High Absorption Cross Section Research Articles

Niobium nitride plasmonic perfect absorbers for tunable infrared superconducting nanowire photodetection.

Quantum technologies such as quantum computing and quantum cryptography exhibit rapid progress. This requires the provision of high-quality photodetectors and the ability to efficiently detect single photons. Hence, conventional avalanche photodiodes for single photon detection are not the first choice anymore. A better alternative are superconducting nanowire single photon detectors, which use the superconducting to normal conductance phase transition. One big challenge is to reduce the product between recovery time and detection efficiency. To address this problem, we enhance the absorption using resonant plasmonic perfect absorber effects, to reach near-100% absorption over small areas. This is aided by the high resonant absorption cross section and the angle insensitivity of plasmonic resonances. In this work we present a superconducting niobium nitride plasmonic perfect absorber structure and use its tunable plasmonic resonance to create a polarization dependent photodetector with near-100% absorption efficiency in the infrared spectral range. Further we fabricated a detector and investigated its response to an external light source. We also demonstrate the resonant plasmonic behavior which manifests itself through a polarization dependence detector response.

One/two-photon sensitive sulfonium salt photoinitiators based on 1,3,5-triphenyl-2-pyrazoline

Three 1,3,5-triphenyl-2-pyrazoline-based sulfonium salt photoinitiators (PIs) were synthesized, and the relationship between their molecular structures and photophysical and photochemical properties under one/two-photon irradiation were presented. The sulfonium salts had absorption peaks from 343 nm to 372 nm that overlapped the emission of 365–425 nm light-emitting diode (LED) light sources. The energy levels of molecular orbitals were closely related to the quantum yield of photoacid generation (ΦH+) as determined by the electrochemical and absorption properties of the PIs, and the introduction of an electron-pushing group could increase ΦH+ due to the enlarged energy gap between the singlet excited states S1 and S2. Interestingly, the wavelength dependence of ΦH+ was due to the nature of the transition. The π–π* transition showed high ΦH+ values (0.56–0.66) under excitation by UV LEDs, while the π–σ* transition showed low efficiency under visible LED irradiation. Intramolecular charge transfer from the pyrazoline ring to sulfonium salts induced efficient photolysis and high ΦH+. The sulfonium salts could efficiently initiate cationic polymerization and free radical polymerization. In addition, their high two-photon absorption cross-sections (δ780 nm = 75–105 GM) reduced the threshold of two-photon microfabrication. These PIs should have potential in LED photocuring and two-photon 3D microfabrication.

Performance and economic assessment of enriched gadolinia burnable absorbers

As a burnable absorber, gadolinium oxide (Gd2O3) is widely used in light water reactors due to the high neutron absorption cross section of several gadolinium isotopes and its good solid solubility in UO2. However, some isotopes of natural Gd cause residual reactivity suppression, while some are not efficient neutron absorbers, reducing the efficiency of the burnable absorber when implemented. In this study, fuel assemblies utilizing gadolinium oxide enriched with 157Gd isotope were modelled using Monte Carlo particle transport methods and compared to fuel with a natural Gd based absorber. Reactivity gains were examined over the life of the assembly utilizing 157Gd-enriched absorber as compared to natural gadolinia. A preliminary economic evaluation is also made to assess the commercial benefits of using 157Gd-enriched burnable absorber. Use of enriched gadolinium oxide is shown to eliminate residual reactivity caused by natural gadolinium oxide, and similar reactivity properties (and therefore criticality margins) can be achieved with less burnable absorber in the fuel. The financial cost of incorporating enriched Gd isotopes into nuclear fuel has also been estimated.

Extreme ultraviolet photoemission of a tin-based photoresist

Tin is a suitable element for inclusion in extreme ultraviolet photoresists because of its relatively high-absorption cross section at 92 eV. The electrons emitted after photon absorption are expected to generate secondary electrons in the solid film. In this way, several pathways lead to reactive species that cause a solubility switch. Here, we report the photoelectron spectra of tin oxo cage photoresists over the photon energy range 60–150 eV, and the relative yields of photoelectrons from the valence band of the resist, from the Sn 4d orbitals, and of inelastically scattered electrons. The experimental excitation spectra differ considerably from those predicted by commonly used database cross section values, and from the combined computed subshell spectra: the maximum efficiency of ionization of Sn 4d both in the photoresists and in Sn metal occurs near the industrially relevant EUV wavelength of 13.5 nm.

