Charge Shift Research Articles

Label-free detection of Cu(II) in fish using a graphene field-effect transistor gated by structure-switching aptamer probes

Copper sulfate is a widely used agent to control insects, bacteria and algae for fishery. However, excess amount of copper ions in water accumulate in aquatic products through the ecological cycle system, highly threatening food safety and public health. Therefore, it is urgent to develop a rapid and efficient method for the determination of copper content in aquatic products. In this study, we developed a label-free biosensor for Cu(II) based on a graphene field-effect transistor gated by structure-switching aptamer probes (SSA-GFET) against Cu(II) we obtained before. The detection mechanism of the biosensor is attributed to the surface charge shift and the potential change of the gate electrode upon the specific binding of Cu(II). The SSA-GFET biosensor has a low detection limit of 10 nM and a linear range of 10 nM to 3 μM to Cu(II). In addition to the excellent selectivity to Cu(II), the biosensor also showes the advantage of high recovery rate for detection of Cu(II) in real fish samples. Because of the detection characteristics of label-free SSA-GFET, it has great advantages in the field of food safety and environmental detection.

New insights for improving ilmenite flotation via surface modification with lead ions

In order to further investigate the mechanism of lead ions in activation ilmenite flotation, the adsorption behaviour of lead ions on ilmenite surface was deeply illustrated using the combination of adsorption amount, zeta potential, inductively coupled plasma mass spectrometry (ICP), energy-dispersive X-ray spectroscopy Mapping (EDS-Mapping), and X-ray photoelectron spectroscopy (XPS) in this study. The results revealed that lead ions activated the ilmenite flotation by promoting the adsorption of sodium oleate. This promotion impact could be attributed to the positive shift of surface charge and the increase in surface active sites after lead adsorption. The changes transferred the adsorption mode of sodium oleate on ilmenite surface into electrostatic adsorption and chemisorption involving double active site (Pb, Fe). The Pb(OH)+ was certified as the main active species on activating ilmenite flotation through the analysis of lead adsorption amounts and solution chemistry. Furthermore, the EDS-Mapping and XPS high-resolution spectra analysis evidenced that the Pb(OH)+ adsorbed onto the surface sites of O, Fe, and Ti on ilmenite surface by resorting the bridging action of the O atom.

Intramolecular photo-driven charge transfer in a series of pyridyl substituted phenyloxazoles. Structural relaxation in meta-substituted ethylpyridinium derivative of phenyloxazole.

A series of pyridyl (pyridinium) substituted benzoxazoles were studied by steady state absorption, fluorescence spectroscopy, time-resolved fluorescence spectroscopy, fs pulse absorption and polarization spectroscopy, and quantum-chemical calculations. The spectral and kinetic parameters of the fluorophores in MeCN and EtOAc were obtained experimentally and were calculated by means of DFT and TDDFT methods. A scheme including four transient excited states was proposed for the interpretation of differential absorption kinetics of the charged fluorophores. Expressions describing the actual kinetics graphs, the decay associated spectra, and the species-associated spectra were derived. The charge shift step was found to be dependent on average solvation times. A charge shift followed by the formation of the twisted conformer was found for the excited 1-ethyl-3-(5-phenyloxazol-2-yl)pyridinium 4-methyl-1-benzenesulfonate in MeCN and EtOAc. Conformational analysis confirms a large amplitude motion of the meta-substituted ethylpyridinium group as an additional structural relaxation path producing an abnormally large fluorescence Stokes shift.

