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Structure of heroin in a solution revealed by chiroptical spectroscopy
摘要： In this work, the 3-D structure of the well-known opioid drug heroin in a solution was investigated. The goal was to provide a complete and detailed description of the stable conformers with their relative abundances. This knowledge is very important from the pharmaceutical and forensic point of view as it could help significantly with deeper understanding of heroin's metabolism and the development of antagonist medicines for the case of an overdose. As heroin is a chiral compound with five stereogenic centres, the methods of chiroptical spectroscopy supplemented by density functional theory (DFT) calculations were applied to study its conformations in chloroform solution. The selected chiroptical methods, namely, electronic circular dichroism (ECD) and vibrational circular dichroism (VCD), are inherently sensitive to the 3-D structure of small- to medium-sized chiral organic molecules. A thorough conformational analysis revealed four stable conformers of heroin in chloroform solution, where the conductor-like polarizable continuum model of the solvent was used for all the calculations. The simulated ultraviolet (UV), infrared (IR), ECD, and VCD spectra were compared with the experimental ones and very good agreement was found, which enabled a detailed structure description and interpretation of the spectra. Chiroptical spectroscopy in combination with DFT calculations proved to be a very sensitive tool for the analysis of the 3-D structure of heroin in a solution in contrast with conventional spectroscopic methods. Especially, the application of VCD seems to be a promising approach for monitoring structural changes, for instance, those caused by solvents or interactions with other agents.
关键词： 3-D structure,DFT calculations,drugs,chiroptical spectroscopy,circular dichroism,heroin
更新于2025-09-23 15:19:57
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Cyclic versus straight chain oligofuran as sensor: A detailed DFT study
摘要： This study is a novel approach for exploring the sensitivity and selectivity of cyclic oligofuran (5/6/7CF) toward gaseous analytes and their comparison with straight chain analogues (5/6/7SF). The work is not only vital to understand the superior sensitivity but also for rational design of new sensors based on cyclic ring structures of oligofuran. Interaction of cyclic and straight chain oligofuran with NH3, CO, CO2, N2H4, HCN, H2O2, H2S, CH4, CH3OH, SO2, SO3 and H2O analytes is studied via DFT calculation at B3LYP-D3/6-31++G (d, p) level of theory. The sensitivity and selectivity are illustrated by the energetic parameters (Ebind, SAPT0 energies, NCI analysis) electronic properties (H-L gap, percentage of average energy gap, CHELPG charge transfer, DOS spectra) and UV-Vis analysis. All these properties are simulated at B3LYP/6-31G (d) level of theory while UV-Vis is calculated at TD-DFT method. Cyclic oligofuran has high binding energy with analytes compared to 5/6/7SF which corresponds the higher sensitivity of 5/6/7CF. Furthermore, the cyclization of oligofuran significantly improve the sensitivity and selectivity of the system. Alteration in electronic properties of 5/6/7CF and 5/6/7SF is remarkably high upon complexation with SO2 and SO3. Further the stability of rings (5, 6 and 7 membered cyclic oligofurans) and their SO3 complexes is also confirmed by molecular dynamics calculations. The finding of the work clearly suggests that the cyclic geometry enhances not only sensitivity but also selectivity of conducting polymers (oligofuran).
