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Template-Assisted Synthesis of Luminescent Carbon Nanofibers from Beverage-Related Precursors by Microwave Heating.

ABSTRACT: Luminescent carbon nanomaterials are important materials for sensing, imaging, and display technologies. This work describes the use of microwave heating for the template-assisted preparation of luminescent carbon nanofibers (CNFs) from the reaction of a range of beverage-related precursors with the nitrogen-rich polyethyleneimine. Highly luminescent robust carbon fibers that were 10 to 30 m in length and had a diameter of 200 nm were obtained under moderate conditions of temperature (250-260 °C) and a short reaction time (6 min). The high aspect ratio fibers showed wavelength-dependent emission that can be readily imaged using epifluorescence. The development of these multi-emissive one-dimensional (1D) carbon nanomaterials offers potential for a range of applications.

SUBMITTER: Deeney C

PROVIDER: S-EPMC6515550 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Template-Assisted Synthesis of Luminescent Carbon Nanofibers from Beverage-Related Precursors by Microwave Heating.

Deeney Clara C McKiernan Eoin P EP Belhout Samir A SA Rodriguez Brian J BJ Redmond Gareth G Quinn Susan J SJ

Molecules (Basel, Switzerland) 20190412 8

Luminescent carbon nanomaterials are important materials for sensing, imaging, and display technologies. This work describes the use of microwave heating for the template-assisted preparation of luminescent carbon nanofibers (CNFs) from the reaction of a range of beverage-related precursors with the nitrogen-rich polyethyleneimine. Highly luminescent robust carbon fibers that were 10 to 30 m in length and had a diameter of 200 nm were obtained under moderate conditions of temperature (250-260 °C ...[more]

PMID: 31013798

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Project description:Carbon dots (CDs) are a diverse and wide-reaching field of study which encompasses multiple scientific disciplines. This, along with their extensive applications, calls for the need to continually seek to improve their synthesis efficiency. To this end, we focused upon the effects of altering the heating method on the characteristics and quality of the final CD product. In our approach, two different versions of heating techniques were used including the common oven-based hydrothermal method and a microwave (MW)-assisted hydrothermal method. The MW-assisted heating involved the implementation of a pressure vessel (similar to oven hydrothermal vessel) for improved yield of luminescent CDs. We found that this MW method yielded CDs of bright intensity with comparable shape, size, and dispersity to that produced using conventional hydrothermal methods. Specifically, the CDs average particle diameters were determined to be between 1.8 and 2.0 nm for either method. The MW method also demonstrated certain advantages over the oven method in terms of required reaction time and particle yield. The total reaction and cooldown time was reduced by ∼75% (with ideal MW heating time) and an estimation of the average CDs particle density revealed that the MW method was able to produce approximately 1.2 times more particles than the oven method in less time. Correcting for the same processing time, larger yields are available in microwave synthesis. We were able to also demonstrate that both versions of synthesized CDs can serve as viable fluorescence probes for in vitro imaging experiments due to the fact that, under the determined working conditions, their fluorescence emission is significantly greater than that of cell autofluorescence [oven: p = 1.47 × 10-27 (blue), p = 6.98 × 10-4 (green); 60 second MW: p = 7.59 × 10-10 (blue), p = 3.03 × 10-4 (green)] and the CDs were not cytotoxic. This rapid, simple synthesis approach can be applied to other forms of carbon dots and serves as a high-yield alternative to hydrothermal synthesis.

Project description:We describe a synthetic strategy for the preparation of bis-heteroleptic polypyridyl Ru(II) complexes of the type [Ru(L1)2(L2)]2+ (L1 and L2 = diimine ligands) from well-defined Ru(II) precursors. For this purpose, a series of six neutral, anionic, and cationic cis-locked Ru(II)-DMSO complexes (2-7) of the general formula [Y] fac-[RuX(DMSO-S)3(O-O)]n (where O-O is a symmetrical chelating anion: oxalate (ox), malonate (mal), acetylacetonate (acac); X = DMSO-O or Cl-; n = -1/0/+1 depending on the nature and charge of X and O-O; when present, Y = K+ or PF6-) were efficiently prepared from the well-known cis-[RuCl2(DMSO)4] (1). When treated with diimine chelating ligands (L1 = bpy, phen, dpphen), the compounds 2-7 afforded the target [Ru(L1)2(O-O)]0/+ complex together with the undesired (and unexpected) [Ru(L1)3]2+ species. Nevertheless, we found that the formation of [Ru(L1)3]2+can be minimized by carefully adjusting the reaction conditions: in particular, high selectivity toward [Ru(L1)2(O-O)]0/+ and almost complete conversion of the precursor was obtained within minutes, also on a 100-200 mg scale, when the reactions were performed in absolute ethanol at 150 °C in a microwave reactor. Depending on the nature of L1 and concentration, with the oxalate and malonate precursors, the neutral product [Ru(L1)2(O-O)] can precipitate spontaneously from the final mixture, in pure form and acceptable-to-good yields. When spontaneous precipitation of the disubstituted product does not occur, purification from [Ru(L1)3]2+ can be rather easily accomplished by column chromatography or solvent extraction. By comparison, under the same conditions, compound 1 is much less selective, thus demonstrating that locking the geometry of the precursor through the introduction of O-O in the coordination sphere of Ru is a valid strategic approach. By virtue of its proton-sensitive nature, facile and quantitative replacement of O-O in [Ru(L1)2(O-O)]0/+ by L2, selectively affording [Ru(L1)2(L2)]2+, was accomplished in refluxing ethanol in the presence of a slight excess of trifluoroacetic acid or HPF6.

Dataset Information

Template-Assisted Synthesis of Luminescent Carbon Nanofibers from Beverage-Related Precursors by Microwave Heating.

Publications

Template-Assisted Synthesis of Luminescent Carbon Nanofibers from Beverage-Related Precursors by Microwave Heating.

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