A systematic study has been performed on the spectral characteristics of the full spectrum of He ... more A systematic study has been performed on the spectral characteristics of the full spectrum of He emission lines and their time dependent behaviors measured from the He gas plasmas generated by a nanosecond neodymium-doped yttrium aluminum garnet laser. It is shown that among the major emission lines observed, the triplet He(I) 587.6 nm emission line stands out as the most prominent and long-lasting line, associated with de-excitation of the metastable triplet (S = 1) excited state (1s(1) 3d(1)). The role of this metastable excited state is manifested in the intensity enhancement and prolonged life time of the Cu emission with narrow full width half-maximum, as demonstrated in an orthogonal double-pulse experiment using a picosecond laser for the target ablation and a nanosecond laser for the prior generation of the ambient He gas plasma. These desirable emission features are in dire contrast to the characteristics of emission spectra observed with N2 ambient gas having no metastable...
A simple homemade microscope has been devised using a single water droplet lens, which proved to ... more A simple homemade microscope has been devised using a single water droplet lens, which proved to be practical for classroom use in school. In order to prevent evaporation of water, the water droplet lens was encapsulated in a plastic vessel together with wetted paper. By changing the amount of water in a metal ring (4.5 mm diameter with thickness 0.6 mm) attached to the bottom of the plastic vessel, the magnification could be varied from around ×6 to ×30. It was also demonstrated that microphotographs could be taken readily using an ordinary compact camera. This microscope is expected to make a significant contribution to science education in developing countries.
An experimental study has been carried out on the dynamical process taking place in the plasma ge... more An experimental study has been carried out on the dynamical process taking place in the plasma generated by a TEA CO 2 laser (400 mJ, 100 ns) on a zinc target when surrounded by helium gas of pressure ranging from 2 Torr to 1 atm. Plasma characteristics were examined in detail on the emission lines of Zn I 481.0 nm and He I 587.6 nm by means of an unique time-resolved spatial distribution technique in addition to an ordinary time-resolved emission measurement technique. The results reveal, for the first time, persistent shock wave characteristics in all cases throughout the entire pressure range considered. Further analysis of the data has clarified the distinct characteristics of laser plasmas generated in different ranges of gas pressure. It is concluded that three types of shock wave plasma can be identified; namely, a target shock wave plasma in the pressure range from 2 Torr to around 50 Torr; a coupling shock wave plasma in the pressure range from around 50 Torr to 200 Torr and a gas breakdown shock wave plasma in the pressure range from around 200 Torr to 1 atm. These distinct characteristics are found to be ascribable to the different extents of the gas breakdown process taking place at the different gas pressures. These results, obtained for a TEA CO 2 laser, will provide a useful basis for the analyses of plasmas induced by other lasers.
The effect of surrounding air pressure and repeated irradiation on selective vaporization in lase... more The effect of surrounding air pressure and repeated irradiation on selective vaporization in laser induced shock wave plasma has been studied on brass target using tightly focused beam of a Q-switched Nd: YAG laser operated at 26 mJ. The vaporization effects of Zn and Cu were studied in terms of their emission characteristics. It was found out that selective vaporization in favor of Zn atoms always takes place under various conditions considered in this study and tends to enhance with the number of repeated irradiation on the same spot of the sample surface. On the other hand, this undesirable effect could be significantly suppressed by increasing the air pressure. These results as well as other features exhibited by the time-dependent emission intensities and the spatially integrated emission intensities have been shown to be explicable in terms of the shock excitation mechanism associated with the laser induced shock wave model.
THE 4TH INTERNATIONAL CONFERENCE ON MATHEMATICS AND SCIENCE EDUCATION (ICoMSE) 2020: Innovative Research in Science and Mathematics Education in The Disruptive Era, 2021
In this research, teflon coating for microwave absorption applications was investigated. The micr... more In this research, teflon coating for microwave absorption applications was investigated. The microwave absorption properties of teflon with thicknesses of 1, 2, 3, 4, 5, 6, 7, and 8 mm were investigated using a vector network analyzer (VNA) in the frequency range of 7-13 GHz. Based on the reflected signal (S11) and transmitted signal (S21), the complex permeability (μ) and permittivity () of teflon were resulted. The optimal absorption properties were achieved with a reflection loss of less than 10 dB (90% absorption) for 17.35 dB at 10.5 GHz at a thickness of 8 mm.
