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Nanoporous gold electrodes are of great interest in electroanalytical chemistry, because of their unusual activity and large surface area. The electrochemical activity can be further improved by coating with molecular catalysts such as the tetraruthenated cobalt-tetrapyridylporphyrazines investigated in this work. The plasmonic enhancement of the scattered light at the nanoholes and borders modifies the electrode's optical characteristics, improving the transmission through the surface-enhanced Raman scattering (SERS) effect. When monitored by hyperspectral dark-field and confocal Raman microscopy, this effect allows probing of the porphyrazine species at the plasmonic nanholes, improving the understanding of the chemically modified gold electrodes.

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Co-abietate and Cu-abietate complexes were obtained by a low-cost and eco-friendly route. The synthesis process used Pinus elliottii resin and an aqueous solution of CuSO4/CoSO4 at a mild temperature (80 °C) without organic solvents. The obtained complexes are functional pigments for commercial architectural paints with antipathogenic activity. The pigments were characterized by Fourier-transform infrared spectroscopy (FTIR), mass spectrometry (MS), thermogravimetry (TG), near-edge X-ray absorption fine structure (NEXAFS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and colorimetric analysis. In addition, the antibacterial efficiency was evaluated using the minimum inhibitory concentration (MIC) test, and the antiviral tests followed an adaptation of the ISO 21702:2019 guideline. Finally, virus inactivation was measured using the RT-PCR protocol using 10% (w/w) of abietate complex in commercial white paint. The Co-abietate and Cu-abietate showed inactivation of >4 log against SARS-CoV-2 and a MIC value of 4.50 µg·mL-1 against both bacteria Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The results suggest that the obtained Co-abietate and Cu-abietate complexes could be applied as pigments in architectural paints for healthcare centers, homes, and public places.

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Urease is an enzyme containing a dinuclear nickel active center responsible for the hydrolysis of urea into carbon dioxide and ammonia. Interestingly, inorganic models of urease are unable to mimic its mechanism despite their similarities to the enzyme active site. The reason behind the discrepancy in urea decomposition mechanisms between inorganic models and urease is still unknown. To evaluate this factor, we synthesized two bis-nickel complexes, [Ni2L(OAc)] (1) and [Ni2L(Cl)(Et3N)2] (2), based on the Trost bis-Pro-Phenol ligand (L) and encompassing different ligand labilities with coordination geometries similar to the active site of jack bean urease. Both mimetic complexes produced ammonia from urea, (1) and (2), were ten- and four-fold slower than urease, respectively. The presence and importance of several reaction intermediates were evaluated both experimentally and theoretically, indicating the aquo intermediate as a key intermediate, coordinating urea in an outer-sphere manner. Both complexes produced isocyanate, revealing an activated water molecule acting as a base. In addition, the reaction with different substrates indicated the biomimetic complexes were able to hydrolyze isocyanate. Thus, our results indicate that the formation of an outer-sphere complex in the urease analogues might be the reason urease performs a different mechanism.

