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A Design Strategy for Surface Nanostructures to Realize Sensitive Refractive-Index Optical Sensors. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:3081. [PMID: 38132979 PMCID: PMC10745670 DOI: 10.3390/nano13243081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 11/28/2023] [Accepted: 12/01/2023] [Indexed: 12/23/2023]
Abstract
Refractive-index optical sensors have been extensively studied. Originally, they were surface plasmon resonance sensors using only a flat gold film. Currently, to develop practically useful label-free optical sensors, numerous proposals for refractive index sensors have been made using various nanostructures composed of metals and dielectrics. In this study, we explored a rational design strategy for sensors using surface nanostructures comprising metals or dielectrics. Optical responses, such as reflection and transmission, and resonant electromagnetic fields were computed using a numerical method of rigorous coupled-wave analysis combined with a scattering-matrix algorithm. As a result, good performance that almost reached the physical limit was achieved using a plasmonic surface lattice structure. Furthermore, to precisely trace the refractive-index change, a scheme using two physical quantities, resonant wavelength and reflection amplitude, was found to be valid for a 2D silicon metasurface.
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Improved supercapacitor performances by adding carbonized C 60-based nanospheres to PVA/TEMPO-cellulose hydrogel-based electrolyte. RSC Adv 2023; 13:21502-21509. [PMID: 37469969 PMCID: PMC10352703 DOI: 10.1039/d3ra03349j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 07/08/2023] [Indexed: 07/21/2023] Open
Abstract
With the emergence of the energy crisis and the development of flexible electronics, there is an urgent need to develop new reliable energy supply devices with good flexibility, stable energy storage, and efficient energy transfer. Porous carbon materials have been proven to enhance the efficiency of ion transport, as the nanospaces within them serve as pathways for mass transport. However, they have been mainly investigated in the electrodes of supercapacitors and batteries. To elucidate their function in the solid electrolytes, we introduced C60-based carbonized nanospheres into PVA/TEMPO-cellulose-based hydrogels by exploiting the electrostatic interaction between the carboxyl groups of TEMPO-cellulose and the carbonized nanospheres. The obtained hydrogels were further utilized as the solid electrolytes for the supercapacitors. Through a comprehensive investigation, we found that the carbonized nanospheres can act as physical crosslinking points and increase the maximum stress of the hydrogel from 0.12 to 0.31 MPa without affecting the maximum strain. In addition, the nanospaces of the carbonized nanospheres provided a pathway for ion transport, improving the capacitance of the supercapacitor from 344.83 to 369.18 mF cm-2 at 0.5 mA cm-2. The capacitance retention was also improved from 53% to 62% at 10 mA cm-2. Collectively, this study provides new insights into the application of carbonized materials to solid electrolytes.
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Extremely Tough, Stretchable Gel Electrolytes with Strong Interpolymer Hydrogen Bonding Prepared Using Concentrated Electrolytes to Stabilize Lithium-Metal Anodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2211679. [PMID: 37073627 DOI: 10.1002/adma.202211679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 02/21/2023] [Indexed: 05/03/2023]
Abstract
Extremely tough and stretchable gel electrolytes, which can be prepared by leveraging the strong interpolymer hydrogen bonding in concentrated lithium (Li)-salt electrolytes, are reported. These electrolytes can be realized by optimizing the competitive hydrogen-bonding interactions between polymer chains, solvent molecules, Li cations, and counteranions. Free polar solvent molecules, which typically impede interpolymer hydrogen bonding, are scarce in concentrated electrolytes; this feature can be exploited to prepare hydrogen-bonded gel electrolytes with unprecedented toughness. In contrast, free solvent molecules are abundant in electrolytes with typical concentrations, yielding considerably weaker gel electrolytes. The tough gel electrolyte can be used an artificial protective layer for Li-metal anodes, as it considerably enhances the cycling stability of a Li symmetric cell through uniform Li deposition/dissolution. Additionally, employing the gel electrolyte as the protecting layer significantly improves the cycling performance of the Li||LiNi0.6 Co0.2 Mn0.2 O2 full cell.
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Abstract
The orientation and motion of reactants play important roles in reactions. The small rotational excitations involved render the reactants susceptible to dynamical steering, making direct comparison between experiments and theory rather challenging. Using space-quantized molecular beams, we directly probed the (polar and azimuthal) orientation dependence of O2 chemisorption on Cu(110) and Cu3Au(110). We observed polar and azimuthal anisotropies on both surfaces. Chemisorption proceeded rather favorably with the O-O bond axis oriented parallel (vs perpendicular) to the surface and rather favorably with the O-O bond axis oriented along [001] (vs along [1̅10]). The presence of Au hindered the surface from further oxidation, introducing a higher activation barrier to chemisorption and rendering an almost negligible azimuthal anisotropy. The presence of Au also prevented the cartwheel-like rotations of O2.