In this work, the microwave absorption performance of barium hexaferrite multi-nanolayers synthes... more In this work, the microwave absorption performance of barium hexaferrite multi-nanolayers synthesized by aceramic method was investigated. The microwave absorption performances of BaFe12O19 and BaCoZnFe10O19 multi-nanolayers with thicknesses of 25, 50, 75, 100, 200, 300, 500, and 1000 nm were evaluated using a vector network analyser (VNA) at room temperature to characterize the reflected signal (S11) and transmitted signal (S21) in the frequency range of 7–13 GHz. The microwave absorption performance of the multilayer structure was enhanced due to the combination of nanolayers. The optimal absorption performance was achieved with a reflection loss of less than –30 dB (99.9% absorption) for a layer thicknesses of less than 500 nm.
In order to enhance a new microwave absorbing capabilities in the X-band frequency range, polycry... more In order to enhance a new microwave absorbing capabilities in the X-band frequency range, polycrystalline magnetic materials of BaFe12O19 barium hexaferrite were fabricated through conventional ceramic method and the Fe3O4 powder from iron sand were prepared through magnetic separation after milling process by using planetary ball mill. Microwave absorbing capabilities of multilayer absorbers, composed of BaFe12O19 barium hexaferrite and the Fe3O4 powder, with a total thickness of 10 mm, were investigated by a vector network analyzer (VNA) in the range of 8.2 –12.4 GHz. According to transmission line theory, reflection of microwave radiations from multilayer magnetic materials is calculated. The reflection loss (RL) strongly depends on thickness of multilayer absorbers and showed an optimal RL. Keywords : BaFe12O19, Fe3O4 powder, reflection loss, multilayer absorbers.
Microwave absorption characteristics of double layer of barium hexaferrite attached on the silica... more Microwave absorption characteristics of double layer of barium hexaferrite attached on the silica to from a composite on the basis of wave propagation theory have been investigated. Barium hexaferrite, BaFe12O19, was synthesized through ceramic method from stoichiometric mixtures of BaCO3 and Fe2O3 as precursors. The mixture was pelletized under the pressure of 10 MPa and sintered at 1100 °C for 5 hours. Silica in the forms of powder was purified by using HCl. The crystal structure of the samples was characterized using X-ray diffraction (XRD), microstructure was examined using scanning electron microscope (SEM), hysteresis curves recorded by PERMAGRAPH techniques, whereas the microwave absorbing properties for X-band was recorded using a vector network analyzer (VNA). Relative complex permeability and permittivity, and reflection loss values were calculated at given thickness according to transmittance line theory within the range 8.2–12.4 GHz. Based on this study, the layer dimens...
Jurnal Penelitian & Pengembangan Pendidikan Fisika, 2016
This research is aimed to develop the experimental instrument that is thermoelectric generator as... more This research is aimed to develop the experimental instrument that is thermoelectric generator as the instructional media for energy resource. Used Research Development method with ADDIE (Analyze-Design-Develop-Implementation-Evaluation) models. The media is designed and developed by using Solid Works app. This media is equipped with screen, so the temperature value, electric current, and voltage that produced by the experiment will appear on it. Beside that, this media is user friendly for student because they no need to assemble this instrument, and also the measurement is accurate because this instrument is digital based. This media has been validated with the media experts and subject matter experts. The result is showing that thermoelectric generator is worthy to use as instructional media for energy resource subject in senior high school grade 3.
