Delocalization Properties Research Articles

Micro-regulating defect-charge delocalization in Cr-doped SrTiO3 for boosting visible-light-driven overall water splitting

Difficulties in developing efficient visible-light-response photocatalysts have led to a lack of optimism in the utilization of large-scale solar energy. This article enhances the understanding of the Cr-SrTiO3 catalyst for photocatalytic overall water splitting from the perspective of micro-regulation of Ti3+ defects and oxygen vacancy concentration. The advanced characterization techniques including XPS and EPR confirm these analyses. Compared to pure Cr-SrTiO3, the Na, Cr-SrTiO3 achieve a H2 production of 40.09 μmol∙h−1, indicating that adjusting the defect state can have a major impact on carrier migration. In addition, DFT calculations show that the phenomenon of charge localization varies with the introduction of Na+/K+/Cs+, and compared to pure SrTiO3 and Cr-SrTiO3, the additional introduction of Na+ causes the best delocalization properties cooperating with Cr3+, indicating a significant transition from deep traps centered on Ti3+ to shallow defects, which is the key to improving photocatalytic activity.

Stabilizing Lead Halide Perovskites via an Organometallic Chemical Bridge for Efficient and Stable Photovoltaics.

Defects around the surface and grain boundaries of perovskite films normally cause severe nonradiative recombination and imbalanced charge carrier transport, further limiting both the efficiency and stability of perovskite solar cells (PSCs). To tackle this critical issue, we propose a chemical bridge strategy to reconstruct the interface using organometallic molecules. The commercially available molecule bis(diphenylphosphino)ferrocene (FcP2), with a unique bridge molecular structure, anchors and chelates Pb atoms by forming strong Pb-P bonds and further passivates both surfaces and grain boundaries. Detailed characterization revealed that bridge molecule FcP2 reconstruction can effectively suppress nonradiative recombination, and the electron delocalization properties of the ferrocene core can further achieve more balanced interfacial carrier transport. The resultant N-i-P PSC device outputs close to 25% efficiency together with one of the best reported operational stabilities, maintaining over 95% of the initial efficiency after 1000 h of continuous operation at the maximum power point under 1-sun illumination.

Furan-oxadiazole hybrids as promising antioxidants: Synthesis, characterization, ADME and molecular docking studies on peroxiredoxin-2

The study involves the synthesis and characterization of a novel series of furan-based compounds 1–9 incorporating strategic modifications with isatin, pyrazole, and oxadiazole motifs. The synthesized compounds were characterized and assigned with different spectroscopic techniques such as FT-IR, 1H NMR, 13C NMR and mass spectra. Antioxidant screening assays using the DPPH radical scavenging method revealed that the oxadiazole derivative 9 exhibited exceptional antioxidant activity, with an EC50 value of 0.0038 mM, attributed to the oxadiazole ring's favourable electron delocalization and radical stabilization properties. Molecular docking simulations with the Peroxiredoxin-2 (Prdx-2) crystal structure (PDB: 5IJT) predicted favourable binding interactions for the synthesized compounds, with docking scores ranging from -6.1629 to -7.9878 kcal/mol. The sugar moieties facilitated hydrogen bonding interactions with key active site residues, while the furan and phenyl rings contributed to π-hydrogen interactions. Furthermore, in silico ADME prediction studies assessed the drug-likeness and pharmacokinetic properties of the compounds, identifying promising lead candidates for further optimization and development as potential antioxidant therapeutics targeting Prdx-2.

Iodinated Electron Acceptor with Significantly Extended Exciton Diffusion Length for Efficient Organic Photovoltaic Cells.

