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In this study, top-down syntheses of carbon dots (CDs) from four different carbon precursors, namely, carbon nano powders, graphite, graphene, and carbon nanotubes, were carried out. Systematic study demonstrated that the optical properties and surface functionalities of the CDs were quite similar and mainly influenced by the synthesis method, while the sizes, morphologies, chemical compositions, and core structures of the CDs were heavily influenced by the carbon precursors. On the basis of these studies, the formation processes and structural models of these four top-down CDs were proposed. The cell cytotoxicity and photothermal conversion efficiency of these CDs were also carefully evaluated, demonstrating their potential applications in photothermal therapy.

The synthesis of lignin-based graphene quantum dots (GQDs) with excellent fluorescence stability, quantum yield, and biocompatibility for sensitive and selective detection of Fe 3+ and ascorbic acid (AA) has remained a challenging endeavor. Using an acidolysis process with 17.5% nitric acid followed by hydrothermal treatment at 200 °C, this study provided an improved synthesis route for the production of high-quality GQDs from alkali lignin. The nitrogen-doped GQDs exhibit remarkable fluorescence stability under a wide range of pH (3-10), duration (1-12 h), and [NaCl] (0-1000 mM) conditions, and have a high quantum yield of 28%. The GQDs or GQDs/Fe 3+ sensing systems ([GQDs] at 50 mg L -1 , [Fe 3+ ] at 500 μmol L -1 , and UV excitation at 370 nm) for fluorescence sensing of Fe 3+ or AA have excellent sensitivity, selectivity, and reproducibility. For Fe 3+ and AA, the limit of detection is 1.49 and 1.62 μmol L -1 , respectively. Mechanism investigation shows that photoluminescence quenching is caused by the formation of GQDs-Fe 3+ complexes, whereas fluorescence recovery is due to Fe 3+ reduction by AA., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Glutathione (GSH) is a thiol that plays a significant role in nutrient metabolism, antioxidant defense and the regulation of cellular events. GSH deficiency is related to variety of diseases, so it is useful to develop novel approaches for GSH evaluation and detection. In this study we used nitrogen and phosphorus co-doped carbon dot-gold nanoparticle (NPCD-AuNP) composites to fabricate a simple and selective fluorescence sensor for GSH detection. We employed the reductant potential of the nitrogen and phosphorus co-doped carbon dots (NPCDs) themselves to form AuNPs, and subsequently NPCD-AuNP composites from Au 3+ . The composites were characterized by using a range of spectroscopic and electron microscopic techniques, including electrophoretic light scattering and X-ray diffraction. The overlap of the fluorescence emission spectrum of NPCDs and the absorption spectrum of AuNPs resulted in an effective inner filter effect (IFE) in the composite material, leading to a quenching of the fluorescence intensity. In the presence of GSH, the fluorescence intensity of the composite was recovered, which increased proportionally to increasing the GSH concentration. In addition, our GSH sensing method showed good selectivity and sensing potential in human serum with a limit of detection of 0.1 µM and acceptable results.

In this work, binding interaction between molybdenum disulfide quantum dots (MoS 2 QDs) and human serum albumin (HSA) was researched deeply to dissect the conformational variation and fibrillation of HSA affected by MoS 2 QDs. The results revealed that MoS 2 QDs bound strongly with HSA with molar ratio of 1:1 under the joint actions of hydrogen bond and van der Waals force, leading to the static fluorescence quenching of HSA. MoS 2 QDs caused the secondary structure transition of HSA from α-helix stepwise to β-turn, β-sheet, and random coil gradually. MoS 2 QDs reduced both the molar enthalpy change and the melting temperature of HSA, reducing the thermal stability of HSA significantly. It is worth noting that MoS 2 QDs inhibited the fibrillation process of HSA according to the reduced hydrophobic environment and the disturbance of disulfide bonds in HSA network structure. These results reveal the precise binding mechanism of MoS 2 QDs with HSA at molecular level, providing indispensable information for the potential application of MoS 2 QDs in biological fields., (Copyright © 2021 Elsevier B.V. All rights reserved.)

We prepared the magnetic chitosan carbon quantum dot nanoparticles (Fe 3 O 4 @CQD NPs) via the hydrothermal treatment of chitosan biopolymer and then its magnetization with Fe 3 O 4 nanoparticles. (4-Acetylphenyl)boronic acid compound was utilized for the modification of surface of Fe 3 O 4 @CQD nanoparticles via the covalent imine bond formation between NH 2 groups of chitosan quantum dot with carbonyl functional of acetyl-substituted arylboronic acid. The synthesized Fe 3 O 4 @CQD@AP-B(OH) 2 was characterized by FE-SEM, EDS, XRD, VSM and ICP-OES analysis and its fluorescence property was studied. This magnetic multifunctional nanoplatform sensor has shown high potential sensitivity for Cu 2+ ions (in the range of 1.0-30.0 μM with limit of detection 0.3 μM) through interaction of cupric ions with the boronic-acid moiety., (Copyright © 2021 Elsevier B.V. All rights reserved.)

There is an urgent need for materials that can efficiently generate reactive oxygen species (ROS) and be used in photodynamic therapy (PDT) as two-photon imaging contrast probes. In this study, graphene quantum dots (GQDs) were subjected to amino group functionalization and nitrogen doping (amino-N-GQDs) via annealing and hydrothermal ammonia autoclave treatments. The synthesized dots could serve as a photosensitizer in PDT and generate more ROS than conventional GQDs under 60-s low-energy (fixed output power: 0.07 W·cm -2 ) excitation exerted by a 670-nm continuous-wave laser. The generated ROS were used to completely eliminate a multidrug-resistant strain of methicillin-resistant Staphylococcus aureus (MRSA), a Gram-positive bacterium. Compared with conventional GQDs, the amino-N-GQDs had superior optical properties, including stronger absorption, higher quantum yield (0.34), stronger luminescence, and high stability under exposure. The high photostability and intrinsic luminescence of amino-N-GQDs contribute to their suitability as contrast probes for use in biomedical imaging, in addition to their bacteria tracking and localization abilities. Herein, the dual-modality amino-N-GQDs in PDT easily eliminated multidrug-resistant bacteria, ultimately revealing their potential for use in future clinical applications.

Overexpression of collagenase, elastase, and tyrosinase is caused by external factors such as ultraviolet (UV) radiation and stress, resulting in wrinkle formation and freckles through the loss of skin elasticity and skin pigmentation. In this study, we developed novel carbon quantum dots (CQDs) with antioxidant and anti-aging properties using tannic acid as a carbon source through a simple microwave-assisted pyrolysis method. The synthesized tannic acid-derived CQDs (T-CQDs) showed bright blue fluorescence (QY = 28.2 ± 4.0%), exhibiting maximum emission at 430 nm under 350 nm excitation. Even though small amount of the T-CQDs (3 μ g ml -1 ) was used, they exhibited excellent free radical scavenging ability (82.8 ± 4.3%). Also, the T-CQDs (10 μ g ml -1 ) revealed remarkable inhibitory activity against skin aging-related collagenase (77.6 ± 4.8%), elastase (52.6 ± 1.0%), and tyrosinase (44.2 ± 1.3%), demonstrating their antioxidant and anti-aging effects. Furthermore, their antioxidant and anti-aging properties were superior to those of tannic acid, L-ascorbic acid, and quercetin used as positive controls. Finally, the T-CQDs effectively suppressed UV-induced reactive oxygen species generation by 30% at the cellular levels and showed high cell viability (99.7 ± 0.8%) even at 500 μ g ml -1 . These results demonstrate that the T-CQDs with superior antioxidant, anti-aging properties, and low cytotoxicity can be utilized as novel anti-aging materials in cosmetic and nanomedicine fields., (© 2021 IOP Publishing Ltd.)

