Oxidized Carbon Dots Research Articles

Transforming crustacean waste into a powerful antibacterial nanocomposite: unveiling the synergistic potential of novel copper doped zinc oxide–carbon dot nanocomposite

Transforming crustacean waste into a powerful antibacterial nanocomposite: unveiling the synergistic potential of novel copper doped zinc oxide–carbon dot nanocomposite

Magnetic graphene oxide carbon dot nanocomposites as an efficient quantification tool against parabens in water and cosmetic samples.

A new method is developed for the simultaneous detection and extraction of parabens, including methyl paraben (MP), ethyl paraben (EP), propyl paraben (PP), and butyl paraben (BP), based on magnetic graphene oxide carbon dot nanocomposites (Fe3O4@GO@CD). Fe3O4@GO@CD has been synthesized using one pot hydrothermal method by intercalating iron oxide and carbon dots between the layers of graphene oxide. Fe3O4@GO@CD was applied as the magnetic solid phase sorbent for the simultaneous extraction and detection of parabens from water (tap and river water) and cosmetic samples (hair serum and sunscreen cream). MP was measured at concentration of 0.25-0.26ng/mL in hair serum, while PP at 0.32-0.33ng/mL in sunscreen cream. Notably, good recoveries (88.74-98.03%; RSD = 2.31-6.88%) for river and tap water with detection limit of 0.039-0.046ng/mL were attained. The method has good cyclability up to 16 cycles and was highly repeatable. All these findings suggest that the Fe3O4@GO@CD would be potential sorbent for the analysis of parabens.

Constructing Oxygen-related Defects in Carbon Nanodots with Janus Optical Properties: Noninvasive NIR Fluorescent Imaging and Effective Photocatalytic Therapy.

Noninvasive fluorescence (FL) imaging and high-performance photocatalytic therapy (PCT) are opposing optical properties that are difficult to combine in a single material system. Herein, we report a facile approach to introducing oxygen-related defects in carbon dots (CDs) via post-oxidation with 2-iodoxybenzoic acid (IBX), in which some nitrogen atoms were substituted by oxygen atoms. Unpaired electrons in these oxygen-related defects rearranged the electronic structure of the oxidized carbon dots (ox-CDs), resulting in an emerging near-infrared (NIR) absorption band. These defects not only contributed to enhanced NIR bandgap emission but also acted as trappers for photoexcited electrons to promote efficient charge separation on the surface, leading to abundant photo-generated holes on the ox-CDs surface under visible-light irradiation. Under white LED torch irradiation, the photo-generated holes oxidized hydroxide to hydroxyl radicals in the acidification of the aqueous solution. In contrast, no hydroxyl radicals were detected in the ox-CDs aqueous solution under 730nm laser irradiation, indicating noninvasive NIR FL imaging potential. Utilizing the Janus optical properties of the ox-CDs, the in vivo NIR FL imaging of sentinel lymph nodes around tumors and efficient photothermal enhanced tumor PCT were demonstrated. This article is protected by copyright. All rights reserved.

Intrinsic dual emissive carbon dots for ratiometric sensing of acetylcholinesterase fluctuation induced by organophosphorus pesticide intoxication

Recently, the ratiometric analysis of AChE activity based on the intrinsic dual-emissive fluorescent (FL) nanomaterials is urgently required. The AChE activity can serve as a promising biomarker of neuro-toxicity induced by organophosphorus pesticides. In this work, oxidized carbon dots (ox-CDs) with intrinsic dual FL peaks at 650 and 680 nm are obtained. Moreover, the FL peak at 680 nm can be effectively quenched by Ag+ or Hg2+ while that at 650 nm can be served as self-reference signal. The introduction of AChE and acetylthiocholine (ATCh) contribute to the generation of TCh, which can capture the metal ions via competitive association to recover their FL signal to the initial status. Furthermore, the AChE activity can be determined by the ratio of FL intensity at 680 nm to that at 650 nm. As for the ox-CDs-Ag+ system, the linear range is determined to be 0.5–10 mU/mL and LOD is 0.127 mU/mL, while those for ox-CDs-Hg2+ system are 0.05–1.6 mU/mL and 0.019 mU/mL, respectively. Furthermore, the fluctuation of plasma and cerebrospinal fluid (CSF) AChE activity in dichlorvos-poisoned and pralidoxime therapeutic rats has been monitored by the ox-CDs-Ag+ system, which is essential for early diagnostics and prognostics of dichlorvos triggered neurotoxicity.

