Обучение по природни науки и върхови технологии

2015/6, стр. 849 - 862

SURFACE FUNCTIONALIZATION OF SILICA SOL-GEL MICROPARTICLES WITH EUROPIUM COMPLEXES

Nina Danchova
University of Sofia
Bulgaria
Gulay Ahmed
University of Sofia
Bulgaria
Michael Bredol
Fachhochschule Muenster
Germany
Stoyan Gutzov
E-mail: sgutzov@chem.uni-sofia.bg
Department of Physical Chemistry
University of Sofia
1 James Bourchier Blvd.
1164 Sofia Bulgaria

Резюме: The present contribution is focused on the relation preparation – structure – optical properties of hybrid silica powders containing Eu(III) complexes: \(\mathrm{SiO}_{2}\) : \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) and \(\mathrm{SiO}_{2}\) : \(\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\). New methods for surface functionalization of silica microparticles \({ }_{2}\) based on adsorption of 1,10-phenantroline and \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\), are proposed in the framework of preparation of red emitting hybrid composites with quantum efficiency \(20-50 \%\). The optical properties of rare earth ions incorporated in silica composites are used to explore the site symmetry (\(\mathrm{D}_{2}\), \(\mathrm{C}_{2 \mathrm{v}}\) or lower) of the \(\mathrm{Eu}^{3+}\) optical centers in the hybrid composites. Quantum yields of the investigated sol-gel micropowders and quantification of their optical spectra are presented. X-Ray diffraction patterns of the investigated hybrid composites are presented. A short overview of sol-gel technology as a method for preparation of functional nanomaterials is presented.

Ключови думи: silica, europium complexes, luminescence, sol-gel

Introduction

Sol-gel materials functionalized with rare earth ions and their complexes display important optical properties like luminescence, coloration and energy transfer and give opportunity for wide technical applications. This paper deals with colloidal preparation strategies of silica gels doped with europium complexes. Such materials have potential application as red emitting materials for photo conversion of light, ultraviolet sensors and in labeling of materials (Brinker & Scherrer, 1990). From materials science point of view sol-gel materials functionalized with rare earth ions are hybrid materials as they contain an organic ligand or complex in an inorganic matrix. The oxide matrix is usually prepared using sol-gel chemistry. To transform an inorganic silica or zirconia matrix into a system with desired optical properties it is necessary to incorporate into the matrix an optical active component using a physico - chemical doping procedure. Here, the optical active components are strong red emitting europium (III) complexes (Bünzli, 2014). As a model of europium complexes in this paper following species are used: (a) \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\), containing 4,4,4-trifluoro-1-(naphthalene-2-yl) butan-1,3-dione (Hntac) and pyrazino[2,3-f][1,10-phenathroline-2,3-dicarbonitrile (pphendcn). It is a relatively new luminescent complex, detailed described by Bünzli (2014), Petkova et al. (2011a), Petkova et al. (2011b), Danchova & Gutzov (2014), Danchova et al., 2014 and Danchova & Gutzov (2014). The quantum efficiency of the solid complex is \(10-15 \%\); (b) \(\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\), europium (III) diphenathroline nitrate. It is a well known luminescent complex, detailed described by Mirochnik et al (2002). The quantum efficiency of the solid complex is \(35-40 \%\).

The basic principles of sol-gel chemistry as a tool for preparation of functional nanomaterials are given bellow. Sol-gel technology is a powerful method for preparation of oxide nanomaterials at low temperatures (bellow \(150{ }^{\circ} \mathrm{C}\) ). Most important advantages of sol-gel technology are the use of liquid chemicals, the possibility for preparation of complicated chemical compositions and the use of low temperature of preparation. Sol-gel chemistry, however, displays some disadvantages like individual preparation schemes for solving each problem, long duration times of gelation and lot of physico - chemical measurements necessary for a reproducible preparation. Sol-gel chemistry offers a possibility for the ambient preparation of optical materials like xerogels or layers doped with rare earth ions. In the same way a wide range of useful ceramic materials like \(\mathrm{Al}_{2} \mathrm{O}_{3}, \mathrm{ZrO}_{2}, \mathrm{SnO}_{2}, \mathrm{SiO}_{2}, \mathrm{Al}_{2} \mathrm{O}_{3}\) can be easily prepared.

Gels are solids confining a solvent in a three-dimensional network. The solvent may be enclosed as quasi-liquid in a pore system. At this state, the gels are called hydrogels (water as solvent) or alcogels (alcohol as solvent), etc. If the network has nanodimensions or is index-matched, the gel looks transparent. If the solvent is removed without destruction of the porous network, the resulting body is called a aerogel. The density of aerogels is in the range of \(0.05 \mathrm{~g} / \mathrm{cm}^{3}\). Drying with destruction of the porous network leads to typical xerogel monoliths with a density in the range of \(0.5-1 \mathrm{~g} / \mathrm{cm}\) (Petkova et al., 2011a; Büzli, 2014; Gutzov & Bredol, 2006).

It is known, that sol gel-chemisrty is based on three simple chemical reactions: water hydrolysis of liquid alkoxides followed by condensation. Condensation (better known as gelation), could be performed as a water condensation or alcohol condensation. The results of sol-gel process strongly depend on the reaction conditions: it is possible to obtain micro- or nanopowders, transparent xerogels, transparent thin films or even aerogels by changing reaction conditions.

The europium (III) ion is responsible for the red component of the tricolor luminescent lamps due to a strong emission peak at 615 nm. The optical properties of europium ion are well known, they are explained by the weak crystal field approximation. In addition, the europium ion optical spectra give information about the site symmetry of the europium ion, the so called “spectra structure correlation” (Blasse & Grabmaier, 1994).

The optical transitions of lanthanide ions are weak to produce light and therefore their intensity must be increased. Sensitizer ions or molecules absorb ultraviolet energy and transfer this energy to the europium ion. The europium ion itself goes to an excited state and emits in the red spectral region. In this way the quantum yield can be increased more than ten times. As organic sensitizing ligands many organic molecules like phenathroline or acethylacetone and their derivates are used. Cerium ion is a typical example for inorganic ions with sensitizing properties. More about the energy transfer is given in the monographs (Binker & Scherer, 1990; Büzli, 2014). In the case of an efficient energy transfer the weak sharp Eu(III) peaks in the excitation spectra are replaced by strong, broad features dominated from sensitizers.

In Fig. 1. a typical sol-gel preparation equipment in the laboratory of Functional Optical Materials (FOM) in the Department of Physical Chemistry is shown. The used chemicals are liquids – metal alcoxides, alcohol and water, as well as doping solutions, lanthanide solutions and other solutions. The laboratory is specialized in doping of zirconia and silica gels with lanthanide ions and their complexes. Some details the solgel process are: the preparation of oxides consists two steps, hydrolysis of alcoxides and gelataion of the prepared colloidal nanoparticles. The hydrolysis is acid catalized, the condensation / gelation/ step - basic catalized. Drying conditions are very important to obtain gels with desired properties. Reproducibility is one of the most important problems in sol-gel chemistry due to the complicated physic-chemical nature of the processes in sol-gel technology. Parameters which must be controlled during the solgel process are pH, temperature and chemical composition to obtain materials with a given chemistry, transparency, phase composition and microstructure.

Fig. 1. Preparation of sol-gel materials: pH control, temperature control and liquid chemicals used for preparation of functionalized gels

In Fig. 2 some results connected with functionalized inorganic silica gels are presented. Silica gels doped with samarium ions are materials with potential application as ultraviolet filters. Left – low doped with samarium ions silica gels are displayed, they are transparent. Increasing the degree of doping leads to a weak yellow color and makes the gels translucent, because nano- crystals of samarium nitrate are formed during the sol-gel process. Under special conditions and using basic condensation conditions, microspheres instead of transparent gels, could be obtained.

The photos of Dr. GulayAhmed (Fig. 2) are made through doped gels with a thickness of about 2 mm with a different samarium concentration. In summary, transparency of inorganic sol-gel materials depends on doping concentration and/or porous system properties. Also Fig. 2 shows interesting applications of sol-gel chemistry, preparation of uniform silica microspheres, known as “Stöber’s silica”. Under special conditions and using basic condensation conditions, uniform microspheres instead of transparent gels could be obtained (Brinker & Scherrer, 1990).

Fig. 2. Inorganic doped silica gels with controlled shape and optical properties. By varying of physico-chemical preparation conditions materials for optical filters (left) or silica microspheres with application as coating materials (right) can be prepared

Zirconia sol-gel chemistry is much more complicated compared to silica chemistry, because of the high reactivity of zirconium alcoxides. In the case of zirconia solgel chemistry the rates of hydrolysis and condensation are high and a fast formation of micropowders, as in the case of chemical precipitation takes place. This is why zirconium alcoxides must be protected with organic ligands as acethylacetone or acetic acid, which form chelate complexes with zirconium.

