Integrating sol-gel and carbon dots chemistry for the fabrication of fluorescent hybrid organic-inorganic films

Stefania Mura,Carlo Maria Carbonaro,Róbert Ludmerczki,Maria Francesca Casula,Luigi Stagi,Pier Carlo Ricci,Luca Malfatti,Plinio Innocenzi,Sebastiano Garroni

doi:10.1038/s41598-020-61517-x

Abstract

Highly fluorescent blue and green-emitting carbon dots have been designed to be integrated into sol-gel processing of hybrid organic-inorganic materials through surface modification with an organosilane, 3-(aminopropyl)triethoxysilane (APTES). The carbon dots have been synthesised using citric acid and urea as precursors; the intense fluorescence exhibited by the nanoparticles, among the highest reported in the scientific literature, has been stabilised against quenching by APTES. When the modification is carried out in an aqueous solution, it leads to the formation of silica around the C-dots and an increase of luminescence, but also to the formation of large clusters which do not allow the deposition of optically transparent films. On the contrary, when the C-dots are modified in ethanol, the APTES improves the stability in the precursor sol even if any passivating thin silica shell does not form. Hybrid films containing APTES-functionalized C-dots are transparent with no traces of C-dots aggregation and show an intense luminescence in the blue and green range.

Highlights

Fluorescent blue and green-emitting carbon dots have been designed to be integrated into solgel processing of hybrid organic-inorganic materials through surface modification with an organosilane, 3-(aminopropyl)triethoxysilane (APTES)
Keeping in mind the purpose of the present work we have developed a simple but effective synthesis which allows preparing highly fluorescent Carbon dots (C-dots) modified with an organofunctional alkoxide, 3-(aminopropyl)triethoxysilane (APTES)
A simplified synthesis based on citric acid and urea has been designed to produce highly fluorescent blue and green C-dots with a high quantum yield, among the highest reported so far

Summary

Introduction

Fluorescent blue and green-emitting carbon dots have been designed to be integrated into solgel processing of hybrid organic-inorganic materials through surface modification with an organosilane, 3-(aminopropyl)triethoxysilane (APTES). A comparison of the different QY reported in literature should be made with care because most of the measures have been performed using a reference fluorescent dye (Relative Quantum Yield) and at different wavelengths; this could result in a much higher QYs with respect to the real absolute value Another important goal is the production of functionalized C-dots to be integrated into materials and processed in the form of films for solid-state photonic applications. Only a few examples have reported on surface modification for embedding the C-dots into polymeric matrixes and even less in inorganic or hybrid organic-inorganic hosts obtained via sol-gel processing[9] To fulfil this goal, we have developed highly emissive blue and green C-dots which have been functionalised by 3-aminopropyltriethoxysilane to achieve effective incorporation within a hybrid film. This step is very important for the future development of solid-state optical devices based on C-dots

Methods

Results

Conclusion