UV Vis Spectroscopy Research Articles

A New Bioactive Thiazolidinone-based Azo Dye for Naked-eye Colorimetric Detection of Cyanide Ions

Abstract: A new bioactive azo dye embedding a thiazolidinone heterocyclic core was designed and synthesized for antibacterial application and colorimetric sensing of cyanide ion (CNˉ) in organic solutions. The structure of the prepared dye was elucidated from its 1H NMR, FT-IR and UV-Vis spectral data. It proved to be a fast and sensitive colorogenic sensor for detection of CNˉ. Spectroscopic studies were carried out to investigate the effect of different CNˉ concentrations on the detection efficiency. Moreover, the studies revealed no significant competition or influence of other anions on the sensitivity of CNˉ detection by the synthesized dye. A Job's plot indicated a 1:1 stoichiometry of the dye and CNˉ in their colorful complex. Further development of the method for naked-eye detection of CNˉ in low-concentration aqueous solutions was achieved by using the cellulose papers painted with the dye. The as-prepared testing paper allowed CNˉ sensing in concentrations as low as 2 μM. Evaluation of the dye for antibacterial activities using the well diffusion technique displayed that its inhibitory activity is at least as good as and in some cases superior to ampicillin against the bacterial strains employed in the zone assay. In response to CN¯, the dye changes color from yellow to reddish brown which accounts for its significant interactions with CNˉ and affords a naked-eye sensing method without resorting to any spectroscopic instrumentation.

Chitosan-TPP encapsulated quercetin nanoparticles: amplified protection mechanisms unveiled against Ethion-induced developmental toxicity through comprehensive in-vivo and in-silico elucidation.

The study investigated Ethion-induced developmental toxicity in Wistar albino rats and the potential ameliorative effects of quercetin and nano-quercetin co-administration. Further, In-silico docking of Ethion and quercetin with MCL-1 was conducted. Quercetin nanoparticles were synthesized by ionic-gelation method. The encapsulated quercetin nanoparticles were characterized for Zeta size, UV-Vis spectroscopy, encapsulation efficiency, and TEM studies. Male rats were administered Ethion (high/low dose), quercetin, and nano-quercetin alone or in combination for 60 days. Female rats were introduced for mating on the 61st day, and pregnant females were observed for 20 gestational days. On GD 20, rats were sacrificed and evaluated for body/organ weight, reproductive indices, fetal morphology, skeletal, and visceral deformities.In silico binding energies of ethion and quercetin with MCL-1 were determined. Nanoparticle size was 363.2 ± 1.23 nm on day 0 and 385.63 ± 1.53 nm on day 60, with PDI of 0.247 and charge of 22.9 mV. Absorbance maxima were at 374 nm, with encapsulation efficacy of 85.16 ± 0.33%. EHD male crossed females showed decreased body/organ weights, reduced fertility, hematoma, cleft palate, tail curling, and absence of extremity. Nano-quercetin co-administration normalized parameters comparable to controls. Both Ethion and quercetin interacted with MCL-1, with quercetin exhibiting stronger binding energy. Nano-quercetin demonstrated stronger antioxidant properties than quercetin, counteracting ethion-induced maternal/fetal abnormalities.

Enhancement in the optical and carbon dioxide gas sensing properties of polythiophene by dispersion of manganese dioxide nanoparticles

The present research article demonstrates the dispersion of manganese dioxide (MnO2) nanoparticles in polythiophene (PTh) to enhance the optical and gas sensing properties of PTh/MnO2 nanocomposites. The structural aspects of the as-synthesized nanocomposites were demonstrated by the techniques such as X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM). Furthermore, the optical characterization of the resulting composite was investigated using UV-Vis spectroscopy. UV-Vis analyses of obtained nanocomposite revealed a forbidden band of ∼ 3.7 eV. The prepared nanocomposites were exposed to CO2 gas to investigate the composites suitability for gas sensing application, which prove to be promising materials. The prominent exploit of the present work is that 0.8 Wt.% MnO2 loaded PTh composite material exhibits significant sensing response at low operating temperature including good stability and fast response and recovery time. The core objective of this work is the discussion of the enhancement in stability, response and recovery time as a consequence of the interaction between the CO2 gas and the as-synthesized nanocomposites.

