Abstract Silver (Ag) nanospheres were chemically reduced from 1 mM silver nitrate (AgNO3) solutions using mulberry (Morus alba Linn.) leaf extracts. The increase of pH in the synthesis from 9 to 13 modified the surface plasmon resonance peak in UV-Vis spectra relating to the particle diameter around 20 nm. Smaller nanoparticles were obtained from the syntheses at pH 7.4-7.7 and their density was slightly increased with the increase in synthesis temperature from 25 (C to 90 (C. The particle size was increased with increasing AgNO3 concentration from 0.1 to 0.5 M but the mixed phases were obtained from the 0.5 M AgNO3 precursor. After storing for 10 months at room temperature, the nanosuspensions remained without Ag sediment but their colors had significantly changed due to particle agglomerations. The colors were characterized by the smartphone colorimetry according to the RGB, CIE space, as well as chroma and hue angle. Based on the chroma and CIE b* values, the effect of synthesis pH in the stored nanosuspensions was comparable to that before the storage. Although the temperature had only moderate effects, nanosuspensions synthesized at 25 (C, 80 (C, and 90 (C were clearly distinguished by the hue and CIE b* values.

Magnetic properties of monodisperse nanoparticles for ultrahigh density recording and biomedical applications are sensitive to their shape and size distributions. These attributes are, in turns, dictated by several parameters during the synthesis and heat treatments. In this work, monodisperse FePt-based magnetic nanoparticles around 5 nm in diameter were synthesized by the reaction between iron acetylacetonate (Fe(acac)3) and platinum acetylacetonate (Pt(acac)2) in benzyl ether. X-ray absorption near-edge structure (XANES) spectra agreed with transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) that as-synthesized nanoparticles were composed of Pt-rich nuclei and iron oxides. Whereas their composition and size was not sensitive to the variation in the amount of surfactants (oleic acid and oleylamine), the nanoparticles exhibited a larger variation in shape with the increase in each surfactant from 1.5 to 4.5 mmol. After annealing in argon atmosphere at 650°C for 1 hour, the nanoparticles tended to agglomerate. Higher amounts of surfactants surrounded the nanoparticles apparently allowed more sintering because the decomposed carbon from the excess surfactants facilitated the reduction ofiron oxides. More Fe in the large annealed particles then resulted in ferromagnetic properties. By contrast, the ferromagnetic behavior and the highest coercivity were obtained without such agglomeration in the case ofannealed particles synthesized by using the minimum surfactants.

Movimentos de queda de objetos no em meios líquidos foram registrados por uma câmera digital convencional e analisados por um software aberto chamado Tracker. A posição dos objetos em movimento a cada 33 ms foi registrada a partir de uma série de imagens, e a velocidade média foi calculada a partir da mudança de posição durante cada intervalo. Na experiência de queda no ar, verificou-se que o deslocamento era proporcional ao quadrado do tempo, confirmando-se a teoria pelo valor da aceleração da gravidade, obtido com nível aceitável de precisão. Além disso, foram investigados os efeitos da altura de queda, da distância da câmara, bem como a cor da bola e o meio ambiente. No caso de queda em glicerol, a velocidade média de uma bolinha de metal foi aumentou inicialmente com o tempo de queda até atingir o valor constante da velocidade terminal.

Motions of falling objects through air and liquid media were captured by a conventional digital camera and analyzed by a video analysis open source called Tracker. The position of the moving objects at every 33 ms was evaluated from series of images and the velocity was averaged from the change in position during each interval. For the falling in air experiment, the displacement of a ball was proportional to the time squared and the agreement with the theory was indicated by the derivation of the acceleration due to the gravity with an acceptable level of accuracy. In additions, the effects of the height of falling, the camera distance as well as the color of ball and background were investigated. In the case of falling in glycerol, the average velocity of a metal bead was initially increased with the time of falling until reaching a constant value of the terminal velocity.