Deposition and characterization of nanocrystalline silicon

Deponirani su tanki filmovi silicija, silicijevog dioksida i silicijem bogatog oksida (SiOx) metodom LPVCD (Low Pressure Chemical Vapor Deposition). Depozicije su se odvijale pod različitim uvjetima u okviru kojih se varirao sastav i parcijalni tlak radnih plinova i temperatura depozicije. Termičkim oporavkom SiOx slojeva na temperaturama od 800 do 1200 oC dobile su se različite nanočestice silicija. Navedene nanočestice karakterizirane su pomoću Ramanove, infracrvene i apsorpcijske spektroskopije i pretražne elektronske mikroskopije. Razvijen je i teorijski model za Ramanovo raspršenje na optičkim i akustičkim vibracijama nanočestičnog silicija.Thin silicon, silicon-dioxide and silicon-rich oxide (SiOx) films were produced using the LPCVD (Low Pressure Chemical Vapor Deposition) method. The depositions were made under different conditions, where the composition and the partial pressures of the reactant gasses and the deposition temperature were varied. By thermal annealing of SiOx films under temperatures from 800 to 1200 oC nanoparticles of different sizes were formed. The nanoparticles were characterised using Raman, infrared and absorption spectroscopy and scanning electron microscopy. The theoretical model of Raman scattering on optical and acoustical vibrational modes of silicon nanoparticles was developed

Urban deciduous tree leaves as biomonitors of trace element (As, V and Cd) atmospheric pollution in Belgrade, Serbia

Leaves of common deciduous trees: horse chestnut (Aesculus hippocastanum) and linden (Tilia spp.) from three parks within the urban area of Belgrade were studied as biomonitors of trace element (As, V, and Cd) atmospheric pollution. The May–September trace element accumulation in the leaves, and their temporal trends, were assayed in a multi-year period (2002–2006). Significant accumulation in the leaves was evident for As and V, but not so regularly for Cd. Slightly decreasing temporal trends of V and As ac-cumulated in the leaf tissues were observed over the years. During the time span, the concentrations of Cd remained approximately on the same level, except in May 2002 and September 2005, when a rapid increase was observed. The May–September accumulations of As and V were higher in horse chestnut than in linden, although both may be used as biomonitors for these elements, and optionally for Cd in conditions of its high atmospheric loadings

HEMOCHROMATOSIS GENE MUTATIONS IN PATIENTS WITH ELEVATED SERUM IRON

Cilj našeg istraživanja bio je ustanoviti učestalost C282Y i H63D mutacija u bolesnika s povišenim vrijednostima serumskog željeza različite etiologije. U istraživanje je bilo uključeno 105 bolesnika (84 muškarca i 21 žena) koji su podijeljeni u dvije skupine. U prvoj je skupini bilo 55 bolesnika s povišenim vrijednostima serumskog željeza, koji su prekomjerno konzumirali alkohol, a u drugoj 50 bolesnika s povišenim vrijednostima serumskog željeza nepoznate etiologije. Prisutnost mutacija u HFE genu ustanovili smo metodom lančane reakcije polimeraze (PCR) nakon koje je slijedila restrikcija s odgovarajućim restrikcijskim endonukleazama. Prema dobivenim rezultatima, frekvencije C282Y i H63D alela u skupini bolesnika koji su konzumirali alkohol, iznose 4,5% i 20,1%, a u bolesnika s povišenim vrijednostima serumskog željeza nepoznate etiologije 18,0% i 19,0%. Usporedbom učestalosti HFE alela i genotipova između navedenih skupina bolesnika utvrdili smo statistički značajnu razliku (p<0,05) u frekvenciji C282Y alela kao i u frekvenciji C282Y homozigota. Naši rezultati upućuju na to da je analiza mutacija HFE gena korisna u bolesnika s povišenim vrijednostima serumskog `eljeza, pogotovo kad nije jasno ima li bolesnik jetrenu bolest s povišenim vrijednostima serumskog željeza ili ima nasljednu hemokromatozu uz povišene nalaze jetrenih enzima.To study the role of hemochromatosis gene mutations in patients with elevated serum iron, we have analysed C282Y and H63D mutations of the HFE gene. The investigation included 105 patients (84 males and 21 females) divided in two groups: 55 active alcoholic individuals (49 males and 6 females) and 50 individuals (35 males and 15 females) with elevated serum iron of unknown etiology. The analysis of HFE gene mutations was performed using the PCR-RFLP method. According to our results C282Y and H63D allele frequencies were 4.54% and 20.09% in active alcoholics and 18.00% and 19.00% in the second group of patients without the history of alcohol consumption, respectively. Comparing the HFE allele and genotype frequencies between investigated groups statistically significant differences (p 0.05) were observed in the frequency of C282Y allele and the frequency of C282Y homozygotes. Our results suggest that the analysis of HFE mutations can be useful in patients with the elevated serum iron, especially in patients with unclear hereditary hemochromatosis or another liver disease, such as alcoholic liver diseas

