Ultraviolet-visible-near Infrared Research Articles

Photoluminescence Properties of CaO-BaO-P<sub>2</sub>O<sub>5</sub> Glass Systems Doped with Sm<sup>3+</sup>

This paper reports on physical, optical and photoluminescence properties of Sm3+doped calcium barium phosphate (CaO: BaO: P2O5: Sm2O3) glass systems. The glass samples have been prepared by the melt-quenching technique at 1200°C. It was found that the density of glasses tended to increase with increasing of Sm2O3 concentration. While, the molar volume of glasses tended to decrease with increasing of Sm2O3 concentration higher than 0.1 mol%. The absorption spectra of glasses were recorded in the ultraviolet visible near infrared (UV-Vis-NIR) region. The absorption bands centered at 374, 402, 416, 438, 473, 527, 946, 1083, 1236, 1382, 1483, 1531 and 1977 nm, respectively have been observed. The emission spectra of glass samples centered at 561, 597, 643 and 704 nm corresponding to the energy levels from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively have been observed with 402 nm excitation wavelength.

α-Substituted Bis(octabutoxyphthalocyaninato)Terbium(III) Double-Decker Complexes: Preparation and Study of Protonation by NMR and DFT.

Synthesis of the anionic, α-substituted, bis(phthalocyaninato)Tb(III) complex [Tb(α-obPc)2](-) ([1](-)) (obPc = α-octabutoxyphthalocyaninato) leads to the isolation of its protonated form [1H](0). This complex was characterized by X-ray diffraction (XRD), mass spectroscopy (MS), infrared (IR) and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy. Crystal structure analysis did not allow localization of the additional proton, which is probably attached to the meso-N atom or isoindole-N atom of the phthalocyaninato ligand. [1H](0) can easily be deprotonated or protonated, giving the corresponding anionic and cationic complexes. The three compounds [1H](0), [1](-), and [1HH](+) were studied by a combination of paramagnetic NMR experiments ((1)H, (13)C, variable-temperature measurements, two-dimensional nuclear magnetic resonance and DFT calculations (done on Y(III) analogues with octamethoxyphthalocyaninato ligands), for the purpose of elucidating the positions of the acidic protons and for understanding the structural changes of the coordination environment of the Tb ion induced by protonation.

Porous Silicon Covered with Silver Nanoparticles as Surface-Enhanced Raman Scattering (SERS) Substrate for Ultra-Low Concentration Detection.

Microporous and macro-mesoporous silicon templates for surface-enhanced Raman scattering (SERS) substrates were produced by anodization of low doped p-type silicon wafers. By immersion plating in AgNO3, the templates were covered with silver metallic film consisting of different silver nanostructures. Scanning electron microscopy (SEM) micrographs of these SERS substrates showed diverse morphology with significant difference in an average size and size distribution of silver nanoparticles. Ultraviolet-visible-near-infrared (UV-Vis-NIR) reflection spectroscopy showed plasmonic absorption at 398 and 469 nm, which is in accordance with the SEM findings. The activity of the SERS substrates was tested using rhodamine 6G (R6G) dye molecules and 514.5 nm laser excitation. Contrary to the microporous silicon template, the SERS substrate prepared from macro-mesoporous silicon template showed significantly broader size distribution of irregular silver nanoparticles as well as localized surface plasmon resonance closer to excitation laser wavelength. Such silver morphology has high SERS sensitivity that enables ultralow concentration detection of R6G dye molecules up to 10(-15) M. To our knowledge, this is the lowest concentration detected of R6G dye molecules on porous silicon-based SERS substrates, which might even indicate possible single molecule detection.

