Scholarly Publications - Chemistry

Permanent URI for this collectionhttps://hdl.handle.net/11693/115489

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Open Access
3d cobalt dicyanamide derived 2d- ayered co(oh)2 based catalyst for light driven hydrogen evolution
(American Chemical Society, 2024-02-09) Akbari, Sina Sadigh; Karadaş, Ferdi
Derivation of 3D coordination polymers to produce active catalysts has been a feasible strategy to achieve a precise coordination sphere for the catalytic site. This study demonstrates the partial conversion of a 3D cobalt dicyanamide coordination polymer, Co-dca, to a 2D layered hydroxide-oxyhydroxide structure under photocatalytic conditions. The catalyst exhibits an activity as high as 28.3 mmol h(-1) g(-1) in the presence of a [Ru(bpy)(3)](2+)/triethylamine (TEA) couple to maintain it for at least 12 h. Photocatalytic and characterization studies reveal that the dicyanamide ligand within the coordination polymer is crucial for governing modification and achieving a superior H-2 evolution rate. Moreover, we observed the critical role of TEA as the hydrolyzing agent for the transformation process. This study displays that the metal dicyanamides can be utilized as templates for preparing active and robust catalysts.
Open Access
Periodic stratification of colloids in a liquid phase produced by a precipitation reaction and gel swelling
(American Chemical Society, 2024-05-17) Tootoonchian, Pedram; Holló, Gábor ; Uzunlar, Rana; Lagzi, Istvan; Baytekin, Bilge
Pattern formation is a frequent phenomenon occurring in animate and inanimate systems. The interplay between the mass transport of the chemical species and the underlying chemical reaction networks generates most patterns in chemical systems. Periodic precipitation is an emblematic example of reaction–diffusion patterns, in which the process generates a spatial periodic structure in porous media. Here, we use the dormant reagent method to produce colloidal particles of Prussian blue (PB) and PB analogues at the liquid–gel interface. The generated particles produced a stable periodic stratification pattern in time in the liquid phase placed on top of the solid hydrogel. The phenomenon is governed by periodic swelling of the gel driven by the osmotic stress and stability of the formed particles. To illustrate the phenomenon, we developed an extended reaction–diffusion model, which incorporated the gel swelling and sedimentation effect of the formed colloids and could qualitatively reproduce the pattern formation in the liquid phase.
Open Access
Oil-in-water emulsions probed using fluorescence multivariate-curve-resolution spectroscopy
(American Chemical Society, 2024-06-11) Gündoğdu, Gülsüm; Topuzlu, Ezgi Yılmaz; Mutlu, Ferhat; Ertekin, Umay Eren; Okur, Halil İbrahim
Hydrophobic surfaces in contact with aqueous media are omnipresent in nature. A plethora of key biological and physiological processes occur at the interface of immiscible fluids. Besides its fundamental importance, probing such interfaces is rather challenging, especially when one medium is bathed in the other. Herein, we demonstrate a fluorescence-based method that probes the oil–water interface and interfacial processes through surface dielectric perturbations. The fluorescence response of Nile Red is measured in hexadecane in water nanoemulsions. Three major spectral components appear: two from the bulk liquid media (hexadecane and water) and a distinct band at around 640 nm due to the interfacial component. Such spectra are deconvoluted using the multivariate-curve-resolution algorithm, and interface-correlated fluorescence spectra are attained. The influence of anionic sodium dodecylbenzenesulfonate (SDBS) and cationic cetyltrimethylammonium bromide (CTAB) surfactants on the oil–water interface is elucidated with concentration-dependent measurements. A charge-dependent spectral shift is observed. The interface correlated band at 641 nm for bare hexadecane nanoemulsions red shifts in the presence of anionic surfactants, indicating an apparent dielectric increase. In contrast, the same band gradually blue shifts with increasing cationic surfactant concentration, indicating an apparent interface dielectric decrease. Such a method can be utilized to probe alterations at interfaces beyond the oil/water interface.
