Luminescence Spectrometer Research Articles

Inorganic interpretation of luminescent materials encountered by the Perseverance rover on Mars.

A major objective of the Mars 2020 mission is to sample rocks in Jezero crater that may preserve organic matter for later return to Earth. Using an ultraviolet Raman and luminescence spectrometer, the Perseverance rover detected luminescence signals with maximal intensities at 330 to 350 nanometers and 270 to 290 nanometers that were initially reported as consistent with organics. Here, we test the alternative hypothesis that the 330- to 350-nanometer and 270- to 290-nanometer luminescence signals trace Ce3+ in phosphate and silicate defects, respectively. By comparing the distributions of luminescence signals with the rover detections of x-ray fluorescence from P2O5 and Si-bearing materials, we show that, while an organic origin is not excluded, the observed luminescence can be explained by purely inorganic materials. These findings highlight the importance of eventual laboratory analyses to detect and characterize organic compounds in the returned samples.

Development of new calibrating material for luminescence spectrometer from Eu3+ doped aluminum sodium calcium borate glass

The calibration standards are formulated to correct emissions spectra and systematically monitor sensitivity fluctuations in luminescence spectrometers. This study outlines the development of luminescence calibration standards utilizing glass doped with lanthanide ions, specifically focusing on Eu3+ ions chosen for their robust emission properties. Glasses composed of aluminum calcium sodium borate doped with Eu3+ ions were prepared using the melt-quenching technique, with varying compositions of 20Al2O3–20CaO–20Na2O–(40–x)B2O3–xEu2O3 (where x = 0.0, 0.5, 1.0, 3.0, 5.0, and 7.0 mol%). The intense red emission around 615 nm through the 5D0 to 7F2 transition of Eu3+ was detected. To ensure measurement reliability, this study conducted measurements under four different stimulations: ultraviolet–visible light (photoluminescence), X–ray (radioluminescence), proton (protonluminescence), and electron (cathodoluminescence), verifying consistent peak positions. The findings from this study validate the potential of aluminum sodium calcium borate glasses doped with Eu3+, particularly those containing 3.0 mol% of Eu2O3, as effective calibration materials for luminescence spectrometers. This highlights their capability for accurate and consistent calibration, emphasizing their importance in maintaining measurement precision in the luminescence spectrometer.

Optical Properties of Gd2O3 with Silver doped Zinc Borate Glasses

Glasses with chemical composition ZnO-B2O3-Gd2O3-Ag2O were prepared using melt quenching method. The synthesized glass was characterized using X-ray diffraction method. The densities of these glasses were measured using the Archimedes method, and the corresponding molar volumes were calculated using the corresponding formula. Absorption spectra were recorded using a UV-visible spectrometer. The energy bandgap was investigated using the Tauc’s diagram. The variation of band gap energy in relation to Gd2O3 concentration has been discussed. Study the structure and functional groups of the prepared samples were studied using FTIR spectra. Emission and excitation spectra were recorded using a luminescence spectrometer. Photoluminescence spectra provides stable blue light emission in rich in Gd2+ ions glass, Color coordination has also been decided using CIE chromaticity diagram and showing that blue emission was observed in all samples with slightly different positions.

An analytical approach based on excitation-emission fluorescence spectroscopy and chemometrics for the screening of prostate cancer through urine analysis: A proof–of–concept study

In the present feasibility study, excitation-emission fluorescence spectroscopy has been investigated, as a rapid and accurate analytical method for the development of a tentative model for the early screening of prostate cancer directly through urine analysis in order to provide reliable results while improving patient compliance.Sixty-nine urine samples (46 samples from patients with histologically proven prostate cancer and 23 from healthy donors) were provided, by the University of Pisa, Urology Unit. The excitation-emission fluorescence measurements were performed on centrifugated urine samples at room temperature on a Perkin-Elmer LS55B luminescence spectrometer and the corresponding data array was analysed with parallel factor analysis (PARAFAC).From a synergistic analysis of the obtained results, four main fluorophores, corresponding to four selected PARAFAC factors, were recognizable in the urine excitation-emission matrices (EEMs) and the respective species could be potential markers in the differentiation among healthy and cancer samples. PARAFAC results, in terms of extracted scores, coupled with discriminant algorithms, allowed to develop a first attempt of healthy/cancer discrimination model. The chemometrics models show promising correlation between some of the depicted fluorophores and the disease state. However, considering the limited cohort (not only in terms of number but also of representativeness), this study must be considered as a proof of concept; a more sound and statistically relevant sampling must be performed in order to consider the confounding factors in the cohort treated and to develop an analytical approach applicable in real scenarios.

