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Spectral analysis for photoacoustic pressure sensor designs: Theoretical model improvement and experimental validation
摘要： In the pulsed laser photoacoustic (PA) detection and spectroscopy applications, the fundamental frequency of the PA signal produced, and the sensor resonance frequency should be as close as possible to each other so that analyzes from the obtained signals can be performed effectively. In order to determine the fundamental frequency of the PA wave, a theoretical model approach based on the development of the frequency domain solution of the PA wave equation is presented for use in the PA pressure sensor designs. For the validation of the theoretical model approach, a PA experimental setup was established, and measurements were made in distilled water. The theoretical and experimental PA frequency spectra were determined to be very compatible with each other. Thus, the theoretical model approach was experimentally validated. According to the theoretical model approach, fundamental frequency values obtained from the experimental measurement results were determined with an average accuracy of ? 4.212%. Furthermore, it has been determined that this value has fallen to ?0.267% in the measurements. With the obtained results from the theoretical model approach, we propose that PA pressure sensors with the more selective and narrower band can be designed for more sensitive detection. Moreover, in this study the effects of different laser parameters such that pulse duration, and laser beam width, on the spectral content of the obtained PA signal are analyzed. These analyses will shed light on the vision of acoustic pressure sensor design by helping to select the most optimum parameters for PA detection.
关键词： Theoretical model approach,Photoacoustic wave equation,Acoustic pressure sensor,Frequency domain solution,Pulsed laser photoacoustic method,Spectroscopy
更新于2025-09-23 15:23:52
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Crystal growth, structural and electrical properties of (Cu1-Ag )7GeS5I superionic solid solutions
摘要： Single crystals of (Cu1-хAgx)7GeS5I solid solutions were grown by vertical zone crystallization method. XRD studies have shown that they crystallize in face-centered cubic lattice of the argyrodite structure (space group F m4 3 , Z = 4). Structural studies were performed on the basis of original structure model by means of Rietveld re?nement method. Electrical measurements were carried out in the temperature interval 300–360 K and in the range of frequencies 10 Hz–10 GHz. Temperature and frequency dependences of electrical conductivity were analyzed. In?uence of cation substitution on the electrical conductivity as well as relationship between structural and electrical properties of (Cu1-хAgx)7GeS5I solid solutions were studied.
关键词： Arrhenius law,XRD studies,Superionic conductor,Impedance spectroscopy,Electrical conductivity
更新于2025-09-23 15:23:52
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Li- and Mg-codoped bismuth niobate pyrochlores: Synthesis, structure, electrical properties
摘要： The structure and conductivity of the new Li- and Mg-codoped bismuth niobates Bi1.5Mg1?xLixNb1.5O7?δ (0 ≤ x ≤ 0.50) with the pyrochlore structure have been investigated. The samples were synthesized by the method of organic-inorganic precursors combustion. A structural characterization was performed using 7Li nuclear magnetic resonance (NMR) spectroscopy in combination with the ?tting of X-ray di?raction patterns. The Li+ cations dynamics were studied by temperature-dependent 7Li NMR lineshape analysis. The measurements have shown that the Li+ cations are distributed in one of two possible sublattices in the structure and are not mobile up to 120 °C. According to the results of structural analysis of the Bi1.5Mg1?xLixNb1.5O7?δ (x = 0.25; 0.50) pyrochlores the lithium atoms are distributed in the bismuth sites. The electrical properties were investigated by impedance spectroscopy method in the air, oxygen and “wet” atmospheres in the 25–750 °C temperature range. The activation energy value of dc conductivity is about 1.2–1.3 eV for the all samples and corresponds to the ionic (oxygen) conductivity at T > 400 °C. Electronic (p-type) conductivity was determined at T < 360 °C. 1H MAS NMR data and the results of the comparison of the conductivity of Li- and Mg-codoped bismuth niobates in dry and “wet” atmospheres point to the proton conductivity up to 500 °C. The dielectric permittivity ε′ values increase with lithium content from 86 (x = 0) to 143 (x = 0.5) at the same dielectric loss tanδ = 0.002 (1 MHz, 25 °C), TCC values vary from ?590 to ?530 ppm/°C in the 25–280 °C temperature range.
关键词： Conductivity,Dielectric properties,Pyrochlore,Dopant distribution,NMR spectroscopy,Bismuth niobate
更新于2025-09-23 15:23:52
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On the homogeneity of the external quantum efficiency in a free OPV roll-to-roll flexible solar module
摘要： We present a microscopic characterization of an organic photovoltaic (OPV) module demonstrator, fabricated within the “freeOPV” project. The local properties of the module are discussed on di?erent length scales, from the submicrometric to the centimeters one, inferring the module structure and the origin of the di?erent contributions to the optical and photoelectrical spatial inhomogeneity. We show that the local external quantum e?ciency (EQE) in the individual cells of the module exhibits typical variations within 6–8% of the peak value over about 0.4 mm2. Larger variations are observed when comparing di?erent cells across the module surface, with di?erences in the EQE peak values up to 1.6 times. Our results suggest that the roll-to-roll OPV module performance can be further improved by optimizing the printing uniformity as well as the charge extraction e?ciency of electrodes.
