Elsevier

Talanta

Volume 132, 15 January 2015, Pages 845-850
Talanta

Microwave-assisted synthesis of carbon dots and its potential as analysis of four heterocyclic aromatic amines

https://doi.org/10.1016/j.talanta.2014.10.008Get rights and content

Highlights

  • Novel synthesis of fluorescent CDs from MW assisted HCl treatment.

  • CDs has been characterized and analyzed by DLS, XPS and fluorescence techniques.

  • The quenching caused by HAAs proposed analytical method.

  • The static mechanism was demonstrated by fluorescence lifetime analysis.

  • The wide range of interferences studied make suitable for sensor.

Abstract

Fluorescent water soluble carbon nanoparticles, in short carbon dots (CDs), was synthesized from lactose by microwave assisted hydrochloric acid method. Characterized by TEM and DLS to obtain the morphology shape (average 10 nm in size), with a higher negative surface charge supported by the composition was obtained by XPS spectroscopy. The maximum of the emission was centered at 450 nm with a lifetime of 2.1 ns. Without further functionalization of the CDs a nanosensor was obtained that responded exponentially to HAAs in the 0.35–0.45 mg L−1 concentration range by fluorescence static quenching, demonstrated by the lifetime analysis of the CDs in presence of HAAs. Some amino compounds were selected as model for interferences to evaluate the selectivity of this method, showing a notorious added value, with recoveries around 98%. The accuracy of the method was in terms of RSD about 2.5%. The results suggest their promising applications in chemical sensing.

Introduction

The International Agency for Research on Cancer (IARC) regards some of the heterocyclic aromatic amines (HAAs) as possible human carcinogens such as (2-amino-3,4-dimethyl-imidazo [4,5-f]-quinoline, 2-amino-3,8-dimethyl-imidazo [4,5-f] quinoxaline and 2-amino-3,4,8-trimethylimidazo [4,5-f]-quinoxaline, 2-amino-3,7,8-trimethyl-imidazo [4,5-f]-quinoxaline (class 2B) and 2-amino-3-methylimidazo [4,5-f]-quinoline (class 2A) [1], [2], [3]. Therefore, an important issue in Analytical Chemistry as the main source is the cooked food when the proteins are converted at high temperatures due to the incomplete their combustion process.

Chromatographic methods are the most widely used when analyzed grilled, barbecued or fried meat and fish and urine samples, being HPLC–MS the main analytical technique used previous micro-extraction procedure [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. HPLC with different detection systems such as UV [14], [15], [16] and fluorescence [17], [18]; GC–MS [19], [20], [21], [22], [23] and by electrophoresis capillary (CE) [24], [25], [26], [27], [28], an extensive revision of all this techniques and compared can be found in literature [29]. Very few references to other techniques have been found in the literature for the analysis of these harmful metabolites, except for improvements in the processes of extraction prior to chromatographic analysis such as the used of supercritical fluids [27] and ionic liquids [30], making interesting the development of new alternatives as the sensitive luminescent techniques for their analysis is an important and interesting challenge in the analysis of HAAs [31].

Nanotechnology offers the best alternative, which combines the easiest design of nanoparticles with their cheap cost and luminescent properties, being the emerging system based in carbon dots (CDs) the best candidates to be applied as a detection system of any analyte to study due to its application in many other areas of analysis. These systems are the one of the lasts discover where heavily functionalized carbon networks are involved, which were firstly discovered by simple purification of carbon nanotubes and nowadays can be obtained by means a great variety of simple process [32], [33], [34], [35], [36], [37].

This work shows the photoluminescent characteristics of CDs prepared from lactose using microwave process. The advantages of this treatment include faster preparation method, good fluorescence efficiency, reproducibility and stability of the obtained nanoparticles. Furthermore, the exploitation of the sensorial ability of these CDs gives rise to an excellent tool for the quantification, and without any further functionalization, of four different HAAs, by the quenching effect on the fluorescence of CDs.

Section snippets

Chemicals

Lactose monohydrate (99%) and hydrochloric ( 37%) were purchased from Panreac S.A.U. (Barcelona, Spain), 2-amino-3,4-dimethyl-imidazo [4,5-f]-quinoline (MeIQ), 2-amino-3,8-dimethyl-imidazo [4,5-f]-quinoxaline(8-MeIQx), 2-amino-3,4,8-trimethylimidazo [4,5-f]-quinoxaline (4,8-DiMeIQx), 2-amino-3,7,8-trimethyl-imidazo [4,5-f]-quinoxaline (7,8-DiMeIQx), 2-Amino-1-methyl-6-phenyilimidazo [4,5-b]-pyridine (PhIP) and 2-amino-1-methyl-imidazo [4,5-f]-quinoline (iso-IQ) (Fig. 1), were supplied from

Results and discussion

An easiest, rapid and hydrothermal procedure, assisted by microwave treatment, previous purification process, was chosen to obtain CDs from lactose which exhibited a strong emission. The most attractive feature of this method is that the surface passivation step is not necessary, since the starting material. Fig. 2A and B shows the TEM images of CDs at different magnifications revealing, that the synthesis procedure without any modification, could easily disperse in water with a narrow size

Conclusions

In summary, a fluorescent analytical method based on the quenching of the un-functionalized carbon fluorescent nanoparticles, obtained by the assisted microwave treatment of lactose by HCl, and was used as potential system to quantify heterocyclic aromatic amines at μM range of concentration static quenching effect was demonstrated, after analysis of the fluorescence lifetime decay curves, no effect was detected when used 4,8-DiMeIQx as heterocyclic aromatic amine probe at different

Acknowledgements

Authors are gratefully to Grant SFRH/BD/84318/2012 to FCT (Lisbon, Portugal) and Andalucía Tech Program from Univ Málaga (Spain). Financial support from the Spanish Ministry of Economy and Competitiveness (CTQ2013-48411-P) is gratefully acknowledged. The support given through an “INCRECYT” research contract to M. Zougagh is also acknowledged.

References (43)

  • K. John et al.

    Heterocyclic Aromatic Amines

    (2014)
  • K. Puangsombat et al.

    Meat Sci.

    (2012)
  • P. Pais et al.

    J. Chromatogr. A

    (1997)
  • E. Barceló-Barrachina et al.

    J. Chromatogr. A

    (2004)
  • M.R. Khan et al.

    J. Chromatogr. A

    (2008)
  • T. Polak et al.

    LWT Food Sci. Technol

    (2009)
  • M. Iwasaki et al.

    J. Food Compos. Anal.

    (2010)
  • H. Kataoka et al.

    Anal. Chim. Acta

    (2013)
  • J.H. Shin et al.

    Anal. Bioanal. Chem

    (2014)
  • J.H. Shin et al.

    Anal. Biochem

    (2014)
  • U. Gerbl et al.

    J. Chromatogr. B

    (2004)
  • B. Janoszka

    Food Chem.

    (2010)
  • M.G Knize et al.

    J. Chromatogr. A

    (1997)
  • R. Reistad et al.

    Food Chem. Toxicol.

    (1997)
  • L. Warzecha et al.

    J. Chromatogr. B

    (2004)
  • S. Sentellas et al.

    J. Chromatogr. A

    (2004)
  • P. Viberg et al.

    J. Chromatogr. A

    (2006)
  • X.Q Fei et al.

    J. Chromatogr. B

    (2007)
  • J.C.G. Esteves da Silva et al.

    Trends Anal. Chem

    (2011)
  • A. Cayuela et al.

    Anal. Chim. Acta

    (2013)
  • Y. Dong et al.

    Carbon

    (2012)
  • Cited by (0)

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