Effect of surfactant's charge properties on behavior, physiology, and biochemistry and the release of microcystins of Microcystis aeruginosa

Surfactant pollution is escalatitheng in eutrophic waters, but the effect of surfactant charge properties on the physiological and biochemical properties of toxin-producing microalgae remains inadequately explored. To address this gap, this study explores the effects and mechanisms of three common surfactants―cetyltrimethylammonium bromide (CTAB, cationic), sodium dodecyl sulfate (SDS, anionic), and Triton X-100 (nonionic)―found in surface waters, on the agglomeration behavior, physiological indicators, and Microcystin-LR (MC-LR) release of Microcystis aeruginosa (M. aeruginosa) by using UV-visible spectroscope, Malvern Zetasizer, fluorescence spectrometer, etc. Results suggest that charge properties significantly affect cyanobacterial aggregation and cellular metabolism. The CTAB-treated group demonstrates a ∼5.74 and ∼9.74 times higher aggregation effect compared to Triton X-100 and SDS (300 mg/L for 180 min) due to strong electrostatic attraction. Triton X-100 outperforms CTAB and SDS in polysaccharide extraction, attributed to its higher water solubility and lower critical micelle concentration. CTAB stimulates cyanobacteria to secrete proteins, xanthohumic acid, and humic acids to maintain normal physiological cells. Additionally, the results of SEM and ion content showed that CTAB damages the cell membrane, resulting in a ∼90% increase in the release of intracellular MC-LR without cell disintegration. Ionic analyses confirm that all three surfactants alter cell membrane permeability and disrupt ionic metabolic pathways in microalgae. This study highlights the relationship between the surface charge properties of typical surfactants and the dispersion/agglomeration behavior of cyanobacteria. It provides insights into the impact mechanism of exogenous surfactants on toxic algae production in eutrophic water bodies, offering theoretical references for managing surfactant pollution and treating algae blooms.

Synthesis, characterization and structural analysis of complexes from 2,2':6',2''-terpyridine derivatives with transition metals.

The synthesis and structural characterization of three families of coordination complexes synthesized from 4'-phenyl-2,2':6',2''-terpyridine (8, Ph-TPY), 4'-(4-chlorophenyl)-2,2':6',2''-terpyridine (9, ClPh-TPY) and 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine (10, MeOPh-TPY) ligands with the divalent metals Co2+, Fe2+, Mn2+ and Ni2+ are reported. The compounds were synthesized from a 1:2 mixture of the metal and ligand, resulting in a series of complexes with the general formula [M(R-TPY)2](ClO4)2 (where M= Co2+, Fe2+, Mn2+ and Ni2+, and R-TPY= Ph-TPY, ClPh-TPY and MeOPh-TPY). The general formula and structural and supramolecular features were determinated by single-crystal X-ray diffraction for bis(4'-phenyl-2,2':6',2''-terpyridine)nickel(II) bis(perchlorate), [Ni(C21H15N3)2](ClO4)2 or [Ni(Ph-TPY)2](ClO4)2, bis[4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine]manganese(II) bis(perchlorate), [Mn(C22H17N3O)2](ClO4)2 or [Mn(MeOPh-TPY)2](ClO4)2, and bis(4'-phenyl-2,2':6',2''-terpyridine)manganese(II) bis(perchlorate), [Mn(C21H15N3)2](ClO4)2 or [Mn(Ph-TPY)2](ClO4)2. In all three cases, the complexes present distorted octahedral coordination polyhedra and the crystal packing is determined mainly by weak C-H...π interactions. All the compounds (except for the Ni derivatives, for which FT-IR, UV-Vis and thermal analysis are reported) were fully characterized by spectroscopic (FT-IR, UV-Vis and NMR spectroscopy) and thermal (TGA-DSC, thermogravimetric analysis-differential scanning calorimetry) methods.

