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We report the connection between the piezoelectric effect and the crystalline structure of NaNbO3. Rietveld refinement and piezoresponse force microscopy were important tools to discover that the fibers are composed of a mix of phases.

Due to the potential of heterogeneous photocatalysis for wastewater treatment, the researches concerning the improvement materials modifications for its photocatalytic activity have been widely increased. One of the most employed methods is the metal doping into semiconductors. Herewith, we demonstrated the influence of Cu doping into TiO2 in its photocatalytic properties. The powder samples with 0.0 to 0.7% mol were obtained by the Pechini method and characterized by XRD, micro-Raman spectroscopy, FE-SEM, and photoluminescence spectroscopy. The Cu insertion into TiO2 structure induced the stabilization of anatase phase, increasing its content in the samples in relation to the bare TiO2. The PL results indicated that a decrease in the PL emission intensity and a shift of the emission band to the blue region. The photocatalytic activity for rhodamine B degradation under UV light irradiation indicated that the Cu-doping into TiO2 led to an enhancement of the photocatalytic activity compared to the bare one.

Flexible multiferroic composite films are perspective materials for sensors, actuators and similar components of wearable and stretchable devices. Here we present the study of functional properties of flexible composites prepared by embedding nickel zinc ferrite and barium titanate powder into polyvinylidene fluoride (PVDF) polymer optimizing the ratio of polymer and fillers to get the best flexibility and functionality. ATR-FTIR analysis revealed that hot pressing of the flexible films caused a transformation of about 38% of the electro-inactive PVDF α phase into electrically active β and γ phases. Broadband dielectric spectroscopy revealed two relaxation processes responsible for PVDF and space charge relaxations. Activation energies of both processes and the freezing temperature of PVDF to the glass phase were estimated for all films. Ferroelectric measurements have shown unsaturated hysteresis loops for all samples, although the clear dependence of the amount of the electrically active phase on polarization values of composites is visible.

Structural concretes must have a set of chemical characteristics to present a satisfactory resistance to the degradation in environment conditions. Besides the several types of mineralogical compositions, the calcium-rich sulfates, silicates and aluminates phases appear as majority components, but the gypsum one seems to play the most important rule in morphological changes during the concrete cure. In this work, it was carried out several characterizations in commercial Portland cement and the structural concrete sample. Nitrogen adsorption isotherms at 77 K for Portland cement showed the thermal treatment at 500 oC does not undergo significant decreasing in surface area due the high content of porous silicates and aluminates components. The additional resistance to the corrosion of structural concretes exposed at environment conditions can be associated to presence of slag metallic aggregates, which could be characterized successfully by thermal analysis. The amount of embedded metallic component in concrete sample was detected by typical weight gain originated form oxygen incorporation above 700 oC.

Made available in DSpace on 2021-06-25T11:44:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-07 LNLS, Campinas, SP, Brazil Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) In this study, we report the potential of ethylenediamine (En) in the modification of the morphological, structural, optical and catalytic properties of alpha-Ag2WO4 crystals decorated with Ag nanoparticles (Ag NPs). Experimental techniques were used to characterize the as-synthesized samples such as X-ray diffraction, Raman, electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and photoluminescence spectroscopy. The results confirmed the efficiency of En in the decoration with the formation of Ag/alpha-Ag2WO4 crystals and also the modification of alpha-Ag2WO4 morphology that indicated its influence on the crystal growth mechanism via self-assembly and Ostwald ripening. En affects the degree of order/disorder of the crystalline structures in long and short-ranges. In addition, photoluminescence measurements revealed a blue shift of the optical emission caused by a reduction of oxygen vacancies and an increase in structural disorder due to the En concentration used in the synthesis processes. Regarding the photocatalysis experiments, the reduction in oxygen vacancies also caused a decrease in the photoactivity of alpha-Ag2WO4 against the rhodamine B dye, thus confirming the relevance of oxygen vacancies for the development of alpha-Ag2WO4 photocatalysts. Univ Fed Sao Carlos, Ctr Dev Funct Mat, Rod Washington Luiz,Km 235, BR-13565904 Sao Carlos, SP, Brazil Sao Paulo State Univ, Interdisciplinary Lab Ceram Studies, BR-14800900 Araraquara, SP, Brazil Univ Estadual Campinas, Inst Chem, Dept Phys Chem, BR-13083970 Campinas, SP, Brazil Univ Fed Sao Carlos, Dept Phys, Rod Washington Luiz,Km 235, BR-13565905 Sao Carlos, SP, Brazil Sao Paulo State Univ, Interdisciplinary Lab Ceram Studies, BR-14800900 Araraquara, SP, Brazil LNLS, Campinas, SP, Brazil: XAFS2-20180338 CNPq: 443733/2018-0 FAPESP: 2013/07296-2 FAPESP: 2017/12437-5 CAPES: 001

