| 1. |
- Beal, Jacob, et al.
(författare)
-
Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Banerjee, Debashree, et al.
(författare)
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Electrical tuning of radiative cooling at ambient conditions
- 2023
-
Ingår i: Cell Reports Physical Science. - : ELSEVIER. - 2666-3864. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Passive radiative cooling forms a sustainable means for cooling of objects through thermal radiation. Along with progress on static cooling systems, there is an emerging need for dynamic control to enable thermoregulation. Here, we demonstrate temperature regu-lation of devices at ambient pressure and temperature by electri-cally tuning their radiative cooling power. Our concept exploits the possibility to electrochemically tune the thermal emissivity and thereby cooling power of a conducting polymer, which enabled reversible control of device temperatures of around 0.25 degrees C at ambient conditions in a sky simulator. Besides tuneable radiative cooling by exposure to the sky, the concept could also contribute to reduced needs for indoor climate control by enabling dynamic control of thermal energy flows between indoor objects, such as be-tween people and walls.
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| 3. |
- Chen, Shangzhi, et al.
(författare)
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Conductive polymer nanoantennas for dynamic organic plasmonics
- 2020
-
Ingår i: Nature Nanotechnology. - London : Nature Publishing Group. - 1748-3387 .- 1748-3395. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- Being able to dynamically shape light at the nanoscale is oneof the ultimate goals in nano-optics1. Resonant light–matterinteraction can be achieved using conventional plasmonicsbased on metal nanostructures, but their tunability is highlylimited due to a fixed permittivity2. Materials with switchablestates and methods for dynamic control of light–matterinteraction at the nanoscale are therefore desired. Here weshow that nanodisks of a conductive polymer can supportlocalized surface plasmon resonances in the near-infraredand function as dynamic nano-optical antennas, with their resonancebehaviour tunable by chemical redox reactions. Theseplasmons originate from the mobile polaronic charge carriersof a poly(3,4-ethylenedioxythiophene:sulfate) (PEDOT:Sulf)polymer network. We demonstrate complete and reversibleswitching of the optical response of the nanoantennasby chemical tuning of their redox state, which modulatesthe material permittivity between plasmonic and dielectricregimes via non-volatile changes in the mobile chargecarrier density. Further research may study different conductivepolymers and nanostructures and explore their usein various applications, such as dynamic meta-optics andreflective displays.
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| 4. |
- Chen, Shangzhi, et al.
(författare)
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Dynamic Conducting Polymer Plasmonics and Metasurfaces
- 2023
-
Ingår i: ACS Photonics. - : AMER CHEMICAL SOC. - 2330-4022. ; 10:3, s. 571-581
-
Tidskriftsartikel (refereegranskat)abstract
- Metals have been the dominant plasmonic materials for decades, but they suffer from limited tunability. By contrast, conducting polymers offer exceptional tunability and were recently introduced as a new category of dynamic plasmonic materials. Their charge carrier density can be drastically modulated via their redox state, offering reversible and gradual transitions between optically metallic and dielectric behavior. Nanoantennas made from conducting polymers can therefore be reversibly turned off and on again. This enables phase gradient metasurfaces with tunable functionalities, holding promise for applications such as video holograms. In this Perspective, we discuss the emergence of dynamic conducting polymer plasmonics as a new research direction, including recent developments, remaining challenges, and opportunities for future research. We hope that this Perspective will encourage more researchers to join the journey and contribute toward a rapid development of this interdisciplinary field.
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| 5. |
- Chen, Shangzhi, et al.
(författare)
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Dynamic plasmonics based on conducting polymers
- 2023
-
Ingår i: International Conference on Metamaterials, Photonic Crystals and Plasmonics. - : META Conference. ; , s. 571-571
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Plasmonics based on conventional metals are broadly used for biosensing and optoelectronic devices, but suffer from limited optical tunability. We recently demonstrated conducting polymers as a new category of plasmonic materials exhibiting excellent optical tunability. In this talk, I will briefly introduce the emergence, current status, and future prospects of using conducting polymers for dynamic plasmonics.
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| 6. |
- Chen, Shangzhi, et al.
