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The study explores carbazole‐based organic molecules as transport layers in durable perovskite solar cells, focusing on their optoelectronic and charge transfer properties. Thirteen carbazole derivatives are systematically analyzed via density functional theory (DFT) calculations to understand their structure and optoelectronic characteristics. Substituents like bromo, phenyl, thiophenyl, and pyridyl at positions 3,6‐ and 2,7‐ of carbazole were studied. Phenyl and thiophenyl substitutions lowered highest occupied molecular orbital (HOMO) energy levels, while bromo and pyridyl increased them, tuning HOMO energies from −5.45 to −6.03 eV. These energies align well with perovskite materials valence bands, with absorbance primarily below 400 nm, complementing perovskite absorption. The compounds showed high light‐harvesting efficiencies (LHEs) (0.22 to 0.94) and improved radiative lifetimes. Theoretical investigations identified most compounds as effective p‐type hole‐transport materials (HTM), except 3,6‐ and 2,7‐dithiophenyl carbazoles, which exhibited n‐type behavior due to low hole reorganization energies. Overall, the study highlights computational design's role in developing carbazole derivatives as promising charge carrier precursors for perovskite solar cells. [ABSTRACT FROM AUTHOR]

Fused polycyclic aromatic compounds containing carbazole and diazapyrene skeletons as electron donors and acceptors, respectively, were synthesized in a few steps from readily accessible starting materials. The incorporation of diazapyrene units into the polycyclic compounds resulted in significant bathochromic shifts in their absorption and emission bands compared to those of the corresponding carbazole derivatives. Electrochemical measurements and density functional theory calculations were performed to gain further insight into their electronic properties. Our findings demonstrate that the incorporation of nitrogen atoms and substituents, as well as the different topologies of the fused‐ring system, exert a profound effect on the electronic properties of the polycyclic compounds. [ABSTRACT FROM AUTHOR]

The novelty and the essential purpose of this research is the preparation of new anti-inflammatory iron complexes in water green solvent using critical micelle concentration of anionic surface active agent (SAA). Three new anti-inflammatory iron complexes have been prepared. Thiophene-electron (es) donor (D) Schiff base (2-(2-OH-benzylidene)-amino)-4, 5, 6, 7-tetrah ydrobenzo[b] thiophene-3-carbonitrile) has been prepared. Molecular structures of all samples were confirmed based on CNH analysis, 1H NMR and 13C NMR spectra. The molecular structure of Schiff base is further confirmed by computational chemistry using the DFT-B3LYP method, 6-31G (d) basis set. Observed and simulated 1H NMR, UV–Vis. IR/Raman spectra confirmed the molecular structure of D. This Schiff base is intercalated to ferric chloride (FeCl3) giving pure iron charge transfer complex (CTCs). In vitro and kinetic studies confirmed Fe-CTC complexes had (concentration-dependent) potent antimicrobial-, good anti-inflammatory activities. Free radical scavenging activity nitrous oxide (NO.) of Fe (III)CTCs is attributed to geometry Fe(III) ions as distorted octahedral (either monoclinic or triclinic single crystals) via functional groups (-C]N–O, NH2). Elemental analysis and EDS spectra confirmed strong binding between iron and hetero atoms (N, S, O) of D molecules.

The widespread use of flat electric heaters in equipment and household appliances requires the search for simpler and cheaper technologies for their production. This paper proposes a method for producing an electrically conductive coating (NiAl) and an electrically insulating layer (glass ceramics) in one stage: self-propagating high-temperature synthesis in a thermally coupled (Ni + Al)/(PbO2 + B + Al2O3 + glass) powder mixture. The combustion wave front propagation process is investigated, and the effect of layer thickness along with the ratio of the PbO2 + B + Al2O3 + glass powder mixture components on the wave front propagation velocity and the wave front temperature is described. It is revealed that the wave front of the exothermic process expands when a PbO2 + B mixture is added to the bottom layer. The addition of this mixture makes it possible to reduce the NiAl layer thickness and ensure the formation of a uniform dielectric coating. The phase composition and microstructure of the coating are studied. Optimal ratios are determined for layer thicknesses and the composition of the powder mixture of the layers. The fundamental possibility of forming an electrically conductive and dielectric coating by the method of self-propagating high-temperature synthesis in one stage is shown. [ABSTRACT FROM AUTHOR]

With a decrease in the thickness of the walls separating the space of pores in porous semiconductors, the potential energy of interaction between an electron and a donor (or a hole and an acceptor) can become greater than the kinetic energy of a free charge carrier. As a consequence, such interlayers lose their conductivity and transit into the dielectric state (Mott phase transition). With regard to the conditions of electrochemical pore formation, this means that as the pore channels approach each other during anodic etching to a distance at which the current flow through the wall that separates them stops, the potential of its surface ceases to be determined by the external electric bias and the electrochemical process, that leads to a further decrease in the thickness of such a wall, stops. Expressions are obtained for the limiting thickness of the walls of pores formed in degenerate semiconductors of n- and p-type conductivity. In contrast to the well-known model that relates the loss of conductivity by pore walls to the combination of space charge layers, the proposed model allows a consistent explanation for the experimental data for both n- and p-type silicon with doping levels above 1018 cm–3. [ABSTRACT FROM AUTHOR]