Multicolor and multimode luminescence regulation and anti-counterfeiting application of lanthanide ions doped Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub> phosphors

Multicolor and multimode luminescence materials have important applications in the field of information security encryption. However, the design and synthesis of multicolor multimode luminescent materials is still a challenge, and only several materials have been reported. In this paper, a series of single doped and double doped Li<sub>1–<i>x</i></sub>K<sub><i>x</i></sub>NbO<sub>3</sub>:Pr<sup>3+</sup>/Er<sup>3+</sup>/Tm<sup>3+</sup> phosphors are prepared by high temperature solid state method. The structure, morphology, optical properties and thermoluminescence (TL) spectra are characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), luminescence spectrometer and self-made heating device. Firstly, the effects of different values of K<sup>+</sup> content on the luminescence and trap distribution of LiNbO<sub>3</sub> materials are studied. The results show that the ionic lattice is distorted when a small quantity of K<sup>+</sup> ions replace Li<sup>+</sup>. With the addition of K<sup>+</sup>, the photoluminescence excitation (PLE) spectra monitored emission of 620 nm shows that the ratios of the absorption peaks from matrix (200–310 nm) to absorption peaks from the intrinsic transition of Pr<sup>3+</sup> ions 4f→5d (310–430 nm) change significantly, showing a double-peak characteristic. When the concentration of K<sup>+</sup> ions is 0.5, the absorption peak from the matrix disappears, which may be due to the phase transition of the matrix lattice caused by excessive K<sup>+</sup> ions or the introduction of a large number of defect energy levels into the matrix lattice. Moreover, K<sup>+</sup> ion doping can regulate the density and distribution of traps. TL curves show that a small quantity of K<sup>+</sup> doping increases the trap density of shallow traps. When a large quantity of K<sup>+</sup> is doped, the phase changes of matrix lattice and the defect density decrease. Secondly, the doping of Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub> matrix by different luminescent centers (Pr<sup>3+</sup>/Er<sup>3+</sup>/Tm<sup>3+</sup>) is studied. The results show that the multicolor luminescence emission in red, blue and green bands and the tunable multimode luminescence (up/down conversion luminescence, afterglow luminescence and photo-stimulated luminescence) are realized by the selective excitation. According to the multicolor and multimode characteristics of the phosphors, a butterfly-shaped anti-counterfeiting pattern is designed. Owing to the different energy level positions of the luminescence centers, dynamic multicolor photoluminescence is realized by selective excitation at different wavelengths. Based on the upconversion luminescence characteristics of Er<sup>3+</sup> and the excellent afterglow characteristics of Pr<sup>3+</sup> in Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub> material, the designed anti-counterfeiting pattern shows the dynamic color change and multicolor, multimode high-order anti-counterfeiting application.

Phosphorescence lifetime measurements with sensor materials: Comparison of the four different detection platforms

Using several types of Pt-porphyrin based oxygen sensing materials and conditions, we evaluated comparatively four different detection platforms that perform phosphorescence lifetime (PLT) measurements in the microsecond time domain. The time-resolved fluorescence reader Victor 2, which utilises Rapid Lifetime Determination method and Xe-flash lamp excitation, produced stable but inaccurate readings at PLT values < 15 µs, affected by the flash-lamp afterglow and sensor heterogeneity in oxygenated conditions. The luminescence spectrometer Cary Eclipse, which utilises multi-point phosphorescence decay method, was able to partly correct these interfering factors and produce more accurate PLT values from mono- and bi-exponential fits, however short PLT values were still affected by Xe-flash lamp afterglow. The wide-field Tpx3Cam cam-era-based macroscope and the confocal laser-scanning FLIM/PLIM microscope, which use short-pulse excitation (ns LED or ps diode laser pulses, respectively) and TCSPC method, revealed the presence of short-lived components (1.5–6.0 µs) in sample decays, which have to be considered in PLT calculations. The imaging platforms produced more accurate and in-formative PLT data, but they operate with large volumes of raw and processed data. Overall, for each PLT platform a number of potential sources of error and measurement artefacts have been revealed, which can be minimised by careful optimisation of settings and validation with alternative platforms and sensor materials.

