Peering into the formation of template-free hierarchical flowerlike nanostructures of SrTiO3

The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike nanostructures of SrTiO3 have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO3, which is fundamental to the synthesis of perovskite-type materials with tailored properties

Polypyrrole/ionic liquid/Au nanoparticle counter-electrodes for dye-sensitized solar cells : improving charge-transfer resistance at the CE/electrolyte interface

To provide a viable alternative for counter electrodes used in dye sensitized solar cells, polypyrrole (PPy) based films have been synthesized via electrochemical deposition in the presence of the ionic liquid 1-butyl-3-methylimidazolium bis-(trifluoromethanesulfonyl) imidate (NTf2) and incorporated with gold nanoparticles (Aunanop). The films were analyzed by SEM, UV-Vis-NIR, Raman, Electrochemical impedance spectroscopy, Cyclic voltammetry and Conductivity measurements. The presence of the ionic liquid is found to result in a more conductive film, to improve catalytic reduction of I3 − and the electrochemical reversibility of the electrode. In addition to increase conductivity, impedance spectroscopy has shown that incorporating Aunanop in the PPy/NTf2 film helps improving the interfacial charge transportation, the electrocatalytic properties and solar energy conversion efficiency. DSSCs assembled with PPy based CE presented nearly the same J-V characteristic parameters as observed from conventional Pt based devic

Enzymatic electrochemical biosensor for detection carbaryl pesticide using a functional polypyrrole film

Este trabalho teve como objetivo estudar as propriedades ópticas, morfológicas, estruturais e eletroquímicas de filmes de nanocompósitos de polipirrol contendo nanopartículas de ouro e como dopantes simultâneos índigo carmim e dodecilsulfato. Afim de obter uma superfície favorável para a imobilização da enzima acetilcolinesterase para aplicar como biossensor eletroquímico para detecção do pesticida carbaril, diferentes filmes de nanocompósitos foram sintetizados variando a concentração de dodecilsulfato abaixo e acima da sua concentração micelar critica. Os eletrodos foram caracterizados por microscopia eletrônica de varredura, miscroscopia de força atômica, ângulo de contato, voltametria cíclica, espectroscopia de ultravioleta visível, espectroscopia Raman e por análises de espectroscopia Raman in situ. A presença de dodecilsulfato contribuiu para o aumento da rugosidade, hidrofobicidade, grau de oxidação, condutividade e área superficial eletroativa do polímero, que facilita o transporte e a difusão de carga durante o processo redox. As análises eletroquímicas de voltametria cíclica sugeriram que o filme sintetizado com concentração de dodecilsulfato abaixo da concentração micelar crítica foi o mais adequado para a aplicação como biossensor Esta técnica eletroquímica também foi utilizada para determinar os parâmetros experimentais para a detecção do pesticida carbaril. O biossensor foi caracterizado por microscopia eletrônica de varredura e espectroscopia Raman, demonstrando sucesso na imobilização da enzima acetilcolinesterase. A detecção do pesticida carbaril, baseada na inibição da enzima, foi realizada através de medidas de cronoamperometria. O biossensor apresentou um limite de detecção de 0,06 ng.mL-1, estando abaixo da concentração de limite máximo permitido para o uso desse pesticida em águas salinas. Este limite de detecção apresentou menor valor quando comparado a outros trabalhos reportados na literatura.In this work we have investigated the optical, morphological, structural and electrochemical properties of polypyrrole nanocomposite films containing gold nanoparticles and as simultaneous dopants indigo carmine and dodecylsulfate. In order to achieve a suitable surface for immobilization of acetylcholinesterase enzyme to apply as electrochemical biosensor for detecting the pesticide carbaryl, different nanocomposites films were synthesized by changing the concentration of dodecylsulfate below and above its critical micellar concentration. The electrodes were characterized by scanning electron microscopy, atomic force microscopy, contact angle, cyclic voltammetry, ultraviolet visible spectroscopy, Raman spectroscopy and in situ Raman spectroscopy. The presence of dodecyl sulfate contributed to an increase in roughness, hydrophobicity, oxidation degree, conductivity and electroactive surface area of the polymer, which facilitates the transport and diffusion of charge during the redox process. The electrochemical analysis suggested that synthesized film with dodecylsulphate below the critical micellar concentration are more suitable for the application as biosensors. This electrochemical technique was also used to determine the experimental parameters for the detection of the pesticide carbaryl The biosensor was characterized by scanning electron microscopy and Raman spectroscopy, showing success in the immobilization of the acetylcholinesterase enzyme. Detection of the pesticide carbaryl, based on the inhibition of acetylcholinesterase enzyme, was performed by chronoamperometry measurements. The biosensor presented a detection limit of 0.06 ng.mL-1, below the maximum concentration allowed in salt water for this pesticide. This detection limit is lower than that in other works reported in the literature

Synthesis and characterization of indigo carmine doped polypyrrole with gold nanoparticles nanocomposite.

