Acceptor Species Research Articles

Mechanistic insights into uptake, transfer and exchange of metal ions by the three-metal clusters of a metalloprotein.

Metallothioneins (MTs) are small proteins that coordinate d-block metal ions in sulfur-metal clusters to control metal ion concentrations within the cell. Here we study metal cluster formation in the MT of the periwinkle Littorina littorea (LlMT) by nuclear magnetic resonance (NMR). We demonstrate that the three Cd2+ ions in each domain are taken up highly cooperatively, that is, in an all-or-none fashion, with a four- to six-fold higher affinity for the C-terminal domain. During the transfer of metal ions from Cd2+-loaded MT to apo MT, Cd2+ is most efficiently transferred from the metalated protein to the apo C-terminal domain. This behavior might be connected to unique structural motifs in the C-terminal domain, such as two double-CXC motifs and an increased proportion of positively charged residues. In Cd2+/Zn2+ metal exchange experiments, the N-terminal domain displayed the most efficient inter-molecular metal exchange. Amide hydrogen exchange reveals fewer protected amides for the N-terminal domain, suggesting the structure might more easily "open up" to facilitate metal exchange. Experiments with a physical separation of donor and acceptor species demonstrate that metal exchange and transfer require protein-protein contacts. These findings provide insights into the mechanism of metal uptake and metal transfer, which are important processes during metal detoxification in snail MTs.

Layered sodium manganese oxides for toxic nitrogen dioxide gas removal in ambient conditions

In this study, Na0.7MnO2 samples were successfully synthesized using a solid-state synthesis route with Na and Mn acetate precursors. The resulting Na0.7MnO2 crystallized in a hexagonal lattice with space group P63/mmc. These materials were investigated for their capacity to adsorb 100 ppm of NO2 gas at room temperature. Na0.7MnO2 exhibited an exceptional NO2 adsorption capacity of 163.3 mg/g, surpassing many previously reported porous and non-porous materials. Comprehensive experimental and spectroscopic analyses confirmed the formation of NO, NO2–, and NO3– species, following NO2 adsorption on the Na0.7MnO2 surface. Theoretical calculations further supported the chemisorption of NO2 gas molecules on the Na0.7MnO2 surface, with a maximum adsorption energy of –1.937 eV. Spectroscopic and Bader charge analyses confirmed that the NO2 gas molecule acted as a charge acceptor species on the oxide surface. This work represents the first detailed study validating Na0.7MnO2 as an effective room-temperature adsorbent for capturing and mineralizing NO2 gas. The exceptional NO2 adsorption capacity and the mechanistic insights into the adsorption process suggest the promising potential of Na0.7MnO2 and related oxides for applications in NO2 gas capture and conversion.

Unexpected enhancement effects of phosphate on co-immobilization of uranyl arsenate under acidic conditions

Understanding the formation of uranyl-arsenate compounds (M(UO2)2(AsO4)2·nH2O, M represents divalent metallic cations) is of great importance in controlling the mobility and fate of uranium (U) and arsenic (As) in the natural environment. Phosphate is a ubiquitous coexisting ion with properties similar to arsenate and can complex with uranyl to form uranyl phosphate compounds, thus potentially affecting the formation of uranyl-arsenate compounds. Herein, the effect of phosphate, on the immobilization of uranyl, arsenate and divalent metallic cations (e.g., Fe2+, Mg2+, Ni2+, Cu2+) was explored. Surprisingly, the presence of phosphate promoted the immobilization of uranyl arsenate with the divalent metallic cations under acidic conditions. For example, at pH 3.0, the immobilization efficiency of uranyl and arsenate in the uranyl-arsenate-Fe2+ system increased from 20.6 % and 18.6 % to 82.6 % and 52.2 %, respectively. Moreover, the chemical stability of the formed uranyl arsenate-bearing compounds in the presence of phosphate is significantly improved, and the TCLP leachability of As and U decreased by 81 % and 97 %, respectively. The experimental results illustrated that with PO43- served as a proton acceptor, uranyl and arsenate species were changed and more metallic cations participate in immobilization. Gibbs free energy and Gibbs free energies change also illustrated that the formation of Fe(UO2)2(AsO4)2·5H2O was relatively thermodynamically favorable in the presence of phosphate. The results of thermodynamic calculations could account for the enhancement effects of phosphate on immobilization of uranyl arsenate. The findings have important implications for the mobility and fate of U and As and the solution of their co-contamination, especially in acidic environments.

