Activated fluorescence was achieved for nanoparticle based systems. One particulate system consisting of a poly(propargyl acrylate) (PA) core with covalently attached derivatized fluorescein and modified bovine serum albumin covalently conjugated to a cyanine 3 derivative was initially nonfluorescent. Upon trypsin addition and subsequent proteolytic digestion, Förster resonance energy transfer (FRET) was induced. The other particulate system consisted of a PA core with covalently attached azide modified BSA, which was covalently attached to a silicon phthalocyanine derivative (PA/BSA/akSiPc600). Both systems were biocompatible. To investigate activated fluorescence with the PA/BSA/akSiPc600 system in cancer cells, human non-small cell lung cancer cells (A549 cell line) were used as a model system. The PA/BSA/akSiPc600 system was incubated with the cells at varying time points in an effort to see a fluorescence increase over time as the cells uptake the particles and as they digest the BSA, most probably, via endocytosis. It was seen, through live cell scanning confocal microscopy, that the fluorescence was activated in the cell.
The functionalization of colloidal surfaces has been an area of scientific research for several decades.
With the emergence of click reactions, particularly the copper(I) catalyzed version of Huisgen 1,3-dipolar
cycloaddition between azides and alkynes, new pathways to functionalize the particle surface in aqueous
environments have opened for researchers to explore. In colloidal systems synthesized by free radical
polymerization with monomers containing azides or alkynes, networked polymers are produced due to
the bifunctionality of both monomers. The primary means of characterizing the success of these reactions
due to the rigidity of the crosslinked particle is the use of a chromophore as the "clicked' material or
titrations of a weak acid that has been "clicked'. Herein, the piecewise process of building a core-shell
particle is described that avoids the unwanted crosslinking of an alkyne containing monomer. Due to the
control of the piecewise fabrication, the polymer shell can removed with a favorable solvent pre- or post-functionalization
with an azide-functionalized anthracene molecule.
The intrinsic deterioration in device performance of polymeric single layer OLEDs that were doped with a
fluorescent emitter was studied. The specific focus was on the role that thermal aging, at sub-glass transition
temperatures of the polymeric layer, has on the phase separation of the active layer. This was accomplished
by the rational design of an oxadiazole-containing methylacrylate monomer that was energetically similar to
the technologically important electron- transporting small molecule 2-biphenyl-4-yl-5-(4-tert-butylphenyl)-1,3,4-
oxadiazole (tBu-PBD). This monomer was copolymerized with a carbazole containing hole-transporting monomer
2-(9H-carbazol-9-yl)ethyl 2-methylacrylate (CE) and the resulting copolymer was utilized as the active layer with
coumarin 6. With coumarin 6, the devices exhibited a stable mean luminance of ca. 400 cd/m2 with thermal
aging at temperatures ranging from 23 °C to 130 °C, while a comparable poly(9-vinyl-9H-carbazole)/tBu-PBD
blend device exhibited a drop from an initial mean luminance of 2500 cd/m2 to 1.6 cd/m2. The reduction in
luminance and luminance efficiency for the blend system was attributed to phase separation in the blend.
The conductivity of colloidal inks composed of poly(ethylene glycol) (PEG), 2-(4-tert-Butylphenyl)-5-(4-biphenylyl)-
1,3,4-oxadiazole (tPBD) or polystyrene-tPBD copolymerized colloids (PS-PBD) and carbon black (CB) were
investigated to establish their percolation characteristics. The PS-PBD colloid supported inks (PEG/PS-PBD/CB)
exhibited reduced percolation thresholds and enhanced conductivities above that of the individually carbon filled
(PEG/CB) and small molecule blend (PEG/tPBD/CB) inks. Based on the DC conductivity analysis, the percolation
threshold of the PEG/PS-PBD/CB composites was 3.6 vol%. The electrical resistivity of the PEG/PS-PBD/CB ink is
lower than that of PEG/PBD/CB ink with the same CB content in the percolation region by 8 orders of magnitude. The
percolation reduction was attributed to the heterogeneous dispersion of conductive filler aggregates "bridged" by PSPBD
colloids. The aggregated dispersion of PS-PBD colloids in the ink matrix was characterized by photoluminescence
spectroscopy (PL) which produced a red-shift at high concentrations, signaling the required proximity of PS-PBD
colloids to form energy transfer complexes.
