scholarly journals Structural Defects in Graphene Quantum Dots: A Review

2021 ◽  
Author(s):  
Ramisha Rabeya ◽  
Savisha Mahalingam ◽  
Abreeza BTE ABD. Manap ◽  
Meenaloshini Satgunam ◽  
Md. Akhtaruzzaman ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Surface Defect ◽  
High Surface ◽  
Graphene Quantum Dots ◽  
High Surface Area ◽  
Morphological Properties ◽  
Structural Defects ◽  
Wales Defect ◽  
Edge Defects ◽  
Low Toxicity

Graphene quantum dots (GQDs) are known for their low toxicity, strong fluorescence, high surface area, large solubility and tunable band gaps. However, the change in their properties depends on the preparation processes of GQDs. Thus, certain types of preparation lead to certain defects, such as surface defect, edge defects, Stone-Wales defect. These structural defects are responsible for hindering GQDs to possess their regular shape that affects the morphological properties of GQDs. Thus, the optical and electrical properties get affected. The GQDs, which are synthesized via acidic methods are generally more vulnerable to defects compared to those synthesized using eco-friendly methods. Thereby, the aim of this review is to discuss the causes of structural defects. Moreover, it focuses on how they affect the properties of GQDs and to what extent they affect them. The processes of regulating defects have been elucidated so that more efficient applications can be designed using GQDs with controlled amounts of defects.

scholarly journals Precise Blood Glucose Sensing by Nitrogen-Doped Graphene Quantum Dots for Tight Control of Diabetes

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Seyyed Mojtaba Mousavi ◽  
Seyyed Alireza Hashemi ◽  
Ahmad Gholami ◽  
Sargol Mazraedoost ◽  
Wei-Hung Chiang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Carbon Nanomaterials ◽  
High Surface ◽  
Graphene Quantum Dots ◽  
High Surface Area ◽  
Critical Factor ◽  
Glucose Sensing ◽  
Nitrogen Doped ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene

Graphene quantum dots (GQD) are novel fluorescent carbon nanomaterials based on a graphite structure. Thanks to extraordinary properties such as high surface area and enhanced prevalent optical properties, they have received more interest for special applications. Glucose sensing is a critical factor for the diagnosis, and treatment of diabetes plays an important role and could contribute to the monitoring of diabetes and other related parameters, which has been effectively underscoring the health society. Detecting glucose has been cultivated through different systems, for example, electrochemical or optical techniques. Novel transducers made with GQD that fluorescent coordinate methods have considered the improvement of cutting-edge glucose sensors with prevalent affectability and accommodation. Currently, detection of glucose by nitrogen-doped GQD frameworks concerning the determined objectives has been considerably considered. Here, we explored the properties of fluorescent nitrogen-doped GQD as an excellent and effective index that significantly could promote nitrogen-doped GQDs and make them an appropriate candidate for detecting glucose.

scholarly journals Facile Synthesis of L-Cysteine Functionalized Graphene Quantum Dots as a Bioimaging and Photosensitive Agent

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1879
Author(s):  
Mila Milenković ◽  
Aleksandra Mišović ◽  
Dragana Jovanović ◽  
Ana Popović Bijelić ◽  
Gabriele Ciasca ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Gamma Irradiation ◽  
Hela Cells ◽  
Graphene Quantum Dots ◽  
Morphological Properties ◽  
Paramagnetic Resonance ◽  
Chemical Reagents ◽  
Amino Amide ◽  
Gamma Irradiated ◽  
Electron Paramagnetic

Nowadays, a larger number of aggressive and corrosive chemical reagents as well as toxic solvents are used to achieve structural modification and cleaning of the final products. These lead to the production of residual, waste chemicals, which are often reactive, cancerogenic, and toxic to the environment. This study shows a new approach to the modification of graphene quantum dots (GQDs) using gamma irradiation where the usage of reagents was avoided. We achieved the incorporation of S and N atoms in the GQD structure by selecting an aqueous solution of L-cysteine as an irradiation medium. GQDs were exposed to gamma-irradiation at doses of 25, 50 and 200 kGy. After irradiation, the optical, structural, and morphological properties, as well as the possibility of their use as an agent in bioimaging and photodynamic therapy, were studied. We measured an enhanced quantum yield of photoluminescence with the highest dose of 25 kGy (21.60%). Both S- and N-functional groups were detected in all gamma-irradiated GQDs: amino, amide, thiol, and thione. Spin trap electron paramagnetic resonance showed that GQDs irradiated with 25 kGy can generate singlet oxygen upon illumination. Bioimaging on HeLa cells showed the best visibility for cells treated with GQDs irradiated with 25 kGy, while cytotoxicity was not detected after treatment of HeLa cells with gamma-irradiated GQDs.

scholarly journals Graphene- and Graphene Oxide-Based Nanocomposite Platforms for Electrochemical Biosensing Applications

