Band Intensity Research Articles

Numerical Simulation of Spectral Radiation for Hypersonic Vehicles

The spectral radiation of hypersonic vehicles and surrounding flow fields is crucial for optical target detection. A novel approach combines Low-Discrepancy Sequences with the Reverse Monte Carlo Method to simulate the spectral radiation of hypersonic missiles. The effects of chemical non-equilibrium reactions and high-emissivity coating failures on the spectral radiation of a typical biconical hypersonic missile were investigated. Significant differences were found among chemical equilibrium, non-equilibrium, non-reactive, and catalytic wall models. High-emissivity coating failures occur mainly in the high-temperature regions of the nose cone and fins. The non-equilibrium model shows a transition peak distribution of NO in the head shock layer within the ultraviolet gamma band, with integrated ultraviolet radiation (200–300 nm) three times higher than the equilibrium model. In the 1–3 μm band, the non-equilibrium model’s radiation intensity at a 120° horizontal detection angle is about 1.46 times that of the equilibrium model. Using real coating emissivity, the 3–5 μm band radiation intensity is about 5% higher, and the 8–14 μm band is about 8.51% lower than the uniform emissivity model. When high-emissivity coating emissivity fails by 40%, the 3–5 μm band intensity decreases by about 15.38%, and the 8–14 μm band intensity decreases by about 12.67%.

Colorimetric and Fluorimetric Detection of Fe(III) Using a Rhodamine-Imidazole Hydrazone Based Chemosensor: Photophysical Properties, DFT, TGA, and DSC Studies.

Rhodamine-imidazole hydrazones (RIH-1 & RIH-2) based chemosensors have been synthesized. These are characterised and evaluated by FT-IR spectroscopy, 1H-NMR, 13C-NMR, LCMS, absorption and fluorescence spectroscopy. These chemosensors exhibit enhanced sensitivity and selectivity in detecting the biologically significant Fe3+ metal ion through both colorimetric and fluorescence changes. The optical properties have been investigated using binary acetonitrile-water (7:3 v/v) semi-aqueous solution. The probe RIH-1 can be deployed as a fluorescent and colorimetric probe for the detection of Fe3+ ion. It shows an absorption band at 559nm and an intensity band at 579nm increasing up to 50-fold with the increase in the concentration of Fe3+ with the detection limit as low as 11nM. In the visible light, RIH-1 helps in the detection of Fe3+ ion through the naked eye, while the addition of Fe3+ to the probe RIH-1 results in a colour change from colourless to pink. This is primarily due to the opening of the lactone ring in RIH-1. Notably, RIH-1 probe displays a high quantum yield of 0.51, after binding with Fe3+ ions. Indeed, it has been found that sensor RIH-1 is very effective in sensing Fe3+ ions through both fluorescence based and visual detection methods. Additionally, DFT studies of these chemosensors have been evaluated, TGA and DSC analysis showed good thermal stability.

Synthesis, Structure, and Properties of Nontrivial Iridium(III) Complexes Based on Anthracene-Decorated Benzimidazole Ligand.

Reactions of iridium trichloride hydrate with bulky 2-(9-anthracenyl)-1-phenyl-benzimidazole (anbi) in the presence of N-donor ligands afforded a number of unique noncyclometalated complexes, while attempts to prepare a common μ-chloro-bridged bis-cyclometalated dimer systematically gave a monocyclometalated complex cis-[Ir(C,N-anbi)(N-anbi)Cl2] instead. The obtained complexes were characterized by 1H NMR, high-resolution mass spectrometry, single-crystal and powder X-ray diffraction, UV-vis spectroscopy, and cyclic voltammetry. The noncyclometalated complexes fac-[Ir(N-anbi)(N^N)Cl3)], where N^N are 4,4'-disubstituted 2,2'-bipyridines, are octahedral and contain the anthracene and 2,2'-bipyridine units in a close cofacial arrangement. These complexes were found to be exceptionally inert to the chloride ligand exchange even in the presence of silver triflate, forming a rare trinuclear Ir-μ-Cl3-Ag-μ-Cl3-Ir structure instead. In the monocyclometalated complex, the Ir(III) ion is pentacoordinated in a rare square-pyramidal geometry, where the bulky anthracene fragment is involved in the steric shielding of the metal center. This is in line with the results of gas-phase density functional theory calculations, demonstrating that the experimentally observed structure is energetically most preferable. The monocyclometalated complex is deeply colored due to intense charge-transfer absorption bands in the range 450-650 nm with ε = 2000-5000 M-1 cm-1, superior to the noncyclometalated complexes. The synthesis, structures, and properties of the new complexes are discussed in the context of the related mono-, bis-, and noncyclometalated iridium(III) compounds.

