Poopalasingam Sivakumar

Tag-femtosecond laser-induced breakdown spectroscopy for the sensitive detection of cancer antigen 125 in blood plasma

Successful treatment of cancers requires detecting early signs of the disease. One promising way to approach this is to develop minimally invasive tests for the sensitive and specific detection of biomarkers in blood. Irrespective of the detection approach one uses, this remains a challenging task because biomarkers are typically present in low concentrations and there are signals that interfere strongly with prevailing compounds of human fluids. In this paper, we show that elemental encoded particle assay coupled with femtosecond laser-induced breakdown spectroscopy for simultaneous multi-elemental analysis can significantly improve biomarker detectability. An estimated near single molecule per particle efficiency of this method leads to sensitive detection of ovarian cancer biomarker CA125 in human blood plasma. This work opens new ways for earlier detection of cancers and for multiplex assay developments in various analytical applications from proteomics, genomics, and neurology fields.

Pseudo-continuous resonance enhanced multiphoton ionisation: application to the determination of the hyperfine constants of 208Pb19F

A highly efficient pseudo continuous resonance enhanced multiphoton ionisation detection scheme is presented that combines the sensitivity of resonance enhanced multiphoton ionisation (REMPI) with high resolution. This detection scheme is employed to obtain the A(v′ = 1) ← X 1(v = 0) spectra of 208Pb19F with a resolution of 90 MHz. The observed 19F hyperfine splittings are analysed in terms of effective hyperfine parameters that describe the interaction between the fluorine nuclear spin and that of the unpaired electron in the A and X 1 states of the molecule.

Detection and identification of amino acids in Ficoll solutions with femtosecond laser-induced breakdown spectroscopy

We report femtosecond Laser-induced Breakdown Spectroscopy (fs-LIBS) measurements on several amino acids (Serine, Glutamine, and Cysteine) and Albumin protein solutions mixed with Ficoll polysaccharide at different proportions. The goal is to assess the effects of a host matrix on the identification and spectral characterization of amino acids by fs-LIBS. fs-LIBS utilizes an intense short laser pulse to obliterate a sample into basic constituents and to record the emission spectrum of atoms, ions, and molecules in the cooling down of the plasma plume. Several spectral peaks associated primarily with elemental composition of a sample were observed in the fs-LIBS spectra in a range from 200 to 950 nm. In addition, some molecular information associated with diatomic vibrational modes in certain molecules such as C-C and C-N were also obtained. The presence of Ficoll affects the relative intensity and broadening of the CN band, which could be considered as signatures of the amino acids. The fs-LIBS data and their analysis compare favorably with those derived from Fourier Transform Infrared Spectroscopy (FTIR). Interpretation of the spectral information enclosed in the emission of the diatomic molecules during laser ablation may lead to a better understanding of plume chemistry with a direct consequence on chemical analysis of complex samples such as amino acids. Altogether, the results demonstrate the potential of fs-LIBS technique as a detection method of biomolecules and for probing interactions of these biomolecules with a host matrix.

Multiphoton ionization of lead monofluoride resonantly enhanced by the X{sub 1} {sup 2}{pi}{sub 1} at {sub {approx}}{sub sol{approx}} at {sub 2}{yields}B {sup 2}{sigma}{sub 1} at {sub {approx}}{sub sol{approx}} at {sub 2} transition

Resonance enhanced multiphoton ionization of the

Packing density effects on the fluctuations of the emission lines in laser-induced breakdown spectroscopy☆

{X}_{1}phantom{rule{0.2em}{0ex}}^{2}ensuremath{Pi}_{1∕2}

An experimental observation of the different behavior of ionic and neutral lines of iron as a function of number density in a binary carbon–iron mixture

state of lead monofluoride

State-selective detection of the PbF molecule by doubly resonant multiphoton ionization

(^{208}mathrm{Pb}^{19}mathrm{F})

Multiphoton ionization of lead monofluoride resonantly enhanced by the X 1 Π 1 ∕ 2 2 → B Σ 1 ∕ 2 2 transition

via the

Spectroscopic Constants of the Known Electronic States of Lead Monofluoride

Bphantom{rule{0.2em}{0ex}}^{2}ensuremath{Sigma}_{1∕2}

Importance of Emulsification in Calibrating Infrared Spectroscopes for Analyzing Water Contamination in Used or In-Service Engine Oil

state is demonstrated. The ionization potential is observed to be