Abstract
Carbon quantum dots (CQDs), a novel class of zero-dimensional carbon nanostructures with diameters below 10 nm, have recently come into existence. The authors have synthesized and analyzed carbon-based quantum dots from aloe-vera, rice, and sugar. The characterization of these quantum dots is done via UV-visible spectrophotometer. The quantum dots that are made from chemicals are toxic and are harmful to both humans and animals. However, the carbon quantum dots (CQD) which they have synthesized in this research work are bio-compatible, less toxic, and have the property of high aqueous dispersibility. CQDs are being used in various fields of applications such as bio-imaging, medical diagnosis, bio-sensing, chemical sensing, photo catalysis, and photovoltaic devices. This study helps the scientific community to understand the nature of carbon quantum dots and gives a brief idea of suitable materials that create CQD.
TopIntroduction
Now-a-days, the usage of chemicals has increased to a great extent. For instance, the biomedical industry makes extensive use of toxic semiconductor QDs including cadmium selenide (CdSe), cadmium sulphide (CdS), silver sulphide (Ag2S), and PbSe (lead selenide) (Hetsch et al., 2013; Prabaharan & Mano, 2006; Sun et al., 2013; Yang et al., 2019). These chemicals are toxic and are not eco-friendly as they may cause harm to people if they can be used frequently. QD degradation with release of free cadmium and generation of reactive oxygen species makes them toxic. Noble metal nanoparticles, namely silver and gold nanoparticles with alginate residues, are used because of their improved effectiveness in medication delivery and wound healing applications (Brus, 1984; Brus, 1986; Kramer & Sargent, 2011; Sun et al., 2006). The cytotoxicity of such noble metal nanoparticles is not entirely absent. The level of pollution has been increasing (water, air, soil pollution) due to the increase in the usage of chemicals. The health of humans and animals are also at risk. Some of the species have become endangered. In the realm of biomedical application, the nearly non-toxic, luminous CQDs are likewise regarded as the ideal substitute for hazardous semiconductor QDs like cadmium selenide (CdSe), cadmium sulphide (CdS), silver sulphide (Ag2S), and lead selenide (PbSe) (Ekimov & Onushchenko, 1981; Kim, Jo, Yoon et al, 2019; Tang et al., 2012; Zhang et al., 2019). These functional nanoparticles are widely used as a promising candidate in bio-imaging, sensors, drug delivery, ink, photo catalysis, and optoelectronics because of their distinctive properties, including tunable photoluminescence, photo stability, low cytotoxicity, robust chemical inertness, and excellent biocompatibility, etc. (Kim, Han, Yang et al, 2019; Moraitis et al., 2019; Russo et al., 2007; Rybak, 2006).
Key Terms in this Chapter
Absorption: A physical or chemical phenomena or process known as absorption occurs when atoms, molecules, or ions enter a liquid or solid material's bulk phase.
Carbonization: By use of destructive distillation, carbonization refers to the conversion of organic materials like dead plants and animal remains into carbon.
UV-Visible Spectrophotometer: In the ultraviolet and the entire, neighboring visible parts of the electromagnetic spectrum, absorption spectroscopy or reflectance spectroscopy is referred to as UV-visible spectrophotometer.
Energy Band Gap: A band gap, also known as an energy gap in solid-state physics, is an energy range in a solid where no electronic states can exist.
Quantum Dot: A quantum dot is a semiconductor nanometer-sized particle that typically has a core-shell structure.
Nano-Materials: Nano-materials, in general, refer to substances with a unit size between 1 and 100 nm.
Ultrasonication: In order to extract different substances from plants, microalgae, and seaweeds, sonication is the process of using sound energy to stir up particles in a sample. Since ultrasonic frequencies are typically employed, the procedure is also referred to as “ultrasonication” or “ultra-sonication.”