Iodination has unlocked new potentials in organic photovoltaics (OPVs). A newly designed and synthesized iodinated non-fullerene acceptor, BO-4I, showcases exceptional excitation delocalization property with the exciton diffusion length increased to 80 nm. The enhanced electron delocalization property is attributed to the larger atomic radius and electron orbit of the iodine atom, which facilitates the formation of intra-moiety excitations in the acceptor phase. This effectively circumvents the charge transfer state-related recombination mechanisms, leading to a substantial reduction in non-radiative energy loss (ΔEnr ). As a result, OPV cell based on PBDB-TF : BO-4I achieves an impressive efficiency of 18.9 % with a notable ΔEnr of 0.189 eV, markedly surpassing their fluorinated counterparts. This contribution highlights the pivotal role of iodination in reducing energy loss, thereby affirming its potential as a key strategy in the development of advanced next-generation OPV cells.

Iodinated Electron Acceptor with Significantly Extended Exciton Diffusion Length for Efficient Organic Photovoltaic Cells

AbstractIodination has unlocked new potentials in organic photovoltaics (OPVs). A newly designed and synthesized iodinated non‐fullerene acceptor, BO‐4I, showcases exceptional excitation delocalization property with the exciton diffusion length increased to 80 nm. The enhanced electron delocalization property is attributed to the larger atomic radius and electron orbit of the iodine atom, which facilitates the formation of intra‐moiety excitations in the acceptor phase. This effectively circumvents the charge transfer state‐related recombination mechanisms, leading to a substantial reduction in non‐radiative energy loss (ΔEnr). As a result, OPV cell based on PBDB‐TF : BO‐4I achieves an impressive efficiency of 18.9 % with a notable ΔEnr of 0.189 eV, markedly surpassing their fluorinated counterparts. This contribution highlights the pivotal role of iodination in reducing energy loss, thereby affirming its potential as a key strategy in the development of advanced next‐generation OPV cells.

Iodonium Initiators: Paving the Air‐free Oxidation of Spiro‐OMeTAD for Efficient and Stable Perovskite Solar Cells

AbstractTo date, perovskite solar cells (pero‐SCs) with doped 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (Spiro‐OMeTAD) hole transporting layers (HTLs) have shown the highest recorded power conversion efficiencies (PCEs). However, their commercialization is still impeded by poor device stability owing to the hygroscopic lithium bis(trifluoromethanesulfonyl)imide and volatile 4‐tert‐butylpyridine dopants as well as time‐consuming oxidation in air. In this study, we explored a series of single‐component iodonium initiators with strong oxidability and different electron delocalization properties to precisely manipulate the oxidation states of Spiro‐OMeTAD without air assistance, and the oxidation mechanism was clearly understood. Iodine (III) in the diphenyliodonium cation (IP+) can accept a single electron from Spiro‐OMeTAD and forms Spiro‐OMeTAD⋅+ owing to its strong oxidability. Moreover, because of the coordination of the strongly delocalized TFSI− with Spiro‐OMeTAD⋅+ in a stable radical complex, the resulting hole mobility was 30 times higher than that of pristine Spiro‐OMeTAD. In addition, the IP‐TFSI initiator facilitated the growth of a homogeneous and pinhole‐free Spiro‐OMeTAD film. The pero‐SCs based on this oxidizing HTL showed excellent efficiencies of 25.16 % (certified: 24.85 % for 0.062‐cm2) and 20.71 % for a 15.03‐cm2 module as well as remarkable overall stability.

Iodonium Initiators: Paving the Air-free Oxidation of Spiro-OMeTAD for Efficient and Stable Perovskite Solar Cells.

To date, perovskite solar cells (pero-SCs) with doped 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) hole transporting layers (HTLs) have shown the highest recorded power conversion efficiencies (PCEs). However, their commercialization is still impeded by poor device stability owing to the hygroscopic lithium bis(trifluoromethanesulfonyl)imide and volatile 4-tert-butylpyridine dopants as well as time-consuming oxidation in air. In this study, we explored a series of single-component iodonium initiators with strong oxidability and different electron delocalization properties to precisely manipulate the oxidation states of Spiro-OMeTAD without air assistance, and the oxidation mechanism was clearly understood. Iodine (III) in the diphenyliodonium cation (IP+ ) can accept a single electron from Spiro-OMeTAD and forms Spiro-OMeTAD⋅+ owing to its strong oxidability. Moreover, because of the coordination of the strongly delocalized TFSI- with Spiro-OMeTAD⋅+ in a stable radical complex, the resulting hole mobility was 30 times higher than that of pristine Spiro-OMeTAD. In addition, the IP-TFSI initiator facilitated the growth of a homogeneous and pinhole-free Spiro-OMeTAD film. The pero-SCs based on this oxidizing HTL showed excellent efficiencies of 25.16 % (certified: 24.85 % for 0.062-cm2 ) and 20.71 % for a 15.03-cm2 module as well as remarkable overall stability.

