Enhanced detection of 4-nitrophenol in drinking water: ECL sensor utilizing velvet-like graphitic carbon nitride and molecular imprinting

In this work, a molecularly imprinted electrochemiluminescence (ECL) sensor was developed for selective detection of 4-nitrophenol (4-NP) in drinking water for the first time. By synthesizing velvet-like graphitic carbon nitride (V-g-C3N4) via one-step thermal polycondensation and integrating it with a molecularly imprinted polymer (MIP), the ECL sensor was fabricated. The MIP-modified V-g-C3N4 composites (MIP/V-g-C3N4) were synthesized using a sol-gel method with 4-NP as the template molecule. Under optimal conditions, the ECL sensor exhibited a wide detection range (5 × 10-10-1 × 10-5 mol/L) and a low detection limit (1.8 × 10-10 mol/L). In testing with actual drinking water samples, it displayed high accuracy (recoveries for intraday and inter-day: 93.50-106.2% and 97.00-107.3%, separately) and precision (RSDs for intraday and inter-day: 1.54-4.59% and 1.53-4.28%, respectively). The developed MIP-based ECL sensor demonstrated excellent selectivity, stability, and reproducibility, offering a promising and reliable approach for highly sensitive and selective determination of 4-NP in drinking water.

Development of isoniazid electrochemical sensor using nickel ferrite - nitrogen and sulfur co-doped graphene quantum dot nanocomposite as a new electrode modifier

This work reports the synthesis of nickel ferrite decorated nitrogen and sulfur co-doped graphene quantum dot (NF@N, S:GQD) and its use as an electrode modifier. The developed NF@N, S:GQD modified glassy carbon electrode (NF@N, S:GQD/GCE) was applied to assess isoniazid (INZ) concentration based on its oxidation at the surface of the proposed electrode. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as appropriate electrochemical techniques to study the electrochemical behavior of INZ and determine it. Based on combined evidence from surveys, research, and personal results, it is thought that the combination of nickel ferrite and doped graphene quantum dots can synergistically affect results, leading to increased sensitivity and reduced detection limits. This is probably mainly due to the high electrical conductivity of N, S-GQD structure, the electrocatalytic effect of nickel ferrite, and increased surface area resulting from the nano size of the modifier. The optimum conditions for preparing of the modified electrode and determination of INZ are selected by performing electrochemical experiments. The voltammetric response of the sensor is linear from 0.3 to 40 nM INZ under optimal conditions and the detection limit of the sensor is 0.1 nM. The validity and performance of the prepared sensor were confirmed by determining the amount of INZ in the drug and urine as real samples. The composite of doped nanoparticles and nickel ferrite is an innovative modification material to create electrochemical sensors with high sensitivity and selectivity that can be used in pharmaceutical applications.

Methylene blue-assisted molecularly-imprinted film modified nitrogen and sulfur co-doped molybdenum carbide for simultaneous electrochemical determination of two hepatotoxic drugs

A novel electrochemical sensor with a dual-template molecular imprinting technology was fabricated for the simultaneous detection of paracetamol (PAR) and isoniazid (INZ). The sensor was constructed using nitrogen and sulfur co-doped molybdenum carbide (N, S@Mo2C) and a thin layer of electro-polymerized methylene blue was applied onto the surface of the N, S@Mo2C. The electrochemical sensor demonstrated remarkable analytical efficiency for the concurrent PAR and INZ quantification under optimal circumstances. The system achieved an exceptionally low limit of detection (S/N = 3) of  3.7 nM for PAR, with a concentration range  of  0.013 and 140 µM.  A LOD of 7.6 nM was attained for INZ, with a linear range  between 0.025 and 140 µM. Furthermore, the platform's selectivity was evaluated using differential pulse voltammetry  (DPV). The designed platform successfully detected PAR and INZ in authentic samples with recoveries varying between 98.3% and 104.9%. The relative standard deviations (RSD) for these measurements ranged from 2.7 to 4.0%, demonstrating that the proposed sensor is extremely stable, repeatable, and reproducible. These promising results suggest that the sensor holds potential for the detection of various (bio) molecules, paving the way for future applications in sensing fields.

Nitrogen-doped Carbon@TiO2 double-shelled hollow spheres as electrochemical sensor for simultaneous determination of dopamine and paracetamol in human serum and saliva