Open Access
Single-material solvent-driven polydimethylsiloxane sponge bending actuators
(Mary Ann Liebert, Inc. Publishers, 2024-10) Mutlutürk, Esma; Özbek, Doğa; Özcan, Onur; Demirel, Gökçen Birlik; Baytekin, Bilge
Soft robots mimic the agility of living organisms without rigid joints and muscles. Continuum bending (CB) is one type of motion living organisms can display. CB can be achieved using pneumatic, electroactive, or thermal actuators prepared by casting an active layer on a passive layer. The corresponding input actuates only the active layer in the assembly resulting in the bending of the structure. These two different layers must be laminated well during manufacturing. However, the formed bilayer can still delaminate later, and the detachment hampers the actuator's reversible, long-time use. An approach to creating a single material bending actuator was previously reported, for which spatial gradient swelling was used. This authentic approach allows a single material to be manufactured as a bending actuator, allowing easy access to such actuators without lamination. In this study, we show spatial porosity differences in the sponges of polydimethylsiloxane (PDMS) (a common material in soft robotics) can be used to create the required anisotropy for bending. The spongy polymers are manufactured through table sugar templates and actuated by (organic) solvent absorption/desorption. This enables some versatility in the mechanical properties, shape, actuation force, and actuation speed. The one-material system's straightforward production and seamless nature are advantageous for reversible and repetitive bending. This simple method can further be developed in hydrogels and polymers for soft robotics and functional materials.
Open Access
Lyotropic “salty” tuning for straightforward diversification and anisotropy in hydrogel actuators
(American Chemical Society, 2025-01-01) Tootoonchian, Pedram; Bahçeci, Levent; Budnyk, Andriy; Okur, Halil İbrahim; Baytekin, Bilge
The specific ion effect (SIE), the control of polymer solubility in aqueous solutions by the added ions, has been a phenomenon known for more than a century. The seemingly simple nature of the ion–polymer–water interactions can lead to complex behaviors, which have also been exploited in many applications in biochemistry, electrochemistry, and energy harvesting. Here, we show an emerging diversification of actuation behaviors in “salty” hydrogel and hydrogel-paper actuators. SIE controls not only the dehydration speeds but also the water diffusion and mechanical properties of the gels, leading to composite actuation behavior. Most reported thermally activated hydrogel actuators suffer from expensive precursors or complex fabrication processes. This work addresses these issues by using a physicochemical effect displayed within an inexpensive gel with common salts. SIE-controlled anisotropic actuation in geometrically different systems provides a demonstration of how such physicochemical effects can lead to higher complexity in basic soft material design and hydrogel soft robotics.
Open Access
Non-ionic surfactant self-assembly in calcium nitrate tetrahydrate and related salts
(Royal Society of Chemistry, 2025-02-21) Zahid, Yashfeen; Li, Yizhen; Dağ, Ömer; Warr, Gregory G.; Albayrak, Cemal
Self-assembly of amphiphilic molecules can take place in extremely concentrated salt solutions, such as inorganic molten salt hydrates or hydrous melts. The intermolecular interactions governing the organization of amphiphilic molecules under such extreme conditions are not yet fully understood. In this study, we investigated the specific effects of ions on the self-assembly of the non-ionic surfactant C12H25(OCH2CH2)10OH (C12E10) under extreme salt concentrations, using calcium nitrate tetrahydrate as a reference. The mixtures of Ca(NO3)2·4H2O and C12E10 displayed lyotropic (H1 and I1) and micellar phases, in contrast to CaCl2·xH2O–C12E10 or CaBr2·xH2O–C12E10 mixtures where mesostructurally ordered salt–surfactant complexes were observed. The Ca(NO3)2·4H2O–C12E10 system was thoroughly investigated by constructing its binary phase diagram and performing thermal and spectral comparisons with other salt hydrates. The Ca(NO3)2 system displayed significantly higher isotropization temperatures than zinc, aluminium, and lithium nitrate systems. ATR-FTIR analysis revealed that Ca2+ primarily interacts with the surfactant head groups through ion–dipole interactions, while these interactions were less pronounced with other cations. The results show that an intermediate hydration/coordination energy of the metal ion can lead to stronger metal–surfactant interactions and thermally more stable liquid crystals. Comparison between the Ca(NO3)2, CaCl2, and CaBr2 systems suggests that reduced ion pair formation enhances the interactions between Ca2+ and oxyethylene groups, leading to the salting-out of salt–surfactant complexes. Despite its low water content and strong intermolecular interactions, the Ca(NO3)2·xH2O–C12E10 system exhibited an electrical conductivity of up to 1.0 × 10−3 S cm−1 with 4 water molecules per salt, making it a promising medium for electrochemical applications.
