Papers by Keyword: Infrared Absorption

Abstract: Understanding molecular electronics is critical in advance of organic devices. Intermolecular interaction between copper phthalocyanine (CuPc) and multi-walled carbon nanotubes (MWCNT) was studied using infrared spectroscopy and confocal Raman microscope. The organics were prepared using solution processing method at ambient atmosphere. The infrared spectrum showed the signal from the lower wavenumber was largely dominated by broad absorption and the lacking of ‘fingerprints’ peaks provided no information on the MWCNT. Raman absorption spectra under normal (λ = 532 nm) and resonant (λ = 633 nm) were obtained to tackle the disadvantages in the former method. Fingerprint peaks of CuPc in frequency of 600 - 1600 cm^-1 emerged under both excitation wavelengths. New 480 cm^-1, 1100 cm^-1 and 1300 cm^-1 peaks were found in resonant spectra. There were no strong evidence of presence and interaction between CuPc and MWCNT detected in these measurements possibly due to overlapping vibrational states between the two compounds and insufficient quantity of MWCNT in the sample.

Abstract: Optimizing the rare earth doping in inorganic binary glasses for tuneable structural and optical properties is ever-demanding for lasing glass. A series of Er³⁺ and Nd³⁺ doped lithium niobate tellurite glasses with compositions of (70-x-y)TeO₂–15Li₂CO₃–15Nb₂O₅–(x)Er₂O₃–(y)Nd₂O_3, where x = 0.0, 1.0 mol % and 0 ≤ y ≤ 1.0 mol% are synthesized using melt-quench technique. Influence of Nd³⁺ ion concentrations on physical and optical behaviour is examined. X–Ray diffraction pattern confirm the amorphous nature of glasses. The strong dependence of spectral properties on rare-earth dopant indicates the alteration in structures and bonding of glass network. The structural properties of the glass represented by the FTIR spectrum indicate that as Nd₂O₃ content increases, the sharp infrared absorption peaks are shifted from 474.7 cm^-1 to 499.4 cm^-1. These peaks are due to Nb-O, Te-O-Te and O-Te-O bond linkage bending vibrations. For TeO₄ trigonal bipyramid, the peak occurred at 676.5 cm^-1 whereas for TeO₃ trigonal pyramid, two infrared band peaks are found at 787.5 cm^-1 and 887.6cm^-1, respectively. The absorption peaks around 1382.7 cm^-1 is due to the Te – O – Nb stretching vibration while peaks at 1635.5cm^-1 and 3411.7 cm^-1 are due to the stretching vibrations of the hydroxyl group participating in the strong metal bonding as well as in the hydrogen bonding, respectively.

Abstract: A glass system based on composition of 80TeO₂-(10-x) B₂O₃ -10PbO-xNd₂O₃, where 0.0mol% ≤ x ≥ 2.5mol% was successfully prepared by melt-quenching method. The structural and optical behavior of the Nd³⁺ doped borotellurite glasses are well studied by mean of their FTIR, XRD as well as UV-Vis -NIR spectroscopy. The XRD pattern obtained confirms the amorphous nature of the glass. Meanwhile, the infra-red absorption spectra of glass samples obtained are recorded using an FTIR spectrometer in the wave number ranging from 400 to 4000 cm^-1. The bands observed were attributed to the different modes of vibrations of Te-O band. From the absorption spectral measurements, the value of optical band gap (E_opt) and the Urbach energy (ΔE) values were calculated with the results were then been discussed nor reported. Quantitative justification of these absorption bands shows that the values of the experimental wave number for most absorption bands are in agreement with the theoretical ones. Optical absorption spectra show that the absorption edge has a tail extending towards lower energies. In general, an increment or a decrement in Urbach’s energy can be considered to be due to a deformation of glass network.