Fluorescence spotting of latent sweat fingerprints with zinc oxide carbon dots embedded in a silica gel nanopowder: a green approach

In this research article, the green synthesized CZnO-dots/Si nanopowder is expended as the LFs fluorescent tagging agent by the dust blowing method.

One-step hydrothermal preparation of highly stable N doped oxidized carbon dots for toxic organic pollutants sensing and bioimaging

A simple one-pot hydrothermally fabricated N- doped oxidized carbon dots (NOCDs) revealed an excellent photostability under constant illumination with 344 nm UV radiation for 24,000 s and intermittently tested stability under ambient conditions for over 18 months. The general susceptibility of their PL was tested under different conditions of pH and temperature. The NOCDs were found to act as optical fluorometric sensors for pH and temperature revealing a linear, cyclic and reversible trend in their fluorescence intensity between pH 3 and pH 9 (response time ≤60 s) and 25 °C–70 °C temperature range (response time: ≤240 s). As reasonable temperature and pH sensing agent, a good linear fit with an excellent regression coefficients of 0.979 and 0.989 respectively, were revealed. Typical organic pollutants such as anionic (methyl Orange (MO) and Bromophenol blue (BrPB)) and cationic (Methylene Blue (MB), Rhodamine 6 G (Rh6G)) dyes were found to quench the corresponding fluorescence through an inner filter effect. This is the first report on detection of organic pollutants (MO, Rh6G and BrPB) using NOCDs as optical sensing probe. In vitro imaging on three different kinds of cells (HEK293, A549 and MDA-MB-231) confirms their biocombatibility. The work represents great opportunities from experimental research towards the practical applications with a possibility to develop them as highly stable fluorescent imaging agents for the applications in bio-imaging and sensing.

N-doped oxidized carbon dots for methanol sensing in alcoholic beverages.

Methanol (MeOH) adulteration in alcoholic beverages resulting in irreparable health damage demands highly sensitive and cost-effective sensors for its quantification. As carbon dots are emerging as new biocompatible and sustainable light-emitting detectors, this work demonstrates the hydrothermally prepared nitrogen-doped oxidized carbon dots (NOCDs) as on-off fluorescent nanoprobes to detect MeOH traces in water and alcoholic beverages. The presence of 1% of MeOH in distilled water is found to decrease the NOCD fluorescent emission intensity by more than 90% whereas up to 70% ethanol (EtOH) content changes the signal to within 20% of its initial value. HR-TEM analysis reveals the agglomeration of the nanoprobes suspended in MeOH. Due to their selectivity towards MeOH, the fluorescent nanoprobes were successfully tested using a few MeOH spiked branded and unbranded Mexican alcoholic beverages. Varying degrees of signal quenching is observed from the fluorescent nanoprobes dispersed in different pristine beverages with a detection limit of less than 0.11 v%. Herein, we establish a new perspective towards economically viable non-toxic fluorescent probes as a potential alternative for the detection of MeOH in alcoholic beverages.

Molecular Mechanisms of the Ultra-Strong Inhibition Effect of Oxidized Carbon Dots on Human Insulin Fibrillation.

