Delocalization Of Charge Carriers Research Articles

Combination of Counterion Size and Doping Concentration Determines the Electronic and Thermoelectric Properties of Semiconducting Polymers.

In both chemical and electrochemical doping of organic semiconductors (OSCs), a counterion, either from the electrolyte or ionized dopant, balances the charge introduced to the OSC. Despite the large influence of this counterion on OSC optical and electronic response, there remains substantial debate on how a fundamental parameter, ion size, impacts these properties. This work resolves much of this debateby accounting for two doping regimes. In the low-doping regime, the Coulomb binding energies between charge carrierson the OSC and the counterions are significant, and larger counterions lead to decreased Coulomb interactions, more delocalized charge carriers, and higher electrical conductivities. In the high-doping regime, the Coulomb binding energies become negligible due to the increased dielectric constant of the films and a smoothing of the energy landscape; thereby, the electrical conductivities depend primarily on the extent of morphological disorder in the OSC. Moreover, in regioregular poly(3-hexylthiophene), rr-P3HT, smaller counterions lead to greater bipolaron concentrations in the low-doping regime due to the increased Coulomb interactions. Emphasizing the impact of the counterion size, it is shown that larger counterions can lead to increased thermoelectric power factors for rr-P3HT.

Giant excitonic magneto-optical Faraday rotation in single semimagnetic CdTe/Cd1-xMnxTe quantum ring

Magnetic tuning of the bound exciton states and corresponding giant Zeeman splitting (GZS) between σ+ and σ− excitonic transitions in CdTe/Cd1-xMnxTe quantum ring has been investigated in the Faraday configuration for various concentrations of Mn2+ ions, using the variational technique in the effective mass approximation. The sp-d exchange interaction between the localized magnetic impurity ions and the delocalized charge carriers has been accounted via mean-field theory with the inclusion of a modified Brillouin function. The enhancement of the GZS, and in turn, the effective g-factor with the application of an external magnetic field, is strikingly manifested in type-I – type-II transition in the band structure, which has been well explained by computing the overlap integral between the electron and hole, and the in-plane exciton radius. This highlights the extraordinary magneto-optical properties, including the giant Faraday rotation and associated Verdet constant, which have been calculated using single oscillator model. The oscillator strength has been estimated, and is found to be larger than in the bulk diluted magnetic semiconductors (DMS) and quantum wells, reflecting stronger confinement inside the quantum ring. More extensive Zeeman splitting and a higher oscillator strength in the DMS-based QR lead to an ultra-high Verdet constant of 2.6×109rad/Teslam, which are a few orders of magnitude larger than in the existing quantum systems and magneto-optical materials.

Enhancing Z-scheme photocatalytic CO2 methanation at extended visible light (>600 nm): Insight into charge transport and surface catalytic reaction mechanisms

This article reports Z-scheme photocatalytic CO2 methanation at the extended visible light (>500 nm) in absence of sacrificial electron donor/acceptor and noble metal cocatalysts. This Z-scheme photocatalyst consists of reduced graphene oxide (rGO) sandwiched between two different redox active photocatalysts (Ca-doped Bi2O3 and Cu2O). The rGO acts as a mediator by relaying electrons from Ca-doped Bi2O3 and holes from Cu2O that enables Z-scheme spatial confinement of electrons in Cu2O while holes in Ca-doped Bi2O3. This charge carrier delocalization enforces the enhanced oxidation strength of holes in Ca-doped Bi2O3 and reduction strength of electrons in Cu2O. As a result, it has exhibited methane (CH4) production rate under wider range of visible light (up to 700 nm) absorption. This Z-scheme photocatalyst therefore advents a new ‘600 nm-class photocatalyst’ for CO2 methanation. With the help of 13C isotopic measurements, first principles calculations and photoelectrochemical measurements, we have revealed the atomistic insight into the charge transport and surface catalytic reactions mechanisms to understand the rate limiting factors towards unassisted PCR.