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Active Pt-Nanocoated Layer with Pt-O-Ce Bonds on a CeO x Nanowire Cathode Formed by Electron Beam Irradiation. ACS OMEGA 2022; 7:25822-25836. [PMID: 35910162 PMCID: PMC9330286 DOI: 10.1021/acsomega.2c03348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A Pt-nanocoated layer (thickness of approx. 10-20 nm) with Pt-O-Ce bonds was created through the water radiolysis reaction on a CeO x nanowire (NW), which was induced by electron beam irradiation to the mixed suspension of K2PtCl4 aqueous solution and the CeO x NW. In turn, when Pt-nanocoated CeO x NW/C (Pt/C ratio = 0.2) was used in the cathode layer of a membrane electrode assembly (MEA), both an improved fuel cell performance and stability were achieved. The fuel cell performance observed for the MEA using Pt-nanocoated CeO x NW/C with Pt-O-Ce bonds, which was prepared using the electron beam irradiation method, improved and maintained its performance (observed cell potential of approximately 0.8 V at 100 mW cm-2) from 30 to 140 h after the start of operation. In addition, the activation overpotential at 100 mA cm-2 (0.17 V) obtained for MEA using Pt-nanocoated CeO x NW/C was approximately half of the value at 100 mA cm-2 (0.35 V) of MEA using a standard Pt/C cathode. In contrast, the fuel cell performance (0.775 V at 100 mW cm-2 after 80 h of operation) of MEA using a nanosized Pt-loaded CeO x NW (Pt/C = 0.2), which was prepared using the conventional chemical reduction method, was lower than that of MEA using a Pt-nanocoated CeO x /C cathode and showed reduction after 80 h of operation. It is considered why the nanocoated layer having Pt-O-Ce bonds heterogeneously formed on the surface of the CeO x NW and the bare CeO2 surface consisting of Ce4+ cations would become unstable in an acidic atmosphere. Furthermore, when a conventional low-amount Pt/C cathode (Pt/C = 0.04) was used as the cathode layer of the MEA, its stable performance could not be measured after 80 h of operation as a result of flooding caused by a lowering of electrocatalytic activity on the Pt/C cathode in the MEA. In contrast, a low-amount Pt-nanocoated CeO x NW (Pt/C = 0.04) could maintain a low activation overpotential (0.22 V at 100 mA cm-2) of MEA at the same operation time. Our surface first-principles modeling indicates that the high quality and stable performance observed for the Pt-nanocoated CeO x NW cathode of MEA can be attributed to the formation of a homogeneous electric double layer on the sample. Since the MEA performance can be improved by examining a more effective method of electron beam irradiation to all surfaces of the sample, the present work result shows the usefulness of the electron beam irradiation method in preparing active surfaces. In addition, the quantum beam technology such as the electron beam irradiation method was shown to be useful for increasing both performance and stability of fuel cells.
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Surface Passivation of Sputtered NiO x Using a SAM Interface Layer to Enhance the Performance of Perovskite Solar Cells. ACS OMEGA 2022; 7:12147-12157. [PMID: 35449936 PMCID: PMC9016879 DOI: 10.1021/acsomega.2c00509] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 03/11/2022] [Indexed: 06/14/2023]
Abstract
Sputtered NiO x (sp-NiO x ) is a preferred hole transporting material for perovskite solar cells because of its hole mobility, ease of manufacturability, good stability, and suitable Fermi level for hole extraction. However, uncontrolled defects in sp-NiO x can limit the efficiency of solar cells fabricated with this hole transporting layer. An interfacial layer has been proposed to modify the sp-NiO x /perovskite interface, which can contribute to improving the crystallinity of the perovskite film. Herein, a 2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) self-assembled monolayer was used to modify an sp-NiO x surface. We found that the MeO-2PACz interlayer improves the quality of the perovskite film due to an enlarged domain size, reduced charge recombination at the sp-NiO x /perovskite interface, and passivation of the defects in sp-NiO x surfaces. In addition, the band tail states are also reduced, as indicated by photothermal deflection spectroscopy, which thus indicates a reduction in defect levels. The overall outcome is an improvement in the device efficiency from 11.9% to 17.2% due to the modified sp-NiO x /perovskite interface, with an active area of 1 cm2 (certified efficiency of 16.25%). On the basis of these results, the interfacial engineering of the electronic properties of sp-NiO x /MeO-2PACz/perovskite is discussed in relation to the improved device performance.
