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In this study, carbon dots (CDs)-encapsulated luminescent metal-organic frameworks@surface molecularly imprinted polymer (CDs@MOF@SMIP) was facilely prepared and applied as fluorescent probe for specific identification and sensitive detection of chloramphenicol (CAP) in food. Fluorescent CDs, serving as signal tags, were encapsulated within metal-organic backbones (ZIF-8), yielding luminescent MOF materials (CDs@ZIF-8). The synthesized CDs, CDs@ZIF-8 and CDs@ZIF-8@SMIP were investigated by morphological and structural characterizations (UV-Vis, XRD, FT-IR, BET, TEM). The CDs@ZIF-8@SMIP probe was demonstrated to have remarkable selectivity and sensitivity towards CAP. Its fluorescence decreased linearly with CAP concentration from 0.323 μg L -1 (0.001 μM) to 8075.0 μg L -1 (25.0 μM), featuring a low detection limit of 0.08 μg L -1 . The CDs@ZIF-8@SMIP-based fluorescence strategy achieved satisfactory recoveries (95.5 % - 101.0 %) in CAP-spiked commercial foods with RSD < 4.4 % (n = 3). These results indicate that this method can effectively detect trace CAP in food matrices and has broad application prospects., 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 © 2024 Elsevier Ltd. All rights reserved.)

Active antibacterial materials play an important role in solving food safety problems caused by pathogen contamination. In this study, a composite active antibacterial material with the synergistic antibacterial effectiveness of photothermal, photodynamic and the surface charge of polyphenols was developed, where the multi-porous polyphenol functionalized metal-organic frameworks (ZIF-8-TA) were used as the framework carrier, and black phosphorus quantum dots (BPQDs) were used as the photosensitive source. The resulted ZIF-8-TA/PBQDs possesses excellent photothermal conversion efficiency (27.92%), photodynamic performance and surface charge, and these factors ensure the outstanding broad-spectrum antibacterial performance (100%). Multifunctional characteristics and excellent biocompatibility endow the materials with vast potential for foodstuff packaging. The results showed that the composite antibacterial film produced by doping ZIF-8-TA/PBQDs into chitosan could effectively prolong the shelf life of foodstuff compared with commercial membrane. The successful implementation of this research provides a new idea for controlling microbial contamination and developing multifunctional antibacterial materials., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Qiliang Deng reports financial support was provided by Ministry of Science and Technology of China. Futai Lu reports financial support was provided by National Natural Science Foundation of China. If there are other authors, they 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 © 2024 Elsevier Ltd. All rights reserved.)

To improve the performance of peanut allergen Ara h 3 detection, depending on boron and nitrogen carbon dots (B/N-CDs), a nanobody (Nb) mediated dual-mode immunoassay was established, which combines the dominance of colorimetry with ratiometric fluorescence techniques. With the catalysis of Horseradish peroxidase (HRP), the oxidization of o-phenylenediamine (o-PD) in the presence of H 2 O 2 , leading to the production of yellow 2,3-diaminophenolazine (DAP) with an absorption peak at 431 nm. Owing to inner filter effect (IFE), DAP quenched the fluorescence of B/N-CDs at 426 nm, and it emerged a new emission peak at 549 nm. The fluorescence intensity ratio and absorption intensity can be utilized for quantitative analysis of Ara h 3 concentration. Under optimal conditions, the detection limits were 6.61 and 9.79 ng·mL -1 , respectively. The dual-mode immunoassay was assessed containing specificity, stability, reproducibility, and practicability. This method paved the way for sensitive detection of Ara h 3 without background Interference., 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 © 2023 Elsevier Ltd. All rights reserved.)

Rapid, portable, and sensitive detection of tetracycline (TC) is crucial for the environment and human health. In this study, we developed carbon dots (CDs)-based fluorescent molecularly imprinted photonic crystal hydrogel (FMIPH) strips for TC detection in animal-derived foods. CDs emit fluorescent signals, and molecularly imprinted polymers provide specific recognition sites for TC. Inverse opal photonic crystals afford stable 3D macroporous mass transfer channels that considerably reduce binding time between TC and the strips. The portable FMIPH strip exhibited a linear fluorescence response to TC in the concentration range of 0.1-50 μg mL -1 , with a detection limit of 0.067 μg mL -1 . Good recoveries of TC (93.86-112.59%) were observed in TC-spiked commercially available pork, eggs, and milk. A combination of FMIPH strips with a portable fluorescent reading device could achieve sensitive, on-site, and real-time detection of TC in animal-derived foods., 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 © 2023 Elsevier Ltd. All rights reserved.)

Two carbon dots (CDs) (λ Em  = 525 nm, G-CDs and λ Em  = 640 nm, R-CDs) were synthesized from citric acid and urea. The bovine serum albumin (BSA) responsiveness of the R-CDs was used to develop a "fluorescence-wavelength" label-free point of care testing (POCT) for the detection of the milk quality marker BSA with the detection limit (LOD) of 4.89 μg/mL for fluorescence mode and 3.38 μg/mL for wavelength mode. In addition, R-CDs were found to have hydroxyl radical (·OH)-dependent fluorescence quenching properties, and a "fluorescence-photothermal" immunosensor based on nanobodies was constructed by introducing the fluorescence signal of R-CDs@BSA and the photothermal signal of oxTMB for the detection of β-lactoglobulin (β-LG) with the LOD of 0.034 ng/mL for fluorescence mode and 0.075 ng/mL for photothermal mode. The tandem detection of POCT and immunosensor enables the simultaneous and highly sensitive detection of BSA and β-LG after only simple dilution of less than 5 µL of sample., 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 © 2023 Elsevier Ltd. All rights reserved.)

The residue of chlortetracycline is potentially hazardous to human health; it is meaningful to exploit a portable, rapid, sensitive, and selective method for detection of chlortetracycline (CTC). In this study, a novel fluorescence bionic sensing probe (NH 2 -MIL-53&N,P-CDs@MIP) was successfully prepared based on the nitrogen and phosphorus codoped carbon dots decorated iron-based metal-organic frameworks combining with molecular imprinted polymer for the detection of CTC. A fluorescence intensity-responsive "on-off" detection of CTC on account of the inner-filter effect (IFE) was achieved by NH 2 -MIL-53&N,P-CDs@MIP. Under the optimal conditions, the fluorescence quenching degree of NH 2 -MIL-53&N,P-CDs@MIP presented a good linear relationship with the CTC concentration in the range 0.06-30 μg mL -1 and the limit of detection (LOD) was 0.019 μg mL -1 . The fluorescent probe was applied to detect CTC in milk samples, and experimental results showed a good recovery rate (88.73%-96.28%). Additionally, a smartphone-integrated fluorescence sensing device based on NH 2 -MIL-53&N,P-CDs@MIP was exploited to replace the expensive and bulky fluorescence spectrophotometer for quantitative determination of CTC with the LOD of 0.033 μg mL -1 . The sensing system showed high selectivity, strong stability, high specificity, and portability, which provide a great strategy for the quantitative detection of antibiotic residue.

