Applied Spectroscopy最新文献

Butterfly wings exhibit optical phenomena resulting from pigments as well as from intricate nanostructures of the scales that plays an important role in their ecology mainly, communication, thermoregulation as well as mating. In our study, we examined the optical behavior of butterfly wing scales by analyzing their percent reflectance, absorbance, percent transmittance, and effective refractive index using ultraviolet-visible near-infrared (UVVis-NIR) spectroscopy which is a valuable analytical technique that provide details of the optical properties of materials. In the study conducted with 10 butterflies, the UV, visible, and NIR regions are highlighted to determine the optical properties of butterflies. From the study, it is explored that the UV region exhibit major absorbance, the visible region exhibits major reflectance, and infrared regions exhibit minor reflectance. Optical parameters other than reflectance and absorbance are derived from the spectroscopic data and plotted using Origin software. The percent reflectance, absorbance, percent transmittance, effective refractive index, and their respective wavelength of butterflies studied vary across species. Ariadne merione is observed to have the highest percent reflectance and the lowest is observed in the Eurema hecabe. The overall percentage of reflectance observed in the study ranges between 46%-68%. The absorbance is observed highest for Parantica aglea and lowest for Ypthima huebneri with optimum absorbance ranging between 1.23-0.82. The highest transmittance percentage is observed for Tirumala septentrionis, and the lowest value is observed in Mycalesis mineus and E. hecabe with optimum transmittance ranging between 63% to 47%, respectively. The refractive index was analyzed using the Fresnel equation, followed by an empirical Cauchy dispersion fit to characterize its wavelength dependence. The results revealed unusually high refractive index values for a biological specimen, indicating an effective refractive index behavior influenced by structural, pigmentation and optical complexity rather than representing the intrinsic material refractive index. This study is the first record on comprehensively determining the optical properties of Indian butterflies especially effective refractive index using UVVis-NIR spectroscopy.

Soil reflectance spectroscopy is a powerful tool for rapid, non-destructive assessment of soil properties and the foundation for data-driven soil science applications. However, systematic discrepancies during routine spectral measurement procedures, particularly those arising from contamination or deterioration of white reference (WR) calibration panels, may compromise spectral data stability and hinder harmonization practices across laboratories. This study investigates the impact of using a non-contaminated WR panel as a calibration target to measure soil reflectance across the visible (Vis), near-infrared (NIR), and short-wavelength infrared (SWIR) spectral regions. The study evaluates the effectiveness of an internal soil standard (ISS) Lucky Bay sand to correct discrepancies within a controlled laboratory setting. Twelve soils from the Israeli Legacy Soil Spectral Library were analyzed using a contact-probe setup that was calibrated with both a clean and a contaminated WR. The spectral correction method, based on IEEE P4005 protocols and the ISS calibration, significantly reduced spectral inconsistencies, especially in the Vis region where contamination effects were most pronounced. Results show that the ISS effectively harmonized spectra acquired under different WR conditions, reducing the modified average spectral difference stability (mASDS) measure across all samples. While ISS correction is commonly employed for cross-laboratory harmonization, our findings highlight its critical role in enhancing intra-laboratory consistency under routine operational variability. We recommend that every WR calibration process will be accompanied with ISS measurements. The continuous use of a well-maintained WR and ISS improves the reliability of soil spectral datasets and supports the long-term harmonization of soil spectral libraries.

Laser-induced breakdown spectroscopy (LIBS) offers a promising alternative due to its minimal sample preparation, real-time analysis capabilities, and versatility in analyzing a broad range of materials. However, the challenge lies in determining its ability to effectively distinguish high-iron ore content from mineralogically similar ores with lower iron content. This study focuses on differentiating iron ore from a variety of ores with lower iron content, including calcite, biotite, dolomite, chalcopyrite, rutile, chromite, olivine, limonite, and astrophyllite, using LIBS. By comparing the obtained spectra and applying receiver operating characteristic (ROC) curve analysis, the study assesses the specificity of the technique. The results demonstrate a high specificity (>70%) in distinguishing iron ore from biotite, dolomite, chalcopyrite, rutile, olivine, and astrophyllite, revealing the potential of LIBS for effectively identifying iron ore from some ore types. However, when comparing iron ore to other ore types, such as limonite, chromite, and calcite, the results are not statistically significant. This means that the spectral or compositional similarities between these ores may limit the method's capacity to give clear separation in certain situations. To further validate the results, two common classification models, principal component analysis followed by linear discriminant analysis (PCA + LDA) and k-nearest neighbors (KNN) were applied to the spectral data. The comparison results demonstrate the resilience of LIBS classification and the impact of mineral matrix influences on diagnostic performance.

In this paper, a lanthanide complex-based fluorescent sensor Tb(4-MBA) was developed for the selective recognition of diabetic ketoacidosis (DKA) and the diabetes biomarker β-hydroxybutyric (β-Hb). β-Hb significantly enhanced the fluorescence emission of the Tb(4-MBA) complex at 539  nm. Based on the analysis of the surface electrostatic potential distribution and time-resolved spectra, we speculate that in the reaction system of β-Hb with Tb(4-MBA), β-Hb and Tb(4-MBA) may form a complex through hydrogen bonding interactions, which brings β-Hb closer to Tb³⁺ and thus reduces the non-radiative energy loss of the solvent molecules to Tb³⁺ and significantly enhances the Tb(4-MBA) fluorescence intensity. The linear range of Tb(4-MBA) for β-Hb was 2-55 μM, and the limit of detection (LOD) was 50.6 nM. This sensor has high sensitivity and selectivity and shows great potential in the field of screening and diagnosis of diabetes mellitus and DKA.