Croconaine-based nanoparticles enable efficient optoacoustic imaging of murine brain tumors

Contrast enhancement in optoacoustic (photoacoustic) imaging can be achieved with agents that exhibit high absorption cross-sections, high photostability, low quantum yield, low toxicity, and preferential bio-distribution and clearance profiles. Based on advantageous photophysical properties of croconaine dyes, we explored croconaine-based nanoparticles (CR780RGD-NPs) as highly efficient contrast agents for targeted optoacoustic imaging of challenging preclinical tumor targets. Initial characterization of the CR780 dye was followed by modifications using polyethylene glycol and the cancer-targeting c(RGDyC) peptide, resulting in self-assembled ultrasmall particles with long circulation time and active tumor targeting. Preferential bio-distribution was demonstrated in orthotopic mouse brain tumor models by multispectral optoacoustic tomography (MSOT) imaging and histological analysis. Our findings showcase particle accumulation in brain tumors with sustainable strong optoacoustic signals and minimal toxic side effects. This work points to CR780RGD-NPs as a promising optoacoustic contrast agent for potential use in the diagnosis and image-guided resection of brain tumors.

Ultrahigh mid-infrared electric field enhancement via nanoantenna plasmonic resonance coupled to a novel hyperbolic metalens

Concentrating optical energy to areas much smaller than the diffraction limit, with high field enhancement in mid-infrared (MIR) using noble metals such as gold (Au) or silver (Ag), is not feasible because of high losses, lack of tunability, low resolution, and low-intensity enhancement. Our methods are based on appropriate metamaterial selection, coupling system (a hyperbolic metalens and a nanoantenna), and optimizations of their geometries. Doped indium arsenide (InAs) is used as an alternative to plasmonic metals when designing a Fresnel zone plate (FZP). A hyperbolic metamaterial (HMM), placed under FZP, is formed by stacking layers of doped and undoped InAs. By combining the focal spot of the metalens with the excited plasmons of a nanoantenna, the resulting structure exhibits an ultrahigh field-intensity enhancement factor of about 1012 with a high absorption cross-section and a focusing resolution of up to 10−3 λ at the operating wavelength of 7.8 μm.

Numerical assessment of transition metal nitrides nanofluids for improved performance of direct absorption solar collectors

Abstract Metallic nanostructures have attracted the attention for solar applications due to their high optical absorption cross-section, which is associated to the localized surface plasmon resonances phenomenon. In this work, the thermo-optical performance of a direct absorption solar collector using working-fluids composed of TiN, ZrN, and HfN nanospheres in an aqueous medium was evaluated using Mie theory and numerical solutions of a two-dimensional heat transfer model. The influence of nanoparticle size, volume fraction, collector height, and working-fluid temperature for the collector thermal and exergy efficiencies was investigated. Results revealed the transition metal nitrides nanoparticles have small scattering cross-sections and broad absorption peaks, matching well the solar radiation spectrum. The thermal efficiency is higher than 80% for collectors with all three nitrides nanoparticles. The collectors using TiN, ZrN, and HfN nanofluids exhibit thermal performance 50.4%, 36.5%, and 41.8%, respectively, higher than with Au nanofluid, which is a reference plasmonic material for solar applications. Moreover, collectors using transition metal nitrides reach higher outlet temperatures than with gold, leading to higher exergy efficiencies with low volume fraction. The maximum exergy efficiencies of DASC using TiN, ZrN, and HfN NF are 6.3%, 5.2%, and 5.6%, respectively, while using Au NF is 2.9%. The superior performance in a low-concentration regime allows the application of nanoparticles in the collector without increasing the required pumping work. The findings related to the photo-thermal efficiencies of transition metal nitride nanofluids, in addition to their low cost and high chemical stability, make them suitable to use for solar-related heating technologies.

