Elsevier

Carbon

Volume 50, Issue 3, March 2012, Pages 1298-1302
Carbon

Photoluminescent carbon nanoparticles produced by confined combustion of aromatic compounds

https://doi.org/10.1016/j.carbon.2011.10.052Get rights and content

Abstract

We report new photoluminescent carbon nanoparticles having an average particle size of 50 nm. When dispersed in chloroform and excited with 325 nm wavelength, the solution showed strong photoluminescence at 475 nm with 12–13% quantum yield. A well dispersed photoluminescent solution can also be prepared with ethanol, xylene or hexane using the nanoparticles. The nanoparticles were prepared by a simple confined combustion of an aromatic compound such as benzene, toluene, xylene or a mixture thereof in air.

Introduction

Carbon is unique among the elements in the vast number and variety of compounds it can form. Without carbon, the basis for life would be impossible. Production of carbon nanoparticles has become an area of increasing interest in material research because they are biocompatible, chemically inert and can be surface modified [1]. It was discovered that carbon nanoparticles display intense light emission, and it is expected to yield new insights into practical applications such as in bioimaging [2], [3], [4], their ability to suppress fluorescence in resonance Raman spectroscopy [5], sensor [6] and catalyst support in DMFC [7], [8]. To date, a variety of techniques have been developed for fabricating carbon nanoparticles including laser ablation [1], [9], non-thermal plasma [10], microwave plasma chemical vapor deposition [11], microwave of conducting polymers [12], thermal carbonization of bis(2-chloroethyl) amine hydrochloride at 260 °C [13], arc in water method with forced convective jet [14] and others [15], [16]. Liu et al. reported the preparation and fluorescent carbon nanoparticles derived from candle soot [17]. Tian et al. adopted a procedure to synthesize carbon nanoparticles from the combustion soot of natural gas instead of candles [18]. Stasio et al. investigated the microstructure of propane–air diffusion flame soot using TEM. He observed three classes of nanoparticles: the class primary particles 20–50 nm, the sub-primary graphitical particles 6–9 nm and elementary particles <5 nm [19]. These methods have limitations in terms of size selectivity and economical production capability because of their non-selective harsh synthesis conditions, low production rate and high capital investment. In this regard, the synthesis of carbon nanoparticles with tailored composition, structure, morphology and size by a simple and cheap method is very attractive.

Here, we report a new method to obtain carbon nanoparticles by a controlled combustion of an aromatic compound (benzene, toluene, or xylene) or a mixture thereof in a confined space (Pyrex® glass container) in air. Under our present experimental conditions, the majority of the product resulting from the combustion is deposited in the wall of the container (yield: 45%). Only a small amount was deposited in the bottom. Since the combustion process can be continued until the liquid aromatic compound is completely consumed and no complex apparatus is needed, the present technique could be readily scalable for mass production.

Section snippets

Experimental

Carbon soot (aggregates of carbon nanoparticles (CNPs)) was collected after a confined combustion of benzene, toluene, xylene or mixture in air in a Pyrex® jar as shown in Fig. 1. As-synthesized sample (∼1.70 mg) was dispersed in 20 ml chloroform using sonication and then further diluted with chloroform to have ∼6.8 mg/l concentration. This dispersed solution was used for the measurement of photoluminescence at the excitation wavelength range of 250–420 nm. Additional solvents such as ethanol,

Results and discussion

Large quantities of carbon nanoparticles (CNPs) were collected from the wall of the glass container. Fig. 2a, b and d shows the TEM of the as-produced carbon nanoparticles collected from the container wall. One can see that the sample consisted of aggregated nanoparticles having flat and round morphology with relatively regular size as also supported by SEM result shown in Fig. 2c. Based on statistical analysis of several samples, the average size of the nanoparticles was found to be

Summary

We reported new photoluminescent carbon nanoparticles (CNPs) having an average size of 50 nm. The CNPs were found to emit strong fluorescence in the visible with peak intensity at 475 nm when excited with a wide wavelength range with peak excitation at 325 nm with 12–13% quantum yield. It is postulated that CNPs become photoluminescence due to the oxygen presence. Its presence was confirmed by FTIR and element analyses. We will also measure other physical properties of the CNPs to find their

Acknowledgment

The authors would like to thank the Department of Chemistry and the AG MacDiarmid NanoTech Institute at the University of Texas at Dallas for providing support.

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