Photocatalytic deactivation of sulphate reducing bacteria using visible light active CuO/TiO2 nanocomposite photocatalysts synthesized by ultrasonic processing.

Sulphate-reducing bacteria wreaks havoc to oil pipelines, as it is an active agent for scale formation in the oil production tubing, and plugging of reservoir rock around the oil wells, and this leads to the degradation of oil quality. In this work, we synthesized copper oxide/titanium dioxide nanocomposite photocatalysts with three different mass contents of copper oxide (10%, 20% and 30%) and used them as an effective photo-catalyst in the process of photo-catalytic deactivation of sulphate-reducing bacteria. The anchoring of copper oxide on titanium dioxide brought about the following positive attributes in copper oxide/titanium dioxide nanocomposite pertained to the photo-catalyst: (i) the material transformed to visible light active with the potential to harness the more efficient visible spectral region of the solar radiation, (ii) increased surface area on the photo-catalyst enhanced the number of active reaction sites in the material, and (iii) efficiently retarded the undesired photo-generated electron hole recombination to promote the photo-catalytic activity. Although, the photo-catalyst effective under both UV and visible light, the deactivation was found to be higher in visible radiation, particularly the nanocomposite with 20%- copper oxide on titanium dioxide showed the highest photocatalytic degradation with of Sulphate-reducing bacteria with a decay constant as high as 1.38 min -1 and the total depletion time as low as 8 min. It was confirmed that the bacterial deactivation was neither due to the bactericidal effect of the nanocomposite nor due to the light mediated deactivation.

Customization of surface wettability of nano-SiO2 by coating Trimethoxy(vinyl)silane modifier for oil-water separation: Fabrication of metal-based functional superwetting nanomaterial, characterizations and performance evaluation.

The wettability of nano-SiO2 surface was transformed from the inherent hydrophilicity to functional superhyderophobicity by coating Trimethoxy (vinyl)silane modifier, and the resultant surface showed contrasting wettability for water and oil (Superhydrophobic and Superoleophilic), which is a desired characteristic for the membranes used in oil-water separation. Initially Trimethoxy (vinyl)silane coated SiO2 nanoparticles (TMVS@SiO2) were synthesized by hydrolysis and poly-condensation reactions, and this nano dispersion was spray coated on the annealed stainless-steel mesh surface, whose resulting hierarchical surface texture brought about the desired wettability, with the water-surface-air (θWA) and oil-surface-air (θOA) interfacial contact angles of 150° and 0° respectively. In addition to the wettability studies (contact angles), FTIR, morphological, and elemental characterizations of the TMVS@SiO2 coated surfaces were carried out to understand the alterations that have taken place on the TMVS@SiO2 surface that in turn rendered superhydrophobicity and superoleophilicity to the surface. The FTIR absorption peaks indicate that after modifying SiO2 with TMVS, the -OH groups on SiO2 surface are clearly replaced by -CH3. The morphological studies indicated that modification of SiO2 leads to better cross-linking between coating composition and nanoparticles and EDS spectra and elemental mapping of the modified surface showed the presence of Si, O and C elements. Finally, this surface was tested for its efficiency and stability as a membrane in the process of separating oil and water from the oily water using gravity driven method. The oil-water separation efficiency was estimated to be 99% for this membrane and also it was found to be quite stable as the surface effectively retained this oil-water separation efficiency even after 10 cycles of separation process.

Polyimide based super-wettable membranes/materials for high performance oil/water mixture and emulsion separation: A review.

