Photoluminescent Carbon Nanostructures

Kozák, Ondřej; Sudolská, Mária; Pramanik, Goutam; Cígler, Petr; Otyepka, Michal; Zbořil, Radek

doi:10.1021/acs.chemmater.6b01372

Cited by 185 publications

(147 citation statements)

References 573 publications

(1,141 reference statements)

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“…As shown in Figure 2c and d, all the initial geometries in the 30 trajectories at the FC point have an S 1 -S 0 state energy difference of~3.0 eV; soon after starting the simulation, there is a quick decrease in energy to approximately 2.3 eV, corresponding to the S 1 state minima, as predicted by TD-DFT geometry optimization. [37] It is predictable that such fast nonradiative decays can be a nonnegligible competitor to the radiative decay channels and thus affect the luminescent efficiencies of the materials. [32] In contrast, the other 20 trajectories only show deviations in the emission energies around the equilibrium (~2.3 eV) until the end of the simulation (at the final step of these 20 trajectories, the oscillator strengths of the S 1 -S 0 transitions are predicted to vary from 0.0772 to 0.1604, proving the optically allowed nature of the transitions; see Table S3 for details).…”

Section: Resultsmentioning

confidence: 99%

Nonradiative Excited‐State Decay via Conical Intersection in Graphene Nanostructures

et al. 2019

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Chemical groups are known to tune the luminescent efficiencies of graphene-related nanomaterials, but some species, including the epoxide group (À COCÀ ), are suspected to act as emissionquenching sites. Herein, by performing nonadiabatic excitedstate dynamics simulations, we reveal a fast (within 300 fs) nonradiative excited-state decay of a graphene epoxide nanostructure from the lowest excited singlet (S 1 ) state to the ground (S 0 ) state via a conical intersection (CI), at which the energy difference between the S 1 and S 0 states is approximately zero. This CI is induced after breaking one CÀ O bond at the À COCÀ moiety during excited-state structural relaxation. This study ascertains the role of epoxide groups in inducing the nonradiative recombination of the excited electron-hole, providing important insights into the CI-promoted nonradiative deexcitations and the luminescence tuning of relevant materials. In addition, it shows the feasibility of utilizing nonadiabatic excited-state dynamics simulations to investigate the photophysical processes of the excited states of graphene nanomaterials. Computational DetailsThe ground-and excited-state properties were studied by density functional theory (DFT) and time-dependent DFT (TD-DFT), respectively, as implemented by the Gaussian 09[a] S.

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Section: Resultsmentioning

confidence: 99%

Nonradiative Excited‐State Decay via Conical Intersection in Graphene Nanostructures

et al. 2019

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“…Graphene is a two-dimensional (2D) carbon allotrope containing Sp2 bonded carbon atoms, which are arranged hexagonally isolated from its parent material, graphite (Kozak et al, 2016). Graphene has shown its potential in diverse fields because of its distinctive magnetism, electronic and mechanical properties (Chang, Yan, Shang, & Liu, 2014).…”

Section: Introductionmentioning

confidence: 99%

Graphene oxide induces cytotoxicity and oxidative stress in bluegill sunfish cells

Srikanth

Sundar

Pereira

et al. 2017

J of Applied Toxicology

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Graphene oxide (GO) is considered a promising material for biological application due to its unique properties. However, the potential toxicity of GO to aquatic organism particularly bluegill sun fish cells (BF-2) is unexplored or remains poorly understood. GO-induced cytotoxicity and oxidative stress in BF-2 cells were assessed using a battery of biomarkers. Two different biological assays (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and neutral red uptake were used to evaluate the cytotoxicity of GO on BF-2 cells. It was found that GO induced dose- and time-dependent cytotoxicity on BF-2 cells. BF-2 cells exposed to lower concentration of GO (40 μg ml ) for 24 induced morphological changes when compared to their respective controls. As evidence for oxidative stress lipid peroxidation, superoxide dismutase, catalase, reactive oxygen species and 8-hydroxy-2'-deoxyguanosine levels were increased and glutathione levels were found to decline in BF-2 cells after treatment with GO. Our findings demonstrate that GO when exposed to BF-2 fish cells cause oxidative stress.

