Search Results (3,172)

Candida albicans (C. albicans) is an opportunistic fungal pathogen and a major cause of nosocomial infections, especially in immunocompromised patients. Conventional diagnostic approaches such as blood culture and biochemical assays are accurate but require multi-step sample processing and prolonged turnaround times, limiting their applicability for rapid clinical screening. In the present study, we developed an electrochemical biosensor based on molecularly imprinted polymer (MIP) technology for the rapid and selective detection of intact C. albicans cells. The MIP layer was electropolymerized onto a screen-printed carbon electrode (SPCE), forming selective recognition cavities complementary to the fungal morphology. Electrochemical characterization and detection were performed using cyclic voltammetry in phosphate-buffered saline (PBS). The system demonstrated a wide linear detection range, enabling reliable quantification of C. albicans across concentrations spanning from 1 to 10⁴ CFU/mL and achieved an ultralow limit of detection (LOD) of 1.30 CFU/mL, demonstrating high sensitivity. High selectivity was confirmed against E. coli, S. aureus, and P. aeruginosa, demonstrating that the imprinted cavities effectively distinguish fungal cells from bacterial contaminants. These findings highlight the promise of MIP-based electrochemical biosensors as a simple, low-cost, and portable alternative for early fungal diagnostics. Full article

Salophen-type Schiff base ligands derived from salicylaldehyde and naphthalene aldehydes were synthesized and coordinated to Ni(II) to obtain three nickel complexes (NiL1–NiL3), which were evaluated as heterogeneous electrocatalysts for the methanol electro-oxidation reaction (MOR) in alkaline media. The ligands and complexes were fully characterized by FT-IR, ¹H NMR, EPR, DART-MS, and elemental analysis, confirming tetradentate coordination through imine nitrogen and phenoxide oxygen donors. Electrochemical studies were carried out using carbon paste electrodes modified with 15 wt % of each complex. Cyclic voltammetry revealed that the electrocatalytic activity is mediated by the Ni(II)/Ni(III) redox couple, with Ni(III) oxohydroxide species acting as the active sites for methanol oxidation. Among the evaluated systems, NiL1@CPE showed superior performance at low methanol concentrations, while NiL2@CPE and NiL3@CPE exhibited higher current densities at elevated methanol concentrations. Scan-rate studies indicated that the oxidation process is diffusion-controlled, and a linear response to methanol concentration was observed over a wide concentration range. The results demonstrate that ligand structure and coordination geometry play a crucial role in modulating the electrocatalytic behavior of Ni(II) Schiff base complexes, highlighting their potential as cost-effective molecular catalysts for alkaline methanol oxidation. Full article

Haemophilus influenzae (H. influenzae) is an important respiratory pathogen that can cause various invasive and non-invasive bacterial infections requiring rapid and sensitive detection. In recent years, electrochemical biosensors have emerged as a practical alternative for pathogen detection due to their high sensitivity, portability and short analysis time. Molecularly imprinted polymers (MIPs) are a class of synthetic receptors designed to mimic biological recognition through template-directed polymerization. In this study, an electrochemical biosensor based on MIPs was developed for the selective detection of H. influenzae. The polymeric film composed of methacrylamide (MAM), acrylamide (AAM), and vinylpyrrolidone (VP) monomers was fabricated on a gold screen-printed electrode (gold-SPE). The results of cyclic voltammetry (CV) revealed a strong redox current shift corresponding to bacteria concentrations within an analytical range of 1–10,000 CFU/mL with LOD 1.03 CFU/mL, with relative standard deviation (RSD) values below 9% across the tested concentration range. The optimized composition yielded and exhibited excellent selectivity when tested against non-target bacteria such as Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. Full article

