Multi-functional carbon dots for visual detection of picric acid and white-light emission

doi:10.1016/j.materresbull.2021.111223

Materials Research Bulletin

Volume 138, June 2021, 111223

https://doi.org/10.1016/j.materresbull.2021.111223 Get rights and content

Highlights

•
The single-pot, fast and facile synthesis protocol for multi-functional carbon dots (CDs).
•
The selective and sensitive detection of picric acid, via luminescence quenching of CDs.
•
White-light emission was realized using Poly vinyl alcohol (PVA)-CDs composite as a the colour converting phosphor.

Abstract

Herein we report the synthesis of multifunctional carbon dots (CDs) through microwave-assisted pyrolysis of 2-aminoterephthalic acid and polyethylene glycol. The CDs exhibited relatively high photoluminescence quantum yield of about 67 %, and has been found to be selective and ultrasensitive to the nitroaromatic explosive picric acid, with a detection limit as low as 18 nM. The visual detection of the analyte was realized using CDs in the solid-phase, after coating the dots on silica-based thin-layer chromatographic plates. Furthermore, the broad-band luminescence was exploited for UV-to-visible light conversion, to obtain the color parameters of CIE (0.35, 0.33), CRI of 92 and CCT of 5246 K, representing the cool, white-gamut region of 1931 CIE chromaticity diagram.

Graphical abstract

Introduction

Luminescent carbon dots are zero-dimensional carbon-based nanoparticles, identified for the first time in 2004, during the purification of single-walled carbon nanotubes [1]. By virtue of their remarkable properties such as low toxicity, high water-solubility, photostability and tailorable surface functionalities, CDs have been exploited in a spectrum of applications including chemical sensing, bioimaging, catalysis and energy conversion applications [[2], [3], [4]]. The optical properties of the CDs, such as fluorescence, phosphorescence, down- and up-conversion photoluminescence root from the recombination of photoexcited electrons at the emissive sites generated due to the hybridization between the carbon backbones and the surface-functional groups [5,6]. During the formation of CDs following bottom-up synthesis methods, the functional groups present in the precursors (or the reaction medium) get attached to the dangling bonds of the carbon core [[7], [8], [9], [10]]. This offers the possibility of custom-tailoring the surface chemistry to suit certain applications via the judicious selection of the precursors; or even in the design of single-pot synthesis protocol of CDs which exhibit multifunctional applications [[11], [12], [13], [14]]. Through the engineering of the surface states on the CDs, broad-band luminescence covering the entire visible range of frequencies upon single-wavelength excitation has been demonstrated [[6], [7], [8]]. The broad-band luminescence of the CDs has been utilized in the fabrication of white-light-emitting diodes (w-LEDs) following remote-phosphor technology, i.e., by incorporating the dots in suitable polymer matrices and then coating the composite on to UV-LED chips [[15], [16], [17], [18], [19]]. Furthermore, the emission traits of the CDs (wavelength as well as quantum yield) are highly sensitive to the chemical environment which the surface-moieties are subjected to. This property has been exploited for the design of CDs-based chemosensors to identify trace quantities of analytes in the solvent medium [[20], [21], [22], [23], [24]].

In this work, we report a simple, one-step route for the fabrication of multifunctional CDs from 2-aminoterephthalic acid (ATA) and polyethylene glycol (PEG) using microwave-assisted synthesis. The choice of the precursors was done with the intension to introduce amino, carboxyl and hydroxyl functional groups on the CDs. The as-prepared CDs demonstrated excellent aqueous solubility, extremely broad-band fluorescence, with a relatively high luminescence quantum yield of ∼ 67 % (λ_ex =410 nm). We have investigated the versatility of the CDs in diverse applications such as a chemosensor for the detection of nitroaromatic explosives and as a UV-to-visible light converter phosphor for solid-state lighting. The fluorescence intensity of the CDs in aqueous dispersion was found to selectively decrease in the presence of picric acid (PA), which was utilized for luminescence quenching-based detection of PA. The broad-band luminescence of the CDs was preserved even after dispersing the dots in solid-state polymer matrices, and hence the nanodots-dispersed polymer has been exploited as the phosphor to convert UV electroluminescence to white light with Commission Internationale de L’Eclairage (CIE) parameter of (0.35, 0.33).

Section snippets

Materials and chemicals

Materials used include 2-aminoterephthalic acid (ATA), polyethylene glycol (PEG) and orthophosphoric acid (H₃PO₄). ATA was purchased from Alfa Aesar (India), PEG and H₃PO₄ were obtained from Merck Millipore. Dialysis tubing having molecular weight cut-off 1 kDa was supplied by Spectrum Laboratories (USA). The ultrapure water provided by Labostar TWF water purification system (18.2 MΩ cm, Siemens Ultrapure Water Systems) was used for all experiments.

Synthesis of carbon dots

Microwave-assisted pyrolysis was adopted for

Physico-chemical characterization

The surface morphological studies of the carbon dots were characterized by transmission electron microscopy (TEM). A representative TEM image of the carbon dots is included in Fig. 1, which shows non-uniformity in the particle size distribution; with smaller dots in the size range 3−10 nm, and also the presence of agglomerated, larger particles. The high-resolution transmission electron microscopy (HRTEM) of a typical carbon dot is depicted in the inset of Fig. 1, which exhibits graphitic

Conclusions

In conclusion, we report a simple, microwave-assisted technique to fabricate CDs using 2-aminoterephtalic acid and polyethylene glycol as the precursors. The as-synthesized carbon dots show excellent aqueous solubility and exhibit broad-band emission, which covers a significant fraction of the visible range, under UV excitation; with a fluorescence quantum yield of 67 % (λ_ex =410 nm). The fluorescence intensity of the dots was found to specifically and selectively quench in the presence of

Author statement

The corresponding author is responsible for ensuring that the descriptions are accurate and agreed by all authors.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors acknowledge the financial assistance from UGC-DAE CSR Kalpakkam Node, under the CRS project scheme (CSR-KN/CRS-106/2018-19/1045).

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Multi-functional carbon dots for visual detection of picric acid and white-light emission

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials and chemicals

Synthesis of carbon dots

Physico-chemical characterization

Conclusions

Author statement

Declaration of Competing Interest

Acknowledgements

Mater. Res. Bull.

Microchim. Acta

J. Lumin.

J. Alloys Compd.

J. Photochem. Photobiol. Chem.

Sci. Total Environ.

Spectrochim. Acta A Mol. Biomol. Spectrosc.

Chem. Phys.

Electrophoretic analysis and purification of fluorescent single-walled carbon nanotube fragments

J. Am. Chem. Soc.

Facile synthesis of novel carbon quantum dots from biomass waste for highly sensitive detection of iron ions

Mater. Res. Bull.

Photo-to-thermal conversion: effective utilization of futile solid-state Carbon Quantum Dots (CQDs) for energy harvesting applications

New J. Chem.

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J. Appl. Phys.

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J. Mater. Chem. C

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Nanoscale

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Anal. Methods

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Small

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Talanta

One-step microwave-assisted preparation of oxygen-rich multifunctional carbon quantum dots and their application for Cu²⁺-curcumin detection