HEMOCHROMATOSIS GENE MUTATIONS IN PATIENTS WITH ELEVATED SERUM IRON

Cilj našeg istraživanja bio je ustanoviti učestalost C282Y i H63D mutacija u bolesnika s povišenim vrijednostima serumskog željeza različite etiologije. U istraživanje je bilo uključeno 105 bolesnika (84 muškarca i 21 žena) koji su podijeljeni u dvije skupine. U prvoj je skupini bilo 55 bolesnika s povišenim vrijednostima serumskog željeza, koji su prekomjerno konzumirali alkohol, a u drugoj 50 bolesnika s povišenim vrijednostima serumskog željeza nepoznate etiologije. Prisutnost mutacija u HFE genu ustanovili smo metodom lančane reakcije polimeraze (PCR) nakon koje je slijedila restrikcija s odgovarajućim restrikcijskim endonukleazama. Prema dobivenim rezultatima, frekvencije C282Y i H63D alela u skupini bolesnika koji su konzumirali alkohol, iznose 4,5% i 20,1%, a u bolesnika s povišenim vrijednostima serumskog željeza nepoznate etiologije 18,0% i 19,0%. Usporedbom učestalosti HFE alela i genotipova između navedenih skupina bolesnika utvrdili smo statistički značajnu razliku (p<0,05) u frekvenciji C282Y alela kao i u frekvenciji C282Y homozigota. Naši rezultati upućuju na to da je analiza mutacija HFE gena korisna u bolesnika s povišenim vrijednostima serumskog `eljeza, pogotovo kad nije jasno ima li bolesnik jetrenu bolest s povišenim vrijednostima serumskog željeza ili ima nasljednu hemokromatozu uz povišene nalaze jetrenih enzima.To study the role of hemochromatosis gene mutations in patients with elevated serum iron, we have analysed C282Y and H63D mutations of the HFE gene. The investigation included 105 patients (84 males and 21 females) divided in two groups: 55 active alcoholic individuals (49 males and 6 females) and 50 individuals (35 males and 15 females) with elevated serum iron of unknown etiology. The analysis of HFE gene mutations was performed using the PCR-RFLP method. According to our results C282Y and H63D allele frequencies were 4.54% and 20.09% in active alcoholics and 18.00% and 19.00% in the second group of patients without the history of alcohol consumption, respectively. Comparing the HFE allele and genotype frequencies between investigated groups statistically significant differences (p 0.05) were observed in the frequency of C282Y allele and the frequency of C282Y homozygotes. Our results suggest that the analysis of HFE mutations can be useful in patients with the elevated serum iron, especially in patients with unclear hereditary hemochromatosis or another liver disease, such as alcoholic liver diseas

ZnO nanoparticles with optimized surface-to-bulk defect ratio for potential biomedical application

Due to tunable opto-electronic properties ZnO-based nanoparticles (ZnONPs) have been used for application in electronics, optoelectronics, photo(electro)catalysis, etc. Besides, as bio-inert, ZnONPs have a great potential in medicine for biosensing, bioimaging, drug and gene delivery, implants or as antimicrobial and anticancer agents. One of suggested governing mechanism of the biological activities of ZnONPs is based on the formation of reactive oxygen species (ROS). Actually, when ZnONP absorb photon with energy equal or greater than its band gap, electrons (e−) are excited from the valence band (VB) to the conduction band (CB) leaving the holes (h+) in VB. In following, the photogenerated h+ and e− migrate from bulk to surface. The photogenerated h+ at the VB react with water molecules adsorbed at the particle surface to produce hydroxyl radicals (OH•), while e− in CB react with oxygen molecules generating anionic superoxide radicals (O2−•). Radicals can be transformed in highly reactive hydroxyl radicals and so on. Derivatives of this active oxygen can damage the bacterial/tumor cells. However, in sufficiency ROS can damage normal cells as well. Thus, an understanding of ZnONPs crystal structure-activity relationship is crucial for the design of materials safe for application in treating diseases like cancer. In this study we established correlation between the surface-to-bulk defects ratio in ZnONPs and ROS formation. To vary surface-to-bulk defects ratio, series of ZnONP samples were synthesized by microwave processing of precipitate in the presence of a different amount (5, 10 and 20 wt.%) of surfactants, precisely, CTAB and citric acid. The particles crystallinity and phase purity were investigated by X-ray diffraction, Raman and FTIR spectroscopy. The particles morphology and texture properties were observed with FE–SEM and BET, respectively. The optical properties were studied using UV–Vis DRS and PL spectroscopy. ZnONP samples with different surface-to-bulk defect ratio were examined on ROS formation. Surface-to-bulk defect ratio in ZnONP was correlated with ROS formation, besides; their influence on cytotoxicity to normal and cancerous cells was comprehended