In Fig. 3 three sol-gel approaches for preparation of zirconia sol-gel materials depending on protection conditions of the sol are shown. In the left scheme nanopowders, fast produced without protection are displayed. In the middle scheme a protection with acethylaceton as complex forming ligand is given. The result is a transparent gel with increased ultraviolet absorption. Right an example for production of zirconia gels with protection of acetic acid, the most successful way to produce hybrid materials. The photo of Dr. Nina Danchova (Fig. 3) is made through a zirconia gel to demonstrate the optical transparency of the produced zirconia materials. The high transparency in the case of zirconia is combined with a high refractive index, zirconia is well known as “artificial diamond”. The strong gel coloration in Fig. 3 comes from \(\mathrm{Zr}(\) IV \()\)-acetyl acetone complexes with a high UV – absorption, \(\varepsilon=24001 / \mathrm{mol} \cdot \mathrm{cm}\) at 285 nm (Petkova et al., 2011a; Georgieva et al., 2011).

Fig. 3. Three sol-gel approaches for preparation of zirconia sol-gel materials depending on protection conditions of the sol. The acetic acid protection leads to highly transparent materials with an increased refractive index. Zirconia materials are also known as “artificial diamond” because of their high refractive index

Experimental

The europium complexes \(\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) and \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) were synthesized according procedures by Petkova et al. (2011b). Elemental analysis was performed on a Vario III instrument. A SpectraPro 300i spectrophotometer was used for measurement of diffuse reflectance, excitation / luminescence spectra and quantum yield of powdered samples. As standard, the Lumogen T Rot GG from BASF with maximum wavelength of excitation at 350 nm and maximum wavelength of emission at 615 nm was chosen. The Quantum Yield (QY) of the investigated samples was determined using the comparison method. Emission spectra were integrated between 430 and 750 nm and excitation spectra between 235 and 430 nm. The luminescence and reflectance measurements were used to estimate QY of investigated samples (defined as the ratio of the number of photons emitted to the number of photons absorbed). In this study, the presented luminescence spectra are mathematically threated as overlapping Gaussion curves to obtain relative intensities, peak number, peak maxima and half widths of each luminescence peak. The Eu – content in all samples prepared was checked using a ICP Ultima2 Horiba-Jobin Yvon unit.

To prepare silica microparticles with an intense red emission two physico-chemical functionalization techniques are used:

Surface functionalization of silica micro particles with [Eu(ntac) ] \({ }_{3}\) ][pphendcn] (physical functionalization)

The preparation of hybrid silica micro composites includes the following basic steps: (1) Preparation of \(\mathrm{SiO}_{2}\) matrix, using a classical base catalyzed sol-gel process (Danchova & Gutzov, 2013); (2) Homogenization of the solid matrix in mortar to obtain silica micro particles in size 100-300 μm; (3) Impregnation of silica micro particles with solution of \(0.0107 \mathrm{M}\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) in ethanol (48 h at room temperature).

Preparation of functionalized micro particles starting from \(\mathrm{SiO}_{2}\) :Eu (chemical functionalization

The preparation includes the following basic steps: (1) Synthesis of doped \(\mathrm{SiO}_{2}: \mathrm{Eu}^{3+}\) sol-gel bulk materials with molar ratio \(\mathrm{n}_{\mathrm{Eu}} / \mathrm{n}_{\mathrm{Si}}=0.05\) using the procedure by Danchova & Gutzov (2013); (2) Homogenization of silica gel in mortar to obtain \(\mathrm{SiO}_{2}: \mathrm{Eu}^{3+}\) silica micro particles; (3) Impregnation of doped \(\mathrm{SiO}_{2}\) micro particles with ethanol solution of 1.1M 1,10-phenanthroline (48 h at room temperature with molar ratio \(\mathrm{n}_{\mathrm{Eu}}\) / \(\mathrm{n}_{\text {phen }}=9.4 \cdot 10^{-3}, \mathrm{n}_{\mathrm{Si}} / \mathrm{n}_{\text {phen }}=0.18\); (4) Washing the micropowders with absolute ethanol to remove the excess amount of ligand.

Experimental results and discussion

In Fig. 4 a typical luminescence spectrum of \(\mathrm{SiO}_{2}:\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) powders produced from \(\mathrm{SiO}_{2}: 0.05 \mathrm{Eu}^{3+}\) functionalized using adsorption of 1,10-phenanthroline (chemical functionalization) is presented. The relative intensity of the \(\mathrm{Eu}^{3+5} \mathrm{D}_{0} \rightarrow{ }^{7} \mathrm{~F}_{2}\) transition is high, about \(80-82 \%\) from the overall \(\mathrm{Eu}^{3+}\) luminescence intensity between 570 nm and 750 nm. It follows from second derivative luminescence spectra, that the most probable symmetry of \(\mathrm{Eu}^{3+}\) is \(\mathrm{D}_{2}\) (Görller-Walrand & Binnemans, 1998). Surface formation of \(\left[\mathrm{Eu}(\text { phen })_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) as a result of the functionalization of \(\mathrm{SiO}_{2}\) : Eu with \(1,10-\) phenanthroline has been confirmed by X-Ray diffraction by comparing data of pure solid complexes and functionalized silica samples. X-Ray diagrams of the investigated samples are presented in Fig. 5, here a pure solid complex \(\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) and solid \(1,10-\) phenanthroline are used as a reference. In the case of solid \(\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) and functionalized \(\mathrm{SiO}_{2}:[\mathrm{Eu}(\) phen \()]\left(\mathrm{NO}_{3}\right)_{3}\) we have a very weak \({ }^{5} \mathrm{D}_{0} \rightarrow{ }^{7} \mathrm{~F}_{0}\) transition at 585 nm, visible in second – derivative spectra, which refers that the most probable site symmetry of \(\mathrm{Eu}^{3+}\) here is \(\mathrm{D}_{2}\) and / or \(\mathrm{C}_{2 \mathrm{v}}\) (Danchova et al., 2 2014). The presence of two kind of optical centers in the described hybrid materials is also possible. The exact site symmetry evaluation here needs additional investigations.

Fig. 4. A typical luminescence spectrum of \(\mathrm{SiO}_{2}\) : \(\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) powders at 352 nm excitation. The Eu3+ 5D07F 0,1,2,3,4 transitions are denoted as 0-1,2,3,4. The \(\mathrm{Eu}^{3+}{ }^{5} \mathrm{D}_{0} \rightarrow{ }^{7} \mathrm{~F}_{0,1,2,3,4}\) transitions are denoted as \(0-1,2,3,4\). The optical properties of the complex are shown (Görller-Walrand & Binnemans, 1998)

Fig. 5. X-Ray diagrams of the investigated functionalized powders. The diagrams of a pure solid complex \(\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) and solid 1, \(10-\) phenanthroline are used as a reference

In Fig. 6 luminescence spectra of solid \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) and functionalized \(\mathrm{SiO}_{2}:\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) are presented. The relative intensity of the \(\mathrm{Eu}^{3+}{ }^{5} \mathrm{D}_{0} \rightarrow{ }^{7} \mathrm{~F}_{2}\) transition is about \(83-85 \%\). Differences in the luminescence spectra of solid complex and functionalized sol-gel samples have been detected. The luminescence spectrum of \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) has a relative strong \({ }^{5} \mathrm{D}_{0} \rightarrow{ }^{7} \mathrm{~F}_{0}\) transition and a site symmetry of \(\mathrm{Eu}^{3+} \mathrm{C}_{2 \mathrm{v}}\) or lower (Görller-Walrand & Binnemans, 1998). Spectral differences indicate a change of chemical environment and / or site symmetry of \(\mathrm{Eu}^{3+}\) as a result of the adsorption of \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) on the silica surface. In the terms \(\mathrm{Eu}^{3+}\) site symmetry/spectra correlation, the most probable site symmetry in \(\mathrm{SiO}_{2}:\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right]\) [pphendcn] is \(\mathrm{D}_{2}\) (Bünzli, 2014). The luminescence spectral maximum changes from 612 nm to 618 nm as a result of functionalization most probable due to lowering of crystal field strength on the silica surface.

Fig. 6. Luminescence spectra of \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) and functionalized \(\mathrm{SiO}_{2}:\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) at 400 nm excitation. The \(\mathrm{Eu}^{3+}{ }^{5} \mathrm{D}_{0} \rightarrow 7 \mathrm{Fj}\) transitions are denoted as \(0-1,0-2,0-3\) and \(0-4\)

The luminescence emission of the prepared samples \(\mathrm{SiO}_{2}:\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) and \(\mathrm{SiO}_{2}:\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) are very stable for long period of times (more than 1 year). We do not observed additional blue lines coming from surface complex destruction.

Table 1 presents the quantum yields of the investigated samples together with the doping level of the europium activator. In addition, the most probable site symmetry of the europium ion, exctracted from the luminescence spectra, is given. The high quantum yields confirm unambiguously that a ligand→europium charge transfer take place in all of the samples. The relative error of QY using the described procedure is about 0.1, quantum yields of pure complexes are given for comparison. The relative high quantum yields in table 1. allow the potential application of the described hybrid powders as potential UV – sensors and label materials for chemical and biological applications. The quantum yield of europium complexes increases after incorporation in the sol-gel matrix due to a lack of concentration quenching.