The effect of 1 MeV electron irradiation on charge carrier localization in graphene quantum dot array of reduced graphene oxide

This paper presents a study of the effect of 1 MeV electron irradiation on the localization of charge carriers in graphene quantum dots (GQDs) located in a reduced graphene oxide (RGO). The electrical properties were analyzed in a wide temperature range of 4.2–340 K for fluences of 0–160 × 1015 cm−2. The localization length, dielectric permittivity, and density of localized states were estimated. It was found that the conductivity and charge localization parameters exhibit non-monotonic behavior depending on the electron fluences. It can change several times in the vicinity of a fluence of 10 × 1015 cm−2 compared to the higher or lower fluence. It is shown that electron irradiation affects the disordered surrounding matrix, which leads to an increase in the content of oxygen and functional groups. At the same time, the size of the sp2‑carbon domains does not depend on the fluence. It is assumed that electron irradiation indirectly affects the properties of GQDs. The transformation of the surrounding disordered matrix leads to a modification of the electronic properties of the GQDs array and the RGO as a whole. The non-monotonic behavior of the RGO conductivity upon irradiation is due to the features of the energy spectrum of the GQDs array, which is characterized by the presence of periodic peaks in the density of states. The irradiation-induced structural modification likely leads to a shift in the Fermi level and a change in the density of states. It is shown that the RGO behaves like a wide-band doped semiconductor. The difference is that the impurity level was formed by GQDs. At temperatures above 310 K, the RGO conductivity exhibits an Arrhenius behavior with an activation energy of about 60 meV due to charge carrier delocalization at thermal ejection into the extended band.

(Invited) Signatures of Charge Carrier (De)Localization in Semiconducting Single-Walled Carbon Nanotubes

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are attractive materials for a variety of opto-electronic devices and applications due their strong and energetically tunable optical absorption, and high charge carrier mobilities that result from the delocalized nature of the π-electron system. To realize the full potential of s-SWCNTs in these applications, it is critical to understand the generation, transport, interfacial transfer, and recombination of free charge carriers (electrons and holes). As with many pi-conjugated semiconductors, there remain uncertainties regarding the degree of (de)localization for charge carriers generated in s-SWCNTs either through photogenerated exciton dissociation or through charge injection by adsorbed redox dopants or gating. In this presentation, I will compare the various signatures of charge carrier localization and delocalization that appear in spectroscopic and transport studies of s-SWCNTs in a variety of different environments and over several decades of carrier density. These comparisons help to elucidate the important roles of intrinsic and extrinsic factors on carrier (de)localization and the information that spectroscopic signatures in the visible, near-IR, and mid-IR can provide on such (de)localization.

(Invited) Record-High Charge Carrier Mobilities in 2D Covalent- and Metal- Organic Frameworks

