Detection of silver(I) ion based on mixed surfactant-adsorbed CdS quantum dots

A fluorescent probe using phosphorus-doped graphite carbon nitride nanosheets for the detection of silver ions and cell imaging

The fluorescent phosphorus-doped graphite carbon nitride (P-g-C3N4) nanosheets have been synthesized as a fluorescence probe using an ultrasonic exfoliating method. The as-prepared P-g-C3N4 nanosheets were characterized by multiple analytical techniques such as transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and infrared spectroscopy. The fluorescence intensity of P-g-C3N4 nanosheets decreases with the increase in concentration of silver ions. A good linear relationship was achieved between the corresponding fluorescence intensity of P-g-C3N4 nanosheets and the concentration of silver ions in the range of 20 nmol/L – 3.2 μmol/L. The quenching mechanism of interaction between P-g-C3N4 nanosheets and silver ions was primarily discussed. The proposed fluorescence probe has been successfully applied to detect silver ions in real water samples and the recoveries range from 96.8% to 103.7%.

A luminous off-on probe for the determination of 2,6-pyridinedicarboxylic acid as an anthrax biomarker based on water-soluble cadmium sulfide quantum dots

A fluorescence off-on sensing platform was developed based on thioglycolic acid-stabilized cadmium sulfide quantum dots (CdS QDs) as fluorescence probe for the sensitive and selective detection of 2,6-pyridinedicarboxylic acid (DPA) in spores. The fluorescence emission intensity of the quantum dots at 650 nm when excited at 460 nm was first quenched by mixing with europium ions (Eu³⁺) and then recovered after the addition of DPA. The interaction of DPA with Eu³⁺ relieved the quenching effect of Eu³⁺ toward CdS QDs. As the DPA concentration increases, the color of the probe changes from colorless to red. The method exhibits a wide linear range from 1 to 120 μM for DPA determination, with a detection limit of 0.2 μM. The CdS QDs based nanoprobe was successfully applied for sensitive determination of DPA released from bacteria spores. In this case, the detection limit is 3.5 × 10⁴ CFU·mL^-1. Graphical abstract An off-on fluorescence sensor for detecting anthrax markers -2,6-pyridinedicarboxylic acid though restoring the fluorescence of cadmium sulfide quantum dots quenching by europium ions.

One-step hydrothermal synthesis of thioglycolic acid capped CdS quantum dots as fluorescence determination of cobalt ion

Highly luminescent CdS quantum dots capped with thioglycolic acid (TGA@CdS QDs) were synthesized from cadmium chloride and thiourea as cadmium and sulfur sources via simple hydrothermal method. The room temperature photoluminescence (RTPL) properties of TGA@CdS QDs were investigated. The results indicate that the polarity of the solvent and the surface trap state resulted in the broadness Stokes shift between the maximum absorption wavelength and the emission wavelength of TGA@CdS QDs. The Co²⁺ sensing properties of fluorescence determination were investigated using TGA@CdS QDs. The as-synthesized CdS QDs exhibits the excellent selectivity and sensitivity of fluorescence quenching for cobalt ion (Co²⁺). The limit of detection (LOD) is as low as 0.05 μM which is much lower than maximum limit of cobalt ions in drinking water. The linear response range of Co²⁺ was from 0.5 to 80 μM. The sensing system revealed the advantages of low detection limit, excellent selectivity, high sensitivity, convenience and low cost. The color change of CdS QDs shows potential applications in the detection of Co²⁺.

Detection of Ag(+) using graphite carbon nitride nanosheets based on fluorescence quenching

The graphite carbon nitride (g-C3N4) nanosheets were synthesized and applied for the detection of Ag(+) ion in aqueous solutions. Transmission electron microscopy, Fourier infrared spectroscopy, x-ray diffraction, ultraviolet/visible and photoluminescence spectroscopy were used for characterization of g-C3N4 nanosheets. The fluorescence intensity of g-C3N4 nanosheets decreases with the increase in the concentration of Ag(+). The fluorescence probe can be applied for detection of Ag(+). The results show that it has high selectivity to Ag(+) and exhibits a good linearity over the concentration range 0.020-2.0μM with a detection limit of 27nM. Most cations do not have any interference on the detection of Ag(+). The quenching process is assessed and discussed. Finally, the g-C3N4 nanosheets have been successfully used for the detection of Ag(+) in real water samples. The recoveries of spiked water samples are >97%.