Full Spectrum Range Research Articles

Rare-Earth Metals-Doped Nickel Aluminate Spinels for Photocatalytic Degradation of Organic Pollutants

Visible-light-activated photocatalysts based on samarium-doped, europium-doped, and gadolinium-doped nickel aluminates (SmNA, EuNA, GdNA) were synthesized. The spinel crystalline structures of the doped mixed metal oxides were demonstrated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The presence of the rare-earth metals (REMs) was confirmed by the energy-dispersive X-ray (EDX) studies. Ultraviolet-visible-near-infrared (UV-Vis-NIR) spectra revealed that the REMs-doped catalysts absorb in the full solar spectrum range covering both visible and near infrared wavelengths. Scanning electron microscopy (SEM) visualized the profound morphological alterations of the doped nickel aluminate samples. Consequently, the pore volume and the Brunauer-Emmett-Teller (BET) surface area decreased, while nanoparticles sizes increased. Fourier-transform infrared spectroscopy (FTIR) exposed that surfaces of REMs-doped nickel aluminates are rich in hydroxyl groups. Finally, the photocatalytic performance was notably increased through doping nickel aluminate (NA) with REMs; the highest activity was observed for EuNA.

Fine-Tuning the Homometallic Interface of Au-on-Au Nanorods and Their Photothermal Therapy in the NIR-II Window.

The localized surface plasmon resonance (LSPR) of plasmonic nanomaterials is highly dependent on their structures. Going beyond simple shape and size, further structural diversification demands the growth of non-wetting domains. Now, two new dimensions of synthetic controls in Au-on-Au homometallic nanohybrids are presented: the number of the Au islands and the emerging shapes. By controlling the interfacial energy and growth kinetics, a series of Au-on-AuNR hybrid structures are successfully obtained, with the newly grown Au domains being sphere and branched wire (nanocoral). The structural variety allowed the LSPR to be fine-tuned in full spectrum range, making them excellent candidates for plasmonic applications. The nanocorals exhibit black-body absorption and outstanding photothermal conversion capability in NIR-II window. In vitro and in vivo experiments verified them as excellent photothermal therapy and photoacoustic imaging agents.

Fine‐Tuning the Homometallic Interface of Au‐on‐Au Nanorods and Their Photothermal Therapy in the NIR‐II Window

AbstractThe localized surface plasmon resonance (LSPR) of plasmonic nanomaterials is highly dependent on their structures. Going beyond simple shape and size, further structural diversification demands the growth of non‐wetting domains. Now, two new dimensions of synthetic controls in Au‐on‐Au homometallic nanohybrids are presented: the number of the Au islands and the emerging shapes. By controlling the interfacial energy and growth kinetics, a series of Au‐on‐AuNR hybrid structures are successfully obtained, with the newly grown Au domains being sphere and branched wire (nanocoral). The structural variety allowed the LSPR to be fine‐tuned in full spectrum range, making them excellent candidates for plasmonic applications. The nanocorals exhibit black‐body absorption and outstanding photothermal conversion capability in NIR‐II window. In vitro and in vivo experiments verified them as excellent photothermal therapy and photoacoustic imaging agents.

Characterization of chlorophyll fluorescence, absorbed photosynthetically active radiation, and reflectance-based vegetation index spectroradiometer measurements

