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Quantum dot (QD)-based single-photon emitter devices today are based on self-assembled random position nucleated QDs emitting at random wavelengths. Deterministic QD growth in position and emitter wavelength would be highly appreciated for industry-scale high-yield device manufacturing from wafers. Local droplet etching during molecular beam epitaxy is an all in situ method that allows excellent density control and predetermines the nucleation site of quantum dots. This method can produce strain-free GaAs QDs with excellent photonic and spin properties. Here, we focus on the emitter wavelength homogeneity. By wafer rotation-synchronized shutter opening time and adapted growth parameters, we grow QDs with a narrow peak emission wavelength homogeneity with no more than 1.2 nm shifts on a 45 mm diameter area and a narrow inhomogeneous ensemble broadening of only 2 nm at 4 K. The emission wavelength of these strain-free GaAs QDs is <800 nm, attractive for quantum optics experiments and quantum memory applications. We can use a similar random local droplet nucleation, nanohole drilling, and now, InAs infilling to produce QDs emitting in the telecommunication optical fiber transparency window around 1.3 µm, the so-called O-band. For this approach, we demonstrate good wavelength homogeneity and excellent density homogeneity beyond the possibilities of standard Stranski–Krastanov self-assembly. We discuss our methodology, structural and optical properties, and limitations set by our current setup capabilities. [ABSTRACT FROM AUTHOR]

Atomically thin molybdenum disulfide (MoS2) is a two-dimensional semiconductor with versatile applications. The recent adoption of liquid molybdenum precursors in chemical vapor deposition has contributed significantly to the reproducible wafer-scale synthesis of MoS2 monolayer and few-layer films. In this work, we study the effects of the carrier gas flow rate on the properties of two-dimensional molybdenum disulfide grown by liquid-precursor-intermediate chemical vapor deposition on SiO2/Si substrates. We characterized the samples using Optical Microscopy, Scanning Electron Microscopy, Raman spectroscopy, and Photoluminescence spectroscopy. We analyzed samples grown with different nitrogen carrier flows, ranging from 150 to 300 sccm, and discussed the effect of carrier gas flows on their properties. We found a correlation between MoS2 flake lateral size, shape, and number of layers, and we present a qualitative growth model based on changes in sulfur provision caused by different carrier flows. We show how the use of liquid precursors can allow for the synthesis of homogeneous, single-layer flakes up to 100 µm in lateral size by optimizing the gas flow rate. These results are essential for gaining a deeper understanding of the growth process of MoS2. [ABSTRACT FROM AUTHOR]

Internal quantum efficiency (IQE) of AlGaN‐based multiple quantum wells (MQWs) on face‐to‐face‐annealed sputter‐deposited AlN templates is examined by photoluminescence spectroscopy. The excitation power density dependence of IQE is evaluated as a function of temperature under the selective excitation of the quantum wells. The temperature dependences of the maximum IQE and the corresponding excitation power density (EPD) are analyzed based on the rate equation models for carriers and excitons. The decrease of the maximum IQE and increase of the corresponding EPD are mainly due to the increase in the nonradiative recombination rate via nonradiative recombination centers. Furthermore, the nonradiative recombination rate for the MQW with an emission wavelength around 220 nm is activated at a lower temperature than the other samples, which is expected to lead to the lower IQE of the MQW with an emission wavelength around 220 nm. [ABSTRACT FROM AUTHOR]

Undoped and Cr doped β-Ga2O3 (100) single crystals are grown by optical floating zone method. The full width at half maximum of rocking curve is found to be 106 arc.sec for undoped β-Ga2O3 crystals whereas the 100 and 200 ppm of Cr doped β-Ga2O3 crystals display multiple rocking curves with large peak widths indicating the presence of structural defects. Raman measurements reveal broadening in the vibrational mode of ~ 350 cm− 1 with a shoulder peak indicating the Cr3+ dopants preferentially substitute for Ga3+ at the octahedral sites. Further, the Cr doped β-Ga2O3 crystals display strong optical absorption bands about 420 and 597 nm in the UV-Vis spectroscopy. Moreover, the observation of sharp characteristic photoluminescence emission lines at 690 and 697 nm also confirms the Cr substitution in the doped crystals. The indentation hardness increases nearly linear from 13.0 ± 0.6 to 17.9 ± 0.4 GPa whilst the indentation modulus decreases from 224.9 ± 21.4 to 202.4 ± 11.9 GPa upon Cr doping of 200 ppm in β-Ga2O3. The structural defects caused by the Cr doping interrupt the movement of indentation induced dislocations that results in the increase of hardness of the Cr doped β-Ga2O3 (100) single crystals. [ABSTRACT FROM AUTHOR]

The detection of Pyrene, a toxic polycyclic aromatic hydrocarbon, is crucial for environmental monitoring due to its negative impacts on health and ecosystems. While photoluminescence (PL) spectroscopy holds promise for Pyrene detection, its current application is limited. This research aimed to address this gap by developing a novel PL spectroscopy method for Pyrene detection. The method utilizes a simple, low limit of detection (LOD), affordable, rapid, and user-friendly approach. A polyaniline-graphene quantum dot (PANI-GQD) nanocomposite film was synthesized as the sensing layer. For comparison, PL spectroscopy measurements were also taken using GQD and PANI alone. The fabricated thin films were thoroughly characterized using various techniques (FT-IR, UV–Vis, Raman, XRD, FE-SEM, EDX, TGA) to analyze their chemical, optical, physical, and structural properties. The developed PANI-GQD nanocomposite film-based PL spectroscopy successfully detected Pyrene concentrations ranging from 0.001 to 10 × 10–9 mol L−1. Notably, the method achieved an outstanding LOD of 0.40 × 10–9 mol L−1 (S/N = 5) for low-concentration Pyrene detection, surpassing previous limitations. This LOD is well within the WHO's set standards for Pyrene in aquatic environments (3.461 × 10–9 mol L−1). Overall, this research presents a valuable tool for detecting toxic materials relevant to environmental monitoring, with potential for significant socio-economic impact. [ABSTRACT FROM AUTHOR]

High-quality monolithic Ge-on-Si is sought for CMOS-compatible optoelectronic devices. We examine the structural characteristics of Ge-on-Si grown by the aspect ratio trapping (ART) method on a SiO2/Si(001) template in pre-patterned holes. Transmission electron microscopy and surface topography analysis revealed high-quality Ge islands overgrown from the ART holes in SiO2. The superior crystal quality of Ge ART growth was also confirmed by comparing x-ray diffraction (XRD) data of Ge ART and Ge planar epilayer samples. The XRD and micro-Raman data additionally show a small residual strain in the islands which vanishes by reducing the hole diameter from 280 nm to 180 nm, while leading to only a minor increase in the crystallographic inclinations of the Ge islands from 0.34 deg to 0.54 deg. With finite element method simulations, we find that the small residual strain in Ge originates during the cool-down from growth to room temperature because of thermal expansion coefficient mismatch between Ge and SiO2. A tensile force develops along the [001] axis of the Ge pillar whose faster shrinkage to the room temperature volume is restricted by the oversized surface island. [ABSTRACT FROM AUTHOR]

The paper investigates optical and spectral properties of ZnO nanoparticles dispersed p-(n-heptyloxy)benzoic acid (7-OBA) liquid crystalline (LC) compounds with the concentration of 1 to 2.5 wt.%. The prepared samples are characterized by various experimental techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy, differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and photoluminescence (PL) spectroscopy. The presence of ZnO nanoparticles is confirmed by the XRD. The crystallite size is found to be 68 nm. Phase transition temperatures and enthalpy values of pure and nanodispersed LC materials are measured by DSC. The texture of pure and nanodispersed LC phases like nematic and smectic, is observed through POM. Photoluminescence spectroscopy shows the dispersion of 2.5 wt.% ZnO nanoparticles in 7-OBA compound; the blue emission maximum shifts from 368 to 375 nm. The peak observed at 655 nm, is determined by point defects in the bandgap, namely vacancies and interstitial known as deep level emission. [ABSTRACT FROM AUTHOR]

