Sonochemical Synthesis of Optically Tuneable Conjugated Polymer Nanoparticles

Abstract

the development of novel and simple methodologies for the obtaining of semiconductive nanoparticles with fine-tuned optical (especially emission) properties, [9] due to its implicit technological relevance and the applications that can be derived from there. So far, spectral emission tuning of bulk semiconductive polymers has raised lots of interest and has been reported through encapsulation and confinement in nano porous silica NPs, [10] systematic variation of solvent and polymer concentration [11] or after postfabrication annealing/cooling or pressure/mechanical cycles. [12][13][14] Alternative chemical strategies include polymer modification with different core units [15] / side substituents, [16] or the controlled synthesis of oligomeric species differing on the number of repetitive monomers (and therefore conjugation length). [17] Only very recently the synthesis of nanoparticles with tunable optical properties has been partially achieved through the synthesis of poly mer dots with packing-dependent emission. [5,18] Therefore, there is a need to find novel approaches for the simultaneous spectral tuning and nanostructuration of semiconductive polymers.Sonication in chloroform/water mixtures can be an excellent technique to achieve this target. First, emulsification induced by ultrasonic radiation is a process broadly used for the formation of nanoparticles. Second, sonication of chloroform/water mixture is known to generate reactive species (Scheme S1, Supporting Information) such as chlorine radicals (·Cl, ·CHCl 2 , ·CCl 3 ) [19] and hypochlorous acid (HOCl), [20] which can be used to systematically cleave conjugated species, and therefore to modify the final optical properties. Indeed, chlorine radicals obtained by different means such as daylight, [21] γ-radiations [22] or thermal treatment, [23,24] have already been shown to tune the properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) upon polymer fragmentation, [21][22][23][24] whereas HOCl acts as strong oxidative species cleaving linear conjugated systems. [25][26][27] Conjugated polymer scission and chain shortening caused by oxidative species (i.e., H 2 O 2 ) has been previously exploited to confer biodegradability to fluorescent CPNs suitable for bioimaging, [28] but no controlled tuning of the emission properties has been reported. Therefore, herein we hypothesize that sonication of the semiconductive polymer of the polymer. Here, starting from poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], this objective is achieved with the one-pot synthesis of oligomers with tunable conjugation length and their nanostructuration, employing a miniemulsion method. Ultrasound irradiation of heterogeneous mixtures leads to the formation of hypochlorous acid that disrupts the electronic conjugation through polymer chain cleavage. Moreover, control over the degree of the electronic conjugation of the oligomers, and therefore of the optical properties, is achieved simply by varying the polymer concentration of the initial so...

Conception and Theoretical Study of a New Copolymer Based on MEH-PPV and P3HT: Enhancement of the Optoelectronic Properties for Organic Photovoltaic Cells

“…This latter can confirm the great contribution of the P3HT blocks. Moreover, the characteristic peaks of MEH-PPV that appear in the spectrum of copolymers are approximate to those donated by the Raman spectra of P3HT oligomers, which correspond to 1632 cm −1 , 1692 cm −1 (C=C stretching modes in vinylene group) [ 41 , 42 ].…”

Effect of Different Ionic Surfactants on the Structural, Photophysical, and Morphological Properties of Water‐Based P3HT:PCBM Nanoparticle Dispersions and Films

“…[ 22 ] P3HT and PCBM dissolved in CH 2 Cl 2 (oil phase) were injected in the aqueous phase in the presence of the selected surfactant, followed by ultrasonication and finally removal of the organic solvent by heating. The selection of CH 2 Cl 2 instead of the most commonly employed chloroform (CHCl 3 ) as organic solvent was motivated by: i) the need to avoid the formation of oxidative species during the ultrasonication of H 2 O/CHCl 3 mixture that can react with conjugated polymers, [ 17 ] and ii) an improved aggregation and self‐assembly tendency of P3HT films when processed from CH 2 Cl 2 . [ 49 ]…”

“…[ 15,16 ] Thus, in recent years, the approach involving the preparation of semiconducting polymer nanoparticles (SPNs) has attracted growing interest. [ 17–20 ] SPNs offer the great advantage of replacing organic solvents by water for safer transportation, storage and processing. [ 21–23 ] In SPNs, the polymer is typically enveloped in a shell of surfactant, which allows its controlled dispersion in an aqueous environment.…”

UV-enhanced oxidative quenching of PFO–PFPV Pdots for ratiometric quantification and imaging of hypochlorous acid in living cells

“…These observations from both UV-vis and fluorescence spectra suggest that HOCl can oxidize PFPV Pdots, and the oxidation reaction can be enhanced by UV irradiation. In PFPV Pdots, ClOoxidizes the carbon double bond (C=C) in PFPV backbone and the backbones are broken into inhomogeneous oxidized fragments [48,49]. With the aid of UV irradiation, HO Á /O Áand Cl Á can be generated due to the UV photolysis of HOCl/ClO - [50].…”