Table 1. Excitation wavelengths, quantum yields (QY) and europium content of the investigated powdered samples at 615 nm emission wavelength. The most probable site symmetry of \(\mathrm{Eu}^{3+}\) is given

Sample / ChemistryExcitation[nm] QY[%] Eu[%] Site symmetryof Eu3+SiO2:[Eu(ntac) 3][pphendcn] 40017.40.1D2SiO2: [Eu(phen) 2](NO3) 335239.65.4D2and / or C2v[Eu(ntac) 3][pphendcn] 39610.811.4C2vor lower[Eu(phen) 2](NO3) 335235.412.7D2and / or C2v

It is well known, that using a quantification of \(\mathrm{Eu}^{3+}\) luminescence spectra the site symmetry of the activator ion on molecular level can be obtained in different host matrixes, the so called “spectra-structure correlation”. In this way the site symmetry of europium doped crystals and amorphous materials can be investigated.

From physical point of view the optical transitions of the \(\mathrm{Eu}^{3+}\) ion are magnetic dipole transitions or electric dipole transition described by the low crystal field approximation and quantified by the Judd – Ofelt theory. The Judd – Ofelt theory allows to calculate the oscillator strengths of the f-f transitions of lanthanide ions. The intensities of electronic transitions of europium ions incorporated in sol-gel matrices are characterized by their experimental oscillator strength (Görller-Walrand & Binnemans, 1998; Schmidt, 2000; Brinker & Scherer, 1990):

(1) \[ f=\tfrac{4.32 \cdot 10^{-9}}{C \cdot d} \int A(\widetilde{v}) d \widetilde{v} \]

where \(A(\widetilde{v})\) is the absorbance, C is the \(\mathrm{Eu}^{3+}\) concentration in \(\mathrm{mol} \cdot \mathrm{dm}^{-3}, \mathrm{~d}\) is the optical pathlength in cm and \(\widetilde{v}\) is he wavenumber in \(\mathrm{cm}^{-1}\). The Judd-Ofelt theory allows for the calculation of oscillator strengths according to:

(2) \[ f=4 \cdot \pi \cdot \varepsilon_{0} \tfrac{8 \cdot \pi^{2} \cdot m_{e} \cdot v_{0}}{3 \cdot h \cdot(2 J+1) e^{2}}\left[\chi_{e d} \cdot S_{e d}+\chi_{m d} \cdot S_{m d}\right] \]

Here, \(\chi_{e d}\) and \(\chi_{m d}\) are weighting the electric-dipole and magnetic-dipole contributions, respectively. According to the Judd and Ofelt theory the transition moment for electric dipole \(\mathrm{f} \rightarrow \mathrm{f}\) transitions can be expresses by

(3) \[ \left.S_{e d}=\tfrac{e^{2}}{4 \cdot \pi \cdot \varepsilon_{0}} \sum_{k=2,4,6} \Omega_{k}\left|\left\langle f^{N} \psi J\right| U^{(k)}\right| f^{N} \psi^{\prime} J^{\prime}\right\rangle\left.\right|^{2} \]

and that of the magnetic dipole f-f transition is given by:

(4) \[ \left.S_{m d}=\tfrac{1}{4 \cdot \pi \cdot \varepsilon_{0}} \tfrac{e^{2}}{4 \cdot m^{2} \cdot c^{2}} \sum_{k=2,4,6} \Omega_{k}\left|\left\langle f^{N} \psi J\right| L+2 S\right| f^{N} \psi^{\prime} J^{\prime}\right\rangle\left.\right|^{2} \]

Here, \(\Omega_{\mathrm{k}}\) aretheso-calledJudd-Ofeltintensityparametersand \(\left.\left|\left\langle f^{N} \psi J\right| U^{(k)}\right| f^{N} \psi^{\prime} J^{\prime}\right\rangle \mid\) and \(\left.\left|\left\langle f^{N} \psi J\right| L+2 S\right| f^{N} \psi^{\prime} J^{\prime}\right\rangle \mid\) the reduced matrix elements connecting initial and final states J and J’, respectively. They are commonly assumed to be independent of the host material and have been calculated by Blasse & Grabmaier (1994) and Görller-Walrand & Binnemans, (1998). Conventionally, the \(\Omega_{\mathrm{k}}(\mathrm{k}=2,4,6)\) are determined from experimental spectra taken at room temperature. Hence, a possible temperature dependence of spectral intensity is not accounted for by the standard \(\Omega_{\mathrm{k}}\) values.

The quantum yield of europium doped gels \(\mathrm{QY}_{\text {sam }}\) in this paper is calculated from integrated absorption and luminescence intensity using the comparison method as follows (Schmidt, 2000):

(5) \[ Q Y_{s a m}=Q Y_{r e f} \cdot \tfrac{I_{s a m} \cdot A_{r e f}}{I_{r e f} \cdot A_{s a m}} \cdot 100 \]

Here, \(\mathrm{QY}_{\text {ref }}\) is the quantum yield of the reference sample; \(\mathrm{I}_{\text {sam }}\) and \(\mathrm{I}_{\text {ref }}\) are the integrated luminescence peaks of the investigated sample and the reference and Aref and \(\mathrm{A}_{\text {ref }}\) and \(\mathrm{A}_{\text {sam }}\) are the integrated absorption peaks of the reference and of the investigated sample.

If the \(\mathrm{Eu}^{3+}\) ion occupies sites with an inversion symmetry, the magnetic dipole transition \({ }^{5} \mathrm{D}_{0} \rightarrow{ }^{7} \mathrm{~F}_{1}\) at 5 590 nm is relatively strong. If the \(\mathrm{Eu}^{3+}\) occupies sites without an inversion symmetry, the electric dipole transition \({ }^{5} \mathrm{D}_{0} \rightarrow{ }^{7} \mathrm{~F}_{2}\) at 615 nm is very strong. In addition, the peak number in the region of each Stark multiplet increases when a europium ion occupies sites with a low symmetry. There are quantitative approaches to obtain the site symmetry group from peak numbers in the region of each Stark multiplet, which has been used to determine the most probable site symmetry of \(\mathrm{Eu}^{3+}\) ion, presented in Table 1.

Conclusions

In this paper surface functionalization of sol-gel \(\mathrm{SiO}_{2}\) microparticles with \(\left[\mathrm{Eu}(\mathrm{ntac})_{3}\right][\mathrm{pphendcn}]\) and \(\left[\mathrm{Eu}(\mathrm{phen})_{2}\right]\left(\mathrm{NO}_{3}\right)_{3}\) complexes is described.

Two colloidal methods of surface functionalization, chemical and physical functionalization for preparation of hybrid optical materials are discussed. All the functionalized samples show a pure, stable in time \(\mathrm{Eu}-\) luminescence with quantum yield \(10-40 \%\) due to energy transfer from organic ligands. Surface functionalization is accompanied with a site-symmetry change of \(\mathrm{Eu}^{3+}\) ions followed using luminescence spectroscopy.

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Алвина Илин, Валентина Ткачова, Петя Петрова

БЕБЕШКИ ШАМПОАН ОТ ЯДЛИВИ СЪСТАВКИ: ФОРМУЛИРАНЕ НА НОВ КОЗМЕТИЧЕН ПРОДУКТ

Хана Крипендорф, 5, Даниел Кунев, 5, Цветелина Стоянова

БЪЛГАРСКОТО ИМЕ НА ДЪЛГОЛЕТИЕТО

Сияна Краишникова, Анелия Иванова

ХИМИЯ НА МОНЕТИТЕ

Кристина Анкова, Сияна Христова, Ростислава Цанева

ХИМИЯ НА ШОКОЛАДА

Камелия Вунчева, Мария-Сара Мандил, Марияна Георгиева

ХИМИЯТА НА ПАРИТЕ

Биляна Куртева, Ралица Ранчова

АЛУМИНИЯТ В КРИОГЕНИКАТА

Даниел Анков, Ива Петкова, Марияна Георгиева

ПРИЛОЖЕНИЕ НА АЛУМИНИЯ ВЪВ ВАКСИНИТЕ

Станислав Милчев, Петя Вълкова

АЛУМИНИЙ: „КРИЛА НА ЧОВЕЧЕСТВОТО – ЛЮБИМЕЦ 13“

Ростислав Стойков, Пепа Георгиева

ХИМИЯТА В ПЧЕЛНИЯ МЕД

Сиана Каракашева, Симона Тричкова, Майя Найденова-Георгиева

ХИМИЯ НА МЛЕЧНИТЕ ПРОДУКТИ

Пламена Боиклиева, 10 клас, Дафинка Юрчиева

ХИМИЯ В МАСЛИНИТЕ

Симона Гочева, Майя Найденова

ХИМИЯ НА ЛЮТОТО

Марта Пенчева, Васка Сотирова

ХИНАП – ИЗСЛЕДВАНЕ НА СЪДЪРЖАНИЕТО НА ВИТАМИН С

Елица Нейкова, Елисавета Григорова, Майя Найденова

ХИМИЯ НA ПAРИТE

Игликa Кoлeвa, Eмилия Ивaнoвa

ВЛИЯНИЕ НА МАРИНАТИТЕ ВЪРХУ МЕСОТО

Емил Мирчев, Галя Петрова

АНАЛИЗ НА ПРИРОДНИ ВОДИ В ОБЩИНА СЛИВЕН

Никола Урумов, Анелия Иванова

ТРИНАДЕСЕТИЯТ ЕЛЕМЕНТ – СПАСИТЕЛ ИЛИ ТИХ РАЗРУШИТЕЛ?