Photocatalytic degradation of methylene blue dye under solar light irradiation by zinc oxide nanoparticles using aqueous extract of Cleome gynandra

A simple green synthetic technique is proposed for the synthesis of zinc oxide nanoparticles (ZnONPs) using the plant extract Cleome gynandra as a bio-template. The morphological, functional and structural characterization of synthesized ZnONPs was investigated using several techniques, such as energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy. The synthesized ZnONPs have a wurtzite hexagonal nanostructure with an average size of 15.20 nm. Furthermore, the photocatalytic degradation of methylene blue (MB) in an aqueous solution was carried out using the synthesized ZnONPs. The photocatalytic activity of ZnONPs was investigated by adjusting physicochemical variables as reaction time, medium pH, precursor concentration, and photocatalyst dosage. All results indicate that ZnONPs produced by the green approach exhibits significant photocatalytic activity against dye molecules.

Apoptotic efficiency of Dicoma anomala biosynthesized silver nanoparticles against A549 lung cancer cells

Lung cancer is one of the common forms of cancer that affects both men and women and is regarded as the leading cause of cancer related deaths. It is characterized by unregulated cell division of altered cells within the lung tissues. Green nanotechnology is a promising therapeutic option that is adopted in cancer research. Dicoma anomala (D. anomala) is one of the commonly used African medicinal plant in the treatment of different medical conditions including cancer. In the present study, silver nanoparticles (AgNPs) were synthesized using D. anomala MeOH root extract. We evaluated the anticancer efficacy of the synthesized AgNPs as an individual treatment as well as in combination with pheophorbide a (PPBa) mediated photodynamic therapy (PDT) in vitro. UV–VIS spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) was used to confirm the formation of D.A AgNPs. Post 24 h treatment, A549 cells were evaluated for ATP proliferation, morphological changes supported by LIVE/DEAD assay, and caspase activities. All experiments were repeated four times (n=4), with findings being analysed using SPSS statistical software version 27 set at 0.95 confidence interval. The results from the present study revealed a dose-dependent decrease in cell proliferation in both individual and combination therapy of PPBa mediated PDT and D.A AgNPs on A549 lung cancer cells with significant morphological changes. Additionally, LIVE/DEAD assay displayed a significant increase in the number of dead cell population in individual treatments (i.e., IC50’s treated A549 cells) as well as in combination therapy. In conclusion, the findings from this study demonstrated the anticancer efficacy of green synthesized AgNPs as a mono-therapeutic drug as well as in combination with a chlorophyll derivative PPBa in PDT. Taken together, the findings highlight the therapeutic potential of green nanotechnology in medicine.

Improving the Transparency of a MgAl2O4 Spinel Damaged by Sandblasting through a SiO2-ZrO2 Coating

Transparent materials in contact with harmful environments such as sandstorms are exposed to surface damage. Transparent MgAl2O4 spinel used as protective window, lens or laser exit port, among others, is one of the materials affected by natural aggressions. The impact of sand particles can cause significant defects on the exposed surface, thus affecting its optical and mechanical behavior. The aim of this work is to improve the surface state of a spinel damaged surface by the deposition of a thin layer of SiO2-ZrO2. For this purpose, spinel samples obtained from different commercial powders sintered by Spark Plasma Sintering were sandblasted and further coated with a SiO2-ZrO2 thin layer. The coating was successfully synthesized by the sol/gel method, deposited on the sandblasted samples and then treated at 900 °C, reaching a final thickness of 250 nm. The results indicated that sandblasting significantly affects the surface of the spinel samples as well as the optical transmission, confirmed by UV-visible spectroscopy and profilometry tests. However, the deposition of a SiO2-ZrO2 coating modifies the UV-visible response. Thus, the optical transmission of the S25CRX12 sample presents the best transmission values of 81%, followed by the S25CRX14 sample then the S30CR sample at 550 nm wavelength. An important difference was observed between sandblasted samples and coated samples at low and high wavelengths. At low wavelengths (around 200 nm), sandblasting tends to improve significantly the transmission of spinel samples, which exhibit a low transmission in the pristine state. This phenomenon can be attributed to the healing of small superficial defects responsible for the degradation of transmission such as pores or flaws. When the initial transmission at 200 nm is high, the sandblasting worsens the transmission. Sandblasting reduces slightly the transmission values for long wavelengths due to the formation of large superficial defects like chipping by creation and propagation of lateral cracks. The coating of the sandblasted samples exhibits some healing of defects induced by sandblasting. The deposition of the SiO2-ZrO2 layer induces a clear increase in the optical transmission values, sometimes exceeding the initial values of the transmission in the pristine state.

