Charge-transfer Configurations Research Articles

Highly efficient pure-blue organic light-emitting diodes based on rationally designed heterocyclic phenophosphazinine-containing emitters

Multi-resonance thermally activated delayed fluorophores have been actively studied for high-resolution photonic applications due to their exceptional color purity. However, these compounds encounter challenges associated with the inefficient spin-flip process, compromising device performance. Herein, we report two pure-blue emitters based on an organoboron multi-resonance core, incorporating a conformationally flexible donor, 10-phenyl-5H-phenophosphazinine 10-oxide (or sulfide). This design concept selectively modifies the orbital type of high-lying excited states to a charge transfer configuration while simultaneously providing the necessary conformational freedom to enhance the density of excited states without sacrificing color purity. We show that the different embedded phosphorus motifs (phosphine oxide/sulfide) of the donor can finely tune the electronic structure and conformational freedom, resulting in an accelerated spin-flip process through intense spin-vibronic coupling, achieving over a 20-fold increase in the reverse intersystem crossing rate compared to the parent multi-resonance emitter. Utilizing these emitters, we achieve high-performance pure-blue organic light-emitting diodes, showcasing a top-tier external quantum efficiency of 37.6% with reduced efficiency roll-offs. This proposed strategy not only challenges the conventional notion that flexible electron-donors are undesirable for constructing narrowband emitters but also offer a pathway for designing efficient narrow-spectrum blue organic light-emitting diodes.

Constructing Direct Z-Scheme Y2TmSbO7/GdYBiNbO7 Heterojunction Photocatalyst with Enhanced Photocatalytic Degradation of Acetochlor under Visible Light Irradiation.

This study presents a pioneering synthesis of a direct Z-scheme Y2TmSbO7/GdYBiNbO7 heterojunction photocatalyst (YGHP) using an ultrasound-assisted hydrothermal synthesis technique. Additionally, novel photocatalytic nanomaterials, namely Y2TmSbO7 and GdYBiNbO7, were fabricated via the hydrothermal fabrication technique. A comprehensive range of characterization techniques, including X-ray diffractometry, Fourier-transform infrared spectroscopy, Raman spectroscopy, UV-visible spectrophotometry, X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray energy-dispersive spectroscopy, fluorescence spectroscopy, photocurrent testing, electrochemical impedance spectroscopy, ultraviolet photoelectron spectroscopy, and electron paramagnetic resonance, was employed to thoroughly investigate the morphological features, composition, chemical, optical, and photoelectric properties of the fabricated samples. The photocatalytic performance of YGHP was assessed in the degradation of the pesticide acetochlor (AC) and the mineralization of total organic carbon (TOC) under visible light exposure, demonstrating eximious removal efficiencies. Specifically, AC and TOC exhibited removal rates of 99.75% and 97.90%, respectively. Comparative analysis revealed that YGHP showcased significantly higher removal efficiencies for AC compared to the Y2TmSbO7, GdYBiNbO7, or N-doped TiO2 photocatalyst, with removal rates being 1.12 times, 1.21 times, or 3.07 times higher, respectively. Similarly, YGHP demonstrated substantially higher removal efficiencies for TOC than the aforementioned photocatalysts, with removal rates 1.15 times, 1.28 times, or 3.51 times higher, respectively. These improvements could be attributed to the Z-scheme charge transfer configuration, which preserved the preferable redox capacities of Y2TmSbO7 and GdYBiNbO7. Furthermore, the stability and durability of YGHP were confirmed, affirming its potential for practical applications. Trapping experiments and electron spin resonance analyses identified active species generated by YGHP, namely •OH, •O2-, and h+, allowing for comprehensive analysis of the degradation mechanisms and pathways of AC. Overall, this investigation advances the development of efficient Z-scheme heterostructural materials and provides valuable insights into formulating sustainable remediation strategies for combatting AC contamination.

