Synthesis, Separation, and Characterization of Small and Highly Fluorescent Nitrogen‐Doped Carbon NanoDots

Abstract

A facile bottom-up approach to carbon nanodots (CNDs) is reported, using a microwave-assisted procedure under controlled conditions. The as-prepared nitrogen-doped CNDs (NCNDs) show narrow size-distribution, abundant surface traps and functional groups, resulting in tunable fluorescent emission and excellent solubility in water. Moreover, we present a general method for the separation of NCNDs by low-pressure size-exclusion chromatography, leading to an even narrower size distribution, different surface composition, and optical properties. They display among the smallest size and the highest FLQYs reported so far. (13)C-enriched starting materials produced N(13) CNDs suitable for thorough NMR studies, which gave useful information on their molecular structure. Moreover, they can be easily functionalized and can be used as water-soluble carriers. This work provides an avenue to size- and surface-controllable and structurally defined NCNDs for applications in areas such as optoelectronics, biomedicine, and bioimaging.

Amine‐Rich Nitrogen‐Doped Carbon Nanodots as a Platform for Self‐Enhancing Electrochemiluminescence

“…[15][16][17][18][19][20] They would not only avoid the addition of TPrA, but also provide aself-enhanced ECL emission due to an intramolecular,a nd thus more efficient, electron transfer. [24] TheN CNDs thus produced showed arather homogeneous size distribution with an average size of 2.5 AE 0.8 nm, multiple oxygen and nitrogen functional groups on their surface and excellent solubility in water (up to 80 mg mL À1 ). [21][22][23] However,a part from ar ecent study in which benzylic alcohol moieties were used as co-reactant sites, [21] the identification of the functional groups responsible of their co-reactant behavior is often difficult, though fundamental.…”

“…In the ECL context, the use of CNDs as carrier for fluorophores has so far not been reported, while their use as co-reactant is still at the initial stages. [24] Herein, we report aN CNDs/Ru(bpy) 3 2+ system in which primary or tertiary amino groups on the NCND surface act as powerful "oxidative-reduction" co-reactant for Ru(bpy) 3 2+ ECL generation in aqueous solution, suitable for bioanalytical purposes ( Figure 1). Recently,w er eported as traightforward approach to the synthesis of nitrogendoped CNDs (NCNDs), using am icrowave reactor under controlled conditions.…”

“…[25] In NCNDs,the presence of primary amino groups was already confirmed by as trongly positive Kaiser test. [24] Also,the high current and steep slope of the monoelectron oxidation peak (+ 1.14 Vv s. SCE) in the cyclic voltammogram (CV) of NCNDs ( Figure S1, black trace and Figure S2 in the Supporting Information) suggest that ah igh number of amino groups on the NCND surface can be easily oxidized. [24] Also,the high current and steep slope of the monoelectron oxidation peak (+ 1.14 Vv s. SCE) in the cyclic voltammogram (CV) of NCNDs ( Figure S1, black trace and Figure S2 in the Supporting Information) suggest that ah igh number of amino groups on the NCND surface can be easily oxidized.…”

Customizing the Electrochemical Properties of Carbon Nanodots by Using Quinones in Bottom‐Up Synthesis

“…[22][23][24][25] Additionally,w es howed that the CND emission can be tailored through arational choice of organic precursors. [22][23][24][25] Additionally,w es howed that the CND emission can be tailored through arational choice of organic precursors.…”

“…[32][33][34] Since CNDs could play an important role in applications such as energy conversion and photocatalysis, [10] for example,h ydrogen evolution, [35][36][37][38][39] several improvements have been proposed, among which are graphitization and N-doping. [24] To obtain CNDs with tuned redox potentials,v arious commercially available quinones were introduced in the reaction mixture for the synthesis of CNDs 2-7 ( Figure 1). [39] Herein, we report asimple synthetic strategy based on fast and controlled microwave heating, to showcase the in situ tuning of electrochemical properties,l eading to ar edox library of CNDs.A sastarting point in our strategy,w e employed Arg and EDAa sp recursors,w hich produce Ndoped CNDs (CND 1), under our previously reported hydrothermal MW-assisted protocol.…”