Bio-inspired synthesis of silver nanoparticles usingsalsola imbricataand its application as antibacterial additive in glass ionomer cement.

Nanotechnology has gained immense popularity and observed rapid development due to the remarkable physio-chemical properties of nanoparticles (NPs) and related nanomaterials. The green production of nanoparticles has many benefits over traditional techniques because the current procedures are expensive, time-consuming, and involve harmful substances that limit their applicability. This study aimed to use a novel green source, the Salsola imbricata (SI) plant, which is commonly found in Central Asia and known for its medicinal properties as a reducing and stabilizing agent for the synthesis of AgNPs. The current study also utilized efficient statistical design, the Plackett-Burman Design of Experiment (DOE) method to synthesize the nanoparticles. The characterization of nanoparticles was carried out using UV-Vis spectroscopy, Fourier Transform Infrared Spectroscopy, and scanning electron microscopy (SEM). The Plackett-Burman design results showed that only two out of four factors i.e., AgNO3 concentration and incubation time, were significant for the synthesis of AgNPs. While remaining factors, incubation temperature and plant extract: AgNO3 ratio were non-significant. The SEM analysis result showed that SI-AgNPs had a size of 20-50nm. The SI-AgNPs demonstrated strong antimicrobial activity against oral pathogens such as Streptococcus mutans and Lactobacillus acidophilus, with the highest efficacy observed at a concentration of 2 mg/ml. The addition of SI-AgNPs in glass ionomer cement significantly increased the antimicrobial efficacy of GIC at different concentration (p≤0.000 for 0.2% and 0.1%, p≤0.01 for 0.05% and p≤0.05 for 0.025% respectively). Based on the results of the current study, the plant based AgNPs can be further evaluated in detail as alternate antimicrobial agent either alone or in combination with other antimicrobial agents for different dental applications.

A comparative study of the biosynthesis of CuNPs by Niallia circulans G9 and Paenibacillus sp. S4c strains: characterization and application as antimicrobial agents

BackgroundBiosynthesis of metallic nanoparticles using microorganisms are a fabulous and emerging eco-friendly science with well-defined sizes, shapes and controlled monodispersity. Copper nanoparticles, among other metal particles, have sparked increased attention due to their applications in electronics, optics, catalysis, and antimicrobial agents.ResultsThis investigation explains the biosynthesis and characterization of copper nanoparticles from soil strains, Niallia circulans G9 and Paenibacillus sp. S4c by an eco-friendly method. The maximum reduction of copper ions and maximum synthesis CuNPs was provided by these strains. Biogenic formation of CuNPs have been characterized by UV–visible absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray analysis and transmission electron microscopy analysis. Using UV-visible spectrum scanning, the synthesised CuNPs’ SPR spectra showed maximum absorption peaks at λ304&308 nm. TEM investigation of the produced CuNPs revealed the development of spherical/hexagonal nanoparticles with a size range of 13–100 nm by the G9 strain and spherical nanoparticles with a size range of 5–40 nm by the S4c strain. Functional groups and chemical composition of CuONPs were also confirmed. The antimicrobial activity of the biosynthesized CuNPs were investigated against some human pathogens. CuNPs produced from the G9 strain had the highest activity against Candida albicans ATCC 10,231 and the lowest against Pseudomonas aeruginosa ATCC 9027. CuNPs from the S4c strain demonstrated the highest activity against Escherichia coli ATCC 10,231 and the lowest activity against Klebsiella pneumonia ATCC 13,883.ConclusionThe present work focused on increasing the CuNPs production by two isolates, Niallia circulans G9 and Paenibacillus sp. S4c, which were then characterized alongside. The used analytics and chemical composition techniques validated the existence of CuONPs in the G9 and S4c biosynthesized nano cupper. CuNPs of S4c are smaller and have a more varied shape than those of G9 strain, according to TEM images. In terms of antibacterial activity, the biosynthesized CuNPs from G9 and S4c were found to be more effective against Candida albicans ATCC 10,231 and E. coli ATCC 10,231, respectively.

