Nanostructures that can undergo redox reactions have significant potential for electrochemical analysis. They can act as signal amplifiers to determine concentrations of targets in biological samples. In this work, a rational combination of electroactive copper‐based metal‐organic frameworks (Cu‐MOFs) and ferrocene carboxylic acid (Fc) was designed for ratiometric electrochemical detection of creatinine. The synthesized Fc@Cu‐MOFs exhibited two redox signals from the Cu²⁺/Cu⁺ and Fe³⁺/Fe²⁺ systems in the skeleton of Cu‐MOFs and Fc, respectively. In the presence of chloride (Cl⁻), the oxidation current of Cu⁺ increased due to formation of solid‐state cuprous chloride (CuCl). Adding strong Cu⁺ chelators, e. g. creatinine, coordinated with Cu⁺ and caused the current output of solid‐state CuCl to decrease significantly. The anodic current of Fc did not appreciably change, serving as an internal reference signal. The ratiometric responses (I_Cu(I)/I_Fc) changed with increasing concentrations of creatinine from 0.017–130 μM with a detection limit (S/N=3) of 0.005 μM. The main advantages of Fc@Cu‐MOFs are the low LOD, high selectivity, and reliability, making it a suitable platform for determining creatinine in human serum and urine samples. The as‐fabricated sensor is a reliable approach for determining (bio) molecules that can form stable complexes with Cu⁺ ions.

In this research paper, a novel “signal on–off” ratiometric-based electrochemical platform was developed for the sensitive and selective detection of captopril. Ratiometric responses were achieved by fabricating molecularly imprinted polymers (MIPs) on the surface of a graphite electrode (GE) decorated with nitrogen (N) and sulfur (S) co-doped porous carbon and silver nanoparticles (Ag). The MIP layer was formed via electropolymerization of copper coordinated with pyrrole-3-carboxylic acid (functional monomer). Silver nanoparticles (Ag) were incorporated to enhance conductivity and surface area and to serve as an internal reference output. Upon the addition of captopril, there was a decrease in the anodic oxidation current of Ag+ at around 0.067 V, coupled with an increase in the oxidation current at 0.54 V (Ag–captopril complex). Under optimized conditions, the electrochemical responses (IAg–captopril/IAg 

In the current study, the potential interaction mechanisms between capmatinib (CAP), a selective tyrosine kinase inhibitor, and calf thymus double-stranded DNA (ds-DNA) were evaluated. In this research, we construct an amplified electrochemical platform based on a disposable pencil graphite electrode (PGE) modified with nanostructured CeO2 decorated carbon nanofiber ceramic film (CeNPs@CNF-CF) for monitoring CAP–dsDNA interaction at physiological pH. The morphology and structure of the obtained CeNPs@CNF nanocomposite were characterized. The CeNPs@CNF-CF/PGE was characterized by scanning electron microscopy (SEM). The CAP–dsDNA interaction was examined using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Voltammetric experiments were conducted using CeNPs@CNF-CF/PGE. The interaction of CAP with dsDNA was investigated after applying …

In the current study, the first voltammetric method is constructed for the ultrasensitive quantification of capmatinib (CMT), a targeted therapy drug falls within the category of tyrosine kinase inhibitors (TKIs), using a modified carbon nanofibers paste electrode (CNFs-PE). Nanogold-loaded porous acetylene black (Au@PAB) as a conductive hybrid nanofiller incorporating carbon nanofiber networks (CNFs) was synthesized. The surface morphology of the synthesized Au@PAB and the ternary nanocomposite Au@PAB/CNFs was elucidated using various analytical techniques. The results show Au@PAB hybrid nanofiller incorporated CNFs has a critical property that increases electrocatalytic performance. The impact of scan rate, pH, and supporting electrolyte on the electrocatalytic response of CMT was explored on the Au@PAB/CNFs-PE nanosensor. Under optimum adsorptive stripping square-wave voltammetric …

In this study, we have constructed a novel voltammetric sensor based on montmorillonite clay (MMT) incorporated with CeO₂ nanoparticles using a composite graphite paste electrode as a cross linker (MMT-CeO₂NPs/GPG-PE) for the trace determination of tadalafil (TAD) drug. The characterization of CeO₂ nanoparticles has been conducted using various analytical techniques, including X-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy. The morphology of the composite of CPG and MMT-CeO₂NPs/CPG was elucidated through scanning electron microscopy (SEM). The newly developed sensor (MMT-CeO₂NPs/CPG-PE) exhibited remarkable efficiency towards TAD oxidation using adsorptive stripping square-wave voltammetry (AdS-SWV) in Mcllvaine buffer solution (pH 8.0). A highly selective and sensitive method for TAD detection has been successfully …

