Investigating the effect of changing the substrate material analyzed by laser-induced breakdown spectroscopy on the antenna performance.

Miniaturized microstrip antennas are efficiently utilized in MICS band wearable and implantable medical applications. However, the properties of the materials employed for antenna fabrication influence its resultant parameters and play a vital role in its performance. Rogers have been widely used as a substrate material in various antenna designs. In this work, a proof of concept study has been conducted to determine how altering the substrate used in antenna construction affects antenna performance. Using the laser-induced breakdown spectroscopy (LIBS) approach, the elements present in the two distinct substrate raw materials were compared to investigate potential effects on the antenna's performance. Given their accessibility and widespread use, two types of Rogers' substrates, RO 3210 and RO 4003, were selected. Furthermore, two identical antenna designs were modeled and fabricated using the two substrate materials. The reflection coefficient (S11) and other antenna parameters were determined and compared. Moreover, the recorded LIBS spectra were evaluated using principle component analysis and partial least square regression techniques. The LIBS spectra showed different copper and iron contents between the two Rogers (i.e., other dielectric properties), leading to a frequency shift. Additionally, impurities in the fabricated material increase the possible losses. Consequently, the elemental contents of the utilized Rogers control the antenna's performance and can ensure its safety in wearable and implant applications.

Scattering and absorption properties modification of optically cleared skeletal muscles: an ex vivo study.

Optical clearing is a relatively new approach to enhancing the optical transparency of biological tissues by reducing their scattering properties. The optical clearing effect is achievable via various chemical, physical, and photo-thermal techniques. The present work studied optical parameters of bovine skeletal muscles under different clearing protocols: immersion optical clearing in 99% glycerol and photo-thermal optical clearing via exposure to IR laser irradiation. Moreover, the two techniques were combined with different immersion time intervals after multiple exposure periods to get optimum results. The muscle samples' diffuse reflectance and total transmittance were measured using a single integrating sphere and introduced to the Kubleka-Munk mathematical model to determine the absorption and reduced scattering coefficients. Results revealed a 6% scattering reduction after irradiating the sample for 10 min and immersing it in glycerol for 18 min and 8% after 20 min of laser irradiation and 18 min of immersion. Moreover, increases of 6.5% and 7.5% in penetration depth were prominent for the total treatment times of 28 min and 38 min, respectively. Furthermore, the measurements' accuracy and sensitivity were analyzed and evaluated using the receiver operating characteristic method. The accuracy ranged from 0.93 to 0.98, with sensitivity from 0.93 to 0.99 for each clearing protocol. Although laser irradiation and application of 99% glycerol separately produced scattering light reduction, the maximal clearing effect was obtained while irradiating the sample with a laser for 20 min and then immersing it in 99% glycerol for a maximum of 18 min.

Discriminating two bacteria via laser-induced breakdown spectroscopy and artificial neural network.

Rapid and successful clinical diagnosis and bacterial infection treatment depend on accurate identification and differentiation between different pathogenic bacterial species. A lot of efforts have been made to utilize modern techniques which avoid the laborious work and time-consuming of conventional methods to fulfill this task. Among such techniques, laser-induced breakdown spectroscopy (LIBS) can tell much about bacterial identity and functionality. In the present study, a sensitivity-improved version of LIBS, i.e. nano-enhanced LIBS (NELIBS), has been used to discriminate between two different bacteria (Pseudomonas aeruginosa and Proteus mirabilis) belonging to different taxonomic orders. Biogenic silver nanoparticles (AgNPs) are sprinkled onto the samples' surface to have better discrimination capability of the technique. The obtained spectroscopic results of the NELIBS approach revealed superior differentiation between the two bacterial species compared to the results of the conventional LIBS. Identification of each bacterial species has been achieved in light of the presence of spectral lines of certain elements. On the other hand, the discrimination was successful by comparing the intensity of the spectral lines in the spectra of the two bacteria. In addition, an artificial neural network (ANN) model has been created to assess the variation between the two data sets, affecting the differentiation process. The results revealed that NELIBS provides higher sensitivity and more intense spectral lines with increased detectable elements. The ANN results showed that the accuracy rates are 88% and 92% for LIBS and NELIBS, respectively. In the present work, it has been demonstrated that NELIBS combined with ANN successfully differentiated between both bacteria rapidly with high precision compared to conventional microbiological discrimination techniques and with minimum sample preparation.

