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11 pages, 2799 KiB

Open AccessArticle

The Detection of Anthrax Biomarker DPA by Ratiometric Fluorescence Probe of Carbon Quantum Dots and Europium Hybrid Material Based on Poly(ionic)- Liquid

by Dongliang Zhang, Dongsheng Jia, Zhou Fang, Hua Min, Xiaoyi Xu and Ying Li

Molecules 2023, 28(18), 6557; https://doi.org/10.3390/molecules28186557 - 11 Sep 2023

Cited by 6 | Viewed by 1861

Abstract

Bacillus anthracis has gained international attention as a deadly bacterium and a potentially deadly biological warfare agent. Dipicolinic acid (DPA) is the main component of the protective layer of anthracis spores, and is also an anthrax biomarker. Therefore, it is of great significance [...] Read more.

Bacillus anthracis has gained international attention as a deadly bacterium and a potentially deadly biological warfare agent. Dipicolinic acid (DPA) is the main component of the protective layer of anthracis spores, and is also an anthrax biomarker. Therefore, it is of great significance to explore an efficient and sensitive DPA detection method. Herein, a novel ratio hybrid probe (CQDs-PIL-Eu³⁺) was prepared by a simple one-step hydrothermal method using carbon quantum dots (CQDs) as an internal reference fluorescence and a covalent bond between CQDs and Eu³⁺ by using a polyionic liquid (PIL) as a bridge molecule. The ratiometric fluorescence probe was found to have the characteristics of sensitive fluorescence visual sensing in detecting DPA. The structure and the sensing properties of CQDs-PIL-Eu³⁺ were investigated in detail. In particular, the fluorescence intensity ratio of Eu³⁺ to CQDs (I₆₁₆/I₄₄₀) was linear with the concentration of DPA in the range of 0–50 μM, so the detection limit of the probe was as low as 32 nm, which was far lower than the DPA dose released by the number of anthrax spores in human body (60 μM) and, thus, can achieve sensitive detection. Therefore, the ratiometric fluorescence probe in this work has the characteristics of strong anti-interference, visual sensing, and high sensitivity, which provides a very promising scheme for the realization of anthrax biomarker DPA detection. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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10 pages, 3475 KiB

Open AccessCommunication

Oxygen Vacancies Defective La₂Ti₂O₇ Nanosheets Enhanced Photocatalytic Activity of Hydrogen Evolution under Visible Light Irradiation

by Zhigang Wang, Hongliang Yu and Zhuoyuan Liu

Molecules 2023, 28(15), 5792; https://doi.org/10.3390/molecules28155792 - 31 Jul 2023

Cited by 4 | Viewed by 1305

Abstract

A novel and efficient technique has been designed for the creation of oxygen vacancies on La₂Ti₂O₇ (LTO) nanosheets. This is achieved via a controlled solid-state reaction between NaBH₄ and LTO nanosheets. Transmission electron microscopy (TEM) analyses expose [...] Read more.

A novel and efficient technique has been designed for the creation of oxygen vacancies on La₂Ti₂O₇ (LTO) nanosheets. This is achieved via a controlled solid-state reaction between NaBH₄ and LTO nanosheets. Transmission electron microscopy (TEM) analyses expose that these processed LTO specimens possess a unique crystalline core/amorphous shell structure, represented as La₂Ti₂O₇@La₂Ti₂O_7-x. According to X-ray photoelectron spectroscopy (XPS) observations, there is a notable correlation between the reaction time, temperature, and the concentration of oxygen vacancies. The concentration of these vacancies tends to increase along with the reaction time and temperature. Concurrently, UV-Visible spectra and photocatalytic tests reveal a significant impact of oxygen vacancies on the LTO surface on both light absorption and photocatalytic functionality. Most notably, the LTO nanosheets with engineered oxygen vacancies have demonstrated an exceptional photocatalytic capacity for hydrogen production under visible light. The maximal activity recorded was an impressive 149 μmol g⁻¹ h⁻¹, which is noticeably superior to the performance of the pristine La₂Ti₂O₇. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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12 pages, 2393 KiB

Open AccessArticle

Study of Preparation and Properties of Stereoregular Poly(cyclohexenylene carbonate)

by Ming Zhang, Chengqian Zhang, Pengyuan Zhang and Zhengyong Liang

Molecules 2023, 28(13), 5235; https://doi.org/10.3390/molecules28135235 - 5 Jul 2023

Cited by 2 | Viewed by 1157

Abstract

Fixing carbon dioxide as a polymer material is an effective and environmentally beneficial approach for reducing the harm of CO₂ greenhouse gas. In this paper, carbon dioxide and cyclohexene oxide were used as co-monomers, and a chiral binuclear cobalt complex with a [...] Read more.