(författare)
-
On the anomalous optical conductivity dispersion of electrically conducting polymers : Ultra-wide spectral range ellipsometry combined with a Drude-Lorentz model
- 2019
-
Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 7:15, s. 4350-4362
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically conducting polymers (ECPs) are becoming increasingly important in areas such as optoelectronics, biomedical devices, and energy systems. Still, their detailed charge transport properties produce an anomalous optical conductivity dispersion that is not yet fully understood in terms of physical model equations for the broad range optical response. Several modifications to the classical Drude model have been proposed to account for a strong non-Drude behavior from terahertz (THz) to infrared (IR) ranges, typically by implementing negative amplitude oscillator functions to the model dielectric function that effectively reduce the conductivity in those ranges. Here we present an alternative description that modifies the Drude model via addition of positive-amplitude Lorentz oscillator functions. We evaluate this so-called Drude-Lorentz (DL) model based on the first ultra-wide spectral range ellipsometry study of ECPs, spanning over four orders of magnitude: from 0.41 meV in the THz range to 5.90 eV in the ultraviolet range, using thin films of poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:Tos) as a model system. The model could accurately fit the experimental data in the whole ultrawide spectral range and provide the complex anisotropic optical conductivity of the material. Examining the resonance frequencies and widths of the Lorentz oscillators reveals that both spectrally narrow vibrational resonances and broader resonances due to localization processes contribute significantly to the deviation from the Drude optical conductivity dispersion. As verified by independent electrical measurements, the DL model accurately determines the electrical properties of the thin film, including DC conductivity, charge density, and (anisotropic) mobility. The ellipsometric method combined with the DL model may thereby become an effective and reliable tool in determining both optical and electrical properties of ECPs, indicating its future potential as a contact-free alternative to traditional electrical characterization.
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| 7. |
- Chen, Shangzhi
(författare)
-
Optics of Conducting Polymer Thin Films and Nanostructures
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intrinsically conducting polymers forms a category of doped conjugated polymers that can conduct electricity. Since their discovery in the late 1970s, they have been widely applied in many fields, ranging from optoelectronic devices to biosensors. The most common type of conducting polymers is poly(3,4-ethylenedioxythiophene), or PEDOT. PEDOT has been popularly used as electrodes for solar cells or light-emitting diodes, as channels for organic electrochemical transistors, and as p-type legs for organic thermoelectric generators. Although many studies have been dedicated to PEDOT-based materials, there has been a lack of a unified model to describe their optical properties across different spectral ranges. In addition, the interesting optical properties of PEDOT-based materials, benefiting from its semi-metallic character, have only been rarely studied and utilized, and could potentially enable new applications.Plasmonics is a research field focusing on interactions between light and metals, such as the noble metals (gold and silver). It has enabled various opportunities in fundamental photonics as well as practical applications, varying from biosensors to colour displays. This thesis explores highly conducting polymers as alternatives to noble metals and as a new type of active plasmonic materials. Despite high degrees of microstructural disorder, conducting polymers can possess electrical conductivity approaching that of poor metals, with particularly high conductivity for PEDOT deposited via vapour phase polymerization (VPP). In this thesis, we systematically studied the optical and structural properties of VPP PEDOT thin films and their nanostructures for plasmonics and other optical applications. We employed ultra-wide spectral range ellipsometry to characterize thin VPP PEDOT films and proposed an anisotropic Drude-Lorentz model to describe their optical conductivity, covering the ultraviolet, visible, infrared, and terahertz ranges. Based on this model, PEDOT doped with tosylate (PEDOT:Tos) presented negative real permittivity in the near infrared range. While this indicated optical metallic character, the material also showed comparably large imaginary permittivity and associated losses. To better understand the VPP process, we carefully examined films with a collection of microstructural and spectroscopic characterization methods and found a vertical layer stratification in these polymer films. We unveiled the cause as related to unbalanced transport of polymerization precursors. By selection of suitable counterions, e.g., trifluoromethane sulfonate (OTf), and optimization of reaction conditions, we were able to obtain PEDOT films with electrical conductivity exceeding 5000 S/cm. In the near infrared range from 1 to 5 µm, these PEDOT:OTf films provided a well-defined plasmonic regime, characterized by negative real permittivity and lower magnitude imaginary component. Using a colloidal lithography-based approach, we managed to fabricate nanodisks of PEDOT:OTf and showed that they exhibited clear plasmonic absorption features. The experimental results matched theoretical calculations and numerical simulations. Benefiting from their mixed ionic-electronic conducting characters, such organic plasmonic materials possess redox-tunable properties that make them promising as tuneable optical nanoantennas for spatiotemporally dynamic systems. Finally, we presented a low-cost and efficient method to create structural colour surfaces and images based on UV-treated PEDOT films on metallic mirrors. The concept generates beautiful and vivid colours through-out the visible range utilizing a synergistic effect of simultaneously modulating polymer absorption and film thickness. The simplicity of the device structure, facile fabrication process, and tunability make this proof-of-concept device a potential candidate for future low-cost backlight-free displays and labels.