Purpose: Sensitive and selective point-of-care biosensor is an urgent pursuit of serological antibody detection to control parasite pathogen. For specific, quantitative and on-site screening of Trichinella spiralis infection in livestock, a quantum dot nanobead-monoclonal antibody (QB-mAb) probe-based immunochromatographic assay (ICA) was developed by introducing a competitive sandwich strategy (QB-CICA)., Methods: In the QB-CICA, QB-mAb probes competed with serum antibody for a particular epitope, followed by immunocomplexes binding to capture antibody on the test line. With the accumulation of target antibody, captured probes served as signal elements for fluorescent readout in a "turn off" mode, along with the fluorescence gradually weakened. The sensitivity and standard calibration curve of the QB-CICA were quantified using swine sera as negative control (n = 200) and artificial infected swine sera (n = 80) compared with a commercial ELISA kit. Besides, Trichinella spiralis -antibody targeting test ability of the QB-CICA, instead of other parasites or viruses antibodies (n = 10), was evaluated., Results: The QB-CICA exhibited a good linear range, a low detection limit of 189.92 ng mL -1 and 100% selectivity that was higher than commercial ELISA kit (90%), as well as the same serological positive rate (100%) with commercial ELISA kit in different infection dose models., Conclusion: Taking advantage of its simplicity, short response time (25 min), sensitivity and specificity, the proposed QB-CICA has potential applications for parasite-related antibody monitoring in food safety and clinical diagnosis fields., Competing Interests: None of the authors has any financial or personal relationship with other people or organisations that could inappropriately influence or bias the work reported in this paper., (© 2021 Xu et al.)

Background: It is well known that smoking is harmful to health; however, it can also ameliorate anxiety. To date, it is unclear whether any nanoparticles found in cigarette mainstream smoke (CS) contribute to this effect., Aim: The aim of this study was to assess the particle composition of CS to identify novel anti-anxiety components., Methods: Carbon dots (CDs) from CS (CS-CDs) were characterised using high-resolution transmission electron microscopy, Fourier-transform infrared, ultraviolet, fluorescence, X-ray photoelectron spectroscopy, X-ray diffraction and high-performance liquid chromatography. The anti-anxiety effects of CS-CDs in mouse models were evaluated and confirmed with the elevated plus maze and open-field tests., Results: The quantum yield of CS-CDs was 13.74%, with a composition of C, O, and N. In addition, the surface groups contained O-H, C-H, C=O, C-N, N-H, C-O-C, and COO- bonds. Acute toxicity testing revealed that CS-CDs had low in vitro and in vivo toxicity within a certain concentration range. The results of the elevated plus maze and open-field tests showed that CS-CDs had a significant anti-anxiety effect and a certain sedative effect in mice. The mechanism of these effects may be related to the decrease in glutamate levels and promotion of norepinephrine production in the mouse brain, and the decrease in dopamine in mouse serum due to CS-CDs., Conclusion: CS-CDs may have anti-anxiety and certain sedative effects. This study provides a new perspective for a more comprehensive understanding of the components, properties, and functions of CS. Furthermore, it offers a novel target for the development of smoking cessation treatments, such as nicotine replacement therapy., Competing Interests: The authors declare that they have no conflicts of interest for this work., (© 2021 Zhao et al.)

Background: Carbon dots (CDs) emitting near-infrared fluorescence were recently synthesized from green leaves. However, the Hg 2+ detection of CDs was limited because of the insufficient water solubility, low fluorescence and poor stability., Methods: Dual fluorescence emission water-soluble CD (Dual-CD) was prepared through a solvothermal method from holly leaves and low toxic PEI 1.8k . PEG was further grafted onto the surface to improve the water solubility and stability., Results: The Dual-CD solution can emit 487 nm and 676 nm fluorescence under single excitation and exhibit high quantum yield of 16.8%. The fluorescence at 678 nm decreased remarkably while the emission at 470 nm was slightly affected by the addition of Hg 2+ . The ratiometric Hg 2+ detection had a wide linear range of 0-100 μM and low detection limit of 14.0 nM. In A549 cells, there was a good linear relation between F 487 /F 676 and the concentration of Hg 2+ in the range of 0-60 μM; the detection limit was 477 nM. Furthermore, Dual-CD showed visual fluorescence change under Hg 2+ ., Conclusion: Dual-CD has ratiometric responsiveness to Hg 2+ and can be applied for quantitative Hg 2+ detection in living cells., Competing Interests: The authors report no conflicts of interest for this work., (© 2021 Wang et al.)

Requirement for medication from pathogenic human viruses and cancer diseases are urgently considered, while, numerous reports were focused on investigating easily manufactured and excellently effective therapeutic reagents. Herein, CQDs were prepared with size of 2.1 nm from both of carrageenan and pullulan. CQDs nucleated from pullulan showed higher anti-proliferative effects against cancer cells, while, treatment with 100 μg/mL of CQDs colloids originated from pullulan and carrageenan separately resulted in diminishing of cancer cell viability percent to be 42.1 & 58.7%, respectively. Plaque reduction assay was also affirmed that, 2.5 μg/L of both of pullulan and carrageenan based CQDs exhibited viral inhibition with percent of 44.3& 59.5%, respectively. As a conclusion, pullulan showed seniority over carrageenan in nucleation of CQDs with higher anticancer activities. While, estimation of antiviral performance of the prepared CQDs confirmed the priority of carrageenan compared to pullulan in preparation of CQDs as antiviral laborer., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Chiral carbon dots (CDs) integrated the advantages of achiral CDs and the unique chiral property, which expand the prospect of the biological applications of CDs. However, the structure control and the origin of chirality for chiral CDs remain unclear. Herein, chiral CDs were obtained by thermal polymerization of chiral amino acids and citric acid, and their handedness of chirality could be controlled by adjusting the reaction temperature, which leads to different kinds of surface modifications. With aliphatic amino acids as a chiral source, all of the CDs that reacted at different temperatures (90-200 °C) have the same handedness of the chiral source. But with aromatic amino acids as a chiral source, CDs with maintained or inversed handedness compared with the chiral source could be obtained by adjusting the reaction temperature. Below a temperature of 120 °C, the chiral source was modified with CDs by esterification and transferred the handedness of chirality; at high temperatures (above 150 °C), which mainly connected by amidation accompanying with the formation of rigid structure generated by the π conjugation between the aromatic nucleus of chiral source and the carbon core of CDs, caused the inversing of the chiral signal. Further, we investigated the chiral effects of CDs on the glucose oxidase activity for a highly sensitive electrochemical biosensor.

Cadmium Oxide nanoparticles have the lowest toxicity when compared to nanoparticles of other semiconductors and they are not detrimental to human and mammalian cells, thereby making them candidates for targeting cancer cells. Synadenium cupulare plant extracts were used to synthesize CdO/CdCO 3 nanocomposite using cadmium nitrate tetrahydrate 98% as a precursor salt. The resultant nanoparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The nanoparticles were then screened for effect on breast cancer cell lines (MCF-7 and MDA MB-231) and Vero cell line to determine their growth inhibition effect. Cytotoxicity effect was evaluated using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. XRD showed the peaks of monteponite CdO and otavite CdCO 3 nanoparticles. TEM results showed irregular and spherical particles of varying sizes, whilst SEM revealed a non-uniform morphology. FTIR results showed peaks of functional groups which are present in some of the phytochemical compounds found in S. cupulare, and point to the presence of CdO. Annealed CdO/CdCO 3 NPs showed selectivity for MCF7 and MDA MB231 in comparison to Vero cell line, thereby supporting the hypothesis that cadmium oxide nanoparticles inhibit growth of cancerous cells more than non-cancerous cells.

