Graphene quantum dots from graphite by liquid exfoliation showing excitation-independent emission, fluorescence upconversion and delayed fluorescence

Sarkar, Suprabhat; Gandla, Dayakar; Venkatesh, Yeduru; Bangal, Prakriti Ranjan; Ghosh, Sutapa; Yang, Yang; Misra, Sunil

doi:10.1039/c6cp01528j

Cited by 129 publications

(100 citation statements)

References 66 publications

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“…Another consequence of the absence of hydrogen bonds (with water) in aprotic solvent DMF may be the aggregation of graphene dots observed in DMF experimentally. 49 These observations are in accord with experiments 48 , 49 and show the reliability of the presented model for CDs.…”

Section: Results and Discussionsupporting

confidence: 88%

Structural Dynamics of Carbon Dots in Water and N,N-Dimethylformamide Probed by All-Atom Molecular Dynamics Simulations

Paloncýová

Langer

Otyepka

2018

J. Chem. Theory Comput.

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Carbon dots (CDs), one of the youngest members of the carbon nanostructure family, are now widely experimentally studied for their tunable fluorescence properties, bleaching resistance, and biocompatibility. Their interaction with biomolecular systems has also been explored experimentally. However, many atomistic details still remain unresolved. Molecular dynamics (MD) simulations enabling atomistic and femtosecond resolutions simultaneously are a well-established tool of computational chemistry which can provide useful insights into investigated systems. Here we present a full procedure for performing MD simulations of CDs. We developed a builder for generating CDs of a desired size and with various oxygen-containing surface functional groups. Further, we analyzed the behavior of various CDs differing in size, surface functional groups, and degrees of functionalization by MD simulations. These simulations showed that surface functionalized CDs are stable in a water environment through the formation of an extensive hydrogen bonding network. We also analyzed the internal dynamics of individual layers of CDs and evaluated the role of surface functional groups on CD stability. We observed that carboxyl groups interconnected the neighboring layers and decreased the rate of internal rotations. Further, we monitored changes in the CD shape caused by an excess of charged carboxyl groups or carbonyl groups. In addition to simulations in water, we analyzed the behavior of CDs in the organic solvent DMF, which decreased the stability of pure CDs but increased the level of interlayer hydrogen bonding. We believe that the developed protocol, builder, and parameters will facilitate future studies addressing various aspects of structural features of CDs and nanocomposites containing CDs.

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Section: Results and Discussionsupporting

confidence: 88%

Structural Dynamics of Carbon Dots in Water and N,N-Dimethylformamide Probed by All-Atom Molecular Dynamics Simulations

Paloncýová

Langer

Otyepka

2018

J. Chem. Theory Comput.

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“…It is noted that the C1s spectrum is deconvoluted into four peaks, corresponding to CC (sp 2 C) at 284.8 eV, CC (sp 3 C) at 286.2 eV, CO at 287.5 eV, and OCO at 288.7 eV, respectively (Figure g). Obviously, the N‐GQDs show a larger sp 3 /sp 2 ratio (0.63) compared to that of N‐GNSs (0.36), indicating the presence of more defects in the resulting N‐GQDs . As shown in Figure h, the N1s spectrum is divided into three peaks, which correspond to pyrrolic‐N (at 398.6 eV), pyridinic‐N (at 400.1 eV), and graphitic‐N (at 401.9 eV).…”

Section: Resultsmentioning

confidence: 95%

Advanced Electrode Materials Comprising of Structure‐Engineered Quantum Dots for High‐Performance Asymmetric Micro‐Supercapacitors

Liu

Zhang

et al. 2020

Advanced Energy Materials

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Micro‐supercapacitors (MSCs) as a new class of energy storage devices have attracted great attention due to their unique merits. However, the narrow operating voltage, slow frequency response, and relatively low energy density of MSCs are still insufficient. Therefore, an effective strategy to improve their electrochemical performance by innovating upon the design from various aspects remains a huge challenge. Here, surface and structural engineering by downsizing to quantum dot scale, doping heteroatoms, creating more structural defects, and introducing rich functional groups to two dimensional (2D) materials is employed to tailor their physicochemical properties. The resulting nitrogen‐doped graphene quantum dots (N‐GQDs) and molybdenum disulfide quantum dots (MoS2‐QDs) show outstanding electrochemical performance as negative and positive electrode materials, respectively. Importantly, the obtained N‐GQDs//MoS2‐QDs asymmetric MSCs device exhibits a large operating voltage up to 1.5 V (far exceeding that of most reported MSCs), an ultrafast frequency response (with a short time constant of 0.087 ms), a high energy density of 0.55 mWh cm−3, and long‐term cycling stability. This work not only provides a novel concept for the design of MSCs with enhanced performance but also may have broad application in other energy storage and conversion devices based on QDs materials.