2019 ◽  
Vol 20 (12) ◽  
pp. 2975 ◽  
Author(s):  
Madasamy Thangamuthu ◽  
Kuan Yu Hsieh ◽  
Priyank V. Kumar ◽  
Guan-Yu Chen
Keyword(s):  
Quantum Dots ◽  
Graphene Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Cell Capture ◽  
Structure Property ◽  
Structure Property Relationships ◽  
Electrochemical Biosensing ◽  
Graphene Derivatives ◽  
Enzymatic Biosensors

Graphene and its derivatives such as graphene oxide (GO) and reduced GO (rGO) offer excellent electrical, mechanical and electrochemical properties. Further, due to the presence of high surface area, and a rich oxygen and defect framework, they are able to form nanocomposites with metal/semiconductor nanoparticles, metal oxides, quantum dots and polymers. Such nanocomposites are becoming increasingly useful as electrochemical biosensing platforms. In this review, we present a brief introduction on the aforementioned graphene derivatives, and discuss their synthetic strategies and structure–property relationships important for biosensing. We then highlight different nanocomposite platforms that have been developed for electrochemical biosensing, introducing enzymatic biosensors, followed by non-enzymatic biosensors and immunosensors. Additionally, we briefly discuss their role in the emerging field of biomedical cell capture. Finally, a brief outlook on these topics is presented.

scholarly journals New Assembly Method for Cellulose Derived Graphene Quantum Dots-Sensitized Solar Cells

2021 ◽  
Author(s):  
Savisha Mahalingam ◽  
Kam Sheng Lau ◽  
Azimah Omar ◽  
Abreeza Manap ◽  
Puvaneswaran Chelvanathan ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Solar Cells ◽  
Collection Efficiency ◽  
High Surface ◽  
Graphene Quantum Dots ◽  
Layer By Layer ◽  
Charge Collection Efficiency ◽  
Oh Groups ◽  
Assembly Method ◽  
Sensitized Solar Cells

Abstract Unambiguously layer by layer (LBL) assembly of graphene quantum dots (GQDs) and dye (GQDs/dye) on TiO2 photoanode is the traditional and straightforward approach in the fabrication of graphene quantum dot-sensitized solar cells (QDSSCs). Unfortunately, limited light absorption and low affinity of GQDs to TiO2 surface shadow the advantages of LBL and constrains its practical application. Herein, a new strategy of mixture configuration (GQDs+dye) was investigated. A distinctive nanoporous honeycomb hexagonal carbon network of GQDs was found with fewer defects single crystalline structure, and an average size of 9.87 nm was produced from cellulose. Experimental results demonstrated that LBL exhibited the highest efficiency of 16.76 % under low illumination but a lower efficiency (1.43%) than the mixture method (2.91%) under standard light. The increased Jsc (5.075 mA/cm2) and high charge collection efficiency (0.96) in the mixture sample indicated enhanced electron collection at TiO2. The less -OH groups on TiO2 provides a good surface intact of GQDs and N719. In addition to that, the high surface potential (33.47 mV) of the premixed sample restricted the photogenerated electrons to go into a deep state, reducing back electron transfer. Therefore, mixture assembly of co-sensitization is an effective approach for light-harvesting in QDSSC.

scholarly journals Graphene-Based Nanomaterials for Theranostic Applications

2017 ◽  
Vol 01 (04) ◽  
pp. 1750011 ◽  
Author(s):  
Shounak Roy ◽  
Amit Jaiswal
Keyword(s):  
Graphene Oxide ◽  
High Surface ◽  
Graphene Quantum Dots ◽  
High Surface Area ◽  
Nucleic Acid Delivery ◽  
Efficient Detection ◽  
Reduced Graphene ◽  
Theranostic Applications

Graphene and graphene-based nanomaterials such as graphene oxide (GO), reduced graphene oxide (rGO) and graphene quantum dots (GQDs) have gained a lot of attention from diverse scientific fields for applications in sensing, catalysis, nanoelectronics, material engineering, energy storage and biomedicine due to its unique structural, optical, electrical and mechanical properties. Graphene-based nanomaterials emerge as a novel class of nanomedicine for cancer therapy for several reasons. Firstly, its structural properties like high surface area and aromaticity enables easy loading of hydrophobic drugs. Secondly, presence of oxygen containing functional groups improve its physiological stability and also act as site for biofunctionalization. Thirdly, its optical absorption in the NIR region enable them to act as photoagents for photothermal and photodynamic therapies of cancer, both in vitro and in vivo. Finally, its intrinsic fluorescence property helps in bioimaging of cancer cells. Overall, graphene-based nanomaterials can act as agents for developing multifunctional theranostic platforms for carrying out more efficient detection and treatment of cancers. This review provides a detailed summary of the different applications of graphene-based nanomaterials in drug delivery, nucleic acid delivery, phototherapy, bioimaging and theranostics.

scholarly journals Development of Green and Sustainable Cellulose Acetate/Graphene Oxide Nanocomposite Films as Efficient Adsorbents for Wastewater Treatment