As the most commonly used antipyretic and analgesic drug, paracetamol (PA) coexists with neurotransmitter dopamine (DA) in real biological samples. Their simultaneous determination is extremely important for human health, but they also interfere with each other. In order to improve the conductivity, adsorption affinity, sensitivity, and selectivity of TiO₂-based electrochemical sensor, N-doped carbon@TiO₂ double-shelled hollow sphere (H–C/N@TiO₂) is designed and synthesized by simple alcoholic and hydrothermal method, using polystyrene sphere (PS) as a template. Meanwhile, TiO₂ hollow spheres (H–TiO₂) or N-doped carbon hollow spheres (H–C/N) are also prepared by the same method. H–C/N@TiO₂ has good conductivity, charge separation, and the highly enhanced and stable current responses for the detection of PA and DA. The detection limit and linear range are 50.0 nmol/L and 0.3–50 μmol/L for PA, 40.0 nmol/L and 0.3–50 μmol/L for DA, respectively, which are better than those of carbon-based sensors. Moreover, this electrochemical sensor, with high selectivity, strong anti-interference, high reliability, and long time durability, can be used for the simultaneous detection of PA and DA in human blood serum and saliva. The high electrochemical performance of H–C/N@TiO₂ is attributed to the multi-functional combination of different layers, because of good conductivity, absorption and electrons transfer ability from in-situ N-doped carbon and electrocatalytic activity from TiO₂.

•

Nitrogen-doped carbon@TiO₂ double-shelled hollow spheres are constructed.

•

Double-shelled hollow spheres bring more heterojunctions interface and multi-active sites.

•

Paracetamol and dopamine are simultaneously determined by electrochemical sensor.

•

Synergistic effect of N-doped carbon, TiO₂ and double-shelled structure are observed.

A Redox-induced Dual-mode Colorimetric and Fluorometric Method based on N-CDs and MnO2 for Determination of Isoniazid in Tablets and Plasma Samples

We develop a simple hydrothermal method to prepare a novel nitrogen-doped carbon dots (N-CDs) originated from green carbon source Liu-bao tea and ethylene diamine. The N-CDs emits strong and stable blue fluorescence (E_m = 440 nm) under the excitation wavelength of 350 nm with a quantum yield of 35%. And it is used as an excellent fluorescent output for the sensitive and visual dual-mode determination of isoniazid. The fluorescence of N-CDs is "turned off" first by manganese dioxide (MnO₂) nanosheets due to inner filter effect, MnO₂ nanosheets can also oxidize TMB (3,3',5,5'- tetramethylbenzidine) to blue oxTMB. Isoniazid, however, can reduce MnO₂ nanosheets to Mn²⁺, turning on the fluorescence again. The color of the solution fades from blue to colorless because less TMB can be oxidized. Under the optimal conditions, the dual-mode method has a satisfying linear relationship ranging from 2.0 to 120.0 μM with a limit of detection of 0.7 μM (S/N = 3). And it has been applied successfully to colorimetric and fluorescent determination of isoniazid in tablets and clinical plasma samples, with recoveries ranging from 94.0% to 102.4%. The properties of N-CDs and MnO₂ nanosheets were thoroughly characterized using TEM, FT-IR, XPS, AFM and fluorescence spectrophotometer, the quenching mechanism was also discussed.

A molecularly imprinted electrochemiluminescence nanoprobe based on complexes consisting of CdTe and multiwall carbon nanotube for sensitive determination of clenbuterol

An electrochemiluminescence (ECL) nanoprobe was fabricated for the determination of clenbuterol (CLB). A molecularly imprinted polymer (MIP) film was coated on the surface of the glassy carbon electrode modified with CdTe-doped multiwall carbon nanotubes. The MIP film with CLB as the template molecule improves the selectivity of the nanoprobe, CdTe is used as ECL signal amplifier, and MWCNT works as the carrier. The ECL intensity is altered by elution and reabsorption of CLB. The possible reaction mechanism and experimental parameters of the nanoprobe are discussed. Under optimized conditions, the quenched ECL intensity and the CLB concentration have a linear relationship in the range 2.3 × 10^-9 to 1.5 × 10^-5 mol·L^-1, and the detection limit is 1.0 × 10^-9 mol·L^-1 (S/N = 3). The nanoprobe was successfully applied to the determination of CLB in pork samples. Graphical abstract Schematic representation of the molecularly imprinted electrochemiluminescence nanoprobe based on complexes consisting of CdTe and multiwall carbon nanotube used to determinate clenbuterol.

Highly sensitive bioaffinity electrochemiluminescence sensors: Recent advances and future directions

Electrogenerated chemiluminescence (also called electrochemiluminescence and abbreviated ECL) has attracted much attention in various fields of analysis due to the potential remarkably high sensitivity, extremely wide dynamic range and excellent controllability. Electrochemiluminescence biosensor, by taking the advantage of the selectivity of the biological recognition elements and the high sensitivity of ECL technique was applied as a powerful analytical device for ultrasensitive detection of biomolecule. In this review, we summarize the latest sensing applications of ECL bioanalysis in the field of bio affinity ECL sensors including aptasensors, immunoassays and DNA analysis, cytosensor, molecularly imprinted sensors, ECL resonance energy transfer and ratiometric biosensors and give future perspectives for new developments in ECL analytical technology. Furthermore, the results herein discussed would demonstrate that the use of nanomaterials with unique chemical and physical properties in the ECL biosensing systems is one of the most interesting research lines for the development of ultrasensitive electrochemiluminescence biosensors. In addition, ECL based sensing assays for clinical samples analysis and medical diagnostics and developing of immunosensors, aptasensors and cytosensor for this purpose is also highlighted.