Using Adiabatic Energy Splitting To Compute Dexter Energy Transfer Couplings.

Dexter energy transfer and transport (DET) are of broad interest in energy science, and DET rates depend on electronic couplings between donor and acceptor species. DET couplings are challenging to compute since they originate from both one- and two-particle interactions, and the strength of this interaction drops approximately exponentially with donor-acceptor distances. Using adiabatic energy splitting to compute DET couplings has advantages because adiabatic states can be calculated directly using conventional quantum chemical methods. We describe a minimum energy splitting method to compute the DET coupling by altering molecular geometries to drive the systems into a T1/T2 energy quasi-degenerate-activated DA complex. We explore the accuracy of various quantum chemical approaches to calculate the Dexter couplings.

Reabsorption‐Free Scintillating Hetero‐Ligand MOF Crystals Activated by Ultrafast Energy Transfer

AbstractFast photoluminescence and scintillation with a Stokes shift larger than 1 eV is achieved in hetero‐ligand metal–organic framework (MOF) crystals comprising inorganic linking nodes and fluorescent conjugated ligands. By finely engineering the MOF composition with the use of ligands with strictly complementary emission and absorption properties and highly delocalized molecular electronic orbitals, the singlet excitons diffusion is enhanced through the ligand framework, fully exploiting both Förster and Dexter energy transfer mechanisms. This allows for the sensitization of energy acceptor ligand fluorescence by ultrafast non‐radiative energy transfer with a rate up to the THz range. This efficient antenna effect instantly activates the MOF scintillation with a Stokes shift as large as 1.3 eV in the blue spectral range, matching the highest sensitivity spectral window of the best photodetector available. This is obtained using a minimal doping level of the energy acceptor species, with a consequent elimination of emission re‐absorption that allows the achievement of a 500% increment of the MOFs scintillation efficiency and the detection of the radioactive krypton isotope 85Kr from the gas phase with an improved sensitivity compared with the reference material.

Enhancing predictive modeling of photovoltaic materials’ solar power conversion efficiency using explainable AI

We present a study on Explainable AI-based prediction of power conversion efficiency (PCE) of organic solar cells, conducted on a dataset of 566 small-molecule organic solar cell materials samples with varying donor and acceptor species combinations. This research uncovers an interesting phenomenon, the first of its kind to be reported, of PCE quantization, where the PCE values increase in steps with the increase in feature values. Our findings have significant implications for the development of efficient organic solar cells, as they provide a better understanding of the factors that influence PCE, and highlight the feature value ranges for which more efficient PCE would be achieved. Our study demonstrates the power of XAI techniques in uncovering hidden patterns in scientific datasets and highlights the importance of interdisciplinary research in the field of materials science.

Trap or Triplet? Excited-State Interactions in 2D Perovskite Colloids with Chromophoric Cations.

Movement of energy within light-harvesting assemblies is typically carried out with separately synthesized donor and acceptor species, which are then brought together to induce an interaction. Recently, two-dimensional (2D) lead halide perovskites have gained interest for their ability to accommodate and assemble chromophoric molecules within their lattice, creating hybrid organic-inorganic compositions. Using a combination of steady-state and time-resolved absorption and emission spectroscopy, we have now succeeded in establishing the competition between energy transfer and charge trapping in 2D halide perovskite colloids containing naphthalene-derived cations (i.e., NEA2PbX4, where NEA = naphthylethylamine). The presence of room-temperature triplet emission from the naphthalene moiety depends on the ratio of bromide to iodide in the lead halide sublattice (i.e., x in NEA2Pb(Br1-xIx)4), with only bromide-rich compositions showing sensitized emission. Photoluminescence lifetime measurements of the sensitized naphthalene reveal the formation of the naphthalene triplet excimer at room temperature. From transient absorption measurements, we find the rate constant of triplet energy transfer (kEnT) to be on the order of ∼109 s-1. At low temperatures (77 K) a new broad emission feature arising from trap states is observed in all samples ranging from pure bromide to pure iodide composition. These results reveal the interplay between sensitized triplet energy transfer and charge trapping in 2D lead halide perovskites, highlighting the need to carefully parse contributions from competing de-excitation pathways for optoelectronic applications.