View the article online for updates and enhancements. Content from this work may be used under th... more View the article online for updates and enhancements. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Spectrochimica Acta Part B: Atomic Spectroscopy, Oct 1, 2000
An experimental study has been carried out on the dynamical process taking place in laser plasma,... more An experimental study has been carried out on the dynamical process taking place in laser plasma, generated by Ž. TEA CO laser 400 mJ, 100 ns irradiation on glass samples surrounding by air of high pressures up to 760 torr. 2 Accurate dynamical characterization was performed by simultaneous observation of the plasma emission front and the shock wave front. The shock wave front was detected by a modified shadowgraph technique while the emission front was detected by observing the rising time at various slit positions. In spite of the occurrence of a new feature uncommon to laser plasma, generated in low air pressures, it is found that the two fronts coincide and move together at the initial stage of the laser plasma, but eventually separate from each other, with the emission front being left behind the shock wave front at a later stage. These characteristics hold for the atomic emission lines of all elements contained in the glass samples examined, regardless of their different atomic weights. It is therefore strongly indicative of the shock wave mechanism in the laser plasma generation and the emission in the high-pressure surrounding air.
Abstract The Moringa oleifera tree, including the leaves, flowers, pods, and seeds, is highly nut... more Abstract The Moringa oleifera tree, including the leaves, flowers, pods, and seeds, is highly nutritious and useful for the prevention and control of various diseases. Here we have probed the micronutrients in Moringa oleifera leaves using laser-induced breakdown spectroscopy (LIBS). The time-resolved and time-integrated LIBS data reveal the presence of Ca, Mg, K, C, Si, Fe, Al, Ti, Sr, Na, H, O, and Li. The plasma temperature and electron number density required for the elemental composition analysis were estimated to be (6375 ± 500) K from the Saha-Boltzmann plot and (1.0 ± 0.2) 1017 cm−3 from the Stark broadened Hα line, respectively. Elemental analysis of the samples was performed using one-line calibration free LIBS (CF-LIBS). The results reveal that C is the major element together with Ca, Mg, K, Fe Na, Al, Ti, Sr, and Li as micronutrients. The concentrations of the micronutrients determined by CF-LIBS were validated by inductively coupled plasma – optical emission spectrometry (ICP-OES). LIBS has been demonstrated to be a practical candidate for the detection of potentially toxic elements (Li, Al, Si, and Sr) as well as for the compositional analysis.
This study introduces a novel and extremely simple way for suppressing the self-absorption effect... more This study introduces a novel and extremely simple way for suppressing the self-absorption effect in laser-induced breakdown spectroscopy (LIBS) by utilizing a defocusing laser irradiation technique. It is claimed that defocusing laser irradiation produces more uniform laser plasma due to lower fluence than tight focus laser irradiation, hence greatly lowering the effect of self-absorption in the laser plasma. KCl and NaCl pellet samples were used to demonstrate this achievement. When the defocus position is adjusted to – 6 mm for KCl and NaCl samples, the self-reversal emission lines K I 766.4 nm, K I 769.9 nm, Na I 588.9 nm, and Na I 589.5 nm vanish. Meanwhile, the FWHM values of K I 766.4 and K I 769.9 nm are 0.29 nm and 0.23 nm, respectively, during -6 mm defocus laser irradiation, as opposed to 1.24 nm and 0.86 nm, under tight focus laser irradiation. Additionally, this work demonstrates that when the laser energy is changed in between 10 to 50 mJ, no self-reversal emission occ...
Dalam penelitian ini dikembangkan suatu metode untuk mendeteksi kandungan boraks dalam makanan de... more Dalam penelitian ini dikembangkan suatu metode untuk mendeteksi kandungan boraks dalam makanan dengan menggunakan teknik Laser Induced Breakdown Spectroscopy (LIBS). Dalam teknik ini boraks (Na2B4O7) yang berupa serbuk dicampur dengan bahan makanan (tepung) dengan konsentrasi boron sebanyak 1%, 3%, 5%, 7%, dan 10% dalam 10 gram sampel. Sampel yang sudah digerus sampai halus kemudian dikompaksi untuk menjadi pellet dengan diameter 10 mm dan tebalnya antara 1-2 mm. Dalam penelitian ini digunakan berkas laser dari Nd:YAG (355 nm, 8 ns) yang difokuskan pada permukaan sampel pellet sehingga timbul plasma. Spektrum emisi plasma yang terekam pada komputer kemudian dianalisis untuk melihat garis emisi boron yang menandakan kehadiran boraks pada sampel. Kata-kata kunci: Laser Induced Breakdown Spectroscopy (LIBS), spektrum emisi plasma, boron.
