Porphin-Based Carbon Dots for "Turn Off-On" Phosphate Sensing and Cell Imaging.

Jing Wu,Zonghua Wang,Wenjing Wang

doi:10.3390/nano10020326

Abstract

Porphin-based carbon dots (denoted as PCDs) are prepared through a one-step hydrothermal method by using meso-tetra (4-carboxyphenyl) porphin (TCPP), citric acid, and ethanediamine as precursor. PCDs give rise to the optimal photoluminescence at λex/λem = 375/645 nm, exhibit an excitation-independent property, excellent water solubility, and good biocompatibility, which provide red emission and avoid the autofluorescence as an efficient fluorescent imaging probe. On the other hand, when Eu3+ is added into PCDs, the carboxylate groups located on the surface of PCDs exhibit high affinity to Eu3+, resulting in the fluorescence of PCDs turning off via static quenching. In the presence of phosphate, owing to the strong coordination with Eu3+, the fluorescence of PCDs turns on. Based on this performance, a novel “turn off–on” phosphate sensing system is developed. The detection limit of this sensing system can attain 3.59 × 10−3 μmol L−1. This system has been utilized for the detection of phosphate in real samples successfully, which further demonstrates potential applications in biological diagnostic and environmental analysis.

Highlights

Carbon dots (CDs), as an emerging photoluminescent nanomaterial, have attracted widespread attention since their initial discovery in 2004 [1]
According to the photoluminescent mechanism of CDs, red-emissive CDs can be obtained through regulating particle size [17,18], shifting the excitation wavelength on the basic of excitation-dependent emission [19,20], extending the size of isolated sp2 domains [21,22,23,24], enhancing surface oxidation degree [25,26], or adopting heteroatomic doping [27,28,29,30,31]
Among these, expanding conjugated aromatic π system has been approved to be an effective way to enhance the size of isolated sp2 domains [32]

Summary

Introduction

Carbon dots (CDs), as an emerging photoluminescent nanomaterial, have attracted widespread attention since their initial discovery in 2004 [1]. Due to their superior optical properties, outstanding biocompatibility, excellent dispersibility, facile surface functionalization, simple, and low-cost synthesis process [2], CDs have been demonstrated to be a future perspective fluorescence nanomaterial in various applications including bioimaging [3,4,5,6], drug delivery [7], chemical sensing [8,9,10,11,12], photocatalysis [13], and anti-counterfeiting [14]. Various kinds of precursors with aromatic structure, such as p-phenylenediamine [25], 1,3-dihydroxynaphthalene [33], 2,5-diaminotoluene sulfate [34], polythiophene derivatives [35], trinitropyrene [36], or other IR/NIR dye molecules [37], are employed to construct red-emissive carbon dots

Methods

Results

Conclusion