Spectroscopic, electrochemical and enzymatic methods for assessing honey authenticity and quality

Lithium (Li) plating on graphite is a significant degradation mechanism in Li-ion batteries. While numerous experimental techniques have been used to study Li plating in laboratory cells, investigations of commercial high-energy cells often rely on electrochemical methods. Here we present and classify various methods for detecting Li plating on a commercial A123 pouch cell. In a round robin study across multiple battery research laboratories, Li-plated graphitic electrode material was analyzed using electrochemical, microscopic, and spectroscopic methods capable of detecting metallic Li deposits. After cell opening, their overall distribution on the anode surface was examined using a flatbed scanner to ensure comparability of the samples. Optical and electron microscopy provided detailed surface and, in combination with a focused ion beam, subsurface structure and morphology. Spectroscopic methods confirmed the presence and onset of plated Li with varying sensitivity. Moreover, spectroscopic and imaging techniques were combined correlatively where possible. Availability and measurement duration of each technique was compared. Optical methods are fast and easy to use; thus, they are recommended for most samples, with spectroscopic confirmation reserved for reference samples. This multimodal study demonstrates a range of methods that can be used alone or in combination to qualitatively or quantitatively detect Li-plating.

Novel spectroelectrochemical cell for in-situ XAFS spectroscopy on gas generating electrodes

Methylene blue is a toxic dye that is extensively used as a colorant in textile industries. Industrial effluent containing methylene blue, when drained into water bodies without proper treatment, poses a serious threat to aquatic and human lives. In order to protect the biocycle, various methods have been established to detect and remove hazardous dyes from aqueous systems. Electrochemical methods are preferred, owing to their characteristic features of simplicity, portability, potential selectivity, cost effectiveness, and rapid responsiveness. Based on these considerations, an electrochemical sensor consisting of amino-group-functionalized, multi-walled carbon nanotubes (NH2-fMWCNTs) immobilized on a glassy carbon electrode (GCE) was developed for the sensitive detection of methylene blue in aqueous solutions. The performance of the designed sensor was analyzed by electrochemical impedance spectroscopy, cyclic voltammetry, and square wave voltammetry. The developed sensing tool demonstrated promising features of sensitivity, selectivity, stability, fast responsiveness, and the ability to work with a very small volume of the analyte, i.e., in microliters, for analysis. Amino groups rich in electrons provide a negative charge to multi-walled carbon nanotubes, which significantly enhances the electrocatalytic activity of NH2-fMWCNTs for cationic dyes such as methylene blue. Using the designed sensing platform, a linear calibration plot with a limit of detection of 0.21 nM was obtained for methylene blue under optimized conditions. The designed sensor was also employed to monitor the extent and kinetics of the degradation of methylene blue. Titania nanoparticles were used for photocatalytic degradation, and the kinetics of degradation was monitored by both UV-Visible spectroscopic and electrochemical methods. The results revealed more than 95% removal of methylene blue in a time span of just 30 min.