GaAs‐AlGaAs based nanowire (NW) lasers hold great potential for on‐chip photonic applications, where lasing metrics have steadily improved over the years by optimizing resonator design and surface passivation methods. The factor that will ultimately limit the performance will depend on material properties, such as native‐ or impurity‐induced point defects and their impact on non‐radiative recombination. Here, the role of impurity‐induced point defects on the lasing performance of low‐threshold GaAs(Sb)‐AlGaAs NW‐lasers is evaluated, particularly by exploring Si‐dopants and their associated vacancy complexes. Si‐induced point defects and their self‐compensating nature are identified using correlated atom probe tomography, resonant Raman scattering, and photoluminescence experiments. Under pulsed optical excitation the lasing threshold is remarkably low (<10 µJ cm−2) and insensitive to impurity defects over a wide range of Si doping densities, while excess doping ([Si]>1019 cm−3) imposes increased threshold at low temperature. These characteristics coincide with increased Shockley‐Read‐Hall recombination, reflected by shorter carrier lifetimes, and reduced internal quantum efficiencies (IQE). Remarkably, despite the lower IQE the presence of self‐compensating Si‐vacancy defects provides an improved temperature stability in lasing threshold with higher characteristic temperature and room‐temperature lasing. These findings highlight an overall large tolerance of lasing metrics to impurity defects in GaAs‐AlGaAs based NW‐lasers. [ABSTRACT FROM AUTHOR]

Techniques for effectively harnessing lead (Pb) deposits for optimum utilization have attracted a lot of research interest. Results obtained from investigating the elemental composition, vibrational modes, and structural properties of a fired Pb composite deposit, which is purified using an electric kiln furnace and further annealed in palladium‐diffused hydrogen ambient, are reported in the present study. Both atomic force microscopy and scanning electron microscopy analysis on the deposit indicate that the Pb composite is composed of crystal‐like morphology. The vibrational modes obtained from the material are identical to the Raman spectrum reported for PbSO4. Also, data acquired from the energy‐dispersive X‐ray analysis of the annealed Pb composite material confirm the presence of zinc, carbon, silicon, sulfur, and oxygen in the material. At the same time, Pb appears to be the primary constituent with reference to its weight percentage composition compared to other elements. The findings from the present study may be vital for providing an improved understanding of the electronic and structural properties of the annealed Pb composite deposit while promoting the development of a feasible approach for the recovery and recycling of Pb for future related applications. [ABSTRACT FROM AUTHOR]

The purpose of the presented study is to examine the impact of zinc oxide nanoparticles (ZnO NPs) on the spectrum features of poly [2-methoxy-5-(3′,7′-dimethyloctyloxy)-1, 4-phenylenevinylene] (MDMO-PPV). The characteristics of the MDMO-PPV and doped ZnO NPS samples were assessed using several techniques. A set of solutions of MDMO-PPV in toluene that were doped with different ratio percentages of ZnO NPs was prepared to obtain thin films. Pristine and composite solutions were spin-coated on glass substrates. It was observed that MDMO-PPV had two distinct absorbance bands at 310 and 500   nm in its absorption spectrum. The UV-Vis spectrum was dramatically changed when 5 % of ZnO NPs were added. The result showed a significant reduction in absorption of the band 500   nm , while 310   nm absorption increased rapidly and became more pronounced. Upon adding (10%) ZnONPs to the sample, no noticeable change was observed in the 500 nm band. However, the 310 nm band shifted towards the blue region. There is a dominant peak in the PL spectrum of MDMO-PPV in its pristine form around 575   nm and a smaller hump around 600   nm of the spectrum. The spectral profile at 600 nm and the intensity of both bands are improved by raising the ZnO NP concentration. These bands feature two vibronic transitions identified as (0-0) and (0-1). When the dopant concentration increased to the maximum dopant percentage ( 10 % ), the energy band gap values increased by 0.21   eV compared to the pristine MDMO-PPV. In addition, the refractive index (n) decreased to its lowest value of 2.30 with the presence of concentrations of ZnO NPs. [ABSTRACT FROM AUTHOR]

We compared the photoluminescence (PL) properties of AlInAsSb digital alloy samples with different periods grown on GaSb (001) substrates by molecular beam epitaxy. Temperature-dependent S-shape behavior is observed and explained using a thermally activated redistribution model within a Gaussian distribution of localized states. There are two different mechanisms for the origin of the PL intensity quenching for the AlInAsSb digital alloy. The high-temperature activation energy E 1 is positively correlated with the interface thickness, whereas the low-temperature activation energy E 2 is negatively correlated with the interface thickness. A quantitative high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) study shows that the interface quality improves as the interface thickness increases. Our results confirm that E 1 comes from carrier trapping at a state in the InSb interface layer, while E 2 originates from the exciton binding energy due to the roughness of the AlAs interface layer. [ABSTRACT FROM AUTHOR]

Polymer blends have got considerable attention for their potential optoelectronic and photonic applications due to several advantages such as easy processing, low cost, flexibility, and good mechanical properties. This work reports the structure and optical properties of solution cast binary blends of poly (methyl methacrylate) (PMMA) and poly (vinyl carbazole) (PVK). Here, the position and/or intensity of characteristic FTIR peaks reveal the changes of the structure of PMMA on PVK content while the surface morphology changes from highly smooth for pure PMMA to flaky structured (PVK 5%) and then to agglomerated morphologies for these blends. A red shift in optical absorption edge and decrease in optical transmission with PVK content in PMMA based blends. The emission spectra exhibit intensity escalation by 340 times with respect to PMMA for PVK-15 blends and then decreases with further addition of PVK in these blends. These results are very important for the advent of new optoelectronic functionalities for these polymer blends. [ABSTRACT FROM AUTHOR]

Photoluminescence from the surface of Nafion polymer membrane upon swelling in water under irradiation by electromagnetic waves at a frequency of 100 MHz was studied. In these experiments, natural deionized (DI) water with a deuterium content of 157 ppm and deuterium-depleted water (DDW, deuterium content is 1 ppm) were explored. We have studied for the first time the effect of linearly and randomly polarized low-frequency electromagnetic radiation on the luminescence excitation. To obtain low-frequency electromagnetic radiation with random polarizations, anisotropic solid submicron-sized particles, which result in depolarization effects upon scattering of the initially linearly polarized radiation, were used. We compared two types of colloidal particles: spherically symmetric (isotropic) and elongated (anisotropic). If the radiation is linearly polarized, the intensity of luminescence from the Nafion surface decreases exponentially as the polymer is soaked, and such a behavior is observed both in natural DI water and DDW. When spherically symmetric submicron-sized particles are added to a liquid sample, the luminescence intensity also decreases exponentially upon swelling in both natural DI water and DDW. At the same time, when anisotropic submicron-sized particles are added to DI water, random jumps in the luminescence intensity appear during swelling. At the same time, the exponential decrease in the luminescence intensity is retained upon swelling in DDW. A qualitative theoretical model for the occurrence of random jumps in the luminescence intensity is presented. [ABSTRACT FROM AUTHOR]

The production of superlattices with pseudomorphically strained quantum wells (QWs) {InxGa1–xAs/GaAs} grown by molecular beam epitaxy on GaAs substrates with (100), (110), and (111)A crystallographic surface orientations is reported. The quality of the crystal structure of epitaxial samples is assessed using the atomic force microscopy of their surface. The manifestation of a piezoelectric field in the photoluminescence spectra is reported. [ABSTRACT FROM AUTHOR]

