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91.
92.
Electron transfer behavior at polyoxometalate-adsorbed alkanethiol self-assembled monolayers 总被引:1,自引:0,他引:1
Yeonyi ChuJandee Kim Suhee ChoiChoong Kyun Rhee Jongwon Kim 《Applied Surface Science》2011,257(22):9490-9497
The interaction between polyoxometalate (POM) anions, SiMo12O404−, and a self-assembled monolayer (SAM) of dodecanethiol (DT) on Au surfaces was investigated using electrochemical methods, X-ray photoelectron spectroscopy, and scanning probe microscopy. The SiMo12O404− ions adsorb on the SAM of DT on Au to form a composite organic-inorganic hybrid layer. The adsorbed SiMo12O404− ion on the SAM layer shows its characteristic redox waves with an electron transfer rate slower than that on a bare Au electrode. The electron transfer behavior at DT−SAM could be regulated by the adsorption of SiMo12O404− depending on the charge of the investigated electroactive species: a significant increase toward a positively charged Ru(NH3)63+ ion, a moderate increase toward a neutral 1,1′-ferrocenedimethanol molecule and a slight decrease toward a negatively charged Fe(CN)63− ion. The effect of the chain length of alkanethiols on the adsorption of SiMo12O404− ion was also investigated: as the chain length decreases, the amount of the adsorbed POM increases and the electron transfer rate through the composite layers increases. The nature of SiMo12O404− ions adsorbed on the SAMs of alkanethiols on Au is discussed in detail. 相似文献
93.
Chul‐Soon Lee Zhengfei Dai Seong‐Yong Jeong Chang‐Hoon Kwak Bo‐Young Kim Do Hong Kim Prof. Ho Won Jang Joon‐Shik Park Prof. Jong‐Heun Lee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(21):7102-7107
Monolayers of periodic porous Co3O4 inverse opal (IO) thin films for gas‐sensor applications were prepared by transferring cobalt‐solution‐dipped polystyrene (PS) monolayers onto sensor substrates and subsequent removal of the PS template by heat treatment. Monolayer Co3O4 IO thin films having periodic pores (d≈500 nm) showed a high response of 112.9 to 5 ppm C2H5OH at 200 °C with low cross‐responses to other interfering gases. Moreover, the selective detection of xylene and methyl benzenes (xylene+toluene) could be achieved simply by tuning the sensor temperature to 250 and 275 °C, respectively, so that multiple gases can be detected with a single chemiresistor. Unprecedentedly high ethanol response and temperature‐modulated control of selectivity with respect to ethanol, xylene, and methyl benzenes were attributed to the highly chemiresistive IO nanoarchitecture and to the tuned catalytic promotion of different gas‐sensing reactions, respectively. These well‐ordered porous nanostructures could have potential in the field of high‐performance gas sensors based on p‐type oxide semiconductors. 相似文献
94.
The preparation and characterization of octadecylsilane, C18, monolayers on indium–tin oxide (ITO) have been studied carefully. A reproducible procedure was developed for the formation of C18/ITO employing octadecyltrimethoxysilane (OTMS) as a monomer. The films were studied by means of electrochemistry, wettability, infrared and atomic force microscopy. All these measurements provide evidence for the formation of a disorganized, ‘brush-type’ monolayer with a maximum surface fractional coverage of 0.90±0.04. The surface coverage can be controlled through the silanization time. The applications and implications of such disorganized monolayers in electroanalytical chemistry are discussed. 相似文献
95.
The procedure of microphase adsorption–spectral correction is applied to the interaction of eosine Y (EO) to the micelles of cetyl trimethyl ammonium bromide (CTAB). The Langmuir aggregation of EO on CTAB occurs owing to microelectrostatic attraction. The results have shown that at pH 3.8, monomeric and micellar aggregates have the structure EO5·CTAB2 and (EO5·CTAB2)39. The adsorption constant of an aggregate is 7.01·105, its molar absorption coefficient is = 8.8·104 liters·mole–1·cm–1 at 550 nm. Application of the aggregation of EO on CTAB gives satisfactory results for quantitative determination of cation surfaceactive agents (surfactants). 相似文献
96.
97.
Thin films of barium strontium titanate (Ba1−xSrx TiO3 (BSTO)) have been used in coupled microstrip phase shifters (CMPS) for possible insertion in satellite and wireless communication platforms primarily because of their high dielectric constant, low loss, large tunability, and good structural stability. In an attempt to improve the figure of merit K (phase shift °/dB of loss) of phase shifters, modification of the metal/BSTO interface of these devices has been done through surface modification of the BSTO layer using a self-assembled monolayer approach. The impact of this nanotechnology promises to reduce RF losses by improving the quality of the metal/BSTO interface. In this study, compounds such as 3-mercaptopropyltrimethoxysilane (MPS), 16-mercaptohexadecanois acid (MHDA) and 3-mercaptopropionic acid (MPA) were used to form the self-assembled monolayers on the BSTO surface. As a result of the previous modification, chemical derivatization of the self-assembled monolayers was done in order to increase the chain length. Chemical derivatization was done using 3-aminopropyltrimethoxysilane (APS) and 16-mercaptohexadecanoic acid. Surface chemical analysis was done to reveal the composition of the derivatization via X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared (FT-IR). Low and high frequencies measurements of phase shifters were done in order measure the performance of these devices for insertion in antennas. X-ray photoelectron spectroscopy characterization of modified BSTO thin films with MPS showed a binding energy peak at 162.9 eV, indicative of a possible SO interaction: sulfur of the mercapto compound, MPS, used to modify the surface with the oxygen site of the BSTO thin film. This interaction is at higher binding energies compared with the thiolate interaction. This behavior is observed with the other mercapto compounds such as: MHDA and MPA. An FT-IR analysis present a band at 780 cm−1, which is characteristic of an OSC stretching and reveals the modification of the BSTO thin film by the coupling of the O of the BSTO with the S of the mercapto compound. All the modification using mercapto compounds is through sulfur to the BSTO thin film. MHDA SAM on BSTO thin film was chemically derivatized using APS shown by XPS and FT-IR. The SAMs modified phase shifters showed an improvement in performance with respect to those phase shifters fabricated with standard methods. 相似文献
98.
The adsorption of cetyltrimethylammonium bromide (CTAB) on disturbed n-alkanethiolate self-assembled monolayers (SAMs) was investigated by electrochemical methods with potassium ferricyanide [K3Fe(CN)6] as a probe. Compared with the completely restrained signal at ordinary compact n-alkanethiolate SAMs, the electrochemical response of K3Fe(CN)6 at the disturbed n-alkanethiolate SAMs was partly restored and became progressively reversible in the presence of increasing concentrations of CTAB, which was employed to characterize the adsorption of cationic surfactants on hydrophobic SAMs. The effect of CTAB concentration on electrochemical impedance spectroscopy (EIS) plots indicated that CTAB experienced two different types of adsorptive behavior at the disturbed n-alkanethiolate SAMs: monomer adsorption at low concentrations below 1×10–6 M and monolayer adsorption at CTAB concentrations above 1×10–5 M. The adsorption of a series of cationic surfactants with similar structures to CTAB on disturbed n-alkanethiolate SAMs was also explored. These surfactants had similar adsorptive behavior and showed nearly linear adsorption characteristics with the length of their hydrophobic tails. 相似文献
99.
100.