Theoretical investigation of nonlinear optical behavior for rod and T-Shaped phenothiazine based D-π-A organic compounds and their derivatives

The exploration of novel materials with excellent nonlinear optical (NLO) features is an area of frontline investigation for scientific community from technological point of view. This study reports the novel phenothiazine-based rod-shaped and T-shaped NLO molecules which are quantum chemically designed from synthesized compounds: rod-shaped (CFA and CBA) and T-shaped (CTA, CCA and CPA). Structural tailoring was performed on D-π-π-A centered CPA chromophore and the effect of various π-spacers, as well as solvents on NLO response properties is investigated. Density functional theory (DFT) along with time dependent DFT (TDDFT) calculations have been executed at B3LYP/6-311G(d,p) functional to examine entire analysis. Results showed a smaller energy gap in structurally modified compounds as compared to reference CPA. Global reactivity parameters analysis revealed smaller hardness and larger softness values in T-shaped compounds. UV–Vis analysis of investigated molecules displayed a red shift in absorption maximum value as compared to CPA. Natural bond orbital (NBO) and frontier molecular orbital (FMO) analysis revealed the stability and intra-molecular electron transferring (ICT) process in investigated molecules. ICT showed the effective charge shift from donor to acceptor via π-spacers. Overall, promising NLO response exists in gas phase and different solvents (acetonitrile, ethyl alcohol and water). Interestingly, proposed molecule CPP presented a maximum value of linear polarizability < α > as 1518.23 a.u and first hyperpolarizability (βtot) as 755322.39 a.u in acetonitrile solvent. In short, entitled chromophores exhibited excellent NLO properties due to their lower charge transport resistance. This NLO study may open a new topic for researchers to discover novel NLO for hi-tech submissions of modern era.

Classification of So-Called Non-Covalent Interactions Based on VSEPR Model.

The variety of interactions have been analyzed in numerous studies. They are often compared with the hydrogen bond that is crucial in numerous chemical and biological processes. One can mention such interactions as the halogen bond, pnicogen bond, and others that may be classified as σ-hole bonds. However, not only σ-holes may act as Lewis acid centers. Numerous species are characterized by the occurrence of π-holes, which also may play a role of the electron acceptor. The situation is complicated since numerous interactions, such as the pnicogen bond or the chalcogen bond, for example, may be classified as a σ-hole bond or π-hole bond; it ultimately depends on the configuration at the Lewis acid centre. The disadvantage of classifications of interactions is also connected with their names, derived from the names of groups such as halogen and tetrel bonds or from single elements such as hydrogen and carbon bonds. The chaos is aggravated by the properties of elements. For example, a hydrogen atom can act as the Lewis acid or as the Lewis base site if it is positively or negatively charged, respectively. Hence names of the corresponding interactions occur in literature, namely hydrogen bonds and hydride bonds. There are other numerous disadvantages connected with classifications and names of interactions; these are discussed in this study. Several studies show that the majority of interactions are ruled by the same mechanisms related to the electron charge shifts, and that the occurrence of numerous interactions leads to specific changes in geometries of interacting species. These changes follow the rules of the valence-shell electron-pair repulsion model (VSEPR). That is why the simple classification of interactions based on VSEPR is proposed here. This classification is still open since numerous processes and interactions not discussed in this study may be included within it.

Solar Energy Conversion Schemes: Photon- and Charge-Management

In Nature, energy and electron transfer processes in the photosynthetic machinery following light absorption have been perfectionated. To mimic the aforementioned, that is, efficiently utilizing light to separate charges and, in turn, to generate solar fuels, a great variety of multicomponent artificial photosynthetic systems have been designed and synthesized. Incentives for the design build around molecules have been taken from Nature: For example, implementing suitable electrochemical gradients across arrays of several molecular building blocks have enabled the unidirectional transformation of solar energy into electrical energy. A key parameter is the right balance between the reduction / oxidation strengths of the individual building blocks and their spatial arrangements. Both affect the thermodynamic driving forces for each step and, in turn, the overall efficiency. Notably, acceptor-donor1-donor2 or acceptor-donor1-donor2-donor3 types of artificial photosynthetic systems have been reported. Besides an initial charge transfer, charge shifts take place via oxidative electron transfers from donor1 to donor2 and, eventually, to donor3.Considering the effectiveness of multicomponent systems, in which photoexcitation triggers a cascade of short range electron transfers, we report on two sets of novel multicomponent DA1A2s – Figure 2. These DA1A2 types feature electron transport chains with C60 and C70 of different electron acceptor strengths to create an electrochemical gradient. As a complement to electron accepting C60 / C70 either zinc porphyrins (ZnP) and zinc phthalocyanines (ZnPc) were employed. The motivation for our pump-probe investigations was to establish the role of ZnPc or ZnP as light harvester and electron donor to power unidirectional (reductive) charge shift reactions along a variety of electron transport chains.In summary, we will demonstrate the control over unidirectional charge shift along electron transport chains en route towards highly energetic, long-lived charge separated states. Key is, however, a charge shift mediating state, whose relative energy determines the overall efficiency. If the energy of the mediating state, on one hand, is higher than the charge separated state, resonance conditions enable efficiencies as high as 50%. If the energy, on the other hand, is lower than the charge separated state, deactivation to the ground state limits the efficiency to 10%.

