UV–Vis–NIR Full‐Range Responsive Carbon Dots with Large Multiphoton Absorption Cross Sections and Deep‐Red Fluorescence at Nucleoli and In Vivo

Abstract

Carbon dots (CDs), with excellent optical property and cytocompatibility, are an ideal class of nanomaterials applied in the field of biomedicine. However, the weak response of CDs in the near‐infrared (NIR) region impedes their practical applications. Here, UV–vis–NIR full‐range responsive fluorine and nitrogen doped CDs (N‐CDs‐F) are designed and synthesized that own a favorable donor‐π‐acceptor (D‐π‐A) configuration and exhibit excellent two‐photon (λex = 1060 nm), three‐photon (λex = 1600 nm), and four‐photon (λex = 2000 nm) excitation upconversion fluorescence. D‐π‐A‐conjugated CDs prepared by solvothermal synthesis under the assistance of ammonia fluoride are reported and are endowed with larger multiphoton absorption (MPA) cross sections (3PA: 9.55 × 10−80 cm6 s2 photon−2, 4PA: 6.32 × 10−80 cm8 s3 photon−3) than conventional organic compounds. Furthermore, the N‐CDs‐F show bright deep‐red to NIR fluorescence both in vitro and in vivo, and can even stain the nucleoli of tumor cells. A plausible mechanism is proposed on the basis of the strong inter‐dot and intra‐dot hydrogen bonds through NH···F that can facilitate the expanding of conjugated sp2 domains, and thus not only result in lower highest occupied molecular orbital‐lowest unoccupied molecular orbital energy level but also larger MPA cross sections than those of undoped CDs.

Carbon Nanodots in Photodynamic Antimicrobial Therapy: A Review

“…In total, this structure is on the order of less than 10 nm in size. Typical absorption and sample emission spectra are shown in Figure 2 b, demonstrating the strong UV absorption and visible absorption tail inherent to carbon dot structures; studies have been conducted to further extend the absorption of carbon dots into the visible or even NIR region [ 37 , 38 , 39 ]. Carbon dots are also known to be capable of up-conversion photoluminescence [ 27 , 40 ] which will be discussed further in the context of antimicrobial applications in Section 4.2 .…”

Hydrothermal synthesis of blue‐green emitting carbon dots based on the liquid products of biodegradation of coal

“…Moreover, the peak at 400.94 eV should be attributed to pyrrolic N 61,63 . The O 1s can be described by two peaks at 531.47 eV and 532.66 eV, which correspond to the C=O/OH and C‐O, respectively 61,64 …”

On-off Fluorescent Switching of Excitation-independent Near-ultraviolet Emission Carbon Nanobelts for Ultrasensitive Detection Nimesulide in Pharmaceutical Tablet

“…The XPS spectrum of the C1s (Fig. 2B) was deconvoluted into four peaks at 284.6, 285.7, 286.8, and 288.9 eV, which belonged to the C=C/C-C, C-N, C-O, and C=O bonds, [17][18][19][20] respectively. And the two peaks at 531.5 and 532.7 eV in the high-resolution O1s spectrum (Fig.…”