A novel self-enhancement molecularly imprinted electrochemiluminescence (ECL) sensor (MIP/M-Ag@MoS 2 -QDs/GCE) was constructed to detect thiabendazole (TBZ) in food. Melamine was used as template to chelate Ag + to prepare composite nanomaterials (M-Ag). M-Ag possesses both ECL properties and coreactant catalytic properties, which can realize the self-enhancement of ECL luminophore. MoS 2 -QDs with excellent edge activity and electrochemical reaction catalytic activity were used to accelerate the reaction rate of the microsystem and further enhance the ECL intensity. The specific detection method of TBZ was established by investigating the ECL response mechanism and specific recognition mechanism of MIP/M-Ag@MoS 2 -QDs/GCE. The ECL intensity was proportioned to the lg C (TBZ) in the linear range 5 × 10 -8 mol L -1 -5 × 10 -5 mol L -1 with a limit detection of 1.42 × 10 -8 mol L -1 . The satisfactory recovery rate (83.57%-101.03%) was obtained in sample analysis, which was in good agreement with the analysis result of HPLC., 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 © 2023 Elsevier Ltd. All rights reserved.)

Tetracycline (TC) residues not only endanger human health, but also are detrimental to the sustainable development of aquaculture and animal husbandry. Herein, a novel fluorescence sensor with high sensitivity and selectivity was developed based on nitrogen-doped carbon dots embedded in zinc-based metal-organic frameworks and incorporating molecularly imprinted polymer (ZIF-8&N-CDs@MIP). The physical and chemical properties of the ZIF-8&N-CDs@MIP had been characterized by SEM, TEM, FTIR, XRD, BET, TGA, etc. Under optimal conditions, the limit of detection (LOD) of the novel sensor was 0.045 μg mL -1 with the concentration of TC in the range of 0.1-4.0 μg mL -1 . In addition, the prepared imprinted polymers showed superior adsorption selectivity to tetracycline compared with non-imprinted polymers, and the quenching mechanism of ZIF-8&N-CDs@MIP was demonstrated to be attributed to the inner filter effect (IFE). This work provided an effective and reliable method for the specific detection of tetracycline and was successfully applied in milk and egg samples with satisfactory recoveries (80.67-95.22%)., 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 © 2023 Elsevier B.V. All rights reserved.)

Background: Ascorbic acid (AA) is an essential nutrient for humans, which must be obtained from vegetables, fruits, and other foods. The content of AA has become an important standard to evaluate the quality and nutritional value of food. The fluorescence sensing method based on nanomaterials is a good alternative for the rapid detection of AA. In this study, we developed an inner filter effect-based fluorescent probe that hybridized nitrogen-doped carbon dots (NCDs) with cobalt oxyhydroxide nanoflakes (CoOOH NFs)., Results: An optimal NCDs was successfully selected because it has a strong fluorescence at 430 nm and the most significant quenching phenomenon with CoOOH NFs due to the inner filter effect. When adding AA into the NCDs-CoOOH NFs probe solution, a specific redox reaction will occur between the enediol group of AA and the CoOOH NFs to interfere with the quenching ability of CoOOH NFs and recover the fluorescence of NCDs. The recovered fluorescence intensities demonstrated a linear relationship with the concentrations of AA. The assay based on the NCDs-CoOOH NFs probe allows AA to be tested in a wide range of 5-200 μmol L -1 with a detection limit of 2.31 nmol L -1 . Furthermore, to evaluate its practical application, the NCDs-CoOOH NFs fluorescence probe was utilized to analyze AA in vegetable, fruit, and serum matrixes with satisfactory results., Conclusion: An inner filter effect-based fluorescence probe for the rapid detection of AA was developed, and it has a good potential to be applied in both food and clinical testing. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

A straightforward, largely instrument-free, smartphone-based analytical strategy for hexavalent chromium and lysine (Lys) on-site detection via exploitation of dual-emission carbon quantum dots (DECQDs) has been demonstrated. DECQDs show dual-emission peaks at 439 and 630 nm with the excitation at 375 nm. As a dual-mode detection probe, the fluorescence and ultraviolet adsorption spectra of DECQDs vary with hexavalent chromium concentrations. Most importantly, Lys can restore the fluorescence of the hexavalent chromium added DECQD nanoprobe and change the color of the probe under natural light. At the same time, based on the participation of smartphones, the prepared DECQD probes favor the establishment of visual smart sensors that can also be used for the in-situ detection of targets. The on-site quantitative analysis exhibited a linear range of 5.3-320 μM with a detection limit of 1.6 μM towards Cr(VI) and the differentiation of Lys variation from 1 to 75 mM with a detection limit of 0.3 mM. The probe has been applied for the first time to enable vision-based colorimetric in complex samples such as water, milk and egg. The recoveries of Cr(VI) and Lys in real samples were between 90 and 104%, and the relative standard deviation (RSD) was as low as 0.4%. This work offers new perspectives for fundamental understanding and new design of functional luminescent materials that are applicable for food-safety and rapid and intelligent inspection. A straightforward, large instrument-free, smartphone-based analytical strategy with dual-emission carbon quantum dots was developed for hexavalent chromium and Lys on-site detection via fluorescent and colorimetric twofold readout measure., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Hydrogel dressings are highly biocompatible and can maintain a moist wound environment, suggesting constructing an efficient multi-modal antibacterial hydrogel platform is a promising strategy for treating bacterial wound infections. In this work, a composite Ag 2 S quantum dot/mSiO 2 NPs hydrogel (NP hydrogel) with antibacterial ability was constructed by incorporating Ag 2 S quantum dots (QDs) modified by mesoporous silica (mSiO 2 ) into the network structure of 3-(trimethoxylmethosilyl) propyl methacrylate based on free radical polymerization. The NP hydrogel showed outstanding controllable photothermal and photodynamic characteristics under 808 nm near infrared (NIR) light irradiation, with a photothermal conversion efficiency of 57.3%. Additionally, the release of Ag + could be controlled by the inherent volume change of the NP hydrogel made of N-isopropylacrylamide (NIPAAm) and acrylamide (AAm) during NIR laser exposure, with the embedded Ag 2 S QDs working as a reservoir to release Ag + continuously from the hydrogel matrix to achieve bactericidal activity. The synergetic effects between hyperthermia, radical oxygen species, and Ag + released under NIR radiation endowed the NP hydrogel with prominent antibacterial properties against Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA), with an inhibition rate of 99.7% and 99.8%, respectively. In vivo wound healing experiments indicated that the NP hydrogel could enhance bacterial clearance, increase collagen coverage area and up-regulate VEGF expression, exhibiting high biocompatibility. Overall, this study proposed an efficient and highly biocompatible multi-modal therapeutic nanohydrogel, opening up a new way for developing broad-spectrum antibacterial wound dressings to treat bacterial wound infections. STATEMENT OF SIGNIFICANCE: Bacterial wound infection is still one of the most difficult medical problems. In this work, a stimulating NIR-responsive hydrogel encapsulating functional Ag 2 S QDs was prepared, which showed high photothermal conversion efficiency (57.3%) and outstanding antibacterial ability under 808 nm NIR laser, killing 99.7% and 99.8% of E. coli and MRSA in 4 min, respectively. During NIR light irradiation, the release rate of Ag + could be regulated by the intrinsic volume transition of the hydrogel, leading to remarkable antibacterial properties in vitro and in vivo under the combined action of hyperthermia, radical oxygen species and Ag + released. This study proposed a novel multi-modal therapeutic nanohydrogel, opening up a new way for developing broad-spectrum antibacterial wound dressings to treat bacterial wound infections., 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 © 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Functional nanoprobes which detect specific food hazards quickly and simply are still in high demand in the field of food-safety inspection research. In the present work, a dual-emission metal-organic framework-based ratiometric fluorescence probe was integrated to detect Cu 2+ and Pb 2+ with rapidness and ease. Specifically, quantum dots (QDs) and carbon quantum dots (CQDs) were successfully embedded into zeolitic imidazolate framework-67 (ZIF-67) to function as a novel ratiometric fluorescent sensing composite. The ratiometric fluorescence signal of CQDs/QDs@ZIF-67 was significantly aligned with the concentration of metal ions to give an extremely low detection limit of 0.3324 nM. The highly sensitive and selective CQDs/QDs@ZIF-67 composite showed potential for the rapid and cost-effective detection of two metal ions.

