Biofuel cells allow for constructing sensors that leverage the specificity of enzymes without the need for an external power source. In this work, we design a self-powered glucose sensor based on a biofuel cell. The redox enzymes glucose dehydrogenase (NAD-GDH), glucose oxidase (GOx), and horseradish peroxidase (HRP) were immobilized as biocatalysts on the electrodes, which were previously engineered using carbon nanostructures, including multi-wall carbon nanotubes (MWCNTs) and reduced graphene oxide (rGO). Additional polymers were also introduced to improve biocatalyst immobilization. The reported design offers three main advantages: (i) by using glucose as the substrate for the both anode and cathode, a more compact and robust design is enabled, (ii) the system operates under air-saturating conditions, with no need for gas purge, and (iii) the combination of carbon nanostructures and a multi-enzyme cascade maximizes the sensitivity of the biosensor. Our design allows the reliable detection of glucose in the range of 0.1–7.0 mM, which is perfectly suited for common biofluids and industrial food samples.

A chalcone series (3a–f) with electron push–pull effect was synthesized via a one-pot Claisen–Schmidt reaction with a simple purification step. The compounds exhibited strong emission, peaking around 512–567 nm with mega-stokes shift (∆λ = 93–139 nm) in polar solvents (DMSO, MeOH, and PBS) and showed good photo-stability. Therefore, 3a–f were applied in cellular imaging. After 3 h of incubation, green fluorescence was clearly brighter in cancer cells (HepG2) compared to normal cells (HEK-293), suggesting preferential accumulation in cancer cells. Moreover, all compounds exhibited higher cytotoxicity within 24 h toward cancer cells (IC₅₀ values ranging from 45 to 100 μM) than normal cells (IC₅₀ value >100 μM). Furthermore, the antimicrobial properties of chalcones 3a–f were investigated. Interestingly, 3a–f exhibited antibacterial activities against Escherichia coli and Staphylococcus aureus, with minimum bactericidal concentrations (MBC) of 0.10–0.60 mg/mL (375–1000 µM), suggesting their potential antibacterial activity against both Gram-negative and Gram-positive bacteria. Thus, this series of chalcone-derived fluorescent dyes with facile synthesis shows great potential for the development of antibiotics and cancer cell staining agents.

Among lanthanide-based compounds, cerium compounds exhibit a significant role in a variety of research fields due to their distinct tetravalency, high economic feasibility, and high stability of Ce(IV) complexes. Herein, a systematic investigation of crystallographic information, chemical properties, and mechanistic formation of the novel Ce(IV) complex synthesized from cerium(III) nitrate hexahydrate and 2,2′-(methylazanediyl)bis(methylene)bis(4-methylphenol) (MMD) ligand has been explored. According to the analysis of the crystallographic information, the obtained complex crystal consists of the Ce(IV) center coordinated with two nitrate ligands and two bidentate coordinated (N-protonated and O,O-deprotonated) MMD ligands. The fingerprint plots and the Hirshfeld surface analyses suggest that the C–H⋯O and C–H⋯π interactions significantly contribute to the crystal packing. The C–H⋯O and C–H⋯π contacts link the molecules into infinite molecular chains propagating along the [100] and [010] directions. Synchrotron powder X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques have been employed to gain an understanding of the oxidative complexation of Ce(IV)-MMD complex in detail. This finding would provide the possibility to systematically control the synthetic parameters and wisely design the precursor components in order to achieve the desired properties of novel materials for specific applications.

The determination of paracetamol is a common need in pharmaceutical and environmental samples for which a low-cost, rapid, and accurate sensor would be highly desirable. We develop a novel pencil graphite lead electrode (PGE) modified with single-wall carbon nanotubes (SWCNTs) and polyvinylpyrrolidone (PVP) polymer (PVP/SWCNT/PGE) for the voltammetric quantification of paracetamol. The sensor shows remarkable analytical performance in the determination of paracetamol at neutral pH, with a limit of detection of 0.38 μM and a linear response from 1 to 500 μM using square-wave voltammetry (SWV), which are well suited to the analysis of pharmaceutical preparations. The introduction of the polymer PVP can cause dramatic changes in the sensing performance of the electrode, depending on its specific architecture. These effects were investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The results indicate that the co-localization and dispersion of PVP throughout the carbon nanotubes on the electrode are key to its superior electrochemical performance, facilitating the electrical contact between the nanotubes and with the electrode surface. The application of this sensor to commercial syrup and tablet preparations is demonstrated with excellent results.

A novel pyridylhydrazone-tethered BODIPY (BODIPY-PH) was synthesized, fully characterized via nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopic (FTIR), and single-crystal X-ray diffraction (SC-XRD) techniques, and developed for the selective detection of Fe³⁺ through fluorescent enhancement process. This derivative showed 1:1 binding with Fe³⁺ in an acetonitrile-water mixture (1:9 v/v) with the binding constant (K) of 5.4 × 10⁴ M⁻¹ and the limit of detection of 0.58 µM. The Fe³⁺ complexation reaction has been proved to be a reversible process and could be effectively repeated up to three cycles. The electronic properties of BODIPY-PH and its Fe³⁺ complex modeled by the density functional theory (DFT) method suggested the presence of chelation-enhanced fluorescence (CHEF) effect in the Fe³⁺ binding reaction. The X-ray absorption spectroscopy (XAS) probed at Fe K-edge confirmed the complex formation between BODIPY-PH and the Fe³⁺ in an octahedral geometry. Finally, bioimaging against human embryonic kidney (Hek293) cell, through confocal fluorescence microscopic technique indicated that the BODIPY-PH displayed good permeability and low toxicity toward the tested cell lines and showed enhanced fluorescent signal in the cells incubated with Fe³⁺ proving its capability for Fe³⁺ analysis in cellular matrix.

This work reports a facile synthesis of nitrogen-doped amorphous carbon nanodots (N-CNDs) and their use as a fluorometric paper-based sensor for the determination of Pb²⁺ at a low concentration.