Reactivity of Li+@C60@C240 and Photoinduced Charge Shift in Li+ Doped Giant Nested Fullerenes

Over the last years, carbon nano-onions (CNOs) have been in focus in material science research. Apart from its prospective use in solar cells, the number of potential applications of CNOs have grown in the last decades. Among them, we can mention their application in gas storage processes, solid lubrication, or heterogeneous catalysis, and also as electrode materials in capacitors, anode materials in lithium-ion batteries, catalyst support in fuel cells, or electro-optical devices. From the analysis of the polarizability of CNOs, it was concluded that CNOs behave as near perfect nanoscopic Faraday cages.[1] If CNOs behave as ideal Faraday cages, the reactivity of the C240 cage should be the same in Li+@C240 and Li+@C60@C240. In the first part of this work, we have analyzed the Diels-Alder reaction of cyclopentadiene to the free C240 cage and the C60@C240 CNO together with their Li+-doped counterparts using density functional theory (DFT). We find that in all cases the preferred cycloaddition is on bond [6,6] of type B of the C240 cage. From the comparison between the reactivity of Li+@C240 and Li+@C60@C240, we conclude that C60@C240 does not act as a perfect Faraday cage.[2] In the second part of this work, we perform a systematic study of excited state properties of six double-layered Li+ doped fullerenes of Ih symmetry: [Li@C60@C240]+, [Li@C60@C540]+, [Li@C60@C960]+, [Li@C240@C540]+, [Li@C240@C960]+ and [Li@C540@C960]+. On the basis of TDDFT calculations, we show that the long-wave absorption by the Li+ doped species leads to charge transfer (CT) between the inner and the outer shells unlike their neutral double-layered precursors. The CT energy depends strongly on the size of the concentric fullerenes and it can easily be tuned by varying both the encapsulated metal ion and the size of the shells. Two types of low-lying excited states are identified (1) capacitor-like structures, as Li+@C60 -@C240 +, with alternating positive and negative charges, and (2) states, where the positive charge is delocalized over the outer shell, as in Li@C240@C540 +.[3] References [1] R. R. Zope, J. Phys. B: At. Mol. Opt. Phys. 41 (2008) 41, 085101; [b] R. R. Zope, S. Bhusal, L. Basurto, T. Baruah and K. Jackson, J. Chem. Phys. 143 (2015) 084306.[2] A. J. Luque-Urrutia, A. Poater and M. Solà. Chem. Eur. J., 26 (2020) 804-808.[3] A. J. Stasyuk, O. A. Stasyuk, M. Solà and A. A. Voityuk. J. Phys. Chem. C 123 (2019) 16525-16532. Figure 1

Enhanced Antitumor Efficacy through an "AND gate" Reactive Oxygen-Species-Dependent pH-Responsive Nanomedicine Approach.