In this study, quantum chemical calculations of phenazine-based organic molecules applied in organic dye-sensitized solar cells (DSSCs) have been made and interpreted. Since DSSC molecules work with the electron push–pull system, the sequence of other compounds (2–8) from compound 1 is designed as a donor–π bridge (weak acceptor)–acceptor (D–π–A). Later, the studied molecules were expanded from 2a to 8c by lengthening the conjugation with phenyl, thiophene, and furan to the acceptor parts. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are practiced to investigate all structures and absorption spectra of molecules, respectively. It has been observed that the phenazine-based molecule series are good candidates for DSSCs, both with their band gap and their absorption spectrum results. It can be assumed that changing the HOMO and LUMO energy values of all designed structures according to compound 1 can absorb light in the organic dye-sensitized solar cells and transfer electrons to the conductivity band of TiO2. As a result, it has been resolved that various dyes can be designed for dye-sensitizing solar cells by calculating electronic energies, HOMO–LUMO energies, and absorption wavelengths.

Due to the low cost, light weight, semitransparency, good flexibility, and large manufacturing area of organic solar cells (OSCs), OSCs have the opportunity to become the next generation of solar cells in some specific applications. So far, the efficiency of the OSC device has been improved by more than 20%. The optical band gap between the lowest unoccupied molecular orbital (LUMO) level and the highest occupied molecular orbital (HOMO) level is an important factor affecting the performance of the device. Selenophene, a derivative of aromatic pentacyclic thiophene, is easy to polarize, its LUMO energy level is very low, and hence the optical band gap can be reduced. In addition, the selenium atoms in selenophene and other oxygen atoms or sulfur atoms can form an intermolecular interaction, so as to improve the stacking order of the active layer blend film and improve the carrier transport efficiency. This paper introduces the organic solar active layer materials containing selenium benzene in recent years, which can be simply divided into donor materials and acceptor materials. Replacing sulfur atoms with selenium atoms in these materials can effectively reduce the corresponding optical band gap of materials, improve the mutual solubility of donor recipient materials, and ultimately improve the device efficiency. Therefore, the sulfur in thiophene can be completely replaced by selenium or oxygen of the same family, which can be used in the active layer materials of organic solar cells. This article mainly describes the application of selenium instead of sulfur in OSCs. [ABSTRACT FROM AUTHOR]

Herein, some novel metal-free 1,3,4-oxadiazole compounds O1–O7 were evaluated for their photovoltaic properties using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations to determine if they can serve as metal-free organic dyes in the use of dye-sensitized solar cells (DSSCs). To understand the trends in the relative efficiencies of the investigated compounds as dyes in DSSCs, their electron contributions, hole contributions, and electron–hole overlaps for each respective atom and fragment within the molecule were analyzed with a particular focus on the electron densities on the anchoring segments. As transition density matrices (TDM) provide details about the departure of each electron from its corresponding hole during excitations, which results in charge transfer (CT), the charge separation distance (Δr) between the electron and its corresponding hole was studied, in addition to the degree of electron–hole overlap (Λ). The latter, single-point excitation energy of each electron, the percentage electron contribution to the anchoring segments of each compound, the incident-photon-conversion-efficiency (IPCE), charge recombination, light harvesting efficiency (LHE), electron injection (Φinj), and charge collection efficiency (ncollect) were then compared to Δr to determine whether the expected relationships hold. Moreover, parameters such as diffusion constant (Dπ) and electron lifetime (t), amongst others, were also used to describe electron excitation processes. Since IPCE is the key parameter in determining the efficiency, O3 was found to be the best dye due to its highest value. [ABSTRACT FROM AUTHOR]

In this study, we incorporated nanometal surface energy transfer (NSET) in lateral flow immunoassay (LFIA) and explored the relationship between fluorescence quenching efficiency and detection sensitivity to improve sensitivity of NSET-LFIA system. We developed nine gold nanoparticles (GNPs) with absorption spectrum in the range of 520–605 nm as acceptors and quantum dot microspheres (QDMs) with emission spectrum of 530, 570, and 610 nm as donors. By analyzing the overlap integral area, fluorescence quenching efficiency, and detection sensitivity of 27 donor-acceptor pairs, we observed that the larger overlap integral area led to higher fluorescence quenching efficiency and detection sensitivity. A maximum fluorescence quenching efficiency of 91.0% was obtained from the combination of GNPs at 605 nm and QDMs at 610 nm, achieving the highest detection sensitivity. We developed NSET-LFIA for the detection of T2 toxin with a limit of detection of 0.04 ng/mL, which was 10-times higher than that obtained via conventional GNP-LFIA. NSET-LFIA represents a versatile, ultrasensitive and valuable screening tool for small molecules in real samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Two innovative second-order nonlinear optical chromophores, designated as B–C, have been synthesized, featuring thiophene-derived donors and a tricyanovinyldihydrofuran bridge as acceptors. These chromophores have undergone comprehensive characterization. Notably, the donor components of chromophores B–C were (methyl(phenyl)amino)thiophene and (4-methoxyphenylamino)thiophene, respectively, in contrast to the diethylamino phenyl unit present in chromophore A. Density functional theory calculations suggested that the first hyperpolarizability of chromophore C, with a (methoxyphenyl amino) thiophene donor, was approximately 60 % higher than that of chromophores A and B. This indicates that merely substituting the benzene ring with thiophene does not significantly enhance the electron-donating ability of the donor. Polymeric thin films doped with 25 wt% of chromophores A-C exhibited r33 values of 39 p.m./V, 46 p.m./V, and 76 p.m./V, respectively. The electro-optic coefficients of chromophores B and C were 18 % and 95 % higher than that of chromophore A, respectively. These findings confirm that thiophene-derived donors, particularly those with multiple heteroatoms, can effectively enhance the electro-optical coefficient of chromophores. [Display omitted] • TCF based chromophores A-B with different double donors had been synthesized. • A large r 33 value (76 p.m./V) at 1310 nm have been achieved for film. • The decomposition temperatures of the three chromophores was higher than 220 °C. [ABSTRACT FROM AUTHOR]

