Design of Carbon Dots Photoluminescence through Organo-Functional Silane Grafting for Solid-State Emitting Devices

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.

On the Emission Properties of Carbon Dots: Reviewing Data and Discussing Models

“…Indeed, PDs show an excitation-dependent emission feature, which was ascribed to the presence of amine-based fluorescent centers whose rotational and vibrational motions are hindered by the crosslinked polymeric skeleton [81]. Surface states can also be involved in the engineering of the emission from CDs when supported in host matrices, such as silica or ZnO, in view of solid-state applications [24,29,82]. Recently, Righetto et al [76] claimed the observation of free molecules by combining fluorescence correlation spectroscopy and time-resolved electron paramagnetic resonance.…”

“…Since then, the research on this matter is exponentially increasing (according to Scopus, the search engine by Elsevier, more than 1900 search results for 2019 to date and even 28 already dated 2020), with thousands of papers published on the subject in the last few years [4]. Besides a high QY (even larger than 80% [5][6][7][8][9]), other appealing features of CDs are low toxicity, biocompatibility, and photo-and water stability [10][11][12], which make them suitable for applications in luminescence-related fields, such as bioimaging and sensing [13][14][15], photocatalysis [16,17], LED [18,19], lasing [20,21], printing, and cosmetics [22,23] or displays [24]. In addition, drug delivery applications were proposed, exploiting the easy surface functionalization of CDs' surface [23,25,26].…”

Carbon Dots from Citric Acid and its Intermediates Formed by Thermal Decomposition

“…The functionalisation of the citrate‐based C‐dots with organosilanes to stabilise the optical properties and to be employed in sol‐gel processed hybrid organic–inorganic materials appears, therefore, to be a very important issue . Functionalisation with organosilanes modifies the optical response, but a precise correlation is still far to be defined.…”

Sol‐Gel Chemistry for Carbon Dots

“…An example of this strategy is the modification of C‐dots surface by an organosilane which is at the same time a surface modifier through a grafting reaction and network former of the silica backbone. 3‐glycidyloxypropyltrimethoxysilane (GPTMS), which can react with primary and secondary amines by a nucleophilic attack, has been grafted to the C‐dots surface by epoxy‐opening induced by the amines . The Si(OCH 3 ) 3 groups are available to form the silica network via sol‐gel reactions.…”