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Spectral Imaging Technology - A Review on Skin and Endoscopy Applications
摘要： Spectral imaging technology is an emerging modality that combines the advantages of both imaging and spectroscopy (high spatial and spectral resolution) in one device. The technology has potential in numerous medical imaging and diagnostic applications. In this review, we describe the techniques used to acquire spectral images and the methods used for analyzing spectral images. We then provide detailed review about the progress of the spectral imaging technology in skin and endoscopy applications. This review also covers the recent patents on spectral imaging devices, methods, and data analysis algorithms.
关键词： optical scattering,spectroscopy,Endoscopy,spectral imaging,tissue reflectance,skin diagnosis,medical diagnosis,optical absorption
更新于2025-09-10 09:29:36
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Comparison and convergence of optical absorption spectra of noble metal nanoparticles computed using linear-response and real-time time-dependent density functional theories
摘要： The real-time time-dependent density functional theory (RT-TDDFT) is rapidly gaining prominence as an alternative approach to capture optical properties of molecular systems, which warrants the necessity to benchmark the traditional linear response (LR) method and the RT approach. We calculate the absorption spectra of noble metal nanoparticles with a variety of sizes and shapes to demonstrate the consistency of the two methods over a broad range of energy. The RT spectrum obtained using a grid-based basis set with pseudopotentials achieves results in good agreement with the LR spectrum obtained with large QZ4P atom-centered basis sets. Factors that lead to convergence of the spectra are considered. In addition, the real-time variation of the electron density is visualized to show the collective oscillation of electron density for the plasmon modes of noble metal nanoparticles. The RT approach is most useful when calculating wide absorption spectra of larger gold or silver nanoparticles.
关键词： optical absorption spectra,noble metal nanoparticles,RT-TDDFT,LR-TDDFT,plasmon modes
更新于2025-09-10 09:29:36
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Enhanced photocatalytic H2 evolution and phenol degradation over sulfur doped meso/macroporous g-C3N4 spheres with continuous channels
摘要： S-doped meso/macroporous g-C3N4 spheres (SMCN) were successfully synthesized via an in situ novel method utilizing millimeter-scale porous silica spheres as template and thiourea as precursor and S source. Such SMCN possessed millimeter-scale spherical morphology with continuous channels at 20e80 nm in the interior of the spheres, and exhibited increased H2 generation rate (15 times) and phenol degradation rate (5 times) under visible light irradiation compared with that over pristine g-C3N4, mainly due to the enlarged surface area, enhanced mass transfer and improved ef?ciency of charges separation all stemming from the synergetic effects of the S doping and pore creating. Notably, density functional theory (DFT) calculations were employed to further understand the mechanism of the photocatalytic enhancement with regard to the optical absorption property at atomic level. Combined with the ?nite difference time domain (FDTD) simulations aiming at evaluating the effect of the nanoscale pore architecture on the optical absorption ability, it was revealed that not only the S doping but also the meso/macroporous structure resulted in the enhancement of the optical absorption, which was considered to be an essential role for the enhanced photocatalytic performances over SMCN.
关键词： Continuous channels,FDTD simulation,Optical absorption,DFT,S-doping
更新于2025-09-10 09:29:36
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Ultranarrow-band metagrating absorbers for sensing and modulation
摘要： Nanostructured plasmonic metamaterials are an excellent platform for narrowband optical absorption, which has wide applications in sensing, filtering, modulation, and emission tailoring. However, achieving a subnanometer absorption bandwidth for optical sensing and dynamical control of light is still challenging. Here, we propose an asymmetric metagrating structure and make use of the propagating surface plasmonic mode that has a small dissipation rate, to achieve perfect optical absorption with a bandwidth of 0.28 nm near the wavelength of 1.55 μm. Our proposed structure can be used in solution environments as a chemical or biological sensor in the visible spectral range just by changing the structural parameters. The sensor possesses a sensitivity of 440 nm/RIU and figure of merit of 1333.33 RIU?1. In addition, by combining an organic electro-optic material with this metagrating, our device can be reconfigurable with a dynamic range of 15.52 dB. Therefore, our proposed metagrating platform not only works as an ultranarrow-band absorber, but also can be employed for optical sensing and dynamic control of light.
