Size and pH dependent photoluminescence of graphene quantum dots with low oxygen content

The smaller GQDs show blue emission and is insensitive to the pH, whereas the bigger sized GQDs show a red-shifted emission and a color change according to the pH. This is due to the difference of defects and oxygen.

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Ultrafast Method for Selective Design of Graphene Quantum Dots with Highly Efficient Blue Emission

Scientific Reports ◽

10.1038/srep38423 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 23

Author(s):

Suk Hyun Kang ◽

Sungwook Mhin ◽

Hyuksu Han ◽

Kang Min Kim ◽

Jacob L. Jones ◽

...

Keyword(s):

Quantum Dots ◽

Graphene Quantum Dots ◽

Blue Emission ◽

Highly Efficient

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Highly fluorescent nitrogen-doped graphene quantum dots as a green, economical and facile sensor for the determination of sunitinib in real samples

New Journal of Chemistry ◽

10.1039/c7nj00262a ◽

2017 ◽

Vol 41 (14) ◽

pp. 6875-6882 ◽

Cited By ~ 14

Author(s):

H. Mahmood Kashani ◽

T. Madrakian ◽

A. Afkhami

Keyword(s):

Quantum Dots ◽

Graphene Quantum Dots ◽

Blue Emission ◽

High Quantum Yield ◽

Real Samples ◽

Nitrogen Doped ◽

Synthetic Procedure ◽

Nitrogen Doped Graphene ◽

Doped Graphene

The preparation of nitrogen-doped graphene quantum dots (N-GQDs), by a simple and inexpensive synthetic procedure, is reported with blue emission and a high quantum yield of 78%.

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Transforming Carbon Black into Graphene Oxide Quantum Dots by Pulsed Laser Ablation in Ethanol

Korean Journal of Metals and Materials ◽

10.3365/kjmm.2020.58.11.808 ◽

2020 ◽

Vol 58 (11) ◽

pp. 808-814

Author(s):

Jung-Il Lee ◽

Jeong Ho Ryu

Keyword(s):

Quantum Dots ◽

Graphene Oxide ◽

Laser Ablation ◽

Carbon Black ◽

Graphene Quantum Dots ◽

Pulsed Laser ◽

Blue Emission ◽

Pulsed Laser Ablation ◽

Absorption Bands ◽

Graphene Oxide Quantum Dots

Graphene oxide quantum dots (GOQDs) are nanometer-sized graphene oxide fragments that exhibit unique properties, making them interesting candidates for a range of new applications. Carbon black, one of the commercially available carbon precursors, is produced by the thermal decomposition or incomplete combustion of organic compounds. It is commonly used as a supporting material for catalysts because of its excellent electrical conductivity, high surface area, and stability. In this paper, we report the transformation of carbon black into GOQDs in 10 min using a one-step facile approach. This transformation was achieved by pulsed laser ablation (PLA) in ethanol using the earth-abundant and low-cost carbon black as precursor. Only ethanol and carbon black were used for the transformation. The carbon clusters ablated from the carbon black were completely transformed into GOQDs with a homogeneous size distribution and heights in the range of 0.3-1.7 nm. This confirmed that the transformed GOQDs consisted of only single- or few-layered graphene quantum dots. The UV-vis spectra showed absorption bands at 215, 260, and 320 nm, which were attributed to the π→π* transition of the C=C of the sp<sup>2</sup> C bond in the sp<sup>3</sup> C matrix. A distinct blue emission peak at 450 nm was evident at an excitation wavelength of 360 nm. The broader PL emission spectra are due to the oxygen-related functional groups emitting PL between 300 and 440 nm.

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Blue emission at atomically sharp 1D heterojunctions between graphene and h-BN

Nature Communications ◽

10.1038/s41467-020-19181-2 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Gwangwoo Kim ◽

Kyung Yeol Ma ◽

Minsu Park ◽

Minsu Kim ◽

Jonghyuk Jeon ◽

...

Keyword(s):

Quantum Dots ◽

Boron Nitride ◽

Physical Properties ◽

Hexagonal Boron Nitride ◽

Graphene Quantum Dots ◽

Blue Emission ◽

Electronic States ◽

Optoelectronic Property ◽

Two Dimensional ◽

One Dimensional

Abstract Atomically sharp heterojunctions in lateral two-dimensional heterostructures can provide the narrowest one-dimensional functionalities driven by unusual interfacial electronic states. For instance, the highly controlled growth of patchworks of graphene and hexagonal boron nitride (h-BN) would be a potential platform to explore unknown electronic, thermal, spin or optoelectronic property. However, to date, the possible emergence of physical properties and functionalities monitored by the interfaces between metallic graphene and insulating h-BN remains largely unexplored. Here, we demonstrate a blue emitting atomic-resolved heterojunction between graphene and h-BN. Such emission is tentatively attributed to localized energy states formed at the disordered boundaries of h-BN and graphene. The weak blue emission at the heterojunctions in simple in-plane heterostructures of h-BN and graphene can be enhanced by increasing the density of the interface in graphene quantum dots array embedded in the h-BN monolayer. This work suggests that the narrowest, atomically resolved heterojunctions of in-plane two-dimensional heterostructures provides a future playground for optoelectronics.

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Room temperature pH-dependent ammonia gas sensors using graphene quantum dots

Sensors and Actuators B Chemical ◽

10.1016/j.snb.2015.09.002 ◽

2016 ◽

Vol 222 ◽

pp. 763-768 ◽

Cited By ~ 34

Author(s):

Wei Chen ◽

Fushan Li ◽

Poh Choon Ooi ◽

Yun Ye ◽

Tae Whan Kim ◽

...

