Theophylline (TP) is a methylxanthine derivative, which serves as a valuable compound in treating respiratory disorders and acts as a bronchodilator agent. However, TP has a limited therapeutic range (20-100 μmol L-1), demanding precise monitoring to prevent potential drug toxicity even with slight level fluctuations during treatment. Thus, to overcome this limitation, electrochemical methods have been extensively used due to their efficacy in achieving sensitivity, selectivity, and accuracy. In the context of electrochemical sensors, nanocarbon-based materials have gained widespread recognition for their extensive applications. Therefore, this review aims to explore the latest advancements in carbon-based electrodes particularly used for the precise determination of TP through electrochemical methods. The results are expected to provide insights into the profound significance of the methods in enhancing the accuracy and sensitivity for the detection of TP.
Methylammonium lead iodide (MAPbI3) is a benchmark absorber for low-cost, high-efficiency perovskite solar cells (PSCs), but its practical deployment is constrained by small grain sizes, high defect densities, and moisture-sensitive surfaces that limit both efficiency and stability. Here, we demonstrate that covalent organic frameworks (COFs) built from commercially available building blocks provide a powerful, multifunctional route to overcome these limitations by simultaneously regulating crystallization, passivating defects, and tuning surface properties in MAPbI3 thin films. Three hydrazone-linked and β-ketoenamine frameworks, denoted DMTH-COF, Boc-PDA-COF and Tp-COF, were prepared by condensing 2,5-dimethoxyterephthalohydrazide (DMTH), Boc-PDA-phenylenediamine (Boc-PDA), and 1,3,5-triformylphloroglucinol (Tp), respectively, and were incorporated at low loading into the MAPbI3 precursor solution. X-ray diffraction and FE-SEM reveal that all three additives preserve the tetragonal perovskite phase while enlarging the grain size from a few hundred nanometers in pristine films to about 1 μm for DMTH-modified layers, accompanied by narrowed diffraction peaks and reduced microstrain. Raman and FTIR spectroscopy show COF-induced modifications of Pb-I and CH3NH3+ vibrational modes, indicating specific coordination and hydrogen-bonding interactions that stabilize the lattice and reduce trap density. UV-Vis spectra confirm strong visible-light absorption at an unchanged optical bandgap of 1.56 eV across all films, while steady-state PL and EQE measurements evidence enhanced radiative efficiency and improved photon-to-current conversion, particularly at longer wavelengths. X-ray photoelectron spectroscopy confirms that the framework is retained within the film after annealing, the modified absorber showing a N 1s component at 399.7 eV that is absent from the pristine reference, while the Pb 4f and I 3d core levels shift in parallel with their spin-orbit splittings preserved and no metallic lead detected. These material-level improvements translate into substantial device gains in n-i-p PSCs (FTO/c-TiO2/m-TiO2/COF:MAPbI3/Spiro-OMeTAD/Au). Relative to pristine MAPbI3 cells (PCE ≈ 14.7%), COF-modified devices exhibit higher Voc, Jsc, and FF, with DMTH-COF-modified cells achieving Voc = 1.183 V, Jsc = 22.98 mA cm-2, FF = 76.46%, and PCE = 20.78%, alongside reduced series resistance, increased shunt resistance, and improved device-to-device reproducibility. Water-contact-angle and EDX analyses confirm that COF addition increases surface hydrophobicity and preserves near-ideal Pb:I stoichiometry, supporting enhanced environmental stability. This study introduces bulk COF doping as a simple, scalable strategy to engineer MAPbI3 microstructure, energetics, and surface chemistry in a single processing step, and identifies DMTH-COF as the most effective of the three frameworks. More broadly, it positions COF-perovskite hybrids as a tunable platform for high-efficiency, durable perovskite optoelectronics.
Overuse of levofloxacin (LEV) is often associated with bacterial resistance and serious health problems, underscoring the need for reliable sensing and monitoring of LEV molecules. Therefore, this study aimed to investigate LEV using boron-doped diamond (BDD) and boron-doped diamond modified with MXene (Ti3C2TX) (BDD-MXene) electrode. The successful deposition of MXene on the BDD surface was confirmed using scanning electron microscope (SEM). Cyclic voltammetry (CV) and square wave voltammetry (SWV) methods were also applied to evaluate the electrochemical behavior. The results showed that both electrodes had a linear response in the range of 30-100 μM. The limit of detection (LOD) and limit of quantitation (LOQ) were found to be 1.0 × 10-6 M and 3.37 × 10-6 M for bare-BDD, while on BDD-MXene, the values were 3.90 × 10-7 M and 1.30 × 10-6 M, respectively. Furthermore, both electrodes showed good responses on selectivity tests with glucose and another fluoroquinolone antibiotic such as ciprofloxacin. The results also indicated good precision with %RSD less than 5%. In real sample applications using wastewater, bare-BDD and BDD-MXene produced excellent %recovery of 92.96% and 101.29%, respectively.