The work reports a number of results on the dynamics of swelling and inferred nanostructure of the ion-exchange polymer membrane Nafion in different aqueous solutions. The techniques used were photoluminescent and Fourier transform IR (FTIR) spectroscopy. The centers of photoluminescence were identified as the sulfonic groups localized at the ends of the perfluorovinyl ether (Teflon) groups that form the backbone of Nafion. Changes in deuterium content of water induced unexpected results revealed in the process of polymer swelling. In these experiments, deionized (DI) water (deuterium content 157 ppm) and deuterium depleted water (DDW) with deuterium content 3 PPM, were investigated. The strong hydration of sulfonic groups involves a competition between ortho- and para-magnetic forms of a water molecule. Deuterium, as it seems, adsorbs competitively on the sulfonic groups and thus can change the geometry of the sulfate bonds. With photoluminescent spectroscopy experiments, this is reflected in the unwinding of the polymer fibers into the bulk of the adjoining water on swelling. The unwound fibers do not tear off from the polymer substrate. They form a vastly extended "brush" type structure normal to the membrane surface. This may have implications for specificity of ion transport in biology, where the ubiquitous glycocalyx of cells and tissues invariably involves highly sulfated polymers such asheparan and chondroitin sulfate. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC), as a wide-band gap semiconductor, plays an important role in high temperature and high-power devices, and the spin defect has great application prospect in quantum technology. Divacancy in SiC (V C V Si , VV) has attracted more and more attention. There are a lot of experimental studies on color center preparation by ion implantation, but the mechanism of atomic scale defects in the experimental preparation process is not fully understood. EPI epitaxial 4H–SiC was implanted with 250 keV proton at room temperature under three fluence of 1E14 cm−2, 1E15 cm−2, 1E16 cm−2. Defects of implanted 4H–SiC samples were characterized by photoluminescence spectrum and electron paramagnetic resonance (EPR). The existence of the optimal implantation fluence for V Si and V C V Si (VV) color centers by hydrogen ion implantation was found. Molecular dynamics (MD) simulation by considering the ionization energy loss for swift ion implantation were used to study the defect distribution and transformation at atomic-scale during hydrogen ion implantation and post-annealing. The optimal implantation fluence was found and confirmed by comparing the atomic-scale implantation simulation with the experimental results. In the annealing simulation, the optimal annealing temperature for the color centers in 4H–SiC was verified, and its formation mechanism was analyzed by accurately calculating the defect transformation during the annealing process. Finally, in order to accurately control the depth of color center in 4H–SiC, dual ions implantation of carbon and proton has been studied to realize the optimal divacancy yield by SRIM and MD simulations. Molecular dynamics simulation results showed that low-fluence C pre-implantation is helpful to improve the color center yield for the dual ions implantation. [ABSTRACT FROM AUTHOR]

Nowadays, quantification in some spectroscopic techniques is a milestone to be achieved. This work aims to develop a new universal methodology to correlate the arbitrary intensity units from a photoluminescence spectrometer with luminance (µcd/mm2), to quantify the photoluminescent intensity of materials. Reference sample composites with different concentrations (0.1–10 % by weight) of Eu 2 O 3 particles in an epoxy matrix were prepared and characterized by photoluminescence and their luminance was then measured with a luminancemeter. The results show that the proposed method successfully relates and quantifies the arbitrary units obtained from a photoluminescence spectrometer with the luminance at a given excitation wavelength. In addition, this study reveals that the method is applicable for quantifying luminescence measurements with a Raman spectrometer, provided that the photoluminescent materials have an excitation response near typical Raman excitation laser wavelengths. Furthermore, this new methodology was validated in the anti-counterfeiting application of value documents. [Display omitted] • Homogeneous epoxy-based composites with different concentrations of Eu 2 O 3 particles were studied. • The optical responses of composites are not linear with Eu 2 O 3 concentrations. • Luminance values are quantified in both photoluminescence and Raman spectroscopies. • The proposed methodology has been validated in security paper as an anti-counterfeiting application. • The developed method allows quantifying the luminance even in isolated particles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of high quality pristine and nitrogen-doped Cu 2 O films on Au(111) and Pt(111). • Thorough surface-science analysis of the doped films by XPS, STM, LEED and PL spectroscopy. • Measuring the thermal stability of the N-dopants in the Cu 2 O matrix. • Identifying O substitutional sites as primary binding positions of the N-atoms. • Determining the nitrogen desorption temperature to 500 K, too low for practical applications. Nitrogen doping of Cu 2 O films grown on Au(111) and Pt(111) supports was explored by a variety of surface-science techniques, including electron-diffraction, X-ray photoelectron-spectroscopy (XPS), scanning tunneling microscopy and photoluminescence spectroscopy (PL). The films were prepared by Cu vapor deposition and high-pressure oxidation at 50 mbar O 2. Nitrogen was inserted by adding N 2 to the reactive gas or via sputter doping. Only the latter resulted in a clear N 1s signal in XPS, compatible with the insertion of N-atoms at O substitutional sites. The N-doping caused an overall degradation of the oxide lattice and suppressed the formation of the (√3×√3)R30° surface reconstruction observed on pristine Cu 2 O(1 1 1). Moreover, the oxide Fermi level shifted from the valence-band top into the band gap, indicative for a reduced p-type conductivity of the sample upon doping. The N-dopants featured low thermal stability and largely desorbed at around 500 K, leaving behind a pronounced 850 nm PL peak due to O vacancy emission. Our findings indicate that the N-atoms initially occupy O substitutional sites but get removed easily at moderate temperature, casting doubts whether N-doping is a suitable pathway to improve the conductance and luminescence behavior of Cu 2 O. [ABSTRACT FROM AUTHOR]

In this work, the response of the CR-39 nuclear track detector (NTD) exposed to different low doses of gamma rays was investigated using UV–Vis and photoluminescence spectroscopy. Five NTDs of CR-39 were irradiated with low gamma-ray doses ranging from 10 to 120 kGy using a60Co source. The dose of gamma rays correlates with red shift in the absorption spectra of a gamma-irradiated CR-39 detector. As the gamma dose increases, the indirect and direct energy band gaps, as well as Urbach energy, decrease gradually. However, the decrease in the indirect optical band gap is greater than the decrease in the direct band gap. The observed spectra of the CR-39 detector after being irradiated with different doses of γ-rays showed an acceptable variation in photoluminescence (PL) emission spectra generated by a well-defined excitation wavelength of 290 nm. Starting at 45 kGy dose, the integrated area of the photoluminescence peak increases and tends to saturate, whereas the photoluminescence peak height is linearly correlated with the gamma dose with high sensitivity, which is 53.1 ± 6.3 CPS. kGy−1. According to the current findings, photoluminescence (PL) spectroscopy has a greater sensitivity than UV–Vis spectroscopy for measuring the response of the CR-39 detector to gamma rays in the dose range of 10–120 kGy. The results reflected a potential possibility of using the CR-39 detector in dosimetric applications of low gamma ray doses through the high resolution achieved by photoluminescence (PL) and UV–Vis spectroscopy. • CR-39 NTDs is applied in low doses gamma ray dosimetry. • UV–Vis spectra are red shifted as gamma ray dose increase from 10 to 120 kGy. • Photoluminescence (PL) emission spectra is generated excitation wavelength of 290 nm. • Photoluminescence (PL) is of higher sensitivity than UV–Vis spectroscopy. • The photoluminescence peak height is linearly correlated with the gamma dose. [ABSTRACT FROM AUTHOR]

In Glass-to-Metal (GTM) seals, glass matrix composites (GMCs) are frequently utilized to enhance sealing performance. However, the incorporation of reinforcements inevitably impacts the residual stress, a critical determinant of the hermeticity of GTM seals. Hence, revealing the effect of reinforcements on the residual stress is urgently needed. This study investigates the correlation between residual stress and varying alumina content. Theoretically, the total residual stress in GTM seals comprises both intrinsic residual stress and extra compressive stress. The former is due to the thermal mismatch between the glass matrix and reinforcements, while the latter arises from the cooling-induced shrinkage of the metal housing. To empirically validate this theoretical framework, Cr3+-doped Al 2 O 3 particles were incorporated into borosilicate glass to prepare GMCs with alumina contents ranging from 3 wt% to 20 wt%. Leveraging the stress-sensitive photoluminescence property, photoluminescence spectroscopy (PLS) was applied to experimentally measure stress, enabling a detailed examination of stress distribution within GTM seals. Concurrently, finite element modeling was employed to estimate the extra compressive stress imposed by the metal housing. The experimentally detected stresses closely align with the theoretical predictions, thus verifying the accuracy of the theoretical framework. A significant finding is the observed reduction in residual stress within GTM seals with increasing alumina content. This trend is explained through strain energy theory, offering comprehensive insights into the influence of alumina content on the residual stress. The findings provide a robust foundation for the design and optimization of the stress in GTM seals. [Display omitted] • A novel approach using photoluminescence spectroscopy to detect residual stress in glass-to-metal seals. • Increasing alumina in glass composites lowers residual stress. • Demonstrates the applicability of strain energy theory to explain stress behavior in glass-to-metal seals. [ABSTRACT FROM AUTHOR]