Aromaticity Reversal Induced by Vibrations in Cyclo[16]carbon.

Aromaticity is typically regarded as an intrinsic property of a molecule, correlated with electron delocalization, stability, and other properties. Small variations in the molecular geometry usually result in small changes in aromaticity, in line with Hammond's postulate. For example, introducing bond-length alternation in benzene and square cyclobutadiene by modulating the geometry along the Kekulé vibration gradually decreases the magnitude of their ring currents, making them less aromatic and less antiaromatic, respectively. A sign change in the ring current, corresponding to a reversal of aromaticity, typically requires a gross perturbation such as electronic excitation, addition or removal of two electrons, or a dramatic change in the molecular geometry. Here, we use multireference calculations to show how movement along the Kekulé vibration, which controls bond-length alternation, induces a sudden reversal in the ring current of cyclo[16]carbon, C16. This reversal occurs when the two orthogonal π systems of C16 sustain opposing currents. These results are rationalized by a Hückel model which includes bond-length alternation, and which is combined with a minimal model accounting for orbital contributions to the ring current. Finally, we successfully describe the electronic structure of C16 with a "divide-and-conquer" approach suitable for execution on a quantum computer.

(Invited) Understanding Chemical Doping and Transport in Dispersions of Isolated Carbon Nanotubes

Recently we demonstrated that the chemical structure of the redox charge-carrier dopant plays a significant role in the delocalization and transport properties of the injected charge-carriers in networks of enriched semiconducting single-walled carbon nanotubes (s-SWCNT). Here, we seek to gain a deeper understanding of the charge-carrier doping and transport processes for isolated polymer-wrapped s-SWCNT in a low dielectric constant solution-phase environment. We compare solution-phase s-SWCNT samples in toluene that are p-type doped by either 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) or (2,3,4,5,6-pentafluoro)benzyloxy-substituted icosahedral dodecaborane cluster (DDB-F60). We show that DDB-F60 is a more potent charge-carrier dopant than F4-TCNQ at low concentrations but that the ultimate injected hole charge-carrier density is limited by the large size of the DDB-F60 counteranion, due to saturation of the carbon nanotube surface area that is accessible to the dopant molecules. Using a non-contact spectroscopy technique in the microwave frequency region (ca. 9 GHz), we show that the holes injected by DDB-F60 are more delocalized and mobile, consistent with calculations that suggest a smaller coulombic binding energy between the hole on the carbon nanotube and the electron on the DDB-F60 counteranion. However, samples doped by F4-TCNQ reach a higher peak conductance than is achieved by DDB-F60 doping, where the conductance in the latter case is limited by the maximum achievable hole charge-carrier density and hole scattering processes that reduce the carrier mobility at high hole densities. Our observations point to the need to understand the subtle balance between the carrier-counterion interactions and the injected charge-carrier density to optimize charge-carrier transport in chemically doped s-SWCNT systems.