Organic based 2D layered materials (2DLMs) including 2D covalent and metal organic frameworks (COFs and MOFs) are promising candidates for traditional applications in gas storage and separation as well as catalysis. This is due to the long-range crystalline order that can be achieved in them as well as their tunable porosity and chemistry. Synthetic chemistry efforts aiming an enhanced coupling between their building block constituents have recently led to the design of (semi-)conducting MOFs and COFs displaying high conductivities and record charge carrier mobilities. These achievements have opened the path for their application in opto-electronics. Yet, despite being a critical aspect for the development of 2DLM based electronics, understanding the true nature of charge transport in these novel materials by stabilising reliable structure-property-function relations is largely unexplored.Here I will present time-resolved high-frequency (terahertz) conductivity studies of state-of-the-art organic based 2DLMs materials revealing semiconducting behaviour and record charge carrier mobilities. First, I will present a detailed characterization for the electronic properties of Zn– and Cu–phthalocyanine-based pyrazine-linked 2D COFs [1,2]. These 2D COFs, synthesized by condensation of metal–phthalocyanine (M = Zn and Cu) and pyrene derivatives, are obtained as polycrystalline-layered semiconductors displaying p-type doping and a band gap of ∼1.2 eV. Hall effect measurements (dc limit) and terahertz (THz) spectroscopy (ac limit) in combination with density functional theory (DFT) calculations demonstrate that varying metal center from Cu to Zn in the phthalocyanine moiety has a negligible effect in the conductivity (∼5 × 10–7 S/cm), charge carrier density (∼1012 cm–3), charge carrier scattering rate (∼3 × 1013 s–1), and effective mass (∼2.3m0) of majority carriers (holes). However, both samples reveal slightly different mobilities that can be attributed to charge carrier localization at crystalline grain boundaries. Furthermore we analyse the effect of iodine doping on the Zn based 2D COFs. The resultant 2D c-COF ZnPc-pz-I2 maintains its structural integrity and displays enhanced conductivity by 3 orders of magnitude, as a result of improved charge carrier concentrations. Hall effect reveal a charge carrier mobility reaching ∼22 cm2/Vs for ZnPc-pz-I2, which represent a record value for 2D c-COFs. An improved mobility upon doping can be traced to an increase in scattering time for free charge carriers, indicating that scattering mechanisms limiting the mobility are mitigated by doping.In the second part of my talk, I present the results concerning a Fe3(THT)2 (THT=2,3,6,7,10,11-hexathioltriphenylene) 2D MOFs [3]. The π-d conjugated samples, synthesized through interfacial method at room temperature, are obtained as a large-area, free-standing films with tunable geometry (size and thickness). The Fe3(THT)2 films are porous (specific surface area of 526±5 m2/g) and semiconducting (with a ~250 meV direct bandgap), and remarkably display band-like charge transport. This finding is directly demonstrated from the Drude-type high-frequency (terahertz) photo-conductivity response obtained in the samples; revealing free-moving, delocalized charge carriers displaying ~220 cm2/Vs mobilities at room temperature; a record charge carrier mobility for MOFs. The temperature dependence of the mobility reveals that the main scattering mechanism limiting the mobility and hence band-like charge transport in this material is related to impurity scattering, so that material improvements may further increase the mobility.The demonstration of band-like charge transport and record-high mobilities in semiconducting 2D COFs and MOFs reveal the potential of (porous) electrically conductive 2DLMs to be employed as active materials in opto-electronics devices.

Thiophene Backbone Enables Two-Dimensional Poly(arylene vinylene)s with High Charge Carrier Mobility.

Linear conjugated polymers have attracted significant attention in organic electronics in recent decades. However, despite intrachain π-delocalization, interchain hopping represents their transport bottleneck. In contrast, two-dimensional (2D) conjugated polymers, as represented by 2D π-conjugated covalent organic frameworks (2D c-COFs), can provide multiple conjugated strands to enhance the delocalization of charge carriers in space. Herein, we demonstrate the first example of thiophene-based 2D poly(arylene vinylene)s (PAVs, 2DPAV-BDT-BT and 2DPAV-BDT-BP, BDT= benzodithiophene, BT=bithiophene, BP=biphenyl) via Knoevenagel polycondensation. Compared with 2DPAV-BDT-BP, the fully thiophene-based 2DPAV-BDT-BT exhibits enhanced planarity and π-delocalization with a small band gap (1.62 eV) and large electronic band dispersion, as revealed by the optical absorption and density functional theory calculations. Remarkably, temperature-dependent terahertz spectroscopy discloses a unique band-like transport and outstanding room-temperature charge mobility for 2DPAV-BDT-BT (65 cm2V-1s-1), which far exceeds that of the linear PAVs, 2DPAV-BDT-BP, and the reported 2D c-COFs in the powder form. This work highlights the great potential of thiophene-based 2D PAVs as candidates for high-performance opto-electronics.