A novel deep eutectic solvent-based extraction and sulfur-doped carbon quantum dots (S-CQDs) serving as fluorescence probes to detect pirimicarb in cereals were established. The deep eutectic solvent was synthesized using choline chloride and butanediol, achieving direct and efficient extraction of pirimicarb residue in the cereals. The fluorescence quenching of S-CQDs was caused by the electrostatic interaction between the negatively charged S-CQDs and positively charged thiocholine, which was the hydrolysate of acetylthiocholine. The fluorescence of S-CQDs was enhanced as the activity of acetylcholinesterase (AChE) was inhibited by pirimicarb, achieving the detection of pirimicarb in the cereal samples. The limit of detection (LOD) was 0.006 μg mL -1 . The recovery ranged from 96.6% to 108.2%. This extraction and detection method of pirimicarb based on an environmentally friendly DES and S-CQD fluorescent sensor maintains good stability and convenience, offering a promising strategy for extracting and testing harmful substances in food samples., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The rapid development of nanomaterials has provided a good theoretical basis and technical support to solve the problems of food safety inspection. The combination of functionalized composite nanomaterials and well-known detection methods is gradually applied to detect hazardous substances, such as chemical residues and toxins, in agricultural food products. This review concentrates on the latest agro-food safety inspection techniques and methodologies constructed with the assistance of new hybrid micro/nanoentities, such as molecular imprinting polymers integrated with quantum dots (MIPs@QDs), molecular imprinting polymers integrated with upconversion luminescent nanoparticles (MIPs@UCNPs), upconversion luminescent nanoparticles combined with metal-organic frameworks (UCNPs@MOFs), magnetic metal-organic frameworks (MOFs@Fe 3 O 4 ), magnetic covalent-organic frameworks (Fe 3 O 4 @COFs), covalent-organic frameworks doped with quantum dots (COFs@QDs), nanobody-involved immunoassay for fast inspection, etc. The presented summary and discussion favor a relevant outlook for further integrating various disciplines, like material science, nanotechnology, and analytical methodology, for addressing new challenges that emerge in agro-food research fields.

A facile, friendly and one-step hydrothermal protocol was used to synthesize nitrogen-doped carbon dots (N-CDs) by utilizing hexamethylenetetramine and ethanediamine as the carbon and nitrogen sources. It demonstrated good water solubility and fluorescence properties were stable, whether in acidic or alkaline. Quantum yield (QY) of N-CDs was 8.3% at an excitation wavelength of 325 nm with maximum emission at 425 nm. The fluorescence of N-CDs achieved very high fluorescence quenching of 60% in the detection of p-nitrophenol (p-NP) in aqueous medium via fluorescence resonance energy transfer (FRET) mechanisms. Under optimum conditions, fluorescence probs of N-CDs had strong selectivity to p-NP, and the fluorescence intensity was linearly proportional to p-NP concentration from 0.5 to 70.0 μM with a detection limit of 0.201 μM. The corresponding cell experiments were also performed, indicating that the prepared N-CDs possessed low cytotoxicity and good biocompatibility. Meanwhile, the N-CDs can be used for the determination of p-NP in river water and industrial wastewater., 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 © 2021 Elsevier B.V. All rights reserved.)

Antibiotics have been overused in recent years because of their remarkable curative effect, but this has led to considerable environmental pollution. Therefore, the development of approaches aimed at the effective detection and control of the antibiotics is vital for protecting the environment and human health. Many conventional strategies (such as high-performance liquid chromatography (HPLC), gas chromatography (GC), high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS)) are currently in use for the detection of antibiotics. These strategies have aroused a great deal of interest because of their outstanding features of high efficiency and speed, good reproducibility, automation, etc. However, various problems such as tedious sample pretreatment, low detection sensitivity, and high cost must be overcome for the effective detection of antibiotics in environmental samples. Consequently, it is of great significance to improve the detection sensitivity of antibiotics. The development of new materials combined with the existing detection technology has great potential to improve the detection results for antibiotics. Carbon dots (CDs) are a new class of nanomaterials with particle sizes in the range of 0-10 nm. In addition, CDs have desirable properties such as small particle effect, excellent electrical properties, unique optical properties, and good biocompatibility. Hence, they have been widely utilized for the detection of antibiotics in environmental samples. In this review, the application of CDs combined with sensors and chromatographic technology for the detection of antibiotics in the last five years are summarized. The development prospects of CD-based materials and their application to the analysis and detection of antibiotics are presented. In this review, many new sensors (CDs combined with molecularly imprinted polymer sensors, aptamer sensors, electrochemiluminescence sensors, fluorescence sensors, and electrochemical sensors) combined with CD-based materials and their use in the detection of antibiotics are summarized. Furthermore, advanced analysis methods such as ratiometric sensor and array sensor methods are reviewed. The novel analysis methods provide a new direction toward the detection of antibiotics by CDs combined with a sensor. Moreover, CD-based chromatographic stationary phases for the separation of antibiotics are also summarized in this manuscript. It is reported that the detection sensitivity for antibiotics can be greatly improved by the combination of CDs and a sensor. Nevertheless, a literature survey reveals that the detection of antibiotics in complex environmental samples is confronted with numerous challenges, including the fabrication of highly sensitive sensors in combination with CDs. Furthermore, the development of novel high-performance materials is of imperative. In addition, it is important to develop new methods for effective data processing. The separation of antibiotics with CDs as the chromatographic stationary phases is in the preliminary stage, and the separation mechanism remains to be clarified. In conclusion, there are still many problems to be overcome when using CDs as novel materials for the detection of antibiotics in environmental samples. Nowadays, CD-based materials are being intensively studied, and various analytical detection technologies are being rapidly developed. In the future, CD-based materials are expected to play an important role in the detection of antibiotics and other environmental pollutants.