Виктория Дечкова, Никола Велчев, Нели Иванова

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MATHEMATICAL MODELLING OF THE TRANSMISSION DYNAMICS OF PNEUMONIA AND MENINGITIS COINFECTION WITH VACCINATION

Deborah O. Daniel, Sefiu A. Onitilo, Omolade B. Benjamin, Ayoola A. Olasunkanmi

2024 година
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2023 година
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ПОДКАСТ – КОГА, АКО НЕ СЕГА?

Христо Чукурлиев

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2022 година
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METEOROLOGICAL DETERMINANTS OF COVID-19 DISEASE: A LITERATURE REVIEW

Z. Mateeva, E. Batchvarova, Z. Spasova, I. Ivanov, B. Kazakov, S. Matev, A. Simidchiev, A. Kitev

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MATHEMATICAL MODELLING OF THE TRANSMISSION MECHANISM OF PLAMODIUM FALCIPARUM

Onitilo S. A, Usman M. A., Daniel D. O. Odetunde O. S., Ogunwobi Z. O., Hammed F. A., Olubanwo O. O., Ajani A. S., Sanusi A. S., Haruna A. H.

ПОСТАНОВКА ЗА ИЗМЕРВАНЕ СКОРОСТТА НА ЗВУКА ВЪВ ВЪЗДУХ

Станислав Сланев, Хафизе Шабан, Шебнем Шабан, Анета Маринова

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MAGNETIC PROPERTIES

Sofija Blagojević, Lana Vujanović, Andreana Kovačević Ćurić

„TAP, TAP WATER“ QUANTUM TUNNELING DEMONSTRATION

Katarina Borković, Andreana Kovačević Ćurić

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КОМЕТИТЕ – I ЧАСТ

Пенчо Маркишки

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DISTANCE LEARNING: HOMEMADE COLLOIDAL SILVER

Ana Sofía Covarrubias-Montero, Jorge G. Ibanez

2021 година
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STUDY OF COMPOSITIONS FOR SELECTIVE WATER ISOLATION IN GAS WELLS

Al-Obaidi S.H., Hofmann M., Smirnov V.I., Khalaf F.H., Alwan H.H.

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POTENTIAL APPLICATIONS OF ANTIBACTERIAL COMPOUNDS IN EDIBLE COATING AS FISH PRESERVATIVE

Maulidan Firdaus, Desy Nila Rahmana, Diah Fitri Carolina, Nisrina Rahma Firdausi, Zulfaa Afiifah, Berlian Ayu Rismawati Sugiarto

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PROBLEM OF THE 8-TH EXPERIMENTAL PHYSICS OLYMPIAD, SKOPJE, 8 MAY 2021 DETERMINATION OF PLANCK CONSTANT BY LED

Todor M. Mishonov, Aleksander P. Petkov, Matteo Andreoni, Emil G. Petkov, Albert M. Varonov, Iglika M. Dimitrova, , Leonora Velkoska, Riste Popeski-Dimovski

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INVESTIGATION OF \(^{238}\)U, \(^{234}\)U AND \(^{210}\)PO CONTENT IN SELECTED BULGARIAN DRINKING WATER

Bozhidar Slavchev, Elena Geleva, Blagorodka Veleva, Hristo Protohristov, Lyuben Dobrev, Desislava Dimitrova, Vladimir Bashev, Dimitar Tonev

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DEMONSTRATION OF DAMPED ELECTRICAL OSCILLATIONS

Elena Grebenakova, Stojan Manolev

2020 година
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ДОЦ. Д-Р МАРЧЕЛ КОСТОВ КОСТОВ ЖИВОТ И ТВОРЧЕСТВО

Здравка Костова, Елена Георгиева

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JACOB’S LADDER FOR THE PHYSICS CLASSROOM

Kristijan Shishkoski, Vera Zoroska

COMPARATIVE PERFORMANCE AND DIGESTIBILITY OF NUTRIENTS IN AFSHARI AND GHEZEL RAM LAMBS

Morteza Karami, Fardis Fathizadeh, Arash Yadollahi, Mehran Aboozari, Yaser Rahimian, Reza Alipoor Filabadi

КАЛЦИЙ, ФОСФОР И ДРУГИ ФАКТОРИ ЗА КОСТНО ЗДРАВЕ

Радка Томова, Светла Асенова, Павлина Косева

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THE DAY OF THE INDUCTANCE: PROBLEMS OF THE 7\(^{TH}\) EXPERIMENTAL PHYSICS OLYMPIAD, SKOPJE, 2019

Todor M. Mishonov, Riste Popeski-Dimovski, Leonora Velkoska, Iglika M. Dimitrova, Vassil N. Gourev, Aleksander P. Petkov, Emil G. Petkov, Albert M. Varonov

MATHEMATICAL MODELING OF 2019 NOVEL CORONAVIRUS (2019 – NCOV) PANDEMIC IN NIGERIA

Sefiu A. Onitilo, Mustapha A. Usman, Olutunde S. Odetunde, Fatai A. Hammed, Zacheous O. Ogunwobi, Hammed A. Haruna, Deborah O. Daniel

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МОЛЕКУЛИТЕ НА УДОВОЛСТВИЕТО

Веселина Янкова, Снежана Демирова, Цветанка Митева, Явор Князов, Христо Желев, Димитър Георгиев, Габриела Стоянова

WATER PURIFICATION WITH LASER RADIATION

Lyubomir Lazov, Hristina Deneva, Galina Gencheva

2019 година
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LASER MICRO-PERFORATION AND FIELDS OF APPLICATION

Hristina Deneva, Lyubomir Lazov, Edmunds Teirumnieks

ПРИЛОЖНА ФОТОНИКА И АНТИОКСИДАНТНИ СВОЙСТВА НА ВИСОКООЛЕИНОВО СЛЪНЧОГЛЕДОВО МАСЛО С БИЛКОВИ ПРИМЕСИ

Кръстена Николова, Стефка Минкова, Поли Радушева, Георги Бошев, Еркан Фаридин, Нурал Джамбазов, Мариана Перифанова-Немска

ПРОЦЕСЪТ ДИФУЗИЯ – ОСНОВА НА ДИАЛИЗАТА

Берна Сабит, Джемиле Дервиш, Мая Никова, Йорданка Енева

IN VITRO EVALUATION OF THE ANTIOXIDANT PROPERTIES OF OLIVE LEAF EXTRACTS – CAPSULES VERSUS POWDER

Hugo Saint-James, Gergana Bekova, Zhanina Guberkova, Nadya Hristova-Avakumova, Liliya Atanasova, Svobodan Alexandrov, Trayko Traykov, Vera Hadjimitova

2019 − THE INTERNATIONAL YEAR OF THE PERIODIC TABLE OF CHEMICAL ELEMENTS

Maria Atanassova, Radoslav Angelov, Dessislava Gerginova, Alexander Zahariev

ТЕХНОЛОГИЯ

Б. В. Тошев

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ЗЕЛЕНА ХИМИЯ В УЧИЛИЩНАТА ЛАБОРАТОРИЯ

Александрия Генджова, Мая Тавлинова-Кирилова, Александра Камушева

ON THE GENETIC TIES BETWEEN EUROPEAN NATIONS

Jordan Tabov, Nevena Sabeva-Koleva, Georgi Gachev

CAN BRING PEOPLE TOGETHER

Nadya Kantareva-Baruh

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CHEMOMETRIC ANALYSIS OF SCHOOL LIFE IN VARNA

Radka Tomova, Petinka Galcheva, Ivajlo Trajkov, Antoaneta Hineva, Stela Grigorova, Rumyana Slavova, 6Miglena Slavova

ЦИКЛИТЕ НА КРЕБС

Ивелин Кулев

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ПРИНЦИПИТЕ НА КАРИЕРНОТО РАЗВИТИЕ НА МЛАДИЯ УЧЕН

И. Панчева, М. Недялкова, С. Кирилова, П. Петков, В. Симеонов

UTILISATION OF THE STATIC EVANS METHOD TO MEASURE MAGNETIC SUSCEPTIBILITIES OF TRANSITION METAL ACETYLACETONATE COMPLEXES AS PART OF AN UNDERGRADUATE INORGANIC LABORATORY CLASS

Anton Dobzhenetskiy, Callum A. Gater, Alexander T. M. Wilcock, Stuart K. Langley, Rachel M. Brignall, David C. Williamson, Ryan E. Mewis

A TALE OF SEVEN SCIENTISTS

Savina Kirilova

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DEVELOPMENT OF A LESSON PLAN ON THE TEACHING OF MODULE “WATER CONDUCTIVITY”

