Temperature‐Dependent Dual Emission from Sucrose‐Derived Carbon Nanodots: A Ratiometric Fluorescent Thermometer

Abstract

Carbon nanodots( CNDs) with conspicuous dual emission (at 450 and5 17 nm) were fabricatedb yh ydrothermal treatment of aqueous sucrose solution.T he temperature-dependent photoluminescence (PL) and time-resolved PL werei nvestigated. The trapping of excited electrons by the nonradiative defects should substantially account for the PL quenching as the temperature increases. The sucrose-derivedC NDs show great potential for applications as ratiometric fluorescent thermometers with asensitivity of approximately 2.15 % 8C À1.Carbon nanodots (CNDs) are at ype of biocompatible fluorescent nanomaterials that can be obtainedt hrough simple, lowtoxicity, low-costc hemical reactions. [1][2][3] Recently,t here has been plenty of literature reporting the fluorescencef rom CNDs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] However,t he fluorescence properties reported by differentg roups vary greatly, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] for instance, some of them are excitation-dependentw hile others are excitation-independent. [4,5] This diversity may be ascribed to different preparation methods and reactants, which lead to different surfaces, sizes and structures. Regardless of the fabrication strategies used for the fluorescent CNDs,t hey are widely appliedf or bioimaging and biosensing, [7][8][9][10][11][12][13] such as in fluorescent sensors for temperature, pH andm etal-ion concentration. [10][11][12][13] Generally speaking, fluorescent sensors work based on the principle that variations in circumstances cause changes in fluorescentc haracteristics such as wavelength,l ifetime and intensity.I no ther words, the fluorescent variationsr eflect the changes in temperature, pH and metal-ion concentration, etc. of the surroundings. However,t he variation in wavelength is usually too slight to be resolved. In addition, the lifetime determinationi st ime-consuming and requires an expensive timecorrelated single photo-counting system.[19] Therefore mosto f the fluorescent sensors are based on fluorescenti ntensity. But this type of sensor also suffers am ajor drawback;t he fluorescent intensity is dependento ne xcitation intensity,d etection efficiency and sensor concentration.A saresult, the measurement of singlee mission intensity is unreliable.[19] As ac ompetitive candidate, ratiometric sensors with dual emission are very advantageous. [20,21] In the past years, many works have contributed to develop fluorescent CNDs. Particularly,r atiometric fluorescent sensors have been designed by doping and surfacem odification. [10,[22][23][24][25] Howeveri ti ss till rare that CNDs exhibit conspicuous dual emission under single-wavelength excitation without introducing any additional fluorescent moiety,w hich implies easy preparation andl ow cost. [12,16,17] Previous works have revealed that both graphene quantum dots (GQDs)a nd CNDs have two emissive centers:o ne is ac arbon defect state and the other is the sp 2 carbon cluster with size effect. [26][27][28][29] Gaussian fitting of the ...

Molecular Origin and Self-Assembly of Fluorescent Carbon Nanodots in Polar Solvents

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Photoluminescence of Diphenylalanine Peptide Nano/Microstructures: From Mechanisms to Applications

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Ratiometric intracellular pH sensors based on nitrogen-doped graphene oxide quantum dots

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