ABSTRACT Spectroscopy plays a key role in Earth observations, especially for studies involving vegetation function and structure. These measurements are critical in the context of carbon cycle monitoring from leaf to global scales. Reflectance-based vegetation indices (RIs) have been used extensively in remote sensing studies from the unpiloted aerial vehicle, aerial, and space-based platforms to model quantities related to productivity, such as gross primary production (GPP), while more recently chlorophyll fluorescence (CF) measurements are increasingly exploited to track GPP. CF and RI measurements vary in magnitude, depend on different portions of the spectrum, and are derived from unique equations; thus, instrument uncertainty manifests distinctly for these measurements. Although this is well known, it is often unexamined in experiments and analyses. We use a portable spectroradiometer to make measurements of reflectance-based vegetation indices (RIs) and chlorophyll fluorescence (CF) in order to characterize how measurements of RIs and CF compare to one another. In particular, we examine fluorescence (F) and fluorescence yield (F Yield) under a light-emitting diode grow light (LED), solar-induced fluorescence (SIF), solar-induced fluorescence yield (SIFYield), absorbed photosynthetically active radiation (APAR), and reflectance-based vegetation indices (the normalized difference vegetation index (NDVI), the chlorophyll/carotenoid index (CCI), and the photochemical reflectance index (PRI)) and include maximized propagated uncertainty of the spectroradiometer for each measurement. We show that RIs have a significantly lower propagated error relative to the mean (0.01% to 0.28%) than CF measurements (0.01% to 1.28%) and that while fine resolution spectrometer CF measurements are outside the noise of the instrument and have potential to provide relative measurements of productivity, show why this instrument having fine spectral resolution and sampling is more effective for measurements of APAR and RIs. We also demonstrate that F and F Yield measurements have low propagated uncertainty and propose that future studies of plant function using this spectrometer/LED technique and the full range of spectra be undertaken. Finally, measurements of SIF, F, and APAR can provide estimates of SIFYieldand F Yield in the same order of magnitude, but further examination is required to determine how these measurements compare under a range of illumination and environmental conditions and how they might compare to PRI.

ATR-MIR Spectroscopy Predicts Total Phenolics and Colour for Extracts Produced by Microwave-Assisted or Conventional Thermal Extraction Methods Applied Separately to Mixtures of Grape Skins from White or Red Commercial Cultivars

Attenuated total reflectance mid-infrared (ATR-MIR) spectra were collected from 480 grape skin extracts produced in a wide range of conditions. The conditions were created at different phases in parallel response surface RS-optimisation experiments aiming to maximise the total phenolics in red and white grape skin extractions by microwave-assisted (MAE) or conventional thermal (CTE) methods. Skins mixtures for six white and six red Australian commercial cultivars were prepared from grapes collected at veraison and harvest. The total phenolics were measured for individual extracts with the Folin-Ciocalteu method. Partial least squares (PLS1) regression was employed on the spectra to predict the total phenolics (TP) and colour (CIELAB chroma C*) of individual extracts. Models based on the raw spectra and their second derivative (Savitzky-Golay, 20 points) were examined using the full range of spectra 4000–400 cm−1, and sub-ranges: 4000–1100 cm−1, 1500–400 cm−1, 1500–1100 cm−1 and 1457–1168 cm−1. The PLS1 models based on the second derivative of the range of 4000–1100 cm−1 provided the best results for both TP and C*, for each skin colour. Overall, the residual predictive deviation (RPD) exceeded 3.0, indicating the PLS1 models’ ability for fair classification, suitable for screening. A comparative analysis was performed for the range of 4000–1100 cm−1 between the spectra of white and red skin mixture extracts: the peaks at 3840 cm−1, 2940 cm−1, 2358 cm−1, 2197 cm−1, 2136 cm−1, 1725 cm−1, 1100 cm−1 and 1148 cm−1 are flagged to be investigated in further research. ATR-MIR spectroscopy can reduce the time and costs of TP and C* analyses in grape skin extracts.

Effect of Genetic Algorithm-Based Wavelength Selection as a Preprocessing Tool on Multivariate Simultaneous Determination of Paracetamol, Orphenadrine Citrate, and Caffeine in the Presence of p-Aminophenol Impurity.

The utilization of selection methods such as genetic algorithm (GA) aims to construct better partial least squares (PLS) and principal component regression (PCR) models than those established from the full-spectrum range. Determination of paracetamol (PAR), orphenadrine citrate (Or.cit), and caffeine (CAF) in the presence of PAR nephrotoxic impurity [p-aminophenol (PAP)]. GA was applied to select the optimum wavelengths used. A calibration set was prepared in which the three drugs, together with PAP, were modeled by multilevel multifactor design. This calibration set was used to build the PLS and PCR models, either with or without preprocessing the data using GA. Results were compared with and without preprocessing, and this revealed that GA can find an optimized combination of spectral wavelengths, yielding a lower root mean square error of prediction as well as a lower number of latent variables used. The results of the two models show that simultaneous determination of the aforementioned drugs can be performed in the concentration ranges of 20-60, 3-11, and 1-9 μg/mL for PAR, Or.cit, and CAF, respectively. The proposed models were applied for the determination of the three drugs in their pharmaceutical formulations, and the results were verified by the standard addition technique. GA can be useful as a wavelength selection tool before applying multivariate PLS and PCR methods. GA gives an improvement in the predictive ability of the models with lower RMSEP and less number of latent variables (LVs). The proposed PLS, PCR, GA-PLS, and GA-PCR spectrophotometric methods were able to determine paracetamol, orphenadrine citrate, and caffeine in the presence of p-aminophenol and severe spectral overlapping.