Anticancer drug delivery strategies are designed to take advantage of the differential chemical environment in solid tumors independently, or to high levels of reactive oxygen species (ROS) or to low pH, compared to healthy tissue. Here, the design and thorough characterization of two functionalizable "AND gate" multiresponsive (MR) block amphiphilic copolymers are reported, aimed to take full advantage of the coexistence of two chemical cues-ROS and low pH-present in the tumor microenvironment. The hydrophobic blocks contain masked pH-responsive side chains, which are exposed exclusively in response to ROS. Hence, the hydrophobic polymer side chains will undergo a charge shift in a very relevant pH window present in the extracellular milieu in most solid tumors (pH 5.6-7.2) after demasking by ROS. Doxorubicin (DOX)-loaded nanosized "AND gate" MR polymersomes (MRPs) are fabricated via microfluidic self-assembly. Chemical characterization reveals ROS-dependent pH sensitivity and accelerated DOX release under influence of both ROS and low pH. Treatment of tumor-bearing mice with DOX-loaded nonresponsive and "AND gate" MRPs dramatically decreases cardiac toxicity. The most optimal "AND gate" MRPs outperform free DOX in terms of tumor growth inhibition and survival, shedding light on chemical requirements for successful cancer nanomedicine.

Surface phase stability of surface segregated AgPd and AgCu nanoalloys in an oxygen atmosphere

The geometric structure of 38-atom AgPd and AgCu nanoalloys is obtained by the genetic algorithm and density functional theory for all compositions and their surface phase stability diagrams are established to provide a clear image for the initial oxidation process. Ag surface segregation is confirmed for both AgPd and AgCu nanoalloys in vacuum. Pure Pd and Cu nanoparticles have lower surface phase stability than bulk metals to be oxidized and the alloying can improve the oxidation resistance. Segregated AgCu nanoalloys have higher phase stability than mixed AgCu in vacuum and have lower surface phase stability than mixed AgCu nanoalloys in an oxygen atmosphere. Unexpectedly, segregated AgPd nanoalloys have both higher phase stability in vacuum and higher surface phase stability in an oxygen atmosphere than that of mixed AgPd nanoalloys. The higher surface phase stability of segregated AgPd nanoalloy could be attributed to the slight elevation of Pd Milliken charge and negative shift of d-band center. Compared with the selective oxidation in conventional alloy oxidation models where the selective oxidation is related to alloy composition, the nanoalloy oxidation is proposed to correlate with surface segregation in AgPd and AgCu nanoalloys in this work, which promotes the development of the conventional alloy oxidation models in that the surface segregation is a precursor to the surface oxidation of nanoalloy and plays a critical role in the selective oxidation of nanoalloy.

Screening Nanographene‐Mediated Inter(Porphyrin) Communication to Optimize Inter(Porphyrin–Fullerene) Forces

AbstractMultifunctional molecular materials comprising porphyrins and fullerenes have served as perfect prototypes to study key aspects of natural photosynthesis starting at light harvesting and energy transfer processes all the way to charge separation, charge shift, and charge recombination. Herein, hexa‐peri‐hexabenzocoronenes (HBCs) are explored, decorated with one, two, and six porphyrins at their peripheral positions, within the context of replicating key steps of photosynthesis. The major focus of the investigations is to screen inter(porphyrin) communications across the HBC platform as a function of the substitution pattern and to optimize the intermolecular forces with fullerenes. To this end, the ground‐ and excited‐state features are investigated in the absence of C60 and C70 by employing an arsenal of spectroscopic methods. Further insights into inter(porphyrin) communications come from time‐dependent density‐functional theory (TDDFT) calculations. In the presence of C60 and C70, X‐ray crystallography, steady‐state and time‐resolved spectroscopy, and mass spectrometry corroborate exceptionally strong inter(porphyrin–fullerene) interactions in the solid, liquid, and gas phases. The experiments are backed‐up with DFT calculations of the geometrically optimized and energetically stable complex configuration.

Sunlight driven photocatalytic degradation of organic pollutants using a MnV2O6/BiVO4 heterojunction: mechanistic perception and degradation pathways.

