High Quality Optical Properties Research Articles

Effect of Ga/Al ratio on the luminescent properties of inorganic scintillating GGAG:(4 mol%)Ce ceramic powder

Gadolinium gallium aluminum garnet doped with cerium (GGAG:Ce), a promising ceramic scintillator material, is being excessively explored for its high quality optical properties by the bandgap engineering with different Ga/Al ratio. In this study, GGAG:Ce powders were synthesized using a solvothermal method and sintered at 1300 °C to investigate the impact of the gallium-to-aluminum (Ga/Al) ratio on optical characteristics. The results revealed that a decrease in the Ga/Al ratio led to a decrease in particle size. This observation can be attributed to the different reactivity and growth kinetics of gallium and aluminum precursors during the solvothermal process. Perturbations from the optimized Ga/Al ratio of 1.5–1.77 and 1.27 resulted in substantially enhanced photoluminescence (PL) and radioluminescence (RL) spectra intensities. PL lifetime measurements of various Ga/Al ratio exhibit average PL lifetime between 48 and 57 ns. Specifically, the deviations to 1.77 and 1.27 ratios yielded approximately 125 % and 106 %, respectively, in observed luminescent measurements compared to other ratios. This enhancement in PL and RL intensity suggests that the Ga/Al ratio plays a critical role in modulating the optical properties of GGAG:Ce ceramic powders. The results of this study also highlight the importance of the Ga/Al ratio in tailoring the optical or luminescence characteristics of GGAG:Ce powders.

Vertically Well-Aligned ZnO Nanoscintillator Arrays with Improved Photoluminescence and Scintillation Properties.

ZnO nanoarrays were grown via a low-temperature hydrothermal method. Solutions, each with different additive combinations, were prepared and evaluated. The effects of the additives involved in the growth procedure, i.e., ammonium hydroxide and sodium citrate, were studied in terms of the morphological, optical and scintillation properties of the ZnO nanostructures. Measurement of the nanorod (NR) length, corresponding photoluminescence (PL) and scintillation spectra and their dependence on the additives present in the solution are discussed. ZnO NRs grown on a silica substrate, whose UV transmission was found to be better than glass, showed high-quality structural and optical properties. It was found that the addition of sodium citrate significantly reduced defects and correspondingly increased the intrinsic near-band-edge (NBE) UV emission intensity at ~380 nm. To obtain high-quality nanostructures, samples were annealed in a 10% H2 + 90% N2 atmosphere. The anneal in the forming gas atmosphere enhanced the emission of the UV peak by reducing defects in the nanostructure. NRs are highly tapered towards the end of the structure. The tapering process was monitored using time growth studies, and its effect on PL and reflectance spectra are discussed. A good alpha particle response was obtained for the grown ZnO NRs, confirming its potential to be used as an alpha particle scintillator. After optimizing the reaction parameters, it was concluded that when ammonium hydroxide and sodium citrate were used, vertically well-aligned and long ZnO nanoarrays with highly improved optical and scintillation properties were obtained.

Epitaxial growth of V2O3 thin films on Si(1 1 1) by molecular beam epitaxy

Vanadium sesquioxide (V2O3) is a strongly correlated electron material exhibiting two distinct metal–insulator transitions that can be tuned via strain, doping, or pressure, making it an interesting material for new-generation sensors or smart devices. For this purpose, it is required to achieve well-ordered epitaxial thin film growth with high-quality electrical and optical properties on technologically relevant substrates. We report the successful growth of epitaxial thin films of V2O3 via molecular beam epitaxy, in the paramagnetic insulating (PI) phase on the (111) plane of silicon, by tailoring the growth conditions. Extensive electrical, structural, and morphological characterization both in situ and ex situ has been performed on all samples. The structural analysis reveals that temperature plays a more impactful role in affecting the thin film microstructures than the oxygen partial pressure. When the epitaxy of V2O3 occurs on the unoxidized (111) plane of silicon, four equivalent epitaxial domains begin to form, leading to twin boundaries in the bulk of the film. The considerable lattice mismatch between silicon and V2O3 induces the growth of the corundum PI phase. Lastly, small deviations from stoichiometry due to different oxygen inflow during growth alter significantly the resistivity change upon cooling.