Synthesis of CuIn<I><SUB>1-x</SUB></I>Ga<I><SUB>x</SUB></I>Se<SUB>2</SUB> Nanoparticles by Thermal Decomposition Method with Tunable Ga Content

Chalcopyrite Culn(1-x)Ga(x)Se2 (CIGS) nanoparticles were synthesized by mixing copper (I) chloride (CuCl), Indium (III) chloride (InCl3), gallium (III) chloride (GaCl3) and selenium (Se) in oleylamine (OLA) at 260 degrees C for 4 h under nitrogen atmosphere. The Ga/(In+ Ga) ratio was tuned across the entire stoichiometric range from 0 to 1. X-ray diffraction analysis (XRD) revealed chalcopyrite crystal structure for samples prepared with x = 0, 0.3, 0.5, 0.7 and 1. The lattice parameters a and c decreased linearly with increasing Ga concentration which is consistent with Vegard's law. Raman spectra exhibited A, optical phonon vibrational mode for synthesized nanoparticles which gradually shifted to higher wavenumber with increasing Ga content. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images showed irregular as well as hexagonal plate like morphologies in the size range of 100 to 400 nm. High-resolution transmission electron microscopy (HR-TEM) images showed well-defined lattice fringes and d-spacing correspond to (112) plane which gradually decreases with increasing Ga content. The material compositions of synthesized CIGS nanoparticles with x = 0, 0.3, 0.5, 0.7 and 1 were very close to the desired stoichiometry which was confirmed by energy dispersive X-ray analysis (EDAX). Ultraviolet visible near infrared (UV-VIS-NIR) absorption spectra of the synthesized CIGS nanoparticles revealed that the bandgap could be tuned over the range 1 to 1.7 eV by varying the Ga/(In+Ga) ratio.

Optical Properties of Multi-layer TiNO/AlCrNO/Al Cermet Films Using DC Magnetron Sputtering

Among many the oxynitrides, TiNO and AlCrNO, have diverse applications in different technological fields. We prepared TiNO/AlCrNO/Al thin films on aluminum substrates using the method of dc reactive magnetron sputtering. The reactive gas flow, gas mixture, and target potential were applied as the sputtering conditions during the deposition in order to control the chemical composition. The multi-layer films have been prepared in an Ar and O₂+N₂ gas mixture rate. The surface properties were estimated by performing scanning electron microscopy (SEM). At a wavelength range of 0.3~2.5 μm, the exact composition and optical properties of thin films were measured by Auger electron spectroscopy (AES) and Ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometry. The optimal absorptance of multi-layer films was exhibited above 95.5% in the visible region of the electromagnetic spectrum, and the reflectance was achieved below 1.89%.

Fabrication and properties of zinc oxide thin film prepared by sol-gel dip coating method

Abstract ZnO thin films were deposited on a glass substrate by dip coating technique using a solution of zinc acetate, ethanol and distilled water. Optical constants, such as refractive index n and extinction coefficient k. were determined from transmittance spectrum in the ultraviolet-visible-near infrared (UV-Vis-NIR) regions using envelope methods. The films were found to exhibit high transmittance, low absorbance and low reflectance in the visible regions. Absorption coefficient α and the thickness of the film t were calculated from interference of transmittance spectra. The direct optical band gap of the films was in the range of 3.98 to 3.54 eV and the thickness of the films was evaluated in the range of 173 to 323 nm, while the refractive index slightly varied in the range of 1.515 to 1.622 with an increase in withdrawal speed from 100 to 250 mm/s. The crystallographic structure of the films was analyzed with X-ray diffractometer. The films were amorphous in nature.

Testing the uncertainty of diffuse reflectance spectroscopy methods for estimating marine sediment components by full-resolution spectrophotometry and principle component analyses

Estimating terrestrial and biogenic component variations in marine sediment cores provide essential information in paleoceanographic studies. The variations of terrestrial and biogenic components can be used to infer the changes of sediment provenances that are important for understanding what processes have governed the sediment compositional changes in the cores. One non-destructive technique, diffuse reflectance spectroscopy (DRS), is now commonly used to capture high-resolution information on sediment component changes. The DRS method is a quick and cost-effective procedure for sediment core analysis that requires no chemical analysis with complicated procedures. Recently, one DRS device for capturing visible (VIS) color reflectance data (CRD) (400–700nm) from core surfaces, the Minolta CM-2600d, has become a standard tool in all marine sediment core analysis. However, by capturing the visible wavelength of CRD only, there are uncertainties in the CRD near the ultraviolet (UV) and near-infrared (NIR) obtained by Minolta CM-2600d are poorly known. In this study, we used a full-resolution (FR) DRS device, the Analytical Spectral Device (ASD) LabSpec® Pro FR ultraviolet/visible/near-infrared (UV/VIS/NIR) spectrometer (250–2500nm) to compare with the CRD obtained from the Minolta CM-2600d, using the marine sediment core MD103264 taken from offshore southwestern Taiwan. We compared the differences in the VIS wavelength range of CRD between the two devices by analyzing the derivatives and a VARIMAX-rotated Principle Components Analysis (VPCA) of the CRD from 420 samples from core MD103264. Our results show significant uncertainties in CRD near the wavelengths of 400–450 and 650–700nm in the data from the Minolta CM-2600d. These uncertainties could result in biased or erroneous estimates for terrestrial and biogenic components of marine sediment cores. Our experiments indicate that the CRD obtained with any device with VIS wavelength range only should be interpreted with caution, particularly in the 400–450 and 650–700nm range.