Computationally engineering optoelectronic properties and photocatalytic performance in graphene quantum dot/platinum(II) complex photocatalysts

This study delves into the impact of various substituents on bipyridyl Pt(II) bisstilbenylacetylide complexes when attached to Graphene quantum dots (GQDs), a material with promising photocatalytic potential. Using density functional theory calculations, the research uncovers that the substituents significantly alter properties of the resulting nanocomposites. These include the geometric and electronic structures, optical absorption profiles, charge transfer configurations, and chemical reactivity. Electron-withdrawing groups cause blueshifts in absorption peaks, while electron-donating ones induce redshifts. These shifts are more pronounced when the complexes are attached to GQDs. The attachment of GQDs also impacts the molecular orbital structure, stabilizing the highest occupied molecular orbital (HOMO), but destabilizing the lowest unoccupied molecular orbital (LUMO). Furthermore, the incorporation of GQDs into the composite enhances overall stability while diminishing reactivity. The formation of the nanocomposite reduces the energetic favorability of electron injection and regeneration processes. Interestingly, the substituents affect the charge transfer length more significantly for nanocomposites compared to isolated complexes. Overall, this study provides valuable insights into fine-tuning optoelectronic and photocatalytic properties of GQD hybrid photocatalysts, useful in applications like solar energy conversion and pollutant degradation. These findings significantly advance the understanding of the structure–function relationship in GQD nanocomposites for photocatalysis.

Effect of Vacancy Defects and Hydroxyl on the Adsorption of Glycine on Mg(0001): A First-Principles Study

Glycine (Gly), as one of the fundamental components of biomolecules, plays a crucial role in functional biomolecular coatings. The presence of structural defects and hydroxyl-containing functional groups in magnesium (Mg) materials, which are commonly used as biomedical materials, significantly affects their biocompatibility and corrosion resistance performance. This study computationally investigates the influence of vacancy defects and hydroxyl groups on the adsorption behavior of Gly on Mg(0001) surfaces. All potential adsorption configurations are considered through first-principles calculations. The findings indicate that stronger chemisorption occurs when Gly is positioned at the edge of the groove, where the surface has a vacancy defect concentration of 1/3. Among the four adsorption locations, the fcc-hollow site is determined to be the most favorable adsorption site for hydroxyl. The adsorption energy of Gly on the Mg(0001) surface containing the hydroxyl (−1.11 eV) is 0.05 eV more than that of on the Mg(0001) surface (−1.16 eV). The adsorption energies, electronic properties, charge transfer, and stable configurations are calculated to evaluate the interaction mechanism between Gly and defective surfaces. Calculated results provide a comprehensive understanding of the interaction mechanism of biomolecules on defective Mg surfaces and also indicate the directions for future experimental research.

A smart chemosensor with different response mechanisms to multi-analytes: Chromogenic and fluorogenic recognition of Cu2+, Fe3+, and Zn2+

Single-component sensors that can detect multiple analytes have drawn great research attentions. Herein, a smart chemosensor TPBS that can recognize multiple targets was developed by connecting triphenylamine with benzothiazole via an imine link. The N atoms with lone pair electrons on the flexible imine link served as potential coordination sites to allow for variations in charge transfer and molecular configurations. In CH3CN, TPBS simultaneously achieved the recognition of Cu2+ through a chromogenic response (colorless to red) via ligand-metal charge transfer, and the recognition of Fe3+ through a “turn-on” fluorogenic response (non-emission to blue) via the chelation-enhanced fluorescence effect. In aqueous solution, TPBS recognized Zn2+ via a “turn-on” fluorogenic response (non-emission to green) based on the aggregation-induced emission behavior. The detection limits were as low as 0.45 μM, 3.24 μM, and 3.22 μM for Cu2+, Fe3+, and Zn2+, respectively. A 1:1 binding stoichiometry and exact complex modes between TPBS and the target metal ions were deduced using Job's plot and FT-IR analyses. Both experiments and theoretical calculations supported the deduced coordination mechanisms. The ability of TPBS to recognize Cu2+, Fe3+, and Zn2+ was then tested in real-life water samples and through on-site detection of Zn2+ using test strips.