Determination of boron in in-house graphite reference material by instrumental charged particle activation analysis

Due to high thermal neutron absorption cross-section, boron (B) content is a binding specification for nuclear grade graphite. Reliable analytical methods are essential to determine boron at trace to ultra-trace levels. Analytical Chemistry Division, Bhabha Atomic Research Centre, India has prepared an in-house graphite reference material (GRM). A Charged particle activation analysis methodology has been developed for quantification of B in graphite matrix. Detection limit for boron using this methodology is 1.4 mg kg−1. This in-house GRM can be used for quantification of B in unknown graphite samples, validating existing analytical methods and for the development of new analytical methods.

Transparent glass-ceramics based on Co2+-doped γ-GaxAl2−xO3 spinel nanocrystals for passive Q-switching of Er lasers

Transparent glass-ceramics (GCs) based on Co2+-doped γ-GaxAl2−xO3 spinel nanocrystals were developed in the lithium aluminogallosilicate glass system with TiO2 as a nucleating agent. The initial glass contains spinel nanocrystals with sizes less than 3 nm. Secondary heat-treatments in the temperature range of 680–800 °C result in fabrication of transparent GCs based on γ-GaxAl2−xO3 crystals enriched in aluminum with cubic spinel structure (sp. gr. Fd3m) and a mean size up to 5.5 nm. At higher temperatures, GCs become translucent and then opaque due to additional crystallization of lithium aluminosilicate solid solutions (ss) with β-quartz structure and lithium aluminogallium silicate ss with β-spodumene (keatite) structure. The introduction of gallium oxide improves the temperature stability of spinel crystals that are not decomposed at high heat-treatment temperatures when aluminosilicate crystals evolve. The Co2+ ions in GCs enter the spinel crystals predominantly in tetrahedral sites. Transparent GCs feature broadband absorption (1.15–1.7 μm) owing to the 4A2(4F) → 4T1(4F) transition of IVCo2+ species in spinel nanocrystals. They exhibit saturable absorption and high ground-state absorption (GSA) cross-section σGSA of 3.1 ± 0.4 × 10−19 cm2 at 1.54 μm. Glass-ceramic based on γ-GaxAl2−xO3 crystals is employed as a saturable absorber of an eye-safe diode-side-pumped Er3+,Yb3+:glass laser delivering 1.1 mJ/42 ns pulses at 1535 nm.

Noble Metal Nanomaterials for NIR-Triggered Photothermal Therapy in Cancer.

It is of great significance to develop anticancer therapeutic agents or technologies with high degree of specificity and patient compliance, while low toxicity. The emerging photothermal therapy (PTT) has become a new and powerful therapeutic technology due to its noninvasiveness, high specificity, low side effects to normal tissues and strong anticancer efficacy. Noble metal nanomaterials possess strong surface plasmon resonance (SPR) effect and synthetic tunability, which make them facile and effective PTT agents with superior optical and photothermal characteristics, such as high absorption cross-section, incomparable optical-thermal conversion efficiency in the near infrared (NIR) region, as well as the potential of bioimaging. By incorporating with various functional reagents such as antibodies, peptides, biocompatible polymers, chemo-drug and immune factors, noble metal nanomaterials have presented strong potential in multifunctional cancer therapy. Herein, the recent development regarding the application of noble metal nanomaterials for NIR-triggered PTT in cancer treatment is summarized. A variety of studies with good therapeutic effects against cancer from impressive photothermal efficacy of noble metal nanomaterials are concluded. Intelligent nanoplatforms through ingenious fabrication showing potential of multifunctional PTT, combined with chemo-therapy, immunotherapy, photodynamic therapy (PDT), as well as simultaneous imaging modality are also demonstrated.