A novel alternating donor–acceptor polymer PQ1 is designed and synthesized by palladium-catalyzed Stille coupling between quinoxaline as an electron-deficient unit and indacenodithiophene (IDT) as electron-rich groups. Polymer PQ1 presents not only a strong intramolecular charge transfer effect, which is beneficial for the charge transport within single molecules but also a narrow electrochemical band gap and a high highest occupied molecular orbital (HOMO) energy level. In addition, the optical absorption study indicates that the PQ1 film exhibits good aggregation, which is an advantage for the charge transport between neighboring molecules. As a consequence, PQ1 presents p-type semiconductor properties with a high hole mobility of up to 0.12 cm2 V−1 s−1. This study reveals the great potential of quinoxaline-type chromophores in constructing novel organic semiconductors.

In the last few decades, organic solar cells (OSCs) have drawn broad interest owing to their advantages such as being low cost, flexible, semitransparent, non-toxic, and ideal for roll-to-roll large-scale processing. Significant advances have been made in the field of OSCs containing high-performance active layer materials, electrodes, and interlayers, as well as novel device structures. Particularly, the innovation of active layer materials, including novel acceptors and donors, has contributed significantly to the power conversion efficiency (PCE) improvement in OSCs. In this review, high-performance acceptors, containing fullerene derivatives, small molecular, and polymeric non-fullerene acceptors (NFAs), are discussed in detail. Meanwhile, highly efficient donor materials designed for fullerene- and NFA-based OSCs are also presented. Additionally, motivated by the incessant developments of donor and acceptor materials, recent advances in the field of ternary and tandem OSCs are reviewed as well. [ABSTRACT FROM AUTHOR]

Semiconductor scintillators are worth studying because they include both the highest luminosities and shortest decay times of all known scintillators. Moreover, many semiconductors have the heaviest stable elements (Tl, Hg, Pb, Bi) as a major constituent and a high ion pair yield that is proportional to the energy deposited. We review the scintillation properties of semiconductors activated by native defects, isoelectronic impurities, donors and acceptors with special emphasis on those that have exceptionally high luminosities (e.g. ZnO:Zn, ZnS:Ag,Cl, CdS:Ag,Cl) and those that have ultra-fast decay times (e.g. ZnO:Ga; CdS:In). We discuss underlying mechanisms that are consistent with these properties and the possibilities for achieving (1) 200,000 photons/MeV and 1% fwhm energy resolution for 662 keV gamma rays, (2) ultra-fast (ns) decay times and coincident resolving times of 30 ps fwhm for time-of-flight positron emission tomography, and (3) both a high luminosity and an ultra-fast decay time from the same scintillator at cryogenic temperatures.

The ecofriendly cellulose and gelatin provided sustainable and abundant sugars: d -ribofuranose, and 2-Deoxy-ribofuranose (starting reactants for preparative synthetic green chemistry pathways of charge transfer complexes. The natural available sugars d -ribofuranose, and 2-Deoxy-ribofuranose were obtained from facile hydrolysis of cellulose and gelatin natural macromolecules. Successive, low cost and facile alkaline- and acid hydrolysis of Deoxyribonucleic acid (DNA, from gelatin animal source) and ribonucleic acid (RNA, from cellulose plant source) yield the simple sugars: d -ribofuranose and 2-Deoxy-ribofuranose. Eight optically and biologically active charge transfer complexes were prepared from the reaction of the above sugars efficiently intercalated with two new prepared thiophene Schiff Lewis (electron donors) bases: 2-((2Hydroxybenzylidene) amino)-4, 5, 6, 7-tetrahydrobenzo [b] thiophene-3-carbonitrile (D1, 2-((Furan-2ylmethylene) amino) 4,5,6,7 tetrahydrobenzo [b] thiophene-3-carbonitrile (D2). The chemical structures of these prepared Schiff bases were confirmed using the mass spectra. The successful intercalation of the sugar units with the Lewis bases was ascertained using powder x ray diffraction. The molecular structures of the reaction products were proposed based on FTIR, 1H NMR. The optical activity of charge transfer complexes were confirmed using UV–Vis. Absorption spectroscopy. The surface morphology, microstructures, and particle size of the donors and charge transfer complexes were determined using scanning electron microscopy (SEM). The Lewis bases (D1) and (D2) showed no antimicrobial activity, while their charge transfer complexes showed good antimicrobial activity, suggesting their pharmaceutical and medicinal applications due to the potent biological activity against wide spread microbial microorganisms of Gram positive and Gram positive bacteria as well as some fungal species. [ABSTRACT FROM AUTHOR]

