Nm For Excitation Research Articles

Optical and sign-flipping nonlinear optical properties of NiO/PMMA/PANI nanocomposite films

In this study, we introduce an efficient nanocomposite system to enhance optical properties of Nickel oxide (NiO) integrated with two polymers matrix. NiO nanoparticles is prepared using chemical co-precipitation method and its nanocomposite films (NCFs) were prepared with poly methyl methacrylate (PMMA) and polyaniline (PANI) using drop-casting method on glass substrate and was optimized by changing the concentration of NiO. The prepared NCFs were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), ultraviolet (UV)-visible absorption spectroscopy, photoluminescence (PL) spectroscopy and X-ray photoelectron (XPS) spectroscopy. The open-aperture z-scan method is employed for nonlinear optical investigations, utilizing a nanosecond pulsed laser with a wavelength of 532 nm for excitation. The findings indicate that the NCFs exhibit sign-flipping nonlinear behavior, indicating a transition from saturable absorption to reverse saturable absorption. This suggests that our NCFs exhibit optical limiting properties and potential for applications in photonic devices, such as optical switches and laser protection systems.

(Invited) Optical Probes for Resonance-Enhanced Gold Growth on Nanooptical Substrates

We investigate light-stimulated growth of gold metal lines to technically mimic the growth of long-range axonal connections for neuromorphic computing architectures. Photocatalytic gold growth from an aqueous gold chloride precursor solution (HAuCl4) on a photoactive titanium dioxide layer is used. It is known that local gold growth may be obtained by UV illumination through a shadow mask [1]. To obtain a wavelength and angle dependent growth of metal lines – and thus stimulus-dependent resistances – we suggest to employ a nanooptical template. Inspired by the typical number of 2 to 10 connections to a node found, e.g., in the neuronal system of the biological species Hydra, we decided on the implementation of a hexagonal design. The edges are formed by periodic grating nanostructures with 10 to 20 periods and a grating pitch of 170 nm to 210 nm for excitation in the UV. In order to investigate the resonant optical enhancement, we employ optical probes. It is well known that colloidal quantum dots show enhanced fluorescence emission on photonic crystal surfaces due to resonant excitation and resonant outcoupling [2]. In our initial experiments for investigation of the resonant enhancement, we use 4,4’-Bis(2,2-diphenylvinyl)-1,1’-biphenyl (DBVBi) as the emitter material. Its absorption maximum matches the excitation laser at 355 nm and fluorescence in the visible spectrum around 455 nm may be monitored with our camera and spectrometer setup.The nanostructure master was fabricated by electron-beam lithography (Kelvin Nanotechnology Ltd.) according to our design. We transfer the nanostructure pattern onto 1.1 mm thick soda-lime glass substrates by UV-nanoimprint lithography. Subsequently, a 100 nm titanium dioxide layer is deposited. The 150 nm emissive DBVBi layer is then added by thermal evaporation. The samples are characterized optically with a camera setup and magnifying optics on an in-plane rotatable xy-stage. We use a Cobolt Zouk 355 nm 10 mW laser to excite the emissive layer. The output power of the laser is set to 2 mW and its output beam is widened with a collimating lens setup to a diameter of approximately 1.5 mm². The widened beam is essential to obtain a homogeneous excitation. We observe the successful resonant excitation by the higher emission intensity of DPVBi in specific regions of the nanostructure at specific excitation angles. Already for 10 periods of the grating structure resonance effects are observed. A stronger enhancement is obtained for 20 periods. Further, the enhancement depends on the grating pitch as connections with nanograting pitches below 190 nm are no longer visible. They do not meet the criteria for resonant excitation.This method of using optical probes on the nanooptical template works well for initial characterization of the resonance enhancement at different excitation angles. Now the setup is ready for performing gold growth under different excitation conditions. Without the additional emissive layer, the waveguide thickness change needs to be compensated with an increased titanium dioxide layer thickness. For online monitoring of the resonant enhancement during growth optical probes may be employed below the photoactive titanium dioxide layer. It is expected that the resonance enhancement is reduced with the addition of gold due to the increased absorption and thus reduced quality factor as was previously studied in the context of nanostructured OLEDs [3].We acknowledge funding by the DFG (German Research Foundation) with the CRC 1461- Neurotronics (Project-ID 434434223 – SFB 1461).[1] S. Veziroglu et al. (2018). Photocatalytic growth of hierarchical au needle clusters on highly active TiO2 thin film. Advanced Materials Interfaces, 5(15), 1800465.[2] N. Ganesh et al. (2007). Enhanced fluorescence emission from quantum dots on a photonic crystal surface. Nature nanotechnology, 2(8), 515-520.[3] J. Buhl et al. (2023). Resonance‐Based Directional Light Emission from Organic Light‐Emitting Diodes: Comparing Integrated Nanopatterns and Color Conversion Waveguide Gratings. Advanced Photonics Research, 4(2), 2200143. Figure 1. (Left) Fluorescence image of optical probe layer on nanooptical substrate for 355 nm laser excitation. (Middle) Schematic of nanooptical substrate with grating pitch (in nm) and number of periods given. Same colors represent identical grating features. (Right) Field emission scanning electron microscopy (FESEM) image of one node with 6 connections. Figure 1

Dual benefits of NBD-Cl fluorogenic action and sample pretreatment (SALLE) technology in the assessment of anticoagulant medication: Dabigatran in pharmaceutical capsules and plasma samples.

Dabigatran (DBG), marketed as Pradaxa, is an anticoagulant medication prescribed for the treatment and mitigation of blood clots and to lower the risk of stroke in individuals with the heart condition known as atrial fibrillation. This medication is specifically indicated for preventing blood clots post hip or knee replacement surgeries and in patients with a prior history of clots. Compared to warfarin, dabigatran serves as a viable alternative that does not necessitate routine blood monitoring tests. The complimentary benefits associated with SALL (salting-out assisted liquid-liquid extraction) and the fluorogenic capabilities of benzofurazan. These methods were combined to provide an affordable and sensitive DBG assaying method. The spectral strength of the yellow luminous product was examined at 533.8nm and by adjustment of a wavelength of 474.7nm for excitation. To assess its linearity, the calibration chart was tested across a DBG concentration range of 30-500 ng/ml. Via accurate computation based on ICH, the detection limit (LD) was determined to be 9.5ng/ml, and the strategy can quantify the DBG to a limit of 28 ng/ml. To ensure success, various crucial parameters for method implementation have been extensively studied and adapted. The validation of the strategy adhered to the policies outlined by ICH, affirming its precision in quantifying DBG in capsules. Furthermore, the inclusion of SALLE steps facilitated accurate monitoring of DBG in plasma samples, introducing a unique and advanced methodology for analyzing this compound in biological samples.

La:ZnO nanoparticles: an investigation on structural, optical, and microwave properties

This paper presents the utilization of ethylene glycol monomethyl ether (EGME) during the synthesis of ZnO and La:ZnO with two tasks as a solvent and a fuel source within the gel combustion technique. The use of EGME for this purpose provides one-step production of the nanoparticles (NPs) and saves a considerable amount of time. The detailed characterization of the nanoparticles was carried out by X-ray diffractometer (XRD), scanning electron microscope (SEM), particle size analyzer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Vector Network Analyzer (VNA) measurements, respectively. The NPs exhibited a hexagonal wurtzite structure with good crystallinity and a porous spongy morphology. The photoluminescence emission maxima of the synthesized NPs appeared at 500, 560, and 676 nm, upon excitation by the 372 nm of excitation. La:ZnO NPs showed significantly better photoluminescent characteristics than La-free ZnO forms. When excited at the same wavelength, La-free ZnO, 3%, and 7% La:ZnO exhibited 92, 45, and 35 μs average decay times, respectively. Finally, the microwave properties of the relative complex permittivity and permeability characteristics were also investigated and discussed in detail, which were derived from the scattering parameters of S11 and S21 in the X band regime.

Development of Two Green and High-Throughput Microwell Spectrometric Platforms for Determination of Reboxetine, the First FDA-Approved Selective Noradrenaline Reuptake Inhibitor Antidepressant Drug.

Reboxetine (RBX) is the first FDA-approved antidepressant drug of the selective noradrenaline reuptake inhibitors class. There is a serious need for a convenient analytical tool for the quantitation of RBX in its dosage form. This study aims toward the development and validation of two green and high-throughput microwell spectrometric platforms for the pharmaceutical analysis of RBX. The two platforms, abbreviated as MW-AB and MW-FL, involved microwell-based analysis assisted with a multifunction microplate plate reader for measuring absorbance and fluorescence signals, respectively. The MW-AB and MW-FL platforms involved the formation of colored and fluorescent derivatives upon the reaction of RBX with oxidized pyrocatechol reagent (OPC) and tetracyanoquinodimethane (TCNQ), respectively. The absorbance of colored RBX-OPC derivative at 520 nm, and the fluorescence of RBX-TCNQ charge transfer complex at 283 and 484 nm for excitation and emission, respectively. The optimum conditions of both reactions were established, their molar ratios were determined, and reaction mechanisms were postulated. Both platforms were optimized and validated according to the guidelines of the International Council on Harmonization. The limits of quantitation were 19.6 µg/mL and 27 ng/mL for MW-AB and MW-FL, respectively. Both platforms were applied with excellent reliability to the quantitation of RBX content in Edranox® tablets and their drug uniformity. The greenness levels of both platforms were assessed by two comprehensive tools, and the results confirmed the high level of greenness for both platforms. Both platforms involved one-step reactions, adapted microwell analysis, and simultaneous handling of large number of samples. Therefore, they have the advantages of greenness and high-throughput analysis. The proposed two platforms are valuable tools for the rapid quantitation of RBX.

Photoluminescent polypropylene nanofiber-supported polyethylene terephthalate integrated with strontium aluminate phosphor

In order to develop photochromic materials with persistent afterglow emission, such as concrete and smart windows, electrospun polypropylene nanofibers (PPNF) were incorporated into polyethylene terephthalate (PET) for reinforcement. Nanoparticles of lanthanide-activated strontium aluminum oxide (NLSA) were physically embedded into polyethylene terephthalate films to produce transparent PPNF@PET smart membranes. Electrospinning was utilized to create PPNF, which were subsequently included as a roughening agent into PET membranes. The green coloration detected upon exposing the PPNF@PET film to ultraviolet light was verified by CIE Lab coordinates and photoluminescence analysis. The PPNF@PET hybrids with low quantities of NLSA were found to immediately reverse this emission activity after removing the ultraviolet source, which suggest fluorescence emission. Afterglow photoluminescence was detected at higher phosphor concentrations in PPNF@PET by slow reversibility of the light emission, which suggests glow in the dark emission. After 365 nm of excitation, a 517 nm emission band could be monitored from the PPNF@PET hybrids. The chemical structure and morphology of LSA nanoparticles and PPNF were studied, showing diameters of 80–120 nm and 75–180 nm, respectively. Different analysis methods were employed to examine the morphologies of PPNF@PET membranes. As compared to a NLSA-free polyethylene terephthalate control sample, the PPNF@PET smart membranes demonstrated improved scratch resistance. The hydrophobicity and UV resistance of the PPNF@PET smart membranes were improved with an increase in the concentration of NLSA.

Opto-magnetic nanoparticles with upconverting properties for optical imaging and photothermal therapies

Multifunctional opto-magnetic nanoparticles (NPs) with upconverting properties were designed for cancer detection and treatment. The upconversion was achieved from NaYF4 doped by 20 %Yb and 2 % Er nanoparticles (UCNPs). The UCNPs were coated by a thin SiO2 shell and decorated with 6 nm magnetic Fe3O4 that resulted in the formation of NaYF4:Yb,Er@SiO2@Fe3O4 multifunctional nanoplatform. The connection between UCNPs and Fe3O4 NPs was proved by SEM, TEM, SQUID, absorption, and luminescence techniques. The specific absorption rate (SAR) values for prepared colloids were calculated for colloidal suspension of heterostructures after 808 and 880 nm laser irradiation as a function of lasers power. The highest conversion effectiveness was obtained for an 880 nm light source with 1600 mW (SAR = 87 W/g). The low MDA-MB-231 cells cytotoxicity of NaYF4:Yb,Er@SiO2@Fe3O4 NPs was observed (up to 500 µg/ml). At the same time, a strong upconverting signal after 980 nm of excitation was observed from the sites of the cells without autofluorescence from its components. This phenomenon with relatively good SAR parameters suggested that multifunctional nanoconstructs for simultaneous cancer detection (imaging) and photothermal therapy have been successfully obtained.

Development of green, high throughput, and sensitive universal microwell spectrofluorimetric method for one-step determination of sartans in their dosage forms and plasma

This study describes, for the first time, the development of a novel one-step universal and green microwell spectrofluorimetric method with high sensitivity and throughput for the determination of sartans. The method was developed using 4 sartans, as representative examples. These saratns were losartan potassium, irbesartan, candesartan cilexetil, and valsartan. The method comprised the measurement of enhanced native fluorescence of sartans in acidic solutions by using a fluorescence microplate reader at 260 and 410 nm for excitation and emission, respectively. The variables affecting the fluorescence intensity were optimized. The method was linear in a range of 20–1000 ng/mL. The limits of detection ranged between 7.3 and 13.4 ng/mL, and those of quantitation ranged between 22.5 and 40.6 ng/mL. The proposed method showed high levels of precision and accuracy. The method was successfully applied to the estimation of sartans in their dosage form, in-vitro drug release testing, and analysis of plasma samples. The proposed method is the first spectrofluorimetric method that can analyze all sartans on a single analysis system without alterations in the measuring wavelengths. The greenness of the method was assessed using three distinct metric tools, which conclusively demonstrated its adherence to green analytical principles. Moreover, the method has high throughput capacity as it is able to concurrently process large number of micro-volume samples. In conclusion, the proposed method is valuable for the rapid and routine determination of sartans for the purposes of quality control and bioequivalence studies.

One step synthesis-functionalization of Carbon Quantum Dost by carbonization of beetroot fruit (Beta Vulgaris) bagasse and their performance in sensing of Ag+ and Cu2+ ions

Water-dispersible and fluorescence-stable carbon quantum dots (CQDs) have been synthesized from waste Beetroot fruit (bagasse) through a low-cost synthesis-functionalization process at different times and temperatures of carbonization. At 254 nm of excitation, the obtained CQDs have emission in different colors: light purple, yellow and blue. By FT-IR analysis was determined that carbonyl groups from betalainic compounds present in beetroot fruit were responsible of surface passivation and consequently the presence of photoluminescent properties. Raman spectroscopy showed that the obtained CQDs are mainly made up of sp2 graphitic carbon with sp3 carbon defects and oxygen functional groups. The obtained CQDs were used in model Cu2+ and Ag+ solutions with the aim to study relationship of time and temperature carbonization with decrease of intensity emission to stablish their potential use as a sensor of metallic ions. The novelty of this work lies in obtaining CQDs by organic waste, which offers a solution from biomass waste disposal problems, especially in developing countries where these wastes are increasing considerably, and in addition the obtained product can be used as a metal ions sensor.

Quantitative spectrofluorimetric method for determination of octreotide acetate synthetic peptide derivative in pure and its Sandostatin ampules forms

A unique spectrofluorimetric protocol has been conceived for octreotide (a synthetic peptide drug) quantitation in both its authentic form and its application to dosage form. The protocol has been established simply upon condensation of octreotide by ninhydrin / phenyl acetaldehyde reagent in buffered media (pH 6.2). An intense fluorescence product has been formed and quantified at 463 nm (390 nm for excitation). After optimization for various experimental conditions, a wide linear interval (0.2–4.0 µg/ml) has been used to construct the calibration curve with a determination coefficient (r2) of 0.9994, a slope ± SD of 81.147 ± 0.7985, and a highly sensitive detection and quantitation limits nearly equal to 0.066 and 0.2 µg/ml, respectively. A proposed protocol has been checked in accordance with ICH validation guidelines, which indicate good accuracy and high precision of the proposed method. Furthermore, this protocol could be perfectly applied for the quantitative estimation of octreotide in its ampoules with a high degree of accuracy and precision. As a result, a developed protocol is ideally appropriate for fast and simple octreotide quantitative estimation in quality control laboratories.

Dual fluorescence enhancement of loratidine by photoinduced electron transfer blocking and micellization: Application to the development of novel highly sensitive microwell spectrofluorimetric assay for analysis of dosage forms and urine samples

This study describes the enhancement of the weak native fluorescence of loratadine (LOR) by dual strategy via photoinduced electron transfer (PET) blocking followed by micellization into sodium dodecyl sulfate micelles. The enhanced fluorescence was employed as a basis for the development of a novel microwell spectrofluorimetric assay (MW-SFA) for the determination of LOR in its pharmaceutical dosage forms and urine samples. The assay was conducted in 96-microwell assay plates, and the enhanced fluorescence signals were measured by a microplate reader at 290 and 435 nm for excitation and emission, respectively. The optimum conditions of the assay were established, calibration curve was generated, and the linear regression equation was computed. The relation between the fluorescence signals and LOR concentrations was linear with good determination coefficients (0.9992) in the range of 10 – 2000 ng mL−1. The assay limits of detection and quantitation were 4.1 and 12.5 ng mL−1, respectively. The precision was satisfactory, with values of relative standard deviation not exceeding 1.68%, and the assay’s accuracy was ≥ 99.1%. The proposed was successfully applied to the analysis of LOR in its pharmaceutical dosage forms with acceptable accuracy and precision. The label claims were 99.3 – 100.5% (±0.95 – 1.59%). Statistical analysis comparing the results of the proposed assay with those obtained by a reported pre-validated assay revealed no significant difference between both methods in terms of the accuracy and precision at the 95% confidence level. The assay was also applied to the analysis of urine samples containing LOR with accuracy ≥ 98.24%. The greenness of the proposed assay was confirmed by three efficient metric tools. In overall conclusion, the proposed assay is characterized by high sensitivity, procedure simplicity, and high throughput, enabling the simultaneous analysis of many samples in a short time. Therefore, it is a valuable tool for rapid routine application in pharmaceutical quality control units and clinical laboratories for the determination of LOR.

Analysis of the Structure and Luminescence Properties of Sr3Y2Ge3O12:0.05Eu3+ (SYGO:Eu3+) According to Judd–ofelt Theory

In this report, SYGO:Eu3+ red phosphor have been successfully synthesized by sol-gel method. The X-ray diffraction results show that the sample has a cubic crystal structure, belonging to the space group Ia3d (230) without any doping. Scanning electron microscopy (FE-SEM) combined with EDS was performed to determine the microstructure and elemental composition of the fabricated phosphor. The particles are significantly agglomerated and are about ∼200 nm in size. The results of fluorescence property investigation (PLE-PL) show that, the maximum emission spectrum at 612 nm under ultraviolet light close to 395 nm for excitation. Calculating the J-O intensity parameters, the result is that Ω2 is larger than Ω4 which proves that the surrounding local structure of the doped ion is asymmetric. In addition, the luminescence efficiency approximately calculation is 70%. Phosphor SYGO:Eu3+ has been fabricated which can be used as a solid lighting material for WLED.

Uronic acid and their oligomer microanalysis by normal-phase partition chromatography with fluorescence derivatization

Algal alginates, which consist of two uronic acids (i.e. D-mannuronate and L-guluronate), are important resources for a lot of industrial materials. The ratio of D-mannuronate to L-guluronate influences the physical properties of polysaccharide preparations and gels in industry. Furthermore, the influences of the percentage and configuration of each uronic acid oligomer on biological and physiochemical properties of polysaccharides have also been reported. Therefore, a highly sensitive analytical technique for uronic acids and their oligomers would be useful for both biological studies and manufacturers’ quality control. To develop a fluorimetric high-performance liquid chromatography (HPLC) technique for microanalysis for uronic acid monomers and oligomers, a saline mobile phase and the postcolumn fluorimetric determination system of reducing saccharides with benzamidine were combined. Fluorescence measurement was performed at 288 nm for excitation and 470 nm for emission. A linear gradient elution system was found to be a suitable method for the simultaneous microanalysis of uronic acid monomers and oligomers. The proposed method was successfully applied to uronic acid microanalysis and should prove useful for automated simultaneous microanalysis of uronic acid monomers and oligomers in alginate hydrolysates.

Mn2+ Luminescence in Ca9Zn1-xMnxNa(PO4)7 Solid Solution, 0 ≤ x ≤ 1.

The solid solution Ca9Zn1-xMnxNa(PO4)7 (0 ≤ x ≤ 1.0) was obtained by solid-phase reactions under the control of a reducing atmosphere. It was demonstrated that Mn2+-doped phosphors can be obtained using activated carbon in a closed chamber, which is a simple and robust method. The crystal structure of Ca9Zn1-xMnxNa(PO4)7 corresponds to the non-centrosymmetric β-Ca3(PO4)2 type (space group R3c), as confirmed by powder X-ray diffraction (PXRD) and optical second-harmonic generation methods. The luminescence spectra in visible area consist of a broad red emission peak centered at 650 nm under 406 nm of excitation. This band is attributed to the 4T1 → 6A1 electron transition of Mn2+ ions in the β-Ca3(PO4)2-type host. The absence of transitions corresponding to Mn4+ ions confirms the success of the reduction synthesis. The intensity of the Mn2+ emission band in Ca9Zn1-xMnxNa(PO4)7 rising linearly with increasing of x at 0.05 ≤ x ≤ 0.5. However, a negative deviation of the luminescence intensity was observed at x = 0.7. This trend is associated with the beginning of a concentration quenching. At higher x values, the intensity of luminescence continues to increase but at a slower rate. PXRD analysis of the samples with x = 0.2 and x = 0.5 showed that Mn2+ and Zn2+ ions replace calcium in the M5 (octahedral) sites in the β-Ca3(PO4)2 crystal structure. According to Rietveld refinement, Mn2+ and Zn2+ ions jointly occupy the M5 site, which remains the only one for all manganese atoms within the range of 0.05 ≤ x ≤ 0.5. The deviation of the mean interatomic distance (∆l) was calculated and the strongest bond length asymmetry, ∆l = 0.393 Å, corresponds to x = 1.0. The large average interatomic distances between Mn2+ ions in the neighboring M5 sites are responsible for the lack of concentration quenching of luminescence below x = 0.5.

Development of Novel Microwell-Based Spectrofluorimetry and High-Performance Liquid Chromatography with Fluorescence Detection Methods and High Throughput for Quantitation of Alectinib in Bulk Powder and Urine Samples

Background and Objectives: This study presents the development and validation of the 96-microwell-based spectrofluorimetric (MW-SFL) and high performance liquid chromatography (HPLC) with fluorescence detection (HPLC-FD) methods for the quantitation of alectinib (ALC) in its bulk powder form and in urine samples. Materials and Methods: The MW-SFL was based on the enhancement of the native fluorescence of ALC by the formation of micelles with the surfactant cremophor RH 40 (Cr RH 40) in aqueous media. The MW-SFL was executed in a 96-microwell plate and the relative fluorescence intensity (RFI) was recorded by utilizing a fluorescence plate reader at 450 nm after excitation at 280 nm. The HPLC-FD involved the chromatographic separation of ALC and ponatinib (PTB), as an internal standard (IS), on a C18 column and a mobile phase composed of methanol:potassium dihydrogen phosphate pH 7 (80:20, v/v) at a flow rate of 2 mL min-1. The eluted ALC and PTB were detected by utilizing a fluorescence detector set at 365 nm for excitation and 450 nm for emission. Results: Validation of the MW-SFL and HPLC-FD analytical methods was carried out in accordance with the recommendations issued by the International Council for Harmonization (ICH) for the process of validating analytical procedures. Both methods were efficaciously applied for ALC quantitation in its bulk form as well as in spiked urine; the mean recovery values were ≥86.90 and 95.45% for the MW-SFL and HPLC-FD methods, respectively. Conclusions: Both methodologies are valuable for routine use in quality control (QC) laboratories for determination of ALC in pure powder form and in human urine samples.

Multicolor and warm white luminescence from Dy3+/Eu3+ co-activated glasses for indoor and solid-state lighting applications

Multicolor emitting Dy3+/Eu3+ coactivated lithium zinc borate (LZB) glasses were prepared by the melt-quenching method and their structural, vibrational, morphological, and luminescence properties were investigated. Dy3+ glasses exhibited blue, yellow, and red photoluminescence (PL) bands at 481 nm (4F9/2 → 6H15/2), 576 nm (4F9/2 → 6H13/2), and 665 nm (4F9/2 → 6H11/2) under 386 nm excitation. Eu3+ glasses exhibited strong orange and reddish-orange emissions at 589 nm (5D0→7F1) and 612 nm (5D0→7F2) at 393 nm of excitation. 0.5 mol% Dy3+ is codoped with various Eu3+ concentrations and the energy transfer mechanism is analyzed from the spectral overlay of Dy3+ emission and Eu3+ absorption, Dy3+/Eu3+ PL, and decay profiles as well as from energy transfer parameters. Dy3+/Eu3+ codoped glasses stimulated under different excitation wavelengths of Dy3+ (349, 363, and 386 nm) displayed a decline in the intensity of Dy3+ PL bands and a simultaneous rise in Eu3+ PL bands, demonstrating efficient energy transfer from Dy3+: 4F9/2 → Eu3+: 5D0 due to dipole-dipole interaction. The energy transfer process is supported by a decrement in the lifetimes of Dy3+ when co-doped with Eu3+ compared with singly doped Dy3+ones. The color coordinates and corresponding color temperatures were shifted from neutral to a warm white light region depending on the Eu3+ concentration. The aforementioned results demonstrate the importance of the near-ultraviolet-driven LZB: Dy3+/Eu3+ glasses for their potential application in warm white light and multicolor emitting devices.

Sr3LiSbO6: Er3+ phosphors for green LEDs and solar cell applications

In the present work, Er3+ doped Sr3LiSbO6 ceramics phosphors have been synthesized by the solid-state method. Crystal structure and phase formation were analyzed from XRD and Rietveld refinement of the XRD data. FESEM, EDX, HRTEM and elemental mapping techniques were employed to analyze the surface morphology and elemental configuration of the phosphor. Binding energy and oxidation states were analyzed by XPS measurements. Raman spectra exhibit the characteristic vibrational band associated with the host lattice and dopant ion. The optical band gap of the reported material was estimated from UV–Vis diffuse reflection study. Photoluminescence up conversion (UC) and down conversion (DC) characteristics of the prepared phosphors have been studied based on excitation and emission spectra. The average decay time of the excited state of all samples has been determined from the exponential fitting results of the decay curves obtained from PL at 378 nm and 547 nm of excitation and emission wavelengths respectively. Power-dependent PL UC measurement was executed under the laser excitation of 980 nm. The obtained characteristics of the prepared sample recommend that the proposed phosphor can be a promising material for green component of LEDs or solar spectral conversion agents in solar cell applications.

Bright red luminescence from Eu3+-activated noncytotoxic SnO2 quantum dots for latent fingerprint detection

