Electronic Structure of Edge-Modified Graphene Quantum Dots Interacting with Polyaniline: Vibrational and Optical Properties

2017 ◽  
Vol 121 (30) ◽  
pp. 16576-16583 ◽  
Author(s):  
Dominique Mombrú ◽  
Mariano Romero ◽  
Ricardo Faccio ◽  
Álvaro W. Mombrú
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Electronic Structure ◽  
Graphene Quantum Dots ◽  
Modified Graphene

Sulphur doping: a facile approach to tune the electronic structure and optical properties of graphene quantum dots

Nanoscale ◽  
2014 ◽  
Vol 6 (10) ◽  
pp. 5323-5328 ◽  
Author(s):  
Xueming Li ◽  
Shu Ping Lau ◽  
Libin Tang ◽  
Rongbin Ji ◽  
Peizhi Yang
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Electronic Structure ◽  
Graphene Quantum Dots ◽  
Doped Graphene

Sulphur-doped graphene quantum dots emit a variety of colours.

scholarly journals Theory of optical properties of graphene quantum dots

2015 ◽  
Vol 10 (1) ◽  
pp. 102-110 ◽  
Author(s):  
Isil Ozfidan ◽  
A. D. Güçlü ◽  
Marek Korkusinski ◽  
Pawel Hawrylak
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Graphene Quantum Dots

Tuning the electronic and optical properties of hexagonal boron-nitride nanosheet by inserting graphene quantum dots

2018 ◽  
Vol 32 (06) ◽  
pp. 1850084 ◽  
Author(s):  
Yi-Min Ding ◽  
Jun-Jie Shi ◽  
Min Zhang ◽  
Meng Wu ◽  
Hui Wang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Graphene Quantum Dots ◽  
Band Gaps ◽  
Hybrid Structures ◽  
Electronic And Optical Properties ◽  
Boron Nitride Nanosheet ◽  
Optoelectronic Nanodevices

It is difficult to integrate two-dimensional (2D) graphene and hexagonal boron-nitride (h-BN) in optoelectronic nanodevices, due to the semi-metal and insulator characteristic of graphene and h-BN, respectively. Using the state-of-the-art first-principles calculations based on many-body perturbation theory, we investigate the electronic and optical properties of h-BN nanosheet embedded with graphene dots. We find that C atom impurities doped in h-BN nanosheet tend to phase-separate into graphene quantum dots (QD), and BNC hybrid structure, i.e. a graphene dot within a h-BN background, can be formed. The band gaps of BNC hybrid structures have an inverse relationship with the size of graphene dot. The calculated optical band gaps for BNC structures vary from 4.71 eV to 3.77 eV, which are much smaller than that of h-BN nanosheet. Furthermore, the valence band maximum is located in C atoms bonded to B atoms and conduction band minimum is located in C atoms bonded to N atoms, which means the electron and hole wave functions are closely distributed around the graphene dot. The bound excitons, localized around the graphene dot, determine the optical spectra of the BNC hybrid structures, in which the exciton binding energies decrease with increase in the size of graphene dots. Our results provide an important theoretical basis for the design and development of BNC-based optoelectronic nanodevices.

The Role of Reduced Graphene Oxide Concentration as Ablated Material on Optical Properties of Graphene Quantum Dots

2019 ◽  
Vol 948 ◽  
pp. 267-273 ◽  
Author(s):  
Fiqhri Heda Murdaka ◽  
Ahmad Kusumaatmaja ◽  
Isnaeni ◽  
Iman Santoso
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Graphene Oxide ◽  
Band Gap ◽  
Reduced Graphene Oxide ◽  
Optical Band Gap ◽  
Graphene Quantum Dots ◽  
Absorption Peak ◽  
Oxygen Defect ◽  
Reduced Graphene

We report the synthesize of Graphene Quantum Dots (GQDs) using ablation method with reduced Graphene Oxide (rGO) solution as a starting material. We have varied the concentration of rGO as following: 0.5, 2, 5 mg/ml and then have ablated them using 800 nm Ti-Sapphire femtosecond laser to obtain GQDs. From the UV-Vis data, we observed that the more concentration of rGO is being ablated, the more secondary absorption peak at 255.1 nm appeared. This secondary absorption peak is a characteristic of n-π* bonding due to the presence of oxygen defect which occurs as a result of the interaction between the laser and the water in rGO solution. We conclude that the population of oxigen defect in GQDs is increasing, following the increase of rGO concentration and could alter the optical properties of GQD. On the other hand, using Tauc’s plot, we confirm that the increase of rGO concentration as the ablated material does not alter GQDs optical band gap. However, it will slightly reduce both, direct and indirect Oxygen defect related optical band gap.

scholarly journals High yield synthesis of graphene quantum dots from biomass waste as a highly selective probe for Fe3+ sensing

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Aumber Abbas ◽  
Tanveer A. Tabish ◽  
Steve J. Bull ◽  
Tuti Mariana Lim ◽  
Anh N. Phan
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Low Cost ◽  
Graphene Quantum Dots ◽  
Cost Effective ◽  
Renewable Resource ◽  
Microwave Treatment ◽  
High Yield ◽  
Biomass Waste ◽  
Practical Applications

AbstractGraphene quantum dots (GQDs), a novel type of zero-dimensional fluorescent materials, have gained considerable attention owing to their unique optical properties, size and quantum confinement. However, their high cost and low yield remain open challenges for practical applications. In this work, a low cost, green and renewable biomass resource is utilised for the high yield synthesis of GQDs via microwave treatment. The synthesis approach involves oxidative cutting of short range ordered carbon derived from pyrolysis of biomass waste. The GQDs are successfully synthesised with a high yield of over 84%, the highest value reported to date for biomass derived GQDs. As prepared GQDs are highly hydrophilic and exhibit unique excitation independent photoluminescence emission, attributed to their single-emission fluorescence centre. As prepared GQDs are further modified by simple hydrothermal treatment and exhibit pronounced optical properties with a high quantum yield of 0.23. These modified GQDs are used for the highly selective and sensitive sensing of ferric ions (Fe3+). A sensitive sensor is prepared for the selective detection of Fe3+ ions with a detection limit of as low as 2.5 × 10–6 M. The utilisation of renewable resource along with facile microwave treatment paves the way to sustainable, high yield and cost-effective synthesis of GQDs for practical applications.

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