Strong luminescence of Carbon Dots induced by acetone passivation: Efficient sensor for a rapid analysis of two different pollutants

doi:10.1016/j.aca.2013.10.031

Analytica Chimica Acta

Volume 804, 4 December 2013, Pages 246-251

https://doi.org/10.1016/j.aca.2013.10.031 Get rights and content

Highlights

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Passivation of CDs with acetone has not been described until now.
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Highly improvement in luminescence of CDs when passivated with acetone is shown.
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Carboxylic groups in surface of CDs may be responsible of PL features.
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pH influences strongly the ability of CDs to detect different analytes.
•
A proposed method for determine two pollutants is presented.

Abstract

The important photoluminescence enhancement found in Carbon Dots (CDs) obtained from carbonaceous nanomaterials when passivating with acetone is shown in this paper, in which this type of passivation has not been reported previously. Analytical fluorescent assays were performed with the selected CDs using two different pollutants as target analytes. The results show that the optimal conditions for detecting 2,4-dinitrophenol (DNP) were at pH 3.5 while in case of 2-amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (4,8-DiMeIQx) were found at physiological pH. The fascinating ability of CDs to interact with certain molecules under certain conditions gave rise to explore some useful applications for a quick detection of contaminants by simply monitoring the photoluminescence of CDs as shown in this article.

Graphical abstract

Introduction

The development of low-cost photoluminescent (PL) nanomaterials is growing exponentially in the last decades. Since the discovery of CDs with the purification of carbon nanotubes (CNTs) in 2004 [1], these materials have evoked great interest among researchers as a consequence of their tunable PL properties, with dependence between emission wavelength and size attributed to the surface defects sites [2], [3], [4], [5], [6], [7], mechanism that supports the fact that the smallest CDs with similar surface passivation have been found to be highly luminescent [8], [9].

Few analytical applications for these carbonaceous nanomaterials had been described until now. Most authors have focused on the development of applications related to metal ions as analyte [10], [11], [12], [13], specially, Hg(II) [14], [15], [16], [20], [22]. Other CDs applications are the determination of iodine [17], [18], the detection of DNA [19] or Ru(bpy)₃²⁺ species [20], and the exploitation of the ability of CDs to donate or accept electrons in aqueous solutions [4]. The interesting features of CDs gives rise to a multitude number of other analytical applications for the exploitation of this type of nanosensor against other substances.

2,4-Dinitrophenol (DNP) is an anthropogenic substance extensively detected in industrial effluent steams. In addition, DNP had gained popularity for weight loss under a number of names such as weight loss/slimming aid. DNP has also been used as herbicide and as a photographic developing chemical, and its use has now resurfaced via the internet. Methods based on spectrophotomety [21], GC/MS spectrometry [22] and electrochemical spectroscopy [23], [24] have been used for the determination of DNP.

Other family of pollutants found in industrial waters and in well-fried meat and fish is heterocyclic amines, specially the carcinogenic 2-amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (4,8-DiMeIQx). Chromatographic techniques like GC/MS [25], HPLC [26] or LC/MS [27] had been used for detecting this type of amine.

However, the instrumentation mentioned before for the detection of both analytes is very expensive and unavailable in most of laboratories. Thanks to recent developments on nanotechnology, sensors like photoluminescent (PL) carbon nanoparticles could be an attractive alternative for an easy, cheap and effective determination of different types of analytes.

This paper study the PL characteristics of CDs prepared from different precursors and passivated with acetone. Furthermore, the exploitation of the sensorial ability of CDs gives rise to an excellent tool for determining at certain conditions several targets such as carcinogenic substances by simply monitoring the fluorescence of CDs. The effect of pH, concentration of salts, and presence of other interferences were investigated. A developed method for determining DNP and 4,8-DiMeIQx is presented.

Section snippets

Reagents and materials

Sulfuric acid (95–98%), nitric acid (69%) and sodium hydroxide (98%) were purchased from PANREAC, S.A.U. Barcelona, Spain; 2,4-dinitrophenol (DNP, 95%), m-nitrophenol (99%), 2,5-dichlorophenol (98%), o-xylene (99%), m-xylene (99%), pyrene (98%), ethylamine (97%), trimethylamine (99%), histamine (99%), phenylalanine-D (98%), tryptophan (98%), sodium carbonate (99.95%), citric acid monohydrate (99%), acetone (99.8%) and quinine hemisulfate salt monohydrate (98%) from Sigma–Aldrich, Madrid, Spain;

Fluorescence features of CDs prepared from different precursors and passivated

The nanoparticles presented in this paper were obtained by chemical oxidation of the different precursors (SWCNTs, MWCNTs and C₆₀) under acidic conditions at high temperatures. Tao and coworkers [28] have synthesized CDs from MWCNT and SWCNT as well but we have made some improvements such as reducing the reaction time and in the purification and passivation steps. Although most of authors purify nanoparticles by dialysis procedures, in these experiments the nanoparticles were purified by

Conclusions

Highly fluorescent CDs were obtained from MWCNTs and passivated with acetone with more intense and narrower fluorescence emission band, which results in narrower size-distribution and surface passivation of nanoparticles. In addition, their emission is strongly influenced by the pH of the media, being higher at lower pH. The role of acetone is to incorporate hydrogen-bonded carboxylic groups to the surface of CDs. Surface sensitive CDs thus obtained were ideal as environmentally-responsible

Acknowledgments

The authors would like to express their gratitude to the Spanish Ministry of Innovation and Science for Project CTQ2011-23790 and Junta de Andalucía (Project FQM-4801).

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View full text

Strong luminescence of Carbon Dots induced by acetone passivation: Efficient sensor for a rapid analysis of two different pollutants

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Reagents and materials

Fluorescence features of CDs prepared from different precursors and passivated

Conclusions

Acknowledgments

Biosens. Bioelectron.

Anal. Chim. Acta

Anal. Chim. Acta

J. Chromatogr. B

Int. J. Electrochem. Sci.

J. Chromatogr. B: Analyt. Technol. Biomed Life Sci.

J. Food Compos. Anal.

Polymer

J. Am. Chem. Soc.

J. Mater. Chem.

J. Phys. Chem. C

Chem. Commun.

Chem. Mater.

Am. Chem. Soc.

Chem. Mater.

J. Phys. Chem. C

Appl. Mech. Mater.