Two-photon excitation (TPE) with near-infrared (NIR) photons as the excitation source has important advantages over conventional one-photon excitation (OPE) in the field of biomedical imaging. ?-cyclodextrin polymer (?CDP)-based two-photon absorption (TPA) fluorescent nanomicelle exhibits desirable two-photon-sensitized fluorescence properties, high photostability, high cell-permeability and excellent biocompatibility. By combination of the nanostructured two-photon dye (TPdye)/?CDP nanomicelle with the TPE technique, herein we have designed a TPdye/?CDP nanomicelle-based TPA fluorescent nanoconjugate for enzymatic activity assay in biological fluids, live cells and tissues. This sensing system is composed of a trans-4-[p-(N,N-diethylamino)styryl]-N-methylpyridinium iodide (DEASPI)/?CDP nanomicelle as TPA fluorophore and carrier vehicle for delivery of a specific peptide sequence to live cell through fast endocytosis, and an adamantine (Ad)-GRRRDEVDK-BHQ2 (black hole quencher 2) peptide (denoted as Ad-DEVD-BHQ2) anchored on the DEASPI/?CDP nanomicelle's surface to form TPA DEASPI/?CDP@Ad-DEVD-BHQ2 nanoconjugate by the ?CD/Ad host-guest inclusion strategy. Successful in vitro and in vivo enzymatic activities assay of caspase-3 was demonstrated with this sensing strategy. Our results reveal that this DEASPI/?CDP@Ad-DEVD-BHQ2 nanoconjugate not only is a robust, sensitive and selective sensor for quantitative assay of caspase-3 in the complex biological environment but also can be efficiently delivered into live cells as well as tissues and act as a "signal-on" fluorescent biosensor for specific, high-contrast imaging of enzymatic activities. This DEASPI/?CDP@Ad-DEVD-BHQ2 nanoconjugate provides a new opportunity to screen enzyme inhibitors and evaluate the apoptosis-associated disease progression. Moreover, our design also provides a methodology model scheme for development of future TPdye/?CDP nanomicelle-based two-photon fluorescent probes for in vitro or in vivo determination of biological or biologically relevant species.
A new stationary phase for high-performance liquid chromatography was prepared by covalently bonding a heteroatom-bridged cyclophane onto silica gel using 3-aminopropyltriethoxysilane as the coupling reagent. The structure of the new material was characterized by IR spectroscopy, elemental analysis and thermogravimetric analysis. The linear solvation energy relationship method was successfully employed to evaluate the new phase with a set of 25 solutes, and compared with octadecylsilyl and p-tert-butyl-calixarene bonded stationary phases. The retention characteristics of the new phase are similar to the octadecylsilyl and conventional calixarene phases, and it also has distinctive features. In addition, the chromatographic behavior of the phase was illustrated by eluting alkylbenzenes and inorganic anions in the reversed phase mode and anion-exchange mode, respectively. Thus, multi-interaction mechanisms and mixed-mode separation of the new phase can very likely guarantee its promising application in the analysis of complex samples. The column has been successfully employed for the analysis of triazines in milk, and it is demonstrated to be a competitive alternative analytical method for the determination of triazine herbicide residues. This article is protected by copyright. All rights reserved.
A new stationary phase for high-performance liquid chromatography was prepared by covalently bonding a V-shape cage heteroatom-bridged calixarene onto silica gel using 3-aminopropyltriethoxysilane as coupling reagent. The structure of the new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Linear solvation energy relationship method was successfully employed to evaluate the new phase with a set of 34 solutes. The retention characteristic of the new phase shows significant similarities with ODS, as well as distinctive features. Multiple mechanisms including hydrophobic, hydrogen bonding, ?-? and n-? interaction are involved. The chromatographic behavior of the phase was illustrated by using alkylbenzenes, aromatics positional isomers and flavonoids as probes. Moreover, inorganic anions were individually separated in anion-exchange mode by using the same column. Thus, multi-interaction mechanisms and mixed-mode separation of the new phase can very likely guarantee its excellent chromatographic performance for the analysis of complex samples. The column has been successfully employed for the analysis of clenbuterol in animal urine, and it is demonstrated to be suitable and a competitive alternative analytical method for the determination of clenbuterol.