Simulating excited-state complex ensembles: Fluorescence and solvatochromism in amine-arene exciplexes.

Exciplexes are excited-state complexes formed as a result of partial charge transfer from the donor to the acceptor species when one moiety of the donor-acceptor pair is electronically excited. The arene-amine exciplex formed between oligo-(p-phenylene) (OPP) and triethylamine (TEA) is of interest in the catalytic photoreduction of CO2 because it can compete with complete electron transfer to the OPP catalyst. Therefore, formation of the exciplex can hinder the generation of a radical anion OPP·- necessary for subsequent CO2 reduction. We report an implementation of a workflow automating quantum-chemistry calculations that generate and characterize an ensemble of structures to represent this exciplex state. We use FireWorks, Pymatgen, and Custodian Python packages for high-throughput ensemble generation. The workflow includes time-dependent density functional theory optimization, verification of excited-state minima, and exciplex characterization with natural transition orbitals, exciton analysis, excited-state Mulliken charges, and energy decomposition analysis. Fluorescence spectra computed for these ensembles using Boltzmann-weighted contributions of each structure agree better with experiment than our previous calculations based on a single representative exciplex structure [Kron et al., J. Phys. Chem. A 126, 2319-2329 (2022)]. The ensemble description of the exciplex state also reproduces an experimentally observed red shift of the emission spectrum of [OPP-4-TEA]* relative to [OPP-3-TEA]*. The workflow developed here streamlines otherwise labor-intensive calculations that would require significant user involvement and intervention.

Gold nanoparticles modified reduced graphene oxide nanosheets based dual-quencher for highly sensitive detection of carcinoembryonic antigen

In the current scenario, the dominance of cancer is becoming a disastrous threat to mankind. Therefore, an advanced analytical approach is desired as the need of the hour for early diagnosis to curb the menace of cancer. In this context, the present work reports the development of nano surface energy transfer (NSET) based fluorescent immunosensor for carcinoembryonic antigen (CEA) detection utilizing protein functionalized graphene quantum dots (anti-CEA/amine-GQDs) and a nanocomposite of nanostructured gold and reduced graphene oxide (AuNPs@rGO) as energy donor-acceptor pair, respectively. The obtained AuNPs@rGO nanocomposite has been characterized by different advanced analytical techniques. The functionality of the biosensor depends on quenching the fluorescence of anti-CEA/amine-GQDs donor species by AuNPs@rGO acceptor species, followed by the gradual recovery of GQDs' fluorescence after CEA addition. The efficient energy transfer kinetics have been envisaged by utilizing the AuNPs@rGO nanocomposite as a dual-quencher nanoprobe that revealed improved energy transfer and quenching efficiency (∼62 %, 88 %) compared to AuNPs (∼43 %, 81 %) as a single quencher. Further, the developed biosensing platform successfully detected CEA biomarker with notable biosensing parameters, including a wider linear detection range (0.001–500 ng mL−1), fast response time (24 min), and a significantly low detection limit (0.35 pg mL−1).

Direct Observation of Group-V Dopant Substitutional Defects in CdTe Single Crystals.

Point defect chemistry strongly affects the fundamental properties of materials and has a decisive impact on device performance. The Group-V dopant is prominent acceptor species with high hole concentration in CdTe; however, its local atomic structure is still not clear owing to difficulties in definitive measurements and discrepancies between experimental observations and theoretical models. Herein, we report on direct observation of the local structure for the As dopant in CdTe single crystals by the X-ray fluorescence holography (XFH) technique, which is a powerful tool to visualize three-dimensional atomic configurations around a specific element. The XFH result shows the As substituting on both Cd (AsCd) and Te (AsTe) sites. Although AsTe has been well known as a shallow acceptor, AsCd has not attracted much attention and been discussed so far. Our results provide new insights into point defects by expanding the experimental XFH study in combination with theoretical first-principles studies in II-VI semiconductors.