Open Access
Chemical reactions with Liesegang rings: generation of non-permanent thermal patterns
(Royal Society of Chemistry, 2025-01-08) Arı, Hatice; Uzunlar, Rana; Akbulut, Elif Sıla; Lagzi, Istvan; Baytekin, Bilge
Patterns are encountered and employed in nature, such as in the communication or growth of organisms and sophisticated behaviors such as camouflage. Artificial patterns are not rare, either. They can also be used in sensing, recording information, and manipulating material properties. Natural or artificial, most patterns have the colors of visible light. Patterns of infrared radiation are rare, even though some organisms and artificial sensors can detect infrared. In this work, we display a formation of non-permanent infrared Liesegang patterns in different gel media. We used the exothermic neutralization of the solid Mg(OH)2 formed as Liesegang patterns (LPs) to obtain these patterns. The LPs of infrared radiation (IR patterns) appear due to a temperature increase of up to 4 °C on the gel surface. We also show that it is possible to ‘read’ the information with an IR camera when the patterns are concealed and invisible. The idea can be expanded to other chemical systems and used to communicate with IR. On the other hand, the chemical reactions on the patterned solids can also be used to pattern other artificial material patterns directly inaccessible with the existing reaction–diffusion systems.
Open Access
Utility of Lissajous plots for electrochemical impedance spectroscopy measurements: detection of non-linearity and non-stationarity
(Electrochemical Society, Inc., 2024-01-10) Zabara, M. A.; Goh, J. M.; Gaudio, V. M.; Zou, L.; Orazem, M. E.; Ülgüt, Burak
Correct interpretation of Electrochemical Impedance Spectroscopy (EIS) data is bound to the linearity and stationarity of the measurement. Current-Potential traces, also known as Lissajous figures for EIS measurements, contain valuable information regarding the linearity and the stationarity of the obtained data. Here, the behavior of the Lissajous figures is analyzed for various scenarios. The Lissajous analysis is shown to be helpful in the determination of the linearity and the stationarity of the data, especially for situations where Kramers-Kronig compatibility tests fail. The averaging of the Lissajous plots is shown to change the EIS results for non-linear and non-stationary systems. Further, the analysis of the Lissajous figures in the frequency domain by means of Fourier transforms is found to be very useful in differentiating between the non-linear and the non-stationary behaviors in the obtained data. The effect of averaging the Lissajous figures is also shown to make a difference when the system is non-stationary.
Open Access
On the proper use of a warburg impedance
(Electrochemical Society, Inc., 2024-04-17) Orazem, Mark E.; Ülgüt, Burak
Recent battery papers commonly employ interpretation models for which diffusion impedances are in series with interfacial impedance. The models are fundamentally flawed because the diffusion impedance is inherently part of the interfacial impedance. A derivation for faradaic impedance is presented which shows how the charge-transfer resistance and diffusion resistance are functions of the concentration of reacting species at the electrode surface, and the resulting impedance model incorporates diffusion impedances as part of the interfacial impedance. Conditions are identified under which the two model formulations yield the same results. These conditions do not apply for batteries.
