Abstract
The fluorescent carbon quantum dots (CQDs) represent an emerging subset of carbonaceous nanomaterials, recently becoming a powerful tool for biosensing, bioimaging, and drug and gene delivery. In general, carbon dots are defined as zero-dimensional (0D), spherical-like nanoparticles with <10 nm in size. Their unique chemical, optical, and electronic properties make CQDs versatile materials for a wide spectrum of applications, mainly for the sensing and biomedical purposes. Due to their good biocompatibility, water solubility, and relatively facile modification, these novel materials have attracted tremendous interest in recent years, which is especially important for nanotechnology and nanoscience expertise. The preparation of the biomass-derived CQDs has attracted growing interest recently due to their low-cost, renewable, and green biomass resources, presenting also the variability of possible modification for the enhancement of CQDs’ properties. This review is primarily focused on the recent developments in carbon dots and their application in the sensing of different chemical species within the last five years. Furthermore, special emphasis has been made regarding the green approaches for obtaining CQDs and nanomaterial characterization toward better understanding the mechanisms of photoluminescent behavior and sensing performance. In addition, some of the challenges and future outlooks in CQDs research have been briefly outlined.
Highlights
Carbon-based nanomaterials have recently gained significant research interest due to their extraordinary properties, including thermal stability, mechanical strength, good biocompatibility, and non-toxicity, which opens up a wide range of applications in various research fields [1]
A great deal of effort has been devoted into exploring new and green methods for Carbon quantum dots (CQDs) preparation with an emphasis on the environmentally friendly approach, simplicity, high quantum yield (QY), uniform size distribution, and large-scale production. It is well-known that the synthesis of transition metal quantum dots (such as cadmium selenide (CdSe), cadmium telluride (CdTe), cadmium sulfide (CdS), etc.) exhibits good performance in the terms of stability and optical characteristics; high synthetic costs and low biocompatibility has limited their application in biomedicine, more precisely in theranostic purposes [12]
The sensing mechanism related to quercetin detection was proposed, and it was concluded that an inner filter effect (IFE) and static quenching effect are responsible for the fluorescence behavior of the nitrogen-doped carbon quantum dots (N-CQDs)-QT system, as zeta-potential measurements indicated that no complexation could occur
Summary
Carbon-based nanomaterials have recently gained significant research interest due to their extraordinary properties, including thermal stability, mechanical strength, good biocompatibility, and non-toxicity, which opens up a wide range of applications in various research fields [1]. A great deal of effort has been devoted into exploring new and green methods for CQDs preparation with an emphasis on the environmentally friendly approach, simplicity, high QY, uniform size distribution, and large-scale production It is well-known that the synthesis of transition metal quantum dots (such as cadmium selenide (CdSe), cadmium telluride (CdTe), cadmium sulfide (CdS), etc.) exhibits good performance in the terms of stability and optical characteristics; high synthetic costs and low biocompatibility has limited their application in biomedicine, more precisely in theranostic purposes [12]. The emphasis has been placed on the recent developments in the synthesis as well as potential modifications, doping, functionalization, and characterization of CQDs and biomass-derived CQDs with the aim of properties enhancement, which could provide new insights into the mechanisms and future detection methods of different chemical species with superior performance Their optical and chemical properties, emphasizing the advances and novel green approaches toward obtaining fluorescent nanomaterials with a wide spectrum of applications in sensing, are discussed in detail. New perspectives are brought up in order to emphasize the numerous opportunities, as well as the challenges that are still being raised and are critical toward discovering the full potential of these powerful nanomaterials
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