315 research outputs found
Organic & Hybrid Photonic Crystals
No full textPhotonic crystals (PhC) are composite systems where materials possessing different refractive index are arranged in a highly regular periodical structure having a length scale comparable to the wavelength of visible light[1]. The periodicity of the system can be extended over 1-, 2- or 3-dimensions.
The concept of PhC have been disclosed about twenty-five years ago by Yablonovitch[2] and John[3] with two seminal papers tackling fundamental issues like inhibition of spontaneous emission and light localization. Nowadays, PhCs find application in different fields spanning from photonics to photovoltaics and are gaining a great interest for sensing.[4-9] While the most widespread techniques used to growth photonic crystals are top-down ones, a great interest is currently devoted to fabrication of novel PhC structures with bottom-up methods or by processing from solution/melt. Moreover, their functionalization with suitable groups and/or with photoactive organic/hybrid materials in order to tailor their responsive properties for selected applications is intensively pursued.[4-5, 9-11]
In this communication, we will review the opportunities provided by organic PhC and we will focus on recent results obtained with 2D and 3D colloidal arrays (respectively, microsphere monolayers and opals) as well as on 1D all-polymer structures, which may add to photonic functionality unprecedented properties for their inorganic counterpart such as self-support (no need for a substrate) and mechanical flexibility.
1D all-polymer photonic crystals (i.e. Distributed Bragg Reflectors and microcavities) are grown by spin-coating by using polymer solutions in orthogonal solvents.[12-13] Even though, the technique is very simple, cheap and well known, limitations occurs when different constraints, such as high dielectric contrast, orthogonal solvents, control of the interfaces, transparency, lack of light scattering, have to be simultaneously considered. In spite of that, the technique allows to prepare free-standing and flexible DBR and microcavities, which can be successfully doped with photoactive materials (semiconducting, photochromic and clathrating polymers, J-aggregates) in order to obtain photonic platforms suitable for lasing, switching and sensing[12-14].
2D PhC, i.e. microsphere arrays can be prepared by floating[15]. Such systems have been successfully used as a template for grazing incident gold evaporation thus generating nanocrescents possessing different kind of anisotropic plasmonic resonances[15], which interact with photonic modes in opals. Moreover, microsphere monolayers show unusual second harmonic generation of circular dichroism[16].
Finally, artificial opals, the well-known playground for 3D photonic crystals have been used to show fluorescence enhancement effects and modulation of the radiative fluorescence lifetime. Three examples are described such as opals infiltrated with fluorescent solutions, opal infiltrated with conjugated polymers, and core-shell opals where the microspheres have been engineered in order to possess a shell doped with a fluorophore[17-18].
References
[1] J. D. Joannopulos; R. D. Meade; J. N. Win, Photonic Crystals: Molding the Flow of the Light. Princeton University Press: Princeton, 1995.
[2] E. Yablonovitch, Phys. Rev. Lett. 1987, 58.
[3] S. John, Phys. Rev. Lett. 1987, 58.
[4] J. Ge; Y. Yin, Angew. Chem. Int. Ed. 2011, 50, 1492.
[5] F. Li; D. P. Josephson; A. Stein, Angew. Chem. Int. Ed. 2011, 50, 360.
[6] T. Asano; S. Noda, Nature 2004, 429, 6988.
[7] D. Graham-Rowe, Nat Photon 2009, 3.
[8] M. F. Limonov; R. M. D. L. Rue, Optical Properties of Photonic Structures: Interplay of Order and Disorder. Taylor & Francis: 2012.
[9] J.-H. Lee; C. Y. Koh; J. P. Singer; S.-J. Jeon; M. Maldovan; O. Stein; E. L. Thomas, Adv. Mater. 2013, 26, 532.
[10] J. H. Moon; S. Yang, Chemical Reviews 2009, 110, 547.
[11] S. Furumi; H. Fudouzi; H. T. Miyazaki; Y. Sakka, Adv. Mater. 2007, 19.
[12] L. Frezza; M. Patrini; M. Liscidini; D. Comoretto, J. Phys. Chem. C 2011, 115, 19939.
[13] G. Canazza; F. Scotognella; G. Lanzani; S. D. Silvestri; M. Zavelani-Rossi; D. Comoretto, Laser Phys. Lett. in press (2014).
[14] S. Pirotta; M. Patrini; M. Liscidini; M. Galli; G. Dacarro; G. Canazza; G. Guizzetti; D. Comoretto; D. Bajoni, Appl. Phys. Lett. 2014, 104.
[15] V. Robbiano; M. Giordano; C. Martella; F. D. Stasio; D. Chiappe; F. B. d. Mongeot; D. Comoretto, Adv. Optical Mater. 2013, 1, 389.
[16] A. Belardini; A. Benedetti; M. Centini; G. Leahu; F. Mura; S. Sennato; C. Sibilia; V. Robbiano; M. C. Giordano; C. Martella; D. Comoretto; F. Buatier de Mongeot, Adv. Optical Mater. DOI: 10.1002/adom.201300385.
[17] L. Berti; M. Cucini; F. Di Stasio; D. Comoretto; M. Galli; F. Marabelli; N. Manfredi; C. Marinzi; A. Abbotto, J. Phys. Chem. C 2010, 114, 2403.