Made available in DSpace on 2022-04-29T08:32:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 1,4-dihydro-1,2,4,5-tetraarylpyrrolo[3,2-b]pyrroles are a versatile class of materials with simple synthesis and promising application in organic electronic devices. In this work we present a method of synthesis of new 1,4-dihydro-1,2,4,5-tetraarylpyrrolo[3,2-b]pyrrole derivatives, with ester and carboxylic acid groups as anchoring groups, by multicomponent reactions using niobium pentachloride as catalyst. The new materials were structurally and optically characterized. Also, it was compared the bonding of different moieties to the titanium dioxide mesoporous film. The preliminary tests as dyes in standard configuration in dye-sensitized solar cells have shown a potential performance in the energy conversion. Universidade Estadual Paulista (UNESP) Instituto de Química Universidade Estadual Paulista (UNESP) Faculdade de Ciências Departamento de Química Universidade Estadual Paulista (UNESP) Instituto de Química Universidade Estadual Paulista (UNESP) Faculdade de Ciências Departamento de Química

Made available in DSpace on 2019-10-06T17:09:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-08-15 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) CaO/SrTiO3 heterostructures were fabricated, and their photocatalytic activity for the discoloration of Rhodamine B (RhB) dye was evaluated. SrTiO3 particles were obtained via a polymer precursor method, and heterojunctions in which CaO grew on SrTiO3 crystalline particles were prepared via a sol-gel route. Characterization was performed using X-ray diffraction, transmission electron microscopy, and ultraviolet/visible/near-infrared, Raman, and photoluminescence spectroscopy. The photocatalytic activity of the heterostructures was verified by the discoloration of RhB using UV light. Defects caused by tensile strain in the interface region were verified when the calcium oxide grew on the strontium titanate, altering the defects of the material. In the heterojunctions, the defects of the monoionized and doubly ionized O (oxygen) vacancies had a greater contribution to the photocatalytic process than the defects at deep levels generated in the stress region and the direct transfer of charge between the conduction and valence bands. LIEC – Chemistry Institute São Paulo State University – UNESP Department of Chemistry – Federal Institute of São Paulo – IFSP Faculty of Engineering of Guaratingueta - UNESP LIEC - Department of Chemistry São Carlos Federal University - UFSCar LIEC – Chemistry Institute São Paulo State University – UNESP Faculty of Engineering of Guaratingueta - UNESP FAPESP: 2013/07296-2 FAPESP: 2017/19143-7

Made available in DSpace on 2022-04-28T19:52:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-06-01 Bismuth ferrite (BiFeO3) powders were synthesized by auto-combustion method using glycine as a fuel. Doping ions of different valence were used to study the influence on electrical conductivity and ferroelectric properties. Powders were mixed and hot-pressed with α-PVDF to form flexible composite samples. Composites endured significantly higher electrical fields with lower leakage and retained the weak ferromagnetism present in powders. Dielectric properties were improved by doping with Zr4+, Y3+ and Ca2+ as well as the electrical resistivity. Flexible composites exhibited improved electrical resistivity and modified conduction mechanism. Relatively high magnetization of powders completely originates from magnetite particles formed during the combustion, while sintered samples exhibited typical antiferromagnetic behaviour. Institute for Multidisciplinary Research University of Belgrade Federal University of Goiás Institute of Chemistry, Goiás Institute of Nuclear Sciences “Vinča” University of Belgrade São Paulo State University (UNESP) Institute of Chemistry, São Paulo Academy of Engineering Sciences of Serbia São Paulo State University (UNESP) Institute of Chemistry, São Paulo