Regulating the Interplay at the Buried Interface for Efficient and Stable Carbon-Based CsPbI2Br Perovskite Solar Cells

Buried interface modification is promising for preparing high-performance perovskite solar cells (PSCs) by improving the film quality and adjusting the interfacial energy level alignment. In this work, multifunctional ethylenediaminetetraacetic acid diammonium (EAD)-modulated ZnO is employed as an effective buried interface to regulate the interplay between SnO2 and CsPbI2Br in carbon-based inorganic PSCs (C-IPSCs). The burying of EAD into the ZnO interlayer not only enhances the photoelectric properties of ZnO by passivating oxygen defects but also adjusts the energy level alignment of the buried interface. More importantly, the perovskite quality is optimized and the buried interface defects are passivated due to the formation of coordination and hydrogen bondings. Benefiting from such a robust and efficient charge transfer configuration, a maximum power conversion efficiency of 14.58% is achieved in the optimized device, which represents the highest performance reported among those of low-temperature CsPbI2Br C-IPSCs. In addition, the unencapsulated device demonstrates better long-term and thermal stability.

Long-range corrected fragment molecular orbital density functional tight-binding method for excited states in large molecular systems.

Herein, we present a new method to efficiently calculate electronically excited states in large molecular assemblies, consisting of hundreds of molecules. For this purpose, we combine the long-range corrected tight-binding density functional fragment molecular orbital method (FMO-LC-DFTB) with an excitonic Hamiltonian, which is constructed in the basis of locally excited and charge-transfer configuration state functions calculated for embedded monomers and dimers and accounts explicitly for the electronic coupling between all types of excitons. We first evaluate both the accuracy and efficiency of our fragmentation approach for molecular dimers and aggregates by comparing it with the full LC-TD-DFTB method. The comparison of the calculated spectra of an anthracene cluster shows a very good agreement between our method and the LC-TD-DFTB reference. The effective computational scaling of our method has been explored for anthracene clusters and for perylene bisimide aggregates. We demonstrate the applicability of our method by the calculation of the excited state properties of pentacene crystal models consisting of up to 319 molecules. Furthermore, the participation ratio of the monomer fragments to the excited states is analyzed by the calculation of natural transition orbital participation numbers, which are verified by the hole and particle density for a chosen pentacene cluster. The use of our FMO-LC-TDDFTB method will allow for future studies of excitonic dynamics and charge transport to be performed on complex molecular systems consisting of thousands of atoms.

Origin of Ferromagnetic Exchange Coupling in Donor–Acceptor Biradical Analogues of Charge-Separated Excited States

A new donor-acceptor biradical complex, TpCum,MeZn(SQ-VD) (TpCum,MeZn+ = zinc(II) hydro-tris(3-cumenyl-5-methylpyrazolyl)borate complex cation; SQ = orthosemiquinone; VD = oxoverdazyl), which is a ground-state analogue of a charge-separated excited state, has been synthesized and structurally characterized. The magnetic exchange interaction between the S = 1/2 SQ and the S = 1/2 VD within the SQ-VD biradical ligand is observed to be ferromagnetic, with JSQ-VD = +77 cm-1 (H = -2JSQ-VDŜSQ·ŜVD) determined from an analysis of the variable-temperature magnetic susceptibility data. The pairwise biradical exchange interaction in TpCum,MeZn(SQ-VD) can be compared with that of the related donor-acceptor biradical complex TpCum,MeZn(SQ-NN) (NN = nitronyl nitroxide, S = 1/2), where JSQ-NN ≅ +550 cm-1. This represents a dramatic reduction in the biradical exchange by a factor of ∼7, despite the isolobal nature of the VD and NN acceptor radical SOMOs. Computations assessing the magnitude of the exchange were performed using a broken-symmetry density functional theory (DFT) approach. These computations are in good agreement with those computed at the CASSCF NEVPT2 level, which also reveals an S = 1 triplet ground state as observed in the magnetic susceptibility measurements. A combination of electronic absorption spectroscopy and CASSCF computations has been used to elucidate the electronic origin of the large difference in the magnitude of the biradical exchange coupling between TpCum,MeZn(SQ-VD) and TpCum,MeZn(SQ-NN). A Valence Bond Configuration Interaction (VBCI) model was previously employed to highlight the importance of mixing an SQSOMO → NNLUMO charge transfer configuration into the electronic ground state to facilitate the stabilization of the high-spin triplet (S = 1) ground state in TpCum,MeZn(SQ-NN). Here, CASSCF computations confirm the importance of mixing the pendant radical (e.g., VD, NN) LUMO (VDLUMO and NNLUMO) with the SOMO of the SQ radical (SQSOMO) for stabilizing the triplet, in addition to spin polarization and charge transfer contributions to the exchange. An important electronic structure difference between TpCum,MeZn(SQ-VD) and TpCum,MeZn(SQ-NN), which leads to their different exchange couplings, is the reduced admixture of excited states that promote ferromagnetic exchange into the TpCum,MeZn(SQ-VD) ground state, and the intrinsically weaker mixing between the VDLUMO and the SQSOMO compared to that observed for TpCum,MeZn(SQ-NN), where this orbital mixing is significant. The results of this comparative study contribute to a greater understanding of biradical exchange interactions, which are important to our understanding of excited-state singlet-triplet energy gaps, electron delocalization, and the generation of electron spin polarization in both the ground and excited states of (bpy)Pt(CAT-radical) complexes.

