Synthesis of Carbon Quantum Dots with Special Reference to Biomass as a Source - A Review

Abstract

Quantum dots (QDs) have received much attention due to their extraordinary optical application in medical diagnostics, optoelectronics and in energy storage devices. The most conventional QDs are based on semiconductors that comprise heavy metals whose applications are limited due to toxicity and potential environmental hazard. Of late, researchers are focusing on carbon-based quantum dots, which have recently emerged as a new family of zero-dimensional nanostructured materials. They are spherical in shape with a size below 10 nm and exhibit excitation-wavelength-dependent photoluminescence (PL). Carbon quantum dots (CQDs) have unique optical, photoluminescence and electrochemical properties. They are environment-friendly with low toxicity as compared to toxic heavy metal quantum dots. Generally, CQDs are derived from chemical precursor materials, but recently researchers have focused their attention on the production of CQDs from waste biomass materials due to the economic and environmental exigency. In this review, recent advances in the synthesis of CQDs from waste biomass materials, functionalization and modulation of CQDs and their potential application of biosensing are focused. This review also brings out some challenges and future perspectives for developing smart biosensing gadgets based on CQDs.

Recent advances of biomass carbon dots on syntheses, characterization, luminescence mechanism, and sensing applications

“…Other preparation methods of biomass carbon dots have been discussed in detail in some reports. [ 69,70 ] The following will focus on the different chemical synthesis methods including hydrothermal method, solvothermal method, chemical oxidation method and pyrolysis method.…”

Synthesis and Characterization of Green Carbon Dots for Scavenging Radical Oxygen Species in Aqueous and Oil Samples

“…Furthermore, due to their ability for scavenging reactive oxygen species, CDs demonstrate significant potential, particularly for biological applications [ 5 , 6 , 7 ]. CDs can be prepared from different natural resources such as albumin, chitosan, gelatin, peels of fruits, grains or other plant matters as well from vegetable wastes (e.g., apple or grape pomace), which make them “green” nanoparticles, as described in several excellent reviews devoted to the synthesis of CDs from green biomass wastes, their surface modification to improve their physico-chemical properties and their applications in bioimaging, biosensing, catalysis, forensics and optoelectronics [ 8 , 9 , 10 , 11 , 12 ]. The study of CDs as antioxidant nanoparticles is still in its infancy and some examples are exemplified in Table 1 , in which it could be observed that most of precursors used to produce CDs with antioxidant properties are vegetal-based materials.…”

Biomass‐derived Carbon Quantum Dots – A Review. Part 1: Preparation and Characterization

“…Carbon quantum dots (∼1 nm) were discovered accidently by Xu et al. during the preparation of single‐walled carbon nanotubes through arc discharge method 19, 20. Carbon quantum dots (CQDs) 19, carbon nitride dots (CNDs) 21, carbon nanodots (CNDs) 19, carbon dots (CDs) 22, carbon nanocrystals (CNCs) 23, and graphene quantum dots (GQDs) 24 are a group of carbon‐based nanomaterials whose dimensions are in the size range of 1–10 nm and are in the category of 0D carbon materials 25, 26.…”

“…during the preparation of single‐walled carbon nanotubes through arc discharge method 19, 20. Carbon quantum dots (CQDs) 19, carbon nitride dots (CNDs) 21, carbon nanodots (CNDs) 19, carbon dots (CDs) 22, carbon nanocrystals (CNCs) 23, and graphene quantum dots (GQDs) 24 are a group of carbon‐based nanomaterials whose dimensions are in the size range of 1–10 nm and are in the category of 0D carbon materials 25, 26. Graphene and graphene‐based material has nanostructures but it has different nomenclature, which reveals that the carbon material contains a single or a few monolayers of graphene.…”

“…But, the process of refining them from crude biomass is cumbersome. Generally, hydrothermal carbonization (HTC) 19, 44–46 and pyrolysis processes 47–49 are employed for this purpose as they are cost‐effective and convenient for mass production without the involvement of any refractory solvents 19, 39. CQDs have many hydroxyl‐amino, carbonyl, epoxide and carboxylic acid moieties at their surface (i.e., functionalized CQDs) and basal planes that act as reaction sites which offer excellent water solubility and suitability for subsequent functionalization with different functional groups of molecules 19, 46, 50.…”