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  • 1
    Online Resource
    Online Resource
    Sustainable Synthesis of Bright Fluorescent Nitrogen-Doped Carbon Dots from Terminalia chebula for In Vitro Imaging
    MDPI AG ; 2022
    In:  Molecules Vol. 27, No. 22 ( 2022-11-21), p. 8085-
    Details
    In: Molecules, MDPI AG, Vol. 27, No. 22 ( 2022-11-21), p. 8085-
    Abstract: In this study, sustainable, low-cost, and environmentally friendly biomass (Terminalia chebula) was employed as a precursor for the formation of nitrogen-doped carbon dots (N-CDs). The hydrothermally assisted Terminalia chebula fruit-derived N-CDs (TC-CDs) emitted different bright fluorescent colors under various excitation wavelengths. The prepared TC-CDs showed a spherical morphology with a narrow size distribution and excellent water dispensability due to their abundant functionalities, such as oxygen- and nitrogen-bearing molecules on the surfaces of the TC-CDs. Additionally, these TC-CDs exhibited high photostability, good biocompatibility, very low toxicity, and excellent cell permeability against HCT-116 human colon carcinoma cells. The cell viability of HCT-116 human colon carcinoma cells in the presence of TC-CDs aqueous solution was calculated by MTT assay, and cell viability was higher than 95%, even at a higher concentration of 200 μg mL−1 after 24 h incubation time. Finally, the uptake of TC-CDs by HCT-116 human colon carcinoma cells displayed distinguished blue, green, and red colors during in vitro imaging when excited by three filters with different wavelengths under a laser scanning confocal microscope. Thus, TC-CDs could be used as a potential candidate for various biomedical applications. Moreover, the conversion of low-cost/waste natural biomass into products of value promotes the sustainable development of the economy and human society.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    URL: Article
    DOI: 10.3390/molecules27228085
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2008644-1
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  • 2
    Online Resource
    Online Resource
    Sustainable Synthesis of Silver Nanoparticles Using Marine Algae for Catalytic Degradation of Methylene Blue
    MDPI AG ; 2021
    In:  Catalysts Vol. 11, No. 11 ( 2021-11-15), p. 1377-
    Details
    In: Catalysts, MDPI AG, Vol. 11, No. 11 ( 2021-11-15), p. 1377-
    Abstract: Herein, Sargassum coreanum (marine algae)-mediated silver nanoparticles (AgNPs) were successfully synthesized by a simple reduction method. The synthesized AgNPs were characterized using ultraviolet-visible spectroscopy, attenuated total reflection Fourier transformed infrared spectroscopy, X-ray diffractometry, field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray (EDX) spectroscopy, and high-resolution transmission electron microscopy (HR-TEM) analysis. The acquired colloidal AgNPs were strongly absorbed around 420 nm and displayed brown color under visible light. The XRD pattern of AgNPs exposed their face-centered cubic geometry along with crystalline nature. The HRTEM images of synthesized AgNPs confirmed the mean particle size of 19 nm with a distorted spherical shape, and the calculated interlayer distance (d-spacing value) was about 0.24 nm. Further, the catalytic degradation of methylene blue using sodium borohydride and AgNPs was monitored using UV–vis spectroscopy. The result revealed that AgNPs performed as a superior catalyst, which completely degraded MB in 20 min. The rate constant for MB degradation was calculated to be 0.106 min−1, demonstrating that the marine algae-mediated AgNPs had outstanding catalytic activity. This approach is easy and environmentally benign, which can be applied for environmental-based applications such as dye degradation and pollutant detoxification.
