Polymer based nanocomposites

Dispersions consisting of spherical CdS and α-Fe2O3 particles in the nanometer and sub-micron size range, as well as β-FeOOH nanorods with three different aspect ratios were prepared using colloidal chemistry methods. After incorporation of filler particles into polystyrene and poly(methyl methacrylate) matrices influence of filler particles on the thermal stability and the glass transition temperature of polymer matrices was studied in details. Significant influence of content, size and shape of filler particles on thermal properties of polymer matrices was found.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Synthesis and characterization of Co2+ doped TiO2 nanoparticles

Scrolled titania nanotubes were synthesized by a hydrothermal method using commercial TiO2 powder in proton-deficient aqueous systems. In presence of CoCl2 extended hydrothermal treatment of TiO2 nanotubes lead to formation Co2+ doped TiO2 nanoparticles. TEM and HRTEM measurement were used for determining the shape, dimension and structure of doped nanoaprticles. XRD confirmed anatase crystalline structure od Co2+ doped TiO2. The presence of Co2+ ions did not induce distortions of the overall anatase crystal structure of TiO2 matrix. The concentration of Co2+ ions was 1.5% compared with the amount of Ti4+ ions.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Photoluminescence properties of Eu3+ doped TiO2 nanoparticles

Eu3+ doped TiO2 nanoparticles were synthesized during extended hydrothermal treatment of TiO2 nanotubes dispersion in the presence of Eu(NO3)3. Eu3+ ions occupy two different sites of titania nanoparticles having different binding energies: core octahedral sites and undercoordinated surface sites. Photoluminescence spectra of Eu3+ doped TiO2 nanoparticles independently of dopant concentration consist of three characteristic peaks located at λ=543, 596, and 617 nm attributed to the intra-4f transitions of Eu3+ ion. Removal of excess of Eu3+ ions from the surface and from the undercoordinated surface sites applying post synthetic dialysis of the sample affects its photoluminescence spectrum. The peak intensity at λ=617 nm (5D0→7F2 transition) decreases after dialysis. Such “self-purification” process of nanoparticles is a consequence of fact that dopant ions which substitute Ti atoms in the undercoordinated coordination environment of reconstructed surfaces are weakly bound to the anatase lattice

Gamma irradiation induced synthesis of PbS/PVA hydrogel nanocomposite

This work describes radiolytic in situ incorporation of lead sulfide nanoparticles (PbS NPs) in poly(vinyl alcohol) (PVA) hydrogel. Optical, structural, swelling and diffusion properties of prepared PbS/PVA hydrogel nanocomposite were investigated. Obtained results indicate formation of PbS NPs with a cubic crystal structure and diameter around 3 nm. Incorporation of PbS NPs in PVA hydrogel causes a change in the swelling and diffusion properties

Room temperature ferromagnetism in Cu2+ doped TiO2 nanocrystals

Hydrothermal synthesis of Cu2+ doped TiO2 nanocrystals, using dispersion of titania nanotubes in the presence of Cu2+ ions as precursor, which showed room temperature ferromagnetism, is reported. Morphology of Cu2+ doped TiO2 nanocrystals was characterized by transmission electron microscopy (TEM). An average size of polygonal nanocrystals mainly of square/rectangular shape was around 13 nm. The x-ray powder diffraction (XRPD) analysis of resultant powder confirmed the anatase crystal phase of Cu2+ doped TiO2 nanocrystals. Room temperature ferromagnetic ordering with saturation magnetic moment of the order of 2 x 10-2 μB per Cu atom was observed

Characterization of Sm3+ doped Tio2 and Ni2+ doped Tio2 nanocrystals

We report on a new approach toward synthesis of Sm3+ doped TiO2 and Ni2+ doped TiO2 nanocrystals by shape transformation of hydrothermally treated titania nanotubes in the presence of Sm3+ or Ni2+ ions. The percentage ratio of Sm3+ (or Ni2+) to Ti4+ ions in doped nanocrystals was determined using ICP atomic emission spectroscopy. The XRD patterns revealed the homogeneous anatase crystal phase of both 0.4 at% Sm3+ doped TiO2 and 0.12 at% Ni2+ doped TiO2 nanoparticles. An average size of polyhedral Sm3+ doped TiO2 nanocrystals was between 12 and 14 nm. In the orange-red spectral region, room temperature photoluminescence signals associated with 4 G5/2 →6 HJ (J = 5/2, 7/2 and 9/2) transitions of Sm3+ was observed in Sm3+ doped TiO2 nanocrystals. Optically transparent film made of 0.12 at% Ni2+ doped TiO2 nanoparticles showed room temperature ferromagnetic ordering. The coercive field was found to be HC ~ 80 Oe.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Optical properties of CdSe and CdSe/ZnS quantum dots dispersed in solvents of different polarity

Original organic capping TOPO/TOP groups of CdSe and CdSe/ZnS quantum dots (QDs), from mother solution were replaced with 2_mercaptoethanol, which was chosen as model compound, in order to achieve water solubility. Obtained water dispersions of CdSe and CdSe/ZnS QDs were characterized by UV/VIS absorption and luminescence techniques. Luminescence measurements revealed that bare cores are very sensitive to surface capping, transfer into water diminished emission intensity. Core/shell, CdSe/ZnS, QDs are much more resistant to changes of the capping and solvent, and significant part of emission intensity was preserved in water.9th International Conference on Fundamental and Applied Aspects of Physical Chemistry, Sep 24-26, 2008, Belgrade, Serbi

Испитивање оптичких, магнетних и фотокаталитичких особина допираних ТIО2 нанокристала и нанокомпозита на бази полимера за различите примене