Fixing carbon dioxide as a polymer material is an effective and environmentally beneficial approach for reducing the harm of CO₂ greenhouse gas. In this paper, carbon dioxide and cyclohexene oxide were used as co-monomers, and a chiral binuclear cobalt complex with a biphenyl linker was employed as the catalyst to successfully prepare a poly(cyclohexenylene carbonate) with high stereoregularity. The influence of catalyst structure, CO₂ pressure, and operating temperature on the copolymerization rate and polymer structure were systematically investigated. Optimal catalyst structure and operating conditions were determined, resulting in an excellent poly(cyclohexenylene carbonate) with a stereoregularity as high as 93.5%. Performance testing revealed that the polyester had a molecular weight of approximately 20 kg/mol, a glass transition temperature of 129.7 °C, an onset decomposition temperature of 290 °C, and a tensile strength of 42.8 MPa. These results demonstrate high thermal stability and mechanical strength, indicating the potential for expanding the applications of aliphatic polycarbonate materials. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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12 pages, 6070 KiB

Open AccessArticle

Blue, Yellow, and Red Carbon Dots from Aromatic Precursors for Light-Emitting Diodes

by Zhenzhen Liu, Xiaofei Lu, Menglin Liu and Wenjing Wang

Molecules 2023, 28(7), 2957; https://doi.org/10.3390/molecules28072957 - 26 Mar 2023

Cited by 9 | Viewed by 3190

Abstract

In this work, multicolor fluorescent carbon dots with red (R-CDs), yellow (Y-CDs), and blue (B-CDs) emissions were prepared by choosing proper aromatic precursors with different amounts of benzene rings through a simple solvothermal method. The characterization showed that the prepared carbon dots were [...] Read more.

In this work, multicolor fluorescent carbon dots with red (R-CDs), yellow (Y-CDs), and blue (B-CDs) emissions were prepared by choosing proper aromatic precursors with different amounts of benzene rings through a simple solvothermal method. The characterization showed that the prepared carbon dots were spherical with a size under 10 nm, rich surface functional groups, and good stability. The emission wavelengths were located at 440, 530, and 580 nm under the excitation of 370 nm. The relative fluorescence quantum yield (QY) of R-CDs, Y-CDs, and B-CDs was 11%, 59%, and 33%, respectively. The related characterization demonstrated that the redshift in the photoluminescence was caused by the synergistic effect of the increasing graphitic nitrogen content, quantum size effect and surface oxidation state. By mixing the three prepared CDs into a PVA matrix, the transparent and flexible films produced relucent blue, yellow, and red emissions under 365 nm UV light, and solid-state quenching was effectively avoided. LEDs were fabricated by using B-CDs, Y-CDs, and R-CDs/PVA with a semiconductor chip. These CDs-based LEDs produced bright blue, yellow, and red light with CIE color coordinates of (0.16, 0.02), (0.38, 0.58), and (0.50, 0.49) were successfully manufactured utilizing the prepared blue, yellow and red multicolor carbon dots as the solid luminescent materials. The results showed that the synthesized CDs can be potentially applied in multi-color monitors as a promising candidate for light-emitting diodes (LEDs). This work blazes a novel trail for the controllable preparation of multicolor fluorescent carbon dots. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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19 pages, 3402 KiB

Open AccessArticle

A Novel Drug with Potential to Treat Hyperbilirubinemia and Prevent Liver Damage Induced by Hyperbilirubinemia: Carbon Dots Derived from Platycodon grandiflorum

by Rui Chen, Huagen Ma, Xiaopeng Li, Meijun Wang, Yunbo Yang, Tong Wu, Yue Zhang, Hui Kong, Huihua Qu and Yan Zhao

Molecules 2023, 28(6), 2720; https://doi.org/10.3390/molecules28062720 - 17 Mar 2023

Cited by 4 | Viewed by 2057

Abstract

Platycodon grandiflorum (PG) is a traditional Chinese medicine with a long history, but its active compounds have not been reported. In this study, novel carbon dots (CDs), PG-based CDs (PGC-CDs), were discovered and prepared from PG via calcinations and characterized by transmission electron [...] Read more.