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2501
Author(s):  
Ali Aldalbahi ◽  
Mehrez El-Naggar ◽  
Tawfik Khattab ◽  
Meram Abdelrahman ◽  
Mostafizur Rahaman ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Cellulose Acetate ◽  
Sugarcane Bagasse ◽  
Ethylenediaminetetraacetic Acid ◽  
High Surface ◽  
High Surface Area ◽  
Total Content ◽  
Nanocomposite Films ◽  
Morphological Properties ◽  
Time Range

Novel ecofriendly adsorbents, cellulose acetate/graphene oxide (CA-GO) nanocomposite, were prepared from sugarcane bagasse agro-waste for removing Ni2+ ions from wastewater. Graphene oxide (GO) was prepared by the oxidation of sugarcane bagasse using ferrocene under air atmosphere. Cellulose acetate (CA) was also prepared from sugarcane bagasse by extraction of cellulose through a successive treatments with sulfuric acid (10% v/v), sodium hydroxide (5% w/v), ethylenediaminetetraacetic acid, and hydrogen peroxide, and finally, followed by acetylation. CA-GO was prepared via mixing of GO and CA in the presence of calcium carbonate and different concentrations of GO, including 5, 10, 15, 20, 25, and 30 wt% relative to the weight of CA. The CA-GO nanocomposite showed porous microstructures with high surface area, which enhance their ability towars the adsorption of Ni2+ ions from wastewater. The morphological properties of the prepared adsorbents were explored by scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FT-IR). The efficiency of the CA-GO towards the adsorption of Ni2+ ions from wastewater was explored against as time, temperature, and total content of Ni2+ ions. The adsorption measurements of Ni2+ ions were investigated within the concentration range of 10–40 mg/L, time range between 15 and 90 min, and temperature range between 25 °C and 55 °C. The results displayed a considerable improvement in the adsorption process of Ni2+ ions by CA-GO-2 with a removal efficiency of 96.77%. The isotherms were monitored to best fit the Langmuir model. Finally, the adsorption performance of the prepared CA-GO nanocomposite films demonstrated promising properties as green, sustainable and cheap adsorbents for water pollutants.

Rapid synthesis of high surface area anatase Titanium Oxide quantum dots

2014 ◽  
Vol 40 (8) ◽  
pp. 12675-12680 ◽  
Author(s):  
Rehan Danish ◽  
Faheem Ahmed ◽  
Bon Heun Koo
Keyword(s):  
Quantum Dots ◽  
Surface Area ◽  
Titanium Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Rapid Synthesis

scholarly journals Low Temperature Synthesis of Li2SiO3: Effect on Its Morphological and Textural Properties

2008 ◽  
Vol 2008 ◽  
pp. 1-4 ◽  
Author(s):  
Georgina Mondragón-Gutiérrez ◽  
Daniel Cruz ◽  
Heriberto Pfeiffer ◽  
Silvia Bulbulian
Keyword(s):  
Low Temperature ◽  
High Surface ◽  
Hollow Spheres ◽  
High Surface Area ◽  
Textural Properties ◽  
Particle Morphology ◽  
Ceramic Particle ◽  
Morphological Properties ◽  
Tem Analysis ◽  
Molar Ratios

Synthesis, at low temperature, of Li2SiO3 was investigated using different Li : Si molar ratios and urea, which was used as template. This new synthesis was performed in order to look for different textural and morphological properties than those obtained usually by conventional methods in this kind of ceramics. XRD and SEM analyses showed that Li2SiO3 was obtained pure and with ceramic particle morphology of hollow spheres of 2–6 μm. TEM analysis showed that those spheres were composed by needle-like particles crosslinked among them. This morphology provided a high surface area, probed by N2 adsorption. Therefore, this method of synthesis may be used to obtain other similar ceramics and test them in different applications.

Review of research of nanocomposites based on graphene quantum dots

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Aleksey E. Kuznetsov
Keyword(s):  
Quantum Dots ◽  
Quantum Confinement ◽  
Carbon Nanomaterials ◽  
Graphene Quantum Dots ◽  
Band Gaps ◽  
Computational Studies ◽  
Significant Interest ◽  
Low Toxicity ◽  
Water Dispersibility ◽  
High Fluorescence

AbstractGraphene quantum dots (GQDs) belong to the vast and versatile family of carbon nanomaterials. Their unique position amongst versatile carbon nanoparticles (NPs) originates from the properties of quantum confinement and edge effects. GQDs are similar to conventional semiconductor QDs due to their tunable band gaps and high photoluminescence activity. However, GQDs have superior characteristics due to their excellent biocompatibility, low toxicity, good water dispersibility, large optical absorptivity, high fluorescence activity and photostability. These properties have generated significant interest in GQDs applications in various fields: nanosensor fabrication, drug delivery, photocatalysis, photovoltaics, and photodynamic therapy. Numerous GQD-based nanocomposites/nanohybrides have been synthesized and/or studied computationally. This review focuses on recent computational studies of various GQD-based nanocomposites/nanohybrides and systems which can be related to them.

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