Preparation of carbon quantum dots using bike pollutant soot: Evaluation of structural, optical and moisture sensing properties

Humidity sensor-based carbon quantum dots (CQDs) have been prepared using waste bike pollutant soot. The synthesized CQDs were characterized using a UV–Visible light chamber, UV–Visible spectroscopy , photoluminescence spectroscopy, TEM, and FTIR research. Initially, the sample was exposed in a closed chamber to UV–Visible light, which produced green luminescence. The photo luminescent spectrometer revealed the emission of green spectra as well as the approximate size of the CQDs. TEM and HRTEM confirmed the spherical shaped particles ∼2 nm in size. The FTIR spectra indicated the existence of a functional group. The sensing element was fabricated using the spin coating method on a borosilicate substrate and was used as a humidity sensor. Carbon quantum dots have excellent humidity sensing properties, as evidenced by measurements of sensitivity, ageing effect, repeatability, reaction, and recovery times. Many humidity sensors based on metal oxides, semiconductors, and polymers have been investigated and developed. The novelty of the work, electrical humidity sensor has been proposed using the waste pollutant soot. • The sustainable, cost effective and rapid synthesis of pollutant bike soot carbon quantum dot. • The prepared were imperiled for electrical humidity sensing. • The first, second, third and fourth layers of sensing characteristics are reported. • The beauty of the experiment is that the electrical humidity sensor is proposed to design by using the waste pollutant soot.

Metal Filled Light Emitting Porous Silicon as Platform for Tunable Optical and Magnetic Properties

The electrochemical filling of luminescent microporous silicon (PSi) with magnetic metals (Ni, Co) is presented which results in a composite system with specific magnetic and optical properties. The achieved physical properties are compared with mesoporous silicon loaded with Ni nanoparticles (NPs) of comparable size.The light emitting PSi samples are fabricated by electrochemical etching of a moderately doped p-type silicon wafer in a 10 wt% hydrofluoric acid solution. The achieved porous silicon offers a branched morphology with structure sizes in the range of a few nanometers. The observable visible luminescence is due to quantum confinement effects [1]. The challenging metal filling of these pores is carried out under cathodic conditions by pulsed electrodeposition. As electrolytes aqueous NiSO4 and CoSO4 solutions are employed. Correlated to the branched morphology of the PSi and thus also the deposited nanosized metal structures are interconnected. The structure size of the porous samples is estimated by photoluminescence measurements to 5 nm which also determines the diameter of the deposits.Mesoporous silicon is produced by anodization of a highly n-doped silicon wafer resulting in oriented pores with an average diameter of 50 nm [2]. The loading of these samples with Ni NPs is also carried out by electrodeposition. In contrast to microporous silicon the morphology of mesoporous silicon (mPSi) shows straight pores, grown perpendicular to the sample surface with a diameter up to 50 nm.Magnetic filling of meso- and microporous silicon, respectively means a change in the morphology as well as in the structure size of the magnetic precipitations and both influence the magnetic behavior of the composite system drastically.In the case of light emitting PSi also the luminescence is influenced in its intensity and wavelength by the magnetic filling. With enhanced metal filling a blueshift of the photoluminescence peak is observed.The magnetic properties are investigated with a Vibrating Sample Magnetometer (VSM) and a SQUID, respectively. A luminescence spectrometer is used to measure the intensity and the peak position with respect to the wavelength of the photoluminescence spectrum. The structure is investigated by SEM and TEM.Field dependent magnetization measurements show a distinct difference between metal filled luminescent PSi and mPSi loaded with Ni NPs. Considering luminescent PSi filled with Ni and Co, respectively a strong magnetic anisotropy between the two magnetization directions applying a magnetic field perpendicular and parallel to the surface, is observed, whereas in the case of Co this behavior is even more pronounced. The coercivities do not vary in a broad range between Ni and Co samples, mostly around 10% but the saturation field differs drastically between the two materials. Figure 1 depicts field dependent magnetization curves of luminescent porous silicon filled with Ni and Co, respectively. In contrast mesoporous silicon loaded with Ni NPs offers only a small magnetic anisotropy and also the role of easy axis and hard axis is changed. This different behavior of the two systems can be explained by the differing magnetic interactions between the metal deposits in the two systems. The presented systems which merge optical and magnetic properties within on system are of interest for optoelectronics and magneto optical on-chip devices.[1] Handbook of Porous Silicon, Ed. L. Canham, Springer Int. Publishing (2018).[2] P. Granitzer, K. Rumpf, Front. Phys. 8, 121 (2020). Figure 1