Preparation and characterization of single (200)-oriented TiN thin films deposited by DC magnetron reactive sputtering

Single (200)-oriented TiN thin films were deposited on quartz substrate by direct current (DC) magnetron reactive sputtering process at a wide range of substrate temperature from 200 to 600 °C. The effects of sputtering pressure and substrate temperature on the crystalline nature, morphology, electrical and optical properties of the deposited thin films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), four-point resistivity test system and ultraviolet visible near-infrared (UV-Vis-NIR) spectroscopy, respectively. The results show that single (200)-oriented TiN thin films can be obtained at a wide range of substrate temperature from 200 to 600 °C with the grain size increasing from 35.9 to 64.5 nm. The resistivity of the product is as low as 95 μΩ·cm, and the value of the optical reflectance is above 68 % in the near-infrared (NIR) range of 760–1500 nm.

Optical Absorption of Er<sup>3+</sup>/Nd<sup>3+</sup> Codoped Lithium Niobate Tellurite Glass

Keywords: Tellurite Glass, UV-Vis-NIR, absorption, Urbach energy. Abstract: To improve the optical behaviour of Lithium Niobate Tellurite glass with rare- earth dopant are the important issue from application and device perspectives. Er3+ and Nd3+ doped tellurite glasses of molar composition (70-x-y)TeO2 – 15Li2CO3 – 15Nb2O5 – xEr2O3 – yNd2O3 system (x = 0 mol % and 1.0 mol %) (0 mol % ≤ y ≤ 1.0 mol %) have successfully been made by using melt quenching technique. The physical properties of the glass sample are obtained. From Ultraviolet- Visible- Near Infrared (UV-Vis-NIR) Spectroscopy, it is observed that the spectrum consists absorption peaks which corresponded to transitions from both ground state of Erbium, 4I15/2 to the excited state of 4I15/2, 4I13/2, 4I3/2, 4I11/2, 2H9/2, 4I9/2, 2H11/2, 4S3/2, 2H11/2 and 4F7/2 respectively and Neodymium, 4I9/2 to the excited state of 4I15/2, 4I15/2, 4I3/2, 4F9/2, 2G7/2, 2G9/2 and 2G11/2 respectively. The indirect band gaps obtained from the above dependence are the interband transitions, but later it involves the phonon interaction where the values of indirect optical band gaps lie between 2.84 eV to 3.12 eV as the Nd2O3 content increase. The Urbach energy for the glass system decreases from 0.31 eV to 0.21 eV as the Nd2O3 content increase.

Discrimination of various paper types using diffuse reflectance ultraviolet-visible near-infrared (UV-Vis-NIR) spectroscopy: forensic application to questioned documents.