Platycodon grandiflorum (PG) is a traditional Chinese medicine with a long history, but its active compounds have not been reported. In this study, novel carbon dots (CDs), PG-based CDs (PGC-CDs), were discovered and prepared from PG via calcinations and characterized by transmission electron microscopy; high-resolution transmission electron microscopy; X-ray diffraction, fluorescence, ultraviolet-visible, and Fourier-transform infrared spectrometers; X-ray photoelectron spectroscopy; and high-performance liquid chromatography. In addition, the safety and antioxidant activity of PGC-CDs was evaluated by RAW264.7 cells and LO2 cells. The therapeutic effects of PGC-CDs on hyperbilirubinemia and liver protection were evaluated in a bilirubin-induced hyperbilirubinemia mice model. The experiment confirmed that the diameter range of PGC-CDs was from 1.2 to 3.6 nm. PGC-CDs had no toxicity to RAW264.7 cells and LO2 cells at a concentration of 3.91 to 1000 µg/mL and could reduce the oxidative damage of cells caused by H₂O₂. PGC-CDs could inhibit the increase levels of bilirubin and inflammation factors and increase the levels of antioxidants and survival rate, demonstrating that PGC-CDs possessed anti-inflammatory and anti-oxidation activity. PGC-CDs may reduce the content of bilirubin, so as to reduce a series of pathological lesions caused by bilirubin, which has potential in treating hyperbilirubinemia and preventing liver damage induced by hyperbilirubinemia. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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16 pages, 6570 KiB

Open AccessArticle

Glycyrrhizae radix et Rhizoma-Derived Carbon Dots and Their Effect on Menopause Syndrome in Ovariectomized Mice

by Ying Zhang, Yumin Chen, Xue Bai, Guoliang Cheng, Tianyou Cao, Liyang Dong, Jie Zhao, Yue Zhang, Huihua Qu, Hui Kong and Yan Zhao

Molecules 2023, 28(4), 1830; https://doi.org/10.3390/molecules28041830 - 15 Feb 2023

Cited by 3 | Viewed by 1830

Abstract

With the extension of the human life span and the increasing pressure of women’s work and life, menopause syndrome (MPS) refers to a problem that puzzles almost all women worldwide. Hormone replacement treatment (HRT) can effectively mitigate the symptoms but can also exert [...] Read more.

With the extension of the human life span and the increasing pressure of women’s work and life, menopause syndrome (MPS) refers to a problem that puzzles almost all women worldwide. Hormone replacement treatment (HRT) can effectively mitigate the symptoms but can also exert adverse effects to a certain extent. Glycyrrhizae radix et rhizome (GRR) is commonly made into a charcoal processed product, termed GRR Carbonisatas (GRRC), for use in traditional Chinese medicine (TCM). GRRC is widely used to treat MPS and other gynecological diseases. In this study, GRRC was prepared through pyrolysis. Subsequently, GRR-derived carbon dots (GRR-CDs) were purified through dialysis and characterized using transmission electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared, ultraviolet, fluorescence, X-ray photoelectron microscopy, and high-performance liquid chromatography. The effects of GRR-CDs on MPS were examined and confirmed using ovariectomized female mice models. The GRR-CDs ranged from 1.0 to 3.0 nm in diameter and with multiple surface chemical groups, as indicated by the results. GRR-CDs can elevate the estradiol (E2) level of healthy female mice. Moreover, GRR-CDs can alleviate MPS using the typical ovariectomized mice model, as confirmed by elevating the estradiol (E2) level and reducing the degree of follicle stimulating hormone (FSH) and luteinizing hormone (LH) and raising the degree of uterine atrophy. The results of this study suggested that GRR-CDs may be a potential clinical candidate for the treatment of MPS, which also provides a possibility for nanodrugs to treat hormonal diseases. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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13 pages, 4015 KiB