Background: Azo dyes are the most widely used synthetic colorants in the textile, food, pharmaceutical, cosmetic, and other industries, accounting for nearly 70% of all dyestuffs consumed. Recently, much research attention has been paid to efficient monitoring of these hazardous chemicals and their related metabolites because of their potentially harmful effect on environmental issues. In contrast to the complex and expensive instrumental procedures, the detection system based on the quantum dots (QDs) with the superior optochemical properties provides a new era in the pollution sensing and prevention., Methods: We have developed a QD-enzyme hybrid system to probe methyl red (MR) in aqueous solutions using a fluorescence quenching procedure., Results: The azoreductase enzyme catalyzed the reduction of azo group in MR, which can efficiently decrease the Förster resonance energy transfer between the QDs and MR molecules. The correlation between the QDs photoluminescence recovery and MR enzymatic decolorization at the neutral phosphate buffer permitted the creation of a fluorescence quenching-based sensor. The synthesized biosensor can be used for the accurate detection of MR in a linear calibration over MR concentrations of 5-84 μM, with the limit of detection of 0.5 μM in response time of three minutes., Conclusion: Our findings revealed that this fluorometric sensor has the potential to be successfully applied for monitoring a wide linear range of MR concentration with the relative standard deviation of 4% rather than the other method.

A nanohybrid prepared from green source (nanocellulose, NC) and nitrogen, sulfur co-doped graphene quantum dots (N, S@GQDs) was prepared for the electrochemical detection of olanzapine (OLZ), atypical antipsychotic primarily used to treat schizophrenia and bipolar disorder. Polar groups on the surface of NC and N, S@GQDs provide more anchoring sites for adsorption of OLZ onto the electrode surface. In addition, it provides high conductivity, good mechanical strength, large surface area, and excellent electrical conductivity. The nanocomposite was characterized morphologically and electrochemically by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and square wave adsorptive stripping voltammetry (SWAdSV). Under the optimized conditions, the modified electrode has a good response in the range of 1.5-90.0 × 10 -8  M with LOD of 0.5 × 10 -8  M. The proposed electrode offers high sensitivity, selectivity, and reliability towards OLZ detection. The SWAdSV was used to determine OLZ in pharmaceutical tablets, human plasma and urine with good recoveries % and reasonable RSD% values., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: The excess production of reactive oxygen species (ROS) after traumatic spinal cord injury (TSCI) has been identified as a leading cause of secondary injury, which can significantly exacerbate acute damage in the injured spinal cord. Thus, scavenging of ROS has emerged as an effective route to ameliorate secondary spinal cord injury., Purpose: Selenium-doped carbon quantum dots (Se-CQDs) with the ability to scavenge reactive oxygen species were prepared and used for efficiently ameliorating secondary injury in TSCI., Methods: Water-soluble Se-CQDs were easily synthesized via hydrothermal treatment of l-selenocystine. The chemical structure, size, and morphology of the Se-CQDs were characterized in detail. The biocompatibility and protective effects of the Se-CQDs against H 2 O 2 -induced oxidative damage were investigated in vitro. Moreover, the behavioral test, bladder function, histological observation, Western blot were used to investigate the neuroprotective effect of Se-CQDs in a rat model of contusion TSCI., Results: The obtained Se-CQDs exhibited good biocompatibility and remarkable protective effect against H 2 O 2 -induced oxidative damage in astrocytes and PC12 cells. Moreover, Se-CQDs displayed marked anti-inflammatory and anti-apoptotic activities, which thereby reduced the formation of glial scars and increased the survival of neurons with unscathed myelin sheaths in vivo. As a result, Se-CQDs were capable of largely improving locomotor function of rats with TSCI., Conclusion: This study suggests that Se-CQDs can be used as a promising therapeutic platform for ameliorating secondary injury in TSCI., Competing Interests: The authors report no conflicts of interest for this work., (© 2020 Luo et al.)

The shortcomings in Boron neutron capture therapy (BNCT) and Hyperthermia for killing the tumor cell desired for the synthesis of a new kind of material suitable to be first used in BNCT and later on enable the conditions for Hyperthermia to destroy the tumor cell. The desire led to the synthesis of large band gap semiconductor nano-size Boron-10 enriched crystals of hexagonal boron nitride ( 10 BNNCs). The contents of 10 BNNCs are analyzed with the help of x-ray photoelectron spectroscopy (XPS) and counter checked with Raman and XRD. The 10 B-contents in 10 BNNCs produce 7 Li and 4 He nuclei. A Part of the 7 Li and 4 He particles released in the cell is allowed to kill the tumor (via BNCT) whereas the rest produce electron-hole pairs in the semiconductor layer of 10 BNNCs suggested to work in Hyperthermia with an externally applied field., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Introduction: The charcoal processed product of Paeoniae Radix Alba (PRA), PRA Carbonisata (PRAC), has long been used for its hepatoprotective effects. However, the material basis and mechanism of action of PRAC remain unclear., Aim: To explore the hepatoprotective effects of Paeoniae Radix Alba Carbonisata-derived carbon dots (PRAC-CDs)., Methods: PRAC-CDs were characterized using transmission electron microscopy, high-resolution transmission electron microscopy, ultraviolet, fluorescence, Fourier transform infrared and X-ray photoelectron spectroscopy, X-ray diffraction, and high-performance liquid chromatography. The hepatoprotective effect of PRAC-CDs was evaluated and confirmed using the classic carbon tetrachloride acute liver injury model., Results: PRAC-CDs averaged 1.0-2.4 nm in size and exhibited a quantum yield of 5.34% at a maximum excitation wavelength of 320 nm and emission at 411 nm. PRAC-CDs can reduce the ALT and AST levels of mice with carbon tetrachloride-induced acute liver injury and have a mitigating effect on the rise in TBA and TBIL. More interestingly, PRAC-CDs can significantly reduce MDA and increase SOD levels, demonstrating that PRAC-CDs can improve the body's ability to scavenge oxygen free radicals and inhibit free radical-induced liver cell lipid peroxidation, thereby preventing liver cell damage., Conclusion: These results demonstrate the remarkable hepatoprotective effects of PRAC-CDs against carbon tetrachloride-induced acute liver injury, which provide new insights into potential biomedical and healthcare applications of CDs., Competing Interests: The authors report no conflicts of interest for this work., (© 2020 Zhao et al.)

In the present research, we prepared new glycodendrimer containing β-cyclodextrin (β-CD) in three steps. At first, graphene quantum dots (GQDs) synthesized through pyrolysis of the citric acid (CA). Then the polyamidoamine (PAMAM) dendrimer was grown from the surface of the modified GQDs (GQDs-PAMAM). Finally, the prepared GQDs-PAMAM was functionalized with β-CD to obtain the glycodendrimer (GQDs-PAMAM-β-CD). The synthesized glycodendrimer characterized using several techniques. The phenol-sulfuric acid test obtained the amount of the β-CD about 30.37 %. 61.2 % of doxorubicin (DOX) was loaded in the prepared glycodendrimer. DOX@GQDs-PAMAM-β-CD displayed the pH-sensitive drug release profile, which fitted the Higuchi kinetic model. The biological test outcomes showed that the GQDs-PAMAM-β-CD is a safe carrier with good capability in penetration to the cancer cells. Moreover, DOX@GQDs-PAMAM-β-CD exhibited more efficiency in the killing of the cancer cells compared to neat DOX. Obtained results suggested that prepared glycodendrimer could be a potential nanosystem for breast cancer treatment., Competing Interests: Declaration of Competing Interest The authors declare that there are no conflicts of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

While carbon-based materials have spearheaded numerous breakthroughs in biomedicine, they also have procreated many logical concerns on their overall toxicity. Carbon dots (CDs) as a respectively new member have been extensively explored in nucleus directed delivery and bioimaging due to their intrinsic fluorescence properties coupled with their small size and surface properties. Although various in vitro/in vivo studies have shown that CDs are mostly biocompatible, sufficient information is lacking regarding genotoxicity of them and underlying mechanisms. This study aims to analyze the real-time cytotoxicity of super tiny CDs (2.05 ± 0.22 nm) on human breast cancer cells (MCF7) and human primary dermal fibroblast cell cultures (HDFa) by xCELLigence analysis system for further evaluating their genotoxicity and clastogenicity to evaluate the anti-tumor potential of CDs on breast adenocarcinoma. As combined with flow cytometry studies, comet assay and cytokinesis-block micronucleus assay suggest that the CDs can penetrate to the cell nuclei, interact with the genetic material, and explode DNA damage and G0/G1 phase arrest in cancer cells even at very low concentrations (0.025 ppm) which provide a strong foundation for the design of potentially promising CD-based functional nanomaterials for DNA-damage induced treatment in cancer therapy.