Made available in DSpace on 2021-06-25T11:05:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Na2Ti3O7/H2Ti3O7 heterojunction nanotubes were obtained through the microwave-assisted hydrothermal method (MAH) with different band gap energy engineering. This study aimed to synthesize sodium titanate nanotubes and evaluate the influence of H+ insertion on their photocatalytic properties. Heterojunctions were identified by X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy, and their electronic levels and defects were investigated using diffuse reflectance and photoluminescence spectroscopies in the UV–Vis region. The cation exchange process promotes the formation of Na2Ti3O7/H2Ti3O7 heterojunction with coexistence of both phases in the nanotube. Photocatalytic results of Rhodamine-B (Rh-B) dye discoloration show that the prepared materials have activity under visible and UV light irradiation, and are dependent on the proportion of hydrogen and sodium-titanate phases present. The material with highest sodium concentration showed discoloration with a half-life time of 23 min under visible light irradiation. Theoretical results reveal the heterojunction band offset as a staggered gap, with the effective bandgap occurring between the O-2p of Na2Ti3O7 and Ti-3d of H2Ti3O7. The charge carrier transfer mechanism in the heterojunctions is well described by Z-scheme, with H2Ti3O7 and Na2Ti3O7 as the main oxidation and reduction phases for dye discoloration. LIEC – Chemistry Institute São Paulo State University – UNESP LIEC – Departament of Chemistry São Carlos Federal University – UFSCar Modeling and Molecular Simulations Group Sao Paulo State University UNESP Departament of Chemistry Federal Institute of São Paulo – IFSP Faculty of Engineering of Guaratinguetá – UNESP Department of Physics São Carlos Federal University – UFSCar LIEC – Chemistry Institute São Paulo State University – UNESP Modeling and Molecular Simulations Group Sao Paulo State University UNESP Faculty of Engineering of Guaratinguetá – UNESP CNPq: 142035/2017-3

Made available in DSpace on 2021-06-25T11:11:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In this work a new semiconductor based on calcium heterojunction (CaO/CaTiO3) was evaluated to the optical properties correlated to crystalline lattice defects. The heterojunctions of the semiconductor were prepared by the sol–gel route and its formation was confirmed by the intimate contact interface between crystalline phases. Morphology and elemental composition of the nanometric heterojunction were evaluated. Chemical environment and composition of the surface were used to determine the oxidation state of the material constituents. The electronic structure was evaluated and the relationship among band gap energy, photoluminescent emission energy, and photocatalytic activity of the materials was demonstrated. Oxygen vacancies located on the surface promoted photoluminescent spectra emission in the green wavelength, making them more photoactive than those defects that emitted in the red region. The use of active species scavenger indicated that the photogenerated species with the greatest photocatalytic action was the superoxide radical. This study has developed calcium heterojunctions for application as photocatalysts, demonstrating the importance of the defects generated in the production of heterojunctions and the activity of photogenerated species, studied using scavengers. LIEC - Chemistry Institute São Paulo State University - UNESP Department of Chemistry Federal Institute of São Paulo - IFSP Faculty of Engineering of Guaratinguetá UNESP LIEC - Department of Chemistry São Carlos Federal University - UFSCar LIEC - Chemistry Institute São Paulo State University - UNESP Faculty of Engineering of Guaratinguetá UNESP FAPESP: 2017/19143-7