Assuntos

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The search for less expensive and viable products is always one of the challenges for research development. Commonly, the synthesis of coordination compounds involves expensive ligands, through expensive and low-yield routes, in addition to generating toxic and unusable residues. In this work, the organic ligand used is derived from the resin of a reforestation tree, Pinus elliottii var. elliottii. The synthesis method used Pinus resin and an aqueous solution of vanadium(III) chloride at a temperature of 80 °C. The procedure does not involve organic solvents and does not generate toxic residues, thus imparting the complex formation reaction a green chemistry character. The synthesis resulted in an unprecedented oxovanadium(IV)-bis(abietate) complex, which was characterized by mass spectrometry (MS), chemical analysis (CHN), vibrational (FTIR) and electronic spectra (VISIBLE), X-ray diffraction (XRD), and thermal analysis (TG/DTA). Colorimetric studies were performed according to the CIELAB color space. The structural formula found, consisted of a complex containing two abietate ligands, [VO(C20H29O2)2]. The VO(IV)-bis(abietate) complex was applied against microorganisms and showed promising results in antibacterial and antifungal activity. The best result of inhibitory action was against the strains of Gram-positive bacteria S. aureus and L. monocytogenes, with minimum inhibitory concentration (MIC) values of 62.5 and 125 µmol L−1, respectively. For Gram-negative strains the results were 500 µmol L−1 for E. coli; and 1000 µmol L−1 for Salmonella enterica Typhimurium. Antifungal activity was performed against Candida albicans, where the MIC was 15.62 µmol L−1, and for C. tropicalis it was 62.5 µmol L−1. According to the MFC analysis, the complex presented, in addition to the fungistatic action, a fungicidal action, as there was no growth of fungi on the plates tested. The results found for the tests demonstrate that the VO(IV)-bis(abietate) complex has great potential as an antimicrobial and mainly antifungal agent. In this way, the pigmented ink with antimicrobial activity could be used in environments with a potential risk of contamination, preventing the spread of microorganisms harmful to health.

Assuntos

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This data article is associated with the work "Ecofriendly synthesis of Zn-abietate complex derived from Pinus elliottii resin and its application as an antibacterial pigment against S. aureus and E. coli". The characterization data of the Zn-abietate complex obtained from Pinus elliottii resin and their reactional intermediary (Na-abietate) are reported. The Na-abietate was prepared with purified Pinus resin and sodium hydroxide (≥ 99%) in a stoichiometric ratio of 1:1. For the Zn-abietate synthesis was used ZnSO4 and Na-abietate solutions were at mild temperature and stirring without using organic solvents to ensuring the green character of the synthesis. Spectroscopic and structural characterization was consistent with an octahedral complex involving three carboxylate ligands per metal ion. X-ray photoelectron spectroscopy (XPS) analysis of the Na-abietate salt confirms the presence of carbonyl groups, carbon-oxygen atoms simple bonds (O-C/O=C), and carboxylate groups oxygen atoms (O-C=O). Analysis of the Zn LMM Auger, for the Zn-abietate complex, indicates the presence of zinc atoms with oxidation state Zn2+, this is supported by the distance between Zn 2p3/2 and 1p1/2 in the XPS spectrum. Together, these data will be useful for the structural representation of the samples.

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The analytical determination of lithium ions is usually performed by atomic absorption and X-ray fluorescence methods. Chemical analysis based on polyfluoroporphyrin chromogenic methods is also being employed, especially for biological samples. However, all existing methods are expensive and not suitable for routine work or field assays. The alternative method proposed here is based on the formation of a LiKFe(IO6) compound which is converted into a tris(1,10-phenanthroline)iron(ii) complex and monitored by spectrophotometric or colorimetric methods, the latter using a smartphone app. Under similar conditions, these two methods proved superior to the X-ray fluorescence method. A one pot analysis of lithium ions is also described, using an Eppendorf microtube previously modified for performing reaction, filtration and detection. This method is simple and very convenient for didactic and field assays.

Assuntos

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Inspired on the outstanding behavior of the BODIPY dye, a new fluorescent boron fluoride derivative of the classical 2,2'-dihydroxy-1,1'-naphtalazine or YELLOW 101 dye has been synthesized and investigated in this work. Analogously to YELLOW 101 (λemission = 510 nm), the new species, here denoted BYELLOW 101, exhibits strong fluorescence around 570 and 535 nm in the solid form and in organic solvents, respectively. The observed red shift of the luminescence emission can be explored in the superparamagnetic fluorescent materials employed in MPI (magnetic particle inspection) technology, decreasing the influence of the FRET mechanism, - a critical limitation in this type of system. BYELLOW 101 is stable in solid form, but in organic solvents, it hydrolyses very slowly regenerating the initial dye, keeping the fluorescence emission but exhibiting a small blue shift along the time.