Effect of target thickness and laser irradiance on the back-reflection-enhanced laser-induced breakdown spectroscopy signal in glass.

In the work that is being presented here, the effect of sample thickness and laser irradiance on the reduction of the signal-to-background ratio SBG and the plasma parameters, specifically electron temperature and electron density, is being investigated using back-reflection-enhanced laser-induced breakdown spectroscopy (BRELIBS). Copper and silver discs that had been highly polished were attached to the back surface of the glass target, and the Nd-YAG laser beam that was focused on the front surface of the target was tuned to its fundamental wavelength. The thicknesses of the transparent glass samples that were analysed were 1 mm, 3 mm, and 6 mm. One is able to achieve a range of different laser irradiance levels by adjusting the working distance that exists between the target sample and the focusing lens. The end result of this is that the signal-to-background ratio in the BRELIBS spectra of thicker glass samples is significantly lower as compared to the ratio in the spectra of thinner glass samples. In addition, a significant influence of modifying the laser irradiance (by increasing the working distance on the SBG ratio) is seen at various glass thicknesses for both BRELIBS and LIBS, with BRELIBS having a better SBG. Nevertheless, the laser-induced plasma parameter known as the electron temperature has not been significantly impacted by the decrease in the glass thickness.

Adaptive optics-based wavefront-enhanced laser-induced fluorescence (WELIF) for improved analytical performance.

The current study proposes a novel optical approach based on an adaptive optics (AO) system to enhance the fluorescence intensity in the laser-induced fluorescence (LIF) technique. The proposed method, wavefront-enhanced LIF (WELIF), relies mainly on compensating for the aberrations arising from the excitation-laser wavefront. The AO system consists of an active correction element (deformable mirror (DM)) integrated with a Shack-Hartmann wavefront sensor (SHWFS). The overall system operates in a closed-loop configuration to compensate for the laser beam aberrations in real time. The performance of the interaction of the aberration-free excitation laser beam with solid samples, e.g., bone, leaf, polymer sheet, and with liquid samples, e.g., extra virgin olive oil (EVOO), showed a pronounced improvement in the fluorescence peak intensity. As an analytical application example, detailed WELIF measurements have been performed on five EVOO brands to demonstrate the validity of the new approach. Furthermore, the effectiveness of the proposed system was evaluated by measuring the enhancement factor, i.e., the ratio between the fluorescence peak intensity after aberration compensation (AC) relative to the initial peak intensity before aberration compensation (BC). The results reveal that the fluorescence peak intensities have been enhanced with ranges from 20% to 98% after compensation (AC). Besides, the results were statistically assessed based on the receiver operator characteristic (ROC) curve (84% sensitivity AC and 82% BC) and partial least squares regression, PLSR, with a 0.94 coefficient of determination AC compared to 0.90 BC.

Reflection-enhanced laser-induced fluorescence spectroscopy to improve the analytical sensitivity in liquids.

