Recent Developments in Synthesis and Photocatalytic Applications of Carbon Dots (original) (raw)
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Precursor-Dependent Photocatalytic Activity of Carbon Dots
Molecules
This work systematically compares both structural features and photocatalytic performance of a series of graphitic and amorphous carbon dots (CDs) prepared in a bottom-up manner from fructose, glucose, and citric acid. We demonstrate that the carbon source and synthetic procedures diversely affect the structural and optical properties of the CDs, which in turn unpredictably influence their photo electron transfer ability. The latter was evaluated by studying the photo-reduction of methyl viologen. Overall, citric acid-CDs were found to provide the best photocatalytic performance followed by fructose- and glucose-CDs. However, while the graphitization of glucose- and citric acid-CDs favored the photo-reaction, a reverse structure–activity dependence was observed for fructose-CDs due to the formation of a large graphitic-like supramolecular assembly. This study highlights the complexity to design in advance photo-active bio-based carbon nanomaterials.
Recent Progress on Carbon Quantum Dots Based Photocatalysis
Frontiers in Chemistry
As a novel carbon allotrope, carbon quantum dots (CQDs) have been investigated in various fields, including photocatalysis, bioimaging, optoelectronics, energy and photovoltaic devices, biosensing, and drug delivery owing to their unique optical and electronic properties. In particular, CQDs' excellent sunlight harvesting ability, tunable photoluminescence (PL), up-conversion photoluminescence (UCPL), and efficient photoexcited electron transfer have enabled their applications in photocatalysis. This work focuses on the recent progress on CQDs-related materials' synthesis, properties, and applications in photocatalysis.
Carbon Dots for Photocatalytic Degradation of Aqueous Pollutants: Recent Advancements
Advanced Optical Materials, 2021
Compared to other allotropes of carbon, C-dots have unique photophysical and chemical properties such as light absorption over a wide range, [3,4] bright photoluminescence (PL), [5] electron mediation, [6,7] excellent photostability, [8] high aqueous solubility, [9] upconversion, [10,11] photosensitization, [12] chemical inertness, [13] facile functionalization, [14] and low toxicity due to their nonmetallic nature. In addition, a plethora of inexpensive precursors and a variety of approaches are available for their synthesis. All these features lead to their explosive utilization in distinct areas such as photocatalysis, [15,16] biomedical imaging, [17] sensors, [18] photovoltaic panels, [19,20] drug delivery, [21] and numerous other technologies. [22-24] The structural core of carbon dots can be either amorphous, crystalline, or partially crystalline. Crystalline carbon dots are usually derived from graphene via topdown synthetic methods and are denoted as graphene quantum dots (GQDs). [25] However, there are multiple reports where carbon dots with crystalline graphitic core are obtained via bottom-up synthetic methods and subsequently referred to as GQDs. [26-28] On the contrary, other research groups preferred to call them carbon quantum dots (CQDs). [10,29,30] Further, the CQDs term is also interchangeably used for amorphous carbon dots. Other terms include carbon nanodots (CNDs) or simply carbon dots (CDs) for amorphous or partially crystalline structures. [31,32] For the sake of simplicity, in this review, we will stick with the term "C-dots" for all of the above-mentioned carbon dot structures with sizes in the range of <10 nm. Tons of industrial and domestic pollutants are spilled each day into waterways, which are harmful not only to the environment and human health but also to natural echo systems. [32,33] Efficient and cost-effective removal of these pollutants is crucial for our sustainable future. Among many contenders, photocatalytic technologies stand out due to the utilization of semiconductors and inexpensive sunlight for the removal of these pollutants. [34] Most pollutants in waterways can either be small organic compounds such as dyes, drugs, or long-chain organic molecules such as perfluorooctanoic acid and perfluorooctane sulfonate, which are regarded as persistent organic pollutants. Other major category includes toxic metals such as Cd and Cr.
Nature Communications, 2017
Carbon dots (CDs) are a versatile nanomaterial with attractive photoluminescent and photocatalytic properties. Here we show that these two functionalities can be easily tuned through a simple synthetic means, using a microwave irradiation, with citric acid and varying concentrations of nitrogen-containing branched polyethyleneimine (BPEI) as precursors. The amount of BPEI determines the degree of nitrogen incorporation and the different inclusion modes within the CDs. At intermediate levels of BPEI, domains grow containing mainly graphitic nitrogen, producing a high photoluminescence yield. For very high (and very low) BPEI content, the nitrogen atoms are located primarily at the edge sites of the aromatic domains. Accordingly, they attract photogenerated electrons, enabling efficient charge separation and enhanced photocatalytic hydrogen generation from water. The ensuing ability to switch between emissive and photocatalytic behavior of CDs is expected to bring substantial improvements on their efficiency for on-demand light emission or energy conversion applications.