On the enhanced performance of Pt-based high-entropy alloys catalyst during water–gas shift reaction: A density functional theory study

Electricity production from clean energy sources has gained attention during these decades. However, many power plants worldwide still use coal and natural gas as raw materials, which generates toxic gases, especially CO and CO2. To deal with this problem, transforming generated CO into another useful precursor before supplying it to the chemical process is a good idea. One of the most effective approaches is WGSR using a highly effective catalyst. In this work, we elucidate the insight information of PtPdRhFeCo HEA(111) surface improving the catalytic efficiency of Pt(111) surface. Interestingly, the homogenous form of electron distribution along Pt(111) surface is changed to heterogeneous forms creating unique electronic properties in which the electron donor and acceptor species exist simultaneously. The weakening interaction of CO corresponding to the strengthening interaction of CO2 on HEA(111) surface are advantages to preventing CO poison and trapping the CO2 after the WGSR. Moreover, the HEA(111) surface can thermodynamically promote the dissociation of H2O in pre-WGSR, creating active species of H*, O*, and OH* supplying to further the WGSR process. Nevertheless, consideration of PES along WGSR demonstrates that all possible pathways, including carboxyl, redox, and formate pathways along HEA(111) surface, are significantly improved by enhancing the thermodynamic driving force producing CO2.

Synthesis of the Branched Tetrasaccharide Fragment of Saccharomicin A.

A synthesis of the branched tetrasaccharide fragment of saccharomicin A using 1-OTBS donors to stereoselectively synthesize both α- and β-linked disaccharides is reported. The disaccharides were united using BSP/Tf2O to afford the tetrasaccharide fragment as a single α-anomer in 72% yield. This branched tetrasaccharide fragment can be used as donor and acceptor species to synthesize larger fragments of saccharomicin A.

Phase behavior of π-conjugated polymer and non-fullerene acceptor (PTB7-Th:ITIC) solutions and blends

Phase diagrams of ternary π-bonded polymer (PTB7-Th) solutions were constructed as a function of molecular weight, temperature, and electron acceptor species (ITIC, PC61BM and PC71BM). For this purpose, the Flory–Huggins lattice theory was employed with a constant χ interaction parameter, describing a binodal, spinodal, tie line, and critical point. Then, the morphologies of the blends composed of highly disordered PTB7-Th and crystallizable ITIC were investigated by atomic force microscopy. Subsequently, the surface polarities of the PTB7-Th:ITIC thin films were examined by water contact-angle goniometer, exhibiting a transition at the composition of ~ 60 ± 10 wt.% ITIC. Furthermore, X-ray diffraction indicated the presence of ITIC’s crystallites at ≥ 70 wt.% ITIC. Hence, the PTB7-Th:ITIC system was observed to undergo a phase transition at ~ 60–70 wt.% ITIC.

Evaluation of most efficient redox couple based on compatibility of donor–acceptor in photogalvanic cell for simultaneous solar power conversion and storage

• To evaluate the most efficient redox (dye-reductant combination) couple based on compatibility of electron donor (reductant) and acceptor (dye) species for the PG cell. • The photogalvanic study for four (BCB-fructose, BCB-AA, MB-fructose and MB-AA) redox systems has been done, simultaneously. The order for redox couple based on electrical output is: MB-AA > MB-fructose > BCB-AA > BCB-fructose. • The electrical output is high when MB is used as a photosensitizer with both fructose and AA. It may be because of the larger λ max and the low molecular weight of MB than BCB. • The literature photogalvanic data for the different dye-AA systems clearly indicate that the electrical output has a lower than MB-AA redox couple of present study. • Thus, for the PG cell, the MB-AA redox couple has highest compatibility for electron acceptor and donor out of four redox systems. There are several devices for direct conversion of solar energy to electric energy, but, all have zero storage capacity. Photogalvanic cell (PG) has both properties to convert and store (chemical form) the solar energy. Therefore, the PG cells may be playing a very important role to fulfill energy demand in the future. Here, our aim is to evaluate the most efficient redox (dye-reductant combination) couple based on the compatibility of the donor (reductant) and acceptor (dye) species for the PG cell. For this, we have completed photogalvanics (measurement and calculation of different electrical parameters of each cell) for brilliant cresyl blue (BCB) or methylene blue (MB)-fructose/ascorbic acid (AA) redox couple for solar power conversion and storage. Here, MB/BCB and fructose/AA have been used as photosensitizers and reductants, respectively. Results show the order for redox couple based on electrical output is: MB-AA > MB-fructose > BCB-AA > BCB-fructose. The electrical output is high when MB is used as a photosensitizer with both fructose and AA. It may be because of the larger λ max and the low molecular weight of MB than BCB. Indeed, the generation of electricity in the PG cell is the outcome of the diffusion process of molecules or ions in an electrolytic solution. The results reported in the literature for the different dye-AA systems of the PG cells clearly indicate that the electrical output of every system has a lower value as compared to the MB-AA redox couple of present study. Hence, MB-AA is the most efficient and stable system out of the four redox couples. Thus, the dye and reductant having structures like MB and AA are more compatible for electron acceptor and donor power in the PG cell for simultaneous solar power conversion and storage in the PG cell.