Thiophenbasierte Polymergerüste ermöglichen zweidimensionale Poly(arylenvinylen)e mit hoher Ladungsträgermobilität

AbstractLineare konjugierte Polymere haben in den letzten Jahrzehnten große Aufmerksamkeit in der organischen Elektronik erhalten. Trotz der π‐Delokalisierung innerhalb der Polymerkette stellen Interketten‐Ladungsträgersprünge ihr hauptsächliches Transportproblem dar. Im Gegensatz dazu können zweidimensionale (2D) konjugierte Polymere, wie z. B. 2D π‐konjugierte Covalent Organic Frameworks (2D c‐COFs), mehrere konjugierte Stränge für eine verbesserte Delokalisierung von Ladungsträgern im Raum bereitstellen. Hierin zeigen wir das erste Beispiel von thiophenbasierten 2D‐Poly(arylenvinylen)en (PAVs, 2DPAV‐BDT‐BT und 2DPAV‐BDT‐BP, BDT=Benzodithiophen, BT=Bithiophen, BP=Biphenyl) synthetisiert über Knoevenagel‐Polykondensation. Im Vergleich zu 2DPAV‐BDT‐BP weist das vollständig thiophenbasierte 2DPAV‐BDT‐BT eine erhöhte Planarität und π‐Delokalisierung mit einer niedrigen elektronischen Bandlücke (1.62 eV) und einer hohen elektronischen Banddispersion auf, wie die optische Absorption und Dichtefunktionaltheorie Berechnungen zeigen. Bemerkenswerterweise offenbart die temperaturabhängige Terahertz‐Spektroskopie‐Messung einen einzigartigen bandartigen Transport und eine herausragende Raumtemperatur‐Ladungsbeweglichkeit für 2DPAV‐BDT‐BT (65 cm2 V−1 s−1), die die der linearen PAVs, 2DPAV‐BDT‐BP und der publizierten 2D c‐COFs in Pulverform weit übertrifft. Diese Arbeit unterstreicht das große Potenzial von thiophenbasierten 2D‐PAVs als Kandidaten für Hochleistungs‐Optoelektronik.

Cu-MOF nanosheets modified nickel foam: A versatile platform for highly sensitive electrochemical detection of transferrin in simulated human blood serum

Transferrin (TRF) is a type of glycoprotein present in blood plasma that plays a vital role in facilitating the absorption, storage, and movement of iron(III) ions within the circulatory system of multiple vertebrates. Herein, we report one-pot solvothermal synthesis of Copper Metal-Organic Framework nanosheets modified nickel foam (Cu-MOF/NF) for electrochemical detection of transferrin (TRF) in simulated human blood serum. The crystal structure of the Cu-MOF nanosheets was determined through X-ray diffraction (XRD), while Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR) analysis were employed to investigate the vibrational modes and the presence of surface OH groups, respectively. The nanosheet morphology of the Cu-MOF was observed and characterized using scanning electron microscopy (SEM) micrographs.The as-fabricated Cu-MOF/NF exhibits a sensitivity of 1.36 mA/x (x = mg.mL−1cm−2) for a linear range of concentrations from 1 mg mL−1 – 100 mg mL−1 with a low limit of detection (LOD) of 0.81 mg mL−1. The sensor exhibited good selectivity for TRF, even in the presence of interfering ions such as bovine serum albumin, ascorbic acid, uric acid, and urea, with concentrations 100-fold higher than TRF. The porous nickel foam with high conductivity, offers numerous active sites and pathways for ion transport, as well as pathways for electron transport during electrochemical catalytic reactions. This performance of the sensor is attributed to Cu 2+/Cu+ redox couple at the octahedral sites of the Cu-MOF facilitating the electro-oxidation of TRF and charge-carrier delocalization during the catalytic reaction. The as-fabricated sensor is successful in the determination of trace level TRF concentration the human blood serum with excellent recovery percentages of 108.33% This proves Cu-MOF/NF as a promising platform for various electrochemical analytical applications.