Made available in DSpace on 2021-06-25T10:14:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-21 In general, the properties of oxide materials are directly related to the formation of defects in their structure. In this work, a correlation between the intrinsic defects of SnO2 nanowires with their optoelectronic and transport properties and the influence of illumination was traced. Photoluminescence experiments revealed that SnO2 nanowires are characterized by three emission centers related to oxygen vacancies, V 0 + (red), (V 0 +) iso (yellow/orange), and V 0 + + (green), the latter being active only below 100 K. This metastable defect was associated with the anomalous behavior observed in the temperature-dependent resistivity curves of ohmic single-nanowire devices under the influence of light. Two activation energies for a single nanowire in different temperature regions (T < 100 K and T > 100 K) were identified by photocurrent measurements. The activation energy for T < 100 K (7 meV) is consistent with the small value obtained in the photoluminescence experiments for the green-emitting center (3 meV). For the high-temperature region (T > 100 K), a higher activation energy value (220 meV) was observed. LIEC Instituto de Química Universidade Estadual Paulista-UNESP NanOLaB Departamento de Física Universidade Federal de São Carlos Grupo de Nanoestruturas Semicondutoras Departamento de Física Universidade Federal de São Carlos LIEC Instituto de Química Universidade Estadual Paulista-UNESP

The persistent photoconductivity (PPC) effect is a commonly observed behavior in SnO

Submitted by Alexandre Zirpoli Simões (zirpoli.simoes@unesp.br) on 2020-09-26T17:59:45Z No. of bitstreams: 1 Amoresi-2020_Metallic behavior STO-LAT_versao final vol doi.pdf: 1428668 bytes, checksum: 1fe4199f2f3f22c7fe7cb777d664cb09 (MD5) Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2021-07-26T23:37:48Z (GMT) No. of bitstreams: 1 amoresi_rac_artigo_guara_metallic.pdf: 1428668 bytes, checksum: 1fe4199f2f3f22c7fe7cb777d664cb09 (MD5) Made available in DSpace on 2021-07-26T23:37:48Z (GMT). No. of bitstreams: 1 amoresi_rac_artigo_guara_metallic.pdf: 1428668 bytes, checksum: 1fe4199f2f3f22c7fe7cb777d664cb09 (MD5) Previous issue date: 2020-06-16 Outra Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The search for new and low-power switching devices involving the integration of semiconductor thin films is of interest, and has led to renewed research because such devices may exhibit innovative properties. Here, we investigate the two-dimensional electron gas (2DEG) at the LaAlO3/SrTiO3 interface with metallic and insulator behavior. Insight is offered by quantifying the interface charge distribution associated with structural and electronic order-disorder effects. Variations in the electron conductivity were observed to be associated with different specific clustering arrangements of both Ti and Al cations of the co-exposed surfaces at the interface, i.e., structural and electronic connectivity among the undercoordinated [TiO ]5 and [AlO ]5 clusters. These results indicate facet control as a strategy for enhancing the electric and magnetic properties of a device via the quantum confinement of electron Faculty of Engineering of Guaratingueta, São Paulo State University, UNESP Department of Analytical and Physical Chemistry, University Jaume I (UJI), Castello Department of Physics FederalUniversity of São Carlos, UFSCAR Institute of Physics of São Carlos, University of São Paulo – USP Interdisciplinary Laboratory of Electrochemistry and Ceramics, LIEC, Chemistry Institute, São Paulo State University, UNESP FAPESP: 2013/07296-2. 2017/19143-7. 2018/01914-0. 2019/09296-6 CNPq: 150949/2018-9 Capes - 001

Present theoretical and experimental work provides an in-depth understanding of the morphological, structural, electronic, and optical properties of hexagonal and monoclinic polymorphs of bismuth phosphate (BiPO