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| 8. |
- Chen, Shangzhi, et al.
(författare)
-
Redox-tunable structural colour images by UV-patterned conducting polymer nanofilms on metal surfaces
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Precise manipulation of light-matter interaction has enabled a wide variety of approaches to create bright and vivid structural colours. Techniques utilizing photonic crystals, Fabry-Pérot cavities, plasmonics, or high-refractive index dielectric metasurfaces have been studied for applications ranging from optical coatings to reflective displays. However, complicated fabrication procedures for sub-wavelength nanostructures, limited active areas, and inherent absence of tunability of these approaches significantly impede their further development towards flexible, large-scale, and switchable devices compatible with facile and cost-effective production. Herein, we present a simple and efficient method to generate structural colours based on nanoscale conducting polymer films prepared on metallic surfaces via vapour phase polymerization and ultraviolet (UV) light patterning. Varying the UV dose enables synergistic control of both nanoscale film thickness and polymer permittivity, which generates controllable colours from violet to red. Together with greyscale photomasks this enables fabrication of high-resolution colour images using single exposure steps. We further demonstrate spatiotemporal tuning of the structurally coloured surfaces and images via electrochemical modulation of the polymer redox state. The simple structure, facile fabrication, wide colour gamut, and dynamic colour tuning make this concept competitive for future multi-functional and smart displays.
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| 9. |
- Chen, Shangzhi, et al.
(författare)
-
Tunable Structural Color Images by UV-Patterned Conducting Polymer Nanofilms on Metal Surfaces.
- 2021
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 33:33
-
Tidskriftsartikel (refereegranskat)abstract
- Precise manipulation of light-matter interactions has enabled a wide variety of approaches to create bright and vivid structural colors. Techniques utilizing photonic crystals, Fabry-Pérot cavities, plasmonics, or high-refractive-index dielectric metasurfaces have been studied for applications ranging from optical coatings to reflective displays. However, complicated fabrication procedures for sub-wavelength nanostructures, limited active areas, and inherent absence of tunability of these approaches impede their further development toward flexible, large-scale, and switchable devices compatible with facile and cost-effective production. Here, a novel method is presented to generate structural color images based on monochromic conducting polymer films prepared on metallic surfaces via vapor phase polymerization and ultraviolet (UV) light patterning. Varying the UV dose enables synergistic control of both nanoscale film thickness and polymer permittivity, which generates controllable structural colors from violet to red. Together with grayscale photomasks this enables facile fabrication of high-resolution structural color images. Dynamic tuning of colored surfaces and images via electrochemical modulation of the polymer redox state is further demonstrated. The simple structure, facile fabrication, wide color gamut, and dynamic color tuning make this concept competitive for applications like multifunctional displays.
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| 10. |
- Chen, Shangzhi, et al.