Thermal Decomposition of Silicon-rich Oxides Deposited by the LPCVD Method

Silicon-rich oxide (SiOx, 0 < x < 2) thin films were deposited using the Low Pressure Chemical Vapor Deposition (LPCVD) method at temperature of 570 °C using silane (SiH4) and oxygen as the reactant gasses. The films were annealed at temperatures of 800, 900, 1000, and 1100 °C to induce the separation of excess silicon in the SiOx films into nanosized crystalline silicon particles inside an amorphous SiOx matrix. The size of the silicon particles was determined using Raman spectroscopy. (doi: 10.5562/cca1969

Micro and Nano Structure of Electrochemically Etched Silicon Epitaxial Wafers

Silicon epitaxial wafers, consisting of 280 μm thick n-type substrate layer and 4–5 μm thick epitaxial layer, were electrochemically etched in hydrofluoric acid ethanol solution, to produce porous silicon samples. The resistivity of epitaxial layer was 1 Ω cm, while the substrate was much better conductor with resistivity 0.015 Ω cm. By varying the etching time, the micro- and nano-pores of different sizes were obtained within the epitaxial layer, and on the substrate surface. Due to the lateral etching the epitaxial layer was partially detached from the substrate and could be peeled off. The influence of etching time duration on the optical and structural properties of porous samples was investigated by Raman, infrared and photoluminescence spectroscopy. The samples were analysed immediately after the etching and six months later, while being stored in ambient air. The Raman spectra showed the shift in positions of transversal optical (TO) phonon bands, between freshly etched samples and the one stored in ambient air. Infrared spectra indicated the presence of SiHx species in the freshly etched samples, and appearance of oxidation after prolonged storage. Photoluminescence spectra were very weak in freshly etched samples, but their intensity has increased substantially in six month period. (doi: 10.5562/cca1971

Sensing Properties of Oxidized Nanostructured Silicon Surface on Vaporized Molecules

Porous silicon has been intensely studied for the past several decades and its applications were found in photovoltaics, biomedicine, and sensors. An important aspect for sensing devices is their long–term stability. One of the more prominent changes that occur with porous silicon as it is exposed to atmosphere is oxidation. In this work we study the influence of oxidation on the sensing properties of porous silicon. Porous silicon layers were prepared by electrochemical etching and oxidized in a tube furnace. We observed that electrical resistance of oxidized samples rises in response to the increasing ambient concentration of organic vapours and ammonia gas. Furthermore, we note the sensitivity is dependent on the oxygen treatment of the porous layer. This indicates that porous silicon has a potential use in sensing of organic vapours and ammonia gas when covered with an oxide layer

Low Temperature Deposition of SiNx Thin Films by the LPCVD Method

Thin silicon rich nitride (SiNx) films were deposited using the LPCVD (Low Pressure Chemical Vapor Deposition) method. Silane diluted in argon and ammonia were used as the reactant gasses, and the low temperature deposition at 570 °C was used. The films were deposited on silicon (111) substrates. Films with the different values of the nitrogen content were deposited by varying the ratio of the flows of ammonia and silane in the horizontal tube reactor. The films were characterized in terms on the surface quality (by scanning electron microscopy), in terms of the nitrogen content x by time of flight elastic recoil detection analysis and by Raman and FTIR spectroscopy. The thickness and dielectric constant were measured by ellipsometry. The films were found to have a very smooth, homogeneous surface with nitrogen content that vary from x = 0 to x = 1 in dependence on the deposition parameters. The intensity of the Si–N stretching peak has shown strong correlation with the film thickness measured by ellipsometry. The films showed a smooth surface layer and the value of dielectric constant easily controllable by the ratio of the flow of the gases in the reactor. (doi: 10.5562/cca1970

The Role of Iron and Iron Overload in Chronic Liver Disease

The liver plays a major role in iron homeostasis; thus, in patients with chronic liver disease, iron regulation may be disturbed. Higher iron levels are present not only in patients with hereditary hemochromatosis, but also in those with alcoholic liver disease, nonalcoholic fatty liver disease, and hepatitis C viral infection. Chronic liver disease decreases the synthetic functions of the liver, including the production of hepcidin, a key protein in iron metabolism. Lower levels of hepcidin result in iron overload, which leads to iron deposits in the liver and higher levels of non-transferrin-bound iron in the bloodstream. Iron combined with reactive oxygen species leads to an increase in hydroxyl radicals, which are responsible for phospholipid peroxidation, oxidation of amino acid side chains, DNA strain breaks, and protein fragmentation. Iron-induced cellular damage may be prevented by regulating the production of hepcidin or by administering hepcidin agonists. Both of these methods have yielded successful results in mouse models