Self-Matrix N-Doped Room Temperature Phosphorescent Carbon Dots Triggered by Visible and Ultraviolet Light Dual Modes

• Published in: Nanomaterials (Basel, Switzerland) Switzerland), 2022-06, Vol.12 (13), p.2210
• Main Authors: Wang, Huiyong, Yu, Hongmei, AL-Zubi, Ayman, Zhu, Xiuhui, Nie, Guochao, Wang, Shaoyan, Chen, Wei
• Format: Article
• Language: English
• Subjects: Acids; Acrylic acid; Amino groups; Ammonium; anti-counterfeiting; Atomic energy levels; Carbon; Carbon dots; Crosslinking; Excitation; Fourier transforms; Hemodialysis; High pressure; High temperature; Hydrogen bonding; Hydrogen bonds; Light; Morphology; Oxalic acid; Particle size; Phosphorescence; Phosphors; Polymerization; Polymers; Polyvinyl alcohol; Room temperature; room temperature phosphorescence; Spectrum analysis; Triplet state; Ultraviolet radiation; Vibration; visible/ultraviolet light excitation
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano12132210

The synthesis of room temperature phosphorescent carbon dots (RTP-CDs) without any matrix is important in various applications. In particular, RTP-CDs with dual modes of excitation are more interesting. Here, we successfully synthesized matrix-free carbonized polymer dots (CPDs) that can generate green RTP under visible and ultraviolet light dual-mode excitation. Using acrylic acid (AA) and ammonium oxalate as precursors, a simple one-pot hydrothermal method was selected to prepare AA-CPDs. Here, acrylic acid is easy to polymerize under high temperature and high pressure, which makes AA-CPDs form a dense cross-linked internal structure. Ammonium oxalate as a nitrogen source can form amino groups during the reaction, which reacts with a large number of pendant carboxyl groups on the polymer chains to further form a cross-linked structure. The carboxyl and amino groups on the surface of AA-CPDs are connected by intermolecular hydrogen bonds. These hydrogen bonds can provide space protection (isolation of oxygen) around the AA-CPDs phosphor, which can stably excite the triplet state. This self-matrix structure effectively inhibits the non-radiative transition by blocking the intramolecular motion of CPDs. Under the excitation of WLED and 365 nm ultraviolet light, AA-CPDs exhibit the phosphorescence emission at 464 nm and 476 nm, respectively. The naked-eye observation exceeds 5 s and 10 s, respectively, and the average lifetime at 365 nm excitation wavelength is as long as 412.03 ms. In addition, it successfully proved the potential application of AA-CPDs in image anti-counterfeiting.