Switching Of Mechanism Research Articles

Unlocking the potential of lattice oxygen evolution in stainless steel to achieve efficient OER catalytic performance

Excellent OER catalysts can enhance the efficiency of hydrogen production from electrolytic water. The development of low-cost, abundant, and highly efficient catalysts remains crucial for the electrolytic hydrogen production industry. In this work, we have developed a highly efficient and cost-effective stainless steel-based OER catalyst using a strategy combining anodic corrosion and structural reconstruction. This approach is not only simple and easy to scale up production, but more importantly, it can also achieve controllable switching of lattice oxygen evolution mechanism (LOM). Specifically, in a 1 M KOH electrolyte, this catalyst achieves current densities of 500 mA/cm² and 1000 mA/cm² with remarkably low overpotentials of only 347 mV and 382 mV, respectively. Moreover, the catalyst exhibits exceptional stability even under high industrial current densities. In-situ differential electrochemical mass spectrometry (DEMS) experiments provide direct evidence of the transition from the adsorbate evolution mechanism (AEM) to the LOM. Through comprehensive characterizations and density functional theory (DFT) calculations, we have elucidated the underlying mechanism responsible for the improved performance and identified key factors influencing the induction of the LOM. This work provides support and new insights for the design and preparation of high-performance steel-based electrolytic water catalysts.

A Proline-Based Artificial Enzyme That Favors Aldol Condensation Enables Facile Synthesis of Aliphatic Ketones via Tandem Catalysis.

A proline-based artificial enzyme is prepared by grafting the l-proline moieties onto the surface of bovine serum albumin (BSA) protein through atom transfer radical polymerization (ATRP). The artificial enzyme, the BSA-PolyProline conjugate, prefers to catalyze the formation of unsaturated ketones rather than β-hydroxy ketones in the reaction between acetone and aldehydes, which is difficult to achieve in free-proline catalysis. The altered reaction selectivity is ascribed to the locally concentrated l-proline moieties surrounding the BSA molecule, indicating a microenvironmental effect-induced switching of the reaction mechanism. Taking advantage of this selectivity, we used this artificial enzyme in conjunction with a natural enzyme, old yellow enzyme 1 (OYE1), to demonstrate a simple synthesis of different aliphatic ketones from acetone and aldehydes via tandem catalysis.

Numerical Modeling of In-Flight Molten Metal Droplet Dynamics and Particle Oxidation in Atmospheric Plasma Spraying

In Atmospheric Plasma Spraying (APS), it is important to understand the controlling factors dominating molten metal droplets’ reaction dynamics to control final coating compositions and properties. The present paper focuses on a novel Computational Fluid Dynamics (CFD) modeling of mass transfer mechanisms of an inflight molten metal droplet leading to droplet oxidation control during APS. The onset conditions of droplet internal circulation and its effect on the deoxidizer oxidation behavior during APS are theoretically examined. Moreover, rapidly supplying these elements from the inside to the droplet surface requires the rapid switching of the mass transfer mechanism to rapid convective flow due to a very limited in-flight time of less than 1ms. The temperature and velocity variations within the droplet would influence the thermo-physical properties of the droplet and the plasma gas and it controls the onset of the internal circulations within the droplets. A novel User Defined Function (UDF) is developed to capture the onset of Hill’s vortex formation and its effect on the rapid-rate convective mass transfer mechanism during APS. Further, a detailed analysis of particle size effect on in-flight in-situ deoxidation during APS of NiAlC droplets was performed. It is observed that the smaller size droplets will undergo more severe oxidation during a flight than larger size droplets due to more molecules of O2 available for reaction in the smaller droplet.

Development of dual-main excitation mechanism modes electromagnet EMAT for testing ferromagnetic materials