This study demonstrates a new approach for suppressing the self-absorption effect in single-pulse... more This study demonstrates a new approach for suppressing the self-absorption effect in single-pulse laser-induced breakdown spectroscopy (LIBS) using unusual parallel laser irradiation. A nanosecond Nd:YAG laser with a wavelength of 1064 nm was fired parallel to and focused at a very close distance of 1 mm to the sample surface. The experiment was carried out in air at atmospheric pressure. In this configuration, the sample was ablated by a shockwave generated from the air breakdown plasma formed near the sample surface. Under this condition, we successfully obtained spectra of the resonance emission line for high concentration K (K I 766.4 nm and K I 769.9 nm) that are free from self-reversal and weakly affected by the self-absorption. Furthermore, the quantitative analysis results for the element K showed that a linear calibration curve over a wide concentration range could be achieved, which indicates the effectiveness of this technique in reducing the self-absorption effect and im...
Laser-induced breakdown spectroscopy (LIBS) to detect the light elements such as lithium (Li) and... more Laser-induced breakdown spectroscopy (LIBS) to detect the light elements such as lithium (Li) and boron (B) and heavy elements such as copper (Cu) and lead (Pb) in raw fish samples is reported in this work. This is made possible by understanding that the soft target absorbs recoil energy and as a result, the ablated atoms gushing from the soft target do not acquire sufficient speed to form a shock wave. In order to overcome this problem, we set a subtarget on the back of the soft target so as to produce the repulsion force by which the gushing speed of the ablated atoms is increased, yielding a sufficiently high plasma temperature or sufficiently large thermal energy needed for the excitation of the ablated atoms. Excellent spectral qualities of various soft samples such as margarine, butter, peanut butter, strawberry jam, raw tuna, raw gindara, and raw salmon are presented. Furthermore, a linear calibration curve with a zero intercept is also obtained for Li, Cu, and Pb. The detection limit of Li, Cu, and Pb is found to be around 0.1 mg/L. This modification of LIBS for soft samples by using a subtarget effect clearly promises a rapid and in situ soft sample analysis since there is practically no sample digestion in the analysis.
Several experiments are performed to explore the possible benefits of using bamboo charcoal as a ... more Several experiments are performed to explore the possible benefits of using bamboo charcoal as a sample holder for rapid powder analysis using laser-induced breakdown spectroscopy at low-pressure helium ambient gas. Standard powdered samples such as ZnS and CuSO4 are used to demonstrate the feasibility of using cheap and widely available bamboo charcoal as a sample holder. A commercial baby milk powder and several sets of soil samples with a tiny amount of impurities are also introduced to show the potential application of bamboo charcoal as a powder holder. By appropriately adjusting the laser pulse energy and the thickness of the powder layer, we successfully obtained a spectrum that is free from the undesirable matrix effect. A remarkable result was obtained, even using a tiny amount of the powder sample. This proposed method is considered notably promising for the rapid analysis of the powder sample, especially with a very limited amount.
Self-absorption, which is known to severely disturb identification of the emission peak intensity... more Self-absorption, which is known to severely disturb identification of the emission peak intensity in emission-based spectroscopy, was first studied using ordinary single pulse laser-induced breakdown spectroscopy (LIBS). It was found that severe self-absorption, with an evident self-reversal, occurs in the resonance emission lines of high concentration Na, K, and Al, and thus it is impossible to obtain the linear calibration curve required for quantitative analysis. To overcome this problem, we introduce a double pulse orthogonal technique in which the first laser is fired in a parallel orientation at a varied distance of 2–6 mm from the sample surface. It is well known that the strong shock wave generated by this laser irradiation temporarily creates a vacuum-like condition immediately in front of the sample surface. This action is followed by a second laser irradiation oriented perpendicular to the sample surface. The sample ablated by the second laser irradiation expands followin...
