Spectra Of Pigments Research Articles

A method to standardize the temperature for near infrared spectra of the indigo pigment in non-dairy cream based on symbolic regression

Near infrared (NIR) spectroscopy is sensitive to physical conditions such as sample temperature, meaning that rapid detection methods based on NIR spectroscopy are significantly influenced by temperature. To address this challenge, symbolic regression was employed to mitigate the effects of temperature. The Weighted Windowed Adaptive Optimization algorithm was proposed and combined with the Sequential Projection Algorithm to extract temperature-related feature points and remove redundant data. Subsequent 3D modeling of these feature points revealed that absorbance alterations due to temperature comprised two distinct segments. Consequently, based on symbolic regression, the temperature standardization algorithm was devised to generate piecewise equations. This algorithm surpassed genetic programming and non-segmented methods in performance metrics. The piecewise function equations generated by the algorithm were used to regress the absorbance at different temperatures to the standard temperature. Non-dairy cream, with different indigo pigment contents, was temperature standardized using a piecewise function to obtain spectra at two standard temperatures; 18°C and 28°C. The r2 for the quantitative regression model improved from 0.71 to 0.95 at 18°C and from 0.63 to 0.85 at 28°C. The temperature standardization method offers interpretable equations for spectra that model the complex changes with temperature, factoring out the temperature variation, thereby facilitating the practical use of NIR spectroscopy in rapid detection applications.

Semi-commercial scale fermentation of prawn waste by Exiguobacterium sp. GM010 for bioactive pigment production: Safety and efficacy assessment in Wistar rats

Pigment producing Exiguobacterium sp. GM010 demonstrates utilization of prawn carapace hydrolysate. Accordingly, our investigation was focused to produce cost effective bioactive pigment in 15 L semi-commercial scale. Further acute and subacute toxicities were evaluated as per OECD guidelines for application as nutraceutical. The biomass and pigment extract yield were 28.76 ± 1.78 and 0.82 ± 0.04 g/L, respectively, at 1.5 L of aeration. The UV–visible spectrum of pigment showed absorption peaks at 357, 466, and 491 nm indicating carotenoid like pigment. This was correlated with colour distribution in yellowish-orange region of CIE Lab spectrum. The qualitative and quantitative characteristics of pigment were similar between lab-scale and bioreactor production. The acute toxic dose (2000 mg/kg bw) exhibited the toxicity as determined by haematological analysis. While subacute toxic dose (250, 500, 1000 mg/kg bw) demonstrated no adverse effects on parameters such as food intake, body weight gain, vital organ weight, haematological and histopathological examination. Serum biochemistry results showed significant increase in HDL and decrease in SGPT values in treated groups compared to control. The results revealed that, Exiguobacterium sp. GM010 has efficiently utilised prawn waste to produce bioactive pigment. The dose of Exiguobacterium sp. GM010 pigment lower than 1000 mg/kg bw can be regarded as safe.

The Application of Cathodoluminescence (CL) for the Characterization of Blue Pigments

The combined application of Cathodoluminescence (CL) with Scanning Electron Microscopy (SEM) on paintings and painted surfaces has the potential to identify both organic and inorganic pigments on a micrometre or even nanometre scale. Additionally, the combination with Energy-Dispersive Spectrometry (EDS) allows for a more holistic, elemental, and mineralogical characterization of pigments. In addressing the need for the creation of a robust, open access database of characteristic CL spectra of pigments, a large project has been undertaken, focusing primarily on common organic and inorganic pigments. The present paper focuses on the CL characterization of 10 significant blue pigments in pure powder form: cerulean blue, Egyptian blue, Han blue, indigo, lapis lazuli, Maya blue, phthalo blue, vivianite, ultramarine blue, and zirconium blue. The CL spectra present characteristic bands for most of the pigments, allowing their secure identification, especially when combining the results with the EDS analyses. The effect of binding media and of the mixture of different pigments was also studied, via the analysis of mixtures of pigments with oil painted over canvas. Overall, both the binding medium and the mixture of pigments do not appear to create significant differences in the occurring spectra, thus allowing the identification of individual pigments. EDS and RAMAN spectra are included in order to facilitate comparison with other databases.