Made available in DSpace on 2020-12-12T01:25:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-06-01 Present theoretical and experimental work provides an in-depth understanding of the morphological, structural, electronic, and optical properties of hexagonal and monoclinic polymorphs of bismuth phosphate (BiPO4). Herein, we demonstrate how microwave irradiation induces the transformation of a hexagonal phase to a monoclinic phase in a short period of time and, thus, the photocatalytic performance of BiPO4. To complement and rationalize the experimental results, first-principles calculations have been performed within the framework of density functional theory. This was aimed at obtaining the geometric, energetic, and structural parameters as well as vibrational frequencies; further, the electronic properties (band structure diagram and density of states) of the bulk and corresponding surfaces of both the hexagonal and monoclinic phases of BiPO4 were also acquired. A detailed characterization of the low vibrational modes of both the hexagonal and monoclinic polymorphs is key to explaining the irreversible phase transformation from hexagonal to monoclinic. On the basis of the calculated values of the surface energies, a map of the available morphologies of both phases was obtained by using Wulff construction and compared to the observed scanning electron microscopy images. The BiPO4 crystals obtained after 16-32 min of microwave irradiation provided excellent photodegradation of Rhodamine B under visible-light irradiation. This enhancement was found to be related to the surface energy and the types of clusters formed on the exposed surfaces of the morphology. These findings provide details of the hexagonal-to-monoclinic phase transition in BiPO4 during microwave irradiation; further, the results will assist in the design of electronic devices with higher efficiency and reliability. Chemistry Department CDMF LIEC Federal University of São Carlos, P.O. Box 676 Instituto de Química de São Carlos Universidade de São Paulo, P.O. Box 780 CDMF LIEC Chemistry Institute of the Paulista State University UNESP, P.O. Box 1680 Department of Physical and Analytical Chemistry University Jaume i Physics Department Federal University of São Carlos, P.O. Box 676 Brazilian Nanotechnology National Laboratory, Rua Giuseppe Maximo Scolfa no. 10000 CDMF LIEC Chemistry Institute of the Paulista State University UNESP, P.O. Box 1680

Made available in DSpace on 2020-12-12T01:25:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-07-01 Regione Piemonte A versatile and efficient surface-enhanced Raman scattering (SERS) substrate based on a hybrid aerogel composed of reduced graphene oxide (rGO) decorated with silver nanoparticles (AgNPs), suitable for highly sensitive label-free detection of chemical and biological species, is presented. The simple and low-cost one-pot hydrothermal synthesis allows obtaining of a 3D nanostructured spongy-like matrix that shows good spatial distribution of Ag nanoparticles in intimate contact with rGO flakes, characterized by means of several morphological, structural, and compositional techniques. The nanostructured material, tested by SERS analysis with both rhodamine 6G (R6G) and 4-mercaptobenzoic acid (MBA), shows a satisfying SERS efficiency, quantified in terms of minimum detectable concentration of 10−10 and 10−7 m, corresponding to on- and off-resonant excitation, respectively. The versatility of chemical/biochemical functionalization is successfully demonstrated by exploiting different routes, by immobilizing both protoporphyrin IX (PRPIX) and hemin (H) that take advantage of π−π non-covalent bonding with the graphene layers, as well as thiol-ended oligonucleotides (DNA probes/aptamers) directly grafted on the AgNPs. Finally, after the successful integration of the hybrid aerogel into a microfluidic chip, the biorecognition of miR222 is obtained demonstrating the reliability of the aerogel substrate as SERS platform for biosensing. CDMF – Functional Materials Development Center Institute of Chemistry São Paulo State University-UNESP DISAT-Department of Applied Science and Technology Politecnico di Torino, C.so Duca degli Abruzzi 24 Center for Sustainable Future Technologies IIT-Istituto Italiano di Tecnologia, Via Livorno 60 CDMF – Functional Materials Development Center Institute of Chemistry São Paulo State University-UNESP

Made available in DSpace on 2019-10-06T15:23:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-01 TiO2/SrTiO3 heterojunction powders were obtained and characterized, and their photocatalytic potential was evaluated. The formation of the solid–solid interface was evidenced by secondary-phase formation in the interface region, which was observed using transmission electron microscopy. The photocatalytic efficiency of the TiO2/SrTiO3 heterojunction was higher than that of pure TiO2 and SrTiO3 samples. The photocatalytic behavior was investigated via scavenger experiments, which indicated that the mechanism of charge transfer for the heterojunction was the direct transfer of the electrons at the interface. A surface compositional analysis of the materials revealed that effective electronic-transfer properties of the materials are more important than the content of pre-adsorbed species on the surface for redox reactions. Photoluminescence spectroscopy analyses showed a reduction in the photoluminescent intensity for the heterojunction and emission in distinct regions depending on the defects formed in the heterojunction. These differences in behavior may be related to the different photocatalytic responses observed for pure compounds and heterojunctions; a broad analysis indicates that the mono (VO·) and double (VO··) ionized vacancies affect the performance of the photocatalyst in the degradation of micropollutants. LIEC-Chemistry Institute São Paulo State University-UNESP Department of Chemistry Federal Institute of São Paulo-IFSP Faculty of Engineering of Guaratingueta-UNESP LIEC-Department of Chemistry Universidade Federal de São Carlos-UFSCAR LIEC-Chemistry Institute São Paulo State University-UNESP Faculty of Engineering of Guaratingueta-UNESP