Metallic AgInS2 nanocrystals with sulfur vacancies boost atmospheric CO2 photoreduction under near-infrared light illumination

Unraveling the function of vacancy engineering in influencing the intrinsic CO2 photoreduction with low photon energy directly from air remains a significant challenge. Here, a metallic photocatalyst, ultrafine AgInS2 nanocrystals with sulfur vacancies (VS-AgInS2) is designed to exhibit superior atmospheric CO2 reduction performance under near-infrared (NIR) light. Theoretical calculations reveal that the presence of sulfur vacancies and metallic characteristics result in extended spectrum absorption to the NIR region and efficient separation of charge carriers. As evidenced by In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiment and theoretical calculations, the unique properties of charge delocalization around the vacancy-induced dual sites at AgInS2 nanocrystals contribute to COOH* intermediates for CO production while simultaneously inhibiting the formation of CHO* intermediates. Consequently, the metallic VS-AgInS2 nanocrystals demonstrate nearly 100% selective CO production with a rate of 8.04 μmol g−1 h−1 under NIR irradiation, even directly from atmospheric CO2 in the air.

Information measures on matter-wave solitons in Bose–Einstein condensates

We consider quasi-one-dimensional Bose–Einstein condensates and study the properties of matter-wave bright solitons within the framework information theoretic approach. In the limit of negligible trapping effect, we calculate Shannon entropy, Fisher information, and Rényi entropy for different mean-field interactions, and study the interplay between group velocity dispersion and nonlinear atomic interaction. We see that information theoretic approach can clearly reveal localization and delocalization properties of matter-wave density distribution. In all the cases, entropic uncertainties are found to be satisfied.

Thiacalixarene Appended Azo-based Supramolecular Systems: Self-assembly and Photo Tuning Reversible Liquid Crystalline Properties.

Four new azo-based supramolecular materials containing thiacalixarene core substituted by variable alkoxy groups (TFA1 -TFA4 ) have been designed and synthesized for the mesomorphic and photoswitching properties. The liquid crystalline behavior were accomplished by using DSC, POM, and XRD studies. All azo-based thiacalixarene based materials with short and higher chain length display columnar hexagonal mesophase with broad temperature range. The thermal behavior of all the materials was investigated by DSC and TGA study. The structural and conformational study of the lower rim functionalized materials was confirmed by using different techniques. These thiacalixarene moulded liquid crystalline compounds shows columnar self-assembly type behavior and higher thermal stability. The introduction of bi-substituted azo-ester network towards the lower rim of thiacalixarene core has impact on the electron delocalization and liquid crystalline properties. The photoswitching properties suggested cis and trans azo-isomerization under radiation of UV light and higher thermal back relaxation time. The mesogenic behaviour of compound TFA2 and TFA4 were demolished by the influence of cis and trans isomerization. The structure-property correlation is studied to understand the variation in mesogenic properties with the substitution of variable alkoxy side chain.

NLO ACTIVITY AND COMPUTATIONAL DISCUSSION OF HALOGEN-SUBSTITUTED CHALCONE DERIVATIVES

The four halogen-substituted chalcones 1–4 have been synthesized and analyzed to FT-Infrared, UV-Visible, GC-MS spectrometer, and 1D NMR (1H and 13C) spectroscopy techniques. Computational calculations were carried out for geometrical optimization of structure regards bond length, bond angle, and torsional angle estimated. The molecular properties of donor-acceptor electron delocalization (NBO), Electron density, and bond critical point are carryover in (AIM), the polar site of molecules is determined by (MEP), HOMO-LUMO, and the dipole moment was calculated by GAUSSUION-09 Package. The polarizability and first-order hyperpolarizability calculations derived from non-linear optical (NLO) properties for the synthesized compounds (1-4). The disc diffusion method was used to investigate the microbial activity of antibacterial and antifungal activity.

Charge delocalization and aromaticity of doubly reduced double-walled carbon nanohoops.