ToF-SIMS spectra of historical inorganic pigments: Natural and synthetic ultramarine blues and smalt in both polarities

ToF-SIMS spectra of historical inorganic pigments: Natural and synthetic ultramarine blues and smalt in both polarities

ToF-SIMS spectra of historical inorganic pigments: Lead-based pigments in negative polarity

ToF-SIMS spectra of historical inorganic pigments: Lead-based pigments in negative polarity

SPECTRAL PROPERTIES OF CHLOROPHYLLS IN EDIBLE PLANTS INTENDED FOR DIAGNOSTICS

Abstract. This study examined the absorption and fluorescence spectra of chlorophylls and other pigments extracted in ethanol solutions from common edible plant species. Chlorophyll-a was the dominant fluorescent chromophore in all plant varieties. The fluorescence curves for all extracted solutions exhibit after optimizing by concentration dilution an increase in the fluorescence with a typical prominent leading Gaussian peak at a wavelength of 674 nm. This peak is followed by a decreasing shoulder extending into the near-infrared range beyond 724 nm. The dilution of the solutions with ethanol reduces the optical absorption from the other pigments and shows simultaneously an improved resolution of the chlorophyll-a spectral absorption peaks. This investigation provides new insights into the optical absorbance and other photo-excited processes that impact the fluorescence of chlorophylls, such as agglomeration, photobleaching and photo-aggregation. The findings may be used for biodiagnostics, fluorescent quantum dots and bio-sensors.

ToF-SIMS spectra of historical inorganic pigments: Lead-based pigments in positive polarity

ToF-SIMS is increasingly used to analyze cultural heritage materials because it can simultaneously detect organic and inorganic materials while mapping them on a surface. The precise identification of a pigment in a specific layer of a painting or of remaining color on a statue can inform about the technique used or the time of manufacture as well as expose possible forgeries when anachronistic ingredients are identified. Reference spectra are required to confidently identify a given pigment using ToF-SIMS. This database focuses on eight lead-based historical inorganic pigments, manufactured following traditional recipes. Lead pigments have been widely used in painting until the late 19th century. Here, the positive polarity ToF-SIMS reference spectra using a Bi3+ primary ion species are presented.

Charge compensator adjusts the luminescence intensity of ZnWO4: Sm3+ full spectrum phosphors: A bifunctional phosphors for plant growth lights and FIR thermometers

Full spectrum white LED plant growth light sources are suitable for use in conditions requiring a high color rendering index. In addition to red and blue light, green light was shown to have a positive impact on plant growth in earlier studies. In this work, a series of Sm3+ doped ZnWO4 phosphors was prepared using the high-temperature solid-state reaction method. Li+ serves as a charge compensator to reduce lattice defects caused by non-equivalent isomorphism. XRD measurements and Rietveld refinement were used to investigate the phase composition and structural properties of the samples. The luminescent properties of the samples were tested using a fluorescence spectrophotometer. The Li + introduction can significantly improve the energy transfer from the matrix to Sm3+ and the luminescence intensity of Sm3+. In addition, this phenomenon was explained with non-equivalent isomorphism and the charge density difference diagram. The LED lamp was prepared using ZnWO4: 0.004Sm3+, 0.004Li + phosphor and LED chip. The emitted full spectrum light can match well with the absorption spectrum of plant pigments. The color rendering index of the LED lamp is greater than 91. And the comparative experiment of plant cultivation shows that the prepared LED plant lamp has good effects. The dependence of luminescence properties of ZnWO4: 0.004Sm3+, 0.004Li+ phosphor on temperature was determined. Based on fluorescence intensity ratio (FIR) technology, the maximum SaMAX and SrMAX are 52 % K−1 at 453 K and 9.31 % K−1 at 303 K, respectively. As the temperature increases, the chromaticity shift (Δs) value is 0.254. The benefits of the ZnWO4: 0.004Sm3+, 0.004Li+ phosphor are the straightforward synthesis process, low cost, pure phase, full spectrum, high color rendering index, tunable red-to-blue ratio, and temperature monitoring function. Therefore, this phosphor is an ideal material in plant growth and optical temperature measurement.