关键词： Confocal spectroscopy,Organic solar cells
更新于2025-09-23 15:23:52
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Ultrasensitive analysis of kanamycin residue in milk by SERS-based aptasensor
摘要： An ultrasensitive method for the kanamycin (KANA) detection in milk sample using surface-enhanced Raman spectroscopy-based aptasensor was employed in the current study. Double strand DNA binding bimetallic gold@ silver nanoparticles were developed as a sensing platform. Probe DNAs were first embedded on the surface of gold nanoparticles by the end-modified thiol, and after silver shell encapsulating, KANA aptamer DNAs with the Raman reporter Cy3 were then hybridized with probe DNAs by complementary base pairing. Results showed that with increase in the KANA concentration, the Raman intensity of Cy3 decreased. Besides achieving selectivity, an ultralow detection limit of 0.90 pg/mL, a broad linear relationship ranging from 10 μg/mL to 100 ng/mL in aqueous reagent and satisfactory recoveries of 90.4–112% in liquid whole milk were obtained. The result of actual sample proved that this aptasensor was promising in trace determination of KANA residue.
关键词： Milk,Kanamycin,Aptamer,Surface enhanced Raman spectroscopy
更新于2025-09-23 15:23:52
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Diamond like carbon films with embedded Cu nanoclusters deposited by reactive high power impulse magnetron sputtering: Pulse length effects
摘要： In the present study diamond like carbon films with embedded Cu nanoclusters (DLC:Cu films) were deposited by reactive high power impulse magnetron sputtering (HIPIMS). HIPIMS pulse length (pulse on time) effects were considered. The dependence of the chemical composition on pulse length was found. Structure of diamond like carbon matrix of the nanocomposite films studied by Raman scattering spectroscopy has indicated weak increase of the sp3/sp2 carbon bond ratio with HIPIMS pulse length. Studies of the shape and dimensions of copper nanoclusters performed by He ion microscopy have shown that increase of the HIPIMS pulse on time resulted in increased number of the nanoclusters and subsequent increase of the Cu nanoclusters size. Study of optical properties revealed surface plasmon resonance effect in all investigated films. Correlation between the optical absorption spectra and photoexcited charge carrier relaxation time recorded by the pump probe spectroscopy was found. The highest relaxation time was observed at the excitation wavelength close to the absorption surface plasmon resonance peak wavelength The highest maximum relaxation time was observed for the DLC:Cu film deposited by using HIPIMS pulse of 400 μs on time. It was explained by the dependence of the relaxation time on Cu nanocluster size.
关键词： Pulse length,Diamond-like carbon,High-power pulsed magnetron sputtering,Structure,Optical properties,X-ray photoelectron spectroscopy,Copper,Nanoclusters
更新于2025-09-23 15:23:52
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Performance anaysis and small signal identification of time-resolved stand-off Raman spectroscopy system
摘要： Performance anaysis and small signal identification of time-resolved stand-off Raman spectroscopy system. Over the last decade, the time-resolved stand-off Raman spectroscopy has attracted considerable attention due to its daytime measurement model and fluorescent suppression. Suffering from the small Raman scattering efficiency, this system perusing large detection distance requires both large power consumption and optical system, which blocks its applications. In order to seek for high signal collection efficient, in this work, we designed a 2-inch refractive telescope system, and obtained 20 m detection distance using a frequency-doubled 532 nm Nd: YAG laser with pulse energy of 30 mJ. By adjusting the excitation energy through a variable attenuator, we investigate the interrelations of input power, the signal and the noise consisting of the internal and signal-induced noises. For both main peak and sub peak, the signal-induced noises are subject to a power function of the signal intensity, and can be filtered and smoothed by the norm-distribution-function weighted moving average method (WMAM) without the loss of the signal information. After transforming the correlation spectrum, defined by the multiplication of the noise and signal spectrum, iteratively by WMAM, we can identify the small signal of about 1 count beyond the internal noise limitation. With help of the iteration method, the requirement of integration time as well as the excitation energy can be greatly reduced.