A systematic study has been performed on the spectral characteristics of the full spectrum of He ... more A systematic study has been performed on the spectral characteristics of the full spectrum of He emission lines and their time dependent behaviors measured from the He gas plasmas generated by a nanosecond neodymium-doped yttrium aluminum garnet laser. It is shown that among the major emission lines observed, the triplet He(I) 587.6 nm emission line stands out as the most prominent and long-lasting line, associated with de-excitation of the metastable triplet (S = 1) excited state (1s(1) 3d(1)). The role of this metastable excited state is manifested in the intensity enhancement and prolonged life time of the Cu emission with narrow full width half-maximum, as demonstrated in an orthogonal double-pulse experiment using a picosecond laser for the target ablation and a nanosecond laser for the prior generation of the ambient He gas plasma. These desirable emission features are in dire contrast to the characteristics of emission spectra observed with N2 ambient gas having no metastable...
A simple homemade microscope has been devised using a single water droplet lens, which proved to ... more A simple homemade microscope has been devised using a single water droplet lens, which proved to be practical for classroom use in school. In order to prevent evaporation of water, the water droplet lens was encapsulated in a plastic vessel together with wetted paper. By changing the amount of water in a metal ring (4.5 mm diameter with thickness 0.6 mm) attached to the bottom of the plastic vessel, the magnification could be varied from around ×6 to ×30. It was also demonstrated that microphotographs could be taken readily using an ordinary compact camera. This microscope is expected to make a significant contribution to science education in developing countries.
An experimental study has been carried out on the dynamical process taking place in the plasma ge... more An experimental study has been carried out on the dynamical process taking place in the plasma generated by a TEA CO 2 laser (400 mJ, 100 ns) on a zinc target when surrounded by helium gas of pressure ranging from 2 Torr to 1 atm. Plasma characteristics were examined in detail on the emission lines of Zn I 481.0 nm and He I 587.6 nm by means of an unique time-resolved spatial distribution technique in addition to an ordinary time-resolved emission measurement technique. The results reveal, for the first time, persistent shock wave characteristics in all cases throughout the entire pressure range considered. Further analysis of the data has clarified the distinct characteristics of laser plasmas generated in different ranges of gas pressure. It is concluded that three types of shock wave plasma can be identified; namely, a target shock wave plasma in the pressure range from 2 Torr to around 50 Torr; a coupling shock wave plasma in the pressure range from around 50 Torr to 200 Torr and a gas breakdown shock wave plasma in the pressure range from around 200 Torr to 1 atm. These distinct characteristics are found to be ascribable to the different extents of the gas breakdown process taking place at the different gas pressures. These results, obtained for a TEA CO 2 laser, will provide a useful basis for the analyses of plasmas induced by other lasers.
The effect of surrounding air pressure and repeated irradiation on selective vaporization in lase... more The effect of surrounding air pressure and repeated irradiation on selective vaporization in laser induced shock wave plasma has been studied on brass target using tightly focused beam of a Q-switched Nd: YAG laser operated at 26 mJ. The vaporization effects of Zn and Cu were studied in terms of their emission characteristics. It was found out that selective vaporization in favor of Zn atoms always takes place under various conditions considered in this study and tends to enhance with the number of repeated irradiation on the same spot of the sample surface. On the other hand, this undesirable effect could be significantly suppressed by increasing the air pressure. These results as well as other features exhibited by the time-dependent emission intensities and the spatially integrated emission intensities have been shown to be explicable in terms of the shock excitation mechanism associated with the laser induced shock wave model.
THE 4TH INTERNATIONAL CONFERENCE ON MATHEMATICS AND SCIENCE EDUCATION (ICoMSE) 2020: Innovative Research in Science and Mathematics Education in The Disruptive Era, 2021
In this research, teflon coating for microwave absorption applications was investigated. The micr... more In this research, teflon coating for microwave absorption applications was investigated. The microwave absorption properties of teflon with thicknesses of 1, 2, 3, 4, 5, 6, 7, and 8 mm were investigated using a vector network analyzer (VNA) in the frequency range of 7-13 GHz. Based on the reflected signal (S11) and transmitted signal (S21), the complex permeability (μ) and permittivity () of teflon were resulted. The optimal absorption properties were achieved with a reflection loss of less than 10 dB (90% absorption) for 17.35 dB at 10.5 GHz at a thickness of 8 mm.