In this study, carbon quantum dots/Cu2O nanocubes (CQDs/Cu2O NCBs) nanomaterial has been successfully synthesized using a simple and easy-to-implement method with a quick reaction time (90 min) at 80°C. In particular, carbon quantum dots (CQDs) were obtained by green and environmentally friendly synthesis methods, using abundant and naturally available raw materials from rice flour and applying hydrothermal approach. Besides, cuprous oxide nanocubes (Cu2O NCBs) were also synthesized through non-toxic compounds. The morphology and composition of CQDs/Cu2O NCBs and Cu2O NCBs were analyzed through UV-vis, FTIR, XRD, FE-SEM, TEM, and EDX spectroscopy. The results showed that Cu2O NCBs have a cubic shape with an average particle size of ~ 29–31 nm, and CQDs have spherical shape with a size of ~ 4–8 nm. In addition, CQDs/Cu2O NCBs nanomaterial was also employed as a “turn-on” fluorescence sensor” for application in metal ions detection. The obtained results showed that the CQDs/Cu2O NCBs are potential and promising in detecting Pb2+ ions in the wide range from 1.8 M to 10− 9 M and extremely low limit of detection of 27.8 nM at the excitation wavelength of 340 nm. CQDs/Cu2O NCBs-based sensors are highly sensitive and selective for Pb2+ detection. Therefore, CQDs/Cu2O are promising as photocatalytic materials for various applications, including sensors, bio-probes biomedical, optoelectronics, etc.Graphical Abstract: In this study, carbon quantum dots/Cu2O nanocubes (CQDs/Cu2O NCBs) nanomaterial has been successfully synthesized using a simple and easy-to-implement method with a quick reaction time (90 min) at 80°C. In particular, carbon quantum dots (CQDs) were obtained by green and environmentally friendly synthesis methods, using abundant and naturally available raw materials from rice flour and applying hydrothermal approach. Besides, cuprous oxide nanocubes (Cu2O NCBs) were also synthesized through non-toxic compounds. The morphology and composition of CQDs/Cu2O NCBs and Cu2O NCBs were analyzed through UV-vis, FTIR, XRD, FE-SEM, TEM, and EDX spectroscopy. The results showed that Cu2O NCBs have a cubic shape with an average particle size of ~ 29–31 nm, and CQDs have spherical shape with a size of ~ 4–8 nm. In addition, CQDs/Cu2O NCBs nanomaterial was also employed as a “turn-on” fluorescence sensor” for application in metal ions detection. The obtained results showed that the CQDs/Cu2O NCBs are potential and promising in detecting Pb2+ ions in the wide range from 1.8 M to 10− 9 M and extremely low limit of detection of 27.8 nM at the excitation wavelength of 340 nm. CQDs/Cu2O NCBs-based sensors are highly sensitive and selective for Pb2+ detection. Therefore, CQDs/Cu2O are promising as photocatalytic materials for various applications, including sensors, bio-probes biomedical, optoelectronics, etc. [ABSTRACT FROM AUTHOR]

This study examines the synthesis of two geminal bisphosphonate ester-supported Ln3+ complexes [Ln(L3)2(NO3)3] (Ln = Nd3+ (5), La3+ (6)) and optical properties of the neodymium(III) complex. These results are compared to known mono-phosphonate ester-based Nd3+ complexes [Nd(L1/L2)3X3]n (X = NO3−, n = 1; Cl−, n = 2) (1–4). The optical properties of Nd3+ compounds are determined by micro-photoluminescence (µ-PL) spectroscopy which reveals three characteristic metal-centered emission bands in the NIR region related to transitions from 4F3/2 excited state. Additionally, two emission bands from 4F5/2, 2H9/2 → 4IJ (J = 11/2, 13/2) transitions were observed. PL spectroscopy of equimolar complex solutions in dry dichloromethane (DCM) revealed remarkably higher emission intensity of the mono-phosphonate ester-based complexes in comparison to their bisphosphonate ester congener. The temperature-dependent PL measurements enable assignment of the emission lines of the 4F3/2 → 4I9/2 transition. Furthermore, low-temperature polarization-dependent measurements of the transitions from R1 and R2 Stark sublevel of 4F3/2 state to the 4I9/2 state for crystals of [Nd(L3)2(NO3)3] (5) are discussed. [ABSTRACT FROM AUTHOR]

Mn‐based materials are excellent catalysts with applications in many complex heterogeneous charge transfer processes because of their ability to exist in several stable oxidation states. However, accurate detection of Mn valence states is challenging due to the limitations of X‐ray‐based spectroscopic techniques to successfully resolve individual oxidation states. In this work, we performed a combined photoluminescence (PL) and X‐ray photoelectron spectroscopy (XPS) analysis of many Mn compounds to show that PL spectroscopy can consistently detect Mn in different oxidation states and their composition can be determined through a simple fitting procedure. The results suggest that PL spectroscopy can be a relatively simpler, benchtop alternative to X‐ray based techniques for direct metal cation detection without the need for multiplet fitting analysis. [ABSTRACT FROM AUTHOR]

We have studied the crystalline, optical and photo-response properties of epitaxial GaN films grown on bare- and pre-nitridated a-sapphire substrates with different thicknesses of low temperature (LT) GaN buffer layer using laser-assisted molecular beam epitaxy (LMBE). It is found that the GaN grows epitaxially on a-sapphire along the c-axis and has low biaxial stress of ~ 0.3 GPa. Room-temperature photoluminescence spectroscopy disclosed the near band edge emission peak at ~ 3.4 eV with a line width of 100 ~ 110 meV for GaN grown on thin LT-GaN buffer, whereas an additional prominent blue luminescence emission is obtained for GaN film grown on thicker LT-GaN buffer. Metal–semiconductor-metal based ultra-violet (UV) photodetectors (PD) fabricated on GaN film grown on pre-nitridated sapphire with thin LT-GaN buffer showed a responsivity of ~ 1.35 A/W at 3 V applied bias. It is also observed that the PDs with thin LT-GaN buffer have nearly 5 times higher responsivity with a faster response than that with thick LT-GaN buffer. We found that the photoresponse characteristics of GaN-based UV PDs on a-sapphire are critically dependent on crystalline and optical defects. [ABSTRACT FROM AUTHOR]

The physical characterization and magnetic interactions of cadmium-doped zinc ferrite nanoparticles Zn 1 - x Cd x Fe 2 O 4 , x ≤ 10 % have been studied. The samples were synthesized using the co-precipitation technique and analyzed for the structural phases, morphological, mechanical, optical, and magnetic properties using XRD, SEM, FTIR, DRS, PL, and VSM techniques. The spinel structure's lattice parameters increased, and the size of the nanoparticles increased with the additional quantity of the dopant. SEM images revealed the existence of spherical particles with an average particle size of 36.32–39.57 nm. FTIR spectral analysis indicated the existence of absorption bands of metal oxide at higher and lower frequency regimes due to the stretching vibrations of both octahedral and tetrahedral sites. Diffuse reflectance spectral analysis (DRS) was used to measure the bandgap energies with the estimated values of 1.897, 2.012, 2.027, and 2.036 eV, which increased as the dopant concentration increased. The photoluminescence (PL) spectra for the emission wavelengths range from 485 to 478 nm with emission energies of 2.56–2.60 eV for the PL peaks. The magnetic properties were determined by employing a vibrating sample magnetometer (VSM) with an applied magnetic field up to 50 kOe at low and room temperatures (4 and 300 K). The magnetic hysteresis loops show a decrease in magnetic saturation from 36.458 to 6.682 emu/g, large coercivity and magneto-crystalline anisotropies at 4 K, and a decrease in magnetic moments and permeabilities with the doping of Cd 2 + ions. Interionic and magnetic interactions were explained by the Yafet–Kittel (YK) model. [ABSTRACT FROM AUTHOR]

Undoped ZnO and Zn1−xGdxO nanoparticles are made using a sono‐chemical co‐precipitation approach. X‐ray diffraction and transmission electron microscopy investigations verified the formation of a wurtzite structure with spherical geometry. All the samples are found to be nanocrystalline by transmission electron microscopy, with crystallite diameters ranging from 14 to 22 nm. The optical constants are calculated via diffuse reflectance spectroscopy. The Urbach energy and photoluminescence spectrum both showed that all doped nanoparticle samples contained defects and disorder due to vacancies. The band structure finding suggest that the forbidden gap of ZnO may change due to the conduction band shift, Burstein‐Moss shift, and shrinkage effect. The near band emission in the ultraviolet region and deep level emission of the photoluminescence spectrum are both strong and decreased with increasing Gd3+ concentration. Studies using X‐ray absorption near edge spectroscopy revealed that the host nano‐lattice Zn sites are substituted with Gd3+ cations to preserve the symmetry with minor distortion. Investigations into charge transfer through the oxygen bands (Gd‐O‐Zn) are made using O K‐edge spectra. The defect emission bands identified through Gd doping indicated that these emissions may be changed for ZnO samples, which could be advantageous for applications in phosphors and light‐emitting devices. [ABSTRACT FROM AUTHOR]