Diffuse reflectance ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy is applied as a means of differentiating various types of writing, office, and photocopy papers (collected from stationery shops in India) on the basis of reflectance and absorbance spectra that otherwise seem to be almost alike in different illumination conditions. In order to minimize bias, spectra from both sides of paper were obtained. In addition, three spectra from three different locations (from one side) were recorded covering the upper, middle, and bottom portions of the paper sample, and the mean average reflectivity of both the sides was calculated. A significant difference was observed in mean average reflectivity of Side A and Side B of the paper using Student's pair >t-test. Three different approaches were used for discrimination: (1) qualitative features of the whole set of samples, (2) principal component analysis, and (3) a combination of both approaches. On the basis of the first approach, i.e., qualitative features, 96.49% discriminating power (DP) was observed, which shows highly significant results with the UV-Vis-NIR technique. In the second approach the discriminating power is further enhanced by incorporating the principal component analysis (PCA) statistical method, where this method describes each UV-Vis spectrum in a group through numerical loading values connected to the first few principal components. All components described 100% variance of the samples, but only the first three PCs are good enough to explain the variance (PC1 = 51.64%, PC2 = 47.52%, and PC3 = 0.54%) of the samples; i.e., the first three PCs described 99.70% of the data, whereas in the third approach, the four samples, C, G, K, and N, out of a total 19 samples, which were not differentiated using qualitative features (approach no. 1), were therefore subjected to PCA. The first two PCs described 99.37% of the spectral features. The discrimination was achieved by using a loading plot between PC1 and PC2. It is therefore concluded that maximum discrimination of writing, office, and photocopy paper could be achieved on the basis of the second approach. Hence, the present inexpensive analytical method can be appropriate for application to routine questioned document examination work in forensic laboratories because it provides nondestructive, quantitative, reliable, and repeatable results.

Electrical Properties of Tin-Doped Zinc Oxide Nanostructures Doped at Different Dopant Concentrations

This project has been focused on the electrical and optical properties respectively on the effect of Tin doped zinc oxide (ZnO) thin films at different dopant concentrations. These thin films were doped with different Sn dopant concentrations at 1 at%, 2 at%, 3 at%, 4 at% and 5 at% was selected as the parameter to optimize the thin films quality while the annealing temperature is fixed 500 oC. Sn doped ZnO solutions were deposited onto the glass substrates using sol-gel spin coating method. This project was involved with three phases, which are thin films preparation, deposition and characterization. The thin films were characterized using Current Voltage (I-V) measurement and ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometer (Perkin Elmer Lambda 750) for electrical properties and optical properties. The electrical properties show that the resistivity is the lowest at 4 at% Sn doping concentration with the value 3.08 × 103Ωcm-1. The absorption coefficient spectrum obtained shows all films exhibit very low absorption in the visible (400-800nm) and near infrared (NIR) (>800nm) range but exhibit high absorption in the UV range.

Enhanced light trapping and plasmonic properties of aluminum nanorods fabricated by glancing angle deposition

Vertically aligned arrays of aluminum (Al) nanorods were fabricated by glancing angle deposition (GLAD) method. Nanorods with maximum lengths of 200 and 350 nm were grown on 100 nm flat Al thin film. Total and diffuse reflectance profiles were measured using an ultraviolet–visible–near infrared (UV-Vis-NIR) spectrophotometer utilizing an integrating sphere to study detailed optical properties of Al nanorods in comparison to conventional planar Al thin film samples. Finite-difference-time-domain (FDTD) optical modeling method was utilized to simulate the optical response of Al nanorod array and thin film structures. FDTD simulations were carried out for periodic and random arrays of Al nanorods as well as for an isolated single nanorod in order to investigate effects of geometrical structure on plasmonic and light trapping effects. UV-Vis-NIR spectrum results reveal that total reflectance is inversely proportional with nanorod length, and decreases down to as low as ∼25%–30% in the visible spectrum at wavelengths smaller than ∼750 nm, while it stays at ∼85%–90% for flat Al thin films at those wavelengths. FDTD simulation results indicate significant light absorption by GLAD Al nanorods mainly originating from enhanced light trapping and surface plasmon resonance among the nanorods.

Optical Absorption Microspectroscopy (μ-OAS) Based on Schwarzschild-Type Cassegrain Optics.

A new experimental setup, combining a custom-designed Schwarzschild-type Cassegrain-based microscope and an ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometer, has been developed, focusing the light beam down to 20 μm diameter. Optical absorption spectra (in the 300-2500 nm range) have been measured on micrometer-sized natural glass inclusions providing information on iron speciation in magmatic melts. The absence of contribution from the host crystal matrix provides a test of the efficiency of micro-focusing. A microthermometric stage has been adapted on the microscope for measuring optical absorption spectra up to 900 K with application to the thermochromism of minute natural spinel crystals (MgAl2O4:Fe(2+),Cr(3+)). This experimental setup provides an easy and fast way to follow the evolution of spectral properties and color of glasses or crystals with temperature as well as the possibility of measuring spatially resolved optical absorption spectra.