关键词： Oligofuran,Noncovalent interaction index (NCI),Density Functional Theory (DFT),CHELPG charge transfer,Symmetry adopted perturbation theory (SAPT)
更新于2025-09-23 15:19:57
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Conductivity tuning of charged triazine and heptazine graphitic carbon nitride (g-C3N4) quantum dots via nonmetal (B, O, S, P) doping: DFT calculations
摘要： Chemical doping of graphitic carbon nitride (g-C3N4) quantum dots with nontoxic heteroatoms has proven to be an effective means for tuning the electrical properties of this two-dimensional (2D) nanomaterial. In this investigation, triazine (tg-CN) and heptazine (hg-CN) clusters were doped with the p-block (B, O, S, and P) elements, and were further compared in terms of siting and conductance using density functional theory (DFT) at the HSE06/6-311tG* level. The calculation results predicted that B doping in both types of g-C3N4 was favored in place of carbon atoms while the O, S, and P dopants preferred nitrogen atoms, where P siting was dependent on the type of material. Both the initial HOMO–LUMO gap and global hardness were decreased after the substitution, with the most substantial changes after the O and S doping in the hg-CN and tg-CN structures, respectively. The HOMO–LUMO gap changed most significantly (by up to 3.79 eV) with the [t/(cid:0) ] charge switching for the O-doped nanocluster. In contrast to hg-CN, tg-CN turned from an insulator into metallic or half-metallic material upon electron charging. Finally, both hg-CN and tg-CN became better electrophiles after modification, particularly with B doping.
关键词： Doping,Semiconductor,Graphitic carbon nitride,DFT,Quantum dot
更新于2025-09-23 15:19:57
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Theoretical Study of a Class of Organic Da????a??A Dyes for Polymer Solar Cells: Influence of Various ??a??Spacers
摘要： A class of D‐π‐A compounds that can be used as dyes for applications in polymer solar cells has theoretically been designed and studied, on the basis of the dyes recently shown by experiment to have the highest power conversion efficiency (PCE), namely the poly[4,8‐bis(5‐(2‐(PBDTS‐TZNT) butylhexylthio)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b’]dithiophene‐2,6‐diyl‐alt‐TZNT] and poly[4,8‐bis(4‐fluoro‐5‐(2‐butylhexylthio)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b’]dithiophene‐2,6‐ diyl‐alt‐TZNT] (PBDTSF‐TZNT) substances. Electronic structure theory computations were carried out with density functional theory and time‐dependent density functional theory methods in conjunction with the 6?311G (d, p) basis set. The PBDTS donor and the TZNT (naphtho[1,2‐c:5,6‐c]bis(2‐octyl‐[1,2,3]triazole) acceptor components were established from the original substances upon replacement of long alkyl groups within the thiophene and azole rings with methyl groups. In particular, the effects of several π‐spacers were investigated. The calculated results confirmed that dithieno[3,2‐b:2′,3′‐d] silole (DTS) acts as an excellent π‐linker, even better than the thiophene bridge in the original substances in terms of well‐known criteria. Indeed, a PBDTS‐DTS‐TZNT combination forms a D‐π‐A substance that has a flatter structure, more rigidity in going from the neutral to the cationic form, and a better conjugation than the original compounds. The highest occupied molecular orbital (HOMO)‐lowest unoccupied molecular orbital (LUMO) energy gap of such a D‐π‐A substance becomes smaller and its absorption spectrum is more intense and red‐shifted, which enhances the intramolecular charge transfer and makes it a promising candidate to attain higher PCEs.
关键词： DFT calculations,PCEs,DTS,PBDTS‐TZNT and PBDTSF‐TZNT,D‐π‐A dyes,polymer solar cells
更新于2025-09-23 15:19:57
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Revealing the Origin of the Beneficial Effect of Cesium in Highly Efficient Cu(In,Ga)Se 2 Solar Cells
摘要： The record conversion efficiency of thin-film solar cells based on Cu(In,Ga)Se2 (CIGS) absorbers has exceeded 23 %. Such a high performance is currently only attainable by the incorporation of heavy alkali metals like Cs into the absorber through an alkali fluoride post-deposition treatment (PDT). As the effect of the incorporated heavy alkali metals is under discussion, we investigated the local composition and microstructure of high efficiency CIGS solar cells via various high-resolution techniques in a combinatory approach. An accumulation of Cs is clearly detected at the p-n junction along with variations in the local CIGS composition, showing the formation of a beneficial secondary phase with a laterally inhomogeneous distribution. Additionally, Cs accumulations were detected at grain boundaries with a random misorientation of the adjacent grains where a reduced Cu concentration and increased In and Se concentrations are detected. No accumulation was found at Σ3 twin boundaries as well as the grain interior. These experimental findings are in excellent agreement with complementary ab-initio calculations, demonstrating that the grain boundaries are passivated by the presence of Cs. Further, it is unlikely that Cs with its large ionic radius is incorporated into the CIGS grains where it would cause detrimental defects.