Open Access
Observing the effect of architecture on spiral and bobbin lithium thionyl chloride (Li/SOCl₂) batteries with temperature-dependent electrochemical impedance spectroscopy (EIS)
(Electrochemical Society, Inc., 2024-07-09) Katırcı, Gökberk; Civan, Fazlı Eren; Zabara, Mohammed Ahmed; Ülgüt, Burak
Electrochemical Impedance Spectroscopy (EIS) has been utilized as an in situ, non-destructive diagnostic tool for the comprehensive electrochemical characterization of lithium thionyl chloride (Li/SOCl₂) batteries. Li/SOCl₂ batteries come in various geometries or architectures tailored for the application area and required specifications. In this study, detailed EIS studies of spiral and bobbin-type Li/SOCl₂ batteries are performed at different temperatures to investigate the impedance response, calculate the activation energy of various processes, and observe the effect of geometry. An extensive comparison between the two geometries reveals that the processes can be differentiated by their time constants and capacitances. It was observed that the current collector impedance masks the high-frequency response of bobbin-type at elevated temperatures with similar Li redox processes in the middle-frequency region. Additionally, transmission line fit is performed on the bobbin type to investigate diffusion-related cathodic processes.
Embargo
Manganese-doped iron sulfide nanoplatelets on carbon cloth: a negative electrode material for flexible and wearable supercapacitors
(Elsevier BV, 2025-02-15) Gözütok, Almila Nur; Durukan, Mete Batuhan; Koçak, Yusuf; Özensoy, Emrah; Unalan, Husnu Emrah; Nalbant, Emren
Herein, we report the direct growth of manganese-doped iron sulfide (pyrrhotite) nanoplatelets on the carbon cloth (CC) fibers by a one-step hydrothermal method without the need for organic binders. Manganese-doped iron sulfide nanoplatelets on CC (MFS-CC) revealed surface enrichment of polysulfide species over sulfites, exhibited a variety of $Mn^{2+/3+/4+}$, $Fe^{3+/4+}$ surface species as well as unique $Fe_x$$Mn_y$$O_z$$S_n$ surface domains resulting in a multitude of electroactive sites, enhancing ion transport and an exceptional electrochemical performance. As-prepared electrodes yielded a high specific capacitance of 206 F $g^{−1}$ at a scan rate of 10 $mVs^{−1}$. Moreover, once constructed, the electrodes were encapsulated with polyvinyl chloride (PVC) to ensure efficient operation for up to three months. As a result, the device demonstrated remarkable cyclic stability, enduring up to 11,000 cycles without degradation. Finally, the assembled electrodes were integrated to form an asymmetric wearable supercapacitor, and this device effectively illuminated a green light emitting diode (LED) integrated into a hoodie, showcasing its potential for powering wearable electronics.
Open Access
Solutions of three-particle Faddeev equations above the breakup threshold via separable expansions of two-particle resolvents in a basis of two-particle pseudostates
(American Physical Society, 2024-05-30) Kuruoğlu, Zeki Cemal
A separable expansion of the two-particle free resolvent in terms of two-particle pseudostates is used to convert Alt-Grassberger-Sandhas (AGS) integral equations into a set of effective two-body equations in spectator degrees of freedom. The resulting effective two-body equations are much like the multichannel Lippmann-Schwinger (LS) equations of inelastic scattering with real, energy independent, nonsingular potential matrices. Hence, they are more conducive to computations than the effective equations that ensue in the conventional approach based on separable expansions of two-particle transition operators. In particular, the problem of moving singularities of the conventional approach is avoided. The effective propagator matrix is complex and nondiagonal, and exhibits simple-pole singularities in diagonal elements corresponding to open rearrangement channels. These singularities can be handled by simple subtraction procedures well known from two-particle scattering. After regularization of the kernel, the set of coupled LS-type equations in the spectator momenta are solved rather straightforwardly via the Nystr & ouml;m method in which the integrals over spectator momenta are discretized using suitable quadrature rules. Solutions of effective two-body equations are then used to calculate the breakup amplitudes using the well-known relationship between rearrangement and breakup amplitudes. This proposed method has been tested on two models: (i) particle-dimer collisions in a three-boson model with s-wave separable pair potentials and (ii) an s-wave benchmark model with local pair potentials of then + d collisions. Calculations reported in the present article show that rather accurate results for elastic and breakup amplitudes can be obtained with pseudostates generated from a relatively small number of local basis functions in momentum space.
