Fluorescent carbon and graphene oxide nanoparticles synthesized by the laser ablation in liquid

Applied Physics A, Mar 2018

The results of synthesis of the fluorescent carbon dots (CDots) from graphite target and reduced graphene oxide (rGO) nanoparticles performed by the nanosecond laser ablation in polyethylene glycol 200 (PEG200) are shown. Two-step laser irradiation (first graphite target, next achieved suspension) revealed a very effective production of CDots. However, the ablation in PEG appeared to be effective with 1064 nm laser pulse in contrast to the ablation with 355 nm laser pulse. In the case of rGO nanoparticles similar laser irradiation procedure was less efficient. In both cases, received nanoparticles exhibited strong, broadband photoluminescence with a maximum dependent on the excitation wavelength. The size distribution for obtained CDots was evaluated using the DLS technique and HRTEM images. The results from both methods show quite good agreement in nanoparticle size estimation although the DLS method slightly overestimates nanoparticle’s diameter.

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Fluorescent carbon and graphene oxide nanoparticles synthesized by the laser ablation in liquid

Applied Physics A Fluorescent carbon and graphene oxide nanoparticles synthesized by the laser ablation in liquid A. Małolepszy 0 1 2 S. Błonski 0 1 2 J. Chrzanowska‑Giżyńska 0 1 2 M. Wojasiński 0 1 2 T. Płocinski 0 1 2 L. Stobinski 0 1 2 Z. Szymanski 0 1 2 0 Faculty of Materials Science and Engineering, Warsaw University of Technology , Wołoska 141, 02-507 Warsaw , Poland 1 Institute of Fundamental Technological Research, Polish Academy of Sciences , Pawinskiego 5B, 02-106 Warsaw , Poland 2 Faculty of Chemical and Process Engineering, Warsaw University of Technology , Warynskiego 1, 00-645 Warsaw , Poland 3 Z. Szymanski The results of synthesis of the fluorescent carbon dots (CDots) from graphite target and reduced graphene oxide (rGO) nanoparticles performed by the nanosecond laser ablation in polyethylene glycol 200 (PEG200) are shown. Two-step laser irradiation (first graphite target, next achieved suspension) revealed a very effective production of CDots. However, the ablation in PEG appeared to be effective with 1064 nm laser pulse in contrast to the ablation with 355 nm laser pulse. In the case of rGO nanoparticles similar laser irradiation procedure was less efficient. In both cases, received nanoparticles exhibited strong, broadband photoluminescence with a maximum dependent on the excitation wavelength. The size distribution for obtained CDots was evaluated using the DLS technique and HRTEM images. The results from both methods show quite good agreement in nanoparticle size estimation although the DLS method slightly overestimates nanoparticle's diameter. 1 Introduction Pulsed laser ablation in liquid (PLAL) is a widely recognized method of synthesizing contamination-free nanostructures especially nanoparticles [ 1, 2 ] among them fluorescent carbon nanoparticles (FCNPs) [3], carbon polyynes [ 4 ], etc. Most of the attention is given to fluorescent nanoparticles, especially with diameters of 2–8 nm called carbon dots, which are widely used for purposes of fluorescent imaging, mainly of cells and tissues [ 5, 6 ]. Their most remarkable property is the excitation-dependent fluorescence emission. The laser synthesis of fluorescent carbon nanoparticles was performed in several liquids such as deionized water [7], isopropyl alcohol (IPA), acetone [ 8 ], polyethylene glycol (PEG) [ 5 ], ethylenediamine (EDA) and ionic liquids [ 9 ]. In the case of water, the fluorescent carbon dots are obtained only after further functionalization, either with the use of UV radiation [ 7 ] or by attaching simple organic species to the acid-treated carbon particles [ 5 ]. A comprehensive review of laser synthesis of nanoparticles in liquids has previously been presented [ 2 ]. Nanoparticles (NPs) approved in preclinical studies for both imaging and therapy often include polyethylene glycol. Attachment of PEG (PEGylation) improves the bioavailability, safety and prolongs circulation time in the blood of therapeutic agents [ 10 ]. Since NPs permeate through the leaky tumor vasculature to a higher degree than through the healthy tissue and remain in the area, they can be used for signaling or therapy [ 11 ] and, therefore, PEG is increasingly used to improve the properties of nanoparticles used as therapeutic or diagnostic agents in biomedicine. In addition, nanoparticles suspended in other liquids had the tendency to agglomeration. Nanoparticles aggregate when the attraction between particles is stronger than the attraction with solvent particles. PEG decreases the surface energy of NPs and minimizes van der Waals attraction [ 10 ]. In addition, PEG is a very effective passivation agent and surface functionalization (passivation) of carbon nanoparticles is necessary to make them fluorescent. Although the origin of fluorescence from carbon nanoparticles is still not completely clear the fluorescence properties of carbon dots are associated with the particles’ surface, specifically “surface defects” responsible for light absorbance. The photoluminescence originates from the surface functional groups attached to carbon nanodots and functionalization with hydrocarbon chains such as in PEG is very effective [ 5 ]. However, the experiments with laser synthesis in PEG are rather scarce [ 3, 5, 12, 13 ] and most of them were made in graphite powder [ 3, 12, 13 ]. For carbon dots produced by laser ablation of a carbon target in the presence of water vapor photoluminescence was achieved only after dots’ surface passivation [5]. In this paper, the results of the synthesis of the fluorescent carbon dots (CDots) from solid carbon target and reduced graphene oxide (rGO) nanoparticles performed by the laser ablation in PEG200 are presented. 2 Synthesis Graphite target irradiation was performed in a quartz beaker with diameter 40 mm using an Nd:YAG laser (Quantel, 981 E). The laser operated at a wavelength of 1064 and 355 nm with a 10 ns pulse duration and repetition rate of 10 Hz. The thickness of (...truncated)


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A. Małolepszy, S. Błonski, J. Chrzanowska-Giżyńska, M. Wojasiński, T. Płocinski, L. Stobinski, Z. Szymanski. Fluorescent carbon and graphene oxide nanoparticles synthesized by the laser ablation in liquid, Applied Physics A, 2018, pp. 282, Volume 124, Issue 4, DOI: 10.1007/s00339-018-1711-5