Synthesis and Characterization of a Carborane-containing Precursor for B<sub>4</sub>C Ceramics

B₄C ceramic is one of widely used ceramics with properties of low density, high hardness, high thermal-stability and high neutron absorption cross-section. However, the high melting point and high hardness of B₄C make it difficult to be prepared as materials with complex shape. Precursor derived method is an effective approach to prepare special-shaped ceramics. In the early research of B₄C ceramic precursors, highly toxic and unstable decaborane was generally used as the boron source material, and precursors were also unstable and difficult to synthesize. In this work, a new B₄C precursor is designed and synthesized, and m-carborane, which has stable chemical properties and high thermal stability, is used as the boron source. Firstly, m-carborane is converted into lithium salt after removing active hydrogen by n-butyllithium. Then, catalyzed by Cu(I), the lithium salt reacts with m-chloroiodobenzene so that monomer, bis(3-chlorophenyl)-m-carborane, is prepared. The monomer is polymerized through Ullmann Coupling reaction at the present of Ni(0) catalyst and Zinc powder, and precursor poly[bis(3-chlorophenyl)-m-carborane] is finally synthesized. The precursor is stable at room temperature in air and soluble in Tetrahydrofuran, with Mw of 1013g/mol, and ceramic yield of 62.20% at 900°C in N₂. The precursor pyrolytic product is composed of B₄C and graphite after heat treated at 1600°C in inert atmosphere.

Diagnosis of fatty liver disease by a multiphoton-active and lipid-droplet-specific AIEgen with nonaromatic rotors

We present a two-photon AIEgen, ABCXF with nonaromatic rotors (–CF3), a high two-photon absorption cross-section, bright red emission in the solid-state, and remarkably high photostability for fatty liver disease diagnosis.

CRITICALITY SAFETY ANALYSIS OF GBC-32 SPENT FUEL CASK WITH IMPROVED NEUTRON ABSORBER CONCEPT

Higher enrichment of nuclear fuel along the manufacturing limit of boron content in steel and aluminum alloys represents a significant challenge in designing spent fuel transport and storage facilities. One possible solution for spent fuel pools and casks is the burnup credit method that allows for decreasing very high safety margins associated with fresh fuel assumption in spent fuel facilities. An alternative solution based on placing neutron absorber material directly into the fuel assembly is proposed here. A neutron absorber permanently fixed in guide tubes decreases system reactivity more efficiently than absorber sheets between the assemblies. The efficiency of the newly proposed concept is demonstrated on the criticality safety analysis of the GBC-32 spent fuel cask. Absorber rods from 8 different elements are placed within Westinghouse OFA 17x17 guide tubes. Currently used boron is a good option because of high absorption cross section, low atomic mass and chemical compatibility with various alloys. Alternative options (e.g., Sm, Eu, Gd, Dy, Hf, Re, Ir) are based on very good absorbers that do not require alloy compatibility since the absorbers can be placed inside zirconium or steel cladding. Because of high efficiency of the newly proposed absorber concept, boron content in BORAL sheets can be decreased to more competitive economics. Moreover, fuel assembly pitch is investigated in order to change cask wall inner diameter that will result in lower material consumption for the cask wall with the same shielding thickness.

A dual-channel incoherent broadband cavity-enhanced absorption spectrometer for sensitive atmospheric NOx measurements.

We describe and characterize a dual-channel incoherent broadband cavity-enhanced absorption spectrometer (DC-IBBCEAS) for the sensitive measurements of NOx: the sum of nitrogen monoxide (NO) and nitrogen dioxide (NO2) in the atmosphere. The instrument employs two 1 m long optical cavities, with air being extracted from a common sampling line. The first channel (cavity-1) spans 340-380 nm and the second channel (cavity-2) spans the 405-460 nm spectral range, both measuring NO2 simultaneously. High absorption cross-sections of NO2 in both channels are effectively utilized for its sensitive quantification. NO is quantified by titrating it with ozone to NO2 in channel-2, where the difference of NO2 measured from that in channel-1 corresponds to the NO concentration in the sampled air. The instrument offers 1-ppb detection sensitivity for both NO and NO2 with a maximum possible uncertainty of ∼9%. The use of close yet different spectral regions in the two channels readily extended measurements to a broader range without compromising its sensitivity to NOx quantification. This would extend the DC-IBBCEAS applicability to simultaneously monitor interfering species with significant absorption cross-sections in the region in either channel, such as glyoxal (CHOCHO), methylglyoxal (CH3COCHO), and nitrous acid (HONO).