Modulating Supramolecular Charge-Transfer Interactions in the Solid State using Compressible Macrocyclic Hosts.

Modulating intermolecular charge-transfer (ICT) interactions between specific donor and acceptor species in host-guest systems is a big challenge and full of research value in supramolecular chemistry and materials science. In this work, a strategy to modulate the supramolecular ICT interactions in the solid state is developed by compressing the binding cavity of a macrocyclic host named perethylated leaning pillar[6]arene (p-EtLP6). The solid-state ICT affinities of p-EtLP6 toward multi-types of electron-deficient planar guests could be significantly enhanced by transforming the macrocyclic backbone from the original para-bridged mode into a hybrid para- and meta-bridged isomeric form (m-EtLP6). X-ray single-crystal structural analyses incorporating theoretical calculation demonstrate that the improved ICT affinities are mainly attributed to the superior host-guest size fit arising from the compressed binding cavity in m-EtLP6 as compared with p-EtLP6.

Modulating Supramolecular Charge‐Transfer Interactions in the Solid State using Compressible Macrocyclic Hosts

AbstractModulating intermolecular charge‐transfer (ICT) interactions between specific donor and acceptor species in host–guest systems is a big challenge and full of research value in supramolecular chemistry and materials science. In this work, a strategy to modulate the supramolecular ICT interactions in the solid state is developed by compressing the binding cavity of a macrocyclic host named perethylated leaning pillar[6]arene (p‐EtLP6). The solid‐state ICT affinities ofp‐EtLP6toward multi‐types of electron‐deficient planar guests could be significantly enhanced by transforming the macrocyclic backbone from the originalpara‐bridged mode into a hybridpara‐ andmeta‐bridged isomeric form (m‐EtLP6). X‐ray single‐crystal structural analyses incorporating theoretical calculation demonstrate that the improved ICT affinities are mainly attributed to the superior host–guest size fit arising from the compressed binding cavity inm‐EtLP6as compared withp‐EtLP6.

Design of highly stable thermally activated delayed fluorescence emitters via the overlap degree of HOMO-LUMO distributions

Two questions including the judgement of thermally activated delayed fluorescence (TADF) property and high stability are crucial for designing TADF emitters. In this work, based on the experimental TADF emitters, we investigated the essential reason of improving the stability of TADF device by introducing tert-butyl and phenyl into the peripheral position of carbazole, and suggested to judge the TADF property via the concrete HOMO-LUMO overlap calculation. To design highly stable TADF emitters, several pairs of positional isomers combining tert-Butyl-substituted carbazole as donor with different acceptors are designed by connecting the donor and acceptor groups through the orth-, meta- and para-position. Via the HOMO-LUMO overlap calculation, the potential TADF emitters have been point out. Our results find that the HOMO-LUMO overlap values are dependent on the linkage styles and acceptor species. For example, the designed molecules m-Cz-BF/BF-Cz/NOBF2-DTCz/CPS, o-CNImPy-Cz/PQM-Cz, and m-, p-Cz-NAI have the potential to perform better TADF performance than other isomers. These results indicate that the HOMO-LUMO overlap could be used to identify synthetic motifs for promising TADF candidates among structural isomers.

