Ultraviolet-visible Transmission Research Articles

Mechanical Properties and Microstructure of Graphene-Cement Composites

In this work, two type graphene were dispersed in aqueous solution via sonication, and graphene nanoplatelets (GP) and graphene oxide (GO) were characterized by means of ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, the effects of different graphene (GP and GO) on mechanical properties and microstructure of cement-based materials were investigated via filed emission scanning electron microscopy (FESEM). The results suggested that the incorporation of GP and GO both improved the flexural and compressive strength of cement, and the GP had a more prominent impact on the strengths of cement, compared with GO. The flexural and compressive strength of cement increased up to 23.5% and 7.5% with 0.05 wt% GP, respectively. FESEM analysis indicated that the microstructure of GP-cement paste was similar to that of control sample without graphene, whereas, a few flower-like crystals were generated in GO-cement paste. This work could provide a new understanding for further researches of graphene-cement composites.

Effects of carbon content and plasma power on room temperature photoluminescence characteristics of hydrogenated amorphous silicon carbide thin films deposited by PECVD

The room temperature photoluminescence characteristics of a-SiCx:H thin films, deposited by plasma enhanced chemical vapor deposition technique with various carbon contents (x), at lower (30mW/cm2) (LP) and higher (90mW/cm2) (HP) power densities, were analyzed. The carbon content of the a-SiCx:H thin films was determined by X-ray photoelectron spectroscopy. The peak energies and the full width half maxima of the PL spectra were compared with the optical energies, determined by ultraviolet–visible transmittance measurements and a linearly correlated increase was observed as a function of x. PL peak energies shifted from 1.99eV to 2.60eV for LP and from 1.89 to 2.91eV for HP films. The PL mechanisms were investigated in the frame of the static disorder model and the stokes shift model. Our analyses indicated that for LP films the stokes shift model and for HP films the static disorder model are the dominant mechanisms of PL; moreover it was determined that both of these independent models have contributions to PL mechanism. Additionally, PL spectra were analyzed by the joint density of tail states (JDOS) PL model. The increase in the PL peak energies and spectrum widths by the increase in the plasma power and carbon content considerably fitted to JDOS PL model, which could exclusively represent the PL mechanism by itself.

Coating of green-synthesized silver nanoparticles on cotton fabric

Silver nanoparticles were synthesized by a green method and coated on cotton fabric using dip and ultrasonication processes. The synthesized silver nanoparticles were characterized using ultraviolet visible spectra, X-ray diffractometry and transmission electron microscopy. Through transmission electron microscopy, the nanostructure was confirmed. The prepared silver nanoparticles were about 86 nm in size with a face-centered cubic crystalline nature. The silver nanoparticles coated on cotton fabric were characterized using a scanning electron microscope. The scanning electron microscope images showed uniform coating of silver nanoparticles on the surface of fabrics. The antibacterial activities of the silver nanoparticle-coated fabric were investigated against the strain of Staphylococcus aureus culture, and it exhibited good antibacterial activity. The tensile strength of the cotton fabric increased considerably when the silver nanoparticles were coated on it. The ultrasonication process gave rise to the higher tensile strength.

Rapid Synthesis of Gold Nanoparticles from Quercus incana and Their Antimicrobial Potential against Human Pathogens

In current study, bioreduction of tetrachloroauric acid (HAuCl4·3H2O) was carried out using leaves extract of Quercus incana for nanoparticle synthesis. The nanoparticles were characterized by ultraviolet visible spectrum (UV), Fourier-transform infrared (FT-IR), and transmission electron microscopy (TEM) analysis. The gold nanoparticles (GNPs) were generally clumpy agglomerates of polydispersed particles, with an average size in the range 5.5–10 nm. The Gas chromatography–mass spectrometry (GC–MS) qualitative analysis and FT-IR data supported the presence of bioactive compounds, which are responsible for the metal reduction and nanoparticles stabilization. The biocompatibility of synthesized GNPs was evaluated via antibacterial activity by using human bacterial pathogens. The results showed that synthesized GNPs showed enhanced antibacterial activity against all bacterial pathogens.

