Ultraviolet-visible-near Infrared Research Articles

Control of Methyl Tertiary-Butyl Ether via Carbon-Doped Photocatalysts under Visible-Light Irradiation

The light absorbance of photocatalysts and reaction kinetics of environmental pollutants at the liquid-solid and gas-solid interfaces differ from each other. Nevertheless, many previous photocatalytic studies have applied the science to aqueopus applications without due consideration of the environment. As such, this work reports the surface and morphological characteristics and photocatalytic activities of carbon-embedded (C-TiO2) photocatalysts for control of gas-phase methyl tertiary-butyl ether (MTBE) under a range of different operational conditions. The C-TiO2 photocatalysts were prepared by oxidizing titanium carbide powders at 350 o C. The charac- teristics of the C-TiO2 photocatalysts, along with pure TiC and the reference pure TiO2, were then determined by X-ray diffraction, scan- ning emission microscope, diffuse reflectance ultraviolet-visible-near infrared (UV-VIS-NIR), and Fourier transform infrared spectros- copy. The C-TiO2 powders showed a clear shift in the absorbance spectrum towards the visible region, which indicated that the C-TiO2 photocatalyst could be activated effectively by visible-light irradiation. The MTBE decomposition efficiency depended on operational parameters, including the air flow rate (AFR), input concentration (IC), and relative humidity (RH). As the AFRs decreased from 1.5 to 0.1 L/min, the average efficiencies for MTBE increased from 11% to 77%. The average decomposition efficiencies for the ICs of 0.1, 0.5, 1.0, and 2.0 ppm were 77%, 77%, 54%, and 38%, respectively. In addition, the decomposition efficiencies for RHs of 20% , 45%, 70%, and 95% were 92%, 76%, 50%, and 32%, respectively. These findings indicate that the prepared photocatalysts could be effectively applied to control airborne MTBE if their operational conditions were optimized.

A Comparative Study of the Structural, Optical, and Electrochemical Properties of Squarate-Based Coordination Frameworks

Systematic studies of the thermal expansion, optical, and redox properties of a series of six squarate-based frameworks, [MII(C4O4)(H2O)2] (MII = MnII, FeII, CoII, NiII, ZnII, CdII) have revealed that five members of the series exhibit cubic structures in which the squarate ligands are configured in an ‘eclipsed’ phase, while the CdII analogue exhibits a trigonal structure with a ‘staggered’ orientation of the ligands. The ‘eclipsed’ structures are characterised by a positive coefficient of thermal expansion, while the CdII analogue exhibits zero thermal expansion. Ultraviolet-visible-near infrared (UV-Vis-NIR) spectra and electrochemical measurements indicate that electron delocalisation across the dianionic squarate bridge is absent.

Multi-Wavelength Transmission Spectroscopy Revisited for Micron and Submicron Particle Characterization

Multi-wavelength transmission (MWT) ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy, a technique underappreciated for particle characterization, is systematically explored using a set of NIST traceable standards over the nominal size range of 20 to 20,000 nm. Experimental results demonstrate that the particle size distributions obtained from MWT spectral data are in excellent agreement with the values reported by the manufacturer. In addition, it is shown that quantitative information on the particle concentration can be obtained--which is not currently accessible from commercially available light scattering instrumentation. The results validate that MWT UV-Vis-NIR spectroscopy has a considerable dynamic range for particle size measurements and offers significant advantages over other particle characterization techniques. Among these are the simplicity of the instrumentation and the measurements and the wealth of quantitative information contained in the MWT spectra. Most importantly, with standardized measurement protocols and standardized spectrometer configurations, MWT measurements can be used to provide the user and the manufacturer of particles with traceable data (i.e., the spectra and the quantitative analysis) for quality assurance.

Quantitative analysis of neodymium, uranium, and palladium in nitric acid solution by reflection absorption spectrophotometry

Quantitative analysis of Nd, U, or Pd in 3 mol dm−3 (M) HNO3 was performed by reflection absorption spectrophotometry at ultraviolet–visible–near-infrared (UV/Vis/NIR) region. A sample chamber with optics for reflection measurement was designed and attached to a UV/Vis/NIR spectrophotometer by optical fibers. The reflection absorbance showed linear relations with concentrations of Nd, U, and Pd at the absorbance region less than 0.1. The quantitative analysis was found to be possible for 3 M HNO3 solutions containing [Nd] ~0.2 M, [U] ~0.04 M, or [Pd] ~0.01 M.