Open AccessArticle

Study on the Preparation and Properties of Jute Microcrystalline Cellulose Membrane

by Zhengyong Liang, Xing Li, Meng Li and Yulu Hong

Molecules 2023, 28(4), 1783; https://doi.org/10.3390/molecules28041783 - 13 Feb 2023

Cited by 5 | Viewed by 1997

Abstract

The preparation and performance control of the cellulose membrane are one of the hot topics in the environmentally friendly separation membrane field. In this study, microcrystalline cellulose (MCC) was prepared by microwave-assisted acidic hydrolysis of cellulose obtained from jute, followed by the use [...] Read more.

The preparation and performance control of the cellulose membrane are one of the hot topics in the environmentally friendly separation membrane field. In this study, microcrystalline cellulose (MCC) was prepared by microwave-assisted acidic hydrolysis of cellulose obtained from jute, followed by the use of a mixture of N-methylmorpholine-N-oxide and water as a solvent to obtain the homogeneous casting liquid, which was scraped and subsequently immersed in the coagulation bath to form a smooth and dense cellulose membrane. During membrane formation, the crystal structure of MCC changed from type I to type II, but the chemical structure remained unchanged. The mechanical strength and separation performance of the membrane were related to the content of MCC in the casting liquid. When the content of MCC was about 7%, the tensile strength of the membrane reached a maximum value of 13.49 MPa, and the corresponding elongation at break was 68.12%. The water flux (J) and rejection rate (R) for the bovine serum albumin were 19.51 L/(m²·h) and 95.37%, respectively, under an optimized pressure of 0.2 MPa. In addition, the coagulation bath had a significant effect on the membrane separation performance, and J and R were positively and negatively correlated with the polarity of the coagulation bath. Among them, it was note-worthy that J and R of membrane formed in ethanol were 33.95 L/(m²·h) and 91.43%, separately. Compared with water as a coagulation bath, J was increased by 74% at the situation and R was roughly equivalent, showing better separation performance. More importantly, the relationship between the structure and separation performances has also been studied preliminarily. This work provides certain guidance for the preparation of high-performance MCC membranes. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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10 pages, 2497 KiB

Open AccessCommunication

Rational Design of Nitrogen-Doped Carbon Dots for Inhibiting β-Amyloid Aggregation

by Hong Liu, Huazhang Guo, Yibin Fang, Liang Wang and Peng Li

Molecules 2023, 28(3), 1451; https://doi.org/10.3390/molecules28031451 - 2 Feb 2023

Cited by 7 | Viewed by 2329 | Correction

Abstract

The fibrillization and abnormal aggregation of β-amyloid (Aβ) peptides are commonly recognized risk factors for Alzheimer’s disease (AD) brain, and require an effective strategy to inhibit the Aβ deposition and treat AD. Herein, we designed and synthesized nitrogen-doped carbon [...] Read more.

The fibrillization and abnormal aggregation of β-amyloid (Aβ) peptides are commonly recognized risk factors for Alzheimer’s disease (AD) brain, and require an effective strategy to inhibit the Aβ deposition and treat AD. Herein, we designed and synthesized nitrogen-doped carbon dots (N-CDs) as an Aβ-targeted probe, which exhibits the capacity of inhibiting the 1–42 Aβ (Aβ_1–42) self-assembly in vitro. The N-CDs exhibited orange emission with an emission wavelength of 570 nm, which demonstrates their excellent optical properties with excitation-independent behavior. Meanwhile, the N-CDs have spherical morphologies with an average size of 2.2 nm, whose surface enriches the amino, carboxyl, and hydroxyl groups. These preparties are conducive to improving their biological water solubility and provide a large number of chemical bonds for further interaction with proteins. Contrary to this, the kinetic process, size evolutions, and morphologies changes of Aβ_1–42 were inhibited in the presence of N-CDs in the determination of a thioflavin T assay, dynamic light scattering, transmission electron microscope, etc. Finally, the safety application of N-CDs on Aβ_1–42-induced cytotoxicity was further demonstrated via in vitro cytotoxicity experiments. This work demonstrates the effective outcome of suppressing Aβ aggregation, which provides a new view into the high-efficiency and low-cytotoxicity strategy in AD theranostics. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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19 pages, 5900 KiB