Mercury ions and thiophanate methyl (TM), are common contaminants present in the environment and food products. These contaminants cause neurovirulence and carcinogenicity effect on the human body. Herein, thioctic acid-carbon dots (SCDs) was synthesized and applied in a fluorescent "turn-off-on" probe to detect Hg 2+ and TM. The presence of other common metal ions and pesticides did not affect the response of the developed sensor. Further investigation revealed that the fluorescent "turn-off-on" model were static, wherein the "turn-off" was induced by an electron transfer effect, while the "turn-on" was caused by the formation of TM-Hg complexes. Under optimal conditions, the fluorescence sensor method exhibited limits of detection as low as 33.3 nmol/L and 7.6 nmol/L for Hg 2+ and TM, respectively. The developed sensor was designed to detect Hg 2+ and TM in real tap water, grape juice and Citri Reticulatae Pericarpium (CRP) water samples., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Silver ions, as a commonly used industrial heavy metal, tends to deposit in the body and induce many diseases. In this work, modified CdTe QDs with green and red emission were synthesized to assemble dual-QDs, which could be efficient and selective utilized for Ag + determination through the electron transfer progress between surface functional group of dual-QDs and Ag + , and the aggregation of Ag + on the surface of dual-QDs. Under the appropriate pH value and volume ratio, the interaction between the surface functional groups of assembled dual-QDs reduce the affinity of Hg 2+ in this system. The fluorescent signal of dual-QDs simultaneously attenuation or enhancement in the same proportion remove the interference of Cu 2+ and other metal ions. Therefore, this method can selectively detect Ag + without any masking agents. The linear region of detection was from 0 to 800 nmol/L (R 2  > 0.998), and low of detection (LOD) was 7.7 nmol/L, which could meet the corresponding standards of World Health Organization (WHO) and Environmental Protection Agency (EPA). This effective proposed dual-QDs ratios fluorescent probe has been applied to detect Ag + in real environment water, tea and Citri Reticulatae Pericarpium (CRP) water., 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.)

Colorimetric sensor array is a sensitive, rapid, and inexpensive detection technology which simulates human olfaction system based on various organic dyes. In this work, a sensor array based on acid-sensitive CdTe QDs coupled with chemometrics method was developed and proved to be a rapid, accurate and sensitive method for identification of 32 kinds of Chinese traditional cereal vinegars (CTCV). The specificity of identification of this method was mainly depends on the organic acids and melanoidins of CTCV. Among them, organic acids can quench the fluorescence of QDs through enhancing their electron transfer (hydrogen bond) and resonance energy transfer, and the fluorescence intensity of melanoidin was closely related to the brewing technology and aging year of CTCV. The types and aging time of 32 CTCV can be 100% identified at a dilution of 1000 by partial least squares discriminant analysis, when the latent variables were 4. And only one kind of QDs is needed instead of various organic dyes to this kind of colorimetric sensor array. Except for vinegar, this method can also be used in the identification of other food which rich in organic acid., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this study, a novel fluorescent "turn-on" aptasensor was developed for sensitive and rapid detection of tetracycline (TC) in animal-derived food. It is based on aptamer-functionalized nitrogen-doped graphene quantum dots (N-GQDs-aptamer) coupled with cobalt oxyhydroxide (CoOOH) nanoflakes. The CoOOH nanoflakes are efficient fluorescence quenchers in homogeneous solutions, and this is due to their advantages of excellent optical properties, superior flexibility, and water dispersibility. The proposed method's mechanism is driven by quenching based on the fluorescence resonance energy transfer (FRET) between the donor (N-GQDs) and the acceptor (CoOOH nanoflakes). On the other hand, fluorescence recovery is caused by the structure switching behavior of the aptamer. Compared with previous methods, our developed method exhibits better behavior in terms of being easy to fabricate and being simple in detection procedure and maintains the detection limit low enough in TC determination: a linear range from 1 to 100 ng mL -1 and a detection limit of 0.95 ng mL -1 (S/N = 3). Furthermore, the proposed method was applied to five animal-derived food samples (milk, honey, fish, eggs, and chicken muscle) and demonstrated practical applicability. As well, the method has the advantages of simplicity in pre-treatment and convenience in instruments, saves times, and is cost-effective. Finally, the proposed method demonstrates significant potential for sensitive and rapid detection of specific components in real samples. Graphical abstract.

A fluorometric method is described for the determination of fipronil, a frequently-used insecticide. It exploits the blue fluorescence of carbon quantum dots (CQDs) and the selectivity of molecularly imprinted silica (MIS). The MIS was prepared via the sol-gel method by using fipronil as the template, 3-aminopropyltriethoxysilane as functional monomer, and tetraethoxysilane as cross-linker in the presence of CQDs. The blue fluorescence of the CQD@MIS, with excitation/emission peaks at 340/422 nm, is quenched by fipronil. The assay works in the 0. 70 pM to 47 μM fipronil concentration range, and the limit of detection is 19 pM. The method was successfully applied to the quantitation of fipronil in spiked eggs, milk, and tap water. Recoveries between 83.8 and 114.0% were achieved. The corresponding relative standard deviations (RSD) are less than 6.67%. Graphical abstractSchematic representation of a high sensitivite and selectivite fluorescence nanoprobe constructed by combining the excellent fluorescence property of carbon quantum dots and the predicted selectivity of molecularly imprinted silica. It was applied to analyze fipronil in egg, milk and tap water, respectively.

Folic acid (FA) is an essential vitamin in humans, and thus, rapid, accurate, and sensitive methods for its quantification in different biological samples are needed. This work describes a novel, simple, and effective dual-emission fluorescence nanoprobe for FA detection and quantification. The probe was covalently linked to amino-modified orange quantum dots (QDs) and carboxyl-modified blue graphene quantum dots (GQDs). The resulting material exhibited two emission peaks at 401 and 605 nm upon excitation at 310 nm. The probe had good selectivity and sensitivity toward FA with an exceptionally low detection limit (LOD = 0.09 nM). This probe was effectively used to quantify FA in animal serum samples. The method has potential utility for FA analysis in different types of biological samples. Graphical abstract.