Ancillary ligand control of electronic structure in o-benzoquinonediimine-ruthenium complex redox series: structures, electron paramagnetic resonance (EPR), and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroelectrochemistry.

The compounds Ru(acac)2(Q) (1), [Ru(bpy)2(Q)](ClO4)2 ([2](ClO4)2), and [Ru(pap)2(Q)]PF6 ([3]PF6), containing Q = N,N'-diphenyl-o-benzoquinonediimine and donating 2,4-pentanedionate ligands (acac(-)), π-accepting 2,2(/)-bipyridine (bpy), or strongly π-accepting 2-phenylazopyridine (pap) were prepared and structurally identified. The electronic structures of the complexes and several accessible oxidized and reduced forms were studied experimentally (electrochemistry, magnetic resonance, ultraviolet-visible-near-infrared (UV-vis-NIR) spectroelectrochemistry) and computationally (DFT/TD-DFT) to reveal significantly variable electron transfer behavior and charge distribution. While the redox system 1(+)-1(-) prefers trivalent ruthenium with corresponding oxidation states Q(0)-Q(2-) of the noninnocent ligand, the series 2(2+)-2(0) and 3(2+)-3(-) retain Ru(II). The bpy and pap co-ligands are not only spectators but can also be reduced prior to a second reduction of Q. The present study with new experimental and computational evidence on the influence of co-ligands on the metal is complementary to a report on the substituent effects in o-quinonediimine ligands [Kalinina et al., Inorg. Chem. 2008, 47, 10110] and to the discussion of the most appropriate oxidation state formulation Ru(II)(Q(0)) or Ru(III)(Q(• -)).

Crystallographic and optical properties of CuSbS 2 and CuSb(S 1-x Se x ) 2 solid solution

Abstract We synthesized CuSbS 2 (CAS), CuSbSe 2 (CASe), and their solid solutions by only a mechanochemical process. CAS powder with good crystallinity was obtained by post-heating at 400 and 500 °C. CASe powder with good crystallinity was obtained by post-heating at 400 and 450 °C. The CuSb(S 1 - x Se x ) 2 (CASSe) solid solutions with 0.0 ≤ x ≤ 1.0 were synthesized by post-heating at 450 °C. The crystal structure of CASSe was analyzed by Rietveld refinement using X-ray diffraction data. CAS, CASe, and CASSe solid solutions have a chalcostibite structure with an orthorhombic system of space group (Pnma). Both indirect and direct band gap energies of CASSe solid solutions were estimated by the diffuse reflectance spectra of ultraviolet/visible/near-infrared (UV-vis-NIR) spectroscopy. The indirect band gap of the CASSe solid solution linearly decreased from 1.40 eV of CuSbS 2 ( x = 0.0) to 1.04 eV of CuSbSe 2 ( x = 1.0). The direct band gap of the CASSe solid solution linearly decreased from 1.45 eV of CuSbS 2 ( x = 0.0) to 1.08 eV of CuSbSe 2 ( x = 1.0). CuSbS 0.8 Se 1.2 ( x = 0.6) and CuSbS 0.4 Se 1.6 ( x = 0.8) had a suitable band gap of about 1.15 eV for an absorber material of a high-efficiency thin-film polycrystalline solar cell.