A. Thysiadou, S. Christoforidis, P. Giannakoudakis

AMPEROMETRIC NITRIC OXIDE SENSOR BASED ON MWCNT CHROMIUM(III) OXIDE NANOCOMPOSITE

Arsim Maloku, Epir Qeriqi, Liridon S. Berisha, Ilir Mazreku, Tahir Arbneshi, Kurt Kalcher

THE EFFECT OF AGING TIME ON Mg/Al HYDROTALCITES STRUCTURES

Eddy Heraldy, Triyono, Sri Juari Santosa, Karna Wijaya, Shogo Shimazu

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A CONTENT ANALYSIS OF THE RESULTS FROM THE STATE MATRICULATION EXAMINATION IN MATHEMATICS

Elena Karashtranova, Nikolay Karashtranov, Vladimir Vladimirov

SOME CONCEPTS FROM PROBABILITY AND STATISTICS AND OPPORTUNITIES TO INTEGRATE THEM IN TEACHING NATURAL SCIENCES

Elena Karashtranova, Nikolay Karashtranov, Nadezhda Borisova, Dafina Kostadinova

45. МЕЖДУНАРОДНА ОЛИМПИАДА ПО ХИМИЯ

Донка Ташева, Пенка Василева

2018 година
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ЗДРАВЕ И ОКОЛНА СРЕДА

Кадрие Шукри, Светлана Великова, Едис Мехмед

РОБОТИКА ЗА НАЧИНАЕЩИ ЕНТУСИАСТИ

Даниела Узунова, Борис Велковски, Илко Симеонов, Владислав Шабански, Димитър Колев

DESIGN AND DOCKING STUDIES OF HIS-LEU ANALOGUES AS POTENTIOAL ACE INHIBITORS

Rumen Georgiev, , Tatyana Dzimbova, Atanas Chapkanov

ELECTROCHEMICAL IMPEDANCE STUDY OF BSCCO (2212) CUPRATE CERAMIC ADDITIVE TO THE ZINC ELECTRODE IN Ni-Zn BATTERIES

A. Vasev, P. Lilov, G. Ivanova, Y. Marinov, A. Stoyanova, V. Mikli, A. Stoyanova-Ivanova

CALIBRATION OF GC/MS METHOD FOR DETERMINATION OF PHTHALATES

N. Dineva, I. Givechev, D. Tanev, D. Danalev

SONOCHEMICAL SYNTHESIS OF 4-AMINOANTIPYRINE SCHIFF BASES A ND EVALUATION OF THEIR ANTIMICROBIAL, ANTI-TYROSINASE AND DPPH SCAVENGING ACTIVITIES

Maya Chochkova, Boyka Stoykova, Iva Romanova, Petranka Petrova, Iva Tsvetkova, Hristo Najdenski, Lubomira Nikolaeva- Glomb, Nadya Nikolova, Galya Ivanova, Atanas Chapkanov, Tsenka Milkova, Martin Štícha, Ivan Nemec

ELECTROSYNTHESIS OF CADMIUM SELENIDE NANOPARTICLES WITH SIMULTANEOUS EXTRACTION INTO P-XYLENE

S. S. Fomanyuk, V. O. Smilyk, G. Y. Kolbasov, I. A. Rusetskyi, T. A. Mirnaya

БИОЛОГИЧЕН АСПЕКТ НА РЕКАНАЛИЗАЦИЯ С ВЕНОЗНА ТРОМБОЛИЗА

Мариела Филипова, Даниела Попова, Стоян Везенков

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ИМОБИЛИЗИРАНЕНАФРУКТОЗИЛТРАНСФЕРАЗА ВЪРХУКОМПОЗИТНИФИЛМИОТПОЛИМЛЕЧНА КИСЕЛИНА, КСАНТАН И ХИТОЗАН

Илия Илиев, Тонка Василева, Веселин Биволарски, Ася Виранева, Иван Бодуров, Мария Марудова, Теменужка Йовчева

ELECTRICAL IMPEDANCE SPECTROSCOPY OF GRAPHENE-E7 LIQUID-CRYSTAL NANOCOMPOSITE

Todor Vlakhov, Yordan Marinov, Georgi. Hadjichristov, Alexander Petrov

ON THE POSSIBILITY TO ANALYZE AMBIENT NOISERECORDED BYAMOBILEDEVICETHROUGH THE H/V SPECTRAL RATIO TECHNIQUE

Dragomir Gospodinov, Delko Zlatanski, Boyko Ranguelov, Alexander Kandilarov

RHEOLOGICAL PROPERTIES OF BATTER FOR GLUTEN FREE BREAD

G. Zsivanovits, D. Iserliyska, M. Momchilova, M. Marudova

ПОЛУЧАВАНЕ НА ПОЛИЕЛЕКТРОЛИТНИ КОМПЛЕКСИ ОТ ХИТОЗАН И КАЗЕИН

Антоанета Маринова, Теменужка Йовчева, Ася Виранева, Иван Бодуров, Мария Марудова

CHEMILUMINESCENT AND PHOTOMETRIC DETERMINATION OF THE ANTIOXIDANT ACTIVITY OF COCOON EXTRACTS

Y. Evtimova, V. Mihailova, L. A. Atanasova, N. G. Hristova-Avakumova, M. V. Panayotov, V. A. Hadjimitova

ИЗСЛЕДОВАТЕЛСКИ ПРАКТИКУМ

Ивелина Димитрова, Гошо Гоев, Савина Георгиева, Цвета Цанова, Любомира Иванова, Борислав Георгиев

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PARAMETRIC INTERACTION OF OPTICAL PULSES IN NONLINEAR ISOTROPIC MEDIUM

A. Dakova, V. Slavchev, D. Dakova, L. Kovachev

ДЕЙСТВИЕ НА ГАМА-ЛЪЧИТЕ ВЪРХУ ДЕЗОКСИРИБОНУКЛЕИНОВАТА КИСЕЛИНА

Мирела Вачева, Хари Стефанов, Йоана Гвоздейкова, Йорданка Енева

RADIATION PROTECTION

Natasha Ivanova, Bistra Manusheva

СРАВНИТЕЛЕН АНАЛИЗ НА СЪДЪРЖАЩИТЕ СЕ ЕСТЕСТВЕНИ РАДИОНУКЛИДИ В НЕВЕН И ЛАЙКА

Сияна Димова, Цветелина Стефанова, Йорданка Енева, Нина Архангелова

СТАБИЛНОСТ НА ЕМУЛСИИ ОТ ТИПА МАСЛО/ ВОДА С КОНЮГИРАНА ЛИНОЛОВА КИСЕЛИНА

И. Милкова-Томова, Д. Бухалова, К. Николова, И. Алексиева, И. Минчев, Г. Рунтолев

THE EFFECT OF EXTRA VIRGIN OLIVE OIL ON THE HUMAN BODY AND QUALITY CONTROL BY USING OPTICAL METHODS

Carsten Tottmann, Valentin Hedderich, Poli Radusheva, Krastena Nikolova

ИНФРАЧЕРВЕНА ТЕРМОГРАФИЯ ЗА ДИАГНОСТИКА НА ФОКАЛНА ИНФЕКЦИЯ

Рая Грозданова-Узунова, Тодор Узунов, Пепа Узунова

ЕКСПЕРИМЕНТЪТ ПО ПРИЛОЖНА ФИЗИКА И НЕГОВАТА РОЛЯ ПРИ УСВОЯВАНЕТО НА ПРАКТИКО-ПРИЛОЖНИТЕ ЗНАНИЯ ОТ КУРСАНТИТЕ И СТУДЕНТИТЕ

Николай Тодоров Долчинков, Бонка Енчева Караиванова-Долчинкова, Nikolay Dolchinkov, Bonka Karaivanova-Dolchinkova

ЕЛЕКТРИЧНИ СВОЙСТВА НА КОМПОЗИТНИ ФИЛМИ ОТ ПОЛИМЛЕЧНА КИСЕЛИНА

Ася Виранева, Иван Бодуров, Теменужка Йовчева

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PHYSICS IS AN EVER YOUNG SCIENCE