Hybrid particles from insoluble luminescent π-conjugated polymers were formed through a miniemulsion approach.
The color characteristics of the PL for the particles could be tuned by exploiting the Förster resonance
energy transfer between the polymers within a particle, while suppressing energy transfer between particles,
and exhibited 1931 CIE x,y-color coordinates that ranged from 0.153, 0.071 to 0.267, 0.559 with corresponding
dominant wavelengths of 466 nm to 536 nm with an excitation energy at a wavelength of 389 nm.
The prospect of an inexpensive organic laser which can dynamically alter its lasing wavelength is desirable for a number
of display and communication technologies. In this effort, real-time tuning of the lasing wavelength is accomplished
through the use of colloidal crystals to provide the required reflectivity in an external resonator cavity design in which a
gain medium is sandwiched between a dielectric stack and colloidal crystal. Optical pumping of the gain medium lead to
a lasing peak that corresponded to the stop band of the photonic crystal. By varying the compressive strain placed on the
colloidal crystal, the lasing could be tuned across the photoluminescent spectrum of the gain material. Repeated straining
of the assembly did not appear to alter its proclivity to lase when photo-excited or introduce hysteresis in the lasing
wavelength strain relationship. The fast response of the crystal to compressive strain could lead to pulsed organic lasers
operating at kHz modulation frequencies.
Integrated optical circuits are an important technology for future high tech products. At present there is great interest in producing polymer based optical circuits. These circuits have a number of potential advantages over current silica/semiconductor based systems. These polymer optical circuits have been used to produce waveguide technology. However in general the production of laser systems for these circuits still depends on older semiconductor technologies. Polymer lasers provide a possible candidate for integrated flexible lasers. Many of the systems demonstrated to date use silica/semiconductor substrates to provide sufficient refractive index variation to provide efficient feedback. A novel alternative to this technology is the holographic distributed feedback (DFB) laser geometry. In this system the lasing material is dispersed in a photopolymer holographic recording material. DFB is then provided by a refractive index structure recorded in the material using holographic techniques. In this paper we discuss a range of holographically recorded feedback geometries and examine the possibility of using this technique to produce organic DFB lasers using non contact holographic patterning.
Fluoropolymers are viable material options for short haul fiber and planar waveguide photonic applications. This work provides the refractive index, extinction coefficient, Sellmeier coefficients, and infrared absorption for two perfluorocyclobutyl-based (PFCB) polymers. These PFCB fluoropolymers have marked themselves as alternatives to the more well known fluoropolymers based on their solution processability and broad tailorability of optical, thermal, and mechanical properties.
KEYWORDS: Polymers, Composites, Nanocomposites, Single walled carbon nanotubes, Photonic crystals, Chemical analysis, Sensors, Biological and chemical sensing, Organic photovoltaics, Photovoltaics
The promise, some fact and some fanciful, of nanotechnology has led to a well funded global race to develop new materials, components, and devices for use in a remarkably diverse range of applications. Towards the true realization of commercial- and defense-relevant devices, this paper focuses on passive and active optical detecting and sensing devices whose performance is markedly improved, with respect to traditional analogs, through the use of nanocomposite materials. Specifically to be discussed are efficient organic photovoltaics (OPVs) fabricated using doped and undoped carbon nanotube-containing conjugated polymers. All-organic photonic crystals based on ordered arrays of nanoparticles encapsulated in elastomeric matrices also are discussed. These nanocomposites exhibit bandstops that are highly tunable though stain generated by mechanical forces (mechano-chromism) or chemical affinity (chemo-chromism) which opens new doors for optical beam steering and chemical sensing.
