UV Vis Transmission Spectra Research Articles

Significant enhancement in the cold emission characteristics of chemically synthesized super-hydrophobic zinc oxide rods by nickel doping.

The current article presents a huge enhancement in the field emission characteristics of zinc oxide (ZnO) micro/nanorods by nickel doping. The synthesis of pure and nickel-doped zinc oxide (ZnO) micro/nanorods was done by a simple low-temperature chemical method. Both the as-prepared pure and doped samples were analyzed by X-ray diffraction and electron microscopy to confirm the proper phase formation and the developed microstructure. UV-vis transmittance spectra helped in determining the band gap of the samples. Fourier-Transform Infrared Spectroscopy (FTIR) spectra showed the different bonds present in the sample, whereas X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of nickel in the doped sample. Photoluminescence (PL) spectra showed that after doping, the band-to-band transition was affected, whereas defect-induced transition had increased significantly. After the nickel doping, contact angle measurement revealed a significant decrease in the sample's surface energy, leading to a remarkably high water contact angle (within the superhydrophobic region). Simulation through ANSYS suggested that the doped sample has the potential to function as an efficient cold emitter, which was also verified experimentally. The cold emission characteristics of the doped sample showed a significant improvement, with the turn-on field (corresponding to J = 1 μA cm-2) reduced from 5.34 to 2.84 V μm-1. The enhancement factor for the doped sample reached 3426, approximately 1.5 times higher compared to pure ZnO. Efforts have been made to explain the results, given the favorable band bending as well as the increased number of effective emission sites.

Effect of different sulfur pressure annealing on properties of sputtering-deposited ZnS thin films

ZnS, a kind of wide-band gap semiconductor, has attracted extensive attention in recent years due to its excellent photoelectric performance, which has broad application prospects in solar cells, photocatalysts and sensors. In this work, ZnS thin films are first deposited by radio-frequency (RF) magnetron sputtering, and then annealed at 600 ℃ and different sulfur pressures. The crystal structure, surface morphology, grain size, composition, transmittance and defects of ZnS thin films are analyzed by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, UV-vis transmission spectra, and positron annihilation Doppler broadening spectroscopy. The results show that the crystallinities of ZnS films can be improved by being annealed in sulfur atmosphere, and the optical band gaps of ZnS films after being annealed are in a range of 3.43–3.58 eV. When the sulfur pressure is higher than 0.49 atm, the sulfur interstitial atoms in the ZnS and the elemental sulfur on the surface reduce the transmittance of the film in the visible region. The Doppler broadening spectroscopy results also show that the defect concentrations of ZnS films decrease gradually from their surface layers to the inner layers, and the defects of ZnS films decrease with the increase of sulfur pressure. Meanwhile, the 3γ annihilation also proves that the interior of the film is relatively dense, and the open porosity of the film will increase due to vulcanization. Adsorbed sulfur occupies the position of sulfur vacancy defect in the crystal through internal diffusion, which leads the defect concentration to decrease and the film quality to be improved.

Porous highly fluorinated polyimide/polydopamine nanocomposite films with simultaneously enhanced toughness, UV-shielding and photostability for aerospace applications

Polydopamine (PDA), also known as artificial melanin, was adopted as ultraviolet absorbent to prepare a series of porous highly fluorinated polyimide/polydopamine (FPI/PDA) films by cyclodehydration via chemical and thermal imidization. The hydrogen bond and porous structure endowed the reinforced thermal, mechanical, UV-shielding and photostability. The initial decomposition and glass transition temperatures of FPI/PDA (1 wt %) film were as high as 461.5 °C and 341.5 °C, respectively beyond pure FPI by 54.1 °C and 26.0 °C. The stress-strain curves indicated that tensile strength and fracture elongation first increased and then decreased with the increase of PDA content, and reached the maximum at 0.5 wt % PDA content, which were 1.41 and 29.47 times of FPI, respectively. UV–vis transmittance spectra, curcumin photolysis and recyclability measurement confirmed the splendid UV-shielding properties with simultaneous excellent visible light transmittance and durability of porous FPI/PDA film. FTIR and AFM manifested its superior photostability with mild variation in carbonyl absorption peaks and surface roughness after 720 h UV irradiation. The above enhancement mechanisms included synergistic UV absorption of porous FPI and PDA, photothermal conversion in a stable FPI, and PDA's free radical trapping, promoting porous FPI/PDA film as an aerospace UV shielding material.