Embargo
Greasy cations bind to neutral macromolecules in aqueous solution
(American Chemical Society, 2024-06-05) Ertekin, Umay Eren; Okur, Halil İbrahim
Ions influence the solution properties of macromolecules. Although much is known about anions, cationic effects are considered mostly in terms of weak interactions or exclusion from neutral interfaces. Herein, we have systematically studied the effect of quaternary tetraalkylammonium cations ($NH_4+, NMe_4+, NEt_4+, NPr_4+, NBu_4+$) on the phase transition of poly(N-isopropylacrylamide) (PNIPAM) in aqueous solution. Solubility measurements were coupled to H-1 NMR and ATR-FTIR spectroscopic measurements. The solubility and NMR measurements revealed a direct binding between the greasiest cations and the isopropyl group of the macromolecule, evidenced from the nonlinear, Langmuir-type chemical shift response only at the isopropyl NMR signals with increasing salt concentrations. The ATR-FTIR measurements focusing on the amide oxygen showed that it is not the main direct-binding site. Additionally, the salting-out effects of the greasier cations correlate with their hydration entropies. These results demonstrate that the most weakly hydrated cations can bind to macromolecules as strongly as the weakly hydrated Hofmeister anions.
Embargo
AC-modulated XPS enables to externally control the electrical field distributions on metal electrode/Ionic Liquid devices
(American Chemical Society, 2024-04-20) Kutbay, Ezgi; İnce, Süleyman; Süzer, Şefik
X-Ray Photoelectron Spectroscopy (XPS) has been utilized to extract local electrical potential profiles by recording core-level binding energy shifts upon application of the AC [square-wave (SQW)] bias with different frequencies. An electrochemical system consisting of a coplanar capacitor with a polyethylene membrane (PEM) coated with the Ionic Liquid (IL) N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI) as the electrolyte is investigated. Analyses are carried out in operando, such that XPS measurements are recorded simultaneously with current measurements. ILs have complex charging/discharging processes, in addition to the formation of Electrical Double Layers (EDL) at the interfaces, and certain properties of these processes can be captured using AC modulation within appropriate time windows of observation. Herein, we select two frequencies, namely, 10 kHz and 0.1 Hz, to separate effects of the fast polarization and slow migratory motions, respectively. Moreover, the local potential developments after adding two equivalent series resistors at three different physical positions of the device have been carefully evaluated from the binding energy shifts in the F 1s peak representing the anion of the IL. This circuit modification allows us to quantify the AC currents passing through the device, as well as the system's impedance, in addition to revealing the potential variations due the IR drops. The complex AC-modulated local XPS data recorded can also be faithfully reproduced using the unmodulated F 1s spectrum and by convoluting it with electrical circuit output provided by the LT-Spice software. The outcome of these efforts is a more realistic equivalent circuit model, which can be related to chemical/physical makeup of the electrochemical system. An important finding of this methodology emerges as the possibility to induce additional local electrical field developments within the device, the directions of which can be reversed controllably.
Open Access
Reexamination of the coupled-reaction-channels method: Derivation from the triad of three-particle Lippmann-Schwinger equations and its use with separable resolvent expansions
(American Physical Society, 2024-11-24) Kuruoğlu, Zeki Cemal
An interesting connection is found between the coupled-reaction-channel (CRC) approach and the triad of Lippmann-Schwinger (LS) equations for the three-particle scattering state. It turns out that the CRC decomposition ansatz can be used as a vehicle to couple the three uncoupled LS equations. The possibility of using CRC decomposition as a means of coupling the three LS equations does not seem to have been noticed before. This finding allows one to introduce a set of coupled equations for CRC rearrangement operators in which two-particle resolvents appear naturally as the propagator term. The formal operator equations are then reduced to effective two-body form by employing two different separable expansions of the two-particle resolvent. The two versions of the ensuing CRC effective two-body equations are applied to a benchmark model of n+d scattering. Although the two CRC versions differ considerably in the way breakup channel manifests itself in the effective two-body equations, both sets of results for elastic and breakup amplitudes of the benchmark model are almost the same and are in good agreement with the results available in the literature. This study further corroborates that the CRC approach is an alternative versatile tool for three-particle dynamics and is on par with approaches based on Faddeev theory.