Highly-sensitive and selective determination of bisphenol A in milk samples based on self-assembled graphene nanoplatelets-multiwalled carbon nanotube-chitosan nanostructure

Graphene nanoplatelets (GNPs), multiwalled carbon nanotube (MWCNTs) and chitosan (CS) were self-assembled by a facile one-step hydrothermal reaction to obtain novel MWCNTs-CS enfolded GNPs (GNPs-MWCNTs-CS) composite. Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), UV-visible (UV-vis) absorption spectroscopy and zeta potential analysis were employed to characterize the morphology, surface composition, interaction, surface charge and stability of the GNPs-MWCNTs-CS composite. The electrochemical behaviors of GNPs-MWCNTs-CS composite modified glassy carbon electrode (GNPs-MWCNTs-CS/GCE) were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The GNPs-MWCNTs-CS/GCE was used for fast and high sensitive determination of bisphenol A (BPA) by differential pulse voltammetry (DPV). Under the optimum conditions, the calibration curve obtained is linear for the current versus the BPA concentration in the range 0.1-100 μM with a detection limit of 0.05 nM (signal-to-noise ratio of 3, S/N = 3). The between-sensor reproducibility was 1.29% (n = 6) for 0.04 mM BPA. The proposed GNPs-MWCNTs-CS/GCE based sensor showed high resistance to interference, good repeatability and excellent reproducibility. Trace BPA in milk samples could also be reliably determined.

Recent advances in electrogenerated chemiluminescence biosensing methods for pharmaceuticals

Electrogenerated chemiluminescence (electrochemiluminescence, ECL) generates species at electrode surfaces, which undergoes electron-transfer reactions and forms excited states to emit light. It has become a very powerful analytical technique and has been widely used in such as clinical testing, biowarfare agent detection, and pharmaceutical analysis. This review focuses on the current trends of molecular recognition-based biosensing methods for pharmaceutical analysis since 2010. It introduces a background of ECL and presents the recent ECL developments in ECL immunoassay (ECLIA), immunosensors, enzyme-based biosensors, aptamer-based biosensors, and molecularly imprinted polymers (MIP)-based sensors. At last, the future perspective for these analytical methods is briefly discussed.

A molecularly imprinted sensor with enzymatic enhancement of electrochemiluminescence of quantum dots for ultratrace clopyralid determination

A new molecularly imprinted polymer electrochemiluminescence (ECL) sensor was developed for the detection of clopyralid (CPD) based on enzyme-biocatalyzed amplification. CdTe quantum dots were immobilized on the surface of an electrode by reaction with p-aminothiophenol preadsorbed on the electrode. Then a molecularly imprinted film was formed by electrochemical polymerization of o-phenylenediamine in the presence of CPD on the CdTe-modified gold electrode. During the analytical cycle, horseradish peroxidase (HRP)-labeled CPD was replaced by CPD in the sample. The amount of HRP on the molecularly imprinted polymer electrode decreased, and then less H₂O₂ was catalytically decomposed. Subsequently, the ECL intensity of the CdTe-H₂O₂ system was enhanced. There was a good linear relationship between ECL intensity and the concentration of CPD in the range from 2.0 × 10^-11 to 2.5 × 10^-10 mol/L and in the range from 2.5 × 10^-10 to 3.5 × 10^-8 mol/L. The detection limit was 4.1 × 10^-12 mol/L. The sensor was applied to determine CPD in vegetable samples. Graphical abstract A molecularly imprinted electrochemiluminescence sensor was fabricated for ultratrace clopyralid determination. The sensitivity was significantly improved with the enhancement of the ECL intensity of quantum dot via the enzymatic reaction of HRP.

Fabrication of a SnO2–graphene nanocomposite based electrode for sensitive monitoring of an anti-tuberculosis agent in human fluids

For electrochemical oxidation of INH on a SnO₂–Gr/GC electrode the voltammetric signal was observed at various electrolyte pH values.

A molecularly imprinted sensor based on an electrochemiluminescent membrane for ultratrace doxycycline determination

A new electrochemical luminescence sensor was developed based on a molecularly imprinted membrane prepared by electropolymerization of pyrogallol doped with alizarin red. The ECL signal was produced by the oxidation of the polypyrogallol polymer, which was then reacted with alizarin red, and enhanced by doxycycline molecules due to energy transfer.

Novel magnetic multi-template molecularly imprinted polymers for specific separation and determination of three endocrine disrupting compounds simultaneously in environmental water samples

A novel type of superparamagnetic molecularly imprinted polymers introducing unique concept of multi-template for specific separation and determination of three endocrine disrupting compounds (EDCs) simultaneously.

A molecularly imprinted electrochemical enzymeless sensor based on functionalized gold nanoparticle decorated carbon nanotubes for methyl-parathion detection

Schematic of MP MIP sensor and the possible mechanism.