Magnesium-aluminum hydrotalcites can be co-substituted with others trivalent cations, such as iron III in aluminum site, which can be a promising way to modify the properties of that synthetic adsorptive material. In the present work, hydrotalcite containing 5 mol% iron III in co-substitution to the aluminum was prepared by precipitation process and compared with no co-substituted sample along the temperature of calcination at 100 and 500 oC for 4 hours. The calcined samples were characterized by simultaneous TG/DTA, X-ray Diffraction and nitrogen adsorption-desorption techniques. The iron (III) insertion showed positive results in order to provide more stable structure against high temperatures of calcination, which was observed by lesser structural decomposition of rhombohedral hydrotalcite and a more mesoporous structure.

Made available in DSpace on 2020-12-12T01:00:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ZnO nanorods comprised of biosensors with Au nanoparticles are described in this study for detecting Hepatitis C virus (HCV). The biosensor device was constructed on a glass substrate with silver and gold electrodes. The ZnO nanorods were grown by microwave hydrothermal synthesis, and the Au nanoparticles were deposited by the sputtering method. The Au nanoparticles were deposited because of the right efficient of anti-HCV antibodies with cystamine and glutaraldehyde. The ZnO nanorods were evaluated using SEM images. The electrochemical biosensor shows a sensitive response to HCV with a detection limit of 0.25 μg/μL. The proposed sensor characteristics of high specificity, good reproducibility and remarkable stability will provide a sensitive, selective, and convenient approach for the detection of HCV. LIEC Institute of Chemistry São Paulo State University-UNESP School of Pharmaceutical Sciences São Paulo State University-UNESP LIEC Institute of Chemistry São Paulo State University-UNESP School of Pharmaceutical Sciences São Paulo State University-UNESP FAPESP: 2016/05269-6

Made available in DSpace on 2018-12-11T17:34:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-04-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Researches on solids heterojunctions has proven to be an important field for technological applications due to synergism achieved by interface phenomena. In this work, we present an understanding of SrTiO3/TiO2 interface and its effects on structural and microstructural characteristics, and relate them to photoluminescence properties of heterojunctions obtained by a simple method. It was observed that SrTiO3 proportion directly influences the structural order-disorder, as observed by X-Ray diffraction, Raman spectroscopy and Transmission electron microscopy. Photoluminescence behavior of heterojunction with 1% of SrTiO3 showed a shift to blue emission region compared to TiO2, and enhanced of emission intensity compared to SrTiO3, resulted from defects generated by interface effects, attracting possible applications on selective color emitter. Therefore, we conclude that in same materials phases, nature and concentration of structural defects has strong dependence of SrTiO3 concentration, which leads to different photoluminescence properties. Interdisciplinary Laboratory of Electrochemistry and Ceramics LIEC – Chemistry Institute São Paulo State University – UNESP Interdisciplinary Laboratory of Electrochemistry and Ceramics LIEC – Department of Chemistry Universidade Federal de São Carlos – UFSCAR Institute of Physics of São Carlos University of São Paulo – USP Faculty of Engineering of Guaratinguetá São Paulo State University – UNESP Interdisciplinary Laboratory of Electrochemistry and Ceramics LIEC – Chemistry Institute São Paulo State University – UNESP Faculty of Engineering of Guaratinguetá São Paulo State University – UNESP FAPESP: CEPID/CDMF – FAPESP: 2013/07296-2