The present work describes the synthesis and characterization of nanocomposites of indigo carmine doped polypyrrole embedded with gold nanoparticles, aiming to study the effect of the metallic nanoparticles on the electrochromic properties of polypyrrole doped with indigo carmine. The first part of this work concerned the determination of the ideal synthesis condition, (indigo carmine concentration, synthesis temperature, electrolyte composition and electrochemical method for film deposition), to obtain nanocomposites of indigo carmine doped polypyrrole embedded with pre-synthesized (PPY/IC/NPAu) and in situ synthesized gold nanoparticles, by using HAuCl4 in the polymerization electrolyte solution (PPY/IC/HAuCl4). The ideal synthesis parameters were obtained by considering the films with lowest energy gap, obtained from optical measurements. The second part concerned the optical, structural, morphological, electrochemical and electrochromic characterization of the obtained films, by using UV-Vis spectroscopy, infrared-spectroscopy, scanning electron microscopy, cyclic voltammetry and in situ UV-Vis spectroelectrochemistry. The obtained results shows efficient doping by indigo carmine, presenting optical spectra characteristic of polaron state and uniform morphology. In addition, the results clearly show improved charge density and enhanced electrochromic properties from the nanocomposite PPY/IC/HAuCl4 synthesized at 10ºC, presenting optical contrast 2.2 times higher than PPY/IC obtained at the same conditions.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESEste trabalho descreve a síntese eletroquímica e caracterização de nanocompósitos formados de polipirrol dopado com índigo carmim e nanopartículas de ouro com o objetivo de estudar o efeito das nanopartículas metálicas nas propriedades eletrocrômicas do polipirrol dopado com índigo carmim. Na primeira parte do trabalho é realizada a determinação da condição ideal de síntese (concentração de índigo carmim, método eletroquímico de deposição do filme, temperatura de síntese e composição do eletrólito utilizado na síntese) para obtenção de nanocompósitos de polipirrol dopado com índigo carmim com nanopartículas de ouro pré-sintetizadas (PPI/IC/NPAu) e sintetizadas in situ, adicionando HAuCl4 na solução eletrolítica usada durante a polimerização (PPI/IC/HAuCl4). Os parâmetros de síntese ideais foram obtidos considerando os filmes com menor energia de gap (valores obtidos a partir de medidas ópticas). Na segunda parte, realizaram-se caracterizações ópticas, estruturais, morfológicas, eletroquímica e eletrocrômica dos filmes obtidos, usando espectroscopia UV-Vis, espectroscopia no infravermelho, microscopia eletrônica de varredura, voltametria cíclica e espectroeletroquímica UV-Vis in situ. Os resultados obtidos mostram dopagem eficiente pelo índigo carmim, apresentando espectros ópticos característicos do estado polaron e morfologia uniforme. Adicionalmente, os resultados claramente mostram melhoras na densidade de carga e propriedades eletrocrômicas do nanocompósito PPI/IC/HAuCl4 sintetizado a 10°C, apresentando contraste óptico 2,2 vezes maior que PPI/IC obtido nas mesmas condições

Active carbon preparation from treads of tire waste for dye removal in waste water

Bandas de rodagem de sucatas de pneus apresentam baixos teores de cargas inorgânicas e grande quantidade de negro de fumo em sua formulação. Neste trabalho, esse material foi tratado com hidróxido de potássio e cloreto de zinco e, em seguida, realizou-se a pirólise a 500 e 700 °C. Foi investigado o desempenho dos produtos na remoção dos corantes azul de metileno e alaranjado de metila em condições ambientais de pH e concentração. Carbonos obtidos com KOH e pirólise a 700 °C apresentam uma melhor capacidade de adsorção. A simulação deste processo permitiu a caracterização dos gases que contribuem para o desenvolvimento da superfície. Os produtos obtidos apresentam estrutura mesoporosa e estreita distribuição no tamanho de partícula. A presença de contaminantes oriundos desses carbonos foi investigada em meio aquoso. A ausência de zinco e enxofre e o excelente desempenho para remoção de corantes fazem esses materiais úteis no tratamento de água.Treads of scrap tires present low contents of inorganic fillers and a large amount of carbon black. In this work, this material was treated with potassium hydroxide and zinc chloride followed by pyrolysis at 500 and 700 °C. The ability to remove methylene blue and methyl orange were investigated under environmental conditions of pH and concentration. Carbons obtained with KOH at 700 °C present superior adsorption capacity. A simulation of this process permitted the characterization of the gases which contributed to surface development. The obtained products present a mesoporous structure and narrow particle size distribution. The presence of contaminants originated from these carbons was investigated in the aqueous media. The absence of zinc and sulfur releasing and the excellent ability to remove organic dye make these materials useful in the treatment of waste water

Simple One-Step Method to Synthesize Polypyrrole-Indigo Carmine-Silver Nanocomposite

A nanocomposite of indigo carmine doped polypyrrole/silver nanoparticles was obtained by a one-step electrochemical process. The nanocomposite was characterized by scanning electron microscopy, infrared spectroscopy, ultraviolet-visible-near infrared spectroscopy, and cyclic voltammetry. The simple one-step process allowed the growth of silver nanoparticles during the polymerization of polypyrrole, resulting in films with electrochromic behavior and improved electroactivity. In addition, polypyrrole chains in the nanocomposite were found to present longer conjugation length than pristine polypyrrole films