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Charge Dynamics and Metal–Insulator Transition in Perovskite SrIr <sub/>1?</sub><i> <sub/>x</sub></i> Sn <i> <sub/>x</sub></i> O <sub/>3</sub>
摘要： We investigate the variation of charge dynamics upon the metal–insulator transition for perovskite SrIr1?xSnxO3 by employing the optical spectroscopy. The Dirac semimetal of SrIrO3 turns into the antiferromagnetic insulator with a gap of 0.1 eV by the Sn-substitution, accompanying the reconstruction of electronic structure on an energy scale of 1 eV. The spectral intensity of optical excitation between Je? = 1=2-orbitals is signi?cantly reduced with increasing x, while that between the Je? = 3=2- and 1=2-orbital shows merely moderate x-dependence. We anticipate that the substituted Sn signi?cantly renormalizes the e?ective bandwidth of Je? = 1=2-orbital while modestly changing the Je? = 3=2-orbital.
关键词： charge dynamics,optical spectroscopy,electronic structure,Je? = 3=2-orbital,perovskite,metal–insulator transition,Dirac semimetal,Je? = 1=2-orbitals,SrIr1?xSnxO3,antiferromagnetic insulator,Sn-substitution
更新于2025-09-10 09:29:36
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Sol-gel synthesis of Ag-loaded TiO2-ZnO thin films with enhanced photocatalytic activity
摘要： Ag-loaded TiO2-ZnO thin films, with low ZnO content, were synthesized by a one-step sol-gel process. The Ag content varied in the interval 0-4 mol% Ag. The films were deposited on glass substrates and post-annealed at 500 °C to induce crystallinity. By using the Tauc model, it was determined that the higher the Ag concentration the higher the optical band-gap energy of the films, a result attributed to the Burstein-Moss effect. Images obtained by scanning electron microscopy and transmission electron microscopy depicted aggregated particles with grain size close to 20 to 25 nm for the oxides with no Ag, whereas the particle size decreased with the addition of Ag. X-ray photoelectron spectroscopy measurements indicated the formation of the Ti4+ and Zn2+ oxidation states, while Ag was found in the metallic state. A depth profile analysis, performed by secondary ion mass spectrometry, confirmed the presence of Ti, Zn, and Ag in the films. X-ray diffraction patterns displayed the anatase phase of TiO2. For (TiO2)0.95-(ZnO)0.05 thin films, a BET analysis showed that the specific surface area increased from 4.56 up to 48.84 m2/g as a consequence of Ag doping. The photocatalytic degradation of the materials under UV irradiation was assessed by using methylene blue as a model pollutant. For (TiO2)1-x-(ZnO)x compounds with no Ag, the highest response corresponded to x = 0.05. In addition, the optimum photodegradation was found for (TiO2)0.95-(ZnO)0.05 thin films with 2 mol% Ag.
关键词： Optical spectroscopy,Catalysis,X-ray diffraction,Sol-gel process,Thin films,Oxide materials
更新于2025-09-10 09:29:36
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Encyclopedia of Spectroscopy and Spectrometry || Optical Spectroscopy of Rare-Earth Ions in the Solid State
摘要： The birth of optical spectroscopy as science can be considered from the time when in 1672 Isaac Newton published his famous paper describing the results of experiments where, using a glass prism, he decomposed a beam of sunlight into its optical spectral components ranging from blue to red. Since that time, scientists and engineers studied a broad range of phenomena associated with the interaction of light with matter, using the fact that light actually contains different spectral components. Within a field of optical spectroscopy, it is hard to underestimate the importance of optical spectroscopy of different optical centers in solid-state materials because of numerous scientific and industrial applications of such optical systems. These applications range from studying fundamental properties of impurity centers in solids, solid-state material properties, up-conversion devices, scintillators, and Faraday rotators to a creation of solid-state lasers.