Insight into the Photodynamics of Photostabilizer Molecules.

Solar exposure of avobenzone, one of the most widely used commercial UVA filters on the market, is known to cause significant degradation. This finding has fueled research into developing photostabilizer molecules. In an effort to provide insight into their stand-alone photoprotection properties, the excited state dynamics of the photostabilizer, 3-(3,4,5-trimethoxybenzylidene) pentane-2,4-dione (TMBP), and its phenolic derivative, 3-(4-hydroxy-3,5-dimethoxybenzylidene) pentane-2,4-dione (DMBP), were studied with ultrafast transient absorption spectroscopy. Solutions of TMPB and DMBP in ethanol and in an industry-standard emollient, as well as TMBP and DMBP deposited on synthetic skin mimic, were investigated. These experiments were allied with computational methods to aid interpretation of the experimental data. Upon photoexcitation, these photostabilizers repopulate the electronic ground state via nonradiative decay within a few picoseconds involving a twisted intramolecular charge transfer configuration in the excited state, followed by internal conversion and subsequent vibrational cooling in the ground state. This finding implies that, aside from acting as a photostabilizer to certain UV filters, TMBP and DMBP may offer additional photoprotection in a sunscreen formulation as a stand-alone UV filter. Finally, TMBP and DMBP could also find applications as molecular photon-to-heat converters.

Recent advances on Z-scheme engineered BiVO4-based semiconductor photocatalysts for CO2 reduction: A review

The designs of two or more absorber materials in a Z-scheme charge transfer configuration have paved the way for efficient CO2 photoreduction to high-value chemicals and fuels using the artificial photosynthesis approach. Under visible light irradiation or natural solar illumination, semiconductors that themselves do not satisfy minimum thermodynamic requirements for CO2 reduction or accompanying oxidation reactions can be used for targeted specific half-reactions. In this context, BiVO4 has been extensively investigated for water oxidation showing promising activity under visible-light illumination but is restricted as a single reduction photocatalyst since its conduction band is not negative enough. This review provides an overview of the basic principles and fundamentals of CO2 photoreduction and highlights the recent advances in the literature using BiVO4-based Z-scheme photocatalysts. We show that using BiVO4 as the oxidation photocatalyst, together with a reduction photocatalyst (Cu2O, CdZnS, ZnIn2S4, CuGaS2, g-C3N4, others) and under the Z-scheme charge transfer, is strategic for increasing visible-light absorption and facilitating charge separations while keeping the high redox potentials of the individual semiconductor components. This approach additionally helps to avoid undesired photocorrosion reactions triggered by trapped charges. Finally, some critical comments are raised for future research directions to improve CO2 capture and photocatalytic conversion to green fuels and chemicals.

Solvent-Mediated Charge Transfer Dynamics of a Model Brown Carbon Aerosol Chromophore: Photophysics of 1-Phenylpyrrole Induced by Water Solvation.

