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Keywords = red fluorescent CdTe quantum dots (QDs)

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15 pages, 4756 KiB  
Article
Low-Toxicity and High-Stability Fluorescence Sensor for the Selective, Rapid, and Visual Detection Tetracycline in Food Samples
by Jixiang Wang, Yaowei Qin, Yue Ma, Minjia Meng and Yeqing Xu
Molecules 2024, 29(24), 5888; https://doi.org/10.3390/molecules29245888 - 13 Dec 2024
Cited by 2 | Viewed by 1265
Abstract
With the development and improvement of analysis and detection systems, low-toxicity and harmless detection systems have received much attention, especially in the field of food detection. In this paper, a low-toxicity dual-emission molecularly imprinted fluorescence sensor (CdTe QDs@SiO2/N-CDs@MIPs) was successfully designed [...] Read more.
With the development and improvement of analysis and detection systems, low-toxicity and harmless detection systems have received much attention, especially in the field of food detection. In this paper, a low-toxicity dual-emission molecularly imprinted fluorescence sensor (CdTe QDs@SiO2/N-CDs@MIPs) was successfully designed for highly selective recognition and visual detection of tetracycline (TC) in food samples. Specifically, the non-toxic blue-emission N-doped carbon dots (N-CDs) with high luminous performance acted as the response signals to contact TC via the covalent bond between amino and carboxyl groups. The red-emission CdTe quantum dots (CdTe QDs) were coated in silica nanospheres as stable reference signals, which effectively avoided the direct contact of CdTe QDs. Under optimum conditions, CdTe QDs@SiO2/N-CDs@MIPs had a rapid response within 1.0 min to TC, and the detection limit of CdTe QDs@SiO2/N-CDs@MIPs was calculated at 0.846 μM in the linear range of 0–140 μM. In complex environments, the CdTe QDs@SiO2/N-CDs@MIPs also exhibited excellent capabilities for the selective, rapid, and visual detection of TC. Furthermore, the accuracy of CdTe QDs@SiO2/N-CDs@MIPs to detect TC was verified by the HPLC method, and satisfactory results were obtained. Moreover, CdTe QDs@SiO2/N-CDs@MIPs showed a satisfactory recovery when measuring TC in milk and egg samples. This work provided an ideal approach for low-toxicity fluorescence sensor design and application. Full article
(This article belongs to the Special Issue New Achievements and Challenges in Food Chemistry)
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15 pages, 5227 KiB  
Article
One-Pot Preparation of Ratiometric Fluorescent Molecularly Imprinted Polymer Nanosensor for Sensitive and Selective Detection of 2,4-Dichlorophenoxyacetic Acid
by Yuhong Cui, Xintai Li, Xianhong Wang, Yingchun Liu, Xiuli Hu, Shengli Chen and Xiongwei Qu
Sensors 2024, 24(15), 5039; https://doi.org/10.3390/s24155039 - 3 Aug 2024
Cited by 2 | Viewed by 1780
Abstract
The development of fluorescent molecular imprinting sensors for direct, rapid, and sensitive detection of small organic molecules in aqueous systems has always presented a significant challenge in the field of detection. In this study, we successfully prepared a hydrophilic colloidal molecular imprinted polymer [...] Read more.