ABSTRACT In the ultrasonic testing of the mechanical properties of ferromagnetic materials, the main excitation mechanism modes of ultrasonic waves are Lorentz force mechanism ultrasonic and magnetostriction mechanism ultrasonic. Lorentz force mechanism ultrasonic mainly detects the conductive characteristics of materials, while magnetostriction mechanism ultrasonic mainly detects the hysteresis characteristics of materials. However, conventional electromagnetic acoustic transducers (EMATs) cannot simultaneously characterise these two characteristics of ferromagnetic materials. In this study, we conclude from the finite element simulation that a quantitative lift-off distance (i.e. the distance between EMAT and the specimen) can change the main mechanism mode of the excited ultrasonic wave. Based on this conclusion, an electromagnet electromagnetic acoustic transducer with dual main excitation modes (DM-E-EMAT) is designed, which can realise the dual mode switching of the main Lorentz force mechanism and main magnetostriction mechanism by adding or removing hollow square gasket. The ultrasonic testing of ferromagnetic materials based on the two main mechanisms of DM-E-EMAT can simultaneously characterise the conductivity and magnetostriction properties of ferromagnetic materials, which enables the characterisations of two types of characteristic parameters with one transducer, improves the efficiency of electromagnetic ultrasonic non-destructive testing of the mechanical properties and reduces the detection errors of ferromagnetic material.

Facile synthesis of defect induced CeO2/MIL-53(Fe) nanocatalyst: Strategically switching the charge transfer dynamics for remarkable enhancement of photocatalytic Bisphenol A degradation and H2 evolution

This work reports the fabrication of heterojunction between defect induced CeO2 and iron based metal organic framework (MIL-53). A simple chemical redox etching methodology was adopted to narrow the band gap of pristine CeO2 through oxygen vacancy engineering. The photocatalytic efficacy of defect induced CeO2/MIL-53 (MCO-X) heterojunction was studied in Bisphenol A (BPA) breakdown and photocatalytic hydrogen generation from water splitting. The significantly improved photocatalytic application of MCO-X heterojunction could be attributed to the switching of charge dynamics mechanism from Type-1 to Type-II due to defect formation in the pristine CeO2. The optimal photocatalyst (MCO-30) displayed the highest photocatalytic BPA degradation with rate constant (0.045 min−1) and H2 evolution (3286.2 μmol.h−1. g−1) respectively. This study provides a comprehensive analysis on how defect in pristine CeO2 in MCO-X heterojunction can switch the charge transfer mechanism from Type-1 to Type-II to achieve remarkable visible light harnessing capacity and photocatalytic activity.

Reduced graphene oxide-nano zerovalent iron assisted anaerobic digestion of dairy wastewater: A potential strategy for CH4 enrichment

Efficient waste management and alternatives for waste reduction have been the prime factors in achieving sustainable development goals. Large quantities of waste biomass can be transformed to energy by anaerobic fermentation. This study focused on improving the electron transport and subsequent CH4 enrichment in the anaerobic digestion of dairy wastewater by adding reduced graphene oxide-nano zerovalent iron (RGO-NZVI) composite. Different ratios (wt/wt) of RGO and NZVI were added to the anaerobic digesters and monitored their effects on biogas volume, composition, COD removal and VFA accumulation. There was 86.27 ± 2.8% high CH4 and 47.37 ± 1.3% improved COD removal in the digester containing the conductive additive compared to control. Comparing different ratios of RGO-NZVI revealed that a proportion of 2:1 was beneficial for maximum CH4 generation. Further, it was found that higher concentrations of the conductive additives could be fatal for microbial metabolism. A ratio of 0.5:1 had minimal support on degradation and the composition of CH4 in this digester was 34.14 ± 1.5% less than control. The metagenomic analysis showed that the diversification of microbial community and switching of major mechanism to direct interspecies electron transfer caused higher CH4 generation.

Theoretical study of the mechanism of the hydrogen evolution reaction on the V2C MXene: Thermodynamic and kinetic aspects

Both experimentally and theoretically, the MXene family has shown promising hydrogen evolution reaction (HER) capabilities. However, so far, the theoretical approach has been relying on the well-known thermodynamic descriptor, ΔGH, whereas experimental studies report Tafel plots, containing kinetic rather than thermodynamic information. Aiming to link theory to experiments, the present study explores five different HER pathways over the exemplary V2C (0001) MXene by density functional theory calculations. While the surface coverage under HER conditions (with either H* or OH* adsorbates) is extracted from a Pourbaix diagram, we determine the energetics of the reaction intermediates and transition states for both surface species as active sites. This enables the construction of free-energy diagrams for the Volmer-Heyrovsky and Volmer-Tafel mechanisms and allows for the simulation of Tafel plots by a rigorous microkinetic framework. While the active-site motif V2C-OH seems to be less relevant for the HER under typical reaction conditions, we demonstrate that the HER is kinetically facile on the V2C-H surface. For this surface termination, we report a potential-depending switching of the preferred mechanism from the Volmer-Heyrovsky to the Volmer-Tafel description with increasing overpotential while encountering similarities to the HER over Pt.

