Category Archives: ChemistryOpen

Triplet‐Singlet Emission of d‐Block Metal Complexes Characterized by Spin‐Orbit Natural Transition Orbitals

Posted on 5 March 2024 by nA. Zaichenko, nJ. Autschbachn

In the present study, the SO- NTO technique was applied to analyze triplet-to-singlet emission in a set of transition metal complexes with Mo, W, Re, and Ir. The source of intensity in the spin-orbit forbidden transitions has been demonstrated and discussed.

Abstract

Spin-orbit natural transition orbital (SO-NTO) methodology, recently developed in our group for complete and restricted active space (CAS/RAS) wavefunction calculations, is applied to analyze triplet-to-singlet emission in transition metal complexes. The lowest-energy (longest-wavelength) spin-forbidden transition is studied for for [Ir(pbt)2(acac)] and [Re(CO)4(pbt)] and the complexes [W(CO)4(bpy)] and [Mo(CO)4(bpy)]. For the latter complexes, spin-forbidden transitions from higher spin-triplet levels are additionally analyzed. SO-NTOs are compared with spin-free NTOs for the transitions under consideration. The major assignment of a spin-forbidden transition is obtained from the spin-free NTO analysis, while the source of intensity of the electronic transition is revealed by the SO-NTOs.

Wearable Electrochemical Sensor for Sweat‐Based Potassium Ion and Glucose Detection in Exercise Health Monitoring

Posted on 5 March 2024 by nLei Ma, nWenhao Hou, nZhi Ji, nZiheng Sun, nMuxi Li, nBolin Liann

This study developed a wearable device to provide users with real-time insights into their physiological state during exercise. By collecting sweat and utilizing electrochemical techniques, it detects glucose and potassium levels and offers individuals a molecular-level health perspective. It has the potential to aid in disease prevention and exercise motivation.

Abstract

The increasing prevalence of wearable devices has sparked a growing interest in real-time health monitoring and physiological parameter tracking. This study focuses on the development of a cost-effective sweat analysis device, utilizing microfluidic technology and selective electrochemical electrodes for non-invasive monitoring of glucose and potassium ions. The device, through real-time monitoring of glucose and potassium ion levels in sweat during physical activity, issues a warning signal when reaching experimentally set thresholds (K+ concentration at 7.5 mM, glucose concentrations at 60 μM and 120 μM). This alerts users to potential dehydration and hypoglycemic conditions. Through the integration of microfluidic devices and precise electrochemical analysis techniques, the device enables accurate and real-time monitoring of glucose and potassium ions in sweat. This advancement in wearable technology holds significant potential for personalized health management and preventive care, promoting overall well-being, and optimizing performance during physical activities.

Adjusting UV‐Vis Spectrum of Alizarin by Insertion of Auxochromes

Posted on 5 March 2024 by

Adjusting UV-Vis Spectrum of Alizarin: Introduction of an electron-donor group causes the transition bands to be significantly red-shifted whereas electron-withdrawing groups cause a minor blue-shifting.

Abstract

First synthesized in 1868, alizarin became one of the first synthetic dyes and was widely used as a red dye in the textile industry, making it more affordable and readily available than the traditional red dyes derived from natural sources. Despite extensive both experimental and computational analyses on the electronic effects of substituents on the shape of the visible spectrum of alizarin and alizarin Red S, no previous systematic work has been undertaken with the aim to fine tune the dominant absorption region defining its color by introducing other electron-withdrawing or electron-donor groups. For such, we have performed a comprehensive study of electronic effects of substituents in position C₃ of alizarin by means of a time dependent DFT approach. These auxochromes attached to the chromophore are proven to alter both the wavelength and intensity of absorption. It is shown that the introduction of an electron-donor group in alizarin causes the transition bands to be significantly red-shifted whereas electron-withdrawing groups cause a minor blue-shifting.

First‐Principles Studies on Transition Metal Doped Mo2B2 as Anode Material for Li‐Ion Batteries

Posted on 5 March 2024 by nJianjian Shi, nChaojie Yu, nWei Kang, nXiuchan Xiao, nXiaoli Sunn

Few studies have investigated whether the electrochemical performance of Mo₂B₂ as an LIB anode material can be improved via doping to increase the charge-discharge rates. In this study, we successfully manipulated Mo₂B₂ as an LIB anode material via transition-metal doping and screened out better TM-doped Mo₂B₂, such as Co-doped Mo₂B₂, to provide theoretical support.