In order to develop a sensitive immunoassay for Aflatoxin B1 (AFB1) monitoring, a hybridoma secreting anti-AFB1 monoclonal antibody with high binding affinity was screened. A new type of CdTe/CdS/ZnS quantum dot was synthesized and conjugated with an artificial antigen for use as a fluorescent probe in a simple one-step fluorescence immunoassay (FLISA). The developed FLISA allowed a sensitive determination of AFB1 in cereal samples in a wide linear range, from 0.08 to 1.97 ng mL -1 , with a detection limit of 0.01 ng mL -1 in cereal samples. The corresponding immunoglobulin genes of the Fab fragment were cloned and sequenced, and expression of Fab was successfully verified in HEK293 cells, with a K D value of 1.09 × 10 -7  mol L -1 for AFB1. To investigate the interactions between the antibody and AFB1, molecular docking, molecular dynamic simulation, and quantum-chemical computation were performed on AFB1 and a homology model of the Fab fragment. Our results showed that residues Ser32, Trp93, and Trp98 played the most important roles in the binding through hydrogen bonds formation, Pi-Pi stacked/Pi-alkyl interactions, and van der Waals interactions. In addition, the electrostatic potential study of AFB1 demonstrated that electrostatic interactions also played an important role in the recognition process. Results from theoretical studies provide guidance for hapten design and antibody improvement through genetic engineering., (Copyright © 2018 Elsevier B.V. All rights reserved.)

CdTe/CdS/ZnS quantum dots (QDs) were synthesized in aqueous phase and conjugated with a new anti-zearalenone (ZEN) monoclonal antibody. Using this novel fluorescent probe, a fluoroimmunoassay (FLISA) and a rapid immunochromatographic strip (ICTS) were developed for the detection of ZEN in maize. Our proposed FLISA allowed for ZEN determination in the range of 0.038-0.977 ng/mL with an IC 50 of 0.162 ng/mL and a limit of detection (LOD) of 0.012 ng/mL occurring in maize. The rapid ICTS had a visual LOD of 1.0 ng/mL in buffer solution and 1.5 ng/mL in maize extract. These two QDs-based immunoassays were all successfully verified by commercial ELISA kits. The results confirmed that: firstly, the FLISA can be used as a robust method for the sensitive detection of ZEN; and secondly, the ICTS is ideally suited for rapidly screening large numbers of samples., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

It is found that the fluorescence of carbon dots (CD) with an emission peak at 459 nm is strongly quenched by silver nanoparticles (AgNPs) with their absorption peak at 430 nm. The finding was applied in a fluorescence quenchometric lateral flow immunochromatographic assay for detection of zearalenone (ZEN) with CDs conjugated to ovalbumin (OVA) as donor signal probe and AgNP-Ab as acceptor signal probe. The assay has an LOD of 0.1 μg·L -1 for ZEN. This is 10 times better than the respective "turn-off" AgNP-based LFIA. In case of cereal samples and their products, the LODs range from 1 to 2.5 μg·kg -1 . Only minor cross reactivity is found for fusarium toxins, and no cross-sensitivity for aflatoxin B1, T-2 mycotoxin, ochratoxin A, deoxynivalenol, and fumonisin B1. The assay represents a simple, sensitive, and rapid tool for determination of ZEN in cereal samples and their products. Graphical abstract Schematic presentation of fluorescence quenching lateral flow immunochromatographic assay (FLFIA) based on carbon dots (CD) and silver nanoparticle (AgNP) fluorescence resonance energy transfer (FRET) system for the rapid high sensitive detection of zearalenone (ZEN) in cereal samples.

Colloidal gold, quantum dots and polystyrene microspheres were used as labels in three kinds of lateral flow immunochromatographic assays (ICAs) for the detection of zearalenone (ZEN) in cereal samples. The assays allow ZEN to be quantified within 20 min. The LODs are 10 μg·L -1 of ZEN for the colloidal gold-based ICA, and 1 μg·L -1 for both the quantum dot and polystyrene microsphere based ICAs. The respective data are 60 μg·kg -1 , 6 μg·kg -1 and 6 μg·kg -1 , respectively, for spiked samples and cereals. Only minor cross-sensitivity occurred between ZEN and fusarium toxins, and no cross-sensitivity if found for aflatoxin B 1 , T-2 mycotoxin, ochratoxin A, deoxynivalenol, and fumonisin B 1 . LODs of the three assays are lower than the maximum limits of ZEN set by most standardization agencies. Graphical abstract Schematic presentation of three lateral flow immunochromatographic assays (ICAs) based on the use of (a) colloidal gold (CG), (b) fluorescent quantum dots (QD), and, ((c) polystyrene microspheres (PMs) as signalling labels for the rapid and sensitive determination of zearalenone (ZEN) in cereal samples.)

