850-nm Wavelength Research Articles

Ratiometric optical fiber dissolved oxygen sensor based on metalloporphyrin and CdSe quantum dots embedded in sol–gel matrix

A simple, low cost technique to fabricate a ratiometric optical fiber dissolved oxygen sensor has been presented. The ratiometric optical fiber dissolved oxygen sensor comprising a plastic optical fiber coated at one end with Pd(II)/CdSe QDs or Pt(II)/CdSe QDs embedded in sol–gel matrix. Using an LED with a central wavelength of 405nm as an excitation source, it is shown that the emission wavelengths of the oxygen-sensitive dye (PdTFPP, PdTCPP, PtTFPP and PtOEP) and the reference CdSe QDs have no spectral overlap and therefore permit the dissolved oxygen concentration to be measured using a ratiometric-based method.The sensitivity of optical fiber dissolved oxygen sensor is quantified in terms of the ratio I0/I100, where I0 and I100 represent the detected luminescence intensities in fully-deoxygenated and fully-oxygenated water, respectively. The experimental results show that the sensitivities of the ratiometric optical fiber dissolved oxygen sensors are estimated to be 21.7 for PdTFPP-doped sensor, 7.4 for PdTCPP-doped sensor, 6.5 for PtTFPP-doped sensor and 9.2 for PtOEP-doped sensor. The ratiometric sensing approach presented in this study has the advantage of suppressing the effects of spurious fluctuations in the intensity of the excitation source and optical transmission properties of the optic fiber.

Carbon dots preparation as a fluorescent sensing platform for highly efficient detection of Fe(III) ions in biological systems

Water-soluble carbon dots (CDs) were prepared, using a facile hydrothermal oxidation route of cyclic oligosaccharide α-CD, as carbon sources, and alkali as additives. The successful synthesis of CDs was confirmed by scanning electron microscopy (SEM), dynamic light scattering (DLS), FTIR, UV–visible absorption, and emission fluorescence. The characterizations showed that the prepared CDs are spherical and well-dispersed in water with average diameters of approximately 2nm. These water-soluble CDs have excellent photo stability towards photo bleaching during 30days. The obtained CDs showed a strong emission at the wavelength of 450nm, with an optimum excitation of 360nm. The fluorescence quenching of CDs in the presence of Fe(III) ions was used as fluorescent probes for quantifying Fe(III) ions in aqueous solution. Under optimum condition, the fluorescence intensity versus Fe(III) concentration gave a linear response, according to Stern–Volmer equation. The linearity range of the calibration curve and the limit of detection were 1.60×10−5 to 16.6×10−5molL−1, and 6.05×10−6molL−1, respectively, which was in the range for serum analysis of Fe(III). It was concluded that the prepared CDs had a great potential as fluorescent probes for applications in analysis of Fe(III) ions in the blood serum samples, which is hardly interfered by other ions.

Low-temperature plasma-enhanced chemical vapour deposition of transfer-free graphene thin films

Large area transfer free graphene films were deposited at low substrate temperature of 380°C by plasma-enhanced chemical vapour deposition (PECVD) using a nickel buffer layer. The Raman spectrum indicated a structure of highly disordered sp2-C. The current–voltage characteristics of the films showed ohmic behaviour with sheet resistance of ~10.1kΩ/sq and transmittance of 70% at wavelength of 550nm. This transfer-free graphene growth technique is reproducible and is promising for applications in devices.