Amyloid fibrillation of protein is associated with a great variety of pathologic conditions. The aggregation of protein is a complicated process with multisteps, whereas most of the inhibitors with elaborately designed structures can show an inhibition effect only on the nucleation stages of protein fibrillation. Herein, oxidized carbon dots (CDs) were achieved to study the relationship between the surface properties of CDs and their inhibition effect on human insulin (HI) fibrillation. More oxygen-containing function groups can be obtained after oxidation reaction of CDs, such as -OH and -COOH. The results show that 10-1 CDs (the mass ratios of CD/KMnO4 is 10:1), with the highest carboxyl group content, possess the best inhibition ability. All the nucleation, growth, and final phases can be retarded by 10-1 CDs, which have been studied in detail by fluorescence spectra. However, CDs without oxidation can show only a weak inhibition effect on the nucleation stage. The 10-1 CDs is demonstrated to binding with HI monomers much stronger than that of CDs by isothermal titration calorimetry (ITC). Moreover, molecular dynamics simulations (MD) studies indicate that CDs with more carboxyl groups can show stronger affinities with native or unfolded HI monomers, which may be mainly derived from the active binding sites of histidine residues (His5 and His10) on B-chain through electrostatic interaction. Because the unfolding of B-chain in HI is prior to that of A-chain in our MD simulations, the later aggregation of HI can be inhibited effectively by the stronger binding forces between 10 and 1 CDs and the B-chain of HI.

4-nitrophenol optical sensing with N doped oxidized carbon dots

In this work, we report a facile strategy for 4-nitrophenol (4-NP) sensing using highly luminescent nitrogen-doped oxidized carbon dots. The quenching of fluorescence (turn OFF), with the addition of trace amounts of organic pollutant (4-NP) in NOCDs, has been attributed to the complete reduction of nitrogen-doped oxidized carbon dots (NOCDs) to reduced nitrogen-doped oxidized carbon dots (rNOCDs) and its formation was confirmed by infrared, X-ray diffraction and X-ray photoelectron spectroscopy measurements. The chemical changes in oxygen-containing functional groups of NOCDs, in the presence of 4-NP, are elucidated and corresponding characterization through XPS reveals the changes in the peak intensities of CC (284.5 eV) and OCO (288.6 eV), indicating a decrement in hydroxyl groups that hinder its complete reduction to NOCDs. The sensitivity of NOCDs towards 4-NP has been tested in spiked tap water in the concentration range 2 μM to 2 mM with the minimum detection limit of 2 μM (linear detection range from 2 to 100 μM with regression coefficient R2 =0.99). The proposed simple sensing platform can be used to reduce NOCDs and simultaneously sense low concentrations of 4-NP. Finally, an effective treatment to improve the reduction of nitrogen-doped graphene oxide is proposed.

Superior flame retardancy of cotton by synergetic effect of cellulose-derived nano-graphene oxide carbon dots and disulphide-containing polyamidoamines

Linear polyamidoamines containing disulphide groups (SS-PAAs) were prepared by polyaddition of L-cystine with 2,2-bisacrylamidoacetic acid (B-CYSS), N,N′-methylenebisacrylamide (M-CYSS) and 1,4-bisacryloylpiperazine (BP-CYSS). They were evaluated as flame retardants for cotton, alone or with cellulose-derived nano-graphene oxide (nGO) carbon dots, to assess whether, due to their potential as radical scavengers, the latter would improve the already good performance of SS-PAAs. In vertical flame spread tests (VFST), cotton treated with 1% nGO burned as quickly as cotton, whereas B-CYSS, M-CYSS and BP-CYSS extinguished the flame at add-ons ≥ 12, 16 and 20%, respectively. Probably, the gaseous products of SS-PAA thermal degradation quenched the radicals involved in oxidation. Cotton treated with 8, 12 and 15%, respectively, of B-CYSS, M-CYSS and BP-CYSS burned completely, but further addition of 1% nGO either inhibited ignition or shortly extinguished the flame, demonstrating synergism between the two components. Synergism was confirmed by assessing the synergism effectiveness parameter for the residual mass fraction (RMF) and by comparing the calculated and experimental TG curves in air for the cotton/SS-PAA-nGO systems. In cone calorimetry tests, the presence of nGO did not improve the already good performances of SS-PAAs, supporting the hypothesis that the action of both takes place in the gas phase.

Cover Feature: Manipulating the Optical Properties of Carbon Dots by Fine‐Tuning their Structural Features (ChemSusChem 19/2019)

The Cover Feature shows emission in oxidized and reduced carbon dots. The interaction between oxidized carbon dots (upper left) with UV light results in green emission whereas in the case of reduced carbon dots (lower right) mainly photo-assisted thermal relaxation is detected. Such different phenomena occurring within the exited states of hydrothermal carbon dots are controlled by different structural features, with oxidized carbon dots containing more oxygen functionalities and reduced carbon dots having mainly conjugated domains. More information can be found in the Full Paper by H. Luo et al. on page 4432 in Issue 19, 2019 (DOI: 10.1002/cssc.201901795).

