Microwave-assisted conversion of palm kernel shell biomass waste to photoluminescent carbon dots

Abstract

In the present work, palm kernel shell (PKS) biomass waste has been used as a low-cost and easily available precursor to prepare carbon dots (CDs) via microwave irradiation method. The impacts of the reacting medium: water and diethylene glycol (DEG), and irradiation period, as well as the presence of chitosan on the CDs properties, have been investigated. The synthesized CDs were characterized by several physical and optical analyses. The performance of the CDs in terms of bacteria cell imaging and copper (II) ions sensing and removal were also explored. All the CDs possessed a size of 6–7 nm in diameter and the presence of hydroxyl and alkene functional groups indicated the successful transformation of PKS into CDs with carbon core consisting of C = C elementary unit. The highest quantum yield (44.0%) obtained was from the CDs synthesised with DEG as the reacting medium at irradiation period of 1 min. It was postulated that the high boiling point of DEG resulted in a complete carbonisation of PKS into CDs. Subsequently, the absorbance intensity and photoluminescence intensity were also much higher compared to other precursor formulation. All the CDs fluoresced in the bacteria culture, and fluorescence quenching occurred in the presence of heavy metal ions. These showed the potential of CDs synthesised from PKS could be used for cellular imaging and detection as well as removal of heavy metal ions.

Co‐Hydrothermal Carbonization of Cotton Stalks and MnO2 for Direct Solar Steam Generation with High Efficiency

“…This can be attributed to two reasons: 1) the catalytic effect of organic acids as discussed earlier; 2) wood‐based biomass, such as CS, generates carbon dots (CDs, a type of carbon particles with a particle size of less than 20 nm and with fluorescent properties [ 49 ] ) during HTC, which has a certain photothermal property. [ 50 ] In this study, the HTF‐F was circulated. The organic matters contained in it are continuously decarboxylated, polymerized, and other complex reactions.…”

Effect of post-treatment drying processes on the optical and photothermal properties of carbon nanodots derived via microwave-assisted method

“…Other broad peaks between 2750-3050 cm -1 suggest that stretching vibrations of C-H are formed [23]. The absorption peak at 1650 cm -1 along with a small peak at 1770 cm -1 correspond to the C=O stretching vibration of carbonyl groups [17,34]. The existence of amide bonding in CNDs was confirmed by the presence of primary amide and secondary amide groups.…”

“…The former approach involves breaking down the higher dimensional carbonbased materials into a nanoscale particle through a physical or chemical synthesis, including laser ablation, electrochemical, or arc discharge [13][14][15]. On the other hand, bottom-up techniques, which include microwave, hydrothermal, solvothermal, plasma and chemical treatment, form CNDs from a smaller carbon-based molecule through carbonization and polymerization processes [16,17]. Among the methods mentioned above, the microwave was chosen due to rapid and uniform heating, energy saving, lower processing cost, and ease to scale up.…”

“…Among the methods mentioned above, the microwave was chosen due to rapid and uniform heating, energy saving, lower processing cost, and ease to scale up. Several works have revealed the successful synthesis of CNDs using microwave-assisted synthesis [10,[17][18][19].…”

Sulfur-doped carbon dots synthesis under microwave irradiation as turn-off fluorescent sensor for Cr(III)

“…In contrast, the bottom-up method is a method of arranging atoms or molecules to form the desired nanometer-sized particles like hydrothermal (Chahal et al 2020), solvothermal (Zheng et al 2020), pyrolysis (Li et al 2020), microwave, and sonochemical assisted (Ashritha et al 2021). The microwave method is a common bottom-up method for synthetic CDs due to being simple, fast, cost-efficient, and environmentally friendly (Ang et al 2020). This method works by vibrating the carbon chain to undergo rearrangement (Guan et al 2020).…”