Abstract

New two-dimensional (2D) transition-metal borides have attracted considerable interest in research on electrode materials for Li-ion batteries (LIBs) owing to their promising properties. In this study, 2D molybdenum boride (Mo₂B₂) with and without transition metal (TM, TM=Mn, Fe, Co, Ni, Ru, and Pt) atom doping was investigated. Our results indicated that all TM-doped Mo₂B₂ samples exhibited excellent electronic conductivity, similar to the intrinsic 2D Mo₂B₂ metal behavior, which is highly beneficial for application in LIBs. Moreover, we found that the diffusion energy barriers of Li along paths 1 and 2 for all TM-doped Mo₂B₂ samples are smaller than 0.30 and 0.24 eV of the pristine Mo₂B₂. In particular, for 2D Co-doped Mo₂B₂, the diffusion energy barriers of Li along paths 1 and 2 are reduced to 0.14 and 0.11 eV, respectively, making them the lowest Li diffusion barriers in both paths 1 and 2. This indicates that TM doping can improve the electrochemical performance of 2D Mo₂B₂ and that Co-doped Mo₂B₂ is a promising electrode material for LIBs. Our work not only identifies electrode materials with promising electrochemical performance but also provides guidance for the design of high-performance electrode materials for LIBs.

Effect of Co‐Surfactants on Properties and Bactericidal Activity of Cu2O and Hybrid Cu2O/Ag Particles

Posted on 1 March 2024 by

This study focuses on a green synthesis of Cu₂O and Cu₂O−Ag particles using ascorbic acid (LAA) as a reducing agent in the presence of two surfactants, polyethylene glycol 6000 and sodium dodecyl sulfate. The hybrid materials exhibit strongly antibacterial activity and are potential for the application in the acrylic emulsion coating.

Abstract

Nanomaterials based on metal oxides, especially Cu₂O, have received much attention in recent years due to the many unique properties of the surface plasmon resonance they provide. The report presented the co-precipitation method, a simple preparation method to produce Cu₂O oxide particles. In addition, to improve the unique antibacterial properties of Cu₂O, a proposed method is to attach Ag nanoparticles to the surface of Cu₂O particles. The Cu₂O and Cu₂O−Ag particles were synthesized based on redox reactions using ascorbic acid (LAA) as a reducing agent. Moreover, in this experiment, two surfactants, polyethylene glycol 6000 (PEG 6000) and sodium dodecyl sulfate (SDS), were added during the manufacturing process to create particle samples and particle combinations with better properties than the original sample. Changes in the characteristics and properties of particle samples are determined by many different physical and chemical methods such as ultraviolet-visible spectroscopy (UV-Vis), infrared spectroscopy (IR), noise X-ray radiation (XRD), scanning electron microscope (SEM), dynamic light scattering (DLS), energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). Finally, the activity against bacteria, including E. coli and S. aureus, was also tested using the agar well diffusion method to determine the zone of inhibition. The results improved the particle size value, which decreased by half to 200 nm when two additional surfactants, PEG and SDS, were added. In addition, the antibacterial ability has also been shown to increase significantly when the diameter of the bacterial inhibition zone increased significantly, reaching values of 20 mm (Cu₂O/Ag/SDS) and 32 mm (Cu₂O/Ag/PEG) for the E. coli bacterial strain. The initial test sample was only about 14 mm in size. The S. aureus bacterial strain also had a similar improvement trend after adding Ag to the Cu₂O surface with the appearance of two surfactants, SDS and PEG. The inhibition zone diameter values reached the optimal value at 36 mm in the Cu₂O/Ag/PEG particle combination sample compared to only the initial 26 mm in the Cu₂O particle sample. Finally, the particle samples are added to the acrylic emulsion paint film to evaluate the changes. Positive results were obtained, such as improvement in adhesion (1.22 MPa), relative hardness (240/425), and sand drop resistance (100 L/mil) in the Cu₂O/Ag/PEG particle combination sample, which showed the correctness and accuracy of the research.