Unknown
Roll-to-roll fabrication of lithiophilic Sn-modified Cu mesh via chemical tin plating approach for long-cycling lithium metal batteries
(Beijing Youse Jinshu Yanjiu Zongyuan, 2024-07-22) Liu, Ke-Xin; Tan, Ran; Zheng, Zhong; Zhao, Rui-Rui; Ülgüt, Burak; Ai, Xin-Ping; Qian, Jiang-Feng
Lithium metal, with its exceptionally high theoretical capacity, emerges as the optimal anode choice for high-energy-density rechargeable batteries. Nevertheless, the practical application of lithium metal batteries (LMBs) is constrained by issues such as lithium dendrite growth and low Coulombic efficiency (CE). Herein, a roll-to-roll approach is adopted to prepare meter-scale, lithiophilic Sn-modified Cu mesh (Sn@Cu mesh) as the current collector for long-cycle lithium metal batteries. The two-dimensional (2D) nucleation mechanism on Sn@Cu mesh electrodes promotes a uniform Li flux, facilitating the deposition of Li metal in a large granular morphology. Simultaneously, experimental and computational analyses revealed that the distribution of the electric field in the Cu mesh skeleton induces Li inward growth, thereby generating a uniform, dense composite Li anode. Moreover, the Sn@Cu mesh-Li symmetrical cell demonstrates stable cycling for over 2000 h with an ultra-low 10 mV voltage polarization. In Li parallel to Cu half-cells, the Sn@Cu mesh electrode demonstrates stable cycling for 100 cycles at a high areal capacity of 5 mAh.cm(-2), achieving a CE of 99.2%. This study introduces a simple and large-scale approach for the production of lithiophilic three-dimensional (3D) current collectors, providing more possibilities for the scalable application of Li metal batteries.
Unknown
Sulfide-capped ınp/zns quantum dot nanoassemblies for a photoactive antibacterial surface
(American Chemical Society, 2024-03-05) Khan, Saad Ullah; Surme, Saliha; Eren, Guncem Ozgun; Almammadov, Toghrul; Pehlivan, Cigdem; Kaya, Lokman; Hassnain, Muhammad; Onal, Asim; Balamur, Ridvan; Sahin, Afsun; Vanalakar, Sharadrao; Kolemen, Safacan; Alkan, Fahri; Kavakli, Ibrahim Halil; Nizamoglu, Sedat
Semiconductor photocatalysis has recently emerged as a promising method for microbial inactivation. So far, quantum dots have generally been investigated as antibacterial suspension. Instead, here we demonstrate a InP/ZnS quantum dot nanoassembly film against both Gram-negative and Gram-positive bacteria. For effective operation in the solid phase, a thin layer of ZnS shell was grown on InP QD and the native long-chain ligand of stearic acid was replaced with sulfide that led to a high quantum yield of superoxide generation as 4.9%. QDs are assembled onto solid surfaces through sequential dip coating of positively charged poly(diallyldimethylammonium chloride) and negatively charged QDs. These QD nanoassemblies demonstrate growth inhibition against Escherichia coli and multidrug-resistant Staphylococcus aureus under illumination. Interestingly, such an approach can be directly applied to irregular surfaces, as well. This study unveils the potential of the nanoengineering of QDs for antibacterial coatings.