Nitrogen heterocycles are known to be important light-absorbing chromophores in a newly discovered class of aerosols, commonly referred to as "brown carbon" (BrC) aerosols. Due to their significant absorption and spectral overlap with the solar actinic flux, these BrC chromophores steer the physical and optical properties of aerosols. To model the local aqueous solvation environment surrounding BrC chromophores, we generated cold molecular complexes with water and a prototypical BrC chromophore, 1-phenylpyrrole (1PhPy), using supersonic jet-cooling and explored their intermolecular interactions using single-conformation spectroscopy. Herein, we utilized resonant two-photon ionization (R2PI) and UV holeburning (UV HB) double-resonance spectroscopies to obtain a molecular-level understanding of the role of water microsolvation in charge transfer upon photoexcitation of 1PhPy. Quantum chemical calculations and one-dimensional discrete variable representation simulations revealed insights into the charge transfer efficacy of 1PhPy with and without addition of a single water molecule. Taken together, our results indicate that the intermolecular interactions with water guide the geometry of 1PhPy to adopt a more twisted intramolecular charge transfer (TICT) configuration, thus facilitating charge transfer from the pyrrole donor to the phenyl ring acceptor. Furthermore, the water network surrounding 1PhPy reports on the charge transfer such that the H2O solvent primarily interacts with the pyrrole ring donor in the ground state, whereas it preferentially interacts with the phenyl ring acceptor in the excited state. Large Franck-Condon activity is evident in the 1PhPy + 1H2O excitation spectrum for the water-migration vibronic bands, supporting H2O solvent reorganization upon excitation of the 1PhPy chromophore. Fluorescence measurements with increasing H2O % volume corroborated our gas-phase studies by indicating that a polar water solvation environment stabilizes the TICT configuration of 1PhPy in the excited electronic state, from which emission is observed at a lower energy compared to the locally excited configuration.

Bridging between NiAl-LDH and g-C3N4 by using carbon quantum dots for highly enhanced photoreduction of CO2 into CO

A series of treble NiAl-LDH/g-C3N4/carbon quantum dots (LDH/CN/CQDs) photocatalysts is successfully prepared for the photoreduction of CO2 to CO via a facile hydrothermal pathway. In the 3D flower-like LDH/CN/CQDs, CQDs not only achieve the efficient inhibition of charge recombination but also act as the unhindered “electronic bridges” to synergistically construct a classical type-Ⅱ charge transfer configuration, which synchronously permits the effluence of photogenerated electrons from CN to LDH and holes from LDH to CN, and promotes ultraviolet–visible irradiation respondence. The sample of LDH/CN/CQDs-6 is the optimal one amongst the LDH/CN/CQDs with a larger special surface area (98.43 m2g−1) and an appropriate content of CQDs (66.9 wt%), exhibiting the highest CO evolution rate (5.2 μmol·g−1·h−1) under visible light irradiation without any sacrificial agent or photosensitizer in water. This is 26.8- and 20.9-fold higher than those of the pristine LDH, pure CN, and their binary counterparts, respectively, and also outperforms most reported LDH-based photocatalysts. As unhindered electron conduction bridges, the highly dispersed CQDs in the LDH/CN heterojunction significantly increase utilization efficiency of light energy and separation efficiency of photogenerated electron-hole pairs. This work provides a beneficial attempt to integrate CQDs with LDH/CN for the positive synergetic effect on both photoelectric properties and electron transfer to obtain highly enhanced photocatalytic activity of CO2 into CO, and expected to be extended towards broader photocatalytic applications.

Enhanced Polychromatic Luminescence of Bionic Peptidyl Nanoparticles Driven by Hydrogen Bonds

AbstractOwing to their good biocompatibility, flexible structure, and ease of assembling, peptide nanomaterials have become one of the excellent candidates for the construction of fluorescent molecules and attracted much attention in the field of biomedicine. Inspired by green fluorescent protein and its mutants, a series of dipeptide derivatives are designed. The dipeptides aggregate into nanoparticles and bind together by intermolecular forces to produce multicolor fluorescence. Aromatic stacking and hydrogen bond networks may cause the residues on the side chains of dipeptides to form charge transfer configurations with cyclopentadiene in the nanoparticles. In particular, the ferrocene‐phenylalanine histidine (Fc–FH) dipeptide assembly contains abundant hydrogen bonds. Hydrogen atoms in hydrogen bonds can shuttle between donor and acceptor groups, causing changes in electron configuration to reduce bandgap energy, resulting in an obvious redshift of the emission spectrum and effectively extending the fluorescence spectrum to the visible light range. The stable fluorescence of ferrocene‐diphenylalanine, ferrocene‐phenylalanine tyrosine, and Fc–FH dipeptides can be detected in the visible light range and used for cell imaging, which shows great potential applications in the field of bioimaging.