Latent fingerprint detection and identification using yellow-emitting YOF:Pr3+ nanophosphor

In this study, YOF:Pr3+ nanophosphors were synthesized using the microwave-assisted hydrothermal route. The structural and morphological properties of the nanophosphors calcined at different temperatures were studied in detail to optimize the synthesis conditions. The visible region and near-infrared (NIR) photoluminescence (PL) properties of the nanophosphors were obtained. Intense emission bands were observed in the blue and red regions under 250 nm excitation. The CIE chromaticity diagram showed that the color coordinates of the nanophosphors were located in the yellow region. The optimum Pr3+-concentration was found to be 0.002 mol fraction. The application of YOF: 0.002 Pr3+ nanophosphor for latent fingerprint detection was examined and evaluated on different types of surfaces. The nanophosphor demonstrated excellent adherence to the ridge patterns and sufficient sensitivity required for distinguishing between the ridges and the furrows. Different levels of detail were also observed that provided necessary information for the individualization of the fingerprints. The results suggest that the prepared YOF:Pr3+ nanophosphor can be a potential candidate for the rapid visualization and detection of latent fingerprints.

Determination of 4-n-butylresorcinol by fluorescence derivatization based on dopamine

4-n-butylresorcinol (4nBR) is a frequently utilized as whitening ingredients in skincare cosmetics. Compared with other whitening ingredients, it can effectively inhibit tyrosinase with lower toxicity and superior inhibition efficacy. Under alkaline conditions, an induced oxidative coupling reaction can occur between 4nBR and dopamine (DA) to generate strong fluorescent substance azamonardine with an intense emission band centering at 476 nm when excited at 440 nm. This phenomenon can be used to establish a fluorescence analysis method for 4nBR. The results indicated that the linear range of the method was 1.0–24.0 nmol L−1, and the detection limit was as low as 0.25 nmol L−1. The method showed high sensitivity, good selectivity, mild experimental conditions and low cost. The proposed method was successfully used to detect 4nBR in cosmetics, and the results were consistent with those of HPLC. The spiking recoveries were between 98.2% and 108 %.

Tb3+-doped a zero-dimensional all-inorganic metal halide perovskite scintillator Cs2ScCl5·H2O for X-ray imaging

All-inorganic zero-dimensional (0D) metal halide perovskite materials have been widely studied in solid-state lighting due to their unique optical properties. However, there are few researchs on their potential applications in X-ray imaging. Herein, we synthesized an all-inorganic 0D metal halide perovskite scintillator, Cs2ScCl5·H2O:Tb3+, was prepared by using a hydrothermal method. Upon 240 nm excitation, the emission spectrum of Cs2ScCl5·H2O:Tb3+ is primarily composed of characteristic emissions from Tb3+, with the strongest emission peak at 548 nm. Additionally, under X-ray excitation, it exhibits blue light showing an intense emission band centered at 425 nm due to self-trapped (STE) emission, and a rather weaker green emission caused by energy transfer from STE emission to Tb3+ ions. Based on this, a flexible film prepared by using the as-obtained scintillator Cs2ScCl5·H2O:Tb3+ demonstrates real-time X-ray imaging with a resolution of 9.5 lp mm−1. These results suggest the potential application prospect of Cs2ScCl5·H2O:Tb3+ in X-ray detection and imaging.

Structural Study on the Novel Plasmonic Optical Materials with Copper Selenide Nanoparticles