Designed complexes combining brazilein and brazilin with betanidin for dye-sensitized solar cell application: DFT and TD-DFT study

Dye-sensitized solar cells (DSSCs) are promising third-generation photovoltaic cell technology owing to their easy fabrication, flexibility and better performance under diffuse light conditions. Natural pigment sensitizers are abundantly available and environmentally friendliness. However, narrow absorption spectra of natural pigments result in low efficiencies of the DSSCs. Therefore, combining two or more pigments with complementary absorption spectra is considered an appropriate method to broaden the absorption band and boost efficiency. This study reports three complex molecules: brazilin-betanidin-oxane (Braz-Bd-oxane), brazilin-betanidin-ether (Braz-Bd-ether) and brazilein-betanidin-ether (Braze-Bd-ether), obtained from the etherification and bi-etherification reactions of brazilin dye and brazilein dye with betanidin dye. The equilibrium geometrical structure properties, frontier molecular orbital, electrostatic surface potential, reorganization energy, chemical reactivities, and non-linear optical properties of the studied dyes were investigated using density functional theory (DFT)/B3LYP methods, with 6-31+G(d,p) basis sets and LANL2DZ for light atom and heavy atoms respectively. The optical-electronic properties were calculated using TD-DFT/B3LYP/6-31+G(d,p) for isolated dye and TD-DFT/CAM-B3LYP/6-31G(d,p)/LANL2DZ for dyes@(TiO2)9H4. The results reveal that spectra for Braz-Bd-oxane and Braze-Bd-ether complexes red-shifted compared to the individually selected dyes. The simulated absorption spectra of the adsorbed dyes on (TiO2)9H4 are red-shifted compared to the free dye. Moreover, Braz-Bd-oxane and Braz-Bd-ether exhibit better charge transfer and photovoltaic properties than the selected natural dyes forming these complexes. Based on the dyes' optoelectronic properties and photovoltaic properties, the designed molecules Braz-Bd-oxane and Braze-Bd-ether are considered better candidates to be used as photosensitizers in dye solar cells.

Precise in-situ detection of inorganic pigments in ancient architectural color paintings by HH-XRF

The handheld X-ray fluorescence spectrometer (HH-XRF) is commonly used to detect the inorganic elemental composition of pigments on-site. However, the accuracy of in-situ detection results can be affected by the characteristics of the painted surface contaminants and the layered structure of pigments in ancient architectural color paintings. To mitigate this error, a method was proposed that combined the XRF spectra of inorganic pigments with the elemental concentration values obtained through principal component analysis (PCA). Additionally, this study discussed the typical surface contaminants and pigment layering found in color paintings separately. Firstly, experiments were conducted on dust accumulation layers of varying thicknesses. The results indicated that the condition of color paintings after pretreatment of dust accumulation tended to resemble the situation with thin dust accumulation during in-situ testing. A fitting formula was derived to establish a relationship between field testing and laboratory testing results. Secondly, experiments were conducted using various combinations of pigment layers. Based on the findings, it was hypothesized that there was a connection between XRF detection results and the maximum concentration value of a single element (as determined by XRF, in an unmixed or unlayered pigment sample without dust or smoke accumulation). The test results were fitted using a Polynomial formula, providing evidence for the existence of a nonlinear functional relationship between these two variables. Finally, an empirical formula for predicting the concentration values of the top color layer with different base colors was proposed. This study offered a precise method for accurately assessing pigments of ancient architectural color paintings through in-situ testing.

HEXOKINASE1 and glucose-6-phosphate fuel plant growth and development.