Photocrosslinked Chitosan Hydrogels Reinforced with Chitosan‐Derived Nano‐Graphene Oxide

AbstractChitosan and chitosan‐derived nano‐graphene oxide carbon dots are successfully methacrylated and utilized for the fabrication of photocurable hydrogels. The addition of the nano‐graphene oxide (nGO) does not significantly delay the polymer network build‐up, but significantly reduces the storage modulus of the crosslinked network, with important detrimental effects on the mechanical performance. By replacing nGO with methacrylated M‐nGO, the mechanical performance of the crosslinked polymer network is improved with an increase of the storage modulus as a function of increasing the M‐nGO content in the photocurable formulation.

Near-infrared light-mediated photodynamic/photothermal therapy nanoplatform by the assembly of Fe3O4 carbon dots with graphitic black phosphorus quantum dots.

BackgroundRecently, combined photodynamic therapy (PDT) and photothermal therapy (PTT) has become a desired treatment for cancer. However, the development of economic, high-efficiency, and safe photosensitizers/photothermal agents remains a significant challenge.MethodsA novel nanocomposite has been developed via the assembly of iron oxide carbon dot (Fe3O4-CDs) nanoparticles and black phosphorus quantum dots (genipin [GP]-polyglutamic acid [PGA]-Fe3O4-CDs@BPQDs), and this nanocomposite shows a broad light-absorption band and a photodegradable character.ResultsIn vitro and in vivo assays indicated that GP-PGA-Fe3O4-CDs@BPQDs were highly biocompatible and exhibited excellent tumor-inhibition efficacy, due to the synergistic PTT and PDT via a near-infrared laser. Importantly, in vivo tumor magnetic resonance imaging (MRI) results illustrated that GP-PGA-Fe3O4-CDs@BPQDs can be specifically applied for enhanced T2 MRI of tumors. This work presents the first combined application of a PDT and PTT effect deriving from BPQDs and MRI from Fe3O4-CDs, which may promote utilization of black BPQDs in biomedicine.ConclusionAs expected, GP-PGA-Fe3O4-CDs@BPQDs displayed a dramatically enhanced ability to destroy tumor cells, due to the synergistic combination of PTT and PDT.

Construction of Bioactive and Reinforced Bioresorbable Nanocomposites by Reduced Nano-Graphene Oxide Carbon Dots

Bioactive and reinforced poly(ε-caprolactone) (PCL) films were constructed by incorporation of cellulose derived reduced nanographene oxide (r-nGO) carbon nanodots. Two different microwave-assisted reduction routes in superheated water were utilized to obtain r-nGO and r-nGO-CA. For the latter, a green reducing agent caffeic acid (CA), was incorporated in the reduction process. The materials were extruded and compression molded to obtain proper dispersion of the carbon nanodots in the polymer matrix. FTIR results revealed favorable interactions between r-nGO-CA and PCL that improved the dispersion of r-nGO-CA. r-nGO, and r-nGO-CA endorsed PCL with several advantageous functionalities including improved storage modulus and creep resistance. The considerable increase in storage modulus demonstrated that the carbon nanodots had a significant reinforcing effect on PCL. The PCL films with r-nGO-CA were also evaluated for their osteobioactivity and cytocompatibility. Bioactivity was demonstrated by formation of hydroxyapatite (HA) minerals on the surface of r-nGO-CA loaded nanocomposites. At the same time, the good cytocompatibility of PCL was retained asillustrated by the good cell viability to MG63 osteoblast-like cells giving promise for bone tissue engineering applications.

Purification, Selection, and Partition Coefficient of Highly Oxidized Carbon Dots in Aqueous Two-Phase Systems Based on Polymer-Salt Pairs.