In this study, two novel fluorescence quenching immune chromatographic strips (FQICS) were developed to detect sulfaquinoxaline (SQX) in foods of animal origin. These proposed FQICSs were based on fluorescence resonance energy transfer (FRET) from fluorescence donors (quantum dots or upconversion nanoparticles) to fluorescence acceptors (colloidal gold nanoparticles). Compared with traditional colloidal gold-based immune chromatographic strips (ICS), these FQICSs showed positive correlation between the fluorescent signals and the targets, and allowed user to get test results from weak fluorescent signals. The visual detection limits of these two FQICSs were both 1 ng mL -1 in standard solution and 8 μg kg -1 in samples, while the visual detection limit of the colloidal gold-based ICS was 10 ng mL -1 in standard solution and 80 μg kg -1 in samples. Besides, the results we obtained by the use of FQICS showed high agreement with those obtained by the use of commercial ELISA kits, indicating the good accuracy of these strips. As a conclusion, these proposed FQICS based on quantum dots and upconversion nanoparticles can be applied in sensitive, rapid and on-site detection of SQX in foods of animal origin., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A novel strategy is reported for the fabrication of bis-aniline-crosslinked Au nanoparticles (NPs)-CdSe/ZnS quantum dots (QDs) array composite by facil one-step co-electropolymerization of thioaniline-functionalized AuNPs and thioaniline-functionalized CdSe/ZnS QDs onto thioaniline-functionalized Au elctrodes (AuE). Stable and enhanced cathodic electrochemiluminescence (ECL) of CdSe/ZnS QDs is observed on the modified electrode in neutral solution, suggesting promising applications in ECL sensing. An advanced ECL sensor is explored for detection of 2-methyl-4-chlorophenoxyacetic acid (MCPA) which quenches the ECL signal through electron-transfer pathway. The sensitive determination of MCPA with limit of detection (LOD) of 2.2 nmolL(-1) (S/N=3) is achieved by π-donor-acceptor interactions between MCPA and the bis-aniline bridging units. Impressively, the imprinting of molecular recognition sites into the bis-aniline-crosslinked AuNPs-CdSe/ZnS QDs array yields a functionalized electrode with an extremely sensitive response to MCPA in a linear range of 10 pmolL(-1)-50 μmolL(-1) with a LOD of 4.3 pmolL(-1 ()S/N=3). The proposed ECL sensor with high sensitivity, good selectivity, reproducibility and stability has been successfully applied for the determination of MCPA in real samples with satisfactory recoveries. In this study, ECL sensor combined the merits of QDs-ECL and molecularly imprinting technology is reported for the first time. The developed ECL sensor holds great promise for the fabrication of QDs-based ECL sensors with improved sensitivity and furthermore opens the door to wide applications of QDs-based ECL in food safety and environmental monitoring., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The large external antigen (LEA) is a cell surface glycoprotein that has been proven to be highly expressed in colorectal cancer (CRC) as a tumor-associated antigen. To evaluate and validate the relationship between LEA expression and clinical characteristics of CRC with high efficiency, LEA expression levels were detected in 85 tissue blocks from CRC patients by quantum dot-based immunohistochemistry (QD-IHC) combined with imaging quantitative analysis using quantum dots with a 605 nm emission wavelength (QD605) conjugated to an ND-1 monoclonal antibody against LEA as a probe. Conventional IHC was performed in parallel for comparison. Both QD-IHC and conventional IHC showed that LEA was specifically expressed in CRC, but not in non-CRC tissues, and high LEA expression was significantly associated with a more advanced T-stage (P<0.05), indicating that LEA is likely to serve as a CRC prognostic marker. Compared with conventional IHC, receiver operating characteristic analysis revealed that QD-IHC possessed higher sensitivity, resulting in an increased positive detection rate of CRC, from 70.1% to 89.6%. In addition, a simpler operation, objective analysis of results, and excellent repeatability make QD-IHC an attractive alternative to conventional IHC in clinical practice. Furthermore, to explore whether the QD probes can be utilized to quantitatively detect living cells or single cells, quantum dot-based immunocytochemistry (QD-ICC) combined with imaging quantitative analysis was developed to evaluate LEA expression in several CRC cell lines. It was demonstrated that QD-ICC could also predict the correlation between LEA expression and the T-stage characteristics of the cell lines, which was confirmed by flow cytometry. The results of this study indicate that QD-ICC has the potential to noninvasively detect rare circulating tumor cells in clinical samples in real clinical applications.

A triple-dimensional sensing chip is developed based on simultaneous utilization of fluorescence (FL), electrochemical (ECL) and mass-sensitivity (MS) properties of a novel nanocomposites. The sensing nanomaterial is composed of CdSe/ZnS quantum dots (QDs) and graphene through a one-pot room-temperature reverse microemulsion polymerization. Here, full integration of QDs and graphene on one chip provides triple-dimensional sensing signals. It enables quick and accurate discrimination of eight analytes in a "lab-on-a-nanomaterial" approach and notably improves the overall sensor performance. Unknown samples randomly taken from the training set at concentrations of 0.7 μM are successfully classified by principal component analysis (PCA) with accuracies of 92.5%, compared with the high performance liquid chromatography (HPLC) method. We further apply it to discriminate eight antioxidants from real oil samples, and explore the mechanism., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A novel molecularly imprinted polymer (MIP) based on hydrophobic CdSe quantum dots (QDs) was synthesized using a one-pot room-temperature reverse microemulsion polymerization, and this polymer was applied as a molecular recognition element to construct a ractopamine (RAC) optosensor. Here, hydrophobic CdSe QDs were first introduced to the hydrophilic analyte-imprinted polymer for highly selective and sensitive detection of RAC via the change in fluorescence intensity, because of the high-quality hydrophobic QDs with high quantum yield, sharp photoluminescence spectra and chemical and fluorescent stability. Under optimal conditions, the relative fluorescence intensity of MIP based on hydrophobic QDs decreased linearly with the increasing concentration of RAC in the range of 1.21 × 10(-9) -3.03 × 10(-6)mol L(-1) with a detection limit of 7.57 × 10(-10)mol L(-1), and the precision for five replicate detections of 1.51 × 10(-8)mol L(-1) RAC was 2.09% (relative standard deviation). The proposed method was successfully applied for the determination of trace RAC in pork samples, with good recoveries ranging from 82.79% to 97.23%., (© 2013 The Authors. Published by Elsevier B.V. All rights reserved.)

This work prepared a novel ionic liquid stabilized molecularly imprinted optosensing material based on quantum dots (QDs) and graphene oxide (GO) composites using a one-step polymerization for highly selective and sensitive specific recognition of vitamin E (VE). Here, GO was first introduced to the molecularly imprinted polymer (MIP) because of its ultra-high specific surface area which increases the rate of mass-transfer relative to that of traditional bulk MIP. The ionic liquid was used to provide the desired surface binding groups between the QDs and the GO, but also to improve their fluorescence stability by virtue of its high thermal and chemical stability. Under optimal conditions, the relative fluorescence intensity of MIP decreased linearly with the increasing concentration of VE in the range of 2.30×10(-2)-9.20×10(2)μM with a detection limit of 3.5nM and the precision for five replicate detections of 92μM VE was 1.67% (relative standard deviation). At three concentration levels, the recoveries for two samples achieved were 93.00-100.14% and 92.00-102.00%, respectively., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A novel dual-function material was synthesized by anchoring a molecularly imprinted polymer (MIP) layer on CdTe/ZnS quantum dots (QDs) using a sol-gel with surface imprinting. The material exhibited highly selective and sensitive determination of ractopamine (RAC) through spectrofluorometry and solid-phase extraction (SPE) coupled with high performance liquid chromatography (HPLC). A series of adsorption experiments revealed that the material showed high selectivity, good adsorption capacity and a fast mass transfer rate. Fluorescence from the MIP-coated QDs was more strongly quenched by RAC than that of the non-imprinted polymer, which indicated that the MIP-coated QDs acted as a fluorescence sensing material could recognize RAC. In addition, the MIP-coated QDs as a sorbent was also shown to be promising for SPE coupled with HPLC for the determination of trace RAC in feeding stuffs and pork samples. Under optimal conditions, the spectrofluorometry and SPE-HPLC methods using the MIP-coated QDs had linear ranges of 5.00×10(-10)-3.55×10(-7) and 1.50×10(-10)-8.90×10(-8) mol L(-1), respectively, with limits of detection of 1.47×10(-10) and 8.30×10(-11) mol L(-1), the relative standard deviations for six repeat experiments of RAC (2.90×10(-9) mol L(-1)) were below 2.83% and 7.11%., (Copyright © 2012 Elsevier B.V. All rights reserved.)

