scholarly journals Optically Controlled Supercapacitors: Functional Active Carbon Electrodes with Semiconductor Particles

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4183
Author(s):  
Haim Grebel

Supercapacitors, S-C—capacitors that take advantage of the large capacitance at the interface between an electrode and an electrolyte—have found many short-term energy applications. The parallel plate cells were made of two transparent electrodes (ITO), each covered with a semiconductor-embedded, active carbon (A-C) layer. While A-C appears black, it is not an ideal blackbody absorber that absorbs all spectral light indiscriminately. In addition to a relatively flat optical absorption background, A-C exhibits two distinct absorption bands: in the near-infrared (near-IR and in the blue. The first may be attributed to absorption by the OH− group and the latter, by scattering, possibly through surface plasmons at the pore/electrolyte interface. Here, optical and thermal effects of sub-μm SiC particles that are embedded in A-C electrodes, are presented. Similar to nano-Si particles, SiC exhibits blue band absorption, but it is less likely to oxidize. Using Charge-Discharge (CD) experiments, the relative optically related capacitance increase may be as large as ~34% (68% when the illuminated area is taken into account). Capacitance increase was noted as the illuminated samples became hotter. This thermal effect amounts to <20% of the overall relative capacitance change using CD experiments. The thermal effect was quite large when the SiC particles were replaced by CdSe/ZnS quantum dots; for the latter, the thermal effect was 35% compared to 10% for the optical effect. When analyzing the optical effect one may consider two processes: ionization of the semiconductor particles and charge displacement under the cell’s terminals—a dipole effect. A model suggests that the capacitance increase is related to an optically induced dipole effect.

1993 ◽  
Vol 155 ◽  
pp. 335-335
Author(s):  
B.J. Hrivnak ◽  
S. Kwok ◽  
T.R. Geballe

Sixteen candidates for proto-planetary nebulae have been observed with low-resolution infrared spectroscopy in the H and K bands, and 6 in the L band, using the United Kingdom Infrared Telescope. In the H band, the objects show hydrogen Brackett lines in absorption. In the K band, absorption bands (del v=2) of CO were observed, and in three cases the CO bands are in emission. The CO spectrum of IRAS 22272+5435 was found to change from emission to absorption over a three-month interval. This CO emission can be interpreted as an indication of some recent episodes of mass loss in these objects. Four of the objects were found to possess an emission feature at 3.3 um, usually associated with PAHs, and two of these show an unusually strong 3.4 um emission feature (Geballe, Tielens, Kwok, & Hrivnak 1992, ApJ, 387, L89).


Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 114
Author(s):  
Steve Kamau ◽  
Safaa Hassan ◽  
Khadijah Alnasser ◽  
Hualiang Zhang ◽  
Jingbiao Cui ◽  
...  

It is challenging to realize the complete broadband absorption of near-infrared in thin optical devices. In this paper, we studied high light absorption in two devices: a stack of Au-pattern/insulator/Au-film and a stack of Au-pattern/weakly-absorbing-material/Au-film where the Au-pattern was structured in graded photonic super-crystal. We observed multiple-band absorption, including one near 1500 nm, in a stack of Au-pattern/spacer/Au-film. The multiple-band absorption is due to the gap surface plasmon polariton when the spacer thickness is less than 30 nm. Broadband absorption appears in the near-infrared when the insulator spacer is replaced by a weakly absorbing material. E-field intensity was simulated and confirmed the formation of gap surface plasmon polaritons and their coupling with Fabry–Pérot resonance.


2007 ◽  
Vol 22 (9) ◽  
pp. 2531-2538 ◽  
Author(s):  
Mei Chee Tan ◽  
Jackie Y. Ying ◽  
Gan Moog Chow

Near infrared (NIR) absorbing nanoparticles synthesized by the reduction of HAuCl4 with Na2S exhibited absorption bands at ∼530 nm, and in the NIR region of 650–1100 nm. The NIR optical properties were not found to be related to the earlier proposed Au2S–Au core-shell microstructure in previous studies. From a detailed study of the structure and microstructure of as-synthesized particles in this work, S-containing, Au-rich, multiply-twinned nanoparticles were found to exhibit NIR absorption. They consisted of amorphous AuxS (where x = 2), mostly well mixed within crystalline Au, with a small degree of surface segregation of S. Therefore, NIR absorption was likely due to interfacial effects on particle polarization from the introduction of AuxS into Au particles, and not the dielectric confinement of plasmons associated with a core-shell microstructure.


