Nanostructured gold has attracted significant interest from materials science, chemistry, optics and photonics, and biology due to their extraordinary potential for manipulating visible and ...near‐infrared light through the excitation of plasmon resonances. However, gold nanostructures are rarely measured experimentally in their plasmonic properties and hardly used for high‐temperature applications because of the inherent instability in mass and shape due to the high surface energy at elevated temperatures. In this work, the first direct observation of thermally excited surface plasmons in gold nanorods at 1100 K is demonstrated. By coupling with an optical fiber in the near‐field, the thermally excited surface plasmons from gold nanorods can be converted into the propagating modes in the optical fiber and experimentally characterized in a remote manner. This fiber‐coupled technique can effectively characterize the near‐field thermoplasmonic emission from gold nanorods. A direct simulation scheme is also developed to quantitively understand the thermal emission from the array of gold nanorods. The experimental work in conjunction with the direct simulation results paves the way of using gold nanostructures as high‐temperature plasmonic nanomaterials, which has important implications in thermal energy conversion, thermal emission control, and chemical sensing.
Thermoplasmonic emission of gold nanorods (GNRs) is studied at temperatures up to 1100 K. GNRs are confined in nanopore channels of an anodic aluminum oxide (AAO) layer coupled with an optical fiber in order to preserve their shapes and measure their thermal emission at a remote distance. Direct simulation is also performed to understand the thermal emission from GNR arrays.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Sensing technologies based on plasmonic nanomaterials are of interest for various chemical, biological, environmental, and medical applications. In this work, w e report an incorporation strategy of ...colloidal plasmonic nanoparticles (pNPs) in microporous polymer for realizing distinct sorption-induced plasmonic sensing. This approach is demonstrated by introducing tin-doped indium oxide pNPs into a polymer with intrinsic microporosity (PIM-1). The composite film (pNPs-polymer) provides distinct and tunable optical features on the fiber optic (FO) platform that can be used as a signal transducer for gas sensing (e.g., CO
) under atmospheric conditions. The resulting pNPs-polymer composite demonstrates high sensitivity response on FO in the evanescent field configuration, provided by the dramatic response of modes above the total-internal-reflection angle. Furthermore, by varying the pNPs content in the polymer matrix, the optical behavior of the pNPs-polymer composite can be tuned to affect the operational wavelength by over several hundred nanometers and the sensitivity of the sensor in the near-infrared range. W e also show that the pNPs-polymer composite film exhibits remarkable stability, over a period of more than ten months, by mitigating the physical aging issue of the polymer. This article is protected by copyright. All rights reserved.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Despite significant advantages in terms of portability and cost, near-infrared (NIR) gas sensing still remains a great challenge due to its relatively weak overtone absorption from the fundamental ...vibrational bond absorption at the mid-IR frequency. In this paper, we demonstrated ultra-sensitive NIR gas sensing for carbon dioxide (CO2) at 1.57μm wavelength through nanoporous Cu-BTC (BTC=benzene-1,3,5-tricarboxylate) metal-organic framework (MOF) coated single-mode optical fiber. For the first time, we obtained high-resolution NIR spectroscopy of CO2 sorbed in MOF without seeing any rotational side band, indicating that the tightly confined gas molecules in the MOF pores do not have any freedom of rotation. Real-time measurement of the mixed gas flow of CO2 and Ar showed different response time depending on the concentration of CO2, which is attributed to the complex sorption mechanism of CO2 in Cu-BTC MOF. Most importantly, we realized ultra-low detection limit of CO2 (<20ppm) with only 5cm long Cu-BTC MOF thin film coated on single-mode optical fibers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Metal–organic framework (MOF)-based chemical sensors have recently been demonstrated to be highly selective, sensitive, and reversible for CO2 sensing across a range of platforms including optical ...fiber and surface acoustic wave-based sensors. However, interference of water molecules is a primary issue in CO2 sensing systems based upon MOF layers due to cross-sensitivity, stability of MOF-based materials in humid conditions, and associated baseline drift over the lifetime of sensors. Herein, we develop a simple approach of alleviating the negative effect of water vapor to the optical fiber sensor by using alkylamine (i.e., oleylamine) to form a protective hydrophobic layer on the surface of MOFs for improving water stability. Alkylamine-modification of a MOF-coated optical fiber sensor provides a reversible and stable sensing response to a wide range of CO2 concentrations while also enhancing the CO2 sensitivity of the sensor under wet conditions. The FT-IR and breakthrough studies on the oleylamine-modified MOF confirm that the water vapor does not adversely impact the intrinsic CO2 sorption capacities. Thus, this simple stratrgy for enhancing the CO2/H2O selectivity in the MOF sorbent could also be useful for improving CO2 capture/separation performance in flue gas stream.
