Transient nature of graphene quantum dot formation via a hydrothermal reaction

Ogi, Takashi; Iwasaki, Hideharu; Aishima, Kana; Iskandar, Ferry; Wang, Wei‐Ning; Takimiya, Kazuo; Okuyama, Kikuo

doi:10.1039/c4ra09159k

Cited by 92 publications

(85 citation statements)

References 31 publications

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“…Upon Gaussian deconvolution of the XPS, the high‐resolution C1s spectrum demonstrates two peaks at 284.0 and 288.2 eV, as it can be seen in the Figure (d). The binding energy peak at 284.0 eV may be assigned to C–C, C=C and C–H bonds, while the peak at 288.2 eV is assigned to O=C–O, O=C bonds, respectively . The above results indicate that the basic structure of the sample is the heterocyclic compound unit.…”

Section: Resultsmentioning

confidence: 99%

Fluorescence Based Platform to Discriminate Protein Using Carbon Quantum Dots

et al. 2019

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There is an urgent demand to develop a cheap, fast and robust methodology to sense proteins, since these biomolecules are often used as biomarker responsible for diagnosing of some diseases, such as cancer. In this regard, we report a theoretical and experimental study, as well as a cheap and effective ‘chemical‐nose’ strategy based on carbon quantum dots (CQDs) and metallic cations (M) to discriminate proteins at concentration as low as 50 nM. Thus, the CQDs were firstly synthesized through citric acid thermolysis and their characteristics were fully investigated by UV‐Vis absorption, fluorescence, infrared (FTIR), XPS and Raman spectroscopies and atomic force microscopy (AFM). These results pointed out for quasi‐spherical CQDs with diameters in the range of 1.2‐7 nm, presence of stacked graphitic layers and oxygenated functional groups, as well as disordered carbon. Based on the structural and morphological features, computational simulations were carried out to obtain a better understanding of the atomic structure. Our results evidenced a carbon‐based nanoparticle formed by stacked graphene nanoflakes containing defects due to the presence of functional groups within the graphene layers. Afterwards, a ‘tongue’‐based approach was developed by using three distinct CQDs – M (M=Fe3+, Cu2+ or Ni2+) ensembles, which allowed us to acquire different and reproducible fluorescence patterns for four proteins (bovine serum albumin, hemoglobin, myoglobin and cytochrome C) at 50 nM. Subsequently, the pattern recognition was performed using linear discriminant analysis and 36 samples were correctly identified affording 100% of accuracy.

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Section: Resultsmentioning

confidence: 99%

Fluorescence Based Platform to Discriminate Protein Using Carbon Quantum Dots

et al. 2019

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“…The graphene quantum dots were prepared via a hydrothermal method utilizing pyrolyzed citric acid (CA) as the precursor in an alkaline environment according to some previously reported literature [28–30]. Typically, 0.21 g (1 mmol) CA and 0.12 g (3 mmol) sodium hydroxide (NaOH) were dissolved into 5 mL water and stirred to form a clear solution.…”

Section: Methods/experimentalmentioning

confidence: 99%

High-Performance Ultraviolet Photodetector Based on Graphene Quantum Dots Decorated ZnO Nanorods/GaN Film Isotype Heterojunctions

Liu

Gao

et al. 2018

Nanoscale Res Lett

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A novel isotype heterojunction ultraviolet photodetector was fabricated by growing n-ZnO nanorod arrays on n-GaN thin films and then spin-coated with graphene quantum dots (GQDs). Exposed to UV illumination with a wavelength of 365 nm, the time-dependent photoresponse of the hybrid detectors manifests high sensitivity and consistent transients with a rise time of 100 ms and a decay time of 120 ms. Meanwhile, an ultra-high specific detectivity (up to ~ 1012 Jones) and high photoresponsivity (up to 34 mA W−1) are obtained at 10 V bias. Compared to the bare heterojunction detectors, the excellent performance of the GQDs decorated n-ZnO/n-GaN heterostructure is attributed to the efficient immobilization of GQDs on the ZnO nanorod arrays. GQDs were exploited as a light absorber and act like an electron donor to effectively improve the effective carrier concentration in interfacial junction. Moreover, appropriate energy band alignment in GQDs decorated ZnO/GaN hybrids can also be a potential factor in facilitating the UV-induced photocurrent and response speed.

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“…Bottom‐up hydrothermal GQD synthesis again involves the use of a Teflon‐lined autoclave vessel, which in this case is charged with one or more small organic precursor compounds. The reaction can be performed neat or as a solution with various solvents, over a range of temperatures and reaction times . The basic premise of GQD formation is the same as that for pyrolysis, whereby the small precursor compounds bind together to form the small graphitic structures upon heating, and the diameter and degree of carbonization of the GQDs can be effectively controlled using this method.…”

Section: Synthesis and Chemical Functionality Of Gqdsmentioning

confidence: 99%

“…Although secondary interactions inherently provide weaker binding, ionic, hydrogen bonding, π–π, van der Waals, and metal–ion interactions have all been utilized in recent times to coat the GQD exterior for cellular imaging,[1c] drug delivery, sensing, and gel formation applications. [40b,111]…”

Section: Functionalization Of Gqdsmentioning

confidence: 99%

A Practical Guide to Prepare and Synthetically Modify Graphene Quantum Dots

Sweetman

Hickey

Brooks

et al. 2019

Adv Funct Materials

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Due to the favorable properties of graphene quantum dots (GQDs), there has been a rapid development of sensors, devices, and composite materials, which incorporate this 0D nanomaterial. GQDs provide a means to instill superior optical, electronic, mechanical, and adsorptive properties to various platforms and have found use as biosensors, photovoltaic devices, polymer composites, and drug delivery vehicles. One of the key factors to successfully integrating GQD technology is the intelligent choice of synthetic chemical pathways to fabricate, modify, and instill functionality in the developed platform. GQDs are decorated with a variety of functional groups that are amenable to traditional synthetic chemistry transformations; however, the technology for post-synthetic modifications is only in its infancy. Herein, a comprehensive analysis of the chemistry available for modifying GQDs is provided; starting from methods for GQD fabrication and synthetic chemical pathways for producing functional GQDs, to the advantages, disadvantages, and challenges of specific chemistries, and finally techniques for the appropriate characterization of these functional materials. This review is meant for researchers considering entering the GQD field, as well as those more experienced, providing a practical guide on how to prepare, modify, and characterize GQDs for a broad range of applications.

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Transient nature of graphene quantum dot formation via a hydrothermal reaction

Abstract: A facile, economic and environmentally friendly one-step approach for the preparation of highly luminescent graphene quantum dots (GQDs) was developed using a hydrothermal reaction between citric acid and urea.

Cited by 92 publications

References 31 publications

Fluorescence Based Platform to Discriminate Protein Using Carbon Quantum Dots

Fluorescence Based Platform to Discriminate Protein Using Carbon Quantum Dots

High-Performance Ultraviolet Photodetector Based on Graphene Quantum Dots Decorated ZnO Nanorods/GaN Film Isotype Heterojunctions

A Practical Guide to Prepare and Synthetically Modify Graphene Quantum Dots

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