In this work, the microwave absorption performance of barium hexaferrite multi-nanolayers synthes... more In this work, the microwave absorption performance of barium hexaferrite multi-nanolayers synthesized by aceramic method was investigated. The microwave absorption performances of BaFe12O19 and BaCoZnFe10O19 multi-nanolayers with thicknesses of 25, 50, 75, 100, 200, 300, 500, and 1000 nm were evaluated using a vector network analyser (VNA) at room temperature to characterize the reflected signal (S11) and transmitted signal (S21) in the frequency range of 7–13 GHz. The microwave absorption performance of the multilayer structure was enhanced due to the combination of nanolayers. The optimal absorption performance was achieved with a reflection loss of less than –30 dB (99.9% absorption) for a layer thicknesses of less than 500 nm.
In order to enhance a new microwave absorbing capabilities in the X-band frequency range, polycry... more In order to enhance a new microwave absorbing capabilities in the X-band frequency range, polycrystalline magnetic materials of BaFe12O19 barium hexaferrite were fabricated through conventional ceramic method and the Fe3O4 powder from iron sand were prepared through magnetic separation after milling process by using planetary ball mill. Microwave absorbing capabilities of multilayer absorbers, composed of BaFe12O19 barium hexaferrite and the Fe3O4 powder, with a total thickness of 10 mm, were investigated by a vector network analyzer (VNA) in the range of 8.2 –12.4 GHz. According to transmission line theory, reflection of microwave radiations from multilayer magnetic materials is calculated. The reflection loss (RL) strongly depends on thickness of multilayer absorbers and showed an optimal RL. Keywords : BaFe12O19, Fe3O4 powder, reflection loss, multilayer absorbers.
Microwave absorption characteristics of double layer of barium hexaferrite attached on the silica... more Microwave absorption characteristics of double layer of barium hexaferrite attached on the silica to from a composite on the basis of wave propagation theory have been investigated. Barium hexaferrite, BaFe12O19, was synthesized through ceramic method from stoichiometric mixtures of BaCO3 and Fe2O3 as precursors. The mixture was pelletized under the pressure of 10 MPa and sintered at 1100 °C for 5 hours. Silica in the forms of powder was purified by using HCl. The crystal structure of the samples was characterized using X-ray diffraction (XRD), microstructure was examined using scanning electron microscope (SEM), hysteresis curves recorded by PERMAGRAPH techniques, whereas the microwave absorbing properties for X-band was recorded using a vector network analyzer (VNA). Relative complex permeability and permittivity, and reflection loss values were calculated at given thickness according to transmittance line theory within the range 8.2–12.4 GHz. Based on this study, the layer dimens...
Jurnal Penelitian & Pengembangan Pendidikan Fisika, 2016
This research is aimed to develop the experimental instrument that is thermoelectric generator as... more This research is aimed to develop the experimental instrument that is thermoelectric generator as the instructional media for energy resource. Used Research Development method with ADDIE (Analyze-Design-Develop-Implementation-Evaluation) models. The media is designed and developed by using Solid Works app. This media is equipped with screen, so the temperature value, electric current, and voltage that produced by the experiment will appear on it. Beside that, this media is user friendly for student because they no need to assemble this instrument, and also the measurement is accurate because this instrument is digital based. This media has been validated with the media experts and subject matter experts. The result is showing that thermoelectric generator is worthy to use as instructional media for energy resource subject in senior high school grade 3.