Synthesis ZnO nanoclusters micro active area using continues wave blue laser-assisted chemical bath deposition based on UV photodetector

In this study, zinc oxide (ZnO) thin films were utilized to create metal–semiconductor–metal (MSM) structured ultraviolet (UV) photodetectors using laser assisted chemical bath deposition (LACBD). For the first time, LACBD has successfully manufactured zinc oxide (ZnO) nanoclusters (NCs) with high-quality structural, optical, and electrical properties on a glass substrate coated with iron (Fe) to construct an MSM UV photodetector with high responsivity. The thin film was created by irradiating the chemical bath in situ using a continuous wave semiconductor laser with wavelength(460 nm), output power (1 W), and irradiation laser time (30 min). The thin film was characterized using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analyses, and X-ray diffractometry (XRD). Our findings revealed that LACBD promoted the development of a high-crystallinity ZnO thin film. The effectiveness of ZnO NCs in UV detection has also been examined to account for the potential of these nanostructures. The device's current-voltage (I-V) characteristics were tested in dark and light situations, confirming the UV photodetector's excellent responsiveness and stability. Optical confinement, a high surface-to-volume ratio, and the superior structural quality of the NCs, as confirmed by time-resolved spectroscopy, are all factors in the great photodetector performance.

Micro spot ZnO nanotubes using laser assisted chemical bath deposition: A low-cost approach to UV photodetector fabrication

Due to its outstanding characteristics across a wide variety of applications, such as electrical, photonic, electrochemical, and electromechanical devices, one-dimensional Zinc oxide (ZnO) is one of the most promising nanostructures. Using a continuous wave semiconductor laser with a wavelength of 460 nm and a power of 1 W, functional ZnO nanostructures known as nanotubes (NTs) with high-quality structural, optical, and electrical properties on a glass substrate coated with iron (Fe) to construct a UV photoconductive detector with high responsivity were produced for first time by using a simple and quick laser assisted chemical bath deposition (LACBD). X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray (EDX)analyses were used to investigate the evolution of the material's physical and structural characteristics. Our findings revealed that laser-assisted in-situ irradiation of the chemical solution resulted in faster growth of ZnO thin films. To account for the potential of these nanostructures, the effectiveness of ZnO nanotubes (NTs) in ultraviolet (UV) detection has also been investigated. The NT-based photodetector has outstanding stability and responsiveness in both dark and light conditions. Exciton confinement is identified using time-resolved spectroscopy, suggesting that the high surface-to-volume ratio, optical confinement, and high structural quality of the NTs are responsible.

Single photon emission from ODT passivated near-surface GaAs quantum dots

Epitaxially grown semiconductor quantum dots are promising candidates for pure single photon and polarization-entangled photon pair emission. Excellent optical properties can typically be ensured only if these so-called “artificial atoms” are buried deep inside the semiconductor host material. Quantum dots grown close to the surface are prone to charge carrier fluctuations and trap states on the surface, degrading the brightness, coherence, and stability of the emission. We report on high-purity single photon emission [g(2)(0) = 0.016 ± 0.015] of GaAs/AlGaAs quantum dots that were grown only 20 nm below the surface. Chemical surface passivation with sulfur compounds such as octadecanethiol has been performed on quantum dots with 20, 40, and 98 nm from the surface. The reduction of the density and influence of surface states causes improvements in linewidth and photoluminescence intensity as well as a well-preserved single photon emission. Therefore, the realization of hybrid nanophotonic devices, comprising near-field coupling and high-quality optical properties, comes into reach.

Excellent relaxivity and X-ray attenuation combo properties of Fe3O4@Au CSNPs produced via Rapid sonochemical synthesis for MRI and CT imaging

Core@shell nanoparticles (Fe3O4@Au CSNPs) have multiple functions obtained in one stable entity and thus have been extensively investigated. Fe3O4 NPs have unique superparamagnetic properties which allow for their application in different fields, and Au NPs stand out in biomedical applications because of their chemical stability, oxidation resistance and high-quality intrinsic optical properties. Combining Fe3O4 and Au NPs in one core@shell nanostructure is a promising strategy for diagnostic biomedical applications. However, the conventional direct methods for Fe3O4@Au CSNP synthesis are laborious and time consuming. Therefore, this study presents a facile and rapid sonochemical technique of synthesising Fe3O4@Au CNPs with excellent physicochemical properties for magnetic resonance imaging (MRI) and computed tomography (CT) scan. A Vibra Cell ultrasonic solid horn with a tip size of ½ inch, 20 kHz frequency and power output of 750 W were used, and the synthesis is achieved in just 10 min. Several techniques were used to characterise the Fe3O4@Au CSNPs and confirmed their average size of 21 nm and the formation of spherical Au shell on the Fe3O4 core. The Fe3O4@Au CNPs showed good biocompatibility and great potential as a dual-mode contrast agent for MRI/CT imaging. The transverse relaxivity values and X-ray attenuation of the as-synthesised NPs (222.28 mM−1s−1 and HU = 418) are greater than those of NPs prepared using conventional methods and commercial NPs. This work reveals considerable progress on Fe3O4@Au CSNPs by providing a facile and rapid method to synthesise high-quality Au-coated Fe3O4 NPs.

Two-dimensional high-quality Ag/Py magnetoplasmonic crystals

We demonstrate a perspective approach for the fabrication of functional high-quality magnetoplasmonic crystals based on a 2D periodical perforated silver film covered by a thin layer of ferromagnetic metal (Permalloy). The wavelength-angular spectra of the 2D crystals reveal a large number of high-quality resonant features associated with the excitation of surface plasmon-polariton modes of various orders. Due to the presence of a ferromagnetic material on both plasmonic interfaces, pronounced magnetic effects are observed for all excitations and are influenced by the coupling between various modes. The suggested magnetoplasmonic crystal composition with high-quality resonant optical and magneto-optical properties gives perspective for the control over the light propagation as well as for sensor applications.

Abstract 2285: Comparison of the nCyte Dx and CellSearch systems for CTC enumeration

Abstract Introduction: Circulating Tumor Cells (CTCs) have clinical utility for cancer prognosis and monitoring disease. The goal of this study was to compare CTC enumeration by the FDA-approved CellSearch technology to a new technology, the nCyte Dx system by Axon Dx, LLC. Methods: Duplicate peripheral blood samples from 24 patients with advanced prostate cancer were collected in CellSave tubes as standard of care and submitted for CTC quantification using the CellSearch system at ARUP Laboratories. Following CellSearch testing, a paired sample was sent from ARUP to Axon Dx for nCyte Dx analyses. For every pair of samples, the blood was collected at the same time, but the sample tested by Axon Dx was aged 24 to 72 hours beyond the sample tested with CellSearch. CellSearch identifies CTCs by immunomagnetic capture of EpCAM-postive cells, while nCyte Dx does not incorporate specific CTC enrichment. With nCyte Dx, all PBMCs are isolated via density-based separation in a CPT tube and stained with Axon’s immunofluorescent cocktail (nPac). The cells are drawn down onto semi-porous membranes and placed onto microscope slides. Slides are imaged with the nCyte, a rapid fluorescent scanning instrument, and Axon’s advanced cell finding and analysis software (nAble) facilitates automated CTC detection. Due to the high-quality optical properties of the nCyte, the detected material can be characterized and categorized based on morphology and cellular structure. Results: CellSearch-derived CTC counts were compared with the enumeration results from the nCyte Dx system. Results were reported per 7.5mL blood for both methods. Bland-Altman analysis demonstrates that CellSearch and nCyte Dx results agreed in 22 of the 24 patient sample sets tested within a 95% confidence interval (CI). For both discrepant samples, the CellSearch count was found to be higher. The nCyte Dx method generally detected more CTCs than CellSearch in the lower enumeration range (<10 CTCs). Because previous data from Axon Dx shows no CTCs detected in healthy patients, this finding may be attributable to increased sensitivity rather than decreased specificity. Differences between the results may also be attributable to the natural variation between duplicate blood draws, best characterized by the Poisson distribution model. Summary and Conclusions: A comparison of CTC enumeration results using the CellSearch and nCyte Dx platforms was performed using duplicate blood samples from 24 prostate cancer patients. The results reveal high similarity between the two technologies, with 22 of 24 patients (92%) having enumeration results that agreed within a 95% CI. While both technologies deliver similar results, there are notable advantages of the nCyte Dx system over CellSearch, including a lack of bias toward EpCAM positive material. Additionally, the superior image quality of nCyte Dx may limit subjectivity in CTC identification and offer the ability to characterize CTC heterogeneity. Citation Format: Josefa Andrade, Ramsey Mohl, Stephanie Thomas, John Kearney, Phillip Bernard, Hillary S. Sloane. Comparison of the nCyte Dx and CellSearch systems for CTC enumeration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2285.

InGaN Platelets: Synthesis and Applications toward Green and Red Light-Emitting Diodes.

In this work, we present a method to synthesize arrays of hexagonal InGaN submicrometer platelets with a top c-plane area having an extension of a few hundred nanometers by selective area metal-organic vapor-phase epitaxy. The InGaN platelets were made by in situ annealing of InGaN pyramids, whereby InGaN from the pyramid apex was thermally etched away, leaving a c-plane surface, while the inclined {101̅1} planes of the pyramids were intact. The as-formed c-planes, which are rough with islands of a few tens of nanometers, can be flattened with InGaN regrowth, showing single bilayer steps and high-quality optical properties (full width at half-maximum of photoluminescence at room temperature: 107 meV for In0.09Ga0.91N and 151 meV for In0.18Ga0.82N). Such platelets offer surfaces having relaxed lattice constants, thus enabling shifting the quantum well emission from blue (as when grown on GaN) to green and red. For single InGaN quantum wells grown on the c-plane of such InGaN platelets, a sharp interface between the quantum well and the barriers was observed. The emission energy from the quantum well, grown under the same conditions, was shifted from 2.17 eV on In0.09Ga0.91N platelets to 1.95 eV on In0.18Ga0.82N platelets as a result of a thicker quantum well and a reduced indium pulling effect on In0.18Ga0.82N platelets. On the basis of this method, prototype light-emitting diodes were demonstrated with green emission on In0.09Ga0.91N platelets and red emission on In0.18Ga0.82N platelets.

Template-Free Synthesis of High-Yield Fe-Doped Cesium Lead Halide Perovskite Ultralong Microwires with Enhanced Two-Photon Absorption.

Doping in perovskite is challenging and competitive due to the inherently fast growth mechanism of perovskite structure. Here, we demonstrate successful synthesis of high-yield Fe-doped cesium lead halide perovskite ultralong microwires (MWs) that have diameters up to ∼5 μm and lengths up to millimeters via an antisolvent vapor-assisted template-free method. Microstructure characterization confirms the uniformly doped Fe in the high-quality crystal perovskite MWs. Significantly, doping the Fe(III) concentration can affect both the MW morphology and photoluminescence (PL). The band edge emission of the MW at variable excitation has been accounted for by the superposition and combination of optical transitions of nearby singlet, triplet, and magnetic polaronic excitons. High-quality two-photon PL emission and the enhanced nonlinear absorption coefficient of Fe-doped MWs have been experimentally demonstrated. This superhigh nonlinear absorption coefficient and high-quality optical properties endow it with promising applications in spin-related optical switching and optical limiting devices.

A Photodetector Based on p-Si/n-ZnO Nanotube Heterojunctions with High Ultraviolet Responsivity.

Enhanced ultraviolet (UV) photodetectors (PDs) with high responsivity comparable to that of visible and infrared photodetectors are needed for commercial applications. n-Type ZnO nanotubes (NTs) with high-quality optical, structural, and electrical properties on a p-type Si(100) substrate are successfully fabricated by pulsed laser deposition (PLD) to produce a UV PD with high responsivity, for the first time. We measure the current-voltage characteristics of the device under dark and illuminated conditions and demonstrated the high stability and responsivity (that reaches ∼101.2 A W-1) of the fabricated UV PD. Time-resolved spectroscopy is employed to identify exciton confinement, indicating that the high PD performance is due to optical confinement, the high surface-to-volume ratio, the high structural quality of the NTs, and the high photoinduced carrier density. The superior detectivity and responsivity of our NT-based PD clearly demonstrate that fabrication of high-performance UV detection devices for commercial applications is possible.