Recyclable Ag-Au bimetallic nanoparticles supported on acid functionalized multi walled carbon nanotubes for effective catalytic applications

In the present investigation, in situ green reduction approach is used to uniformly decorate the Ag-Au bimetallic nanoparticles (BNPs) on the surface of acid functionalised multi-walled carbon nanotubes (MWCNTs). The adsorbed Terminalia catappa aqueous leaf extract biopolymers on the surface of MWCNTs can increase the in situ reduction of Ag, Au ions to Ag-Au BNPs and stabilise them which can operate as a capper/stabiliser and reductant agent. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy - energy dispersive x-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FT-IR) and UV–visible spectroscopy techniques were employed to examine the structures, morphologies, composition, chemical bonds and optical properties of the functionalised MWCNTs and the nanohybrid. The results revealed that the spherical T.C-Ag-Au bimetallic nanoparticle with average size 12.4 nm was uniformly distributed on the surface of modified MWCNTs. Finally, evaluation of the catalytic activity of the T.C-Ag-Au BNPs decorated MWCNTs exhibited excellent catalytic performance for completing the reduction of 4-Nitrophenol (4-NP) and degradation of alizarin red (AR) dye at ambient temperature with a great rate constant and the degradation efficiency of 98.7% and 96.4%, respectively. The order of reaction, rate constant, half-life and mechanism of catalytic activity of the T.C-Ag-Au BNPs@COOH-MWCNTs nanohybrid were calculated using the Langmuir–Hinshelwood model. The catalyst can be retained and reapplied eight times without affecting its catalytic performance. The interaction between T.C-Ag-Au BNPs and MWCNTs has a synergistic effect, which is accountable for the enhanced catalytic activity.

EDTA functionalized pine needle biochar (EDTA@BC); a valorized bio-material for removal of Ni(II) from aqueous solution.