Highly smooth and refractive films fabricated from titanium oxide hydrate solution

Highly smooth, refractive, and transparent films have recently received attention in the fields of lighting and display applications for being used as energy saving devices via light extraction. Here, we have prepared a titanium oxide hydrate solution from titanium (IV) butoxide in N, N-dimethyl acetamide (DMAc) and evaluated inorganic films fabricated from the solution. The solution was transparent and homogenous mainly due to the complexation of titanium oxide hydrate with DMAc. The solution was spin-coated on a silicon wafer or a glass plate and dried under nitrogen to create a transparent film. The refractive index of the film was ca.1.97 at a wavelength of 550nm, even when it was annealed at a low temperature of 150°C. Atomic force microscope (AFM) results showed that the films were highly smooth and that the root-mean-square (Ra) values of the film׳s surface roughness were sub-nm scale, irrespective of the film drying condition. We identified our titanium oxide hydrate solution in DMAc as a possible good candidate material for films with a high refractive index and surface evenness.

Optical constants of silicon germanium films grown on silicon substrates

Silicon germanium (Si1−xGex) is a material with high mobility and relatively low bandgap making it an attractive candidate for the bottom subcell in a multi-junction solar cell. Optical constants of Si1−xGex films grown on silicon substrates with germanium (Ge) compositions of 77%, 82%, 85% and 88% from wavelength of 400nm to 1450nm at room temperature are reported. Spectroscopic ellipsometry is used to obtain the real part of refractive index for the whole wavelength range and the extinction coefficients for short wavelengths. Optical transmittance ratio of two structures being different only in the thicknesses of the Si1−xGex films is used to extract the extinction coefficients for long wavelengths. We demonstrate that the optical constants of Si1−xGex films grown on silicon substrates with the aid of graded buffer layers are similar to that of their corresponding bulk materials. However, the absorption coefficients of Si1−xGex with 88% Ge determined by us at around 1000nm is three times higher than previously interpolated results. The main reason for this discrepancy may be due to the inaccuracy of interpolation in the wavelength range where the material's bandgap changes very quickly. In addition, it should be noted that the Ge composition of the Si1−xGex films we are able to obtain are determined to be ±1% which is much more accurate than the previous experimentally determined results which have an accuracy of ±5%.

Spectrofluorimetric determination of aluminium in water samples using N-((2-hydroxynaphthalen-1-yl)methylene) acetylhydrazide

A sensitive and selective spectrofluorimetric method has been developed for the rapid determination of aluminium. This method is based on the formation of a complex between aluminium and N-((2-hydroxynaphthalen-1-yl)methylene) acetylhydrazide (HNMA). The fluorescence of the complex is monitored at an emission wavelength of 450nm with excitation at 385nm. Optimum complex formation occurred in Tris buffer at pH 6.0. Under the optimum conditions, linear calibration curves were obtained from 50 to 800ppb. The detection limit was 9.2ppb (ngmL−1). The maximum relative standard deviation of the method for an aluminium standard of 200ppb was 2.5%. The effects of surfactants and interference from other ions were studied. The method was successfully applied for the determination of aluminium ions in water samples.

Fabrication of YAG transparent ceramics using carbonate precipitated yttria powder

Well-dispersed yttria nanopowders were synthesized by a precipitation method from yttrium nitrate solution using ammonium hydrogen carbonate as a precipitant. Needle-like precursor Y2(CO3)3·2.79 H2O undergoes fragmentation and decomposition into isolated quasi-spherical Y2O3 particles upon calcination in air. Highly transparent YAG ceramics were fabricated from the as-synthesized Y2O3 powder and the commercial α-Al2O3 powder by vacuum sintering. Phase transformation, morphology evolution, and sinterability of Y2O3 powders, microstructure and optical properties of YAG ceramics were investigated in detail. The densification, grain growth, linear shrinkage and phase transformation of the as-sintered ceramics were also explored. The activation energy for grain growth in the ceramic sample is 881kJ/mol. With optimized preparation conditions, YAG ceramics with the average grain size of about 20μm were fabricated by sintering at 1780°C for 20h, whose in-line transmittance reached 83.7% and 80.3% at the wavelength of 1064nm and 400nm, respectively.