ERINS: Novel Sequence Insertion Detection by Constructing an Extended Reference.

Next generation sequencing technology has led to the development of methods for the detection of novel sequence insertions (nsINS). Multiple signatures from short reads are usually extracted to improve nsINS detection performance. However, characterization of nsINSs larger than the mean insert size is still challenging. This article presents a new method, ERINS, to detect nsINS contents and genotypes of full spectrum range size. It integrates the features of structural variations and mapping states of split reads to find nsINS breakpoints, and then adopts a left-most mapping strategy to infer nsINS content by iteratively extending the standard reference at each breakpoint. Finally, it realigns all reads to the extended reference and infers nsINS genotypes through statistical testing on read counts. We test and validate the performance of ERINS on simulation and real sequencing datasets. The simulation experimental results demonstrate that it outperforms several peer methods with respect to sensitivity and precision. The real data application indicates that ERINS obtains high consistent results with those of previously reported and detects nsINSs over 200 base pairs that many other methods fail. In conclusion, ERINS can be used as a supplement to existing tools and will become a routine approach for characterizing nsINSs.

Use of FTIR Spectroscopy and Chemometrics with Respect to Storage Conditions of Moldavian Dragonhead Oil

Oils often have similar properties and can be difficult to identify based on color, smell or taste alone. The present paper suggests the use of Fourier-transform infrared spectroscopy (FTIR) in combination with chemometric methods to explore similarities and differentiate between samples of Moldavian dragonhead oil subjected to different storage conditions. Dragonhead is a plant characterized by very good honey output and ease of cultivation. Principal component analysis (PCA) was applied to a standard, full range of FTIR spectra. Additionally, hierarchical cluster analysis (HCA) was employed to explore the organization of the samples in groups relative to their “proximity” (similarity), by way of Euclidean distance measurement. PC1 and PC2 accounted respectively for 85.4% and 10.1% of the total data variance. PC1 and PC2 were strongly, negatively correlated within the entire spectral range; the only exception was the region corresponding to νs(-C-Hvst, -CH2) vibrations (aliphatic groups in triglycerides), where PC2 was positively correlated. The use of FTIR spectral analysis revealed noticeable differences in the intensity of bands characteristic of the ageing processes (markers of oxidative processes, etc.) taking place in oleaginous samples and related to the processes of fatty acids oxidation.

Solar-Intensified Ultrafiltration System Based on Porous Photothermal Membrane for Efficient Water Treatment

Membrane separation is widely regarded as a promising technology for water treatment. To run the membrane at the optimal conditions, preheating of feedwater before being sent into the membrane unit is often employed, which results in high energy consumption. Here we report a multifunctional system that combines traditional pressure-driven membrane filtration with solar thermal technology based on a photothermal membrane for high-efficiency water treatment. The multifunctional membrane consists of multiwalled carbon nanotubes and polysulfone (MWCNT-PSf), which not only facilitates the water permeation through the membrane but also effectively heats the feed solution by sustainable solar energy. The composite membrane containing MWCNT demonstrates excellent light absorption of 94% over the full solar spectrum range, which can effectively preheat the feedwater. With the assistance of light irradiation, the MWCNT-PSf photothermal membrane exhibits high water flux over 314 L m–2 h–1 with a rejection above 95% ...