(författare)
-
Unraveling vertical inhomogeneity in vapour phase polymerized PEDOT:Tos films
- 2020
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 8, s. 18726-18734
-
Tidskriftsartikel (refereegranskat)abstract
- The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) forms a promising alternative to conventional inorganic conductors, where deposition of thin films via vapour phase polymerization (VPP) has gained particular interest owing to high electrical conductivity within the plane of the film. The conductivity perpendicular to the film is typically much lower, which may be related not only to preferential alignment of PEDOT crystallites but also to vertical stratification across the film. In this study, we reveal non-linear vertical microstructural variations across VPP PEDOT:Tos thin films, as well as significant differences in doping level between the top and bottom surfaces. The results are consistent with a VPP mechanism based on diffusion-limited transport of polymerization precursors. Conducting polymer films with vertical inhomogeneity may find applications in gradient-index optics, functionally graded thermoelectrics, and optoelectronic devices requiring gradient doping.
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| 11. |
- Chen, Shangzhi, et al.
(författare)
-
Unraveling vertical inhomogeneity in vapour phase polymerized PEDOT:Tos films
- 2020
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 8:36, s. 18726-18734
-
Tidskriftsartikel (refereegranskat)abstract
- The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) forms a promising alternative to conventional inorganic conductors, where deposition of thin filmsviavapour phase polymerization (VPP) has gained particular interest owing to high electrical conductivity within the plane of the film. The conductivity perpendicular to the film is typically much lower, which may be related not only to preferential alignment of PEDOT crystallites but also to vertical stratification across the film. In this study, we reveal non-linear vertical microstructural variations across VPP PEDOT:Tos thin films, as well as significant differences in doping level between the top and bottom surfaces. The results are consistent with a VPP mechanism based on diffusion-limited transport of polymerization precursors. Conducting polymer films with vertical inhomogeneity may find applications in gradient-index optics, functionally graded thermoelectrics, and optoelectronic devices requiring gradient doping.
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| 12. |
- Duan, Yulong, et al.
(författare)
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Tuneable Anisotropic Plasmonics with Shape-Symmetric Conducting Polymer Nanoantennas
- 2023
-
Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095.
-
Tidskriftsartikel (refereegranskat)abstract
- A wide range of nanophotonic applications rely on polarization-dependent plasmonic resonances, which usually requires metallic nanostructures that have anisotropic shape. This work demonstrates polarization-dependent plasmonic resonances instead by breaking symmetry via material permittivity. The study shows that molecular alignment of a conducting polymer can lead to a material with polarization-dependent plasma frequency and corresponding in-plane hyperbolic permittivity region. This result is not expected based only on anisotropic charge mobility but implies that also the effective mass of the charge carriers becomes anisotropic upon polymer alignment. This unique feature is used to demonstrate circularly symmetric nanoantennas that provide different plasmonic resonances parallel and perpendicular to the alignment direction. The nanoantennas are further tuneable via the redox state of the polymer. Importantly, polymer alignment could blueshift the plasma wavelength and resonances by several hundreds of nanometers, forming a novel approach toward reaching the ultimate goal of redox-tunable conducting polymer nanoantennas for visible light. Traditional anisotropic nanoantennas have asymmetric shape. In this work, symmetry is instead broken by straining of a conducting polymer, leading to an in-plane anisotropic plasma frequency. This enables circularly symmetric nanoantennas with polarization-dependent localized surface plasmon resonances. The polarization dependence is consistent with inverse changes of the effective mass and mobility of thecharge carriers along different in-plane directions.image
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| 13. |
- Han, Shaobo, et al.
(författare)
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Insulating polymers for flexible thermoelectric composites: A multi-perspective review
- 2021
-
Ingår i: COMPOSITES COMMUNICATIONS. - : ELSEVIER SCI LTD. - 2452-2139. ; 28
-
Tidskriftsartikel (refereegranskat)abstract
- The explosive development of wearable electronic devices places new requirements on the flexibility of component materials. As one of the key energy harvesting sources for wearable electronic devices, thermoelectric (TE) generators convert waste heat into electric energy and can operate without producing any noise or requiring any external stimuli (e.g., light, or mechanical motion). However, conventional materials developed for TE possess very limited flexibility and their performances remain low towards practical applications. TE composites represent an effective way to "reshape" the properties of the pristine materials further enhancing their performances. Among various fillers for TE composites, insulating polymers are now becoming one of the promising candidates since they possess excellent flexibility and could efficiently decouple the dependence between electrical conductivity, Seebeck coefficient, and thermal conductivity. Currently, there is a relatively limited knowledge of this new category of TE composites and lots of research progress on them have already demonstrated their potentials for practical applications. In this review, we will discuss this new type of TE composites from a unique perspective and attempt to summarize the basic properties, design rules, and the latest research progresses on them. A brief discussion on their potential applications, remaining challenges, and future prospects will also be included in the last section.