Cation-exchange reaction to prepare Na2WO2F4:Mn4+ with intense zero phonon line at 619 nm avoiding disproportionation reaction

We report that in the case of synthesizing the Na2WO2F4:Mn4+ red luminescent phosphor, the cation-exchange reaction is superior to a conventional co-precipitation reaction for a brighter luminescence, because it avoided the disproportionation reaction of K2MnF6. As evidenced by the UV–Vis transmittance spectra, during the co-precipitation reaction, the WO42− contained in Na2WO4 induced a catalytic effect on the disproportionation reaction of MnF62−, which led to valence change (from Mn4+ to Mn7+, Mn3+, etc.) and fluorescence quenching of Mn4+. Fluorination of Na2WO4 to get Na2WO2F4 for cation-exchange reaction with K2MnF6 under presence of HF solution was found to be effective in suppressing this disproportionation reaction. At optimized conditions, the phosphor prepared via the cation-exchange reaction shows a luminescence intensity 19-fold higher than that prepared via the co-precipitation method. The Na2WO2F4:Mn4+ obtained via cation-exchange reaction exhibits red luminescence peaking at 619 nm that is ascribed to the zero phonon line (ZPL) emission, and the ZPL to Stokes ν6 phonon sideband intensity ratio reached as high as 117.7%–138.2%.

Impact of Defects for AlN Single Crystal Thin Film by Metal Nitride Vapor Phase Epitaxy.

Herein, the defect-related properties of an AlN sample prepared based on the optimal process parameters by metal nitride vapor phase epitaxy (MNVPE) were investigated. The FWHM values of the (0002)/(101̅2) planes of the sample by MNVPE are 397/422 arcsec; the advantages of similar FWHM values of (0002) and (101̅2) planes will have a huge advantage over other preparation methods such as MOCVD. From the cross-sectional TEM images of the AlN sample, it is found that the fusion of a large number of a + c type dislocations occur at the interface of the low temperature buffer layer and the epitaxial layer, which affects the growth mode of the epitaxial layer. The lower FHWM value of the E 2(high) peak of the Raman spectrum, the lower the point defect concentration, which made the sample gain higher energy defect emission bands in the PL spectra and higher transmittance in the UV-vis transmission spectrum.

Study the properties of Cu2Se thin films for optoelectronic applications

Copper selenide (Cu2Se) thin films were prepared by thermal evaporation at RT with thickness 500 nm. The heat-treating for (400 &500) K for the absorber layer has been investigated. This research includes, studying the structural properties of X-ray diffraction (XRD) that show the Cu2Se thin film (Cubic) and has a polycrystalline orientation prevalent (220). Moreover, studying the effect of annealing on their surface morphology properties by using Atomic Force Microscopy AFM. Optical properties were considered using the transmittance and absorbance spectra had been recorded when wavelength range (400 - 1000) nm in order to study the absorption coefficient and energy gap. It was found that these films had allowed direct transition optical band gap which decreases with the increasing effect of annealing, while it increasing with the increase in the annealing temperature at all ratio UV-Visible transmission spectrum. Hall Effect results presented that all thin films have P-type. It is quite possible that the heterojunction (p-Cu2Se/n-Si) solar cell device is a buried. The illumination current- voltage (I-V) characteristics showed that the solar cell, with (t=500 nm and T=500 K ) has highest efficiency (η =1.4 %).

Effect of substrate temperature and RF power on the structural and optical properties of sputtered ZnO thin films

ZnO thin films have been deposited on glass substrates by radio frequency (RF) magnetron sputtering from a zinc oxide target in order to investigate the effect of RF power and substrate temperature on the properties of the deposited films. The structural and optical properties of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Vis transmission spectra and photoluminescence (PL). All ZnO thin films exhibited diffraction peak of (002) corresponding to c-axis orientation and the film deposited at 450°C exhibited the larger grain size as a result of stress relaxation. It is observed that the increase in substrate temperature or sputtering power can facilitate the growth of ZnO in (100) and (101) direction. PL emission was obtained at UV and visible region for the excitation wavelengths of 280 nm and 390 nm respectively. PL study indicated that both the crystal quality and stoichiometry can influence the UV PL emission in ZnO thin films. Dependence of temperature and power on transmission spectra was studied and the optical band gap was calculated.