Near-unity, full-spectrum, nanoscale solar absorbers and near-perfect blackbody emitters

The design of sub-wavelength structure with full-spectrum near-unity solar absorption is a long-sought-after goal of crucial importance for optoelectronic materials and technology. To date, numerous attempts to tackle this problem consisted either of using stronger absorption-but narrowband or the broader spectrum-but moderate light trapping mechanisms. Herein, a novel strategy that achieves perfect absorption for solar energy in the full-spectrum range of the sun's radiance is presented by the thin-film refractory metal resonators. This impressive absorption mainly stems from the cooperative effect of strong plasmonic resonances and the intrinsic broadband spectral responses by the refractory metals, such as Ti, V, W, etc. The full-spectrum weighted solar absorption efficiency is exceeding 98%, showing a near-unity light trapping for the sun's radiation. Moreover, excellent thermal emitting with the spectral averaged efficiency ~ 91% is achieved in the wavelength range (280–4000 nm) by the W-based absorber, suggesting a platform for near-perfect blackbody emitting source. More importantly, the investigations on achieving full-spectrum solar absorbers and thermal emitters provide new insight on the mechanism and philosophy for the design. Just like the proverb, in order to catch bandits, the first thing is to catch the ringleader. As for the purpose of achieving full-spectrum near-unity absorbers or radiators, the key point is to perfectly trap or excite the solar/thermal power in the main distribution ranges for the sunlight or the blackbody radiation. Accordingly, these attractive properties and findings suggest that the investigation and the related full-spectrum solar absorbers and blackbody radiator might have promising applications in the fields related to energy harvesting and conversion.

Enhanced coupling of broadband light into amorphous silicon via periodic nanoplasmonic arrays**DISTRIBUTION STATEMENT A. Approved for public release: distribution unlimited. This material is based upon work supported by the Department of the Army under Air Force Contract No. FA8721-05-C-0002 and/or FA8702-15-D-0001. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily

Achieving enhanced coupling of solar radiation over the full range of the silicon absorption spectrum up to the bandgap is essential for increased efficiency of solar cells, especially thin film versions. While many designs for enhancing trapping of radiation have been explored, detailed measurements of light scattering inside silicon cells is still lacking. Here, we demonstrate experimentally and computationally that plasmonic-assisted localized and traveling modes can efficiently couple red and infrared radiation into ultrathin amorphous silicon (a-Si) layers. Utilizing patterned periodic arrays of aluminum nanostructures on thin a-Si, we perform specular and diffuse reflectivity and transmission measurements over a broad spectrum. Based on these results, we are able to separate parasitic absorption in aluminum plasmonic arrays from enhanced light absorption in the 200 nm thick amorphous silicon layer, as compared to a blank silicon layer. We discover a very efficient near-infrared a-Si absorption mechanism that occurs at the transition from the radiative to evanescent diffractive coupling, analogous to earlier surface-enhanced infrared studies. These results represent a direct demonstration of enhanced radiation coupling into silicon due to large angle scattering and show a path forward to improved ultrathin solar cell efficiency.

Realizing single-crystalline vertically-oriented and high-density electrospun nanofibril bundles by controlled postcalcination

For the first time, single-crystal (SC), vertically-oriented and high-density electrospun ultrafine nanofiber/fibre bundles (NFBs) were achieved by the controlled postcalcination of as-spun fibers. The formation of high-density SC strontium carbonate (i.e. SrCO3) nanoneedles (NNs) quasi-vertically grown with an average diameter of ∼20 nm, several micrometers long that stand perpendicular to the growth surface, is demonstrated. Furthermore, under electron-beam irradiation, an individual as-calcined SC SrCO3 NN undergoes sequential structural transitions from the [110] SC—to—polycrystalline—to—[102] SC SrCO3 NN, which was revealed by in situ transmission electron microscopy. Photoluminescence quenching over the full solar spectrum range was observed in the as-calcined vertically-oriented SrCO3 NFBs.