In this paper, a rapid and effective HPLC method, using tetraazacalixarenetriazine-modified silica gel (NCSi) as solid-phase extraction (SPE) sorbent, was developed for the purification and determination of trace acrylamide in starchy foodstuffs. The main influence factors of SPE including amount of NCSi sorbent, sample flow rate, and volume and composition of washing solution were investigated and evaluated in the sample pretreatment step. The optimized purification effect was achieved at the sample flow rate of 3 mL/min with 100 mg of NCSi and 2 mL of washing solution (water, 100%). The HPLC separation was carried out on a C18 column (250×4.6 mm i.d., 5 ?m) with a mobile phase of methanol/water (10:90, v/v). The linear range of the calibration curve was 4-4000 ng/mL with s correlation coefficient of >0.9999. The intraday and interday RSDs (n=5) of peak areas of acrylamide were 0.22 and 0.90% and the intraday and interday RSDs (n=5) of retention times were 0.50 and 1.63%, respectively. In addition, overall recoveries through the extraction and NCSi-SPE purification ranged from 73.13 to 98%. Compared with the commercial SPE sorbents, NCSi featured excellent selectivity to retain polar and nonpolar interferences in the sample matrices. The improved method was simple, rapid, accurate, and promising for the determination of trace acrylamide in starchy foods with a complex matrix.
In traditional electrochemical sensors, the electrochemical signal transduction of the redox-active material is usually controlled by the analytical target. Due to non-specific interaction between the redox mediator and the target, false signal by single stimulus may not be avoided. To address this issue, we have developed a new electrochemical sensor that uses a functional spiropyran, an important class of photo and thermochromic compounds, as both recognition receptor and latent redox mediator, to realize simultaneous photochemical and target-modulated electron transfer. As a proof of principle, ?-galactosidase was chosen as a model target. The new synthesized spiropyran probe, SP-?-gal, undergoes reversibly structural isomerization to form merocyanine under UV light irradiation. After the glycosidic bond being cleaved by ?-galactosidase, the opened merocyanine of SP-?-gal forms redox-active 2-(2.5-dihydroxystyryl)-1.3.3-trimethyl-3H-indolium, and thus produces a pair of reversible redox current peaks under the electrochemical scanning. To amplify the detection signal, SP-?-gal was self-assembled with single-walled carbon nanotubes (SWCNTs) on the surface of glass carbon electrode. Kinetics experiments confirm that the probe is an ideal candidate for the determination of different concentrations of ?-galactosidase digestion kinetics. Further, the SP-?-gal/SWCNTs-modified electrode is chemically stable in complex biological fluids. It was successfully applied to monitor ?-galactosidase activity in the 10% calf thymus. This work represents not only a significant step forward in the further development of low-dimensional carbon nanomaterials/small organic molecular probes-based electrochemical biosensors, but also a new platform which may be extended to the assay of other enzyme such as ?-D-glycosidase and so on by translating the biorecognition into electrochemical signal responses.
New poly(ionic liquid) immobilized magnetic nanoparticles (PIL-MNPs) were synthesized via co-polymerization of 1-vinyl-3-hexylimidazolium-based ionic liquid and vinyl-modified magnetic particles and were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetic measurements. The PIL-MNPs were utilized as adsorbent phases in magnetic solid-phase extraction (MSPE). The extraction and enrichment efficiency were evaluated by using four organophosphorus pesticides (parathion, fenthion, phoxim and temephos) as test analytes. Various parameters, such as amount of adsorbent, adsorption time, desorption solvent and time, and ionic strength were investigated. The proposed method showed good linearity for the analytes in the concentration range of 1-200?gL(-1) with a correlation coefficient (R)>0.9963. Low limit of detection of 0.01?gL(-1) and high enrichment factors ranging from 84 to 161 were achieved. The proposed method has been successfully used to determine organophosphorus pesticides from three tea drink samples with satisfactory recovery of 81.4-112.6% and RSDs of 4.5-11.3%. The PIL-MNP adsorbent can be reused for 20 times without a noticeable decrease in extraction efficiency.
