Facile Synthesis of Multifunctional Carbon Dots from Spent Gromwell Roots and Their Application as Coating Agents

Spent Gromwell root-based multifunctional carbon dots (g-CDs) and sulfur-functionalized g-CDs (g-SCDs) were synthesized using a hydrothermal method. The mean particle size of g-CDs was confirmed to be 9.1 nm by TEM (transmission electron microscopy) analysis. The zeta potentials of g-CDs and g-SCDs were mostly negative with a value of -12.5 mV, indicating their stability in colloidal dispersion. Antioxidant activities were 76.9 ± 1.6% and 58.9 ± 0.8% for g-CDs, and 99.0 ± 0.1% and 62.5 ± 0.5% for g-SCDs by 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging tests, respectively. In addition, the bathochromic shift of g-CDs is observed when their emission peaks appear at a higher wavelength than the excitation peaks. The prepared g-CDs and g-SCDs solutions were used as a coating agent for potato slices. The browning index of the control potato slices increased significantly from 5.0 to 33.5% during 24 to 72 h storage. However, the sample potato slices coated with g-CDs or g-SCDs suppressed the increase in the browning index. In particular, the browning index of the potato slices coated with g-SCDs ranged from 1.4 to 5.5%, whereas the potato slices coated with g-CDs had a browning index ranging from 3.5 to 26.1%. The g-SCDs were more effective in delaying oxidation or browning in foods. The g-CDs and g-SCDs also played a catalytic role in the Rhodamine B dye degradation activity. This activity will be useful in the future to break down toxins and adulterants in food commodities.

Analysis of sulfur compounds for crude oil fingerprinting using gas chromatography with sulfur chemiluminescence detector

Oil spills are a severe problem worldwide due to the resulting damage to marine and coastal ecosystems and to local economies. Identification of the source of spilled oils can be challenging, especially if the oils have undergone severe weathering. Due to their high durability, biomarker compounds (e.g. hopanes, steranes) are widely used for oil fingerprinting. Some sulfur-containing heterocyclic compounds e.g. alkylated dibenzothiophenes are also considered to be highly resistant. In this study, the use of Gas Chromatography with Sulfur Chemiluminescence Detection was investigated as a means of oil fingerprinting using the distribution the sulfur compounds in five different fresh and weathered crude oils. Chemometric analysis was also performed. The results indicate that the sulfur compounds distribution is unique for each crude oil. The distributions of the heavy sulfur compounds (i.e., C2DBTs and C3DBTs) are unchanged after weathering. Therefore, the GC-SCD technique can be considered to support the oil spill identification.