Label-free vapor selectivity by polymer-inorganic composite photonic crystals sensors

The lack of sensors for continuous and extensive detection of vapor pollutants is a concern for health and safety. Colorimetric sensors, such as polymer distributed Bragg reflectors, could achieve this task thanks to their low cost and easy signal transduction, but are affected by low vapor permeability and lack of selectivity without chemical labels. We demonstrate label-free selective sensing of organic volatile compounds by all-polymer Bragg reflectors relying on a high free volume hybrid inorganic-polymer nanocomposite to achieve vapor permeability, and on different intercalation kinetic of organic analytes to achieve selectivity

Thin Polymer Films: Simple Optical Determination of Molecular Diffusion Coefficients

The possibility to assess diffusion coefficients of small molecules in packaging polymer films directly on the shelf, or even along the fabrication line, without the use laboratory equipment commonly employed for gravimetric methods would represent a paradigm changer in the evaluation of barrier properties and byproduct formation in goods packaging and device encapsulation. In this work, we demonstrate a simple, effective and versatile method for the determination of the molecular diffusion coefficients that exploits simple UV-Vis spectroscopy and is suitable for any polymer film. This simple method also allows the direct identification of the intercalating molecule without the need for chemical targeting or of complex laboratory equipment. For this purpose, we report on the assessment of diffusion coefficients of both polar and non-polar molecules including water, ammonia, methanol, ethanol, toluene, and even hexafluorobenzene into polyvinyl chloride wrap commercialized for food packagin

Planar microcavities: Materials and processing for light control

Microcavities are a class of optical structures providing a versatile approach to engineering light matter interactions. In light of recent developments in materials processing technologies, in particular for organic and hybrid ones, and of the need for high efficiency optical systems, there has been extensive innovation and improvement in their design and realization leading to a multitude of structures and materials. Among these, closed multi-material microcavities or microresonators based on the effect of dielectric contrast have been attractive for their low losses, applicability in a wide spectral range, and customizability. High-dielectric contrast microcavities based on distributed Bragg reflectors have been adapted early on for their highly controlled fabrication and strong light confinement and proved to be essential in current technologies including lasers and light emitting diodes. In this review, we map their evolution from planar one-dimensional inorganic structures to more sophisticated designs incorporating various categories of organic and hybrid materials. Additionally, we provide an overview of state-of-the-art developments and limitations of this class of structures

Solution Processed Polymer-ABX4 Perovskite-Like Microcavities

Thanks to solution processability and broad emission in the visible spectral range, 2D hybrid perovskite-like materials are interesting for the realization of large area and flexible lighting devices. However, the deposition of these materials requires broad-spectrum solvents that can easily dissolve most of the commercial polymers and make perovskites incompatible with flexible photonics. Here, we demonstrated the integration of broadband-emitting (EDBE)PbCl4 (where EDBE = 2,2-(ethylenedioxy)bis(ethylammonium)) thin films with a solution-processed polymer planar microcavities, employing a sacrificial polymer multilayer. This approach allowed for spectral and angular redistribution of the perovskite-like material, photoluminescence, that can pave the way to all-solution-processed and flexible lightning devices that do not require complex and costly fabrication techniques

Demonstration of fluorescence enhancement: via Bloch surface waves in all-polymer multilayer structures

An all-polymer photonic structure constituted by a distributed Bragg reflector topped with an ultrathin fluorescent polymer film has been studied. A Bloch surface wave resonance has been exploited to improve pumping efficiency. A strongly polarization and angle dependent fluorescence signal is found with respect to the light pumping beam and the emitted wavelength. Matching the most favorable condition for the pump coupling and the collection geometry, the signal obtained from the structure appears to be two orders of magnitude larger than the one of the bare emitting film

Strong coupling between excitons in organic semiconductors and Bloch Surface Waves

We report on the strong coupling between the Bloch surface wave supported by an inorganic multilayer structure and $J$-aggregate excitons in an organic semiconductor. The dispersion curves of the resulting polariton modes are investigated by means of angle-resolved attenuated total reflection as well as photoluminescence experiments. The measured Rabi splitting is 290 meV. These results are in good agreement with those obtained from our theoretical model

Directional Fluorescence Spectral Narrowing in All-Polymer Microcavities Doped with CdSe/CdS Dot-in-Rod Nanocrystals