Unknown
Na-promoted bimetallic hydroxide nanoparticles for aerobic c-h activation catalyst design principles and insights into reaction mechanism
(American Chemical Society, 2024-10-25) Erdivan, Beyzanur; Çalıkyılmaz, Eylül; Bilgin, Suay; Erdali, Ayşe Dilay; Gül, Damla Nur; Ercan, Kerem Emre; Türkmen, Yunus Emre; Özensoy, Emrah
A precious metal-free bimetallic Fe x Mn1-x (OH) y hydroxide catalyst was developed that is capable of catalyzing aerobic C-H oxidation reactions at low temperatures, without the need for an initiator, relying sustainably on molecular oxygen. Through a systematic synthetic effort, we scanned a wide nanoparticle synthesis parameter space to lay out a detailed set of catalyst design principles unraveling how the Fe/Mn cation ratio, NaOH(aq) concentration used in the synthesis, catalyst washing procedures, extent of residual Na+ promoters on the catalyst surface, reaction temperature, and catalyst loading influence catalytic C-H activation performance as a function of the electronic, surface chemical, and crystal structure of Fe x Mn1-x (OH) y bimetallic hydroxide nanostructures. Our comprehensive XRD, XPS, BET, ICP-MS, 1H NMR, and XANES structural/product characterization results as well as mechanistic kinetic isotope effect (KIE) studies provided the following valuable insights into the molecular level origins of the catalytic performance of the bimetallic Fe x Mn1-x (OH) y hydroxide nanostructures: (i) catalytic reactivity is due to the coexistence and synergistic operation of Fe3+ and Mn3+ cationic sites (with minor contributions from Fe2+ and Mn2+ sites) on the catalyst surface, where in the absence of one of these synergistic sites (i.e., in the presence of monometallic hydroxides), catalytic activity almost entirely vanishes, (ii) residual Na+ species on the catalyst surface act as efficient electronic promoters by increasing the electron density on the Fe3+ and Mn3+ cationic sites, which in turn, presumably enhance the electrophilic adsorption of organic reactants and strengthen the interaction between molecular oxygen and the catalyst surface, (iii) in the fluorene oxidation reaction the step dictating the reaction rate likely involved the breaking of a C-H bond (k H /k D = 2.4), (iv) reactivity patterns of a variety of alkylarene substrates indicate that the C-H bond cleavage follows a stepwise PT-ET (proton transfer-electron transfer) pathway.
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Template-directed selective photodimerization reactions of 5-arylpenta-2,4-dienoic acids
(American Chemical Society, 2024-07-10) Munir, Badar; Yağcı, Bilge Banu; Zorlu, Yunus; Türkmen, Yunus Emre
We developed an efficient method that enables selective photodimerization of 5-arylpenta-2,4-dienoic acids (i.e., vinylogous cinnamic acids). The use of 1,8-dihydroxynaphthalene as a template ensures proximity of the two reacting olefins so that irradiation of template-bound dienoic acids gives mono [2 + 2] cycloaddition products in good to excellent yields (up to 99%), as single regioisomers, and with high diastereoselectivities (dr = 3:1 to 13:1). The geometrical and stereochemical features of compounds 12a, 16a, and 22a were analyzed by X-ray crystallography.
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Electrochemical Impedance Spectroscopy (EIS) and non-linear harmonic analysis (NHA) of Li-SOCl2/SO2Cl2 batteries
(Pergamon-Elsevier Science Ltd., 2024-03-20) Katırcı, Gökberk; Civan, Fazlı Eren; Jung, Sunghoon; Lee, Chae Bong; Ülgüt, Burak
Electrochemical Impedance Spectroscopy (EIS) is a valuable tool for characterizing primary lithium batteries. Before fitting the spectrum, the so-called Kramers-Kronig(KK) method has to be checked for the reliability and accuracy of the EIS spectrum. The decision to further fit and analyze the spectrum for physical events in the system is made after checking the KK compatibility of the spectrum. In this paper, we propose further confirmation of the reliability and the accuracy of the EIS spectrum by using the Non-linear harmonic analysis (NHA) of the measurement. The study shows that the KK-compatible EIS spectrum shows homogeneous higher harmonics results where one can further verify the spectrum. The phase of the excitation signal and its effects on the NHA are discussed. A measurement method for measuring Li/SOCl2 and SO2Cl2 batteries to obtain the KK-compatible EIS spectrum is introduced.