As photoautotrophic organisms, plants produce an incredible spectrum of pigments, anti-herbivory compounds, structural materials and energic intermediates. These biosynthetic routes help plants grow, reproduce and mitigate stress. HEXOKINASE1 (HXK1), a metabolic enzyme and glucose sensor, catalyzes the phosphorylation of hexoses, a key introductory step for many of these pathways. However, previous studies have largely focused on the glucose sensing and signaling functions of HXK1, and the importance of the enzyme's catalytic function is only recently being connected to plant development. In this brief Spotlight, we describe the developmental significance of plant HXK1 and its role in plant metabolic pathways, specifically in glucose-6-phosphate production. Furthermore, we describe the emerging connections between metabolism and development and suggest that HXK1 signaling and catalytic activity regulate discrete areas of plant development.

Gaussian Decomposition vs. Semiclassical Quantum Simulation: Obtaining the High-Order Derivatives of a Spectrum in the Case of Photosynthetic Pigment Optical Properties Studying.

In this paper, a procedure for obtaining undistorted high derivatives (up to the eighth order) of the optical absorption spectra of biomolecule pigments has been developed. To assess the effectiveness of the procedure, the theoretical spectra of bacteriochlorophyll a, chlorophyll a, spheroidene, and spheroidenone were simulated by fitting the experimental spectra using the differential evolution algorithm. The experimental spectra were also approximated using sets of Gaussians to calculate the model absorption spectra. Theoretical and model spectra can be differentiated without smoothing (high-frequency noise filtering) to obtain high derivatives. Superimposition of the noise track on the model spectra allows us to obtain test spectra similar to the experimental ones. Comparison of the high derivatives of the model spectra with those of the test spectra allows us to find the optimal parameters of the filter, the application of which leads to minimal differences between the high derivatives of the model and test spectra. For all four studied pigments, it was shown that smoothing the experimental spectra with optimal filters makes it possible to obtain the eighth derivatives of the experimental spectra, which were close to the eighth derivatives of their theoretical spectra.

Formulation of calcium based 8-HQ fluorescent paint for fluorescent paint applications

We report the formulation of luminous paints with calcium-based quinoline complex, bis(8-hydroxyquinoline) (calcium) – Caq2 as a pigment (where Ca = Calcium, q = 8-hydroxy quinoline). Fourier transform infrared (FTIR) spectra, UV–Visible absorption, Photoluminescence (PL) spectra and photometric evaluation of the pigment were probed to evaluate its structural, optical and photometric properties. The excitation spectra of Caq2 pigment portrays a broad excitation peak at 370 nm, while emission spectra reveal a broad peak, registered at 473 nm which falls in the bluish-green region of the visible spectrum. Further, fluorescent paints were formulated on glass slides with epoxy resin/ urea formaldehyde as binder and toluene as solvent. The results reveal the change in intensity of the painted panels in the following order IZnO Epoxy(50%) > IEpoxy based pure pigment > IUF based pure pigment > IZnO Epoxy(10%) > IZnO UF(10%). These results reveal the potential of the pigment as one of the components of fluorescent paint.

Bioproduction and Application of Orange and Yellow Pigments Obtained from Chryseomicrobium palamuruense and Micrococcus luteus

Colour is a fundamental and most likely one of the primary attributes to be observed by the human senses, making it an essential part of human life and culture. This study investigates the bioproduction and potential application of bacterial pigments obtained from abattoir wastewater. Bacteria isolates recovered from abattoir wastewater were screened for pigment production and identified using the 16S rRNA gene sequence. Optimal physicochemical conditions of parameters were investigated and harnessed for bulk pigment production. Pigments produced were characterised using UV-Visible Spectrophotometer and Fourier Transform Infra-Red (FTIR) Analysis. The antibacterial and dyeing ability of the extracted pigments were evaluated. Two bacteria namely, Chryseomicrobium palamuruense strain PUI and Micrococcus luteus strain 1k produced orange and yellow pigments respectively. The UV-visible spectrum of the orange pigment produced by Chryseomicrobium palamuruense showed surface plasmon resonance peaks at 262, 426, and 453 nm while that of the yellow pigment produced by Micrococcus luteus showed a single peak at 260 nm. The FTIR analysis of the extracted pigments indicated the presence of some functional groups namely hydroxyl (OH), C-H, primary and secondary C-O, and skeletal C-C vibrations. Chryseomicrobium palamuruense and Micrococcus luteus showed no antibacterial activity against the selected typed bacterial isolates assessed in this study. The orange pigment extracted from Chryseomicrobium palamuruense was retained on cotton and polyester producing different shades of colour on the two fabrics when used as a dyeing agent. The pigment-producing potentials of these organisms suggest their relevance as promising dyes in textile industry.