We report on the fluorescence properties of high optical quality all-polymer planar microcavities embedding core 12shell dot-in-rod CdSe/CdS nanocrystals. Properly tuned microcavities allow a 10-fold sharpening of the nanocrystals fluorescence spectrum, resulting in a reduction of the bandwidth from 24 to 2.4 nm, which corresponds to a quality factor larger than 250. A 5-fold peak photoluminescence intensity enhancement is measured, while the overall number of emitted photons is reduced. Time-resolved photoluminescence and quantum yield for microcavities and suitable references show the presence of two decays related to differences in nanocrystal size distribution. The slower decay rate, which becomes faster when the nanocrystals are embedded into the microcavity, is assigned to longer nanorods with emission spectrally overlapped to the cavity mode. Conversely, the short-living component, which is assigned to an impurity of shorter nanorods, remains unaffected by the microcavity

Colorimetric Detection of Perfluorinated Compounds by All-Polymer Photonic Transducers

We report on the highly sensitive optical and colorimetric detection of perfluorinated compounds in the vapor phase achieved by all-polymer dielectric mirrors. High optical quality and uniformly distributed Bragg reflectors were fabricated by alternating thin films of poly(N-vinylcarbazole) and Hyflon AD polymers as high and low refractive index medium, respectively. A new processing procedure has been developed to compatibilize the deposition of poly(N-vinylcarbazole) with the highly solvophobic Hyflon AD polymer layers to achieve mutual processability between the two polymers and fabricate the devices. As a proof of principle, sensing measurements were performed using the Galden HT55 polymer as a prototype of the perfluorinated compound. The Bragg stacks show a strong chromatic response upon exposure to this compound, clearly detectable as both spectral and intensity variations. Conversely, Bragg mirrors fabricated without fluorinated polymers do not show any detectable response, demonstrating that the Hyflon AD polymer acts as the active and selective medium for sensing perfluorinated species. These results demonstrate that organic dielectric mirrors containing perfluorinated polymers can represent an innovative colorimetric monitoring system for fluorinated compounds, suitable to improve both environmental safety and quality of life

2,5-Diisopropenylthiophene by Suzuki\u2013Miyaura cross-coupling reaction and its exploitation in inverse vulcanization: a case study

A novel thiophene derivative, namely 2,5-diisopropenylthiophene (DIT) was synthetized by Suzuki\u2013Miyaura cross-coupling reaction (SMCCR). The influence of reaction parameters, such as temperature, solvent, stoichiometry of reagents, role of the base and reaction medium were thoroughly discussed in view of yield optimization and environmental impact minimization. Basic design of experiment (DoE) and multiple linear regression (MLR) modeling methods were used to interpret the obtained results. DIT was then employed as a comonomer in the copolymerization with waste elemental sulfur through a green process, inverse vulcanization (IV), to obtain sulfur-rich polymers named inverse vulcanized polymers (IVPs) possessing high refractive index (n z 1.8). The DIT comonomer was purposely designed to (i) favor the IV process owing to the high reactivity of the isopropenyl functionalities and (ii) enhance the refractive index of the ensuing IVPs owing to the presence of the sulfur atom itself and to the high electronic polarizability of the p-conjugated thiophene ring. A series of random sulfur-rdiisopropenylthiophene (S-r-DIT) copolymers with sulfur content from 50 up to 90 wt% were synthesized by varying the S/DIT feed ratio. Spectroscopic, thermal and optical characterizations of the new IVPs were carried out to assess their main chemical\u2013physical feature

All-Polymer Photonic Microcavities Doped with Perylene Bisimide J-Aggregates

Thanks to exciting chemical and optical features, perylene bisimide (PBI) J-aggregates are ideal candidates to be employed for high-performance plastic photonic devices. However, they generally tend to form - stacked H-aggregates that are unsuitable for implementation in polymer resonant cavities. In this work, we demonstrate the efficient compatibilization of a tailored perylene bisimide forming robust J-aggregated supramolecular polymers into amorphous polypropylene. The new nanocomposite was then implemented into an all-polymer planar microcavity which provides strong and directional spectral redistribution of the J-aggregate photoluminescence, owing to a strong modification of the photonic states. A systematic analysis of the photoemitting processes, including photoluminescence decay and quantum yields, shows that the optical confinement in the polymeric microcavity does not introduce any additional nonradiative de-excitation pathways to those already found in the J-aggregate nanocomposite film and pave the way to PBI-based high-performance plastic photonic devices