Испитиване су допиране и недопиране наночестице титан (IV) оксида (ТiО2 ), великог енергијског процепа, различитих облика (сферични, тубуларни, штапићасти (елипсоидни)), величина кристалних структура, као и хибридни материјали-нанокомпозити на бази проводног полимера (полианилин, ПАНИ) и наночестица TiO2 . Испитивања утицаја величине, облика, структуре и нивоа допираности наночестица ТiО2 на њихове оптичке, магнетне и фотокаталитичке особине, као и разумевање интеракције наночестица и полимерне матрице (ПАНИ) у циљу креирања нанокомпозита одговарајућих фотокаталитичких својстава представљају главне правце овог истраживања. Обзиром на структуру енергетског процепа наночестица TiO2 , допирање јонима ретких земаља отвара могућност за контролу њихових оптичких карактеристика. Нанокристали TiO2 допирани јонима Sm3+ показују наранџасто-црвену емисију, која је последица f-f прелаза јона Sm3+ (4 G5/2→6 HJ (J=5/2, 7/2 i 9/2)) и која потврђује постојање енергијског трансфера. Допирање наночестица TiO2 јонима Ni2+ отвара могућност за синтезу транспарентних наноструктурних филмова који показују феромагнeтно уређење на собној температури (HC ~ 150-200 Oe) и сатурациону магнетизацију у опсегу 10-3- 5x10-2 μB/Ni, у зависности од концентрације допанта. Следећи циљ ових истраживања био је повећање фотокаталитичке ефикасности/активности наночестица TiO2 површинском модификацијом проводним ПАНИ полимером у карбонизованој форми, уз дефинисање механизма процеса фотокаталитичке деградације модел молекула метиленско плавог (Methylene blue) и родамина Б (Rhodamine B). У поређењу са немодификованим наночестицама TiO2 , ПАНИ/TiO2 нанокомпозити, ексцитовани белом светлошћу, показали су значајно већу фотокаталитичку ефикасност. Процес карбонизације полианилина у ПАНИ/TiO2 нанокомпозитима је довео до даљег повећања њихове фотокаталитичке ефикасности. Фотокаталитичка активност нанокомпозита је условљена њиховом површинском структуром, високом мобилношћу носилаца наелектрисања и апсорпционим коефицијентом полианилина у видљивом делу спектра, као и молекулском структуром испитиваних боја.– This research paper focuses on doped TiO2 nanocrystals of different shape, size and structures, in addition to nanocomposites consisting of TiO2 nanocrystals and conductive polymers (Polyaniline (PANI)). The primary objective of this research paper is to ensure understanding of the influence of size, shape, structure and doping level on optical and magnetic properties of TiO2 nanoparticles, as well as the interaction between nanoparticles and PANI due to the creation of desired photocatalytic properties of nanocomposites. The doping of TiO2 nanocrystals with rare earth ions opens up the possibility of controlling their optical properties. The Sm3+ doped TiO2 faceted nanocrystals exhibited red photoluminescence, associated with 4 G5/2-6 HJ (J=5/2, 7/2 and 9/2) f–f transitions of Sm3+ in the 4f5 configuration, after band-to-band excitation, confirming the accomplishment of energy transfers. The Ni2+ doped TiO2 nanocrystals enabled the synthesis of optically transparent nanostructured films that showed room-temperature ferromagnetism with almost closed loop (HC ~ 150-200 Oe) and saturation magnetization in the range of 10-3-5x10-2 μB/Ni depending on dopant concentration. Ni2+ ions that substitute core Ti atoms were found to participate in the light excitation processes, too. The improvement of photocatalytic efficiency of TiO2 nanocrystals by surface modification with carbonized form of PANI was tested in degradation processes of Rhodamine B and Methylene blue. The carbonized PANI/TiO2 nanocomposites showed significantly higher photocatalytic efficacy compared to the bare TiO2 and the non-carbonized PANI/TiO2 nanocomposites. Their photocatalytic activity is influenced by their surface and crystalline structures, absorption coefficient in the visible part of the spectrum, high mobility of charge carriers and finally by the molecular structures of the organic dyes used.Lecture series / Serbian Academy of Sciences and Arts ; book

Presence of Room Temperature Ferromagnetism in CO2+ Doped TiO2 Nanoparticles Synthesized through Shape Transformation

New approach for synthesis of Co2+ doped TiO2 nanoparticles showing room temperature ferromagnetic behavior, through shape transformation of hydrothermally treated scrolled titania nanotubes in the presence of Co2+ ions is described. The XRD and ICP measurements demonstrated successful incorporation of 0.46 at % Co2+ ions in preserved anatase crystal structure of TiO2 nanoparticles, without presence of Co-oxide Clustering, metallic Co, or Various Co-Ti oxide species. HRTEM measurements revealed that majority of the nanoparticles have polygonal shapes with average dimension of similar to 6-10 nm. Obtained Value of 3.06 eV for band gap energy of Co2+ doped TiO2 nanoparticles explained altered optical properties of TiO2 matrix and indicates narrowing of the electronic properties in respect to the undoped anatase TiO2 nanomaterials. The Co2+ doped TiO2 nanocrystals enabled synthesis of optically transparent film that shows room temperature ferromagnetic ordering with a saturation magnetic moment of 0 25 mu B per Co atom The proposed explanation for room temperature ferromagnetic behavior is based oil the presence of critical amount of oxygen vacancies that mediate interaction between Co2+ spins trapped in the lattice Structure of titania nanoparticles with undercoordinated surface defect sites