Influence of ZnO: Ce3+/ Eu3+ doped and co-doped nanopowders on the properties of poly (ε-caprolactone) nanocomposites

In this work the novel poly (ε-caprolactone) (PCL)/ZnO: Ce3+, Eu3+ nanocomposites have been prepared through the solution casting method using acetophenone as solvent. The properties of the final composites were investigated by XRD, SEM, TGA, DSC, UV and PL. Diffraction patterns showed crystalline peaks at Bragg angles 2θ = 21.3° and 23.6° for PCL and the nanocomposite. Nanosphosphors are clearly dispersed and seem to have occupied PCL micro-cavities with expected elemental composition. The degree of crystallinity and overall thermal stability of the PCL nanocomposites are lower than of the pristine polymer. UV–vis transmittance spectra of the PCL showed absorption edge at lower wavelengths than all nanocomposites and nanopowders. There is an apparent improvement in the luminescent properties of the solution casted nanocomposites. In fact, the luminescence intensity of the co-doped nanocomposite samples has increased roughly10 times compared to PCL.

Synthesis of tin monosulfide SnS thin films via spray pyrolysis method based on Taguchi design for solar absorber

In this study, the effect of controlled conditions on the optical properties of tin monosulfide (SnS) thin films was successfully investigated by the chemistry spray pyrolysis deposition method on glass substrates. The Taguchi model is reported to find the most important factor for the deposition process of SnS thin films with orthogonal L9 (34) alignment. We also derive the band gap energy from transmittance data used to determine S/N relation. The selected influencing parameters are: tin-[Sn-] and sulfide-[S] concentrations, deposition substrate temperature (°C) Td and deposition time (min). The results show that the deposited film has a uniform, pure orthorhombic SnS phase and smooth morphology. Energy dispersive X-ray spectroscopy (EDS) utilizes the chemical composition of the prepared layers. In addition, the UV–Vis transmittance spectrum of the obtained film via the optimum conditions showed low transmittance in the visible region. Also, the SnS thin film shows the best gap interstitial energy of 1.52 eV. However, the SnS thin films produced by optimizing the Taguchi model display good optical properties and suggest that SnS thin films may be one of the potential solar cell absorbers in photovoltaic devices.

The study of the particle size effect on the physical properties of TiO2/cellulose acetate composite films

Abstract The cast method was used to synthesize cellulose acetate (CA)/titanium oxide (TiO2) composites by varying TiO2 particle sizes at different weight ratios of 1, 1.5, 2, 2.5, and 3 wt%. The relationship between structural diversity and performance was explored. Microstructures and chemical composition of as-prepared composite films were revealed using field-emission scanning electron microscopy and Fourier-transform infrared spectroscopy. The tensile strength increased from 46.8 MPa for pure CA to 54.7 MPa for the CA-1% micro-TiO2 composite and 81.7 MPa for the CA-2% nano-TiO2 composite, according to the mechanical properties. The tensile strength decreased due to some degrees of agglomeration of filler particles above a critical content. UV-vis transmittance spectra showed that pure CA was almost transparent, CA-micro-TiO2 films were less transparent than pure CA, and CA-nano-TiO2 films could efficiently block the light. XRD diffraction for the synthesized membranes was performed. The patterns of micro-TiO2 and nano-TiO2 were shown as 2θ = 25° for the anatase phase and 2θ = 18.5 for the pure CA film, respectively. The hydrophilicity of films was also measured using the sessile drop technique. The contact angle value for the pure CA was 61.3°. As the amount of TiO2 added to the films increased, the contact angles of the CA-micro TiO2 and CA-nano TiO2 films reduced from 53.2° to 29° and from 51.5° to 27°, respectively. The produced films’ improved wettability indicated that these films could be employed as filters.