The development of fluorescent molecular imprinting sensors for direct, rapid, and sensitive detection of small organic molecules in aqueous systems has always presented a significant challenge in the field of detection. In this study, we successfully prepared a hydrophilic colloidal molecular imprinted polymer (MIP) with 2,4-dichlorophenoxyacetic acid (2,4-D) using a one-pot approach that incorporated polyglycerol methacrylate (PGMMA-TTC), a hydrophilic macromolecular chain transfer agent, to mediate reversible addition-fragmentation chain transfer precipitation polymerization (RAFTPP). To simplify the polymerization process while achieving ratiometric fluorescence detection, red fluorescent CdTe quantum dots (QDs) and green fluorescent nitrobenzodiazole (NBD) were introduced as fluorophores (with NBD serving as an enhancer to the template and QDs being inert). This strategy effectively eliminated background noise and significantly improved detection accuracy. Uniform-sized MIP microspheres with high surface hydrophilicity and incorporated ratiometric fluorescent labels were successfully synthesized. In aqueous systems, the hydrophilic ratio fluorescent MIP exhibited a linear response range from 0 to 25 μM for the template molecule 2,4-D with a detection limit of 0.13 μM. These results demonstrate that the ratiometric fluorescent MIP possesses excellent recognition characteristics and selectivity towards 2,4-D, thus, making it suitable for selective detection of trace amounts of pesticide 2,4-D in aqueous systems. Full article
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22 pages, 14158 KiB  
Article
Controlling Fluorescence Wavelength in the Synthesis of TGA-Capped CdTe Quantum Dots
by Catarina S. M. Martins, Ana L. Silva, Luís Pleno de Gouveia, Ihsan Çaha, Oleksandr Bondarchuk, Alec P. LaGrow, Francis Leonard Deepak and João A. V. Prior
Chemosensors 2024, 12(4), 70; https://doi.org/10.3390/chemosensors12040070 - 21 Apr 2024
Cited by 5 | Viewed by 2612
Abstract
Quantum dots (QDs) are semiconductor materials, with a size range between 1–10 nm, showcasing unique size-dependent physical and chemical properties. Such properties have potentiated their use in areas like medical imaging and biosensing. Herein, we present an open-air approach for synthesis of QDs, [...] Read more.
Quantum dots (QDs) are semiconductor materials, with a size range between 1–10 nm, showcasing unique size-dependent physical and chemical properties. Such properties have potentiated their use in areas like medical imaging and biosensing. Herein, we present an open-air approach for synthesis of QDs, reducing the need for controllable atmospheric conditions. Furthermore, we present a predictive mathematical model for maximum emission wavelength (λmax) control. Through a straightforward microwave-based aqueous synthesis of TGA-CdTe QDs, we investigated the influence of time, temperature, and Te:Cd and TGA:Cd molar ratios on λmax, using a chemometric experimental design approach. CdTe-QDs were characterized by UV-Vis and fluorescence spectroscopies. Additionally, Fourier-Transform Infrared spectroscopy, X-ray photoelectron spectroscopy, Transmission Electron Microscopy, and Energy Dispersive X-ray were conducted. Stable QDs with fluorescence ranging from green to red (527.6 nm to 629.2 nm) were obtained. A statistical analysis of the results revealed that time and temperature were the most significant factors influencing λmax. After fine-tuning the variables, a mathematical model with 97.7% of prediction accurately forecasted experimental conditions for synthesizing TGA-CdTe QDs at predefined λmax. Stability tests demonstrated that the QDs retained their optical characteristics for over a month at 4 °C, facilitating diverse applications. Full article
(This article belongs to the Section Optical Chemical Sensors)
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10 pages, 16821 KiB  
Communication
Ratiometric Fluorescence Probe Based on Deep-Red Emissive CdTe Quantum Dots and Eu3+ Hybrid for Oxytetracycline Detection
by Siyi Tan, Qin Wang, Qiuxia Tan, Shaojing Zhao, Lei Huang, Benhua Wang, Xiangzhi Song and Minhuan Lan
Chemosensors 2023, 11(1), 62; https://doi.org/10.3390/chemosensors11010062 - 13 Jan 2023
Cited by 5 | Viewed by 2778
Abstract
Oxytetracycline (OTC) is an environmental pollutant caused by the abuse of antibiotics, and its content in water is closely related to human health. Therefore, the development of a simple, rapid, and accurate method to detect OTC has become desirable. In this work, a [...] Read more.
Oxytetracycline (OTC) is an environmental pollutant caused by the abuse of antibiotics, and its content in water is closely related to human health. Therefore, the development of a simple, rapid, and accurate method to detect OTC has become desirable. In this work, a ratiometric fluorescence probe based on deep red emissive CdTe quantum dots (QDs) modified by mercaptopropionic acid and Eu3+ is developed to accurately and rapidly detect OTC in water. After the addition of OTC, the photoluminescence intensity of CdTe QDs at 698 nm remains almost unchanged, while the peak at 617 nm intensifies within 40 s due to the coordination of Eu3+ with OTC. An excellent linear relationship is present between the photoluminescence intensity ratio of I617/I698 and the concentration of OTC. The limit of detection of the probe towards OCT is 5.4 nM. In addition, the probe shows good selectivity and anti-interference ability for OTC in the presence of other antibiotics, including other antibiotics, ions, and amino acids. The probe has been successfully applied to detect OTC in actual samples, demonstrating its potential for environmental application. Full article
(This article belongs to the Special Issue Fluorescent Probe for Sensing and Bioimaging)
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19 pages, 9764 KiB  
Article
Direct Laser Patterning of CdTe QDs and Their Optical Properties Control through Laser Parameters
by Francesco Antolini, Francesca Limosani and Rocco Carcione
Nanomaterials 2022, 12(9), 1551; https://doi.org/10.3390/nano12091551 - 4 May 2022
Cited by 4 | Viewed by 2286
Abstract
Direct laser patterning is a potential and powerful technique to localize nanomaterials within a host matrix. The main goal of this study is to demonstrate that by tuning some parameters of a laser source, like power and laser pulse frequency, it is possible [...] Read more.