View the article online for updates and enhancements. Content from this work may be used under th... more View the article online for updates and enhancements. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Spectrochimica Acta Part B: Atomic Spectroscopy, Oct 1, 2000
An experimental study has been carried out on the dynamical process taking place in laser plasma,... more An experimental study has been carried out on the dynamical process taking place in laser plasma, generated by Ž. TEA CO laser 400 mJ, 100 ns irradiation on glass samples surrounding by air of high pressures up to 760 torr. 2 Accurate dynamical characterization was performed by simultaneous observation of the plasma emission front and the shock wave front. The shock wave front was detected by a modified shadowgraph technique while the emission front was detected by observing the rising time at various slit positions. In spite of the occurrence of a new feature uncommon to laser plasma, generated in low air pressures, it is found that the two fronts coincide and move together at the initial stage of the laser plasma, but eventually separate from each other, with the emission front being left behind the shock wave front at a later stage. These characteristics hold for the atomic emission lines of all elements contained in the glass samples examined, regardless of their different atomic weights. It is therefore strongly indicative of the shock wave mechanism in the laser plasma generation and the emission in the high-pressure surrounding air.
Abstract The Moringa oleifera tree, including the leaves, flowers, pods, and seeds, is highly nut... more Abstract The Moringa oleifera tree, including the leaves, flowers, pods, and seeds, is highly nutritious and useful for the prevention and control of various diseases. Here we have probed the micronutrients in Moringa oleifera leaves using laser-induced breakdown spectroscopy (LIBS). The time-resolved and time-integrated LIBS data reveal the presence of Ca, Mg, K, C, Si, Fe, Al, Ti, Sr, Na, H, O, and Li. The plasma temperature and electron number density required for the elemental composition analysis were estimated to be (6375 ± 500) K from the Saha-Boltzmann plot and (1.0 ± 0.2) 1017 cm−3 from the Stark broadened Hα line, respectively. Elemental analysis of the samples was performed using one-line calibration free LIBS (CF-LIBS). The results reveal that C is the major element together with Ca, Mg, K, Fe Na, Al, Ti, Sr, and Li as micronutrients. The concentrations of the micronutrients determined by CF-LIBS were validated by inductively coupled plasma – optical emission spectrometry (ICP-OES). LIBS has been demonstrated to be a practical candidate for the detection of potentially toxic elements (Li, Al, Si, and Sr) as well as for the compositional analysis.
This study introduces a novel and extremely simple way for suppressing the self-absorption effect... more This study introduces a novel and extremely simple way for suppressing the self-absorption effect in laser-induced breakdown spectroscopy (LIBS) by utilizing a defocusing laser irradiation technique. It is claimed that defocusing laser irradiation produces more uniform laser plasma due to lower fluence than tight focus laser irradiation, hence greatly lowering the effect of self-absorption in the laser plasma. KCl and NaCl pellet samples were used to demonstrate this achievement. When the defocus position is adjusted to – 6 mm for KCl and NaCl samples, the self-reversal emission lines K I 766.4 nm, K I 769.9 nm, Na I 588.9 nm, and Na I 589.5 nm vanish. Meanwhile, the FWHM values of K I 766.4 and K I 769.9 nm are 0.29 nm and 0.23 nm, respectively, during -6 mm defocus laser irradiation, as opposed to 1.24 nm and 0.86 nm, under tight focus laser irradiation. Additionally, this work demonstrates that when the laser energy is changed in between 10 to 50 mJ, no self-reversal emission occ...
Dalam penelitian ini dikembangkan suatu metode untuk mendeteksi kandungan boraks dalam makanan de... more Dalam penelitian ini dikembangkan suatu metode untuk mendeteksi kandungan boraks dalam makanan dengan menggunakan teknik Laser Induced Breakdown Spectroscopy (LIBS). Dalam teknik ini boraks (Na2B4O7) yang berupa serbuk dicampur dengan bahan makanan (tepung) dengan konsentrasi boron sebanyak 1%, 3%, 5%, 7%, dan 10% dalam 10 gram sampel. Sampel yang sudah digerus sampai halus kemudian dikompaksi untuk menjadi pellet dengan diameter 10 mm dan tebalnya antara 1-2 mm. Dalam penelitian ini digunakan berkas laser dari Nd:YAG (355 nm, 8 ns) yang difokuskan pada permukaan sampel pellet sehingga timbul plasma. Spektrum emisi plasma yang terekam pada komputer kemudian dianalisis untuk melihat garis emisi boron yang menandakan kehadiran boraks pada sampel. Kata-kata kunci: Laser Induced Breakdown Spectroscopy (LIBS), spektrum emisi plasma, boron.