Tropical mosquitoes transmit diseases like malaria, yellow fever, and Zika. Classifying mosquitoes by species, sex, age, and gravidity offers vital insights for assessing transmission risk and effective mitigations. Photonic monitoring for mosquito classification can be used in distributed sensors or lidars on longer ranges. However, a reflectance model and its parameters are lacking in the current literature. This study investigates mosquitoes of different species, sexes, age groups, and gravidity states, and reports metric pathlengths of wing chitin, body melanin, and water. We use hyperspectral push-broom imaging and laser multiplexing with a rotation stage to measure near-infrared spectra from different angles and develop simple models for spectral reflectance, including wing thickness and equivalent absorption path lengths for melanin and water. We demonstrate wing thickness of 174 (±1) nm - the thinnest wings reported to our knowledge. Water and melanin pathlengths are determined with ∼10 µm precision, and spectral models achieve adjusted R² values exceeding 95%. While mosquito aspect angle impacts the optical cross-section, it alters shortwave infrared spectra minimally (∼2%). These results demonstrate the potential for remote retrieval of micro- and nanoscopic mosquito features using spectral sensors and lidars irrespective of insect body orientation. Improved specificity of vector monitoring can be foreseen.

The waxy gene of maize is a high value breeding target, but it is time consuming to separate waxy and wild-type kernels. A common method involves staining the endosperm with iodine. Near-infrared reflectance (NIR) spectroscopy has been used in several species including maize with success. A custom-built single kernel NIR spectroscopy instrument was used to scan 2880 individual kernels from 60 samples with a diversity of pedigrees, with both waxy, wild type, and heterozygous kernels represented. Chemical analysis was performed to classify the kernels with the waxy or wild type phenotypes. Linear discriminant analysis (LDA) was conducted to develop a prediction equation for single kernel NIR spectroscopy. The discriminant results showed that there was an 88% accuracy in predicting waxy kernels as waxy, and a 96% accuracy in predicting wild type kernels as wild type. A receiver operating characteristic (ROC) curve was determined to allow threshold adjustment to meet desired true positive or false negative rates. Thus, the prediction equation can be used in breeding programs to select for waxy kernels in an efficient and effective manner using a single kernel NIR instrument. This approach will benefit breeders of waxy corn by providing a rapid, automated non-destructive method for identification of waxy kernels in segregating breeding populations.

Polymer films with a thickness in the two-digit micrometer range are coated with nanometer-thin oxide layers in roll-to-roll coating systems. The coating improves the properties of the film, such as gas or water permeation. Maintaining a sufficiently large coating thickness is crucial to ensure its barrier function; thus, inline quality control of the thickness is indispensable. For this purpose, we have developed a sensing principle that addresses specific absorption bands of the coating via a reflection measurement in the infrared spectral range. However, for thin and weakly absorbing polymer substrates, light is reflected not only by the coating and the surface of the polymer. Partly it is also transmitted and reflected by the backside of the film, leading to interference effects that significantly affect the measurement signal. As industrial films vary in thickness by several percent and their exact values are unknown, determining the thickness of an oxide coating is hindered. In this paper, we demonstrate an approach for measuring coating thickness on such varying polymer films by averaging the interferences obtained at multiple angles of incidence. Calculations and measurements on industrial film samples indicate the effectiveness of our approach. It produces results with $\pm 2$ nm precision and $\pm 5$ nm accuracy for a thickness in the range of 5-100 nm. Furthermore, we discuss a possible implementation of this approach in an inline measurement system by fulfilling its requirements, for example, versatility and compactness.

Classical quantitative chemometrics based on absorbance spectra has been routinely performed for approximately 40 years. Since absorbance is a function of the absorption index, it is natural to extend chemometric methods to the refractive index function. This function, related to the absorption index via the Kramers--Kronig relations, is derived from corrections applied to absorbance spectra to ensure compliance with wave optics principles. In this note, we demonstrate that, at least in the quasi-thermodynamically ideal binary system of benzene and toluene, classical quantitative chemometrics performs better when based on refractive index spectra than when based on absorption index spectra. The primary reason for this difference is that the refractive index at a given wavenumber integrates all changes resulting from absorptions at higher wavenumbers. This property is particularly advantageous in non-absorbing regions, where absorption index spectra provide no information about the system's composition.

This paper presents a novel analytical technique for evaluating fluorescence lifetimes excited by a nanosecond pulsed laser using a linearized rate equation approach that accounts for the incident pulse temporal distribution, an equivalent instrument response function, and non-exponential fluorescence decay which limits the application of traditional fluorescence lifetime techniques in stand-off applications. The approach is applied to model the fluorescence of a variety of pharmaceutical powders and phosphorescing samples exhibiting non-exponential decay and compared to results obtained with the maximum entropy method. Fluorescence lifetimes are found to be 3-5  ns, typical for organic fluorescent powders, and phosphorescence lifetimes were on the order of hundreds of nanoseconds. The approach also shows potential for determining the composition of mixed samples and can be readily extended to model increasingly complex scenarios with additional fluorescing or phosphorescing components.