Electrochemical intercalation of anions into graphite: Fundamental aspects, material synthesis, and application to the cathode of dual‐ion batteries

Posted on 1 March 2024 by nYoshiaki Matsuo, nAkane Inoo, nJunichi Inamoton

This article first describes fundamental aspects of the electrochemical intercalation of anions into graphite. Then, the electrochemical preparation of covalent-type graphite intercalation comopouds, especially, graphite oxide and application of graphite as the cathode of dual-ion battery are discussed.

Abstract

In this review, fundamental aspects of the electrochemical intercalation of anions into graphite have been first summarized, and then described the electrochemical preparation of covalent-type GICs and application of graphite as the cathode of dual-ion battery. Electrochemical overoxidation of anion GICs provides graphite oxide and covalent-fluorine GICs, which are key functional materials for various applications including energy storage devices. The reaction conditions to obtain fully oxidized graphite has been mentioned. Concerning the application of graphite for the cathode of dual-ion battery, it stably delivers about 110 mA h g⁻¹ of reversible capacity in usual organic electrolyte solutions. The combination of anion and solvent as well as the concentration of the anions in the electrolyte solutions greatly affect the performance of graphite cathode such as oxidation potential, rate capability, cycling properties, etc. The interfacial phenomenon is also important, and fundamental studies of charge transfer resistance, anion diffusion coefficient, and surface film formation behavior have also been summarized. The use of smaller anions, such as AlCl₄ ⁻, Br⁻ can increase the capacity of graphite cathode. Several efforts on the structural modification of graphite and development of electrolyte solutions in which graphite cathode delivers higher capacity were also described.

Computational Design of Phosphotriesterase Improves V‐Agent Degradation Efficiency

Posted on 1 March 2024 by

Organophosphates (OPs) are potent neurotoxins whose current remedies are not very effective. Here we design and characterize variants of the enzyme phosphotriesterase, which can degrade OPs. We report mutations improving catalytic efficiency between 2- and 5-fold and confirm folding and stability of the resulting variants. These findings are a step towards improved OP bioscavengers.

Abstract

Organophosphates (OPs) are a class of neurotoxic acetylcholinesterase inhibitors including widely used pesticides as well as nerve agents such as VX and VR. Current treatment of these toxins relies on reactivating acetylcholinesterase, which remains ineffective. Enzymatic scavengers are of interest for their ability to degrade OPs systemically before they reach their target. Here we describe a library of computationally designed variants of phosphotriesterase (PTE), an enzyme that is known to break down OPs. The mutations G208D, F104A, K77A, A80V, H254G, and I274N broadly improve catalytic efficiency of VX and VR hydrolysis without impacting the structure of the enzyme. The mutation I106 A improves catalysis of VR and L271E abolishes activity, likely due to disruptions of PTE's structure. This study elucidates the importance of these residues and contributes to the design of enzymatic OP scavengers with improved efficiency.

Studying the adsorption of emerging organic contaminants in zeolites with dispersion‐corrected density functional theory calculations: From numbers to recommendations

Posted on 22 February 2024 by nMichael Fischer, nJakob Brauern

The performance of 13 dispersion-corrected density functional theory methods is compared systematically for adsorption energy calculations of emerging organic contaminants in all-silica zeolites . While qualitative trends are similar, large differences in absolute values are observed. Among the tested approaches, the rev-vdW-DF2 functional reproduces reference values from high-level wave function calculations most accurately.

Abstract

Adsorption energies obtained from dispersion-corrected density functional theory (DFT) calculations show a considerable dependence on the choice of exchange-correlation functional and dispersion correction. A number of investigations have employed different approaches to compute adsorption energies of small molecules in zeolites, using reference values from high-level calculations and/or experiments. Such comparative studies are lacking for larger functional organic molecules such as pharmaceuticals or personal care products, despite their potential relevance for applications, e. g., in contaminant removal or drug delivery. The present study aims to fill this gap by comparing adsorption energies and, for selected cases, equilibrium structures of emerging organic contaminants adsorbed in MOR- and FAU-type all-silica zeolites. A total of 13 dispersion-corrected DFT approaches are compared, including methods using a pairwise dispersion correction as well as non-local van der Waals density functionals. While absolute values of adsorption energies vary widely, qualitative trends across the set of zeolite-guest combinations are not strongly dependent on the choice of functional. For selected cluster models, DFT adsorption energies are compared to reference values from coupled cluster (DLPNO-CCSD(T)) calculations. Although all DFT approaches deliver systematically more negative adsorption energies than the coupled cluster reference, this tendency is least pronounced for the rev-vdW-DF2 functional.