Open AccessArticle

Milk-Derived Carbon Quantum Dots: Study of Biological and Chemical Properties Provides Evidence of Toxicity

by Hasan Shabbir, Konrad Wojtaszek, Bogdan Rutkowski, Edit Csapó, Marek Bednarski, Anita Adamiec, Monika Głuch-Lutwin, Barbara Mordyl, Julia Druciarek, Magdalena Kotańska, Piotr Ozga and Marek Wojnicki

Molecules 2022, 27(24), 8728; https://doi.org/10.3390/molecules27248728 - 9 Dec 2022

Cited by 16 | Viewed by 2636

Abstract

Carbon dots (CDs) are carbon-based zero-dimensional nanomaterials that can be prepared from a number of organic precursors. In this research, they are prepared using fat-free UHT cow milk through the hydrothermal method. FTIR analysis shows C=O and C-H bond presence, as well as [...] Read more.

Carbon dots (CDs) are carbon-based zero-dimensional nanomaterials that can be prepared from a number of organic precursors. In this research, they are prepared using fat-free UHT cow milk through the hydrothermal method. FTIR analysis shows C=O and C-H bond presence, as well as nitrogen-based bond like C-N, C=N and –NH₂ presence in CDs, while the absorption spectra show the absorption band at 280 ± 3 nm. Next, the Biuret test was performed, with the results showing no presence of unreacted proteins in CDs. It can be said that all proteins are converted in CDs. Photo luminance spectra shows the emission of CDs is 420 nm and a toxicity study of CDs was performed. The Presto Blue method was used to test the toxicity of CDs for murine hippocampal cells. CDs at a concentration of 4 mg/mL were hazardous independent of synthesis time, while the toxicity was higher for lower synthesis times of 1 and 2 h. When the concentration is reduced in 1 and 2 h synthesized CDs, the cytotoxic effect also decreases significantly, ensuring a survival rate of 60–80%. However, when the synthesis time of CDs is increased, the cytotoxic effect decreases to a lesser extent. The CDs with the highest synthesis time of 8 h do not show a cytotoxic effect above 60%. The cytotoxicity study shows that CDs may have a concentration and time–dependent cytotoxic effect, reducing the number of viable cells by 40%. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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11 pages, 5251 KiB

Open AccessCommunication

Facile Synthesis of Aminated Graphene Quantum Dots for Promising and Selective Detection of Cobalt and Copper Ions in Aqueous Media

by Weitao Li, Ningjia Jiang, Luoman Zhang, Yongqian Chen, Jie Gao, Jihang Zhang, Baoshuo Yang and Jianxin He

Molecules 2022, 27(22), 7844; https://doi.org/10.3390/molecules27227844 - 14 Nov 2022

Cited by 5 | Viewed by 1879

Abstract

Due to the rapid development of industrialization, various environmental problems such as water resource pollution are gradually emerging, among which heavy metal pollution is harmful to both human beings and the environment. As a result, there are many metal ion detection methods, among [...] Read more.

Due to the rapid development of industrialization, various environmental problems such as water resource pollution are gradually emerging, among which heavy metal pollution is harmful to both human beings and the environment. As a result, there are many metal ion detection methods, among which fluorescence detection stands out because of its rapid, sensitive, low cost and non-toxic characteristics. In recent years, graphene quantum dots have been widely used and studied due to their excellent properties such as high stability, low toxicity and water solubility, and have a broad prospect in the field of metal ion detection. A novel high fluorescence Cu²⁺, Co²⁺ sensing probe produced by graphene quantum hydrothermal treatment is reported. After heat treatment with hydrazine hydrate, the small-molecule precursor nitronaphthalene synthesized by self-nitrification was transformed from blue fluorescent GQDs to green fluorescent amino-functionalized N–GQDs. Compared with other metal ions, N–GQDs are more sensitive to Cu²⁺ and Co²⁺ on the surface, and N–GQDs have much higher selectivity to Cu²⁺ and Co²⁺ than GQDs. The strategy proposed here is simple and economical in design. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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15 pages, 2705 KiB