关键词： sensing,optical absorption,metagrating,plasmonic metamaterials,modulation
更新于2025-09-10 09:29:36
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Applied Nanophotonics || Quantum confinement effects in semiconductors
摘要： Absorption and emission of light by atoms, molecules, and solids arise from electron transitions. Electron confinement phenomena in solids with restricted geometry like nanoparticles, nanorods, or nanoplatelets gives rise to the modification of optical absorption and emission spectra and transition probabilities in semiconductor nanostructures. These phenomena are direct consequences of the wave properties of electrons. In this chapter we describe size-dependent optical properties of semiconductor nanostructures related to quantum confinement.
关键词： optical absorption,semiconductors,nanostructures,emission spectra,Quantum confinement
更新于2025-09-09 09:28:46
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A Combined Experimental and Theoretical Investigation on Organic Cation Dichlorocopper (II): Structural Characterization, Hirshfeld Surface Analysis, Spectroscopic Properties and DFT Calculation
摘要： The (ethylenediamine) dichlorocopper(II) complex, {[Cu(en)]Cl2}n(en:C2H8N2), was synthesized by hydrothermal technique. The X-ray structure of {[Cu(en)]Cl2}n shows that the compound crystallizes as a one dimensional chain with one chlorine that is non-bridging and the other chlorine which is triply bridging. It crystallizes at room temperature in the centrosymmetric space group P21/m. The structure of {Cu(en)Cl2}n was originally reported by Kumara et al. The surrounding copper is best described as distorted octahedral. The crystal structure was stabilized with an extensive network of N-H…Cl classical hydrogen bond interactions. The investigation on that close intermolecular interactions between the molecules via Hirshfeld surface analyses is presented to reveal subtle differences and similarities in the crystal structures. The decomposition of the fingerprint plot area provides a percentage of each intermolecular interaction, allowing for a quantified analysis of close contacts within the crystal. The optimized molecular structure and vibrational spectra were calculated by the Density Functional Theory (DFT) method using the B3LYP function with the LanL2DZ basis set. Good consistency is found between the calculated results and the experimental structure, FT-IR, and FT-Raman spectra. The detailed interpretation of the vibrational modes was carried out. Optical transmission measurements performed on thin films of {[Cu(en)]Cl2}n revealed two absorption bands at 3.64 eV and 1.907 eV. The calculated HOMO-LUMO energies reveal that charge transfer occurs within the molecule.
关键词： Optical absorption,Synthesis hydrothermal,Complex copper (II),Hirchfeld surface analysis,Crystal structure,DFT vibrational assignment
更新于2025-09-09 09:28:46
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Numerical simulation and validity of the surface photovoltage method in amorphous silicon with a Schottky contact
摘要： The steady-state surface photovoltage technique (SPV) is widely used to evaluate minority photocarriers diffusion length (Lp) of hydrogenated amorphous silicon (a-Si:H) even though the space charge region is reduced. In this work, we propose a formula to predict more accurately minority diffusion length Lp depending on apparent diffusion length (Lapp) and space charge width (W). This formula is deduced by Moore’s analytical solution in relation to assumptions involving W are explored for a set of parameters of the a-Si:H density of states. This numerical simulation shows a linear dependence of Lapp up on the valence band tail energy, which agrees well with the experimental results. The Lp values obtained by the new formula are compared to Lapp and discussed for a typical DOS parameters of a-Si:H.