Improved surface coverage of an optical fibre with nanocrystalline diamond by the application of dip-coating seeding

Growth processes of diamond thin films on the fused silica optical fibres (10cm in length) were investigated at various temperatures. Fused silica pre-treatment by dip-coating in a dispersion consisting of detonation nanodiamond (DND) in dimethyl sulfoxide (DMSO) with polyvinyl alcohol (PVA) was applied. Nanocrystalline diamond (NCD) films were deposited on the fibres using the microwave plasma assisted chemical vapour deposition (MW PA CVD) method. The longitudinal variation of NCD morphology, structure and optical parameters were specifically investigated. The evolution of the film morphology and film thickness along the fibre length was studied using scanning electron microscopy (SEM). The chemical composition of the NCD film was examined with micro-Raman Spectroscopy. The sp3/sp2 band ratio was calculated using the Raman spectra deconvolution method. An approximately 5cm-long homogeneous diamond film has been obtained on the surface of the fibre sample. Thickness, roughness and optical properties of NCD films in the VIS–NIR range were investigated on the reference quartz slides using spectroscopic ellipsometry. The samples exhibited relatively low deviations of refractive index (2.3±0.25) and extinction coefficient (0.05±0.02) along the length of 5cm, as estimated at a wavelength of 550nm. In order to show the effectiveness of deposition process on optical fibres, diamond films were also grown on the fibre with induced long-period grating (LPG). The results of transmission measurements demonstrated that an LPG with diamond overlay exhibits the appropriate dependency on the optical properties of external medium. Thus, the deposition process has a negligible effect on the fibre transmission properties.

Exploration of metaphosphate glasses dispersed with Eu-doped SiAlON for white LED applications

Ca-α-SiAlON:Eu2+ oxynitride phosphors are typical luminescent materials with a high thermal tolerance. A series of metaphosphate glass samples (50MO–50P2O5; mol%, M=Zn, Ca, and Ba) were prepared in order to investigate their ability to disperse Ca-α-SiAlON:Eu2+ phosphor powders. The glass structures of all of the samples were formed using Q2 species and composed in long chain networks by investigation of the NMR and Raman spectra. In the glass samples, SiAlON was dispersed until reaching 5 or 6mass%. The color due to irradiation by a blue LED (wavelength of 450nm) depended on the glass composition, concentration of SiAlON, and thickness of the composite. Regarding the glass formation and quantum efficiency, the BaP glass with between 3 and 4mass% SiAlON composite was determined to be the most suitable for use as a host material for white LEDs.

Defect-sealing of Al2O3/ZrO2 multilayer for barrier coating by plasma-enhanced atomic layer deposition process

Barrier layers were coated by plasma enhanced atomic layer deposition. They had inevitable defects for several reasons and these defects deteriorated the diffusion barrier properties. The size of the pinhole defect decreased with the increase of the layer thickness resulting in enhanced barrier properties, until the thickness reached 20nm for a single-component aluminum oxide (Al2O3) or zirconium oxide (ZrO2) layer. No more enhancement of barrier properties was observed with a further increase of layer thickness, since the defects tended to grow in single-component layers. Alternation of Al2O3 and ZrO2 layers prevented defect growth by covering the defects with another component, and enhanced the barrier properties when compared with single-component layers. Increase of the number of Al2O3/ZrO2 stacks with the same total layer thickness remarkably reduced the water vapor transmission rates value to below 5×10−5g/m2day at 38°C and 100% relative humidity. The Al2O3/ZrO2 multilayer formed on a polyethylene naphthalate substrate at optimized conditions showed light transmittance greater than 86% at a wavelength of 550nm, for application as flexible display substrate.