Generation of multiple triplet states in an orthogonal bodipy dimer: a breakthrough spectroscopic and theoretical approach.

Generation of triplet states in assemblies of organic chromophores is extremely appealing for their potential use in optoelectronic applications. In this work, we investigate the intricacies of triplet state generation in an orthogonal BODIPY dimer by combining delayed photoemission techniques with electronic structure calculations. Our analysis provides a deep understanding of the electronic states involved, and describes different competing deactivation channels beyond prompt radiative decay. In particular, we identify charge-transfer (CT) mediated intersystem crossing (ISC) as the most likely mechanism for the triplet state generation in this system. The different emission bands at long times can be associated with delayed fluorescence, CT emission and phosphorescence from multiple low-energy triplets. Interestingly, the dependence of the yield of triplet state population and emission profiles with the solvent polarity evidences the decisive role of the CT configuration in the fate of the photoactivated dimer, controlling the relative ISC, reverse ISC, and internal conversion efficiencies. Overall, the present results provide a rather complete description of the delayed photophysics in the BODIPY dimer, but are not able to fully rationalize the unexpected photoluminescence recorded at long wavelengths (≥ 900 nm). We hypothesize that the origin of this emission, not present in BODIPY monomers, emerges from intermonomer interactions triggered by intramolecular distortions opening up a new vision in the controverted mechanism driving the photophysical behavior from orthogonally linked organic monomers.

Construction of direct Z-scheme Bi5O7I/UiO-66-NH2 heterojunction photocatalysts for enhanced degradation of ciprofloxacin: Mechanism insight, pathway analysis and toxicity evaluation

Direct Z-scheme Bi5O7I/UiO-66-NH2 (denoted as BU-x) heterojunction photocatalysts were successfully constructed through ball-milling method. Photocatalytic activities of the as-prepared BU-x samples were determined by using a typical fluoroquinolone antibiotic, ciprofloxacin (CIP). All BU-x heterojunctions exhibited better CIP removal performances than that of pristine Bi5O7I and UiO-66-NH2 upon exposure to white light irradiation. In comparison, the heterojunction with UiO-66-NH2 content of 50 wt% (BU-5) showed excellent structural stability and the optimal adsorption-photodegradation efficiency for the CIP removal. The removal efficiency of CIP (10 mg/L) over BU-5 (0.75 g/L) achieved 96.1% within 120 min illumination. Meanwhile, the effect of photocatalyst dosage, pH and inorganic anions were systemically explored. Reactive species trapping experiments, electron spin resonance (ESR) signals, Mott-Schottky measurements and density functional theory (DFT) simulation revealed that the photo-generated holes (h+), hydroxyl radical (·OH) and superoxide radical (·O2–) played crucial roles in CIP degradation. This result can be ascribed to that the unique Z-scheme charge transfer configuration retained the excellent redox capacities of Bi5O7I and UiO-66-NH2. Meanwhile, the CIP degradation pathways and the toxicity of various intermediates were subsequently analyzed. This work provided a feasible idea for removing antibiotics by bismuth-rich bismuth oxyhalide/MOF-based heterostructured photocatalysts.

Nonlocal Interactions in the Double Perovskite Sr2FeMoO6 from Core-Level X-ray Spectroscopy

The valence electronic structure of the half-metallic double perovskite Sr2FeMoO6 forms from a strongly hybridized band in the spin-down channel of Fe 3d and Mo 4d states that provides metallic conductivity and a gapped spin-up channel. The ground-state description has previously been explored in terms of many-body interactions where local and nonlocal interactions produce states with a combination of a charge-transfer configuration and intersite charge fluctuations. Here, we provide a qualitative understanding on nonlocal effects in Sr2FeMoO6 using a combination of core-level X-ray spectroscopies, specifically X-ray absorption, emission, and photoelectron spectroscopies. Our spectroscopic data indicate intersite Fe 4p–O 2p–Mo 4d interactions to be the origin of these nonlocalized transitions. Close to the Fermi level, this interaction is dominated by Mo 4d–O 2p character. When our data are compared against first-principles electronic structure calculations, we conclude that a full understanding of the nature of these states requires a spin-resolved description of the hybridization functions and that the nonlocal screening occurs predominantly through hybridization in the minority spin channel of the Mo 4d bands.

