Applied Mechanics and Materials Vol. 473

Abstract: A high accuracy BiCMOS sample and hold (S/H) circuit employed in the front end of a12bit 10 MS/s Pipeline ADC is presented. To reduce the nonlinearity error cause by the sampling switch, a signal dependent clock bootstrapping system is introduced. It is implemented using 0.6 um BiCMOS process. An 88.77 dB spurious-free dynamic range (SFDR), and a -105.20 dB total harmonic distortion (THD) are obtained.

Abstract: The geometric structures of the agostic hydrogen bond formed between Cu⁺, Cu²⁺ and [2-hydroxy-1(S)-methy-containing N-methylglycine anion ligand were investigated by density functional B3LYP(Becke, three-parameter, Lee-Yang-Parr)/6-311G** theoretical method. The calculation results showed that the C-HCu agnostic bond formed when Cu⁺ coordination binding to only one [2-hydroxy-1(S)-methy-containing N-methylglycine anion. Natural bond orbital and atoms in molecules theories analysis show that the C-HCu agnostic bond intensity and electronic behavior are quite different from these of hydrogen bond structures.

Abstract: The SiC surfaces were cleaned by the hydrogen plasma with ECRPEMOCVD plasma system at low temperature of 200°C, after the traditional wet cleaning. The surfaces were investigated by RHEED and X-ray Photoelectron Spectroscopy before and after hydrogen plasma treatment. The RHEED imagines showed that the SiC surfaces by hydrogen plasma treatment were more flatter than the SiC surfaces by the traditional wet cleaning, and we found the result that more treatment time, more flatter. The XPS spectra examinations indicated that the surface oxides reduced obviously and the C/C-H compounds on the SiC surface were removed by hydrogen plasma treatment, so the antioxidant ability of the SiC surface was improved.

Abstract: A symmetrical photochromic diarylethene 1a has been synthesized. Its photochemical properties, including photochromic behavior and kinetics, have been investigated in detail. The compound showed good photochromism both in solution and in solid state. The back irradiation by appropriate wavelength visible light regenerated its open-ring isomers and recovered the original emission intensity. Using diarylethene 1a as recording medium, polarization holographic optical recording was carried out successfully.

Abstract: A new photoinduced fluorescent switch based on a photochromic diarylethene, 1-(2-methyl-3-benzothiophenyl)-2-[2-methyl-5-(4-azidomethylphenyl)-3-thienyperfluorocyclope-ntene was synthesized and its photochromism was investigated. The results showed that this compound exhibited reversible photochromism, changing from colorless to purple upon irradiation with UV light both in solution and in PMMA amorphous film. In acetonitrile, the open-ring isomer of the diarylethene 1o exhibited relatively strong fluorescence at 473 nm when excited at 320 nm. The results demonstrated that the diarylethene can be also functioned as a fluorescence switch.

Abstract: A new unsymmetrical isomeric photochromic diarylethene, 1-[2-methyl-3-benzene]-2-[2-methyl-5-(10-phenanthrenyl)-3-thienyperfluorocyclopentene, was designed and synthesized. Its photochromic and fluorescent properties were also investigated in detail. The compound exhibited excellent photochromism, changing from colorless to orchid after irradiation with UV light both in solution and in PMMA film. Furthermore, the fluorescence intensity of the photochromic diarylethene 1a declined remarkably, when irradiation with UV light. Using this diarylethene 1a as optical storage and fluorescence switches was performed successfully.

Abstract: An unsymmetrical photochromic diarylethene 1-(2-trifluoromethylphenyl)-2-[2-methyl-5-(3-N,N-dimethylphenyl)-3-thienyperfluorocyclopentene (1a) was synthesized and its photochromism, fluorescent properties and reaction kinetics of cyclization and cycloreversion were studied in detail. The compound exhibited remarkable photochromism and its absorption maxima were observed at 552 nm in hexane and at 569 nm in PMMA films upon irradiation with 297 nm UV light. The fluorescence intensity of diarylethene decreased upon irradiation with 297 nm UV light. In addiation, reaction kinetics of the cyclization and cycloreversion processes of the compound were determined to be the zeroth and first order reaction by UV-Vis spectra, respectively.

Abstract: An unsymmetrical photochromic diarylethene 1-(2-methyl-3-benzothiophenyl)-2-[2-methyl-5-(4-azidomethyl)-3-thienyperfluorocyclopentene was synthesized, and its optoelectronic properties were also investigated. The results showed that this compound exhibited reversible photochromism, changing from colorless to darkorange after irradiation with UV light in solution. The open-ring isomer of the diarylethene 1o exhibited relatively strong fluorescence at 457 nm in acetonitrile solution (2×10-5 mol L-1) when excited at 287 nm. The fluorescence intensity decreased along with the photochromism upon irradiation with 297 nm light. The electrochemical properties indicated that the oxidation onset and the Eg of the open-ring isomer were lower than the closed-ring isomer.

Abstract: An unsymmertrical diarylethene compound 1-(2-methyl-1-benzofuran-3-yl)-2-[2-methyl-1-benzothiophene-3-y Perfluorocyclopentene was synthesized and its photochromism was investigated, the results showed that this compound exhibited reversible photochromism, inducing cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light both in solution and in PMMA film. When irradiated 297 nm UV light, the maximum absorption was observed at 498 nm and 509 nm in hexane solution and in PMMA film, respectively.

Abstract: An unsymmetrical photochromic diarylethene was synthesized and its photochromism properties were investigated in detail. The compound exhibited remarkable photochromism, changing from colorless to light pink after irradiation with 297 nm UV light, in which absorption maxima were observed at 498 nm in hexane and at 505 nm in PMMA amorphous films, respectively. The photochromic reaction kinetics was studied in solution and their cyclization/cycloreversion processes belong to zeroth/first order reaction in hexane.