Effect of organic solar cells using various sheet resistances of indium tin oxide and different cathodes: Aluminum, silver

The effect of different electrodes on organic solar cells (OSCs) performance was studied. Various sheet resistances of indium tin oxide (ITO) were used as an anode to find out which is suitable for OSCs application. The efficiency of OSCs based on small molecule material using different ITO substrates is almost the same due to the low absorption efficiency of active layer. In contrast, the efficiency of device based on polymer material using ITO (15Ω/sq) has a better efficiency, which is attributed to reaching the optimal balance between the light transmittance and the carrier extraction. In cathode, the commonly used for OSCs are aluminum (Al) and silver (Ag), respectively. When substituting Ag for Al as a cathode, the efficiency of device based on copper phthalocyanine and C60 increased from 0.71% to 0.86% and the efficiency of device based on boron subphthalocyanine chloride and C60 increased from 2.61% to 2.96%. The performance enhancement is mainly ascribed to the current density (Jsc) improvement which is resulted from the difference of optical characteristic between the Al and Ag. The reflectance of Ag is higher than that of Al above wavelength of 405nm, indicating that the light reflected from the Ag is more than that of Al. As a result, the more light can be absorbed in the active layer, leading to the efficiency of device using Ag as a cathode have above 10% improvement. However, the most commonly used cathode in OSCs is Al rather than Ag, which is also investigated.

Highly transparent triethoxysilane-terminated copolyimide and its SiO2 composite with enhanced thermal stability and reduced thermal expansion

A highly transparent and colorless copolyimide was synthesized to contain electron withdrawing sulfone and fluorine groups. Then, the triethoxysilane terminal groups were introduced by reacting the anhydride end groups of the polymer with (3-aminopropyl)-triethoxysilane. Based on the triethoxysilane-terminated copolyimide, a series of composites of the copolyimide (PI6FDA-TFDB-mBAPS(Si)) with inorganic SiO2 network was successfully fabricated in order to satisfy the requirements for transparent insulators with high thermal stability. Because the hybrid with inorganic SiO2 networks, the composite (PI6FDA-TFDB-mBAPS(Si)_SiO2) can complementarily improve the thermal resistant drawbacks of organic systems. As a result, the composite films exhibit small values of the coefficient of thermal expansion (CTE) with the increasing SiO2 content. The coefficient of thermal expansion (CTE) of the hybrid PI6FDA-TFDB-mBAPS(Si)_SiO2-40% film is 14.4ppm°C−1 in the temperature range from 80 to 170°C. Compared to a value of 34.7ppm°C−1 for the pristine PI, a 57% reduction is achieved for the composite. The composite possesses the glass transition temperature (Tg) of 276.0°C and shows good optical transmittance of 94% at the wavelength of 450nm. The incorporation of cross-linked SiO2 networks by using the triethoxysilane-terminated PI preserves the high transparency and enhances the thermal stability for the composite films. Due to these optimized properties, the composite can show potential applications in the micro-flexible transparent electronic devices such as transparent insulating panel of advanced transparent display devices and transparent flexible circuit board.

Ratiometric optical sensor for dual sensing of temperature and oxygen

This paper proposes a ratiometric optical temperature and oxygen sensor that incorporates a sol–gel matrix doped with platinum tetrakis pentafluorophenyl porphine (PtTFPP) as the oxygen-sensitive material, 7-amino-4-trifluoromethyl coumarin (AFC) as the temperature-sensing material, and rhodamine 110 (Rh110) as the temperature/oxygen-independent fluorescent dye. The feasibility of coating a color sensor with the sensing film for fabricating a ratiometric optical dual sensing device is investigated. Using an LED with a central wavelength of 405nm as the excitation source, it is shown that the emission wavelengths of the temperature-sensitive, oxygen-sensitive, and reference dyes have no spectral overlap and therefore permit the temperature and oxygen concentration to be measured using a ratiometric-based method. The ratiometric optical dual sensor was tested with regard to monitoring various temperatures and oxygen concentrations. The results show that the luminescence properties of the temperature sensor are independent of the presence of the oxygen sensor, and have a uniquely good linear response in the 25–65°C range. The oxygen sensing scheme presented in this work is intended for use in temperature compensation. The proposed ratiometric sensing approach suppresses the effects of spurious fluctuations in the intensity of the excitation source.