Made available in DSpace on 2018-12-11T17:35:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-02-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In this work, a high photocatalytic activity was attained by intercalating a Pt layer between SnO2 and TiO2 semiconductors, which yielded a TiO2/Pt/SnO2 - type heterostructure used in the discoloration of blue methylene (MB) solution. The porous films and platinum layer were obtained by electrophoretic deposition and DC Sputtering, respectively, and were both characterized morphologically and structurally by FE-SEM and XRD. The films with the Pt interlayer were evaluated by photocatalytic activity through exposure to UV light. An increase in efficiency of 22% was obtained for these films compared to those without platinum deposition. Studies on the reutilization of the films pointed out high efficiency and recovery of the photocatalyst, rendering the methodology favorable for the construction of fixed bed photocatalytic reactors. A proposal associated with the mechanism is discussed in this work in terms of the difference in Schottky barrier between the semiconductors and the electrons transfer and trapping cycle. These are fundamental factors for boosting photocatalytic efficiency. Interdisciplinary Laboratory of Electrochemistry and Ceramics LIEC – Chemistry Institute São Paulo State University - UNESP Laboratory of Photocatalysis and Microwave Sintering – Chemistry Institute São Paulo State University - UNESP Interdisciplinary Laboratory of Electrochemistry and Ceramics LIEC – Chemistry Institute São Paulo State University - UNESP Laboratory of Photocatalysis and Microwave Sintering – Chemistry Institute São Paulo State University - UNESP FAPESP: 2013/07296-2

Made available in DSpace on 2018-11-26T16:00:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 FUNDECT-MS Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) FINEP Anionic clays are structures capable of adsorbing large quantities of water and other polar molecules in aqueous medium due to an ordered lamellar arrangement. Generally, the most stable composition contains magnesium and aluminum hydroxides, but other trivalent metal cations with similar ionic radii may also be inserted in co-substitution to the aluminum cation, targeting changes in the specificities of the adsorbed molecules, such as the chromium (III) one. The main objective of this work was to investigate the thermal stability of the carbonated magnesium-aluminum hydrotalcite when different amount of aluminium (III) cation is replaced by chromium (III) one. For that purposes, the hydrotalcite samples were obtained through the coprecipitation method at pH 11, followed by ageing stage at 80 degrees C, washing and drying at 100 degrees C for 24 h. The results obtained by thermal analysis, FTIR spectroscopy, and Xray diffractometry techniques have permitted to conclude that chromium insertion leads to turbostratic disorder along the c-axis, which affects also the thermal stability and crystallinity of the precipitated materials. The chromium- based hydrotalcites showed to be more easily dehydrated at lower temperatures, with dependence predominantly kinetic, which leads to significant volume contraction and the hindering of the subsequent dehydroxylation stage at higher temperatures. Univ Estadual Mato Grosso do Sul, CDTEQ, LIMAN, R Emilio Mascoli 275, BR-79950000 Navirai, MS, Brazil Univ Fed Mato Grosso do Sul, INQUI, Av Senador Filinto Muller 1555, BR-79064470 Campo Grande, MS, Brazil Univ Estadual Paulista, IQCar, LIEC, Rod Araraquara Jau Km, BR-14800901 Araraquara, SP, Brazil Univ Estadual Paulista, IQCar, LIEC, Rod Araraquara Jau Km, BR-14800901 Araraquara, SP, Brazil

Made available in DSpace on 2022-04-28T19:41:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-10-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In this work, we report the effects of Sb doping on the optical and electrical properties of the SnO2 nanowires obtained by the vapor-liquid-solid (VLS) method. The absorption edges were found to be 3.30 eV and 3.66 eV for undoped SnO2 and Sb-doped SnO2 (ATO) nanowires, respectively. The energy shift was related to the Burstein-Moss effect taking place in the doped nanowires. We studied the ATO optical bandgap (ΔE = 0.36 eV) shift as a function of carrier concentration. The incorporation of Sb caused the resistivity to decrease three orders of magnitude for single-nanowire ATO devices. In addition, it was found that undoped SnO2 nanowires exhibit semiconductor characteristics while a metal-insulator transition (MIT), around 170 K, was observed in the ATO nanowires. LIEC Instituto de Química Universidade Estadual Paulista - UNESP Departamento de Física Universidade Federal de São Carlos LIEC Instituto de Química Universidade Estadual Paulista - UNESP CNPq: 150856/2019–9 FAPESP: 2013/07296–2 FAPESP: 2014/01371–5 FAPESP: 2017/23663–6 FAPESP: 2019/12383–8 CNPq: 305656/2018–0