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| 14. |
- Kang, Evan, et al.
(författare)
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Charge transport in phthalocyanine thin-film transistors coupled with Fabry-Perot cavities
- 2021
-
Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 9:7, s. 2368-2374
-
Tidskriftsartikel (refereegranskat)abstract
- Strong light-matter coupling can form hybrid states at new energy levels that share properties of both light and matter. This principle offers new routes to control material functions without modifying the chemical structure of molecules. In this work, we coupled ambipolar semiconducting thin films to a Fabry-Perot cavity and investigated effects on charge transport. By constructing thin-film transistors inside optical cavities, we could simultaneously study coupling features and charge transport in the same samples. The cavity resonance was detuned by controlling the thickness of the top spacer layer in the cavity. We found no significant influence on charge transport for our systems, which may be related to insufficiently strong coupling. Possible additional origins and future directions are also discussed.
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| 15. |
- Kang, Evan S. H., et al.
(författare)
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Organic Anisotropic Excitonic Optical Nanoantennas
- 2022
-
Ingår i: Advanced Science. - : Wiley. - 2198-3844 .- 2198-3844. ; 9:23
-
Tidskriftsartikel (refereegranskat)abstract
- Optical nanoantennas provide control of light at the nanoscale, which makes them important for diverse areas ranging from photocatalysis and flat metaoptics to sensors and biomolecular tweezing. They have traditionally been limited to metallic and dielectric nanostructures that sustain plasmonic and Mie resonances, respectively. More recently, nanostructures of organic J-aggregate excitonic materials have been proposed capable of also supporting nanooptical resonances, although their advance has been hampered from difficulty in nanostructuring. Here, the authors present the realization of organic J-aggregate excitonic nanostructures, using nanocylinder arrays as model system. Extinction spectra show that they can sustain both plasmon-like resonances and dielectric resonances, owing to the material providing negative and large positive permittivity regions at the different sides of its exciton resonance. Furthermore, it is found that the material is highly anisotropic, leading to hyperbolic and elliptic permittivity regions. Nearfield analysis using optical simulation reveals that the nanostructures therefore support hyperbolic localized surface exciton resonances and elliptic Mie resonances, neither of which has been previously demonstrated for this type of material. The anisotropic nanostructures form a new type of optical nanoantennas, which combined with the presented fabrication process opens up for applications such as fully organic excitonic metasurfaces.
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| 16. |
- Kang, Evan S. H., et al.
(författare)
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Strong Plasmon-Exciton Coupling with Directional Absorption Features in Optically Thin Hybrid Nanohole Metasurfaces
- 2018
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 5:10, s. 4046-4064
-
Tidskriftsartikel (refereegranskat)abstract
- Plasmons and excitons can interact to form new hybridized light-matter states, with a multitude of potential applications including optical logic circuits and single-photon switches. Here, we report the first observation of strong coupling based on optically thin plasmonic nanohole films. The absorptive plasmon resonances of these nanohole films lead to suppressed transmission and Fano-shaped extinction peaks. We prepared silver nanohole films by colloidal lithography, which enables large-scale fabrication of nanoholes distributed in a short-range order. When coated with J-aggregate molecules, both extinction and absorption spectra show clear formation of two separated polariton resonances, with vacuum Rabi splitting on the order of 300 meV determined from anticrossing experiments. In accordance with strong coupling theory, the splitting magnitude increases linearly with the square root of molecular concentration. The extinction peak positions are blue-shifted from the absorption polariton positions, as explained by additional Fano interference between the hybridized states and the metal film. This highlights that absorption measurements are important not only to prove strong coupling but also to correctly determine hybridized polariton positions and splitting magnitudes in hybrid plasmonic nanohole systems. The polariton absorption peaks also show strong dependence on illumination direction, as found related to inherent directionality of the plasmonic nanohole metasurface and differences in light interaction with nonhybridized molecules. Importantly, optical simulations could successfully reproduce the experimental results and all coupling features. Furthermore, simulated spatial distribution of the absorption provides additional evidence of strong coupling in the hybrid nanohole system. The work paves the way toward strong coupling applications based on optically thin nanohole systems, as further promoted by the scalable fabrication.