Microstructural and Optical Properties of Porous Alumina Elaborated on Glass Substrate

A transparent porous anodized aluminum oxide (AAO) nanostructure was formed on a glass substrate using the anodization of a highly pure evaporated aluminum layer. A parametric study was carried out in order to achieve a fine control of the microstructural and optical properties of the elaborated films. The microstructural and surface morphologies of the porous alumina films were characterized by x-ray diffraction and atomic force microscopy. Pore diameter, inter-pore separation, and the porous structure as a function of anodization conditions were investigated. It was then found that the pores density decreases with increasing the anodization time. Regular cylindrical porous AAO films with a flat bottom structure were formed by chemical etching and anodization. A high transmittance in the 300-900 nm range is reported, indicating a fulfilled growth of the transparent sample (alumina) from the aluminum metal. The data showed typical interference oscillations as a result of the transparent characteristics of the film throughout the visible spectral range. The thickness and the optical constants (n and k) of the porous anodic alumina films, as a function of anodizing time, were obtained using spectroscopic ellipsometry in the ultravioletvisible-near infrared (UV-vis-NIR) regions.

Effect of substrate temperature on physical properties of In2O3:Sn films deposited by e-beam technique

Indium tin oxide (ITO) thin films were prepared by electron beam evaporation at different substrate temperatures. The structural studies were carried out by X-ray diffraction. Optical properties of the films were studied in the ultraviolet-visible-near infrared (UV-Vis-NIR) region (200 to 2500 nm). Electrical studies were carried out at room temperature of ITO films. The results showed that with increase in substrate temperature, the optical transmittance gradually increased up to 93% in the visible region, the transmittance edge gradually shifted to short wavelength and the corresponding refractive index and thermal emissivity decreased. The structure of ITO films was polycrystalline and the crystallinity was improved with increasing substrate temperature. The electrical resistivity decreased and attained its minimum value of 5.2 × 10-4 W cm at 300°C. Key words: Thin films, electron beam; indium tin oxide (ITO), optical constants, electrical properties, structure properties.

Research Progress on the Optical Properties of Gold Nanorods

Gold nanorods exhibit unique and tunable surface plasmon resonance(SPR) derived optical properties in the ultraviolet-visible-near infrared(UV-Vis-NIR) region.The high stability,low biological toxicity,bright color,and versatility of gold nanorods have inspired an explosion of research interest in their properties and applications(which include roles in catalysis,data storage,and biomedicine).This paper presents a brief overview of current research progress on the optical properties of gold nanorods,including surface plasmon resonance,local field enhancement,plasmon coupling,fluorescence,and application outlook.

氧氩比对SnO2/Ag/SnO2透明导电膜光电性能的影响

SnO2/Ag/SnO2 tri-layer thin films were prepared on glass substrates by RF magnetron sputtering of SnO2 with different O2/Ar ratio and DC magnetron sputtering of Ag.Several analytical tools such as Hall measurements,four-point probe and ultraviolet-visible-near infrared(UV-Vis-NIR) spectrophotometer were used to explore the causes of the changes in electrical and optical properties.When O2/Ar ratio is 1∶14,the film had a figure of merit of 1.69×10-2 Ω-1,the resistivity is 9.8×10-5 Ω·cm,and the sheet resistance is 9.68Ω/sq,while the average transmittance is still as high as 85% in the visible light region.In addition,when O2/Ar ratio is 1:14,The flexible SnO2/Ag/SnO2 tri-layer thin films with excellent photoelectric performance can be obtained by magnetron sputtering on PET substrates,the average transmittance is above 85%,the resistivity is 1.22×10-4 Ω·cm,and the sheet resistance is 12.05 Ω/sq.

Comparison on the Electrical, Structural and Optical Properties of CuI Thin Films Deposited by Spin Coating and by Atomization Method

In this study, a novel approach of using two different methods was investigated to prepare the CuI thin films. The CuI thin films in this research were prepared by spin coating method and by mister atomizer. Both methods used CuI powder as a precursor and acetonitrile as a solvent. The thickness of CuI films in this research range from nm – um thickness depending on the deposition technique. The 2 point probe I-V measurement was used to measure the electrical properties. The resistivity of about 106 Ω cm-101 Ω cm was observed with CuI thin films using spin coating technique. Then, the surface morphology shows all the films exhibit a microsturucture CuI particles in a case of mister atomizer method. For optical measurement, the ultraviolet-visible- near infrared (UV-VIS-NIR) measurement (Perkin Elmer Lambda 750) was used. The optical band gap of about ±3.1 eV and ±2.9 eV were observed in those CuI films. These properties of different technique are applicable for application in electronic devices such as in solar cells.

