Synthesis Of C-dots Research Articles

Carbon dots from sour whey to develop a novel antimicrobial packaging for fiordilatte cheese

In this study, monodispersed and quasi-spherical C-Dots with an average size of 7.2 nm were successfully synthesized from sour whey solution by a hydrothermal method (200 °C for 9 h) for fiordilatte cheese packaging. C-Dots (2500 and 5000 mgL-1) were added to the cheese through an alginate-based coating or directly to the cheese brine. No significant changes in TM4 cell viability were observed at concentrations lower than 10,000 mgL-1. Microbiological and sensory properties of cheese coated and uncoated with C-Dots indicate a substantial preserving effect of the C-Dots. The uncoated control fiordilatte exhibited unacceptable levels of microbial proliferation within 3.5 days. Conversely, the coated cheese remained within acceptable limits, effectively doubling its shelf life compared to the control, primarily due to the coating protection rather than the addition of C-Dots. When compared to the control fiordilatte, the addition of C-Dots in the brine at 5000 mgL-1 resulted in an extension of over 10 days in cheese shelf life. Considering the significance of the sustainable approach in C-Dots synthesis and the exceptional use of C-Dots in the food industry, these findings hold great potential in terms of research and industrial applications.

Synthesis of carbon dots based on corn cobs as heavy metal ion sensors using the microwave method

<p class="Abstract">Carbon dots (CDots) are nanomaterials that can be applied as a heavy metal ion sensor. CDotss ware synthesized from corncobs which are abundant and underutilized. This study aims to determine the effect of variations in the concentration of corncobs on optical properties of CDots and their application as Fe<sup>3+</sup> ion sensors. CDots were synthesized with variations of corncobs’ mass 5, 10, 15, and 20 g and variations in metal ion concentrations 10<sup>-7</sup>, 10<sup>-6</sup>, 10<sup>-5</sup>, 10<sup>-4</sup>, and 10<sup>-3</sup> M. The success of CDots synthesis was indicated by luminescence green when exposed to UV light. UV-Vis characterization showed that the greater the concentration of CDots could cause a shift in the absorbance peak towards longer wavelengths and peaks at wavelengths of 290, 291, 295, 298, and 323 nm, respectively. Photoluminescence (PL) characterization showed CDots emission peaks at 511, 504, 503, and 495 nm. The greater the concentration of CDots can cause a shift in the emission peak towards a shorter wavelength and increase the intensity. The PL characterization can identify the presence of Fe<sup>3+</sup> metal ions with a wavelength shift that indicates a change in the CDots structure. The synthesis of CDots from corncobs have great potential to be applied as sensors.</p>

Formation, photoluminescence and in vitro bioimaging of polyethylene glycol-derived carbon dots: The molecular weight effects

Despite their wide applications, less effort has been devoted for the elucidation of synthesis and photoluminescence mechanism of carbon dots (C-dots), which significantly limits their further developments. In this study, a series of C-dots were prepared from polyethylene glycol (PEG) of different molecular weights (M.W.), and the effects of PEG M.W. on the formation, structural and optical properties of C-dots were carefully investigated. Our study shown that the synthesis of C-dots from PEG went through an “oxidized decomposition – crosslinking – carbonization” process, and as such, the M.W. had a significant influence on the particle sizes, fluorescence intensities, surface chemistry, thermal stability, and bioimaging capabilities of C-dots. These C-dots demonstrated extremely low cytotoxicity and were good agents for cellular bioimaging.

Au/Cdot-Nanohybrid Electrocatalyst Synthesized by Rice-Straw-Derived Carbon Dots as a Reducing Agent for Improved Hydrogen Evolution Reactions

We report a facile method by which to synthesize Au/Cdot nanohybrids using carbon dots (Cdots) obtained from rice straw as a direct reducing agent as well as a stabilizer. Rice-straw-derived Cdots possess oxygen-containing functional groups that act as an electron-donating source to reduce Au3+ to Au0 without the use of chemical reagents for the reduction of Au precursors. Additionally, the strong Au-carbon interaction promotes a high electron transfer of the Au/Cdot nanohybrid electrocatalyst, resulting in enhanced performance of the hydrogen evolution reaction (HER). The overpotential is 150 mV at a current density of 10 mA·cm−2 and the TOF value is 0.06·s−1, representing the most outstanding HER performance among Au-based catalysts as a non-Pt HER electrocatalyst. The HER activity is stably maintained for 2000 cycles as well as for 48 h. The synthesis of Cdots, the hybridization of Au/Cdot electrocatalyst, and the production of clean hydrogen fuel using Au/Cdots are zero CO2 emission strategies, not only preventing the emission of pollutants but also satisfying the energy needs of humankind.