Ultrahigh Rectification Ratio in an Asymmetric Metal/Semiconductor/Metal Nanoscale Tunneling Junction: Implications for High-Frequency Rectifiers

The ultrafast quantum-based electron-transport mechanism with a typical tunneling time of femtoseconds is appealing to fabricate high-frequency rectifier diode devices for applications such as solar energy harvesting, THz mixers, and infrared detectors. Here, we demonstrate an ultrahigh rectification of more than 104 and a large forward current density of 13.8 A/cm2 at −2 V in the structure of a metal/semiconductor/metal (MSM, Pt/ZnO/TiN) nanoscale tunneling junction. Technology computer-aided design (TCAD) simulations demonstrate that high rectification originates from the switching of the electron-transport mechanism between direct tunneling (DT) and Fowler–Nordheim tunneling (FNT) under positive and negative voltage biases, respectively. The quantum-based FNT mechanism gives very slight temperature dependence of currents in a wide temperature range of 100–400 K. This work opens an avenue for high-frequency rectifier diodes based on MSM nanoscale tunneling junctions.

Hopping or Tunneling? Tailoring the Electron Transport Mechanisms through Hydrogen Bonding Geometry in the Boron-Doped Diamond Molecular Junctions.

Mechanisms of charge transport in molecular junctions involving hydrogen bonds are complex and remain mostly unclear. This study is focused on the elucidation of the electron transfer in a molecular device consisting of two boron-doped diamond interfaces bound with an aromatic linker and a hydrogen bonding surrogating molecule. The projected local density of states (PLODS) analysis coupled with transmission spectra and current–voltage (I–V) simulations show that hydrogen bonding through electron-donating hydroxyl groups in the aromatic linker facilitates electron transfer, while the electron-withdrawing carboxyl group inhibits electron transfer across the junction. Moreover, slight variations in the geometry of hydrogen bonding lead to significant changes in the alignment of the energy levels and positions of the transmission modes. As a result, we observe the switching of the electron transport mechanism from tunneling to hopping accompanied by a change in the shape of the I–V curves and current magnitudes. These results give important information on the tailoring of the electronic properties of molecular junctions.

Influence of injection angle on liquid jet in crossflow

The influence of changing the injection angle of a liquid jet injected into airstream in crossflow was investigated. The injection angles from 90 to 30 degrees were considered. Based on liquid velocity and air speed, liquid and gas Weber numbers from 8 to 600 and 0.2 to 27 were considered, respectively. Many flow parameters such as: Rayleigh-Taylor wavelengths, liquid jet trajectories, breakup lengths and penetration lengths by means of high-speed photography and shadowgraph technique were measured and reported. Based on the relative importance of the aerodynamic forces of the crossflow to the liquid momentum and surface tension forces different breakup regimes occurred. Using gas Weber number, the following liquid jet breakup regimes: column breakup, arc breakup, bag breakup and multimode breakup were observed at various injection angles. It was found that at lower injection angles the required gas Weber number to transition between regimes was slightly increased.At lower gas Weber number flows, increasing the injection angle caused the liquid jet to penetrate farther into the airstream and this process was gradual. However, at higher gas Weber number flows, there was a bifurcation in behavior: At the lower injection angles, the behavior was the same, but at the higher injection angles, the penetration behavior reversed and the penetration of liquid jet into airstream decreased as the injection angle was increased. We believe this phenomenon was due to switching of the breakup mechanism from Rayleigh-Taylor instability to shear breakup mechanisms at higher injection angles.Theoretical models for prediction of liquid jet trajectory and its breakup point taking the effect of injection angle into account were developed and presented. The models’ predictions were compared with our measurements and other published data resulting in good agreements.