The photocatalysis of chemical reactions in organic chemistry by the light of visible wavelengths has undergone great development in recent years, however many challenges remain. The effort to create reducing agent with power of alkali metals using light from the visible region of the spectrum remains unattained. Alkali metals are still used in some organic reactions as reducing agents despite the known risks and formation of undesirable by-products.Flavin derivatives, which are the subject of this work, have the potential to accomplish these challenges. By the reduction and subsequent excitation by the visible light, flavine derivatives create long-lived excited states which behaves as extremely strong reduction agents (reduction potential comparable to sodium). These properties could be used to perform a number of hardly realizable reactions. Because it is a matter of redox processes and properties and the electron transfer, the electrochemical approach to this issue is very suitable. Most of published works deal with the use of flavines as oxidizing agents and by them catalyzed transformations. However, these substances have the potential to act as extreme reducing agents, which has not yet received such attention as their oxidizing abilities. It is therefore desirable to investigate their photo-reduction capabilities and their use in the field of organic synthesis.The aim of this work is to study selected flavine derivatives using electrochemical and spectroscopic methods and use gained knowledge to generate extremely strong reducing agents in situ and then perform model reactions. Combining electrochemical reduction and photochemical excitation with subsequent chemical reaction in one reaction cell would significantly save time, amount of solvents and the overall cost of performing these otherwise hardly realizable reactions.At first, selected flavine derivatives were characterized by cyclic voltammetry (using different materials of electrodes) and DC-polarography. The first reduction step of isoalloxazine and alloxazine derivatives is diffusion controlled and reversible with potential of -0,8 V (vs. SCE) for isoalloxazine and -1,3 V (vs. SCE) for alloxazine (both in acetonitrile). In the second stage of this work measured reduction potentials are used in potentiostatic electrolyses of flavine derivatives with aryl halides in one photo-electrochemical reaction cell. The cell is irradiated by visible light (450 nm) during the electrolysis. The combination of applied potential and visible light irradiation in one moment leads to electro-photocatalytic dehalogenation creating aryl radical. Afterwards, the products of model reactions are studied by spectroscopic methods like UV/VIS and NMR spectroscopy and correlated with quantum chemical calculations.Derivatives of isoalloxazine, alloxazine and 5-deazaflavin have been selected as model substances, whose excited states may have the potential to reduce aryl halides forming an aryl radical, which may be directly used in organic synthesis. All experiments were performed in the non-aqueous solvent (acetonitrile) without the presence of oxygen.Acknowledgement:The financial support of the grant 19-22806S (Czech Science Foundation - GAČR) and the institutional support RVO: 61388955 are highly appreciated. The authors are grateful to Prof. R. Cibulka for introduction to this problem and for valuable discussion. Figure 1

Cyclometalated ruthenium complexes having C(^)N and N(^)C type coordinating ligands with NAD(+)/NADH function have been synthesized and characterized by spectroscopic methods. The variation of the coordinating position of σ-donating carbon atom leads to a drastic change in their properties. Both the complex Ru(phbn)(phen)(2)]PF(6) ([1]PF(6)) and [Ru(pad)(phen)(2)]PF(6) ([2]PF(6)) reduced to Ru(phbnHH)(phen)(2)]PF(6) ([1HH]PF(6)) and [Ru(padHH)(phen)(2)]PF(6) ([2HH]PF(6)) by chemical and electrochemical methods. Complex [1]PF(6) photochemically reduced to [1HH]PF(6) in the presence of the sacrificial agent triethylamine (TEA) upon irradiation of visible light (λ ≥ 420 nm), whereas photochemical reduction of [2]PF(6) was not successful. Both experimental results and theoretical calculations reveal that upon protonation the energy level of the π* orbital of either of the ligands phbn or pad is drastically stabilized compared to the nonprotonated forms. In the protonated complex [Ru(padH)(phen)(2)](PF(6))(2) {[2H](PF(6))(2)}, the Ru-C bond exists in a tautomeric equilibrium with Ru═C coordination and behaves as a remote N-heterocyclic carbene (rNHC) compex; on the contrary, this behavior could not be observed in protonated complex [Ru(phbnH)(phen)(2)](PF(6))(2) {[1H](PF(6))(2)}.

In this chapter, detection methods are discussed, with emphasis on both the hardware considerations and the chemistry underlying each approach. The discussion will be restricted to separations achieved using ion exchange because this separation mode is the most widespread; moreover, other separation modes such as ion interaction chromatography generally use the same detection procedures after suitable modification to accommodate any special mobile phases employed. It is convenient to subdivide detection methods into three broad categories: (a) electrochemical methods (that is, those using conductivity, amperometry, or potentiometry as the basis of detection); (b) spectroscopic methods [that is, those using ultraviolet / visible (UV /vis) absorbance, refractive index, fluorescence, atomic absorption, or atomic emission for detection] ; and (c) those detection methods based on postcolumn reactions. Each of these approaches will be discussed separately.