Some novel metal-free 1,2,4-triazole compounds A1-A8, based on the 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole derivatives were examined for photovoltaic properties using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations to test their suitability as metal-free organic dyes for use in dye-sensitized solar cells (DSSCs). Through deductive logic, the fluorescence emission (Φf) and charge collection (ηc) efficiencies of these compounds as dyes were obtained and used to determine each dye's incident conversion efficiency (IPCE). From the analyses, A2 displayed the highest IPCE value, followed by A6 and A1. This technique is restricted to evaluating compounds for potential metal-free organic dyes only. [ABSTRACT FROM AUTHOR]

Förster resonance energy transfer (FRET)–based sensing has been steadily gaining popularity in the areas of biochemical analysis, environmental monitoring, and disease diagnosis in the past 20 years. Two-dimensional (2D) nanomaterials are extensively used as donors and acceptors in the FRET sensing because of their attractive optical and chemical properties. In this review, we first present the FRET theory and calculations to give readers a better understanding of the FRET phenomenon. Then, we discuss the recent research advances in using 2D nanomaterials as donors and acceptor in FRET sensing. Finally, we summarize the existing challenges and future directions of 2D nanomaterials in the FRET sensing applications.

A series of six coumarin based dye derivatives were investigated and their geometry and optoelectronic properties elucidated for suitability in dye-sensitized solar cells (DSSCs) using TD-DFT/B3LYP with 6-31G basis set. D-π-A schemes were developed by attaching various donors and acceptors to coumarin dye (CM) to calculate changes in their photovoltaic properties. D2-CM-A2 and D4-CM-A4 showed less dihedral angle because of the low steric effect between donor and connector. The D1-CM-A1 and D2-CM-A2 results of intramolecular charge transfer were higher because of low bond length and a strong group of electron donors. The results revealed that LUMO energies of D1-CM-A1, D2-CM-A2, D3-CM-A3 and D4-CM-A4 were higher than the conduction band edge of TiO2 electrode (−4.0 eV) suggesting that these dyes will inject the electrons into the conduction band of the semiconductor. In addition, the light harvest efficiency (LHE), open-circuit voltage (VOC) and band energy gap (Eg) values are calculated in the gas phase, as well as in the solvent phase. This study shows that D1-CM-D1 and D2-CM-A2 derivatives have better properties for application in the DSSCs.

Due to the low cost, light weight, semitransparency, good flexibility, and large manufacturing area of organic solar cells (OSCs), OSCs have the opportunity to become the next generation of solar cells in some specific applications. So far, the efficiency of the OSC device has been improved by more than 20%. The optical band gap between the lowest unoccupied molecular orbital (LUMO) level and the highest occupied molecular orbital (HOMO) level is an important factor affecting the performance of the device. Selenophene, a derivative of aromatic pentacyclic thiophene, is easy to polarize, its LUMO energy level is very low, and hence the optical band gap can be reduced. In addition, the selenium atoms in selenophene and other oxygen atoms or sulfur atoms can form an intermolecular interaction, so as to improve the stacking order of the active layer blend film and improve the carrier transport efficiency. This paper introduces the organic solar active layer materials containing selenium benzene in recent years, which can be simply divided into donor materials and acceptor materials. Replacing sulfur atoms with selenium atoms in these materials can effectively reduce the corresponding optical band gap of materials, improve the mutual solubility of donor recipient materials, and ultimately improve the device efficiency. Therefore, the sulfur in thiophene can be completely replaced by selenium or oxygen of the same family, which can be used in the active layer materials of organic solar cells. This article mainly describes the application of selenium instead of sulfur in OSCs.

This article is related to a research paper entitled “Exploring the charge-transfer chemistry of fluorine-containing pyrazolin-5-ones: The complexation of 1-methyl-3-trifluoromethyl-2-pyrazoline-5-one with five π-acceptors” [J. Mol. Liq. 331 (2021) 115814] [1]. Herein we present photographic data that showed the color change after mixing methanolic solutions of 1-methyl-3-trifluoromethyl-2-pyrazoline-5-one (donor) with each of the investigated π-acceptor [picric acid (PA), chloranilic acid (CLA), fluoranil (TFQ), DDQ, and TCNQ]. Stoichiometry data for the interaction of the donor with all acceptors determined in solution state by the spectrophotometric titration method and the Job's continuous variation method were presented. The data presented are useful for understand that the charge-transfer (CT) complexation between a donor and an acceptor, generally, is characterized by a strong color change, and to understand the stoichiometry between these molecules.