Hot Carrier Cooling and Biexciton Dynamics of Anisotropic-Shaped CsPbBr3 Perovskite Nanocrystals

Fast hot-carrier (HC) cooling and the Auger recombination (AR) rate in solar absorbers act as a fundamental barrier toward the harvest of improved solar-energy efficiency. The recent emergence of lead halide perovskite (LHP) has shown enormous potential in high-performance solar cells; however, they are primarily limited to isotropic cubic shapes. It is thus essential to assess whether other anisotropic shapes can be utilized for improving the device’s functionality. Herein, we have studied HC relaxation and AR rates in hexapod CsPbBr3 NCs using ultrafast transient absorption (TA) spectroscopy. Our results indicate a prolonged HC cooling time and bi-exciton lifetime in a hexapod nanostructure compared to cubic CsPbBr3. In coordination with the HC temperature, we further confirm the slower HC relaxation rate in hexapod CsPbBr3 NCs by employing the electron–phonon coupling model, suggesting a retarded decay of longitudinal optical (LO) phonons. We demonstrate that the delocalization of charge carriers in the shallow trap states leads to a reduced overlap of electron and hole wave functions that is responsible for suppressing the bi-exciton AR rate.

Double Doping of Semiconducting Polymers Using Ion‐Exchange with a Dianion

AbstractThe interactions between counterions and electronic carriers in electrically doped semiconducting polymers are important for delocalization of charge carriers, electronic conductivity, and thermal stability. The introduction of a dianions in semiconducting polymers leads to double doping where there is one counterion for two charge carriers. Double doping minimizes structural distortions, but changes the electrostatic interactions between the carriers and counterions. Polymeric ionic liquids (PIL) with croconate dianions are helpful to investigate the role of the counterion in p‐type semiconducting polymers. PILs prevent diffusion of the cation into the semiconducting polymers during ion exchange. The redox‐active croconate dianions undergo ion exchange with doped semiconducting polymers depending on their ionization energy. Croconate dianions are found to reduce doped films of poly(3‐hexyl thiophene), but undergo ion exchange with a polythiophene with tetraethylene glycol side chains, P(g42T‐T), that has a lower ionization energy. The croconate dianion maintains crystalline order in P(g42T‐T) and leads to a lower activation energy for the electrical conductivity than PF6− counterions. The control of the doping level with croconate allows optimization of the thermoelectric performance of the semiconducting polymer. The thermal stability of the doped films of P(g42T‐T) is found to depend strongly on the nature of the counterion.

Investigation of the Photocatalytic Hydrogen Production of Semiconductor Nanocrystal-Based Hydrogels.

Destabilization of a ligand-stabilized semiconductor nanocrystal solution with an oxidizing agent can lead to a macroscopic highly porous self-supporting nanocrystal network entitled hydrogel, with good accessibility to the surface. The previously reported charge carrier delocalization beyond a single nanocrystal building block in such gels can extend the charge carrier mobility and make a photocatalytic reaction more probable. The synthesis of ligand-stabilized nanocrystals with specific physicochemical properties is possible, thanks to the advances in colloid chemistry made in the last decades. Combining the properties of these nanocrystals with the advantages of nanocrystal-based hydrogels will lead to novel materials with optimized photocatalytic properties. Thisworkdemonstrates that CdSe quantum dots, CdS nanorods, and CdSe/CdS dot-in-rod-shaped nanorods as nanocrystal-based hydrogels can exhibit a much higher hydrogen production rate compared to their ligand-stabilized nanocrystal solutions. The gel synthesis through controlled destabilization by ligand oxidation preserves the high surface-to-volume ratio, ensures the accessible surface area even in hole-trapping solutions and facilitates photocatalytic hydrogen production without a co-catalyst. Especially with such self-supporting networks of nanocrystals, the problem of colloidal (in)stability in photocatalysis is circumvented. X-ray photoelectron spectroscopy and photoelectrochemical measurements reveal the advantageous properties of the 3D networks for application in photocatalytic hydrogen production.