In the present paper, a new calixarene derivatized chitosan bonded stationary phase (CCS4) for high performance liquid chromatography (HPLC) was synthesized and characterized. Its chromatographic performance and retention mechanism were evaluated in reversed-phase mode compared with ODS using different solute probes including mono-substituted benzenes, phenols and nucleosides. The results showed that CCS4 stationary phase could provide various interactions with solutes, such as hydrophobic, hydrophilic, ?-?, and inclusion interactions. It could perform the mixed-mode separation including RP and HILIC.
The real-time distribution of anticancer 1403C in fermentation broth of marine fungus Halorosellinia sp. was investigated. It was closely related with pH variations, which was, 1403C in the supernatant decreased while that in the mycelia increased with pH rising. There was only 0.5 % of the total 1403C left in the supernatant when pH reached 7.0. The scanning electron microscope then provided information that compounds precipitated on the mycelia when pH rose. Then, the pH-regulation experiments proved that 1403C mainly secreted extracellular and easily dissolved in acidic condition but precipitated and absorbed on the mycelia with the increase of broth pH. Thereby, a pH-regulation strategy was proposed and applied to accumulate 1403C on the mycelia before draw-off of fermentation broth. It significantly simplified purification process and is critical for 1403C preparation of industrial scale.
In this study, silica modified with a 30-membered macrocyclic polyamine was synthesized and first used as an adsorbent material in SPE. The SPE was further combined with ionic liquid (IL) dispersive liquid-liquid microextraction (DLLME). Five polycyclic aromatic hydrocarbons were employed as model analytes to evaluate the extraction procedure and were determined by HPLC combined with UV/Vis detection. Acetone was used as the elution solvent in SPE as well as the dispersive solvent in DLLME. The enrichment of analytes was achieved using the 1,3-dibutylimidazolium bis[(trifluoromethyl)sulfonyl]imide IL/acetone/water system. Experimental conditions for the overall macrocycle-SPE-IL-DLLME method, such as the amount of adsorbent, sample solution volume, sample solution pH, type of elution solvent as well as addition of salt, were studied and optimized. The developed method could be successfully applied to the analysis of four real water samples. The macrocyclic polyamine offered higher extraction efficiency for analytes compared with commercially available C18 cartridge, and the developed method provided higher enrichment factors (2768-5409) for model analytes compared with the single DLLME. Good linearity with the correlation coefficients ranging from 0.9983 to 0.9999 and LODs as low as 0.002 ?g/L were obtained in the proposed method.
Fluoride ion (F(-)), the smallest anion, exhibits considerable significance in a wide range of environmental and biochemical processes. To address the two fundamental and unsolved issues of current F(-) sensors based on the specific chemical reaction (i.e., the long response time and low sensitivity) and as a part of our ongoing interest in the spiropyran sensor design, we reported here a new F(-) sensing approach that, via assembly of a F(-)-specific silyl-appended spiropyran dye with graphene oxide (GO), allows rapid and sensitive detection of F(-) in aqueous solution. 6-(tert-Butyldimethylsilyloxy)-1,3,3-trimethylspiro [chromene- 2,2-indoline] (SPS), a spiropyran-based silylated dye with a unique reaction activity for F(-), was designed and synthesized. The nucleophilic substitution reaction between SPS and F(-) triggers cleavage of the Si-O bond to promote the closed spiropyran to convert to its opened merocyanine form, leading to the color changing from colorless to orange-yellow with good selectivity over other anions. With the aid of GO, the response time of SPS for F(-) was shortened from 180 to 30 min, and the detection limit was lowered more than 1 order of magnitude compared to the free SPS. Furthermore, due to the protective effect of nanomaterials, the SPS/GO nanocomposite can function in a complex biological environment. The SPS/GO nanocomposite was characterized by XPS and AFM, etc., and the mechanism for sensing F(-) was studied by (1)H NMR and ESI-MS. Finally, this SPS/GO nanocomposite was successfully applied to monitoring F(-) in the serum.