Two-dimensional (2D) van der Waals transition metal dichalcogenides (TMDs) are a new class of electronic materials offering tremendous opportunities for advanced technologies and fundamental studies. Similar to conventional semiconductors, substitutional doping is key to tailoring their electronic properties and enabling their device applications. Here, we review recent progress in doping methods and understanding of doping effects in group 6 TMDs (MX2, M = Mo, W; X = S, Se, Te), which are the most widely studied model 2D semiconductor system. Experimental and theoretical studies have shown that a number of different elements can substitute either M or X atoms in these materials and act as n- or p-type dopants. This review will survey the impact of substitutional doping on the electrical and optical properties of these materials, discuss open questions, and provide an outlook for further studies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thiophene functionalized naphthalene diimide redox active architecture (NDI-Th) is synthesized. • Specific capacitance for NDI-Th/GF in three-electrode SC device is 173.33F/g at 0.5 A/g. • SSC cell exhibits Csp of 77.76F/g at 0.5 A/g with capacitance retention of 84.83% after 10,000 GCD cycles. • NDI-Th/GF//NDI-Th/GF SSC device displayed ED and PD of 11.66 Wh kg−1 at 899.92 W kg−1, respectively. Organic material (OM) offers an opportunity to utilize renewable sources to fabricate electrode materials for supercapacitor (SC) applications. OM electrodes have shown great potential in SC applications due to lower cost, lower device weight, high energy density, high power density and longer cycling stability with excellent faradaic reversible redox reactions. Among the reported materials, naphthalene diimide (NDI) is a promising n -type OM to be utilized for fabrication of electrode for pseudocapacitor (PSC) applications. Herein, four thiophene functionalized core substituted NDI (NDI-Th) is designed as donor (D)-acceptor (A) scaffolds to be used as active electrode materials in combination with graphite foil (GF). The NDI-Th could provide redox active surface resulting into higher capacitance due to the PSC charge storage mechanism due to higher conductivity. In a three-electrode PSC system, NDI-Th/GF in 1 M H 2 SO 4 electrolyte shows specific capacitance (C sp) of 173.33F g-1 at 0.5 A/g current density. Moreover, in two-electrode symmetric supercapacitor configuration, the NDI-Th/GF based electrode provides a C sp of 77.76F/g at 0.5 A/g current density and a stable cycle life with 84.83 % capacitance retention after 10,000 GCD cycles. An impressive energy density was found to be 11.66 Wh kg−1 at 899.92 W kg−1 power density. The NDI-Th/GF electrode material in this work pave a new way to design and fabricate OM based electrodes for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Herein, some novel metal-free 1,3,4-oxadiazole compounds O1–O7 were evaluated for their photovoltaic properties using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations to determine if they can serve as metal-free organic dyes in the use of dye-sensitized solar cells (DSSCs). To understand the trends in the relative efficiencies of the investigated compounds as dyes in DSSCs, their electron contributions, hole contributions, and electron–hole overlaps for each respective atom and fragment within the molecule were analyzed with a particular focus on the electron densities on the anchoring segments. As transition density matrices (TDM) provide details about the departure of each electron from its corresponding hole during excitations, which results in charge transfer (CT), the charge separation distance (Δr) between the electron and its corresponding hole was studied, in addition to the degree of electron–hole overlap (Λ). The latter, single-point excitation energy of each electron, the percentage electron contribution to the anchoring segments of each compound, the incident-photon-conversion-efficiency (IPCE), charge recombination, light harvesting efficiency (LHE), electron injection (Φinj), and charge collection efficiency (ncollect) were then compared to Δr to determine whether the expected relationships hold. Moreover, parameters such as diffusion constant (Dπ) and electron lifetime (t), amongst others, were also used to describe electron excitation processes. Since IPCE is the key parameter in determining the efficiency, O3 was found to be the best dye due to its highest value.

In the last few decades, organic solar cells (OSCs) have drawn broad interest owing to their advantages such as being low cost, flexible, semitransparent, non-toxic, and ideal for roll-to-roll large-scale processing. Significant advances have been made in the field of OSCs containing high-performance active layer materials, electrodes, and interlayers, as well as novel device structures. Particularly, the innovation of active layer materials, including novel acceptors and donors, has contributed significantly to the power conversion efficiency (PCE) improvement in OSCs. In this review, high-performance acceptors, containing fullerene derivatives, small molecular, and polymeric non-fullerene acceptors (NFAs), are discussed in detail. Meanwhile, highly efficient donor materials designed for fullerene- and NFA-based OSCs are also presented. Additionally, motivated by the incessant developments of donor and acceptor materials, recent advances in the field of ternary and tandem OSCs are reviewed as well.