In the field of photocatalysis, fabrication of a heterojunction structure with effective charge separation at the interface and charge shift to enhance the photocatalytic activity has acquired extensive consideration. In the present investigation, MnV2O6/BiVO4 heterojunction samples with excellent photocatalytic performance under sunlight irradiation were conveniently synthesized by a hydrothermal technique, and characterized by UV-Vis, FTIR, XRD, FESEM, HRTEM, PL, BET and XPS techniques. The prepared samples were investigated as photocatalysts for degrading MB and RhB dyes under sunlight. Among various samples of MnV2O6/BiVO4, the S-V hetero-junction sample exhibited maximum photocatalytic activity with 98% and 96% degradation of MB and RhB dyes, respectively, in 6 and 35 min. The high photocatalytic activity of MnV2O6/BiVO4 may be due to the successful generation and shift of charges in the presence of visible light. The average reduction of chemical oxygen demand (COD) was found to be 75% after irradiation with direct sunlight. In the degradation process of dyes, superoxide anion radicals were the main responsive species, as revealed by trapping experiments. The degradation efficiency of MnV2O6/BiVO4 heterojunction did not diminish even after four cycles. In addition, the catalytic performance of the fabricated heterojunction was also explored for reducing 4-nitrophenols (4-NP) by using NaBH4. Absolute conversion of 4-NP to 4-aminophenol (4-AP) occurred without the production of intermediate byproducts.

Chromosomal Organization and Regulation of Genetic Function in Escherichia coli Integrates the DNA Analog and Digital Information.

In this article, we summarize our current understanding of the bacterial genetic regulation brought about by decades of studies using the Escherichia coli model. It became increasingly evident that the cellular genetic regulation system is organizationally closed, and a major challenge is to describe its circular operation in quantitative terms. We argue that integration of the DNA analog information (i.e., the probability distribution of the thermodynamic stability of base steps) and digital information (i.e., the probability distribution of unique triplets) in the genome provides a key to understanding the organizational logic of genetic control. During bacterial growth and adaptation, this integration is mediated by changes of DNA supercoiling contingent on environmentally induced shifts in intracellular ionic strength and energy charge. More specifically, coupling of dynamic alterations of the local intrinsic helical repeat in the structurally heterogeneous DNA polymer with structural-compositional changes of RNA polymerase holoenzyme emerges as a fundamental organizational principle of the genetic regulation system. We present a model of genetic regulation integrating the genomic pattern of DNA thermodynamic stability with the gene order and function along the chromosomal OriC-Ter axis, which acts as a principal coordinate system organizing the regulatory interactions in the genome.

First-principles identification of the charge-shifting mechanism and ferroelectricity in hybrid halide perovskites

Hybrid halide perovskite solar cells have recently attracted substantial attention, mainly because of their high power conversion efficiency. Among diverse variants, (CH3NH3)PbI3 and HC(NH2)2PbI3 are particularly promising candidates because their bandgap well matches the energy range of visible light. Here, we demonstrate that the large nonlinear photocurrent in β-(CH3NH3)PbI3 and α-HC(NH2)2PbI3 is mostly determined by the intrinsic electronic band properties near the Fermi level, rooted in the inorganic backbone, whereas the ferroelectric polarization of the hybrid halide perovskite is largely dominated by the ionic contribution of the molecular cation. The spatial charge shift upon excitation is attributed to the charge transfer from iodine to lead atoms in the backbone, which is independent of the presence of the cationic molecules. Our findings can serve as a guiding principle for the design of future materials for halide-perovskite solar cells with further enhanced photovoltaic performance.

How relevant is anisotropy in bimolecular electron transfer reactions in liquid crystals?