Peroxymonosulfate activation by black TiO2 nanotube arrays under solar light: Switching the activation mechanism and enhancing catalytic activity and stability

Black TiO2 nanotube arrays (black TNAs) suffer from the low activity and deactivation for peroxymonosulfate (PMS) activation, which limit their application in the oxidative destruction of organic pollutants in water. Here, we report an efficient, environmentally benign, and cost-effective method to enhance the catalytic activity and prevent the deactivation of black TNAs in PMS activation by utilizing solar energy. Optical absorption and electrochemical analysis and density functional theory calculations demonstrated that abundant oxygen vacancies (estimated to be 26%) on the black TNAs surface markedly improved solar light absorption and electrical conductivity and played a critical role as a catalytic active site for PMS activation. As a result, the solar light-irradiated black TNAs/PMS system exhibited the higher phenol degradation rate (k = 0.0488 min−1) and total organic carbon (TOC) removal efficiency (~70%) compared to other TNAs systems. These results were ascribed to the switching of the reaction mechanism from non-radical mechanism to radical-involved. Black TNAs oxidized organic pollutants by mediating electron transfer from organics to PMS in the dark (i.e., a non-radical pathway). On the other hand, PMS activation under solar light irradiation involved the production of highly reactive sulfate and hydroxyl radicals (i.e., radical pathway), markedly improving the degradation and mineralization of organics. Additionally, the solar light-irradiated black TNAs showed relative pH-independence for PMS activation and durable catalytic performance without the loss of activity during the repetitive reaction cycles.

Non-Aqueous electro-deposition of novel one-dimensional Sm2Co17 nanostructures and magnetic field annealing effect on structural and magnetic properties

Through a versatile and quite economical technique of DC electro-deposition, Sm2Co17 nanowires (NWs) have been fabricated into the nanochannels of anodic aluminum oxide (AAO) templates by using non-aqueous electrolyte. The average diameter and length of NWs are 80 nm and 3 µm respectively. The structural and magnetic properties of NWs have been investigated before and after magnetic field (MF) annealing with magnetic field strength of 1 T applied parallel to the NWs axis at temperature of 300 °C. SEM and TEM have been employed to observe the morphology of NWs after partial and full etching respectively. Deposition of SmCo alloy has been confirmed through EDX analysis whereas XRD peaks shows hexagonal closed packed (hcp-P63/mmc) as the dominant phase with (203) preferred orientation. After MF annealing the crystallinity got improved as manifested by the increase in peak sharpness. Furthermore, after the said field assisted heat treatment the magnetic parameters including coercivity (Hc) from 91 to 527 Oe for θ = 0°, from 101 to 151 Oe for θ = 90° and squareness (SQ) from 0.040 to 0.16 for θ = 0°, from 0.037 to 0.032 for θ = 90° have been observed through VSM. A switching of magnetization reversal mechanism from curling to coherent rotation has been observed after MF annealing due to the stronger inter-wire coupling which leads to parallel alignment of magnetic moments of adjacent NWs. Temperature dependent study has been carried out employing PPMS manifesting gradual increase in Hc from 67 to 440 Oe, Ms from 5.4 × 10−3 to 6.1 × 10−3 emu and SQ from 0.19 to 0.25 with the decrease in temperature up to 5 K.

Online design of green urban garden landscape based on machine learning and computer simulation technology

With the development of machine learning and computer simulation technology, green urban garden landscapes have also made breakthrough progress in modeling. Based on the existing basic technology and its shortcomings, this article discusses the timeliness of the Agent model, defines the time granularity of simulation machine learning, and establishes an Agent model related to the time granularity of machine learning. The corresponding time management mechanism under real-time simulation is constructed, and the switching of machine learning time granularity, real-time guarantee and message interaction mechanism are studied. We use the new model to model the spatial entities to illustrate the modeling method, and design the message interaction between the spatial entities. We analyze the parametric works in the design world from the aspects of nature, art and computer, and summarize the general law of parametric design. Computer-aided design includes the study of traditional calculation-aided design methods. This paper analyzes its existing problems and proposes new methods of parametric design and the generation of computer geometric algorithms. We compare with Auto CAD, which is commonly used in garden and landscape design, and summarize their advantages and disadvantages. The application of the machine learning Grasshopper parameter platform to the design process of actual projects fully reflects its scientific, rational and advanced nature. • The article discusses the timeliness of the Agent model. • We establish an Agent model related to the time granularity of machine learning. • We propose a new method of parametric design.