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“…Figure 5s hows that PFO with 10 %m ass of Y 3 N@C 80 has an ew band at 708 nm owing to the electro-luminescence of Y 3 N@C 80 ,which is absent in the device made from pure PFO.The quantum yield of Y 3 N@C 80 is rather low at room temperature for an efficient application, but afurther increase of the QY may be achieved via derivatization, [7b] by changing the temperature (Figure 1), or by supramolecular assemblies. [22] Ac o-existence of PFO fluorescence and Y 3 N@C 80 luminescence in Figure 5a lso indicates that the energy transfer in this device is not very efficient and needs further optimization.…”

Section: Angewandte Chemiementioning

confidence: 98%

Thermally Activated Delayed Fluorescence in a Y₃N@C₈₀ Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies

et al. 2017

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Abstract:The endohedral fullerene Y 3 N@C 80 exhibits luminescence with reasonable quantum yield and extraordinary long lifetime.B yv ariable-temperatures teady-state and timeresolved luminescence spectroscopy, it is demonstrated that above6 0Kthe Y 3 N@C 80 exhibits thermally activated delayed fluorescence with maximum emission at 120 Kand anegligible prompt fluorescence.B elow 60 K, ap hosphorescence with al ifetime of 192 AE 1msi so bserved. Spin distribution and dynamics in the triplet excited state is investigated with X-and W-band EPR and ENDOR spectroscopies and DFT computations.Finally,electroluminescence of the Y 3 N@C 80 /PFO film is demonstrated opening the possibility for red-emitting fullerene-based organic light-emitting diodes (OLEDs).Fullerenes usually exhibit low quantum yields (QY) of fluorescence (in the range of 10 À4 )owing to the slow radiative decay and af ast and efficient inter-system crossing (ISC), leading to an almost quantitative formation of triplet states with slow non-radiative decay.E xohedral chemical derivatization can substantially modify the p-system of fullerenes and produce highly luminescent multi-adducts.[1] Another way to enhance the quantum yield of luminescence of fullerenes is based on the thermal repopulation of the S 1 state,v ia the T 1 state,i ft he S 1 -T 1 gap is sufficiently small. This process is known as thermally activated delayed fluorescence (TADF) and has been found to increase the fluorescence quantum yield of C 70 up to 0.08 at high temperatures.[2] TADF is currently an extensively examined phenomenon in the field of organic light-emitting diodes (OLEDs) as it allows to harvest up to 100 %ofelectrically formed excitons. [3] With the exception of several Er-and Tm-based endohedral metallofullerenes (EMFs), [4] with metal-based emission, EMFs are also non-luminescent.[5] Thei nternal heavy-atom effect leads to even faster ISC in EMFs than in empty fullerenes.T he lifetime of the S 1 state in Sc 3 N@C 80 is only 48 ps.[6] Surprisingly,Y 3 N@C 80 exhibits luminescence with reasonable quantum yield of ca 1% or even 8% in ac ycloadduct, [7] and an unusually long luminescence lifetime of 200-800 ns at room temperature.H erein, we explore the photoemission mechanism of Y 3 N@C 80 with variable-temperature time-resolved luminescence spectroscopy and EPR spectroscopy.The former reveals the evolution of the emission spectra and lifetimes with temperature,w hereas the latter provides information on relaxation dynamics and spin density distribution in the triplet state of Y 3 N@C 80 .W eshow that efficient photoemission of Y 3 N@C 80 is caused by the small S 1 -T 1 gap leading to TADF above 60 K. In ab lend with polyfluorene (PFO), Y 3 N@C 80 exhibits electroluminescence,w hich suggests that after suitable optimization and boost of the QY, Y 3 N@C 80 may be used for red or NIR-emitting OLEDs.In deoxygenated toluene solution, Y 3 N@C 80 exhibits luminescence with aQ Yo f1 .7 %a nd lifetime of 0.95 msa t 296 K. Saturation with air leads to athreefold reduction of...

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Photoluminescent Carbon Nanostructures

Abstract: SUDOLSKA, M.; PRAMANIK, G.; CIGLER*, P.; OTYEPKA, M.; ZBORIL, R.; Chem. Mater. 28 (2016) 12, 4085-4128, http://dx.doi.org/10.1021/acs.chemmater.6b01372 ; Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech Republic; Eng.) -Schramke 33-208

Cited by 185 publications

References 573 publications

Nonradiative Excited‐State Decay via Conical Intersection in Graphene Nanostructures

Nonradiative Excited‐State Decay via Conical Intersection in Graphene Nanostructures

Graphene oxide induces cytotoxicity and oxidative stress in bluegill sunfish cells

Thermally Activated Delayed Fluorescence in a Y₃N@C₈₀ Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies

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Photoluminescent Carbon Nanostructures

Abstract: SUDOLSKA, M.; PRAMANIK, G.; CIGLER*, P.; OTYEPKA, M.; ZBORIL, R.; Chem. Mater. 28 (2016) 12, 4085-4128, http://dx.doi.org/10.1021/acs.chemmater.6b01372 ; Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech Republic; Eng.) -Schramke 33-208

Cited by 185 publications

References 573 publications

Nonradiative Excited‐State Decay via Conical Intersection in Graphene Nanostructures

Nonradiative Excited‐State Decay via Conical Intersection in Graphene Nanostructures

Graphene oxide induces cytotoxicity and oxidative stress in bluegill sunfish cells

Thermally Activated Delayed Fluorescence in a Y3N@C80 Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies

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Thermally Activated Delayed Fluorescence in a Y₃N@C₈₀ Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies