Reflectance Spectroscopy Measurements Research Articles

Enhancing hole-transport efficiency in (CH3NH3)2CuClxBr4-x perovskite solar cells through functionalization of multi-walled carbon nanotubes

This study addresses the conductivity limitation of conventional hole-transporting layers (HTLs) like Spiro-OMeTAD in perovskite solar cells. We integrate functionalized multi-walled carbon nanotubes (MWCNTs) into Spiro-OMeTAD and examine the impact of chemical oxidation/functionalization of MWCNTs on their application in perovskite solar cells. Various ratios of H2SO4/HNO3 mixture were employed to functionalize MWCNTs, with FTIR analysis confirming functional group attachments on the nanotube walls. Raman spectroscopy was utilized to analyze defect formation in the MWCNTs, while FESEM images displayed both the tubular structure and morphological alterations resulting from functionalization. XRD analysis was conducted to examine the structural variances resulting from different functionalization ratios. A lead-free copper-based perovskite (CH3NH3)2CuBr4-xClx (x = 0.5), synthesized via a straightforward solution method, served as the active material for solar cells. The XRD assessment of the active material confirmed perovskite formation, with morphological analysis revealing a layered structure. Diffuse Reflectance Spectroscopy (DRS) measurements yielded a bandgap of approximately 1.86 eV for the perovskite. Dark I–V measurements were executed for Spiro-OMeTAD films incorporated with pure and functionalized MWCNTs, showcasing improved conductivity attributed to charge carrier conduction via defect passivation. Hybrid solar cells were fabricated with structures such as TiO2/(CH3NH3)2CuBr4-xClx (x = 0.5)/Spiro-OMeTAD/Ag, and TiO2/(CH3NH3)2CuBr4-xClx (x = 0.5)/functionalized MWCNTs/Spiro-OMeTAD/Ag. These cells demonstrated enhanced stability, retaining over 65 % of their initial efficiency after 10 days of storage, attributed to improved moisture permeability inferred from contact angle measurements and XRD analysis. Photovoltaic characterization revealed significant improvements in fill factor (∼70 %), short-circuit current density (2.94 mA), open-circuit voltage (0.70 V), and power conversion efficiency (PCE) (1.6 %) for the FTO/TiO2/(CH3NH3)2CuCl0·5Br3.5/Spiro-MWCNT-1/Ag device.

Nanocasting synthesis of mesoporous CeO2 particle abrasives from mesoporous SiO2 hard templates for enhanced chemical mechanical polishing performance

Mesoporous abrasive particles exhibit superior chemical mechanical polishing/planarization (CMP) performance, as compared with the corresponding bulk materials. Nevertheless, the lack of control over the shape and particle size or distribution extremely restricts the development of mesoporous abrasives and their potential applications. To overwhelm these drawbacks, pure and ytterbium-doped mesoporous ceria (mCeO2 and mCeYbO2) spheres with well-defined morphology and good uniformity were synthesized via a straightforward nanocasting strategy using high-quality mesoporous silica spheres as hard templates and metal nitrates as precursors. The resulting samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, Zeta potential, and N2 adsorption-desorption measurements. The as-prepared mCeO2 and mCeYbO2 products exhibited enriched surface defects (trivalent Ce, vacancy oxygen, hydroxyls) and polycrystalline porous frameworks with a surface area of up to 160 m2/g and pore size of 4–7 nm. Benefiting from these synergistic attributes, the flexible and defective particle abrasives enabled significant improvements in both surface quality and removal efficiency during oxide-CMP, as compared to commercial CeO2. A possible CMP mechanism was proposed on the basis of the physical contact state, adsorption and adhesion behavior, as well as tribochemical interaction occurred at CeO2–SiO2 interfaces. This work demonstrates highly promising abrasive materials advancement combining architecture and defect engineering towards high-performance oxide-CMP.

Synthesis, characterization and application of CNTs@Co-MOF and FCNTs@Co-MOF as superior supercapacitor: Experimental and theoretical studies

Supercapacitor offers high power density and quick charge/discharge speed. Herein, a cobalt-metal organic framework (Co-MOF) is synthesized, and the chemical structure is investigated via XRD, FTIR, XPs, and SEM-EDX. Photoluminescence and diffuse reflectance spectroscopy measurements determine the optical properties and band gap. The band gap of Co-MOF is calculated and found to be 1.94 eV, indicating its capability to be applied as a supercapacitor. Carbon nanotubes (CNTs) and functionalized carbon nanotubes (FCNTs) are mixed with Co-MOF to form CNTs@Co-MOFs and FCNTs@Co-MOFs, respectively. The performance of these MOFs as supercapacitors is evaluated using electrochemical measurements. According to the analysis of the super capacitance of the synthesized compounds, FCNTs@Co-MOF shows the highest specific supercapacitance of 454 F g−1, whereas Co-MOF and CNTs@Co-MOF have 263 F g−1 and 338 F g−1, respectively. Besides, the semi-empirical quantum method is used to assess the relationship between the electronic and the experimental data. Experimental and theoretical results recommended the usage of the investigated MOFs as superior supercapacitors.

Solution-Free Melt-Grown CsGeI3 Polycrystals for Lead-Free Perovskite Photovoltaics: Synthesis, Characterization, and Theoretical Insights

Inorganic lead-free metal halide perovskites are being rigorously explored as a substitute for organic lead-based materials for various energy device applications. Germanium as a replacement for lead has been proven to give exemplary results theoretically, and there have been promising results. The current work presents the investigation of CsGeI3 (CGI) polycrystals grown using a solution-free melt-growth technique with low-cost precursors. A soak-ramp profile was designed to synthesize polycrystalline powders, which were evaluated for stability. X-ray diffraction and Raman spectroscopy analysis suggest the formation of CsGeI3 perovskite powders, matching the reported literature. Diffuse reflectance spectroscopy measurements showed the bandgap of the polycrystals to be around 1.6 eV. A prominent photoluminescence peak was obtained at 767 nm. The powders were examined using thermogravimetric analysis to assess the thermal degradation pathways. The as-grown inorganic perovskite polycrystals were relatively stable during storage under ambient conditions. Theoretical studies were also carried out to support the experimental data. Calculations were performed with different approximations, including local density approximation (LDA), generalized gradient approximation (GGA), and Heyd–Scuseria–Ernzerhof (HSE) approximation, out of which the HSE approximation yielded the most accurate results that matched the experimental findings. Moreover, for the CGI device with Ag electrodes simulated using SCAPS-1D software, highest incident photon-to-electron conversion efficiency was observed. The obtained optical and structural properties indicate the suitability of the synthesized CsGeI3 perovskite polycrystals for photovoltaic applications, specifically solar cells and light-emitting diodes.

Superconductivity in TiZrNb and TiZrNbHf bulk equimolar alloys

We have prepared and investigated superconducting equimolar medium-entropy alloys of TiZrNb and TiZrNbHf. Their basic superconducting parameters, as the values of the critical temperature Tc, upper critical magnetic field Bc2 and the superconducting energy gap Δ have been studied with the use of magnetic susceptibility and point-contact Andreev reflection (PCAR) spectroscopy measurements. Although our samples have different critical temperatures, namely Tc ∼ 8.2 K for TiZrNb and Tc ∼ 6.3 K for TiZrNbHf, their zero-temperature critical magnetic field has the same value Bc2(0) = 12 T, from the vicinity of the Clogston limit. We have observed the presence of degraded phases on the surfaces of all the investigated samples using PCAR measurements. Still, we were able to show that the bulk phase in both systems exhibits BCS weakly coupled superconductivity with 2Δ(0)/kBTc ∼ 3.5.