Switching of alternative electrochemical charging mechanism inside single-walled carbon nanotubes: a quartz crystal microbalance study.

We probed electrochemical ion storage in single-walled carbon nanotubes (SWCNTs) of different diameters in two different organic electrolytes using electrochemical quartz crystal microbalance (EQCM) tracking. The measurements showed that charge storage probed by cyclic voltammetry did not deteriorate when steric effects seemed to hinder the accessibility of counter-ions into SWCNTs, and instead proceeded predominantly by co-ion desorption, as was shown by the decrease in the electrode mass probed by EQCM. The dominant mechanism correlated with the SWCNT diameter/ion size ratio; counter-ion adsorption dominated in the whole potential range when the diameter of SWCNTs was comparable to the size of the largest ion, whereas for larger diameters the charge increase coincided with a decrease in the electrode mass, indicating the dominance of co-ion desorption. The dominance of co-ion desorption was not observed in activated carbon, nor was it previously reported for other carbon materials, and is likely switched on because the carrier density of SWCNT increases with applied potential, and maintains the electrode capacity by co-ion desorption to overcome the steric hindrances to counter-ion adsorption.

(Invited) Mechanistic Studies for Electrochemical Self-Assembly of Cuscn/Stilbazolium Dye Hybrid Thin Films

We have established electrochemical self-assembly (ESA) of inorganic / organic hybrid thin films in which the inorganic is CuSCN, known as a wide bandgap p-type semiconductor, whereas the organic is 4-N,N-dimethylamino-4’-N’-methylstilbazolium chromophore (abbreviated as DAS+) as its salt with tosylate (DAST) known to exhibit second-order nonlinear optical property for terahertz emitters. The CuSCN/DAS hybrid thin films by ESA show concerted photoluminescence based on energy transfer from inorganic CuSCN to organic DAS, making us anticipate its potential use in optoelectronic devices [1]. Understanding the mechanism of ESA to obtain tuning knob to maximize its functionality is therefore important.In our previous study, switching of dye loading mechanism has been suggested, depending on DAS concentration (C DAS) in the bath [2]. With low C DAS, the loading is limited by diffusion so that DAS is entrapped within CuSCN crystal grains, while surface reaction of hybridization begins to limit the dye loading with high C DAS, resulting in formation of unique nanostructures as well as phase separation of inorganic and organic domains. The border for the switching of dye loading mechanism was found as the ratio between bulk concentrations of dye and the [Cu(SCN)]+ complex, C DAS/C comp = ca. 1/31 in case of DAS+ [3].In this study, electrochemical analysis has been performed employing rotating disk electrode (RDE) under variation of bulk concentration of dye (DAST and CNST = 4-cyano-4’-(N’-methyl)stilbazolium tosylate for comparison) to verify the proposed mechanism. CNS+ has a strongly electron withdrawing -CN group and therefore bears a much larger dipole moment of 23.5016 Debye than that of DAS+ (10.1442 Debye) as determined by DFT calculation. Thus, a much stronger interaction of CNS+ with CuSCN (essentially with SCN- ion) is expected than DAS+.The overall behavior of CNS+ has been found exactly the same as DAS+ such as changing the crystal orientation of β-CuSCN to lay down its c-axis and phase transition from β- to α-CuSCN. However, such transitions were found for smaller concentrations of CNS+ than DAS+ because of its stronger affinity with CuSCN. The switching dye loading mechanism and associated change of the hybrid structure has also been observed for CNS. Fig. 1 shows plots of amount of dye loaded into the hybrid thin films against the dye concentrations in the electrolytic bath for DAS+ and CNS+. The steep slopes in low dye concentration range represent diffusion limited loading, whereas the moderate slopes are those limited by surface reaction. The bending points, C DAS = 60 μmol dm-3 and C CNS = 200 μmol dm-3, indicate the switching borders for C comp = 2.5 mM. Because of the increased stability of adsorption of CNS+ on CuSCN surface, diffusion limited loading, thus all dyes reaching the electrode surface buried inside the film, continues to operate up to this high dye concentration. The increased stability of CuSCN/CNS surface complex also resulted in about 3 times more efficient dye uptake in the surface reaction limited regime. These results nicely confirm the validity of the proposed mechanism both for DAS+ and CNS+, and that the switching border can be varied by the stability of CuSCN/dye complex. Full analysis should be able to determine C CNS/C comp ratio as the switching border.[1] K. Uda et al. ACS Omega, 4, 4056-4062 (2019).[2] Y. Tsuda et al., Monatshefte für Chemie, 148, 845-854 (2017).[3] Y. Tsuda et al., J. Electrochem. Soc. 166(9) B3096-B3102 (2019). Figure 1

