β-C₃N₄ Nanocrystals: Carbon Dots with Extraordinary Morphological, Structural, and Optical Homogeneity

Abstract

Carbon nanodots are known for their appealing optical properties, especially their intense fluorescence tunable in the visible range. However, they are often affected by considerable issues of optical and structural heterogeneity, which limit their optical performance and limit the practical possibility of applying these nanoparticles in several fields.Here we developed a synthesis method capable of producing a unique variety of carbon nanodots displaying an extremely high visible absorption strength (ε > 3 × 10 6 M(dot) −1 cm −1 ) and a high fluorescence quantum yield (73%). The high homogeneity of these dots reflects in many domains: morphological (narrow size distribution), structural (quasiperfect nanocrystals with large electronic bandgaps), and optical (nontunable fluorescence from a single electronic transition). Moreover, we provide the proof of principle that an aqueous solution of these dots can be used as an active medium in a laser cavity, displaying a very efficient laser emission with dye-like characteristics, which reflects the benefits of such a highly homogeneous type of carbon-based nanodots.

Carbon Dots Dispersed on Graphene/SiO2/Si: A Morphological Study

“…Furthermore, the intensity ratio I 2D /I G >2 and the symmetric shape of 2D peak with a full width at half maximum in the range 30–36 cm −1 are typical of single layer graphene (Figure S1, Supporting Information). The Raman spectra of the CDs/Gr systems deposited on SiO 2 (Figure a and b) showed the graphene peaks superimposed to a large photoluminescence band centered at ≈1500 cm −1 (2.15 eV) evidently due to the presence of the CDs. Indeed, this band is consistent with previous data collected from CDs in solution .…”

“…The Raman spectra of the CDs/Gr systems deposited on SiO 2 (Figure a and b) showed the graphene peaks superimposed to a large photoluminescence band centered at ≈1500 cm −1 (2.15 eV) evidently due to the presence of the CDs. Indeed, this band is consistent with previous data collected from CDs in solution . Absorption and emission spectra with excitation wavelength 530 nm have been recorded for CDs solutions of ethanol and water (see supplementary information) .…”

“…A first dispersion (ethanol‐CDs) was prepared putting the as‐synthesized CD powder in ethanol, in a concentration of 0.1 g L −1 . For a second solution (aqueous‐CDs in a concentration of 0.1 g L −1 ), a size exclusion chromatography in Milli‐Q water was performed to fractionate the as‐synthesized sample separating the most luminescent fraction …”

“…For a second solution (aqueous-CDs in a concentration of 0.1 g L À1 ), a size exclusion chromatography in Milli-Q water was performed to fractionate the as-synthesized sample separating the most luminescent fraction. [31] Finally, for the realization of CDs/Gr systems, both CDs dispersions were diluted by a factor 10 4 in volume of the stock solutions. From each diluted dispersion, 1 mL was deposited onto the two different graphene/SiO 2 /Si samples by drop-casting.…”

Kohlenstoffnitridmaterialien für photochemische Zellen zur Wasserspaltung

“…4) Schnelle Reaktionskinetik an der CN-Elektrolyt-Grenzfläche und Langzeitstabilität: Bei den meisten der kürzlich berichteten Hochleistungs-PEC umfasst die beste Konfiguration häufig einen Halbleiter und OER-Cokatalysatoren (an der Photoanode). In diesem Fall ist sowohl die Nutzung eines Cokatalysators [116,154] zeitaufgelçste Fluoreszenzmessungen [116,161] und zeitaufgelçste Mikrowellenleitfähigkeit, [5] hilfreich sein, um tiefere Einblicke in die beteiligten photoelektrochemischen Prozesse zu gewinnen. Es gibt mehrere Faktoren, die beim Integrieren eines Cokatalysators auf einer CN-Schicht berücksichtigt werden sollten.…”