Direct laser patterning is a potential and powerful technique to localize nanomaterials within a host matrix. The main goal of this study is to demonstrate that by tuning some parameters of a laser source, like power and laser pulse frequency, it is possible to modify and tune the optical properties of the generated quantum dots (QDs) within a host matrix of a specific chemical composition. The study is realized by using cadmium telluride (CdTe) QD precursors, embedded in polymethylmethacrylate (PMMA) host matrix, as starting materials. The patterning of the CdTe QDs is carried out by using a UV nanosecond laser source at 355. Fluorescence microscopy and photoluminescence spectroscopy, associated with transmission electron microscopy, indicate that it is possible to obtain desired patterns of QDs emitting from green to red of the visible spectrum, due to the formed CdTe QDs. Preliminary highlights of the CdTe QDs’ formation mechanism are given in terms of laser power and laser pulse frequency (repetition rate). Full article
(This article belongs to the Special Issue Nanoscience for Photonics and Spectroscopy)
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14 pages, 3455 KiB  
Article
Light-Induced Oxidase Activity of DNAzyme-Modified Quantum Dots
by Krzysztof Żukowski, Joanna Kosman and Bernard Juskowiak
Int. J. Mol. Sci. 2020, 21(21), 8190; https://doi.org/10.3390/ijms21218190 - 1 Nov 2020
Cited by 2 | Viewed by 3268
Abstract
Here, we report the synthesis of a quantum dot (QD)-DNA covalent conjugate to be used as an H2O2-free DNAzyme system with oxidase activity. Amino-coupling conjugation was carried out between amino-modified oligonucleotides (CatG4-NH2) and carboxylated quantum dots (CdTe@COOH [...] Read more.
Here, we report the synthesis of a quantum dot (QD)-DNA covalent conjugate to be used as an H2O2-free DNAzyme system with oxidase activity. Amino-coupling conjugation was carried out between amino-modified oligonucleotides (CatG4-NH2) and carboxylated quantum dots (CdTe@COOH QDs). The obtained products were characterized by spectroscopic methods (UV-Vis, fluorescence, circular dichroizm (CD), and IR) and the transmission electron microscopy (TEM) technique. A QD-DNA system with a low polydispersity and high stability in aqueous solutions was successfully obtained. The catalytic activity of the QD-DNA conjugate was examined with Amplex Red and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate)) indicators using reactive oxygen species (ROS) generated by visible light irradiation. The synthesized QD-DNAzyme exhibited enhanced catalytic activity compared with the reference system (a mixture of QDs and DNAzyme). This proved the assumption that the covalent attachment of DNAzyme to the surface of QD resulted in a beneficial effect on its catalytic activity. The results proved that the QD-DNAzyme system can be used for generation of the signal by light irradiation. The light-induced oxidase activity of the conjugate was demonstrated, proving that the QD-DNAzyme system can be useful for the development of new cellular bioassays, e.g., for the determination of oxygen radical scavengers. Full article
(This article belongs to the Special Issue Oligonucleotide, Therapy, and Applications)
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20 pages, 1674 KiB  
Article
Study of Physico-Chemical Changes of CdTe QDs after Their Exposure to Environmental Conditions
by Bozena Hosnedlova, Michaela Vsetickova, Martina Stankova, Dagmar Uhlirova, Branislav Ruttkay-Nedecky, Augustine Ofomaja, Carlos Fernandez, Marta Kepinska, Mojmir Baron, Bach Duong Ngoc, Hoai Viet Nguyen, Ha Pham Thi Thu, Jiri Sochor and Rene Kizek
Nanomaterials 2020, 10(5), 865; https://doi.org/10.3390/nano10050865 - 30 Apr 2020
Cited by 12 | Viewed by 3827
Abstract
The irradiance of ultraviolet (UV) radiation is a physical parameter that significantly influences biological molecules by affecting their molecular structure. The influence of UV radiation on nanoparticles has not been investigated much. In this work, the ability of cadmium telluride quantum dots (CdTe [...] Read more.