We have successfully synthesized GSH and TGA co-capped CdTe quantum dots (QDs) with good biological compatibility and high fluorescence intensity. The effects of different reaction time, temperature, pH value, ligand concentration and the molar ratio of GSH/TGA were carefully investigated to optimize the synthesis condition. The optical properties of as-prepared CdTe QDs were studied by UV-visible absorption spectrum and fluorescence spectrum, meanwhile their structure and morphology were characterized using transmission electron microscope (TEM), Fourier transform infrared spectra (FT-IR) and X-ray powder diffraction (XRD). Compared with the CdTe QDs that are single-capped with either GSH or TGA, the GSH-TGA co-capped CdTe QDs demonstrated significantly improved fluorescence intensity and optical stability. In addition, GSH-TGA co-capped CdTe QDs were conjugated to amonoclonal antibody ND-1. The GSH-TGA co-capped CdTe QDs-antibody probe was successfully used to label colorectal cancer cells, CCL187, in vitro., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Quantum dots (QDs) were prepared in genetically engineered Escherichia coli (E. coli) through the introduction of foreign genes encoding a CdS binding peptide. The CdS QDs were successfully separated from the bacteria through two methods, lysis and freezing-thawing of cells, and purified with an anion-exchange resin. High-resolution transmission electron microscopy, X-ray diffraction, luminescence spectroscopy, and energy dispersive X-ray spectroscopy were applied to characterize the as-prepared CdS QDs. The effects of reactant concentrations, bacteria incubation times, and reaction times on QD growth were systematically investigated. Our work demonstrates that genetically engineered bacteria can be used to synthesize QDs. The biologically synthesized QDs are expected to be more biocompatible probes in bio-labeling and imaging., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The realization of improved charge transport with suppressed recombination at the interface of perovskite and carbon electrode is the main key for remarkably increasing the power conversion efficiency of carbon‐based hole transport material (HTM)‐free perovskite solar cells (PSCs). Herein, a strategy that builds a perovskite quantum dot (PQD) interlayer is demonstrated, for the first time, to bridge the perovskite absorber and carbon electrode for solving the interface issue in HTM‐free PSCs. It is found that the introduced PQD interlayer concurrently functions as a morphology changer, a defect passivator, and a photogenerated hole extractor. Compared with the pristine perovskite film, the PQD‐modified perovskite absorber shows increased contact area and high compatibility with carbon electrode, prolonged carrier lifetime, deduced defect density as well as suppressed recombination. These positive effects, combined with a heterostructure created by perovskite bulks and PQDs facilitating hole transport at the interface, enable an improvement in device efficiency from 16.71% to 17.93%. [ABSTRACT FROM AUTHOR]

A detailed picture of temperature dependent behavior of CsxFA1-xPbI3 perovskite quantum dots across the composition range is constructed by performing in situ optical spectroscopic and structural measurements, supported by theoretical calculations that focus on the relation between A-site chemical composition and surface ligand binding. The thermal degradation mechanism depends not only on the exact chemical composition, but also on the ligand binding energy. The thermal degradation of Cs-rich perovskite quantum dots is induced by a phase transition from black γ-phase to yellow δ-phase, while FA-rich perovskite quantum dots with higher ligand binding energy directly decompose into PbI2. Quantum dot growth to form large bulk size grain is observed for all CsxFA1-xPbI3 perovskite quantum dots at elevated temperatures. In addition, FA-rich quantum dots possess stronger electron−longitudinal optical phonon coupling, suggesting that photogenerated excitons in FA-rich quantum dots have higher probability to be dissociated by phonon scattering compared to Cs-rich quantum dots. The lattice strain induced by surface ligands not only stabilizes black phase at room temperature but also enables full-range A-site tuning. Here, authors construct a detailed picture of temperature dependent behaviour of perovskite quantum dots by in situ spectroscopic and structural measurements. [ABSTRACT FROM AUTHOR]

Deep-red and near-infrared emissive carbon dots (CDs) are highly desired for bioimaging, especially in deep tissue imaging, but they are extremely rare and the known ones usually suffer from low-efficient fluorescence in water and aggregation-induced fluorescence quenching in solid state. In this work, CDs with intriguing solvent-dependent and two-photon fluorescence emissions have been prepared by a facile solvothermal method. Detailed characterizations reveal that there is an n→π* interaction between the carboxyl functional groups on CDs and the electron donor groups in solvent, which leads to the increase of energy density of CDs and the decrease of energy level, resulting in the red shift of luminescence with enhanced electron donating ability of solvent. Inspired by this finding, mesoporous silica nanoparticles (MSNs) with suitable pore size and low biological toxicity are modified by amino groups to confine CDs, thus the deep-red fluorescence emission is achieved both in solid state and in water facilitated by the n→π* interaction of host—guest. The as-prepared CDs@EDA-MSN composite exhibits high-efficient fluorescence with 650 nm wavelength, low toxicity, and good biocompatibility, which endow them a promising application in bio-imaging. [ABSTRACT FROM AUTHOR]

Perovskite quantum dots (PQDs) have shown great promise in optoelectronic device applications. Typically, a traditional hot-injection method with heating and high vacuum pressure is used to synthesize these colloidal nanoparticles. In this article, we report a low-cost synthetic method for FAPbI3 PQDs in air at atmospheric pressure with the assistance of ZnI2. Compared with the FAPbI3 PQDs synthesized under vacuum/N2 condition, the air-synthesized Zn:FAPbI3 PQDs exhibit the same crystalline structure with a similar preferential crystallographic orientation but demonstrate higher colloidal stability and higher production yield. Furthermore, we examine the influence of ZnI2 during the synthesis process on morphologies and optoelectronic properties. The results show that the mean size of the obtained FAPbI3 PQDs is decreased by increasing the amount of added ZnI2. More importantly, introducing an optimal amount of ZnI2 into the Pb source precursor enables increasing the carrier lifetime of FAPbI3 PQDs, showing the potential beneficial effect on device performance. [ABSTRACT FROM AUTHOR]

Additives and antibiotic abuse during food production and processing are among the key factors affecting food safety. The efficient and rapid detection of hazardous substances in food is of crucial relevance to ensure food safety. In this study, a water-soluble quantum dot with glutathione as a ligand was synthesized as a fluorescent probe by hydrothermal method to achieve the detection and analysis of H2O2. The detection limits were 0.61 μM in water and 68 μM in milk. Meanwhile, it was used as a fluorescent donor probe and manganese dioxide nanosheets were used as a fluorescent acceptor probe in combination with an immunoassay platform to achieve the rapid detection and analysis of enrofloxacin (ENR) in a variety of foods with detection limits of 0.05–0.25 ng/mL in foods. The proposed systems provided new ideas for the construction of fluorescence sensors with high sensitivity. [ABSTRACT FROM AUTHOR]