A three-dimensional (3D) nitrogen-doped multiwall carbon nanotube (N-MWCNT) sponge possessing junctions induced by both nitrogen and sulfur was synthesized by chemical vapor deposition (CVD). The formation of "elbow" junctions as well as "welded" junctions, which are attributed to the synergistic effect of the nitrogen dopant and the sulfur promoter, plays a critically important role in the formation of 3D nanotube sponges. To the best of our knowledge, this is the first report showing the synthesis of macroscale 3D N-MWCNT sponges. Most importantly, the diameter of N-MWCNT can be simply controlled by varying the concentration of sulfur, which in turn controls both the sponges mechanical and its electrical properties. It was experimentally shown that, with increasing diameter of N-MWCNT, the elastic modulus of the sponge increased while the electrical conductivity decreased. The mechanical behaviors of the sponges have also been quantitatively analyzed by employing strain energy function modeling.
This paper describes the design and implementation of a radiosonde which can measure the meteorological temperature, humidity, pressure, and other atmospheric data. The system is composed of a CPU, microwave module, temperature sensor, pressure sensor and humidity sensor array. In order to effectively solve the humidity sensor condensation problem due to the low temperatures in the high altitude environment, a capacitive humidity sensor including four humidity sensors to collect meteorological humidity and a platinum resistance heater was developed using micro-electro-mechanical-system (MEMS) technology. A platinum resistance wire with 99.999% purity and 0.023 mm in diameter was used to obtain the meteorological temperature. A multi-sensor data fusion technique was applied to process the atmospheric data. Static and dynamic experimental results show that the designed humidity sensor with platinum resistance heater can effectively tackle the sensor condensation problem, shorten response times and enhance sensitivity. The humidity sensor array can improve measurement accuracy and obtain a reliable initial meteorological humidity data, while the multi-sensor data fusion technique eliminates the uncertainty in the measurement. The radiosonde can accurately reflect the meteorological changes.
Tobacco-specific N-nitrosamines (TSNAs), including N-nitrosonornicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, N-nitrosoanatabine, and N-nitrosoanabasine, have been implicated as a source of carcinogenicity in tobacco and cigarette smoke. We present a rapid and effective method comprising SPE based on tetraazacalixarenetriazine-modified silica as sorbent and analysis with HPLC-MS/MS for the determination of TSNAs and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, in rabbit plasma. The linear dynamic ranges were 10-2000 pg/mL for NNAL and 4-2000 pg/mL for the four TSNAs with good correlation coefficients (>0.9965). The LODs were in the range of 0.9-3.7 pg/mL, and the LOQs were between 2.9 and 12.3 pg/mL. The accuracies of the method were also evaluated and found to be in the range of 90.1-113.3%. This method is promising to be applied to the preconcentration and determination of TSNAs and NNAL in smoke and human body fluids.
Patterned micro/nano structural hydrophobic Ni-P films were designed by the combination of electrochemical and chemical deposition. The formation mechanism is illustrated by the gradually changed morphology of the film. This work shows a new method for fabricating a patterned surface morphology with tailored hydrophobicity.