Continuous injection synthesis of indium arsenide quantum dots emissive in the short-wavelength infrared.

With the emergence of applications based on short-wavelength infrared light, indium arsenide quantum dots are promising candidates to address existing shortcomings of other infrared-emissive nanomaterials. However, III–V quantum dots have historically struggled to match the high-quality optical properties of II–VI quantum dots. Here we present an extensive investigation of the kinetics that govern indium arsenide nanocrystal growth. Based on these insights, we design a synthesis of large indium arsenide quantum dots with narrow emission linewidths. We further synthesize indium arsenide-based core-shell-shell nanocrystals with quantum yields up to 82% and improved photo- and long-term storage stability. We then demonstrate non-invasive through-skull fluorescence imaging of the brain vasculature of murine models, and show that our probes exhibit 2–3 orders of magnitude higher quantum yields than commonly employed infrared emitters across the entire infrared camera sensitivity range. We anticipate that these probes will not only enable new biomedical imaging applications, but also improved infrared nanocrystal-LEDs and photon-upconversion technology.

Nano-photo-thermal energy drive MoS_2/ZnO nanoheterojunctions growing

The heterojunction of transition-metal dichalcogenides is an important task for their applications in optoelectronics and nanoelectronics owning to substantial enhancing and enticing the material, optical, and electronic properties. A precise and controllable nanostructure preparing method, although highly desired, remains quite challenging, especially for heterojunction growing. In this work, an inspiring strategy is first reported for the synthesis of the MoS2/ZnO composite structure through driving by the nano-photo-thermal energy. The ZnO NCs exhibit a 2D layer growth way on the surface of MoS2 nanosheets. MoS2/ZnO composite structures possess high quality optical properties for the application of heterojunction. The nano-photo-thermal energy drive nanoheterojunction growing technology is a promising strategy towards the facile and in situ controllable method of novel functional materials.

Table-top femtosecond soft X-ray laser by collisional ionization gating

The advent of X-ray free-electron lasers has granted researchers an unprecedented access to the ultrafast dynamics of matter on the nanometre scale(1-3). Aside from being compact, seeded plasma-based soft X-ray lasers (SXRLs) turn out to be enticing as photon-rich(4) sources (up to 10(15) per pulse) that display high-quality optical properties(5,6). Hitherto, the duration of these sources was limited to the picosecond range(7), which consequently restricts the field of applications. This bottleneck was overcome by gating the gain through ultrafast collisional ionization in a high-density plasma generated by an ultraintense infrared pulse (a few 10(18) W cm(-2)) guided in an optically pre-formed plasma waveguide. For electron densities that ranged from 3 x 10(18) cm(-3) to 1.2 x 10(20) cm(-3), the gain duration was measured to drop from 7 ps to an unprecedented value of about 450 fs, which paves the way to compact and ultrafast SXRL beams with performances previously only accessible in large-scale facilities.

Efficient Photoluminescence of Mn2+-Doped ZnS Quantum Dots Sensitized by Hypocrellin A

Mn2+-doped ZnS semiconductor quantum dots reveal remarkably intense photoluminescence with the4T1(4G) f6A1(6S) transition. In this study, following growth doping technique, Mn2+-doped ZnS quantum dots (ZnS:Mn2+QDs) with high-quality optical properties and narrow size distribution were synthesized successfully. The dopant emission has been optimized with various reaction parameters, and it has been found that the percentage of introduced dopant, reaction temperature, and time as well as the pH of a reaction mixture are key factors for controlling the intensity. Photoluminescence emission (PL) measurements of ZnS:Mn2+QDs show Mn2+d-d orange luminescence along with band-edge blue luminescence. Moreover, the electron transfer from singlet states of hypocrellin A (HA) to colloidal ZnS:Mn2+QDs has been examined by absorption spectra and fluorescence quenching. The absorption spectrum gave an evidence of the increases in the extinction coefficient and the red-shift of the absorption maxima in the absorption spectra of HA in the presence of ZnS:Mn2+QDs, demonstrating the occurrence of surface interactions between the sensitizer and the particle surface. Fluorescence quenching by ZnS:Mn2+QDs also suggested that there were a complex association between HA and ZnS:Mn2+QDs, which was necessary for observing the heterogeneous electron-transfer process at the interface of sensitizer-semiconductor.

