M.A. Gondal

Determination of poisonous metals in wastewater collected from paint manufacturing plant using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) system was developed for determination of toxic metals in wastewater collected from local paint manufacturing plant. The plasma was generated by focusing a pulsed Nd:YAG laser at 1064nm on the solid residue from wastewater collected from paint industry. The concentration of different elements of environmental significance like, lead, copper, chromium, calcium, sulphur, magnesium, zinc, titanium, strontium, nickel, silicone, iron, aluminum, barium, sodium, potassium and zirconium, in paint wastewater were 6, 3, 4, 301, 72, 200, 20, 42, 4, 1, 35, 120, 133, 119, 173, 28 and 12mg kg(-1), respectively. The evaluation of potential and capabilities of LIBS as a rapid tool for paint industry effluent characterization is discussed in detail. Optimal experimental conditions were evaluated for improving the sensitivity of our LIBS system through parametric dependence study. The laser-induced breakdown spectroscopy (LIBS) results were compared with the results obtained using standard analytical technique such as inductively coupled plasma emission spectroscopy (ICP). The relative accuracy of our LIBS system for various elements as compared with ICP method is in the range of 0.03-0.6 at 2.5% error confidence. Limits of detection (LOD) of our LIBS system were also estimated for the above mentioned elements.

Laser Induced Photocatalytic Splitting of Water Over WO3 Catalyst

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.

Direct spectral analysis of tea samples using 266 nm UV pulsed laser-induced breakdown spectroscopy and cross validation of LIBS results with ICP-MS.

Tea is one of the most common and popular beverages spanning vast array of cultures all over the world. The main nutritional benefits of drinking tea are its anti-oxidant properties, presumed protection against certain cancers, inhibition of inflammation and possible protective effects against diabetes. Laser induced breakdown spectrometer (LIBS) was assembled as a powerful tool for qualitative and quantitative analysis of various brands of tea samples using 266 nm pulsed UV laser. LIBS spectra for six brands of tea samples in the wavelength range of 200-900 nm was recorded and all elements present in our tea samples were identified. The major toxic elements detected in several brands of tea samples were bromine, chromium and minerals like iron, calcium, potassium and silicon. The spectral assignment was conducted prior to the determination of concentration of each element. For quantitative analysis, calibration curves were drawn for each element using standard samples prepared in known concentration in the tea matrix. The plasma parameters (electron temperature and electron density) were also determined prior to the tea samples spectroscopic analysis. The concentration of iron, chromium, potassium, bromine, copper, silicon and calcium detected in all tea samples was between 378-656, 96-124, 1421-6785, 99-1476, 17-36, 2-11 and 92-130 mg L(-1) respectively. The limits of detection estimated for Fe, Cr, K, Br, Cu, Si, Ca in tea samples were 22, 12, 14, 11, 6, 1 and 12 mg L(-1) respectively. To further confirm the accuracy of our LIBS results, we determined the concentration of each element present in tea samples by using standard analytical technique like ICP-MS. The concentrations detected with our LIBS system are in excellent agreement with ICP-MS results. The system assembled for spectral analysis in this work could be highly applicable for testing the quality and purity of food and also pharmaceuticals products.

The facile synthesis, characterization and evaluation of photocatalytic activity of bimetallic FeBiO3 in natural sunlight exposure

