Surface Of Carbon Quantum Dots Research Articles

High quantum yield carbon quantum dots as selective fluorescent turn-off probes for dual detection of Fe2+/Fe3+ ions

Carbon quantum dots (CQDs) are fluorescent nanoparticles that have great potential for use as nontoxic fluorescent probes. However, synthesizing CQDs with high photoluminescence quantum yield (QY) in a rapid and facile way from commonly available and low-cost reagents is still challenging. In this work, Tween®80 was used as a surface passivation agent along with citric acid/urea in a one-step microwave procedure to make extremely blue luminous nitrogen doped CQDs. When excited at 350 nm, these CQDs had a fluorescent quantum yield of 75.5 %. The significant high quantum yield and stability of these CQDs are attributed to the high aromatic sp2 domain size within the CQD core and improved carbon and oxygen functional groups at the CQDs surface. We employed the CQDs as a fluorescent probe to detect Fe2+ and Fe3+ ions and could establish a linear relationship between photoluminescence quenching efficiency (F0-F/F0) and ion concentration with a detection limit of 6.5 µM and 2.5 µM for Fe2+ and Fe3+, respectively. Our studies suggest that the highly selective detection of iron ions is a result of partial transfers of excited electrons from the CQDs to the d orbital of the iron ions, instead of contributing to radiative relaxation that induces photoluminescence quenching of the CQDs. Other reported carbon dots for this application have a substantially lower quantum yield and only detect Fe3+ ions. Therefore, our CQDs have considerable benefits over similar probes. Subsequent research may adapt them to other areas due to the high quantum yield and stability.

The effect of microwave power level and post-synthesis annealing treatment on oxygen-based functional groups present on carbon quantum dots

Despite widespread interest in understanding the properties of carbon quantum dots (CDOTs), there appear to be fewer studies systamaticaly investigating CDOTs' luminescent mechanisms. The primary objective of this study is to prepare CDOTs with desirable optical properties and to understand the photoluminescence (PL) mechanisms involved in order to control the emission charectersitcs. The optical properties of CDOTs are strongly influenced by the functional groups (-OH, –CHO, –COOH, –CO, –COO) formed on the surface of the dots. The key factors affecting the nature and number of functional groups are the preparation method, post synthesis treatment, and the precursor materials. Ascorbic acid was used as the starting material in this study to synthesize CDOTs via microwave-assisted synthesis techniques. Then, the effect of microwave power level and post synthesis annealing temperature on the oxygen-based functional groups present on the surface of the dots was evaluated systematically. It was found that the increasing microwave power level increases the density of functional groups present on the surface of CDOTs, which positively affects the PL. However, annealing at high temperatures decreases the concentration of functional groups and reduces the PL intensity. The PL emission peaks were deconvoluted and the emission wavelength corresponding to each functional group was identified. This work underlines the role of oxygen based functional groups on the PL emission and the ways to control them by physical means.

Characterization of N‐doped carbon quantum dots synthesized by DBD‐based cold atmospheric pressure plasma jet

AbstractThis study develops a new approach for the synthesis of fluorescent N‐doped carbon quantum dots (CQDs), using cold atmospheric pressure plasma jet. Herein, the CQDs were synthesized with two plasma exposure times of 30 and 60 min. The UV‐Vis absorption spectrum confirms the existence of carbonic core and surface functional groups. The Fourier transform infrared spectrum shows that carbonyl groups and amide groups exist on the surface of CQDs. Depending on the plasma exposure time, the mean average sizes of CQDs are 3.63 and 5.45 nm with strong photoluminescence emission. Generally, our results indicated that using different mechanisms for plasma discharge, lead to different physical and chemical properties of produced plasma and consequently of synthesized CQDs. The synthesized N‐doped CQDs exhibited strong fluorescence and higher quantum yield compared to previous reports.

Efficient Reduction of Cr(VI) with Carbon Quantum Dots.

