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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: Therapeutic options for the highly pathogenic human coronavirus (HCoV) infections are urgently needed. Anticoronavirus therapy is however challenging, as coronaviruses are biologically diverse and rapidly mutating. In this work, the antiviral activity of seven different carbon quantum dots (CQDs) for the treatment of human coronavirus HCoV 229E infections was investigated. The first generation of antiviral CQDs was derived from hydrothermal carbonization of ethylenediamine/citric acid as carbon precursors and postmodified with boronic acid ligands. These nanostructures showed a concentration dependent virus inactivation with an estimated EC50 of 52 8 mg mL 1. CQDs derived from 4 aminophenylboronic acid without any further modification resulted in the second generation of anti HCoV nanomaterials with an EC50 lowered to 5.2 0.7 mg mL 1. The underlying mechanism of action of these CQDs was revealed to be inhibition of HCoV 229E entry that could be due to interaction of the functional groups of the CQDs with HCoV 229E entry receptors; surprisingly, an equally large inhibition activity was observed at the viral replication step.
author_names: Aleksandra Loczechin

Karin Seron

Alexandre Barras

Emerson Giovanelli

Sandrine Belouzard

Yen-Ting Chen

Nils Metzler-Nolte

Rabah Boukherroub

Jean Dubuisson

Sabine Szunerits
title: Functional Carbon Quantum Dots as Medical Countermeasures to Human Coronavirus
venue: ACS applied materials interfaces
year: 2019

abstract: Abstract Carbon quantum dots (CQDs) are a new class of fluorescence small carbon nanoparticles with a particle size of less than 10 nm and have vast applications in the field of bioimaging, biosensing and disease detection. These are promising materials for nano biotechnology since it has smaller particle size, excellent biocompatibility and excitation wavelength dependent photoluminescence (PL) behavior, photo induced electron transfer, chemical inertness and low toxicity. These materials have excellent fluorescent properties such as broad excitation spectra, narrow and tunable emission spectra, and high photostability against photo bleaching and blinking than other fluorescent semiconductor quantum dots. This review article demonstrate the recent progress in the synthesis, functionalization and technical applications of carbon quantum dots using electrochemical oxidation, combustion/thermal, chemical change, microwave heating, arc discharge, and laser ablation methods from various natural resources. Natural carbon sources are used for the preparation of CQDs due to its low cost, environmental friendly and widely available.
author_names: Rashmita Das

Rajib Bandyopadhyay

Panchanan Pramanik
title: Carbon quantum dots from natural resource: A review
year: 2018

abstract: It is demonstrated that carbon quantum dots derived from curcumin (Cur CQDs) through one step dry heating are effective antiviral agents against enterovirus 71 (EV71) The surface properties of Cur CQDs, as well as their antiviral activity, are highly dependent on the heating temperature during synthesis. The one step heating of curcumin at 180 degC preserves many of the moieties of polymeric curcumin on the surfaces of the as synthesized Cur CQDs, resulting in superior antiviral characteristics. It is proposed that curcumin undergoes a series of structural changes through dehydration, polymerization, and carbonization to form core shell CQDs whose surfaces remain a pyrolytic curcumin like polymer, boosting the antiviral activity. The results reveal that curcumin possesses insignificant inhibitory activity against EV71 infection in RD cells [half maximal effective concentration (EC50 >200 ug mL 1 but exhibits high cytotoxicity toward RD cells (half maximal cytotoxic concentration (CC50 <13 ug mL 1 The EC50 (0.2 ug mL 1 and CC50 (452.2 ug mL 1 of Cur CQDs are >1000 fold lower and >34 fold higher, respectively, than those of curcumin, demonstrating their far superior antiviral capabilities and high biocompatibility. In vivo, intraperitoneal administration of Cur CQDs significantly decreases mortality and provides protection against virus induced hind limb paralysis in new born mice challenged with a lethal dose of EV71.
author_names: Chin-Jung Lin