This study presents the successful electrodeposition of polyaniline (PANI) and TiO₂/PANI composites on boron-doped diamond (BDD) and fluorine-doped tin oxide (FTO) substrates via cyclic voltammetry. Using 20 scan cycles in 0.5 M H₂SO₄, we synthesized thin films with tailored electrochemical properties. The formation of PANI was confirmed by characteristic redox peaks in the voltammograms, while FTIR spectroscopy identified key functional groups and bonding interactions between TiO₂ and PANI. Morphological analysis via optical and scanning electron microscopy revealed uniform but cracked surfaces influenced by TiO₂ loading. Composite electrodes with molar ratios of 2:1, 4:1, and 6:1 (TiO₂:PANI) were compared, showing increased titanium content with higher ratios, as confirmed by EDS. This work offers a reproducible route for designing modified electrodes with enhanced interfacial properties. Full article

Zn-Fe-Cr coatings were successfully deposited on sintered Nd-Fe-B matrix through the addition of the complexing agent etidronic acid (HEDP) to the plating solution; the electrodeposited process of the metal elements and the corrosion behavior of the coatings were also investigated. Through cyclic voltammetry (CV) tests, it was observed that the reduction potential difference between the metal elements was reduced by the addition of HEDP, which contributed to a more feasible electrodeposited process. The surface of Zn-Fe-Cr coating was covered by a chromate conversion film, and its microstructure was identified as the solid solution of Fe and Cr in Zn matrix. Compared with Zn and Zn-Fe coatings, the corrosion current density (J_corr) of Zn-Fe-Cr coating was decreased to 0.28 × 10⁻⁶ A·cm⁻², and the corrosion potential (E_corr) was increased to −1.01 V. Compared with the Zn and Zn-Fe coatings, the corrosion rate of the Zn-Fe-Cr coating has decreased by 90% and 98%, respectively. The corrosion resistance of coatings was further analyzed by neutral salt spray tests (NSS), and the analysis results showed that a composite oxide layer, composed of ZnO and Cr₂O₃, was formed in the corroded area of Zn-Fe-Cr coating during the corrosion process, which is capable of effectively inhibiting the expansion of the corrosion area. This research provides a promising strategy for ensuring the long-term service integrity of sintered Nd-Fe-B materials in marine environments. Full article

While many [FeFe]-hydrogenase biomimetics are effective proton-reduction catalysts, few are active for H₂ oxidation, and examples containing both a pendant amine group, able to act as a proton relay, and a second redox center, both essential features of the enzymes, are rare. Here we report the preparation and oxidation chemistry of two ferrocene-functionalized amino-diphosphines (PCNCP), (CH₂PR₂)₂NCH₂Fc (R = Ph (1), Cy (2)), and their ethylenedithiolate (edt) diiron complexes, [Fe₂(CO)₄(μ-edt){κ²-(R₂PCH₂)₂NCH₂Fc}] (R = Ph (3), Cy (4)). Their crystallographic characterization shows that PCNCP occupies an apical–basal position. CV responses are slightly R-dependent, showing for 3 and 4 in three separate oxidative processes assigned to successive one-electron oxidation of the diiron core (quasireversible), appended Fc (reversible), and the amine–diiron moiety (irreversible), as confirmed by IR and UV–Vis spectroelectrochemical studies supported by Density Functional Theory (DFT) and Time-dependent Density Functional Theory (TDDFT) calculations. The first oxidation results in a structural rearrangement of the Fe(PNP)(CO) unit and the formation of a semi-bridging carbonyl. Slow protonation of 3 with HBF₄∙Et₂O affords the corresponding N-protonated cation in acetone, whilst μ-hydride products dominate for both 3 and 4 in CD₂Cl₂. A preliminary H₂ oxidation study was carried out with 3, and while there was some evidence of activity, it was much lower than reported for alkyl-functionalized PCNPC diiron derivatives. Full article