In this work, we explored a high efficient electrochemiluminescence (ECL) sensor based on the synergistic enhancement strategy of Zn-doped MoS 2 quantum dots (QDs) and reductive Cu(I) particles. On the one hand, Zn-doped MoS 2 QDs with sulfur vacancies were designed to improve the ECL activity of QDs. The regulated sulfur vacancies with zinc doping resulted in adsorption and coordination with transition metals of H 2 O 2 as coreactant. On the other hand, reductive Cu(I) particles were prepared to further catalyze the coreactant in the ECL system. The tight combination of glutathione (GSH) and copper in reductive Cu(I) particles can perfectly stabilize Cu(I) with outstanding catalytic activity in neutral pH condition. Under reduction of the cathode, the reductive Cu(I) particles acted as the catalytic role continuously. As a result, more ·OH were generated from H 2 O 2 . The signal of Zn-doped MoS 2 QDs had 4.5-fold enhancement with the assistance of reductive Cu(I) particles. Furthermore, the DNA walker cycle was designed in presence of T7 exonuclease for HPV 16 DNA detection. The biosensor realized sensitive determination of HPV 16 DNA from 0.1 nmol L -1 to 200 nmol L -1 with the LOD of 0.03 nmol L -1 . Interestingly, the entire sensing system can be reproduced on a simple family-friendly device powered by batteries. The ECL signal captured by a smartphone can be processed into high-resolution imaging by self-developed software, which provides great possibility of point-of-care HPV 16 DNA determination in the future., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Tailoring of the biodegradation of photoluminescent silicon quantum dots (Si QDs) is important for their future applications in diagnostics and therapy. Here, the effect of drying and surface pretreatment on the dissolution rate of Si QDs in model liquids and living cells was studied in vitro using a combination of photoluminescence and Raman micro-spectroscopy. Porous silicon particles were obtained by mechanical milling of electrochemically etched mesoporous silicon films, and consist of interlinked silicon nanocrystals (QDs) and pores. The samples were subjected to super-critical drying with CO2 solvent (SCD) or air drying (AD) and then annealed at 600 °C for 16 hours in 1% oxygen to obtain nano-sized Si QDs. The obtained samples were characterized by a core-shell structure with a crystalline silicon core and a SiO2 layer on the surface. The sizes of the crystalline silicon cores, calculated from Raman scattering spectra, were about 4.5 nm for the initial AD-SiQDs, and about 2 nm for the initial SCD-SiQDs. Both the AD-Si QDs and the SCD-Si QDs exhibited visible photoluminescence (PL) properties due to quantum confinement effects. The dissolution of the nanocrystals was evaluated through their PL quenching, as well as by the presence of a low-frequency shift, broadening, and a decrease in the intensity of the Raman signal. The stability of the AD-Si QDs and the complete dissolution of the SCD-Si QDs during 24 hours of incubation with cells have been demonstrated. This might explain the apparent lower cytotoxicity observed for SCD-Si QDs.

Herein, nitrogen-doped carbon dots (N-CDs) emitting blue fluorescence were prepared using L-tartaric acid and triethylenetetramine through a simple and quick microwave-assisted method. The synthesized N-CDs displayed excitation-dependent fluorescence behavior, and their maximum excitation and emission wavelengths were 350 and 425 nm, respectively. The obtained N-CDs, which featured excellent fluorescence properties with a high fluorescence quantum yield of 31%, were applied to detect metronidazole (MNZ), which can effectively quench the fluorescence intensity of N-CDs due to the inner filter effect. This phenomenon was used as basis to develop a label-free fluorescent method for rapid MNZ determination, with the limit of detection of 0.22 μM and corresponding linear range of 0.5-22 μM. Hence, we had established a fluorescence method for MNZ detection and applied it to detect MNZ in real samples with satisfactory results. Finally, N-CDs with superior biocompatibility were applied for cell imaging and MNZ detection by the changes in fluorescence intensity., Competing Interests: Declaration of competing interest The authors declared there are no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Valorisation of industrial low-value waste residues was preconized. Hence, carbon dots (C-dots) were synthesized from wastewaters of the cork industry-an abundant and affordable, but environmentally-problematic industrial effluent. The carbon nanomaterials were structurally and morphologically characterised, and their photophysical properties were analysed by an ensemble of spectroscopy techniques. Afterwards, they were successfully applied as highly-sensitive fluorescence probes for the direct detection of haemproteins. Haemoglobin, cytochrome c and myoglobin were selected as specific targets owing to their relevant roles in living organisms, wherein their deficiencies or surpluses are associated with several medical conditions. For all of them, remarkable responses were achieved, allowing their detection at nanomolar levels. Steady-state and time-resolved fluorescence, ground-state UV-Vis absorption and electronic circular dichroism techniques were used to investigate the probable mechanisms behind the fluorescence turn-off of C-dots. Extensive experimental evidence points to a static quenching mechanism. Likewise, resonance energy transfer and collisional quenching have been discarded as excited-state deactivating mechanisms. It was additionally found that an oxidative, photoinduced electron transfer occurs for cytochrome c , the most electron-deficient protein. Besides, C-dots prepared from citric acid/ethylenediamine were comparatively assayed for protein detection and the differences between the two types of nanomaterials highlighted.

The detection and differentiation of tetracyclines (TCs) has received increasing attention due to the severe threat they pose to human health and the ecological balance. A dual-channel fluorescence sensor array based on two carbon quantum dots (CDs) was fabricated to distinguish between four TCs, including tetracycline (TC), oxytetracycline (OTC), doxycycline (DOX), and metacycline (MTC). A distinct fluorescence variation pattern (I/I 0 ) was produced when CDs interacted with the four TCs. This pattern was analyzed by LDA and SVM. This was the first time that SVM was used for data processing of fluorescence sensor arrays. LDA and SVM showed that the array has the capacity for parallel and accurate determination of TCs at concentrations between 1.0 μM and 150 μM. In addition, the interference experiment using metal ions and antibiotics as possible coexisting interference substances proves that the sensor array has excellent selectivity and anti-interference ability. The array was also used for the accurate detection and identification of TCs in binary mixtures, and furthermore, the four TCs were successfully identified in river water and milk samples. Besides, the sensor array successfully identified the four TCs in 72 unknown samples with a 100% accuracy. The results proved that SVM can achieve the same accurate classification and prediction as LDA, and considering its additional advantages, it can be used as an optional supplementary method for data processing, thereby expanding the data processing field., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

