Elsevier

Materials Letters

Volume 66, Issue 1, 1 January 2012, Pages 222-224
Materials Letters

Facile synthesis of fluorescent carbon dots using watermelon peel as a carbon source

https://doi.org/10.1016/j.matlet.2011.08.081Get rights and content

Abstract

The synthesis of water-soluble fluorescent carbon dots (C-dots) has received much attention recently. Here, high quality fluorescent C-dots have been synthesized through low-temperature carbonization and simple filtration using watermelon peel, a waste and reproducible raw resource, as a novel carbon resource. This facile approach allows large-scale production of aqueous C-dots dispersions without any post-treatment process. The as-prepared C-dots possess small particle sizes (~ 2.0 nm), strong blue luminescence, acceptable fluorescence lifetime and good stability in a wide range of pH values (pH 2.0–11.0) and at a high salt concentration. Besides, the obtained C-dots have been successfully applied in live cell imaging, indicating these carbon nanoparticles can serve as high-performance optical imaging probes.

Highlights

► Fluorescence C-dots were prepared using watermelon peel as a novel carbon source. ► The proposed method is simple, economical and environmental friendly. ► The as-prepared C-dots have many excellent properties without any post-treatments. ► The process is of great potential for large-scale synthesis of water-soluble C-dots.

Introduction

Fluorescent carbon dots (C-dots) are a class of recently discovered fluorescence nanomaterials [1]. Due to their small particle size (< 10 nm), excitation wavelength dependent photoluminescence (PL) behavior and excellent biocompatibility, C-dots are attracting considerable attention as benign substitutes of quantum dots (QDs) for applications in bioimaging, biosensing and disease detection [2]. At present, a variety of methods have been developed to prepare fluorescent C-dots, including arc-discharge [3], laser ablation [4], [5], electrochemical oxidation [6], [7], combustion/thermal [8], [9], supported synthesis [10] and microwave heating [11]. However, these approaches usually involve complex or post-treatment processes, or require expensive raw materials and severe synthetic conditions, which are unlikely to be extended significantly in the near future. Particularly, a lack of an efficient approach to producing processable fluorescent C-dots in large quantities has been a major obstacle to exploiting most proposed applications.

Here, we report that high-quality fluorescent C-dots can be readily obtained from watermelon peel, a waste and reproducible raw resource, through low-temperature carbonization and filtration. The ease of synthesis and the exceptional solution-phase processability of C-dots make this inexpensive and fluorescent nanostructure attractive not only for future nanobiosensors but also for large-scale applications in high-performance imaging. The obtained C-dots exhibit good water-solubility, small particle size (~ 2.0 nm), high luminescent efficiency and have been successfully applied in live cell imaging.

Section snippets

Synthesis of fluorescent C-dots

The synthetic process of fluorescent C-dots mainly involves two steps (Scheme 1): (i) low-temperature carbonization of watermelon peel; and (ii) separation of the product by filtration. Typically, the fresh watermelon peel was firstly carbonized at 220 °C for 2 h under air atmosphere. The obtained product was dispersed in ultrapure water and sonicated for 30 min, and then filtrated with 0.2 μm filter membrane. The filtrate was centrifuged (18,000 ×g, 20 min), and the resultant supernate containing

Results and discussion

The C-dots were readily obtained from watermelon peel through low-temperature pyrolysis and filtration. The luminescent properties of C-dots were investigated. Fig. 1a shows the typical absorption and PL spectra of the C-dots. No obvious absorption peak but a wide absorption band is observed in absorption spectrum, which is possibly due to the relatively broad size distribution of C-dots [5], [6]. The emission band maximum shifts to longer wavelengths (from 490 to 580 nm) with the increase of

Conclusion

In summary, this method offers several advantages over current synthetic techniques. Firstly, the process is facile without any complex or post-treatment procedures. Secondly, the starting material is green, economical and eco-friendly. Thirdly, the as-prepared C-dots possess good water-solubility, strong blue luminescence and acceptable fluorescence lifetime, and can serve as high-performance optical imaging probes. Particularly, this synthetic method is of great potential for large-scale

Acknowledgments

The authors gratefully acknowledge the support for this research by National Natural Science Foundation of China (20975042), the Program for Academic Pacesetter of Wuhan (200851430484), International Science and Technology Cooperation and Exchange Foundation (2008DFA40270), the Fundamental Research Funds for the Central Universities of China (2010 PY 009, 2009JC005) and Genetically Modified Major Projects (2009ZX08012-015B).

References (13)

  • D. Jagadeesan et al.

    Chem Asian J

    (2010)
  • S.N. Baker et al.

    Angew Chem Int Ed Engl

    (2010)
  • X.Y. Xu et al.

    J Am Chem Soc

    (2004)
  • L. Cao et al.

    J Am Chem Soc

    (2007)
  • Y.P. Sun et al.

    J Am Chem Soc

    (2006)
  • J.G. Zhou et al.

    J Am Chem Soc

    (2007)
There are more references available in the full text version of this article.

Cited by (476)

  • A review of carbon dots in synthesis strategy

    2024, Coordination Chemistry Reviews
View all citing articles on Scopus
1

Equal contribution by the first two authors.

View full text