Investigation of the luminescence properties of ZnO clusters induced by single-photon and two-photon excitation

By using a luminescence spectrometer and femtosecond laser, we have investigated the specific optical properties and excitation mechanism of ZnO clusters with one-photon and two-photon excitations. When the excitation wavelength was chosen to be 360 nm, the strongest luminescence intensity was observed. However, the luminescence intensity decreased gradually and the emission peak was red shifted slowly with increasing excitation wavelength (from 360 to 400 nm). When the excitation wavelength was chosen to be 780 nm, the luminescence intensity increased nonlinearly with increasing excitation intensity. What is even more interesting is that ZnO clusters could be used in the imaging of living cells under two-photon excitation, implying the potential applications for the optical properties of ZnO clusters in the field of biophotonics.

Development of modified polymer dot as stimuli-sensitive and 67Ga radio-carrier, for investigation of in vitro drug delivery, in vivo imaging and drug release kinetic

A polymer dot modified histidine-functionalized graphene quantum dot carrier, PD@His.GQD, was synthesized to investigate the in vitro sunitinib (STB) deliveryvia luminescence spectrometer. The carrier’s synthesis, with an average size of 34 nm, was proved by Fourier transform infrared (FTIR), Transmission Electron Microscopy (TEM), and Dynamic Light Scattering (DLS) analyses. In the in vitro, STB delivery investigation showed that for healthy tissue, the STB was loaded at pH = 7.2 and at 25 = 5.4 at 37 °C with a maximum loading efficiency percentage of 99 % while it was released at pH = 5.4 at 37 °C with a release percentage of 97 %. In the sequel, the STB loaded carrier was labeled with Gallium-67 (67Ga-STB.PD@His.GQD) to produce exceedingly transparent radio-carrier for in vivo kidney cancerous mice imaging via the single photon emission computed tomography (SPECT) device. The radiochemical purity of the 67Ga-STB.PD@His.GQD was obtained as 95 % by Radio Thin Layer Chromatography (RTLC) and High-Performance Liquid Chromatography (HPLC) analysis. All obtained results affirmed that the synthesized PD@His.GQD is an STB stimuli-sensitive and selective targeting carrier. All cancerous mice in vivo images at 10 and 20 h of 67Ga-STB.PD@His.GQD post-injection and its bio-distribution calculations showed its most accumulation in the kidney cancerous tissue. Also, the STB release kinetic was studied via Zero-order, First-order, Higuchi, and Korsmeyer-Peppas models, and the release data were fitted with Korsmeyer-Peppas model that expresses the STB release mechanism is controlled by diffusion.

Magnetic Filling of Microporous Silicon: An Interlink of Optical and Magnetic Behavior