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| 17. |
- Karki, Akchheta, et al.
(författare)
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Doped semiconducting polymer nanoantennas for tunable organic plasmonics
- 2022
-
Ingår i: Communications Materials. - : Springer Nature. - 2662-4443. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Optical nanoantennas based on organic plasmonics are promising for their higher degree of tunability over metallic nanostructures. Here, nanodisks of polythiophene-based semiconducting polymers provide nanooptical antennas with resonances that are tunable over a 1000 nm wavelength range and can be switched off or on by doping modulation. Optical nanoantennas are often based on plasmonic resonances in metal nanostructures, but their dynamic tunability is limited due to the fixed permittivity of conventional metals. Recently, we introduced PEDOT-based conducting polymers as an alternative materials platform for dynamic plasmonics and metasurfaces. Here, we expand dynamic organic plasmonic systems to a wider class of doped polythiophene-based semiconducting polymers. We present nanodisks of PBTTT semiconducting polymer doped with a dicationic salt, enabling a high doping level of around 0.8 charges per monomer, and demonstrate that they can be used as nanooptical antennas via redox-tunable plasmonic resonances. The resonances arise from the polymer being optically metallic in its doped state and dielectric in its non-conducting undoped state. The plasmonic resonances are controllable over a 1000 nm wavelength range by changing the dimensions of the nanodisks. Furthermore, the optical response of the nanoantennas can be reversibly tuned by modulating the doping level of the polymer. Simulations corroborate the experimental results and reveal the possibility to also modulate the optical nearfield response of the nanoantennas.
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| 18. |
- Karki, Akchheta, et al.
(författare)
-
Electrical Tuning of Plasmonic Conducting Polymer Nanoantennas
- 2022
-
Ingår i: Advanced Materials. - : Wiley. - 1521-4095 .- 0935-9648. ; 34:13
-
Tidskriftsartikel (refereegranskat)abstract
- Nanostructures of conventional metals offer manipulation of light at the nanoscale but are largely limited to static behavior due to fixed material properties. To develop the next frontier of dynamic nano-optics and metasurfaces, this study utilizes the redox-tunable optical properties of conducting polymers, as recently shown to be capable of sustaining plasmons in their most conducting oxidized state. Electrically tunable conducting polymer nano-optical antennas are presented, using nanodisks of poly(3,4-ethylenedioxythiophene:sulfate) (PEDOT:Sulf) as a model system. In addition to repeated on/off switching of the polymeric nanoantennas, the concept enables gradual electrical tuning of the nano-optical response, which was found to be related to the modulation of both density and mobility of the mobile polaronic charge carriers in the polymer. The resonance position of the PEDOT:Sulf nanoantennas can be conveniently controlled by disk size, here reported down to a wavelength of around 1270 nm. The presented concept may be used for electrically tunable metasurfaces, with tunable farfield as well as nearfield. The work thereby opens for applications ranging from tunable flat meta-optics to adaptable smart windows.
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| 19. |
- Kim, Nara, 1985-, et al.
(författare)
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Electric transport properties in PEDOT thin films
- 2019. - 4
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Ingår i: Conjugated polymers. - Boca Raton : CRC Press. - 9780429190520 ; , s. 45-128
-
Bokkapitel (refereegranskat)abstract
- In this chapter, the authors summarize their understanding of Poly(3,4-ethylenedioxythiophene) (PEDOT), with respect to its chemical and physical fundamentals. They focus upon the structure of several PEDOT systems, from the angstrom level and up, and the impact on both electronic and ionic transport. The authors discuss the structural properties of PEDOT:X and PEDOT:poly(styrenesulfonate) based on experimental data probed at the scale ranging from angstrom to submicrometer. The morphology of PEDOT is influenced by the nature of counter-ions, especially at high oxidation levels. The doping anions intercalate between PEDOT chains to form a “sandwich” structure to screen the positive charges in PEDOT chains. The authors provide the main transport coefficients such as electrical conductivity s, Seebeck coefficient S, and Peltier coefficient σ, starting from a general thermodynamic consideration. The optical conductivity of PEDOT has also been examined based on the effective medium approximation, which is normally used to describe microscopic permittivity properties of composites made from several different constituents.
