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Laser-induced breakdown spectroscopy (LIBS) was employed to determine Cr, Ni, and Zn in Neem-based beauty soaps and Neem leaves. The measurements were accomplished by attaining the optically thin p...

Effects of laser irradiation on the thermal properties and morphological structure of starch, polyvinyl alcohol (PVA) and their blends were studied. Laser irradiation has an insignificant effect on...

Ordered mesoporous indium oxide nanocrystal (m-In2O3) was synthesized by nanocasting technique, in which highly ordered mesoporous silca (SBA-15) was used as structural matrix. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halanda (BJH) studies were carried out on m-In2O3 and the results revealed that this material has a highly ordered mesoporous surface with reduced grain size, increased surface area and surface volume compared to the non porous indium oxide. The diffuse reluctance spectrum exhibited substantially improved light absorption efficiency in m-In2O3 compared to normal indium oxide, however, no considerable change in the band gap energies of these materials was observed. When m-In2O3 was used as a photo-catalyst in the photo-catalytic process of converting carbon dioxide (CO2) into methanol under the pulsed laser radiation of 266-nm wavelengths, an enhanced photo-catalytic activity with the quantum efficienc...

The present article reports the synthesis of polythiophene-titanium(IV) phosphate nanocomposite (PTh-TiP) by a simple in situ titanium(IV) phosphate assisted chemical polymerization of thiophene. The structure and formation of polymer and its nanocomposite was confirmed by FTIR, XRD, FE-SEM, TEM, and TGA techniques. UV-Visible, fluorescence, and circular dichroism spectrophotometry as well as viscometry and DNA melting studies were used to investigate the DNA binding of PTh and PTh-TiP with calf-thymus DNA. The anticancer activities of these materials against MCF-7 and MDA-MB- 231 cancer cells indicated both PTh and PTh-TiP are moderately active, with the latter being more active than the former.

Laser induced breakdown spectroscopy (LIBS) was applied for the detection of carcinogenic elements like bromine in four representative brands of loaf bread samples and the measured bromine concentrations were 352, 157, 451, and 311 ppm, using Br I (827.2 nm) atomic transition line as the finger print atomic transition. Our LIBS system is equipped with a pulsed laser of wavelength 266 nm with energy 25 mJ pulse(-1), 8 ns pulse duration, 20 Hz repetition rate, and a gated ICCD camera. The LIBS system was calibrated with the standards of known concentrations in the sample (bread) matrix and such plot is linear in 20-500 ppm range. The capability of our system in terms of limit of detection and relative accuracy with respect to the standard inductively coupled plasma mass spectrometry (ICPMS) technique was evaluated and these values were 5.09 ppm and 0.01-0.05, respectively, which ensures the applicability of our system for Br trace level detection, and LIBS results are in excellent agreement with that of ICPMS results.

In this work, two solar-based photo catalytic reactors having different geometries and configurations for the disinfection of contaminated water were designed and tested. These solar-based reactors are stair-type open exposure and parabolic trough concentrator (PTC). For the first type, the stairs were coated with TiO2 using sol-gel method, whereas the parabolic type concentrator used a titania-coated rod. For monitoring of disinfection process, the parameters such as solar irradiation exposure time and bacterial deactivation counts were investigated carefully. On contrary to commercial slurry-based photo reactor reported in the literature, thin film titania-coated reactor’s performance was investigated in this work. Moreover, detailed designed aspects of the reactors, process parameters, and reactor operation are presented and discussed. The target aqueous matrix was drinking water developed in laboratory having 106 CFU/mL bacterial strain. Experimental results revealed that during 20 min of sola...

A laser-based technique for deep desulfurization of diesel and other hydrocarbon fuels by removal of dimethyldibenzothiophene (DMDBT), a persistent sulfur contaminant in fuel oils has been developed. We report a selective laser excitation of DMDBT in diesel and model compounds such as n-hexane in a reaction chamber under oxygen environment where oxidative reactions can take place. ArF laser emitting at 193 nm was employed for excitation of oxygen and DMDBT, while for process optimization, the laser energy was varied from 50 to 200 mJ/cm(2). The laser-irradiated DMDBT solution under continuous oxygen flow was analyzed by UV absorption spectrometer to determine the photochemical oxidative degradation of DMDBT. In just 5 min of laser irradiation time, almost 95% DMDBT was depleted in a diesel containing 200 ppm of DMDBT. This article provides a new method for the removal of sulfur compounds from diesel by laser based photochemical process.

The synthesis, characterization and photocatalytic performance of non-traditional Al2O3-TiO2-based photocatalysts is reported. Al2O3-TiO2 support was loaded with various fractions of CuO and ZrO2. A sound agreement was observed between the bandgaps of synthesized powders measured by UV-Visible diffuse reflectance spectroscopy (DRS) in the solid phase and UV-Visible spectroscopy in the aqueous medium. X-ray diffraction (XRD) analysis revealed the composite nature of the catalysts with the retention of individual identity of each component. The average crystallite size of the individual component was found to be in the range of 20 to 40 nm. Scanning electron microscopy (SEM) analysis authenticated the presence of CuO and ZrO2 at the surface of Al2O3-TiO2 support, while Rutherford Back Scattering Spectroscopy (RBS) confirmed the quantity of the modifiers as per theoretical calculations. The composites showed an enhanced photocatalytic activity in sunlight compared to Al2O3-TiO2 for the degradation of dyes. E...