In the frame of this work microporous silicon (mPSi) is filled with magnetic metals (Ni, Co) resulting in a composite system with specific magnetic properties. The results are compared with mesoporous silicon (PSi) loaded with Ni nanoparticles (NPs) of comparable size. The mPSi offers luminescence in the visible, whereat this behavior is due to the small structure size in the range of a few nanometers (2 – 5 nm) [1]. The morphology of mesoporous silicon shows straight pores with a diameter up to 50 nm.The mPSi samples are fabricated by anodization of a moderately doped p-type silicon wafer in a 10 wt% hydrofluoric acid solution. The challenging metal filling of these pores is carried out under cathodic conditions by pulsed electrodeposition. As electrolytes aqueous NiSO4 and CoSO4 solutions are employed. The microporous silicon offers a branched morphology and thus also the deposited nanosized metal structures are interconnected. The structure size of the porous samples is estimated by photoluminescence measurements to 5 nm which also determines the size of the deposits. Mesoporous silicon is produced by anodization of a highly n-doped silicon wafer resulting in straight pores of about 50 nm in diameter [2]. The loading of these samples with Ni NPs is also performed by electrodeposition.Magnetic filling of meso- and microporous silicon, respectively means a change in the morphology as well as in the structure size of the magnetic precipitations and both influence the magnetic behavior of the composite system drastically. In the case of mPSi also the luminescence is influenced in its intensity and wavelength by the magnetic filling. The magnetic properties are investigated with a Vibrating Sample Magnetometer (VSM) and a SQUID, respectively. A luminescence spectrometer is used to measure the intensity and the peak position of the photoluminescence spectrum. The structure is investigated by SEM and TEM.Field dependent magnetization measurements show a distinct difference between Ni filled mPSi and PSi loaded with Ni NPs. Considering mPSi filled with Ni and Co a strong magnetic anisotropy between the two magnetization directions applying a magnetic field perpendicular and parallel to the surface, respectively is observed, whereas in the case of Co this behavior is even more pronounced. Figure 1 depicts the hysteresis of mPSi and mesoporous silicon filled with Ni. The coercivities do not vary in a broad range between Ni and Co samples but the saturation field differs drastically between the two materials. In contrast mesoporous silicon loaded with Ni NPs offers only a small magnetic anisotropy caused by weak magnetic interactions between the Ni deposits.Since the microporous silicon offers photoluminescence the huge magnetic anisotropy is of interest for magneto-optical applications.Figure 1: Comparison of field dependent magnetization of mPSi and mesoporous silicon filled with Ni.[1] Handbook of Porous Silicon, Ed. L. Canham, Springer Int. Publishing, 2018.[2] P. Granitzer, K. Rumpf, Semiconductor Science and Technology 31, 4004, 2016. Figure 1

OrganiCam: a lightweight time-resolved laser-induced luminescence imager and Raman spectrometer for planetary organic material characterization.

OrganiCam is a laser-induced luminescence imager and spectrometer designed for standoff organic and biosignature detection on planetary bodies. OrganiCam uses a diffused laser beam (12° cone) to cover a large area at several meters distance and records luminescence on half of its intensified detector. The diffuser can be removed to record Raman and fluorescence spectra from a small spot from 2 m standoff distance. OrganiCam's small size and light weight makes it ideal for surveying organics on planetary surfaces. We have designed and built a brassboard version of the OrganiCam instrument and performed initial tests of the system.

Luminescent emission spectrometer adapted to a TL/OSL reader for analysis of aluminum oxide detectors

Thermoluminescent readings are widely used in radiation dosimetry to measure absorbed doses. The signal emitted by thermoluminescent detectors is due to defects in the crystal structure and their emission usually occurs in some specific wavelength ranges. The difficulty in studying the emission spectrum is that, in general, photomultiplier tubes do not discriminate wavelengths and therefore only provide intensity information. The objective of this work was to adapt a RISØ TL/OSL reader to operate as a luminescence emission spectrometer, allowing to select the wavelength to be analyzed before the acquisition of luminescent readings. A monochromator driven by a stepper motor connected to an Arduino module responsible for controlling wavelength adjustments during readings was used. The equipment added spectral resolution to the conventional reader, allowing the determination of the response surface as a function of temperature, wavelength and light emission intensity for the studied detectors.

Suppression of Eu2+ luminescence and enhancement of Eu3+ emission in Eu: CaF2 single crystal via Gd3+ co-doping

Eu-doped calcium fluoride (CaF2) single crystals co-doped with various concentrations of Gd3+ were grown by the Bridgman-Stockbarge method. A broad excitation band in the ultraviolet (UV) region were observed in the crystal, which is attributed to the existence of Eu2+ ions detected with the help of XPS measurements. The Gd3+ doping was found to have a significant influence on the luminescence properties of the Eu: CaF2, resulting in a suppression of Eu2+ luminescence and enhancement of Eu3+ emission at high Gd3+ co-doping level. The photoluminescence excitation and emission spectra of Eu2+ and Eu3+ ions were measured using luminescence spectrometer. The local site symmetry in the crystals was investigated to explain the influence of Gd3+ on suppression of Eu2+ luminescence and emission of 5D3→7FJ (J = 1, 2, 3) in Eu3+ transition. The fluorescence emissions of the 3%Eu, 6%Eu: CaF2 and 3%Eu, 12%Gd: CaF2 crystals excited at 398 nm relate to the Commission internationale de I’éclairage (CIE) color coordinates of (0.6012, 0.3870) and (0.5930, 0.3953), respectively. A highest quantum yield of 40.53% and 5D0→7F1 transition decay time of 9.54 ms were obtained on the 3%Eu, 6%Gd: CaF2 crystal. This investigation suggests that Eu, Gd: CaF2 has great potentials for optimizing solid state UV–visible converter performances through appropriate concentration tuning of dopants.

