Technology Overview

Inventors at the University of North Texas have developed a phosphorescent chemosensor based on trinuclear Au(I) pyrazolate complex stabilized in aqueous chitosan polymer media for silver ion detection. This sensor is capable of detecting silver ions and other heavy metal ions and emits visible luminescent essence visible to the naked eye. In recent years, silver ion detection has been of strong interest to the scientific community due to silver ions’ harmful effects on the environment, on drinking water and aquatic communities, in particular.

Red-Emissive Au3Pz3 synthesis

Au₃Pz₃ ([Au(3- CH₃,5-COOH)Pz]₃), a known chemo-optical sensor, was formed through combining the pyrazole with the chitosan (CS) polymer and water. The pH of the solution was adjusted to resemble the pK for the CS. Next, a submolar quantity of Au(THT)Cl was added to the mixture resulting in a colorless yet red-emissive Au3Pz3 solution with an emission peak at ~685nm. The presence of the CS polymer in the solution not only enhances the formation of AuPz₃, but also promotes aggregation. Additionally, the phosphorescence quantum yield and lifetime of Au₃Pz₃ synthesized in the polymer media were much higher compared to Au₃Pz₃ synthesized in polymer- free media ()

Selective Sensing of Silver with Au₃Pz₃

When adding silver into Au₃Pz₃, a new blue-shifted emission peak appears at a wavelength of 515 nm . With the addition of silver ions, the red emission at ~685 nm disappears, showing there are drastic photophysical differences between Au₃Pz₃ and Au₃Pz₃/Ag+. This Au₃Pz₃/Ag+ solution gives off a greenish emission that provides an easy method of detecting the presence of silver ions. With concentrated levels of CS, there are clear effects on both the detection limit and measurement range of silver ions. The silver adduct exhibits a 4-fold increase in quantum yield (0.19 ± 0.02) compared to Au₃Pz₃ alone (0.05 ± 0.01), along with a corresponding increase in phosphorescence lifetime. Finally, using the well-known chelating agent, ethylenediaminetetraacetic acid (EDTA), the ability to reverse the sensing of silver ions was demonstrated, showing that Au₃Pz₃ is a reusable sensor ().

Sensing other Heavy Metal Ions

While silver was the only salt detectable to Au₃Pz₃ at low concentrations, other salts were detectable at higher concentrations (greater than 1 mM). Au₃Pz₃ showed sensitivity to thallium, developing a new blue emission with peak at 450nm and lead ions with a cyan emission at peak 490nm. Trivalent gadolinium was also tested, showing a new, weak, emission at 468-470nm, while also demonstrating an enhancement of the red emission, while other salts quenched the red ().

Key Features

Phosphorescent chemosensor
Silver-ion detection
High photostability and low photobleaching
Additional heavy metal ion detection

Stage of Development

Lab testing.

Benefits

The only phosphorescent detector of silver ions using a heavy metal-based chemo sensor in aqueous media
The sensing method is simple, fast, easy to use, and detectable to the naked eye
Reusable with the addition of ethylenediaminetetraacetic acid (EDTA)
Highly sensitive (sensing limit is 0.02 ppm or 20 ppb)

A Gold(I) Based Phosphorescent Complex for Selective Sensing of Silver Ions

Patents

IP Status

Seeking