Tailoring Structural and Optical Properties of Cu Doped Chemically Deposited ZnSe Nanostructured Thin Films

Chemical bath deposition has been used for depositing undoped and copper doped ZnSe thin films at 343 K temperature. Growth of the thin film requires zinc sulphate cation and sodium selenosulphate anion. The preparative parameters are optimized with an aim to obtain high quality thin films. Three different concentrations of Cu source are used. XRD pattern indicates the incorporation of copper in to polycrystalline cubic ZnSe in doped thin films and is confirmed by EDAX spectrum. SEM micrographs indicate that ZnSe dispersion in the films is homogeneous. UV–visible transmission spectra of the thin films have put into evidence that the dispersion of ZnSe nanocrystals in the thin film is improved their optical transmission. Room temperature PL spectra have shown that the addition of Cu into ZnSe enhanced the emission with additional green peak other than blue band edge emission. Electrical conductivity also modified on addition of Copper.

Effect of KI Concentration in Correcting Tank on Optical Properties of PVA Polarizing Film.

Polarizer is a key component of the liquid crystal display panel, and the optical properties mainly include transmittance, degree of polarization and chromaticity. Polarizer is made of a multilayer optical film, in which the PVA polarizing film is the core structure for realizing the polarization of the whole polarizer. PVA polarizing film is commonly manufactured through a multi-step craft, including rinsing, dyeing, stretching and correcting. The correction process has a significant impact on the final apparent color and optical properties of the polarizer. In this study, the KI concentration in the correcting tank, ranging from 1% to 3%, was systematically investigated. With the increase in KI concentration, the Raman vibration peak at 160 cm−1 representing ions gradually weakened, while the Raman vibration peak at 110 cm−1 representing ions gradually increased, indicating that the KI in the correcting tank changed the chemical equilibrium of polyiodide ions in PVA. Then abundant chromophore ions were consumed and ions generated, so that the apparent color of PVA polarizing film gradually changed from dark blue to dark gray, and the chromaticity a-value and b-value gradually increased. The change in the concentration of dichroic species ( and ) in PVA polarizing film had directly affected its transmittance in the visible range. From the UV-Vis transmittance spectrum of PVA polarizing film, when the ions were consumed and ions generated, the transmittance of PVA polarizing film in the region of 675–525 nm wavelength increased gradually while the polarization degree also increased.

Optical Properties of Sudan Black Stain Doped PMMA Thin Films at Different Concentration and Gamma Irradiation Effect

In this paper, the optical properties investigated and the effect of the gamma irradiation on the optical constant in addition to the energy band gap (Eg) of Sudan black stain doped Poly Methyl Methacrylate (PMMA) thin films. Thin films of 20% Sudan black stain/PMMA doping ratio was used to prepared three concentrations (1, 0.7, 0.4) x10-3 M. all the Dye/ Polymer solution (three different concentrations) deposited on glass substrate by using a free casting method at room temperature. The UV-Visible absorbance and transmittance spectra at the 300 - 800 nm wavelength range were used to investigate the optical properties of the films. The optical constant such as linear absorption coefficient, the extinction coefficient, and Eg were calculated. Results showed an increasing in the optical properties after irradiation with γ rays with activity 16 gray/hour, while Eg was decreasing after irradiation.

Photoelectrochemical activity of ZnO:Ag/rGO photo-anodes synthesized by two-steps sol-gel method

This work investigated the influence of silver plasmon and reduced graphene oxide (rGO) on the photoelectrochemical performance (PEC) of ZnO thin films synthesized by the sol-gel method. The physicochemical properties of the obtained photo-anodes were systematically studied by using several characterization techniques. The x-ray diffraction analysis showed that all samples presented hexagonal wurtzite structure with a polycrystalline nature. Raman and energy dispersive x-ray (EDX) studies confirmed the existence of both Ag and rGO in ZnO:Ag/rGO thin films. The estimated grain size obtained from scanning electron microscopy (SEM) analysis decreased with Ag doping, then increased to a maximum value after rGO addition. The UV-vis transmission spectra of the as-prepared ZnO:Ag and ZnO:Ag/rGO thin films have shown a reduction in the visible range with a redshift at the absorption edges. The bandgaps were estimated to be around 3.17 eV, 2.7 eV, and 2.52 eV for ZnO, ZnO:Ag, and ZnO:Ag/rGO, respectively. Moreover, the electrical measurements revealed that the charge exchange processes were enhanced at the ZnO:Ag/rGO/electrolyte interface, accompanied by an increase in the (PEC) performance compared to ZnO and ZnO:Ag photo-anodes. Consequently, the photocurrent density of ZnO:Ag/rGO (0.2 mA⋅cm−2) was around 4 and 2.22 times higher than photo-anodes based on undoped ZnO (0.05 mA⋅cm−2) and ZnO:Ag (0.09 mA⋅cm−2), respectively. Finally, from the flat band potential and donor density, deduced from the Mott–Schottky, it was clear that all the samples were n-type semiconductors with the highest carrier density for the ZnO:Ag/rGO photo-anode.