Background: Semiconductor-doped materials have been treated actively throughout the last decades and continue to be of great interest because of the challenges of the features due to various nanosize effects. Among other semiconductors, copper chalcogenides demonstrate the interesting plasmonic properties in line with quantum confinement effects provided by the size factor. Objective: This study aims to study the structural and optical features of the sol-gel-derived silica glasses with copper selenide nanoparticles, demonstrating the appearance of the plasmonic light absorption in the near IR range. Method: The samples under study were fabricated through an original sol-gel technique, which realized the simultaneous synthesis of copper selenide and sintering of mesoporous silica. The copper selenide glasses were characterized with X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and optical absorption spectroscopy. Results: Formation of nanocrystalline Cu2-xSe particles of the size range from 10 nm through 100-150 nm is established with XRD and TEM techniques. The principal optical properties are presented by the featured absorption in the visible and near-IR ranges. Eg was evaluated for the direct transitions in the range of 2.10-2.36 eV. The plasmonic resonance in the nanoparticles due to increased carrier concentration originated by intrinsic deficiency of Cu2-xSe nanoparticles with variable stoichiometry. Its energy can be controlled by the Cu/Se ratio in the synthesis procedure. Conclusion: The silica sol-gel glasses with copper selenide nanoparticles were fabricated and characterized by XRD and TEM methods, and their optical absorbance spectra were investigated. The principal optical properties are presented by the featured absorption in the visible and near-IR ranges: the steplike proper absorption of the semiconductor particles characterized by Eg and the intense near-IR band is associated with the localized plasmonic resonance in the nanoparticles due to increased carrier concentration.

Assessment of Changes in Selected Features of Pine and Birch Wood after Impregnation with Graphene Oxide.

In this work, pine and birch wood were modified by graphene oxide using a single vacuum impregnation method. The research results indicate that the impregnation of wood with graphene oxide increases the crystallinity of cellulose in both pine and birch wood, and the increase in crystallinity observed in the case of birch was more significant than in the case of pine. FT-IR analyses of pine samples impregnated with graphene oxide showed changes in intensity in the absorption bands of 400-600, 700-1500 cm-1, and 3200-3500 cm-1 and a peak separation of 1102 cm-1, which may indicate new C-O-C connections. In the case of birch, only some differences were noticed related to the vibrations of the OH group. The proposed modification also affects changes in the color of the wood surface, with earlywood containing more graphene oxide than latewood. Analysis of scanning electron microscope images revealed that graphene oxide adheres flat to the cell wall. Considering the differences in the anatomical structure of both wood species, the research showed a statistically significant difference in water absorption and retention of graphene oxide in wood cells. Graphene oxide does not block the flow of water in the wood, as evidenced by the absorbability of the working liquid at the level of 580-602 kg/m3, which corresponds to the value of pure water absorption by wood in the impregnation method using a single negative pressure. In this case, higher graphene oxide retention values were obtained for pine wood.

Vitamin B6 appended polypyridyl Co(III) complexes for photo-triggered antibacterial activity.

Three novel polypyridyl-Co(III)-vitamin B6 complexes viz., [Co(CF3-phtpy)(SBVB6)]Cl (Co1), [Co(anthracene-tpy)(SBVB6)]Cl (Co2), [Co(NMe2-phtpy)(SBVB6)]Cl (Co3), where 4'-(4-(trifluoromethyl)phenyl)-2,2':6',2''-terpyridine = CF3-phtpy, 4'-(anthracen-9-yl)-2,2':6',2''-terpyridine = anthracene-tpy;, 4-([2,2':6',2''-terpyridin]-4'-yl)-N,N-dimethylaniline = NMe2-phtpy, (E)-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridin-3-ol = H2SBVB6 was successfully developed for aPDT (antibacterial photodynamic therapy) applications. Co1-Co3 exhibited an intense absorption band at ca. 435-485 nm, which is attributed to ligand-to-metal charge transfer and was beneficial for antibacterial photodynamic therapy. The distorted octahedral geometry of the complexes with CoIIIN4O2 core was evident from the DFT study. The visible light absorption ability and good photo-stability of Co1-Co3 made them good photosensitizers for aPDT. Co1-Co3 displayed significant antibacterial responses against gram-positive (S. aureus) and gram-negative (E. coli) bacteria upon light exposure (10 J cm-2, 400-700 nm) and showed MIC values between 0.01-0.005 µg mL-1. The aPDT activities of these complexes were due to their ability to damage bacterial cell membranes via ROS generation. Overall, this study shows the photo-triggered ROS-mediated bacteria-killing potential of Co(III) complexes.

Double Spin with a Twist: Synthesis and Characterization of a Neutral Mixed-Valence Organic Stable Diradical.