Influence of the pH of anthocyanins on the efficiency of dye sensitized solar cells

The influence of the pH of anthocyanins on photovoltaic performance in dye-sensitized solar cells has been investigated. Anthocyanins were extracted from crushed leaf stocks of Manihot esculenta Crantz (Cassava plant) using methanol acidified with 0.5% trifluoracetic acid. The filtrate was concentrated using a rotary evaporator and partitioned against ethyl acetate. The anode was prepared by screen printing TiO2 paste on a previously cleaned fluorine-doped tin oxide (FTO) glass substrate. The cathode was made by applying plastisol on a previously cleaned FTO glass substrate using an artistic brush and later annealed at 450 °C for 20 min to activate platinum. The performance of the solar cells was measured using a solar simulator fitted with an AM1.5 air filter. Electron transport was studied using electrochemical impedance spectroscopy (EIS). It was observed that the short circuit current and efficiency dropped from pH 2 to pH 6 and peaked at pH 8, with values of 0.399 mA and 0.390%, respectively. It then drops further as the basicity increases. The open circuit voltage was observed to increase consistently from pH 2 to pH 12. EIS results showed that the electron density in the conduction band of TiO2 increases from pH 2 to pH 10 and drops from pH 10 to pH 12. It was concluded that, while a large number of electrons (∼1016m−3) are injected into the conduction band of TiO2, the majority do not contribute to the current but instead recombine with other electron acceptor species in the solar cell. However, the injected electrons cause an upwards shift in the quasi-Fermi level of electrons in the conduction band of TiO2. This explains the large variation in the open circuit voltage compared to the short circuit current.

Deep eutectic solvent (DES) based dispersive Liquid-Phase microextraction of Sunset yellow FCF in food and pharmaceutical products

In this study, a new, sensitive, rapid, simple, cheap, readily available, and rather safe dispersive liquid–liquid microextraction method (DLLME) utilizing a deep eutectic solvent (DES) as the green extraction solvent was developed for the extraction and determination of sunset yellow forColoringFood (FCF), in drugs, vitamins, beverage, foods, and environmental samples. The method is based on the deep eutectic solvent system containing a kind of cationic and anionic (hydrogen bond donor/ hydrogen bond acceptor) species. For this purpose, decanoic acid and tetrabutylammonium bromide (molar ratio of 2:1) were used to obtain a deep eutectic solvent. Sunset yellow FCF is analyzed with a UV–Vis spectrophotometer after ultrasonication-assisted dispersive liquid-phase microextraction procedure. The essential operational parameters such as pH, DES volume, THF volume and sample volume were found 2.0, 200, 400 μL and 20 mL, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were found at pH 2.0 as 0.05 μg L−1 and 0.17 μg L−1, respectively. The enrichment technique was validated by using addition/recovery studies and applied to the determination of analyte content of various drugs, vitamins, beverages, foods, and environmental samples.

Facile synthesis of CaMn1-xFexO3 to incorporate Fe(IV) at high ratio in perovskite structure for efficient in situ adsorption-oxidation of As(III)

Soluble Fe(IV) has been proposed as primary reactive species in advanced oxidation technology, however, Fe(IV) in solid-state oxidant is rarely reported. This study reports a facile synthesis of CaMn1-xFexO3 (0.1 ≤ x ≤ 0.7) containing high ratio of Fe(IV) by low-temperature calcination of the ball milling precursor and evaluates its adsorption-oxidation performances of As(III). Although Fe(IV) and Mn(IV) inside CaMn1-xFexO3 both act as electron acceptor species, with × for Fe ratio increased, charge transport capability and oxidation performance of As(III) to As(V) of the CaMn1-xFexO3 materials can be raised dramatically with more iron incorporated. With sample CaMn0.3Fe0.7O3, the maximal adsorption capacity for As(III) reaches 120.78 mg/g with the ratio of oxidized As(V) as high as 86.4% in a wide pH range of 2 ∼ 10. More importantly, excellent cyclability and stability are observed and 83% of the initial adsorption-oxidation capacity still retains even after 5 cycles, and leaching concentrations of the metal ions (Fe/Mn) are far below the emission standard (0.5 mg/L). With an aid of environment-friendly ball milling process, the idea to obtain high valent Fe by a simple incorporation into a specific crystalline structure of perovskite offers a new approach for synthesizing active oxidizing species of Fe(IV). Further, the synthesis of solid oxidants would transform the redox reactions from a liquid phase reaction process to a solid–liquid reaction process, which could be conducive to the occurrence of in-situ oxidation and fixation of pollutants to reduce their mobility, and much contribution is expected to the development of advanced oxidization process in wastewater treatment using the easy handling solid-state oxidants.