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| 20. |
- Kuang, Chaoyang, et al.
(författare)
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Switchable Broadband Terahertz Absorbers Based on Conducting Polymer-Cellulose Aerogels
- 2023
-
Ingår i: Advanced Science. - : WILEY. - 2198-3844.
-
Tidskriftsartikel (refereegranskat)abstract
- Terahertz (THz) technologies provide opportunities ranging from calibration targets for satellites and telescopes to communication devices and biomedical imaging systems. A main component will be broadband THz absorbers with switchability. However, optically switchable materials in THz are scarce and their modulation is mostly available at narrow bandwidths. Realizing materials with large and broadband modulation in absorption or transmission forms a critical challenge. This study demonstrates that conducting polymer-cellulose aerogels can provide modulation of broadband THz light with large modulation range from ≈ 13% to 91% absolute transmission, while maintaining specular reflection loss < −30 dB. The exceptional THz modulation is associated with the anomalous optical conductivity peak of conducting polymers, which enhances the absorption in its oxidized state. The study also demonstrates the possibility to reduce the surface hydrophilicity by simple chemical modifications, and shows that broadband absorption of the aerogels at optical frequencies enables de-frosting by solar-induced heating. These low-cost, aqueous solution-processable, sustainable, and bio-friendly aerogels may find use in next-generation intelligent THz devices.
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| 21. |
- Lee, Seunghyun, et al.
(författare)
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Plasmonic polymer nanoantenna arrays for electrically tunable and electrode-free metasurfaces
- 2023
-
Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 11:40, s. 21569-21576
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically tunable metasurfaces and interrelated nanofabrication techniques are essential for metasurface-based optoelectronic applications. We present a nanofabrication method suitable for various types of plasmonic polymer metasurfaces including inverted arrays of nanoantennas. Inverted metasurfaces are of particular interest since the metasurface itself can work as an electrode due to its interconnected nature, which enables electrical control without adopting an additional electrode. In comparison with inverted nanodisk arrays that support relatively weak resonance features, we show that inverted nanorod arrays can possess stronger resonances, even comparable with those of nanorod arrays. The origin of plasmon resonances in inverted arrays is systematically investigated using finite-difference time-domain (FDTD) simulations. Further, we demonstrate electrically tunable electrode-free metasurface devices using polymer inverted nanorod arrays, which can operate in the full spectral range of the material including the mid-infrared region. Electrically tunable and electrode-free metasurfaces using plasmonic polymer inverted nanoantenna arrays can operate across the entire spectral range of the material, including the mid-infrared region.
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| 22. |
- Rossi, Stefano, et al.
(författare)
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Dynamically Tuneable Reflective Structural Coloration with Electroactive Conducting Polymer Nanocavities
- 2021
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 33:49
-
Tidskriftsartikel (refereegranskat)abstract
- Dynamic control of structural colors across the visible spectrum with high brightness has proven to be a difficult challenge. Here, this is addressed with a tuneable reflective nano-optical cavity that uses an electroactive conducting polymer (poly(thieno[3,4-b]thiophene)) as spacer layer. Electrochemical doping and dedoping of the polymer spacer layer provides reversible tuning of the cavity's structural color throughout the entire visible range and beyond. Furthermore, the cavity provides high peak reflectance that varies only slightly between the reduced and oxidized states of the polymer. The results indicate that the polymer undergoes large reversible thickness changes upon redox tuning, aided by changes in optical properties and low visible absorption. The electroactive cavity concept may find particular use in reflective displays, by opening for tuneable monopixels that eliminate limitations in brightness of traditional subpixel-based systems.