Sensitive quantitative image analysis of bisulfite based on near-infrared upconversion luminescence total internal reflection platform

Bisulfite (HSO3−), serves as an important additive in food industry, is one of the most widely distributed environmental pollutants. Herein, a fast and efficient quantitative image analysis method for the determination of HSO3− has been developed. The method builds a luminescence energy transfer (LET) system utilized upconversion nanoparticles (UCNPs) as an energy donor and cyanine dye molecules as an energy acceptor. The upconversion luminescence is quenched a lot on the addition of dye molecules and gets recovered well with the addition of HSO3−. All the phenomena can be recorded via traditional luminescence spectrometer and near-infrared upconversion luminescence total internal reflection platform. The quantitative image analysis performed on the near-infrared upconversion luminescence total internal reflection platform can significantly reduce sample consumption (10 μL) as well as make a quick and efficient analysis (0.1 s) with a large amout of data become easy. Meanwhile, it shows a wider linear range (1–120 μM), lower detection limit (0.070 μM) and higher detection speed than that of the classical luminescence spectrometer.

Auto-Phase-Locked Time-Resolved Luminescence Detection: Principles, Applications, and Prospects.

Time-resolved luminescence measurement is a useful technique which can eliminate the background signals from scattering and short-lived autofluorescence. However, the relative instruments always require pulsed excitation sources and high-speed detectors. Moreover, the excitation and detecting shutter should be precisely synchronized by electronic phase matching circuitry, leading to expensiveness and high-complexity. To make time-resolved luminescence instruments simple and cheap, the automatic synchronization method was developed by using a mechanical chopper acted as both of the pulse generator and detection shutter. Therefore, the excitation and detection can be synchronized and locked automatically as the optical paths fixed. In this paper, we first introduced the time-resolved luminescence measurements and review the progress and current state of this field. Then, we discussed low-cost time-resolved techniques, especially chopper-based time-resolved luminescence detections. After that, we focused on auto-phase-locked method and some of its meaningful applications, such as time-gated luminescence imaging, spectrometer, and luminescence lifetime detection. Finally, we concluded with a brief outlook for auto-phase-locked time-resolved luminescence detection systems.

Magnetic Filling of Microporous Silicon: An Interlink of Optical and Magnetic Behavior

In the frame of this work microporous silicon (mPSi) is filled with magnetic metals (Ni, Co) resulting in a composite system with specific magnetic properties. The results are compared with mesoporous silicon (PSi) loaded with Ni nanoparticles (NPs) of comparable size. The mPSi offers luminescence in the visible, whereat this behavior is due to the small structure size in the range of a few nanometers (2 – 5 nm) [1]. The morphology of mesoporous silicon shows straight pores with a diameter up to 50 nm.The mPSi samples are fabricated by anodization of a moderately doped p-type silicon wafer in a 10 wt% hydrofluoric acid solution. The challenging metal filling of these pores is carried out under cathodic conditions by pulsed electrodeposition. As electrolytes aqueous NiSO4 and CoSO4 solutions are employed. The microporous silicon offers a branched morphology and thus also the deposited nanosized metal structures are interconnected. The structure size of the porous samples is estimated by photoluminescence measurements to 5 nm which also determines the size of the deposits. Mesoporous silicon is produced by anodization of a highly n-doped silicon wafer resulting in straight pores of about 50 nm in diameter [2]. The loading of these samples with Ni NPs is also performed by electrodeposition.Magnetic filling of meso- and microporous silicon, respectively means a change in the morphology as well as in the structure size of the magnetic precipitations and both influence the magnetic behavior of the composite system drastically. In the case of mPSi also the luminescence is influenced in its intensity and wavelength by the magnetic filling. The magnetic properties are investigated with a Vibrating Sample Magnetometer (VSM) and a SQUID, respectively. A luminescence spectrometer is used to measure the intensity and the peak position of the photoluminescence spectrum. The structure is investigated by SEM and TEM.Field dependent magnetization measurements show a distinct difference between Ni filled mPSi and PSi loaded with Ni NPs. Considering mPSi filled with Ni and Co a strong magnetic anisotropy between the two magnetization directions applying a magnetic field perpendicular and parallel to the surface, respectively is observed, whereas in the case of Co this behavior is even more pronounced. Figure 1 depicts the hysteresis of mPSi and mesoporous silicon filled with Ni. The coercivities do not vary in a broad range between Ni and Co samples but the saturation field differs drastically between the two materials. In contrast mesoporous silicon loaded with Ni NPs offers only a small magnetic anisotropy caused by weak magnetic interactions between the Ni deposits.Since the microporous silicon offers photoluminescence the huge magnetic anisotropy is of interest for magneto-optical applications.[1] Handbook of Porous Silicon, Ed. L. Canham, Springer Int. Publishing, 2018.[2] P. Granitzer, K. Rumpf, Semiconductor Science and Technology 31, 4004, 2016. Figure 1