The current work demonstrates a novel approach to enhancing the analytical sensitivity of the laser-induced fluorescence (LIF) technique in liquids. An increase in the fluorescence spectral band intensity of about sixfold compared to the conventional LIF has been achieved. Such betterment has been accomplished by having the fluorophore liquid in a cuvette having a reflecting mirror-like side facing the exciting incident laser beam. The silvered or aluminized reflecting side of the cuvette was tested. The pilot test of the proposed cuvette was performed using an excitation laser light of 405 nm wavelength and five mW average power on chlorophyll-a (Chl-a) samples of different concentrations. As a result, a pronounced improvement in the Chl-a fluorescence spectral band intensity is achieved. Such a novel approach, the reflection-enhanced laser-induced fluorescence (RELIF), has been used to analyze six Egyptian brands of extra virgin olive oil (EVOO). Compared to the LIF measurement results on the same EVOO, the RELIF was superior in terms of the fluorescence-spectrum intensity enhancement factor. Both Ag and Al coatings of the cuvette revealed similar results. Statistical analysis of the measured fluorescence spectra via the partial least square regression (PLSR) method for LIF and RELIF revealed a higher coefficient of determination R2 for both RELIF measurements (with silver and aluminum coating) than for LIF. The proposed novel RELIF approach can be utilized for other fluorophore liquids at higher analytical sensitivity than conventional LIF. On the other hand, the RELIF technique is straightforward, cost-effective, and does not complicate the traditional LIF setup.

Optical Characterization of Biological Tissues Based on Fluorescence, Absorption, and Scattering Properties.

Optical diagnostics methods are significantly appealing in biological applications since they are non-destructive, safe, and minimally invasive. Laser-induced fluorescence is a promising optical spectrochemical analytical technique widely employed for tissue classification through molecular analysis of the studied samples after excitation with appropriate short-wavelength laser light. On the other hand, diffuse optics techniques are used for tissue monitoring and differentiation based on their absorption and scattering characteristics in the red to the near-infrared spectra. Therefore, it is strongly foreseen to obtain promising results by combining these techniques. In the present work, tissues under different conditions (hydrated/dry skin and native/boiled adipose fat) were distinguished according to their fluorescence emission, absorption, and scattering properties. The selected tissues' optical absorption and scattering parameters were determined via Kubelka-Munk mathematical model according to the experimental tissue reflectance and transmittance measurements. Such measurements were obtained using an optical configuration of integrating sphere and spectrometer at different laser wavelengths (808, 830, and 980 nm). Moreover, the diffusion equation was solved for the fluence rate at the sample surface using the finite element method. Furthermore, the accuracy of the obtained spectroscopic measurements was evaluated using partial least squares regression statistical analysis with 0.87 and 0.89 R-squared values for skin and adipose fat, respectively.

Utilization of laser-induced breakdown spectroscopy, with principal component analysis and artificial neural networks in revealing adulteration of similarly looking fish fillets.

Fish is an essential source of many nutrients necessary for human health. However, the deliberate mislabeling of similar fish fillet types is common in markets to make use of the relatively high price difference. This is a type of explicit food adulteration. In the present work, spectrochemical analysis and chemometric methods are adopted to disclose this type of fish species cheating. Laser-induced breakdown spectroscopy (LIBS) was utilized to differentiate between the fillets of the low-priced tilapia and the expensive Nile perch. Furthermore, the acquired spectroscopic data were analyzed statistically using principal component analysis (PCA) and artificial neural network (ANN) showing good discrimination in the PCA score plot and a 99% classification accuracy rate of the implemented ANN model. The recorded spectra of the two fish indicated that tilapia has a higher fat content than Nile perch, as evidenced by higher CN and C2 bands and an atomic line at 247.8 nm in its spectrum. The obtained results demonstrated the potential of using LIBS as a simple, fast, and cost-effective analytical technique, combined with statistical analysis for the decisive discrimination between fish fillet species.

Back-reflection-enhanced laser-induced breakdown spectroscopy (BRELIBS) on transparent materials: Application on archaeological glass.

