Heteroatom doped carbon dots for fluorescence-based sensing applications: Recent development and bibliometric analysis

Unlike traditional analytical methods for sensing of various analytes, fluorescent sensors offer a more convenient, eco-friendly, and sustainable approach for the sensing of various analytes and thereby help in environmental monitoring. Fluorescent carbon dots (CDs) are a type of 0 D carbon-containing nanomaterials, which are found to occur as one of the important propitious photoluminescent materials owing to their superior optical, chemical, electrical properties, easy synthesis routes, and have been extensively utilized for sensing of different analytes. In recent studies, most of the undoped or pristine CDs have been reported; however, they have disadvantages of low fluorescence quantum yield (QY), limited sensitivity and selectivity, poorer charge-transfer efficiency, narrower tunability of optical properties, and higher probability of non-radiative recombination. To address those limitations of undoped CDs, heteroatom doping has been employed in many of the studies, which is considered to be an efficient approach to tune the physiochemical properties of CDs. They are produced by the introduction of metal, non-metal, transition metal, or lanthanoids, either independently or by integration of two or multiple elements. Doping with heteroatoms significantly change the electronic, chemical and optical characteristics of pristine CDs by implementing n/p-type charge carrier, functional groups and tuning energy band. In this review, the various doping strategies and synthesis methods for the production of doped CDs are provided. The various sensing mechanism and their diverse applications in sensing of heavy metal ions, antibiotics, pesticides, dyes, as well as other species is also provided. Moreover, a bibliometric analysis is also provided in order to get meaningful insights about the current trends, key contributing countries, upcoming challenges and area of interest in the topic. This review will provide new methodologies or research methods regarding the production of doped CDs and their application as an effective fluorescent probe for sensing of various analytes viz., heavy metals, pesticides, antibiotics, dyes, and other types of analytes.