The irradiance of ultraviolet (UV) radiation is a physical parameter that significantly influences biological molecules by affecting their molecular structure. The influence of UV radiation on nanoparticles has not been investigated much. In this work, the ability of cadmium telluride quantum dots (CdTe QDs) to respond to natural UV radiation was examined. The average size of the yellow QDs was 4 nm, and the sizes of green, red and orange QDs were 2 nm. Quantum yield of green CdTe QDs-MSA (mercaptosuccinic acid)-A, yellow CdTe QDs-MSA-B, orange CdTe QDs-MSA-C and red CdTe QDs-MSA-D were 23.0%, 16.0%, 18.0% and 7.0%, respectively. Green, yellow, orange and red CdTe QDs were replaced every day and exposed to daily UV radiation for 12 h for seven consecutive days in summer with UV index signal integration ranging from 1894 to 2970. The rising dose of UV radiation led to the release of cadmium ions and the change in the size of individual QDs. The shifts were evident in absorption signals (shifts of the absorbance maxima of individual CdTe QDs-MSA were in the range of 6–79 nm), sulfhydryl (SH)-group signals (after UV exposure, the largest changes in the differential signal of the SH groups were observed in the orange, green, and yellow QDs, while in red QDs, there were almost no changes), fluorescence, and electrochemical signals. Yellow, orange and green QDs showed a stronger response to UV radiation than red ones. Full article
(This article belongs to the Special Issue Nano-Hybrids: Synthesis, Characterization and Applications)
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10 pages, 4514 KiB  
Article
Preparation of “Ion-Imprinting” Difunctional Magnetic Fluorescent Nanohybrid and Its Application to Detect Cadmium Ions
by Lina Chen, Yue Lu, Minshu Qin, Fa Liu, Liang Huang, Jing Wang, Hui Xu, Na Li, Guobao Huang, Zhihui Luo and Baodong Zheng
Sensors 2020, 20(4), 995; https://doi.org/10.3390/s20040995 - 13 Feb 2020
Cited by 6 | Viewed by 3077
Abstract
In this work, we have fabricated a novel difunctional magnetic fluorescent nanohybrid (DMFN) for the determination of cadmium ions (Cd2+) in water samples, where the “off-on” model and “ion-imprinting” technique were incorporated simultaneously. The DMFN were composed of CdTe/CdS core-shell quantum [...] Read more.
In this work, we have fabricated a novel difunctional magnetic fluorescent nanohybrid (DMFN) for the determination of cadmium ions (Cd2+) in water samples, where the “off-on” model and “ion-imprinting” technique were incorporated simultaneously. The DMFN were composed of CdTe/CdS core-shell quantum dots (QD) covalently linked onto the surface of polystyrene magnetic microspheres (PMM) and characterized using ultraviolet-visible spectroscopy (UV-Vis), fluorescence spectroscopy, and transmission electron microscopy (TEM). Based on the favorable magnetic and fluorescent properties of the DMFN, the chemical etching of ethylene diamine tetraacetic acid (EDTA) at the surface produced specific Cd2+ recognition sites and quenched the red fluorescence of outer CdTe/CdS QD. Under optimal determination conditions, such as EDTA concentration, pH, and interfering ions, the working curve of determining Cd2+ was obtained; the equation was obtained Y = 34,759X + 254,894 (R = 0.9863) with a line range 0.05–8 μM, and the detection limit was 0.01 μM. Results showed that synthesized magnetic fluorescent microspheres had high sensitivity, selectivity, and reusability in detection. Moreover, they have significant potential value in fields such as biomedicine, analytical chemistry, ion detection, and fluorescence labeling. Full article
(This article belongs to the Section Chemical Sensors)
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19 pages, 5466 KiB  
Article
Dual and Multi-Emission Hybrid Micelles Realized through Coordination-Driven Self-Assembly
by Youxiong Zheng, Yan Tang, Jianwei Yu, Lan Xie, Huiyou Dong, Rongsheng Deng, Fuhua Jia, Bingxin Liu, Li Gao and Junyuan Duan
Materials 2020, 13(2), 440; https://doi.org/10.3390/ma13020440 - 16 Jan 2020
Cited by 4 | Viewed by 2861
Abstract
Building novel functional nanomaterials with a polymer is one of the most dynamic research fields at present. Here, three amphiphilic block copolymers of 8-hydroxyquinoline derivative motifs (MQ) with excellent coordination function were synthesized by Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) polymerization. The coordination [...] Read more.
