized by the dehalogenation of halogenated aromatic compounds using a zero-valent palladium cross-catalyzed reaction in the absence of magnesium-diene complexes and/or cyclooctadienyl nickel (0) catalysts to generate a new carbon-carbon bond (C-C bond) polymerized hydrocarbon units. The ruthenium complex [RuL₁L₂(NCS)₂] showed improved photophysical properties (red-shifted metal-to-ligand charge-transfer transition absorptions and enhanced molar extinction coefficients), luminescence and interesting electrochemical properties. Cyclic and square wave voltammetry revealed five major redox processes. The number of electron(s) transferred by the ruthenium complex was determined by chronocoulometry in each case. The results show that processes I, II and III are multi-electron transfer reactions while processes IV and V involved one-electron transfer reaction. The photophysical property of the complex makes it a promising candidate in the design of chemosensors and photosensitizers, while its redox-active nature makes the complex a potential mediator of electron transfer in photochemical processes. Full article