Open AccessArticle

Carbon-Encased Mixed-Metal Selenide Rooted with Carbon Nanotubes for High-Performance Hybrid Supercapacitors

by Yu Yuan, Panpan Cui, Jie Liu, Wei Ding, Yong Wang and Liping Lv

Molecules 2022, 27(21), 7507; https://doi.org/10.3390/molecules27217507 - 3 Nov 2022

Cited by 6 | Viewed by 1916

Abstract

Transition metal-based compounds with high theoretical capacitance and low cost represent one class of promising electrode materials for high-performance supercapacitors. However, their low intrinsic electrical conductivity impedes their capacitive effect and further limits their practical application. Rational regulation of their composition and structure [...] Read more.

Transition metal-based compounds with high theoretical capacitance and low cost represent one class of promising electrode materials for high-performance supercapacitors. However, their low intrinsic electrical conductivity impedes their capacitive effect and further limits their practical application. Rational regulation of their composition and structure is, therefore, necessary to achieve a high electrode performance. Herein, a well-designed carbon-encased mixed-metal selenide rooted with carbon nanotubes (Ni-Co-Se@C-CNT) was derived from nickel–cobalt bimetallic organic frameworks. Due to the unique porous structure, the synergistic effect of bimetal selenides and the in situ growth of carbon nanotubes, the composite exhibits good electrical conductivity, high structural stability and abundant redox active sites. Benefitting from these merits, the Ni-Co-Se@C-CNT exhibited a high specific capacity of 554.1 C g⁻¹ (1108.2 F g⁻¹) at 1 A g⁻¹ and a superior cycling performance, i.e., 96.4% of the initial capacity was retained after 5000 cycles at 10 A g⁻¹. Furthermore, a hybrid supercapacitor assembled with Ni-Co-Se@C-CNT cathode and activated carbon (AC) anode shows a superior energy density of 38.2 Wh kg⁻¹ at 1602.1 W kg⁻¹. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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12 pages, 3821 KiB

Open AccessCommunication

Fabrication of Orange Fluorescent Boron-Doped Graphene Quantum Dots for Al³⁺ Ion Detection

by Weitao Li, Luoman Zhang, Ningjia Jiang, Yongqian Chen, Jie Gao, Jihang Zhang, Baoshuo Yang and Jialin Liu

Molecules 2022, 27(19), 6771; https://doi.org/10.3390/molecules27196771 - 10 Oct 2022

Cited by 8 | Viewed by 2789

Abstract

Aluminum is a kind of metal that we often encounter. It can also be absorbed by the human body invisibly and will affect our bodies to a certain extent, e.g., by causing symptoms associated with Alzheimer’s disease. Therefore, the detection of aluminum is [...] Read more.

Aluminum is a kind of metal that we often encounter. It can also be absorbed by the human body invisibly and will affect our bodies to a certain extent, e.g., by causing symptoms associated with Alzheimer’s disease. Therefore, the detection of aluminum is particularly important. The methods to detect metal ions include precipitation methods and electrochemical methods, which are cumbersome and costly. Fluorescence detection is a fast and sensitive method with a low cost and non-toxicity. Traditional fluorescent nanomaterials have a high cost, high toxicity, and cause harm to the human body. Graphene quantum dots are a new type of fluorescent nanomaterials with a low cost and non-toxicity that can compensate for the defects of traditional fluorescent nanomaterials. In this paper, c-GQDs and o-GQDs with good performance were prepared by a bottom-up hydrothermal method using o-phenylenediamine as a precursor and citric acid or boric acid as modulators. They have very good optical properties: o-GQDs exhibit orange fluorescence under UV irradiation, while c-GQDs exhibits cyan fluorescence. Then, different metal ions were used for ion detection, and it was found that Al³⁺ had a good quenching effect on the fluorescence of the o-GQDs. The reason for this phenomenon may be related to the strong binding of Al³⁺ ions to the N and O functional groups of the o-GQDs and the rapid chelation kinetics. During the chelation process, the separation of o-GQDs’ photoexcited electron hole pairs leads to their rapid electron transfer to Al³⁺, in turn leading to the occurrence of a fluorescence-quenching phenomenon. In addition, there was a good linear relationship between the concentration of the Al³⁺ ions and the fluorescence intensity, and the correlation coefficient of the linear regression equation was 0.9937. This illustrates the potential for the wide application of GQDs in sensing systems, while also demonstrating that Al³⁺ sensors can be used to detect Al³⁺ ions. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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13 pages, 3674 KiB