[18] F. Di Stasio; L. Berti; S. O. McDonnell; V. Robbiano; H. L. Anderson; D. Comoretto; F. Cacialli, APL Materials 2013, 1
Organic and hybrid photonic crystals - Preface
No full textThis book provides a multidisciplinary perspective (ranging from chemistry to physics and biology) of the current research and applications of organic and hybrid photonic crystals. The authors detail the chemical and physical tools used to develop organic photonic crystals, explain methods for engineering new nano-structures, and propose novel physical phenomena or technological applications based on such materials. Organic and Hybrid Photonic Crystal lasers, sensors, photovoltaic devices and stimuli responsive devices are discussed
IL PREMIO NOBEL PER LA CHIMICA 2000 AGLI SCOPRITORI DEI POLIMERI CONDUTTORI DI ELETTRICITA’
No full textOrganic and hybrid photonic crystals
No full textThe research field of Photonic Crystals, i.e., composite structures where materials
possessing different refractive index are assembled into a highly ordered dielectric
lattice with submicrometric periodicity, was founded in 1987 by the seminal papers
by E. Yablonovitch and S. John published in the same volume of Physical Review
Letters just 3 weeks one after the other. They provided the tools to rationalize the
dielectric lattices optics within a new formalism that not only is able to extend their
theoretical description but also becomes a source of inspiration for novel systems,
structures, and applications.
As it was already observed in other research fields, the development of novel
Photonic Crystals structures was based on the use of top-down approaches to
impart the dielectric structure into inorganic insulators and semiconductors. Such
techniques enable the fabrication of photonic structures possessing extraordinary
precision and finely tailored properties for selected technological applications.
Several books that have been so far published in the field of Photonic Crystals
are usually tuned to a specialist readership mainly composed of Physicists and
Engineers. Even though colloidal chemists and block copolymer scientists provided
important contributions to the field, a cultural and communication gap still exists
between fundamental Physics and Chemistry, as well as other disciplines of potential
interest to the Photonic Crystals field. For instance, novel organic and hybrid
materials that are revolutionizing the field of electronics and sensing can hardly be
nanostructured in the form of Photonic Crystals with top-down techniques. Furthermore,
biomedical applications could greatly benefit from the developments of
the field. In this respect, and in particular when organic and hybrid materials are
used, the use of the bottom-up approach as well as the exploitation of the chemistry
of the self-assembling process, widely exploited in Nature, provides an important
step forward to the field. This book, Organic and Hybrid Photonic Crystals, was
conceived as a bridge between different communities in order to establish a
common set of fundamental concepts and a language to be shared between Physicists,
Chemists, Biologists, Engineers, and Material Scientists.............
Label-free vapor selectivity by polymer-inorganic composite photonic crystals sensors
No full textThe 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
SUPRAMOLECULAR PROPERTIES OF POLYMERS FOR PLASTIC ELECTRONICS
No full textI INTRODUCTION
II FUNDAMENTAL PHYSICAL PROPERTIES
A Electronic Properties: chain orientation
B Photophysics: chain interaction
1 Polydiacetylene
2 Polyalkylthiophene
III PLASTIC ELECTRONICS: THE ROLE OF SUPRAMOLECULAR STRUCTURE
A Conducting and semiconducting polymers: transport properties
B Sensors
C Light Emitting Diodes
D Photovoltaic Cells
E Toward micro-devices
IV PERSPECTIVES & CONCLUSION
Tailoring the properties of polymers for photonic applications with optical nanocomposites
No full textSelf-Assembly of Polyelectrolytes for Photonic Crystal Applications
No full textThe use of polymers in microelectronics and photonics is continuously developing along two main streams: the preparation of polymer structures spanning from nano- to meso-scale and the improvement of semiconducting/conducting functions into the macromolecule thus making their electronic and optical properties suitable to specific goals (charge transport or generation, light emission, optical non linearities ...). In order to step forward these topics, the exploitation of bottom-up self-organization properties of polymers, which work through quasi-equilibrium steps enabling the self-repulsion of defects, is a powerful approach. Indeed, suitable structures ranging from the nano- to the meso-scale might provide the required property or functionality either from the optical or the electronic point of view. Moreover, the use of self-organizing processes is often a need for soft matter since usual techniques used in the top-down approach like UV- or X-ray-lithography could be expensive, energy consuming and, in particular, potentially destructive for organic materials.
The length scales of ordered structures obtained by the self-organization process discriminates their possible application either to optoelectronics or to photonic. Polymer structures of few nanometers might have two different functions: to be a template or to impart a specific electronic/optical role. Block copolymers have a phase behaviour of considerable scientific and technological interest due to the formation of different ordered structures. When the composing blocks do not have electronic functionalities, i.e. are insulating polymers, the nanostructures can be used as an efficient and low-cost mask for the semiconductor industry. Indeed, by using suitable molecular masses, critical dimensions below current lithographic resolution limits can be achieved
Highly oriented poly(paraphenylene vinylene): Polarized optical spectroscopy under pressure
No full textWe investigate the role of intermolecular interactions in thick highly oriented poly(p-phenylene-vinylene)
under applied hydrostatic pressure by polarized reflectance and Raman spectroscopy. Evidence of intramolecular
and intermolecular effects is observed. The analysis of the C=C stretching modes and of the optical
transition at about 3.7 eV previously assigned to conjugation chain ends indicates that the conjugation length
of this highly ordered polymer is weakly affected by the applied pressure. On the other hand, the absorption
onset and the spectral shape of the vibronic progression are deeply influenced by pressure, which generates a
bathochromic shift joined to a broadening of all the optical transitions. By analyzing the data with a suitable
optical model for an anisotropic system, a significant difference between the optical components polarized
parallel and perpendicular to the stretching direction is observed. For the parallel component, a low energy gain
of the oscillator strength, joined to a correspondent reduction in the high energy spectral range, is observed. For
the perpendicular component, an increase in the oscillator strength is instead observed for all wavelengths.
These effects are mainly assigned to intermolecular interactions even though a contribution from electronphonon
coupling cannot be excluded to explain the observed broadening
- …
