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abstract: Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field.
author_names: Shi Ying Lim

Wei Shen

Zhiqiang Gao
title: Carbon quantum dots and their applications.
venue: Chemical Society reviews
year: 2015

abstract: Abstract Background In recent years, carbon quantum dots (CQDs) has received a lot of attentions owing to their great physical and optical properties. There are different kinds of carbon sources applied in various fields, however, CQDs used in the food industry have higher requirements for their safety. Therefore, it is the best way to use natural materials for preparing CQDs without the participation of chemicals. Up to now, there are many natural food products for preparing CQDs. However, food waste is often overlooked. Actually, food waste is rich in carbon sources. And the efficient utilization of food waste plays a positive role in economic benefit and environmental pollution. Scope and approach Proper use of food waste as carbon source not only facilitates food safety detection but also increases byproduct value. This paper was intended to review the research progress of food waste utilization as carbon precursor and applications in food safety detection. The approaches of preparing CQDs from different sorts of food wastes, the characteristics and applications of CQDs were described in detail. Particularly the applications in food quality and safety detection including food additives, heavy metal ions were also elaborated. Key findings and conclusions Currently, food waste as carbon source could be divided into plant byproducts, animal food byproducts and food processing byproducts. Moreover, there are many applications of food waste as carbon precursor in CQDs technology to detect food additives and heavy metal ions. However, detection of pathogens and other harmful substances in food industry is rare. Last but not least, it was concluded that food waste had potential to prepare CQDs and be applied to food safety detection.
author_names: Hanzhi Fan

Min Zhang

Bhesh R Bhandari

Chaohui Yang
title: Food waste as a carbon source in carbon quantum dots technology and their applications in food safety detection
year: 2020

abstract: Carbon quantum dots (CQDs) as an emerging class of quantum dots (QDs) with advantages such as good photoluminescence (PL) properties, easy synthesis routes, economical synthesis, cheap starting materials, water solubility, low levels of toxicity, chemical stability, and easy functionalization have received great attention during recent years. CQDs have been used in versatile sensor applications. CQD sensors could be ultimately sensitive, and the limit of detection (LOD) for these sensors can reach the nanomolar, picomolar or even femtomolar ranges. CQD based sensors and biosensors work with different mechanisms including fluorescence quenching, static quenching, dynamic quenching, energy transfer, inner filter effect (IFE) photo induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) CQD based sensors and biosensors have been applied for the detection of different species such as metal ions, acids, proteins, biothiols, polypeptides, DNA and miRNA, water pollutants, hematin, drugs, vitamins, and other chemicals. It seems that CQD based sensors and biosensors are promising candidates for high performance and yet accurate sensors in different areas. In this review, CQDs are introduced, and the synthesis methods and optical properties of CQDs are discussed. Different types of CQD based sensors and biosensors and their working mechanisms are clarified.
author_names: Mohammad Jafar Molaei
title: Principles, mechanisms, and application of carbon quantum dots in sensors: a review
year: 2020

abstract: Carbon quantum dots (CQDs) are a fascinating class of carbon nanoparticles with sizes around 10 nm. The unique properties of CQDs are low toxicity, chemical inertness, excellent biocompatibility, photo induced electron transfer and highly tunable photoluminescence behaviour. Sustainable raw materials are commonly used for the fabrication of CQDs because they are cost effective, eco friendly and effective to minimise waste production. CQDs can be fabricated using laser ablation, microwave irradiation, hydrothermal reaction, electrochemical oxidation, reflux method and ultrasonication. These methods undergo several chemical reactions such as oxidation, carbonisation, pyrolysis and polymerisation processes to produce CQDs. Due to small particle sizes of CQDs, they possess strong tunable fluorescent properties and highly photo luminescent emissions. It also contains oxygen based functional groups and highly desired properties as semiconductor nanoparticles. Therefore, CQDs are promising nanomaterials for photo catalysis, ions sensing, biological imaging, heavy metal detection, adsorption treatment, supercapacitor, membrane fabrication and water pollution treatment. This review paper will discuss the physical and chemical properties of CQDs, raw materials and methods used in the fabrication of CQDs, the stability of CQDs as well as their potential applications in wastewater treatment and biomedical field.
author_names: Umairah Abd Rani