Detection of Early Rottenness on Apples by Using Hyperspectral Imaging Combined with Spectral Analysis and Image Processing

Detection of early rottenness on apples is still a challenging task for the automatic grading system due to the highly similarity between the rotten and sound tissues both in spectral and spatial domains. This research was conducted to develop an algorithm for detecting the early rottenness on apples by using hyperspectral reflectance imaging system combined with spectral analysis and image processing. In spectral domain, chemometric and pattern recognition methods were conducted for spectral analysis. In order to select the candidate optimal wavelengths that carry the most important information for distinguishing the rottenness from the sound tissues, successive projections algorithm (SPA) was conducted on the full range of average spectra extracted from the (regions of interest (ROIs) of sound and rotten tissues. The efficiency of the selected candidate optimal wavelengths for rottenness detection was also testified by using a binary particle least square discriminant analysis (PLS-DA) classifier in the spectral domain. In spatial domain, combined image processing methods were conducted for spatial analysis. In order to verify that the images at the optimal wavelengths were efficient and develop a robust detection algorithm, both principal component analysis (PCA) and minimum noise fraction (MNF) combined with conventional image processing methods were conducted on the images at the optimal wavelengths for image processing. Finally, the whole detection algorithm based on SPA-PLS-DA-MNF by using hyperspectral imaging combined with spectral analysis and image processing was designed and testified by the 120 testing apples. The results with 98 % overall detection accuracy indicated that the proposed algorithm was efficient and suitable for the rottenness apple detection. This research provides a foundational basis to develop the fast online inspection or real-time monitoring system for rottenness detection on apples both in the postharvest processing line or storage shelf.

Antireflective films with Si–O–P linkages from aqueous colloidal silica: Preparation, formation mechanism and property

The outdoor application of antireflective (AR) films requires not only high transmittance but also such mechanical properties as good abrasion-resistance, certain humidity resistance to resist the damage of the harsh environment. In the study, AR films with excellent performance were prepared by the dip-coating process in which aqueous colloidal silica (ACS) was used as the silica source and orthophosphoric acid as adhesion promoting agent. In the process of heat treatment of the films, the orthophosphoric acid in silica sols firstly transformed into the chain of metaphosphoric acid by the polycondensation reactions and then reacted with surface Si–OH groups from colloidal silica particles and the substrate, resulting in the formation of the numerous Si–O–P cross-linkings and 3SiO2·2P2O5 phase. Because colloidal silica particles were coated with 3SiO2·2P2O5 phase and linked by strong Si–O–P chemical bonds, abrasion-resistant property of films was markedly boosted. When the weight ratio of H3PO4 to silica sols was 2.71%, the pencil hardness grade of corresponding film had reached 6 H. Meanwhile, the average transmittance of the film in the visible spectrum was 97.9% and the weighted average transmittance (WAT) in the full spectrum range was as high as 97.2%, while that of the bare glass substrate was merely 89.6%. Moreover, the average transmittance still remained at around 97.9% after having been soaked in tap water for 30 days.

Non-destructive measurement of total soluble solid (TSS) content of dates using near infrared (NIR) imaging

The total soluble solid (TSS) content is one of the important quality attributes that determines the commercial value of dates. At present, TSS content in dates is measured using destructive techniques that are laborious and time consuming. In this study, the potential of a near infrared (NIR) imaging technique to determine TSS content of dates was evaluated. Date samples of three cultivars (Fardh, Khalas and Naghal) at tamar stage (n=400 fruits) and two ripening stages (tamar and khalal) of Khalas cv. (n=400 fruits) were used in this study. The area scan NIR camera which covers the full spectrum range of 900‒1,700 nm was used to capture the images of individual date fruits. Immediately following image acquisition, the TSS content (ºBrix) of each sample was measured using a digital refractometer. The TSS content of dates was in the range of 34‒63° Brix and 14‒37°Brix for tamar and khalal stages, respectively. Similarly, the percentage of NIR reflectance was 12‒38 and 39‒64 for tamar and khalal stages, respectively. A multiple linear regression (MLR) prediction model along with a dummy variable concept was established between measured TSS and NIR reflectance. NIR reflectance was inversely proportional to the TSS content of dates. The correlation coefficient (r) between TSS content and NIR reflectance was 0.62 and 0.98 for three cultivars and two ripening stages, respectively. The high correlation among ripening stages indicates the opportunities of NIR technique for potential applications in influencing ripening stages. However, further work is warranted to determine the correlation between TSS and NIR reflectance in different ripening stages of other cultivars.

