Prof. Walid Tawfik

Cairo University, National Institute of Laser Enhanced Sciences, Faculty Member

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•Professor Walid Tawfik is the Chairman of the Department of Laser Applications in Metrology, Photochemistry, and Agriculture (LAMPA), leader of laser spectroscopy and ultrafast lasers group, and head of the central lab at the National Institute of Laser (NILES), at Cairo University, Egypt. He received his PhD on 2000 in laser spectroscopy “Study of photon molecular interaction dynamics using short laser pulses”, where he did his experiments at Technical Uni. Munich, Germany. He is interested in the fields of laser-induced plasma spectroscopy, ultrafast lasers, ultrafast spectroscopy, and smart materials applications. He has published two books’ chapters and several papers. He is a senior member of different international professional societies like IEEE, OSA, APS, and SPIE. He has collaborated with different international groups in laser spectroscopy and ultrafast lasers at Georgia Tech USA, Uni. of Electro-Communications Japan, POSTECH Uni. South Korea, Quaid-i-Azam University, Islamabad, Pakistan, Kind Saud Uni. Saudi Arabia, Max-Planck Inst. Germany and Lodz Uni. of Tech. Poland.

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Papers by Prof. Walid Tawfik

Detection of heavy metal elements by using advanced optical techniques

Journal of the Egyptian Society for Basic Sciences-Physics

The presence of heavy metals in the environment presents a significant concern, as it poses a sub... more The presence of heavy metals in the environment presents a significant concern, as it poses a substantial threat to both human health and food safety. Accurate measurement and identification of heavy metals in diverse sample types, encompassing water, soil, food, and biological materials, necessitate utilizing various spectroscopic techniques. In this comprehensive review, a meticulous examination of three prevalent methodologies employed for heavy metal analysis in soil is undertaken: Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Laser-Induced Breakdown Spectroscopy (LIBS), and Atomic Absorption Spectroscopy (AAS). An elaborate exposition of the operational principles underlying each method is provided, their respective strengths and limitations are delineated, and the specific contexts in which they find application are elucidated. Furthermore, recent developments and forthcoming prospects associated with each of these techniques are elucidated, underscoring the potential advantages of their combined use alongside other analytical modalities to augment precision and speed in heavy metal analysis. The analysis emphasizes that (ICP-OES), LIBS, and AAS offer distinct capabilities and restrictions within the domain of heavy metal detection. Selecting the most appropriate technique hinges on the prerequisites and situational aspects characterizing each analytical challenge. This review furnishes a holistic comprehension of these analytical methodologies, underscoring their pivotal role in addressing the pressing issue of heavy metal contamination and providing valuable insights for optimizing the selection and application of these techniques in environmental and food safety assessments.

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A new vision of photothermal therapy assisted with gold nanorods for the treatment of mammary cancers in adult female rats

Nanoscale advances, Dec 31, 2023

Over the past decade, the therapeutic landscape has markedly changed for patients with breast can... more Over the past decade, the therapeutic landscape has markedly changed for patients with breast cancers (BCs), yet few studies have evaluated the power of the photothermal therapy (PTT) technique. The present study aimed to assess the potency of 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary cancer treatment with this technique. In total, forty-two adult virgin female Wistar rats were categorized into seven groups, negative control, polyvinylpyrrolidone-capped gold nanorods (PVP-AuNRs) positive control (400 mL per rat ∼ 78 ppm), NIR laser irradiation 808 nm positive control with an intensity of (808 nm NIR CW diode laser, 200 mW cm -2 for 5 min), DMBA-treatment, DMBA-induced mammary cancer group treated with polyvinylpyrrolidone-capped gold nanorods, DMBA-induced mammary cancer group treated with NIR laser irradiation, and DMBA-induced mammary cancer group treated with polyvinylpyrrolidone-capped gold nanorods and NIR laser irradiation. Treatment with polyvinylpyrrolidone-capped gold nanorods and/or NIR laser irradiation was performed after three weeks of DMBA-induced mammary cancer. The mammary tumor lesions in the rat model induced with DMBA are highly invasive. Synthesis and characterization of gold nanorods (AuNRs) with an aspect ratio ranging from 2.8 to 3 were employed to validate the nanostructure and polyvinylpyrrolidone capping and their stability in absorbing near-infrared light. As a result, the therapy strategy, DMBA + PVP-AuNRs + NIR, effectively treated the tumor and halted its growth. The mammary glands were dissected and subjected to biochemical analysis for serum and tissue. Our treatment technique improved the histological aspects of mammary cancer in various forms of mammary cancer detected. Immuno-histochemical localization and TEM images supported these results reflecting the efficacy of this technique. Finally, our findings uncover for the first time the revolutionary effect of the PTT strategy using PVP-capped AuNRs in selectively destroying mammary cancer cells in rats.