The dependence of the ablation rate on the laser fluence was measured in femtosecond laser processing of polydimethylsiloxane, and the slope of the ablation rate tended to change to three ablation regimes. The laser-irradiated area was analyzed using Raman and photoluminescence spectroscopy to investigate the cause of the changes in the slope in terms of chemical structural changes. We will show that microscopic observation of the cross-sectional sample enables the analysis of grooves with a high aspect ratio that could not be measured by conventional observation from the sample surface. This allows us to discuss the correlation between the ablation rate and chemical structural changes over a wide range of fluences up to the high fluence regime. As a result, it was found that in the low fluence regime, the photochemical process is dominant with the gentle slope of ablation rate, while both photochemical and photothermal processes lead to an increase in the slope in the middle fluence regime. Moreover, the steep slope in the high fluence regime was induced by high temperatures where carbon–carbon bond formation takes place. [ABSTRACT FROM AUTHOR]

[Display omitted] • Controlled in-vitro growth of oxide semiconductor heterostructure. • Buried metallic Zn under hafnium dioxide is converted to oxide through internal oxidation. • Significant migration of O from HfO 2 was observed. • Low temperature photoluminescence spectra exhibits near band edge emissions. Metal-oxides are in the forefront of various applications in optoelectronic, piezo-electronics, magnetism etc. The large bandgap oxide semiconductor hetero-interface growth can be achieved through a controlled conversion of the metallic part of a group II elements of the compound. This study investigates the controlled in-vitro growth of zinc oxide (ZnO) thin films on n-type silicon substrates through the internal oxidation of a buried metallic Zn layer under hafnium dioxide (HfO 2). Controlled annealing in an oxygen atmosphere at 400 °C resulted in the transformation of the underline Zn layer of thickness 44 nm into ZnO layer of thickness 37.5 nm. The comparative structural analysis of the as-grown and annealed Zn/HfO 2 layers by x-ray diffraction clearly indicates complete conversion of the Zn layer to ZnO/HfO x hetero-interface, where x < 2. The x-ray reflectivity and x-ray photoelectron spectroscopy clearly indicates non-stoichiometry in the HfO 2 layer indicating diffusion of O to the underlying Zn layer to convert it to ZnO. The presence of well-defined fringes in the x-ray reflectivity clearly suggest high quality hetero-interfaces which allows us to determine the interfacial layer thicknesses. Low temperature photoluminescence spectra taken at 4 K clearly showed sharp and well-defined multiple order near band edge emission peaks at around 3.37 eV, which falls in the UV region of the spectra. The findings underscore the potential of this method for developing oxide-based buried low-dimensional heterostructures for different applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized FeCoNi/Nd(OH) 3 C-NPs using reactive mechanical milling. • Nanoparticles exhibit strong photoluminescence with visible range emissions. • Demonstrated efficient endocytosis in BEAS-2B cells. • XPS analysis confirms FeCoNi/Nd(OH) 3 heterostructure formation. In this study, FeCoNi alloy nanoparticles were combined with Nd(OH) 3 nanostructures to create unique cotton-like nanoparticles (C-NPs). These C-NPs were synthesized through an accessible, two-step reactive chemical milling process. The nanoparticles originated from a blend of metal chlorides (FeCl 2 , CoCl 2 , and NiCl 2) and sodium (Na), used as a precursor in the reaction, within a SPEX milling apparatus. The Fe, Co, and Ni were maintained at equal weight percentages (1:1:1). Subsequently, NdCl 3 and Na were utilized to facilitate the attachment of Nd(OH) 3 nanostructures onto the FeCoNi nanoparticles through a solid-state reaction in the same SPEX milling setup. The Nd content was varied to investigate its effect on the integration of Nd(OH) 3 onto the surface of CoNiFe nanoparticles. Electron microscopy revealed the formation of cotton-like nanoparticles, and the distribution of elements was identified using secondary ion mass spectrometry. The CoNiFe alloy and Nd(OH) 3 phases were verified by X-ray diffraction analysis. These nanoparticles were internalized into cells via endocytosis, as observed in transmission electron microscopy images after incubation with the BT20 cell line (triple-negative breast cancer), likely due to interactions between –OH groups and the cell membrane. Following this, the cells containing C-NPs underwent photoluminescence studies, revealing two distinct emission peaks at 400 nm, and 486 nm. X-ray photoelectron spectroscopy indicated the presence of various heterostructures within the FeCoNi-Nd(OH) 3 complex, which may be responsible for these emission properties. [ABSTRACT FROM AUTHOR]

This study provides a comprehensive examination of the Cd 0.90 Mn 0.10 Te (CMT) single crystal in its role as a radiation detector. Covering aspects from the growth process to detector performance, the primary emphasis is placed on ensuring the uniformity of composition along the growth axis. A cost-effective custom-built vertical Bridgman (VB) setup is developed for the growth of highly homogeneous Cd 0.90 Mn 0.10 Te (CMT) single crystal. CMT single crystals of 10 mm diameter and 130 mm length with near uniform stoichiometry along the growth axis were grown using VB method. Laue diffraction confirms the single crystallinity of the grown crystal. The measured lattice constant is comparable to the theoretical value calculated using Vegard's law. The two mode vibrations of the CdTe and MnTe sublattices were confirmed by Raman spectroscopy. The observed high optical transmittance in the mid-infra-red (IR) region and a nearly constant bandgap of ∼1.6 eV for the wafers taken at different locations along the growth axis reveals the IR transparency and compositional uniformity of the grown crystal. The energy dispersive X-ray spectroscopy proved that the elemental distribution is uniform in the grown crystal. The IR microscopic imaging shows Te inclusions with a number density in the range of ∼2.6–4.5 × 104 cm−2. The resistivity of the CMT crystal for all wafers was found to be in the order of 109 Ωcm. The γ–ray spectral resolution of ∼22 % of 59.5 keV irradiation from 241Am source is achieved. [Display omitted] • Detector grade Cd 0.90 Mn 0.10 Te crystal grown by home-built vertical Bridgman method. • Vertical bobbing was used for the first time to synthesise the starting material. • Excellent structural and compositional homogeneity observed across crystal length. • CMT crystal displays good response to 241Am γ-irradiation with energy of 59.5 keV. [ABSTRACT FROM AUTHOR]

New anti-octadecaborane(22) laser dyes have been recently introduced. However, their application in solid thin films is limited, despite being very desirable for electronics. Spectroscopic methods, photoluminescence (PL), and infrared reflection–absorption spectroscopy (IRRAS), are here used to reveal structural responses to a temperature change in thin polymer films made of π- and σ-conjugated and non-conjugated polymers and anti-octadecaborane(22) and its tetra-alkylatedderivatives. It has been observed that borane clusters are not firmly fixed within polymer matrices and that their ability for diffusion out of the polymer film is unprecedented, especially at higher temperatures. This ability is related to thermodynamic transitions of polymer macromolecular chains. PL and IRRAS spectra have revealed a clear correlation with β-transition and α-transition of polymers. The influence of structure and molecular weight of a polymer and the concentration and the substitution type of clusters on mobility of borane clusters within the polymer matrix is demonstrated. A solution is proposed that led to an improvement of the temperature stability of films by 45 °C. The well-known spectroscopic methods have proved to be powerful tools for a non-routine description of the temperature behavior of both borane clusters and polymer matrices. [ABSTRACT FROM AUTHOR]