A straightforward and simple method has been proposed in the current work to improve the signal-to-noise ratio of the LIBS spectrum of transparent samples. The idea is to benefit from a highly polished metallic reflector in direct contact with the rear surface of the transparent target. Copper and silver metals have been used as reflectors for the focused laser beam and force it to pass through the plasma plume induced initially onto the front surface of the target. The reflected laser beam reheats the plasma plume increasing the intensity of the light emitted from it. In such a case, the obtained LIBS spectrum accomplishes a pronounced increase in the signal-to-noise ratio compared to the spectrum obtained without a reflector. The new amendment of the LIBS technique setup has been exploited for the elemental analysis of colored glass fragments from archaeological Egyptian Synagogue windows. Quantitative analysis of the samples using the calibration-free LIBS (CF-LIBS) approach has been performed. The results depicted three-to four-fold enhancement in the spectral lines' intensity depending on the glass color and thickness. The results have been validated by the quantitative analysis of the same samples via the Energy-Dispersive X-ray spectroscopy (EDX). The CF-BRELIBS results were in pronounced agreement with that of the EDX. The back-reflection-enhanced laser-induced breakdown spectroscopy (BRELIBS) can be applied to analyze numerous transparent target types such as different glass types, gemstone, plastics, polymers, etc.

Gold Nanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy and Three-Dimensional Contour Imaging of an Aluminum Alloy.

In the present work, nanoparticle-enhanced laser-induced breakdown spectroscopy was used to analyze an aluminum alloy. Although LIBS has numerous advantages, it suffers from low sensitivity and low detection limits compared to other spectrochemical analytical methods. However, using gold nanoparticles helps to overcome such drawbacks and enhances the LIBS sensitivity in analyzing aluminum alloy in the current work. Aluminum was the major element in the analyzed samples (99.9%), while magnesium (Mg) was the minor element (0.1%). The spread of gold nanoparticles onto the Al alloy and using a laser with different pulse energies were exploited to enhance the Al alloy spectral lines. The results showed that Au NPs successfully improved the alloy spectral lines intensity by eight times, which could be useful for detecting many trace elements in higher matrix alloys. Under the assumption of local thermodynamic equilibrium, the Boltzmann plot was used to calculate the plasma temperature. Besides, the electron density was calculated using Mg and H lines at Mg(I) at 285.2 nm and Hα(I) at 656.2 nm, respectively. Three-dimensional contour mapping and color fill images contributed to understanding the behavior of the involved effects.

Comparative study between the photodynamic ability of gold and silver nanoparticles in mediating cell death in breast and lung cancer cell lines.

Cancer is one of the dreadest diseases once diagnosed and has severe impacts on health, social and economic global aspects. Nanomedicine is considered an emerging approach for early cancer diagnosis and treatment. The multifunctional effects of silver and gold nanoparticles (Ag and Au NPs) have rendered them to be potent candidates for biomedical applications. The current work presents a comparative study between Au NPs and Ag NPs as possible potent photosensitizers (PS) in photodynamic therapy (PDT). Transmission electron microscopy (TEM) was used to identify and characterize the shape, size, and cellular localization of Au NPs; the absorption properties of Au NPs were determined using ultraviolet-visible spectroscopy (UV-Vis) and zeta potential was used to identify surface charge. Inverted light microscopy (LM), Trypan blue exclusion assay, adenosine triphosphate luminescence (ATP), and lactate dehydrogenase membrane integrity assays (LDH) were used for investigating the photodynamic ability of these nanostructures on breast (MCF-7) and lung (A549) cancer cell lines. Flow cytometry using Annexin V and propidium iodide (PI) dyes was used to determine the cell death pathway induced. The average size of the synthesized Au NPs was 50 nm, having an absorption peak at 540 nm with -7.85 mV surface net charge. MCF-7 and A549 cells were able to absorb the Au NPs. The latter, when irradiated with laser light in the phototherapeutic window, promoted cytotoxicity and a significant reduction in cell viability and proliferation were observed. The photodynamic activity that was observed in both cancer cell lines was found to be less eminent than that observed in case of the Ag NPs when compared to Au NPs. The present study is the first that compares the photodynamic ability of two different nanoparticles, silver and gold, as photosensitizers without any further functionalization. This study extends the possibilities of using such nanostructures in PDT within the therapeutic window wavelength, yet through the conjugation of Au NPs with other photosensitizers to synergize its effect.