Catalytic nanozyme Zn/Cl-doped carbon quantum dots as ratiometric fluorescent probe for sequential on-off-on detection of riboflavin, Cu2+ and thiamine

Abstract

A novel metal-doped Zn/Cl carbon quantum dots (Zn/Cl-CQDs) was developed successfully as ratiometric fluorescent probes for the sequential on-off-on detection of riboflavin, Cu2+ ion and thiamine. The excellent catalytic performance of the Zn/Cl-CQDs nanozyme serves as an ideal platform for sensitive detection of thiamine. Due to the addition of riboflavin to the Zn/Cl-CQDs, the blue emission peak of Zn/Cl-CQDs at 440 nm remains unaffected and used as an internal reference approach, while the green emission peak of riboflavin at 520 nm appeared and increased remarkably. Following the presence of Cu2+, a quenching blue fluorescence signal of Zn/Cl-CQDs was observed which resulted in consequent fluorescent ‘turn-off’ response toward Cu2+ ion. Finally, upon the addition of thiamine to the above solution under alkaline condition, the blue emission of Zn/Cl-CQDs was gradually recovered. The prepared Zn/Cl-CQDs could act as a nanozyme catalyst for directly catalyzing the oxidation of non-fluorescent substrate of thiamine to produce highly fluorescent substrate of thiochrome. As a result, the blue fluorescence emission peak at 440 nm was recovered. Eventually, the sequential detection properties of ratiometric probes for riboflavin, Cu2+ ion and thiamine were successfully applied in VB2 tablets, drinking water and VB1 tablet with good recoveries of 96.21%, 98.25% and 98.44%, respectively.

Modification of Carbon Dots for Metal‐Ions Detection

“…Ali Mehdinia et al. developed a ratiometric fluorescent probe based on a metal‐doped Zn/Cl carbon quantum dots (Zn/Cl‐CQDs) using zinc gluconate and hydrochloric acid via microwave‐assisted method to simultaneously detect riboflavin, Cu 2+ and thiamine [66] . Zn/Cl‐CQDs had good fluorescence stability and could be stored away from light at a refrigerator (4 °C) for at least 2 months.…”

“…[65] Ali Mehdinia et al developed a ratiometric fluorescent probe based on a metal-doped Zn/Cl carbon quantum dots (Zn/Cl-CQDs) using zinc gluconate and hydrochloric acid via microwave-assisted method to simultaneously detect riboflavin, Cu 2 + and thiamine. [66] Zn/Cl-CQDs had good fluorescence stability and could be stored away from light at a refrigerator (4 °C) for at least 2 months. When riboflavin was gradually added to the Zn/Cl-CQDs solution, a new green emission peak at 520 nm significantly increased, while the blue emission peak at 440 nm slightly changed.…”

Nanozymes: Applications in clinical biomarker detection

“…Therefore, the principle of nanozyme‐based fluorescence assay was the catalytic interaction between nanozyme and fluorophores or fluorescent nanomaterials affected by analytes, leading to the changes of fluorescence signals. Currently, fluorescent detection probes based on nanozymes are mainly classified into single fluorescent probes and ratio fluorescent probes 47 …”

Confined Unimolecular Micelles for Directed Self-Assembly of Ultrastable Multiple-Responsive Ratiometric Fluorescent Ultrasmall Nanoparticle Assemblies

“…Compared with traditional fluorescent probes, ultrasmall nanoparticle fluorescent probes have attracted more and more attention because of their advantages such as simple preparation, low cost, good selectivity, real-time detection, and nondestructive detection. − However, the detection process for most of the reported fluorescent probes was only by increasing or decreasing the fluorescence intensity which has defects in visual discrimination and cannot provide sufficient accuracy for quantitative measurements. − Ratiometric fluorescent probes have two different fluorescence emission peaks which can be self-calibrated to eliminate instrument errors and environmental fluctuations caused by differences in probe concentration via dealing with the emission intensity ratio to offer built-in correction of the harsh environmental impact. − The ratiometric fluorescent probes can also clearly display distinguished fluorescence color changes of the target chemical for fast, sensitive, and highly reliable chemical detection and information encryption. Thus, ratiometric fluorescent probes have been widely used in various fields, such as biosensing, contamination detection, information encryption, etc.…”