M. A. Gondal

Synthesis of Gd2O3:Eu nanoplatelets for MRI and fluorescence imaging.

We synthesized Gd2O3 and Gd2O3 doped by europium (Eu) (2% to 10%) nanoplatelets using the polyol chemical method. The synthesized nanoplatelets were characterized by X-ray diffraction (XRD), FESEM, TEM, and EDX techniques. The optical properties of the synthesized nanoplatelets were investigated by photoluminescence spectroscopy. We also studied the magnetic resonance imaging (MRI) contrast enhancement of T1 relaxivity using 3 T MRI. The XRD for Gd2O3 revealed a cubic crystalline structure. The XRD of Gd2O3:Eu3+ nanoplatelets were highly consistent with Gd2O3 indicating the total incorporation of the Eu3+ ions in the Gd2O3 matrix. The Eu doping of Gd2O3 produced red luminescence around 612 nm corresponding to the radiative transitions from the Eu-excited state 5D0 to the 7F2. The photoluminescence was maximal at 5% Eu doping concentration. The stimulated CIE chromaticity coordinates were also calculated. Judd-Ofelt analysis was used to obtain the radiative properties of the sample from the emission spectra. The MRI contrast enhancement due to Gd2O3 was compared to DOTAREM commercial contrast agent at similar concentration of gadolinium oxide and provided similar contrast enhancement. The incorporation of Eu, however, decreased the MRI contrast due to replacement of gadolinium by Eu.

Laser produced plasma diagnosis of carcinogenic heavy metals in gallstones

Gall bladder cancer [GBC] is a highly fatal malignancy. Geographically, regions of high prevalence of gallstones [GSs] have shown to have higher rates of GBC, which is now a recognized risk factor for GBC. Heavy metal toxicity has also been reported to be associated with GBC. An effort therefore at recognizing and avoiding potential risk factors for GBC occurrence is therefore paramount. It is also known that over time heavy metals can accumulate in the biliary system and hence in GSs. We hereby measured the levels of heavy metals in GSs via a highly sensitive technique using a laser produced plasma by comparing the levels of heavy metals in a 29 year old man to a 65 year old man. For this direct spectral analysis of GSs, a laser produced plasma was created by focusing a 266 nm pulsed UV laser generated by fourth harmonics of a Nd:YAG laser on GS samples. For the first time to the best of our knowledge, the plasma parameters, electron temperature and electron density for the GS matrix were computed from the Boltzmann distribution of the upper energy levels and Stark broadening of selected spectral lines. The determination of plasma parameters is important to satisfy the optically thin plasma (to avoid self-absorption) and obtain local thermodynamic equilibrium (LTE) conditions, which are critical for the quantitative analysis. The heavy metal concentrations of chromium, lead, cadmium, nickel and mercury were determined in two different GS samples by recording the laser induced breakdown spectra (LIBS) and by drawing the calibration curves of the spectral lines of carcinogenic metals like chromium, lead, cadmium, nickel and mercury. The results obtained from LIBS were crosschecked using a standard inductively coupled plasma-mass spectrometer (ICP-MS) technique. The effect of delay time (time between the laser pulse and the ICCD camera gate opening) and laser energy on the intensity of the spectral lines of lead, chromium and calcium was also investigated. The system developed in this study is highly applicable for the rapid analysis of any biological or human tissue samples.

Sol–Gel Synthesis of

A facile single-step method was adopted to synthesize gold-modified copper-doped titania nanocomposites. Physicochemical properties of the synthesized material were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy, photoluminescence (PL), and TEM-based techniques. Our characterizations show that the material consisted of anatase-phase qausi-spherical titania nanoparticles (NPs), with 3-4-nm gold particles anchored on titania surface. According to diffuse UV-visible spectroscopic analysis, gold-modified copper-doped titania shows enhanced absorption in the visible-light spectrum compared with copper-doped titania and pure titania. Furthermore, a decrease in PL emission intensity is observed, and this is due to decreased electron-hole recombination, which is an attribute desired for the enhancement of photocatalytic activity. Our present results highlight that these nanocomposites could be used as a photocatalyst for various applications in conjunction with visible solar radiation. The surface modifications make this material for many applications such as gas sensing and photodetection.

\hbox{Au/Cu-TiO}_{2}

Laser induced breakdown spectroscopy (LIBS) was applied for the detection of trace elements in non-degradable part of plastics known as insoluble organic material, obtained from thermal and catalytic degradation of plastics. LIBS signal intensity for each metal measured in the test sample was unique and different. The capability of this technique is demonstrated by analyzing various trace metals present inside plastics and also compared with ICP results. The metal concentration (ppm) measured with LIBS and verified by ICP for Ag (901), Al (522), Fe (231), Co (628), V (275), Ni (558), Pb (325), Mn (167) and Cd (378) are higher than permissible safe limits.

