Binding of glycine and L-cysteine on Si(111)-7 x 7

The adsorption of glycine and l-cysteine on Si(111)-7 x 7 was investigated using high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS). The observation of the characteristic vibrational modes and electronic structures of NH3+ and COO- groups for physisorbed glycine (l-cysteine) demonstrates the formation of zwitterionic species in multilayers. For chemisorbed molecules, the appearance of nu(Si-H), nu(Si-O), and nu(C=Omicron) and the absence of nu(O-H) clearly indicate that glycine and l-cysteine dissociate to produce monodentate carboxylate adducts on Si(111)-7 x 7. XPS results further verified the coexistence of two chemisorption states for each amino acid, corresponding to a Si-NH-CH2-COO-Si [Si-NHCH(CH2SH)COO-Si] species with new sigma-linkages of Si-N and Si-O, and a NH2-CH2-COO-Si [NH2CH(CH2SH)COO-Si] product through the cleavage of the O-H bond, respectively. Glycine/Si(111)-7 x 7 and l-cysteine/Si(111)-7 x 7 can be viewed as model systems for further modification of Si surfaces with biological molecules.     

Silicon nanotube array/gold electrode for direct electrochemistry of cytochrome c

The highly ordered Si nanotube (SiNT) arrays have been fabricated and demonstrated to be an attractive matrix to accommodate macromolecules, such as proteins, and exhibit facile direct electrochemistry of cytochrome c without any pretreatment. A pair of well-defined redox waves can be observed in the aqueous solution containing cytochrome c on this SiNT electrode using cyclic voltammetry. The peak separation (DeltaEp) between the anodic and the cathodic peaks is 63 mV at the sweep rate of 10 mV/s, and the peak current is proportional to the square root of the sweep rates, which indicates that the redox process is a quasi-reversible process. The experimental results show that the good biocompatibility and nanoscale hollow structure of the SiNT arrays can be applicable to preparing Si-based biosensors and protein characterizations.     

The stability on the solution of the initial value problem

In this paper,using the differentiability of the solution with respect to the initial value and the parameter,we present a method which,different from Liapunov’s direct method.will determine the stability of the non-stationary solution of the initial value problem when the non-stationary solution remains unknown.     

大冷变形对化学镀Ni-Sn-P非晶态合金晶化的影响

本文研究了大冷变形对化学镀Ni-Sn-P非晶合金晶化的影响,结果表明,冷变形促进了晶化,不仅降低了Ni-Sn-P非晶合金的热稳定性,而且在冷变形过程中就有晶化产生.     

化学教育与环保教育

当今,环境保护已为举世瞩目的重大课题,它既需要高新科学技术与理论,又需全体公民的环境教育,中国是发展中国家,环保尤为重要,环境教育应为中学化学教学的重要内容。一、从“环境危机”看环境教育的重要性环境污染,生态失衡,今天正日益严重地威胁着全人类的生存,人类只有一个地球,“环境保护”正唤起人类行动起来,爱护环境,保护家园。值得我们警惕的是：我国西部兰州上空已出现浓重光化学烟雾;我国长江以北地区竟已找不到一条未被污染的主要河流;重庆、贵阳等地近几年常有大量酸雨降落…。环保部门指出：目前我国环境污染程度…     

混合三烃基锡衍生物的研究(Ⅲ)──二丁基一环己基锡羧酸酯的合成、结构表征及生物活性

以丁基替换环己基,合成了20种二丁基一环己基锡羧酸酯。利用IR、NMR及元素分析表征了化合物的结构,确定了化合物的质谱裂解机制。对化合物进行了生物活性普筛试验。结果表明,这类化合物同时具有高效杀菌和杀螨活性。     

氮杂冠醚的研究Ⅱ.N-取代苯并氮杂冠醚的1H和13CNMR谱

本文研究了15种新合成的单、双N取代二苯并18冠6的¹H及¹³C NMR谱。结果表明,¹³C NMR谱的化学位移能显示分子的电荷分布,而¹H NMR谱的偶合常数则部份地反映了大环的构象。氮原子的杂入大环结构和取代基的改变对聚醚环上的电荷分布影响的结果说明,这些改变可能会对冠醚的络合作用发生影响。     

Rayleigh-Schrödinger perturbation theory for electron-phonon interaction in two dimensional quantum dots with asymmetric parabolic potential

Within the framework of the second-order Rayleigh-Schr?dinger perturbation theory, we investigate the effects of the interaction of the electron and longitudinal-optical phonons in two-dimensional semiconductive quantum dots with respect to a general potential. We propose a simple expression for the ground state energy, and compare it with those obtained by Landau-Pekar strong coupling theory. It is shown both analytically and numerically that the results obtained from the second-order Rayleigh-Schr?dinger perturbation theory could be better than those from Landau-Pekar strong coupling theory when the coupling constant is sufficiently small. Moreover, some interesting problems, such as polarons in quasi-one-dimensional quantum wires, and quasi-zero-dimensional asymmetric or symmetric quantum dots can be easily discussed only by taking different limits. After the numerical calculations, we find that there exists a simple dimensional scaling and symmetry relation for the ground state polaron energy. Furthermore, we apply our results to some weak-coupling polar semiconductors such as GaAs, CdS. It is shown that the polaronic effects are found to be quiet appreciable if the confinement lengths and smaller than a few nanometers. Received: 3 December 1997 / Revised: 6 July 1998 / Accepted: 17 September 1998     

2-羟基-3-羧基-5-磺酸基苯基重氮氨基偶氮苯吸光光度法测定微量钯

于pH9.3～10.6Na_2CO_3-NaHCO_3缓冲介质中,在Triton N-101存在下,Pd(Ⅱ)与2-羟基-3-羧基-5-磺酸基苯基重氮氨基偶氮苯(HCSDAA)形成组成比为1:2的红色配合物,其最大吸收波长为530nm,表观摩尔吸光系数为1.05×10~5,线性范围为0～0.7μg·ml~(-1) .结合丁二酮肟螯合,氯仿萃取,方法用于贵金属二次合金中微量钯的测定,相对标准偏差为2.0%(n=6).加标回收率为93.8%～99.3%.     

甲酸甲酯生产甲酰胺催化新工艺的研究

研究了在常压下,由甲酸甲酯与ＮＨ３反应生产甲酰胺的催化新工艺,比较了不同反应器、加或不加催化剂。催化剂活性组分含量、催化剂粒度大小及装量等对反应的影响,并考察了不同反应温度、ＮＨ３流量、反应时间与甲酰胺收率的关系,结果表明用催化新工艺在２ｇ－Ｍ－１０催化剂上,加２０ｍＬ甲酸甲酯,ＮＨ４流量为４Ｌ／ｈ,反应温度７℃,反应２ｈ后,甲酰胺收率可达９９％。