Bis-ortho-Diynyl Arene (BODA) monomers polymerize to network polynapthalene by the thermally-driven Bergman cyclization and subsequent radical polymerization via oligomeric intermediates that can be melt or solution processed. Further heating of the network to 1000 °C affords a high-yield glassy carbon structure that retains the approximate size and dimensions of the polymer precursor. The higher carbon-yield for BODA networks (75- 80 % by mass) is significantly greater than that of traditional phenol-formaldehyde resins and other carbon precursor polymers leading to its greater dimensional stability. Phenyl terminated BODA derived polymers were fabricated using microprocessing such as the micromolding in capillaries (MIMIC) technique, direct microtransfer molding, and molding in quartz capillary tubes. Nano-scale fabrication using closed packed silica spheres as templates was demonstrated with an hydroxy-terminated monomer which exhibits greatly enhanced compatibility for silica surfaces. After pyrolysis to glassy carbon, the silica is chemically etched leaving an inverse carbon opal photonic crystal which is electrically conductive. The wavelength of light diffracted is a function of the average refractive index of the carbon/ filler composite, which can be modified for use as sensitive detector elements.
Polymeric materials, in both fiber and planar form, are finding increasing application in commercial optical communication systems. This paper compares and discusses the intrinsic optical properties of common organic materials used in polymer waveguides as relates to their expected performance in optical fibers and rare earth amplifiers. Specifically considered and compared are polymethyl methacrylate (PMMA), Teflon-AF, Cytop, and perfluorocyclobutyl (PFCB) polymers.
Perfluorocyclobutyl (PFCB) polymers and copolymers enjoy a unique combination of properties well suited for optical applications such as high temperature stability, precisely controlled refractive index, low moisture absorption, excellent melt and solution processability, a variable thermoptic coefficient, and low transmission loss at 1300 and 1550 nm. Copolymerization reactions offer tailored thermal and optical properties by simple choice of comonomer. PFCB copolymers can be solution or melt microfabricated via standard methods and can also be processed via micro-transfer molding in photolithographically generated features. Reliable molding of polymer waveguides offers significant potential to reduce photonic integrated circuit (PIC) fabrication costs and enable the realization of compact, integrated subsystems for a variety of applications. Copolymerization chemistry, thermoptic measurements, and initial results on the first micro-transfer molded waveguide structures are presented.
KEYWORDS: Composites, Actuators, Particles, Glasses, Polymers, Photonic crystals, Crystals, Simulation of CCA and DLA aggregates, Spectroscopy, Reflectivity
Physically robust photonic bandgap (PBG) composites based on electrostatically stabilized polymeric colloidal particles are presented. The glass transition (Tg)of the composites can be varied over a large temperature range through the selection of the monomer(s) used to fabricate the composite. Composites with a subambient Tg exhibited a mechanochromic response and were integrated with a peizoelectric actuator to produce a prototype device which exhibited a fully reversible tunable rejection wavelength, capable of a ca. +/- 86 nm (172 nm full range)stop band shift.
Organic polymers are increasingly attractive alternatives to inorganic materials in telecommunication devices. Polymers offer flexibility, low cost fabrication and connection, high transparency in the visible and near-infrared spectra, and versatility in structure, properties, and grades for task specific integration such as local-area-network applications. Halogenated polymers in particular show negligible transmission losses in the range desired and fluoropolymers represent the lowest loss examples of organic polymers to date. However, commercial perfluoropolymers in general are limited by poor processability, non-trivial refractive index matching, and they typically do not exhibit the thermal and thermomechanical stability required for some commercial processes and extreme environment in-use applications. Our strategy has focused on the thermal cyclopolymerization of trifunctional and bifunctional aryl trifluorovinyl ether monomers to perfluorocyclobutane (PFCB) copolymers. PFCB polymers and copolymers enjoy a unique combination of properties well suited for optical applications such as high temperature stability, precisely controlled refractive index, low moisture absorption, excellent melt and solution processability, a high thermooptic coefficient, and low transmission loss at 1300 and 1550 nm. Copolymerization reactions offer tailored thermal and optical properties by simple choice of comonomer. PFCB polymers can be solution or melt microfabricated via standard methods and can also be processed by soft-lithography techniques. Polymerization and processing parameters and characterization including thermal properties (Tg = 120-350 degree(s)C), optical loss (< 0.2 db/cm at 1550 nm), refractive index tunability (1.449-1.508 at 1550 nm), low birefringence, and optical stability is presented.
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