Open AccessArticle

Fluorine-Nitrogen-Codoped Carbon Dots as Fluorescent Switch Probes for Selective Fe(III) and Ascorbic Acid Sensing in Living Cells

by Shuai Ye, Mingming Zhang, Jiaqing Guo, Xiantong Yu, Jun Song, Pengju Zeng, Junle Qu, Yue Chen and Hao Li

Molecules 2022, 27(19), 6158; https://doi.org/10.3390/molecules27196158 - 20 Sep 2022

Cited by 6 | Viewed by 1856

Abstract

High-quality fluorescent probes based on carbon dots (CDs) have promising applications in many fields owing to their good stability, low toxicity, high quantum yield, and low raw material price. The fluorine- and nitrogen-doped fluorescent CDs (NFCDs) with blue fluorescence was successfully synthesized using [...] Read more.

High-quality fluorescent probes based on carbon dots (CDs) have promising applications in many fields owing to their good stability, low toxicity, high quantum yield, and low raw material price. The fluorine- and nitrogen-doped fluorescent CDs (NFCDs) with blue fluorescence was successfully synthesized using 3-aminophenol and 2,4-difluorobenzoic acid as the raw material by the hydrothermal method. The NFCDs as probe can be used to directly and indirectly detect Fe³⁺ (detection range: 0.1–150 μM and detection limit: 0.14 μM) and ascorbic acid (AA) (detection range: 10–80 μM and detection limit: 0.11 μM). The NFCDs-based probe shows exceptional selectivity and strong anti-interference for Fe³⁺ and ascorbic acid (AA). In addition, we examined the response of NFCDs to Fe³⁺ and AA in living cells, which showed that the timely use of AA can reduce the effects of iron poisoning. This has important biological significance. This means that using NFCDs as fluorescent probes is beneficial for Fe³⁺ and AA detection and observing their dynamic changes in living cells. Thus, this work may contribute to the study of Fe³⁺- and AA-related diseases. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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13 pages, 3153 KiB

Open AccessArticle

Bifunctional Nitrogen and Fluorine Co-Doped Carbon Dots for Selective Detection of Copper and Sulfide Ions in Real Water Samples

by Yutian Zeng, Zhibin Xu, Jiaqing Guo, Xiantong Yu, Pengfei Zhao, Jun Song, Junle Qu, Yu Chen and Hao Li

Molecules 2022, 27(16), 5149; https://doi.org/10.3390/molecules27165149 - 12 Aug 2022

Cited by 8 | Viewed by 2214

Abstract

Copper ions (Cu²⁺) and sulfur ions (S²⁻) are important elements widely used in industry. However, these ions have the risk of polluting the water environment. Therefore, rapid and quantitative detection methods for Cu²⁺ and S²⁻ are urgently [...] Read more.

Copper ions (Cu²⁺) and sulfur ions (S²⁻) are important elements widely used in industry. However, these ions have the risk of polluting the water environment. Therefore, rapid and quantitative detection methods for Cu²⁺ and S²⁻ are urgently required. Using 2,4-difluorobenzoic acid and L-lysine as precursors, nitrogen and fluorine co-doped dots (N, F-CDs) were synthesized in this study via a hydrothermal method. The aqueous N, F-CDs showed excellent stability, exhibited satisfactory selectivity and excellent anti-interference ability for Cu²⁺ detection. The N, F-CDs, based on the redox reactions for selective and quantitative detection of Cu²⁺, showed a wide linear range (0–200 μM) with a detection limit (215 nM). By forming the N, F-CDs@Cu²⁺ sensing platform and based on the high affinity of S²⁻ to Cu²⁺, the N, F-CDs@Cu²⁺ can specifically detect S²⁻ over a linear range of 0–200 μM with a detection limit of 347 nM. In addition, these fluorescent probes achieved good results when used for Cu²⁺ and S²⁻ detection in environmental water samples, implying the good potential for applications. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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12 pages, 2128 KiB