    Type of Medium: Online Resource
    ISSN: 2073-4344
    URL: Article
    DOI: 10.3390/catal11111377
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 3
    Online Resource
    Online Resource
    Natural Nitrogen-Doped Carbon Dots Obtained from Hydrothermal Carbonization of Chebulic Myrobalan and Their Sensing Ability toward Heavy Metal Ions
    MDPI AG ; 2023
    In:  Sensors Vol. 23, No. 2 ( 2023-01-10), p. 787-
    Details
    In: Sensors, MDPI AG, Vol. 23, No. 2 ( 2023-01-10), p. 787-
    Abstract: Chebulic Myrobalan is the main ingredient in the Ayurvedic formulation Triphala, which is used for kidney and liver dysfunctions. Herein, natural nitrogen-doped carbon dots (NN-CDs) were prepared from the hydrothermal carbonization of Chebulic Myrobalan and were demonstrated to sense heavy metal ions in an aqueous medium. Briefly, the NN-CDs were developed from Chebulic Myrobalan by a single-step hydrothermal carbonization approach under a mild temperature (200 °C) without any capping and passivation agents. They were then thoroughly characterized to confirm their structural and optical properties. The resulting NN-CDs had small particles (average diameter: 2.5 ± 0.5 nm) with a narrow size distribution (1–4 nm) and a relatable degree of graphitization. They possessed bright and durable fluorescence with excitation-dependent emission behaviors. Further, the as-synthesized NN-CDs were a good fluorometric sensor for the detection of heavy metal ions in an aqueous medium. The NN-CDs showed sensitive and selective sensing platforms for Fe3+ ions; the detection limit was calculated to be 0.86 μM in the dynamic range of 5–25 μM of the ferric (Fe3+) ion concentration. Moreover, these NN-CDs could expand their application as a potential candidate for biomedical applications and offer a new method of hydrothermally carbonizing waste biomass.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    URL: Article
    DOI: 10.3390/s23020787
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2052857-7
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  • 4
    Online Resource
    Online Resource
    Leftover Kiwi Fruit Peel-Derived Carbon Dots as a Highly Selective Fluorescent Sensor for Detection of Ferric Ion
    MDPI AG ; 2021
    In:  Chemosensors Vol. 9, No. 7 ( 2021-07-02), p. 166-
    Details
    In: Chemosensors, MDPI AG, Vol. 9, No. 7 ( 2021-07-02), p. 166-
    Abstract: Recently, the use of natural products for the synthesis of carbon dots (CDs) has received much attention. Herein, leftover kiwi (Actinidia Deliciosa) fruit peels were successfully turned into beneficial fluorescent carbon dots (KN-CDs) via the hydrothermal-carbonization route. KN-CDs 1 and KN-CDs 2 were prepared without and with ammonium hydroxide, respectively. KN-CDs 1 and KN-CDs 2 were systematically characterized by various analytical techniques. Synthesized KN-CDs showed spherical-shaped morphology with narrow size distribution and excellent optical properties with excitation-independent behaviors. The quantum yields of KN-CDs 1 and KN-CDs 2 were calculated as 14 and 19%, respectively. Additionally, the KN-CDs possess excellent prolonging and photostability. Because of the excellent optical properties of KN-CDs, they were utilized as fluorescent sensors. The strong fluorescence of the KN-CDs was selectively quenched by Fe3+ ion, and quenching behavior showed a linear correlation with the concentrations of Fe3+ ion. KN-CDs 1 and KN-CDs 2 showed the detection of Fe3+ ions within the concentration range of 5–25 µM with the detection limit of 0.95 and 0.85 µM, respectively. Based on the turn-off sensing by the detection of Fe3+ ions, KN-CDs would be a promising candidate as a selective and sensitive fluorescent sensor.
    Type of Medium: Online Resource
    ISSN: 2227-9040
    URL: Article
    DOI: 10.3390/chemosensors9070166
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 5
    Online Resource
    Online Resource
    Highly Fluorescent Carbon Dots as a Potential Fluorescence Probe for Selective Sensing of Ferric Ions in Aqueous Solution
    MDPI AG ; 2021
    In:  Chemosensors Vol. 9, No. 11 ( 2021-10-25), p. 301-
    Details
    In: Chemosensors, MDPI AG, Vol. 9, No. 11 ( 2021-10-25), p. 301-
    Abstract: This paper’s emphasis is on the development of a fluorescent chemosensor for Fe3+ ions in an aqueous solution, using hydrophilic carbon dots (O-CDs). A simple, cost-effective, and environmentally friendly one-step hydrothermal synthesis method was used to synthesize fluorescent hydrophilic O-CDs from Oxalis corniculata (Family; Oxalidaceae). The graphitic structure and size distribution of the O-CDs was verified by X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy studies. The resulting O-CDs had a near-spherical shape and an adequate degree of graphitization at the core, with an average diameter of 4.5 nm. X-ray photoelectron and Fourier transform infrared spectroscopy methods revealed the presence of several hydrophilic groups (carbonyl, amine, carboxyl, and hydroxyl, along with nitrogen and oxygen-rich molecules) on the surface of O-CDs. The synthesized hydrophilic O-CDs with excitation wavelength-dependent emission fluorescence characteristics showed a high quantum yield of about 20%. Besides this, the hydrophilic O-CDs exhibited a bright and controllable fluorescence with prolonged stability and photo-stability. These fluorescent hydrophilic O-CDs were used as a nanoprobe for the fluorometric identification of Fe3+ ions in an aqueous solution, with high sensitivity and selectivity. By quenching the blue emission fluorescence of this nanosensor, a highly sensitive Fe3+ ion in the range of 10–50 µM with a minimum detection limit of 0.73 µM was achieved. In addition, the developed nanosensor can be used to sense intracellular Fe3+ ions with high biocompatibility and cellular imaging capacity, and it has a lot of potential in biomedical applications.