In general, the methodologies for the preparation of carbon dots (CDs) lead to the formation of nanostructures with size and surface chemistry heterogeneity. Because the electronic and optical properties of these nanoparticles are directly associated with these properties, the development of purification and selection strategies is essential. Herein, we report a systematic study of the spontaneous partition and separation of highly oxidized carbon dots (OCDs) prepared by the dehydration and oxidation reactions of cotton cellulose in aqueous two-phase systems (ATPSs) based on polymer-salt pairs. The partition of the CDs was investigated in different ATPSs in which the effects of the cations and anions of the salts, molecular mass and nature of the polymer, tie-line length, initial pH, and surface modification of the nanoparticles on the partition coefficient (K) were evaluated. The results showed that the best separation occurred with a system consisting of PEO1500 + lithium sulfate + water using reduced CDs with hydrazine. Alternatively, the lowest value of K, 0.79, was obtained for a poly(ethylene oxide) PEO1500 + sodium tartrate + water system with pH = 6 using OCDs. The detailed analyses of the top and bottom phases of the systems with fluorescence and ultraviolet-visible spectroscopy showed that ATPSs are capable, in addition to partitioning, of separating the nanoparticles with different optical properties, which are directly associated with the surface properties and particle sizes. We believe that the presented methodology is an alternative, practical, fast, and potentially scalable technique for the separation of carbon nanostructures with different optical properties.

Facile construction of reduced graphene oxide–carbon dot complex embedded molecularly imprinted polymers for dual-amplification and selective electrochemical sensing of rutoside

This article reported reduced graphene oxide–carbon dot embedded molecularly imprinted polymers for sensitive and selective electrochemical sensing of rutoside.

Layer-by-layer self-assembly for carbon dots/chitosan-based multilayer: Morphology, thickness and molecular interactions

Oxidized Carbon dots, prepared from the acid dehydration of cellulose, were used in the preparation of self-assembled films with the biopolymer chitosan. The morphology, thickness and molecular interactions of the films were characterized with a variety of techniques including AFM, FTIR, UV–Vis and Surface Plasmon Resonance (SPR) spectroscopy. We noticed an increase in the thickness of the bilayers with increasing ionic strength and pH provided by the increase of the amount of CD and chitosan deposited in each cycle. This increase was mainly due to higher flexibility of the biopolymer on these conditions and to the formation of agglommerates of carbon dots in high ionic strength. On the other hand, the greater flexibility together with the higher adsorption have generated films with smoother morphology due to the higher coating on the spherical particles. The results described here suggest that the structure of the film, i.e., morphology and thickness can be easily controlled and reproduced, by controlling the conditions of the biopolymer and CD solutions, in addition to the traditional number of dips. Finally, the prepared films have potential application in the development of imunosensors, functional coatings, surface photoactive and UV protection films.

Reduced Carbon Dots versus Oxidized Carbon Dots: Photo‐ and Electrochemiluminescence Investigations for Selected Applications

The study of the composition, morphology, and surface structure of carbon dots (Cdots) is critical to understanding their effect on the photo- and electrochemiluminescence (PL and ECL) of Cdots in selected applications. Herein, two kinds of Cdots were prepared with 3-(3,4-dihydroxyphenyl)-L-alanine (L-DOPA) as precursor. The Cdots prepared by using a carbonization-extraction strategy have a low oxidation level and are denoted as reduced Cdots (r-Cdots). The Cdots obtained with a carbonization-oxidation process are highly oxidized and are denoted as oxidized Cdots (o-Cdots). The o-Cdots have a carbon core and oxygen-containing loose shell, but the r-Cdots consist mainly of the carbon core. Whereas r-Cdots have a strong blue PL but no apparent ECL response, o-Cdots exhibit a relatively weak PL and strong ECL emission. These properties allow for selected applications of the Cdots. The r-Cdots were used in cell imaging with their high PL emission. The o-Cdots, with their high ECL efficiencies, were selected to sense Cu(2+) with Cu(2+) -inducing ECL quenching in the o-Cdots/K2 S2 O8 system. This work provides the possibility to control the composition of Cdots for selected applications and shows a good way to characterize surface traps of Cdots because ECL is characterized by the surface-state and PL is mainly related to the core-state in Cdots.