Possible modifications of chromophore structures with nonlinear optical properties by bonding F atoms and F-containing groups to the acceptor site of the molecules are considered. Quantum chemical calculations of dipole moments and first hyperpolarizability were performed for several nonlinear chromophores based on N-ethyl- N-(2-hydroxyethyl)-4-phenylazoaniline and modified by the addition of F atoms and F-containing groups to the acceptor site. Positions of maxima in the electronic absorption spectrum and the Mulliken charges on the atoms are found. It is shown that addition of F atoms and F-containing groups to the chromophore acceptor site changes (increases) the efficiency parameter, defined as the product of the dipole moment and the first hyperpolarizability. The main parameters of a waveguide modulator made of an electro-optical polymer composite with F-containing chromophores embedded in it are estimated. [ABSTRACT FROM AUTHOR]

The cross‐conjugated vinylogous [4+2] anionic annulation has been newly developed, the cascade process of which has a high preference for regiochemical control and chemoselectivity, giving rise to exclusively Michael‐type adducts in moderate to high yields (up to 94 %, 35 examples). By making use of this approach as a key operation, the first total synthesis of natural antibiotic ABX, in racemic form, has been successfully achieved in a concise 7‐step sequence with an overall yield of about 20 %. [ABSTRACT FROM AUTHOR]

A novel method is proposed to detect the acceptor and donor splice sites using chaos game representation and artificial neural network. In order to achieve high accuracy, inputs to the neural network, or feature vector, shall reflect the true nature of the DNA segments. Therefore it is important to have one-to-one numerical representation, i.e. a feature vector should be able to represent the original data. Chaos game representation (CGR) is an iterative mapping technique that assigns each nucleotide in a DNA sequence to a respective position on the plane in a one-to-one manner. Using CGR, a DNA sequence can be mapped to a numerical sequence that reflects the true nature of the original sequence. In this research, we propose to use CGR as feature input to a neural network to detect splice sites on the NN269 dataset. Computational experiments indicate that this approach gives good accuracy while being simpler than other methods in the literature, with only one neural network component. The code and data for our method can be accessed from this link: https://github.com/thoang3/portfolio/tree/SpliceSites_ANN_CGR. • We propose to use chaos game representation and neural network for splice sites detection. • DNA sequences are mapped to numerical sequences using chaos game representation. • Numerical sequences are used as feature inputs to neural networks for splice sites classification. [ABSTRACT FROM AUTHOR]

Various organic dyes possessing characteristic D-π-A-A configuration have been designed in this article. The analysis of the relation between polarity of charge transfer and the unsymmetrical nature of the benzothiazole group has been studied. The absorption spectra, electronic characteristic properties and non-linear optical responses were simulated using a quantum chemical approach. The results have indicated that the systems show higher polarizability (α) and hyperpolarizability (β) with commonly used polarity in comparison to the reverse polarity. A red-shifted absorption spectra were observed with systems having common polarities. This study illustrates the rule to design non-linear optical material with low energy charge transfer excited states and high value of oscillation.

Ferroelectric films suffer from both aging and degradation under high ac‐field drive conditions due to loss of polarization with time. In this study, the roles of defect chemistry and internal electric fields on the long‐term stability of the properties of piezoelectric films were explored. For this purpose, lead zirconate titanate (PZT) films with a Zr/Ti ratio of 52/48 doped with Mn‐ (PMZT) or Nb‐ (PNZT) were deposited on Pt coated Si substrates by the sol‐gel method. It was demonstrated that the magnitude of the internal field is much higher in PMZT films compared to PNZT films after poling in the temperature range of 25‐200°C under an electric field of −240 kV/cm. The development of the internal field is thermally activated, with activation energies from 0.5 ± 0.06 to 0.8 ± 0.1 eV in Mn doped films and from 0.8 ± 0.1 to 1.2 ± 0.2 eV in Nb doped films. The different activation energies for imprint suggests that the physical mechanism underlying the evolution of the internal field in PMZT and PNZT films differs; the enhanced internal field upon poling is attributed to (a) alignment of oxygen vacancy—acceptor ion defect dipoles ((MnTi″-VO··)x, (MnTi′-VO··)′) in PMZT films, and (b) thermionic injection of electron charges and charge trapping in PNZT films. In either case, the internal field reduces back switching, enhances the remanent piezoelectric properties, and dramatically improves the aging behavior. PMZT films exhibited the greatest enhancement, with reduced high temperature (180°C) aging rates of 2%‐3%/decade due to improved stability of the poled state. In contrast, PNZT films showed significantly larger high temperature aging rates (15.5%/decade) in the piezoelectric coefficient, demonstrating that the fully poled state was not retained with time. [ABSTRACT FROM AUTHOR]

Based on the technology developed by authors of the local diffusion doping of certain parts of the ZnO film of the donor (Ga) and acceptor (Li) impurities, a transparent field-effect transistor with the n-type channel was manufactured. The MgF2 films were used as a gate insulator. The field effect and the dark electrical characteristics of the structures were investigated. The field phototransistors based on these structures have been developed. The photoelectric characteristics of the field phototransistors were investigated, and the mechanism of the photoelectric amplification was proposed. [ABSTRACT FROM AUTHOR]

