A new carbazole-based fluorescent chemosensor (CNS) was synthesized for the detection of Co²⁺ and Cu²⁺ in different solvent systems.

CNS can selectively detect Cu²⁺ and recognize Co²⁺ in a naked eye by UV-vis and fluorescence spectroscopy.

CNS has been successfully applied to fluorescence imaging of Cu²⁺ in HeLa cells and detection of Cu²⁺ in real water samples.

A rhodanine-based fluorescent chemosensor DHM was synthesized for detecting Zn2+. DHM showed unique fluorescence change on detecting Zn²⁺ with a low detection limit (1.33 μM). DHM could analyze Zn2+ in a real environment and be recyclable with EDTA. DHM-doped test kit was used for recognizing Zn2+. Binding feature of DHM to Zn2+ was illustrated by ESI-mass, NMR titration, and calculations.

Colorimetric sensing Fe(II) and Au(III) cations in environmental water samples by using tannic acid as a chemosensor

A new biomimetic sensor (BS) has been prepared by modifying the carbon paste electrode (CPE) based on [Fe(NTB)Cl₂]Cl (FeC) {NTB = tris(2-benzimidazolylmethyl)amine} for the electrochemical detection of acrylamide (AA). the constructed BS was successfully applied for the evaluation of AA in various potato chips and the results were comparable to those obtained from other electrochemical methods.

Magnetic reduced graphene oxide (MRGO) consists of graphene layer tethered with the spherical Fe₃O₄. The oxygen-based functional groups on the surface of MRGO could act as chemically active sites for the attachment of dopamine. The MRGO nanosheet has been proven to be an effective glassy carbon electrode modifier with a remarkable electroactive surface area of approximately 0.0104 cm², demonstrating stable and sensitive electrochemical performance toward dopamine.

Two new Ag(I) complexes were synthesized and characterized. Their Ag(I) centers displayed different coordination geometric structures: two-coordinated linear in 1, whereas four-coordinated distorted tetrahedron in 2. The electrochemical sensing performance of Ag(I) complexe-modified carbon paste electrode (CPE-1 and CPE-2) toward H₂O₂ was evaluated by chronoamperometry in 0.2 M phosphate buffer saline (pH = 6) at −0.2 V. The CPE-1 was found to have a wide linear response from 1.0 × 10⁻⁵ to 4.0 × 10⁻³ M, lower detection limit of 1.73 μM, excellent anti-interference ability, and stability. The CPE-2 does not have recognition properties for H₂O₂, which may be due to the large steric hindrance around Ag(I) centers that is not easy to combine with hydrogen peroxide to form a catalytic transition state. The results reveal that the Ag(I) complexes may be used as effective components of electrode materials.

Schematic illustration of a novel electrochemical sensing platform for the detection of DNA.

A recently new synthesized Schiff base was used as a modifier in carbon paste matrix to develop a potentiometric cation sensor. The constructed modified carbon paste sensor represents a Nernstian slope of 19.4 mV/decade to cerium(III) from 7.5×10^-9 to 1.5×10^-3 M and a low detection limit of 5.4 × 10^-9 M. The sensor was carried out as an indicator electrode in potentiometric titration and determination of cerium(III) ion in mineral and spring water samples.

Reduced graphene oxide and titanium carbide nanocomposite was prepared by the self-assembly method and used for electrode modification. Then, an electrochemical hemoglobin biosensor was prepared on the nanocomposite-modified electrode, and used for the determination of trichloroacetic acid and hydrogen peroxide.

A novel disposable and portable electrochemical aptasensor based on reduced graphene oxide was constructed for the detection of mercury (II) using exonuclease III-induced cyclic reaction as a signal amplification strategy. The use of the designed DNA strand can greatly improve detection selectivity, and the employment of a homogeneous system can effectively save cost and simplify operation steps.

1. A new commercial product which is carbon based with acetaminophen as the pH detection layer.
2. It is a promising alternative device for the potentiometric titration of neutralization experiments.
3. The pK_a, pK_b and pH values determined using the glass electrode and the strip-pH electrode systems differed by less than 5%.

An electrochemical biosensor integrating Nafion-mixed carbon dots and screen-printed carbon electrodes for pyrophosphate ion detection is presented. A linear connection is established between the square wave voltammetry current and the pyrophosphate ion concentration between 50 and 1 μM, and the limit of detection is determined to be 1.01 μM. This assay is suitable for the usage of complicated urine matrices without the inclusion of heavy metals, making it practical for clinical monitoring.

Novel dual-mode color-changing sensor (MOF/PC hydrogel) was achieved by taking advantages of the stimuli-responsive color-changing ability of photonic crystals and the sensing performance of luminescent MOF. When immersed in pH solutions, the structure color of MOF/PC hydrogel changed quickly, and its fluorescence intensity showed good linear relationship with pH, both ensuring the visual and quantitative pH sensing.

A label-free fluorescent sensor was developed for the detection of kojic acid based on the fluorescence internal filtering effect between gold nanocluster and kojic acid. In the presence of kojic acid, the fluorescence intensity decreased significantly owing to the strong absorption of kojic acid on excitation spectrum of gold nanoclusters. The whole detecting procedure could be accomplished within 5 min.

Schematic diagram of the synthesis and sensing applications of fluorescent C dots and MNCs and their future perspectives.

Blue-emitting copper nanoclusters, synthesized for the NaBH4 and ascorbic acid-mediated reduction of copper ions in the presence of pepsin, have been demonstrated to serve as a luminescence turn-off sensor for detecting urinary hemoglobin within 1 min via the inner filter effect

A new surface-enhanced Raman scattering (SERS) biosensor was developed based on green synthesized Au-seed mediated gold nanostars. Subsequently, gold nanostars were modified with vancomycin as recognition phase and immobilized with 4-Mercaptobenzoic acid as Raman reporter as well as linker for vancomycin conjugation. Finally, bacteria were determined by utilizing the bacteria's high affinity with vancomycin and measuring the signal intensity elevation of SERS tags.

• A rapid, sensitive, convenient and accurate assay method for the determination of clinically important biomarker uric acid (UA) in human serum samples has been developed.
• The analytical sensing signal is based on the oxidative addition of 3-HT producing orange colored product.
• Density functional theory supported mechanistic approach for the colored product formation.
• The method has been validated thoroughly by various analytical steps.

In this study, a novel potentiometric sensor was developed for the determination of Cu²⁺ ions. The developed sensor exhibits a linear response over a wide concentration range and has a very low detection limit. In addition, the copper(II)–selective sensor has advantages such as high selectivity, short response time, low cost, good repeatability, and stability.

A novel silver/Graphene–polypyrrole (Ag/G–PPy)-modified electrode for levosimendan detection. The Ag/G–PPy-modified electrode showed current signals toward levosimendan concentrations ranging from 0.21 to 6.88 μM and exhibited a low detection limit of 0.12 μM. Accordingly, the proposed electrode can serve as a simple and inexpensive electrochemical sensor for levosimendan detection.