Abstract
Advanced optical applications of fluorescent carbon dots (C-dots) require highly integrated host-guest solid-state materials with a careful design of C-dots – matrix interface to control the optical response. We have developed a new synthesis based on the grafting of an organo-functional silane (3-glycidyloxypropyltrimethoxysilane, GPTMS) on amino-functionalized C-dots, which enables the fabrication of highly fluorescent organosilica-based hybrid organic-inorganic films through sol-gel process. The GPTMS grafting onto C-dots has been achieved via an epoxy–amine reaction under controlled conditions. Besides providing an efficient strategy to embed C-dots into a hybrid solid-state material, the modification of C-dots surface by GPTMS allows tuning their photoluminescence properties and gives rise to an additional, intense emission around 490 nm. Photoluminescence spectra reveal an interaction between C-dots surface and the polymeric chains which are locally formed by GPTMS polymerization. The present method is a step forward to the development of a surface modification technology aimed at controlling C-dots host-guest systems at the nanoscale.
Highlights
carbon dots (C-dots) fluorescence is, in general, attributed to two contributions: the emission from the carbon-core and surface states[9]
The functionalization of C-dots with GPTMS has been designed to allow a full integration into a hybrid organic-inorganic material through covalent bonding and to modulate the photophysical properties
To synthesize the C-dots with graphitic and well defined structure, we have used a hydrothermal reaction of citric acid (CA) and ethylene diamine (ED)[5], following an optimized procedure described in detail in the methods section
Summary
C-dots fluorescence is, in general, attributed to two contributions: the emission from the carbon-core and surface states[9]. When C-dots structure is composed by sp[2] hybridized carbon atoms, graphitic-nitrogen can be accommodated in both core and surface sites. The authors have supposed that the PL tuning can be caused by the surface defective states, showing a different oxidation state These findings suggest that C-dots fluorescence can be tuned by controlling the state of the surface nitrogen atoms in C-dots structure. The surface functionalization plays a fundamental role for embedding C-dots into solid matrices. This is a technological requirement that should be carefully considered for developing innovative optical devices. GPTMS-grafted C-dots are expected to be a class of more stable phosphors to be dispersed in solid-state. We show that this route allows fabricating stable organosilica-based hybrid films wherein the fluorescent properties of C-dots are preserved or even enhanced in comparison to the liquid phase
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