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91.
Comparison of PAMAM-Au and PPI-Au nanocomposites and their catalytic activity for reduction of 4-nitrophenol 总被引:4,自引:0,他引:4
Dendrimer-Au nanocomposites are prepared in aqueous solutions using poly(amidoammine)dendrimers (PAMAM) (generation 2, 3, and 5) and poly(propyleneimine)dendrimers (PPI)(generation 2, 3, and 4) by wet chemical NaBH(4) method. The Au nanoparticles thus obtained are 2-4 nm in diameter for both dendrimers and no generation dependence on the particle size is observed, whereas the generations of the dendrimers are increased as stabilization of Au-nanoparticles is achieved with lower dendrimer concentrations. Studies of the reduction reaction of 4-nitrophenol using these nanocomposites show that the rate constants for the PAMAM dendrimers (generations 2 and 3) are higher than those for the PPI dendrimers (generations 2 and 3), while a distinct difference in the rate constants is not seen for the PAMAM dendrimer (generation 5) or the PPI dendrimer (generation 4). In addition, the rate constants for the reduction of 4-nitrophenol involving all the dendrimers decrease with increases in dendrimer concentrations. 相似文献
92.
93.
Morita H Kawaguchi H Yoshimura T Tsukurimichi E Shimasaki C Horn E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(21):3976-3983
5-(N-p)-Toluenesulfonyl)iminothianthrenes, whose sulfur atoms are oxidized to a sulfoxide or sulfone at the 10-position, were hydrolysed readily in high yield to N-unsubstituted-sulfilimines by using concentrated H2SO4. During hydrolysis, 10-monoxy-5-N-unsubstituted-sulfilimines were obtained as a separable mixture of the cis and trans isomers. The stereochemical interconversion of these compounds was studied under both hydrolytic and thermal conditions and their structures were elucidated by using X-ray crystallography. 相似文献
94.
A nonlinear optical crystal YCa(4)O(BO(3))(3) (YCOB) is phase matchable for third-harmonic generation (THG) of a Nd:YAG laser by type I mixing between 1.064 and 0.532mum . By partial substitution of Gd for Y in YCOB, a solid solution Gd(x)Y(1-x)Ca(4)O(BO(3))(3) gradually changes the phase-matching angles of THG to (theta, ?)=(90( degrees ), 90 ( degrees )) . We present the properties of noncritically phase-matched THG in Gd(x) Y(1-x)Ca(4)O(BO(3))(3) (x=0.28) . 相似文献
95.
This paper is concerned with the analysis of dynamic deflection and acceleration of a concrete bridge which is subjected to a moving vehicle load. The bridge, to be constructed across the River Brahmaputra in India, consists of 20 main spans, and each main span is assumed to be double cantilever type with a small suspended span. The moving vehicle is modeled as one degree of freedom. The deflections and accelerations at specific locations on the bridge when the vehicle moves at constant speed are analyzed by using the finite element method. 相似文献
96.
97.
98.
Takayoshi Kobayashi 《Optics Communications》1979,28(1):147-149
The spectrum of the picosecond broad-band light generated by focusing picosecond laser light into a cell containing phosphoric acid was measured with an OMA. The dependence of the spectrum on the pumping energy was studied. It is noticed that great care must be taken when the broad-band continuum is used as an interrogation beam for picosecond absorption spectroscopy. 相似文献
99.
100.
Tadayosi Yoshimura 《Fresenius' Journal of Analytical Chemistry》1981,308(5):445-447
Summary The electrode reaction of acetylacetone (AA) was investigated in unbuffered aqueous solutions by using 3 lead dioxide (PbO2) indicator electrode. A pH-range of about 2 to 12 was covered. At a pH higher than 3 and lower than 9, the height of the anodic and cathodic peaks is directly proportional to the AA concentration. The PbO2 electrode seems to be useful for determining a complexing agent such as AA.
Voltammetrische Untersuchung des pH-Verhaltens Acetylaceton in wäßriger Lösung an der Bleidioxid-Elektrode
Zusammenfassung Die Elektrodenreaktion von Acetylaceton wurde in ungepufferten wäßrigen Lösungen an der PbO2-Indicatorelektrode untersucht, wobei ein pH-Bereich von 2 bis 12 erfaßt wurde. Bei pH-Werten > 3 und < 9 ist die Höhe der anodischen und kathodischen Peaks direkt proportional der Acetylacetonkonzentration. Die PbO2-Elektrode scheint für die Bestimmung von Komplexbildnern (wie Acetylaceton) nützlich zu sein.相似文献