Well-Aligned TiO2 Nanotube Arrays with Ag Nanoparticles for Highly Efficient Detection of Fe3+ Ion.

Nowadays, determination of the iron ions with high sensitivity and selectivity with novel methods becomes a matter of urgency for monitoring healthy body and environment. In this paper, for the first time, we present a set of high-performance TiO2 nanotube arrays which are quite sensitive to iron ions. Firstly, the anodic oxidation method was adopted to prepare ordered TiO2 nanotube arrays, followed by functionalized Ag nanoparticle deposition with the enhancement ability in iron ion sensing. Besides, the spectrum of the TiO2 nanotube with/without the Ag nanoparticles was analyzed with an X-ray photoelectron spectrometer, which shows that Ag nanoparticles can effectively reduce the recombination rate of electrons and holes, and increase the conductivity and the charge transfer rate of the electrodes. Further, when functionalized Ag nanoparticles on well-ordered TiO2 nanotube arrays were used, iron ion sensing performed with the anodic stripping voltammetry method was investigated to validate the great potential of TiO2 nanotube arrays with a sensitivity of approximately 30 µA/ug/L in becoming Fe3+ sensors. This method creates new possibilities for developing sensors for monitoring of Fe3+ in biological samples without any sample pretreatment procedure.

Growth models of coexisting p(2 × 1) and c(6 × 2) phases on an oxygen-terminated Cu(110) surface studied by noncontact atomic force microscopy at 78 K.

We present an experimental study of coexisting p(2 × 1) and c(6 × 2) phases on an oxygen-terminated Cu(110) surface by noncontact atomic force microscopy (NC-AFM) at 78 K. Ball models of the growth processes of coexisting p(2 × 1)/c(6 × 2) phases on a terrace and near a step are proposed. We found that the p(2 × 1) and c(6 × 2) phases are grown from the super Cu atoms on both sides of O-Cu-O rows of an atomic spacing. In this paper, we summarize our investigations of an oxygen-terminated Cu(110) surface by NC-AFM employing O- and Cu-terminated tips. Also, we state several problems and issues for future investigation.

[Studies on coumarins from fruit of Cnidium monnieri and their cytotoxic activities].

This study is to study is to investigate the coumarins from Fruit of Cnidium monnieri and their cytotoxic activities. The constituents were separated by column chromatography, and their structures were elucidated by spectroscopic data analyses. The isolated compounds were evaluated for their cytoxic activities by MTT method. Eleven compounds were isolated and identified as osthole (1), bergaptan (2), xanthotoxol (3), xanthotoxin (4), imperatorin (5), isopimpinellin (6), osthenol (7), psoralen (8), 5,7-dimethoxycoumarin (9), oxypeucedaninhydrate (10), and swietenocoumarin F (11). Compounds 7, 9-11 were isolated from the Cnidium genus for the first time. Compounds 1,5,10 and 11 showed significant cytotoxic activities against L1210 cell lines at a concentration of 1 x 10(-5) mol x L(-1) with inhibitory rates of were 70.13, 63.10, 55.77, and 75.08% respectively.

[Studies on flavonoids from stems of Nelumbo nucifera Gaertn and their cytotoxic activities].

This research is to investigate study the flavonoids from stems of Nelumbo nucifera and the cytotoxic activities of iso- lated compounds. The constituents were separated by column chromatography,and their structures were elucidated by spectroscopic data analyses. The isolated compounds were evaluated for cytoxic activities by MTT method. Twelve compounds were isolated and identified as rhamnazin-3-O-beta-D-glucopyranoside (1), luteolin-3', 4'-dimethylether-7-O-beta-D-glucoside (2), kaempferol-3-O-beta-D-xylopyranosyl-(1-->2)-O-beta-D-glucopyranoside (3), quercetin-3,3'-di-O-beta-D-glucopyranoside (4), 1, 8-dihydroxy-3,7-dimethoxyxanthone (5), isorhamnetin-3-O-beta-D-glucopyranoside(6) , kaempferol(7), isorhamnetin (8), quercetin(9), astragalin(10), hyperoside (11) and 1-hy- droxy-3,7,8-trimethoxyxanthone(12). All compounds were isolated from stems of this plant for the first time, and compounds 1-5 were firstly isolated from the family nelumbonaceae. Compounds 24 and 6 showed significant cytotoxic activities against BEL-7402 carcinoma cell lines at a concentration of 1 x 10(-5) mol x L(-1) with the inhibitory rate of 67.36%, 53.25%, 57.78%, 60.13% and 52.11%, respectively.

Potential sensitivities in frequency modulation and heterodyne amplitude modulation Kelvin probe force microscopes.

In this paper, the potential sensitivity in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM) and heterodyne amplitude modulation (AM) modes. We showed theoretically that the minimum detectable contact potential difference (CPD) in FM-KPFM is higher than in heterodyne AM-KPFM. We experimentally confirmed that the signal-to-noise ratio in FM-KPFM is lower than that in heterodyne AM-KPFM, which is due to the higher minimum detectable CPD dependence in FM-KPFM. We also compared the corrugations in the local contact potential difference on the surface of Ge (001), which shows atomic resolution in heterodyne AM-KPFM. In contrast, atomic resolution cannot be obtained in FM-KPFM under the same experimental conditions. The higher potential resolution in heterodyne AM-KPFM was attributed to the lower crosstalk and higher potential sensitivity between topographic and potential measurements.

The stray capacitance effect in Kelvin probe force microscopy using FM, AM and heterodyne AM modes.

The effect of stray capacitance on potential measurements was investigated using Kelvin probe force microscopy (KPFM) at room temperature under ultra-high vacuum (UHV). The stray capacitance effect was explored in three modes, including frequency modulation (FM), amplitude modulation (AM) and heterodyne amplitude modulation (heterodyne AM). We showed theoretically that the distance-dependence of the modulated electrostatic force in AM-KPFM is significantly weaker than in FM- and heterodyne AM-KPFMs and that the stray capacitance of the cantilever, which seriously influences the potential measurements in AM-KPFM, was almost completely eliminated in FM- and heterodyne AM-KPFMs. We experimentally confirmed that the contact potential difference (CPD) in AM-KPFM, which compensates the electrostatic force between the tip and the surface, was significantly larger than in FM- and heterodyne AM-KPFMs due to the stray capacitance effect. We also compared the atomic scale corrugations in the local contact potential difference (LCPD) among the three modes on the surface of Si(111)-7 × 7 finding that the LCPD corrugation in AM-KPFM was significantly weaker than in FM- and heterodyne AM-KPFMs under low AC bias voltage conditions. The very weak LCPD corrugation in AM-KPFM was attributed to the artefact induced by topographic feedback.