In this study, the SnO2 nanoflowers with hierarchical structures sensitized by boron nitride quantum dots (BNQDs) were prepared through a simple hydrothermal method. It was applied for the detection of the BTEX vapors. Further investigation showed that the response value of SnO2 sensitized by different amounts of BNQDs to the BTEX gases have a certain improvement. Especially 10-BNQDs/SnO2 gas sensor exhibited a significant improvement in gas sensing performance and its response values to different BTEX gases was increased up to 2â€"4 folds compared with the intrinsic SnO2 sensor. In addition, SnO2 nanoflowers based gas sensor showed surprisingly fast response and recovery time for BTEX gases with 1â€"2 s. That can be attributed to the sensitization of BNQDs and the hierarchical structure of SnO2 nanoflowers, which provided an easy channel for the gas diffusion. An economically viable gas sensor based on BNQDs sensitized SnO2 nanoflowers exhibited a great potential in BTEX gas detection due to the simple synthesis method, environmentally friendly raw materials and excellent gas sensing performance. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4) is recognized as a promising photocatalyst for energy and environmental remediation. However, its performance has been limited by issues such as sluggish photocarrier transfer and inadequate light absorption. To address such challenges, we fabricated an innovative photocatalyst by implanting zero-dimensional carbon quantum dots (CQDs) within one-dimensional g-C 3 N 4 nanorods. The CQD incorporation accelerated the charge separation/transfer, simultaneously, broadened the light-harvesting ability through the up-converted fluorescent properties. Density functional theory calculations were applied to gain insights into the influence of implanted CQDs on the band gap and charge behavior of CQDs/g-C 3 N 4. Moreover, the π-π conjugation between the g-C 3 N 4 and CQD enabled the photogeneration of charge carriers. As a result, the CQDs/g-C 3 N 4 photocatalyst exhibited superb photocatalytic degradation under visible light irradiation, and the removal rates of tetracycline (TC) was 94.3%, surpassing that of pure g-C 3 N 4 by 1.2 times. Additionally, CQDs/g-C 3 N 4 processed excellent reusability and mineralization for TC degradation. The photocatalytic degradation pathway of TC was proposed using LC-MS. Mechanisms studies revealed that the photogenerated holes (h+), hydroxyl (•OH) and superoxide radicals (•O 2 –) were the primary reactive species responsible for driving the photodegradation process. This study provided a valuable strategy for the design of efficient and stable photocatalysts for antibiotic wastewater remediation. [Display omitted] • g-C 3 N 4 nanorod is fabricated by the rapid cooling treatment using liquid nitrogen. • 0D/1D CQDs/g-C 3 N 4 shows excellent photo-degradation and reuse efficiency for TC. • CQDs promote charge separation/transfer and broaden light-harvesting ability. • Impurity level acts as transport medium and donor for photo electron or hole. • The photocatalytic degradation pathway of TC was rationalized using LC-MS. [ABSTRACT FROM AUTHOR]

BACKGROUND: Ethyl carbamate (EC) is a potentially toxic carcinogen produced during fermentation and storage of fermented foods, and many countries have set thresholds for its content in food. Therefore, sensitive, rapid and accurate detection of EC is meaningful to ensure the quality of fermented food. RESULTS: This study introduces a CdTe quantum dots/nano‐5,10,15,20‐tetrakis (4‐methoxyphenyl)‐porphyrin (nano TPP‐OCH3) fluorescence sensor system detection of EC. The specificity of this sensing mainly relies on a photo‐induced electron transfer and electrostatic force interaction between EC and nano TPP‐OCH3. This sensor presented a linear range of 10 to 1000 μg L−1 (R2 = 0.9903) with a low detection limit of 7.14 μg L−1. Meanwhile, the recovery (91.19–101.09%) and precision [relative standard deviation (RSD) = 0.64–3.05%] of the sensor for the analysis of fermented food (yellow rice wine, soy sauce, Chinese spirits, Pu‐erh tea) samples were good and could meet the requirements of practical detection. Moreover, the detection results of fermented food (yellow rice wine, soy sauce, Chinese spirits, Pu‐erh tea) samples by this sensor are basically consistent with those of high‐performance liquid chromatography with fluorescence detector (HPLC‐FLD). CONCLUSION: This method was expected to provide a potential platform for sensitive and accurate detection of EC in food safety monitoring, which would provide knowledge of the flavor and quality related to fermented food. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

A simple dual-colour fluorescent nanoprobe has been designed composed of blue and yellow emission carbon quantum dots (CQDs). This system is inexpensive and easy to operate and was successfully employed for on-site measurements based on a smartphone app. The designed nanoprobe exhibited increased selectivity for Cr(VI), leading to a double stable response of the two CQDs. The dual-emission nanoprobe showed blue-violet fluorescence upon UV irradiation, and the fluorescent emission peaks were located at 418 nm and 552 nm. The blue light emission of CQDs was quenched with increasing Cr(VI) concentration due to the inner filter effect, whereas the yellow light emission was enhanced due to the aggregation-induced emission effect. The different responses of the dual emissions to Cr(VI) resulted in a fluorescent colour variation, thus enabling facile macroscopic visualization. With a smartphone, the change in the fluorescence colour could be observed more apparently than that of a single fluorescence nanoprobe, and the response increased linearly so that the nanoprobe could be applied to instantaneous measurements. Furthermore, the dual-emission nanoprobe was successfully employed for analysing food and water samples. Accurate concentrations were obtained by constructing a calibration plot using a fluorescence spectrometer and a smartphone app; the recoveries were 81.6% to 107.7%, and the relative standard deviation was below 3.6%. Therefore, this smartphone-integrated dual-emission detection system is promising as a new portable method for the on-site measurement of Cr(VI) ions. [ABSTRACT FROM AUTHOR]

Methylammonium lead halide perovskite quantum dots (MAPB-QDs) have been widely used for photovoltaic devices due to their special electronic structures. In this work, MAPB-QDs were used for the first time to detect polar organochlorine pesticides (OCPs) based on the phenomenon that the fluorescence spectra of MAPB-QDs were blue-shifted in the presence of polar OCPs. Furthermore, 1H NMR, FTIR, XPS and XRD were performed first to illustrate the sensing mechanism. In the presence of polar OCPs, the MAPB-QDs' capping ligands, oleic acid (OA) and oleylamine (OAm), were replaced with OCPs and then the chlorine element was adequately doped into QDs, resulting in the increase of the MAPB-QDs' bandgap. As result of the insufficient stability of MAPB-QDs in the presence of moisture, MAPB-QDs were mixed with PDMS and used as the colorimetric cards for fast detection of OCPs in real samples. [ABSTRACT FROM AUTHOR]