Ultraviolet Light‐Assisted Decontamination of Chemical Warfare Agent Simulant 2‐Chloroethyl Phenyl Sulfide on Metal‐Loaded TiO2/Ti Surfaces

Posted on 20 February 2024 by

UV light emerges as a potent decontaminant for chemical warfare agents (CWAs). Utilizing TiO₂/Ti as a catalyst, this study investigates UV photocatalytic decontamination efficiency against 2-chloroethyl phenyl sulfide. Introduction of Au, Pt, and Cu onto TiO₂/Ti surface is explored. UVC light reveals eight secondary byproducts, while Au overlay notably boosts activity under UVB, uncovering valuable insights for CWA decontamination.

Abstract

The application of ultraviolet (UV) light for the decontamination of chemical warfare agents (CWAs) has gained recognition as an effective method, especially for treating hard-to-reach areas where wet chemical methods are impractical. In this study, TiO₂/Ti was employed as a model catalyst, which was contaminated with 2-chloroethyl phenyl sulfide (CEPS), and subjected to photocatalytic decontamination using both UVB and UVC light. Additionally, photocatalytic decontamination efficiency by introducing Au, Pt, and Cu onto the TiO₂/Ti surface was explored. During the photodecomposition process under UVC light, at least eight distinct secondary byproducts were identified. It was observed that the introduction of overlayer metals did not significantly enhance the photodecomposition under UVC light instead overlaid Au exhibited substantially improved activity under UVB light. Whereas, photodecomposition process under UVB light, only five secondary products were detected, including novel compounds with sulfoxide and sulfone functional groups. This novel study offers valuable insights into the generation of secondary products and sheds light on the roles of overlayer metals and photon wavelength in the photodecontamination process of CWA.

Electrocatalytic oxidation of pyrrole on a quasi‐reversible silver nanodumbbell particle surface for supramolecular porphyrin production

Posted on 13 February 2024 by

This work reports the synthesis of meso-tetrakis(4-hydroxyphenyl)porphyrin through condensation of an electrolyzed pyrrole solution with an acidified 4-hydroxybenzaldehyde at room temperature. It describes the use of silver nanodumbbell particles as sustainable electrode materials for symmetric porphyrin production. Metalation and optical characterizations together with various techniques such as ¹HNMR and ¹³CNMR confirm the synthesis of the targeted product.

Abstract

Photoactive supramolecular porphyrin assemblies are attractive molecules for light-harvesting applications. This is due to their relatively non-toxicity, biological activities and charge and energy exchange characteristics. However, the extreme cost associated with their synthesis and requirements for toxic organic solvents during purification pose a challenge to the sustainability characteristics of their applications. This work presents the first report on the sustainable synthesis, spectroscopic and photophysical characterizations of a near-infrared (NIR) absorbing Ca(II)-meso-tetrakis (4-hydroxyphenyl)porphyrin using an electrolyzed pyrrole solution. The latter was obtained by cycling the pyrrole solution across the silver nanodumbbell particle surface at room temperature. The electrolyzed solution condensed readily with acidified p-hydroxybenzaldehyde, producing the targeted purple porphyrin. The non-electrolyzed pyrrole solution formed a green substance with significantly different optical properties. Remarkable differences were observed in the voltammograms of the silver nanodumbbell particles and those of the conventional gold electrode during the pyrrole cycling, suggesting different routes of porphyrin formation. The rationale behind these formations and the associated mechanisms were extensively discussed. Metalation with aqueous Ca²⁺ ion caused a Stokes shift of 38.75 eV. The current study shows the advantage of the electrochemical method towards obtaining sustainable light-harvesting porphyrin at room temperature without the need for high-energy-dependent conventional processes.