Temenuzhka Yovcheva

ТРИ ИДЕИ ЗА ЕФЕКТИВНО ОБУЧЕНИЕ

Гергана Карафезиева

МАГИЯТА НА ТВОРЧЕСТВОТО КАТО ПЪТ НА ЕСТЕСТВЕНО УЧЕНЕ В УЧЕБНИЯ ПРОЦЕС

Гергана Добрева, Жаклин Жекова, Михаела Чонос

ОБУЧЕНИЕ ПО ПРИРОДНИ НАУКИ ЧРЕЗ МИСЛОВНИ КАРТИ

Виолета Стоянова, Павлина Георгиева

ИГРА НА ДОМИНО В ЧАС ПО ФИЗИКА

Росица Кичукова, Ценка Маринова

ТЪМНАТА МАТЕРИЯ В КЛАСНАТА СТАЯ

Симона Стоянова, Анета Маринова

ПРОБЛЕМИ ПРИ ОБУЧЕНИЕТО ПО ФИЗИКА ВЪВ ВВМУ „Н. Й. ВАПЦАРОВ“

А. Христова, Г. Вангелов, И. Ташев, М. Димидов

ИЗГРАЖДАНЕ НА СИСТЕМА ОТ УЧЕБНИ ИНТЕРНЕТ РЕСУРСИ ПО ФИЗИКА И ОЦЕНКА НА ДИДАКТИЧЕСКАТА ИМ СТОЙНОСТ

Желязка Райкова, Георги Вулджев, Наталия Монева, Нели Комсалова, Айше Наби

ИНОВАЦИИ В БОРБАТА С ТУМОРНИ ОБРАЗУВАНИЯ – ЛЕЧЕНИЕ ЧРЕЗ БРАХИТЕРАПИЯ

Георги Върбанов, Радостин Михайлов, Деница Симеонова, Йорданка Енева

NATURAL RADIONUCLIDES IN DRINKING WATER

Natasha Ivanova, Bistra Manusheva

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АДАПТИРАНЕ НА ОБРАЗОВАНИЕТО ДНЕС ЗА УТРЕШНИЯ ДЕН

И. Панчева, М. Недялкова, П. Петков, Х. Александров, В. Симеонов

INTEGRATED ENGINEERING EDUCATION: THE ROLE OF ANALYSIS OF STUDENTS’ NEEDS

Veselina Kolarski, Dancho Danalev, Senia Terzieva

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ZAGREB CONNECTION INDICES OF \(\mathrm{TiO}_{2}\) NANOTUBES

Sohaib Khalid, Johan Kok, Akbar Ali, Mohsin Bashir

SYNTHESIS OF NEW 3-[(CHROMEN-3-YL) ETHYLIDENEAMINO] -PHENYL] -THIAZOLIDIN-4ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Naser Troni, Hamit Ismaili, Malesore Pllana, Musaj Pacarizi, Veprim Thaçi, Gjyle Mulliqi-Osmani

2017 година
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GEOECOLOGICAL ANALYSIS OF INDUSTRIAL CITIES: ON THE EXAMPLE OF AKTOBE AGGLOMERATION

Zharas Berdenov, Erbolat Mendibaev, Talgat Salihov, Kazhmurat Akhmedenov, Gulshat Ataeva

TECHNOGENESIS OF GEOECOLOGICAL SYSTEMS OF NORTHEN KAZAKHSTAN: PROGRESS, DEVELOPMENT AND EVOLUTION

Kulchichan Dzhanaleyeva, Gulnur Mazhitova, Altyn Zhanguzhina, Zharas Berdenov, Tursynkul Bazarbayeva, Emin Atasoy

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47-А НАЦИОНАЛНА КОНФЕРЕНЦИЯ НА УЧИТЕЛИТЕ ПО ХИМИЯ

В последните години тези традиционни за българското учителство конфе- ренции се организират от Българското дружество по химическо образование и история и философия на химията. То е асоцииран член на Съюза на химици- те в България, който пък е член на Европейската асоциация на химическите и

SYNTHESIS OF TiO 2-M (Cd, Co, Mn) AS A PHOTOCATALYST DEGRADATION OF METHYLENE BLUE DYE

Candra Purnawan, Sayekti Wahyuningsih, Dwita Nur Aisyah

EFFECT OF DIFFERENT CADMIUM CONCENTRATION ON SOME BIOCHEMICAL PARAMETERS IN ‘ISA BROWN’ HYBRID CHICKEN

Imer Haziri, Adem Rama, Fatgzim Latifi, Dorjana Beqiraj-Kalamishi, Ibrahim Mehmeti, Arben Haziri

PHYTOCHEMICAL AND <i>IN VITRO</i> ANTIOXIDANT STUDIES OF <i>PRIMULA VERIS</i> (L.) GROWING WILD IN KOSOVO

Ibrahim Rudhani, Florentina Raci, Hamide Ibrahimi, Arben Mehmeti, Ariana Kameri, Fatmir Faiku, Majlinda Daci, Sevdije Govori, Arben Haziri

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„СИМВОЛНИЯТ КАПИТАЛ“ НА БЪЛГАРСКОТО УЧИЛИЩЕ

Николай Цанков, Веска Гювийска

KINETICS OF PHOTO-ELECTRO-ASSISTED DEGRADATION OF REMAZOL RED 5B

Fitria Rahmawati, Tri Martini, Nina Iswati

ALLELOPATHIC AND IN VITRO ANTICANCER ACTIVITY OF STEVIA AND CHIA

Asya Dragoeva, Vanya Koleva, Zheni Stoyanova, Eli Zayova, Selime Ali

NOVEL HETEROARYLAMINO-CHROMEN-2-ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Naser Troni, Hamit Ismaili, Gjyle Mulliqi-Osmani, Veprim Thaçi

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OPTIMIZATION OF ENGINE OIL FORMULATION USING RESPONSE SURFACE METHODOLOGY AND GENETIC ALGORITHM: A COMPARATIVE STUDY

Behnaz Azmoon, Abolfazl Semnani, Ramin Jaberzadeh Ansari, Hamid Shakoori Langeroodi, Mahboube Shirani, Shima Ghanavati Nasab

CHEMOMETRICASSISTEDSPECTROPHOTOMETRIC ESTIMATION OF LANSOPRAZOLE AND DOMEPERIDONE IN BULK AND COMMERCIAL DOSAGE FORM

Farheen Sami, Shahnaz Majeed, Tengku Azlan Shah Tengku Mohammed, Noor Fatin Amalina Kamaruddin, Mohammad Zulhimi Atan, Syed Amir Javid Bukhari, Namra, Bushra Hasan, Mohammed Tahir Ansari

EVALUATION OF ANTIBACTERIAL ACTIVITY OF DIFFERENT SOLVENT EXTRACTS OF <i>TEUCRIUM CHAMAEDRYS</i> (L. ) GROWING WILD IN KOSOVO

Arben Haziri, Fatmir Faiku, Roze Berisha, Ibrahim Mehmeti, Sevdije Govori, Imer Haziri

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ПРИРОДОНАУЧНАТА ГРАМОТНОСТ НА УЧЕНИЦИТЕ В НАЧАЛОТО НА XXI ВЕК – В ТЪРСЕНЕ НА КОНЦЕПТУАЛНО ЕДИНСТВО

Теодора Коларова, Иса Хаджиали, Мимия Докова, Веселин Александров

COMPUTER SIMULATORS: APPLICATION FOR GRADUATES’ADAPTATION AT OIL AND GAS REFINERIES

Irena O. Dolganova, Igor M. Dolganov, Kseniya A. Vasyuchka

SYNTHESIS OF NEW [(3-NITRO-2-OXO-2H-CHROMEN4-YLAMINO) -PHENYL] -PHENYL-TRIAZOLIDIN-4-ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Hamit Ismaili, Idriz Vehapi, Naser Troni, Gjyle Mulliqi-Osmani, Veprim Thaçi

STABILITY OF RJ-5 FUEL

Lemi Türker, Serhat Variş

A STUDY OF BEGLIKTASH MEGALITHIC COMPLEX

Diana Kjurkchieva, Evgeni Stoykov, Sabin Ivanov, Borislav Borisov, Hristo Hristov, Pencho Kyurkchiev, Dimitar Vladev, Irina Ivanova

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2016 година
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THE EFFECT OF KOH AND KCL ADDITION TO THE DESTILATION OF ETHANOL-WATER MIXTURE

Khoirina Dwi Nugrahaningtyas, Fitria Rahmawati, Avrina Kumalasari

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VOLTAMMERIC SENSOR FOR NITROPHENOLS BASED ON SCREEN-PRINTED ELECTRODE MODIFIED WITH REDUCED GRAPHENE OXIDE

Arsim Maloku, Liridon S. Berisha, Granit Jashari, Eduard Andoni, Tahir Arbneshi

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ИЗСЛЕДВАНЕ НА ПРОФЕСИОНАЛНО-ПЕДАГОГИЧЕСКАТА РЕФЛЕКСИЯ НА УЧИТЕЛЯ ПО БИОЛОГИЯ (ЧАСТ ВТОРА)

Надежда Райчева, Иса Хаджиали, Наташа Цанова, Виктория Нечева

EXISTING NATURE OF SCIENCE TEACHING OF A THAI IN-SERVICE BIOLOGY TEACHER

Wimol Sumranwanich, Sitthipon Art-in, Panee Maneechom, Chokchai Yuenyong

NUTRIENT COMPOSITION OF CUCURBITA MELO GROWING IN KOSOVO

Fatmir Faiku, Arben Haziri, Fatbardh Gashi, Naser Troni

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CONTEXT-BASED CHEMISTRY LAB WORK WITH THE USE OF COMPUTER-ASSISTED LEARNING SYSTEM

N. Y. Stozhko, A. V. Tchernysheva, E.M. Podshivalova, B.I. Bortnik

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ПО ПЪТЯ ON THE ROAD

Б. В. Тошев

INTERDISCIPLINARY PROJECT FOR ENHANCING STUDENTS’ INTEREST IN CHEMISTRY

Stela Georgieva, Petar Todorov, Zlatina Genova, Petia Peneva

2015 година
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COMPLEX SYSTEMS FOR DRUG TRANSPORT ACROSS CELL MEMBRANES

