Visible light photoswitching of conjugated polymer nanoparticle fluorescence (original) (raw)
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Functionalization of Conjugated Polymer Nanoparticles for Fluorescence Photomodulation
Langmuir, 2014
The emission of conjugated polymer nanoparticles (CPNs or Pdots) is often tailored for specific uses by functionalizing CPNs with dyes that act as fluorescence resonance energy transfer (FRET) acceptors. A number of dye functionalization methods for CPNs have been developed, ranging from simple noncovalent doping to covalent attachment. We seek to develop guidelines for when non-covalent doping is acceptable and when covalent attachment is necessary to achieve the desired result. We present results of CPNs functionalized with photochromic spirooxazines by four different methods: simple doping, doping with an amphiphilic coating polymer, covalent functionalization prior to CPN formation, and covalent functionalization after CPN formation. The different CPNs are evaluated in terms of their fluorescence photomodulation properties to determine how the preparation method affects the CPN-dye photophysical interactions. Doping preparations yield the most efficient quenching of CPN emission due to shorter donor-acceptor distances in these CPNs compared to those with covalently-tethered dyes. Aging studies reveal that the photochromic dyes in doped samples degrade over time to a far greater extent than those in covalently-functionalized samples. These results suggest that dye-doped CPNs are appropriate for shortterm experiments where highly efficient FRET is desired while covalent dye functionalization is a better choice for experiments executed over an extended timeframe.
Physical Chemistry Chemical Physics, 2006
The absorption, fluorescence, and photostability of five conjugated chromophores: perylene, 2,5,8,11-tetra-t-butyl perylene (TTBP), perylene orange (PO), perylene red (PR), and a zwitterionic Meisenheimer complex (MHC), are studied as a function of concentration in poly(methyl methacrylate) (PMMA). At 1 mM concentrations, all five molecules exhibit properties consistent with unaggregated chromophores. At higher concentrations, perylene and PO both exhibit excimer formation, while TTBP, PR, and the MHC retain their monomeric fluorescent lineshapes. In these three molecules, however, the fluorescence decay times decrease by 10% (TTBP) to 50% (MHC) at concentrations of 100 mM in PMMA. The fluorescence properties of these highly concentrated samples are sensitive to the sample preparation conditions. In the neat solid where the effective concentration is on the order of 1 M, all three molecules exhibit very fast fluorescence decays, on the order of 150 ps or less, despite the fact that they retain their basic monomeric fluorescence lineshape. In addition to the enhanced nonradiative decay at high concentrations, these three molecules also undergo a concentration-dependent photobleaching. The combined effects of intermolecular nonradiative decay channels and photobleaching appear to be a general obstacle to achieving highly concentrated dye-doped solids.
Sensitized intrinsic phosphorescence from a poly(phenylene-vinylene) derivative
Chemical Physics Letters, 2003
Intrinsic phosphorescence in a phenyl-substituted poly(phenylene-vinylene) (PhPPV) film sensitized by a phosphorescent dye dopant has been directly observed for the first time for PPV class conjugated polymers. Efficient triplet energy transfer from the platinum porphyrin dye molecules to the PhPPV polymer was found to occur as the triplet level of the dopant (1.91 eV) is above the triplet level of PhPPV, which was determined to be at 1.63 eV. Intrinsic phosphorescence emission has been observed at room temperature as well. A significant decrease in emission intensity of phosphorescence has been found, if the sample was measured in air indicating quenching of triplets by oxygen.
European Polymer Journal, 2017
Spiropyran derivatized vinylic monomer (MSP) was prepared by coupling a typical spiropyran dye, 1′-(2-hydroxyethyl)-3′,3′-dimethyl-6-nitrospiro(2H-1-benzo-pyran-2,2′-indoline), to methacryloyl chloride. Poly(styrene-butylmethacrylatedivinylbenzene-MSP), P(S-BMA-DVB-MSP), photochromic fluorescent nanoparticles (NPs) of narrow size distribution were prepared by emulsion polymerization of the vinylic monomers: S, BMA, DVB and MSP. The influence of various polymerization parameters (e.g., concentration of the monomers, initiator and surfactant and pH) on the diameter, diameter distribution and photochromic fluorescence properties of the particles was elucidated. Spiropyran type molecules as well as MSP are colorless and non-fluorescent at the Spiro conformation. These compounds at the Merocyanine conformation are nonfluorescent in water or in non-polar organic solvents. However, when the Merocyanine conformation is entrapped within hydrophobic polymer particles, the particles exhibit blue color and strong red fluorescence. Absorbance and fluorescence measurements reveal that increasing the MSP or BMA relative concentration leads to a higher absorbance and fluorescence intensity of the formed P(S-BMA-DVB-MSP) NPs. Photoisomerization switching of the P(S-BMA-DVB-MSP) NPs was studied by exposing the NPs aqueous dispersion to alternating UV and visible light cycles. This study indicates 100% reversibility after five cycles of photoswitching.