Role of threading dislocations and point defects in the performance of GaN-based metal-semiconductor-metal ultraviolet photodetectors

The role of threading dislocations and point defects is investigated by comparing the performance of metal-semiconductor-metal ultraviolet photodetectors (PDs) fabricated on GaN epilayers grown by hydride vapour phase epitaxy (HVPE) and metal organic vapour phase epitaxy (MOVPE) techniques. It is found that the density of threading dislocations is higher in HVPE GaN epilayers, however, the devices fabricated on them show a higher photo response, lower leakage current and faster transient response when compared to those fabricated on MOVPE GaN epilayers. It is noticed that a high density of threading dislocations of HVPE grown GaN epilayers doesn't always restrict their usefulness in the development of specific devices. On the other hand, an inferior performance of PDs fabricated on MOVPE GaN epilayers is observed despite their low dislocation density, which is explained by considering the presence of point defects. Further, the room temperature electronic transport is found to be dominated by thermionic emission (thermionic field emission) mechanism in devices fabricated on GaN epilayers grown by HVPE (MOVPE) technique. In case of HVPE based devices, a switching of dominant transport mechanism is seen at ~200 K during cooling down whereas no such behaviour is observed for MOVPE based devices. Key factors affecting the performance of ultraviolet PDs fabricated on GaN epilayers grown by the two techniques and associated charge transport mechanisms are discussed. • Crystalline quality of MOVPE GaN templates is found to be better than HVPE GaN. • HVPE GaN based MSM devices turn out to be better than those fabricated on MOVPE GaN. • A high dislocation density of HVPE GaN doesn't always restrict their usefulness. • Fundamental physical reasons for a better performance of MSM devices are discussed. • Transport mechanism switches at ~200 K for HVPE based GaN MSM devices.

Inhibition of MUC1 exerts cell-cycle arrest and telomerase suppression in glioblastoma cells

Mucin 1 (MUC1) is a transmembrane glycoprotein involved in tumorigenesis of diverse cancers. However, the role of MUC1 in glioblastoma (GBM) has not yet been fully explored. In this study, the anticancer mechanism of MUC1 suppression in GBM was investigated. The expression level of MUC1 was analyzed in human glioma and paired normal brain tissues. MUC1 was overexpressed in GBM and was negatively associated with overall survival. Moreover, we silenced MUC1 to investigate its effect in GBM cell lines and found that knockdown of MUC1 inhibited cell proliferation and resulted in cell cycle arrest at G1 phase. MUC1 silencing decreased the phosphorylation of RB1 and increased the expression of CDKN1B. Gene set enrichment analysis showed that a series of genes related to cell cycle, telomere maintenance and transforming growth factor Beta (TGF-β) signaling in epithelial mesenchymal transition (EMT) were influenced by MUC1 knockdown. Notably, the reduced TERT expression levels combined with impaired telomerase activity and the switching of telomere maintenance mechanism to alternative lengthening of telomeres (ALT) were observed after MUC1 knockdown. Our results support the role of MUC1 in oncological process in GBM which can be developed as a therapeutic target for cell cycle control and telomere maintenance mechanism.

Electrical and thermal transport properties of natural and synthetic FeAsxS2-x (x ≤ 0.01)

The combined powder X-ray diffraction, microstructural, local and bulk chemical analyses of natural pyrite single crystals from Reiche Zeche, Johangeorgenstadt and Pretzchendorf (Erzgebirge, Saxony, Germany) showed compositions FeAs0.002(1)S1.998(9), FeAs0.004(1)S1.996(9) and FeAs0.005(1)S1.995(9), respectively. The arsenic doping leads to smaller semiconducting energy gaps (Eg ~0.1–0.2 eV) in comparison with binary FeS2 (Eg = 0.96 eV), as well as switching of conduction type mechanism from n-to the p-type. These findings are supported by the measurements of the electrical resistivity and Seebeck coefficient of the synthetic FeAsxS2-x series (maximal As-content x = 0.01 at 773 K). The investigations of sintered FeS2 + MO2 (M = Si, Ti, Zr) composites indicate that some insulating metal oxides as impurities influence less the electrical transport properties of pyrite. All performed studies unambiguously confirmed that p-type conductivity for T > 300 K is a hallmark of the ternary As-doped FeAsxS2-x (x ≥ 0.002) pyrites.

