M. A. Shemis

Detection of carcinogenic metals in kidney stones using ultraviolet laser-induced breakdown spectroscopy

The UV single-pulsed (SP) laser-induced breakdown spectroscopy (LIBS) system was developed to detect the carcinogenic metals in human kidney stones extracted through the surgical operation. A neodymium yttrium aluminium garnet laser operating at 266 nm wavelength and 20 Hz repetition rate along with a spectrometer interfaced with an intensified CCD (ICCD) was applied for spectral analysis of kidney stones. The ICCD camera shutter was synchronized with the laser-trigger pulse and the effect of laser energy and delay time on LIBS signal intensity was investigated. The experimental parameters were optimized to obtain the LIBS plasma in local thermodynamic equilibrium. Laser energy was varied from 25 to 50 mJ in order to enhance the LIBS signal intensity and attain the best signal to noise ratio. The parametric dependence studies were important to improve the limit of detection of trace amounts of toxic elements present inside stones. The carcinogenic metals detected in kidney stones were chromium, cadmium, lead, zinc, phosphate, and vanadium. The results achieved from LIBS system were also compared with the inductively coupled plasma-mass spectrometry analysis and the concentration detected with both techniques was in very good agreement. The plasma parameters (electron temperature and density) for SP-LIBS system were also studied and their dependence on incident laser energy and delay time was investigated as well.

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.

Synthesis and photoluminescence of metal coated ZnO nanoparticles

ZnO nanoparticles were prepared by precipitation method from zinc nitrate and ammonium carbonate solutions, and annealing at 500°C. The XRD pattern shows that the ZnO nanoparticles have pure wurtzite structure. ZnO nanoparticles were coated with Au, Ag and Pd atoms using wet chemical treatment. The effect of coating ZnO nanoparticles with Au, Ag and Pd atoms on the photoluminescence properties is investigated. Results show that ZnO-plasmonics can play an important role in emission enhancement. In particular, it was found that coating ZnO nanoparticles with metals enhances the ZnO band edge emission by about 11 to 20 %, depending on the type of metal, and quenches the visible emission by about 50 %.

64 Gb/s quantum-dash laser based indoor free space optical communication

We demonstrate a single channel free space optical dual polarization - quadrature phase shift keying (DP-QPSK) transmission using an injection-locked InAs/InP quantum dash (Qdash) laser by employing external modulation. A receiver sensitivity of −19 dBm at ∼1621 nm is observed over a 4 m indoor channel at 64 Gb/s transmission rate. This stems the potential of Qdash lasers as a source in optical wireless communication, which is being considered as an alternative optical access technology for future high speed communication networks.

Development of Laser Induced Breakdown Spectrometer for detection of carcinogenic metals in gall bladder stones

Laser Induced Breakdown Spectroscopy (LIBS) technique for the detection of carcinogenic metals in gallbladder stones samples was developed. We have studied the effect of the laser pulse energy and the delay time dependence on LIBS signal intensity. The constituting elements present in the test samples were identified by using the finger prints wavelength of elements of interest using NIST database. The detected carcinogenic metals were Cd, Ni, Cr, Pb and Hg. The plasma temperature and the electron density were also determined to check for the local thermal equilibrium conditions for the laser induced plasma generated by focusing the laser beam on gall bladder samples.