Exploring the Structural, Optical and Photoluminescence Performances of CuCo2O4 and ZnMn2O4 Alloying

The performance of the structural, linear/ nonlinear optical and photoluminescent properties of CuCo2O4 and ZnMn2O4 alloying was investigated. (1−x)CuCo2O4/(x)ZnMn2O4 (x = 0, 0.10, 0.15, 0.2) samples were prepared by the sol-gel and hydrothermal procedures. Synchrotron X-ray diffraction measurements were employed to investigate the structural and microstructural properties applying the Rietveld refinement method. Fourier transform infraed and Raman techniques were applied to explore the structures’ variation and chemical bonding of the obtained phases. Ultraviolet–visible diffuse reflectance spectroscopy measurements were collected to explore the optical properties. The optical band gap values were determined using the Kubelka-Munk method. All samples exhibited two band gaps in the visible-NIR regions. Upon composing with ZnMn2O4, the band gaps of CuCo2O4 declined for x = 0.1 and 0.15, followed by an increase at x = 0.2. The possible electronic band structure of the samples and the photoluminescent performance of the prepared samples was investigated. The observed PL patterns manifest wide and asymmetrical emissions. The CIE chromaticity diagram for all samples was plotted. The obtained findings of (1−x)CuCo2O4/(x)ZnMn2O4 nominate their efficient role in optical device fabrication and photocatalyst applications.

Efficient Photocatalytic Activation of Peroxymonosulfate by Cobalt-Doped Oxygen-Vacancies-Rich BiVO4 for Rapid Tetracycline Degradation.

In this work, cobalt-doped oxygen-vacancies-rich BiVO4 (Co/BiVO4-Vo) was successfully synthesized for the degradation of tetracycline (TC) by activated peroxymonosulfate (PMS) under visible light. The morphologies, microstructures, and optical properties of the photocatalysts were analyzed in detail. Co/BiVO4-Vo exhibited significantly enhanced degradation, removing 92.3% of TC within 10 min, which was greater than those of pure BiVO4 (62.2%) and oxygen-vacancies-rich BiVO4 (BiVO4-Vo) (72.0%), respectively. The photogenerated charge separation and transport properties were explored through surface photovoltage (SPV), photoluminescence spectrum (PL), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) measurements. Additionally, an in-depth investigation was conducted on the photocatalytically assisted advanced oxidation processes based on SO4•- (SR-AOPs) for the degradation of organic pollutants. The experimental results showed that the introduction of oxygen vacancies and Co doping achieved an effective separation of photogenerated carriers, which could accelerate the cycling between Co3+ and Co2+ and further activate PMS. The results of free radical capture experiments and electron spin resonance (ESR) experiments showed that reactive oxygen species (ROSs) such as 1O2, •O2-, and SO4•- played a dominant role in the removal of pollutants. This work provides a novel insight into the further development of efficient and rapid PMS photoactivators for environmental remediation of water bodies.

Judd-Ofelt analysis of Sm3+ doped Ca2LiMg2V3O12 phosphors: Unveiling luminescent and thermometric properties for multifunctional applications

This study investigated the luminescent and thermometric properties of pure and Sm³⁺-doped Ca₂LiMg₂V₃O₁₂ (CLMV) garnet-type vanadates synthesized by the solid-state reaction method. The synthesized materials, with varying Sm³⁺ concentrations (0.01–0.09 mol%), were comprehensively characterized using powder X-ray diffraction (PXRD) analysis to confirm their phase purity. Diffuse reflectance spectroscopy (DRS) measurements were employed to determine the band gap energy of both pure CLMV and CLMV:0.07Sm³⁺ samples. Photoluminescence (PL) excitation and emission spectra were recorded for the pure and Sm³⁺-doped CLMV phosphors using an excitation wavelength of 345 nm and monitoring the emission at 618 nm. These spectra revealed detailed information about the energy levels involved in light emission processes. An efficient energy transfer from the (VO₄)³⁻ groups to the Sm³⁺ ions was observed, exceeding 48%. This energy transfer process is crucial for achieving high-intensity luminescence in Sm³⁺-doped materials. Judd–Ofelt (J-O) theory was applied from the emission spectra and calculate the Judd–Ofelt intensity parameters, which govern the radiative properties of the Sm³⁺ ions. Based on the J-O analysis, the branching ratio (β) was estimated to be greater than 75%. This value, exceeding the threshold of 50% for display devices, signifies the suitability of the phosphor for solid-state lighting applications due to its efficient light emission. The thermal quenching behavior of both the Sm³⁺ ions and the (VO₄)³⁻ groups was further investigated to explore the optical thermometric characteristics of the Sm³⁺-doped CLMV phosphors. Notably, a maximum absolute sensitivity (Sa) of 0.35 K⁻1 and a relative sensitivity (Sr) of 2.55% K⁻1 were achieved, demonstrating the materials potential for non-contact optical temperature sensing applications. Lifetime decay analysis revealed double exponential decay behavior, indicating the presence of multiple luminescence centers within the phosphor. The average lifetime in the millisecond range further supports the suitability of these materials for practical applications. Finally, the CIE color coordinates, correlated color temperature (CCT), and color rendering index (CRI) values were also reported, providing insights into the colorimetric properties of the Sm³⁺-doped CLMV phosphors. These aspects are crucial for optimizing the materials for solid-state lighting applications.