Cycloparaphenylenes (CPPs) exhibit selective host capabilities, featuring the ability to incorporate smaller CPPs to form double-walled host-guest complexes. Moreover, CPPs can also be stabilized by global aromaticity under twofold oxidation or reduction, involving electronic conjugation along with the overall structural backbone. Herein we explore the structural modifications, bonding, electron delocalization and magnetic properties of doubly reduced double-walled CPP complexes with DFT methods, in the isolated and aggregate [n + 5]CPP⊃[n]CPP2- (n = 5-8) species. Our results show that the hosts undergo structural, bonding and delocalization deformations towards quinoidal configurations and exhibit global long-ranged shielding cones similar to global aromatic free dianionic CPPs, accounting for charge delocalization on the outer nanohoops, whereas the guests preserve local aromatic benzenoid configurations, resulting in global and local aromatic circuits within the host-guest aggregate. This observation suggests that in multi-layered related species electronic delocalization will be retained at the outer structural surface. The aromaticity of the hosts is manifested in the strong upfield shifts of the guests 1H-NMR signals. Hence, CPP complexes can be extended to doubly reduced species stabilized by global host aromaticity expanding our understanding of doubled-walled nanotubes at the nanoscale regime.

Prototropy, Intramolecular Interactions, Electron Delocalization, and Physicochemical Properties of 1,8-dihydroxy-9-anthrone—DFT-D3 Study of Substituent Effects

1,8-dihydroxy-9-anthrone are tricyclic compounds with a ketone group in the middle ring and two hydroxyl groups substituted in the side-aromatic rings what results in formation of two intramolecular hydrogen bonds in which the oxygen atom from the ketone group is the proton acceptor. 1,8-dihydroxy-9-anthrones in which intramolecular proton transfer between C10 and CO in the middle ring occurs, can exist in a tautomeric keto-enol equilibrium. For anthralin, the most important representative of this group, this equilibrium has been studied previously, but it has not been studied for its derivatives. Substituents in the middle ring change the geometry of 1,8-dihydroxy-9-anthrones so they are also expected to affect the keto-enol equilibrium. It is also important to study the effect of intramolecular hydrogen bonds on the structure of both tautomeric forms. It was found that the nature of the substituent in the middle ring could affect the antioxidant properties of the investigated compound.

Polariton enhanced free charge carrier generation in donor-acceptor cavity systems by a second-hybridization mechanism.

Cavity quantum electrodynamics has been studied as a potential approach to modify free charge carrier generation in donor-acceptor heterojunctions because of the delocalization and controllable energy level properties of hybridized light-matter states known as polaritons. However, in many experimental systems, cavity coupling decreases charge separation. Here, we theoretically study the quantum dynamics of a coherent and dissipative donor-acceptor cavity system, to investigate the dynamical mechanism and further discover the conditions under which polaritons may enhance free charge carrier generation. We use open quantum system methods based on single-pulse pumping to find that polaritons have the potential to connect excitonic states and charge separated states, further enhancing free charge generation on an ultrafast timescale of several hundred femtoseconds. The mechanism involves polaritons with optimal energy levels that allow the exciton to overcome the high Coulomb barrier induced by electron-hole attraction. Moreover, we propose that a second-hybridization between a polariton state and dark states with similar energy enables the formation of the hybrid charge separated states that are optically active. These two mechanisms lead to a maximum of 50% enhancement of free charge carrier generation on a short timescale. However, our simulation reveals that on the longer timescale of picoseconds, internal conversion and cavity loss dominate and suppress free charge carrier generation, reproducing the experimental results. Thus, our work shows that polaritons can affect the charge separation mechanism and promote free charge carrier generation efficiency, but predominantly on a short timescale after photoexcitation.

Vibrational energies, bonding nature, electronic properties, spectroscopic investigations and analysis of 3-bromo-4-Chlorobenzophenone

In this present study, we investigated pharmaceutically active of 3-Bromo-4-chlorobenzophenone. Structural, electronic properties (HOMO-LUMO, MEP) are investigated using DFT tool. Vibrational spectral analysis for FT-IR and FT-Raman are made of headline molecule. Electronic transition properties are discussed with the help of UV–Vis spectral analysis. Biologically active sites are found from MEP analysis. Electron delocalization properties are studied explored from HOMO-LUMO band gap energy. Moreover, intra molecular interactions are explained from NBO method. Molecular docking studies are performed to find the interactions various pathologies. The topological properties of the electron density have been analyzed.