A convenient design strategy opens access to neutral open-shell mixed-valence species via the redox transformation of charged stable precursors, i.e., the spiro-fused borate anions. We have implemented this strategy for the synthesis of the first neutral mixed-valence diradical: two neutral mixed-valence radical fragments were assembled via a twisted biphenyl bridge. The diradical is a crystalline solid obtained in almost quantitative yield by using a facile synthetic procedure. It is stable at room temperature in the triplet ground state with a very small singlet/triplet gap. This metal-free diradical can reversibly form five redox states. The diradical exhibits an intense IVCT band in the NIR region and can be assigned as a Class 2 Robin-Day MV (mixed valence) system with weakly interacting redox centers. Computations suggest that this diradical finds itself in a unique tug-of-war between two electron delocalization patterns, Kekulé and non-Kekulé, which gives rise to two geometric isomers that are close in energy but drastically different in spin distribution and polarity. Such bistable spin-systems should be intrinsically switchable and promising for the design of functional spin devices. The scope and limitations of the new redox-strategy for the neutral MV radicals were also tested on other types of spiro-fused borates, revealing structural factors responsible for the evolution from transient to persistent and then to stable radicals.

Surviving the extinction vortex? Discovering remnant stands of Senecio hercynicus (Compositae, Senecioneae) evading genetic swamping by its congener S. ovatus in the Bavarian and Bohemian Forest region

Genetic swamping by introgressive hybridisation threatens diversity, caused by climate warming particularly in mountainous regions worldwide. Recent studies resulted in a threatening perspective for Senecio hercynicus in the Bavarian Forest due to genetic swamping by introgressive hybridisation with its cogener S. ovatus. To examine the situation more closely, the distribution and hybridization of S. hercynicus and S. ovatus in high elevation regions of the Bavarian and Bohemian Forest was analyzed by restriction enzyme digestion of nrDNA ITS1 (PCR-RFLP; PCR restriction fragment length polymorphism). For a total of 706 samples from 94 different sample localities a hybrid index was inferred from the fragment band intensities after PCR-RFLP digestion. Boxplot diagrams of the hybrid indices show a tendency of western populations towards S. ovatus genotypes and for populations to the east towards S. hercynicus genotypes. When the hybrid index data was subjected to a regression analysis with nine factors (five habitat patterns inferred during sampling and four bioclimatic variables), only geographical longitude and latitude seemed to describe the observed distribution of S. hercynicus and S. ovatus significantly, arguing for the distribution and hybridisation patterns being shaped rather due to historical than to eco-climatological determinants. While a broad zone of hybridisation between the two species in the Bavarian and Bohemian Forest region was inferred, our study demonstrates that purebred S. hercynicus still exists and remnant stands of this species should be the target of species conservation measures.

Closed-loop circular economy in ‘upcycled’ acrylonitrile–butadiene–styrene vitrimer

Today, the issue of plastic waste pollution has reached unprecedented levels. The increasing production of plastics, combined with a decreasing rate of recycling, has significantly worsened this problem in recent years. While a wide range of plastics are manufactured, thermoplastics are a type that can be recycled relatively easily. However, recycled thermoplastics often have lower mechanical properties compared to new ones. Considering this challenge, making thermoplastics recyclable could revolutionize the recycling process and represent a major advancement towards establishing a circular economy for plastics. In this study, virgin acrylonitrile–butadiene–styrene (ABS) was transformed into a vitrimer through reactive melt extrusion using a bio-derived crosslinker containing dynamic imine linkages. This crosslinker results in a dynamic network, in the melt, as observed from the higher gel fraction and imparts recyclability to the resulting ABS vitrimer, which exhibits higher yield strength (by 15 %) and Young’s modulus (by 19 %). Remarkably, the mechanical and thermal properties of the vitrimer remain largely unchanged even after undergoing five cycles of reprocessing. In addition, the resulting vitrimer is dimensionally stable as inferred from creep studies and shows rapid stress relaxation at higher temperature following Arrhenius behaviour. The electron paramagnetic resonance (EPR) spectra were captured at room temperature for both ABS and its vitrimer. The difference in singlet band intensities in the spectra begins to suggest that the vitrimer is more stable post multiple recycling. While this research focused on virgin ABS, the approach outlined in the study has the potential to be applied to post-consumer recycled (PCR) ABS. This could introduce recyclability to PCR ABS and pave the way for a closed-loop circular economy for ABS plastics.

Effect of Thermal Processing on Food Allergenicity: Mechanisms, Application, Influence Factor, and Future Perspective.