Observation of mid-infrared intersubband absorption in non-polar m-plane AlGaN/GaN multiple quantum wells

Mid-infrared (4.20–4.84 μm) intersubband absorption in non-polar m-plane Al0.5Ga0.5N/GaN multiple-quantum wells is observed at room temperature. 10 period Al0.5Ga0.5N/GaN multiple-quantum wells were grown on free-standing m-plane GaN substrates by metalorganic chemical vapor deposition (MOCVD), and the high-quality structural and optical properties are revealed by x-ray diffraction and photoluminescence studies. Through this we have demonstrated that MOCVD grown non-polar m-plane AlGaN/GaN quantum wells are a promising material for mid-infrared intersubband devices.

Atomic-layer triangular WSe2 sheets: synthesis and layer-dependent photoluminescence property

The exotic band structures and distinctive physical properties of two-dimensional materials have exhibited great potential for fundamental research and technical applications in spintronics, electronics, photonics, optoelectronics, and so forth. Facing the challenge of effective synthesis of WSe2 two-dimensional sheets, for the first time we demonstrate a straightforward catalyst-free vapor–solid (VS) growth method to synthesize ultrathin, even monolayer, WSe2 sheets with high yield, regular shapes and high quality optical properties on sapphire substrates. By detailed layer-number-dependent photoluminescence measurements at a low temperature of 40 K, we find the spin–orbit splitting at the K point of the WSe2 valence band with a fixed energy difference of 0.36 eV independent of layer number and the transition of indirect-to-direct gap when the thickness decreases to monolayer. These results, comparable to those of mechanically peeled WSe2 sheets, further prove the high optical and crystal quality of our WSe2 nanosheets via the VS growth approach. Our efforts may open up new exciting opportunities in future valley-based electronics, optoelectronics and photonics.

Aqueous synthesis of glutathione capped ZnSe nanocrystals: synthesis and optical properties

We have developed an aqueous synthesis for glutathione capped ZnSe nanocrystals. The structure and optical properties of the obtained ZnSe nanocrystals were characterised by X-ray diffraction, dynamic light scattering analysis, TEM, ultraviolet–visible, photoluminescence spectroscopy and Fourier transform infrared spectroscopy. The ZnSe shows a cubic zincblende crystal phase and has a narrow size distribution. Experimental results indicate that the pH value and reaction time play crucial roles in determining optical features. With the pH increasing from 10 to 12, and reaction time from 0 to 2 h, the fluorescence emissions of ZnSe nanocrystals are tuneable between 360 and 405 nm. The high quantum yields are calculated to be in the range of 0·3–22%. Furthermore, the luminescence intensity can be enhanced significantly when the nanocrystal sample is illuminated by room light. The mechanism for the resulting high quality optical properties is also elucidated.

Water-soluble, high-quality ZnSe@ZnS core/shell structure nanocrystals

Water-soluble and high photoluminescence (PL) efficiency ZnSe@ZnS core/shell quantum dots were synthesized by a facile aqueous phase route in the presence of additional glutathione ligand as a stabilizer and thiourea as a sulfur source. The structure and optical properties of the obtained ZnSe@ZnS nanocrystals were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, PL spectroscopy, and Fourier transform infrared spectrometer. The ZnSe@ZnS shows a cubic zinc-blende crystal phase and has a narrow size distribution. Experimental results indicate that the ZnS shell plays a pivotal role in determining optical features. With the reaction time from 0 to 3 h, the fluorescence emissions of ZnSe@ZnS nanocrystals are tunable between 372 and 380 nm. The high quantum yields are calculated to be in the range of 23%–62.8%. The mechanism for the resulting high-quality optical properties is also elucidated.