149
5.6.2 SEM Analysis
The scanning electron microscopy (SEM) is used for observation of specimen surfaces. When the specimen is irradiated with a fine electron beam (called an electron
probe), secondary electrons are emitted from the specimen surface. Topography of
the surface can be observed by two-dimensional scanning of the electron probe over
the surface and acquisition of an image from the detected secondary electrons.
For this pilot research, double-sided adhesive carbon tape is applied to the sample stub, to which a small amount of the sample is attached. The sample is made of
gold; the coating is up to 20 nm thick. The sample thus prepared is placed in the
chamber of a scanning electron microscope, and the necessary analyses are performed by achieving a high vacuum. The analyses were performed using SE (secondary detector) at 30 kV voltage. SEM analyses were conducted in the National
Institute for R&D of Isotopic and Molecular Technologies, Integrated Electron
Microscopy Laboratory, in Cluj, Romania.
5.7 Data Summary and Perspective
5.7.1 Moss Sample SEM Analysis
The energy-dispersive X-ray spectrometer (EDS) is used to analyze characteristic
X-ray spectra by measuring the energies of the X-rays. When the X-rays emitted
from the specimen enter the semiconductor detector, electron-hole pairs are generated whose quantities correspond to the X-ray energy. Measuring these quantities
(electric current) enables to obtain the values of X-ray energy. The detector is cooled
by liquid nitrogen, in order to reduce the electric noise. The advantage of the EDS
is that the X-rays from a wide range of elements from B to U are analyzed simultaneously. The following figures present the X-ray spectrum obtained from EDS for
the analyzed moss samples. Moss surface screening can give us very useful information of the dust composition and moss tissue accumulation of potentially toxic
elements. Given in Figs. 5.1, 5.2, and 5.3 are the qualitative and quantitative chemical analyses of the surface of the Hypnum cupressiforme moss samples (25, 50, and
100 μm). Figures 5.1b, 5.2, and 5.3b represent the following: the X line is the spectral analysis-qualitative analysis element detection, and the Y line is the cps (counts
per seconds), the quantitative analysis determination of the concentration.
Figure 5.4a, b represents the comparison of two spectra of the surface, spectrum 3
(yellow) and spectrum 4 (red) lines, and the differences of the elementary composition into the samples. Spectrum of gold is visible in every analysis, but it does not
count, because the sample is coated with gold so the quantitative analysis of gold is
not showed into the figure (settings conducted before each analysis). Figures 5.1,
5.2, 5.3, and 5.4 are the screening analysis of the Hypnum sample representing as a
control sample (in non-polluted area). The SEM analyses represented in Figs. 5.5,
5 Proposing Chemometric Tool for Efficacy Surface Dust Deposition Tracking…
5.6.2 SEM Analysis
The scanning electron microscopy (SEM) is used for observation of specimen surfaces. When the specimen is irradiated with a fine electron beam (called an electron
probe), secondary electrons are emitted from the specimen surface. Topography of
the surface can be observed by two-dimensional scanning of the electron probe over
the surface and acquisition of an image from the detected secondary electrons.
For this pilot research, double-sided adhesive carbon tape is applied to the sample stub, to which a small amount of the sample is attached. The sample is made of
gold; the coating is up to 20 nm thick. The sample thus prepared is placed in the
chamber of a scanning electron microscope, and the necessary analyses are performed by achieving a high vacuum. The analyses were performed using SE (secondary detector) at 30 kV voltage. SEM analyses were conducted in the National
Institute for R&D of Isotopic and Molecular Technologies, Integrated Electron
Microscopy Laboratory, in Cluj, Romania.
5.7 Data Summary and Perspective
5.7.1 Moss Sample SEM Analysis
The energy-dispersive X-ray spectrometer (EDS) is used to analyze characteristic
X-ray spectra by measuring the energies of the X-rays. When the X-rays emitted
from the specimen enter the semiconductor detector, electron-hole pairs are generated whose quantities correspond to the X-ray energy. Measuring these quantities
(electric current) enables to obtain the values of X-ray energy. The detector is cooled
by liquid nitrogen, in order to reduce the electric noise. The advantage of the EDS
is that the X-rays from a wide range of elements from B to U are analyzed simultaneously. The following figures present the X-ray spectrum obtained from EDS for
the analyzed moss samples. Moss surface screening can give us very useful information of the dust composition and moss tissue accumulation of potentially toxic
elements. Given in Figs. 5.1, 5.2, and 5.3 are the qualitative and quantitative chemical analyses of the surface of the Hypnum cupressiforme moss samples (25, 50, and
100 μm). Figures 5.1b, 5.2, and 5.3b represent the following: the X line is the spectral analysis-qualitative analysis element detection, and the Y line is the cps (counts
per seconds), the quantitative analysis determination of the concentration.
Figure 5.4a, b represents the comparison of two spectra of the surface, spectrum 3
(yellow) and spectrum 4 (red) lines, and the differences of the elementary composition into the samples. Spectrum of gold is visible in every analysis, but it does not
count, because the sample is coated with gold so the quantitative analysis of gold is
not showed into the figure (settings conducted before each analysis). Figures 5.1,
5.2, 5.3, and 5.4 are the screening analysis of the Hypnum sample representing as a
control sample (in non-polluted area). The SEM analyses represented in Figs. 5.5,
5 Proposing Chemometric Tool for Efficacy Surface Dust Deposition Tracking…