Optical transmission as a fast and non‐destructive tool for determination of ethylene‐co‐vinyl acetate curing state in photovoltaic modules

ABSTRACTPoly(ethylene‐co‐vinyl acetate) (EVA) is the primary polymer used for encapsulation of photovoltaic (PV) modules. Its degree of cross‐linking (gel content) is taken as a major quality reference. The EVA gel content is normally measured by Soxhlet extraction and more recently also by Differential Scanning Calorimetry (DSC). The DSC method is proven here to be fast and effective but is, as the Soxhlet extraction method, destructive to the PV module. With the aim of developing a fast and non‐destructive method to determine the gel content, a number of analytical techniques are presented. The most promising method is ultraviolet/visible/near‐infrared (UV/Vis/NIR) optical transmission. The measured diffuse transmission reflects the EVA crystallite size, which is related to the EVA gel content. This opens the possibility to apply an in‐line analysis of every PV module immediately after the lamination step and could significantly contribute to the process quality control that is needed in future high‐throughput production lines of PV modules. Copyright © 2011 John Wiley & Sons, Ltd.

Charging of Self‐Doped Poly(Anilineboronic Acid) Films Studied by in Situ ESR/UV/Vis/NIR Spectroelectrochemistry and ex Situ FTIR Spectroscopy

Charge carriers: The p-doping of self-doped poly(anilineboronic acid) (PANI-BA) is studied by in situ electron spin resonance (ESR)/ultraviolet/visible/near-infrared (UV-vis-NIR) spectroelectrochemistry with respect to the role of the ionic side group at the aniline core (see figure). The results point to a primary polaron-pair formation while a polaron is formed with a further increase of the doping level. At higher doping levels, the formation of diamagnetic species is observed.

흑색 코발트 태양 선택흡수막의 광학적특성과 구조

Black cobalt solar selective coatings were prepared by thermal oxidation of electroplated cobalt metal on copper and nickel substrates. The optical properties and structure of the black cobalt selective coating for solar energy utilizations were characterized by glow discharge spectrometry (GDS), ultraviolet-visible-near infrared (UV-VIS-NIR) spectrometer, atom force microscopy(AFM) and X-ray photoelectron spectroscopy(XPS). The optical properties of optimum black cobalt selective coating prepared on copper substrate were a solar absorptance of 0.82 and a thermal emittance of 0.01. From the GDS depth profile analysis of these coatings, the concentration of cobalt particles near the interface was higher than at the surface, but oxygen concentration at the surface was higher than at the interface. These results suggest that the selective absorption was dominated by this chemical composition variation in the coating. The surface of this film exhibited morphology with root-mean-square(rms) roughness of about 144.3nm. XPS measurements data showed that several phases of Co coexist(,CoO) in the film.

Preparation and Optical Properties of Indium Tin Oxide/Epoxy Nanocomposites with Polyglycidyl Methacrylate Grafted Nanoparticles

Visibly highly transparent indium tin oxide (ITO)/epoxy nanocomposites were prepared by dispersing polyglycidyl methacrylate (PGMA) grafted ITO nanoparticles into a commercial epoxy resin. The oleic acid stabilized, highly crystalline, and near monodisperse ITO nanoparticles were synthesized via a nonaqueous synthetic route with multigram batch quantities. An azido-phosphate ligand was synthesized and used to exchange with oleic acid on the ITO surface. The azide terminal group allows for the grafting of epoxy resin compatible PGMA polymer chains via Cu(I) catalyzed alkyne-azide "click" chemistry. Transmission electron microscopy (TEM) observation shows that PGMA grafted ITO particles were homogeneously dispersed within the epoxy matrix. Optical properties of ITO/epoxy nanocomposites with different ITO concentrations were studied with an ultraviolet-visible-near-infrared (UV-vis-NIR) spectrometer. All the ITO/epoxy nanocomposites show more than 90% optical transparency in the visible light range and absorption of UV light from 300 to 400 nm. In the near-infrared region, ITO/epoxy nanocomposites demonstrate low transmittance and the infrared (IR) transmission cutoff wavelength of the composites shifts toward the lower wavelength with increased ITO concentration. The ITO/epoxy nanocomposites were applied onto both glass and plastic substrates as visibly transparent and UV/IR opaque optical coatings.