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Thermal processing of soft magnetic amorphous and nanocrystalline alloys is explored under the influence of radio‐frequency induction‐heating techniques. Direct induction‐heating concepts based on ...longitudinal and transverse flux heating are examined and the details of electromagnetic fields interaction with metallic strips are discussed by analytical calculations as well as finite element analysis. Initial experimental results confirming spatial control of phase transformations and nanocrystallization within a single strip of Finemet Fe‐based amorphous ribbons are reported. The degree to which primary and secondary crystallization temperature are achieved depends on the spacing between the ribbon relative to the induction coil as well as the coil design and configuration. For transverse coil configurations, the local temperature and therefore microstructural evolution is different across the lateral dimension of processed ribbons, with reduced gap sizes producing enhanced peak temperatures and larger temperature distributions with greater spatial variation in microstructure. In addition, indirect susceptor‐based induction heating under tension is performed and the impact of microstructure is demonstrated. Herein, potential for exploiting spatially optimized phase transformations is illustrated through electromagnetic field–assisted processing in a scalable manufacturing process with amorphous and nanocrystalline soft magnetic alloys.
Radio‐frequency rapid thermal processing enables spatial phase transformation and selective nanocrystallization of soft magnetic amorphous alloy ribbons. The article features novel concepts of induction heating including longitudinal‐, transverse‐, and susceptor‐based techniques providing a viable and attractive pathway toward scalable manufacturing techniques for thermal processing of amorphous and nanocrystalline alloys leveraging electromagnetic field–assisted processing methods.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
For efficient operation of next-generation fossil fuel technologies, development of sensors capable of withstanding harsh environments is required. Optical waveguide based sensing platforms have ...become increasingly important, but a need exists for materials that exhibit useful changes in optical properties in response to changing gas atmospheres at high temperatures. In this manuscript, the onset of a near-IR absorption associated with an increase in free carrier density in doped metal oxide films to form so-called conducting metal oxides is discussed in the context of results obtained for undoped and La-doped SrTiO3 films. Film characterization results are presented along with measured changes in optical absorption resulting from various high temperature treatments in a range of gas atmospheres. Optical property changes are also discussed in the context of a simple model for optical absorption in conducting metal oxide thin films. The combination of experimental results and theoretical modeling presented here suggests that such materials have potential for high temperature optical gas sensing applications. Simulated sensing experiments were performed at 600–800 °C, and a useful, rapid, and reproducible near-IR optical sensing response to H2 confirms that this class of materials shows great promise for optical gas sensing.