The preparation of ethylenediaminetetraacetic acid (EDTA) functionalized pine needles biochar (EDTA@BC) as a low-cost active adsorbent and its effectiveness in removing Ni(II) from aqueous solution at various conditions is reported in this paper. First, alkali activation was selected to render the pine needle biochar with an excellent porous structure and increased concentration of hydroxyl groups to facilitate grafting. Subsequently, a simple method was utilized to graft EDTA onto the biochar. The prepared EDTA@BC was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive x-ray spectrometry (EDX). Batch adsorption studies were conducted to assess the impact of various parameters such as solution pH, adsorbent dosage, adsorbate volume, and shaking time on the removal efficiency of Ni(II). At pH 6, 100 mg dosage, 4 mL of adsorbate volume, and 10 min of shaking time, the maximum removal efficiency of Ni(II) was observed to be 89%. EDTA@BC showed reasonable sorption performance still after the third cycle of regeneration. The effect of interfering ions such as Pb, Cr, Cu, and Hg was evaluated, resulting a decrease of 69%, 78%, 76%, and 68%, respectively, in its sorption capacity. The Langmuir model provided a better fit for Ni(II) in the concentration range of 0.1-2000 ppm under optimized conditions, with qmax of 46.69 ± 1.031 mg/g and KL of 0.001, compared with the Freundlich isotherm, which yielded n = 0.234 and χ2 = 2.7899, Temkin isotherm (R2 = 0.9520), and Redlich-Peterson isotherm (R2 = 0.9725). The removal of Ni(II) by EDTA@BC was found to be the pseudo-second-order kinetics. Thermodynamic studies indicated adsorption process to be endothermic and nonspontaneous. Hence, a sustainable valorized bio-material (EDTA@BC) is prepared having better sorption efficiency of Ni(II) from aqueous solution with possible wide applicability. RESEARCH HIGHLIGHTS: New EDTA functionalized indigenous pine needles biochar (EDTA@BC) was prepared. This low-cost active adsorbent found effective in removing Ni(II) from aqueous solution. FTIR, SEM, and EDX proved synthesis and uptake of Ni(II) from aqueous solution. Ni(II) removal, regeneration, interfering and adsorption studies were performed by UV-Vis spectroscopy.

Detailed Study on the Interfacial Interaction between Different Polyoxometalates and Tetronic Block Copolymers Exploring the Langmuir-Blodgett Technique.

Polyoxometalates (POMs) interact with various biologically relevant entities. A basic understanding of this interaction is very important for various applications in the biological field. In this work, the focus is on the study of the interaction between tetronics and Keggin POMs. T701 and T90R4 are the two tetronics considered here; they have different solubilities in water due to different PPO/PEO ratios. The arrangement of PPO and PEO is also different with respect to the central ethylenediamine groups. Three different Keggin-type POMs, phosphomolybdic acid (PMA), phosphotungstic acid (PTA), and silicotungstic acid (STA), with different charge densities are chosen for an elaborate investigation using Langmuir-Blodgett technique. The observation is analyzed thoroughly, which shows both electrostatic interaction and adsorption of POMs on the PPO blocks of the tetronics due to the chaotropic effect, which is responsible for the binding of POMs (in subphase) with the tetronic monolayer. This interaction results in an expanded yet rigid monolayer for POM-tetronic association on the surface. Surface pressure vs mean molecular area isotherm is the key characterization to reach the conclusion. UV-vis spectroscopy, NMR, ITC, ellipsometric studies, FTIR, and SEM also serve as supportive characterization techniques.

A joint experimental and theoretical investigation of the binding mechanism between zein and folic acid in an ethanol–water solution

ABSTRACT The aim of the present study was to determine the binding mechanisms between zein and folic acid in an ethanol – water solution. Fluorescence spectroscopy demonstrated that folic acid quenched the fluorescence intensity of zein by both dynamic and static fluorescence quenching mechanisms, with static quenching playing a prominent role. The binding constants (Ka) of the zein-folic acid complex at 292, 302, and 312 K were evaluated to be 5.97 × 105, 3.00 × 105 and 1.54 × 105 L/mol, respectively. The process of folic acid binding zein was driven by ∆H0 = –51.24 kJ/mol, ∆S0 = –64.90 J/mol•K. Van der Waals forces and hydrogen bonding primarily governed the formation of the zein-folic acid complex. Confirmation of the complex formation was obtained via UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy, which also revealed alterations in the secondary structure of zein upon binding to folic acid. Measurements of particle size and zeta potential demonstrated an enhancement in the stability of the complex system. Scanning electron microscopy and transmission electron microscopy showed the complex to possess a spherical morphology, with significant changes in the zein’s morphology following its binding to folic acid. Additionally, zein increased the photostability of folic acid against UV light radiation. Molecular docking and molecular dynamics simulations were used to investigate the binding mechanisms involved further, and the results effectively elucidated the observed experimental phenomena. This research establishes a significant theoretical foundation for the utilization of zein as a system for delivering and safeguarding folic acid.