Ligand-modulated electron transfer rates from CsPbBr3 nanocrystals to titanium dioxide

Abstract In most perovskite nanocrystal (PeNC)-based optoelectronic and photonic applications, surface ligands inevitably lead to a donor–bridge–acceptor charge transfer configuration. In this article, we demonstrate successful modulation of electron transfer (ET) rates from all-inorganic CsPbBr3 PeNCs to mesoporous titanium dioxide films, by using different surface ligands including single alkyl chain oleic acid and oleylamine, cross-linked insulating (3-aminopropyl)triethoxysilane and aromatic naphthoic acid molecules as the ligand-bridge. We systematically investigated the ET process through time-resolved photoluminescence spectroscopy. Calculations verified the ligand-bridge barrier effect of the three species upon the ET process. Transient absorption measurements excluded carrier-delocalization effect of the naphthoic acid ligands and confirmed the bridge-barrier effect. Our work provides a perspective for composable and appropriate ligands design for diverse practical purposes.

Doping evolution of the Mott–Hubbard landscape in infinite-layer nickelates

The recent observation of superconductivity in [Formula: see text] has raised fundamental questions about the hierarchy of the underlying electronic structure. Calculations suggest that this system falls in the Mott-Hubbard regime, rather than the charge-transfer configuration of other nickel oxides and the superconducting cuprates. Here, we use state-of-the-art, locally resolved electron energy-loss spectroscopy to directly probe the Mott-Hubbard character of [Formula: see text] Upon doping, we observe emergent hybridization reminiscent of the Zhang-Rice singlet via the oxygen-projected states, modification of the Nd 5d states, and the systematic evolution of Ni 3d hybridization and filling. These experimental data provide direct evidence for the multiband electronic structure of the superconducting infinite-layer nickelates, particularly via the effects of hole doping on not only the oxygen but also nickel and rare-earth bands.

Nickel Nanopillar Arrays Electrodeposited on Silicon Substrates Using Porous Alumina Templates.

Nickel nanopillar arrays were electrodeposited onto silicon substrates using porous alumina membranes as a template. The characterization of the samples was done by scanning electron microscopy, X-ray diffraction, and alternating force gradient magnetometry. Ni nanostructures were directly grown on Si by galvanostatic and potentiostatic electrodeposition techniques in three remarkable charge transfer configurations. Differences in the growth mechanisms of the nanopillars were observed, depending on the deposition method. A high correlation between the height of the nanopillars and the charge synthesis was observed irrespective of the electrochemical technique. The magnetization measurements demonstrated a main dependence with the height of the nanopillars. The synthesis of Ni nanosystems with a controllable aspect ratio provides an effective way to produce well-ordered networks for wide scientific applications.

The combination of multipartitioning of the Hamiltonian with canonical Van Vleck perturbation theory leads to a Hermitian variant of quasidegenerate N-electron valence perturbation theory.

Many recent developments in the area of multistate multireference perturbation theories focused on methods that use a state-averaged 0th order Hamiltonian. We recently found that the dynamic correlation dressed complete active space method fails in describing ligand field and charge transfer states in a balanced way precisely because it uses a state-averaged 0th order Hamiltonian [L. Lang and F. Neese, J. Chem. Phys. 150, 104104 (2019)]. The multipartitioning idea allows the use of state-specific 0th order Hamiltonians in a multistate framework and could therefore alleviate the mentioned problem. However, the effective Hamiltonian is non-Hermitian in the traditional formulation of multipartitioning, which can lead to unphysical behavior, especially for nearly degenerate states. In order to achieve a more balanced treatment of states with different physical character and at the same time have a Hermitian effective Hamiltonian, we combine in this work multipartitioning with canonical Van Vleck perturbation theory. At the 2nd order, the result is a Hermitian variant of multipartitioning quasidegenerate N-electron valence state perturbation theory. The effect of model space noninvariance of the method is discussed and the benefit of a Hermitian formulation is highlighted with numerical examples. The method is shown to give good results for the calculation of electronic transitions of the [CuCl4]2 -complex and for the calculation of electron paramagnetic resonance parameters, which are two examples where the balance between ligand field and charge transfer configurations is of utmost importance.