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Au-nanoparticle incorporated metal oxide based sensing layers show significant promise for high temperature optical sensing applications at temperatures approaching 800°C or even higher depending ...upon the base oxide material. Several Au-nanoparticle incorporated oxide systems were synthesized and investigated here, namely TiO2, ZrO2, and Yttria-Stabilized Zirconia (YSZ). Gas (CO, H2, and O2) and temperature sensing responses were observed at wavelengths near the localized surface plasmon resonance (LSPR) absorption peak of the Au nanoparticles and addition of 1% O2 content to a N2 baseline gas stream resulted in significantly enhanced recovery kinetics for H2 sensing. TiO2 films with a relatively small bandgap as compared to ZrO2 and YSZ enabled band-edge monitoring yielding a strong temperature sensing response with minimal cross-correlation to changes in gas composition. Testing of the films in high H2-level gas streams demonstrated that monotonic responses to H2 up to 98% H2 by volume in 2% O2 balance N2 gas streams could be achieved by interrogation at wavelengths shorter than the transmittance minimum associated with the Au LSPR absorption peak. These results collectively demonstrate the importance of careful wavelength selection or broadband wavelength interrogation to minimize cross-correlation between composition and temperature and to optimize the gas sensing response in high temperature gas streams. Although the tested films were stable in the presence of simple gas mixtures (N2, H2, CO, O2) used for gas and temperature sensing experiments, a preliminary study of film stability in a contaminated (H2S-containing) high temperature fuel gas stream relevant for solid oxide fuel cell applications was also carried out and yielded two important conclusions deserving further investigation: (1) enhanced microstructural stability of Au nanoparticle incorporated TiO2 due to grain boundary pinning and (2) significant mass loss of Au with an associated reduction in LSPR absorption.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Layered double hydroxides (LDHs) are a class of cationic-layered solids that can be synthetically designed for a variety of advanced functions. Facile thin film growth of LDHs is an important ...requisite for a variety of applications including functional coatings, displays, and sensing. In this work we demonstrate, for the first time, an in situ and patternable thin film synthesis of interconnected Zn–Cr LDH particles from a transparent conducting oxide precursor, aluminum-doped zinc oxide, at room temperature within minutes. Synthetic parameters such as chromium(III) nitrate concentration, solvent composition, and reaction time were found to significantly affect the thickness and morphology of the resulting LDH films. These LDH thin films can undergo interlayer anion exchange, which modulates the interlayer distance of the LDH sheets and surface energy of the thin film. Replacement of the interlayer anion with perfluorooctanoate increases the interlayer sheet distance from 0.9 to 2.8 nm and induces a super-hydrophobic thin film that is capable of adsolubilizing and retaining organic guest molecules. The synthetic method and structural analysis of the LDH thin films introduced in this work opens new avenues of application for LDH films.
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One of the major challenges for metal-powder-based additive manufacturing is measuring and mitigating residual strain induced during the manufacturing processes. This article reports distributed ...fiber optic sensors embedded in Inconel alloy components as experimental means to validate numerical models of additive manufacturing process. Electroplating was used to deposit a metal protective jacket onto standard telecom single-mode fibers for strain measurements, Fiber sensors were embedded in an Inconel alloy substrate using the laser engineered net shaping (LENS) process. Using a Rayleigh-scattering optical frequency domain reflectometer (OFDR), temperature changes, and residual strain in the metal substrate were monitored with 5 mm spatial resolution during the LENS process. Using finite element analysis, temperature and strain profiles induced by the LENS deposition processes were also numerically studied. Discrepancies between the simulated temperature and strain profiles and those measured directly were less than 10%. Results presented in this article demonstrates a digital twin approach to fuse modeling results with distributed fiber sensor measurement data to study additive manufacturing process toward design and fabrication process optimization.
The demand for real-time sensors in harsh environments at elevated temperature is significant and increasing. In this manuscript, the chemical and temperature sensing using the optical response ...through the practical fiber platform is demonstrated, and principle component analysis is coupled with targeted experimental film characterization to understand the fundamental sensing layer properties, which dominate measured gas sensing responses in complex gas mixtures. More specifically, tin-doped indium oxide-decorated sensors fabricated with the sol–gel method show stable and stepwise transmission responses varying over a wide range of H2 concentration (5–100%) at 250–350 °C as well as responses to CH4 and CO to a lesser extent. Measured responses are attributed to modifications to the surface plasmon resonance absorption in the near-infrared range and are dominated by the highest concentrations of the most-reducing analyte based upon systematic mixed gas stream experiments. Principal component analysis is utilized for this type of sensor to improve the quantitative and qualitative understanding of responses, clearly identifying that the dominant principle component (PC #1) accounts for ∼78% of total data variance. Correlations between PC #1 and the experimentally derived free carrier concentration confirm that this material property plays the strongest role on the ITO gas sensing mechanism, while correlations between the free carrier mobility and the second most important principle component (PC #2) suggest that this quantity may play a significant but secondary role. As such, the results presented here clarify the relationship between generalized principle components and fundamental sensing materials properties thereby suggesting the pathway toward improved multicomponent gas speciation through sensor layer engineering. The work presented represents a significant step toward the ultimate objective of optical waveguide sensors integrated with multivariate data analytics for multiparameter monitoring with a single sensor element.
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