Spectroscopic Tools to Investigate the Electrochemical Doping Kinetics and Efficiency in Organic Semiconductors

Understanding the electrochemical doping of organic semiconductors plays a crucial role in the current development of organic electronics. In this short review, we present how temperature- and time- dependent visible-near-infrared (Vis-NIR) spectro-electrochemistry and terahertz spectroscopy, combined with multivariate curve resolution analysis, can inform on the fundamental mechanisms governing the doping kinetics and efficiency of two archetypal semiconducting polymers (PEDOT and P3HT). We highlight the experimental procedures and data analysis performed to access (i) the thermodynamic parameters driving the extent and dynamics of electrochemical reactions in doped systems and (ii) how the density and nature of charged species (polarons, bipolarons) impact the charge carrier delocalization, effective THz mobility and hence short-range conductivity.

Phosphorescence and conduction current relaxation in ZnSe crystals

In scintillation crystals, at X-ray or gamma quanta registration, a noticeable time delay of the pulse is observed. This is due to the thermal delocalization of charge carriers from traps. The study of phosphorescence and relaxation of the conduction current can give information on these processes. However, their investigation requires knowing theoretical dependences of phosphorescence intensity attenuation and conduction current relaxation. A multicenter model of a crystal is proposed in which at least three types of traps (shallow, phosphorescent and deep) take part in the delocalization of charge carriers at the excitation temperature. For such a model, theoretical dependences for the phosphorescence intensity and the conduction current relaxation are obtained. These dependences take into account the processes of re-trapping of free charge carriers on more shallow traps. They show that the level of filling of different traps depends not only on the total radiation dose, but also on the intensity of excitation. An explanation of an experimental fact of intersection of phosphorescence and conduction current relaxation curves at the same irradiation dose, but at different excitation intensities, contradicting classical kinetic theory of luminescence, is obtained. All experimental dependences of phosphorescence intensity and conduction current relaxation for ZnSe crystals at different temperatures are well described by the obtained theoretical dependences. It is also established that the time of emptying of each type of traps is determined not only by the probability of thermal delocalization, but also by the ratio of the concentration of these traps to the total concentration of deeper traps.

Infrared fingerprints of water collective dynamics indicate proton transport in biological systems.

Recent publications on spectroscopy of water layers in water bridge structures revealed a significant enhancement of the proton mobility and the dielectric contribution of translational vibrations of water molecules in the interfacial layers compared to bulk water. Herewith, the results of long-term studies of proton dynamics in solid-state acids have shown that proton mobility increases significantly with the predominance of hydronium, but not Zundel, cations in the aqueous phase. In the present work, in the light of these data, we reanalyzed our previously published results on broadband dielectric spectroscopy of bovine heart cytochrome c, bovine serum albumin, and the extracellular matrix and filaments of Shewanella oneidensis MR-1. We revealed that, just as in water bridges, an increase in electrical conductivity in these systems correlates with an increase in the dielectric contribution of water molecular translational vibrations. In addition, the appearance of spectral signatures of the hydronium cations was observed only in those cases when the system revealed noticeable electrical conductivity due to delocalized charge carriers.

Impact of Nanoscale Morphology on Charge Carrier Delocalization and Mobility in an Organic Semiconductor.

A central challenge of organic semiconductor research is to make cheap, disordered materials that exhibit high electrical conductivity. Unfortunately, this endeavor is hampered by the poor fundamental understanding of the relationship between molecular packing structure and charge carrier mobility. Here a novel computational methodology is presented that fills this gap. Using a melt-quench procedure it is shown that amorphous pentacene spontaneously self-assembles to nanocrystalline structures that, at long quench times, form the characteristic herringbone layer of the single crystal. Quantum dynamical simulations of electron hole transport show a clear correlation between the crystallinity of the sample, the quantum delocalization, and the mobility of the charge carrier. Surprisingly, the long-held belief that charge carriers form relatively localized polarons in disordered OS is only valid for fully amorphous structures-for nanocrystalline and crystalline samples, significant charge carrier delocalization over several nanometers occurs that underpins their improved conductivities. The good agreement with experimentally available data makes the presented methodology a robust computational tool for the predictive engineering of disordered organic materials.