Prevention is the most effective management strategy for influenza A infection in humans. In this study, we developed a CdSe/CdS/ZnS quantum dot (QD) fluorescent dye for rapid and sensitive detection of two common subtypes (H1N1 and H3N2) of influenza A virus, and examined its utility. CdSe/CdS/ZnS QD was conjugated with antibody (Ab) after conjugation with latex, making QD conjugate of QD + Latex + Ab. A stable photoluminescence of QD conjugate and advantage of CdSe/CdS/ZnS QD used was characterized in this study. The performance of a rapid fluorescent immunochromatographic test (FICT) employing QD conjugate (QD-FICT) in detecting influenza A/H1N1 was 8-fold and 64-fold higher than that of a europium nanoparticle-based FICT and a rapid diagnostic test (RDT; Standard Diagnostics BIOLINE Influenza A/B), respectively. For influenza A/H3N2, QD-FICT showed 8-fold and 128-fold higher performance than europium nanoparticle-based FICT and RDT, respectively. In clinical evaluations, QD-FICT showed 93.75% clinical sensitivity [45/48; 95% confidence interval (95% CI): 82.80-98.69], 100% clinical specificity (117/117; 95% CI: 96.90-100.00), and strong correlation (kappa; 0.98) with rRT-PCR (20 ≤ Ct ≤ 40). Europium nanoparticle-linked FICT showed 79.17% clinical sensitivity (38/48; 95% CI: 65.01-89.53) and 100% clinical specificity (117/117; 95% CI: 96.90-100.00), whereas RDT showed 77.08% sensitivity (37/48; 95% CI: 62.69-87.97), 100% specificity (117/117; 95% CI: 96.90-100.00), and reasonably good correlation with rRT-PCR (kappa; 0.93). Water-soluble QDs can therefore be used as an effective material for developing fluorescent diagnostic systems for rapid detection of human influenza A virus in clinical specimens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Carbon quantum dots (CQDs) show promising potential for tumor imaging owing to their unique superior fluorescent properties. However, the small particle size limits their practical application. Here, pH/reduction dual-responsive comet-shaped PEGylated CQD-DOX conjugate prodrug, DOX-Hy-CQD-SS-PEG with DOX content of 28.5%, was designed with the hydrophobic acid-labile DOX conjugated CQDs as comet nucleus and the few hydrophilic bioreducible detachable PEG brushes as comet tails. The comet-shaped DOX-Hy-CQD-SS-PEG prodrug could self-assemble into unique micelles with mean diameter of 127 nm. The DOX-Hy-CQD-SS-PEG micelles possessed excellent pH/reduction dual-responsive drug release with low drug leakage of 9% in 150 h. Furthermore, the fluorescent CQDs was recovered after DOX release and de-PEGylation, demonstrating their potential application for real-time response of therapy., Competing Interests: Declaration of competing interest The authors have no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The antioxidant activity of ceria nanoparticles is tightly regulated by size distribution and heteroatom doping. Inspired by this rule, cerium and praseodymium codoped carbon quantum dots (Ce/Pr-CQDs) were synthesized through the one-pot hydrothermal carbonization method. Taking intrinsic advantage of CQDs, the resultant Ce/Pr-CQDs exhibited uniform and ultra-small morphology with an average size of 2.8 nm, which led to an increased proportion of Ce 3+ . In addition, the doping of Pr into Ce-CQDs improved the redox properties. As we expected, the Ce/Pr-CQDs possessed enhanced hydroxyl radical scavenging properties compared with the cerium-doped carbon quantum dots (Ce-CQDs). Furthermore, Ce/Pr-CQDs with favorable biocompatibility and negligible cytotoxicity are readily internalized into cytoplasm, decreasing the level of reactive oxygen species (ROS). Taken together, the resultant Ce/Pr-CQDs displayed great potential for applications relating to oxidative-stress-associated disease.

Nitrogen and sulfur co-doped carbon dots (N,S-CDs) have been widely studied with high quantum yield (QY). The experimental conditions of three different N,S-CDs were optimized. Emission peak position of three different N,S-CDs shown almost remains unchanged or obvious excitation-dependent PL properties, that was likely owed to size distribution. In order to discuss the N,S-CDs stability of photoluminescence property in environment, various experiments such as the photostability, different pH, ionic strengths and temperature were designed. To sum up, three different N,S-CDs exhibited discrepancy property. Molecular interaction of three different N,S-CDs were produced via vary carbon source with human serum albumins have been investigate by various methods. The quenching mechanism, thermodynamic and kinetic parameters, binding sites, electrochemical behavior of three different N,S-CDs with human serum albumins have some different, but conformational change of three different N,S-CDs with human serum albumins alike. The molecular docking had successful applied to study the N,S-CDs interaction with HSA. Different N,S-CDs possessed various characteristic that will have different quenching mechanism when they interaction with human serum albumin, study the mechanism of action at molecular level will help people to choose suitable CDs to apply in nanomedical., Competing Interests: Declaration of competing interest There are no conflicts to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)

ZnS quantum dots (QDs) and their core/shell (CdSe/ZnS) structures were studied for Zn based precursor reactivities. ZnS and CdSe/ZnS QDs were prepared selecting aqueous route and then characterized via XRD, TEM, EDX, PL, RAMAN and FTIR practices. Core/shell nanostructures were synthesized by taking dissimilar precursors for the shell formation. Photoluminescence spectra of prepared QDs corroborate the effectual luminescence. Prepared QDs have large surface area that make them useful alternative as organic antimicrobial agent which are highly irritant and unstable. Study of antimicrobial behavior of QD structures was carried out by disk diffusion method. Antimicrobial study of QDs and their core/shell structures was performed against gram negative and gram positive bacteria, E. coli, A. baumanni and Bacillus subtilis respectively. It is found that elemental composition and size of QDs plays important role in antimicrobial behavior. Prepared QDs are fluorescent and have a key role in complex microbial population studies and identification of bacteria., (Copyright © 2018. Published by Elsevier B.V.)

Mosquito-borne arboviruses compromise human health worldwide. Due to resistance to chemical insecticides, natural compounds have been studied to combat mosquitoes. Previous works have demonstrated a larvicidal activity of the water-soluble Moringa oleifera lectin (WSMoL) against Aedes aegypti, suggesting a mechanism of action based on the interaction between lectin and chitin present in the larvae's peritrophic matrix. In this work, it was investigated the WSMoL activity against Aedes aegypti larvae, by using luminescent bioconjugates of WSMoL conjugated to l-glutathione capped CdTe quantum dots. The conjugation was confirmed by ITC experiments, presenting high enthalpy associated to hydrogen bond interactions between nanoparticles and lectins. The bioconjugate luminescence stability was evaluated by the quantum yield (QY) at different pHs, ionic strengths and heat treatment time. The best parameters reached were pH 7.0, absence of electrolytes and heat treatment, giving QY = 4.4 %. The larvae were exposed to the bioconjugates and analyzed by confocal and fluorescence microscopy. CdTe-WSMol were detected along the entire midgut tract, suggesting a strong interaction with peritrophic matrix and lumen of the Aedes aegypti., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