Lung Chang

Han-Wei Chu

Han-Jia Lin

Pei-Ching Chang

Robert Y L Wang

Binesh Unnikrishnan

Ju-Yi Mao

Shiow-Yi Chen

Chih-Ching Huang
title: High Amplification of the Antiviral Activity of Curcumin through Transformation into Carbon Quantum Dots.
venue: Small
year: 2019

abstract: Highly active, stable, and cheap Pt free catalysts for the hydrogen evolution reaction (HER) are facing increasing demand as a result of their potential use in future energy conversion systems. However, the development of HER electrocatalysts with Pt like or even superior activity, in particular ones that can function under alkaline conditions, remains a significant challenge. Here, the synthesis of a novel carbon loaded ruthenium nanoparticle electrocatalyst (Ru@CQDs) for the HER, using carbon quantum dots (CQDs) is reported. Electrochemical tests reveal that, even under extremely alkaline conditions (1 m KOH) the as formed Ru@CQDs exhibits excellent catalytic behavior with an onset overpotential of 0 mV, a Tafel slope of 47 mV decade 1 and good durability. Most importantly, it only requires an overpotential of 10 mV to achieve the current density of 10 mA cm 2 Such catalytic characteristics are superior to the current commercial Pt/C and most noble metals, non noble metals, and nonmetallic catalysts under basic conditions. These findings open a new field for the application of CQDs and add to the growing family of metal@CQDs with high HER performance.
author_names: Weidong Li

Yuan Liu

Min Wu

Xiaolei Feng

Simon A T Redfern

Yuan Shang

Xue Yong

Tanglue Feng

Kaifeng Wu

Zhong-xia Liu

Baojun Li

Zhimin Chen

John S Tse

Siyu Lu

Bai Yang
title: Carbon Quantum Dots Loaded Ruthenium Nanoparticles as an Efficient Electrocatalyst for Hydrogen Production in Alkaline Media.
venue: Advanced materials
year: 2018

abstract: Nucleolus tracking and nucleus targeted photodynamic therapy are attracting increasing attention due to the importance of nucleolus and the sensitivity of nucleus to various therapeutic stimuli. Herein, a new class of multifunctional fluorescent carbon quantum dots (or carbon dots, CDs) synthesized via the one pot hydrothermal reaction of m phenylenediamine and l cysteine was reported to effectively target nucleolus. The as prepared CDs possess superior properties, such as low cost and facile synthesis, good water dispersibility, various surface groups for further modifications, prominent photostability, excellent compatibility, and rapid/convenient/wash free staining procedures. Besides, as compared with SYTO RNASelect (a commonly used commercial dye for nucleolus imaging) that can only image nucleolus in fixed cells, the CDs can realize high quality nucleolus imaging in not only fixed cells but also living cells, allowing the real time tracking of nucleolus related biological behaviors. Furthermore, after conjugating with protoporphyrin IX (PpIX) a commonly used photosensitizer, the resultant CD PpIX nanomissiles showed remarkably increased cellular uptake and nucleus targeting properties and achieved greatly enhanced phototherapeutic efficiency because the nuclei show poor tolerance to reactive oxygen species produced during the photodynamic therapy. The in vivo experiments revealed that the negatively charged CD PpIX nanomissiles could rapidly and specifically target a tumor site after intravenous injection and cause efficient tumor ablation with no toxic side effects after laser irradiation. It is believed that the present CD based nanosystem will hold great potential in nucleolus imaging and nucleus targeted drug delivery and cancer therapy.
author_names: Xian-Wu Hua

Yan-Wen Bao

Fu-Gen Wu
title: Fluorescent Carbon Quantum Dots with Intrinsic Nucleolus Targeting Capability for Nucleolus Imaging and Enhanced Cytosolic and Nuclear Drug Delivery.
venue: ACS applied materials interfaces
year: 2018

