Spectroscopic Insights into Carbon Dot Systems

Righetto, Marcello; Privitera, Alberto; Fortunati, Ilaria; Mosconi, Dario; Zerbetto, Mirco; Curri, Maria Lucia; Corricelli, Michela; Moretto, Alessandro; Agnoli, Stefano; Franco, Lorenzo; Bozio, Renato; Ferrante, Camilla

doi:10.1021/acs.jpclett.7b00794

Cited by 116 publications

(119 citation statements)

References 55 publications

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“…They are quite similar to the particles emitting light over the whole range of the spectrum, from blue to red [111], so that the excitation spectra shift according to C 2019, 5, 71 9 of 50 the shift of the fluorescence bands demonstrates Stokes shifts similar in magnitude. Therefore, clear separation among these relatively broad bands is commonly observed [11,43,112]. Such spectroscopic behavior is peculiar for C-dots of different composition with crystalline or amorphous carbon cores or with the inclusion of nitrogen-, sulfur-or phosphorous-containing groups at their surface.…”

Section: Variability In Quantum Yield Emission Color and The Strongmentioning

confidence: 98%

Excitons in Carbonic Nanostructures

Demchenko

2019

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Unexpectedly bright photoluminescence emission can be observed in materials incorporating inorganic carbon when their size is reduced from macro–micro to nano. At present, there is no consensus in its understanding, and many suggested explanations are not consistent with the broad range of experimental data. In this Review, I discuss the possible role of collective excitations (excitons) generated by resonance electronic interactions among the chromophore elements within these nanoparticles. The Förster-type resonance energy transfer (FRET) mechanism of energy migration within nanoparticles operates when the composing fluorophores are the localized electronic systems interacting at a distance. Meanwhile, the resonance interactions among closely located fluorophores may lead to delocalization of the excited states over many molecules resulting in Frenkel excitons. The H-aggregate-type quantum coherence originating from strong coupling among the transition dipoles of adjacent chromophores in a co-facial stacking arrangement and exciton transport to emissive traps are the basis of the presented model. It can explain most of the hitherto known experimental observations and must stimulate the progress towards their versatile applications.

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Section: Variability In Quantum Yield Emission Color and The Strongmentioning

confidence: 98%

Excitons in Carbonic Nanostructures

Demchenko

2019

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“…More recently, the emission of CDs produced by some specific (and very popular) bottom-up methods has been the subject of a particularly lively debate. Several authors proposed that the blue emission of these types of CDs is actually due to simple, small fluorescent organic molecules attached to CD surfaces or bound to the π-conjugated core, rather than to the dot itself [182,183], while other works attributed the emission of some types of dual-emitting dots to aggregates of several molecular chromophores [19,184], and some even claimed a role of free molecules diffusing in solution [185]. Indeed, it has been established that some bottom-up syntheses of CDs can produce small fluorescent molecular derivatives, formed alongside with the carbonization process, both if the synthesis is carried out in water [183] or in an organic solvent [15].…”

Section: Emission Mechanismsmentioning

confidence: 99%

Carbon Nanodots: A Review—From the Current Understanding of the Fundamental Photophysics to the Full Control of the Optical Response

2018

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Carbon dots (CDs) are an emerging family of nanosystems displaying a range of fascinating properties. Broadly speaking, they can be described as small, surface-functionalized carbonaceous nanoparticles characterized by an intense and tunable fluorescence, a marked sensitivity to the environment and a range of interesting photochemical properties. CDs are currently the subject of very intense research, motivated by their possible applications in many fields, including bioimaging, solar energy harvesting, nanosensing, light-emitting devices and photocatalyis. This review covers the latest advancements in the field of CDs, with a focus on the fundamental understanding of their key photophysical behaviour, which is still very debated. The photoluminescence mechanism, the origin of their peculiar fluorescence tunability, and their photo-chemical interactions with coupled systems are discussed in light of the latest developments in the field, such as the most recent results obtained by femtosecond time-resolved experiments, which have led to important steps forward in the fundamental understanding of CDs. The optical response of CDs appears to stem from a very complex interplay between the electronic states related to the core structure and those introduced by surface functionalization. In addition, the structure of CD energy levels and the electronic dynamics triggered by photo-excitation finely depend on the microscopic structure of any specific sub-type of CD. On the other hand, this remarkable variability makes CDs extremely versatile, a key benefit in view of their very wide range of applications.

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“…Changes of the optical properties have been attributed to electron transfer from the C-dots to other species, and it has been suggested that the solvent plays an important role due to solvation interactions [10]. Nevertheless, there is still no unanimous agreement in the scientific community about a consistent explanation of the optical properties of C-dots [11]. …”

Section: Introductionmentioning

confidence: 99%

Green synthesis of fluorescent carbon dots from spices for in vitro imaging and tumour cell growth inhibition

Vasimalai

Vilas-Boas

Gallo

et al. 2018

Beilstein J. Nanotechnol.

143

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Carbon dots have demonstrated great potential as luminescent nanoparticles in bioapplications. Although such nanoparticles appear to exhibit low toxicity compared to other metal luminescent nanomaterials, today we know that the toxicity of carbon dots (C-dots) strongly depends on the protocol of fabrication. In this work, aqueous fluorescent C-dots have been synthesized from cinnamon, red chilli, turmeric and black pepper, by a one-pot green hydrothermal method. The synthesized C-dots were firstly characterized by means of UV–vis, fluorescence, Fourier transform infrared and Raman spectroscopy, dynamic light scattering and transmission electron microscopy. The optical performance showed an outstanding ability for imaging purposes, with quantum yields up to 43.6%. Thus, the cytotoxicity of the above mentioned spice-derived C-dots was evaluated in vitro in human glioblastoma cells (LN-229 cancer cell line) and in human kidney cells (HK-2 non-cancerous cell line). Bioimaging and viability studies were performed with different C-dot concentrations from 0.1 to 2 mg·mL−1, exhibiting a higher uptake of C-dots in the cancer cultures compared to the non-cancerous cells. Results showed that the spice-derived C-dots inhibited cell viability dose-dependently after a 24 h incubation period, displaying a higher toxicity in LN-229, than in HK-2 cells. As a control, C-dots synthesized from citric acid did not show any significant toxicity in either cancerous or non-cancerous cells, implying that the tumour cell growth inhibition properties observed in the spice-derived C-dots can be attributed to the starting material employed for their fabrication. These results evidence that functional groups in the surface of the C-dots might be responsible for the selective cytotoxicity, as suggested by the presence of piperine in the surface of black pepper C-dots analysed by ESI-QTOF-MS.

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Spectroscopic Insights into Carbon Dot Systems

Cited by 116 publications

References 55 publications

Excitons in Carbonic Nanostructures

Excitons in Carbonic Nanostructures

Carbon Nanodots: A Review—From the Current Understanding of the Fundamental Photophysics to the Full Control of the Optical Response

Green synthesis of fluorescent carbon dots from spices for in vitro imaging and tumour cell growth inhibition

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