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Tuning the structural, optical, and photocatalytic properties of V 2 O 5 /PMMA nanocomposite films for methylene blue photodegradation

Research Square (Research Square), Nov 13, 2023

In this work, the Poly (methyl methacrylate) (PMMA) lms have been developed for the photodegradat... more In this work, the Poly (methyl methacrylate) (PMMA) lms have been developed for the photodegradation of methylene blue (MB) by incorporating vanadium pentaoxide (V 2 O 5 ) catalysts. The obtained lms were characterized by SEM, XRD, UV-Vis, FTIR and Raman spectroscopy. The XRD patterns revealed the amorphous domains of the PMMA polymer, with an increase in these domains with increasing the V 2 O 5 content. Moreover, the XRD showed shifts of 2θ from 16.55° to 17.8°, which can be attributed to the structural irregularity of the PMMA backbone chain caused by the nano ller doping with no impurity peaks. The observed SEM images showed that V 2 O 5 has a hierarchical nanobelt interconnected structure with thicknesses of 30-150 nm and 50-300 nm in length. According to UV-Vis spectroscopy measurements, the absorbance shifts towards a longer wavelength (270-330 nm) and exhibits intensity increase as V 2 O 5 nanoparticles amount increase. The band gap of PMMA was decreased after the incorporation of V 2 O 5 NPs. The optical conductivity σ op exhibits an increase in the photon energy window (3.8 eV-4.2 eV) by values (2x10 11 -7x10 11 ) as the V 2 O 5 nanoparticles ratio content increases. Interestingly, the 3.3 wt% V 2 O 5 /PMMA photocatalyst lm exhibited the highest photocatalytic degradation of MB (97%) after 45 minutes of UV illumination.

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Ultrafast Picosecond Laser Spectroscopy and ICP-OES Assisted Calibration-free of Toxic Metal Concentrations in Contaminated Agricultural Soils

Research Square (Research Square), Nov 13, 2023

Excess fertilizer and chemical use have contaminated soil with harmful heavy metals near the Abu-... more Excess fertilizer and chemical use have contaminated soil with harmful heavy metals near the Abu-Zaabal facility in Egypt. This study pioneers an approach using picosecond laser-induced plasma spectroscopy (Ps-LIPS) and inductively coupled plasma optical emission spectrometry (ICP-OES) to quantify toxic metal levels without calibration constraints. A 100 mJ Nd: YAG laser with 170 picosecond pulses has been employed for the Ps-LIPS. Systematic soil sampling at six sites near the facility enabled Ps-LIPS to formulate unrestricted calibration-free curves for lead, cadmium, cobalt, zinc, iron, and nickel. Applying the Boltzmann distribution and plot methods anchored to calcium spectral lines determined plasma electron density and temperature under local thermodynamic equilibrium. Models were validated against ICP-OES, affirming Ps-LIPS with under 8% average relative error. Results revealed notable concentration variations contingent on the metal, sampling site, and orientation to the facility. This pioneering Ps-LIPS study demonstrates precise quantification of toxic metals in soils without prior calibration. It provides a pragmatic tool for contamination assessment, representing a seminal advance in environmental analytical methodology.

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Advancing Environmental Monitoring: Unveiling Heavy Metal Contamination with Calibration-Free Picosecond Laser-Induced Breakdown Spectroscopy (CF-PS-LIBS)

Elevated concentrations of heavy metals in environmental matrices are linked to substantial toxic... more Elevated concentrations of heavy metals in environmental matrices are linked to substantial toxicity hazards, impacting human health and ecosystem wellbeing. In this research, Calibration-Free Picosecond Laser-Induced Breakdown Spectroscopy (CF-PS-LIBS) is introduced for determining concentrations of Fe, Zn, Mn, Ni, Pb, and Cr in the roots and shoots of clover plants collected from villages in the Banha and Giza governorates of Egypt. CF-PS-LIBS spectra, generated by a 1064 nm Q-switched Nd: YAG laser with a pulse width of 170 ps and energy of 100 ± 5% J/cm², are analyzed to assess heavy metal content. The study leverages emission intensity and broadening associated with the Ca I characteristic lines at specified wavelengths to provide insights into plasma evolution. Linear variations in electron temperature (Te) and electron density (Ne) are observed in samples with heavy metal concentrations ranging from 0.11 to 0.17 mg/kg for Cr and 429.03 to 2259.51 mg/kg for Fe. Plasma Te escal...

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Calibration free laser-induced breakdown spectroscopy (LIBS) identification of seawater salinity

Optica Applicata, 2007

Laser-induced breakdown spectroscopy (LIBS) has been used as a remote sensing system to analyze s... more Laser-induced breakdown spectroscopy (LIBS) has been used as a remote sensing system to analyze seawater samples and to identify their salinities without ordinary calibration curves. The plasma is generated by focusing a pulsed Nd: YAG laser on the seawater surface in air at atmospheric pressure. Such plasma emission spectrum was collected using wide band fused-silica optical fiber of one-meter length connected to a portable Echelle spectrometer (Mechelle 7500 -Multichannel Instruments, Stockholm, Sweden) with intensified CCD camera. Spectroscopic analysis of plasma evolution of laser produced plasmas has been characterized in terms of their spectra, electron density and electron temperature assuming the local thermodynamic equilibrium (LTE) and optically thin plasma conditions. Three elements Na, Ca and Mg were determined in the obtained spectra to identify the salinity of seawater samples. The electron temperature T e and density N e were determined using the emission intensity and Stark broadening. The obtained values of T e and N e for natural seawater sample (salinity 3.753%) are 11580 K ± 0.35% and 3.33×10 18 cm -3 ± 14.3%. These values exhibit a significant change only if the matrix changes (i.e., the salinity changes). On the other hand, no significant difference was obtained if T e and N e were determined using any of the three elements (Na, Ca and Mg) in the same matrix. It is concluded that T e and N e represent a fingerprint plasma characterization for a given seawater sample and its salinity could be identified using only one element without need to analyze the rest of elements in the seawater matrix. The obtained results indicate that it is possible to improve the exploitation of LIBS in the remote on-line environmental monitoring, by following up only a single element as a marker to identify the seawater matrix composition and salinity without need to analyze that matrix which saves a lot of time and efforts.

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Corrigendum to “Ar plasma waveguide produced by a low-intensity femtosecond laser” [Opt. Commun. 285(10–11) (2012) 2627–2631]

Optics Communications, Jul 1, 2013

Recent Advances in the Investigation of Textiles Using Laser-Induced Breakdown Spectroscopy (LIBS)

IGI Global eBooks, Nov 25, 2022

Ar plasma waveguide produced by a low-intensity femtosecond laser

Optics Communications, May 1, 2012

Using the interaction of a low-intensity femtosecond laser pulse (30 fs, 6 × 10 15 Wcm -2 ) with ... more Using the interaction of a low-intensity femtosecond laser pulse (30 fs, 6 × 10 15 Wcm -2 ) with argon cluster jet produced from a slit nozzle, we experimentally probe the formation of a uniform plasma waveguide by the interferogram analysis. The results about evolution of plasma channel demonstrate that it is feasible to produce the plasma waveguide for an fs laser pulse of low-intensity. It takes tens of nanoseconds to form a plasma waveguide. The simulation by one-dimensional Gaussian plasma hydrodynamic expansion model indicates that the temperature of plasma channel is not high under this condition. Thus it takes tens of nanoseconds to form a plasma waveguide.

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Effect of choosing the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll" id="d1e449" altimg="si277.gif"><mml:msub><mml:mrow><mml:mi>Q</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">α</mml:mi></mml:mrow></mml:msub></mml:math>-values and daughter ...

Annals of Physics, Jul 1, 2019

Abstract We investigated the effects of choosing the α -decay energy ( Q α ) and particular densi... more Abstract We investigated the effects of choosing the α -decay energy ( Q α ) and particular density distributions of the daughter nuclei on predicting unknown magic numbers, or confirming some of them. The Q α values were calculated using three models, namely the finite-range droplet model (FRDM), the Weizsacker–Skyrme (WS4) mass model, and a recent fitting formula. The α -decay half-lives ( T α ) of superheavy nuclei of Z = 118–124 have been calculated within the generalized density-dependent cluster model. The double-folding α +core potential was determined based on the M3Y-Reid nucleon–nucleon interaction. We have used the two-parameter Fermi distribution to represent the nuclear density, with four sets of parameters that were determined based on electron scattering data and different microscopic calculations. Upon investigating the relative stability of the mentioned superheavy isotopic chains, we found that the Q α -values deduced from FRDM and WS4 models predict different neutron magic numbers. The examined fitting formula failed to predict any magic number larger than N = 162. Under normalization to the proton and neutron (N) numbers, the different choices of the density distributions showed almost no effect on the general behavior of T α with N, but changed its values up to one order of magnitude. Even though the maxima and minima of T α clearly follow the characteristic minima and maxima of Q α , respectively, the results showed that precise density distribution and deformations, in addition to a correct preformation probability, are necessarily required for estimating an accurate value of the half-life.

Improved LIBS limit of detection of Be, Mg, Si, Mn, Fe and Cu in aluminum alloy samples using a portable Echelle spectrometer with ICCD camera

Optics and Laser Technology, Feb 1, 2008

Laser-induced breakdown spectroscopy (LIBS) is a laser-based technique that can provide non-intru... more Laser-induced breakdown spectroscopy (LIBS) is a laser-based technique that can provide non-intrusive, qualitative and quantitative measurement of metals in various environments. LIBS uses the plasma generated by a high-energy laser beam to prepare and excite the sample in one step. In the present work, LIBS has been applied to perform elemental analysis of six trace elements simultaneously in aluminum alloy targets. The plasma is generated by focusing a pulsed Nd:YAG laser on the target in air at atmospheric pressure. LIBS limit of detection (LOD) is affected by many experimental parameters such as interferences, self-absorption, spectral overlap and matrix effect. We aimed to improve the LIBS LOD by optimizing these experimental parameters as possible. In doing so, a portable Echelle spectrometer with intensified CCD camera was used to detect the LIBS plasma emission. This advanced Echelle spectrometer provides a constant spectral resolution (CSR) of 7500 corresponding to 4 pixels FWHM over a wavelength range 200-1000 nm displayable in a single spectrum. Then, the calibration curves for iron, beryllium, magnesium, silicon, manganese and copper as minor elements were achieved with linear regression coefficients between 98-99% on average in aluminum standard sample alloys. New LOD values were achieved in the ppm range with high precision (RSD 3-8%). From the application view point, improving LIBS LOD is very important in the on-line industrial process control to follow-up multi-elements for the correct alloying in metals.

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Spectroscopic determination of the stark broadening parameters of Al (I) 305.007 nm in atmospheric air using picosecond time-resolved LIPS

Journal of Molecular Structure

Fast LIBS Identification of Aluminum Alloys

PROGRESS IN PHYSICS, 2007

April, 2007 PROGRESS IN PHYSICS Volume 2 Fast LIBS Identification of Aluminum Alloys Walid Tawfik... more

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Assessment of contamination levels of heavy metals in the agricultural soils using ICP-OES

Soil and Sediment Contamination: An International Journal

The Effects of Fructose on the Developmental Competence, Biochemical Biomarkers and Apoptotic Gene Expression by Murine Oocytes

Egyptian Journal of Veterinary Sciences

T HE goal of the current study was to investigate the effects of fructose supplementation in the ... more T HE goal of the current study was to investigate the effects of fructose supplementation in the culture medium on in vitro maturation, and the developmental competence of murine oocytes, biochemical markers and the expression of apoptotic and HIF-1α in cumulus oocyte cells (COCs). Murine oocytes were matured in IVF media supplemented with 1.25, 2.75 and 5-mM fructose. The developmental parameters (MI, MII, GVBD, degenerated and activated cells) were examined with NO, GPX, GSH, MDA, and TAC biomarkers. The expression of mRNA for apoptotic genes by COCs were evaluated. The low dosage improves significantly (P<0.05) the developmental competence markers than the control and higher doses of fructose. In vitro-matured mouse oocytes with 1.25 mM fructose showed a significant increase (P<0.05) in NO level in the In-vitro matured when compared with the control and other groups. The GPX concentrations in the in-vitro matured oocytes showed a significant decrease (P<0.05) with 5mM fructose. The MDA levels in the vitro-matured oocytes were higher (P<0.05) when the murine oocytes were exposed to 2.75 mM of fructose. The TAC in the oocyte showed no changes (P˂0.05) when the oocytes were exposed to both 1.25 mM. Moreover, the supplementation of IVM media showed a down regulation of apoptotic and HIF-1α genes when compared with the control and high dosage supplementation (P<0.05). Altogether, the supplementation of IVM media with lower dosage of fructose improves the developmental competence markers in the murine oocytes via its effects on oxidant and antioxidant activity and downregulation of apoptotic and HIF-1α genes.

