Organic Interface Research Articles

Enhancing the interaction between Mn and Ce oxides supported on fly ash with organic acid ligands interface modification for effective VOC removal: A combined experimental and DFT + U study

This work reports a procedure for increasing VOC removal from flue gas using binary oxides (Ce-Mn) supported on fly ash by facile mechanochemical synthetic method in the presence of a solid organic acid ligand (OAL). The presence of OAL during the synthesis process helped produce larger and more accessible particle surface areas, by generating an abundance of micro-/meso porous structures. Meanwhile, the Ce-Mn interaction was enhanced in the catalyst produced (Ce-Mn-OFA) by the presence of OAL during the milling process, yielding a higher ratio of Mn3+/Mn4+ and Ce3+/Ce4+, more lattice defects and surface oxygen vacancies, and greater lattice oxygen mobility. The resulting changes in the fly ash properties substantially improved the oxidation and adsorption activity of Ce-Mn-OFA thus enhancing the catalyst’s potential for VOC removal. The Ce-Mn-OFA catalyst showed the highest catalytic activity for benzene, toluene, m-xylene, and ethylene, which reached 90% conversion at 283 °C, 237 °C, 216 °C, and 264 °C, respectively. More importantly, the presence of the OAL increased the reactive oxygen species and acid sites on the surface of Ce-Mn-OFA, thus weakening the inhibiting effect of NO, NH3, H2O, and SO2 on the VOCs oxidation process. Furthermore, when Ce-Mn-OFA was applied using a special injection system to a large-scale pilot unit, the total concentration of 12 VOCs in the flue gas was reduced from 1347.3 μg/m3 to 131.2 μg/m3. The main contributions of the present work can be summarized as follows: 1) Providing a facile and environmentally friendly new process for the preparation of a heterogeneous catalyst; 2) Revealing the mechanism by which OAL enhances the activity of Ce-Mn in a binary metal oxide catalyst; 3) Evaluating the performance of Ce-Mn-OFA in a real flue gas, which provides feasibility support for its industrial application, such as in coal-fired power plants.

Thickness‐Dependent Energy‐Level Alignment at the Organic–Organic Interface Induced by Templated Gap States

AbstractPlanar organic heterostructures are widely explored and employed in photovoltaic cells, light‐emitting diodes, and bilayer field‐effect transistors. An important role for device performance plays the energy level alignment at the inorganic–organic and organic–organic interfaces. In this work, incremental ultraviolet photoelectron spectroscopy measurements and real‐time X‐ray scattering experiments are used to thoroughly investigate the thickness‐dependent electronic and structural properties of a perfluoropentacene (PFP)‐on‐[6]phenacene heterostructure. For both materials an incremental increase of the material work function (positive interface dipole) is found. For [6]phenacene, this can be assigned to a thickness‐dependent change of molecular arrangement evident from a change of the unit cell volume and a consequential alteration of the ionization energy. In the case of PFP the interface dipole stems from charge transfer from the substrate into unoccupied molecular orbitals resulting in an electrostatic potential on the surface. The magnitude of this potential can be correlated with an increased gap state density resulting from templated structural defects mediated by the bottom layer.

Temperature dependent transition of conduction mechanism from carrier injection to multistep tunneling in Fe3O4 (111)/Alq3/Co organic spin valve

We have presented experimental results addressing the origin of spin valve (SV) magneto-resistance (MR), in both injection and tunnel conduction regimes, in our fabricated Fe 3 O 4 (111)/Alq 3 /Co SV device. Experimental evidences have shown that any alternative MR process, such as ‘tunneling anisotropic MR’ is not at the origin of this SV MR. Spin resolved density of states of electrodes indicate that both the conduction mechanisms induce different spin dependent scattering which inturn modify the MR signal of the device. This modification helped in maintaining a non-monotonous quenching of MR signal with increase in temperature. We have also proposed a phenomenological model for device operation where the concept of charge gap modification at Fermi level across Verwey transition is envisaged to offer this unique scenario of tuning the conduction mode and hence MR in this ferrite based organic SV. The model is also supported by an established theoretical study which considers high temperature phonon assisted tunneling through defect states at electrode–organic interface of the device. • Conduction mechanism transition from carrier injection to multistep tunneling. • Transition due to Verwey transition of Fe 3 O 4 . • Spin flip scattering at Alq 3 spacer above Verwey transition temperature. • Non-monotonous MR quenching with temperature. • Room temperature MR signal of hybrid spin valve.