AIE-nanoparticle assisted ultra-deep three-photon microscopy in thein vivomouse brain under 1300 nm excitation

Here we present organic AIE nanoparticles that feature high absorption cross-section under NIR-IIa three-photon excitation, which enables ultra-deep three-photon fluorescence imaging in thein vivomouse brain.

Mixed-dimensional CsPbBr3@ZnO heterostructures for high-performance p-n diodes and photodetectors

Mixed one-dimensional (1D) and three-dimensional (3D) heterostructures, with synergistic advantages of different dimensionalities, have shown unique optical properties due to their large junction areas and high absorption cross-sections, which may also bring superior electrical and optoelectronic performances. However, due to the challenge in designing and constructing a proper 1D-3D p-n junction, their electronic properties and potential application are still unclear. Here, a type of 1D-3D ZnO/CsPbBr3 p-n junction is constructed by liquid-phase growth of crystalline CsPbBr3 microplates on ZnO nanowires, which exhibit excellent properties of p-n diode and serve as high-performance rectifier and photodetector. As a rectifier, it shows characteristics of ambipolar transfer and its rectification ratio reaches up to 106. As a photodetector, it covers light from ultraviolet to visible light. High photoelectric switching ratio (107), responsivity (3.5 × 103 A/W), detectivity (6.6 × 1013 Jones) and external quantum efficiency (1.7 × 106%) are obtained under 254 nm light illumination. Meanwhile, the switching ratio, responsivity, detectivity and external quantum efficiency are 103, 41.5 A/W, 4.96 × 1012 Jones and 1.086 × 103%, respectively, under 473 nm laser illumination. The decay length of photo-generated carriers in ZnO/CsPbBr3 heterojunction is demonstrated longer than that in original CsPbBr3 crystal, which is further controlled by adjusting the potential barriers between the CsPbBr3 and ZnO with a tunable external electric field.

Water Triggered Synthesis of Highly Stable and Biocompatible 1D Nanowire, 2D Nanoplatelet, and 3D Nanocube CsPbBr3 Perovskites for Multicolor Two-Photon Cell Imaging.

Two-photon imaging in the near-infrared window holds huge promise for real life biological imaging due to the increased penetration depth. All-inorganic CsPbX3 nanocrystals with bright luminescence and broad spectral tunability are excellent smart probes for two-photon bioimaging. But, the poor stability in water is a well-documented issue for limiting their practical use. Herein, we present the development of specific antibody attached water-resistant one-dimensional (1D) CsPbBr3 nanowires, two-dimensional (2D) CsPbBr3 nanoplatelets, and three-dimensional (3D) CsPbBr3 nanocubes which can be used for selective and simultaneous two-photon imaging of heterogeneous breast cancer cells in the near IR biological window. The current manuscript reports the design of excellent photoluminescence quantum yield (PLQY), biocompatible and photostable 1D CsPbBr3 nanowires, 2D CsPbBr3 nanoplatelets, and 3D CsPbBr3 nanocubes through an interfacial conversion from zero-dimensional (0D) Cs4PbBr6 nanocrystals via a water triggered strategy. Reported data show that just by varying the amount of water, one can control the dimension of CsPbBr3 perovskite crystals. Time-dependent transition electron microscopy and emission spectra have been reported to find the possible pathway for the formation of 1D, 2D, and 3D CsPbBr3 nanocrystals from 0D Cs4PbBr6 nanocrystals. Biocompatible 1D, 2D, and 3D CsPbBr3 nanocrystals were developed by coating with amine–poly(ethylene glycol)–propionic acid. Experimental data show the water-driven design of 1D, 2D, and 3D CsPbBr3 nanocrystals exhibits strong single-photon PLQY of ∼66–88% as well as excellent two-photon absorption properties (σ2) of ∼8.3 × 105–7.1 × 104 GM. Furthermore, reported data show more than 86% of PL intensity remains for 1D, 2D, and 3D CsPbBr3 nanocrystals after 35 days under water, and they exhibit excellent photostability of keeping 99% PL intensity after 3 h under UV light. The current report demonstrates for the first time that antibody attached 1D and 2D perovskites have capability for simultaneous two-photon imaging of triple negative breast cancer cells and human epidermal growth factor receptor 2 positive breast cancer cells. CsPbBr3 nanocrystals exhibit very high two-photon absorption cross-section and good photostability in water, which are superior to those of commonly used organic probes (σ2 = 11 GM for fluorescein), and therefore, they have capability to be a better probe for bioimaging applications.