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Efficacy of polyvinylpyrrolidone-capped gold nanorods against 7,12 dimethylbenz(a)anthracene-induced oviduct and endometrial cancers in albino rats

Egyptian Journal of Basic and Applied Sciences

Laser spectroscopic applications in cancer nanotechnology

Transcriptomics: open access, Nov 17, 2017

Volume 2 PROGRESS IN PHYSICS Study of the Matrix Effect on the Plasma Characterization of Six Elements in Aluminum Alloys using LIBS With a Portable Echelle Spectrometer

Laser-induced breakdown spectroscopy (LIBS) has been applied to perform a study of the matrix eff... more Laser-induced breakdown spectroscopy (LIBS) has been applied to perform a study of the matrix effect on the plasma characterization of Fe, Mg, Be, Si, Mn, and Cu in aluminum alloy targets. The generated plasma emissions due to focusing of a 100 mj Nd: YAG pulsed laser at 1064 nm at the target surface were detected using a portable Echelle spectrometer with intensified CCD camera. Spectroscopic analysis of plasma evolution of laser produced plasmas has been characterized in terms of their spectra, electron density N e and electron temperature Te assuming the LTE and optically thin plasma conditions. The obtained average values of Te and Ne were 7600 K and 3 × 10 17 cm −3 , respectively, for the six elements in the aluminum alloy samples. The electron density increases with the element concentration while the plasma temperature does not has significance change with concentration. For industrial applications, LIBS with the portable Echelle spectrometer could be applied in the on-line p...

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Experimental study on creation of ultrashort pulses using self-phase modulation in hollow-core fiber

Femtosecond laser pulses have high impact on the state-of-the-art modern developed technologies a... more Femtosecond laser pulses have high impact on the state-of-the-art modern developed technologies and its applications. Generation of high power femtosecond pulses with short pulse durations with a stable profile represent a challenge due to many experimental difficulties. In this work, a table top source of ultrashort laser pulses high energy femtosecond laser system is demonstrated. After optimization, the pulse duration of the observed ultrafast pulses of 5 femtosecond has been achieved. This was accomplished due to the nonlinear propagation of compressed femtosecond pulses into a hollow filled optical fiber with neon gas and initiation of self-phase modulation. By tuning the neon pressure, the overall peak power of the output pulses reached 100 GW. This was achieved with the extreme-temporal compression via a pair of chirped mirrors. The experimentally observed results may give a chance to create ultrafast pulses with shorter wavelength in the X-UV range.

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A method for controlling the bandwidth of high-energy, few-optical-cycle laser pulses tunable from the visible to the near-infrared

Ukrainian Journal of Physical Optics, 2015

In this work we report a new method for controlling the bandwidth of few-cycle optical pulses, us... more In this work we report a new method for controlling the bandwidth of few-cycle optical pulses, using another femtosecond laser pulses chirped in a neonfilled hollow-core fibre. The observed bandwidth varies from 25 to 234 nm in the optical wavelength region 600-950 nm. The pulse energy has for the first time reached a sub-millijoule frontier at 1 kHz. The input pulses are positively chirped using a chirped-pulse amplifier to acquire the widths 32-56 fs at the entrance of the hollow fibre. Then the pulses are highly dispersed due to a self-phase modulation in a nonlinear medium (a neon gas) followed by a pair of chirped mirrors that compensate the dispersion. We have found that this scheme allows for direct tuning of the output-pulse bandwidth while varying the chirping of the input pulses under different neon-gas pressures. Our results can give an opportunity for controlling the interactions in strong electric fields on the ultrafast time scales and are crucial for regenerating attosecond X-ray pulses.

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Prof. Walid Tawfik

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