Hexavalent chromium (Cr(VI)) pollution is a global problem, and the reduction of highly toxic Cr(VI) to less toxic Cr(III) is considered to be an effective method to address Cr(VI) pollution. In this study, low-toxicity carbon quantum dots (CQDs) were used to reduce Cr(VI) in wastewater. The results show that CQDs can directly reduce Cr(VI) at pH 2 and can achieve a reduction efficiency of 94% within 120 min. It is observed that under pH higher than 2, CQDs can activate peroxymonosulfate (PMS) to produce reactive oxygen species (ROS) for the reduction of Cr(VI) and the reduction efficiency can reach 99% within 120 min even under neutral conditions. The investigation of the mechanism shows that the hydroxyl groups on the surface of CQDs can be directly oxidized by Cr(VI) because of the higher redox potential of Cr(VI) at pH 2. As the pH increases, the carbonyl groups on the surface of CQDs can activate PMS to generate ROS, O2•–, and 1O2, which result in Cr(VI) being reduced. To facilitate the practical application of CQDs, the treatment of Cr(VI) in real water samples by CQDs was simulated and the method reduced Cr(VI) from an initial concentration of 5 mg/L to only 8 μg/L in 150 min, which is below the California water quality standard of 10 μg/L. The study provides a new method for the removal of Cr(VI) from wastewater and a theoretical basis for practical application.

Sustainable fabrication of N-doped carbon quantum dots and their applications in fluorescent inks, Fe (III) detection and fluorescent films

N-doped CQDs are efficiently fabricated with a green synthesis avenue, and exhibit huge potential in anticounterfeit application as the fluorescent ink, a smart fluorescent sensor towards ionic detection, and fluorescent polymer films. • One-step hydrothermal strategy is devised for synthesizing N-doped CQDs from garlic skins. • The obtained water-soluble N-doped CQDs exhibit a strong cyan luminescence with a quantum yield of ∼9%. • The CQDs present huge potential in anticounterfeit application as the fluorescent ink. • The CQDs show highly sensitive and selective determination of cations as a smart fluorescent sensor. • The PVA/CQDs film gives high visible transparency and nearly 100% UV-blocking ratio. In this work, the highly fluorescent N-doped carbon quantum dots (CQDs) were successfully synthesized via a simple hydrothermal method by using garlic skins (GSs) as the sole carbon source. The resultant N-doped CQDs with excitation-dependent emission demonstrates remarkable quantum yield of ∼9% and superior fluorescence stability. Their strong cyan-emission character upon irradiation with UV light (365 nm) reveals their huge potential in anticounterfeit field as the fluorescent ink. Owing to the fluorescence quenching resulted from the tightly chelating of Fe 3+ to the surface of N-doped CQDs, the CQDs can be applied a functional sensor for the detection of Fe 3+ , and the limit of detection is estimated as 4.44 μM. Furthermore, the CQDs is dispersed into poly (vinyl alcohol) (PVA) matrix to make PVA/CQDs composite film. The unique optical properties of CQDs are inherited by the PVA/CQDs film, giving intensive cyan fluorescence and high visible transparency, as well as nearly 100% UV-blocking ratio in the UV region.

Amine functionalized carbon quantum dots from paper precursors for selective binding and fluorescent labelling applications

We report a novel synthesis route for preparing carbon quantum dots (CQDs) of customized surface functionality from readily available precursors. The synthetic strategy is based on the chemical modification of paper precursors prior to preparing CQDs from them. The pre-synthesis modification of paper precursors with (3-Aminopropyl) triethoxy silane (APTES) enabled us to synthesize CQDs with amine functional groups on the surface. The silane coupling via condensation between the ethoxy group of APTES and the cellulose hydroxyl group on the paper resulted in the tethering of amine groups on the paper substrates, which are retained as surface-bound species during the synthesis of CQDs from the modified paper. Amine functionalization on the surface of CQDs helped us use them in applications such as DNA binding. We analyzed the interaction of CQDs with calf thymus DNA (CT-DNA), and the results imply their propensity as an efficient biological probe. The synthetic strategy presented here can also be extended to other functional groups.

Structural and luminescent properties of CQDs produced by microwave and conventional hydrothermal methods using pelagic Sargassum as carbon source

The synthesis of carbon quantum dots (CQDs) from biomass could be the best application for biopolymeric materials with no further use in industry and that can have environmental effects when disposed of, such as pelagic Sargassum. This research compared the structural and luminescent properties of CQDs synthetized by two different methods (microwave and conventional hydrothermal synthesis) using pelagic Sargassum extract as a carbon source. The microwave method resulted in a better mass yield, while hydrothermal synthesis generated the best quantum yield (QY). Under optimized synthesis conditions, no statistical differences were observed in CQDs size or surface functional groups, as detected by TEM and FTIR analyses respectively. However, crystalline structure and light absorption varied between samples, explaining the higher values of QY observed in the conventional hydrothermal method. This study thus assists in furthering the understanding of the synthesis process, as well as providing supporting evidence for which synthesis methods are better for CDQ synthesis depending on the future uses of these nanoparticles.