关键词： rare-earth ions,Fu¨chtbauer–Ladenburg theory,optical spectroscopy,Judd–Ofelt theory,McCumber theory,electron–phonon coupling,Franck–Condon principle,solid state
更新于2025-09-10 09:29:36
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Stability of the light-induced hidden charge density wave state within the phase diagram of
摘要： The femtosecond transient optical spectroscopy is employed to study the relaxation dynamics of the equilibrium and hidden metastable charge-density-wave states in single crystals of 1T-TaS2?xSex as a function of the Se doping x. Similar to pristine 1T-TaS2, the transition to a hidden phase is observed at low temperature after a quench with a single 50 fs laser pulse, in the commensurate Mott phase up to x = 0.6. The photo-induced hidden-phase formation is accompanied by a notable change in the coherent phonon spectra, and particularly the collective amplitude mode. While the temperature stability of the hidden phase is only slightly dependent on the Se content, the creation-threshold ?uence strongly increases with Se content from 1 to ～4 mJ/cm2, which is attributed predominantly to the change in optical absorption coef?cient at the laser excitation wavelength, and not an increased barrier of the hidden state with increasing Se.
关键词： hidden phase,charge-density-wave states,1T-TaS2?xSex,coherent phonon spectra,femtosecond transient optical spectroscopy
更新于2025-09-10 09:29:36
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Four-Dimensional Coherent Spectroscopy of Complex Molecular Systems in Solution
摘要： An understanding of microscopic interactions in solution is of fundamental importance in chemistry. However, the structure and dynamics of complex systems in the condensed phase, especially far from thermal equilibrium, are masked by broad and often featureless absorption and emission spectra. Nonlinear optical spectroscopy has proven to be a powerful and general approach to disentangling congested spectra by spreading information across multiple dimensions, revealing features oftentimes hidden in lower-order projections. As the dimensionality of the measurement increases, the better the microscopic interactions are revealed as spectral bands disperse in the large hyper-spectral volume. This capability, however, comes at a steep price as the signal decreases exponentially at higher orders of optical response and added experimental complexity increases noise. Here, we discuss a four-dimensional coherent spectroscopy known as Gradient Assisted Multidimensional Electronic–Raman Spectroscopy (GAMERS) that reveals coupling between electronic and vibrational transitions in complex, condensed phase systems ranging from organic molecules to semiconductor nanocrystals. We reveal that high-resolution spectra may be extracted from these systems even in the presence of severe spectral broadening, both homogeneous and inhomogeneous in origin. The theoretical and experimental underpinnings of this method are discussed. Increasingly, higher-order and higher-dimensionality spectroscopies like GAMERS are needed to understand the microscopic interactions that connect structure to dynamics to function.
关键词： condensed phase,GAMERS,complex systems,electronic and vibrational transitions,Nonlinear optical spectroscopy
更新于2025-09-10 09:29:36
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A review of optical methods for continuous glucose monitoring
摘要： Frequent glucose monitoring is a fundamental part of diabetes management, and good glucose control is important for long-term health outcomes. New types of electrochemical sensors that allow for continuous glucose monitoring (CGM) have become an important tool for diabetes management, although they still have drawbacks such as short lifetime and a need for frequent calibration. Other technologies are still being researched for CGM, in an attempt to replace the electrochemical sensors. Optical methods have several advantages for CGM, including potentially long sensor lifetimes and short measurement times, and many developments have been made over the last decades. This paper will review optical measurement methods for CGM, their challenges, and the current research status. The different methods will be compared, and the future prospects for optical methods will be discussed.
关键词： Optical spectroscopy,glucose sensors,continuous glucose monitoring,quantitative optical methods,biomedical applications
更新于2025-09-09 09:28:46
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Shortening nucleation time to enable ultrafast phase transition in Zn1Sb7Te12 pseudo-binary alloy
摘要： Zn1Sb7Te12 thin films have been deposited by magnetron co-sputtering of ZnTe and Sb2Te3 targets. The microstructure, phase-change speed, optical cycling stability and crystallization kinetics have been investigated during thermal annealing and laser irradiation. The thermal-annealed and laser-irradiated films give clear evidence on coexistence of trigonal Sb2Te3 and cubic ZnTe phases, which are homogeneously distributed in a single alloy as confirmed by advanced scanning transmission electron microscopy. The formation of both phases increases initial nucleation sites, leading to the rapid phase-change speed in the Zn1Sb7Te12 film. The film has a minimum crystallization time of ~3 ns at 70 mW with almost no incubation period for the formation of critical nuclei compared to Ge2Sb2Te5 and other Zn-based films. Moreover, the complete crystallization of Zn1Sb7Te12 thin films is achieved within 10 ns. The ultrafast two-dimensional nucleation and crystal growth speed in Zn1Sb7Te12 obtained from the laser-irradiated system is almost 7 times faster compared to Ge2Sb2Te5 film. Controlling crystallization process through the doping ZnTe into Sb2Te3 is thus promising for the development of high-speed optical switching technology.