Ravishing red luminescent Eu3+-activated SnO2 quantum dot (QD) phosphors were successfully synthesized by employing a simple chemical reduction method. X-ray diffraction analysis confirmed that the Eu3+:SnO2 QDs have a tetragonal structure. The particle size, interplanar distances, and elements existing in the sample were examined by performing transmission electron microscopy, high-resolution transmission electron microscopy, and elemental mapping studies, respectively. Under UV illumination, photoluminescence analyses were performed on pristine SnO2 QDs and Eu3+:SnO2 QDs. Under 294 nm of excitation, a broad emission band was observed for the undoped SnO2 QDs centered at 454 nm. A robust red emission emitted from the Eu3+-activated SnO2 QDs by excitation at 394 nm. The red emission intensity was significantly enhanced by increasing the Eu3+ ion concentration up to 0.3 mol%, and it was decreased drastically by increasing at above 0.3 mol% of Eu3+ ions due to concentration quenching. Furthermore, an energy migration was observed from SnO2 QDs host to Eu3+ ions. The International Commission on Illumination (CIE) color coordinates, correlated color temperature, and color purity values were evaluated for all the Eu3+:SnO2 QDs based on the emission profiles. The obtained CIE coordinates were compared with the standard National Television System Committee coordinates. Additionally, the applicability of the Eu3+:SnO2 QDs was evaluated to visualize the latent fingerprints on smooth surfaces using the powder dusting method. The obtained latent fingerprint images exhibited good sensitivity, high contrast, and appreciable ridge details. The noncytotoxicity of the Eu3+:SnO2 QDs was confirmed by conducting a toxicity test on normal fibroblast cell lines (L929). The results revealed that the noncytotoxic and ravishing luminescent Eu3+:SnO2 QDs can garner significant interest for use in latent fingerprint, biological labeling, imaging, and security encoding. We believe that such a method of producing lanthanide-doped QDs can accelerate the development of QD phosphor-based research.

Nd3+-Doped TiO2 Nanoparticles as Nanothermometer: High Sensitivity in Temperature Evaluation inside Biological Windows.

TiO2 nanoparticles doped with different amounts of Nd3+ (0.5, 1, and 3 wt.%) were synthetized by the sol–gel method, and evaluated as potential temperature nanoprobes using the fluorescence intensity ratio between thermal-sensitive radiative transitions of the Nd3+. XRD characterization identified the anatase phase in all the doped samples. The morphology of the nanoparticles was observed with SEM, TEM and HRTEM microscopies. The relative amount of Nd3+ in TiO2 was obtained by EDXS, and the oxidation state of titanium and neodymium was investigated via XPS and NEXAFS, respectively. Nd3+ was present in all the samples, unlike titanium, where besides Ti4+, a significantly amount of Ti3+ was observed; the relative concentration of Ti3+ increased as the amount of Nd3+ in the TiO2 nanoparticles increased. The photoluminescence of the synthetized nanoparticles was investigated, with excitation wavelengths of 350, 514 and 600 nm. The emission intensity of the broad band that was associated with the presence of defects in the TiO2, increased when the concentration of Nd3+ was increased. Using 600 nm for excitation, the 4F7/2→4I9/2, 4F5/2→4I9/2 and 4F3/2→4I9/2 transitions of Nd3+ ions, centered at 760 nm, 821 nm, and 880 nm, respectively, were observed. Finally, the effect of temperature in the photoluminescence intensity of the synthetized nanoparticles was investigated, with an excitation wavelength of 600 nm. The spectra were collected in the 288–348 K range. For increasing temperatures, the emission intensity of the 4F7/2→4I9/2 and 4F5/2→4I9/2 transitions increased significantly, in contrast to the 4F3/2→4I9/2 transition, in which the intensity emission decreased. The fluorescence intensity ratio between the transitions and were used to calculate the relative sensitivity of the sensors. The relative sensitivity was near 3% K−1 for and near 1% K−1 for .

An ultrasensitive fluorimetric sensor for pre-screening of water microbial contamination risk

In recent years, global efforts have been directed towards the development of water safety routines, consequently demanding cost-effective sensors capable of detecting outbreaks at early stages. This work reports the development and study of an original in-field tryptophan fluorimetric sensor as a potential indicator of real-time microbial contamination in water. The sensor excitation and emission wavelengths were selected with respect to the coliform bacteria tryptophan peak; 280 nm for excitation and 330 nm for emission. The in-lab tests with standard samples show a detection limit of 4.89 nM (≈0.1 μg/l) for L-tryptophan. The sensor exhibited good linearity over three orders of magnitude and considerable detection reproducibility, which was confirmed during calibration tests. Small-scale in situ tests showed that the sensor was better correlated with coliform bacteria than other online sensors such as turbidity. This suggests that the fluorimetric tryptophan sensor can be integrated into early warning systems that quickly assess changes in water microbial quality.