Pyrochlore structured compounds form a special class of ceramics as host matrices in phosphors with better luminescent properties. In the present work, the optical properties of pyrochlore oxide Gd 2-x Tb x Ti 2 O 7 (0 ≤ x ≤ 0.16) were investigated and linked with structural properties via examination of structural distortion produced with the doping of rare-earth element. These oxide compositions were produced through standard solid-state reaction method. The investigations using advanced characterization techniques; X-ray diffraction and Raman spectroscopy give a signature of single phasic pyrochlore structure in the synthesized samples optimized through multiple heating protocol. The diffraction patterns and Raman spectra, both were continuously being shifted towards lower 2θ value and lower wave-number side, respectively with the doping concentration which can be interpreted by the production of defects in cationic lattice. A similar decreasing trend in particle size has been observed from W–H plot (728 Å to 616 Å) and Scanning electron micrographs (0.82 μm–0.78 μm) with the introduction of Tb3+ ion. The band-gap for the host matrix Gd 2 Ti 2 O 7 through UV absorption pattern came out to be 2.26 eV. From photoluminescence excitation (λ em = 545 nm), a broad excitation band was observed in the wavelength range 305 nm–380 nm due to the f→d transition of 4f shell of Tb ion. Furthermore, emission spectra (λ ex = 375 nm) consist of bands at 489 nm, 545 nm, 585 nm and 623 nm due to the transitions at 5D 4 → 7F 6,5,4, and 3 , respectively with doping. For an optimum doping concentration with x = 0.12, a high intensity green emission line at 545 nm came out as 5D 4 → 7F 5 dominating transition of terbium ion. Hence, the results explore the application of Gd 2 Ti 2 O 7 composition as Tb-fluorescence with the optimum doping concentration of 6%. • We have synthesized the Tb3+ doped Gd 2 Ti 2 O 7 through solid-state reaction method. • The pyrochlore structure in synthesized series was confirmed by XRD and Raman spectroscopy. • PL results that green light emission of the Tb3+ ion is dominating by 5D 4 → 7F 5 transition in host matrix due to energy transfer from host to Tb3+ ions upon excitation at λ em = 545 nm. • The band-gap for the host matrix Gd 2 Ti 2 O 7 has been analyzed through UV absorption pattern as 2.26 eV. [ABSTRACT FROM AUTHOR]

Sb2Se3 has emerged as an important photoelectrochemical (PEC) and photovoltaic (PV) material due to its rapid rise in photoconversion efficiencies. However, Sb2Se3 has a complex defect chemistry, which reduces the maximum photovoltage. Thus, it is important to understand these defects and develop defect passivation strategies in Sb2Se3. A comprehensive investigation of the charge carrier dynamics of Sb2Se3 and the influence of sulfur treatment on its optoelectronic properties is performed using time‐resolved microwave conductivity (TRMC), photoluminescence (PL) spectroscopy, and low‐frequency Raman spectroscopy (LFR). The key finding in this work is that upon sulfur treatment of Sb2Se3, the carrier lifetime is increased by the passivation of deep defects in Sb2Se3 in both the surface region and the bulk, which is evidenced by increased charge carrier lifetime of TRMC decay dynamics, increased radiative recombination efficiency, decreased deep defect level emission (PL), and the emergence of new vibration modes by LFR. [ABSTRACT FROM AUTHOR]

Cadmium oxide (CdO) photocatalysts have been prepared using chemically controlled co-precipitation method with the intension to serve as photocatalyst in the degradation of methylene blue dye. Photocatalytic property of CdO was improved by properly undertook calcination at various temperatures 400, 600 and 800 °C, and by doping with Al3+ to different weight percentages (0.5 and 1 wt%). The powder X-ray diffraction patterns of the synthesized CdO and Cd(1−x)AlxO samples exposed the formation of single phase polycrystalline face centered cubic (Fm 3 ¯ m) CdO structure with no impurity phases even after doping with Al3+. Obtained crystallite size in the range 22 to 72 nm was well suited for photocatalytic activity. The presence of Al dopant as Al3+ ion in the CdO lattice was confirmed from the information derived from the XPS spectra. In the SEM images the revealed agglomerated spherical morphology evidenced the presence of round edges and corners that can have more active sites in the photocatalytic process so as to advance the photocatalytic activity. Direct optical band gaps measured from the UV–Vis spectra seemed to lay in the range 2.09 to 2.57 eV and were liable for the greater photocatalytic activity of the readied nanoparticles. In the photoluminescence spectra, for an excitation wavelength of 440 nm, the pure and doped CdO nanoparticles displayed bands about 485, 530 and 600 nm with poorer intensities and exposed its appropriateness to serve as superior photocatalyst. Attained good electrical conductivity of CdO and its enhancement with Al doping exposed the liableness of the samples to use as better photocatalysts. The small-sized Al doped CdO nanoparticles showed evidence of considerably high visible-light-driven photocatalytic activity for the degradation of methylene blue solution, with better degradation percentage and kinetic rate constant compared to pure CdO. [ABSTRACT FROM AUTHOR]

This paper reports the physical, structural, optical and luminescence properties of Er 3 + doped borophosphate glasses. The samples were prepared with melt quenching technique at 1250 ∘ C by varying the concentration of Er 2 O 3 from 0.1 to 0.5 mol%. Density is measured by Archimedes principle and variation in density with erbium's concentration established its participation in the glass structure. X-ray diffraction affirmed the amorphous nature of the prepared glasses. Fourier transform infrared spectroscopy spectra revealed the structural units such as P--O--P , B--O--B and BO 4 present due to stretching and bending vibrations of various bonds. Ultra-violet-visible absorption spectra displayed various absorption peaks/bands originating from ground state of erbium 4 I 15 / 2 to 2 K 15 / 2 , 4 G 9 / 2 , 4 G 11 / 2 , 2 G 9 / 2 , 4 F 5 / 2 , 4 F 7 / 2 , 2 H 11 / 2 , 4 S 3 / 2 and 4 F 9 / 2 . The indirect optical band gap values varied between 2.56 and 3.19 eV. Judd Ofelt parameters ( Ω 2 , Ω 4 , Ω 6 ) were evaluated and they followed Ω 2 > Ω 4 > Ω 6 trend. These parameters helped to calculate radiative transition probability, stimulated emission cross section and gain bandwidth. For luminescence studies, the glass samples were excited at 379 nm and emission occured in the visible region showing peaks at 405 nm, 485 nm and 517 nm. Commission International de I'Eclairage (CIE) coordinates (x and y) were calculated for the glass samples and these coordinates lie in the blue region of CIE chromaticity diagram. [ABSTRACT FROM AUTHOR]

The stress field and stress evolution of compression seals at micron-scale spatial resolution are experimentally quantified for the first time using photoluminescence spectroscopy (PS) technique. In analyzing the resulting dataset based on fluorescence line shift, it is found that the compressive stress is non-uniform from the center to the periphery of glass, and the highest compressive stress (>300 MPa) is located at the distance of 15∼20 μm to the interface. Further in-situ PS experiments performed at the high compressive stress region reveal that the compressive stress decayed near-linearly with increasing temperature, and instantaneous cracking generated by tensile stress was observed at 320 °C. Moreover, the compressive stress at the interface significantly decayed from 289 MPa to 90 MPa after aged for 800 h at 250 °C. The present work demonstrates an effective method to measure the stress field and sheds light on the future compressive stress tailorability for compression seals. [ABSTRACT FROM AUTHOR]

The defect structure of four pure tungsten samples is investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL) and positron annihilation spectroscopy (PAS) techniques before and after annealing. The results of the SEM and XRD analyses show that the grain size is increased up to 43.3 μ m, and their growth in the (2 0 0) orientation occurs at 1673 K. Also, the smooth of the peaks at 1673 K in the PL test demonstrates the increase of the size of defects of the sample. Moreover, the results of the PAS indicate a decrease in the concentration of defects and an increase in their size at 1673 K, which confirms the results obtained from the PL measurement. The collected results from the four examination techniques are in close agreement with each other and reveal that w ith the increase in the annealing temperature of tungsten samples, a gradual coalescence of the defects would happen to lead to an increase in their size and hence a reduction in their number as well as preferred grain growth in the (2 0 0) orientation and virtually perfect recrystallization of the samples at higher temperatures. [ABSTRACT FROM AUTHOR]