Backscattering Properties of Gold Nanoshells: Quantitative Analysis and Optimization for Biological Imaging

In this article, we investigate the dependence of the backscattering properties of gold nanoshells on the core material, core radius, and shell thickness by using Mie theory of a coated sphere. The size-dependent and dispersive dielectric function of metal nanoparticles permits to consider the localized surface plasmon resonance of gold nanoshells with the classical Mie theory. Our results show that gold nanoshells exhibit resonant backscattering feature due to the resonance of the free electrons in gold shells at a specific incident wavelength. The resonance peak intensity depends on the core material and the dimensions of core and shell, and the resonance wavelength can be tuned to the near-infrared region where biological tissues possess high transmissivity. We obtain the maximum backscattering and the corresponding optimal core radii and shell thicknesses of gold nanoshells at four typical wavelengths (830, 840, 900, and 1310nm) frequently-used in biological imaging. It is found that silica core-gold nanoshells have maximum volume backscattering coefficient (7.01μm-1) at wavelength of 830nm when the core radius is 54.2nm and the shell thickness is 10.1nm. For longer wavelength, the optimal core radius is larger while the optimal shell thickness is thinner, and the maximum volume backscattering coefficient become small. If the core material is changed from silica to vacuum, the gold nanoshells have bigger maximum volume backscattering coefficient with larger core radius and thinner shell thickness. The optimized gold nanoshells can be used as the ideal contrast agents for biological imaging.

The Impact of Enzymes in the Hepatic Function

The aim of this study is the application of Alkaline Phosphatase (ALP) and Gamma-glutamyl Transferase (GGT) activity, by using the corresponding kinetic methods, at the Clinical Chemistry Laboratories in our place. Enzymes are proteins synthesized in the cells of living organisms in order to play the role of bio-catalysts. Today are recognized about 2000 different enzymes. Some of those have been isolated in pure form of the chemical. We used serum as a material and we took into consideration 15 healthy patients, 15 patients who had viral hepatitis and 15 patients with idiopathic hyper-bilirubinemia. Solution where the substance is being analyzed, was treated with specific reagents according to the procedures such as incubation, heating, etc, until the color is formed. The absorbance of the coloring solution was measured using photometry at a wavelength of 405nm. As an analytical method for the determination of ALP, we chose 4-nitrophenylphosphate (4NPP) as a substrate, while as a buffer for the optimal pH adjustment of the reaction we used 2-amino-2 methyl -1-propanol (AMP). ALP was within permitted values from 100 to 290 U /l, whereas Gamma-glutamyl Transferase was at normal reference values of 5 to 51 U /l. Automated method was equal to the standard method, with a correlation coefficient of r = 0997. Accuracy within the series of measurements had a variation coefficient of only 1.25%. From the results taken from the laboratories, we had an increased precision, accuracy, sensitivity and reliability as a result of the technological process of electronic engineering of new modern techniques with monoclonal antibodies and immobilized enzymes.

Influence of Excitation on Photoluminescence Properties of Ag doped In2O3 thin Films Prepared by a Cost-effective Mechanism

In this work, we present the results of photoluminescence (PL) by the Ag doped In2O3 thin films prepared by a cost-effective and much simplified perfume atomizer technique. The PL emission behavior was investigated using three distinct excitation wavelengths (350nm, 450nm and 550nm) upon the deposited films coated in a temperature range of 300° C to 450° C. The stokes shift towards red color for three different excitations was analysed and it has been shown that how the PL emission plays a crucial role in indentifying a good display device material. A highly intensed red emission was found commonly in all films with the excitation wavelength of 350nm. All films exhibit four distinct emission peaks for the excitation wavelength of 450nm and two low intensed emissions were found for the excitation wavelength of 550nm. Further, the X-ray diffraction studies revealed the cubic In2O3 structure with preferential orientation growth along (2 2 2) direction, irrespective of the variation in substrate temperature. A negative sign of Hall coefficient was confirmed the n-type conductivity of prepared samples and the optical parameters were also estimated from transmission data measured by UV-Vis-NIR spectrometer.