The important roles that carbohydrates play in biological processes and their potential application in diagnosis, therapeutics, and vaccine development have made them attractive synthetic targets. Despite ongoing challenges, tremendous progresses have been made in recent years for the synthesis of carbohydrates. The chemical glycosylation methods have become more sophisticated and the synthesis of oligosaccharides has become more predictable. Simplified one-pot glycosylation strategy and automated synthesis are increasingly used to obtain biologically important glycans. This review highlights recent progress in chemical synthesis of carbohydrates with a particular focus on the methods developed for the synthesis of oligosaccharides, polysaccharides, glycolipids, and glycosylated natural products. [ABSTRACT FROM AUTHOR]

Abstract In this report, 6 H -indolo[2,3- b ]quinoline (hereafter 2a) was synthesized and employed as an optical chemosensor for fluoride. The sensitivity of 2a towards fluoride was established from the change in both the absorption and emission signals. The various in-situ 1H NMR, UV–Vis, and density functional studies indicate that the 1:2 binding interaction between 2a and fluoride followed by deprotonation to its corresponding di-anion (2a 2− ), which in turn boosted the donor-acceptor interaction between indole and quinoline moiety in 2a 2− via expansion of torsion angle by 10.2° as compared to 2a. Consequently the significant changes in both the absorption and emission signal of 2a allow us to detect and estimate the concentration of fluoride up to 0.2 μM from the mixture of different anions. Graphical Abstract Unlabelled Image Highlights • 6 H -indolo[2,3- b ]quinoline (2a) was synthesized and applied as a selective chemosensor for fluoride. • Mechanism of interaction between 2a and Fluoride has been established from various in-situ experimental and theoretical analysis. • Fluoride induced deprotonation to its corresponding di-anion (2a 2-), which in turn boosted the donor-acceptor interaction between indole and quinoline moiety in 2a 2- via expansion of torsion angle by 10.2° as compared to 2a. • The change in absorption and emission signal of 2a upon addoition of fluoride allow us to detect and estimate the concentration of fluoride up to 0.2 μM from the mixture of different anions. [ABSTRACT FROM AUTHOR]

Abstract Three novel fluorescent NLOphoric push-pull fluorophores (2a-c) constituted by different cyano containing acceptors linked to morpholine-thiourea (donor) and acenaphthene (rotor) hybrid were synthesized and characterized. They exhibit positive absorption and emission solvatochromism. The solvent polarity function based Lippert-Mataga plot provides the validation of charge transfer (CT) characteristics whereas, Rettig plot furnishes an alternative relaxation channel due to twisting around the σ-bonds between donor and acceptor on photoexcitation leading to the twisted intramolecular charge transfer (TICT) state in dyes 2a-c. Viscosity induced emission studies show 4.18, 17.61, and 5.30 fold increase in the emission intensity for dyes 2a , 2b , and 2c respectively which recommends these dyes as fluorescent molecular rotors (FMR). Density Functional Theory (DFT) calculations [(B3LYP/6-311++G(d,p)] give complete information of structural as well as electronic properties of dyes 2a-c. The difference in dipole moment (ca. 4.86–8.23 D) results in a strong non-linear optical (NLO) properties which increases in the order 2a < 2b < 2c. Z-scan studies reveal that the dyes possesses reverse-saturable i.e. positive type of absorption non-linearity resulting in a positive values of β (2c > 2b > 2a). The lower optical limiting threshold values for dyes 2a-c , made them suitable for the use in the application of NLO materials. Graphical abstract Image 1 Highlights • NLOphoric D-π-A dyes based on acenaphthene and morpoline-thiourea, and cyano containing acceptors are studied. • Lippert-Mataga model provides the validation of charge transfer characteristics whereas, the Rettig model furnishes TICT in 2a-c. • Viscosity induced emission enhancement was 4.18, 17.61, and 5.30 fold for 2a , 2b , and 2c respectively. • DFT calculations give complete information on geometrical and electronic properties. • NLO properties were evaluated using Spectroscopic, DFT, and Z-scan methods. [ABSTRACT FROM AUTHOR]

Spectral and luminescent characteristics of a mixture of coumarin 7 and rhodamine B dyes infiltrated into a onedimensional photonic crystal of mesoporous silicon are studied. Electronic excitation energy transfer between molecules that is associated with fluorescence quenching of the donor (coumarin 7) and enhancement of acceptor emission (rhodamine B) is detected. The angular dependence of excitation energy transfer efficiency in the donor-acceptor pair is due to depletion of available photon modes for donor radiative decay in a photonic crystal as compared with a homogeneous medium and depends on the spectral position of the photonic stop zone of a photonic crystal. [ABSTRACT FROM AUTHOR]

Solar energy and its conversion to electricity is an important research in the last decade. Solar cells are consist of a p-type semiconductor as donor and an n-type semiconductor as acceptor. Organic polymers as organic semiconductors are used in an organic solar cell. This research is a theoretical investigation of fullerene C60 as donor and C60 doped derivatives with Silicon and Germanium atoms as acceptors for basic structure of a solar cell. This research is done not only with using related equations but also with investigating theoretical UV-Vis spectrum of the chosen donors-acceptors and their absorption wavelengths, oscillator strength and maximum coefficient absorptions of these solar cells. [ABSTRACT FROM AUTHOR]