Dual Mode Radiative Transition from a Phenoselenazine Derivative and Electrical Switching of the Emission Mechanism.

Dual emission featuring both thermally activated delayed fluorescence (TADF) and phosphorescence was engineered into a single metal-free molecule, phenyl(10-phenyl-10H-phenoselenazin-3-yl)methanone. Selenium incorporated into the molecule increases the spin-orbit coupling to facilitate both TADF and phosphorescence, whereas donor-acceptor units promote TADF emission. The relative contribution of the green TADF and yellow phosphorescence can be controlled by the driving voltage of the devices. At low voltage, phosphorescence emission dominates the electroluminescence, whereas TADF is the major component at high voltages. The mechanism of dual emission was explored using experimental and theoretical methods.

Electrochemical Self-Assembly of CuSCN/4-Cyano-4’-(N’-Methyl)Stilbazolium Hybrid Thin Films

Electrochemically self-assembled (ESA) CuSCN/4-(N,N-dimethylamino)-4’-(N’-methyl)stilbazolium (DAS) hybrid thin film was found to exhibit concerted photoluminescent (PL) property based on energy transfer from CuSCN to DAS [1]. The amount of co-precipitated DAS (P DAS) during ESA linearly increased on increasing DAS concentration (C DAS) in the bath but changes its slope due to switching of dye loading mechanism from diffusion limited to surface reaction limited [2]. The full analysis revealed the switching border to be dependent on the ratio between the concentration of CuSCN precursor complex, [Cu(SCN)]+ (C comp), and C DAS as C comp/C DAS = ca. 31 [3]. When the dye loading operates as surface reaction limited, phase separation of CuSCN and DAS in nano-scale occurs to exhibit efficient PL. Thus, finding an alternative chromophore with higher or lower affinity with CuSCN than DAS should result in shifting of the switching border with smaller or larger C comp/C dye than the above indicated value for DAS. In this study, we employed 4-cyano-4’-(N’-methyl)stilbazolium (CNS) for ESA with CuSCN. CNS has a strong dipole moment due to the presence of strongly electron withdrawing cyano group and thus is expected to exhibit a higher affinity to CuSCN than DAS.CuSCN/CNS hybrid thin films were obtained by cathodic electrolysis with various C CNS while fixing C comp = 2.5 mM. P CNS linearly increased upon increase of C CNS and changes its slope at around 200 μM, far larger than the switching point observed for DAS (around 60 μM). The steep slope for the low C CNS range should be determined by the diffusion of CNS to yield its diffusion coefficient D CNS = 1.49×10-6 cm2 s-1, slightly larger than that found for DAS (D DAS = 1.25×10-6 cm2 s-1). On the other hand, about 3 times larger P CNS for given dye concentrations and steeper slope of surface reaction limited regime for CNS than those found for DAS indicate higher adsorption stability of CNS than DAS to CuSCN surface. Soaking the CuSCN/CNS hybrid thin films electrodeposited at C CNS = 60 and 800 μM to represent the dye loading as diffusion and surface reaction limited, respetively, into dimethylacetamide resulted in partial and total extraction of CNS to reveal entrapment and phase-separation of CNS, just like the case of CuSCN/DAS. The maximum P CNS appears to be saturated when C CNS > 800 μM for CNS aggregate to occupy close to 30% of the total film volume.The present results already nicely support the validity of the switching of ESA mechanism, being common for both DAS and CNS. Smaller C comp/C CNS for the switching border and larger stability constant for surface complex formation are expected for CNS than DAS from full analysis.[1] K. Uda et al., ACS Omega, 4, 4056-4062 (2019).[2] Y. Tsuda et al., Monatsh. Chem., 148, 845 (2017).[3] Y. Tsuda et al., J. Electrochem. Soc., 166, B3096-B3102 (2019). Figure 1