Catalytic role of histidine-114 in the hydrolytic dehalogenation of chlorothalonil by Pseudomonas sp. CTN-3.

Chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile; TPN) is an environmentally persistent fungicide that sees heavy use in the USA and is highly toxic to aquatic species and birds, as well as a probable human carcinogen. The chlorothalonil dehalogenase from Pseudomonas sp. CTN-3 (Chd, UniProtKB C9EBR5) degrades TPN to its less toxic 4-OH-TPN analog making it an exciting candidate for the development of a bioremediation process for TPN; however, little is currently known about its catalytic mechanism. Therefore, an active site residue histidine-114 (His114) which forms a hydrogen bond with the Zn(II)-bound water/hydroxide and has been suggested to be the active site acid/base, was substituted by an Ala residue. Surprisingly, ChdH114A exhibited catalytic activity with a kcat value of 1.07s-1, ~ 5% of wild-type (WT) Chd, and a KM of 32µM. Thus, His114 is catalytically important but not essential. The electronic and structural aspects of the WT Chd and ChdH114A active sites were examined using UV-Vis and EPR spectroscopy on the catalytically competent Co(II)-substituted enzyme as well as all-atomistic molecular dynamics (MD) simulations. Combination of these data suggest His114 can quickly and reversibly move nearly 2Å between one conformation that facilitates catalysis and another that enables product egress and active site recharge. In light of experimental and computational data on ChdH114A, Asn216 appears to play a role in substrate binding and preorganization of the transition-state while Asp116 likely facilitates the deprotonation of the Zn(II)-bound water in the absence of His114. Based on these data, an updated proposed catalytic mechanism for Chd is presented.

Efficient Charge Transfer of p-n Heterojunction UiO-66-NH2/CuFe2O4 Composite for Photocatalytic Hydrogen Production

Using a p-n heterojunction is one of the efficient methods to increase charge transfer in photocatalysis applications. So, herein, p-type UiO-66 (NH2) and n-type CuFe2O4 (CFO) are used to form an effective p-n heterojunction. Due to their poor charge separation in their pristine form, both UiO-66 (NH2) and CFO materials cannot produce hydrogen; however, the composite p-n heterojunction formed between these materials makes fast charge separation and so hydrogen is efficiently produced. The optimized catalyst UCFO 25% produces a maximum of 62.5 µmol/g/h hydrogen in an aqueous methanol solution. The formation of a p-n heterojunction is confirmed by Mott–Schottky analysis and optical properties, crystallinity and the local atomic environment of the material was analyzed by various analytical tools like UV-Vis spectroscopy, XRD, and XANES.

Stability of Graphene/Nafion Composite in PEM FC Electrodes

Ensuring the stable operation of proton exchange membrane fuel cells is conducive to their real-world application. A promising direction for stabilizing electrodes is the stabilization of the ionomer via the formation of surface compounds with graphene. A comprehensive study of the (electrochemical, chemical, and thermal) stability of composites for fuel cell electrodes containing a modifying additive of few-layer graphene was carried out. Electrochemical stability was studied by cycling the potential on a disk electrode for 5000 cycles. Chemical stability was assessed via the resistance of the composites to H2O2 treatment using ion-selective potentiometry. Thermal stability was studied using differential thermal analysis. Composites were characterized by UV-Vis spectroscopy, Raman spectroscopy, EDX, and SEM. It was shown that graphene inhibits Nafion degradation when exposed to heat. Contrariwise, Nafion is corrosive to graphene. During electrochemical and chemical exposure, the determining change for carbon-rich composites is the carbon loss (oxidation) of the carbon material. In the case of carbon-poor composites, the removal of fluorine and sulfur from the Nafion polymer with their partial replacement by oxygen prevails. In all cases, the F/S ratio is stable. The dispersity of Nafion in a sample affects its chemical stability more than the G/Nafion ratio does.