Assuntos

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The time scale for interfacial photoinduced electron transfer (PeT) in plasmonic nanoparticles is not well established and the details are still under debate. This has renewed the interest in studying the electron transfer effect from both experimental and theoretical points of view. We present a quantitative analysis of PeT in single spherical gold (Au) and gold@palladium core@shell (Au@Pd) nanoparticles supported on reduced graphene oxide (RGO) using dark-field hyperspectral microscopy (DFHM) and electrochemical impedance spectroscopy (EIS). By studying the plasmon bandwidth in the scattering spectra of single particles and by correlating it to the plasmon damping processes we showed that PeT occurs from the AuNPs to RGO in a 10 fs time scale with a quantum efficiency of 35%. The introduction of a Pd shell on the AuNPs decreases the PeT time, with transfer occurring in as little as 1.7 fs with quantum yield higher than 74%. Furthermore, EIS showed a smaller resistance for PeT on RGO/Au@PdNPs under green light illumination. Our results can improve the understanding of the chemical interface damping process due to PeT in plasmonic nanomaterials and can enable the design of more efficient plasmon enhanced photocatalysts.

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Pentacyanidoferrate(II) complexes of aromatic N-heterocycles, such as 4-cyanopyridine, exhibit characteristic colors and strong metallochromism associated with the donor-acceptor interactions of the metal ions with the cyanide ligands. In the presence of transition metal ions insoluble polymeric complexes are formed, displaying bright yellow, red, brown and green colors with zinc(II), nickel(II), copper(II) and iron(III) ions, respectively. Such metallochromic response is better observed on filter paper, allowing applications in analytical spot tests. The effects can be explored visually and probed by means of modern instrumental facilities, including spectrophotometric and resonance Raman techniques. In this way, by using the cyanopyridinepentacyanidoferrates, the Prussian Blue test for ferric ions can be extended to the entire row of transition metal elements, providing a new and modern insight of such classical Feigl's spot tests.

Assuntos

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The Raman spectral profile of p-methylcarbohydrazonethioamide (MCHT) is completely changed due to strong SERS effects upon bonding onto gold nanoparticles surface, but some vibrational modes are further enhanced in the presence of Hg(II) ions. The lack of SERS response for most common metal ions indicates that the coordinating groups are interacting with the gold nanoparticles surface and not available for binding metal ions in solution, except for mercury ions. The selective enhancement of some vibrational modes is consistent with significant conformational changes upon binding of Hg(II) ion onto the AuNP@MCHT hybrid, as confirmed by TEM/EDS measurements, demonstrating its potentiality as a highly selective and sensitive SERS substrate.

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An unusual photooxidation of a coordinated 4-mercaptopyridine ( SpyH) ligand in the [Ru(Hmctpy)(dmbpy)(κ S-SpyH)]2+complex (Hmctpy = 4'-carboxy-2,2';6',2″-terpyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine) takes place under visible and UV irradiation, in aerated acetonitrile. The [Ru(mctpy)(dmbpy)(κ S-SO2py)] sulfinato product has been characterized by a variety of methods, including X-ray diffraction which supports the presence of the Ru-κ S-SpyH isomer in the starting complex. The photooxidation of the 4-mercaptopyridine ligand enhances the back-bonding interactions in the complex by means of the strongly acceptor 4-pyridinesulfinato-SO2py species, increasing the redox potential of the Ru(III)/Ru(II) couple significantly from 1.23 to 1.62 V. It also led to pronounced changes in the electronic and NMR spectra of the complexes, corroborated by DFT and ZINDO-S calculations. A possible mechanism based on referenced data of photooxidation has been proposed, which involves the formation of a reactive oxygen species and intermediate endoperoxide species, yielding a very stable Ru-sulfinato product. This novel species exhibits stronger luminescence (Φ f = 0.004) than the starting complex under UV excitation.