Biochar provides a porous scaffold, conductive carbon framework and redox-active surface functional that can promote microbial attachment and extracellular electron flow. However, how feedstock-dependent biochar properties regulate the biochar–cell interface and microbial metabolism during contaminant removal remains insufficiently understood. Here, biochar derived from rice husk, corn straw and corn cob was used to immobilize Pseudomonas chlororaphis for triclocarban removal in batch microcosms. Multiscale analyses, including scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), (electrochemical impedance spectroscopy (EIS) and liquid chromatography–mass spectrometryLC-MS, were combined to link the biochar structure, interface and extracellular metabolism signatures with triclocarban (TCC) removal. Compared with free cells, all composites enhanced TCC removal and exhibited altered interfacial functional-group features together with substantially reduced fitted charge-transfer resistance, indicating facilitated interfacial electron exchange. Untargeted metabolomics further revealed consistent remodeling of extracellular redox-associated metabolite signatures upon immobilization, with increased quinone/polyphenol-associated features and pathway-level shifts related to redox homeostasis. Among feedstocks, the corn cob composite showed the highest triclocarban removal. Overall, this work proposes an evidence-supported “structure–interface–metabolism” framework for interpreting how agricultural-residue biochars modulate biofilm interfaces and redox-related metabolic signatures to improve triclocarban removal, providing guidance for designing biochar-supported bioprocesses for halogenated micropollutants. Full article

In the present study, the electrodeposition of thin Ni–Fe films obtained from aqueous electrolytes containing nickel (II) and iron (II) sulfates and chlorides is investigated. The study particularly emphasizes the influence of electrolyte additives—boric acid, chloride ions, and Na₂EDTA—on the electrochemical behavior, microstructure, and magnetic properties of the deposited layers. Cyclic voltammetry revealed a partial alignment of the reduction potentials of nickel and iron and the suppression of the hydrogen evolution side reaction up to −1 V. Electrodeposition in galvanostatic mode in the range of 0.5 to 1.0 A/dm² allows the formation of layers with iron contents between 20.5 wt. % to 41.4 wt. % and coating thickness from 1.3 to 3.0 µm. SEM and AFM observations demonstrated a pronounced dependence of the surface morphology on the current density, with higher current densities promoting the formation of dendritic structures. X-ray diffraction confirmed the dominance of a face-centered cubic (FCC) Ni-based solid solution, accompanied by minor contributions from non-stoichiometric Fe_1−xO. All the obtained Fe-Ni films have soft magnetic properties. Increasing the current density and the boric acid concentration causes the coercive force and isotropy of the layers to improve. The results demonstrate that thin Ni-Fe films with controlled structure and morphology, with favorable soft ferromagnetic properties suitable for functional applications, could be electrodeposited from complex chloride–sulfate electrolytes by adjusting the current density. Full article

This study investigates the combined effect of electrodeposited gold nanoparticles (AuNPs) and AuNP–polypyrrole (PPy)-modified Saccharomyces cerevisiae on electrochemical glucose sensing. AuNPs were deposited onto electrode surfaces by cyclic voltammetry, and the resulting interfaces were characterized using atomic force microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. AFM analysis confirmed increased surface roughness and height variability after deposition, indicating substantial restructuring of the electrode interface. Electrochemical measurements showed that AuNP deposition altered interfacial charge storage and transfer and increased the measured charge-transfer resistance. Glucose sensing was evaluated in a ferricyanide-mediated system using yeast layers with or without AuNP and PPy modification over a 0–60 mM concentration range. All configurations exhibited saturating, non-linear glucose responses described by Hill fitting. Among the evaluated yeast-modified electrodes, the AuNP–PPy modified yeast produced the strongest glucose-induced current increase and the best low-concentration performance, achieving a limit of detection of 0.540 mM, compared with 1.016 mM and 1.330 mM for single-modified layers and 3.360 mM for unmodified yeast. These results show that combining AuNP electrodeposition with AuNP–PPy yeast modification improves interfacial properties and enhances mediator-assisted electrochemical glucose sensing. Full article