Keyword(s):

Quantum Dots ◽

Gas Sensors ◽

Room Temperature ◽

Graphene Quantum Dots ◽

Ammonia Gas ◽

Ph Dependent ◽

Ammonia Gas Sensors

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The Difference between Iodine Number and Nitrogen Surface Area Determinations for Carbon Blacks

Rubber Chemistry and Technology ◽

10.5254/1.3547922 ◽

2006 ◽

Vol 79 (1) ◽

pp. 120-134 ◽

Cited By ~ 4

Author(s):

J. B. Donnet ◽

A. Santini ◽

D. Maafa ◽

H. Balard ◽

F. Padella ◽

...

Keyword(s):

Iodine Number ◽

Surface Area ◽

Oxygen Content ◽

Analytical Relationship ◽

Low Oxygen ◽

High Oxygen Content ◽

Carbon Blacks ◽

Elementary Analysis ◽

Disordered Carbon ◽

The Difference

Abstract The iodine number furnishes surface area values in disagreement with the NSA technique in the case of disordered carbon i.e., lower than NSA in case of high oxygen content (more than 2%), but higher for low oxygen content (less than 1%). Because carbon blacks are solids which exhibit graphitic structure, some milled graphite samples, were taken as model materials and analyzed. Surface area was determined by using both NSA and N≩I2 techniques, and the difference between the results given by the two techniques were observed and related to the microstructure, which was analyzed by using X-ray diffraction, Raman spectroscopy, and the oxygen content was measured by using elementary analysis. Two different models of iodine adsorption have been proposed, respectively, for the graphitic parts of the graphite grains and for the disordered part of the grains. An analytical relationship between the differences of iodine and nitrogen surface area values, microstructure and oxygen content was proposed and successfully tested. The same relationship was applied to some commercial and experimental carbon black with good results.

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A Facile Microwave-Assisted Hydrothermal Synthesis of Graphene Quantum Dots for Organic Solar Cell Efficiency Improvement

Journal of Nanomaterials ◽

10.1155/2020/3207909 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Thi Thu Hoang ◽

Hoai Phuong Pham ◽

Quang Trung Tran

Keyword(s):

Quantum Dots ◽

Organic Solar Cells ◽

Energy Levels ◽

Graphene Quantum Dots ◽

Blue Emission ◽

Spectroscopic Characterization ◽

Hole Transport ◽

Transport Layer ◽

Hole Transport Layer ◽

Microwave Assisted

Carbon-based nanomaterials have successively remained at the forefront of different research fields and applications for years. Understanding of low-dimension carbon material family (CNT, fullerenes, graphene, and graphene quantum dots) has arrived at a certain extension. In this report, graphene quantum dots were synthesized from graphene oxide with a microwave-assisted hydrothermal method. Compared with conventional time-consuming hydrothermal routes, this novel method requires a much shorter time, around ten minutes. Successful formation of quantum dots derived from graphene sheets was verified with microscopic and spectroscopic characterization. Nanoparticles present a diameter of about 2-8 nm, blue emission under ultraviolet excitation, and good dispersion in polar solvents and can be collected in powder form. The synthesized graphene quantum dots were utilized as a hole transport layer in organic solar cells to enhance the cell quantum efficiency. Such quantum dots possess energy levels (Ec and Ev) relevant to HOMO and LUMO levels of conductive polymers. Mixing P3HT:PCBM polymer and graphene quantum dots of sufficient extent notably helps reduce potential difference at interfaces of the two materials. Overall efficiency consequently advances to 1.43%, an increase of more than 44% compared with pristine cells (0.99%).

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Facile Synthesis of Water-Soluble Graphene Quantum Dots/Graphene for Efficient Photodetector

MRS Advances ◽

10.1557/adv.2018.14 ◽

2018 ◽

Vol 3 (15-16) ◽

pp. 817-824 ◽

Cited By ~ 1

Author(s):

Sanju Gupta ◽

Jared Walden ◽

Alexander Banaszak ◽

Sara B. Carrizosa

Keyword(s):

Quantum Dots ◽

Large Scale ◽

Graphene Quantum Dots ◽

Blue Emission ◽

Water Soluble ◽

Monolayer Graphene ◽

Graphene Sheets ◽

Scale Production ◽

Research Activity ◽

High Efficient

ABSTRACTGraphene quantum dots (GQDs) are zero-dimensional material with characteristics derived from functionalized graphene precursors are graphene sheets a few nanometers in the lateral dimension having a several-layer thickness. Combining the structure of graphene with the quantum confinement and edge effects, GQDs possess unique chemical behavior and physical properties. Intense research activity in GQDs is attributed to their novel phenomena of charge transport and light absorption and photoluminescence excitation. The optical transitions are known to be available up to 6 eV in GQDs, applicable for ultraviolet photonics and optoelectronics devices, biomedical imaging capabilities and technologies. We present facile hydrothermal and solvothermal methods for synthesizing homogenous dispersed and uniform sized GQDs with a strong greenish and violet blue emission peaks at ∼10-14% yield. This approach enabled a large-scale production of aqueous GQD dispersions without the need for chemical stabilizers. The structure and emission mechanism of the GQDs have been studied by combining extensive characterization techniques and rigorous control experiments. We further demonstrate the distinctive advantages of such GQDs as high-performance photodetectors (PDs). Here we also report high-efficient photocurrent (PC) behaviors consisting of multilayer GQDs sandwiched between monolayer graphene sheets. It is conceivable that the observed unique PD characteristics proved to be dominated by tunneling of charge carriers which occurs through the multiple energy states within the bandgap of GQDs, based on bias-dependent variation of the band profiles. This results in novel dark current and PC behaviors. The external quantum efficiency (η) is predicted to be 47% at applied potential 2 V. These findings highlight rich photophysics and comparable performance of graphene/graphene oxide hybrids opening up potential applications as optoelectronic devices.

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