Effect of F doping on the properties of zinc tin oxide thin films for UV photodetector applications prepared by low-cost nebulizer spray pyrolysis method

The fluorine doped zinc tin oxide (FZTO) thin films were fabricated using nebulizer spray pyrolysis method and fluorine doping effect on structural, morphological, optical and photo sensing properties were investigated. The XRD results show that all the prepared films are polycrystalline in nature and exhibit a hexagonal structure with c-axis growth orientation. The SEM images of all the films displays uniform surface without any crack and well packed with defined granules. The EDX spectra establishes that the existence of Zn, Sn O, and F components in the fabricated films with their nominal stoichiometric percentage. The water contact angle assessment indicates the reduction of surface roughness. The UV–Visible transmittance spectra of the films exhibit >75% and the blue shift of energy band gap is indicating the increase of free carriers. The PL emission spectra show that the presence of neutral and singly ionized oxygen vacancies (V0° &V0+) and these defects acting as carrier trap. The prepared films exhibit a good response to UV light and enhance the photo current up to 597 μA and the recorded raise and decay time are 3.29 and 4.17s respectively.

Dichroic Dipole Antenna Membranes from Aligned Linear BOPHY Dyes

AbstractLinear dyes are molecular mimics of dipole antennas that receive UV–vis light. In this work the assembly of linear dyes via the Langmuir technique to achieve uniform dye alignment for optically anisotropic molecular dipole antenna arrays is presented. The molecular orientations in these arrays are quantified from Langmuir isotherms, topography data, and from polarization‐ and angle‐dependent UV–vis transmission spectra. It is achieved the smallest angles by which the transition dipole moment orientation deviates from vertical alignment (16°–30°) in the antenna arrays that have been reported in literature so far. The resulting maximum absorption contrast between grazing and vertical incidence amounts to 75%. This high optical anisotropy enables application as anisotropic receiver arrays in optical communication, as optical layers for privacy applications, or other applications building on dichroic dye layers.

A Study on the Effect of Oxygen Flow Rate on Optical Properties of RF Sputtered a-GaOx Thin Films on Corning Glass Substrate

Transparent amorphous thin films of ultra-wide band gap (Eg ≈ 4.5–5.3 eV) gallium oxide (a-GaOx) were deposited on Corning glass substrates by radio frequency (RF) magnetron reactive sputtering under different oxygen flow rates. Amorphous nature of the deposited films was confirmed using X-ray diffraction method. Surface properties of the films were obtained from field emission scanning electron and atomic force microscopic images. Compositional and surface chemistry analyses were done using energy-dispersive X-ray and X-ray photoelectron spectroscopic techniques respectively. Optical characteristics of the films deposited under varying oxygen flow rates were investigated. UV-visible transmittance spectra showed excellent transparency in the visible region for all the films. Optical band gap values were found to increase with the increase of oxygen flow rates. Thickness of the films and refractive index dispersion relation were studied using spectroscopic ellipsometry by utilizing a Cauchy dispersion model. Refractive index dispersion parameters were obtained using Wemple-DiDomenico model. The results indicate that the presence of oxygen in the sputtering environment significantly alter the deposition rate and thereby optical properties of the films.