This article reviews the application of highly heat and pressure resistant polyimide material for the development of membranes/materials that exhibit unique super-wettability, the characteristics pivotal for the efficient separation of oil-water mixture and emulsion. The polymerization of imide monomer in polyimide brings about the required porosity in the material, which in turn renders the crucial surface roughness, which is instrumental for establishing the desired super-wettability on the polyimide based membrane materials, in addition to the mechanical and thermal robustness. The membrane as the oil-water filtering medium can be either oil passing or water passing depends on the individual wettability of the membrane surface for oil and water, which in turn depend on the respective solid-liquid interfacial energy and the hierarchical surface roughness. Superhydrophobic/superoleophobic wetting characteristic of the surface repels water and allows oil to pass through the membrane medium, and the major disadvantage of this kind of oil/water separation is the rapid oil fouling of the membrane pores and the consequent less efficiency for oil water separation. On the other hand, the membrane surface engineered to have the Superhydrophilic/underwater superoleophobic wetting characteristics can be water passing, and the easy fouling of the membrane surface can be minimized. In the case of polyimide materials, there are lot of scopes to engineer the physical properties like surface energy and surface roughness of the membrane surface in order to obtain the required wettability. There have been many works focused on the application of different variants of polyimide materials for developing membrane for oil water separation. In this review, we present an itemized review of various works on polyimide materials based oil/water separation in terms of chemical, physical, structural and surface characteristics of the material.

Nutritional and toxic elemental analysis of dry fruits using laser induced breakdown spectroscopy (LIBS) and inductively coupled plasma atomic emission spectrometry (ICP-AES).

Quantitative investigation of essential and trace heavy elements present in health-beneficial dry fruits (Pistachio, Almonds, Black walnut, White walnut, and Cashew) was investigated using Laser Induced Breakdown Spectroscopy. For an accurate elemental exposure using LIBS technique, the local thermo-dynamical equilibrium of the laser induced plasma was established and verified using McWhirter criterion based on the electron number density in the plasma. Earlier to engage, our LIBS detector was optimized. For quantification of elements, standard calibration curves (CC)-LIBS method was applied. Using our LIBS system, the nutritional elements such as Al, Mg, Ca, Fe, K, Zn, and Na and toxins like Pb, Cr, and Cu were detected in dry fruits. The elemental quantification of dry fruit contents were validated using standard (ICP-AES) method and the relative accuracy of our experimental setup in comparison to ICP approach was in the ranging from 0.1 to 0.3 at 2.5-% error confidence.

Synthesis, characterization and evaluation of visible light active cadmium sulfide-graphitic carbon nitride nanocomposite: A prospective solar light harvesting photo-catalyst for the deactivation of waterborne pathogen.

Cadmium sulfide-graphitic carbon nitride nanocomposite was synthesized by pulsed laser ablation in liquid, and it was found from the results of optical and morphological characterizations that the proper anchoring of nanostructured cadmium sulfide on the nano-sheets of graphitic carbon nitride took place, which brought about the positive attributes such as enhanced visible light absorption and reduced photo-generated charge recombination, the key features required for an efficient photo-catalyst by solar light harvesting. The pulsed laser ablation in liquid method adopted for the synthesis of cadmium sulfide-graphitic carbon nitride has the following advantages: the shape and size of the synthesized particles can be controlled by altering the experimental parameters such as laser wavelength, pulse laser duration, the pH of the solution, the surfactants and the temperature of the solution, pulsed laser ablation in liquid method neither requires cumbersome equipment nor does it require intermediate chemicals and catalysts nor does it necessitate the post synthesis purification. The enhancement of photo-catalytic activity of cadmium sulfide-graphitic carbon nitride nanocomposite was tested for the photo-catalytic deactivation of Escherichia coli bacteria in water under visible light radiation. As anticipated, a significant improvement of photo-catalytic deactivation was observed, which is attributed to the enhanced and extended light absorption in the visible spectral region, and the formation of herterojunction between the semiconductors, which is instrumental in inhibiting the undesired recombination of photo-generated charge carriers. Quantitatively, the presence of cadmium sulfide on the graphitic carbon nitride surface contributed to a remarkable 129% increase of photo-catalytic degradation constant compared to pure graphitic carbon nitride, which resulted in the decrease of total depletion time of Escherichia coli from 156 min to 67 min with the cadmium sulfide-graphitic carbon nitride nanocomposite synthesized by pulsed laser ablation in liquid method. Our results on the efficient photo-catalytic deactivation of Escherichia coli under visible light assures that cadmium sulfide-graphitic carbon nitride nanocomposite can very well be used for photo-catalytic water purification by harvesting the abundant solar light.

