Thermal carbonization in nanoscale reactors: controlled formation of carbon nanodots inside porous CaCO3 microparticles

Anna V Vostrikova,Nadezda V Tarakina,Ekaterina S Prikhozhdenko,Andrei V Sapelkin,Gleb B Sukhorukov,Irina Yu Goryacheva,Oksana A Mayorova

doi:10.1038/s41598-018-27488-w

Anna V Vostrikova, Nadezda V Tarakina + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-27488-w

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Abstract

Synthesis of carbon nanodots (CNDs) in confined geometry via incorporation of dextran sulphate into pores of CaCO3 microparticles is demonstrated. The preparation process included three steps: co-precipitation of solutions of inorganic salts and carbon source, thermal treatment and CaCO3 matrix removal. We show that geometric constraints can be used to precisely control the amount of source material and to avoid formation of large carbon particles. Analysis of TEM data shows particle size of ~3.7 nm with narrow size distribution. Furthermore, we found that variation in pore morphology has a clear effect on CNDs structure and optical properties. CNDs with graphene oxide like structure were obtained in the nanoporous outer shell layer of CaCO3 microparticles, while less ordered CNDs with the evidence of complex disordered carbons were extracted from the inner microcavity. These results suggest that confined volume synthesis route in CaCO3 nanopores can be used to precisely control the structure and optical properties of CNDs.

Highlights

Light emitting carbon nanodots (CNDs) have recently emerged as a new family of low dimensional nanocarbon materials
CaCO3 microparticles with a spherical shape, porous structure and narrow size distribution (3–4 μm, Fig. 1a) were manufactured and used as the templates for CNDs synthesis
The results clearly show that light emission does not depend on initial concentration of dextran sulfate (DS) in the 2–10 mg/ml range, while the restriction of the reaction volume can be used to influence CNDs structure and light emission and to avoid formation of large microparticles

Summary

Introduction

Light emitting carbon nanodots (CNDs) have recently emerged as a new family of low dimensional nanocarbon materials. Compared to the more conventional light emitting quantum dots (e.g. CdSe, CdS, Si and Ge etc.), CNDs have clear advantages[1,2,3,4] such as low environmental impact, low cytotoxicity, excitation-dependent emission wavelength, excellent biocompatibility, tunable surface functionalities, stability under ambient conditions. Polymeric systems[38] have already been used as a synthesis template while CaCO3 microparticles currently attract a lot of attention due to their ability to encapsulate various substances, controlled permeability, high surface-to-volume ratio and sufficient thermal stability. In this context, polycrystalline vaterite particles have a convenient spherical shape, developed surface and high porosity.

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