NaNbO3 samples were synthesized via a microwave-assisted hydrothermal method for different processing times (ranging from 30 to 90 minutes) at 180 °C using NaOH as a mineralizer. XRD and Rietveld refinement data confirmed the successful preparation of NaNbO3 with an orthorhombic (Pbma) crystallographic structure devoid of secondary phases. Raman scattering spectra reveal that the symmetry of the NaNbO3 space group has vibrational modes associated with the librations and internal vibrational modes of NbO6 the octahedron. The NaNbO3 particles grow in plate-like shape besides presenting high agglomeration degree. However, the particles assume parallelepiped-like shape as increasing synthesis time and the agglomeration degree becomes smaller. With an increase in the processing time, the optical band gap (3.24 eV (30 min), 3.32 eV (60 min), and 3.34 eV (90 min)) presents a slight difference in the density of intermediary energy levels within the band gap, which affects the electronic transitions. The broad band PL emission (350–800 nm) obtained at room temperature with a dominant PL sub-band at ∼455 nm (blue component) indicates that the changes in the electronic density are related to the defects of oxygen vacancies (in the bulk and surface) due to the structural disorder degree in the medium-range, i.e., local distortions of the NbO6 octahedron as result of changes in the Nb–O bond lengths and O–Nb–O bond angles, increasing the degree of structural disorder in the medium-range, and thereby a decline in the PL intensity with an increase in synthesis time. This medium-range structural disorder is able to transform the NaNbO3 ordered structure, which is constituted of clusters, into an ordered-disordered NaNbO3 structure formed by , and complex clusters.

Hydrotalcite-type anionic clays are a group of important materials used in adsorption processes, mainly for organic pollutants removal due the layered double hydroxide structure. The layer-interlayer interactions provide a structural memory even after dehydration and dehydroxylation process, since a very stable interlayer anions are part of material composition, like the carbonate one. A limited numbers of trivalent modifier cations can replace the aluminium cation due the ionic radii mismatch or oxidation state restrictions. Transition metal cations can replace the aluminium one in octahedral site of hydroxide lamellas in order to improve the adsorptive behaviors. In this work, we have investigate three compositions of carbonated magnesium-aluminium hydrotalcite with dif-ferent iron (III) contents through the co-precipitation method at pH 11 and aging step at 60°C for 6 hours. Thermal analysis was performed aiming the determination of the hydration water and hydroxyl amounts in dried precipitate samples, taking in account the results obtained for X-ray diffractometry, infrared spectroscopy, and nitrogen adsorption-desorption characterization for several thermally treated samples. All of synthesized samples showed high surface areas, even for high temperature of thermal treatment. The co-substitution with iron (III) reduced the temperature of dehydration and dehydroxylation process, but the co-substitution at 5 mol% provides other desirables characteristics, like a more amount of rhombohedral HDL phase and higher porosity, even after the thermal treatment at 500°C for 4 hours. This result makes that composition very applicable as a reusable adsorbent material in order to removal several types of micro-pollutant compounds in aqueous media.

The titanium dioxide phase formation is dependent on the synthesis method, temperature of calcination and modifiers insertion. By using chemical methods, such as Polymeric Precursor Method, the organic impurities or extrinsic defects caused by doping play an important rule on the formation of precursor structure before the phase crystallization above 500 oC. Some dopants can change the decomposition mechanism of the precursor, which affects the anatase-rutile phase transition. In this work, the Polymeric Precursor Method was used to synthesize titanium dioxide powder samples in order to investigate the effects of iron (III) and vanadium (V) dopants on the phase formation. Through thermal analysis of polymeric precursors and X-ray diffractometry for calcined powder samples it was possible to show the existence of antagonistic effects for both investigated dopants. While the iron doping reduces the anatase phase tetragonality and delays the rutile phase conversion, the vanadium one changes the mechanism of decomposition of polymeric precursor and leads to more amount of rutile phase.