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Quantitative Correlation of Droplets on Galvanic-Coupled Arrays with Response Current by Image Processing. ACS OMEGA 2021; 6:30818-30825. [PMID: 34805710 PMCID: PMC8600636 DOI: 10.1021/acsomega.1c05161] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 10/22/2021] [Indexed: 06/13/2023]
Abstract
Evaluating the presence of a slight amount of water plays a crucial role in practical applications such as the advanced detection of dew condensation and the microdetermination of perspiration and transpiration. For this purpose, we have developed a configuration for the moisture sensor that consists of a microgalvanic cell composed of narrow metal arrays. It is inferred that the output response current arising from this sensor should depend on the geometric parameters (e.g., number, area, volume, etc.) of water droplets attaching on the sensor surface. In this study, the output current was recorded, while the microscopic images of the sensor surface were captured. The droplets on the sensor surface were analyzed manually and by computational image processing with deep learning and ImageJ. The deep learning technique shortened the processing time to 1/1000 of the manual one and was able to match 90-100% of the manual count. The results revealed that the response current increased with the total projected area of droplets bridging the galvanic-coupled arrays on the sensor surface. In addition, a straight line with relatively strong positive correlation was obtained between the response current and the total volume of the bridging droplets. These findings suggested that our sensor can be practically used to estimate the presence of a slight amount of water.
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Facile Synthesis of Tetra-Branched Tetraimidazolium and Tetrapyrrolidinium Ionic Liquids. ACS OMEGA 2021; 6:19623-19628. [PMID: 34368549 PMCID: PMC8340402 DOI: 10.1021/acsomega.1c02187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 07/09/2021] [Indexed: 05/04/2023]
Abstract
A facile synthetic route for tetra-branched tetraimidazolium and tetrapyrrolidinium ionic liquids was developed. In contrast to the previous synthetic scheme, the new synthetic route requires only three reaction steps instead of seven. The total yield of tetracation was also improved from 17-21 to 39-41%. Using the new synthetic scheme, four kinds of tetracations were synthesized from the combination of two cationic units (imidazolium and pyrrolidinium) and two counteranions [bis(fluorosulfonyl)imide (FSI) and bis(trifluoromethanesulfonyl)imide (TFSI)]. Basic physical properties including glass transition temperature, thermal decomposition temperature, density, viscosity, and ionic conductivity were determined. The counterion exchange from TFSI to FSI resulted in lower glass transition temperature and higher ionic conductivity. Tetrapyrrolidinium exhibited higher viscosity and lower ionic conductivity than tetraimidazolium. The counterion exchange from TFSI to FSI resulted in lower viscosity in the case of tetraimidazolium, while the opposite result was obtained in the case of tetrapyrrolidinium. Tetracations composed of ethyl imidazolium units, diethylene glycol spacers, and FSI counterions exhibited the highest ionic conductivity of 3.5 × 10-4 S cm-1 at 25 °C under anhydrous conditions. This is the best ionic conductivity in the tetracations ever reported.
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Reduction in Work Functions of Transition-Metal Carbides and Oxycarbides upon Oxidation. ACS OMEGA 2021; 6:14559-14565. [PMID: 34124479 PMCID: PMC8190902 DOI: 10.1021/acsomega.1c01671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 05/20/2021] [Indexed: 06/12/2023]
Abstract
Herein, the work functions of group 4 and group 5 transition-metal (Ti, Zr, Hf, V, Nb, and Ta) carbides and transition-metal oxycarbides (TMCOs) were investigated by first-principles calculations for their potential application as electron emitters. The work functions of both groups decreased as the substitution of carbon atoms with oxygen proceeded, and the reduction in group 4 was more than that of group 5. In particular, ZrC1-x O x and HfC1-x O x (x ≥ 0.25) exhibited work functions of less than 3 eV, which were comparable with those of LaB6- and ZrO-coated tungsten. The reduction in the work functions could be explained by the rigid-band model of the electronic density of states. The increase in valence electrons increased the Fermi energy, while it demonstrated a less significant influence on the vacuum potential, resulting in a reduction in the work functions. The phonon dispersion curves indicated that the NaCl-type group 5 TMCOs were less stable than the group 4 TMCOs. This agrees with the experimental findings that TaC1-x O x was not synthesized and NbC1-x O x was synthesized only for smaller values of x (i.e., x < 0.28). From the viewpoints of the work functions and structural stabilities, group 4 (Ti, Zr, and Hf) TMCOs exhibit better potential for application as electron emitters than group 5 (V, Nb, and Ta) TMCOs.