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The kinesin-microtubule pair has attracted much attention in recent years due to their promising use in the development of synthetic nanotransport machines. One of the challenges to study such system is how to observe the motility of either kinesin or microtubule. The usual technique for observation of the molecular machinery pair is by fluorescence microscopy, where fluorescent probes are bound to one, or both species, through a biotin-avidin linker. Here, the use of mercaptopropionic acid (MPA)-capped cadmium telluride (CdTe) quantum dots (QDs) as a direct fluorescent labeling agent to microtubule biomolecules is reported. QDs are able to not only bind to microtubules in vitro, but also to fluorescently label them in the red spectral region. Surface plasmon resonance (SPR) studies showed the binding of synthesized QDs to microtubules, while quantum dots-labeled microtubules were successfully visualized with fluorescence microscopy. It is believed QDs adsorbs to the microtubule surface mainly through the coordination of Cd with histidine, cysteine and methionine residues, as well as through interactions of the nanocrystal's carboxylated surface with free amino groups on microtubules.

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The conversion of carbon dioxide into important industrial feedstock is a subject of growing interest in modern society. A possible way to achieve this goal is by carrying out the CO2/methanol cascade reaction, allowing the recycle of CO2 using either chemical catalysts or enzymes. Efficient and selective reactions can be performed by enzymes; however, due to their low stability, immobilization protocols are required to improve their performance. The cascade reaction to reduce carbon dioxide into methanol has been explored by the authors, using, sequentially, alcohol dehydrogenase (ADH), formaldehyde dehydrogenase (FalDH), and formate dehydrogenase (FDH), powered by NAD+/NADH and glutamate dehydrogenase (GDH) as the co-enzyme regenerating system. All the enzymes have been immobilized on functionalized magnetite nanoparticles, and their reactions investigated separately in order to establish the best performance conditions. Although the stepwise scheme led to only 2.3% yield of methanol per NADH; in a batch system under CO2 pressure, the combination of the four immobilized enzymes increased the methanol yield by 64 fold. The studies indicated a successful regeneration of NADH in situ, envisaging a real possibility of using immobilized enzymes to perform the cascade CO2-methanol reaction.

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ABSTRACT The conversion of carbon dioxide into important industrial feedstock is a subject of growing interest in modern society. A possible way to achieve this goal is by carrying out the CO2/methanol cascade reaction, allowing the recycle of CO2 using either chemical catalysts or enzymes. Efficient and selective reactions can be performed by enzymes; however, due to their low stability, immobilization protocols are required to improve their performance. The cascade reaction to reduce carbon dioxide into methanol has been explored by the authors, using, sequentially, alcohol dehydrogenase (ADH), formaldehyde dehydrogenase (FalDH), and formate dehydrogenase (FDH), powered by NAD+/NADH and glutamate dehydrogenase (GDH) as the co-enzyme regenerating system. All the enzymes have been immobilized on functionalized magnetite nanoparticles, and their reactions investigated separately in order to establish the best performance conditions. Although the stepwise scheme led to only 2.3% yield of methanol per NADH; in a batch system under CO2 pressure, the combination of the four immobilized enzymes increased the methanol yield by 64 fold. The studies indicated a successful regeneration of NADH in situ, envisaging a real possibility of using immobilized enzymes to perform the cascade CO2-methanol reaction.

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Self-supported oligo-layered ZnAlEu LDH nanotubes (∅ 20 nm) self-assemble upon controlled hydrolysis of the metal ions (Zn2+, Al3+, Eu3+) in the presence of 1,3,5-benzenetricarboxylate anions and non-ionic worm-like micelles. Their high surface area and easily accessible cylindrical mesopores (175 m2 g-1; 0.75 cm3 g-1) facilitate interaction with 5 nm CdTe quantum dots, enhancing the overall luminescence behavior.

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We report the unprecedented observation of plasmon coupling between silver nanowires, showing how the surface-enhanced Raman scattering depends upon this interaction and how the spectrum can be shaped by the hot spot. Such observations were accomplished by Raman spectroscopy mapping of silver nanowires modified with rhodamine. The local spectra on the hot spots were measured by darkfield hyperspectral microscopy, a powerful but uncommonly used technique that is capable of determining the location, structure, and spectra of the hot spots. The result obtained by the simulation of two parallel nanowires based on the discrete dipole approximation (DDA) method was in excellent agreement with the results obtained experimentally.