Bovine rotavirus (BRV) is one of the leading causes of neonatal diarrhea in calves and remains a major concern in veterinary medicine due to its high morbidity and economic impact. Rapid, sensitive, and cost-effective diagnostic approaches are therefore required for early detection and disease control. In this study, electrochemical immunosensors were developed for the detection of BRV with the aim of improving existing multiplex diagnostic strategies. Screen-printed carbon electrodes (SPEs) were employed as the sensing platform and modified with molybdenum disulfide nanoparticles (MoS₂ NPs) to enhance electrochemical performance. Mouse monoclonal antibodies against the BRV VP6 protein were immobilized onto the electrode surface, followed by blocking with bovine serum albumin. BRV detection was carried out using differential pulse voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy. To further improve sensitivity, a sandwich immunoassay format was constructed using gold nanoparticle-labeled secondary antibodies. The MoS₂-modified sandwich immunosensor exhibited superior analytical performance, achieving a limit of detection of 1.11 ng/mL, a limit of quantification of 3.72 ng/mL, a relative standard deviation of 1.89% (n = 5), and a linear response with R² = 0.99. The developed immunosensors demonstrated reliable performance in real sample analysis, with a selectivity rate of 100 ± 2.95%. These findings suggest that MoS₂-based electrochemical immunosensors offer a promising platform for rapid and sensitive BRV detection and have potential applications in veterinary diagnostics. Full article

This study presents the synthesis and electrochemical characterization of meso-tetracyanobutadiene (TCBD)-functionalized diphenylporphyrin (DPP) complexes incorporating copper (Cu) and nickel (Ni) metals. These push–pull metallo diphenylporphyrin–TCBD complexes were synthesized via a [2 + 2] cycloaddition–retroelectrocyclization reaction between 5-bromo-15-formyl-10,20-diphenylporphyrin metal(II) complexes (M = Cu, Ni) and tributyl(phenylethynyl)stannate, followed by tetracyanoethylene (TCNE) addition. The resulting TCBD-functionalized porphyrins were obtained in moderate yields (70–75%) and thoroughly characterized by ¹H and ¹³C NMR, UV-Vis spectroscopy, MALDI-TOF-MS, and single-crystal XRD. Although the single-crystal X-ray structure of NiDPP was solved, DFT calculations were used to determine the structures of the donor–acceptor MDPP-TCBD systems and to visualize their electronic structures. HOMO on the porphyrin π system and LUMO on the TCBD entity were observed, and energy level diagrams clearly laid out the electron donor and acceptor parts of the molecular systems. As expected, these novel donor–acceptor porphyrinoid assemblies exhibited enhanced push–pull properties in both the ground and excited states. Femtosecond transient absorption studies revealed that both NiDPP-TCBD and CuDPP-TCBD populate the charge-transfer state upon photoexcitation, with lifetimes of 383.1 ps and 484.7 ps, respectively, in benzonitrile. The charge-transfer states populated the triplet or doublet states (in the case of CuDPP) before returning to the ground state. Full article

Over the past few decades, ionic liquids (ILs) have gained attention as electrolytes, although concerns about their environmental persistence and toxicity challenge their status as green solvents. In this framework, choline chloride (ChCl) offers a more sustainable alternative due to its low toxicity, biodegradability, and cost-effectiveness. Although ChCl has a high melting point, its combination with hydrogen bond donor compounds (HBDs) can result in liquid mixtures at much lower temperatures, known as deep eutectic solvents (DESs). This study presents a comparative evaluation of three ChCl-based DESs, glyceline, ethaline, and reline (obtained from mixtures of ChCl and glycerol, ethylene glycol, and urea), with a focus specifically on their potential as electrolyte candidates for supercapacitors. Using differential scanning calorimetry (DSC), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and nuclear magnetic resonance (NMR), we assess their thermal, electrochemical, and structural properties. All DESs displayed amorphous behavior and a strong tendency to remain liquid even at very low temperatures. Among them, ethaline showed the most promising electrochemical performance, exhibiting the lowest resistivity and the highest capacity. Full article