Bicomponent colorimetric probe based on carbon quantum dots and o-phenylenediamine for sensitive and selective Cu2+ sensing.

A bicomponent colorimetric probe based on carbon quantum dots (CQDs) and o-phenylenediamine (OPD) was established for the detection of Cu2+. Theoretically, light-generated electrons from CQDs were trapped by the dissolved oxygen, resulting in the production of superoxide radicals. The colorless OPD was oxidized by the superoxide radicals to its yellow oxidation product (OPDox). On the other hand, Cu2+ can bind onto the surface of CQDs and change the band gap of the CQDs. This change induces an inhibition of the photo-oxidation of OPD, thus resulting in a decrease of the absorbance of OPDox. The mechanism was demonstrated by a series of control experiments. The parameters influencing the sensing performance as well as potential interferences were investigated. Under the optimum conditions, a limit of detection of 30nM was achieved. Moreover, this sensing system was applied to analyze Cu2+ in seawater and tapwater samples, and achieved satisfying results.

Cation-π aggregation-induced white emission of moisture-resistant carbon quantum dots: a comprehensive spectroscopic study.

Controlling mechanisms involved in the aggregation of carbon quantum dots (CQDs) can lead to new application developments for these quantum dot materials. In this study, an unusual aggregation-induced white emission of CQDs with strong intrinsic green emission is reported. Due to the deprotonation/protonation of the surface functional groups during the aggregation of CQDs induced by pH variations of the solution through the addition of sodium hydroxide, and hydrophobic interactions between CQDs, it results in the formation of aggregated CQDs through an avalanche-like process. Our results suggest that sodium hydroxide not only plays a critical role in the formation of strong cation-π interactions, but also polishes the surface of CQDs, leading to the formation of the aggregated CQDs. The aggregated CQDs present excellent dispersibility characteristics in water. Moreover, optical studies suggest a combined aggregation mechanism in the presence of both J-type and H-type aggregation monoliths involved in forming the aggregated CQDs. The findings obtained from the deconvolution of the as-synthesized CQDs can perceptively elucidate the cation-π aggregation process.

SYNTHESIS AND SPECTRAL CHARACTERISTICS OF Cu(II), Ni(II) AND Fe(III) NANOSIZED COM­PLEXES ON THE SURFACE OF CARBON QUANTUM DOT

Processes of interaction between carbon quantum dots (CQDs) and solutions of Cu(II) Ni(II) and Fe(III) chlorides in the surface layer have been investigated by electron and IR spectroscopy.
 When hydrochloric acid is added to the aqueous suspension of CQDs, there is a signi­ficant batochromic shift of the average absorption band (AB) by 1285 cm-1 with a decrease in its intensity to ε = 23.39. The presence of copper in the suspension of CQDs at room temperature leads to a decrease in the intensity of this AB (ε = 21.80), which indicates the interaction of CQDs with metal ions.
 After heating the suspension for 1 and 3 hours, the gypsochromic shift of this ABs (by 335 cm-1) to 27790 cm-1 with a decrease in intensity depending on the heating time was recorded. Such changes in the UV–Vis Spectrum are due to the redistribution of the electron density of electron transitions n → π *due to the coordination of functional groups with metal ions and the appearance of transitions with charge transfer from ligand to metal (CQD→Cu2+).
 When heating the suspensions significantly increases the absorption intensity of the AB at 22070 cm-1: from ε = 4.59 to ε = 6.75, which indicates the formation of transitions with charge transfer from ligand to metal (ChTLM) due to the coordination of copper ions with CQD.
 In the absorption spectra of CQD suspensions with NiCl2 before heating, a hypsochromic shift of AB at 27305 cm-1 by 150 cm-1 and an increase in the intensity of its to ε = 4.95 were registered. That is, Ni(II) ions also form coordination bonds with functional groups on the periphery of the CQD.
 After heating hydrochloric acid suspensions of CQD with FeCl3, in contrast to the chlorides of previous metals, in the UV-region registered shoulder-shaped AB at 31545 cm-1, the intensity of which increases with heating time (from ε = 9.59 to ε = 12.10), and in the visible region, a weakly intense shoulder-shaped AB at 19345 cm-1 (ε = 3.71 and 4.58), associated with the presence of dd-electron transitions in the metal ion.
 Such changes in the absorption spectra are explained by the fact that iron may interact with CQD in different ways (in addition to coordination with functional donor groups, the formation of coordination bonds with the π-electron system of conjugated CQDs bonds), which leads to additional weak shoulder-like AB at 31545 cm-1.
 The IR-spectra data of CQDs showed the presence of a number of characteristic ABs for functionalized CQDs: ν(N–H) at 3260 сm1, (C=O) at 1830, 1840 and 1850 сm1, –С=O(NH) at 1770 сm1, ν(C=N) at 1680 and δ(N–H) at 1640 сm1 and 320-360 см-1 СП ν(Cu–Cl, Ni–Cl, Fe–Cl), which confirms the coordination of metals on the surface of CQDs.