关键词： nano-XRF,CIGS,DFT,thin-film solar cells,Cs,post-deposition treatment
更新于2025-09-23 15:19:57
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Tunable Photodetectors via In Situ Thermal Conversion of TiS3 to TiO2
摘要： In two-dimensional materials research, oxidation is usually considered as a common source for the degradation of electronic and optoelectronic devices or even device failure. However, in some cases a controlled oxidation can open the possibility to widely tune the band structure of 2D materials. In particular, we demonstrate the controlled oxidation of titanium trisulfide (TiS3), a layered semiconductor that has attracted much attention recently thanks to its quasi-1D electronic and optoelectronic properties and its direct bandgap of 1.1 eV. Heating TiS3 in air above 300 °C gradually converts it into TiO2, a semiconductor with a wide bandgap of 3.2 eV with applications in photoelectrochemistry and catalysis. In this work, we investigate the controlled thermal oxidation of individual TiS3 nanoribbons and its influence on the optoelectronic properties of TiS3-based photodetectors. We observe a step-wise change in the cut-off wavelength from its pristine value ~1000 nm to 450 nm after subjecting the TiS3 devices to subsequent thermal treatment cycles. Ab-initio and many-body calculations confirm an increase in the bandgap of titanium oxysulfide (TiO2-xSx) when increasing the amount of oxygen and reducing the amount of sulfur.
关键词： TiS3,2D materials,photodetectors,DFT GW,oxidation,TiO2,Raman spectroscopy
更新于2025-09-23 15:19:57
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Significance of five membered heterocycles in fine tuning of HOMO-LUMO gap of simple donor-acceptor system as organic solar cell material: A DFT approach
摘要： The significance of five membered heterocycles in simple donor-acceptor system was elaboratively studied by density functional theory (DFT) and time dependent density functional theory (TDDFT). By effectively substituting eight different rings the HOMO-LUMO gap can be reduced considerably. The nuclear independent chemical shift (NICS) calculations help to predict the aromaticity of central heterocyclic systems. The natural bond orbital (NBO) analysis reveals the charge contribution. The close observation of frontier molecular orbitals (FMO) gives a detailed explanation of delocalization.
关键词： NICS,DFT,NBO,TDDFT,HOMO-LUMO
更新于2025-09-23 15:19:57
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Modulating Charge-Carrier Dynamics in Mn-Doped All-Inorganic Halide Perovskite Quantum Dots through the Doping-Induced Deep Trap States
摘要： Transition metal ions doping has been demonstrated effective to tune the photoluminescence properties of perovskite quantum dots (QD). However, it would inevitably introduce defects in the lattice. As the Mn concentration increases, the Mn dopant PL quantum yield (PLQY) first increases and then decreases. Herein, the influence of the dopant and the defect states on the photophysics in Mn doped CsPbCl3 QDs was studied by time-resolved spectroscopies, while the energy levels of the possible defect states were analyzed by Density Functional Theory (DFT) calculations. We reveal the formation of deep interstitials defects (Cli) by Mn2+ doping. The depopulation of initial QDs exciton states is a competition between exciton-dopant energy transfer (ET) and defect trapping at an early time-scale (< 100 ps), which determines the final PLQY of the QDs. The present work establishes a robust material optimization guideline for all the emerging applications where high PLQY is essential.
