3 research outputs found
Enhanced Electrogenerated Chemiluminescence in Thermoresponsive Microgels
The electrochemistry, photoluminescence
and electrogenerated chemiluminescence
of thermoresponsive redox microgels were investigated. For the first
time, reversible ECL enhancement is demonstrated in stimuli-responsive
100-nm microgel particles. Such an unexpected amplification reached
2 orders of magnitude, and it is intrinsically correlated with the
collapse of the microgel particles. The swellâcollapse transition
decreases the average distance between adjacent redox sites and favors
the electron-transfer processes in the microgels resulting in the
enhanced ECL emission
Development of Functionalized Cyclotriveratrylene Analogues: Introduction of Withdrawing and ÏâConjugated Groups
Cyclotriveratrylene analogues (CTVs) are supramolecular
bowl-shaped
molecules known for their ability to complex organic and organometallic
guests, to form liquid crystals, polymers, or nanostructures. In this
Article, we report the synthesis of new cyclotriveratrylene analogues
with fluorescence properties in which various electron-withdrawing
or Ï-extended conjugated groups are appended to the wide rim
ortho to the methoxy-donating groups. Synthetically, these functionalized
CTVs cannot be obtained as CTVs with electron-rich functions by the
typical method (i.e., the trimerization of the corresponding benzyl
alcohol) but are prepared from a common key intermediate, the C<sub>3</sub>-triiodocyclotriveratrylene (CTV-I<sub>3</sub>), in good yields.
Despite the synthetic difficulties encountered due to the presence
of three reactive centers, we have demonstrated the possibility of
performing Sonogashira coupling and Huisgen cycloaddition reactions
directly to the CTV core for the first time. CTVs with Ï-extended
conjugated groups reveal interesting fluorescence profiles. More broadly,
this study utilizes CTV-I<sub>3</sub> to introduce novel functionalities
into CTVs to keep exploring their potential applications
Differential Photoluminescent and Electrochemiluminescent Behavior for Resonance Energy Transfer Processes in Thermoresponsive Microgels
Stimuli-responsive
microgels with redox and luminescent resonance
energy transfer (LRET) properties are reported. PolyÂ(<i>N</i>-isopropylacrylamide) microgels are functionalized simultaneously
with two models dyes: a derivative of trisÂ(bipyridine) ruthenium complex
and cyanine 5. Both moieties are chosen as a pair of luminophores
with a spectral overlap for resonance energy transfer, where the ruthenium
complex acts as a donor and the cyanine an acceptor. The effect of
the temperature on the efficiency of the LRET of the microgels has
been investigated and compared using either photoluminescence (PL)
or electrochemiluminescence (ECL) as the excitation process. In PL,
the synthesized microgels exhibit resonance energy transfer regardless
of the swelling degree of the microgels. The transfer efficiency is
a function of the donorâacceptor distance and can be tuned
either by the swellâcollapse phase transition or by the dye
content in the microgel network. In ECL, the microgels emit light
only at the wavelength of the ruthenium complex because the resonance
energy transfer does not occur. Indeed, even within the microgel matrix,
the cyanine dye is oxidized at the potential required for ECL generation,
which impairs its emitting properties. Thus, both excitation channels
(i.e., PL and ECL) show differential behavior for the resonance energy
transfer processes