Ligand-mediated band structure engineering and physiochemical properties of UiO-66 (Zr) metal-organic frameworks (MOFs) for solar-driven degradation of dye molecules

In this study, Zr-based metal organic frameworks (Zr-MOFs) with different ligands such as terephthalic acid (UiO-66), 2-aminoterephthalic (UiO-66-NH2) and 2-methylimidazole (UiO‐66‐2M) are synthesized using hydrothermal method in order to investigate their ligand-dependent properties towards photocatalytic degradation of dyes molecules under solar light. The structural analysis by XRD revealed the fundamental cubic-topology of the UiO-66 structure for all the synthesized MOFs, and the presence of respective functional groups is confirmed via their ART-IR spectra. A spherical morphology with average size of ~80 and 200 nm are observed for UiO-66 and UiO-66-NH2 MOFs, respectively, whereas, bricks-like morphology is observed for UiO‐66‐2M, which is attributed to the binding habit of the respective ligands. Band gap energy of the synthesized UiO-66, UiO-66-NH2 and UiO‐66‐2M is estimated to be ~3.85, 2.92 and 2.77 eV, respectively. Among the synthesized MOFs, the photocatalytic degradation efficiency of UiO-66-NH2 MOFs is found to be greater towards the cationic rhodamine B (RhB) dye (~95% in 120 min), while it is relatively less efficient in degrading the anionic Congo red (CR) dye, (~64% in 120 min). The insights gained from the fundamental characterizations, Mott-Schottky, scavenger and electrochemical impedance analysis revealed that the amino-groups in UiO-66-NH2 MOFs offered the band edge potentials suitable for the effective generation of energetic radical species with the improved carrier delocalization, recombination resistance and charge transfer properties in the MOFs. The further parametric studies revealed that the UiO-66-NH2 MOFs can be effectively scaled-up and used for dye degradation applications in real-time.

Localization and delocalization properties in quasi-periodically-driven one-dimensional disordered systems.

Localization and delocalization of quantum diffusion in a time-continuous one-dimensional Anderson model perturbed by the quasiperiodic harmonic oscillations of M colors is investigated systematically, which has been partly reported by a preliminary Letter [H. S. Yamada and K. S. Ikeda, Phys. Rev. E 103, L040202 (2021)2470-004510.1103/PhysRevE.103.L040202]. We investigate in detail the localization-delocalization characteristics of the model with respect to three parameters: the disorder strength W, the perturbation strength ε, and the number of colors, M, which plays the similar role of spatial dimension. In particular, attention is focused on the presence of localization-delocalization transition (LDT) and its critical properties. For M≥3 the LDT exists and a normal diffusion is recovered above a critical strength ε, and the characteristics of diffusion dynamics mimic the diffusion process predicted for the stochastically perturbed Anderson model even though M is not large. These results are compared with the results of discrete-time quantum maps, i.e., the Anderson map and the standard map. Further, the features of delocalized dynamics are discussed in comparison with a limit model which has no static disordered part.

Electromagnetically induced moiré optical lattices in a coherent atomic gas

Electromagnetically induced optical (or photonic) lattices via atomic coherence in atomic ensembles have recently received great theoretical and experimental interest. We here conceive a way to generate electromagnetically induced moir\'{e} optical lattices -- a twisted periodic pattern when two identical periodic patterns (lattices) are overlapped in a twisted angle ($\theta$) -- in a three-level coherent atomic gas working under electromagnetically induced transparency. We show that, changing the twisted angle and relative strength between the two constitutive sublattices, the moir\'{e} Bloch bands that are extremely flattened can always appear, resembling the typical flat-band and moir\'{e} physics found in other contexts. Dynamics of light propagation in the induced periodic structures demonstrating the unique linear localization and delocalization properties are also revealed. Our scheme can be implemented in a Rubidium atomic medium, where the predicted moir\'{e} optical lattices and flattened bands are naturally observable.