Excitation-Independent Blue-Emitting Carbon Dots from Mesoporous Aminosilica Nanoreactor for Bioanalytical Application

Abstract

Here we present the first example of excitationindependent blue-emitting carbon dots (iC-dots) obtained by pyrolysis of citric acid (CA) without post-treatment chromatographic separation. To confine the growth and shape of carbon nanoparticles, silica gel with immobilized aminopropyl groups (SiO 2 −NH 2 ) was used as a nanoreactor. It was demonstrated that the carbonization of SiO 2 − NH 2 with embedded CA resulted in the formation of unbound wCdots and immobilized iC-dots. Because of their firm attachment to the surface, iC-dots can be easily separated from low-molecular impurities and wC-dots by simply rinsing the nanocomposite with water. From atomic force and transmission electron microscopies iC-dots can be represented as flattened spheroids with 2−4 nm of height and 5 nm in lateral size. The size distribution profile for wC-dots is very wide with about 95% the particles within the 2.5−5.5 nm size range. Increasing the template pore size from 4.9 up to 9.1 nm has no effect on the size of the iC-dots. From Fourier transform infrared analysis and X-ray photoelectron spectroscopy data it was assumed that iC-dots belong to N-doped C-nanoparticles with 9:1 carbon to nitrogen atomic ratio. As-prepared iC-dots demonstrate excitation-independent photoluminescence at 445 nm with quantum yields up to 16.8%, which makes them attractive for bioanalytical application.

Rational design of large flat nitrogen-doped graphene oxide quantum dots with green-luminescence suitable for biomedical applications

“…The investigation demonstrates that the N-GOQDs have an irregular shape, they are significantly larger but essentially thinner than CNDs. 26 Irregular shape of N-GOQDs particles also logically follows from the mechanism of their formation by chemical shredding of GO. Such difference can be very important in the biomedical application of N-GOQDs, particularly in their cytotoxicity and cell essential changes.…”

Carbon Quantum Dots Conjugated Rhodium Nanoparticles as Hybrid Multimodal Contrast Agents

“…Furthermore, the absence of multiple peaks and shifts along the emission axis in the 2D fluorescence spectrum proves that the synthesized CQDs displayed excitation-independent emission behavior, which represents a critical parameter for bioimaging, to prevent crosstalk between the different fluorophores [ 46 ]. This behavior arises from the highly narrow size distribution, uniformity of surface states and from nitrogen doping of the CQDs [ 47 , 48 , 49 , 50 , 51 ], demonstrated with TEM and FT-IR ( Figures S4a and S5 ). Having confirmed the physicochemical properties of the CQDs, their cytotoxicity was tested in vitro.…”

Carbon Quantum Dots Derived from Different Carbon Sources for Antibacterial Applications

“…This has stimulated the development of templates for the synthesis of carbon quantum dots in a confined volume (“nanoreactors”). Nanoreactors are mostly mesoporous silica nanoparticles because they possess high thermal stability, uniform pore size distribution and large pore volume [ 67 , 68 , 69 , 70 ]. Nanoreactor-assisted synthesis is usually performed through bottom-up pyrolysis, after the absorption of precursor molecules which are dissolved in a fluid phase into the nanoreactor.…”

“…Time consuming, nanoreactor preparation is difficult, only liquid precursors [67][68][69][70] "Top-down" synthesis methods break down large carbon-rich materials as a carbon source, whereas "bottom-up" methods synthesize carbon quantum dots from small precursor molecules. Both the method applied as well as the carbon source or precursor used are determinant factors for the final physico-chemical and functional properties of carbon quantum dots, including their biocompatibility and antibacterial efficacy [71,72].…”