This study was undertaken to develop a methodology suitable for the direct removal and degradation of methyl tertiary butyl ether (MTBE) in water using different nano-catalysts supported laser based photo-oxidation process. For this purpose, nano-structured WO₃ catalyst was synthesized in our laboratory and its photocatalytic activity for the demineralization of MTBE in water was compared with different catalysts such as ZnO, TiO₂, Fe₂O₃ and NiO using 355 nm laser radiations generated by the third harmonic of Nd: YAG laser. The effect of laser irradiation time, amount of catalysts and pH were also investigated for the optimization of MTBE removal process. For 60 min of laser exposure time, the overall percentage of MTBE degradation was found to be 93%, 89%, 82%, 80% and 71% for WO₃, ZnO, Fe₂O₃, NiO and TiO₂, respectively. In addition the photonic efficiencies of different nano-structured catalysts toward degradation of MTBE were estimated, and they were found to follow the trend of WO₃ZnOFe₂O₃NiOTiO₂.

Emission from the lowest quintet state of CO is observed in low power glow discharge. Intersystem crossing from the state to the state makes transition from the state to lower lying states possible. The term values for the three lower vibrational levels of the state are found to be , and above the ground level. The fundamental vibrational frequency of the state is found to be . Analysis of the relaxation pathways of excited CO molecules via the state is carried out and transition lines assigned.

BiOCl-assisted photodegradation of Rhodamine B (Rh. B) molecules was investigated by using white light and green pulsed laser as sources of irradiation in the visible region for the first time. The dependences of removal efficiencies on catalyst dosage, incident pulsed laser energy were investigated and discussed. The dissolved oxygen was found to play an important role during the photochemical reaction. In addition the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) levels of Rh. B molecular were calculated using a Gaussian 03 program. These calculations were valuable to identify the possible photo-catalytic excitation process involved in degradation of Rh.B.

The main aim of this study was to synthesize magnetic separable Nickel/powdered activated carbon (Ni/PAC) and its application as an adsorbent for removal of PFOS from aqueous solution. In this work, the synthesized adsorbent using simple method was characterized by using X-ray diffractionometer (XRD), surface area and pore size analyzer, vibrating sample magnetometer (VSM), and high resolution transmission electron microscope (HRTEM). The surface area, pore volume and pore size of synthesized PAC was 1521.8 m(2)g(-1), 0.96 cm(3)g(-1), 2.54 nm, respectively. Different kinetic models: the pseudo-first-order model, the pseudo-second-order model, and three adsorption isotherms--Langmuir, Freundlich and Temkin--were applied to study the sorption kinetics and isothermal behavior of PFOS onto the surface of an as-prepared adsorbent. The rate constant using the pseudo-second-order model for removal of 150 ppm PFOS was estimated as 8.82×10(-5) and 1.64×10(-4) for PAC and 40% Ni/PAC, respectively. Our results demonstrated that the composite adsorbents exhibited a clear magnetic hysteretic behavior, indicating the potential practical application in magnetic separation of adsorbents from aqueous solution phase as well.

Photoacoustic (PA) gas sensor for the detection of hazardous NO(2) with detection limit as low as few part per billion by volume (ppbV) has been designed and tested with pulsed UV laser. Some design optimization factors such as the optimum cell geometry, buffer gas etc has been proposed. It was found that a cylindrical cell with many acoustic filters considerably dampens the noise level and also argon as a buffer gas improves the photoacoustic signal level and this combination substantially improved the signal to noise ratio and the limit of detection. Ambiguous decline of photo acoustic signal at higher NO(2) concentration due to the adsorption of NO(2) on the walls of the photoacoustic cells and the dependence of this effect on the buffer gases are also discussed. The PA signal dependence on incident laser energy for three cells was also investigated.

A highly sensitive pulsed photoacoustic (PA) spectrometer with different PA cell geometries was designed and fabricated in our laboratory to determine ozone detection at ppb level. The comparative performance and merits of these custom made cells were studied. The excitation source of PA spectrometer is a nanosecond pulsed laser at 266 nm (fourth harmonic of Nd:YAG laser) and a sensitive electret microphone as a photoacoustic detector. The sensitivity optimization of the PA system with different experimental parameters including the resonant acoustic modes of the 3 PA cells was carried out for the detection of ozone. The minimum detection limit for ozone achieved under our experimental conditions, with 3 PA cells were 10, 31 and 26 ppbV for cells designated as cell # 1, cell # 2 and cell # 3, respectively. This limit of ozone detection achieved in our work is quite appreciable to be able to detect ozone under safe permissible limits and the sensitivity achieved in our case is an order of magnitude better than earlier reports using sophisticated laser system like quantum cascade laser.

