Ultrasensitive optical detection of anions by quantum dots

A Luminescent Cd-MOF Used as a Chemosensor for High-Efficiency Sensing of Fe3+, Cr(IV), Trinitrophenol, and Colchicine

A Cd-MOF was constructed based on 3,5-bis(4-carboxyphenyl) pyridine under solvothermal conditions. Its structure and phase purity were verified by single-crystal X-ray diffraction. Thereafter, some studies on the morphology, structure, and luminescent properties of the compound were carried out. The compound exhibited a highly sensitive response to Fe3+, Cr(IV), trinitrophenol (TNP), and colchicine based on the fluorescence-quenching mechanism. The possible mechanism of luminescence quenching was discussed in detail.

Synthesis and characterization of La QDs: sensors for anions and H2O2

The development of sensitive and accurate fluorescence sensors for the detection of anions and reactive oxygen species (ROS, H2O2) is essential as they play significant roles in biological and chemical processes.

Diamond-Based Electrodes for Detection of Metal Ions and Anions

Diamond electrodes have long been a well-known candidate in electrochemical analyte detection. Nano- and micro-level modifications on the diamond electrodes can lead to diverse analytical applications. Doping of crystalline diamond allows the fabrication of suitable electrodes towards specific analyte monitoring. In particular, boron-doped diamond (BDD) electrodes have been reported for metal ions, anions, biomolecules, drugs, beverage hazards, pesticides, organic molecules, dyes, growth stimulant, etc., with exceptional performance in discriminations. Therefore, numerous reviews on the diamond electrode-based sensory utilities towards the specified analyte quantifications were published by many researchers. However, reviews on the nanodiamond-based electrodes for metal ions and anions are still not readily available nowadays. To advance the development of diamond electrodes towards the detection of diverse metal ions and anions, it is essential to provide clear and focused information on the diamond electrode synthesis, structure, and electrical properties. This review provides indispensable information on the diamond-based electrodes towards the determination of metal ions and anions.

Discrimination of copper and silver ions based on the label-free quantum dots

A simple and fast method for copper ions (Cu²⁺) and silver ions (Ag⁺) detection was established with cadmium telluride quantum dots (CdTe QDs) as fluorescent probes. In the presence of Cu²⁺ or Ag⁺, the fluorescence intensity of TGA-CdTe QD can be significantly quenched, which fitted a linear relationship between the fluorescence quenching degree (F₀-F)/F₀ and the concentration of metal ions. In this work, the lowest detected concentration for Cu²⁺ and Ag⁺ was 35.0 nM and 25.3 nM, respectively. In addition, the differentiation of Cu²⁺ and Ag⁺ at different concentrations was realized with the principal component analysis (PCA). Furthermore, Cu²⁺ was successfully detected in body fluids. This method provides a good potential for copper ions and silver ions detection with simplicity, rapidity, and excellent selectivity.

Ratiometric fluorescent nanoprobes for visual detection: Design principles and recent advances - A review

Signal generation techniques for visual detection of analytes have received a great deal of attention in various sensing fields. These approaches are considered to be advantageous when instrumentation cannot be employed, such as for on-site assays, point-of-care tests, and he althcare diagnostics in resource-constrained areas. Amongst various visual detection approaches explored for non-invasive quantitative measurements, ratiometric fluorescence sensing has received particular attention as a potential method to overcome the limitations of intensity-based probes. This technique relies on changes in the intensity of two or more emission bands (induced by an analyte), resulting in an effective internal referencing which improves the sensitivity of the detection. The self-calibration, together with the unique optophysical properties of nanoparticles (NPs) have made the ratiometric fluorescent nanoprobes more sensitive and reliable, which in turn, can result in more precise visual detection of the analytes. Over the past few years, a vast number of ratiometric sensing probes using nanostructured fluorophores have been designed and reported for a wide variety of sensing, imaging, and biomedical applications. In this work, a review on the NP-based ratiometric fluorescent sensors has been presented to meticulously elucidate their development, advances and challenges. With a special emphasis on visual detection, the most important steps in the design of fluorescent ratiometric nanoprobes have been given and based on different classes of analytes, recent applications of fluorescent ratiometric nanoprobes have been summarized. The challenges for the future use of the technique investigated in this review have been also discussed.

One-pot synthesis of highly luminescent N-acetyl-l-cysteine-capped CdTe quantum dots and their size effect on the detection of glutathione

N-Acetyl-l-cysteine-capped CdTe QDs with a large size (3.68 nm) are more suitable for detecting glutathione than the small ones (1.99 nm).

Implementation of a logic gate by chemically induced nitrogen and oxygen rich C-dots for the selective detection of fluoride ions

The widespread pollution of fluoride ions in the environment badly affects the ecological system due to their high toxicity, mobility and the difficulty of their degradation.

Green, Water-Dispersible Photoluminescent On-Off-On Probe for Selective Detection of Fluoride Ions

Considering the high toxicity and widespread availability of fluoride ions in different environmental matrices, it is imperative to design a probe for its detection. In view of this, a selective fluorescent on-off-on probe based on carbon quantum dots (CQDs) and Eu³⁺ has been designed. We have synthesized water-soluble carboxylic acid-functionalized CQDs and monitored their interaction with Eu³⁺. Luminescence quenching in the CQD emission was observed (switch-off) on adding Eu³⁺ ions. We investigate the reason for this luminescence quenching using time-resolved emission and high-resolution transmission electron microscopy (HRTEM) studies and observed that both electron transfer from CQDs to Eu³⁺ and aggregation of CQDs are responsible for the luminescence quenching. ζ-Potential and X-ray photoelectron spectroscopy studies confirm Eu³⁺ binding with the COOH groups on CQD surface. Interestingly, luminescence regains after the addition of fluoride ions to the CQDs/Eu³⁺ system (switch-on). This has been assigned to the removal of Eu³⁺ from the CQD surface due to the formation of EuF₃ and is confirmed by X-ray diffraction and HRTEM measurements. The sensitivity of the probe was tested by carrying out experiments with other competing ions and was found to be selective for fluoride ions. Experiments with variable concentrations of fluoride ions suggest that the working range of the probe is 1-25 ppm. The probe has been successfully tested for the detection of fluoride ions in a toothpaste sample and the results were compared to those of ion chromatography. To the best of our knowledge, this is the first report based on CQDs and Eu³⁺ for the detection of fluoride ions, wherein a clear mechanism of the detection has been demonstrated, which, in turn, will help to develop better detection methods. The suggested probe is green, economical, rapid, efficient, and, most importantly, selective and can be used for the detection of fluoride ions in real environmental samples.