As potential alternatives to conventional semiconductor quantum dots, fluorescent carbon quantum dots (CQDs) have received increasing research attention in biomedical fields owing to their splendid advantages of low cytotoxicity, strong fluorescence and excellent water dispersion. However, the preparation procedures of CQDs with designable chemical properties and functions are complicated and low efficient. In this work, we developed a facile, economical and straightforward strategy to prepare CQDs by a one-step thiol-ene click reaction between multiwalled carbon nanotubes (CNTs) and thiomalic acid (TA). The successful synthesis of CQDs was confirmed by a series of characterization data. The results manifested that CQDs were well combined with TA through surface thiol-ene click chemistry. In addition, the optical property is also desirable, the maximum emission wavelength was located in 500 nm and CQDs still could emit strong blue fluorescent light after irradiation with UV irradiation for 3 h. Besides, the pH value makes no significant changes for fluorescence emission wavelength of CQDs and CQDs can emit strongest fluorescence in weak acid solution. Furthermore, CQDs could be internalized by cells and show great cell dyeing performance and low cytotoxicity. All these features imply that TA functionalized CQDs possess great potential for biological imaging. The one-step thiol-ene click strategy provided a novel tool to prepare functionalized CQDs with great potential for biomedical applications., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The present study investigates the role of reactive oxygen species (ROS) generated on surface of nanophotocatalyst in wastewater treatment discharged from exponentially growing industries. A facile synthetic route is presented to produce reduced graphene oxide/CdS quantum dot (rGO/CdS QD) heterostructure by monowave-assisted solvothermal method where room temperature ionic liquid 1-ethyl-3-methylimidazolium thiocyanate serves as a "green" precursor. The prepared photocatalyst was tested for: (1) photodegradation performance against various cationic dyes, anionic dyes, and antibiotics as model organic water pollutants; and (2) disinfection performance against gram-positive S. aureus and gram-negative E. coli bacterial strains as pathogenic water pollutants. The negative surface charge of rGO/CdS QD precisely attracted the cationic dye molecules to its surface and degraded the dyes at a higher rate. Moreover, excellent antibacterial activity of rGO/CdS QD were observed against S. aureus and E. coli with a minimum inhibitory concentration of 16 μg ml -1 and 32 μg ml -1 , respectively. A plausible mechanism of the photocatalytic activity suggested that ROS with strong oxidizing ability reacts with the organic pollutants to mineralize them into CO 2 , H 2 O or some other small molecules, and reacts with pathogens to damage the macromolecules like proteins, lipids, DNA, etc in the bacterial cells. Among all the surface generated ROS, hydroxyl radicals was found to be the main contributor in the photodegradation and disinfection mechanism., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A fluorescent nanoprobe based on carbon dots (CDs) has been facilely synthesized by a one-step hydrothermal pyrolysis of salicylic acid and utilized for the sequential detection of Fe 3+ and F - in vitro. The fluorescence of CDs can be extinguished dramatically by Fe 3+ based on static quenching and subsequently recovery upon addition of F - due to the formation of stabler FeF 3 . The probe exhibits high selectivity and sensitivity toward Fe 3+ and F - with a good linearity in the range of 10-300 μM and 0.1-200 μM, respectively, and a low detection limit of 52 nM and 8.5 nM, respectively. More importantly, as-prepared CDs with exceedingly fluorescence stability, negligible toxicity and superior biocompatibility have been expanded for detection Fe 3+ and F - in living cell and Escherichia coli. Furthermore, an "AND" logic gate based on as-obtained CDs has been constructed., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The simultaneous determination of anticancer and antibiotic drugs in biological samples with fast and sensitive methods is an essential task for the effective monitoring of drug therapy. A novel electrochemical sensor for the simultaneous determination of anticancer drug Flutamide (FLU) and antibiotic drug Nitrofurantoin (NF) was developed based on the glassy carbon electrode (GCE) modified with N-CQD@Co 3 O 4 /MWCNTs hybrid nanocomposite. The electro-kinetics of the developed sensor was studied using cyclic voltammetry (CV). The electrochemical performance of FLU and NF on the N-CQD@Co 3 O 4 /MWCNTs/GCE surface was examined using CV and differential pulse voltammetry (DPV) techniques. At an optimized condition, the developed sensor exhibits excellent performance in simultaneous determination of FLU and NF with a linear range of 0.05-590 μM and 0.05-1220 μM and detection limit of 0.0169 μM and 0.044 μM respectively. Furthermore, the developed sensor exhibits satisfactory results in the real sample analysis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Monodispersed CdTe quantum dots (QDs) were prepared by using thioglycolic acid as surfactants in aqueous solution. The thioglycolic acid was chemically adsorbed on the surface of CdTe QDs that enables the QDs positively charged. In week acidic media, propafenone is positively charged, which can combine with the CdTe QDs to form larger ion-association complex via electrostatic attraction and hydrogen bond. Moreover, the formed ion-association complex could increase the intensity of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling-scattering (FDS) of CdTe QDs, and quench the CdTe QDs fluorescence. Importantly, under optimal experimental conditions, the increased RRS, SOS and FDS intensity, and quenched fluorescence intensity of CdTe QDs were in direct proportion to the propafenone concentration in a certain range, respectively. Among them, the RRS method exhibited the highest sensitivity. In a wide concentration range of propafenone from 0.003 to 7.0 μg mL -1 , the detection limit could reach 0.96 ng mL -1 , which was much lower than previously reported methods. To simulate practical applications, the possible foreign interfering substances were also investigated, such as common ions, amino acid, and glucide. The proposed method here is rapid, sensitive and shows promising application for detection of ppb level of propafenone in human serum., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Herein, a facile and quick strategy to detect thiourea was conducted based on the reversion of fluorescence quenching of nitrogen doped carbon dots (NCDs) by Hg 2+ . The NCDs with good water solubility and 17% of quantum yield was synthesized by one-step hydrothermal method, using ammonium citrate and dextrin as carbon source and nitrogen source, respectively. The fluorescence of NCDs was obviously quenched by Hg 2+ and can be recovered, due to stronger interaction between thiourea and Hg 2+ . There was a good linear relationship between the recovered fluorescence and the concentration of thiourea within range of 0.90-10.0 μM and the detection limit for thiourea detection was 0.15 μM. The as-prepared NCDs can be used for determination of thiourea in tap water, lake water and rice flour products, and the spike recoveries were between 91.6 and 108%., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Carbon quantum dots (CQDs) are nanoobjects of a size below 10 nm. Due to their favorable features, such as tunable luminescence, unique optical properties, water solubility, and lack of cytotoxicity, they are willingly applied in biomedicine. They can be obtained via bottom-up and top-down methods. However, to increase their quantum yield they must undergo post-processing. The aim of the following research was to obtain a new type of CQDs modified with a rhodamine b derivative to enhance their fluorescence performance without biocompability deterioration. For their preparation glucose was used as a precursor and four different carbonizing agents which affected semi- and final products luminescence properties. The ready nanomaterials were investigated over their chemical structure by FTIR and NMR, whereas morphology was investigated by the TEM method. Their optical properties were determined by UV-VIS spectroscopy. Fluorescence behavior, photo- and pH-stability, as well as solvatochromism showed their applicability in various biomedical applications due to the controlled properties. The samples exhibited excellent antioxidant activity and lack of cytotoxicity on L929 mouse fibroblasts. The results showed that proposed strategy enables preparation of the superior nanomaterials with outstanding luminescence properties such as quantum yield up to 17% which can be successfully applied in cell labelling, bioimaging, and theranostics.