Nikoleta Ivanova, Yana Tsoneva, Nina Ilkova, Anela Ivanova

SURFACE FUNCTIONALIZATION OF SILICA SOL-GEL MICROPARTICLES WITH EUROPIUM COMPLEXES

Nina Danchova, Gulay Ahmed, Michael Bredol, Stoyan Gutzov

INTERFACIAL REORGANIZATION OF MOLECULAR ASSEMBLIES USED AS DRUG DELIVERY SYSTEMS

I. Panaiotov, Tz. Ivanova, K. Balashev, N. Grozev, I. Minkov, K. Mircheva

KINETICS OF THE OSMOTIC PROCESS AND THE POLARIZATION EFFECT

Boryan P. Radoev, Ivan L. Minkov, Emil D. Manev

WETTING BEHAVIOR OF A NATURAL AND A SYNTHETIC THERAPEUTIC PULMONARY SURFACTANTS

Lidia Alexandrova, Michail Nedyalkov, Dimo Platikanov

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TEACHER’S ACCEPTANCE OF STUDENTS WITH DISABILITY

Daniela Dimitrova-Radojchikj, Natasha Chichevska-Jovanova

APPLICATION OF LASER INDUCED BREAKDOWN SPECTROSCOPY AS NONDESDUCTRIVE AND SAFE ANALYSIS METHOD FOR COMPOSITE SOLID PROPELLANTS

Amir Hossein Farhadian, Masoud Kavosh Tehrani, Mohammad Hossein Keshavarz, Seyyed Mohamad Reza Darbany, Mehran Karimi, Amir Hossein Rezayi

THE EFFECT OF DIOCTYLPHTHALATE ON INITIAL PROPERTIES AND FIELD PERFORMANCE OF SOME SEMISYNTHETIC ENGINE OILS

Azadeh Ghasemizadeh, Abolfazl Semnani, Hamid Shakoori Langeroodi, Alireza Nezamzade Ejhieh

QUALITY ASSESSMENT OF RIVER’S WATER OF LUMBARDHI PEJA (KOSOVO)

Fatmir Faiku, Arben Haziri, Fatbardh Gashi, Naser Troni

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БЛАГОДАРЯ ВИ!

Александър Панайотов

ТЕМАТА ВЪГЛЕХИДРАТИ В ПРОГРАМИТЕ ПО ХИМИЯ И БИОЛОГИЯ

Радка Томова, Елена Бояджиева, Миглена Славова, Мариан Николов

BILINGUAL COURSE IN BIOTECHNOLOGY: INTERDISCIPLINARY MODEL1)

V. Kolarski, D. Marinkova, R. Raykova, D. Danalev, S. Terzieva

ХИМИЧНИЯТ ОПИТ – НАУКА И ЗАБАВА

Елица Чорбаджийска, Величка Димитрова, Магдалена Шекерлийска, Галина Бальова, Методийка Ангелова

ЕКОЛОГИЯТА В БЪЛГАРИЯ

Здравка Костова

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SYNTHESIS OF FLUORINATED HYDROXYCINNAMOYL DERIVATIVES OF ANTI-INFLUENZA DRUGS AND THEIR BIOLOGICAL ACTIVITY

Boyka Stoykova, Maya Chochkova, Galya Ivanova, Luchia Mukova, Nadya Nikolova, Lubomira Nikolaeva-Glomb, Pavel Vojtíšek, Tsenka Milkova, Martin Štícha, David Havlíček

SYNTHESIS AND ANTIVIRAL ACTIVITY OF SOME AMINO ACIDS DERIVATIVES OF INFLUENZA VIRUS DRUGS

Radoslav Chayrov, Vesela Veselinova, Vasilka Markova, Luchia Mukova, Angel Galabov, Ivanka Stankova

NEW DERIVATIVES OF OSELTAMIVIR WITH BILE ACIDS

Kiril Chuchkov, Silvia Nakova, Lucia Mukova, Angel Galabov, Ivanka Stankova

MONOHYDROXY FLAVONES. PART III: THE MULLIKEN ANALYSIS

Maria Vakarelska-Popovska, Zhivko Velkov

LEU-ARG ANALOGUES: SYNTHESIS, IR CHARACTERIZATION AND DOCKING STUDIES

Tatyana Dzimbova, Atanas Chapkanov, Tamara Pajpanova

LACTOBACILLUS PLANTARUM AC 11S AS A BIOCATALYST IN MICROBIAL ELECYTOLYSIS CELL

Elitsa Chorbadzhiyska, Yolina Hubenova, Sophia Yankova, Dragomir Yankov, Mario Mitov

STUDYING THE PROCESS OF DEPOSITION OF ANTIMONY WITH CALCIUM CARBONATE

K. B. Omarov, Z. B. Absat, S. K. Aldabergenova, A. B. Siyazova, N. J. Rakhimzhanova, Z. B. Sagindykova

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TEACHING CHEMISTRY AT TECHNICAL UNIVERSITY

Lilyana Nacheva-Skopalik, Milena Koleva

ФОРМИРАЩО ОЦЕНЯВАНЕ PEER INSTRUCTION С ПОМОЩТА НА PLICКERS ТЕХНОЛОГИЯТА

Ивелина Коцева, Мая Гайдарова, Галина Ненчева

VAPOR PRESSURES OF 1-BUTANOL OVER WIDE RANGE OF THEMPERATURES

Javid Safarov, Bahruz Ahmadov, Saleh Mirzayev, Astan Shahverdiyev, Egon Hassel

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РУМЕН ЛЮБОМИРОВ ДОЙЧЕВ (1938 – 1999)

Огнян Димитров, Здравка Костова

NAMING OF CHEMICAL ELEMENTS

Maria Atanassova

2014 година
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LUBRICATION PROPERTIES OF DIFFERENT PENTAERYTHRITOL-OLEIC ACID REACTION PRODUCTS

Abolfazl Semnani, Hamid Shakoori Langeroodi, Mahboube Shirani

ALLELOPATHIC AND CYTOTOXIC ACTIVITY OF ORIGANUM VULGARE SSP. VULGARE GROWING WILD IN BULGARIA

Asya Pencheva Dragoeva, Vanya Petrova Koleva, Zheni Dimitrova Nanova, Mariya Zhivkova Kaschieva, Irina Rumenova Yotova

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GENDER ISSUES OF UKRAINIAN HIGHER EDUCATION

Н.H.Petruchenia, M.I.Vorovka

МНОГОВАРИАЦИОННА СТАТИСТИЧЕСКА ОЦЕНКА НА DREEM – БЪЛГАРИЯ: ВЪЗПРИЕМАНЕ НА ОБРАЗОВАТЕЛНАТА СРЕДА ОТ СТУДЕНТИТЕ В МЕДИЦИНСКИЯ УНИВЕРСИТЕТ – СОФИЯ

Радка Томова, Павлина Гатева, Радка Хаджиолова, Зафер Сабит, Миглена Славова, Гергана Чергарова, Васил Симеонов

MUSSEL BIOADHESIVES: A TOP LESSON FROM NATURE

Saâd Moulay Université Saâd Dahlab de Blida, Algeria

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ЕЛЕКТРОННО ПОМАГАЛO „ОТ АТОМА ДО КОСМОСА“ ЗА УЧЕНИЦИ ОТ Х КЛАС

Силвия Боянова Професионална гимназия „Акад. Сергей П. Корольов“ – Дупница

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Надежда Райчева, Иван Капурдов, Наташа Цанова, Иса Хаджиали, Снежана Томова

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Донка Ташева, Пенка Василева

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Наташа Цанова, Иса Хаджиали, Надежда Райчева

COMPUTER ASSISTED LEARNING SYSTEM FOR STUDYING ANALYTICAL CHEMISTRY

N. Y. Stozhko, A. V. Tchernysheva, L.I. Mironova

С РАКЕТНА ГРАНАТА КЪМ МЕСЕЦА: БОРБА С ЕДНА ЛЕДЕНА ЕПОХА В ГОДИНАТА 3000 СЛЕД ХРИСТА. 3.

С РАКЕТНА ГРАНАТА КЪМ МЕСЕЦА:, БОРБА С ЕДНА ЛЕДЕНА ЕПОХА, В ГОДИНАТА 000 СЛЕД ХРИСТА. .