This work aims to describe anisotropy effects on chemical reactions imposed by the structure of liquid crystals. Photo-induced intermolecular electron transfer is studied by means of fluorescence quenching. The charge shift and charge separation reactions are investigated in two different chemical systems. Steady state and time resolved measurements are performed to track the reaction kinetics. In order to extract the electron transfer parameters which are independent of the solvent, the reactions are also conducted in isotropic media at different temperatures and viscosities. A set of diffusion-reaction models with different levels of anisotropy has been developed as well as a numerical method to solve the corresponding partial differential equations. Only the model which introduces anisotropic diffusion and reactivity gives physically meaningful values for all parameters entering the reactivity. It is therefore shown how to adapt diffusion-reaction models able to accommodate any sort of reactivity to complex environments.

Designing Cascades of Electron Transfer Processes in Multicomponent Graphene Conjugates.

A novel family of nanocarbon‐based materials was designed, synthesized, and probed within the context of charge‐transfer cascades. We integrated electron‐donating ferrocenes with light‐harvesting/electron‐donating (metallo)porphyrins and electron‐accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo‐p‐phenyleneethynylenes of variable lengths by β‐linkages and the Prato–Maggini reaction. With steady‐state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico‐chemical characterization of the photo‐ and redox‐active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond‐lived charge‐separated state featuring a GNP‐delocalized electron and a one‐electron oxidized ferrocenium.

Designing Cascades of Electron Transfer Processes in Multicomponent Graphene Conjugates

AbstractA novel family of nanocarbon‐based materials was designed, synthesized, and probed within the context of charge‐transfer cascades. We integrated electron‐donating ferrocenes with light‐harvesting/electron‐donating (metallo)porphyrins and electron‐accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo‐p‐phenyleneethynylenes of variable lengths by β‐linkages and the Prato–Maggini reaction. With steady‐state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico‐chemical characterization of the photo‐ and redox‐active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond‐lived charge‐separated state featuring a GNP‐delocalized electron and a one‐electron oxidized ferrocenium.

Modeling the Interface between Lithium Metal and Its Native Oxide.

Owing to their high theoretical capacities, batteries that employ lithium (Li) metal as the negative electrode are attractive technologies for next-generation energy storage. However, the successful implementation of lithium metal batteries is limited by several factors, many of which can be traced to an incomplete understanding of surface phenomena involving the Li anode. Here, first-principles calculations are used to characterize the native oxide layer on Li, including several properties associated with the Li/lithium oxide (Li2O) interface. Multiple interface models are examined; the models account for differing interface (chemical) terminations and degrees of atomic ordering (i.e., crystalline vs amorphous). The interfacial energy, formation energy, and strain energies are predicted for these models. The amorphous interface yields the lowest interfacial formation energy, suggesting that it is the most probable model under equilibrium conditions. The work of adhesion is evaluated for the crystalline interfaces, and it is found that the O-terminated interface exhibits a work of adhesion more than 30 times larger than that of the Li-terminated model, implying that Li will strongly wet an oxygen-rich Li2O surface. The electronic structure of the interfaces is characterized using Voronoi charge analysis and shifts in the Li 1s binding energies. The width of the Li/Li2O interface, as determined by deviations from bulklike charges and binding energies, extends beyond the region exhibiting interfacial structural distortions. Finally, the transport of Li ions through the amorphous oxide is quantified using ab initio molecular dynamics. Facile transport of Li+ through the native oxide is observed. Thus, increasing the percentage of amorphous Li2O in the solid electrolyte interphase may be beneficial for battery performance. In total, the phenomena quantified here will aid in the optimization of batteries that employ high-capacity Li metal anodes.

Quantum correction of the Wilson line and entanglement entropy in the pure AdS3 Einstein gravity theory

We calculate the expectation value of the Wilson line in the pure AdS3 Einstein gravity theory and also the entanglement entropy in the boundary theory. Our one-loop calculation of entanglement entropy shows a shift of the central charge 26. Finally, we show that the Wilson line provides the equivalent description to the boundary entanglement entropy. This equivalence leads to a concrete example of the building of “minimum surface=entanglement entropy”.