The development of the Space Environment Viability of Organics (SEVO) experiment aboard the Organism/Organic Exposure to Orbital Stresses (O/OREOS) satellite

The Space Environment Viability of Organics (SEVO) experiment is one of two scientific payloads aboard the triple-cube satellite Organism/ORganic Exposure to Orbital Stresses (O/OREOS). O/OREOS is the first technology demonstration mission of the NASA Astrobiology Small Payloads Program. The 1-kg, 1000-cm3 SEVO cube is investigating the chemical evolution of organic materials in interstellar space and planetary environments by exposing organic molecules under controlled conditions directly to the low-Earth orbit (LEO) particle and electromagnetic radiation environment. O/OREOS was launched on November 19, 2010 into a 650-km, 72°-inclination orbit and has a nominal operational lifetime of six months. Four classes of organic compounds, namely an amino acid, a quinone, a polycyclic aromatic hydrocarbon (PAH), and a metallo-porphyrin are being studied. Initial reaction conditions were established by hermetically sealing the thin-film organic samples in self-contained micro-environments. Chemical changes in the samples caused by direct exposure to LEO radiation and by interactions with the irradiated microenvironments are monitored in situ by ultraviolet/visible/near-infrared (UV/VIS/NIR) absorption spectroscopy using a novel compact fixed-grating CCD spectrometer with the Sun as its light source. The goals of the O/OREOS mission include: (1) demonstrating key small satellite technologies that can enable future low-cost astrobiology experiments, (2) deploying a miniature UV/VIS/NIR spectrometer suitable for in-situ astrobiology and other scientific investigations, (3) testing the capability to establish a variety of experimental reaction conditions to enable the study of astrobiological processes on small satellites, and (4) measuring the chemical evolution of organic molecules in LEO under conditions that can be extrapolated to interstellar and planetary environments. In this paper, the science and technology development of the SEVO instrument payload and its measurements are described.

Analyzing UV/Vis/NIR Spectra—Addition of Oxygen and Nitrogen to ZnO:Al Thin Films

Exact optical analysis of transparent-conductive-oxide (TCO) thin films are necessary to optimize adequate materials for optical sensor and solar cell applications. A non-numerical theoretical concept has been used to extract approximation-free optical, structural and electrical data from ultraviolet/visible/near-infrared (UV/Vis/NIR) spectra. Special focus has been set on double-layer systems, as thin films upon substrates. Complex parameter evaluation is possible. Sputtered aluminum-doped zinc-oxide (ZnO: Al) thin films have been analyzed with respect to oxygen and nitrogen additions to the inert argon process-gas. Based on UV/Vis/NIR spectra and a novel analysis model, complex optical, structural and electrical data have been evaluated for these transparent-conductive-oxide (TCO) layers. Correct extracted physical values as refractive indices, permittivities, absorption coefficients, deposition rates, conductivities and band gap energies allow a reliable dimensioning for optical sensor and solar cell designs. Results are compared with those of the well-known Keradec/Swanepoel model (KSM). The necessity of taking both spectra-transmission and reflection spectra-into account was shown. Results are discussed with structural properties of the thin films, by help of XRD-measurements. A noncontact, optical conductivity measurement possibility by use of UV/Vis/NIR spectroscopy has been shown. Optically measured conductivities have been compared with electrically measured ones.

Analyzing UV/Vis/NIR Spectra—Part II: Correct and Efficient Parameter Extraction

Exact optical analysis of transparent conducting oxide (TCO) and absorber layers are necessary to optimize adequate materials for thin-film solar cell applications. A nonnumerical theoretical concept has been developed to extract approximation-free optical and electrical data from ultraviolet/visible/near-infrared (UV/Vis/NIR) spectra. Special focus has been set on double-layer systems, as thin films upon substrates. Complex parameter evaluation is possible. Sputtered TCO and absorber thin films - aluminum-doped zinc-oxide and tin-sulphide - have been analyzed with respect to process-temperature T. Results were compared with those of the well-known Keradec/Swanepoel model. The necessity of taking both spectra - transmission and reflection spectra - into account has been shown. Results have been discussed with structural properties of the thin films with the help of X-ray diffraction measurements. A noncontact, optical conductivity measurement possibility by use of UV/Vis/NIR spectroscopy has been introduced. Optically measured conductivities σL were compared with those measured electrically with a four-tip measurement system.