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ВИСША МАТЕМАТИКА ЗА УЧИТЕЛИ, УЧЕНИЦИ И СТУДЕНТИ: ДИФЕРЕНЦИАЛНО СМЯТАНЕ

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

ВАСИЛ ХРИСТОВ БОЗАРОВ

Пенка Бозарова, Здравка Костова

ЖИВАТА ПРИРОДА

Б. В. Тошев

БИБЛИОГРАФИЯ НА СТАТИИ ЗА МИСКОНЦЕПЦИИТЕ В ОБУЧЕНИЕТО ПО ПРИРОДНИ НАУКИ ВЪВ ВСИЧКИ ОБРАЗОВАТЕЛНИ НИВА

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

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BOTYU ATANASSOV BOTEV

Zdravka Kostova, Margarita Topashka-Ancheva

CHRONOLOGY OF CHEMICAL ELEMENTS DISCOVERIES

Maria Atanassova, Radoslav Angelov

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КАК ДА МОТИВИРАМЕ УЧЕНИЦИТЕ OT VII КЛАС ДА УЧАТ

Маргарита Бозова, Петко Бозов

ОБРАЗОВАНИЕ ЗА ПРИРОДОНАУЧНА ГРАМОТНОСТ

Адриана Тафрова-Григорова

2013 година
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DIFFERENTIAL TEACHING IN SCHOOL SCIENCE EDUCATION: CONCEPTUAL PRINCIPLES

G. Yuzbasheva Kherson Academy of Continuing Education, Ukraine

АНАЛИЗ НА ПОСТИЖЕНИЯТА НА УЧЕНИЦИТЕ ОТ ШЕСТИ КЛАС ВЪРХУ РАЗДЕЛ „ВЕЩЕСТВА И ТЕХНИТЕ СВОЙСТВА“ ПО „ЧОВЕКЪТ И ПРИРОДАТА“

Иваничка Буровска, Стефан Цаковски Регионален инспекторат по образованието – Ловеч

HISTORY AND PHILOSOPHY OF SCIENCE: SOME RECENT PERIODICALS (2013)

Chemistry: Bulgarian Journal of Science Education

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„Образователни стандарти и природонаучна грамотност“ – това е темата на състоялата се от 25 до 27 октомври 2013 г. в Габрово 45. Национална конфе- ренция на учителите по химия с международно участие, която по традиция се проведе комбинирано с Годишната конференция на Българското дружество за химическо образование и история и философия на химията. Изборът на темата е предизвикан от факта, че развиването на природонаучна грамотност е обща тенденция на реформите на учебните програми и главна

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ЗА ХИМИЯТА НА БИРАТА

Ивелин Кулев

МЕТЕОРИТЪТ ОТ БЕЛОГРАДЧИК

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

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RECASTING THE DERIVATION OF THE CLAPEYRON EQUATION INTO A CONCEPTUALLY SIMPLER FORM

Srihari Murthy Meenakshi Sundararajan Engineering College, India

CHEMICAL REACTIONS DO NOT ALWAYS MODERATE CHANGES IN CONCENTRATION OF AN ACTIVE COMPONENT

Joan J. Solaz-Portolés, Vicent Sanjosé Universitat de Valènciа, Spain

POLYMETALLIC COMPEXES: CV. SYNTHESIS, SPECTRAL, THERMOGRAVIMETRIC, XRD, MOLECULAR MODELLING AND POTENTIAL ANTIBACTERIAL PROPERTIES OF TETRAMERIC COMPLEXES OF Co(II), Ni(II), Cu(II), Zn(II), Cd(II) AND Hg(II) WITH OCTADENTATE AZODYE LIGANDS

Bipin B. Mahapatra, S. N. Dehury, A. K. Sarangi, S. N. Chaulia G. M. Autonomous College, India Covt. College of Engineering Kalahandi, India DAV Junior College, India

ПРОФЕСОР ЕЛЕНА КИРКОВА НАВЪРШИ 90 ГОДИНИ

CELEBRATING 90TH ANNIVERSARY OF PROFESSOR ELENA KIRKOVA

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SIMULATION OF THE FATTY ACID SYNTHASE COMPLEX MECHANISM OF ACTION

M.E.A. Mohammed, Ali Abeer, Fatima Elsamani, O.M. Elsheikh, Abdulrizak Hodow, O. Khamis Haji

FORMING OF CONTENT OF DIFFERENTIAL TEACHING OF CHEMISTRY IN SCHOOL EDUCATION OF UKRAINE

G. Yuzbasheva Kherson Academy of Continuing Education, Ukraine

ИЗСЛЕДВАНЕ НА РАДИКАЛ-УЛАВЯЩА СПОСОБНОСТ

Станислав Станимиров, Живко Велков

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COLORFUL EXPERIMENTS FOR STUDENTS: SYNTHESIS OF INDIGO AND DERIVATIVES

Vanessa BIANDA, Jos-Antonio CONSTENLA, Rolf HAUBRICHS, Pierre-Lonard ZAFFALON

OBSERVING CHANGE IN POTASSIUM ABUNDANCE IN A SOIL EROSION EXPERIMENT WITH FIELD INFRARED SPECTROSCOPY

Mila Ivanova Luleva, Harald van der Werff, Freek van der Meer, Victor Jetten

ЦАРСКАТА ПЕЩЕРА

Рафаил ПОПОВ

УЧИЛИЩНИ ЛАБОРАТОРИИ И ОБОРУДВАНЕ SCHOOL LABORATORIES AND EQUIPMENT

Учебни лаборатории Илюстрации от каталог на Franz Hugershoff, Лайциг, притежаван от бъдещия

2012 година
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ADDRESING STUDENTS’ MISCONCEPTIONS CONCERNING CHEMICAL REACTIONS AND SYMBOLIC REPRESENTATIONS

Marina I. Stojanovska, Vladimir M. Petruševski, Bojan T. Šoptrajanov

АНАЛИЗ НА ПОСТИЖЕНИЯТА НА УЧЕНИЦИТЕ ОТ ПЕТИ КЛАС ВЪРХУ РАЗДЕЛ „ВЕЩЕСТВА И ТЕХНИТЕ СВОЙСТВА“ ПО ЧОВЕКЪТ И ПРИРОДАТА

Иваничка Буровска, Стефан Цаковски Регионален инспекторат по образованието – Ловеч

ЕКОТОКСИКОЛОГИЯ

Васил Симеонов

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КОНЦЕПТУАЛНА СХЕМА НА УЧИЛИЩНИЯ КУРС П О ХИМИЯ – МАКР О СКОПСКИ ПОДХОД

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

ROLE OF ULTRASONIC WAVES TO STUDY MOLECULAR INTERACTIONS IN AQUEOUS SOLUTION OF DICLOFENAC SODIUM

Sunanda S. Aswale, Shashikant R. Aswale, Aparna B. Dhote Lokmanya Tilak Mahavidyalaya, INDIA Nilkanthrao Shinde College, INDIA

SIMULTANEOUS ESTIMATION OF IBUPROFEN AND RANITIDINE HYDROCHLORIDE USING UV SPECTROPHOT O METRIC METHOD

Jadupati Malakar, Amit Kumar Nayak Bengal College of Pharmaceutical Sciences and Research, INDIA

GAPS AND OPPORTUNITIES IN THE USE OF REMOTE SENSING FOR SOIL EROSION ASSESSMENT

Mila Ivanova Luleva, Harald van der Werff, Freek van der Meer, Victor Jetten

РАДИОХИМИЯ И АРХЕОМЕТРИЯ: ПРО Ф. ДХН ИВЕЛИН КУЛЕВ RADIOCHEMISTRY AND ARCHEOMETRY: PROF. IVELIN KULEFF, DSc

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

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TEACHING THE CONSTITUTION OF MATTER

Małgorzata Nodzyńska, Jan Rajmund Paśko

СЪСИРВАЩА СИСТЕМА НА КРЪВТА

Маша Радославова, Ася Драгоева

CATALITIC VOLCANO

CATALITIC VOLCANO

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Донка ТАШЕВА, Пенка ЦАНОВА

ЮБИЛЕЙ: ПРОФ. ДХН БОРИС ГЪЛЪБОВ JUBILEE: PROF. DR. BORIS GALABOV

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

ПЪРВИЯТ ПРАВИЛНИК ЗА УЧЕБНИЦИТЕ (1897 Г.)

Чл. 1. Съставянето и издаване на учебници се предоставя на частната инициа- тива. Забележка: На учителите – съставители на учебници се запрещава сами да разпродават своите учебници. Чл. 2. Министерството на народното просвещение може да определя премии по конкурс за съставяне на учебници за горните класове на гимназиите и специ- алните училища. Чл. 3. Никой учебник не може да бъде въведен в училищата, ако предварително не е прегледан и одобрен от Министерството на народното просвещение. Чл.

JOHN DEWEY: HOW WE THINK (1910)

John Dewey (1859 – 1952)

ИНФОРМАЦИЯ ЗА СПЕЦИАЛНОСТИТЕ В ОБЛАСТТА НА ПРИРОДНИТЕ НАУКИ В СОФИЙСКИЯ УНИВЕРСИТЕТ „СВ. КЛИМЕНТ ОХРИДСКИ“ БИОЛОГИЧЕСКИ ФАКУЛТЕТ

1. Биология Студентите от специалност Биология придобиват знания и практически умения в областта на биологическите науки, като акцентът е поставен на организмово равнище. Те се подготвят да изследват биологията на организмите на клетъчно- организмово, популационно и екосистемно ниво в научно-функционален и прило- жен аспект, с оглед на провеждане на научно-изследователска, научно-приложна, производствена и педагогическа дейност. Чрез широк набор избираеми и факул- тативни курсове студентите

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УЧИТЕЛИТЕ ПО ПРИРОДНИ НАУКИ – ЗА КОНСТРУКТИВИСТКАТА УЧЕБНА СРЕДА В БЪЛГАРСКОТО УЧИЛИЩЕ

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