CARBON QUANTUM DOTS (CQDS) from RAMBUTAN and PANDAN LEAVES for CU2+ DETECTION

A facile and eco-friendly process for the synthesis of carbon quantum dots (CQDs) was carried out via hydrothermal and microwave treatment using Rambutan and Pandan leaves as carbon sources. The effects of synthesis methods on the optical and physical properties of CQDs, and the sensing activity of CQDs through Cu 2+ detection are presented in this study. From the analysis, the band-gap energies of CQDs are found to be ranging from 2.52 to 3.51 eV. The CQDs solutions exhibit significant fluorescence property, in which bright cyan fluorescence can be detected under Ultraviolet (UV) light irradiation at wavelength of around 405 nm. The CQDs synthesized from Pandan and Rambutan leaves using hydrothermal method show quantum yield (QY) values at around 2.46% and 2.70%, respectively. The FT-IR analysis recorded existing functional groups on the surface of CQDs to be of hydroxyl and carbonyl groups, which can serve as adsorption sites for the detection of Cu 2+ . Furthermore, this study indicates that CQDs emission from Pandan and Rambutan leaves using hydrothermal method shows the best turn-off behavior when detecting the presence of Cu 2+ with minimum limit of detection (LoD) as low as 123 µM.

Investigating fluorescence quenching of cysteine-functionalized carbon quantum dots by heavy metal ions: Experimental and QSPR studies

Carbon quantum dots (CQDs) have potential application as fluorescent probesfor the heavy metal detection. But there are few reports on the investigation of the quenching mechanism of CQDs by heavy metal ions. In this study, CQDs were prepared by directly pyrolyzing turmeric powder and functionalized using the thiol functionality of cysteine. Then the fluorescence quenching of cysteine-functionalized CQDs (Cys-CQDs) by 25 heavy metal ions were experimentally measured. Then the effect of the physical and chemical properties of heavy metal ions on the fluorescence quenching of CQDs was investigated by using the quantitative structure–property relationship (QSPR) method. Applying different machine learning method including genetic algorithm, enhanced replacement method, support vector machine, and multi linear regression, some reliable and predictive models were developed. Based on the variables included in the final QSPR model, covalent interactions of metal ions with functional groups on CQDs surface and the atomic environment were significant effect on the quenching of CQDs by heavy metal ions. Briefly, the tendency of metal ion to accept electrons from a donor ligand and the hard and soft acids and bases affinities can be considered as a primary factor governing the mechanism of quenching of CQDs by heavy metal ions.

Highly Selectivity Molecularly Imprinted Fluorescence Sensor Based on Carbon Quantum Dots for the Determination of Anthraquinones.

Due to the complexity of traditional Chinese medicines (TCMs), it is very important to develop a method that can recognize anthraquinones, the active ingredients in TCMs, with high selectivity. Here, a molecularly imprinted fluorescence sensor was coated on the surface of carbon quantum dots (CDs). Allobarbital was used as functional monomer for this application using theoretical calculations and was successfully synthesized and characterized. The template molecule chrysophanol was combined with the functional monomer allobarbital using a hydrogen bond array. Then, a series of adsorption experiments were performed to study the specific recognition of anthraquinones by the prepared sensors. The results showed that the prepared sensor had a good linear response to concentrations of chrysophanol in the concentration range 0.5 mg · L-1 to 8.0 mg · L-1, a low detection limit (5.0 μg · L-1), high stability, and a short response time (20 min). Additionally, the obtained fluorescence sensor was successfully applied to selectively recognize anthraquinones in TCMs with recoveries of 90.1% to 101.7%. The prepared sensor displays excellent sensitivity and high selectivity towards anthraquinones, mainly due to the specific hydrogen binding sites for the target molecules. Overall, this fluorescence sensor can selectively recognize anthraquinones in TCMs, and provide a method for quality monitoring and rational utilization of TCMs.