TiO2 multi-leg nanotubes for surface-enhanced Raman scattering

Abstract In the recent past, significant research efforts have been put forth to fabricate cost-effective substrates for surface-enhanced Raman scattering (SERS) applications. Here we propose semiconducting TiO2 multi-leg nanotubes and Au nanoparticle-coated TiO2 multi-leg nanotubes (TiO2 MLNTs and Au/TiO2 MLNTs) as SERS substrates. The unique multi-leg architecture of TiO2 nanotubes demonstrated enhanced light-harvesting properties facilitated by an induced photonic absorption edge. Remarkable high SERS sensitivity is observed towards the detection of Methylene blue (MB), up to nM concentration (E.F. ∼104) using TiO2 MLNTs. The same is attributed to the resonantly matched photonic absorption edge of TiO2 MLNTs with the wavelength of incident laser probe light. On the other hand, the Au nanoparticle coating further leveraged the light absorption ability of TiO2 MLNTs with the aid of localized surface plasmon resonance mode. As such, Au/TiO2 MLNTs showed excellent enhancement in SERS sensitivity (E.F. ∼105 , for nM of MB) facilitated by the synergy between the plasmonic modes of Au and the photonic absorption mode of TiO2 MLNTs. UV-Vis diffuse reflectance and Raman spectroscopy measurements are highlighted to elucidate the light absorption and SERS sensitivity of the TiO2 and Au/TiO2 MLNTs.

High carrier mobility along the [111] orientation in Cu2O photoelectrodes

Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight1,2. Following a decade of advancement, Cu2O photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials3–5. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance6. Here we demonstrate performance of Cu2O photocathodes beyond the state-of-the-art by exploiting a new conceptual understanding of carrier recombination and transport in single-crystal Cu2O thin films. Using ambient liquid-phase epitaxy, we present a new method to grow single-crystal Cu2O samples with three crystal orientations. Broadband femtosecond transient reflection spectroscopy measurements were used to quantify anisotropic optoelectronic properties, through which the carrier mobility along the [111] direction was found to be an order of magnitude higher than those along other orientations. Driven by these findings, we developed a polycrystalline Cu2O photocathode with an extraordinarily pure (111) orientation and (111) terminating facets using a simple and low-cost method, which delivers 7 mA cm−2 current density (more than 70% improvement compared to that of state-of-the-art electrodeposited devices) at 0.5 V versus a reversible hydrogen electrode under air mass 1.5 G illumination, and stable operation over at least 120 h.

Investigation of the luminescence properties and temperature dependent luminescence properties of Sm3+ doped NaPbBi2(PO4)3 orthophosphate phosphor: A promising candidate for light and light sensing applications

The red phosphor for light application is in high demand. In this regard, a series of orange-red phosphors, NaPbBi2(PO4)3: Sm3+, with a single phase were obtained by the conventional solid state reaction method. The X-ray diffraction (XRD) confirms that the phosphor belongs to the cubic structure with a space group I-43d (220). The optical property of the phosphor was studied through the diffuse reflectance spectroscopy measurements and the characteristic peaks of the Sm3+ ions were identified. Exciting the phosphors at 404 nm, produced a strong orange-red emission at 601 nm. The optimum concentration of the phosphor was found to be 0.03 mol. In all emission transitions of the Sm3+ ions within the host lattice, the energy transfer (ET) occurs among the nearest neighbour ions. The lifetime values were in the order of milliseconds. The photometric parameters revealed that the emission lies in the orange-red region with color coordinates (0.5863, 0.4129) and a color purity of 99.4 %. The temperature dependent luminescence properties of the phosphor were also investigated and all these results showed that the phosphor could serve as a good candidate for light/light sensing applications.