Fast synthesis of gold nanoparticles by cold atmospheric pressure plasma jet in the presence of Au+ ions and a capping agent

Homogeneous gold nanoparticles were synthesized under atmospheric pressure using a non-thermal helium plasma jet in a single-step process. A current power supply was used to generate the plasma discharge rich in diverse reactive species. These species induce rapid chemical reactions responsible for the reduction of the gold salts upon contact with the liquid solution. In this study, spherical and monodispersed gold nanoparticles were obtained within 5 min of plasma exposure using a solution containing gold (III) chloride hydrate (HAuCl4) as a precursor and polyvinylpyrrolidone (PVP) as a capping agent to inhibit agglomerations. The formation of these metal nanoparticles was initially perceptible through a visible change in the sample’s color, transitioning from light yellow to a red/pink color. This was subsequently corroborated by UV-vis spectroscopy, which revealed an optical absorption in the 520‒550 nm range for Au NPs, corresponding to the surface plasmon resonance (SPR) band. An investigation into the impact of various parameters, including plasma discharge duration, precursor and capping agent concentrations, was carried out to optimize conditions for the formation of well-separated, spherical gold nanoparticles. Dynamic light scattering (DLS) was used to measure the size of these nanoparticles, transmission electron microscopy (TEM) was used to observe their morphology and X-ray diffraction (XRD) was also employed to determine their crystallographic structure. The results confirm that homogeneous spherical gold nanoparticles with an average diameter of 13 nm can be easily synthesized through a rapid, straightforward, and environmentally friendly approach utilizing a helium atmospheric pressure plasma.

Synthesis and Antibacterial Studies of a New Au(III) Complex with 6-Methyl-2-Thioxo-2,3-Dihydropyrimidin-4(1H)-One

This article describes the synthesis of a new metal complex using 6-methyl-2-thioxo-2,3-dihydropyrimidin-4(1H)-one. The compound was analyzed using several methods, including determining its melting point and employing UV-Vis, IR, ATR, 1H NMR, HSQC, and Raman spectroscopy for the free ligand. The metal complex was formed by combining aqueous solutions of metal salts with the ligand dissolved in DMSO and water, along with NaOH in a metal-to-ligand-to-base ratio of 1:4:2. The NMR signals of the ligand were assigned using 1H-1H COSY, DEPT-135, HMBC, and HMQC spectra. Furthermore, the compound’s antimicrobial activity against Gram-positive and Gram-negative bacteria, as well as yeasts, was assessed.

Hydrogen peroxide activation and liquid‐phase selective oxidations over Ti,Zr‐based metal–organic framework PCN‐415

A mixed Ti,Zr‐based metal–organic framework, PCN‐415 (Porous Coordination Network), and the corresponding Ti,Zr‐oxocluster [Ti8Zr2O12(CH3COO)16] have been synthesized and comprehensively characterized by powder X‐Ray diffraction (PXRD), low‐temperature nitrogen adsorption, scanning electron microscopy, thermogravimetric analysis, Fourier‐transform infrared spectroscopy, and Raman spectroscopy. The catalytic performance of both PCN‐415 and the Ti,Zr‐oxocluster was evaluated in the selective oxidation of representative thioethers, alkenes, and alkylphenols using aqueous hydrogen peroxide and tert‐butyl hydroperoxide as oxidants. The nature of the oxidation products formed indicates that, most likely, both Ti and Zr sites contribute to the catalytic activity of PCN‐415, although the contribution of Ti seems to be more significant. Examination of PCN‐415 after treatment with H2O2 using diffuse reflectance UV–vis spectroscopy indicates the formation of Ti peroxo complexes while Raman spectroscopy shows evidence for the formation of both Ti and Zr peroxo species. The potential formation of missing linker‐type defects and their role in facilitating catalytic activity were addressed. The stability of the PCN‐415 structure under the catalytic conditions was confirmed by PXRD. The absence of metal leaching and the heterogeneous nature of the catalysis were verified. The catalyst could be easily recovered from the reaction mixture and reused several times without loss of the catalytic properties.