Elsevier

Talanta

Volume 201, 15 August 2019, Pages 1-8
Talanta

Facile green and one-pot synthesis of purple perilla derived carbon quantum dot as a fluorescent sensor for silver ion

https://doi.org/10.1016/j.talanta.2019.03.095Get rights and content

Highlights

  • CQDs were synthesized via one-step hydrothermal treatment of purple perilla.

  • Selective and sensitive detection of Ag+ were achieved based on as-prepared CQDs.

  • The obtained CQDs have low cytotoxicity and good biocompatibility.

  • Fluorescence quenching of CQDs by Ag+ was revealed following a static mechanism.

Abstract

In this work, biomass-derived carbon quantum dots (CQDs) with excellent water solubility, strong fluorescence and favorable biocompatibility were synthesized via one-step hydrothermal treatment of purple perilla for the first time. The functional group composition, morphology, and pH stability of the synthesized CQDs were systematically investigated. And based on fluorescence quenching of CQDs, the as-prepared CQDs were innovatively developed as an effective “signal-off” fluorescent probe for selective and sensitive detection of silver ion (Ag+) with two linear ranges of 0–10 and 10–3000 nM, and a detection limit 1.4 nM. The specificity and selectivity of this fluorescent probe were also verified through challenging the detection by using similarmetallic cations or in real water samples. In addition, the as-prepared CQDs exhibit a low cytotoxicity and a good biocompatibility, revealing its potential bioimaging applications in living cells.

Introduction

Resulting from its advantages including high quantum yield, well water solubility, excellent chemical stability, good biocompatibility and ease of modification, carbon quantum dots (CQDs) have recently emerged as a new nanocarbon materials used for bioimaging, biosensing, drug delivery, efficient visible light-active photocatalysts and so forth [[1], [2], [3], [4], [5], [6], [7]]. Generally, the synthetic method to produce CQDs can be divided into two broad categories, namely bottom-up and top-down. And production of CQDs can be realized through synthetic approaches such as arc-discharge, laser ablation, electrochemical, hydrothermal, ultrasonic and microwave treatment [[8], [9], [10], [11], [12]]. However, the majority of above approaches have some limitations, such as limited spectral efficiency, low product yield, lack of size control, and the use of toxic chemicals or high temperature for experiments. Hydrothermal carbonization has arisen as a powerful and sustainable technology for the synthesis of CQDs in aqueous media since it is green, facile, convenient and efficient. After first biomass-derived CQDs obtained by hydrothermal treatment of grass in 2012 [13], more attentions have been paid to producing CQDs from natural plants, such as cabbage, sweet red pepper, aloe and various vegetables [14]. Especially, biomass-derived CQDs can be easily fabricated by using the variety of natural carbon sources. It also can effectively avoid the use of costly/toxic chemicals and complicated post-treatment processes. In addition, these CQDs derived from biomass have numerbers of advantages including cheap raw materials, easy contronl, massproduction and high yield. Moreover, bioprotein [[14], [15], [16]] and wastes (such as waste pololefins [17], fish scales [18] and even human urine [19]) also can be used as carbon sources for preparing CQDs. In summary, there are multiple inherent advantages in reusing the waste materials and natural bioresources, such as abundance of carbon sources from low-value precursor materials, varieties of heteroatom doping (such as N, S, P), saving of chemical precursors, addressing of environmental issues caused by waste disposal etc [17,20].

Perilla frutescens (L.) Britt. referred to as purple perilla (also called Zisu in China), belonging to the family Labiatae, is distributed worldwide, especially in China, Japan, Korea, and other regions in Asia [21]. In China, the plant of purple perilla is not only used as a traditionally medicinal herb for various diseases, but also as a common flavor for fish and crab cooking with the purposes of detoxification. Till now, various compounds including flavonoids, volatile oils, fatty acids, triterpenes, phenolic compounds have been isolated and identified from this plant, which can serve as an excellent source of carbon and nitrogen to produce CQDs. And compared with organic molecules as precursor to synthesize CQDs, the natural source of carbon and nitrogen from purple perilla possess great characteristics including convenient sources, low price, good water solubility, innocuity and no pollution to environment.

Silver ion (Ag+) is one of several essential trace element species in the human body, and toxicity acts as a stimulant for the production of red blood cells. Nevertheless, high level of Ag+ in organisms might cause serious consequences. And the potential toxicity is continuously escalated as the Ag+ being accumulated by aquatic organisms to poison aquatic animals, plants, and even human body in previously reports [22]. Due to its extreme toxicity, the maximum permissive level of Ag+ in drinking water is set at 0.05 ppm by the World Health Organization [23]. Consequently, monitoring the levels of Ag+ in the environment is deemed important for environmental protection and health reasons. Till now, methods such as atomic absorption spectroscopy [24], electrochemistry [25], fluorescence, and inductively coupled plasma mass spectroscopy have been used to detect metal ions. In which, the fluorescence analysis method is currently considered to be a highly effective way for Ag+ detection. Therefore, it is of great significance to design and prepare a highly sensitive and selective fluorescent probe for Ag+ detection. Compared with other fluorescent materials (conventional dyes, polymers, and semiconductor quantum dots), CQDs could offer the advantageous features of bright fluorescence, high photostability, low toxicity, and resistance to metabolic degradation in bio-applications [26]. In the present study, purple perilla was selected as the source for the facile one-pot synthesis of biomass-derived CQDs for the first time. And, as shown in Scheme 1, the resulting blue fluorescent CQDs was then served as the probe fordetection of silver ion because the luminescence can be effectively quenched by the target (Ag+). The specificity and selectivity of the CQDs probe were also evaluated via challenging the detection by using other metal cations or in complicated lake water. Besides, the related mechanisms of the CQDs formation and the Ag+-induced fluorescence quenching were also illustrated.