Synthesis and characterization of the Cu2ZnSnS4 system for photovoltaic applications

This paper focuses on the synthesis and characterization of a ceramic material based on the Cu2ZnSnS4 system, through the implementation of a hydrothermal route. For this purpose, we started from nitrate dissolutions in a 1.0mol L-1 concentration, which were mixed and treated in a teflon lined vessel steel at 280°C for 48h. The Physicochemical characterization of the solid was evaluated by means of ultraviolet visible spectroscopy (UV-VIS), X-ray diffraction (XRD), Raman spectroscopy, scanning and transmission electron microscopy (SEM-TEM) and solid state impedance spectroscopy (IS). The initial characterization through UV measurements confirms a Band-gap around 1.46eV obtained by the Kubelka-Munk method, which demonstrates the effectiveness of the synthesis method in the obtaining of a semiconductor material. The XRD results confirm the obtaining of a crystalline material of pure phase with tetragonal geometry and I-42m space group. The preferential crystalline orientation was achieved along (2 2 0) facet, with crystallite sizes of nanometric order (6.0nm). The morphological aspects evaluated by means electron microscopy, confirmed the homogeneity of the material, showing specifically a series of textural and surface properties of relevant importance. Finally, the electrical characterizations allow to validate the semiconductor behaviour of CZTS system for development of photovoltaic technologies.

Effects of annealing temperature on the structural and optical properties of ZnO thin films prepared by sol–gel method

ZnO thin films have been prepared by sol–gel method in this paper. Zinc acetate, ethanol and mono-ethanolamine (MEA) were used as a metal precursor, solvent and stabilizer, respectively. The structural and optical properties of ZnO thin films were investigated and found to be strongly dependent on the annealing temperature. X-ray diffraction patterns revealed that as the annealing temperature increased, the crystalline quality of the samples became better. The atomic force microscope images of the samples show larger and compact grains at higher heat-treating temperature. The ultraviolet–visible transmittance spectra indicated that as the temperature increased, the transmittance improved and the energy gap became larger (from 3.11[Formula: see text]eV at 400[Formula: see text]C to 3.22[Formula: see text]eV at 500[Formula: see text]C). The photoluminescence spectra presented a variety of emission peaks, two strong peaks at 390[Formula: see text]nm and 469[Formula: see text]nm, respectively, from the intrinsic emission and point defects, and the intensity of these peaks decreased with the increase of temperature.

Role of annealing on the structural and optical properties of nanostructured diaceto bis-benzimidazole Mn(II) complex thin films

A coordination complex, manganese incorporated benzimidazole, thin films were prepared by chemical bath deposition method. Structural characterization of the deposited films, carried out by Fourier transform infrared spectroscopy, Raman and electron paramagnetic resonance spectral analyses, reveals the distorted tetrahedral environment of the metal ion with bis-benzimidazole ligand. Further the molecular composition of the deposited metal complex was estimated by energy-dispersive X-ray spectroscopy. The prepared thin films were thermally treated to study the effect of annealing temperature on the surface morphology and the results showed that the surface homogeneity of the films increased for thermally treated films up to 150°C. But distortion and voids were observed for the films annealed at 200°C. The Raman analysis reveals the molecular hydrogen bond distortion which leads to the evaporation of the metal complex from the thin film surface with respect to annealing temperature. The linear and nonlinear optical properties of the as prepared and annealed films were studied using ultraviolet-visible transmittance spectroscopy, second harmonic generation and Z-scan analyses. Films annealed at 150°C show a better linear transmittance in the visible region and larger SHG efficiency and third order nonlinear susceptibility when compared with the other samples. Further, the film annealed at 150°C was subjected to optical switching analysis and demonstrated to have an inverted switching behavior.

