Dipolar versus Octupolar Triphenylamine‐Based Fluorescent Organic Nanoparticles as Brilliant One‐ and Two‐Photon Emitters for (Bio)imaging

Venkatakrishnan, Parthasarathy; Fery–Forgues, Suzanne; Campioli, Elisa; Recher, Gaëlle; Terenziani, Francesca; Blanchard‐Desce, Mireille

doi:10.1002/smll.201100726

Cited by 86 publications

(73 citation statements)

References 56 publications

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“…4 The present work offers a unique insight into the energetics of the organization at the interface and opens directions for further improving the colloidal stability of the NPs by engineering the structure of the dipolar dye (nature and length of the π-conjugated system, presence of side groups). In particular the lipophilic/hydrophilic balance and its distribution over the dipolar dye axis will be adjusted in order to further stabilize the polar order of dyes on the NPs' surface.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

Interfacial Organization in Dipolar Dye-Based Organic Nanoparticles Probed by Second-Harmonic Scattering

et al. 2015

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We have undertaken polarization-resolved SHS experiments to investigate a series of two fluorescent organic nanoparticles (FONs) made from dipolar dyes bearing a triphenylamine-donating end-group and a slightly hydrophilic acceptor end-group. The FONs, which show very large negative surface potentials, responsible for their good colloidal stability in water, are very bright SHS emitters in water, attractive for single-particle tracking and bioimaging. With the polarization-resolved SHS technique, we come up with a new and noninvasive method to gain insight into the origin of the surface potential of the FONs, as well as into their evolution upon change of ionic strength by following their multipolar response when adding salt. In pure water, the polarization-resolved SHS spectroscopy reveals the presence of a region of local polar order close to the surface (i.e., orientation of the dipolar dyes), leading to a strong dipolar contribution. Quite interestingly, when adding KCl salt, the initial two-lobe SHS polar plot transforms into a four-lobe pattern with a net decrease of the SHS intensity, revealing a lower surface potential. Second, we have quantified the decrease of the SHS signal when adding salt with the goal to estimate the change of the NPs' colloidal stability in salty media. From a simple equilibrium model that we propose, we have extracted a lower bound free energy for the two FONs, which are thermally accessible and in good accordance with their respective colloidal stability. I n the last decades, nanoparticles have attracted increased interest in biology and optoelectronics fields, mainly due to their unique properties. Among them, luminescent metal-and semiconductor-based nanoparticles have attracted overwhelming attention. A number of them however raise toxicity and biodegradability issues, which is critical with regard to biomedical applications and environmental concerns. In that perspective, molecular-based fluorescent organic nanoparticles (FONs) 1 emerged as a promising alternative toward optical nanomaterials and fluorescent probes for acute biomaging applications. 2 Among them, FONs made from specific dyes, i.e., dipolar (i.e., push−pull or D−π−A compound) chromophores, offer attractive features as tunable luminescent nanomaterials 3 of interest for cellular as well as in vivo bioimaging purposes 4 or as nanotools for single-particle tracking. 5 Interestingly, the colloidal stability of these nanoparticles in water was observed to strongly depend on the structure of the push−pull compound system. 4,6 Furthermore, investigation of the fluorescence properties (in particular fluorescence emission spectra and lifetimes) reveals different environments, pointing to possible nanostructuration of dipolar dyes within the FONs. Conjecturing that this could be ascribed to a specific organization (and local ordering) of the dye subunits near the surface of the spherically shaped FONs (i.e., at the interface with water), we aimed at investigating this hypothesis by using hyper-Rayleigh scattering (HRS),...

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Section: ■ Results and Discussionmentioning

confidence: 98%

Interfacial Organization in Dipolar Dye-Based Organic Nanoparticles Probed by Second-Harmonic Scattering

et al. 2015

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“…The last decade has witnessed a remarkable research effort on investigating photoluminescent micro-and nanomaterials, because of their great potential especially in the areas of biological imaging, [1] fluorescence sensing, [2] and new technology devices.…”

Section: Introductionmentioning

confidence: 99%

Blue‐Emitting Nanocrystals, Microcrystals, and Highly Oriented Nanofibers Prepared by Reprecipitation and Solvent Drop‐Casting of 2‐Phenyl‐naphthoxazoles

Ghodbane¹,

Colléaux²,

Saffon³

et al. 2012

ChemPlusChem

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Three 2‐phenyl‐naphth[2,3‐d]oxazole derivatives, one of them being unsubstituted (1) and the two others bearing a methyl (2) and a tert‐butyl group (3) in the para position of the phenyl ring, were prepared. In the crystalline state, all compounds adopted a crossed‐stacking mode that favors fluorescence emission. They emitted in the blue region and their photoluminescence quantum yield ranged between 25 and 59 %. The preparation of micro/nanoparticles by simple methods was optimized. By using a solvent‐exchange method, the compounds readily gave microcrystals, the size and shape of which closely depend on the nature of the substituent, as well as nanocrystals that measured around 200 nm. The proportion of micro‐ and nanocrystals was modulated by the experimental conditions and the two populations could be separated by filtration for subsequent use. For unsubstituted compound 1, drop‐casting from a solution in tetrahydrofuran spontaneously generated an array of parallel and almost perpendicularly oriented nanofibers that exhibited efficient waveguiding properties. Owing to their robustness, good solid‐state optical properties, and to the simplicity of particle preparation, these naphthoxazole derivatives appear as promising candidates for the fabrication of blue‐emitting tracers and nanofibers.

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“…These studies, both theoretical and experimental, have attempted to shed light on why multichromophoric systems exhibit improved 2PA activity compared to model compounds and why some times 2PA activity is reduced. 20,23,24,[28][29][30][31][32][33] However, several issues remain not well understood, because of the complexity of multi-chromophoric systems, such as the exact effect of the core, the localization (or not) of the excited state on a single chromophore (branch), the effect of solvent etc. Localization of the excited state on a single branch may hinder signicant branch co-operation and enhancement of the 2PA properties.…”

Section: -17mentioning

confidence: 99%

Solvent and branching effect on the two-photon absorption properties of push–pull triphenylamine derivatives

et al. 2016

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The photophysical and two-photon absorption (2PA) properties of two tri-podal molecules and of their quadrupolar and dipolar counterparts are reported for a series of solvents with varying polarity. The molecules possess a tri-phenylamine electron donating group and mono-cyano acceptors while olefinic and acetylenic p-linkers have been used. Branching led to an increase of the molar extinction coefficient and to a slight bathochromic shift of the absorption spectra while the fluorescence quantum yields decrease but they are maintained to relatively high values. Solvatochromic measurements in the tripodal molecules revealed an emitting state with a polar nature. The 2PA cross sections in general increase upon branching but the observed behaviour strongly depends on the type of solvent. The highest 2PA cross sections are obtained in solvents of medium polarity and values as high as 1420 GM are reported.

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Dipolar versus Octupolar Triphenylamine‐Based Fluorescent Organic Nanoparticles as Brilliant One‐ and Two‐Photon Emitters for (Bio)imaging

Cited by 86 publications

References 56 publications

Interfacial Organization in Dipolar Dye-Based Organic Nanoparticles Probed by Second-Harmonic Scattering

Interfacial Organization in Dipolar Dye-Based Organic Nanoparticles Probed by Second-Harmonic Scattering

Blue‐Emitting Nanocrystals, Microcrystals, and Highly Oriented Nanofibers Prepared by Reprecipitation and Solvent Drop‐Casting of 2‐Phenyl‐naphthoxazoles

Solvent and branching effect on the two-photon absorption properties of push–pull triphenylamine derivatives

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