Nanocomposite and Their Morphological and Optical Properties

The main goal of this work was to develop and test advanced techniques for the instant identification of different type of polymers in post-consumer plastics. In order to accomplish this task, infrared (IR), X-ray diffraction (XRD), differential scanning calorimetric (DSC) and laser induced breakdown spectroscopic (LIBS) techniques were applied. The following six model plastics were identified in this study. Low-density polyethylene (LDPE), High-density polyethylene (HDPE), Polypropylenes (PP), Polystyrene (PS), Polyethylene terephthalate (PET) and Polyvinyl chloride (PVC) along with few randomly selected plastics waste such as water bottle and cap, water cups, yogurt container and coke bottle were studied. IR has shown the fingerprinting of polymer types present in plastics waste. The XRD analysis helps to provide characteristic spectral lines whose intensities vary with the type of each constituent polymer. The DSC method provided the different crystalline melting temperature, glass transition, and onset temperature for the peaks and the percent crystallinity data single out different polymers. The ratio of LIBS signals intensities of carbon and hydrogen atoms were employed for the finger printing of the different family of plastics. The combined use of IR, XRD, DSC and LIBS techniques yielded very useful and effective results for plastic waste management.

Determination of trace metals using laser induced breakdown spectroscopy in insoluble organic materials obtained from pyrolysis of plastics waste.

In order to overcome the intrinsic drawback of pristine g-C₃N₄, a nano-composite photo-catalyst Au/S-C₃N₄ with controllable nanoscale gold (Au) particles was successfully synthesized by a facile liquid chemical preparation process. It was found that the content of chloroauric acid (AuCl₃ · HCl · 4H₂O) play crucial role in both the diameter and the density of the Au nanoparticles. The results showed that as-prepared Au/S-C₃N₄ nanosheets with 2 wt% Au loaded content exhibited excellent photocatalytic decomposition of RhB under visible light irradiation as compared with other Au loadings (i.e., 1 wt%, 2 wt%, 3 wt%, 4 wt% and 6 wt%). The photocatalytic activity of Au/S-C₃N₄ with 2 wt% Au loading was twice higher than that of bare S-C₃N₄ (0.00955 min-1). The enhanced performance could be attributed to the synergic effect of gold and sulfur on g-C₃N₄. A possible mechanism for elucidating the better performance of Au/S-C₃N₄ is also proposed and discussed in detail in this work.

Identification of different type of polymers in plastics waste

Graphitic carbon nitride (g-C3N4) and sulfur-doped g-C3N4 were prepared by pyrolysis of melamine and thiourea respectively. Their comparative performance was investigated for photo-degradation of a Rhodamine B (RhB) an organic toxic pollutant. The crystal structure, morphology, microscopic components and properties of the synthesized samples were characterized by XRD, TEM, FT-IR, photoluminescence (PL) emission spectroscopy and zeta potential. TG-DTA is a record of the process for pyrolysis of thiourea. Two simplified kinetic models, pseudo-first-order and pseudo-second-order were applied to predict the adsorption rate constants. Thermodynamic parameters, such as the change in free energy, enthalpy and entropy were also calculated to analyze the process of adsorption. Adsorption isotherms and equilibrium adsorption capacities were established by three well-known isotherm models including Langmuir, Freundlich and Dubinin-Radushkevich (D-R). Both samples were investigated for underlining the reaction mechanism during the photodegradation RhB process and then can be assigned to the overall reaction. The photosensitive hole is regarded as main oxidation species for the degradation by sulfur-doped g-C3N4, but not the exclusive way for g-C3N4. It is worth mentioning that the optimum operating condition can be obtained by orthogonal experiments.

Enhanced Visible Light Photocatalytic Performance of G-C3N4 Photocatalysts Co-Doped with Gold and Sulfur for Degradation of Persistent Pollutant (Rhodamine B)

Pulsed laser ablation in liquids is a simple synthesis process of nano-particles for the production of high purity material with no need for any expensive instrumentation except laser. The 532 nm wavelength laser beam with 5 ns pulse width and 10 Hz repetition rate was an ablating laser source. In order to control the size and stoichiometry of the nano particles, the laser ablation was done in the presence of 9% of H2O2. The optical properties and structure of the prepared samples were studied using different analytical techniques, such as energy dispersive X-ray spectroscope (EDS), X-ray Diffraction, UV-Visible absorption, Photoluminescence, FT-IR. In order to study the morphology of the prepared nano-sized powders, Field Emission Scanning Electron Microscope was used. From the above analytical studies it was found that the particle size was between 13 and 28 nanometer, while the band gap energy was estimated to be 2.46 eV.