Colour of honey: can we trust the Pfund scale? – An alternative graphical tool covering the whole visible spectra

Honey is popular and versatile nutraceutical product, widely used as a sweetener. Its sensory properties, determined by the botanical origin, play a high role in consumers’ decision. Among these, colour is an important, often price-defining property. Colour evaluation of honey can be done by different ways, the most commonly known being the Pfund scale, but Lovibond scale or spectral analysis are used as well. The Pfund method provides a specific evaluation scale for honeys, however, this method is not able to detect slight differences and it also has some deficiencies.Our aim was to provide some examples proving the shortages of the present methodology for determination of honey colour and suggest a solution that could qualify as a possible standardized method. A template providing all the calculations (Pfund value, L*a*b*, C*ab, h°ab, ΔE*ab, ΔC* ab, Δh*ab, ΔH*ab, ΔL*, Δa*, Δb*) based on the UV-VIS transmission spectra, comparing the results of honey samples is attached. The experiment revealed the drawbacks of the Pfund scaling system. We provide an alternative analytical method that can deliver more details and information on honey colour and could overcome the deficiencies of the present protocols.

Optical Properties and Crystallization Behavior of SiO2-Al2O3-BaO-BaF2 Glasses Containing Different Amounts of Bi2O3

The present study aims to investigate the optical properties and crystallization behavior of oxy-fluoride glasses with different amounts of Bi2O3. Glasses with compositions of 45SiO2-15Al2O3-25BaO-15BaF2-xBi2O3 (x=0, 1, 2.5, 4, and 6) (mole ratio) were prepared using melt-quenching method. Owing to the network modifying role of Bi2O3 and increasing number of Non-Bridging Oxygens (NBOs), the molar volume increased from 27.69 to 31.60 cm3 and microhardness was reduced from 720.21 to 613.10 MPa. In order to study the structural changes, the FTIR spectra were recorded, and increment of NBOs by adding Bi2O3 as well as the presence of Bi˚ particles in the sample containing six mole ratios of Bi2O3 were proved. The UV-Vis transmittance spectra were employed to determine the optical properties including Fermi energy, direct and indirect optical band gaps, and Urbach energy. The Fermi energy and optical band gaps were reduced as the Bi2O3 content increased. The degree of structural disorderliness (Urbach energy) increased from 0.170 to 0.212 eV followed by creating more NBOs through Bi2O3 addition. On the basis of UV-Vis-IR transmittance results, the sample containing four mole ratios of Bi2O3 exhibited the highest transmittance in IR region and its IR cut-off shifted to longer wavelengths. Further, the sample with six mole ratios of Bi2O3 was characterized as the highest refractive index (1.7) among other glasses. Finally, evaluation of crystallization behavior of specimens revealed that it was impossible to prepare transparent glass ceramics containing BaF2 nanocrystals due to the surface crystallization in these glasses.

Discussion on structural, optical, thermal, mechanical, dielectric and third-order NLO properties of 3-Nitroanilinium chloride single crystals for optoelectronic applications

Preferable, third-order nonlinear optical (NLO) single crystal, 3-Nitroanilinium chloride (3NACL) was auspiciously synthesised by slow evaporation technique. The crystal system of the synthesised 3NACL crystal was triclinic with centrosymmetric space group \({\text{P}}\bar{1}\) was identified by single-crystal XRD studies. All the functional groups present in the sample and its respective vibrations were analysed through FTIR analysis. UV–Vis transmittance spectrum revealed that the synthesised material showed 83% transmittance and its cut-off wavelength was 281 nm. The mechanical stability and thermal property of the grown 3NACL crystals were ascertained by Vickers microhardness analysis and TG/DTA analysis. The intermolecular interaction of the 3NACL was scrutinized by Hirshfeld surface analysis. Dielectric studies revealed that dielectric constant and dielectric loss were high at lower frequency region due to the space charge polarization. Inclusion-free 3NACL crystal was used to analyse the Laser damage threshold (LDT) studies and its calculated LDT value was 4.3 GW/cm2. The third-order NLO parameters (β = 7.5472 × 10–12 m/W, η2 = 5.6931 × 10–19 m2/W, χ3 = 2.9491 × 10–13 esu) of the 3NACL material were statutorily evaluated by Z-scan studies. Here, β and η2 were positive, due to the saturated absorption and self-focusing effect as observed in open and closed aperture z-scan curve. Above all these findings, 3NACL was a suitable material for NLO and optoelectronic applications.