Efficient removal of phenol was carried out using laser induced photocatalyis process in the presence of Fe(2)O(3) semiconductor catalysts, and under UV laser irradiation. Parametric dependence of the removal process was investigated carefully by variation of laser irradiation time, laser energy, and concentration of the catalysts. pH measurements were also carried out to understand the photocatalytic process for removal of phenol. Maximum phenol removal achieved in this process was more than 90% during 1 hour of laser irradiation. This is considered highly efficient as compared to conventional setups using lamps. Reaction kinetics for the removal of phenol was also studied, and a reaction rate of 0.017 min(- 1) was estimated, following first order kinetics.

Laser-Induced Breakdown Spectroscopy (LIBS) was applied for the identification of various kinds of plastics for management and recycling of plastic waste. In order to fingerprint these plastics, a laser-produced plasma emission was recorded for spectral analysis of various kinds of plastics. The plasma was generated by focusing a Nd:YAG laser radiation at wavelength = 1064 nm having laser energy = 40 mJ. The 6 main family of plastics tested are: Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Polypropylenes (PP), Polystyrene (PS), Polyethylene Terephthalate (PET) and Polyvinyl chloride (PVC). The capability of this technique is demonstrated by the analysis of the major constituents carbon and hydrogen present in polymer matrices. The LIBS signal intensity measured for carbon and hydrogen was detrimental for the fingerprinting of various kinds of plastics. The C/H line intensity ratio was 1.68, 1.51, 1.42, 1.16, 1.01 and 0.91 for HDPE, LDPE, PS, PP, PET and PVC respectively. The detection limits of carbon and hydrogen were found to be approximately 6 micro g/g by applying 20 laser shots. The unique features of LIBS are: it is a simple, rapid, remote, real-time analysis without sampling requirements. The study demonstrated that LIBS could be applied as a best tool for sorting out different kinds plastics on a fast scale for waste management. The health hazards of different kinds of plastics are also described.

Laser-induced breakdown spectroscopy (LIBS) has been applied for the determination of contaminants present in ore samples. The plasma was generated by focusing a pulsed Nd:YAG laser radiation at 1064 nm wavelength on the ore sample collected from one of the open-pit mines located in Saudi Arabia. The concentrations in this ore sample of different elements of environmental significance like Cu, Cr, Ca, Mg, Zn, Ti, Si, Fe and Al were determined by spectral analysis. Parametric dependence for improvement of LIBS sensitivity was carried out. The LIBS results were compared with the results obtained using other analytical techniques such as the inductively coupled plasma emission spectroscopy (ICP-AES). Limits of detection (LOD) of our LIBS system were also calculated for the elements under investigation.

Laser Induced Breakdown Spectroscopy (LIBS) was applied for quantitative elemental analysis of slag samples collected from a local steel plant using an Nd: YAG laser emitting radiation at 1064 nm wavelength. The concentration of different elements of environmental significance such as cadmium, calcium, sulfur, magnesium, chromium, manganese, titanium, barium, phosphorus and silicon were 44, 2193, 1724,78578, 217260, 22220, 5178, 568, 2805, 77871 were mg Kg-1, respectively. Optimal experimental conditions for analysis were investigated. The calibration curves were drawn for different elements. The concentrations determined with our Laser-Induced Breakdown Spectrometers were compared with the results obtained using Inductively Coupled Plasma (ICP) emission spectroscopy. Our study demonstrates that LIBS could be highly appropriate for rapid online analysis of iron slag waste. The relative accuracy of our LIBS system for various elements as compared with ICP method is in the range of 0.001-0.049 at 2.5% error confidence. Limits of detection (LOD) of our LIBS system were also estimated for the elements noted here. The hazardous effects of some of the trace elements present in iron slag exceeding permissible safe limits are also discussed.

The photocatalytic activity of WO 3 semiconductor powder for water splitting into H 2 and O 2 was studied. Instead of conventional broad spectrum light sources like lamps, monochromatic laser radiations in the UV region (γ = 355 nm) were used as the light source for the study of photocatalytic water splitting over WO 3 . An alternate route based upon the photo-chromic properties of WO 3 for the production of hydrogen was suggested. The effect of dissolved metal ions on H 2 and O 2 yield in the presence of various metal ions was also investigated. The effect of the hole-capture agent on H 2 and O 2 yield was also studied by using methanol as a hole-capture agent. The data on pH measurements during the course of reaction was found very useful in explaining the reaction mechanism in general, and metal ions action in particular.

A laser‐based technique for the conversion of methane into higher hydrocarbons and hydrogen has been developed. This technique involves the photo‐dissociation of methane using a high power pulsed ultraviolet laser at 355 nm. The reaction products, such as CH, CH2, C2H2, atomic and molecular hydrogen, are characterized by real‐time laser induced fluorescence for the first time, to our knowledge. In addition to this online fluorescence detection of the species, gas chromatography is also applied to analyze the stable hydrocarbon products generated due to photo‐dissociation of methane. Another interesting result of the laser excitation of methane is the observation of Stimulated Raman lines (Stokes and Antistokes) observed in the 150–850 nm region, which is a manifestation of the inherent characteristics of the laser radiation such as high directionality and high intensity.