Ancient Rock Paintings at Region del Cabo-BCS, Mexico: An Analytical Study

This study focused on the examination of six rock pictorial panels and a solitary figure from four archaeological sites in the Sierra de las Cacachilas (Sector A) in the Region del Cabo, Baja California Sur, Mexico. Scanning Electron Microscopy-energy dispersive X-ray spectroscopy was utilized to analyze tiny samples of the pictorial layers, patina, rocky supports, and natural pigments. The concentrations of C, Mg, Al, Si, P, S, K, Ca, Cr, Ti, Mn, and Fe were subjected to statistical methods and the samples were divided into various clusters. Iron and calcium compounds appear to be the primary constituents of the pictorial layers. The red pigment spectra obtained through Fourier-transform infrared spectroscopy revealed the presence of inorganic compounds and the likelihood of a flora-based composite as the binding agent. The minerals identified through X-ray diffraction in the rocky supports were determined to be intrusive igneous rocks. These findings are significant for the conservation and preservation of the artwork in the Sierra de las Cacachilas.

S 2 − and S3− radicals and the S42− polysulfide ion in lazurite, haüyne, and synthetic ultramarine blue revealed by resonance Raman spectroscopy

Abstract Taking advantage of the Raman resonance effect, we employed 405 and 532 nm excitations to (1) identify sulfur species present in lazurite, haüyne, and synthetic ultramarine blue pigments and (2) investigate the enigmatic ~485 cm–1 band found previously in Raman spectra of lazurite and haüyne collected with 458 nm excitation. In spectra of lazurite and haüyne, bands of the sulfate ion and S2− and S3− radicals can be seen. Spectra collected using 405 nm excitation show the enhancement of the intensity of ν1(S2−) band and its nν1 (n ≤ 7) progression. Spectra collected using 532 nm incident light show the enhancement of intensity of ν1(S3−), ν2(S3−), and ν3(S3−) bands and the nν1 (n ≤ 9) and ν2 + nν1 progressions of the ν1(S3−) band. In spectra collected with 405 nm excitation, we also found features that we ascribe to the S42− polysulfide ion. These include the ν1 symmetric S-S stretching band at ~481 cm–1, the ν2 symmetric S-S stretching band at ~443 cm–1 (only present in spectra of some lazurite samples), the ν3 symmetric S-S bending at 223 cm–1 and the nν1 (n ≤ 5) and nν1+ν3 progressions of the ν1(S42−) band. We observed that under laser illumination, the S42− polysulfide ion rapidly decomposes into two S2− radicals in lazurite while it remains stable in haüyne. In spectra of synthetic ultramarine blue pigments, only features of S2− and S3− radicals were observed. Finally, we verified the identity of the radical and polysulfide ions with ab initio molecular dynamics calculations. We conclude that Raman resonance spectroscopy is a powerful qualitative method to detect polysulfide and sulfur radical species with concentrations below the detection limit of conventional analytical techniques. Owing to the high stability of S42− in haüyne, this mineral structure appears promising as a host material for S42− entrapment, making it potentially useful for applications in optoelectronics.

Cryogenic Single-Molecule Fluorescence Detection of the Mid-Infrared Response of an Intrinsic Pigment in a Light-Harvesting Complex.

We observed the mid-infrared (MIR) response of a single pigment of bacteriochlorophyll a at the B800 binding site of a light-harvesting 2 complex. At a temperature of 1.5 K, a single complex in a spatially isolated spot in a near-infrared (NIR) fluorescence image was selected and was simultaneously irradiated with MIR and NIR light. We found that the temporal behavior of the NIR fluorescence excitation spectrum of individual pigments in a single complex was modulated by the MIR irradiation at 1650 cm-1. The MIR modulation of a single pigment was linearly proportional to the MIR intensity. The MIR linear response was detected in the range from 1580 to 1670 cm-1.

