| 1. |
- Brooke, Robert, et al.
(författare)
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Infrared electrochromic conducting polymer devices
- 2017
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Ingår i: Journal of Materials Chemistry C. - : The Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 5:23, s. 5824-5830
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Tidskriftsartikel (refereegranskat)abstract
- The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is well known for its electrochromic properties in the visible region. Less focus has been devoted to the infrared (IR) wavelength range, although tunable IR properties could enable a wide range of novel applications. As an example, modern day vehicles have thermal cameras to identify pedestrians and animals in total darkness, but road and speed signs cannot be easily visualized by these imaging systems. IR electrochromism could enable a new generation of dynamic road signs that are compatible with thermal imaging, while simultaneously providing contrast also in the visible region. Here, we present the first metal-free flexible IR electrochromic devices, based on PEDOT:Tosylate as both the electrochromic material and electrodes. Lateral electrochromic devices enabled a detailed investigation of the IR electrochromism of thin PEDOT:Tosylate films, revealing large changes in their thermal signature, with effective temperature changes up to 10 [degree]C between the oxidized (1.5 V) and reduced (-1.5 V) states of the polymer. Larger scale (7 [times] 7 cm) vertical electrochromic devices demonstrate practical suitability and showed effective temperature changes of approximately 7 [degree]C, with good optical memory and fast switching (1.9 s from the oxidized state to the reduced state and 3.3 s for the reversed switching). The results are highly encouraging for using PEDOT:Tosylate for IR electrochromic applications.
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| 2. |
- Brooke, Robert, 1989-, et al.
(författare)
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Infrared electrochromic conducting polymer devices
- 2017
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 5:23, s. 5824-5830
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Tidskriftsartikel (refereegranskat)abstract
- The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is well known for its electrochromic properties in the visible region. Less focus has been devoted to the infrared (IR) wavelength range, although tunable IR properties could enable a wide range of novel applications. As an example, modern day vehicles have thermal cameras to identify pedestrians and animals in total darkness, but road and speed signs cannot be easily visualized by these imaging systems. IR electrochromism could enable a new generation of dynamic road signs that are compatible with thermal imaging, while simultaneously providing contrast also in the visible region. Here, we present the first metal-free flexible IR electrochromic devices, based on PEDOT:Tosylate as both the electrochromic material and electrodes. Lateral electrochromic devices enabled a detailed investigation of the IR electrochromism of thin PEDOT:Tosylate films, revealing large changes in their thermal signature, with effective temperature changes up to 10 °C between the oxidized (1.5 V) and reduced (-1.5 V) states of the polymer. Larger scale (7 × 7 cm) vertical electrochromic devices demonstrate practical suitability and showed effective temperature changes of approximately 7 °C, with good optical memory and fast switching (1.9 s from the oxidized state to the reduced state and 3.3 s for the reversed switching). The results are highly encouraging for using PEDOT:Tosylate for IR electrochromic applications.
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| 3. |
- Gamage, Sampath, et al.
(författare)
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Transparent nanocellulose metamaterial enables controlled optical diffusion and radiative cooling
- 2020
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 8:34, s. 11687-11694
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Tidskriftsartikel (refereegranskat)abstract
- Materials that provide independent control of infrared thermal radiation and haze in the visible could benefit many areas and applications, including clothing, packaging and photovoltaics. Here, we study this possibility for a metamaterial composite paper based on cellulose nanofibrils (CNF) and silicon dioxide (SiO2) microparticles with infrared (IR) Fröhlich phonon resonances. This CNF-SiO2composite shows outstanding transparency in the visible wavelength range, with the option of controlling light diffusion and haze from almost zero to 90% by varying the SiO2microparticle concentration. We further show that the transparent metamaterial paper could maintain high thermal emissivity in the atmospheric IR window, as attributed to strong IR absorption of both the nanocellulose and the resonant SiO2microparticles. The high IR emissivity and low visible absorption make the paper suitable for passive radiative cooling and we demonstrate cooling of the paper to around 3 °C below ambient air temperature by exposing it to the sky.
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| 4. |
- 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
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 5:10, s. 4046-4064
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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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| 5. |
- Sardar, Samim, et al.
(författare)
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Role of Central Metal Ion in Hematoporphyrin-Functionalized Titania in Solar Energy Conversion Dynamics
- 2013
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 15:42, s. 18562-18570
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we have investigated the efficacy of electron transfer processes in hematoporphyrin (HP) and iron hematoporphyrin ((Fe) HP) sensitized titania as potential materials for capturing and storing solar energy. Steady-state and picosecond-resolved fluorescence studies show the efficient photoinduced electron transfer processes in hematoporphyrin-TiO2 (HP-TiO2) and Fe(III)-hematoporphyrin-TiO2 (Fe(III)HP-TiO2) nanohybrids, which reveal the role of central metal ions in electron transfer processes. The bidentate covalent attachment of HP onto TiO2 particulates is confirmed by FTIR, Raman scattering and X-ray photoelectron spectroscopy (XPS) studies. The iron oxidation states and the attachment of iron to porphyrin through pyrrole nitrogen atoms were investigated by cyclic voltammetry and FTIR studies, respectively. We also investigated the potential application of HP-TiO2 and Fe(III)HP-TiO2 nanohybrids for the photodegradation of a model organic pollutant methylene blue (MB) in aqueous solution under wavelength dependent light irradiation. To further investigate the role of iron oxidation states in electron transfer processes, photocurrent measurements were done by using Fe(III) and Fe(II) ions in porphyrin. This work demonstrates the role of central metal ions in fundamental electron transfer processes in porphyrin sensitized titania and their implications for dye-sensitized device performance.