This study demonstrates a new approach for suppressing the self-absorption effect in single-pulse... more This study demonstrates a new approach for suppressing the self-absorption effect in single-pulse laser-induced breakdown spectroscopy (LIBS) using unusual parallel laser irradiation. A nanosecond Nd:YAG laser with a wavelength of 1064 nm was fired parallel to and focused at a very close distance of 1 mm to the sample surface. The experiment was carried out in air at atmospheric pressure. In this configuration, the sample was ablated by a shockwave generated from the air breakdown plasma formed near the sample surface. Under this condition, we successfully obtained spectra of the resonance emission line for high concentration K (K I 766.4 nm and K I 769.9 nm) that are free from self-reversal and weakly affected by the self-absorption. Furthermore, the quantitative analysis results for the element K showed that a linear calibration curve over a wide concentration range could be achieved, which indicates the effectiveness of this technique in reducing the self-absorption effect and im...
Laser-induced breakdown spectroscopy (LIBS) to detect the light elements such as lithium (Li) and... more Laser-induced breakdown spectroscopy (LIBS) to detect the light elements such as lithium (Li) and boron (B) and heavy elements such as copper (Cu) and lead (Pb) in raw fish samples is reported in this work. This is made possible by understanding that the soft target absorbs recoil energy and as a result, the ablated atoms gushing from the soft target do not acquire sufficient speed to form a shock wave. In order to overcome this problem, we set a subtarget on the back of the soft target so as to produce the repulsion force by which the gushing speed of the ablated atoms is increased, yielding a sufficiently high plasma temperature or sufficiently large thermal energy needed for the excitation of the ablated atoms. Excellent spectral qualities of various soft samples such as margarine, butter, peanut butter, strawberry jam, raw tuna, raw gindara, and raw salmon are presented. Furthermore, a linear calibration curve with a zero intercept is also obtained for Li, Cu, and Pb. The detection limit of Li, Cu, and Pb is found to be around 0.1 mg/L. This modification of LIBS for soft samples by using a subtarget effect clearly promises a rapid and in situ soft sample analysis since there is practically no sample digestion in the analysis.
Several experiments are performed to explore the possible benefits of using bamboo charcoal as a ... more Several experiments are performed to explore the possible benefits of using bamboo charcoal as a sample holder for rapid powder analysis using laser-induced breakdown spectroscopy at low-pressure helium ambient gas. Standard powdered samples such as ZnS and CuSO4 are used to demonstrate the feasibility of using cheap and widely available bamboo charcoal as a sample holder. A commercial baby milk powder and several sets of soil samples with a tiny amount of impurities are also introduced to show the potential application of bamboo charcoal as a powder holder. By appropriately adjusting the laser pulse energy and the thickness of the powder layer, we successfully obtained a spectrum that is free from the undesirable matrix effect. A remarkable result was obtained, even using a tiny amount of the powder sample. This proposed method is considered notably promising for the rapid analysis of the powder sample, especially with a very limited amount.
Self-absorption, which is known to severely disturb identification of the emission peak intensity... more Self-absorption, which is known to severely disturb identification of the emission peak intensity in emission-based spectroscopy, was first studied using ordinary single pulse laser-induced breakdown spectroscopy (LIBS). It was found that severe self-absorption, with an evident self-reversal, occurs in the resonance emission lines of high concentration Na, K, and Al, and thus it is impossible to obtain the linear calibration curve required for quantitative analysis. To overcome this problem, we introduce a double pulse orthogonal technique in which the first laser is fired in a parallel orientation at a varied distance of 2–6 mm from the sample surface. It is well known that the strong shock wave generated by this laser irradiation temporarily creates a vacuum-like condition immediately in front of the sample surface. This action is followed by a second laser irradiation oriented perpendicular to the sample surface. The sample ablated by the second laser irradiation expands followin...
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