Dependence of surface-enhanced Raman scattering (SERS) from Calf thymus DNA on anions is inves- tigated.With the silver colloid,the bands at 732,960 and 1333 cm^(-1) for adenine (A),1466 cm^(-1) for deoxyribose,and 1652 cm^(-1) for the C=O group of thymine (T) are observably enhanced.With the pres- ence of the C1 or SO^-anions,the bands at 732 and 1326/1329 cm-1 for the symmetric stretching and skeletal vibrational modes of adenine (A) are dramatically enhanced,and the enhancement effect with the SO_4^(2-) ion is more than that with the Cl^-ion.The experimental results show that the DNA molecule can be adsorbed on the silver colloid particles through the C_6N and N_7 of adenine (A),the C=O of thymine (T) and deoxyribose.Moreover,the formed hydrogen bonding of the Cl^-or SO_4^(2-) ions to the C_6NH_2 group of adenine (A) can induce larger C_6N electronegativity,which is favor for the C_6N/N_7 cooperative adsorption on the (Ag)_n^+ colloid particles.
The Ni microcantilevers were fabricated by femtosecond laser. The corrosion behavior of the micro-sized Ni cantilever beams was studied by electrochemical noise and a newly developed fatigue testing method. The results show that the micro-sized specimens exhibit general corrosion behavior under the studied corrosion condition,whereas the ordinary-sized plates exhibit the localized corrosion behavior. The critical load amplitude of the micro-sized Ni specimens under corrosion fatigue status was determined to be 15 mN. The maximum bending loads,which were measured by fatigue tests,decrease gradually prior to final fracture. Corrosion fracture first occurs in the range of notch with a higher tensile bending stress,and exhibits clear evidence of trans-columnar fracture. The variation of maximum bending loads with time agrees with that creep deformation of the micro-sized Ni specimens can easily occur at room temperature,which implies that the micro-sized Ni specimens appear to have an improved resistance towards total crack as compared with the ordinary-sized Ni specimens.