Optoelectronic properties of SnO2 thin films sprayed at different deposition times

This article presents the elaboration of tin oxide (SnO2) thin films on glass substrates by using a home-made spray pyrolysis system. Effects of film thickness on the structural, optical, and electrical film properties are investigated. The films are characterized by several techniques such as x-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet-visible (UV–Vis) transmission, and four-probe point measurements, and the results suggest that the prepared films are uniform and well adherent to the substrates. X-ray diffraction (XRD) patterns show that SnO2 film is of polycrystal with cassiterite tetragonal crystal structure and a preferential orientation along the (110) plane. The calculated grain sizes are in a range from 32.93 nm to 56.88 nm. Optical transmittance spectra of the films show that their high transparency average transmittances are greater than 65% in the visible region. The optical gaps of SnO2 thin films are found to be in a range of 3.64 eV–3.94 eV. Figures of merit for SnO2 thin films reveal that their maximum value is about 1.15 × 10−4 Ω−1 at λ = 550 nm. Moreover, the measured electrical resistivity at room temperature is on the order of 10−2 Ω·cm.

Study of Spectroscopic Properties of Pure and Nd Doped Ca3La2(BO3)4 Glasses

In this paper, we report pure and 5 mol% Nd doped Ca3La2 (BO3)4 glasses and their spectroscopic properties. A ternary system La2O-3CaO-4H3BO3 was adopted and glasses were prepared by using a conventional melt quenching technique. The amorphous nature of the glasses has been confirmed by powder X-ray diffraction analysis. In order to study the spectroscopic properties of fabricated glasses, ultraviolet-visible transmission and absorption spectroscopy has been performed. The absorption spectrum of Nd doped glass shows that the transition 4I9/2→4G5/2+2G7/2 is more intense as compared to the other transitions. Optical band gap energies of both glasses have been determined and found decreased for Nd doped glass as compare to pure glass.

Ultra-Violet Visible Spectrometry and Transmission Electron Microscopy Confirmation of Continued Effectiveness of Turkevich/Frens Method

Ultra-Violet Visible Spectrometry and Transmission Electron Microscopy Confirmation of Continued Effectiveness of Turkevich/Frens Method

Quantum dots modified with quaternized poly(dimethylaminoethyl methacrylate) for selective recognition and killing of bacteria over mammalian cells.

Copper-free click chemistry has been used to graft quaternized poly(dimethylaminoethyl methacrylate) (QPA) modified with azide to the quantum dots (QDs) derived with dibenzocyclooctynes (DBCO). The success of the quaternary ammonium polymer-modified QDs was confirmed by ultraviolet-visible spectrophotometry (UV-Vis), fluorescence spectroscopy, zeta (ζ) potential, size distribution, and transmission electron microscopy (TEM). The QPA-modified QDs exhibited properties of selective recognition and killing of bacteria. The novelty of this study lies in fact that the synthesis method of the antimicrobial QPA-modified QDs is simple. Moreover, from another standpoint, QPA-modified QDs simultaneously possess abilities of selective recognition and killing of bacteria over mammalian cells, which is very different from the currently designed multifunctional antimicrobial systems composed of complicated systematic compositions.

Fabrication and characterization of ultraviolet photodetectors based on silicon nitride nanostructures prepared by magnetron sputtering

In this work, ultraviolet photodetectors have been fabricated by depositing silicon nitride nanoparticles on a p-type silicon substrate by closed-field unbalanced dual magnetron sputtering technique. The structural characteristics of silicon nitride have been identified through X-ray diffraction and scanning electron microscopy. Ultraviolet–visible transmission and absorption spectra of the silicon nitride thin films have been recorded. The maximum spectral responsivities of these photodetectors have been measured. The results show that these photodetectors have quantum efficiencies between 0.421 and 0.479 and specific detectivity up to 2.33 × 1011 cm W−1 Hz−1 at 10 kHz. Accordingly, silicon nitride can be considered as an applicable candidate for ultraviolet photodetectors.