Law Yong Ng

Ching Yin Ng

Ebrahim Mahmoudi
title: A review of carbon quantum dots and their applications in wastewater treatment.
venue: Advances in colloid and interface science
year: 2020

abstract: Abstract Carbon quantum dots (CQDs) are emerging nanostructures which consist of carbon atoms and are typically below 10 nm in size. The CQDs are almost surface passivated or are functionalized with organics or biomolecules. CQDs have superior properties such as fluorescence emission, water solubility, cheap and easy synthesis methods, low toxicity, biocompatibility, easy functionalization, and chemical inertness. The CQDs have found versatile applications in different areas such as in vivo and in vitro bioimaging, drug delivery, gene delivery, sensors, solar energy conversion, photoelectrochemical (PEC) cells, photovoltaic solar cells, photocatalysis, and light emitting diodes (LEDs) CQDs could impart in photocatalytic reactions from two aspects; CQDs can be used alongside semiconductors as electron sink and could suppress electron hole recombination and also CQDs can generate electron hole pairs, as well. The CQDs with a wide spectral absorption and high absorption coefficients can enhance the photocatalytic activity. CQDs can also be used as sensitizers in the photoanode of solar cells. Due to the low cost and low toxicity of the CQDs in comparison to semiconductor quantum dots (QDs) they could be considered as potential alternatives in solar energy conversion applications. In this review, the CQDs are introduced and their optical properties are clarified. Recent advances of the CQDs in photocatalysis, PEC, and solar cells are reviewed.
author_names: Mohammad Jafar Molaei
title: The optical properties and solar energy conversion applications of carbon quantum dots: A review
year: 2020

abstract: Carbon quantum dots (CQDs) have shown great potential in optoelectronic applications. Very recently, CQDs have attracted much attention in white emitting diodes (WLEDs) for lighting due to their characteristic broad emission, tunable fluorescence emission and high thermal stability. This mini review updates the latest research in the design of high performance WLEDs with different correlated color temperatures by tuning the red component using red emissive CQDs and single component white emissive CQDs (SCWE CQDs) The prospects for the development of CQD based WLEDs with higher efficiency and color quality will be discussed.
author_names: Ping He

Yuxin Shi

Ting Meng

Ting Yuan

Yunchao Li

Xiaohong Li

Yang Zhang

Louzhen Fan

Shihe Yang
title: Recent advances in white light emitting diodes of carbon quantum dots.
venue: Nanoscale
year: 2020

abstract: Carbon quantum dots (CQDs) are widely used in optoelectronic catalysis, biological imaging, and ion probes owing to their low toxicity, stable photoluminescence, and ease of chemical modification. However, the low fluorescence yield and monochromatic fluorescence of CQDs limit their practical applications. This review summarizes the commonly used approaches for improving the fluorescence efficiency of CQDs doped with non metallic (heteroatom) elements. Herein, three types of heteroatom doped CQDs have been investigated: (1) CQDs doped with a single heteroatom; (2) CQDs doped with two heteroatoms; and (3) CQDs doped with three heteroatoms. The limitations and future perspectives of doped CQDs from the viewpoint of producing CQDs for specific applications, especially for bioimaging and light emitting diodes, have also been discussed herein.
author_names: Xiaoli Kou