Some transparent semi-conductor metal oxides: Comparative investigations in terms of Wemple–DiDomenico parameters, mechanical performance and Amlouk–Boubaker opto-thermal expansivity

Wemple–DiDomenico model parameters for oxides thin layers (Sb 2O 4, SnO 2, ZnO and WO 3) have been determined from experimental measurement of reflection R( λ) and T( λ) transmission ratios within the Ultraviolet–Visible–Near-Infrared (UV/VIS/NIR) domain (300–1800 nm). This study allowed deducing ε 1( λ) and ε 2( λ) expressions. Exploitation of results concerning their variations enabled estimating the plasma pulse ω p , the relaxation time τ, the dielectric constant ε ∞ and susceptibility χ e . Furthermore, opto-thermal and mechanical investigations have been carried out and discussed relatively to the already established optical and thermal characteristics.

Feasibility study on cubic boron nitride coated glass press molds

We report the feasibility of glass press molds using high-quality, thick cubic boron nitride (cBN) films prepared in a plasma jet by chemical vapor deposition. A press test using a cBN film for an optical glass is carried out at a high temperature (≥ 650 °C), above the glass transition temperature. Surface morphology, chemical composition, and optical transparency of the glass after a press test are examined by atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersion X-ray spectroscopy, and ultraviolet-visible-near-infrared (UV-VIS-near-IR) and IR spectroscopy. The B and N concentrations at the top several nanometers of the glass increase by several at.% after a press test. This is attributed to diffusion of B and N from the film into the glass. The UV-VIS-near-IR transparency of the glass in a short wavelength range (≤ 900 nm) decreases by several % due to light scattering at the roughened glass surface. In contrast, the IR transparency of the glass remains constant despite an increase in the surface roughness.

Formylation of Single-Walled Carbon Nanotubes

We report an improved, elegant method for the covalent formylation of single-wall carbon nanotubes (SWNTs) via formyl transfer from N-formylpiperidine, which could potentially open the gateway for more versatile chemical modification of carbon nanotube (CNT) walls than is possible via other reported functionalisation methods. The formylation reaction does not inflict damage upon the pristine CNT structure, unlike the currently commonly used carboxylation route, and involves much fewer steps, and takes considerably less time, than most other reported routes. The modified SWNTs have been characterised by Raman spectroscopy, ultraviolet-visible-near infrared (UV-vis-NIR) spectroscopy and "covalent tagging" with derivatising groups followed by thermogravimetric analysis-mass spectroscopy (TGA-MS). UV-vis-NIR spectroscopy shows that there is only limited disruption of the intrinsic electronic structure of the SWNTs. This is confirmed from estimates of the extent of functionalisation from TGA-MS, which suggest that it may be as low as 2 atomic per cent.

Current activities of ISO TC229/WG2 on purity evaluation and quality assurance standards for carbon nanotubes

The current standardization activities of ISO (International Organization for Standardization) TC229 on "Nanotechnology" are introduced with focus on the work of WG2 (Working Group 2) for "measurement and characterization". Seven project groups of WG2 are actively preparing standard protocols (technical specifications) for characterization of single-wall carbon nanotubes (SWCNTs) by measurement methods such as TEM (transmission electron microscopy), SEM (scanning electron microscopy), EDX (energy-dispersive X-ray analysis), UV-Vis-NIR (ultraviolet-visible-near infrared) absorption spectroscopy, NIR-photoluminescence spectroscopy, EGA (evolved gas analysis)-GC-MS (gas chromatography-mass spectrometry), TGA (thermogravimetric analysis), and Raman spectroscopy; this work is described. The features of purity evaluation of SWCNTs by these methods are also briefly described and compared. Also described are two project groups of WG2 that are preparing standard protocols for characterization of multiwall CNTs (MWCNTs), aiming at the purity control by measurement of moisture content, ash content, metallic constituents, volatile content, polyaromatic hydrocarbon content, and carbon materials excluding MWCNTs. Other important properties for characterization of MWCNT, for example disorder, burning property, stacking nature, length, morphology, and inner/outer diameter, etc., are also mentioned. Finally, the importance and urgency of standardization for potential risk assessment of CNTs is briefly described, and current joint activity of ISO TC229 WG2 and WG3 for physicochemical characterization of engineered nanoscale materials for toxicological assessment is introduced.