α-Amylase is an endoenzyme that catalyses the hydrolysis of internal α-l,4 glycosidic linkages in polysaccharides to produce maltose, maltotriose, and α-limit dextrins. It is widely used in the laboratorial and industrial workflow for several applications. There are several methods utilizing different techniques and substrates to assess α-amylase activity, among which the spectroscopic methods have found widespread applicability due to their ease of use and cost-effectiveness. Depending upon the reaction principle, these assays are classified into four groups: reducing sugar, enzymatic, chromogenic, and amyloclastic methods. Despite the presence of numerous methods, there is no general reliable method to assess α-amylase activity. Each method is shown to have its own merits and demerits. Many improvements have been made to make the available methods more accurate, reliable, and easy. This communication briefly discusses the basic reaction mechanisms and critically reviews the advantages and shortcomings associated with each method. Further recommendations are made for future development. © 2020 Society of Chemical Industry.

Several palladium(II) complexes with 1,1‘-bis(diphenylphosphino)octamethylferrocene (dppomf) and its oxidized form 1,1‘-bis(diphenylphosphino)octamethylferrocenium (dppomf+) have been synthesized and characterized by spectroscopic and electrochemical methods. For comparative purposes, analogous Pd(II) derivatives with 1,1‘-bis(diphenylphosphino)ferrocene (dppf) have been also prepared. Single-crystal X-ray analyses have been carried out for the square-planar mononuclear compounds [Pd(H2O)2(dppf)](OTf)2 and [Pd(H2O)2(dppomf)](OTf)2 and for the binuclear complex [Pd(μ-OPF2O)(dppomf+)]2(BF4)4·6CH2Cl2 in which two [Pd(dppomf+)]3+ moieties are held together by the oxygen atoms of two bridging PO2F2- groups derived from the oxidative degradation of PF6- ions. Selected dppf and dppomf Pd(II) complexes have been employed as catalyst precursors for the methoxycarbonylation of ethene (600 psi, 1:1 CO/C2H4, 85 °C). It has been found that dppomf generates selective catalysts for the production of methyl propanoate, w...

We report the synthesis and properties of π-stacked polymers consisting of oligothiophene and naphthalene as the stacked π-system and the scaffold, respectively. The titled polymers were obtained by the Suzuki–Miyaura coupling reaction. Oligothiophene units were layered in proximity, ∼3.0 Å from each other. Contribution of the quinoidal structure of the oligothiophene units involving the naphthalene scaffolds in the excited state resulted in relatively high photoluminescence quantum efficiencies. The polymers have potential application to optoelectronic devices such as hole-transporting materials. Oligothiophene-stacked polymers were synthesized by the Suzuki–Miyaura coupling reaction. Oligothiophene units were layered in proximity, ∼3.0 Å from each other. The polymers were characterized by various spectroscopic and electrochemical methods. The polymers have potential application to optoelectronic devices such as hole-transporting materials.

This article describes synthesis and characterization of three oxidovanadium(IV) complexes using BPA (BPA = 2,2’-bis(pyridylmethyl)amine), 2,2-bipyridyl and 1,10-phenanthroline. These complexes were characterized by elemental analysis, spectroscopic (UV-vis, IR and EPR) and electrochemical methods. Room temperature magnetic susceptibility data show the paramagnetic nature of the complexes. Complexes were also characterized by electron paramagnetic resonance (EPR) spectral techniques. The optimized molecular structures show the presence of N3O3/N5O donor atoms in six-coordinate geometry. These complexes were evaluated and compared using thermogravimetric analysis and powder X-ray diffraction techniques. The species exhibit only one-electron reduction wave at a more negative potential. The catalytic activity of these complexes was also explored to mimic α-glucosidase and α-amylase activity. Moderate α-glucosidase and α-amylase inhibitors are shown by all complexes. These observations are expected to expand the possibility of designing new oxidovanadium(IV) complexes with significant anti-diabetic properties.

