Fluorescent ZnO quantum dots synthesized with urea for the selective detection of Cr6+ ion in water with a wide range of concentrations

Exploring Functional Polymers in the Synthesis of Luminescent ZnO Quantum Dots for the Detection of Cr6+, Fe2+, and Cu2

The main aim of this work is to demonstrate that well-defined methacrylate-based copolymers with oligoethylene glycol side chains and functional groups such as thiol and glycidyl, obtained by photo-initiated reversible addition-fragmentation chain transfer (RAFT) in ethanol, are highly suitable as templates in the synthesis and protection of ZnO quantum dots (ZnO QDs) with remarkable photoluminescent properties. While the affinity of thiol groups to metallic surfaces is well established, their interaction with metal oxides has received less scrutiny. Furthermore, under basic conditions, glycidyl groups could react with hydroxyl groups on the surface of ZnO, representing another strategy for hybrid synthesis. The size and crystalline morphology of the resulting hybrids were assessed using DLS, TEM, and XRD, indicating that both polymers, even with a low proportion of functional groups (5% mol) are appropriate as templates and ligands for ZnO QDs synthesis. Notably, thiol-containing polymers yield hybrids with ZnO featuring excellent quantum yield (up to 52%), while polymers with glycidyl groups require combination with the organosilane aminopropyl triethoxysilane (APTES) to achieve optimal results. In both cases, these hybrids exhibited robust stability in both ethanol and aqueous environments. Beyond fundamental research, due to the remarkable photoluminescent properties and affordability, these hybrid ZnO QDs are expected to have potential applications in biotechnology and green science; in particular, in this study, we examined their use in the detection of environmental contaminants like Fe2+, Cr6+, and Cu2+. Specifically, the limit of detection achieved at 1.13 µM for the highly toxic Cr6+ underscores the significant sensing capabilities of the hybrids.

Facile Synthesis of ZnO Nanoparticles for the Photodegradation of Rhodamine-B

River pollution is a problem that is still very poorly handled. Industrial growth is the most significant contributor to produce this wastewater. The industry produces liquid waste such as dyes that do not meet handling standards because of the high cost. Photocatalyst is way better than other methods such as adsorption, coagulation, fluctuation, and others. However, there are still many shortcomings of the existing methods, such as high cost, high temperature, and dangerous by-products. This research seeks to provide a solution by synthesizing zinc oxide (ZnO) nanoparticles as a photocatalyst to reduce rhodamine B dye under visible light irradiation. ZnO nanoparticles were successfully synthesized through a simple sol-gel method in the form of a white powder by heating at a low temperature, 60°C. The XRD results show that the results have a diffraction peak that follows the standard ZnO with a hexagonal wurtzite crystal structure. According to the Scherrer equation, the crystal has a size of 22.61 nm. SEM analysis showed that the particle morphology and particle size were homogeneous with a spherical shape, ranging from 22-24 nm. Optimal ZnO photocatalytic activity at 90 minutes with an efficiency of 98.83%.

Journey of ZnO quantum dots from undoped to rare-earth and transition metal-doped and their applications

Currently, developments in the field of quantum dots (QDs) have attracted researchers worldwide. A large variety of QDs have been discovered in the few years, which have excellent optoelectronic, antibacterial, magnetic, and other properties. However, ZnO is the single known material that can exist in the quantum state and can hold all the above properties. There is a lot of work going on in this field and we will be shorthanded if we do not accommodate this treasure at one place. This manuscript will prove to be a milestone in this noble cause. Having a tremendous potential, there is a developing enthusiasm toward the application of ZnO QDs in diverse areas. Sol-gel method being the simplest is the widely-favored synthetic method. Synthesis via this method is largely affected by a number of factors such as the reaction temperature, duration of the reaction, type of solvent, pH of the solution, and the precipitating agent. Doping enhances the optical, magnetic, anti-bacterial, anti-microbial, and other properties of ZnO QDs. However, doping elements reside mostly on the surface of the QDs. The presence of doping elements inside the core is still a major challenge for doping techniques. In this review article, we have focused on pure, rare-earth, and transition metal-doped ZnO QD properties, and the various synthetic processes and applications. Quantum confinement effect is present in nearly every aspect of the QDs. The effect of quantum confinement has also been summarized in this manuscript. Furthermore, the doping of rare earth elements and transition metal, synthetic methods for different organic molecule-capped ZnO QDs, mechanisms for reactive oxygen species (ROS) generation, drug delivery system for cancer treatment, and many more application are discussed in this paper.

Fluorescence turn off-on probe (β-cyclodextrin-hydroxyquinoline) for monitoring of Cd2+ ions and tetracycline

In this paper, a photoluminescent turn off-on switch probe β-cyclodextrin-hydroxyquinoline (β-CD-HQ) was efficiently applied for detection and measurement of Cd²⁺ ions and detection of tetracycline. The proposed assay has shown an excellent selective fluorescence response toward Cd²⁺ ions over other ions like Al³⁺, Pb²⁺, Zn²⁺, Co²⁺, K⁺, Na⁺ and Sr²⁺. The fluorescence emission intensity of the probe is slightly affected by competing ions. In optimum pH value, 4, the limit of detection and linear concentration range were 0.05 nM and 0.1-1.5 nM, respectively. Additionally, the extraordinary output signal of β-CD-HQ was utilized to investigate the logic behavior of β-CD-HQ in the aqueous media. Accordingly, a solid support logic circuit was made by producing the fluorescence output signal under the stimulation of Cd²⁺ ions and tetracycline as inputs.