Red shifts, intensity enhancements and abnormally thermal quenching of Ba9Lu2Si6O24:Ce3+ emission by nitridation

Ba9Lu2Si6O24:Ce3+ and nitrided Ba9Lu2Si6O24:Ce3+ phosphors were synthesized by a solid state reaction. To show the influence of introduced N3− on Ba9Lu2Si6O24:Ce3+ phosphors, the crystal structure, phase and luminescent properties of the synthesized phosphors were investigated. And various techniques, such as X-ray diffraction and luminescence spectrometer, were used to investigate the synthesized Ba9Lu2Si6O24:Ce3+ and nitrided Ba9Lu2Si6O24:Ce3+ phosphors. The XRD patterns indicate that the synthesized phosphors have rhombohedral phase. Under the excitation at 400 nm, Ba9Lu2Si6O24:Ce3+ phosphors show the emission bands corresponding to the 5d → 4f transitions of Ce3+ ions. The substitution of N3− to O2− leads to the red shift and intensity enhancement of the Ce3+ emission. More importantly, the substitution of N3− to O2− results in an abnormal intensity increase with the increasing temperature.

Influence of nitridation on optical properties of Sr2MgSi2O7:Eu2+ phosphors

Abstract A series of Sr 2 MgSi 2 O 7 :Eu 2+ and nitrided Sr 2 MgSi 2 O 7 :Eu 2+ phosphors were synthesized by solid state reactions under a reduction atmosphere. The properties of the synthesized phosphors were characterized by X-ray diffractometer (XRD), infrared spectrophotometer (FTIR), UV–visible scan spectrophotometer (DRS) and luminescence spectrometer (excitation and emission). The XRD and FTIR results demonstrate that the synthesized phosphors have the purely tetragonal crystal structure and Eu 2+ /N 3− ions respectively substitute Sr 2+ /O 2− ions in Sr 2 MgSi 2 O 7 hosts. Sr 2 MgSi 2 O 7 :Eu 2+ exhibits blue emission under the excitation at 360 nm, and the emission intensity shows clear dependence on Eu 2+ concentration. The introduction of N 3− induces the changes of emission intensity and the red shifts of Eu 2+ emission band, which are induced by the higher covalency and polarizability for Eu 2+ -N 3- bonds than that of Eu 2+ -O 2- bonds.

Ferroelectric and optical behavior of Pb0.5Ba1.5BiNbO6 double perovskite

Solid solution of (Pb0.5Ba1.5BiNbO6 (PBBN) poly-crystalline sample has been traversed here to study its electrical and optical behavior. For preparation of the compound conventional mixed oxide route method was adopted. To study its structure and stability we have taken care of different experimental support like room temperature X-ray diffraction (XRD), scanning electron micrograph (SEM) image, energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy. From XRD and SEM data it is confirmed that material is single phase and highly dense. The purity of the sample/absence of foreign particle was confirmed from EDS analysis. Both stretching and bending type of vibration are dominated in FTIR data of the studied compound. For electrical and optical properties of the material authors have selected the experimental set up like impedance analyzer, UV–vis and photo luminescence spectrometer. The dielectric measurement data shows compound has large value of dielectric constant (at RT) and relaxor type ferroelectric phase transition. From UV–vis and PL data it is seen material has very good optical properties having optical band gap of ∼2.08 eV which is usually useful for photo catalytic blue LED etc.