Decoration of Carbon Nanotubes with Cerium (IV) Oxide

Cerium (IV) oxide (ceria) nanoparticles, 6–10 nm in size, supported on carbon nanotubes (CNTs) were prepared by a chemical reaction between Ce(NO3)3 and NaOH. The effective processing parameters of ceria particles size were discussed. CNTs/CeO2 hybrids were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED), Raman and electron paramagnetic resonance (EPR) spectroscopy. SAED and Raman spectroscopy showed that the CeO2 particles had a cubic crystal structure. EMR spectroscopy showed two paramagnetic signals related to CNTs and a third one belonging to paramagnetic defects of CeO2.Наночастинки оксиду церію (IV) розміром 6-10 нм одержано на вуглецевих нанотрубках (ВНТ) за хімічною реакцією між Се(NО3)3 і NaOH. Встановлено ефективні параметри синтезу наночастинок оксиду церію. Нанокомпозити ВНТ/СеО2 охарактеризовано за допомогою трансмісійної електронної мікроскопії (ТЕМ), електронографії, КР- та ЕПР-спектроскопії. Методами електронографії і КР-спектроскопії виявлено кубічну кристалічну структуру СеО2. ЕПР-спектроскопія показала, що два парамагнітних сигнали мають відношення до ВНТ, а третій обумовлений парамагнітними дефектами CeO2.Наночастицы оксида церия (IV) размером 6-10 нм получены на углеродных нанотрубках (УНТ) в результате химической реакции между Се(NО3)3 и NaOH. Установлены эффективные параметры синтеза наночастиц оксида церия. Нанокомпозиты УНТ/СеО2 охарактеризованы с помощью трансмиссионной электронной микроскопии (ТЭМ), электронографии, КР- и ЭПР-спектроскопии. Методами электронографии и КР-спектроскопии установлена кубическая кристаллическая структура CeO2. ЭПР-спектроскопия показала, что два парамагнитных сигнала имеют отношение к УНТ, а третий обусловлен парамагнитными дефектами CeO2

SERS of Rhodamine 6G on substrates with laterally ordered and random gold nanoislands

Preparation and study of laterally ordered and disordered arrays of Au nanoislands as SERS substrates are reported. Developed technology allows obtaining SERS substrates with long-term stability (up to six months), efficient (up to 10⁴) and laterally homogenous enhancement of the Raman signal from molecular analyte. The substrates developed are suitable for Raman bio-diagnostics, because their plasmon resonance can be tuned within the range 700-900 nm that falls into the transparency window of human tissues. The dependence of optical and enhancement properties of the substrates on their morphology has been studied. The morphology of the Au island film and their plasmon resonance spectrum depend noticeably on the nominal Au thickness and post-annealing temperature, while the duration of annealing is of minor importance. Formation of nanoholes in the case of Au substrates on holographically pre-patterned polymer film opens up the possibility of additional Raman enhancement via the "hot spot"-effect

Stydy on resistivity and micostructure of magnetron sputtered α-C:Si films

Electric resistivity and microstructure of silicon-doped (5 to 38 at. % Si) amorphous carbon (α-C) films deposited by de magnetron sputtering in argon plasma of composed (graphite + single crystalline silicon) target has been studied as a function of silicon content in films. The film resistivity parallel and perpendicular to substrate surface was measured. The film structure was studied by electron diffraction and Raman spectroscopy. Doping with silicon did not influence the resistivity p⊥ over the whole range of silicon concentrations studied, but resulted in marked increase in resistivity p║. Incorporation of silicon atoms into graphite-like cluster structure of carbon films results in distortion and disordering thereof in planes parallel to the substrate surface, thus promoting an increase in p║

Some regularities of diamond phase formation at nonequilibrium transition process of C vapors with low Ті concentration into condensed state