In an effort to develop sunlight active photocatalysts for environmental remediation, a phase pure bimetallic oxide, FeBiO3, was synthesized by a facile route. The optical, structural and morphological properties of the synthesized FeBiO3 were compared with both the parent oxides i.e. α-Fe2O3 and Bi2O3. The synthesized powder exhibited strong absorption in the visible region with the appearance of a distinct optical absorption edge at 2.15 eV. The PL, Raman and IR spectroscopic investigations of the synthesized powder, in comparison to that of pure oxides, confirmed the formation of pure phase FeBiO3 and revealed the dominant role of Fe3+ ions in controlling the optical properties of the material. The X-ray diffraction analysis (XRD) revealed the hexagonal or rhombohedral geometry with an average crystallite size of 20.2 nm, whereas the X-ray photoelectron spectroscopy (XPS) verified the existence of both Fe and Bi in 3+ oxidation states. The electrochemical evaluation of the synthesized catalysts revealed its excellent stability in the neutral and basic pH in the dark and under illumination however, the catalyst was unstable in the harsh acidic medium (pH = 2). A low resistance to electron transfer and better charge retention ability was witnessed by EIS and chronopotentiometry. The photocatalytic activity of the synthesized catalysts was evaluated in the exposure of complete spectrum and visible region of natural sunlight for the removal of chemically stable substrates such as 2-nitrophenol and 2-chlorophenol. The catalysts showed considerably high activity for the removal of both the substrates in the exposure of natural sunlight, whereas 25% less activity was witnessed in visible region in the same span of time. In addition to degradation, the catalyst also exhibited a substantial activity for mineralization (TOC removal). The catalysts unveiled reproducible activity in the repeated scans. The chemical stability and sustained activity both in the complete spectrum and visible region designate it as a potential candidate for photocatalytic environmental remediation.

Qualitative and quantitative spectro-chemical analysis of dates using UV-pulsed laser induced breakdown spectroscopy and inductively coupled plasma mass spectrometry.

Laser Induced Breakdown Spectroscopy (LIBS) is demonstrated for the spectral analysis of nutritional and toxic elements present in several varieties of date fruit samples available in the Saudi Arabia market. The method analyzes the optical emission of a test sample when subjected to pulsed laser ablation. In this demonstration, our primary focus is on calcium (Ca) and magnesium (Mg), as nutritional elements, and on chromium (Cr), as a toxic element. The local thermodynamic equilibrium (LTE) condition was confirmed prior to the elemental characterization of date samples to ensure accuracy of the LIBS analysis. This was achieved by measuring parameters associated with the plasma, such as the electron temperature and the electron number density. These plasma parameters aid interpretation of processes such as ionization, dissociation, and excitation occurring in the plasma plume formed by ablating the date palm sample. The minimum detection limit was established from calibration curves that involved plotting the LIBS signal intensity as a function of standard date samples with known concentrations. The concentration of Ca and Mg detected in different varieties of date samples was between 187 and 515 and 35-196mgL(-1) respectively, while Cr concentration measured between 1.72 and 7.76mgL(-1). In order to optimize our LIBS system, we have studied how the LIBS signal intensity depends on the incident laser energy and the delay time. In order to validate our LIBS analysis results, standard techniques such as inductively coupled plasma mass spectrometry (ICP-MS) were also applied on an identical (duplicate) date samples as those used for the LIBS analysis. The LIBS results exhibit remarkable agreement with those obtained from the ICP-MS analysis. In addition, the finger print wavelengths of other elements present in date samples were also identified and are reported here, which has not been previously reported, to the best of our knowledge.

Synthesis, characterization and visible light photocatalytic activity of Cr3+, Ce3+ and N co-doped TiO2 for the degradation of humic acid

The synthesis, characterization and photocatalytic activity of Cr3+ and Ce3+ co-doped TiON (N-doped TiO2) for the degradation of humic acid with exposure to visible light is reported. The synthesized bimetal (Cr3+ + Ce3+) modified TiON (Cr–Ce/TiON), with an evaluated bandgap of 2.1 eV, exhibited an enhanced spectral response in the visible region as compared to pure and Ce3+ doped TiON (Ce/TiON). The XRD analysis revealed the insertion of Cr3+ and Ce3+ in the crystal lattice along with Ti4+ and N that resulted in the formation of a strained TiON anatase structure with an average crystallite size of ∼10 nm. Raman analysis also supported the formation of stressed rigid structures after bimetal doping. HRTEM confirmed the homogeneous distribution of both the doped metallic components in the crystal lattice of TiON without the formation of surface oxides of either Cr3+ or Ce3+. Electron energy loss spectroscopy (EELS) analysis revealed no change in the oxidation of either Cr or Ce during the synthesis. The synthesized Cr–Ce/TiON catalyst exhibited appreciable photocatalytic activity for the degradation of humic acid on exposure to visible light. Additionally, a noticeable mineralization of carbon rich humic acid was also witnessed. The photocatalytic activity of the synthesized catalyst was compared with pristine and Ce3+ doped TiON.