Thin films of un-doped and cerium (Ce)-doped zinc sulfide (ZnS) with various doping concentrations of Ce (2, 4, 6, 8 and 10 at. %) were prepared and deposited on glass substrates by sol–gel process and dip-coating method. The effects of different Ce doping concentrations on the structural, morphological, optical, and photoluminescence properties of such films were studied using X-ray diffraction (XRD), Fourier-transform infrared (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), UV–visible spectrophotometry, and photoluminescence (PL) spectroscopy. XRD patterns exhibited an amorphous structure for all the synthesized films. FTIR analysis confirmed the presence of the Zn–S band. AFM revealed that the samples presented a smooth and homogenous structure. SEM micrographs showed that the surface morphology of the films was affected by the doping with Ce concentrations. According to the UV–visible spectroscopy measurement, all the films were highly transparent with average visible transmittance values ranging from 60 to 85%. Room temperature PL spectra showed the presence of two peaks in the ultraviolet domain and four very weak emission bands in the visible range. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulation is adopted to discover the formation mechanism of silicon vacancy color center and to study the damage evolution in 4H-SiC during helium ion implantation with different annealing temperatures. The number and distribution of silicon vacancy color centers during He ion implantation can be more accurately simulated by introducing the ionization energy loss during implantation. A new method for numerical statistic of silicon vacancy color centers is proposed, which takes into account the structure around the color centers and makes statistical results more accurate than the Wignerâ€"Seitz defect analysis method. Meanwhile, the photoluminescence spectra of silicon vacancy color centers at different helium ion doses are characterized to verify the correctness of the numerical analysis. The new silicon vacancy color center identification method can help predicting the optimal annealing temperature for silicon vacancy color centers, and provide guidance for subsequent color center annealing experiments. [ABSTRACT FROM AUTHOR]

BACKGROUND: Blue amber is mainly produced in the Dominican Republic, Mexico and Myanmar. Generally speaking, the formation mechanism, composition and spectral characteristics of blue amber are closely related to its specific geographical environment. Therefore, the study on the origin of blue amber has become a hot topic in the field of gemology, archaeology and biological mineralogy, and the origin of geographical districts of blue amber has become a hot research topic. Previous studies mainly used infrared spectroscopy, X-ray fluorescence spectroscopy, mass spectrometry, and isotope tracing to carry out a relatively systematic study on the origin of blue amber, but were limited to the similarity of blue amber, and the spectral characteristics of blue amber from different origins showing similarities. Due to the low popularity of the application of some detection devices, the application of the detection method based on the above-mentioned corresponding devices is greatly limited. OBJECTIVES: To identify photoluminescence (PL), Raman spectroscopy and trace element characteristics of blue amber with different origins. METHODS: Photoluminescence and Raman spectroscopy combined with trace element analysis were used to study the spectral and elemental occurrence characteristics of blue amber from Dominican Republic and Mexico. RESULTS: The results showed that: (1) At room temperature, using PL spectrum with 405 nm as the excitation wavelength, the peaks at 450, 475 and 502 nm appeared simultaneously for blue amber from Dominican Republic. In contrast, there was no significant characteristic peak in Mexican blue amber. The differences in PL spectrum of blue amber from the two origins can be used as a direct basis for the traceability and identification of its origin. (2) Using the Raman spectrum with 785 nm as the excitation wavelength, the Raman peaks of blue amber from Dominican Republic at about 154, 468, 901, 1177 and 1312 cm-1 were more prominent or sharper than those from Mexico. The ratio of the peak intensity at 1653 and 1446 cm-1 (N=I1653/I1446) in the corresponding spectrum of the amber from Dominican Republic was significantly higher than that from Mexico. (3) Trace elements of S, Si, Fe and Cu were present in the blue amber from the two regions, and the content was S>Si>Fe>Cu. The content of Cu in blue amber from Dominican Republic was generally higher than that from Mexico. Therefore, the occurrence and content characteristics of Cu can be used as one of the evidences for the traceability of Dominican blue amber. CONCLUSIONS: The research work provides theoretical and technical support for the origin of blue amber with different geographical locations. It can also provide a salutary reference for identification of the geographical location for other gems. [ABSTRACT FROM AUTHOR]

Semiconductor nanoplatelets (NPLs), with their large exciton binding energy, narrow photoluminescence (PL), and absence of dielectric screening for photons emitted normal to the NPL surface, could be expected to become the fastest luminophores amongst all colloidal nanostructures. However, super‐fast emission is suppressed by a dark (optically passive) exciton ground state, substantially split from a higher‐lying bright (optically active) state. Here, the exciton fine structure in 2–8 monolayer (ML) thick Csn − 1PbnBr3n + 1 NPLs is revealed by merging temperature‐resolved PL spectra and time‐resolved PL decay with an effective mass model taking quantum confinement and dielectric confinement anisotropy into account. This approach exposes a thickness‐dependent bright–dark exciton splitting reaching 32.3 meV for the 2 ML NPLs. The model also reveals a 5–16 meV splitting of the bright exciton states with transition dipoles polarized parallel and perpendicular to the NPL surfaces, the order of which is reversed for the thinnest NPLs, as confirmed by TR‐PL measurements. Accordingly, the individual bright states must be taken into account, while the dark exciton state strongly affects the optical properties of the thinnest NPLs even at room temperature. Significantly, the derived model can be generalized for any isotropically or anisotropically confined nanostructure. [ABSTRACT FROM AUTHOR]

Semiconductor nanoplatelets (NPLs), with their large exciton binding energy, narrow photoluminescence (PL), and absence of dielectric screening for photons emitted normal to the NPL surface, could be expected to become the fastest luminophores amongst all colloidal nanostructures. However, super‐fast emission is suppressed by a dark (optically passive) exciton ground state, substantially split from a higher‐lying bright (optically active) state. Here, the exciton fine structure in 2–8 monolayer (ML) thick Csn − 1PbnBr3n + 1 NPLs is revealed by merging temperature‐resolved PL spectra and time‐resolved PL decay with an effective mass model taking quantum confinement and dielectric confinement anisotropy into account. This approach exposes a thickness‐dependent bright–dark exciton splitting reaching 32.3 meV for the 2 ML NPLs. The model also reveals a 5–16 meV splitting of the bright exciton states with transition dipoles polarized parallel and perpendicular to the NPL surfaces, the order of which is reversed for the thinnest NPLs, as confirmed by TR‐PL measurements. Accordingly, the individual bright states must be taken into account, while the dark exciton state strongly affects the optical properties of the thinnest NPLs even at room temperature. Significantly, the derived model can be generalized for any isotropically or anisotropically confined nanostructure. [ABSTRACT FROM AUTHOR]

The aim of this paper is to compare the spectral features of the response plasmon peak in both the optical absorption and photoluminescence spectra of the Ag/Ag2O composites synthesized by treating silver thin films manufactured by thermal evaporation method with oxygen plasma afterglow. Results show that close values of the relative area and spectral width of the plasmon response peaks in the optical absorption/photoluminescence spectra were obtained in the case of samples with high oxygen content. In addition, the intensity ratio (Iabsorption/Iluminescence) of these samples decreases linearly with increasing silver oxide grain size. [ABSTRACT FROM AUTHOR]

To investigate the role of PbO as a former or a modifier and effect of its compositional variation on the physical, structural and optical properties, lithium lead borophosphate glasses were synthesized by melt quenching technique. For the physical properties of the prepared glasses, density was measured using the Archimedes principle, which showed an increasing trend from 3.13 to 4.51 with increasing concentrations of lead oxide. Additionally, other physical parameters were calculated based on the measured density values. The structural analysis were performed through X-ray diffraction and Fourier transform infrared spectroscopy. Lack of sharp and characteristic peaks in the XRD spectra confirmed the non crystalline nature of the prepared glasses. Structural units due to PbO, P2O5\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\text {P}_{2}\text {O}_{5}$$\end{document} and B2O3\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\text {B}_{2}\text {O}_{3}$$\end{document} were identified from the FTIR spectra. Ultraviolet-visible absorption spectroscopy was performed for optical properties and increase in the indirect band gap from 4.80 eV to 4.90 eV was observed. One glass sample was chosen for doping of erbium, neodymium, thulium and ytterbium, for study of their up-conversion properties. The UV-Vis-NIR absorption spectra of erbium, neodymium, and thulium samples were recorded, and wavelength of 980 nm was chosen for excitation. Ytterbium, acting as a sensitizer, facilitated the conversion of the excitation infrared light into visible light. Upon excitation at 980 nm, the erbium-doped sample emitted light at 520 nm, 547 nm, and 665 nm, utilizing excited state up-conversion (ESA) and energy transfer up-conversion (ETU) mechanisms. Similarly, the neodymium-doped sample emitted at 542 nm, 602 nm, and 660 nm, while the thulium-doped sample emitted at 488 nm, 521 nm, and 649 nm. The results of up-conversion indicate that rare earth-doped lithium lead borophosphate glasses are excellent hosts for up-conversion processes. [ABSTRACT FROM AUTHOR]

