5 research outputs found
Trans-membrane Fluorescence Enhancement by Carbon Dots: Ionic Interactions and Energy Transfer
We report on trans-membrane interactions between blueemitting carbon dots (CDs) and fluorescein. Hydrophobic CDs with a positive surface charge are embedded as-synthesized in the lipophilic sheet of the bilayer membrane of large synthetic phospholipid vesicles. The vesicles are prepared by mixing DOPC phospholipids and lipid molecules that contain anionic fluorescein attached to their hydrophilic head. Due to attractive electrostatic interactions, the CDs and fluorescein conjoin within the vesicle membrane, which leads to photoluminescence enhancement of fluorescein and facilitates trans-membrane energy transfer between the CDs and the dye.Fil: Pritzl, Stefanie D.. Ludwig Maximilians Universitat; AlemaniaFil: Pschunder, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Ehrat, Florian. Ludwig Maximilians Universitat; AlemaniaFil: Bhattacharyya, Santanu. Ludwig Maximilians Universitat; AlemaniaFil: Lohmüller, Theobald. Ludwig Maximilians Universitat; AlemaniaFil: Huergo, María Ana Cristina. Ludwig Maximilians Universitat; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Feldmann, Jochen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin
Trans-membrane fluorescence enhancement by carbon dots: ionic interactions and energy transfer
We report on trans-membrane interactions between blue-emitting carbon dots (CDs) and fluorescein. Hydrophobic CDs with a positive surface charge are embedded as-synthesized in the lipophilic sheet of the bilayer membrane of large synthetic phospholipid vesicles. The vesicles are prepared by mixing DOPC phospholipids and lipid molecules that contain anionic fluorescein attached to their hydrophilic head. Due to attractive electrostatic interactions, the CDs and fluorescein conjoin within the vesicle membrane, which leads to photoluminescence enhancement of fluorescein and facilitates trans-membrane energy transfer between the CDs and the dye.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada
Effect of nitrogen atom positioning on the trade-off between emissive and photocatalytic properties of carbon dots
Carbon dots are an emergent class of nanomaterials that hold promise for innovations in imaging, sensing, and catalytic technologies. Here, Stolarczyk and colleagues control the nitrogen-atom content and location within carbon dots, reporting the resulting impact on emissivity and photocatalytic behaviour
Dilution-Induced Formation of Hybrid Perovskite Nanoplatelets
Perovskite
nanocrystals (NCs) are an important extension to the
fascinating field of hybrid halide perovskites. Showing significantly
enhanced photoluminescence (PL) efficiency and emission wavelengths
tunable through halide content and size, they hold great promise for
light-emitting applications. Despite the rapid advancement in this
field, the physical nature and size-dependent excitonic properties
have not been well investigated due to the challenges associated with
their preparation. Herein we report the spontaneous formation of highly
luminescent, quasi-2D organic–inorganic hybrid perovskite nanoplatelets
(NPls) upon dilution of a dispersion of bulk-like NCs. The fragmentation
of the large NCs is attributed to osmotic swelling induced by the
added solvent. An excess of organic ligands in the solvent quickly
passivates the newly formed surfaces, stabilizing the NPls in the
process. The thickness of the NPls can be controlled both by the dilution
level and by the ligand concentration. Such colloidal NPls and their
thin films were found to be extremely stable under continuous UV light
irradiation. Full tunability of the NPl emission wavelength is achieved
by varying the halide ion used (bromide, iodide). Additionally, time-resolved
PL measurements reveal an increasing radiative decay rate with decreasing
thickness of the NPls, likely due to an increasing exciton binding
energy. Similarly, measurements on iodide-containing NPls show a transformation
from biexponential to monoexponential PL decay with decreasing thickness,
likely due to an increasing fraction of excitonic recombination. This
interesting phenomenon of change in fluorescence upon dilution is
a result of the intricate nature of the perovskite material itself
and is uncommon in inorganic materials. Our findings enable the synthesis
of halide perovskite NCs with high quantum efficiency and good stability
as well as a tuning of both their optical and morphological properties
Carbon Dots: A Unique Fluorescent Cocktail of Polycyclic Aromatic Hydrocarbons
Carbon dots (CDs) have attracted
rapidly growing interest in recent years due to their unique and tunable
optical properties, the low cost of fabrication, and their widespread
uses. However, due to the complex structure of CDs, both the molecular
ingredients and the intrinsic mechanisms governing photoluminescence
of CDs are poorly understood. Among other features, a large Stokes
shift of over 100 nm and a photoluminescence spectrally dependent
on the excitation wavelength have so far not been adequately explained.
In this Letter we investigate CDs and develop a model system to mimic
their optical properties. This system comprised three types of polycyclic
aromatic hydrocarbon (PAH) molecules with fine-tuned concentrations
embedded in a polymer matrix. The model suggests that the Stokes shift
in CDs is due to the self-trapping of an exciton in the PAH network.
The width and the excitation dependence of the emission comes from
a selective excitation of PAHs with slightly different energy gaps
and from energy transfer between them. These insights will help to
tailor the optical properties of CDs and help their implementation
into applications, e.g., light-emitting devices and biomarkers. This
could also lead to “artificial” tunable carbon dots
by locally modifying the composition and consequently the optical
properties of composite PAH films