The Dagulf Psalter (Austrian National Library Cod. 1861): A Multi-Analytical Approach to Study Inks, Dyes, and Pigments of this Early Carolingian Manuscript

Abstract The Dagulf Psalter is a precious Carolingian manuscript on calf parchment, dated to 793–795. Its unique and high historical value required a non-invasive, multi-analytical approach to gain insights into the material composition of gold and silver inks, pigments, and dyes used for writing and illuminations. Elemental mapping based on X-ray fluorescence analysis (XRF), Fibre Optics Reflectance Spectroscopy (FORS) measurements, and hyperspectral imaging (HSI) gave complementary information on colour media and their brilliant shades. Knowledge of the material composition of inks, dyes, and pigments is of crucial importance not only for art historical research, but also for the preservation of the manuscript, as it is known that among other factors, silver inks and some pigments can lead to deterioration of parchment supports. The purple dye orchil and blue indigo were used for painted backgrounds on the initial folios. Lapis lazuli was found in decorative frames on these folios. Orchil, indigo, and lapis lazuli also appear in decorations of small initials throughout the manuscript. Red lead, ochre, cinnabar, orpiment, and lead white were also found in various painted details. Gold and silver inks of high purity were identified. The proof of chlorine in the silver ink indicates the presence of corrosion products.

Intensification of organic pollutant degradation under visible light irradiation using ZnO nanostructured photocatalysts doped with praseodymium

Zinc oxide nanostructures doped with praseodymium (ZnO:Pr) at varying Pr content (0.05 % to 1.0 % w/w) were synthesized using the electrospinning-calcination technique. Comprehensive morphological and structural characterizations were conducted through SEM, XRD, and XPS analyses. In addition, diffuse reflectance and photoluminescence spectroscopy measurements were performed to assess the optical properties of materials. The produced photocatalysts (ZnO:Pr) were then employed for the degradation of methylene blue dye and oxytetracycline under visible-light irradiation. ZnO:Pr(0.1 %) demonstrated the best photocatalytic performance against methylene blue showing a pseudo-first-order rate constant of k = 3.630 × 10-2 min−1. Investigation of oxytetracycline photodegradation with ZnO:Pr(0.1 %) revealed a pseudo-second-order rate constant of ks = 1.165 × 10-1 L mg−1 min−1, resulting in a reaction half-life (τ½) of approximately 1 min under optimal conditions. Total organic carbon and mass spectrometry analyses highlighted mineralization and identified the main reaction intermediates, respectively, for the oxytetracycline photodegradation. The photodegradation mechanism of oxytetracycline was proposed by the photocatalytic degradation measurements in the presence of scavengers such as hydroquinone and isopropanol. These nanostructures exhibited robust photocatalytic activity over multiple cycles, demonstrating excellent stability. This study underlines the promising potential of ZnO:Pr(0.1 %) as an efficient photocatalyst able to intensify the photodegradation of organic pollutants.

Can diffuse reflectance spectroscopy identify shuntodynia in pediatric hydrocephalus patients?