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: Nitrogen doped carbon quantum dots (N CQDs) were successfully synthesized using rice residue and glycine as carbon and nitrogen sources by one step hydrothermal method. High quantum yield (23.48% originated from the effective combination of nitrogen with various functional groups (CO, NH, CN, COOH and COC) The N CQDs showed a fluorescence with the wavelength varied from 420 to 500 nm and the maximum emission wavelength being at 440 nm. N CQDs have been importantly applied as probe to detect Fe3+ and tetracycline (TCs) antibiotics with remarkable performance. Using the linear relationship between fluorescence intensity and Fe3+ concentration, the N CQDs could be employed as a simple, efficient sensor for ultrasensitive Fe3+ detection ranging from 3.32 to 32.26 uM, with a limit of detection (LOD) of 0.7462 uM. The N CQDs showed the applicability to detect TCs. The detection limits of tetracycline, terramycin and chlortetracycline were 0.2367, 0.3739 and 0.2791 uM, respectively. The results of TC by fluorescence method in real water samples were in good agreement with standard Ultraviolet visible (UV vis) method. The N CQDs have various potential applications including sensitive and selective detection of Fe3+ and TCs, and cellular imaging with low cytotoxicity, good biocompatibility and high permeability.
author_names: Houjuan Qi

Min Teng

Miao Liu

Shouxin Liu

Jian Li

Haipeng Yu

Chunbo Teng

Zhanhua Huang

Hu Liu

Qian Shao

Ahmad Umar

Tao Ding

Qiang Gao

Zhanhu Guo
title: Biomass derived nitrogen doped carbon quantum dots: highly selective fluorescent probe for detecting Fe3+ ions and tetracyclines.
venue: Journal of colloid and interface science
year: 2019

abstract: Abstract In this work, highly photoluminescence nitrogen doped carbon quantum dots (N CQD) were synthesized via a simple hydrothermal method from a very low cost and green material. Different analysis were used to approve synthesis of the quantum dots such as X ray diffraction pattern (XRD) energy dispersive X ray analysis (EDAX) and Fourier transform infrared spectroscopy (FT IR) The morphology of the product was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. In addition, the surface topography was studied by atomic force microscopy (AFM) and it was found the product has tiny and uniform particles. The photoluminescence (PL) analysis was served to study the photoluminescence intensity and it was found the product has high photoluminescence intensity. To investigate the photocatalytic activity of the product, five dyes namely Acid Blue, Acid Red, Eosin Y, Eriochrome Black T, Methyl orange and Methylene blue were decomposed under radiation. Surface activity of the product was evaluated by adsorption Cd2+ and Pb2+ from the water and the results showed the carbon dots can remove these two heavy metal ions from the water with 37% and 75% respectively.
author_names: Mohammad Sabet

Kamran Mahdavi
title: Green synthesis of high photoluminescence nitrogen doped carbon quantum dots from grass via a simple hydrothermal method for removing organic and inorganic water pollutions
year: 2019

abstract: In the present study, an ecofriendly and zero cost approach has been demonstrated for the preparation of carbon quantum dots by one pot hydrothermal treatment of leaf extracts of neem (Azadirachta indica) The as synthesized neem carbon quantum dots (N CQDs) exhibited high fluorescent quantum yields (QYs) up to 27.2% Moreover, N CQDs also act with a peroxidase like mimetic activity toward the oxidation of peroxidase substrate 3,3',5,5' tetramethylbenzidine (TMB) in association with hydrogen peroxide (H2O2) Further, the kinetics of peroxidase like catalytic activity follows the Michaelis Menten and ping pong pathway. In addition, the H2O2 sensitive TMB oxidation motivated the colorimetric detection of H2O2 which showed linearity from 0.1 to 0.5 mmol/L with a detection limit (LOD) of 0.035 mmol/L. Furthermore, the blue colors of oxidized TMB (ox TMB) were selectively reduced in native TMB with ascorbic acid (AA) without any interference of other reducing agents. The linear range of AA detection was lying between 5 and 40 mM with a LOD up to 1.773 mM. The practicability assay of the proposed sensing system toward the detection of AA was also investigated in real sample analysis such as common fruits which showed good sensitivity to the presence of AA. Therefore, this convenient, ecofriendly, and cost effective peroxidase based sensing system opens a new platform for analysis of AA in real samples and in complex biological systems.
author_names: Pradeep Kumar Yadav

Vikas Kumar Singh

Subhash Chandra

Daraksha Bano

Vijay Kumar

Mahe Talat

Syed Hadi Hasan
title: Green Synthesis of Fluorescent Carbon Quantum Dots from Azadirachta indica Leaves and Their Peroxidase Mimetic Activity for the Detection of H2O2 and Ascorbic Acid in Common Fresh Fruits.
venue: ACS biomaterials science engineering
year: 2019