Building novel functional nanomaterials with a polymer is one of the most dynamic research fields at present. Here, three amphiphilic block copolymers of 8-hydroxyquinoline derivative motifs (MQ) with excellent coordination function were synthesized by Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) polymerization. The coordination micelles were prepared through the self-assembly process, which the MQ motifs were dispersed in the hydrophobic polystyrene (PSt) blocks and hydrophilic Poly(N-isopropylacrylamide (PNIPAM)) blocks, respectively. The dual-emission micelles including the intrinsic red light emission of quantum dots (QDs) and the coordination green light emission of Zn2+-MQ complexes were built by introducing the CdSe/ZnS and CdTe/ZnS QDs in the core and shell precisely in the coordination micelles through the coordination-driven self-assembly process. Furthermore, based on the principle of three primary colors that produce white light emission, vinyl carbazole units (Polyvinyl Carbazole, PVK) with blue light emission were introduced into the hydrophilic PNIPAM blocks to construct the white light micelles that possess special multi-emission properties in which the intrinsic red light emission of QDs, the coordination green light of Zn2+-MQ complexes, and the blue light emission of PVK were synergized. The dual and multi-emission hybrid micelles have great application prospects in ratiometric fluorescent probes and biomarkers. Full article
(This article belongs to the Section Materials Chemistry)
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14 pages, 15536 KiB  
Article
NIR-Emitting Alloyed CdTeSe QDs and Organic Dye Assemblies: A Nontoxic, Stable, and Efficient FRET System
by Doris E. Ramírez-Herrera, Eustolia Rodríguez-Velázquez, Manuel Alatorre-Meda, Francisco Paraguay-Delgado, Antonio Tirado-Guízar, Pablo Taboada and Georgina Pina-Luis
Nanomaterials 2018, 8(4), 231; https://doi.org/10.3390/nano8040231 - 11 Apr 2018
Cited by 15 | Viewed by 5047
Abstract
In the present work, we synthesize Near Infrared (NIR)-emitting alloyed mercaptopropionic acid (MPA)-capped CdTeSe quantum dots (QDs) in a single-step one-hour process, without the use of an inert atmosphere or any pyrophoric ligands. The quantum dots are water soluble, non-toxic, and highly photostable [...] Read more.
In the present work, we synthesize Near Infrared (NIR)-emitting alloyed mercaptopropionic acid (MPA)-capped CdTeSe quantum dots (QDs) in a single-step one-hour process, without the use of an inert atmosphere or any pyrophoric ligands. The quantum dots are water soluble, non-toxic, and highly photostable and have high quantum yields (QYs) up to 84%. The alloyed MPA-capped CdTeSe QDs exhibit a red-shifted emission, whose color can be tuned between visible and NIR regions (608–750 nm) by controlling the Te:Se molar ratio in the precursor mixtures and/or changing the time reaction. The MPA-capped QDs were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and zeta potential measurements. Photostability studies were performed by irradiating the QDs with a high-power xenon lamp. The ternary MPA-CdTeSe QDs showed greater photostability than the corresponding binary MPA-CdTe QDs. We report the Förster resonance energy transfer (FRET) from the MPA-capped CdTeSe QDs as energy donors and Cyanine5 NHS-ester (Cy5) dye as an energy acceptor with efficiency (E) up to 95%. The distance between the QDs and dye (r), the Förster distance (R0), and the binding constant (K) are reported. Additionally, cytocompatibility and cell internalization experiments conducted on human cancer cells (HeLa) cells revealed that alloyed MPA-capped CdTeSe QDs are more cytocompatible than MPA-capped CdTe QDs and are capable of ordering homogeneously all over the cytoplasm, which allows their use as potential safe, green donors for biological FRET applications. Full article
(This article belongs to the Special Issue Quantum Dots for Following Therapeutic Delivery)
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