Carbon quantum dots: Comprehensively understanding of the internal quenching mechanism and application for catechol detection

Abstract Carbon quantum dots (CQDs), a new member of the nanocarbon family, are emerging as attractive optical sensing material. At present, there is still a lack of in-depth investigation on internal responsive mechanism of CQDs as their fluorescence is quenched by analytes. In this work, ethylenediamine (EDA) functionalized carbon quantum dots (N-CQDs) are synthesized through the protection/deprotection of one amine group and the amidation reaction on CQDs surface. According to the fluorescence response of N-CQDs in catechol (CTC) solution and under different environmental conditions, it is found that the EDA on the surface of N-CQDs could spontaneously combine with CTC via Michael addition or Schiff base reaction to form static compounds, which serve as electron donor to effectively quench the fluorescence originated from sp2 carbogenic core area and “surface state” of N-CQDs, but have little impact on the emission from “edge state” of N-CQDs. This is the first time that the “inertness” of “edge state” was observed. Based on the comprehensive analysis of quenching mechanism, the excitation wavelength (λex=310nm) corresponding to the “core state” of N-CQDs was selected, and a simple, highly sensitive and selective detection platform for CTC quantification is established.

Preparation, characterization and in vitro anticancer performance of nanoconjugate based on carbon quantum dots and 5-Fluorouracil

This study is focused on the development of a nanodevice for loading and release of 5-Fluorouracil (5-FU) with a view to improving its therapeutic efficiency, using as strategy the fabrication of a nanoconjugate through drug anchorage on the surface of carbon quantum dots (CQD). Several physicochemical and analytical techniques were employed to obtain information about materials morphology, structure, and optical properties. The results indicated that the interactions between both entities resulted in good physicochemical properties and photostability. Acid pH favored drug release, indicating a tendency to release 5-FU from 5-FU-CQD into the tumor microenvironment. The cytotoxicity of CQD and 5-FU-CQD nanoconjugate was evaluated against normal human lung fibroblast (GM07492A) and human breast cancer (MCF-7) cell lines. The CQD was non-toxic, indicating that these materials are biocompatible and can be used as a nanocarrier for 5-FU in biological systems. For the 5-FU-CQD nanoconjugate, it was observed a reduction in toxicity for normal cells compared to free 5-FU, suggesting that drug anchoring in CQD reduced drug-associated toxicity, while for cancer cells exhibited an antitumor effect equivalent to that of the free drug, opening perspectives for the application of this material in anticancer therapy.

Microwave-assisted synthesis of multifunctional fluorescent carbon quantum dots from A4/B2 polyamidation monomer sets

Carbon quantum dots (CQDs) are becoming a desirable alternative to metal-based QDs due to their high biocompatibility, low toxicity, ease of preparation, and unique photophysical properties. In the present study, a simple microwave-assisted synthesis using a domestic oven has been adopted to produce multifunctional CQDs from the ethlyenediaminetetraacetic acid (EDTA) and 4, 7, 10-trioxa-1, 13-tridecanediamine (TTDDA) monomers. The molecular surface of the prepared CQDs is composed of hyperbranched polyamides obtained from the polymerization reaction of both EDTA and TTDDA. The controlled functionalities and chemical structures of the molecular surface of CQDs are attained by varying the initial feed ratio of EDTA and TTDDA from 1:1 to 1:2, 1:3, 1:4, 1:5, and 3:1. The T-richCD3 (EDTA: TTDDA = 1:4) with highest mass yield of 25 wt% exhibited five-folds higher photoluminescence quantum yield (PLQY) (53.3%) compared to E-richCD1 (EDTA: TTDDA = 3:1). All synthesized CQDs revealed good sensitivity and selectivity to a Cu2+ ion that is prone to cause different neurodegenerative diseases and obstruct many biological activities, while the sensitivity increased with the decrease in EDTA to TTDDA ratio. The zebrafish model has been used to demonstrate the toxicity, adverse effects, transport, and biocompatibility of CQDs. At higher concentrations (1.0 mg/mL), the T-richCDs exhibited superior cell viability than the E-richCDs for Madin-Darby Canine Kidney (MDCK) and human breast cancer MDA-MB-231 (MDAMB) cells. Because of the excellent down conversion fluorescence ability, T-richCD3 were employed as luminescent down-shifting (LDS) layer in CuInSe2 solar cell to enhance its performance.

