Anthracene modified graphene oxide-silica as an optical sensor for selective detection of Cu2+ and I− ions

A New Sensitive Fluorescence Sensor and Photocatalyst for Determination and Degradation of Sodium Valproate Using g-C3N4@Fe3O4@CuWO4 Nanocomposite and FCCD Optimization

In this research, carbon nitride nanocomposite coupled with Fe3O4 and CuWO4 was thermally synthesized and characterized by different techniques, including SEM, TEM, XRD, EDX, and FTIR. Due to sodium valproate's luminescence quenching of this nanocomposite, a reliable, accurate, sensitive, selective, and fast-acting sodium valproate assay was proposed. Optimization of this fluorescent sensor was carried out by the FCCD approach. In the optimum conditions, the plot of sodium valproate concentration versus nanocomposite fluorescence emission showed a linear response (R2 = 0.9918), with a range of 0-0.55 µM, the limit of detection (S/N = 3) equal to 0.85 nM and limit of qualification equal to 2.82 nM. Photocatalytic activity of g-C3N4@Fe3O4@CuWO4 (40%) nanocomposite exhibited a good potency to sodium valproate degradation. Active species of degradation including superoxide radicals, holes, and hydroxyl radicals were investigated using ammonium oxalate, benzoquinone, and 2-propanol to identify the mechanism of photodegradation action. The activity of benzoquinone in the photocatalytic process led to a reduction in the rate of analyte degradation, which indicates the prominent role of superoxide radicals compared to other species in the degradation process. The degradation rate of the analyte using the Fenton reagent was found to be around two times more than in the Fenton reagent-free process. The possible mechanism for the fluorescence sensor and photocatalytic degradation reaction was also discussed.

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.

Electrochemical Deposition of Copper on Epitaxial Graphene

Understanding the mechanism of metal electrodeposition on graphene as the simplest building block of all graphitic materials is important for electrocatalysis and the creation of metal contacts in electronics. The present work investigates copper electrodeposition onto epitaxial graphene on 4H-SiC by experimental and computational techniques. The two subsequent single-electron transfer steps were coherently quantified by electrochemistry and density functional theory (DFT). The kinetic measurements revealed the instantaneous nucleation mechanism of copper (Cu) electrodeposition, controlled by the convergent diffusion of reactant to the limited number of nucleation sites. Cu can freely migrate across the electrode surface. These findings provide fundamental insights into the nature of copper reduction and nucleation mechanisms and can be used as a starting point for performing more sophisticated investigations and developing real applications.