关键词： surface photovoltage,Minority diffusion length,optical absorption
更新于2025-09-09 09:28:46
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Highly UV sensitive polycrystalline zinc selenide thin film grown by chemical bath deposition technique
摘要： In this communication, we report a significantly high UV sensitivity of polycrystalline zinc selenide thin films prepared by chemical bath deposition technique. A three order of magnitude of photo current to dark current ratio is obtained for the as-deposited film under UV exposure. However, the photosensivity is found to decrease sharply upon open air isochronal annealing of the sample. The variation of the photocurrent to dark current ratio with annealing temperature is attributed to shrinking diameter of nano-wire like structures exhibited by the films, variation of the band gap energy and a decrease in the grain boundary charge density of the material which collectively enhance the free carrier concentration in the band leading to a substantial loss in the photosensitivity of annealed films compared to the as-deposited film.
关键词： ZnSe thin film,UV sensitivity,SEM,Band gap energy,Optical absorption co-efficient,Grain boundary charge density
更新于2025-09-04 15:30:14
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The Effects of Hydrostatic Pressure on the Surface Plasmon Resonance of Gold Nanocrystals
摘要： The surface plasmon resonances of gold nanospheres and nanorods have been measured as a function of hydrostatic pressure up to 17 GPa in methanol-ethanol 4:1 solvent and up to 10 GPa in paraffin. Both the sphere resonance and the longitudinal rod resonance exhibit redshifts while the transverse rod mode shows an extremely weak redshift or blueshift depending on the nanorod aspect ratio. Solidification of the solvent around 11 GPa causes some aggregation of the particles, readily identified through broadening of the SP band and further redshifting. Loading and unloading cycles show only minimal hysteresis in the spectra if the pressure remains below 11 GPa. The surface plasmon shifts are the result of two competing effects. Compression of the conduction electrons in the metals increases the bulk plasma frequency, which causes a blueshift. However, the increase in the solvent density under hydrostatic load leads to an increase in the solvent refractive index, which in turn leads to a redshift. We find that after accounting for the solvent contribution, we can spectroscopically determine the bulk modulus of the gold nanoparticles with a precision of 10%. The value obtained of K0 = 190 GPa is significantly higher than the value for bulk gold (167 GPa). Furthermore, we show that pressure-induced solidification causes a significant broadening and anomalous shift of the surface plasmon band that we attribute to aggregation and nanorod deformation.
关键词： optical absorption,refractive index,hydrostatic pressure,surface plasmon resonance,bulk modulus,gold nanoparticles
更新于2025-09-04 15:30:14
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Monoisotopic Ensembles of Silicon-Vacancy Color Centers with Narrow-Line Luminescence in Homoepitaxial Diamond Layers Grown in H <sub/>2</sub> –CH <sub/>4</sub> – <sup> [ <i>x</i> ] </sup> SiH <sub/>4</sub> Gas Mixtures ( <i>x</i> = 28, 29, 30)
摘要： Silicon-vacancy (SiV?) color center in diamond is of high interest for applications in nanophotonics and quantum information technologies, as a single photon emitter with excellent spectral properties. To obtain spectrally identical SiV? emitters, we doped homoepitaxial diamond ?lms in situ with 28Si, 29Si, and 30Si isotopes using isotopically enriched (>99.9%) silane SiH4 gas added in H2?CH4 mixtures in the course of the microwave plasma-assisted chemical vapor deposition process. Zero-phonon line components as narrow as ～4.8 GHz were measured in both absorption and luminescence spectra for the monoisotopic SiV? ensembles with a concentration of a few parts per billion. We determined with high accuracy the Si isotopic energy shift of SiV? zero-phonon line. The SiV? emission intensity is shown to be easily controlled by the doped epi?lm thickness. Also, we identi?ed and characterized the localized single photon SiV? sources. The developed doping process opens a way to produce the SiV? emitter ensembles with energy con?ned in an extremely narrow range.
关键词： diamond,silicon-vacancy center,CVD synthesis,optical absorption,photoluminescence,doping,silicon isotope
更新于2025-09-04 15:30:14