Electrophysiological investigation of intact retina with soft printed organic neural interface

Objective. Understanding how the retina converts a natural image or an electrically stimulated one into neural firing patterns is the focus of on-going research activities. Ex vivo, the retina can be readily investigated using multi electrode arrays (MEAs). However, MEA recording and stimulation from an intact retina (in the eye) has been so far insufficient. Approach. In the present study, we report new soft carbon electrode arrays suitable for recording and stimulating neural activity in an intact retina. Screen-printing of carbon ink on 20 µm polyurethane (PU) film was used to realize electrode arrays with electrodes as small as 40 µm in diameter. Passivation was achieved with a holey membrane, realized using laser drilling in a thin (50 µm) PU film. Plasma polymerized 3.4-ethylenedioxythiophene was used to coat the electrode array to improve the electrode specific capacitance. Chick retinas, embryonic stage day 13, both explanted and intact inside an enucleated eye, were used. Main results. A novel fabrication process based on printed carbon electrodes was developed and yielded high capacitance electrodes on a soft substrate. Ex vivo electrical recording of retina activity with carbon electrodes is demonstrated. With the addition of organic photo-capacitors, simultaneous photo-electrical stimulation and electrical recording was achieved. Finally, electrical activity recordings from an intact chick retina (inside enucleated eyes) were demonstrated. Both photosensitive retinal ganglion cell responses and spontaneous retina waves were recorded and their features analyzed. Significance. Results of this study demonstrated soft electrode arrays with unique properties, suitable for simultaneous recording and photo-electrical stimulation of the retina at high fidelity. This novel electrode technology opens up new frontiers in the study of neural tissue in vivo.

Efficient solid-state photon upconversion enabled by triplet formation at an organic semiconductor interface

Efficient solid-state photon upconversion enabled by triplet formation at an organic semiconductor interface

Droplet size controllable fabrication of Pickering emulsion stabilized by soy protein isolate-carbon nanotubes/carboxymethyl cellulose sodium

ABSTRACT Pickering emulsion plays an important role in various industrial fields including food, catalysis, and bioscience. Soy protein isolate (SPI) has been proved feasible for stabilizing Pickering emulsion after modification, though such methods were either difficult to proceed or application restrictive. Herein, we report a simple fabrication of oil-in-water Pickering emulsion using a complex of SPI and carbon nanotubes (CNTs)/carboxymethyl cellulose sodium (CMC-Na). The stability of our emulsion could be kept at a wide range of CNTs diameter, oil fraction, and pH, while the emulsion droplet size might be controlled through the tuning of pH and dispersed phase solvent as well. A strong interaction between SPI and CNTs/CMC-Na is a key factor for the homogeneous distribution of CNTs at the aqueous–organic interface, which benefits the Pickering emulsion formation. Our work will offer some useful thoughts for improving the stability of protein-integrated emulsion.