LIBS for the detection of lead in ready to use henna paste and nutrients in fresh henna leaves and cultivated soils.

Commercially available ready to use henna paste, procured from the local market in Pakistan were tested to find the level of hazardous element, lead present in the samples, using Laser Induced Breakdown Spectroscopy (LIBS). The source of lead in the ready to use henna is from the artificial chemical additives in henna paste, added to enhance the color and also to speed up the dying of the henna tattoo in hand, feet, and body. Henna tattooing is an inevitable practice in the social events in the cultures of the Indian subcontinent and the Arabian Peninsula. The frequent reckless use of henna, particularly lavishly administering it to the children is quite dangerous, although the level of lead found in the commercially available ready to use henna samples are within the permissible safe level. For the sensitive detection and quantification of lead, various experimental and plasma parameters in the LIBS detection system were optimized and the system was calibrated. The quantitative analysis of lead, carried out in five different samples of ready to use henna, using LIBS revealed that the concentration of lead in these samples is between 5.5 ±â€¯0.2 mg Kg-1 and 16.0 ±â€¯0.2 mg Kg-1. Moreover, LIBS elemental analysis of natural henna leaves, cultivated in Sindh and Punjab regions of Pakistan, and also the soils taken from the locations of cultivation were carried out and a correlation in the elemental compositions between the henna leaves and the cultivated soil in the proximity were studied. The quantitative analysis of LIBS results were validated by atomic absorption spectroscopy (AAS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES).

Photo-catalytic deactivation of hazardous sulfate reducing bacteria using palladium nanoparticles decorated silicon carbide: A comparative study with pure silicon carbide nanoparticles.

Sulfate reducing bacteria (SRB) wreaks havoc in the oil industry by being an agent for oil souring and building corrosion in pipelines and thereby degrade the quality of crude oil. Palladium nanoparticles decorated silicon carbide nanomaterial (Pd-SiC) was synthesized by a facile single step synthesis process and this nanomaterial as a photo-catalyst, as compared to pure silicon carbide (SiC) nanoparticles showed a significant enhancement in the photo-catalytic efficiency in the process of the photo-catalytic deactivation of hazardous SRB. The morphological characterization studies such as Field emission scanning electron microscopy, Transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy unambiguously revealed that SiC surface was successfully decorated with palladium (Pd) nanoparticles. Also the Pd nanoparticles decorated on the SiC surface was further substantiated by EDX and elemental mapping analysis, which clearly revealed the presence of Pd along with Si and O. The band gap energy estimated using Diffuse reflectance spectra (DRS) showed the reduction of band gap energy from 2.82 eV to 2.72 eV. The observed enhancement in the efficiency of photo-catalytic deactivation of SRB with Pd-SiC can be attributed to the significant reduction in the recombination of photo-generated charge carriers, characteristically resulting from the metal (Pd) semiconductor (SiC) junction established by this synthesis process.

Enhanced photo-catalytic activity of ordered mesoporous indium oxide nanocrystals in the conversion of CO2 into methanol.

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 efficiency of 4.5% and conversion efficiency of 46.3% were observed. It was found that the methanol production yield in this chemical process is as high as 485 µlg-1 h-1 after 150 min of irradiation, which is substantially higher than the yields reported in the literature. It is quite clear from the results that the introduction of mesoporosity in indium oxide, and the consequent enhancement of positive attributes required for a photo-catalyst, transformed photo-catalytically weak indium oxide into an effective photo-catalyst for the conversion of CO2 into methanol.

A Rapid and Cost-Effective Laser Based Synthesis of High Purity Cadmium Selenide Quantum Dots.

A rapid and cost effective method is developed to synthesize high purity cadmium Selenide (CdSe) quantum dots in acetone medium using second harmonic of Nd:YAG nanosecond pulsed laser of 532 nm wavelength. The thermal agglomeration due the nanosecond pulse duration of the laser was successfully eliminated by using unfocussed laser beam and thereby providing a favorable conditions for the synthesis of quantum dots having the grain size of 3 nm. The morphological and optical characterizations like XRD, HRTEM, optical absorption of the synthesized CdSe quantum dots, reveal that the material possesses the similar characteristics of the one synthesized through cumbersome wet chemical methods. Relative to the CdSe bulk material, the synthesized CdSe quantum dots showed a blue shift in the measured band gap energy from near infrared spectral region to visible region, making this material very attractive for many solar energy harvesting applications like photo-catalysis and solar cells.