Bioinspired Synthesis of Carbon Dots/g-C3N4 Nanocomposites for Photocatalytic Application
E3S Web of Conferences
This study reports a fast and green preparative strategy to synthesize water soluble and fluorescent carbon quantum dots (CQDs) through hydrothermal method by using low cost organic waste of human fingernails as the carbon precursor for the first time. The coupling of CQD with pure carbon nitride (g-C3N4) was further explored to enhance the latter’s performance in photocatalysis of 2,4-dicholorophenol (2,4-DCP), a toxic and recalcitrant compound mostly released from industrial effluent. Such coupling overcame the weakness of pure g-C3N4 in photocatalysis process by broadening its visible light absorption and promoting the charge separation. As a result, the removal rate of CQD/ g-C3N4(10) was up to 71.53%, which was approximately 1.5 times higher than that of pure g-C3N4 under sunlight irradiation. The morphological structure, optical properties and chemical compositions of CQDs/g-C3N4 composites were characterized using various spectroscopic techniques including field emission scan...
Carbon Quantum Dot Composites for Photocatalytic Degradation of Organic Pollutants
2018
In the present chapter, basic chemistry of carbon quantum dots (CQDs) has been presented. CQDs actually represent a class of materials comprising of carbon atoms in the nanometric range. These are more important as compared to other quantum dots. The CQDs can be synthesized using different methods such as hydrothermal treatment, microwave method, electrochemical and synthetic route, etc. CQDs are of immense importance due to their eco-friendly nature, easy availability and cost-effectiveness. Different composites based on CQDs have been synthesized in the recent years and being used for a number of applications such as biosensing, bioimaging, photocatalysis and chemical sensing, etc. CQDs based composites have been used as catalysts due to their outstanding electrochemical catalytic activity.
International journal of pharmaceutical quality assurance, 2023
Introduction: The nanostructured form of carbon known as carbon quantum dots has shown promise in a wide range of fields, including bioimaging, optoelectronics, bio-sensing drug delivery systems, photovoltaics, and photocatalysis. They stand out from the crowd thanks to exceptional conductivity, low toxicity, and great photochemical and thermal stability. Objectives: This article provides a concise overview of the last decade's worth of study into the use of carbon quantum dots (QDs) like CDs, GQDs, and PDs in the creation of a fluorescence imaging bio-sensing system for the early detection of cancer. Methods: Recent research in the field of Carbon QD (CQD) in the last 20 years was collected, sorted for their application in analysis and summarized. Results and conclusion: Most recent research on the CQDs has focused on their fluorescence characteristics and photocatalytic properties. The authors offer a glimpse into the future in an effort to help researchers overcome obstacles and dive further into this exciting topic.
Low dimensional carbon enhanced semiconductor nanomaterials for photocatalytic applications
2020
The environmental consequences of burning fossil fuels and the global demand for energy has generated interest in renewable and clean energy sources. Solar water splitting to produce hydrogen using semiconductors is an attractive process as no emissions are generated, using water and sunlight only. Low dimensional carbon nanostructures unique structural, optical and electronic properties have led to more research in photocatalysis. TiO2 has a high band gap of 3.2 eV resulting in strong absorbance in the UV region of the electromagnetic spectrum but constitutes only 4% of the solar spectrum. Initially, there was research in synthesising 0D carbon quantum dots to improve visible light activity in TiO2-A NF/CQDs. However, UV-Vis Spectroscopy showed absorbance of CQDs below 435 nm, which illustrated minimal absorbance in the visible light region. Nanocomposites provide more efficient separation of electron-hole pairs as it is difficult for a single semiconductor to obtain a narrow band ...
Recent Developments in Carbon Quantum Dots: Properties, Fabrication Techniques, and Bio-Applications
2021
Carbon dots have gained tremendous interest attributable to their unique features. Two approaches are involved in the fabrication of quantum dots (Top-down and Bottom-up). Most of the synthesis methods are usually multistep, required harsh conditions, and costly carbon sources that may have a toxic effect, therefore green synthesis is more preferable. Herein, the current review presents the green synthesis of carbon quantum dots (CQDs) and graphene quantum dots (GQDs) that having a wide range of potential applications in bio-sensing, cellular imaging, and drug delivery. However, some drawbacks and limitations are still unclear. Other biomedical and biotechnological applications are also highlighted.