Near-infrared Opacity of Late M Dwarfs and Hot Jupiters: The E3Π–X3Δ Transition of TiO

Abstract The TiO E 3Π–X 3Δ transition is an important opacity source in the near-infrared spectra of late M dwarfs. The 0–0 band of the 48Ti16O E 3Π–X 3Δ electronic transition has been reanalyzed using a recently published set of high-resolution, high temperature absorption cross sections. The analysis has been extended to higher J values and an improved set of spectroscopic constants were determined. Calculated high-precision line lists for the 0–0 and 0–1 bands are provided with line strengths based on a previously measured experimental lifetime.

Crystal growth and spectroscopic characterization of Dy3+:Sr3Gd2(BO3)4 - A potential yellow solid state laser material

Abstract A transparent crystal of Dy-doped Sr3Gd2(BO3)4 was successfully grown by Czochralski (Cz) method. Polarized absorption and fluorescence spectra, and fluorescence decay curve with special attention to the yellow emission have been measured at room temperature. The crystal has a relatively high absorption cross section of 1.02 × 10−21 cm2 (E//c) at 453 nm with a full width at half maximum (FWHM) of 10 nm (E//c). The Judd-Ofelt parameters Ω2, Ω4 and Ω6 were calculated to be 4.16, 1.94 and 2.63, respectively. The emission cross-section corresponding to the 4F9/2 → 6H13/2 transition at 576 nm is 3.75 × 10−21 cm2 (E//c) with a FWHM of 14 nm. The fluorescence time of the 4F9/2 → 6H13/2 transition is 0.411 ms while the radiative lifetime is 0.995 ms, so the crystal has a quantum efficiency of 41.3%. The results mean that the Dy3+:Sr3Gd2(BO3)4 crystal is a kind of potential solid state yellow laser material.

Directed Energy Transfer from Monolayer WS2 to Near-Infrared Emitting PbS-CdS Quantum Dots.

Heterostructures of two-dimensional (2D) transition metal dichalcogenides (TMDs) and inorganic semiconducting zero-dimensional (0D) quantum dots (QDs) offer useful charge and energy transfer pathways, which could form the basis of future optoelectronic devices. To date, most have focused on charge transfer and energy transfer from QDs to TMDs, that is, from 0D to 2D. Here, we present a study of the energy transfer process from a 2D to 0D material, specifically exploring energy transfer from monolayer tungsten disulfide (WS2) to near-infrared emitting lead sulfide–cadmium sulfide (PbS–CdS) QDs. The high absorption cross section of WS2 in the visible region combined with the potentially high photoluminescence (PL) efficiency of PbS QD systems makes this an interesting donor–acceptor system that can effectively use the WS2 as an antenna and the QD as a tunable emitter, in this case, downshifting the emission energy over hundreds of millielectron volts. We study the energy transfer process using photoluminescence excitation and PL microscopy and show that 58% of the QD PL arises due to energy transfer from the WS2. Time-resolved photoluminescence microscopy studies show that the energy transfer process is faster than the intrinsic PL quenching by trap states in the WS2, thus allowing for efficient energy transfer. Our results establish that QDs could be used as tunable and high PL efficiency emitters to modify the emission properties of TMDs. Such TMD-QD heterostructures could have applications in light-emitting technologies or artificial light-harvesting systems or be used to read out the state of TMD devices optically in various logic and computing applications.