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90 O. HOROVITZ, M. TOMOAIA-COTIŞEL, C. RACZ, GH. TOMOAIA, L.-D. BOBOŞ, A. MOCANU Since colloidal silver presents a high sensitivity toward oxygen, at times synthesis was achieved in an inert atmosphere [23]. The formation of silver nanoparticles was also favored by γ radiation [12], laser irradiation [25] or UV illumination [26]. Bioconjugates of the hemoproteins, myoglobin, and hemoglobin have been synthesized by their adsorption on spherical silver nanoparticles [27]. Silver nanoparticle-oligonucleotide conjugates were prepared, based upon DNA with cyclic disulfide-anchoring groups [28]. When silver nanoparticles functionalized with complementary DNA sequences are combined, they assemble to form DNA-linked nanoparticles networks. The interaction between silver nanoparticles and various DNA bases (adenine, guanine, cytosine, and thymine) was described [13]. Silver nanoparticles were adsorbed on the surface of natural wool, as a result of the interaction of silver with sulfur moieties related to the cysteine group [29]. The adsorption of aliphatic-nonpolar amino acids represented by L-methionine on silver nanoparticles was studied by the FT-SERS method [30] and a physical and chemical adsorption by -NH3 + , COO - , S, was identified In previous works, we synthesized gold nanoparticles in aqueous solutions and investigated their functionalization and self aggregation with various biomolecules, such as proteins [31] and amino acids [32-35]. The goal of the present investigation is to obtain silver nanoparticles in colloidal aqueous solution and to study their interaction with α-lipoic acid. RESULTS AND DISCUSSION The colloidal aqueous solution containing silver nanoparticles is yellow. The UV-visible absorption spectrum of this solution presents a well-defined absorption band with a maximum at the wavelength λmax = 399 nm (Fig. 1). This value is characteristic for plasmon absorbance for nanometric Ag particles. The colloidal solution is rather stable; after one month, only slight modifications in the spectrum were observed. As reported in literature, the position of λmax for silver nanoparticles is highly dependent on particle shape and can range from around 400 nm for spherical particles to near 800 nm for sharp-edged triangles. For aggregated particles, a red shift is observed [36]. Wavelength and shape of this band are also affected by various adsorbed solutes [27]. The size of the colloidal silver particles has been measured by TEM imaging (for example, Fig. 2). The particles present mostly spherical or ovoid shape. From the sizes of a great number of particles, measured on the TEM images, the following characteristics were calculated: average size (diameter): 5.9 nm; standard deviation: 2.7 nm (extreme values 1.4 and 13.7 nm); average mass of a particle (considered spherical): 1.1·10 -18 g; average number of silver atoms in a particle: 6·10 3 .
THE INTERACTION OF SILVER NANOPARTICLES WITH LIPOIC ACID Absorbance, a.u. 0,08 0,06 0,04 0,02 0,00 -0,02 -0,04 399 nm 300 400 500 600 700 800 Wavelength, nm Figure 1. Optical spectrum of the colloidal silver solution Figure 2. TEM images for silver nanoparticles Figure 3. Histogram of size distribution for Ag particles 91
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R /(mol m -2 s -1 ) 0.06 0.05 0.04
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ANA-MARIA CORMOS, JOZSEF GASPAR, AN
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Studia Universitatis Babes-Bolyai C
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6 PROFESSOR IOAN BÂLDEA AT HIS 70
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MARCELA ACHIM, DANA MUNTEAN, LAURIA
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STUDIA UNIVERSITATIS BABEŞ-BOLYAI,
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STUDIES ON WO3 THIN FILMS PREPARED
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PREPARATION AND CHARACTERIZATION OF
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32 C. CĂŢĂNAŞ, M. MOGOŞ, D. HO
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34 C. CĂŢĂNAŞ, M. MOGOŞ, D. HO
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C. CĂŢĂNAŞ, M. MOGOŞ, D. HORVA
Page 37 and 38: 38 ANA-MARIA CORMOS, JOZSEF GASPAR,
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Page 49 and 50: 50 EUGEN DARVASI, LADISLAU KÉKEDY-
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Page 61 and 62: MATHEMATICAL MODELING FOR THE CRYST
Page 71 and 72: STUDY OF THE CHROMATOGRAPHIC RETENT
Page 81 and 82: LOWER RIM SILYL SUBSTITUTED CALIX[8
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Page 91 and 92: THE INTERACTION OF SILVER NANOPARTI
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Page 105 and 106: MELINDA-HAYDEE KOVACS, DUMITRU RIST
Page 115 and 116: IRON DOPED CARBON AEROGEL AS CATALY
Page 123 and 124: 128 ANDRADA MĂICĂNEANU, HOREA BED
Page 131 and 132: ANDRADA MĂICĂNEANU, HOREA BEDELEA
Page 137 and 138: CRISTINA MIHALI, GABRIELA OPREA, EL
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144 CRISTINA MIHALI, GABRIELA OPREA
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146 Interfering ion, J - I - DBS -
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CONCLUSIONS 148 CRISTINA MIHALI, GA
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150 CRISTINA MIHALI, GABRIELA OPREA
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152 D. MIHU, L. VLASE, S. IMRE, C.
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154 Intens. x105 1.5 1.0 0.5 0.0 x1
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D. MIHU, L. VLASE, S. IMRE, C. M. M
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162 A. PETER, M. BAIA, F. TODERAS,
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164 (a) V relative [%] (c) V relati
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A. PETER, M. BAIA, F. TODERAS, M. L
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BIOSORPTION OF PHENOL FROM AQUEOUS
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186 ANDREI ROTARU, MIHAI GOŞA, EUG
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ANDREI ROTARU, MIHAI GOŞA, EUGEN S
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194 OCTAVIAN STAICU, VALENTIN MUNTE
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ln(τ i / s) OCTAVIAN STAICU, VALEN
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204 MARIA ŞTEFAN, IOAN BÂLDEA, RO
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EXPERIMENTAL SECTION 210 MARIA ŞTE
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EQUILIBRIUM STUDY ON ADSORPTION PRO
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STRATEGIES OF HEAVY METAL UPTAKE BY
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CORROSION INHIBITION OF BRONZE BY A
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E / mV vs. SCE POTASSIUM-SELECTIVE
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POTASSIUM-SELECTIVE ELECTRODE BASED
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POTASSIUM-SELECTIVE ELECTRODE BASED
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256 CODRUTA VARODI, DELIA GLIGOR, L
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CODRUTA VARODI, DELIA GLIGOR, LEVEN
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PHARMACOKINETIC INTERACTION BETWEEN
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