    Type of Medium: Online Resource
    ISSN: 2227-9040
    URL: Article
    DOI: 10.3390/chemosensors9110301
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 6
    Online Resource
    Online Resource
    Biowaste-Derived Heteroatom-Doped Porous Carbon as a Sustainable Electrocatalyst for Hydrogen Evolution Reaction
    MDPI AG ; 2023
    In:  Catalysts Vol. 13, No. 3 ( 2023-03-08), p. 542-
    Details
    In: Catalysts, MDPI AG, Vol. 13, No. 3 ( 2023-03-08), p. 542-
    Abstract: Heteroatom-doped porous carbon material (H-PCM) was synthesized using Anacardium occidentale (cashew) nut’s skin by a simple pyrolysis route. The resulting H-PCM was thoroughly characterized by various analytical techniques such as field emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray (EDX) spectroscopy, high-resolution transmittance electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The obtained results strongly demonstrated that the synthesized H-PCM exhibited a porous nature, continuous sponge-like and sheet-like smooth morphology, and a moderate degree of graphitization/crystallinity with oxygen-, nitrogen-, and sulfur-containing functionalities in the carbon matrix. After the structural confirmation, as-prepared H-PCM has used a sustainable electrocatalyst for hydrogen evolution reaction (HER) because the metal-free carbonaceous catalysts are one of the most promising candidates. The H-PCM showed excellent HER activities with a lowest Tafel slope of 75 mV dec−1 and durable stability in 0.5 M H2SO4 aqueous solution. Moreover, this work provides a versatile and effective strategy for designing excellent metal-free electrocatalysts from the cheapest biowaste/biomass for large-scale production of hydrogen gas through electrochemical water splitting.
    Type of Medium: Online Resource
    ISSN: 2073-4344
    URL: Article
    DOI: 10.3390/catal13030542
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
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  • 7
    Online Resource
    Online Resource
    Eco-Friendly Synthesis of Functionalized Carbon Nanodots from Cashew Nut Skin Waste for Bioimaging
    MDPI AG ; 2023
    In:  Catalysts Vol. 13, No. 3 ( 2023-03-09), p. 547-
    Details
    In: Catalysts, MDPI AG, Vol. 13, No. 3 ( 2023-03-09), p. 547-
    Abstract: In this study, Anacardium occidentale (A. occidentale) nut skin waste (cashew nut skin waste) was used as a raw material to synthesize functionalized carbon nanodots (F-CNDs). A. occidentale biomass-derived F-CNDs were synthesized at a low temperature (200 °C) using a facile, economical hydrothermal method and subjected to XRD, FESEM, TEM, HRTEM, XPS, Raman Spectroscopy, ATR-FTIR, and Ultraviolet-visible (UV–vis) absorption and fluorescence spectroscopy to determine their structures, chemical compositions, and optical properties. The analysis revealed that dispersed, hydrophilic F-CNDs had a mean diameter of 2.5 nm. XPS and ATR-FTIR showed F-CNDs had a crystalline core and an amorphous surface decorated with –NH2, –COOH, and C=O. In addition, F-CNDs had a quantum yield of 15.5% and exhibited fluorescence with maximum emission at 406 nm when excited at 340 nm. Human colon cancer (HCT-116) cell assays showed that F-CNDs readily penetrated into the cells, had outstanding biocompatibility, high photostability, and minimal toxicity. An MTT assay showed that the viability of HCT-116 cells incubated for 24 h in the presence of F-CNDs (200 μg mL–1) exceeded 95%. Furthermore, when stimulated by filters of three different wavelengths (405, 488, and 555 nm) under a laser scanning confocal microscope, HCT-116 cells containing F-CNDs emitted blue, red, and green, respectively, which suggests F-CNDs might be useful in the biomedical field. Thus, we describe the production of a fluorescent nanoprobe from cashew nut waste potentially suitable for bioimaging applications.