Thermally processed foods are essential in the human diet, and their induced allergic reactions are also very common, seriously affecting human health. This review covers the effects of thermal processing on food allergenicity, involving boiling, water/oil bath heating, roasting, autoclaving, steaming, frying, microwave heating, ohmic heating, infrared heating, and radio frequency heating. It was found that thermal processing decreased the protein electrophoretic band intensity (except for infrared heating and radio frequency heating) responsible for destruction of linear epitopes and changed the protein structure responsible for the masking of linear/conformational epitopes or the destruction of conformational epitopes, thus decreasing food allergenicity. The outcome was related to thermal processing (e.g., temperature, time) and food (e.g., types, pH) condition. Of note, as for conventional thermal processing, it is necessary to control the generation of the advanced glycation end products in roasting/baking and frying, and the increase of structural flexibility in boiling and water/oil bath heating, autoclaving, and steaming must be controlled; otherwise, it might increase food allergenicity. As for novel thermal processing, the temperature nonuniformity of microwave and radio frequency heating, low penetration of infrared heating, and unwanted metal ion production of ohmic heating must be considered; otherwise, it might be the nonuniformity and low effect of allergenicity reduction and safety problems.

Application of Reduced Graphene Oxide-Zinc Oxide Nanocomposite in the Removal of Pb(II) and Cd(II) Contaminated Wastewater

Toxic metal wastewater is a challenge for exposed terrestrial and aquatic environments, as well as the recyclability of the water, prompting inputs for the development of promising treatment methods. Consequently, the rGO/ZnONP nanocomposite was synthesized at room temperature for four hours and was tested for the adsorption of cadmium and lead in wastewater. The optimized nanocomposite had the lowest band gap energy (2.69 eV), and functional group interactions were at 516, 1220, 1732, 3009, and 3460 cm−1. The nanocomposite showed good ZnO nanoparticle size distribution and separation on rGO surfaces. The nanocomposite’s D and G band intensities were almost the same, constituting the ZnO presence on rGO from the Raman spectrum. The adsorption equilibrium time for cadmium and lead was reached within 10 and 90 min with efficiencies of ~100%. Sips and Freundlich best fitted the cadmium and lead adsorption data (R2 ~ 1); therefore, the adsorption was a multilayer coverage for lead and a mixture of heterogenous and homogenous coverage for cadmium adsorption. Both adsorptions were best fitted by the pseudo-first-order model, suggesting the multilayer coverage dominance. The adsorbent was reused for three and seven times for cadmium and lead. The nanocomposite showed selectivity towards lead (95%) and cadmium (100%) in the interfering wastewater matrix. Conclusively, the nanocomposite may be embedded within upcoming lab-scale treatment plants, which could lead to further upscaling and it serving as an industrial wastewater treatment material.

N 2 + Meinel band quenching coefficients for vibrational levels 0 and 1.

Experimental rate coefficients for the quenching of vibrational levels 0 and 1 of the N2+A2Πu state by N2 are presented. The experiments were performed using near-infrared observations of the N2+ Meinel bands excited by electron impact at several pressures of the N2 target/quenching gas. The total removal rate coefficients were derived from a Stern-Volmer analysis of the Meinel band intensities as a function of N2 density and yielded rate coefficients of (2.5 ± 0.5 × 10-10) and (5.6 ± 0.6 × 10-10) cm3⋅molecule-1⋅s-1 for vibrational levels 0 and 1, respectively. It is shown that rate coefficients increase with increasing vibrational level and decreasing energy gap. Our results impact modeling studies of the disturbed atmosphere and ionosphere as the reduced quenching rate coefficients for the preferentially excited A-state vibrational levels <2 lower the quenching altitude in the atmosphere by one scale height, or about 6 km.

Excitation energy transfer in gadolinium tantalum niobates activated with Eu3+ and Tb3+

Series of gadolinium tantalum niobates activated with Eu3+ and Tb3+ ((Gd1-y-zEuyTbz)NbxTa1-xO4 (x = 0, 0.3, 1; y = 0.6; z = 0.06; 0.15; 0.3)) were obtained for the first time. The formation of substitutional solid solutions was demonstrated. The obtained ceramic solid solutions had a monoclinic structure with I2/a space group. Electron probe microanalysis, photoluminescence (PL) and cathodoluminescence (CL) were used for studies of gadolinium tantalates and tantalum niobates series activated with Eu3++Tb3+. CL and PL spectra, concentration dependences of CL intensity and decay times, as well as excitation spectra for 5D0-7F2 Eu3+ and 5D4-7F5 Tb3+ bands were analyzed. It was shown for the first time that both energy transfer from Tb3+ to Eu3+ ions, and a reverse process – energy transfer from Eu3+ to Tb3+ ions are observed. This reverse process led to a decrease in CL intensity and decay times of europium bands in the presence of terbium 3+ in these materials. Presumably this phenomenon is influenced by anti-Stokes luminescence. This is confirmed by the dependences of anti-Stokes luminescence probability on temperature and excitation density.