关键词： Optical spectroscopy,Thin films,Phase transformation kinetics,Optical materials,STEM HAADF
更新于2025-09-09 09:28:46
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Efficient improvement of 2.7μm luminescence of Er3+:oxyfluorideglass containing gallium by Yb3+ions codoping
摘要： Mid-infrared laser materials with low phonon energy have significant applications. However, the development of available glass systems for high-power laser gain medium have posed a great challenge. Therefore, we investigated the 2.7 μm spectroscopic properties of Er3+/Yb3+-codopedoxyfluoride glass containing gallium, which were prepared by typically melting and quenching methods. The 2.7 μm luminescence properties of the Er3+/Yb3+-codopedoxyfluoride glass containing gallium were recorded by a 980 nm laser diode. The Judd–Ofelt parameters, decay curves, emission cross section, energy transfer efficiency, and quantum efficiency were calculated. The maximum emission cross section of YbFGa-0.5 is 1.63×10?20 cm2 by 980 nm excitation. The energy transfer efficiency is calculated to be 77.8% for the YbFGa-0.5 glass around 2700 nm. The quantum efficiency at 1530 nm is 65.6%. The resulting reveals that the best doping concentration ratio of Er3+:Yb3+ ions is 1:0.5, and suggests an effective energy transfer from Yb3+ to Er3+ ions.
关键词： optical materials,rare-earth ions doped,optical spectroscopy,mid-infrared,energy transfer
更新于2025-09-09 09:28:46
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Novel Handheld Diffuse Optical Spectroscopy Probe for Breast Cancer Assessment: Clinical Study
摘要： Diffuse optical spectroscopy (DOS) and diffuse optical tomography (DOT) are non-invasive breast cancer assessment modalities which employ near-infrared (NIR) light to measure optical properties of biological tissue. These properties cannot be measured by other methods including X-ray mammography, ultrasound (US) and magnetic resonance imaging (MRI) which are main breast cancer diagnosis tools. The objective of this paper is to test and validate a recently designed and developed hand-held continuous-wave radio-frequency modulated diffuse optical spectroscopy probe in a clinical trial performed on patients who diagnosed to have breast cancer. The probe has an encapsulated light emitting diode (eLED) including four wavelengths (690 nm, 750 nm, 800 nm and 850 nm) and two photodiodes located in reflectance geometry. The direct approach method has been used to extract concentration of two main chronophers in the breast tissue including deoxy-hemoglobin (Hb) and oxy-hemoglobin (HbO2). The results of the clinical trial, which included fourteen patients, show that the RF-DOS probe can correctly classify the cancerous lesion from healthy tissue in the breast. The results prove that the absorption coefficient of the breast tumor is higher than normal tissue due to higher vascularization level in four mentioned wavelengths. Conclusively, the results show 92 percent sensitivity for the extracted absorption coefficient.
关键词： Diffuse optical spectroscopy,Optical properties of biological tissue,Breast cancer,Clinical trial
更新于2025-09-09 09:28:46
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Discrimination of molecular thin films by surface-sensitive time-resolved optical spectroscopy
摘要： An optical discrimination technique, tailored to nanometric-sized, low optical absorbance molecular complexes adhering to thin metal films, is proposed and demonstrated. It is based on a time-resolved evanescent-wave detection scheme in conjunction with hierarchical cluster analysis and principal value decomposition. The present approach aims to differentiate among molecular films based on statistical methods, without using previous detailed knowledge of the physical mechanisms responsible for the detected signal. The technique is open to integration in lab-on-a-chip architectures and nanoscopy platforms for applications ranging from medical screening to material diagnostics.
关键词： time-resolved optical spectroscopy,principal value decomposition,optical discrimination technique,hierarchical cluster analysis,molecular thin films
更新于2025-09-09 09:28:46