A novel and sensitive fluorescence ratiometric method is developed for urea detection based  on the pH-sensitive response of two fluorescent carbon dot (CD) systems: R-CDs/methyl red (MR) and NIR-CDs/Cu²⁺. The sensing mechanism involves breaking down urea using the enzyme urease, releasing ammonia and increasing pH. At higher pH, the fluorescence of NIR-CDs is quenched due to the enhanced interaction with Cu²⁺, while the fluorescence of R-CDs is restored as the acidic MR converts to its basic form, removing the inner filter effect. The ratiometric signal (F₆₀₈/F₇₅₀) of the R-CDs/MR and NIR-CDs/Cu²⁺ intensities changed in response to the pH induced by urea hydrolysis, enabling selective and sensitive urea detection. Detailed spectroscopic and morphological investigations confirmed the fluorescence probe design and elucidated the sensing mechanism. The method exhibited excellent …

The monitoring of ziram levels is of vital importance due to its widespread application in agriculture and the possible risks it poses to human health and the ecosystem. This work proposes an innovative approach for the highly sensitive and selective sensing of ziram, a widely used dithiocarbamate fungicide, through the formation of copper dimethyldithiocarbamate Cu)DDC)₂ assisted dual quenching of red and blue emission carbon dots (R/NCDs and B/NSCDs). When ziram is added to a system containing copper-bound B/NSCDs and R/NCDs, the displacement of ziram zinc ions by copper ions leads to the formation of a yellow-colored Cu)DDC)₂ complex. This complex induces significant quenching of the fluorescence emissions from both types of carbon dots, consequently enhancing the sensitivity of the detection method. Comprehensive characterization of the R/NCDs and B/NSCDs was conducted using …

This study develops a novel fluorometric method for the sensitive and selective determination of urea, based on unique system comprising nitrogen doped red-emissive carbon dots (NRECDs), zinc-dithizone complex, and the urease enzyme. The underlying principle of this method relies on the pH increase resulting from the enzymatic breakdown of urea by urease. Initially, the fluorescence of the NRECDs is quenched by the red-colored zinc-dithizone complex. However, upon the addition of urea, the subsequent release of ammonia and the consequent rise in pH lead to the dissociation of the zinc-dithizone complex, causing a color change from red to yellow. This spectral shift eliminates the quenching effect, resulting in the restoration of the CDs’ fluorescence. The prepared NRECDs were comprehensively characterized using various spectroscopic techniques, including fluorometry, X-ray diffraction (XRD), X-ray 

Benzene, toluene, ethylbenzene and xylene are known to be lethal environmental contaminants that have carcinogenic and mutagenic influences in human being while styrene and benzaldehyde have a neurotoxic effect. In other hand, the constituents of air freshener considered as a probable source of volatile organic compound. In the present work, a solid phase extraction and gas chromatography–mass spectrometry (GC-MS) technique has been optimized and applied to the fabric, carpet and air freshener samples to determine the trace amounts of benzene, toluene, ethylbenzene, xylene, styrene and benzaldehyde. The Supelclean TM ENVI TM-18 cartridge with dichloromethane extracting solvent were found to be the optimal procedures. The system presented excellent performance in terms of limit of detection (0.08-0.61 ng/mL), coefficient of determination (0.994-0.997), precision with the relative standard deviation values ranging from 0.05-2.57%. According to the results, the concentration of benzene, toluene, ethylbenzene, xylene, styrene and benzaldehyde in fresheners’ samples was found in the range 0.03-53.27, 0.03-7.12, 0.02-6.51, 0.05-96.44, 0.04-7.06 and 0.22-23.02, respectively. The excellent recovery values were also obtained up to 99.93%. The Supelclean TM ENVI TM- 18 GC-MS system was found to appropriate for the monitoring of analytes in fabric, carpet, air freshener samples, and other samples of the similar

This study presents a novel dual-modal approach for glutathione (GSH) detection using blue and yellow dual-emission carbon dots (BY-CDs) and bromothymol blue (BTB) at pH 8.0. The method employs both colorimetric and fluorometric detection modes, offering a new perspective on GSH quantification. BTB's blue coloration induces selective fluorescence quenching of the CDs' 610 nm emission peak, with minimal effect on the 445 nm peak. Upon GSH addition, the quinonoid structure (blue color) of BTB transforms to its benzenoid form (yellow color). This transformation triggers fluorescence restoration at 610 nm and significant quenching at 445 nm, enabling ratiometric fluorescence analysis (F₆₁₀/F₄₄₅). Concurrently, colorimetric detection is also ratiometric, based on measuring the ratio between the emerging yellow color peak (435 nm) and the decreasing blue color peak (618 nm) (A₄₃₅/A₆₁₈). The state-of …