Two-dimensional subpicosecond time-resolved fluorescence anisotropy: Optical Kerr-gating with the excitation of alternating polarizations of light

We have developed a subpicosecond time-resolved fluorescence anisotropy (TRFA) that newly implements a photoelastic modulator to alternate the polarizations of an excitation laser light. The setup facilitates virtually simultaneous detection of the parallel I∥ and the perpendicular I⊥ emission from a photoexcited molecule of interest by means of an ultra-short (optical Kerr-gating) shutter and a spectrograph coupled with a charge-coupled device. From a set of I∥(λ,t) and I⊥(λ,t) that comprise 2-D (two-dimensional) information on both a full range of spectra and subpicosecond time-resolved fluorescence decays, the 2-D TRFA, R(λ,t), is directly given with better accuracy. To claim the merit of the technique we carried out a test for 2-D TRFA of Coumarin 153 in methanol.

The effect of spatial frequency on perceptual learning of inverted faces

We investigated the efficacy of training adults to recognize full spectrum inverted faces presented with different viewpoints. To examine the role of different spatial frequencies in any learning, we also used high-pass filtered faces that preserved featural information and low-pass filtered faces that severely reduced that featural information. Although all groups got faster over the 2 days of training, there was more improvement in accuracy for the group exposed to full spectrum faces than in the two groups exposed to filtered faces, both of which improved more modestly and only when the same faces were shown on the 2 days of training. For the group exposed to the full spectrum range and, to a lesser extent, for those exposed to high frequency faces, training generalized to a new set of full spectrum faces of a different size in a different task, but did not lead to evidence of holistic processing or improved sensitivity to feature shape or spacing in inverted faces. Overall these results demonstrate that only 2h of practice in recognizing full-spectrum inverted faces presented from multiple points of view is sufficient to improve recognition of the trained faces and to generalize to novel instances. Perceptual learning also occurred for low and high frequency faces but to a smaller extent.

Simultaneous determination of acesulfame-K, aspartame and stevioside in sweetener blends by ultraviolet spectroscopy with variable selection by sipls algorithm

A chemometric-assisted UV absorption spectroscopic method is proposed for the simultaneous determination of acesulfame-K, aspartame and stevioside in raw powder mixtures of commercial sweeteners. The synergy interval partial least squares (siPLS) algorithm was applied to select the optimum spectral range and their combinations. The utilization of spectral region selection aims to construct better partial least squares (PLS) model than that established from the full-spectrum range. The results show that the siPLS algorithm can find out an optimized combination of spectral regions, yielding lower relative standard error of prediction (RSEP) and root mean square error of prediction (RMSEP), as well as simplifying the model. The RMSEP and RSEP obtained after selection of intervals by siPLS were 0.1330 μg·ml–1 and 1.50 % for acesulfame-K, 0.2540 μg·ml–1 and 1.64 % for aspartame, 1.4041 μg·ml–1 and 2.03 % for stevioside respectively. The recovery values range from 98.12 % to 101.88 % for acesulfame-K, 98.63 % to 102.96% for aspartame, and 96.38 % to 104.04 % for stevioside respectively.

High resolution full-spectrum water Raman lidar

Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study. For this purpose, we have developed a high resolution full-spectrum water Raman lidar that can collect Raman signals from ice, water droplets and water vapor simultaneously. A double-grating polychromator and a 32-channel photomultiplier-tube detector are used to obtain a spectral resolution of ∼0.19 nm in the full Raman spectrum range of water. Preliminary observations present the water Raman spectrum characteristics of both the mixed-phase cloud and humid air under cloudless condition.

Imaging high-frequency periodic motion in the mouse ear with coherently interleaved optical coherence tomography

Vibratory measurements of the structures of the ear are key to understanding much of the pathology in mouse models of hearing loss. Unfortunately the high-speed sampling required to interrogate the high end of the mouse hearing spectrum is beyond the reach of most optical coherence tomography (OCT) systems. To address this issue, we have developed an algorithm that enables phase-sensitive OCT measurements over the full range of the mouse hearing spectrum (4-90 kHz). The algorithm phase-locks the line-trigger to the acoustic stimulation and then uses interleaved sampling to reconstruct the signal with higher temporal sampling. The algorithm was evaluated by measuring the vibratory response of mouse tympanic membrane to a pure tone stimulus.