Polyacetylene Revisited: A Computational Study of the Molecular Engineering of N-type Polyacetylene.

The development of stable and highly conductive polymers, particularly n-type materials, remains an outstanding challenge in organic electronics. N-doped polyacetylene has long been studied as a highly conductive organic n-type material but suffers from extremely poor stability. Herein, we use DFT to model a series of n-doped polyacetylene derivatives, which have been functionalized with a range of electron-withdrawing substituents, with the goal of identifying attractive candidates for synthesis. We analyze the predicted molecular orbital energies, polymer planarity, and delocalization of charge carriers along the polymer backbone. In so doing, we develop key insights about the ideal substituents for both stable and highly conductive polyacetylene derivatives. This work will inform the modern synthesis and development of new polyacetylene derivatives. Beyond this, the work identifies a variety of new materials that have not yet been synthesized and should be good candidates for emerging optoelectronic applications including soft thermoelectrics, bioelectronics, and flexible device technologies.

Realization of all-in-one hydrogen-evolving photocatalysts via selective atomic substitution

Major challenges of realization of all-in-one hydrogen-evolving photocatalysts are the relatively poor charge separation efficiency and unfavorable hydrogen desorption properties owing to the strong correlation between the catalytic site and adsorbed H. Herein, an example of Ni doped few-layer ZnIn2S4 nanosheets (Ni-ZnIn2S4) is carried out to deeply understand the role of Ni dopant in tailoring the charge separation efficiency and weakening the bond energy between electronegative S sites and adsorbed H (S-Hads). Our theoretical calculations demonstrate that Ni ions preferentially incorporates into tetrahedral Zn sites rather than tetrahedral/octahedral In sites, which endows Ni-ZnIn2S4 with improved electronic conductivity and more delocalized charge carriers involved in hydrogen evolution reaction (HER). More importantly, Ni dopants can be capable of exquisitely altering the electronic structure of S sites, leading to a balanced hydrogen adsorption and desorption ability. Consequently, the as-prepared few-layer Ni-ZnIn2S4 nanosheets enable long-lived photo-excited electrons and enhanced photocatalytic HER performance.

Effect of A-site ordering on IR absorption and magnetotransmission in PrBaMn2O6 double manganite

For double manganites PrBaMn2O6 with different degree of A-site ordering, magnetic and optical properties in near-IR range were studied. Full ordered manganite is characterized by antiferromagnetic state at low temperatures; magnetic phase transition from antiferromagnetic to ferromagnetic state occurs near TN = 262 K and to paramagnetic state near TC = 305 K. Partially disordered manganite consists of few fractions with different state of A-site ordering and shows the transition from ferromagnetic state to paramagnetic one at 190 K. For disordered manganite weak ferromagnetic contribution is observed below 130 K. The optical density spectra and the temperature dependences of light transmission indicate a change in behavior of the charge carrier system (metal–insulator transition) near the magnetic phase transitions. The magnetotransmission effect was measured for the first time in double manganites PrBaMn2O6. Spectral dependence of magnetotransmission lets associate this effect with an increase in the fraction of delocalized charge carriers when a magnetic field is applied.

Supramolecular Polymerization of Triarylamine-Based Macrocycles into Electroactive Nanotubes

A S6-symmetric triarylamine-based macrocycle (i.e., hexaaza[16]paracyclophane), decorated with six lateral amide functions, is synthesized by a convergent and modular strategy. This macrocycle is shown to undergo supramolecular polymerization in o-dichlorobenzene, and its nanotubular structure is elucidated by a combination of spectroscopy and microscopy techniques, together with X-ray scattering and molecular modeling. Upon sequential oxidation, a spectroelectrochemical analysis of the supramolecular polymer suggests an extended electronic delocalization of charge carriers both within the macrocycles (through bond) and between the macrocycles along the stacking direction (through space).