    Type of Medium: Online Resource
    ISSN: 2073-4344
    URL: Article
    DOI: 10.3390/catal13030547
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
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  • 8
    Online Resource
    Online Resource
    Smartphone-Operated Wireless Chemical Sensors: A Review
    MDPI AG ; 2022
    In:  Chemosensors Vol. 10, No. 2 ( 2022-01-30), p. 55-
    Details
    In: Chemosensors, MDPI AG, Vol. 10, No. 2 ( 2022-01-30), p. 55-
    Abstract: Wireless chemical sensors have been developed as a result of advances in chemical sensing and wireless communication technology. Because of their mobility and widespread availability, smartphones have been extensively combined with sensors such as hand-held detectors, sensor chips, and test strips for biochemical detection. Smartphones are frequently used as controllers, analyzers, and displayers for quick, authentic, and point-of-care monitoring, which may considerably streamline the design and lower the cost of sensing systems. This study looks at the most recent wireless and smartphone-supported chemical sensors. The review is divided into four different topics that emphasize the basic types of wireless smartphone-operated chemical sensors. According to a study of 114 original research publications published during recent years, market opportunities for wireless and smartphone-supported chemical sensor systems include environmental monitoring, healthcare and medicine, food quality, sport, and fitness. The issues and illustrations for each of the primary chemical sensors relevant to many application areas are covered. In terms of performance, the advancement of technologies related to chemical sensors will result in smaller and more lightweight, cost-effective, versatile, and durable devices. Given the limitations, we suggest that wireless and smartphone-supported chemical sensor systems play a significant role in the sensor Internet of Things.
    Type of Medium: Online Resource
    ISSN: 2227-9040
    URL: Article
    DOI: 10.3390/chemosensors10020055
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
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  • 9
    Online Resource
    Online Resource
    Green-Routed Carbon Dot-Adorned Silver Nanoparticles for the Catalytic Degradation of Organic Dyes
    MDPI AG ; 2022
    In:  Catalysts Vol. 12, No. 9 ( 2022-08-24), p. 937-
    Details
    In: Catalysts, MDPI AG, Vol. 12, No. 9 ( 2022-08-24), p. 937-
    Abstract: Herein, a simple, cost-effective, and in-situ environmentally friendly approach was adopted to synthesize carbon dot-adorned silver nanoparticles (CDs@AgNPs) from yellow myrobalan (Terminalia chebula) fruit using a hydrothermal treatment without any additional reducing and or stabilizing agents. The as-synthesized CDs@AgNP composite was systematically characterized using multiple analytical techniques: FESEM, TEM, XRD, Raman, ATR-FTIR, XPS, and UV-vis spectroscopy. All the results of the characterization techniques strongly support the idea that the CDs were successfully made to adorn the AgNPs. This effectively synthesized CDs@AgNP composite was applied as a catalyst for the degradation of organic dyes, including methylene blue (MB) and methyl orange (MO). The degradation results revealed that CDs@AgNPs exhibit a superior catalytic activity in the degradation of MB and MO in the presence of NaBH4 (SB) under ambient temperatures. In total, 99.5 and 99.0% rates of degradation of MB and MO were observed using CDs@AgNP composite with SB, respectively. A plausible mechanism for the reductive degradation of MB and MO is discussed in detail. Moreover, the CDs@AgNP composite has great potential for wastewater treatment applications.
    Type of Medium: Online Resource
    ISSN: 2073-4344
    URL: Article
    DOI: 10.3390/catal12090937
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
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