Influence of Inorganic Salts on the Refraction Index of Water

The refractive index of double-distilled water and inorganic salt solutions of concentrations varying from 0.4 to 100 ppt (‰) have been measured at 20 Celsius degrees using Abbe refractometer, respectively. The inorganic salts such as NaCl, MgSO4, KCl and MgCl2,these forming the major constituents of seawater are used as solutes of the water solution. The effect of the concentration of these constituents on the refractive index of the solution is experimentally investigated. And meanwhile, the index of refraction studies are carried out for the laser wavelength of 405nm, 450nm, 532nm and 633nm under the case of varying concentration. The results show that the refractive index of the solution will be linearly increased with the increase of the concentration of these constituents. The index of refraction differs for the different solutes when their concentration is same at a certain wavelength.

Effect of protective layer on enhanced transmittance, mechanical durability, anti-fingerprint, and antibacterial activity of the silver nanoparticles deposited on flexible substrate

Enhanced transmittance, mechanical durability, anti-fingerprint, and antibacterial activity of the silver nanoparticles were investigated using a protective layer (fluoride/SiO2 films) deposited onto the silver nanoparticles (NPs)/polyethylene terephthalate (PET). The 15nm-thick protective layers deposited onto the dense and the uniformly distributed silver NPs showed comparable transmittance to the PET substrate, compared with that of about 70% (at a wavelength of 450nm) in samples without a protective layer. In addition, protective layer showed an effective anti-fingerprint and a good mechanical durability after the repeated swipes and touches. The protective layer did not degrade the antibacterial effect of the silver NPs.

Solution-processed silver nanowires as a transparent conducting electrode for air-stable inverted organic solar cells

Highly efficient and air-stable inverted organic solar cells (IOSCs) were fabricated using solution-processed silver nanowire electrodes. The electrodes showed a low sheet resistance of ~16Ωsq−1 and a high transmittance of ~95% at a wavelength of 550nm. A solution-processed ZnO buffer layer is typically used for electron transport and effective passivation of the surface of Ag NW electrodes. The device performance of the IOSCs that used these Ag NW electrodes, which were fabricated on a glass or plastic substrate, was >94% of that of devices containing indium tin oxide (ITO) electrodes. This indicates that solution-processed Ag NW electrode can replace commercialized ITO and can be utilized in roll-to-roll and large-area fabrication processes.

Synthesis and properties of novel soluble and high T g poly(ether imide)s from diamine containing 4,5-diazafluorene and trifluoromethyl units

The synthesis and properties of soluble, high T-g and transparent aromatic polyimides containing 4,5-diazafluorene and trifluoromethyl units in the polymer backbone on the basis of a novel diamine monomer, 9,9-di[4-(4-amino-2-trifluoromethyl phenoxy)phenylene]-4,5-diazafluorene, are described. Incorporation of 4,5-diazafluorene and trifluoromethyl groups into rigid polyimides improves their solubility and transparency without decreasing their physical properties. All of the thermal imidization polyimides are soluble at room temperature in aprotic and protic polar solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, pyridine and m-cresol and can be solution cast into transparent, flexible and tough films. These films have a UV-visible absorption cutoff wavelength at 386-407nm and light transparencies of 73%-84% at a wavelength of 550nm. In addition, the polymers exhibit high thermal stability with a glass transition temperature (T-g) of 305 to 362 degrees C and 5% weight loss at temperatures ranging from 525 to 543 degrees C in nitrogen and from 521 to 538 degrees C in air. The polyimide films possess tensile strengths in the range 79-113MPa, a tensile modulus of 1.75-2.10GPa and elongations at break of 7%-16%. (c) 2014 Society of Chemical Industry