Grafted Organic Selenide Interface for Sensitive Electrocatalytic Detection of Peroxynitrite (PON): Towards Pon Sensing in Brain Tissue

Peroxynitrite is a very reactive and cytotoxic species that plays important pathophysiological roles, particularly in the brain. It is also suspected to be a factor involved in tissue damage that results from long term deep brain neural stimulation. Accurate determination of peroxynitrite concentration is inherently difficult due to its high reactivity and concentration range. Various methods for peroxynitrite determination have been reported including indirect spectroscopic assays and, recently, direct electrochemical methods. Currently, this field is still actively growing in the pursuit of viable electrochemical probes or catalytic materials as interfaces for efficient peroxynitrite detection. A durable and reliable electrochemical sensor would be valuable in order to monitor peroxynitrite generation near sites of electrical neurostimulation.In this work, we prepared and characterized a functional thin film material based on an organic selenide on graphite electrodes and used the interface in sensitive electrochemical determination of peroxynitrite. First, we describe the preparation and grafting of the catalytic material based on the electrodeposition of organic selenides on graphite electrodes. Next, we report on the characterization of the resulting grafted film material on graphite interface using various physicochemical methods including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS). We then tested the performance of resulting aniline selenide catalytic material on modified electrodes as peroxynitrite sensing interfaces using voltammetry and dose-response amperometry. The grafted thin film material showed a significant enhancement in peroxynitrite oxidative current compared to electrodes with aniline only (i.e. materials devoid of selenium) under the same conditions. In the presentation we will show that the enhancement in peroxynitrite signal is the result of an electrocatalytic mechanism where the grafted selenide-based organic material at the oxidized state mediates the electrocatalytic oxidation of peroxynitrite. In terms of selectivity, the electrocatalytic detection of PON on electrodes modified with the selenide compound responds better and selectively toward PON as a target analyte over other potentially interfering analytes such as nitric oxide, nitrite, and nitrate. To the best of our knowledge, this is the first time a selenium-based organic material electrochemically grafted at an electrode surface is used for catalytic detection and quantification of peroxynitrite.

Ultrafast Speed, Dark Current Suppression, and Self-Powered Enhancement in TiO2-Based Ultraviolet Photodetectors by Organic Layers and Ag Nanowires Regulation.

TiO2-based photodetectors (PDs) have been hotspots in recent years for their excellent thermal stabilities and optoelectronic performance under ultraviolet (UV) light. However, the high dark current caused by defects in TiO2 films has limited the detectivity (D) of these PDs. Here, the dark current of a TiO2-based PD was effectively reduced by 3 magnitudes (from 0.1 mA to 20 nA) and D was increased to 1.2 × 1014 Jones by introducing PC71BM. The TiO2/PC71BM heterojunction also made the PD self-powered, and by further introducing an interface layer of PEDOT:PSS and finely optimizing the electrode Ag nanowires (Ag NWs), the self-powered responsivity (R) was increased to 33 mA/W. Ultrafast rise/decay times (129 ns/1 ms at -1 V and 0.06 s/<1 μs at 0 V) were achieved. This work successfully applied an organic-inorganic heterojunction, an organic interface, and Ag NWs to suppress the dark current and enhance the self-powered photocurrent/R of inorganic PDs, providing a feasible strategy in high-performance UV PDs' design.

Optical and Electrical Properties of Pyrene–Imine Organic Interface Layer Based on p-Si

Optical and Electrical Properties of Pyrene–Imine Organic Interface Layer Based on p-Si

Bottom‐Up Design of a Grafted Organic Selenide Interface for Sensitive Electrocatalytic Detection of Peroxynitrite

AbstractPeroxynitrite is a reactive species that emerged as a major cytotoxic agent implicated in a host of pathophysiological conditions. Reports emphasized deleterious physiological reactivity of peroxynitrite with various cell components. Accurate determination of peroxynitrite concentration is inherently difficult. Detection methods based on electrochemistry are relatively limited and the pursuit of viable electrochemical probes or catalytic materials as interfaces for efficient peroxynitrite detection is still underway. We prepared and characterized a functional thin‐film material based on an organic selenide (4,4’ diaminodiphenyl selenide) grafted on graphite electrodes and used the interface in sensitive electrochemical determination of peroxynitrite. We characterized the grafted film material on the graphite interface using various physicochemical methods. We show that peroxynitrite is electrocatalytically oxidized on the grafted selenide film. The grafted functional film material showed a significant electrocatalytic enhancement in the presence of peroxynitrite compared to controls. The selenide‐based peroxynitrite sensors show a sensitivity of 200 nA/μM and a lower limit of detection of 250 nM. To the best of our knowledge, this is the first time a grafted selenium‐based material on an electrode is used for catalytic detection and quantification of peroxynitrite.