Shi-cui Jiang

Soo-Jin Park

Long-Yue Meng
title: A review: recent advances in preparations and applications of heteroatom doped carbon quantum dots.
venue: Dalton transactions
year: 2020

abstract: Carbon quantum dots (CQDs) with stable physicochemical properties are one of the emerging carbon nanomaterials that have been studied in recent years. In addition to the excellent optical properties such as photoluminescence, photobleaching resistance and light stability, this material also has favorable advantages of good biocompatibility and easy functionalization, which make it an ideal raw material for constructing sensing equipment. In addition, CQDs can combined with other kinds of materials to form the nanostructured composites with unique properties, which provides new insights and ideas for the research of many fields. In the field of food analysis, emerging CQDs have been deeply studied in food composition analysis, detection and monitoring trace harmful substances and made remarkable research progress. This article introduces and compares the various methods for CQDs preparation and reviews its related sensing applications as a new material in food components analysis and food safety inspection in recent years. It is expected to provide a significant guidance for the further study of CQDs in the field of food analysis and detection.
author_names: Mingfei Pan

Xiaoqian Xie

Kaixin Liu

Jingying Yang

Liping Hong

Shuo Wang
title: Fluorescent Carbon Quantum Dots Synthesis, Functionalization and Sensing Application in Food Analysis
venue: Nanomaterials
year: 2020

abstract: Neuro transmitters have been considered to be essential biochemical molecules, which monitor physiological and behavioral function in the peripheral and central nervous systems. Thus, it is of high pharmaceutical and biological significance to analyze neuro transmitters in the biological samples. So far, researchers have devised a lot of techniques for assaying these samples. It has been found that electro chemical sensors possess features of robustness, selectivity, and sensitivity as well as real time measurement. Graphene quantum dots (GQDs) and carbon QDs (CQDs) are considered some of the most promising carbon based nanomaterials at the forefront of this research area. This is due to their characteristics including lower toxicity, higher solubility in various solvents, great electronic features, strong chemical inertness, high specific surface areas, plenty of edge sites for functionalization, and versatility, in addition to their ability to be modified via absorbent surface chemicals and the addition of modifiers or nano materials. Hence in the present review, the synthesis methods of GQDs and CQDs has been summarized and their characterization methods also been analyzed. The applications of carbon based QDs (GQDs and CQDs) in biological and sensing areas, such as biological imaging, drug/gene delivery, antibacterial and antioxidant activity, photoluminescence sensors, electrochemiluminescence sensors and electrochemical sensors, have also been discussed. This study then covers sensing features of key neurotransmitters, including dopamine, tyrosine, epinephrine, norepinephrine, serotonin and acetylcholine. Hence, issues and challenges of the GQDs and CQDs were analyzed for their further development.
author_names: S Tajik

Zahra Dourandish

Kaiqiang Zhang

Hadi Beitollahi

Quyet Van Le

Ho Won Jang

Mohammadreza Shokouhimehr
title: Carbon and graphene quantum dots: a review on syntheses, characterization, biological and sensing applications for neurotransmitter determination
year: 2020

abstract: Abstract Graphene and carbon quantum dots (GQDs and CQDs) are relatively new nanomaterials that have demonstrated impact in multiple different fields thanks to their unique quantum properties and excellent biocompatibility. Biosensing, analyte detection and monitoring wherein a key feature is coupled molecular recognition and signal transduction, is one such field that is being greatly advanced by the use of GQDs and CQDs. In this review, recent progress on the development of biotransducers and biosensors enabled by the creative use of GQDs and CQDs is reviewed, with special emphasis on how these materials specifically interface with biomolecules to improve overall analyte detection. This review also introduces nano enabled biotransducers and different biosensing configurations and strategies, as well as highlights key properties of GQDs and CQDs that are pertinent to functional biotransducer design. Following relevant introductory material, the literature is surveyed with emphasis on work performed over the last 5 years. General comments and suggestions to advance the direction and potential of the field are included throughout the review. The strategic purpose is to inspire and guide future investigations into biosensor design for quality and safety, as well as serve as a primer for developing GQD and CQD based biosensors.
author_names: Brandon K Walther

Cerasela Zoica Dinu

Dirk Michael Guldi

Vladimir G Sergeyev

Stephen E Creager

John P Cooke

Anthony Guiseppi-Elie
title: Nanobiosensing with graphene and carbon quantum dots: Recent advances
year: 2020