Open AccessArticle

Construction of Co,N-Coordinated Carbon Dots for Efficient Oxygen Reduction Reaction

by Mengying Le, Bingjie Hu, Meiying Wu, Huazhang Guo and Liang Wang

Molecules 2022, 27(15), 5021; https://doi.org/10.3390/molecules27155021 - 7 Aug 2022

Cited by 15 | Viewed by 2297

Abstract

For the sake of the oxygen reduction reaction (ORR) catalytic performance, carbon dots (CDs) doped with metal atoms have accelerated their local electron flow for the past few years. However, the influence of CDs doped with metal atoms on binding sites and formation [...] Read more.

For the sake of the oxygen reduction reaction (ORR) catalytic performance, carbon dots (CDs) doped with metal atoms have accelerated their local electron flow for the past few years. However, the influence of CDs doped with metal atoms on binding sites and formation mechanisms is still uncertain. Herein, Co,N-doped CDs were facilely prepared by the low-temperature polymerization–solvent extraction strategy from EDTA-Co. The influence of Co doping on the catalytic performance of Co-CDs was explored, mainly in the following aspects: first, the pyridinic N atom content of Co-CDs significantly increased from 4.2 to 11.27 at% compared with the CDs, which indicates that the Co element in the precursor is advantageous in forming more pyridinic-N-active sites for boosting the ORR performance. Second, Co-CDs are uniformly distributed on the surface of carbon black (CB) to form Co-CDs@CB by the facile hydrothermal route, which can expose more active sites than the aggregation status. Third, the highest graphite N content of Co-CDs@CB was found, by limiting the current density of the catalyst towards the ORR. Composite nanomaterials formed by Co and CB are also used as air electrodes to manufacture high-performance zinc–air batteries. The battery has good cycle stability and realizes stable charges and discharges under different current densities. The outstanding catalytic activity of Co-CDs@CB is attributed to the Co,N synergistic effect induced by Co doping, which pioneer a new metal doping mechanism for gaining high-performance electrocatalysts. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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14 pages, 4566 KiB

Open AccessArticle

Environmentally Friendly g-C₃N₄/Sepiolite Fiber for Enhanced Degradation of Dye under Visible Light

by Jiayue Sun, Lianying Wang, Simei Lu, Zhuoyuan Wang, Menglin Chen, Weixia Liang, Xiu Lin and Xiangfeng Lin

Molecules 2022, 27(8), 2464; https://doi.org/10.3390/molecules27082464 - 11 Apr 2022

Cited by 1 | Viewed by 1846

Abstract

Herein, novel visible light active graphitic carbon nitride (g-C₃N₄)/sepiolite fiber (CN/SS) composites were fabricated via a facile calcination route, exploiting melamine and thiourea as precursors, and sepiolite fiber as support, for efficient degradation of organic dye methylene blue (MB). [...] Read more.

Herein, novel visible light active graphitic carbon nitride (g-C₃N₄)/sepiolite fiber (CN/SS) composites were fabricated via a facile calcination route, exploiting melamine and thiourea as precursors, and sepiolite fiber as support, for efficient degradation of organic dye methylene blue (MB). The as-prepared CN/SS composites were characterized by various characterization techniques based on structural and microstructural analyses. The effects of CN loading amount, catalyst dosage and initial concentration of dye on the removal rate of dye under visible light were systematically studied. The removal rate of MB was as high as 99.5%, 99.6% and 99.6% over the composites when the CN loading amount, catalyst dosage and initial concentration of dye were 20% (mass percent), 0.1 g, and 15 mg/L in 120 min, respectively. The active species scavenging experiments and electron paramagnetic resonance (EPR) measurement indicated that the holes (h⁺), hydroxyl radical (·OH) and superoxide radicals (·O₂⁻) were the main active species. This study provides for the design of low-cost, environmentally friendly and highly efficient catalysts for the removal of organic dye. Full article

(This article belongs to the Special Issue Functional Carbon Quantum Dots: Synthesis and Applications)

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