Electrochemical techniques analyze pharmaceutical compounds through electrical property measurements. Potentiometry measures potential differences between electrodes, enabling pH determination, ion-selective detection, and endpoint determination in pharmaceutical assays. Electrode selection, calibration procedures, and system suitability testing ensure accurate results. Voltammetry techniques including cyclic, differential pulse, and stripping methods quantify drug substances, detect impurities, and characterize redox behavior by measuring current-voltage relationships. Conductometry measures solution conductivity for titration endpoints, ion detection, and water purity assessment in pharmaceutical contexts. These electrochemical methods support drug stability assessment, dissolution media characterization, and manufacturing process monitoring with advantages in sensitivity, cost-effectiveness, and direct analysis capabilities. Electrochemical techniques provide complementary approaches for molecules with electroactive functional groups, offering alternatives to spectroscopic and chromatographic methods.

The one‐step fabrication of gold films by inkjet printing of a gold precursor ink and its photochemical reduction by exposure to UV light is presented. Inkjet printing creates on a substrate with high control micrometer‐thin reaction volumes in which upon direct high‐intensity light irradiation, the gold precursor reduces to pure and well‐adhered Au particles, while all other ink components escape in the gas phase, without the need for any further post‐treatment. The Au precursor ink does neither contain stabilizing agents, such as polymers or surfactants, nor sacrificial compounds, such as photoinitiators, to initiate and accelerate the reduction. This economic and green process is known as Print‐Light‐Synthesis (PLS) and is herein used to create gold patterns of thin compact Au films and separated Au nanoparticles. Gold loadings are in the µg cm−2 range and precisely controlled, thanks to the inkjet printing parameters. The gold films are characterized by spectroscopic and electrochemical methods. Finally, the applicability of Au films as electrochemical sensors is demonstrated for the detection of 1,4‐butanediol in comparison to a commercial screen‐printed Au electrode. The PLS Au electrode shows a 20 times higher sensitivity and opens new possibilities for disposable electrode production.

Due to their flexibility and solution applicability, organic field-effect transistors (OFETs) are considered prominent candidates for application in flexible and low-cost devices. A soluble phthalocyaninato cobalt(ii) complex was designed and synthesized based on a hexadeca-substitution pattern by introducing peripheral phenylethynyl groups and non-peripheral n-butoxy groups. The cobalt phthalocyanine derivative was characterized using a wide range of spectroscopic and electrochemical methods, as well as single-crystal X-ray diffraction analysis. An OFET device was fabricated using a spin-coated film of soluble 1,4,8,11,15,18,22,25-octakisbutoxy-2,3,9,10,16,17,23,24-octakis-ethynyl phenyl phthalocyaninato cobalt(ii) with a bottom-gate top-contact device configuration. The transfer and output characteristics were investigated to evaluate the charge carrier mobility. The mechanisms of the leakage current through the gate dielectric were also investigated, which revealed that the dominant leakage current mechanism is Fowler-Nordheim tunneling.

The drug‐DNA interaction studies provide vital insights for designing and developing effective chemotherapeutic agents used in treatment of different cancers. Thus, the interaction of potential anticancer agent pentoxifylline and calf thymus DNA was analysed by various spectroscopic and electrochemical methods under physiological condition. The absorption spectra of pentoxifylline with calf thymus DNA revealed the formation of complex by hyperchromic effect with a binding constant of 1.461 ×10 4 M −1 . Fluorescence studies, further showed that pentoxifylline binds to calf thymus DNA and form a stable complex with a static quenching mechanism. Thermodynamic analysis further confirms that the interaction process is spontaneous with Vander Waals force or hydrogen bonding playing a major role. The electrochemical studies and circular dichroism spectra signify that pentoxifylline interacts by groove binding mode. Based on electrochemical and spectroscopic results, the mode of pentoxifylline binding to calf thymus DNA is mainly established through groove binding.

Festkörperstruktur, dynamische struktureffekte und elektrochemische charakteristika des clusteranions [HRu 3(CO) 10(SiEt3) 2] −