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“…A fourier transform infrared spectroscopy (FTIR) was performed on these samples in order to study the difference in oxygenrelated functional groups in GO and nGO (Supplementary Figure S2). GO shows peaks corresponding to the frequencies of -OH (3200 cm −1 ), C-H (2928 and 2850 cm −1 ), COOH (1721 cm −1 ), C = 0 (1615 cm −1 ), C-O (1225 cm −1 ), C-OH (1056 cm −1 ), and C-O-C (850 cm −1 ) (Sarkar et al, 2016;Tang et al, 2016). In comparison with GO, the FTIR spectra of nGO reveals the mostly absent absorption band of C-O-C, the relative intensity of C = O, and the decreased absorption band of C-OH.…”

Section: Characterization Of Graphene Oxide and Nanographene Oxide Comentioning

confidence: 99%

Graphene Oxide Mediated Broad-Spectrum Antibacterial Based on Bimodal Action of Photodynamic and Photothermal Effects

et al. 2020

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Graphene oxide (GO) with their interesting properties including thermal and electrical conductivity and antibacterial characteristics have many promising applications in medicine. The prevalence of resistant bacteria is considered a public health problem worldwide, herein, GO has been used as a broad spectrum selective antibacterial agent based on the photothermal therapy (PTT)/photodynamic therapy (PDT) effect. The preparation, characterization, determination of photophysical properties of two different sizes of GO is described. In vitro light dose and concentration-dependent studies were performed using Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria based on the PTT/PDT effect used ultra-low doses (65 mW cm −2 ) of 630 nm light, to achieve efficient bacterial decontamination. The results show that GO and nanographene oxide (nGO) can sensitize the formation of 1 O 2 and allow a temperature rise of 55 • C to 60 • C together nGO and GO to exert combined PTT/PDT effect in the disinfection of gram-positive S. aureus and gram-negative E. coli bacteria. A complete elimination of S. aureus and E. coli bacteria based on GO and nGO is obtained by using a dose of 43-47 J cm −2 for high concentration used in this study, and a dose of around 70 J cm −2 for low dose of GO and nGO. The presence of high concentrations of GO allows the bacterial population of S. aureus and E. coli to be more sensitive to the use of PDT/PTT and the efficiency of S. aureus and E. coli bacteria disinfection in the presence of GO is similar to that of nGO. In human neonatal dermal fibroblast, HDFs, no significant alteration to cell viability was promoted by GO, but in nGO is observed a mild damage in the HDFs cells independent of nGO concentration and light exposure. The unique properties of GO and nGO may be useful for the clinical treatment of disinfection of broad-spectrum antimicrobials. The antibacterial results of PTT and PDT using GO in gram-positive and gram-negative bacteria, using low dose light, allow us to conclude that GO and nGO can be used in dermatologic infections, since the effect on human dermal fibroblasts of this treatment is low compared to the antibacterial effect.

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Graphene quantum dots from graphite by liquid exfoliation showing excitation-independent emission, fluorescence upconversion and delayed fluorescence

Cited by 129 publications

References 66 publications

Structural Dynamics of Carbon Dots in Water and N,N-Dimethylformamide Probed by All-Atom Molecular Dynamics Simulations

Structural Dynamics of Carbon Dots in Water and N,N-Dimethylformamide Probed by All-Atom Molecular Dynamics Simulations

Advanced Electrode Materials Comprising of Structure‐Engineered Quantum Dots for High‐Performance Asymmetric Micro‐Supercapacitors

Graphene Oxide Mediated Broad-Spectrum Antibacterial Based on Bimodal Action of Photodynamic and Photothermal Effects

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