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| 6. |
- Sardar, Samim, et al.
(författare)
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Structural coloration by inkjet-printing of optical microcavities and metasurfaces
- 2019
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 7:28, s. 8698-8704
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Tidskriftsartikel (refereegranskat)abstract
- Structural color generation by plasmonic and other means has attracted significant interest as a solution to avoid inks based on dyes. Prominent advantages include better robustness compared with organic dyes while also providing high chromaticity and brightness in ultrathin films. However, lack of cheap and scalable fabrication techniques has so far limited structural coloration to only a few applications and functional devices. Here, we demonstrate reflective (plasmonic) structural coloration at high resolution by inkjet printing on non-patterned surfaces. The method is flexible, scalable to large areas, and avoids complicated or costly fabrication steps. Optical microcavities on flexible plastic substrates were made starting with an inkjet-printed silver film as a bottom mirror. Inkjet-printed organic dielectric micropixels then served as the spacer layer, resulting in optical microcavities with reflective structural colors after coating with a thin semi-transparent metallic top layer. Optimization of ink formulation allowed for uniform pixels with minimum coffee stain effects as well as control of spacer thickness (around 50-150 nm) and color by varying the solid content of the ink. We investigate the possibility to obtain red, green and blue (RGB) pixels and demonstrate the improvement of particularly the blue coloration using wavelength-dependent plasmon absorption of gold nanoislands as a top mirror. Inkjet printing of optical microcavities and plasmonic cavities may find use in various applications, such as reflective displays in color.
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| 7. |
- Sarkar, Soumik, et al.
(författare)
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Engineering FRET-based solar cells : Manipulation of energy and electron transfer processes in a light harvesting assembly
- 2014
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Ingår i: High-Efficiency Solar Cells. - Cham : American Chemical Society (ACS). ; , s. 267-318
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Bokkapitel (refereegranskat)abstract
- From the prevalent interest in the advancement of renewable energy sources, dye-sensitized solar cells (DSSCs) have emerged as one of the front running prospects due mainly to a constructive balance between cost and efficiency. In this chapter, we will review our works on the utility of using Fo¨rster resonance energy transfer (FRET) in the light harvesting dynamics of zinc oxide (ZnO)-based nanomaterials, which has recently shown promise for significant improvement in various aspects of photoelectrochemical cells. Firstly, we have used ZnO nanoparticles (NPs) and Oxazine 1 as model donor and acceptor, respectively, to investigate the key ultrafast process of FRET in the NP–dye system. The consequence of the energy transfer on the performance of a model ZnO NP-based DSSC has also been explored by using well-known Ruthenium-based sensitizers N719 attached to ZnO NPs offering as an intrinsic co-sensitizer. By using a picosecondresolved FRET technique, we have also demonstrated the role of the gold layer in promoting photoinduced charge transfer from ZnO–Au nanocomposite to a model contaminant methylene blue (MB). Due to the formation of the Schottky barrier at the ZnO–Au interface and the higher optical absorptions of the ZnO–Au photoelectrodes arising from the surface plasmon absorption of the Au NPs, enhanced power-conversion efficiency was achieved compared to bare ZnO-based DSSCs. Finally, potential co-sensitization of extrinsic sensitizer CdTe quantum dots (QDs) in ZnO nanorod (NR)-based DSSCs has been established where we have shown two major pathways by which CdTe QDs may contribute to the net photocurrent in a DSSC: (1) a direct injection of charge carriers from QDs to ZnO semiconductor via photoinduced electron transfer (PET) and (2) an indirect excitation of the sensitizing dye N719 molecules by funneling harvested light via FRET. Based on these advantages, the short-circuit current density and the photoconductivity of the QD-assembled DSSCs with distinct architectures are found to be much higher than DSSCs fabricated with N719 sensitizer only. As demonstrated, the multipath enhancement offered in this device architecture results in an increased and extended photo-response with respect to the individual materials employed. Further engineering of suitable donor acceptor pairs and optimization of charge separation in conjugated molecular blends has the potential to become a continuing avenue toward enhancing hybrid DSSC efficiencies.
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| 8. |
- 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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| 9. |
- Ul Hassan Alvi, Naveed, et al.
(författare)
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Toward Photoactive Wallpapers Based on ZnO-Cellulose Nanocomposites
- 2023
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Ingår i: Global Challenges. - : WILEY-V C H VERLAG GMBH. - 2056-6646. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- The quest for eco-friendly materials with anticipated positive impact for sustainability is crucial to achieve the UN sustainable development goals. Classical strategies of composite materials can be applied on novel nanomaterials and green materials. Besides the actual technology and applications also processing and manufacturing methods should be further advanced to make entire technology concepts sustainable. Here, they show an efficient way to combine two low-cost materials, cellulose and zinc oxide (ZnO), to achieve novel functional and "green" materials via paper-making processes. While cellulose is the most abundant and cost-effective organic material extractable from nature. ZnO is cheap and known of its photocatalytic, antibacterial, and UV absorption properties. ZnO nanowires are grown directly onto cellulose fibers in water solutions and then dewatered in a process mimicking existing steps of large-scale papermaking technology. The ZnO NW paper exhibits excellent photo-conducting properties under simulated sunlight with good ON/OFF switching and long-term stability (90 minutes). It also acts as an efficient photocatalyst for hydrogen peroxide (H2O2) generation (5.7 x 10(-9) m s(-1)) with an envision the possibility of using it in buildings to enable large surfaces to spontaneously produce H2O2 at its outer surface. Such technology promise for fast degradation of microorganisms to suppress the spreading of diseases.
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