One-Pot Synthesis of Fluorescent Carbon Dots from Orange Waste Peels

Tomato waste (TW) was employed as a sustainable source for the synthesis of fluorescent carbon dots (CDs) via a microwave-assisted hydrothermal carbonization (Mw-HTC) method, aiming at its valorization. Several amines were used as nitrogen additives to enhance the fluorescence quantum yield (QY) of CDs, and a set of reaction conditions, including additive/TW mass ratio (0.04–0.32), dwell time (15–60 min), and temperature (200–230 °C) of the HTC process, were scrutinized. The structural analysis of the tomato waste carbon dots (TWCDs) was undertaken by FTIR and 1H NMR techniques, revealing their most relevant features. In solid state, transmission electron microscopy (TEM) analysis showed the presence of nearly spherical nanoparticles with an average lateral size of 8.1 nm. Likewise, the topographical assessment by atomic force microscopy (AFM) also indicated particles’ heights between 3 and 10 nm. Their photophysical properties, revealed by UV–Vis, steady-state, and time-resolved fluorescence spectroscopies, are fully discussed. Higher photoluminescent quantum yields (up to 0.08) were attained when the biomass residues were mixed with organic aliphatic amines during the Mw-HTC process. Emission tunability is a characteristic feature of these CDs, which display an intensity average fluorescence lifetime of 8 ns. The new TWCDs demonstrated good antioxidant properties by the ABTS radical cation method (75% inhibition at TWCDs’ concentration of 5 mg/mL), which proved to be related to the dwell time used in the CDs synthesis. Moreover, the synthesized TWCDs suppressed the growth of Escherichia coli and Staphylococcus aureus at concentrations higher than 2000 μg/mL, encouraging future antibacterial applications.

Microwave-assisted synthesis and formation mechanism of fluorescent carbon dots from starch

Facile approach for green synthesis of fluorescent carbon dots from Manihot esculenta and their potential applications as sensor and bio-imaging agents

Facile and green synthesis of fluorescent carbon dots with tunable emission for sensors and cells imaging

In situ photochemical synthesis of fluorescent carbon dots for optical sensing of hydrogen peroxide and antioxidants

Facile synthesis of fluorescence carbon dots from sweet potato for Fe3 + sensing and cell imaging

Green synthesis of carbon dots originated from Lycii Fructus for effective fluorescent sensing of ferric ion and multicolor cell imaging

Rapid and green synthesis of fluorescent carbon dots from starch for white light-emitting diodes

Har Gabur is the carbide obtained from pig manure by burning. The fluorescent carbon dots (CDs) of Har Gabur were successfully synthesized through simulating the digestion process of human gastrointestinal tract. Transmission Electron Microscope (TEM) analysis showed that the average size of the prepared Har Gabur CDs was 4 nm, with good solubility in water and strong fluorescence under UV irradiation. The X-ray and Raman results showed that the Har Gabur CDs were mainly composed of oxygen “O” and carbon “C” elements, in the forms of “C=O” and “C-O.” The bond energy results showed that the nitrogen “N” atom presented as “C-N” form, which indicated that Har Gabur CDs also contain “N.” In photobleaching assay, Har Gabur CDs showed excellent light stability compared with ordinary organic dye, fluorescein, and Rhodamine B. The fluorescence intensity of Har Gabur CDs was fairly stable within a wide pH range of 3–10. When L-lysine and L-cysteine were applied for the passivation stage, the relative quantum yields were improved by 1.53 and 3.68 times, respectively. Finally, the fluorescence properties of Har Gabur CDs were tested in cells and zebrafish, illustrating that Har Gabur CD has potential in the application of biological labeling and imaging.

The study is devoted to the assessment of the thermodynamic efficiency of the hydrothermal carbonization (HTC) method to produce bio-coal from wet organic waste (biomass). The HTC method is a process of thermochemical conversion of biomass into solid biofuel (bio-coal) as a result of its heating up to 150–280°С in the presence of water. The competitive advantages of the HTC method and the properties of bio-coal produced by this method from various organic waste are analyzed. The energy consumption values for implementation of the HTC process and the conventional torrefaction method are compared. It is demonstrated that the energy consumption in the production of bio-coal by the HTC method is several times lower than in the torrefaction process since water heated at a high pressure remains a liquid. This, in turn, offers a high potential for recovery of thermal energy (approximately 87%) in the HTC process. The heating value of the produce bio-coal is as high as 27 MJ/kg, which is comparable with that of commercial power coals. An analysis of the properties of biochar produced in the HTC process suggests that, in principle, it may be burned at coal-fired power stations together with conventional coal (if proper gas treatment equipment is available). The HTC method can be used for pretreatment of water-rich organic wastes and biomass to produce a quality fuel and a water solution that can be used as a base for production of fertilizers.

Eco friendly synthesis of fluorescent carbon dots for the sensitive detection of ferric ions and cell imaging

A robust method for the synthesis of fluorescent carbon dots (C dots) from camphor, which provides an insight into the mechanism of C dot formation, is reported.

Green and sustainable synthesis of fluorescent carbon dots from crown daisy for information encryption application

Facile synthesis of fluorescent carbon dots using watermelon peel as a carbon source

In recent times, much attention has been drawn to the synthesis of carbon dots from agro waste since they are a cheap source, readily available, non-toxic and in most instances disposed of as waste. Yet, the synthesis of fluorescent carbon dots at low temperatures from agro waste remain a challenge. Herein, we report for the first time on a sucessful synthesis of flourescent carbon dots, with average size 4.7 nm, at low temperature of only 100 °C using hydrothermal method from pomegranate peels as a sole precursor. The crystal structure and the morphological features of the synthesized dots were characterized by XRD, UV-vis absorption spectroscopy, photoluminescence (PL), nanosecond fluorescence lifetime, FTIR and Zeta potential measurments. The synthesized dots showed bluish emission at 440 nm, when excited at a wavelength of 360 nm, with relatively long decay lifetime of 7.4 ns.