Pulse height tests of a large diameter fast LaBr3:Ce scintillation detector.

The pulse height response of a large diameter fast 100 mm × 100 mm LaBr3:Ce detector was measured for 0.1-10 MeV gamma-rays. The detector has a claimed time resolution of 608 ps for 511 keV gamma rays, but has relatively poor energy resolution due to the characteristics of its fast photomultiplier. The detector pulse height response was measured for gamma rays from cobalt, cesium, and bismuth radioisotope sources as well as prompt gamma rays from thermal neutron capture in water samples contaminated with mercury (3.1 wt%), boron (2.5 wt%), cadmium (0.25 wt%), chromium (52 wt%), and nickel (22 wt%) compounds. The energy resolution of the detector was determined from full width at half maximum (FWHM) of element-characteristic gamma ray peaks in the pulse height spectrum associated with the element present in the contaminated water sample. The measured energy resolution of the 100 mm × 100 mm detector varies from 12.7±0.2% to 1.9±0.1% for 0.1 to 10 MeV gamma rays, respectively. The graph showing the energy resolution ΔE/E(%) versus 1/√Eγ was fitted with a linear function to study the detector light collection from the slope of the curve. The slope of the present 100 mm × 100 mm detector is almost twice as large as the slope of a similar curve of previously published data for a 89 mm × 203 mm LaBr3:Ce detector. This indicates almost two times poorer light collection in the 100 mm × 100 mm detector as compared to the other detector.

Detection of carcinogenic chromium in synthetic hair dyes using laser induced breakdown spectroscopy.

A laser induced breakdown spectroscopic (LIBS) system, consisting of a pulsed 266 nm laser radiation, in conjunction with a high-resolution spectrograph, a gated intensified charge coupled device camera, and a built-in delay generator were used to develop a sensitive detector to quantify the concentration of toxic substances such as chromium in synthetic hair dyes available on the local market. The strong atomic transition line of chromium (Cr I) at 427.5 nm wavelength was used as a fingerprint wavelength to calibrate the detection system and also to quantify the levels of chromium in the hair dye samples. The limit of detection achieved by our LIBS detection system for chromium was 1.2 ppm, which enabled us to detect chromium concentration in the range of 5-11 ppm in the commercial hair dyes available on the local market. The concentrations of chromium in the hair dyes measured using our system were validated using a standard analytical technique such as inductively coupled plasma mass spectrometry (ICPMS), and acceptable agreement (nearly 8%) was found between the results obtained by the two methods (LIBS and ICPMS). This study is highly significant for human health, specifically for people using synthetic hair dyes for changing the color of their hair.

Synthesis of Cu/Cu2O nanoparticles by laser ablation in deionized water and their annealing transformation into CuO nanoparticles.

Nano-structured Cupric Oxide (CuO) has been synthesized using pulsed laser ablation of pure copper in water using Q-switched pulsed laser beam of 532 nm wavelength and, 5 nanosecond pulse duration and laser pulse energy of 100 mJ/pulse. In the initial unannealed colloidal suspension, the nanoparticles of Copper (Cu) and Cuprious oxide (Cu2O) were identified. Further the suspension was dried and annealed at different temperatures and we noticed the product (Cu/Cu2O) was converted predominantly into CuO at annealing temperature of 300 degrees C for 3 hours. As the annealing temperature was raised from 300 to 900 degrees C, the grain sizes of CuO reduced to the range of 9 to 26 nm. The structure and the morphology of the prepared samples were investigated using X-ray diffraction and Transmission Electron Microscope. Photoluminescence and UV absorption spectrometry studies revealed that the band gap and other optical properties of nano-structured CuO were changed due to post annealing. Fourier transform spectrometry also confirmed the transformation of Cu/Cu2O into CuO.