Study of surfactant cross-linking by click chemistry on a model water/oil interface.

In this study, we explored how chemical reactions of amphiphile compounds can be characterized and followed-up on model interfaces. A custom-made surfactant containing three alkyne sites was first adsorbed and characterized at a water/oil interface. These amphiphiles then underwent interfacial crosslinking by click chemistry upon the addition of a second reactive agent.

Ultrafast photophysics of the environment-sensitive 4'-methoxy-3-hydroxyflavone fluorescent dye.

The excited state intramolecular proton transfer (ESIPT) of 3-hydroxyflavone derivatives results in a fluorescence spectrum composed of two emission bands, the relative intensity of which is strongly influenced by the interaction with the local environment. We use time-resolved fluorescence and ultrafast transient absorption spectroscopies to investigate the photophysics of 4'-methoxy-3-hydroxyflavone in different solvents characterized by various polarities and hydrogen (H) bonding capabilities. We evidence that in this compound, the ESIPT reaction rate varies by more than 3 orders of magnitude, depending on the H-bonding capability of its local environment.

Protein-Sized Bright Fluorogenic Nanoparticles Based on Cross-Linked Calixarene Micelles with Cyanine Corona.

The key challenge in the field of fluorescent nanoparticles (NPs) for biological applications is to achieve superior brightness for sizes equivalent to single proteins (3-7 nm). We propose a concept of shell-cross-linked fluorescent micelles, in which PEGylated cyanine 3 and 5 bis-azides form a covalently attached corona on micelles of amphiphilic calixarene bearing four alkyne groups. The fluorescence quantum yield of the obtained monodisperse NPs, with a size of 7 nm, is a function of viscosity and reached up to 15 % in glycerol.

Non-coordinating anions assemble cyanine amphiphiles into ultra-small fluorescent nanoparticles.

A non-coordinating anion, fluorinated tetraphenylborate, assembles specially designed cationic cyanine amphiphiles into 7-8 nm fluorescent nanoparticles that are >40-fold brighter than a single cyanine dye. This kind of anion, combining hydrophobic and electrostatic forces in aqueous media, constitutes promising building blocks in the self-assembly of functional nanomaterials.

Fluorinated counterion-enhanced emission of rhodamine aggregates: ultrabright nanoparticles for bioimaging and light-harvesting.

The key to ultrabright fluorescent nanomaterials is the control of dye emission in the aggregated state. Here, lipophilic rhodamine B derivatives are assembled into nanoparticles (NPs) using tetraphenylborate counterions with varied fluorination levels that should tune the short-range dye ordering. Counterion fluorination is found to drastically enhance the emission characteristics of these NPs.

Squaraine as a bright, stable and environment-sensitive far-red label for receptor-specific cellular imaging.

Herein, we show that a far-red arylidene-squaraine dye is stable against nucleophiles, in contrast to arene-squaraines. Owing to the fluorescence enhancement in apolar media together with high brightness and photostability, this dye was successfully applied to detect the oxytocin G protein-coupled receptor and monitor its internalization in living cells.

Tuning the color and photostability of perylene diimides inside polymer nanoparticles: towards biodegradable substitutes of quantum dots.

Fluorescent organic nanoparticles (NPs) are attractive alternatives to quantum dots due to their potential biodegradability. However, preparation of fluorescent organic NPs is challenging due to the problem of self-quenching of the encapsulated dyes. Moreover, the photostability of organic dyes is much lower than that of quantum dots.

Highly lipophilic fluorescent dyes in nano-emulsions: towards bright non-leaking nano-droplets.

Dye-loaded lipid nano-droplets present an attractive alternative to inorganic nanoparticles, as they are composed of non-toxic biodegradable materials and easy to prepare. However, to achieve high fluorescence brightness, the nano-droplets have to be heavily loaded with the dyes avoiding fluorescence self-quenching and release (leakage) of the encapsulated dyes from the nano-droplets in biological media. In the present work, we have designed highly lipophilic fluorescent derivatives of 3-alkoxyflavone (F888) and Nile Red (NR668) that can be encapsulated in the lipophilic core of stable nano-emulsion droplets at exceptionally high concentrations in the oil core, up to 170 mM and 17 mM, respectively, corresponding to ~ 830 and 80 dyes per 40-nm droplet.