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| 23. |
- Shanker, Ravi, et al.
(författare)
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Noniridescent Biomimetic Photonic Microdomes by Inkjet Printing
- 2020
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Ingår i: Nano letters (Print). - : AMER CHEMICAL SOC. - 1530-6984 .- 1530-6992. ; 20:10, s. 7243-7250
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Tidskriftsartikel (refereegranskat)abstract
- Certain bird species have evolved spectacular colors that arise from organized nanostructures of melanin. Its high refractive index (similar to 1.8) and broadband absorptive properties enable vivid structural colors that are nonsusceptible to photo-bleaching. Mimicking natural melanin structural coloration could enable several important applications, in particular, for non-iridescent systems with colors that are independent of incidence angle. Here, we address this by forming melanin photonic crystal microdomes by inkjet printing. Owing to their curved nature, the microdomes exhibit noniridescent vivid structural coloration, tunable throughout the visible range via the size of the nanoparticles. Large-area arrays (>1 cm(2)) of high-quality photonic microdomes could be printed on both rigid and flexible substrates. Combined with scalable fabrication and the nontoxicity of melanin, the presented photonic microdomes with noniridescent structural coloration may find use in a variety of applications, including sensing, displays, and anticounterfeit holograms.
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| 24. |
- Sun, Xiao, et al.
(författare)
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Gradient-Reduced Graphene Oxide Aerogel with Ultrabroadband Absorption from Microwave to Terahertz Bands
- 2023
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Ingår i: ACS Applied Nano Materials. - : AMER CHEMICAL SOC. - 2574-0970.
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Tidskriftsartikel (refereegranskat)abstract
- Ultrabroadband electromagnetic (EM) absorbers, especially those covering microwave to terahertz (THz) bands, are urgently desired in multispectral applications such as 6G communication, radar stealth, atmospheric remote sensing, and radio astronomy. Here, we demonstrate that chemically reduced graphene oxide aerogels can be designed as an excellent absorber with the features of ultrabroadband, light weight, compressibility, and high-temperature resistance. This magnetic-free pyramidal absorber shows remarkably broad qualified absorption bandwidth from 4.7 GHz to 4 THz, with reflection loss < -20 dB in the microwave and < -40 dB in the THz band. Especially, an unprecedentedly excellent average absorption intensity of -53.9 dB (absorptivity over 99.999%) is obtained in the frequency range from 0.5 to 4 THz. We experimentally clarify that the gradient macrostructure together with the porous microstructure underlies the continuous impedance matching in such a large frequency range spanning about 3 orders of magnitude and leads to the consecutive strong EM absorption from microwave to terahertz. We believe that this absorber will offer multifunctional and multispectral applications in many scientific and technological fields.
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| 25. |
- Yao, Nannan, 1992-, et al.
(författare)
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Solution-Processed Highly Efficient Semitransparent Organic Solar Cells with Low Donor Contents
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society. - 2574-0962. ; 4:12, s. 14335-14341
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Tidskriftsartikel (refereegranskat)abstract
- Semitransparent organic solar cells (ST-OSCs) are promising candidates for applications in building-integrated photovoltaics (BIPV) as windows and facades. The challenge to achieve highly efficient ST-OSCs is the trade-off between power conversion efficiency (PCE) and average visible transmittance (AVT). Herein, solution-processed ST-OSCs are demonstrated on the basis a polymer donor, PM6, and a small molecule acceptor, Y6; lowering the visible-absorbing PM6 contents in blends could increase AVT and maintain PCE. Additionally, conductive polymer PEDOT:PSS is used as the top electrode due to its high transparency, good conductivity, and solution processability. Efficient ST-OSCs with 20 wt % PM6 achieve high PCE of 7.46% and AVT of 36.4%. The light utilization efficiency (LUE) of 2.72% is among the best reported values for solution-processed ST-OSCs. This work provides a straightforward approach for solution-processed ST-OSCs by combining a low fraction of visible-wavelength-selective polymer donors with near-infrared nonfullerene acceptors to achieve high PCE and AVT simultaneously.
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