Threads of microbial activity on quasi-anoxic environments: Case studies from Oligocene to Miocene of the Central Paratethys

Microbial activity can be expressed in a wide range of products and forms including boring structures, biofilm-like subproducts, and framboidal pyrite precipitates. Microendolithic structures, in particular, are found in carbonate hardgrounds including tests of planktonic and benthic foraminifera and their traces can provide an extra paleoenvironmental marker of relative paleobathymetry, oxygenation, and environmental stress. Variegated traces of microbial activity including microborings, framboidal pyrite bacterial subproducts, and probable biofilms were herein studied in tests of benthic foraminifera from dysphotic to aphotic, shelf to an upper bathyal hypoxic environment. Collected material is from 6 localities in the Central Paratethys area, the Czech Republic (LOM-1 Mikulov, Hevlín), Slovakia (DNV, LKŠ-1), and Hungary (Rozalia), ranging from Rupelian to Serravalian. Microendolithic morphology was examined from resin casts obtained from the tests resulting in a total of ten ichnospecies and four other forms for which it was only possible to establish affinity on higher ranks. Levels of oxygen depletion were estimated from Benthic Foraminifera Oxygen index (BFOI). The bacterial origin of pyrite was inferred by morphology, grain size, and ẟS34 values. The number of observed microboring structures gradually reduce with the decrease of oxygen content, while the precipitation of framboidal pyrite were increasing at the same time. Biofilm-like structures, apart from the suggestive morphology, also showed an enriched content of elemental iron, sulfur, and phosphorus. Raman spectroscopy shows similarities with organic pigment spectra and is still under investigation.

Raman Spectroscopic Imaging of Human Bladder Resectates towards Intraoperative Cancer Assessment.

Raman spectroscopy offers label-free assessment of bladder tissue for in vivo and ex vivo intraoperative applications. In a retrospective study, control and cancer specimens were prepared from ten human bladder resectates. Raman microspectroscopic images were collected from whole tissue samples in a closed chamber at 785 nm laser excitation using a 20× objective lens and 250 µm step size. Without further preprocessing, Raman images were decomposed by the hyperspectral unmixing algorithm vertex component analysis into endmember spectra and their abundancies. Hierarchical cluster analysis distinguished endmember Raman spectra that were assigned to normal bladder, bladder cancer, necrosis, epithelium and lipid inclusions. Interestingly, Raman spectra of microplastic particles, pigments or carotenoids were detected in 13 out of 20 specimens inside tissue and near tissue margins and their identity was confirmed by spectral library surveys. Hypotheses about the origin of these foreign materials are discussed. In conclusion, our Raman workflow and data processing protocol with minimal user interference offers advantages for future clinical translation such as intraoperative tumor detection and label-free material identification in complex matrices.

Influence of vegetation on occurrence and color of snow algal blooms in Mt. Gassan, Yamagata Prefecture, Japan

ABSTRACT Snow algae are photosynthetic microbes growing on melting snow surfaces, the blooms of which are visible on alpine snowpacks in Japan during the melting season. We characterized the seasonal and altitudinal variations in algal blooms on Mount Gassan, Japan, to assess the influence of vegetation on the algal bloom. From May to July in 2019, we collected colored snow from lower deciduous forest to the upper alpine areas. In the lower forest area, chlorophyll-a concentration in colored snow samples increased concomitantly with deciduous tree budburst, whereas in the alpine area, chlorophyll-a increased from June to July, although at lower levels than in the forest area. The absorption spectra of algal pigments extracted from samples differed among study sites and seasons, with those obtained from forest sites mainly characterized by absorption of chlorophylls and primary carotenoids, whereas those from alpine sites showed an intense secondary carotenoid peak throughout the study period. Chemical solute analyses revealed a general abundance of phosphate in snow, which was significantly higher in forest than in alpine sites and positively correlated with chlorophyll-a concentration. These findings suggest that nutrient supply from the forest canopy largely controls the appearance of colored snow in this area.