Effects of RF Power and Substrate Temperature on the Performance of Thin-Film Silicon Solar Cells

This article shows the characteristics of pin-type solar cells with different radio frequency (RF) power and substrate temperature (Ts). All films of amorphous materials were deposited by 13.56 MHz plasma enhanced chemical vapor deposition (PECVD) method using a mixture of silane (SiH4) and hydrogen (H2). The SiH4 gas was used as a gas source and the doping process was done by gas admixture of 3% diborane (B2H6) diluted in hydrogen (H2) and 1% phosphine (PH3) diluted in H2 for p- and n-layer, respectively. The effects of deposited parameters on the characteristics of a-Si:H films have been investigated by field emission scanning electron microscope (FE-SEM), dark- and photo-conductivity (σd and σph) measurement and ultraviolet-visible-near infrared (UV-VIS-NIR) spectrophotometer, respectively. The results showed that the deposition rate of a-Si:H films increased with increasing of RF power and Ts. The optical band gap (Eopt) of a-Si:H films was increased with increasing of RF power from 20–60 Watt, and slightly decreased at RF power of 60–100 Watt. The various values of open-circuit voltage (Voc), short-circuit current density (Jsc), and conversion efficiency were measured by the solar simulator. It was found that a-Si:H films deposited at RF power of 60 Watt and Ts of 200°C are better suited for thin-film silicon solar cell application.

Improved broadband antireflection in Schottky-like junction of conformal Al-doped ZnO layer on chemically textured Si surfaces

Chemically textured Si with improved absorption in the complete range of solar spectrum is investigated by ultraviolet/visible/near-infrared (UV/Vis/NIR) spectroscopy, showing an average specular reflectance of ∼0.4% in the wavelength of 500–3000 nm. The pyramidal structures on such solar-blind Si can reduce the reflectance further below 0.1% in the UV region by conformal growth of granular Al-doped ZnO (AZO) films. X-ray diffraction analyses suggest the growth of polycrystalline AZO on faceted-Si. Moreover, marginal increase in electrical conductivity of AZO is found on textured surfaces, whereas rise in leakage current in Schottky-like Ag/AZO/Si/Ag heterostructure devices is noticed with increasing Si surface area.

Glass fiber–supported NiO nanofiber webs for reduction of CO and hydrocarbon emissions from diesel engine exhaust

Abstract

Gem quality and archeological green ‘jadeite jade’ versus ‘omphacite jade’

Raman spectroscopy was used for the characterization of seven gem quality green ‘jade’ samples and three green ‘jade’ samples of archaeological importance. The results were also compared with those acquired by other nondestructive techniques such as classical gemology, energy‐dispersive X‐ray fluorescence (EDXRF), ultraviolet‐visible‐near infrared (UV‐Vis‐NIR) in absorption, Fourier transform infrared spectroscopy (FTIR) in absorption and micro‐FTIR in reflectance. Five samples of gem quality and two samples of archaeological interest were found to be ‘jadeite jade’, whereas two samples of gem quality and one sample of archaeological interest were ‘omphacite jade’. Raman spectroscopy is found to be the most efficient method for their characterization. The results were confirmed with EDXRF and micro‐FTIR in reflectance. Data acquired using classical gemology, UV‐Vis‐NIR absorption and FTIR absorption spectroscopy were similar on ‘omphacite jade’ and ‘jadeite jade’. Copyright © 2014 John Wiley & Sons, Ltd.

Thermal protective performance of multilayer fire fighting fabric

Purpose – The purpose of this paper is to investigate thermal protection provided by the fire fighting fabric systems with different layer under high-level thermal hazards with a typical temperature range of 800-1,000°C. The purpose of these fabric systems was to provide actual protection against burn injuries using garments worn by industrial workers, fire fighters and military personnel, etc. Design/methodology/approach – The fabric system was consist of glass with aluminum foil as an outer layer, non-woven basalt, non-woven glass fabric containing NaCl-MgCl2 and Galactitol phase change materials (PCM) which simulate multilayer fire fighter protective clothing system. Thermal protective performance tests were applied for thermal analysis and used as an attempt to quantify the insulating characteristics of fabrics under conditions of flash over temperature. The surface of fire fighting multilayer protective fabric has been characterized using the UV-Vis-NIR (ultraviolet-visible-near infrared) spectrophotometer Findings – The clothing shows good thermal insulation and high-temperature drop during flash over environment and avoid second degree burn. The current PCM obvious advantages such as the ability to work in high temperature, high efficiency a long period of practical performance. Originality/value – Using this design of composite multilayer technology incorporating two stages of PCM may provide people with better protection against the fire exposure and increasing the duration time which was estimated to be more than five minutes to prevent burn injuries.