Microstructure evolution and energy band alignment at the interface of a Si-rich amorphous silicon carbide/c-Si heterostructure

The microstructure evolution of Si-rich amorphous a-SiC:H films obtained under different annealing conditions was investigated by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The influence of its microstructure on the energy band alignment at a Si-rich a-SiC:H/n-type c-Si hetero-interface was analyzed by ultraviolet visible transmission spectroscopy and ultraviolet photoelectron spectroscopy. The results revealed that the as-deposited Si-rich a-SiC:H film was mainly in an amorphous state. After annealing, Si and SiC quantum dots (QDs) formed, and the crystallinity of the QDs and the proportion of SiC QDs increased with increasing the annealing time at the same annealing temperature. It is found that the energy band alignment at the hetero-interface was influenced by the crystallinity of the films, the sizes of the QDs, and the relative proportion of Si to SiC QDs in a-SiC:H films. Moreover, the contact potential at the hetero-interface decreased with the improved crystallinity of the QDs in a-SiC:H film. The determination of energy band alignment at the Si-rich a-SiC:H/c-Si hetero-interface is beneficial to understanding the carrier transport behavior and designing hetero-structure devices.

Structural and optical properties of oxygen to argon flow ratio on the Zn0.98Cr0.02O thin films deposited by RF magnetron sputtering

High quality polycrystalline Zn0.98Cr0.02O thin films were deposited on glass substrates by RF magnetron sputtering technique. The effects of the gas-flow ratio of O2/Ar on the crystallographic structures and optical properties of the thin films were systemically studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and ultraviolet–visible transmittance measurements, respectively. XRD patterns show that all the films with hexagonal wurtzite structure have a preferred orientation with the c-axis perpendicular to the substrate plane. The results from SEM images reveal that the particle size of the Zn0.98Cr0.02O thin films firstly increases and then decreases with the increasing O2/Ar gas flow ratio. In addition, these films have a high optical transmittance in the visible light region. And it is found that the band gap can be enlarged with the O2/Ar gas flow ratio increasing. The PL measurements indicate that the intensity of the near band-edge emission increases gradually, whereas the intensity of the defect-level emission decreases with increasing O2/Ar gas flow ratio. Based on these results, it can be concluded that the O2/Ar ratios play a key role in controlling the stoichiometric and optical properties of the Zn0.98Cr0.02O thin films.

Effective methodology for the production of novel nanocomposite films based on poly(vinyl chloride) and zinc oxide nanoparticles modified with green poly(vinyl alcohol)

Ultrasonic irradiation and solution dispersion methods were used to organize transparent worthwhile poly(vinyl chloride) (PVC) nanocomposite (NC) films which contain different amounts of modified zinc oxide nanoparticles (NP)s. First, modification of ZnO NPs was accomplished by biocompatible poly(vinyl alcohol) (PVA) to increase NCs compatibility and dispersity in the PVC matrix. The investigation followed by the fabrication and characterization of PVC/ZnO-PVA NCs which obtained via fast and facile ultrasonication irradiation. The measurements of X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy were used for the characterization of properties, structure and morphology of the obtained NPs and their NCs. Furthermore, thermal and optical properties of the resulting NCs were also carried out by thermogravimetric analysis, ultraviolet-visible transmission, and absorption spectra. Morphology results demonstrate well-dispersed characteristics of ZnO-PVA NPs incorporated in the PVC matrix which resulted from modification. Also, modified ZnO NPs enhanced mechanical properties of prepared NC films. Prepared NCs could be categorized as self-extinguishing materials on the basis of the limiting oxygen index values. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Structural Investigations of Gamma-Irradiated PbO Glasses

The effects of gamma radiations on the optical, physical and structural properties of zinc lead borate xZnO-2xPbO-(1-3x)B2O3 and zinc lead borosilicate xZnO-2xPbO-1/2(1-3x)B2O3-1/2(1-3x)SiO2 glasses have been investigated. Differential Scanning Calorimetry (DSC), Ultraviolet-Visible (UV-Vis) and Fourier Transmission Infra-red (FTIR) spectroscopic techniques have been used to compare the properties of samples before and after gamma irradiation by a dose of 2.5 kGy. The variation of density, optical band gap (Eg), IR absorption bands and glass transition temperature (Tg) indicates that the structure of glasses changes due to irradiation. The radiation induced changes created by-ray in the optical, physical and thermal parameters in both the prepared series of glasses have been discussed for their possible application as radiation shielding material.