Abstract: The quality of two synthetic quartz crystals, Z lump and Y bar, was researched by the infrared spectrophotometer technology and chemical spectral analysis in this study. The relationships between typical impurity OH and other impurities such as Fe, CO and Mg were discussed which impacted the quality of artificial rock crystal; the defects in artificial rock crystal and crystals, such as lattice dislocation and distortion with a close relation appear at the same time and impact the quality of synthetic quartz. The work in future should begin from the following two aspects in order to improve synthetic quartz crystal quality: the one is to further study the crystal structure characteristics and to explore the cutting type of crystal with convenient cultivation and processing process, high use ratio and high Q value. For example, the research is to make the Z area of Y bar crystals bigger and the other areas smaller or disappear. The other one is to improve the existing technological level and to reduce defects.

Abstract: The reflectance and transmittance spectra for magnesium aluminates spinel single crystals MgO•nAl2O3 and ceramics in the IR spectral range were measured to investigate the nature of vibration modes of constituent ions and incorporated hydrogen. Besides of the earlier observed bands at 545, 710, and 835 cm-1 we registered also two bands 1440 and 1670 cm-1 in single crystals grown by different methods and in spinel optical ceramics. The existence of these bands was supported by measurements of non-stoichiometric spinel crystals and crystals doped with transition metals. The variation of intensity of registered bands in spinel of stoichiometric and non-stoichiometric compositions and spinel ceramics was interpreted in terms of vibration modes of divalent and trivalent cations in different coordination, particularky, at the spatially correlated anti-site defects.

Abstract: This paper presents a novel system for detecting concentration of the CH₄ and CO gases, which exist widely in the coal industry. The system applies micro blazed grating to split the collimated light and may get the infrared absorption light with certain wavelength and bandwidth for the gases detection. The schematic diagram, calculation, signal processing, and setup were described in details. Experimental results indicate that the detection system has the ability to detect methane and carbon monoxide with maximum error of 0.169% and 58.3ppm, stability of 0.76% and 0.22%, respectively.

Abstract: Silicon wafers with different carbon contents have been characterized by Fourier transform infrared spectroscopy technique. An infrared absorption band at 1207cm-1 can be newly observed in the case of carbon content being above 1.7×1017/cm3, whose intensity increases with an increase of carbon concentration in silicon crystal. More interestingly, the 1207cm-1 band cannot be influenced by the long-time annealing in the temperature range of 450-1250oC, suggesting the high thermal stability of this carbon-related defect, which might be related to the presence of silicon carbide in silicon crystals.

Abstract: The surface microstructured silicon prepared by femtosecond laser pulses irradiation in SF₆ shows significantly enhanced light absorption over a wide wavelength range. Absorptance of microstructured silicon is measured from 2 to 16μm, and the absorptance can up to 0.8 in the measured wavelength range. The absorptance of microstructured silicon increases as the height of spikes increases. Emissivity of microstructured silicon at different temperatures(100°C-400°C) is measured from 2.5μm to 25μm. Greatly enhanced emissivity compared to that of flat silicon was observed. At a certain temperature, with increasing the height of the spikes, the emissivity increases. For a sample with 13–14μm high spikes, the emissivity at a temperature of 100°C is approximately 0.96. A tentative explanation for the high absorptance of microstructured silicon has been carried out from three aspects: impurity states, structure defects and multiple reflection of light between spikes. The excellent properties of microstructured silicon make it a promising candidate for applications of infrared detectors, silicon solar cells, flat blackbody source and so on.

Abstract: Quick, accurate and reliable detection of mash gas plays an important role in the coal industry. This paper presents a novel method to get the infrared absorption peak wavelength by light splitting using plane blazed grating, instead of using filter conventionally. The principle and setup of producing 3.433μm and 4.65μm wavelength lights for detecting CH₄ and CO concentration are described in details. The work provides a simple, but efficient option to the infrared absorption gas detection technology.

Abstract: We report on a comprehensive study of the properties of quasi-freestanding monolayer and bilayer graphene produced by conversion of the (6√3×6√3)R30° reconstruction into graphene via intercalation of hydrogen. The conversion is confirmed by photoelectron spectroscopy and Raman spectroscopy. By using infrared absorption spectroscopy we show that the underlying SiC(0001) surface is terminated by hydrogen in the form of Si-H bonds. Using Hall effect measurements we have determined the carrier concentration and type as well as the mobility which lies well above 1000 cm2/Vs despite a significant amount of short range scatterers detected by Raman spectroscopy.