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Surface enhanced Raman spectroelectrochemistry (SERS) spectroelectrochemistry provides a very sensitive technique to investigate the vibrational characteristics of coordination compounds and their particular behavior under the influence of plasmonic surfaces, concomitant with the exploitation of their redox properties and electronic spectra. The results, however, depend upon the mechanisms involved in the intensification of Raman spectra associated with the electromagnetic, resonance Raman and charge-transfer excitation at the Fermi levels. By probing the model complex [(Ru3O)(CH3COO)6(4,4'-bipy)3](n) (n = 1, 0, -1) adsorbed onto rough gold electrode surfaces, contrasting SERS profiles were obtained at several successive redox potentials and oxidation states, which enables a critical discussion on the role of the complex interaction with the gold surface, and the influence of the specific electronic bands in the triruthenium acetate cluster. Density functional theory (DFT) and time-dependent DFT calculations were carried out for the complex bound to an Au20 cluster to show the participation of active lowest unoccupied molecular orbital levels centered on the gold atoms. The corresponding charge-transfer band was predicted around 1200 nm, which supports a charge-transfer interpretation for the SERS response observed at λexc = 1064 nm. The selective enhancement of the vibrational modes was discussed based on the Raman theoretical calculations.

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The structure of polytetraruthenated nickel porphyrin was unveiled for the first time by electrochemistry, Raman spectroelectrochemistry, and a hydroxyl radical trapping assay. The electrocatalytic active material, precipitated on the electrode surface after successive cycling of [NiTPyP{Ru(bipy)2Cl}4](4+) species in strong aqueous alkaline solution (pH 13), was found to be a peroxo-bridged coordination polymer. The electropolymerization process involves hydroxyl radicals (as confirmed by the characteristic set of DMPO/(•)OH adduct EPR peaks) as reaction intermediates, electrocatalytically generated in the 0.80-1.10 V range, that induce the formation of Ni-O-O-Ni coordination polymers, as evidenced by Raman spectroelectrochemistry and molecular modeling studies. The film growth is halted above 1.10 V due to the formation of oxygen gas bubbles.

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The light scattering properties of hexagonal and triangular gold nanodisks were investigated by means of Cytoviva hyperspectral dark-field microscopy, exploring the huge enhancement of the scattered waves associated with the surface plasmon resonance (SPR) effect. Thanks to the high resolution capability of the dark-field microscope, the SPR effect turned it possible to probe the individual nanoparticles directly from their hyperspectral images, extrapolating the classical optical resolution limit, and providing their corresponding extinction spectra. Blue spectral shifts involving the in-plane dipolar modes were observed for the hexagonal gold nanodisks in relation to the triangular ones, allowing their spectroscopic differentiation in the dark-field images.

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The most challenging and wanted development in photodynamic therapy is the control of photosensitizer (PS) cytolocalization and the mechanism of cell death. 5,10,15-triphenyl-20-(3-N-methylpyridinium-yl)porphyrin (3MMe) administered to HeLa cells as DMSO solution accumulates in the cytoplasmic membrane (CM) where it causes severe photodamage and cell necrosis. In contrast, when incorporated in marine atelocollagen/xantham gum polymeric nanocapsules, the PS is shuttled through CM allowing its gradual release and accumulation in mitochondria and lysosomes. Little photodamage was caused to cells in this case, but compelling evidences are presented showing that encapsulation changes the cytolocalization and shifts the cell death mechanism from necrosis to apoptosis. In conclusion, both of those challenges can be overcome by encapsulation of typical PSs such as 3MMe by using the new concept of photodynamic treatment with minimal cell damage by targeting specifically some key organelles. We are confident that these findings are important for the development of more efficient photosensitizers tailored to induce apoptosis while minimizing undesirable side effects such as over-inflammation.

Assuntos