Effects of low dose skin tissue derived peptides on the function and collagen expression of keloid fibroblasts

This study aims to investigate the effects of the skin tissue derived peptides on proliferation, apoptosis, migration and collagen expressions in keloid fibroblasts. From January 2015 to January 2017, patients with hypertrophic scar who underwent surgical excision in department of plastic surgery of Nanjing maternal and child health hospital were included in this retrospective study. Four peptides were selected from the differential peptides between human hypertrophic scar and normal skin tissue. They were named as peptide deregulated in hypertrophic scar 2-5 (PDHPS2-5). Bioinformatics and functional analysis were performed. A low dose of 10 μmol/L of four peptides were respectively added to the culture medium of human primary keloid fibroblasts for 24 h. Cell counting kit-8 (CCK-8) were used to detect the changes in cell viability. Cell apoptosis was detected by flow cytometry. Cell migration ability was checked by Transwell chamber. The protein expressions of collagen COL1A2 (Collagen type I alpha 2) and the myofibroblast marker gene ACTA2 (Actin alpha 2) were analyzed by Western blot. The results showed that bioinformatics prediction analysis revealed that peptide PDHPS4 has the longest half-life and the highest thermal stability. Compared with the control group, low dose of four peptides had no significant effect on the survival rate and apoptosis of keloid fibroblasts tested by CCK-8 assay and flowcytometry. Transwell analysis showed that one peptides (PDHPS5) can significantly inhibit the cell migration ability (The optical density value in Control is 0.81±0.11, in PDHPS5 is 0.27±0.03, t=8.61, P=0.001). Western blot analysis showed that four peptides (PDHPS2, PDHPS3, PDHPS4, PDHPS5) can significantly inhibit the protein expressions of COL1A2 (The relative protein band intensity in Control is 1.02±0.02, in PDHPS2 is 0.21±0.04, in PDHPS3 is 0.26±0.03, in PDHPS4 is 0.53±0.04, in PDHPS5 is 0.73±0.04, t=31.38, 38.54, 18.88, 11.07 respectively, all P value are less than 0.01). Three peptides (PDHPS2, PDHPS3, PDHPS5) can significantly inhibit the protein expressions of ACTA2 (The relative protein band intensity in Control is 1.02±0.02, in PDHPS2 is 0.64±0.05, in PDHPS3 is 0.77±0.06, in PDHPS5 is 0.47±0.07, t=12.08, 6.38, 14.06 respectively, all P value are less than 0.01). In conclusion, the differentially expressed peptides in human hypertrophic scar tissue can affect the function of keloid fibroblasts and collagen expressions to varying degrees. Among them, two peptides (PDHPS2,PDHPS3) significantly inhibit the protein expressions of COL1A2 and ACTA2. The peptide PDHPS5 has high stability, significantly suppresses cell migration, and reduces the protein expressions of COL1A2 and ACTA2, which may provide a new strategy for scar prevention and treatment.

Simultaneous Measurement of Two-Trace Two-Dimensional (2T2D) Near-Infrared (NIR) Asynchronous Correlation Spectra and Small-Angle X-ray Scattering (SAXS) to Characterize Thermally Aged Polypropylene (PP).

In this study, a new system was developed to carry out simultaneous near-infrared (NIR) and small-angle X-ray scattering (SAXS) measurements. Aged polypropylene (PP) was examined with the NIR-SAXS system to demonstrate how it can be utilized to derive pertinent information about the polymer structure. Pairs of SAXS profiles and NIR spectra of PP in its initial state and after aging were measured to derive an in-depth understanding of the aging phenomenon. The SAXS profiles of the PP samples showed a clear shift of the SAXS peak to the lower q direction induced by the thermal aging, indicating an increase in the length of the long-period structure. Two-trace two-dimensional (2T2D) asynchronous correlation spectra derived from NIR spectra clearly revealed that the aging treatment leads to a substantial increase in the spectral intensity of the regularity bands representing the longer helix present in a folded lamellar structure. In other words, it suggests that the long helix structure is more abundantly present than the short helix structure in the aged PP than in the initial PP. By combining the information derived from the SAXS profiles and NIR spectra, the details of the aging-induced variation were clearly determined. Namely, aging causes additional crystallization of the PP by developing more helical structures, which involves an increase in the lamellar thickness as well as a decrease in the amorphous region. The growth of the rigid crystalline phase restricts the elastic deformation in the amorphous structure, which eventually induces the deterioration of PP by making the polymer hard but brittle. Such observation, in turn, implies that retarding or accelerating the crystallized structure of PP substantially works to control the progress of aging.