关键词： small signal,Raman spectroscopy,stand-off
更新于2025-09-23 15:23:52
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Shining light on growth-dependent surface chemistry of organic crystals: a polarised Raman spectroscopic and computational study of aspirin
摘要： Understanding and controlling crystal surfaces is a critical problem in contemporary materials science. Organic crystal surfaces present the additional complexity of multiple terminations with different functional groups. These alternate terminations influence the surface chemistry and exert control on many material properties. While established tools for surface characterization exist, few provide the chemical information required to unambiguously identify functional groups. Polarized Raman spectroscopy is a versatile tool that can provide detailed chemical information on molecular materials, and, when used in a microscope configuration, can be used to map substrates on a micron scale. In this work, we demonstrate the use of polarized Raman to study the surface chemistry of aspirin. By analyzing crystals grown under a variety of conditions, we relate the growth solvent to the surface termination and reconcile the conflicting results in the literature on the nature of the <100> surface. Our results are supported by detailed first-principles modelling of the surfaces and their vibrational spectra. This study establishes the potential of polarized Raman microscopy as a tool for organic surface science that, when combined with predictive modelling, provides a powerful means to understand and ultimately control surface chemistry.
关键词： aspirin,first-principles modelling,crystal growth,polarized Raman spectroscopy,surface termination,lattice dynamics
更新于2025-09-23 15:23:52
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Rapid, non-destructive determination of ginseng seed moisture content by near infrared spectroscopy technology
摘要： Ginseng seed moisture content (SMC) determination and monitoring are of great importance during seed storage and in trading. The traditional oven-drying method for SMC measurement is accurate but takes both time and labour. The objective of this study was to develop a rapid and non-destructive method for ginseng SMC determination using near infrared (NIR) spectroscopy. Eighteen freshly harvested seed lots stored for different periods (days) were used for NIR model development and 12 commercial seed lots were used for validation of the model. The model developed in the present work had an R2 of 0.9913, residual prediction deviation (RPD) of 11.3 and low root mean square errors assessed by cross-validation (RMSECV; 0.387%). For commercial seed lot measurement, the predicted values of SMC were nearly the same as measured ones, with the relative differences less than 2.96%. In conclusion, NIR spectroscopy suitable for rapid and nondestructive determination of ginseng SMC.
关键词： near infrared spectroscopy,seed moisture content,ginseng
更新于2025-09-23 15:23:52
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Microthermometry and Raman spectroscopy of fluid inclusions from El Vapor gold mineralizations, Colombia
摘要： Epigenetic El Vapor gold mineralization is hosted by the Segovia batholith and sedimentary rocks at both sides of El Nús fault, in the eastern flank of the Colombian Andes central cordillera. Gold mineralization is composed by continuous and discontinuous sigmoidal and stockwork veins and veinlets from a few centimeters to two meters of thickness and by hydrothermal breccias. Ore mineralogy includes Pyrite + Galena + Sphalerite + Chalcopyrite + Pyrrhotite + Proustite - Pyrargyrite. Gold occurs as inclusions within pyrite, between quartz crystals and filling fractures within pyrite at a late stage of mineralization. The fluid inclusions in quartz veins occur as clusters of primary inclusions or in alignments of secondary and pseudo-secondary inclusions. Based on petrography and Raman spectroscopy, four types of fluid inclusions could be recognized: (1) Type I are primary biphasic, liquid-rich, with CO2(v) + N2(v) + CH4(v) + KCl(AQ) + NaCl(AQ) + H2O(L), (2) Type II are primary or pseudo-secondary, multi-volatile presenting CO2(V) + CO2(L) + N2(V) + CH4(V) + KCl(AQ) + NaCl(AQ) + H2O(L), (3) Type III are secondary, two-phase, liquid-rich inclusions, composed of H2O(v) + H2O(L) + KCl(AQ) + NaCl(AQ) and have two different times of formation (IIIA and IIIB), (4) Type IV are very rare, three-phasic, secondary inclusions and composed of S + H2O(V) + H2O(L) + KCl(AQ) + NaCl(AQ). The microthermometric and spectroscopic analysis of fluid inclusions indicates that the fluid associated with the first event of mineralization identified in El Vapor have low to moderate salinities (3.5-9.2 wt% NaCl equiv.), with trapping temperatures between 214°C and 350°C and pressures between 0.5kbar and 2.9kbar. Due to the nonexistence of fluid inclusions with variable degree of filling with opposite homogenization and because of the variations of salinity in a restricted homogenization temperatures range, it is proposed an isothermal fluid mixture process, which together with fO2 changes, generated by fluid reaction with the carbonaceous shales of the Segovia sedimentary rocks, could influence the process of gold deposition. Hydrothermal fluids from El Vapor were near neutral and reduced; simlar features have been found in orogenic deposits hosted by turbidite sequences around the world.
关键词： Orogenic,reduced fluids,El Vapor district,Microthermometry,Raman spectroscopy,Gold mineralizations,Fluid inclusions
更新于2025-09-23 15:23:52