Solvent Dependence of Cationic-Exciplex Emission: Limitation of Solvent Polarity Functions and the Role of Hydrogen Bonding.

Conventional exciplexes are products of excited-state charge generation reactions between neutral reactants (e.g., A* + D → A•-D•+), whereas cationic exciplexes are products of charge shift reactions of cations with neutral donors (e.g., A+* + D → A•D•+). Compared herein is the solvent-dependent fluorescence of a cationic exciplex with extant data for conventional exciplexes. Although linear correlations of conventional exciplex emission maxima with the Lippert-Mataga solvent polarity function are well documented in low to moderate polarity solvents, the correlations are often poor in more polar solvents. A number of such plots in moderate to high polarity solvents show a strong curvature. Intriguingly, for these same cases, plots of emission maxima versus the solvent dielectric constant (ε) are remarkably linear. Interestingly, emission maxima for the cationic exciplex of 1+ in nitrile and alcohol solvents also correlate linearly with ε. The solvent dependency for cationic exciplex emission maxima on ε is ca 1/3 of that for conventional exciplexes, which is ascribed to solvent stabilization of both the excited state and the ground state for cationic exciplexes. Differences in exciplex emissions between nitrile and alcohol solvents for 1+ are attributed to hydrogen bonding, with larger differences in higher hydrogen-bond acidity solvents.

(Invited) Reactivity of Li+@C60@C240 and Photoinduced Charge Shift in Li+ Doped Giant Nested Fullerenes

Over the last years, carbon nano-onions (CNOs) have been in focus in material science research. Apart from its prospective use in solar cells, the number of potential applications of CNOs have grown in the last decades. Among them, we can mention their application in gas storage processes, solid lubrication, or heterogeneous catalysis, and also as electrode materials in capacitors, anode materials in lithium-ion batteries, catalyst support in fuel cells, or electro-optical devices. From the analysis of the polarizability of CNOs, it was concluded that CNOs behave as near perfect nanoscopic Faraday cages.[1] If CNOs behave as ideal Faraday cages, the reactivity of the C240 cage should be the same in Li+@C240 and Li+@C60@C240. In the first part of this work, we have analyzed the Diels-Alder reaction of cyclopentadiene to the free C240 cage and the C60@C240 CNO together with their Li+-doped counterparts using density functional theory. We find that in all cases the preferred cycloaddition is on bond [6,6] of type B of the C240 cage. From the comparison between the reactivity of Li+@C240 and Li+@C60@C240, we conclude that C60@C240 does not act as a perfect Faraday cage.[2] In the second part of this work, we perform a systematic study of excited state properties of six double-layered Li+ doped fullerenes of Ih symmetry: [Li@C60@C240]+, [Li@C60@C540]+, [Li@C60@C960]+, [Li@C240@C540]+, [Li@C240@C960]+ and [Li@C540@C960]+. On the basis of TDDFT calculations, we show that the long-wave absorption by the Li+ doped species leads to charge transfer (CT) between the inner and the outer shells unlike their neutral double-layered precursors. The CT energy depends strongly on the size of the concentric fullerenes and it can easily be tuned by varying both the encapsulated metal ion and the size of the shells. Two types of low-lying excited states are identified (1) capacitor-like structures, as Li+@C60 -@C240 +, with alternating positive and negative charges, and (2) states, where the positive charge is delocalized over the outer shell, as in Li@C240@C540 +.[3] References [1] R. R. Zope, J. Phys. B: At. Mol. Opt. Phys. 41 (2008) 41, 085101; [b] R. R. Zope, S. Bhusal, L. Basurto, T. Baruah and K. Jackson, J. Chem. Phys. 143 (2015) 084306.[2] A. J. Luque-Urrutia, A. Poater and M. Solà. Submitted for publication.[3] A. J. Stasyuk, O. A. Stasyuk, M. Solà and A. A. Voityuk. J. Phys. Chem. C 123 (2019) 16525-16532. Figure 1