Water molecules bonded to the carboxylate groups at the inorganic-organic interface of an inorganic nanocrystal coated with alkanoate ligands.

High-quality colloidal nanocrystals are commonly synthesized in hydrocarbon solvents with alkanoates as the most common organic ligand. Water molecules with an approximately equal number of surface alkanoate ligands are identified at the inorganic–organic interface for all types of colloidal nanocrystals studied, and investigated quantitatively using CdSe nanocrystals as the model system. Carboxylate ligands are coordinated to the surface metal ions and the first monolayer of water molecules is found to bond to the carboxylate groups of alkanoate ligands through hydrogen bonds. Additional monolayer(s) of water molecules can further be adsorbed through hydrogen bonds to the first monolayer of water molecules. The nearly ideal environment for hydrogen bonding at the inorganic–organic interface of alkanoate-coated nanocrystals helps to rapidly and stably enrich the interface-bonded water molecules, most of which are difficult to remove through vacuum treatment, thermal annealing and chemical drying. The water-enriched structure of the inorganic–organic interface of high-quality colloidal nanocrystals must be taken into account in order to understand the synthesis, processing and properties of these novel materials.

Cover Feature: Bottom‐Up Design of a Grafted Organic Selenide Interface for Sensitive Electrocatalytic Detection of Peroxynitrite (ChemElectroChem 17/2021)

The Cover Feature shows a modified electrode interface with grafted organic selenide moieties as catalytic sites for sensitive and selective electrochemical detection and quantitation of peroxynitrite. The work shows that the selenium center in the grafted organic material is crucial for peroxynitrite catalytic sensing. The electrochemical method can expand to ultramicroelectrodes for PON monitoring under physiologic settings. More information can be found in the Article by M. Bayachou et al.

The Ionic Liquid-H2O Interface: A New Platform for the Synthesis of Highly Crystalline and Molecular Sieving Covalent Organic Framework Membranes.

Covalent organic frameworks (COFs) are highly porous crystalline polymers with uniform pores and large surface areas. Combined with their modular design principle and excellent properties, COFs are an ideal candidate for separation membranes. Liquid-liquid interfacial polymerization is a well-known approach to synthesize membranes by reacting two monomers at the interface. However, volatile organic solvents are usually used, which may disturb the liquid-liquid interface and affect the COF membrane crystallinity due to solvent evaporation. Simultaneously, the domain size of the organic solvent-water interface, named the reaction zone, can hardly be regulated, and the diffusion control of monomers for favorable crystallinity is only achieved in the water phase. These drawbacks may limit the widespread applications of liquid-liquid interfacial polymerization to synthesize diverse COF membranes with different functionalities. Here, we report a facile strategy to synthesize a series of imine-linked freestanding COF membranes with different thicknesses and morphologies at tunable ionic liquid (IL)-H2O interfaces. Due to the H-bonding of the catalysts with amine monomers and the high viscosity of the ILs, the diffusion of the monomers was simultaneously controlled in water and in ILs. This resulted in the exceptionally high crystallinity of freestanding COF membranes with a Brunauer-Emmett-Teller (BET) surface area up to 4.3 times of that synthesized at a dichloromethane-H2O interface. By varying the alkyl chain length of cations in the ILs, the interfacial region size and interfacial tension could be regulated to further improve the crystallinity of the COF membranes. As a result, the as-fabricated COF membranes exhibited ultrahigh permeance toward water and organic solvents and excellent selective rejection of dyes.