Identification of gamma irradiated polycarbonate-polybutylene terephthalate stiff polymer blend products using HS-GC/MS, FTIR and UV/Vis spectroscopy

In this study, the fragmentation products of Makro-blend stiff polymer due to gamma exposure were identified using Head space (HS), Gas Chromatography, and Mass Spectrometry (HS-GC/MS) techniques and Fourier Transform Infra-Red (FTIR) spectroscopy. As well the electronic transitions due to gamma exposure were examined using UV/Vis spectroscopy. For the un-irradiated and 10 kGy irradiated samples, one product was detected by (HS-GC/MS) method with a clear peak of Dimethoxyethane (MW = 90), which has a peak area percentage of 98.58% and 97.13%, respectively. With increasing gamma doses the number of identified components was increased. At 1200 kGy, ten components were detected: Biethylene (MW = 54), Dimethoxyethane (MW = 90), 1,1-Dimethoxy-2-propanone (MW = 118), 1,1-Dimethoxy-2-propanol (MW = 120), 1,1-Dimethoxycyclopentane (MW = 130), 1,1-Dimethoxyheptane (MW = 160), 1,1-Dimethoxyoctane (MW = 174), Dimethyl terephthalate (MW = 194), 4-(Diethoxymethyl) benzaldehyde (MW = 208), and Terephthalate dihexyl (MW = 334), which have peaks area percentages of 4.22, 2.98, 25.84, 2.2, 10.65, 38.86, 1.57, 5.91, 1.22, and 6.48, respectively. The recorded mass spectrum of each component confirms the molecular ion peak. The FTIR measurements demonstrate the decrease in the detected band intensities following gamma radiation. Accordingly, a chain scission occurs, which causes the carbonate bond to scission, resulting in the creation of a hydroxyl group and the (–H) abstraction from the backbone of the irradiation blend samples. The absorbance edge of the gamma-exposed samples shifted towards a higher wavelength. This pattern shows that the band gap energy is declining. The use of FTIR and HS-GC/MS in mass spectrometry analysis will be useful tools for examining radiation-induced polymeric fragments and advancing our understanding of the process underlying the creation of these fragments in polymers.

Cool white light emitting Dy3+ activated KNaCa2(PO4)2 phosphor for outdoor lighting and optical thermometric applications

Dy3+ incorporated KNaCa2(PO4)2 phosphor (KNCP) with doping concentrations ranging from 0.005 to 0.7 mol were synthesised via high-temperature solid state reaction route. The morphological characteristics were examined using FESEM images and found agglomerated structure in micrometers with an average particle size of 4.037 µm. Photoluminescence emission spectra under 350 nm excitation reveal nearly equal intense blue and yellow emission bands owing to 4F9/2→6H15/2 and 4F9/2→6H13/2 Dy3+ transitions, respectively. The concentration-dependent emission properties were examined and the optimum concentration was found to be 0.03 mol. The synthesized phosphor exhibits a quantum yield of 69.06 % at the optimal Dy³⁺ doping concentration. The time-correlated emission characteristics were analysed from the TRES plot. Furthermore, the emission bands at 479 nm (4F9/2→6H15/2) and 572 nm (4F9/2→6H13/2) under 350 nm excitation follow bi-exponential decay having an average lifetime in the range of 0.90–0.37 ms. The prepared phosphors exhibit an intense cool white light regardless of doping concentration and delay time. Optical thermometric properties of KNCP Dy phosphor were investigated by fluorescence intensity ratio (FIR) technique and exhibit relative thermal sensitivity of 2.57 and 0.7 %K−1 in the temperature range of 90 −230 K and 250–500 K respectively. The excellent quantum yield, sub-millisecond lifetime, cool colour temperature, and higher temperature sensitivities make them ideal for outdoor lighting and optical thermometric applications.