Graphene based nanomaterials are known to provide new avenues to improve semiconductor based light harvesting devices. This work makes use of graphene quantum dots (GQD) to improve the efficiency of a CdSe Quantum Dot Sensitized Solar Cell (QDSSC) by Förster Resonance Energy Transfer (FRET) mechanism. FRET describes non-radiative energy transfer between two adjacent molecules typically in range from 1 to 10 nm with one molecule as donor and other molecule as acceptor. If the acceptor is in close proximity of the excited donor, then their dipoles align resulting in transfer of excitation energy from donor to acceptor. Here graphene quantum dot acts as the energy donor to enhance light harvesting of CdSe quantum dot which acts as an acceptor in the hybrid solar cell. The introduction of GQD increases the efficiency of CdSe sensitized QDSSC from 0.18 to 0.28% showing an efficiency enhancement of 55%. The improved efficiency is mainly attributed to the 46% increase in current density of the GQD-CdSe solar cell compared to the CdSe QDSSC. The increased performance of the QDSSC owes to the existence of non-radiative energy transfer (FRET) between GQD and CdSe evident from photoluminescence (PL) quenching and lifetime measurements. This FRET system of GQD (donor)-CdSe (acceptor) shows an energy transfer of 48.7% providing new insights for selective light harvesting of the solar spectrum which can be utilised for various potential applications in future.

Dye-sensitized solar cell (DSSC) has been attractive to scientific community due to its eco-friendliness, ease of fabrication, and vivid colorful property etc. Among various kinds of sensitizers, such as metal-free organic molecules, metal-complex, natural dyes etc., porphyrin is one of the most promising sensitizers for DSSC. The first application of porphyrin for sensitization of nanocrystaline TiO2 can be traced back to 1993 by using [tetrakis(4-carboxyphenyl) porphyrinato] zinc(II) with an overall conversion efficiency of 2.6%. After 10 years efforts, Officer and Grätzel improved this value to 7.1%. Later in 2009, by constructing porphyrin sensitizer with an arylamine as donor and a benzoic acid as acceptor, Diau and Yeh demonstrated that this donor-acceptor framwork porphyrins could attain remarkable photovoltaic performance. Now the highest efficiencies of DSSC are dominated by donor-acceptor porphyrins, reaching remarkable values around 13.0% with cobalt-based electrolytes. This achievement is largely contributed by the structural development of donor and acceptor groups within push-pull framwork. In this review, we summarized and discussed the developement of donor-acceptor porphyrin sensitizers and their applications in DSSC. A dicussion of the correlation between molecular structure and the spectral and photovoltaic properties is the major target of this review. Deeply dicussion of the substitution group, especially on porphyrin's meso-position were presented. Furthermore, the limitations of DSSC for commercialization, such as the long-term stability, sophisticated synthesis procedures for high efficiency dye etc., have also been discussed.

Abstract Control of the lowest unoccupied molecular orbital (LUMO) energy offset between an electron-donating polymer (D) and electron-accepting molecule (A) is important for the efficient dissociation of photo-induced excitons into free carriers and for improving the power conversion efficiencies (PCEs) of organic photovoltaics (OPVs). The distance between D and A also affects the dissociation of charge transfer (CT) excitons into free carriers, because the exciton binding energy is inversely proportional to the spatial separation in electron-hole coupling. In addition, the distance between D and A influences the probability that photo-induced excitons in the D (or A) domain become CT excitons through the D/A interface. In this study, the influence of D-A separation on OPV characteristics was investigated by fabricating planar OPVs composed of perylenetetracarboxylic diimide derivatives with different alkyl chain lengths (PTCDI-Cn) as A and a low band-gap polymer (PTB7) as D. The D-A separation distance was controlled by the alkyl chain length of the PTCDI-Cn, which functions as a spacer separating D and A. The open-circuit voltage (V oc) improved at the expense of short-circuit current densitie (J sc) with increasing alkyl chain length in PTCDI-Cn. To examine the electron-hole coupling between A and D, the electroluminescence (EL) from CT states was measured. A flat CT EL was observed for the OPVs with PTCDI-C3 (perylenetetracarboxylic diimide with propyl groups), while the maxima of CT EL bands were clearly seen for other PTCDI-Cn-based OPVs. This result indicates the existence of CT excitons with different electron-hole coupling distances at the PTB7/PTCDI-C3 interface, suggesting the existence of a variety of molecular orientations of PTCDI-C3 on the surface of PTB7. This may be the origin of the increased PCE for the PTCDI-C3-based OPVs compared to other PTCDI-Cn-based OPVs. Graphical abstract Image 1 Highlights • Planar OPVs with a PTB7/PTCDI-Cn bilayer were fabricated. • Increasing the alkyl chains in PTCDI-Cn improved V oc at the expense of J sc. • The trade-off relationship indicated that alkyl chains of PTCDI-Cn acted as a spacer. • CT EL spectra exhibited the distribution of binding energies at PTB7/PTCDI-C3. [ABSTRACT FROM AUTHOR]