β-Amylase was immobilized onto GQDs using 3-aminopropyltriethoxysilane and glutaraldehyde. Optimization was carried out by Box-Behnken design and binding was confirmed by SEM, AFM, FTIR and fluorescence microscopy. Predicted optimum immobilization efficiency (88.64%) was very close to actual (87.98%), which confirmed the success of the immobilization process. The immobilized enzyme showed maximum activity at pH 5.0 and 57 °C, whereas K m and V max were found to be 6.40 mg/mL and 714.28 μmol/min/mg, respectively. The enzyme retained 75% activity after 12 uses at 30 °C. Increased values of ΔG° ΔH°, half-life and activation energy of the enzyme inactivation (ΔE d ) revealed that thermo-stability increases after immobilization and the process followed first-order kinetics (r 2  > 0.96). The activation energy of catalysis (ΔE a ) and ΔE d for immobilized enzyme were 22.58 and 158.99 ± 1.10 kJ/mol, respectively which revealed that denaturation of the enzyme requires a higher amount of energy rather than catalysis. Thermodynamic and fluorescence spectroscopic studies revealed that the process is non-spontaneous (ΔG > 0) and endothermic (ΔH > 0) and occurred through protein unfolding rather than aggregation (ΔS > 0). Thus increase in thermo-stability of immobilized fenugreek β-amylase and non-toxic nature of GQDs could be exploited for maltose production in beverage, food and pharmaceutical industries., Competing Interests: Declaration of competing interest Authors have no conflict of interest., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A competitive-type PEC immunosensor for 17β-estradiol (E 2 ) detection was successfully fabricated using ZnIn 2 S 4 @NH 2 -MIL-125(Ti) composite as matrix. The excellent PEC behavior of ZnIn 2 S 4 @NH 2 -MIL-125(Ti) composite could be attributed to that the Ti 4+ -Ti 3+ intervalence cycles in the titanium oxo-cluster of NH 2 -MIL-125(Ti) as well as the matching energy level between ZnIn 2 S 4 and NH 2 -MIL-125(Ti) promote the migration and separation of photocarrier. Besides, polydopamine (PDA) with abundant amino- and quinone-groups was selected to further improve the PEC signals and capture antibody, which implement through the covalent bonding of PDA and BSA-E 2 or carboxyl-group functionalized Mn:ZnCdS QDs in the competitive-type strategy. Concretely, the quinone functional groups in PDA film was applied to immobilize BSA-E 2 through Michael reactions, and the PDA nanosphere loaded Mn:ZnCdS quantum dot (PDA NS/Mn:ZnCdS QDs) was used as antibodies' labels to amplify PEC signals. After PDA NS/Mn:ZnCdS-anti-E 2 immobilized on the modified electrode, a remarkable increase of photocurrent signal was observed owing to the specific bonding of antigen and antibody. Based on the competitive binding of PDA NS/Mn:ZnCdS-anti-E 2 with either free E 2 or bovine serum albumin (BSA)-E 2 causing the change of the photocurrent signal, the standard sample free E 2 could be accuracy detect. Under optimal conditions, the competitive-type PEC immunosensor exhibited the linear range from 0.0005 ng/mL to 20 ng/mL and a limit detection of 0.3 pg/mL (S/N = 3). Meanwhile, the acceptable stability, selectivity and reproducibility of the proposed PEC immunosensing platform indicating the promising detection of small molecular environmental pollutants., (Copyright © 2019. Published by Elsevier B.V.)

We describe a sensitive turn-on fluorescent assay for antioxidants by using fluorescence-tunable graphene quantum dots (GQDs). GQDs exhibited strong fluorescence without dopamine (DA). DA could self-polymerize to a thin polydopamine (PDA) film on the surface of GQDs under alkaline environment, resulting in the fluorescence quenching of GQDs via fluorescence resonance energy transfer (FRET). However, the self-polymerization of DA could be effectively inhibited in the presence of antioxidants including glutathione (GSH), ascorbic acid (AA), cysteine (Cys), and homocysteine (Hcys). Thus, the fluorescence of GQDs restored. The "turn-on" sensing of antioxidants could be achieved with high sensitivity. The detection limit for GSH, AA, Cys, and Hcys could be achieved as low as 2.4 nM, 1.5 nM, 4.2 nM, and 4.4 nM, respectively. Finally, the GQDs@PDA system was applied for monitoring cerebral antioxidants in rat brain microdialysates. This work promises new opportunities to evaluate antioxidant capacity in physiological and pathological fields., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The new ionic liquid capped CdS quantum dots (IL-CdS QDs) as a fluorescent probe was successfully synthesized by a hydrothermal method in a one step process and used for the facile and sensitive determination of florfenicol (FLF) in aqueous media. The new ionic liquid 3-(2-[(5-amino-1,3,4-thiadiazol-2-yl)thio]ethyl)-1-methyl-1H-imidazol-3-ium chloride (IL) was synthesized by introducing 5-amino-1,3,4-thiadiazole-2-thiol as a ligand onto the alkyl chain of the 1-chloroethyl-3-methylimidazolium chloride ILs. This task specific ionic liquid reagent was used for the capping of CdS QDs which played the role of recognition element of FLF. The IL-CdS QDs were characterized by Ultra Violet-Visible absorption -spectroscopy (UV-Vis absorption spectroscopy), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Quenching of fluorescence intensity of the IL-CdS QDs was in proportion to the addition of FLF concentration. Under the optimum conditions, the fluorescence intensity ratio of IL-CdS QDs in the presence and absence of FLF versus FLF concentrations gave a linear response according to the Stern-Volmer equation from 0.1 to 20 μg mL -1 (0.3 to 56 μmol L -1 ) with a limit of detection 0.035 μg mL -1 (0.098 μmol L -1 ). The developed method was applied to the determination of FLF in fish and chicken meats with satisfactory results. This method revealed some advantages such as high sensitivity, precision and wide linear range to FLF. The proposed method can be utilized for rapid screening the quality of meat products., (Copyright © 2019 Elsevier B.V. All rights reserved.)

We report a facile one step in-situ synthesis of amino-functionalized graphene dots. These quantum dots were employed for the detection of glucose in both standard aqueous solutions and commercially available fruit juice to assess its practicability. The characterization of the quantum dots revealed that they were decorated with amine functionality. Additionally, the interaction between glucose and amine functionalized graphene quantum dots gave enhancement in the UV-vis absorption and photoluminescence (PL) due to aggregation of quantum dots via glucose link. Therefore, the quantum dots were able to detect the concentration of glucose in solution exhibiting linearity from 0.1 to 10 mM and 50-500 mM with a sensitivity transition from 10 mM to 50 mM. The limit of detection for the determination of glucose was found to be 10 μM. This determination was agreed from both UV-Vis absorption and PL spectroscopy. However, the PL emission method of determination was most suited with its very high accuracy of 98.04 ± 1.96% and 97.33 ± 2.67% for the linear range of glucose concentration within 0.1-10 mM and 50-500 mM, respectively. The PL enhancement was highly selective towards glucose in mixture of other form of sugars making it suitable for determining glucose in food samples., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this work, we presented a facile microwave method to prepare blue emitting carbon dots (CDs) using lysine as carbon source and realized the specific detection of seven types of antibiotics by CDs and Al 3+ ions via a two-step method. The CDs have good solubility in water and their excitation spectra are exactly coincided with the absorption of some typical antibiotics, which leads to the fluorescence quenching of CDs (OFF state). The inhibition mechanism of fluorescence is induced by the combination of inner filtering effect (IFE) and static quenching effect (SQE). In addition, the quenched fluorescence can be recovered by adding Al 3+ ions (On state), and seven types of antibiotics can be distinguished exactly according to the emission peak position and intensity. It not only provides a new and convenient method for the detection of antibiotics, but also provides a new idea for the further application of CDs in optical sensing., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Purpose: Quantum dots (QDs) are widely used semiconductor nanomaterials. Indium phosphide/zinc sulfide (InP/ZnS) QDs are becoming potential alternatives to toxic heavy metal-containing QDs. However, the potential toxicity and, in particular, the immunotoxicity of InP/ZnS QDs are unknown. This study aimed to investigate the impacts of InP/ZnS QDs on inflammatory responses both in vivo and in vitro., Methods: Mice and mouse bone marrow-derived macrophages (BMMs) were exposed to polyethylene glycol (PEG) coated InP/ZnS QDs. The infiltration of neutrophils and the release of interleukin-6 (IL-6) were measured using a hematology analyzer and an enzyme-linked immunosorbent assay (ELISA) for the in vivo test. Cytotoxicity, IL-6 secretion, oxidative stress and endoplasmic reticulum (ER) stress were studied in the BMMs, and then, inhibitors of oxidative stress and ER stress were used to explore the mechanism of the InP/ZnS QDs., Results: We found that 20 mg/kg PEG-InP/ZnS QDs increased the number of neutrophils and the levels of IL-6 in both peritoneal lavage fluids and blood, which indicated acute phase inflammation in the mice. PEG-InP/ZnS QDs also activated the BMMs and increased the production of IL-6. In addition, PEG-InP/ZnS QDs triggered oxidative stress and the ER stress-related PERK-ATF4 pathway in the BMMs. Moreover, the inflammatory response caused by the PEG-InP/ZnS QDs could be attenuated in the macrophages by blocking the oxidative stress or the ER stress with inhibitors., Conclusion: InP/ZnS QDs can activate macrophages and induce acute phase inflammation both in vivo and in vitro, which may be regulated by oxidative stress and ER stress. Our present work is expected to help clarify the biosafety of InP/ZnS QDs and promote their safe application in biomedical and engineering fields., Competing Interests: The authors report no conflicts of interest in this work., (© 2019 Chen et al.)