The aim of the work was to investigate the adsorption of negatively charged cyanine dye 5,5 0 -disulfopropyl-3,3 0 -dichlorothiacyanine (TC) on the surface of borate capped gold nanoparticles (AuNPs) with average core sizes of 6 and 10 nm. The characterization of AuNPs in the presence and absence of TC was performed by measurements of the absorption, fluorescence and Raman spectra, TEM, DLS and zeta potential. The measurements of fluorescence of the NPs-TC assembly in the presence of low TC concentration clearly indicated that the fluorescence of TC was quenched by AuNPs in the concentration dependent manner. This process was found to be quantitatively related to the surface coverage of AuNPs by TC molecules. NPs surface coverage by TC was obtained from the dependence of TC fluorescence on NPs or TC concentration, keeping the concentration of one of the components of the NPs-TC assembly constant. The calculated values were obtained under the assumption that the monolayer of TC molecules, which were in direct contact with the NPs surface, was adsorbed. The experimentally obtained values were in accordance with the calculated ones for TC orientation along the vertical short side. The formation of TC J-aggregates was evident only in the presence of 6 nm NPs, when TC concentration was high. In this case the experimentally obtained value for C6 concentration needed to completely quench TC dyes' fluorescence was much lower than the calculated, indicating that the dye was accommodated on the surface of these NPs in more than one layer, and most probably in the slanted configuration.
Polymers, 2022
Recent progress in the field of photosensitive materials has prompted a need to develop efficient methods to synthesize materials with basic intermolecular architectural designs and novel properties. Accordingly, in this work we design and study a photoactive polymer as a photo-switchable polymeric system in the presence and absence of ZnS nanoparticles (average size < 10 nm) at 5 wt.%. The influence of UV light irradiation on its properties were also studied. The photoactive block copolymer was obtained from styrene (S) and methyl methacrylate (MMA) as monomers and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6-nitrobenzopyran (SP) was grafted to the block copolymer backbone as a photochromic agent. Furthermore, the incorporation of ZnS (NPs) as photo-optical switch component into the system enhances the purple colored photo-emission, with the open form of the spiropyran derivative (merocyanine, MC). The ZnS stabilize the isomeric equilibrium in the MC interconversion of the photochr...
Improvement of luminescence efficiency and photostability in polymer thin films
Thin Solid Films, 2000
The photodegradation mechanism and luminescence ef®ciency of a series of thin polymer ®lms prepared under a variety of conditions was studied. The conjugated polymer, poly(m-phenylene-co-2,5-dioctoxy-p-phenylenevinylene) (PmPV), is shown by infra-red spectroscopy to degrade via the chain scission of the carbon double bond along the polymer backbone. This causes a reduction in conjugation length and a blue shift in its absorption and photoluminescence (PL) spectra. To reduce photodegradation effects, ®lms were prepared using argon (Ar) gas and were investigated in air and an oxygen free environment. The initial PL intensity increased by over 70% for Ar treated ®lms. The PL decay in air was bi-exponential in nature, with a sharp initial decay linked to atmospheric oxygen, and a longer second decay linked to oxygen embedded in the ®lm. The increase in both PL ef®ciency and degradation lifetime, coupled with device encapsulation, should signi®cantly improve the performance of electroluminescent devices. q
The journal of physical chemistry letters, 2015
Photoswitching of bright fluorescent nanoparticles opens new possibilities for bioimaging with superior temporal and spatial resolution. However, efficient photoswitching of nanoparticles is hard to achieve using Förster resonance energy transfer (FRET) to a photochromic dye, because the particle size is usually larger than the Förster radius. Here, we propose to exploit the exciton diffusion within the FRET donor dyes to boost photoswitching efficiency in dye-doped polymer nanoparticles. To this end, we utilized bulky hydrophobic counterions that prevent self-quenching and favor communication of octadecyl rhodamine B dyes inside a polymer matrix of poly(d,l-lactide-co-glycolide). Among tested counterions, only perfluorinated tetraphenylborate that favors the exciton diffusion enables high photoswitching efficiency (on/off ratio ∼20). The switching improves with donor dye loading and requires only 0.1-0.3 wt % of a diphenylethene photochromic dye. Our nanoparticles were validated bo...
Intra- and inter-molecular photoexcitations in a cyano-substituted poly( p-phenylenevinylene)
Chemical Physics, 1998
We report a study of time-resolved photoluminescence (PL) in a cyano-substituted poly(p-phenylenevinylene). We have investigated the effect of excitation and emission wavelength as well as solvent on the PL. We observe evidence of luminescence from both intra- and inter-molecular photoexcitations. We find that the relative amounts of these excitations depend strongly on the excitation wavelength and solvent mixture used.