Fluorescence quenching in porous silicon/conjugated polymer composites

Pranculis, Vytenis; Karpicz, Renata; Medvids, Artūrs; Gulbinas, Vidmantas

doi:10.1002/pssa.201127309

Cited by 7 publications

(3 citation statements)

References 34 publications

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“…A sizable “blue shift” (∼10 nm) of the fluorescence maximum has been observed for porous Si as compared to the flat substrate. Similar spectral features were observed for MEH-PPV and other conjugated polymers entrapped in nanoporous structures such as porous silica glass, sol–gel, porous Si, − and self-assembly of silica nanospheres . As a rule, the interpretation of the spectral shift was associated with the change of polymer morphology resulting in the existence of isolated chains (suppression of aggregation) inside nanopores similar to a highly diluted solution.…”

Section: Resultsmentioning

confidence: 99%

Deep Infiltration of Emissive Polymers into Mesoporous Silicon Microcavities: Nanoscale Confinement and Advanced Vapor Sensing

et al. 2013

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We present the study of a nanohybrid composite with superior sensing performance consisting of an emissive sensory polymer infiltrated into a mesoporous Si one-dimensional (1D) photonic crystal with a microcavity (MC). It was found that the critical condition for deep polymer infiltration is the presence of an initial low porosity layer (porosity of 45%) in contrast to shallow infiltration governed by an initial high porosity layer (porosity of 58%). This results in a narrow fluorescence peak (due to deep infiltration) or a spectral "hole" in the fluorescence band (shallow infiltration). Such a unique effect is in agreement with the model based on capillary filling and confirmed by secondary ion mass spectrometry (SIMS) data analyzing the profile of polymer infiltration along the MC depth. In the case of deep infiltration, the characteristic filling length exceeds 2 μm, allowing the polymer to impregnate the MC layer. The infiltrated polymer is spatially confined and exists as quasi-isolated chains without pore clogging as can be concluded from the "blue" spectral shift of up to 10 nm as compared with a nonspatially confined film. Polymer isolation over a large surface area along with sufficient pore openings makes this porous Si (PSi) MC/ polymer nanohybrid an ideal material for gas sensing applications. This is due to the high sensitivity in conjunction with a strong fluorescence signal which is not possible with solid polymer films or bare PSi. These results are confirmed by direct observation of higher sensitivity, enhanced specificity, and partial recovery of the optical signal for the nanohybrid composite upon exposure to trinitrotoluene vapors as compared with a conventional polymer film deposited on a flat substrate.

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Section: Resultsmentioning

confidence: 99%

Deep Infiltration of Emissive Polymers into Mesoporous Silicon Microcavities: Nanoscale Confinement and Advanced Vapor Sensing

et al. 2013

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“…In our recent work we investigated PS/polymer composites and showed that polymers are responsible for the quenching of the "blue" PS fluorescence [24]. In the current publication we address PS/laser dye composites and energy transfer in these systems.…”

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confidence: 99%

Excitation energy transfer in porous silicon/laser dye composites

Pranculis

Šimkienė

Treideris

et al. 2013

Phys. Status Solidi A

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Excited state relaxation and energy transfer in porous silicon (PS)/laser dye [oxazine 1 (Ox1), rhodamine 6G (Rh6G)] composites have been studied by means of steady-state and time-resolved fluorescence. Fluorescence decay kinetics reveals the nonradiative energy transfer from PS to the dye. Increased decay rate of the dye luminescence in the composite indicates that opposite energy transfer is also likely. Analysis of the time-resolved fluorescence of the PS/R6G composite also shows that there is no energy transfer from silicon oxide responsible for the "blue" fluorescence band to silicon nanocrystalites, and that interaction between Si nanocrystals responsible for the "red" PS fluorescence is absent or weak. 1 Introduction Since its discovery, porous silicon (PS) proved to be a non-trivial fluorescent system. Having many different energy levels, each with its own relaxation time and at least two distinct fluorescence mechanisms (surface oxide and Si nanocrystallites) PS is still not fully understood.PS/organic material composites were first investigated few years after the discovery of the visible luminescence of PS. Polymers were spin-coated onto PS in order to produce hybrid LEDs with variable fluorescence spectra [1-3], while laser dye impregnation into the pores was motivated by possible application of such composites in laser physics [4][5][6][7]. One of the key processes in such systems -energy transfer, attracted most of the researcher's attention because of its natural complexity resulting from intricate fluorescence of PS.In 1993 Canham [8] reported impregnation of PS with laser dye in order to get a solid state host for optically active media -a goal of great interest still. In his work Canham examined possible energy transfer in such composites. Since then, driven by possible applications of such materials in optoelectronics, a number of researchers investigated PS/ laser dye composites using different techniques and reported energy transfer from PS to the dye as their main findings [9][10][11][12][13].Time-gated fluorescence of PS reveals two bands -high energy "blue" fluorescence, which is intensive but decays in less than 5 ns, and low energy "red" fluorescence, which is

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“…To overcome these problems, polymer-based composites prepared by introducing Si NCs into the polymer matrices have been developed. [18][19][20][21][22] These polymer matrices could chemically stabilize the Si NCs and prevent their aggregation. Signicantly, the composites showed robust photostability, which is suitable for real applications.…”

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confidence: 99%