Effect of Emulsifier Type on the Characterization of O/W Emulsions Using a Spectroscopy Technique

The droplet size distribution (DSD) of emulsions is the result of two competitive effects that take place during emulsification process, i.e., drop breakup and drop coalescence, and it is influenced by the formulation and composition variables, i.e., nature and amount of emulsifier, mixing characteristics, and emulsion preparation, all of which affect the emulsion stability. The aim of this study is to characterize oil-in-water (O/W) emulsions (droplet size and stability) in terms of surfactant concentration and surfactant composition (sodium dodecyl benzene sulphonate (SDBS)/Tween 80 mixture). Ultraviolet-visible (UV-vis) transmission spectroscopy has been applied to obtain droplet size and stability of the emulsions and the verification of emulsion stability with the relative cleared volume technique (time required for a certain amount of emulsion to separate as a cleared phase). It is demonstrated that the DSD of the emulsions is a function of the oil concentration and the surfactant composition with higher stability for emulsions prepared with higher SDBS ratio and lower relative cleared volume with the time. Results also show that smaller oil droplets are generated with increasing Tween 80 ratio and emulsifier concentration.

Pulse laser deposition of epitaxial TiO2 thin films for high-performance ultraviolet photodetectors

The authors report on high quality TiO2 epilayers grown on lattice-matched LaAlO3 substrates by pulsed laser deposition. A prototype of metal–semiconductor–metal ultraviolet (UV) photodetector based on TiO2 was fabricated by employing Au as the Schottky contact metal. The UV–visible transmittance spectrum of the TiO2 epilayer and the spectral response of the photodetector reveal that the deposited anatase TiO2 thin film exhibits excellent visible-blind UV characteristics with an optical bandgap of 3.25eV. In addition, the fabricated photodetector exhibits a high UV-to-visible rejection ratio (R270nm/R400nm) of 105 while displaying a low dark current of 0.25pA under 5V bias and a high responsivity of 0.21A/W, suggesting a potential application in UV photodetection.

Electrical and photovoltaic characteristics of MoS2/Si p-n junctions

Bulk-like molybdenum disulfide (MoS2) thin films were deposited on the surface of p-type Si substrates using dc magnetron sputtering technique and MoS2/Si p-n junctions were formed. The vibrating modes of E12g and A1g were observed from the Raman spectrum of the MoS2 films. The current density versus voltage (J-V) characteristics of the junction were investigated. A typical J-V rectifying effect with a turn-on voltage of 0.2 V was shown. In different voltage range, the electrical transporting of the junction was dominated by diffusion current and recombination current, respectively. Under the light illumination of 15 mW cm−2, the p-n junction exhibited obvious photovoltaic characteristics with a short-circuit current density of 3.2 mA cm−2 and open-circuit voltage of 0.14 V. The fill factor and energy conversion efficiency were 42.4% and 1.3%, respectively. According to the determination of the Fermi-energy level (∼4.65 eV) and energy-band gap (∼1.45 eV) of the MoS2 films by capacitance-voltage curve and ultraviolet-visible transmission spectra, the mechanisms of the electrical and photovoltaic characteristics were discussed in terms of the energy-band structure of the MoS2/Si p-n junctions. The results hold the promise for the integration of MoS2 thin films with commercially available Si-based electronics in high-efficient photovoltaic devices.

Influence of coating pressure on structure and optical properties of GDP films

Using low pressure plasma polymerization technology, glowing discharge polymer films were fabricated at different coating pressures. Surface roughness, chemistry structure and optical properties were measured by atomic force microscopy, infrared absorption spectroscopy and ultraviolet-visible transmittance spectroscopy, respectively. The results show that as the coating pressure increases, the surface roughness of the GDP film and content of the olefinic carbon bonds decrease, while the hydrogen and SP2 CH2 concentration and the optical band gap of GDP films increases.