Background: Early diagnosis of renal cell carcinoma is extremely significant for the effective treatment of kidney cancer. The development of AS1411 aptamer modified Mn-MoS2 QDs provides a promising fluorescence/magnetic resonance (MR) dual-modal imaging probe for the precise diagnosis of renal clear cell carcinoma., Methods: In this work, Mn-MoS 2 QDs were synthesized through a simple "bottom-up" one-step hydrothermal method. AS1411 aptamer was modified on the Mn-MoS 2 QDs to improve the specificity to renal cell carcinoma. The characteristics of Mn-MoS 2 QDs were confirmed by transmission electronic microscopy (TEM), atomic force microscope (AFM), X-ray photoelectron spectrometer (XPS), photoluminescence (PL) emission spectra, etc. Cellular fluorescence labelling was investigated using the Mn-MoS 2 QDs and AS1411-Mn-MoS 2 QDs. The T 1 -weighted MR imaging was assessed by the in vitro MR cell imaging and in vivo MR imaging. Finally, the long-term toxicity of Mn-MoS 2 QDs was investigated by the hematology and histological analysis., Results: The prepared Mn-MoS 2 QDs exhibited excellent aqueous property, intense fluorescence, low toxicity, high quantum yield of 41.45% and high T 1 relaxivity of 16.95 mM -1 s -1 . After conjugated with AS1411 aptamer, the AS1411-Mn-MoS 2 QDs could specifically fluorescently label the renal carcinoma cells and present a specific MRI signal enhancement in the tumor region of mice bearing renal carcinoma tumors. Furthermore, Mn-MoS 2 QDs revealed low toxicity to the mice via hematology and histological analysis., Conclusion: These results demonstrated the potential of AS1411-Mn-MoS 2 QD as a novel nanoprobe for targeted MR imaging and fluorescence labelling of renal cell carcinoma., Competing Interests: There are no conflicts of interest., (© 2019 Zheng et al.)

Upconversion near-infrared (NIR) fluorescent carbon dots (CDs) are important for imaging applications. Herein, thermally activated upconversion photoluminescence (UCPL) in the NIR region, with an emission peak at 784 nm, which appears under 808 nm continuous-wave laser excitation, are realized in the NIR absorbing/emissive CDs (NIR-CDs). The NIR-CDs are synthesized by microwave-assisted exfoliation of red emissive CDs in dimethylformamide, and feature single or few-layered graphene-like cores. This structure provides an enhanced contact area of the graphene-like plates in the core with the electron-acceptor carbonyl groups in dimethylformamide, which contributes to the main NIR absorption band peaked at 724 nm and a tail band in 800-850 nm. Temperature-dependent photoluminescence spectra and transient absorption spectra confirm that the UCPL of NIR-CDs is due to the thermally activated electron transitions in the excited state, rather than the multiphoton absorption process. Temperature dependent upconversion NIR luminescence imaging is demonstrated for NIR-CDs embedded in a polyvinyl pyrrolidone film, and the NIR upconversion luminescence imaging in vivo using NIR-CDs in a mouse model is accomplished., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, nitrogen and sulfur dual-doped carbon quantum dots (N,S-CDs) from naturally renewable biomaterial fungus fibers were prepared by a biosynthesis and hydrothermal method. The N,S-CDs displayed good water solubility, excellent stability, high quantum yield (QY = 28.11%) as well as remarkable features for fluorescence quenching-based detection and cellular imaging of cancer cells. It was worth mentioning that the heteroatoms doped carbon quantum dots made from the fungus fibers had a satisfactory QY and could be used as a selective, efficient, and sensitive fluorescent probe to determine tetracyclines by the synergistic effects of static quenching and internal filtration effect. The probe demonstrated a wide linear range and low detection limit. For tetracycline, the linear range was 0.5 μM to 47.6 μM, and the corresponding detection limit was 15.6 nM. Significantly, the test papers prepared by using N,S-CDs could detect tetracyclines in aquiculture wastewater rapidly. The produced N,S-CDs did not affect the cell viability and showed great promises for cellular imaging., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Here, a target-induced three-dimensional DNA network structure (T-3D Net) produced by catalytic hairpin assembly (CHA) was proposed as a novel signal amplifier to fabricate an ultrasensitive electrochemiluminescence (ECL) biosensor for microRNAs detection. Usually, conventional CHA can produce only one output DNA in each target cycle, while the proposed strategy could produce multiple output DNA by using DNA-functionalized magnetic beads (MBs) and gold nanoparticles (AuNPs) to form T-3D Net. Then, the T-3D Net with high loading capacity could be completely collapsed by dissolving AuNPs to efficiently convert trace microRNA-21 into a large amount of output DNA. Furthermore, the nanocomposite containing Ru(bpy) 3 2+ as luminophore and boron nitride quantum dots (BNQDs) as coreactant provided a strong initial ECL response owing to the short electron transfer distance between luminophore and coreactant (signal-on). Next, the DNA duplex probes labeled with  N -(4-aminobutyl)- N -ethylisoluminol (ABEI) and dopamine (DA) (S1-ABEI/S2-DA) were further immobilized on the nanocomposite to reduce the background signal due to the double quenching effect of DA for both ABEI and Ru(bpy) 3 2+ (signal-off). In the presence of the output DNA with enzyme-assisted self-recycling, S2-DA was displaced and detached from the electrode surface to achieve ECL signal recovery. Simultaneously, S1-ABEI restored a stable hairpin structure, making ABEI close to the electrode surface for more effective resonance energy transfer (RET) between ABEI and Ru(bpy) 3 2+ , which greatly improved the final ECL response (signal-super on). Thus, the ECL biosensor demonstrated superior performance for ultrasensitive detection of microRNA-21 with low detection limit (0.33 aM) and was successfully applied to monitor the expression of microRNA-21 in human cancer cell lysates. This strategy provided an ultrasensitive way for the detection of biomolecules and revealed an effective avenue for diseases diagnosis.

Gout is a disease with a high incidence and causing great harm, and the current treatment drugs are not satisfactory. In this study, novel water-soluble carbon dots (CDs) with anti-gout effect, named Puerariae lobatae Radix CDs (PLR-CDs), are reported. PLR-CDs were synthesized with an improved pyrolysis method at 300 °C, and their characterization was performed with multifaceted approaches, such as transmission electron microscopy (TEM) and ultraviolet-visible (UV-vis) and Fourier-transform infrared (FTIR) spectroscopy. In addition, the biocompatibility of PLR-CDs was studied using the cell counting kit (CCK)-8 in LO2 cells and RAW264.7 cells, and the anti-gout activity of PLR-CDs was examined on animal models of hyperuricemia and gouty arthritis. The characterization of PLR-CDs indicated that they were nearly spherical, with diameters ranging from 3.0 to 10.0 nm, and the lattice spacing was 0.283 nm. The toxicity experiment revealed that PLR-CDs were non-poisonous for LO2 cells and RAW264.7 cells at concentrations below 250 μg/mL. The results of pharmacodynamic experiments showed that PLR-CDs could lower the blood uric acid level in model rats by inhibiting the activity of xanthine oxidase and reduce the degree of swelling and pathological damage of gouty arthritis. Thus, PLR-CDs with anti-gout biological activity and good biocompatibility have the prospect of clinical application for the treatment of gout.