Molecular Fluorophores Self-Organize into C-Dot Seeds and Incorporate into C-Dot Structures.

Various molecular fluorophores have been identified to be present during carbon-dot (C-dot) syntheses. However, the organization of such fluorophores in C-dots is still unknown. We study the self-assembly of 5-oxo-1,2,3,5-tetrahydroimidazo-[1,2-α]-pyridine-7-carboxylic acid (IPCA), a molecular fluorophore present during the synthesis of C-dots from citric acid and ethylenediamine. Both forms of IPCA (neutral and anionic) show a tendency to self-assemble into stacked systems, forming seeds of C-dots during their synthesis. IPCA also interacts with graphitic C-dot building blocks, fragments easily, and incorporates into their structures via π-π stacking. Both IPCA forms are able to create adlayers internally stabilized by an extensive hydrogen bonding network, with an arrangement of layers similar to that in ordinary graphitic C-dots. The results show the tendency of molecular fluorophores to form organized stacked seeds of C-dots and incorporate into C-dot structures. Such noncovalent structures can be further covalently interlinked via the carbonization process during C-dot growth.

Facile synthesis of luminescent carbon dots from mangosteen peel by pyrolysis method

Carbon dots (C-Dots) from mangosteen peel has been synthesized by pyrolysis method. Synthesis of C-Dots is done using precursor solution which is prepared from extract of mangosteen peel as carbon source and urea as passivation agent. C-Dots is successfully formed with absorbance spectra at wavelength 350–550 nm. Urea affects to the formed C-Dots, while the absorbance and the luminescent spectra are independent toward urea. C-Dots from extract of mangosteen peel has size in range ~2–15 nm. The absorbance peaks of C-Dots shows significant wavelength shift at visible region as the increasing of synthesized temperature. Shift of wavelength absorbance indicates the change of electronic transition of C-Dots. Meanwhile, the luminescent of C-Dots can be controlled by synthesized temperature as well. C-Dots luminescent were increasing as higher synthesized temperature. It was shown by the shift of wavelength emission into shorter wavelength, 465 nm at 200 °C, 450 nm at 250 °C, and 423 nm at 300 °C. Synthesized temperature also affects size of C-Dots. It has size ~10–15 nm at 200 °C, ~7–11 nm at 250 °C and ~2–4 nm at 300 °C. In addition, temperature corresponds to the structure of carbon chains and C–N configuration of formed C-Dots from mangosteen peel extract.

Characterization and Analytical Separation of Fluorescent Carbon Nanodots

Carbon nanodots (C-dots) are recently discovered fluorescent carbon nanoparticles with typical sizes of <10 nm. The C-dots have been reported to have excellent photophysical and chemical characteristics. In recent years, the advances in the development and improvement in C-dots synthesis, characterization, and applications are burgeoning. In this review, we introduce the most commonly used techniques for the characterization of C-dots. The characterization techniques for C-dots are briefly classified, described, and illustrated with applied examples. In addition, the analytical separation methods for C-dots (including electrophoresis, chromatography, density gradient centrifugation, differential centrifugation, solvent extraction, and dialysis) are included and discussed according to their analytical characteristics. The review concludes with an outlook towards the future developments in the characterization and the analytical separation of C-dots. The comprehensive overview of the characterization and the analytical separation techniques will safeguard people to use each technique more wisely.

Capillary electrophoretic study of amine/carboxylic acid-functionalized carbon nanodots

Capillary zone electrophoresis (CZE) coupled with UV absorption and laser-induced fluorescence detections has been applied to study the complexity of carbon nanodots (C-dots) products synthesized with microwave-assisted pyrolysis of citric acid (CA) and 1,2-ethylenediamine (EDA). The effects of pH and concentration of run buffer on the CZE separation of C-dots are studied in detail. The optimal acetate run buffer (30mM, pH 3.6) is subsequently employed to investigate the effect of reaction time and mole ratio of amine (NH2) to carboxylic acid (COOH) moieties of the precursors on the C-dots species present in C-dots products. Our results confirm that the synthesis of C-dots could be improved by lengthening the microwave irradiation time and optimizing the initial mole ratio of NH2/COOH in the precursors. Negatively charged C-dots are obtained only when the amount of CA exceeds that of EDA, i.e., the mole ratio of NH2/COOH is 0.25–0.80. By contrast, when the quantity (mole) of NH2 in EDA is equal to or larger than that of COOH in CA, only positively charged and neutral C-dots species are formed, inferring that the C-dots species are predominantly covered by the surface-attached ammonium and amido moieties. This work highlights the merit of CZE to identify the composition of an as-prepared C-dots product which is pretty much dependent on the mole ratio of NH2/COOH. It is anticipated that our CZE methodology will open a new avenue in optimizing the synthetic conditions for producing specific C-dots of desired composition.