Near‐Ultraviolet Fluorescent “ON‐OFF‐ON” Switching Sensors Based on Nitrogen‐Enriched Dual‐Color Single‐Functional Polymer Carbon Nanosheets

Abstract

Graphene quantum-dot-like structures of highly enriched N-based dual-color single-functional polymer carbon nanosheets (GLNPCNs) with an average diameter as large as 170 nm (ca. five layers) are prepared through a facile hydrothermal method. Intermolecular C H N ⋅⋅⋅C H N and/or C H OH chemical polymerization interactions in the liquid state of the peripheral crown-ether-like "hole"-decorated compound GLNPCNs lead to a fascinating 2 D supramolecular polymer architecture, which exhibits near-ultraviolet (NUV) fluorescence, ultrahigh brightness, a narrow full-width at half-maximum, and excellent potential for practical applications. The unique NUV fluorescence of the GLNPCNs might be attributed to the "self-passivated" crown-ether-like layer on their surface; the GLNPCNs exhibit properties independent of the excitation wavelength, which is unexpected in the NUV region. Moreover, these GLNPCNs show highly selective and sensitive detection of hazardous and toxic silver (Ag ) ions, and discriminate other metal ions or anions in the range 1.5 nm to 50 μm through a fluorescence quenching response. The high sensing selectivity toward Ag ions could be attributable to the restricted rigid conformation of the peripheral crown-ether-like "hole", which binds exclusively to the Ag ion. In addition to Ag ion sensing, the GLNPCNs quenched by Ag ions exhibit high selectivity and sensitivity for cysteine (Cys) in the range 2.0 nm to 50 μm through a fluorescence recovery process, which could be attributed to the effective coordination/chelation interactions between Ag ions and the plentiful mercapto and amino groups of Cys. Our results suggest that the facile preparation, biocompatibility, outstanding photoluminescence, and physicochemical properties of these GLNPCNs make them potentially useful in numerous applications such as bioimaging, optical and electrochemical sensors, and energy devices.

Facile and large-scale synthesis of green-emitting carbon nanodots from aspartame and the applications for ferric ions sensing and cell imaging

“…The high-resolution C 1s spectrum of the N-CDs (Fig. 2b) exhibits five peaks at 284.5, 285.3, 286.5, 287.6 and 291.1 eV, corresponding to CAC/C@C, CAN [35], CAO [3,36], C@N/C@O [37] and OAC@O bonds [38], respectively. The presences of C@C, CAN and C@N peaks confirm the graphitic structure of the N-CDs contains heterocyclic aromatic moieties.…”

“…The O 1s spectrum (Fig. 2d) was deconvoluted into three components located at 531.1, 531.9 and 533.3 eV, which are associated with C@O [42], CAOH [38] and CAOAC groups [43], respectively. Consistent with the FT-IR results, XPS results confirm the existence of the polycyclic heterocycles and abundant hydrophilic groups on surface of N-CDs (e.g., hydroxyl, amino and carboxylic groups).…”

Picomolar Level Detection of Copper(II) and Mercury(II) Ions Using Dual-Stabilizer-Capped CdTe Quantum Dots

“…It is obvious that the PL intensity of the mixture is very sensitive to Cu 2+ ions and gradually 2+ ions, respectively. The detection limit is estimated to be 41.6 pM at a signal-to-noise ratio of 3, which is much lower than that of previous PL-based Cu 2+ ion sensors [15,19,20,29,31]. As for Hg 2+ ions, the relative PL quenching of CdTe quantum dots in the presence of Hg 2+ ions is presented in Fig.…”

“…In contrary, the PL chemosensors by the dual-stabilizer-capped quantum dots may be a conceivable strategy to overcome the problems toward the picomolar level detection of multiple heavy metal ions. The development of transition heavy metal ion chemosensors with high sensitivity, selectivity and ultratrace (picomolar) level detection has been receiving considerable attention due to their potential to do great damage to the environment and the human body even at low concentrations [18][19][20][21]. Among the various transition, heavy metal ions, copper(II) (Cu 2+ ) and mercury(II) (Hg 2+ ) ions are significant environmental contamination and two essential trace elements in biological systems [22].…”

Design and Synthesis of Fluorescent Carbon-Dot Polymer and Deciphering Its Electronic Structure

“…The polymeric form of carbon dots i.e. pCDs, is barely reported till date [1][2][3][4][5][6] . Moreover, our understanding regarding their electronic structure and origin of excitation dependent photoluminescence (EDPL) remains vague due to their highly complex nanostructured framework 7 .…”