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Crystal Growth and High-Pressure Effects of Bi-Based Superconducting Whiskers. ACS OMEGA 2021; 6:12179-12186. [PMID: 34056371 PMCID: PMC8154171 DOI: 10.1021/acsomega.1c00880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/07/2021] [Indexed: 06/12/2023]
Abstract
Three growth methods were tested for producing high-transition temperature superconducting Bi2Sr2Ca n-1Cu n O2n+4+δ whiskers, employing different ways to focus a compressive stress and size effect of the precursors. First, thermographic imaging was used to investigate thermal stress from temperature distribution in the precursors during growth annealing. To enhance thermal stress in the precursors, a thermal cycling method and a Ag-paste coating method were proposed and found to significantly accelerate the whisker growth. The use of pulverized precursors also promoted whisker growth, possibly due to contribution from the vapor-liquid-solid growth mechanism. The obtained whiskers revealed the typical composition, diffraction patterns, and superconducting properties of the Bi-2212 phase. The proposed methods were able to stably produce longer whiskers compared to the conventional method. Using the obtained whiskers, electrical transport measurements under high pressure were successfully performed up to around 50 GPa.
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ITO@SiO 2 and ITO@{M 6Br 12}@SiO 2 (M = Nb, Ta) nanocomposite films for ultraviolet-near infrared shielding. NANOSCALE ADVANCES 2019; 1:3693-3698. [PMID: 36133539 PMCID: PMC9416910 DOI: 10.1039/c9na00400a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 08/05/2019] [Indexed: 06/01/2023]
Abstract
Transparent optical thin films for energy saving applications have recently gained substantial prominence for functional window processes. In this study, highly visible transparent nanocomposite films with ultraviolet (UV) and near-infrared (NIR) blocking capabilities are reported. Such nanocomposite films, prepared by electrophoretic deposition on ITO-coated glass, are composed of indium tin oxide (ITO) nanocrystals (9 nm) and octahedral metal atom clusters (1 nm, Nb6 or Ta6) embedded into silica nanoparticles (∼80 nm). The functional silica nanoparticles were prepared by a reverse microemulsion process. The microstructural characterization proved that ITO nanocrystals are centered in the silica nanoparticles, whereas the metal atom clusters are homogeneously distributed in the silica matrix. The optical absorption spectra of these transparent nanocomposite films exhibit distinct and complementary contributions from their ITO nanoparticles and metal atom clusters (absorption in the UV range) and from the ITO layer on silica.
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Realization and direct observation of five normal and parametric modes in silicon nanowire resonators by in situ transmission electron microscopy. NANOSCALE ADVANCES 2019; 1:1784-1790. [PMID: 36134225 PMCID: PMC9418527 DOI: 10.1039/c8na00373d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Accepted: 02/24/2019] [Indexed: 05/13/2023]
Abstract
Mechanical resonators have wide applications in sensing bio-chemical substances, and provide an accurate method to measure the intrinsic elastic properties of oscillating materials. A high resonance order with high response frequency and a small resonator mass are critical for enhancing the sensitivity and precision. Here, we report on the realization and direct observation of high-order and high-frequency silicon nanowire (Si NW) resonators. By using an oscillating electric-field for inducing a mechanical resonance of single-crystalline Si NWs inside a transmission electron microscope (TEM), we observed resonance up to the 5th order, for both normal and parametric modes at ∼100 MHz frequencies. The precision of the resonant frequency was enhanced, as the deviation reduced from 3.14% at the 1st order to 0.25% at the 5th order, correlating with the increase of energy dissipation. The elastic modulus of Si NWs was measured to be ∼169 GPa in the [110] direction, and size scaling effects were found to be absent down to the ∼20 nm level.
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Transparent functional nanocomposite films based on octahedral metal clusters: synthesis by electrophoretic deposition process and characterization. ROYAL SOCIETY OPEN SCIENCE 2019; 6:181647. [PMID: 31032021 PMCID: PMC6458394 DOI: 10.1098/rsos.181647] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 02/08/2019] [Indexed: 05/10/2023]
Abstract
Transparent optical thin films have recently attracted a growing interest for functional window applications. In this study, highly visible transparent nanocomposite films with ultraviolet (UV)-near-infrared (NIR)-blocking capabilities are reported. Such films, composed of Mo6 and Nb6 octahedral metal atom clusters (MC) and polymethylmethacrylate polymer (PMMA), were prepared by electrophoretic deposition on indium tin oxide-coated glass (ITO glass). PMMA was found to improve both the chemical and physical stability of Mo6 and Nb6 MCs, resulting in a relatively homogeneous distribution of the clusters within the PMMA matrix, as seen by microstructural observations. The optical absorption spectrum of these transparent MC@polymer nanocomposite films was marked by contributions from their Mo6 and Nb6-based clusters (absorption in the UV range) and from the ITO layer on silica glass (absorption in the NIR range). Mo6@PMMA nanocomposite films also exhibited excellent photoluminescence properties, which were preserved even after exposure to 50°C at a relative humidity of 70% for one month. These films cumulate high transparency in the visible range with remarkable UV-NIR blocking properties and represent interesting candidates for functional glass application.
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