Mohammed Sewara J, Omer Khalid M, Hawaiz Farouq E
Department of Chemistry, College of Science, University of Sulaimani Qlyasan Street Sulaimani 46002 Kurdistan Regional Government Iraq
Anesthesia Department, College of Health Sciences, Cihan University Sulaimaniya Sulaimaniya 46001 Kurdistan Region Iraq.
RSC Adv. 2023 May 10;13(21):14340-14349. doi: 10.1039/d3ra01646c. eCollection 2023 May 9.
A well-explained mechanism for synthesizing carbon dots (CDs) is not yet explored and is still a subject of great debate and challenge. This study used a one-step hydrothermal method to prepare highly efficient, gram-scale, excellent water solubility, and blue fluorescent nitrogen-doped carbon dots (NCDs) with the particle size average distribution of around 5 nm from 4-aminoantipyrine. The effects of varying synthesis reaction times on the structure and mechanism formation of NCDs were investigated using spectroscopic methods, namely FT-IR, C-NMR, H-NMR, and UV-visible spectroscopies. The spectroscopic results indicated that increasing the reaction time affects the structure of the NCDs. As the hydrothermal synthesis reaction time is extended, the intensity of the peaks in the aromatic region decreases, and new peaks in the aliphatic and carbonyl group regions are generated, which display enhanced intensity. In addition, the photoluminescent quantum yield increases as the reaction time increases. The presence of a benzene ring in 4-aminoantipyrine is thought to contribute to the observed structural changes in NCDs. This is due to the increased noncovalent π-π stacking interactions of the aromatic ring during the carbon dot core formation. Moreover, the hydrolysis of the pyrazole ring in 4-aminoantipyrine results in polar functional groups attached to aliphatic carbons. As the reaction time prolongs, these functional groups progressively cover a larger portion of the surface of the NCDs. After 21 h of the synthesis process, the XRD spectrum of the produced NCDs illustrates a broad peak at 21.1°, indicating an amorphous turbostratic carbon phase. The -spacing measured from the HR-TEM image is about 0.26 nm, which agrees with the (100) plane lattice of graphite carbon and confirms the purity of the NCD product with a surface covered by polar functional groups. This investigation will lead to a greater understanding of the effect of hydrothermal reaction time on the mechanism and structure of carbon dot synthesis. Moreover, it offers a simple, low-cost, and gram-scale method for creating high-quality NCDs crucial for various applications.
尚未探索出一种对碳点（CDs）合成机制的详尽解释，这仍然是一个备受争议和挑战的课题。本研究采用一步水热法，以4-氨基安替比林为原料制备了高效、克级规模、具有优异水溶性且粒径平均分布约为5 nm的蓝色荧光氮掺杂碳点（NCDs）。利用光谱方法，即傅里叶变换红外光谱（FT-IR）、碳核磁共振光谱（C-NMR）、氢核磁共振光谱（H-NMR）和紫外可见光谱，研究了不同合成反应时间对NCDs结构和机制形成的影响。光谱结果表明，延长反应时间会影响NCDs的结构。随着水热合成反应时间的延长，芳香区域的峰强度降低，脂肪族和羰基区域出现新的峰，且强度增强。此外，光致发光量子产率随反应时间增加而提高。4-氨基安替比林中苯环的存在被认为是导致NCDs中观察到的结构变化的原因。这是由于在碳点核心形成过程中芳香环的非共价π-π堆积相互作用增加。此外，4-氨基安替比林中吡唑环的水解导致极性官能团连接到脂肪族碳上。随着反应时间延长，这些官能团逐渐覆盖NCDs表面的更大比例。在合成过程21小时后，所制备的NCDs的X射线衍射光谱在21.1°处显示出一个宽峰，表明为非晶态乱层碳相。从高分辨透射电子显微镜（HR-TEM）图像测得的层间距约为0.26 nm，这与石墨碳的（100）面晶格相符，并证实了表面覆盖有极性官能团的NCD产物的纯度。这项研究将有助于更深入地理解水热反应时间对碳点合成机制和结构的影响。此外，它提供了一种简单、低成本且克级规模的方法来制备对各种应用至关重要的高质量NCDs。
