Green synthesis of colloidal silver nanoparticles using natural rubber latex extracted from Hevea brasiliensis

Colloidal silver nanoparticles were synthesized by an easy green method using thermal treatment of aqueous solutions of silver nitrate and natural rubber latex (NRL) extracted from Hevea brasiliensis. The UV–Vis spectra detected the characteristic surface plasmonic absorption band around 435 nm. Both NRL and AgNO₃ contents in the reaction medium have influence in the Ag nanoparticles formation. Lower AgNO₃ concentration led to decreased particle size. The silver nanoparticles presented diameters ranging from 2 nm to 100 nm and had spherical shape. The selected area electron diffraction (SAED) patterns indicated that the silver nanoparticles have face centered cubic (fcc) crystalline structure. FTIR spectra suggest that reduction of the silver ions are facilitated by their interaction with the amine groups from ammonia, which is used for conservation of the NRL, whereas the stability of the particles results from cis-isoprene binding onto the surface of nanoparticles. Therefore natural rubber latex extracted from H. brasiliensis can be employed in the preparation of stable aqueous dispersions of silver nanoparticles acting as a dispersing and/or capping agent. Moreover, this work provides a new method for the synthesis of silver nanoparticles that is simple, easy to perform, pollutant free and inexpensive.     

Tricyclische CuII- und NiII-Chelate aus 2,2-Bis-(2-hydroxyarylazo)-biphenyl bzw. -diphenylsulfid

Tricyclic Cu^II and Ni^II chelates are produced from some 2,2′-bis-(2-hydroxyaryl-azo)-biphenyls and -diphenyl sulphides. From their electron spectra it is concluded that in the Ni complexes of the azo-biphenyl dyestuffs the central atom is coordinated in a different way (probably planar) from that in the corresponding Cu complexes. On the other hand, the valences of both metals in the azo-diphenyl sulphide complexes seem to have the same steric arrangement. This arrangement is probably the same as that of the Cu^II ion in the azobiphenyl dyestuffs, which could be tetrahedral.     

Magnetic moment of the 72+[404] ground state of 10.5 h 175Ta

The magnetic hyperfine splitting ν_M = |gμ_NB_HF/h| of ${}^{175}\text{Ta}\text{(J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{+}}$; $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 10.5}\text{h}\text{)}$ in Fe has been measured with the technique of nuclear magnetic resonance on oriented nuclei as 320.4(1) MHz. With the known hyperfine field $\text{B}{}_{\mathrm{<mtext>HF</mtext>}}\text{(}\text{Ta}\text{Fe}\text{) = ?648(13)}\text{kG}$ the magnetic moment of the $\text{7}\text{2}{}^{\mathrm{+}}\text{[404]}$ ground state of ¹⁷⁵Ta is deduced to be $\text{¦μ¦ = 2.27(5)μ}{}_{\mathrm{<mtext>N</mtext>}}$.