Multifunctional Conjugated Ligand Engineering for Stable and Efficient Perovskite Solar Cells.

Surface passivation is an effective way to boost the efficiency and stability of perovskite solar cells (PSCs). However, a key challenge faced by most of the passivation strategies is reducing the interface charge recombination without imposing energy barriers to charge extraction. Here, a novel multifunctional semiconducting organic ammonium cationic interface modifier inserted between the light-harvesting perovskite film and the hole-transporting layer is reported. It is shown that the conjugated cations can directly extract holes from perovskite efficiently, and simultaneously reduce interface non-radiative recombination. Together with improved energy level alignment and the stabilized interface in the device, a triple-cation mixed-halide medium-bandgap PSC with an excellent power conversion efficiency of 22.06% (improved from 19.94%) and suppressed ion migration and halide phase segregation, which lead to a long-term operational stability, is demonstrated. This strategy provides a new practical method of interface engineering in PSCs toward improved efficiency and stability.

High thermal stability of anti-ferromagnetic coupled molecules with FeCo layers

We propose the optimization of the magnetic remanence and the thermal stability of Mn phthalocyanine coupled with a ferromagnetic substrate, by exploiting interlayer exchange coupling within an advanced organic spin interface architecture, constituted by a FeCo film covered by a graphene membrane, hosting the MnPc molecular layer. The challenge to obtain magnetic remanence for molecular systems stable up to room temperature has been accomplished thanks to a super-exchange path, mediated by the π orbital of the organic ligands of the molecule and of the graphene sheet, favoring an antiferromagnetic (AFM) alignment for the MnPc molecules with the FeCo film. This spin interface with a strong AFM coupling mediated by a graphene spacer is optimized against thermal fluctuations, presenting a well defined remanence even at room temperature, as demonstrated by the persistent dichroic signal in temperature-dependent circularly polarized x-ray absorption spectra.

Ultrafast electron injection kinetics and effect of plasmonic silver nanoparticle at organic dye-TiO2 interface

Ultrafast electron injection kinetics and effect of plasmonic silver nanoparticle at organic dye-TiO2 interface

Tailoring of graphene–organic frameworks membrane to enable reversed electrical-switchable permselectivity in CO2 separation

Membrane separation has been an efficient and energy saving technique in dealing with greenhouse gases, but the traditional membrane designs might not be able to handle the concomitant environmental pollution due to their fixed properties. Correspondingly, the use of an active-responsive smart membrane appears to be a new trend for membrane development in the coming future, which shows great potential to deal with the obstacles. In this research, we demonstrate a smart graphene-organic framework membrane to enable reversed electrical-switchable permselectivity in CO2 separation. The addition of polydopamine (PDA) to the polyvinylidene fluoride/Graphene (PVDF/G) membranes was done to (i) induce the β-phase of PVDF, since –NH2-functionalized graphene has specific interactions (dipole induced dipole interaction) between graphene-PDA and PVDF; (ii) modify the organic PVDF-inorganic graphene interface; and (iii) facilitate CO2 selective separation. Permeability and permselectivity was increased after applying voltage that resulted in the increase of gas permselectivity in response to the lowest applied voltage range (0–3 V) to the membrane. Digital image correlation method depicted the response of the membrane to voltage and proved that the membrane has high piezoelectric properties that is switchable. Furthermore, PALS studies confirmed the free volume and interlayers in the membrane. This membrane has unique properties because the pore changes from bimodal to single pore distribution.

Pathway Complexity in Supramolecular Porphyrin Self-Assembly at an Immiscible Liquid-Liquid Interface.