Synthesis, characterization and photocatalytic activity of Al2O3-TiO2 based composites

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. Efforts were made to elucidate the enhanced sunlight response of the synthesized composite catalysts compared to Al2O3-TiO2. As monitored by ion chromatography (IC), the synthesized photocatalysts completely mineralized the dyes leaving behind inorganic ions in solution. The kinetics of photocatalytic degradation of dyes was evaluated for optimum correlation with the existing models. The stability of the photocatalysts against the photo-corrosion was monitored by analyzing the samples for respective metals in solution after sunlight exposure. Supplemental materials are available for this article. Go to the publishers online edition of the Journal of Environmental Science and Health, Part A, to view the supplemental file.

Emission spectra of calcium dimer. The A 1∑u+ − X 1∑g+ system

The A 1 ∑ u + −X 1 ∑ g + spectral system of Ca 2 has been studied in two independent experiments. The collision-induced fluorescence due to this band was investigated following the resonant excitation of the 4s4p 3 P 1 metastable state of calcium using a Nd : YAG laser pumped dye laser. In another experiment, a low current glow discharge in calcium vapor was used. We have assigned 86 spectral lines to this band system for vibrational quantum numbers ( v ′ = 10–13 and v″ = 0) by applying a Dunham type analysis. The A 1 ∑ u + state dissociation energy D′ e is estimated to be ~ 8693.6 ± 1 cm −1 . The processes involved in the collisional excitation of the upper molecular state are discussed.

Pharmacological evaluation of poly(3-methylthiophene) and its titanium(IV)phosphate nanocomposite: DNA interaction, molecular docking, and cytotoxic activity.

Cancer and pathogenic microbial diseases have terribly affected human health over a longer period of time. In response to the increasing casualties due to cancer and microbial diseases, unique poly(3-methylthiophene) and poly(3-methylthiophene)-titanium(IV)phosphate composite were prepared via in-situ oxidative chemical polymerization in this work. The poly(3-methylthiophene) and poly(3-methylthiophene)-titanium(IV)phosphate composite were well characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. DNA binding studies by UV-Visible and fluorescence spectroscopic investigations indicated strong binding affinities of poly(3-methylthiophene) and poly(3-methylthiophene)-titanium(IV)phosphate nanocomposite; leading to structural damage of DNA. Poly(3-methylthiophene)-titanium(IV)phosphate nanocomposite showed stronger interactions with DNA as compared to poly(3-methylthiophene) and from dye displacement assay it was confirmed that mode of binding of both the formulations was intercalative. The antimicrobial screening revealed that polymer and its composite displayed stronger antibacterial effects than ampicillin against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhimurium. Besides, the poly(3-methylthiophene) and poly(3-methylthiophene)-titanium(IV)phosphate nanocomposite showed dose dependent effects towards estrogen receptor positive breast cancer (MCF-7) and estrogen receptor negative breast cancer (MDA-MB-231) cell lines; with poly(3-methylthiophene)-titanium(IV)phosphate nanocomposite showing better activities against both cell lines. In all in-vitro biological investigations, poly(3-methylthiophene)-titanium(IV)phosphate composite showed superior properties to that of the pure poly(3-methylthiophene), which encouraged us to suggest its potential as future therapeutic gear in drug delivery and other allied fields.

Observation of thea3Σu+-X1Σg/+ system of calcium dimer

SummaryWe report the observation of collision-induced spectra of calcium dimer in the 680–692 nm region. The spectra were recorded after resonant laser excitation of 4s4p3P1 state of atomic calcium. Here the upper statea3Σu+ is populated through collisions. The same spectra were reproduced in a low-current glow discharge in calcium vapor. The assignment of the observed spectral lines was carried out by applying the Dunham-type analysis and the spectra were assigned to thea3Σu+-X1Σg/+ transition of Ca2. The existence ofa3Σu+ state withν00 = 13850 ± 1 cm−1 andωe ∼ 37.6 cm−1 is confirmed.