High temperature is required in carbon fiber synthesis in the carbonization step. However, direct high-temperature heating without the presence of additive materials would affect the yield and structure of carbon fibers produced. Thus, this study aims to synthesize carbon fibers from poly-vinyl alcohol (PVA), as the precursor and reducing agent, using silver nanoparticles (SNP) from silver nitrate (AgNO3) as additives. The pre-treatment of PVA was performed in three steps, i.e., mixing PVA/AgNO3, electrospinning, and iodination. The interaction of PVA and AgNO3 was assessed by FTIR, and SEM was used to characterize the electro-spun fibers prior and after iodination; Raman spectrophotometer was carried out to confirm the yield of carbon fibers. There was reduction in oxygen groups (3000–3800 cm−1) and emergence of -C=O (1100 cm−1) and -C=C- (1627 cm−1) functional groups, indicating formation of carbon layers. Based on the DT/GA results, the silver nanoparticles reduce the need of high temperature with optimum carbonization at 350°C and lead to the formation of more regular graphene layers. Graphene layers with a size distribution of 0.438 nm and well-organized structures were successfully formed, and the Raman shifting showed higher intensities of G and G’ bands in the presence of Ag. Based on DT/GA results, the yield of carbon fibers with iodinated PVA fibers and SNP as additive had higher rates around 800 µg/min, reaching 33% at 500°C. Thus, it is demonstrated that iodinated PVA/AgNO3 samples can significantly improve carbon fiber yield at low temperatures.
The synthesis of modified carbon dots (N-CDs) from nanocrystalline cellulose, as the carbon source, with the combination of urea and ethylenediamine, as nitrogen dopant agents, was successfully carried out by pyrolysis at 300 °C. The N-CDs dispersed in both ethanol and distilled water generated bright blue fluorescent color under a UV lamp at 365 nm wavelength with a 29% quantum yield value. FTIR analysis confirmed that the surfaces of carbon dots were modified by amine and N-doped groups on the carbon ring structure and the data from the UV-VIS spectrum also showed that assumption. Produced N-CDs had a size distribution of 2-5 nm with an average diameter of around 3.4 nm. The ability of N-CDs as a detector was explored from the fluorescence quenching by Hg 2+ ions, in which it reached 40%. The determination of Hg 2+ could be completed in 10 min with a wide linearity range from 0-100 µM and a detection limit of 59 µM by the static quenching process.
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