Nanostructures that are inaccessible through spontaneous thermodynamic processes may be formed by supramolecular self-assembly under kinetic control. In the past decade, the dynamics of pathway complexity in self-assembly have been elucidated through kinetic models based on aggregate growth by sequential monomer association and dissociation. Immiscible liquid–liquid interfaces are an attractive platform to develop well-ordered self-assembled nanostructures, unattainable in bulk solution, due to the templating interaction of the interface with adsorbed molecules. Here, we report time-resolved in situ UV–vis spectroscopic observations of the self-assembly of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrin (ZnTPPc) at an immiscible aqueous–organic interface. We show that the kinetically favored metastable J-type nanostructures form quickly, but then transform into stable thermodynamically favored H-type nanostructures. Numerical modeling revealed two parallel and competing cooperative pathways leading to the different porphyrin nanostructures. These insights demonstrate that pathway complexity is not unique to self-assembly processes in bulk solution and is equally valid for interfacial self-assembly. Subsequently, the interfacial electrostatic environment was tuned using a kosmotropic anion (citrate) in order to influence the pathway selection. At high concentrations, interfacial nanostructure formation was forced completely down the kinetically favored pathway, and only J-type nanostructures were obtained. Furthermore, we found by atomic force microscopy and scanning electron microscopy that the J- and H-type nanostructures obtained at low and high citric acid concentrations, respectively, are morphologically distinct, which illustrates the pathway-dependent material properties.

Modulating the Pro-Apoptotic Activity of Cytochrome C at a Biomimetic Electrified Liquid|Liquid Interface

Programmed cell death via apoptosis is a natural defence against excessive cell division, crucial at all stages of life from foetal development to maintenance of homeostasis and elimination of precancerous and senescent cells.In this presentation, an electrified liquid|liquid bio-interface is demonstrated that replicates the molecular machinery of the inner mitochondrial membrane at the onset of apoptosis. By mimicking in vivo cytochrome c (Cyt c) interactions with cell membranes, our platform allows us to modulate the conformational plasticity of the protein by simply varying the electrochemical environment at an aqueous|organic interface. Our experimental findings supported by molecular modelling show that adsorption, orientation, restructuring, and pro-apoptotic peroxidase activity of Cyt c can all be precisely manipulated. Remarkably, we observe interfacial electron transfer between an organic electron donor decamethylferrocene and O2, electrocatalysed by Cyt c. This interfacial reaction requires partial Cyt c unfolding, mimicking Cyt c in vivo peroxidase activity.Our electrified liquid|liquid bio-interface motivates development of biomimetic electrochemical platforms to identify drug molecules that can potentially downregulate Cyt c and protect against uncontrolled neuronal cell death in Alzheimer’s and other neurodegenerative diseases. As proof-of-concept, we demonstrate that bifonazole, predicted to target the heme pocket, inhibits the electrocatalytic activity of Cyt c and switches off O2 reduction. Figure 1

Fabrication and Characterisation of Organic EL Devices in the Presence of Cyclodextrin as an Interlayer.

This study examined glass-based organic electroluminescence in the presence of a cyclodextrin polymer as an interlayer. Glass-based organic electroluminescence was achieved by the deposition of five layers of N,N’-Bis(3-methylphenyl)N,N’-bis(phenyl)-benzidine, cyclodextrin polymer (CDP), tris-(8-hydroxyquinolinato) aluminium LiF and Al on an indium tin oxide-coated glass substrate. The glass-based OEL exhibited green emission owing to the fluorescence of tris-(8-hydroxyquinolinato) aluminium. The highest luminance was 19,620 cd m−2. Moreover, the glass-based organic electroluminescence device showed green emission at 6 V in the curved state because of the inhibited aggregation of the cyclodextrin polymer. All organic molecules are insulating, but except CDP, they are standard molecules in conventional organic electroluminescence devices. In this device, the CDP layer contained pores that could allow conventional organic molecules to enter the pores and affect the organic electroluminescence interface. In particular, self-association was suppressed, efficiency was improved, and light emission was observed without the need for a high voltage. Overall, the glass-based organic electroluminescence device using CDP is an environmentally friendly device with a range of potential energy saving applications.