Section snippets

Materials and reagents

Dried purple perilla was bought from local Herbalists (Changsha, China). Quinine sulfate was purchased from Aladdin (Shanghai, China). Na2SO4, Na2SO3, CoSO4, AgNO3, Cu(NO3)2, Pb(NO3)2, LiCl, Zn(NO3)2, Cd(NO3)2, NiSO4, MgSO4, CaCl2, SrCl2, HgCl2, FeCl3.6H2O, FeSO4, MnCl2, CrCl3, AlCl3, KCl, NaCl, Na2S, NaNO3 and Na2CO3 were supplied by Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). All reagents were analytical reagent grade. All aqueous solutions were diluted by ultrapure water with a

Characterization of CQDs

To study the morphology, structure, elements, and surface groups of the prepared CQDs, a series of characterizations including high resolution TEM, XPS, UV–vis, and FT-IR were performed. As the TEM image shown in Fig. 1(a), well monodispersed CQDs have a uniformly spherical shape with the size smaller than 5 nm, and display a narrow size distribution with an average diameter of 2.8 nm (Fig. 1(b)). Besides, the high resolution TEM (HRTEM) image (inserted in Fig. 1(a)) exhibits a clear fringe

Conclusions

In this work, CQDs with fine optical stabilities are synthesized deriving from purple perilla through a facile one-step hydrothermal treatment for the first time. The obtained CQDs are thoroughly characterized to confirm the surface functional groups of CQDs. And based on the biomass-derived CQDs, a fluorescent sensor for sensitive and selective detection of Ag+ is favorably developed as the fluorescence intensity of CQDs can be effectively quenched by Ag+. Compared with other fluorescence

Conflict of interest

The authors have declared no conflict of interest.

Acknowledgments

We gratefully acknowledge the financial support from National Natural Science Foundation of China(No. 21576296 and No. 21878339) and Key Laboratory of Hunan Province for Water Environment and Agriculture Product Safety (No. 2018TP1003).

References (50)

  • D.K. Dang et al.

    One pot solid-state synthesis of highly fluorescent N and S co-doped carbon dots and its use as fluorescent probe for Ag + detection in aqueous solution

    Sensor. Actuator. B Chem.

    (2018)
  • Y. Wang et al.

    Carbon dots with concentration-tunable multicolored photoluminescence for simultaneous detection of Fe 3+ and Cu 2+ ions

    Sensor. Actuator. B Chem.

    (2017)
  • L. Wang et al.

    Rapid and visual detection of aflatoxin B1 in foodstuffs using aptamer/G-quadruplex DNAzyme probe with low background noise

    Food Chem.

    (2019)
  • X. Jin et al.

    pH-sensitive carbon dots for the visualization of regulation of intracellular pH inside living pathogenic fungal cells

    Carbon

    (2015)
  • L. Li et al.

    Nitrogen and sulfur co-doped carbon dots for highly selective and sensitive detection of Hg (II) ions

    Biosens. Bioelectron.

    (2015)
  • L. Matyus et al.

    Steady-state fluorescence quenching applications for studying protein structure and dynamics

    J. Photochem. Photobiol. B Biol.

    (2006)
  • S. Huang et al.

    A carbon dots based fluorescent probe for selective and sensitive detection of hemoglobin

    Sensor. Actuator. B Chem.

    (2015)
  • S. Bian et al.

    Facile synthesis of sulfur-doped graphene quantum dots as fluorescent sensing probes for Ag + ions detection

    Sensor. Actuator. B Chem.

    (2017)
  • Y. Yan et al.

    Sensitive detection of sulfide based on the self-assembly of fluorescent silver nanoclusters on the surface of silica nanospheres

    Talanta

    (2017)
  • Y. Jiang et al.

    Two fluorescence turn-on chemosensors based on pyrrolo[2,1-a]isoquinoline for detection of Ag+ in aqueous solution

    Tetrahedron

    (2015)
  • N. Wang et al.

    Deep eutectic solvent-assisted preparation of nitrogen/chloride-doped carbon dots for intracellular biological sensing and live cell imaging

    ACS Appl. Mater. Interfaces

    (2018)
  • S. Zhu et al.

    Highly photoluminescent carbon dots for multicolor patterning, sensors, and bioimaging

    Angew. Chem.

    (2013)
  • X. Gao et al.

    Carbon quantum dot-based nanoprobes for metal ion detection

    J. Mater. Chem. C

    (2016)
  • Y.-P. Sun et al.

    Quantum-sized carbon dots for bright and colorful photoluminescence

    J. Am. Chem. Soc.

    (2006)
  • S.-L. Hu et al.

    One-step synthesis of fluorescent carbon nanoparticles by laser irradiation

    J. Mater. Chem.

    (2009)
  • Cited by (85)

    View all citing articles on Scopus
    View full text