The mechanisms of structure formation of Ti-C system layers have been studied. The layers have been obtained at nonequilibrium process of transition of vapors with necessary component ratio into condensed state. Various levels of the condensation process nonequilibrium have been reached by exposure of the growth surface by electron streams with different intensities. Some regularities of transition of the metastable compound TiC2 into diamond phase have been determined by complex studies of physical properties of the condensates using methods of electron diffraction analysis, Raman scattering.Изучены механизмы структурообразования слоёв системы Ti-C, полученных при неравновесном процессе перехода паров с необходимым соотношением компонент в конденсированное состояние. Различная степень неравновесности процесса конденсации достигалась облучением ростовой поверхности потоками электронов различной интенсивности. Путем комплексного изучения физических свойств конденсатов с использованием методов электронографии, комбинационного рассеяния были установлены некоторые закономерности перехода метастабильного соединения ТІС2 в алмазную фазу.Вивчено механізми структуроутворення mapiB системи Ті—С, отриманих при нерівноважному процесі переходу пapiв з необхідним співвідношєнням компонєнтів у конденсований стан. Різний ступінь нерівноважності процесу конденсації досягався опроміненням ростової поверхні потоками електронів різної інтенсивності. Шляхом комплексного вивчення фізичних властивостей конденсатів з використанням методів електронографії, комбінаційного розсіяння встановлено деякі закономірності переходу метастабільної сполуки Ті&2 в алмазну фазу

Thin films of Cu₂ZnSnS₄ for solar cells: optical and structural properties

The structure of Cu₂ZnSnS₄ films was investigated by Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, optical reflectance and photoluminescence. The films were formed by thermal annealing layers of copper, zinc and tin sulfides on glass substrates at different substrate temperature and ambient atmosphere. It was revealed that the films have the dominant structure of kesterite with possible inclusions of stannite Cu₂ZnSnS₄ structure. Under certain growth conditions, however, segregation of Cu₂₋xS occurs, as proved by registering the characteristic peak in Raman spectra. No traces of secondary phases of zinc or tin sulphides are found

Spectroscopical study of natural nanostructured carbonaceous material shungite

The correlation between morphology, local structure and magnetic properties of the different origin shungite material with nanocarbon content 25-40 wt. % was studied by SEM, EPR, and Raman scattering methods. It was established that structure of the shungite samples is formed by micron size agglomerations of carbon and silicon dioxide clusters with impregnations of pyrite (FeS₂), iron oxide and aluminium oxide particles. It was found from the Raman data that nanocarbon fraction is formed from sp²-hybridized well ordered carbon clusters, size of which increases from 9 nm up to 12 nm after annealing of the samples. It was found for the first time that origin of L3 and L4 EPR lines is due to oxy-deficiency centers in the silicon dioxide clusters

Properties of graphene flakes obtained by treating graphite with ultrasound

A possibility to obtain graphene and graphene layers with the help of the ultrasound (US) treatment of pyrolytic graphite in an N-methyl pyrrolidone (NMP) solution has been demonstrated. Raman spectroscopy is confirmed to be an effective method for monitoring the graphite transformation into graphene. By varying the time of the ultrasonic treatment of pyrolytic graphite in the NMP solution, optimum regimes for the fabrication of graphene flakes with various numbers of layers are determined. In particular, the US treatment for 5 h is shown to be sufficient for producing a colloidal solution of graphene flakes, most of which are single-layered. It is shown that the longer US treatment results in larger intensities of Raman bands D and D′, which testifies to a larger number of defects in the graphene layers. The average distances between defects are estimated for various times of US treatment. The influence of vacancy and edge defects on the intensity band ratio ID/ID ′ is analyzed. Vacancies are found to be the prevailing type of defects in the graphene flakes

Raman spectroscopy of Cu Sn S ternary compound thin films prepared by the low cost spray pyrolysis technique

Cu Sn S CTS thin films were deposited onto bare and molybdenum Mo coated glass substrates by means of the spray pyrolysis technique under different conditions. The CTS thin films obtained are shown, by means of Raman spectroscopy, to consist of two main phases Cu2SnS3 and Cu3SnS4 as well as of the secondary phase of Cu2 amp; 8722;xS. The electrical conductivity of the spray deposited p type CTS thin films under investigation is determined by two shallow acceptor levels Ev 0.07 eV at T lt; 334 K and Ev 0.1 eV at T gt; 334 K. The material of the CTS thin films was established to be a direct band semiconductor with the bandgap Eg 1.89 eV. The SEM and x ray energy dispersive analysis show the surface and cross section of the CTS thin film deposited onto molybdenum coated glass ceramics substrate with the actual atomic ratios of Cu Sn S being 2.9 1 2.64, which is in good agreement with the Raman spectra. Also, a small content of residual Cl atoms was found in the CTS thin films under investigation as the by product of the pyrolytic reaction