Shuntodynia is patient reported pain at the site of the implanted ventriculoperitoneal (VP) shunt. Pediatric hydrocephalus requiring shunt placement is a chronic and prevalent standard of care treatment and requires lifetime management. Shuntodynia is a subjective measure of shunt dysfunction. Quantitative, white-light tissue spectroscopy could be used to objectively identify this condition in the clinic. Pediatric subjects were recruited for optical sensing during routine clinical follow-up visits, post-VP shunt implantations. Acquired optical signals were translated into skin-hemodynamic signatures and were compared between subjects that reported shuntodynia versus those that did not. Diffuse reflectance spectroscopy (DRS) measurements were collected between 450 and 700nm using a single-channel fiber-optical probe from () patients. Multiple reflectance spectra were obtained by the attending physician from regions both proximal and distal to the VP shunt sites and from a matched contralateral site for each subject. Acquired reflectance spectra were processed quantitatively into functional tissue optical endpoints. A two-way, repeated measures analysis of variance was used to assess whether and which of the optical variables were statistically separable, across subjects with shuntodynia versus those without. Analyses indicated that intrapatient differences in vascular oxygen saturation measured between shunt sites relative to that obtained at the scar or contralateral sites was significantly lower in the pain group. We also find that the total hemoglobin concentrations at the shunt site were lowest relative to the other sites for subjects reporting pain. These findings suggest that shuntodynia pain arises in the scalp tissue around the implanted shunts and may be caused due to hypoxia and inflammation. Optically derived hemodynamic variables were statistically significantly different in subjects presenting with shuntodynia relative to those without. DRS could provide a viable mode in routine bedside monitoring of subjects with VP shunts for clinical management and assessment of shuntodynia.

Refractive index measurement of pharmaceutical powders in the short-wave infrared range using index matching assisted with phase imaging

Refractive index is a fundamental optical property of powder that is used as an important input in light scattering measurements of the size distribution and diffuse reflectance spectroscopy measurements of the absorption and scattering coefficients. In this work, we demonstrate a method that combines index matching with phase imaging to determine the refractive index of complex powder particles at high accuracy without relying on any assumptions. Index matching is robust, but the accuracy is not high by relying on ocular observation of the interface. Phase imaging using interferometry improves the accuracy of determining the match by an order of magnitude. Using the proposed method, we determine the refractive index of four types of pharmaceutical powder in the short-wave infrared range of 1100–1650 nm.

The evaluation of microbubble concentration using the techniques of optical spectroscopy

We present an accurate and low-cost method for the evaluation of concentration of ultrasound contrast agents, microbubbles (MBs) by utilizing light-scattering properties of MBs. Illuminated by near-infrared light, MBs act as Mie scattering particles. We used absorption spectroscopy to detect the optical density immediately after the preparation of Sonovue MBs, and after MB insonification for total of 187 MB samples. Strong linear correlation (r = 0.97) was determined between optical density of MB suspension, evaluated at 790 nm, and MB concentration in vitro (measured by hematocytometer, up to 3.3 × 107 MBs/ml).Optical density of MB suspension was assessed by simultaneously performing diffuse reflectance spectroscopy and absorption spectroscopy measurements in vitro. Further we aimed to assess MB optical density in tibialis cranialis muscles of C57Bl/CBA mice. The results of diagnostic B-scan imaging and diffuse reflectance spectroscopy shows that optical techniques are excellent for monitoring the changes in MB concentration both in vitro and in vivo.

A-Si/SiO2 nanolaminates for tuning the complex refractive index and band gap in optical interference coatings.

A-S i/S i O 2 nanolaminates are deposited by magnetron sputtering and show a decreasing absorption when the a-Si single-layer thickness is reduced from 2.4n m to 0.7n m. Moreover, an increase of the Tauc band gap by 0.18e V is measured. Experimental Tauc band gaps are compared to calculated effective band gaps, utilizing a numerical Schrödinger solver. Further, it is demonstrated that the refractive index can be controlled by adjusting the a-Si and S i O 2 single-layer thicknesses in the nanolaminates. The nanolaminates are optically characterized by spectroscopic ellipsometry, transmittance, and reflectance measurements. Additionally, TEM images reveal uniform, well-separated layers, and EDX measurements show the silicon and oxygen distribution in the nanolaminates.