2008 ◽  
Vol 23 (1) ◽  
pp. 281-293 ◽  
Author(s):  
Mei Chee Tan ◽  
Jackie Y. Ying ◽  
Gan Moog Chow

Near-infrared (NIR)-absorbing nanoparticles synthesized by the reduction of tetrachloroauric acid (HAuCl4) using sodium sulfide (Na2S) exhibited absorption bands at ∼530 nm and at the NIR region of 650−1100 nm. A detailed study on the structure and microstructure of as-synthesized nanoparticles was reported previously. The as-synthesized nanoparticles were found to consist of amorphous AuxS (x = ∼2), mostly well mixed within crystalline Au. In this work, the optical properties were tailored by varying the precursor molar ratios of HAuCl4 and Na2S. In addition, a detailed study of composition and particle-size effects on the optical properties was discussed. The change of polarizability by the introduction of S in the form of AuxS (x = ∼2) had a significant effect on NIR absorption. Also, it was found in this work that exposure of these particles to NIR irradiation using a Nd:YAG laser resulted in loss of the NIR absorption band. Thermal effects generated during NIR irradiation had led to microstructural changes that modified the optical properties of particles.


Author(s):  
Eri Tatsumi ◽  
Marcel Popescu ◽  
Humberto Campins ◽  
Julia de León ◽  
Juan Luis Rizos García ◽  
...  

Abstract Using the multiband imager MapCam onboard the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft, we identified 77 instances of proposed exogenic materials distributed globally on the surface of the B-type asteroid (101955) Bennu. We identified materials as exogenic on the basis of an absorption near 1 µm that is indicative of anhydrous silicates. The exogenic materials are spatially resolved by the telescopic camera PolyCam. All such materials are brighter than their surroundings, and they are expressed in a variety of morphologies: homogeneous, breccia-like, inclusion-like, and others. Inclusion-like features are the most common. Visible spectrophotometry was obtained for 46 of the 77 locations from MapCam images. Principal component analysis indicates at least two trends: (i) mixing of Bennu's average spectrum with a strong 1-µm band absorption, possibly from pyroxene-rich material, and (ii) mixing with a weak 1-µm band absorption. The endmember with a strong 1-µm feature is consistent with Howardite-Eucrite-Diogenite (HED) meteorites, whereas the one showing a weak 1-µm feature may be consistent with HEDs, ordinary chondrites, or carbonaceous chondrites. The variation in the few available near-infrared reflectance spectra strongly suggests varying compositions among the exogenic materials. Thus, Bennu might record the remnants of multiple impacts with different compositions to its parent body, which could have happened in the very early history of the Solar System. Moreover, at least one of the exogenic objects is compositionally different from the exogenic materials found on the similar asteroid (162173) Ryugu, and they suggest different impact tracks.


1994 ◽  
Vol 2 (2) ◽  
pp. 59-65 ◽  
Author(s):  
J. Todd Kuenstner ◽  
Karl H. Norris

Absorbance and first and second derivative absorbance spectra and quarter-millimolar absorptivity coefficients for hemoglobin species including oxy-, deoxy-, carboxy- and methemoglobin in the visible and in the near infrared regions from 620 nm to 2500 nm are presented. At wavelengths longer than 1500 nm, the absorbance and second derivative absorbance spectra of hemoglobin species are similar for all of the species. Absorption bands are present centred at 1690, 1740, 2056, 2170, 2290 and 2350 nm.


2018 ◽  
Vol 20 (28) ◽  
pp. 19110-19119 ◽  
Author(s):  
María Pilar de Lara-Castells ◽  
Carlos Cabrillo ◽  
David A. Micha ◽  
Alexander O. Mitrushchenkov ◽  
Tijo Vazhappilly

This first-principles study reveals how stable subnanometer silver clusters on a TiO2(110) surface lead to the onset of absorption bands in the near-infrared and visible regions.


Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1265 ◽  
Author(s):  
Daler R. Dadadzhanov ◽  
Tigran A. Vartanyan ◽  
Alina Karabchevsky

Molecular overtones stretching modes that occupy the near-infrared (NIR) are weak compared to the fundamental vibrations. Here we report on the enhancement of absorption by molecular vibrations overtones via electromagnetic field enhancement of plasmonic nanoparallelepipeds comprising a square lattice. We explore numerically, using finite element method (FEM), gold metasurfaces on a transparent dielectric substrate covered by weakly absorbing analyte supporting N-H and C-H overtone absorption bands around 1.5 μ m and around 1.67 μ m, respectively. We found that the absorption enhancement in N-H overtone transition can be increased up to the factor of 22.5 due to the combination of localized surface plasmon resonance in prolonged nanoparticles and lattice Rayleigh anomaly. Our approach may be extended for sensitive identification of other functional group overtone transitions in the near-infrared spectral range.


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