The influence of inorganic electrolyte on the properties of carbon quantum dots in electrochemical exfoliation

Abstract Carbon quantum dots (CQDs) with highly graphitic structure are of great importance for electronic performance in applications of optoelectronics or photocatalysis. A facile method to obtain CQDs is the electrochemical exfoliation of graphitic materials. In our previous work, CQDs have been exfoliated from graphite rods in electrolyte of distilled water, organic and inorganic solutions, and the results show that inorganic electrolyte is the best choice in economy and efficiency. According to previous conclusions, the type of electrolyte has a prominent influence on the property and morphology of CQDs in process of exfoliation. However, to the best our knowledge, the type of inorganic electrolyte on behaviors of CQDs has not been researched and reported. Herein, a series of common inorganic salt solution are used as electrolyte and are compared to each other for the best choice of electrochemical exfoliation. Nitrate solution for electrochemical exfoliation of CQDs is better than any others, not only due to its similar photoluminescence, but also possessing common average size of 3.5 nm, which lead to regular and easily distinguishing morphology in TEM image. The lattice spacing of 0.21 nm observed from HRTEM is indicative of graphitic nanostructure. The blue photoluminescence of as-exfoliated CQDs is relative weak with quantum yield of 5.6%. Thus, we are inclined to believe that its photoluminescence mechanism is attribute to quantum confinement effects of carbon core rather than surface functional groups. It can also be supported by XPS and FT-IR results that only some simple groups (-OH and C=O) were form on surface of CQDs during exfoliation. Therefore, the electrolyte of nitrate shows the best suitability for the electrochemical exfoliation of CQDs. Besides, it can provide a way to tune the size of CQDs by electing different electrolyte.

Carbon quantum dots for advanced electrocatalysis

Zero-dimensional (0D) carbon quantum dots (CQDs), as a nanocarbon material in the carbon family, have garnered increasing attention in recent years due to their outstanding features of low cost, nontoxicity, large surface area, high electrical conductivity, and rich surface functional groups. By virtue of their rapid electron transfer and large surface area, CQDs also emerge as promising functional materials for the applications in energy-conversion sectors through electrocatalysis. Besides, the rich functional groups on the surface of CQDs offer abundant anchoring sites and active sites for the engineering of multi-component and high-performance composite materials. More importantly, the heteroatom in the CQDs could effectively tailor the charge distribution to promote the electron transfer via internal interactions, which is crucial to the enhancement of electrocatalytic performance. Herein, an overview about recent progress in preparing CQDs-based composites and employing them as promising electrode materials to promote the catalytic activity and stability for electrocatalysis is provided. The introduced CQDs could enhance the conductivity, modify the morphology and crystal phase, optimize the electronic structure, and provide more active centers and defect sites of composites. After establishing a deep understanding of the relationship between CQDs and electrocatalytic performances, the issues and challenges for the development of CQDs-based composites are discussed.

Rapid hydrothermal method for the preparation of carbon quantum dots in the presence of hydrogen peroxide

Carbon quantum dots (CQDs) have been studied for years as one of the most promising fluorescent nanomaterials. Herein, CQDs were prepared rapidly by a simple, eco-friendly one-pot hydrothermal method in the presence of hydrogen peroxide. Different sizes of CQDs are obtained by changing the reaction time. X-ray photoelectron spectroscopy and Fourier transform infrared spectrometry demonstrated the existence of a large number of oxygen-containing groups on the surface of CQDs. The as-prepared CQDs exhibited bright yellow luminescence under UV light, they are applied for bioimaging of HeLa cells, and showed bright luminescence and excellent biocompatibility.

The Preparation of Carbon Quantum Dots Up-conversion Materials and Its Application

Carbon quantum dots(CQDs)has been widely used in the fields of energy and biomedicine due to its desired advantages of chemical stability,biocompatibility as well as low toxicity.The surface of CQD can easily be functionalized by polymer such as PEG and the photoluminescence characteristics be improved,which make at more effective in bioimaging,disease detection and drug delivery.In addition,carbon materials,also show a prospect application in the fields of catalysis and electronic devices due to their excellent electrochemical performance.This article summarizes the research of CQDs photoluminescent materials in recent years and discusses its application in energy,environment and other fields.