Synthesis and Structural Features of Tunable Emitting Single- Phased Eu3+/ Tb3+ Co- Doped LaAlO3 Nanophosphors

In the prevailing study, single- phased color- tunable La1-x-yEuxTbyAlO3 co- doped nanocrystalline phosphors have been synthesized via the most simplistic and low cost urea- aided solution combustion synthetic route. This was done by adjusting the doping concentration of Eu3+ (x = 0.01, 0.03, 0.05, 0.07 mol) and Tb3+ (y = 0.03 mol) ions in the LaAlO3 host lattice. The X- ray powder diffraction (XRD) and Rietveld refinement analysis confirmed the formation of single- phased La0.97-xAlO3: xEu3+/ 0.03Tb3+ (x = 0.07), co- doped nanophosphor at 800°C. The synthesized nanophosphors were crystallized in cubic crystal system having Pm3̄m space group with 221 space group number. The morphological studies i.e., field emission scanning electron microscopy (FE- SEM), and transmission electron microscope (TEM) images depicted the agglomerated clusters of distinct spherical shaped particles of La0.97-xAlO3: xEu3+/ 0.03Tb3+ in nano- regime. Energy dispersive X- ray analysis (EDAX) was employed to ascertain the real elemental mapping of the fabricated phosphors. Through diffuse reflectance (DR) spectroscopy measurements, the optical band gap value for La0.92Eu0.05Tb0.03AlO3 nanocrystalline phosphor was determined to be 5.26 eV. The photoluminescent excitation (PLE) and photoluminescent emission (PL) spectra were studied in detail as a function of Eu3+ ion contents and La1-x-0.03AlO3: xEu3+/ 0.03Tb3+ (x = 0.05 mol) co- doped sample exhibits strongest emission and over the 0.05 Eu3+ ions doping concentration, the emission intensity falls as a consequence of the quenching phenomenon. The concentration quenching in directed co- doped nanophosphors was attributed to the dipole - dipole interactions. With the exploitation of photoluminescent data, Commission International de I'Eclairage 1931 (CIE) color coordinates (x, y) of co- doped samples have been calculated from the emission spectra, which revealed the color could be tuned i.e., from orange to red region in La0.97-xAlO3: xEu3+/ 0.03Tb3+ samples with divergences in the Eu3+ and other significant photometric assets viz. correlated color temperature (CCT), color purity (CP) of the synthesized La1-x-yAlO3: xEu3+, yTb3+ co- doped nanocrystalline photoluminescent materials were also determined. The studies outcomes suggested that Eu3+/ Tb3+ co- doped LaAlO3 phosphors have great potential as color- tunable luminescent material in solid- state lighting and display technologies.

Insights into the dielectric function of plant leaves under water stress.

In this work, we present a practical approach combining experimental and theoretical analyses to assess water evaporation in Arabica coffee leaves. We examine continuously the changing water content of leaves through optical reflectance spectroscopy and mass loss measurements, beginning from a fully saturated stage and extending beyond the turgor loss point. We establish a relationship between the current water content and the dielectric function, based on the changing of the molecular water dipoles inside the leaf due to evaporation.

Unveiling the effect of Gd3+ doping on enriching the structural, magnetic, optical, and dielectric properties of biocompatible hematite nanoparticles

This work is an attempt to obtain gadolinium-doped hematite GdxFe2−xO3 (x = 0, 0.05, and 0.1) using the hydrothermal method followed by heat treatment. The work also studies the impact of gadolinium doping on the magnetic, electrical, and optical properties of hematite. X-ray diffraction (XRD) analysis, energy-dispersive X-ray spectroscopy (EDAX) and photoelectron spectroscopy (XPS) showed that the obtained phase for all samples was pure hematite with no evidence of secondary phases, indicating a high solubility limit of gadolinium ions in hematite lattice. The morphology and size distribution of the particles were investigated using high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). It was found that the lattice parameters increased with increasing gadolinium concentration. Magnetization was not enhanced whereas, the coercivity decreased considerably. From UV–Vis diffuse reflection spectroscopy (DRS) measurements, the band gap energies of pure and doped α-Fe2O3 decreased from 2.01 to 1.94 eV respectively. Moreover, measurements of electrical properties showed that the dielectric permittivity decreased while the resistivity increased with increasing the gadolinium content. In addition, sulforhodamine B (SRB) test against oral epithelial cell lines showed low cytotoxicity of the particles. Finally, gadolinium doped hematite is introduced as a novel, environmentally benign material for potential applications in various fields including photocatalysis for water treatment, biosensor and as an antibacterial agent.