关键词： photoluminescence,energy transfer,Mn-doped,CsPbCl3,DFT calculations,defect states,quantum dots
更新于2025-09-23 15:19:57
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Impact of Spin Exchange Interaction on Charge Transfer in Dual Polymer Photovoltaic Composites
摘要： Magnetic resonance, relaxation, and dynamic parameters of spin charge carriers photoinitiated in dual polymer composites formed by narrow-bandgap poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(bithiophene)] (F8T2), poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT), poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) copolymers modified with [6,6]-phenyl-C61-butanoic acid methyl ester (PC61BM) as photovoltaic spin subsystem and polyaniline salt doped with para-toluenesulfonic acid (PANI:TSA) as guest spin subsystem were comparatively studied by the direct Light-Induced Electron Paramagnetic Resonance (LEPR) spectroscopy in a wide photon energy and temperature range. Irradiation of dual polymer composite by the photons leads to the formation in its photovoltaic subsystem of polarons and methanofullerene radical anions whose concentration and dynamics are determined by the density and energy of the initiating light photons. A part of such polarons first filled high-energetic spin traps formed in the matrix due to its disordering. A crucial role of exchange interaction between different spin ensembles in the charge excitation, relaxation and transport in multispin narrow-bandgap composites was demonstrated. These processes were interpreted within the framework of hopping of polarons along copolymer chains of photovoltaic subsystems and their exchange interaction with neighboring spin ensembles. Such interaction was shown to facilitate the transfer of charges and inhibits their recombination in multispin dual polymer composites. The distribution of spin density over polymer chains in the dual polymer composites with the π-π-stacked architecture was analyzed in framework of the density functional theory (DFT). It confirmed the transfer of electron spin density between neighboring polymer chains that provokes formation more likely radical pairs in triplet state than singlet one and inhibits their fast geminate recombination. Spin interactions eliminate the selectivity of these systems to the photon energy, extends the range of optical photons they are absorbed and, therefore, increases their efficiency to converse the light energy. Handling electronic properties via intra- and inter-subsystem spin interactions in such multispin composites allows to create on their base a more efficient and functional electronic and spintronic elements.
关键词： LEPR spectroscopy,DFT,charge transfer,spin exchange interaction,dual polymer photovoltaic composites
更新于2025-09-23 15:19:57
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Dissociative Nature of C(sp2)-N(sp3) bonds of Carbazole Based Materials via Conical Intersection: Simple Method to Predict the Exciton Stability of Host Materials for blue OLEDs: A Computational Study
摘要： In this work, the origin of singlet and triplet exciton-induced degradation of host materials with C(sp2)?N(sp3) bonds around nitrogen (carbazoles, acridines etc), connecting donor and acceptor units, were unravelled using DFT and CASSCF methods. The results reveal that molecules (employed in OLEDs) with basic unit containing C(sp2)?N(sp3) bonds (nitrogen connected to carbon in triangular fashion) have natural tendency to fragment at C-N bond through S1/S0 conical intersection (CI). The calculation of barrier heights, to reach dissociation point, indicates that degradation via triplet states is kinetically less feasible (?G* T1-TS >25 kcal mol-1) compared to first singlet excited state (?G* S1-TS ?7-30 kcal mol-1). However, long lifetime of triplets (as compared to singlets) aids in the reverse intersystem crossing from triplet to singlet state for subsequent degradation. From the results and inference, ?G* S1-TS and ?ES1-T1 are proposed to be the controlling factors for exciton-induced degradation of host materials with C(sp2)?N(sp3) bonds. Further, multiple functionalization of carbazole moieties reveal that polycyclic aromatic systems employed as acceptor unit of host materials are best suited for PhOLEDs as they will increase their lifetime due to larger ?G* S1-TS and ?ES1-T1. For TADF-based devices, materials with fused ring systems (with N(sp3) at the centre) in the donor unit is the most recommended one based on the findings of this work, as it avoids the dissociative channel altogether. Negative linear correlation between ?G* S1-TS and HOMO-LUMO gap is observed, which provides indirect way to predict the kinetic stability of these materials in excitonic states. These initial results are promising for future development of QSAR-type approach for smart designing of host materials for long-life blue OLEDs.
关键词： C(sp2)?N(sp3) bonds,OLED,DFT,degradation,host materials,conical intersection,CASSCF
更新于2025-09-23 15:19:57