The resonance photoemission spectroscopy (RPES) studies on pure and Terbium doped CePO 4 nanowires (NWs) are reported here with the supporting characterizations using structural, optical and morphological properties. The NWs with varying Terbium (Tb) doping concentrations were synthesized using chemical synthesis route. Photoluminescence (PL) showed high PL emission intensity in the visible wavelength range indicating strong green luminescence due to efficient Ce3+ to Tb3+ energy transfer. The PL intensity increased up to a doping concentration of 15 wt% Tb3+, beyond which it decreased due to concentration quenching or cross-relaxation effect. Based on PL studies, pure, 5 wt% (the lowest doping amount) and 15 wt% (that shows the highest PL) doped samples were chosen for RPES studies. To understand the comparative contribution of Ce3+ and Ce4+ in the valence band, RPES measurements performed around the Ce 4 d →4 f resonance threshold indicated strong presence of Ce 4 f states in pure CePO 4 NWs, which reduced upon 5 wt% Tb doping in CePO 4 NWs. At 15 wt% Tb3+ doping, the sample did not show resonance of Ce 4 f feature, which may be because Tb3+ ions have replaced Ce3+ ions in the CePO 4 lattice. The results are crucial to understand the relative participation of Ce3+ and Ce4+ oxidation states in the valence band, which is an important factor in defining the optical properties of the material that determine the PL intensity. [Display omitted] • Pure and Tb:CePO 4 nanowires were prepared using green synthesis chemical route. • Tb:CePO 4 nanowires with 15 wt% Tb showed the highest photoluminescence. • Elongated nanowires were observed by transmission electron microscopy. • The first ever Cerium resonance photoemission measurements and analysis is reported. • Strong resonance from Ce3+ oxidation state was observed that resulted in high PL. [ABSTRACT FROM AUTHOR]

• Solvent-induced changes in the ZnO synthesized by sol–gel combustion were studied. • Solvent-dependent growth mechanisms are responsible for the changes in properties. • Wurtzite-phase powders formed of microstructures were obtained despite the solvent. • Powders showed activity vs. S. mutans and S. epidermidis , but not vs. E. faecalis. ZnO powders were synthesized using the sol–gel combustion method, and their properties, along with their activity against microorganisms isolated in the oral cavity, were investigated based on the solvent used in the synthesis. Characterization was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, and photoluminescence (PL) spectroscopies. The results revealed the synthesis of pure ZnO powders without secondary phases, albeit forming microaggregates. Changes in the density of point defects were suggested based on PL results. Despite their size, all the powders exhibited significant antibacterial activity against Streptococcus mutans and Staphylococcus epidermidis. [ABSTRACT FROM AUTHOR]

The influence of charge disorders, non-stoichiometry and oxygen vacancy on the physical properties such as optical properties and magnetic properties of Sr 2 TiCo 1-y O 6-δ exhibiting simple cubic (space group Pm-3m) structure has been investigated in the article. An analysis of energy dispersive X-ray spectrum reveals a deficiency of cobalt ions. Variable range hopping conduction mechanism is observed below 100 K. X-ray photoelectron spectroscopy results indicated the presence of oxygen deficiency accompanied by multiple valent cobalt ions (Co4+ and Co3+) in the material. The optical features of the material are noteworthy, with a wide range of significant optical absorption occurring in the UV range, characterized by a band gap of ∼3.03 eV. In addition, huge photoluminescence emission in the visible range and at room temperature was observed. In this context, Sr 2 TiCo 1-y O 6-δ is a potential material for optical applications due to its high thermal stability with respect to temperature in air environment. Magnetic studies indicate the presence of mixed exchange magnetic interactions among the cobalt ions with different valence states generated during the synthesis. The weak ferromagnetic exchange interactions involved Co3+-O-Co4+ ions. Heterogeneous magnetic interactions in cubic-STCO with a PL emission in the visible region. [Display omitted] • Non-stoichiometric Sr 2 TiCo 1-y O 6-δ was prepared using solid-state synthesis method. • Presence of weak Raman modes with simple cubic (space group Pm-3m) structure indicative of cation disorders. • Below 150 K VRH conduction mechanism was observed. • Enhanced optical absorption by ns-STCO in the UV region and photoluminescence emission in the visible region with high thermal stability is desired for optical harvesting applications. • Heterogeneous magnetic interactions are observed due to the presence of two oxidation states of cobalt ion. [ABSTRACT FROM AUTHOR]

Titania nanotubes (TNTs) are attractive for a variety of applications. In this study, amorphous TNTs have been synthesized by anodization. Annealing of anodized TNTs has been performed to get the anatase phase. Amorphous and annealed TNTs have been electrochemically reduced using 1 M KOH solution. For characterization of amorphous, annealed, electrochemically reduced amorphous and annealed TNTs, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) techniques were used. The presence of C, F and K is detected from the full scan of X-ray photoelectron spectroscopy (XPS) analysis. The effect of electrochemical reduction on optical properties of TNTs under ambient conditions is studied using photoluminescence (PL) spectroscopy. The electrochemical reduction does not cause any appreciable morphological changes (evident from SEM images). However, XRD results show that this treatment produces strain in the anatase phase as a result of the increase in 'd' spacing between (101) and (202) planes. Photoluminescence spectroscopy of TNTs indicates that the defect states lie in the visible region for all the samples. These defects states have been found at 2.93 eV, 2.67 eV, 2.53 eV and 2.35 eV energies for amorphous TNTs. For annealed TNTs, these states have been observed at 2.67 eV and 2.35 eV. PL signal for amorphous TNTs is higher than the annealed TNTs. The electrochemical reduction treatment of the amorphous TNTs efficiently removes defects like F, K and C in addition to creating oxygen vacancies as compared to annealed TNTs. As these electrochemically reduced amorphous TNTs are exposed to ambient air for 7 days, the oxygen vacancies are filled. Moreover, in addition to removal of oxygen vacancies, these exposed and electrochemically reduced amorphous TNTs are devoid of other defects like F, K and C. This results in the significant reduction in PL intensity for such amorphous TNTs samples 7 days after electrochemical reduction. Due to the oxygen scavenging ability of electrochemically reduced TNTs, they could be used for vacuum improvement in various devices. This type of electrochemical reduction/recovery cycle makes these TNTs useful for the solar cell application under special (reduced/absence of oxygen) conditions. [ABSTRACT FROM AUTHOR]

The spectroscopic techniques of cathodoluminescence (CL) and photoluminescence (PL) are used to study the origin of red emission in β‐Ga2O3 grown using the edge‐defined film‐fed grown (EFG) method and hydride vapor phase epitaxy. Room‐temperature CL shows red emission peaks from samples doped with Fe, Sn, and Si and from unintentionally doped (UID) samples. Narrow emission lines around 690 nm are seen strongly in the Fe and UID samples. Temperature‐dependent PL analysis of the two prominent red emission lines reveals properties similar to the R lines in sapphire for all samples but with different levels of emission intensities. These lines are attributed to Cr3+ ionic transitions rather than Fe3+, as reported previously. The most likely origin of the unintentional Cr incorporation is the source material used in the EFG method. [ABSTRACT FROM AUTHOR]

• Scientific legacy of Pr. Michel Che in the field of oxide anions characterization. • EPR and photoluminescence pioneering works and recent developments. • Basicity concepts and recent developments. Surface reactive oxygen species play a fundamental role in selective oxidation and combustion reactions catalyzed by metal oxides. Unravelling the nature of these transient species, and understanding the details of both their electronic structure and reactivity has been for decades one of the prime research areas of surface and catalytic chemistry. The longstanding activity of Michel Che in this area has been a source of inspiration for generation of researchers, and constitute his outstanding and enduring scientific legacy. Present review provides a survey of the surface oxygen species on oxide materials, which moving on from the Che's pioneering works includes noteworthy results obtained during the years by other researchers. In particular, applications of two powerful techniques such as electron paramagnetic resonance (EPR) and photoluminescence (PL) for detailed characterization of paramagnetic (O−, O 2 −, O 3 −) and diamagnetic surface oxygen varieties (O2− surf), respectively, are addressed here. Classification and insights into the formation pathways of these species on various oxide surfaces, as well as their involvement in model and real gas/solid and liquid/solid reactions of catalytic and photocatalytic relevance is also considered. Finally, the relationship between the thermodynamic and kinetic Bronsted basicity of low coordinated O2− Lc anions is discussed, on the basis of Che's fundamental studies and on recent developments. [ABSTRACT FROM AUTHOR]