Neural interfaces created using thin-film fabrication rely primarily on conductive metal traces for electrical interconnects. Here, we explore the use of tantalum (Ta) metal interconnects as a replacement for noble-metal interconnects such as Au, Pt or Ir. Ta has been investigated previously for interconnect metallization in flexible silicon ribbon cables, but the structure and properties of tantalum for neural device metallization have not been extensively reported. In the present work, Ta metal was sputter-deposited onto amorphous silicon carbide (a-SiC), with and without a base titanium (Ti) adhesion layer, and investigated as interconnect metallization. In the absence of a Ti adhesion layer, resistivity measurements revealed a factor of six difference between Ta resistivity depending on the presence of the Ti base layer, with direct deposition on a-SiC nucleating high resistivity β-Ta (ρ = 197 ± 31 µΩ·cm, mean ± standard deviation) and Ta deposited on Ti nucleating low resistivity α-Ta (ρ = 35 ± 6 µΩ·cm). X-ray diffraction confirmed the existence of the two crystal structures. Ta feature sizes of 2 µm were created using photolithography and reactive ion etching (RIE). Finally, planar microelectrode array test structures using α-Ta and Au trace metallization with low-impedance ruthenium oxide (RuO_x) electrodes were fabricated and investigated by cyclic voltammetry (CV) and current pulsing in saline. These devices underwent 500 CV cycles between −0.6 and +0.6 V without evidence of degradation. In response to charge-balanced, biphasic current pulses at 4 nC/phase, a 21 mV increase in access voltage was observed with α-Ta metallization compared to Au. These results warrant further investigation of Ta as thin-film metallization interconnects for neural interface devices. Full article

The electro-oxidation of eugenol (EUG) natural antioxidant was studied by cyclic voltammetry in phosphate buffer solutions (PBS) of different pH at electrochemically partially reduced graphene oxide (GCE/ePRGO). The voltammetric responses were mainly controlled by adsorption at this modified electrode. Current values were higher at pH 2.0 PBS, therefore, this pH was chosen to perform all experiments. DFT calculations of pKa’s and standard potentials defined the possible pathways of eugenol and its oxidation products. These pathways were evaluated through the comparison of voltammetric simulations of adsorbed species with experiments at pH 2.0, which also allowed for the estimation of the values of the kinetic parameters involved in electrochemistry. Our findings suggest a multi-step redox process in which Eugenol is first oxidized to the radical species and then to a cationic product. At this stage, the pathways branch into to methylenquinone and a 4-allyl-1,2-diquinone molecules. 4-allyl-1,2-diquinone is finally reduced in single or double reversible electrochemical step to the hydroquinone species. The present physicochemical work allows for a deeper understanding of the eugenol oxidation mechanism, which was only partially proposed in previous studies. Full article

An anthraquinone chromophore displaying a vivid violet color in solution was synthesized and it was thoroughly characterized both spectroscopically and electrochemically, along with its X-ray crystallography. Single crystal X-ray analysis of the chromophore revealed a nearly planar π-conjugated framework with short intermolecular contacts. Cyclic voltammetry revealed two consecutive one-electron reductions, corresponding to the formation of its radical anion and dianion. The spectroelectrochemistry of the chromophore confirmed two distinct and reversible color changes with the stepwise electrochemical reduction. These were quantified via the CIE L a* b* color space. Large optical differences (98%) between the bleached and colored states were observed along with a coloration efficiency of 698 cm²/C. These parameters confirm the anthraquinone is an ideal electrochrome: capable of reversibly switching its colors with applied potential. The three color changes and color bleaching associated with the neutral, radical anion, dianion, and cation, respectively, are also of interest for extending the palette of colors of molecular electrochromes toward panchromatic color tuning with molecular structure for use in smart windows and displays. Full article