A 25,27-bis(L-phenylalaninemethylester-N-carbonylmethoxy)-26,28-dihydroxy- para-tert-butylcalixarene-bonded silica gel stationary phase was synthesized, structurally characterized and used for LC. Its separation mechanism was studied and compared with octadecyl-bonded stationary phase, as well as our previously prepared para-tert-butylcalixarene-1,2-crown-4 stationary phase. Meanwhile, the chromatographic behaviors were investigated by using polycyclic aromatic hydrocarbons, monosubstituted benzenes, anilines, phenols, Tanaka tests solutes, fluoroquinolones, and flavonoids as probes. Mechanisms involved in the chromatographic separation included hydrophobic, ?-? and ?-electron transfer, hydrogen bonding, and inclusion interactions. Moreover, the column was successfully employed for the analysis of the illegal additive of melamine in milk product.
The chromatographic behaviors of benzoic acid (BAH) were investigated on a self-made p-tert-butyl-calix  arene-1,2-crown-4 (Cx4-4) stationary phase by changing methanol content and pH value of the mobile phase. The results show that hydrophobic interaction is the main interaction in the separation of benzoic acid, moreover, inclusion interaction, pi-pi and hydrogen bonding interactions also play additional roles. A Density Functional Theory (DFT) method with the base set of B3LYP/STO-3G* was employed to explain the interaction between BAH and Cx4-4, and the optimized supramolecular structure (Cx4-4 and BAH), the Gibbs free energy change (delta G) and stabilization energy change (delta E) were obtained. With the assistance of quantum chemistry calculation, the separation mechanism is further discussed. The quantum chemical calculation results were consistent with the retention behavior of BAH on Cx4-4 stationary phase. Finally, by using the self-made Cx4-4 column, a high performance liquid chromatographic (HPLC) method for the analysis of BAH in tuber mustard and vinegar was developed.
A new high-performance liquid chromatography stationary phase has been prepared by covalently bonding 14-membered tetraazamacrocycle to silica gel using ?-chloropropyltrimethoxylsilane as coupling agent. The structure of the new material was characterized by infrared spectroscopy and elemental analysis. With 32 solutes including aromatic and aliphatic compounds, the linear solvation energy relationship method was successfully used to chromatographically evaluate the new phase in reversed phase mode. The retention property of the new phase shows evident similarity with that of ODS stationary phase, as well as distinctive, unique retention characteristics. The separations of n-alkylbenzene, carbamate and organophosphorus pesticides with diversified functional groups as well as phenolic compounds demonstrate that in addition to hydrophobic interaction, dipole-dipole interaction and hydrogen bonding interaction plus acid-base equilibrium could also be simultaneously offered by this new stationary phase, as a result excellent chromatographic performances are guaranteed.
A new oxo-bridged calixarenetriazine bonded stationary phase (OCATS) for high performance liquid chromatography (HPLC) was prepared using 3-aminopropyltriethoxysilane as coupling reagent. The structure of new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic performance and retention mechanism of the new stationary phase were evaluated in reversed-phase mode compared with ODS using different solute probes including polycyclic aromatic hydrocarbons (PAHs), mono-substituted benzenes, disubstituted benzene isomers. The new OCATS stationary phase could provide various interactions for different solutes, such as hydrophobic, hydrogen bonding, ?? and inclusion interactions. The synergistic effects resulting from aromatic rings, bridging oxygen atoms and triazine nitrogen atoms and alkyl linkers in the new material improved the separation selectivity by multiple retention mechanisms. The retention behaviors of the analytes on OCATS column were explained with the assistance of quantum chemistry calculation results using DFT-B3LYP/STO-3G* base group. The OCATS column was successfully employed for the analysis of melamine in infant formula.
The droplet control, especially for the self-propelled Leidenfrost droplet, has attracted many researchers attention in applied and fundamental fields. In this paper, the ratchet thin film was fabricated by magnetron sputtering and hybrid ion beams deposition. The micro- and nanoscale structure of the film was characterized by field emission scanning electron microscope. This study reports an interesting phenomenon that the self-propelled Leidenfrost water droplet was initiated at low temperature. The Leidenfrost point of droplets was controlled by the surface wettability and parameters of the asymmetric ratchet substrate. This novel self-propelled interfacial material and preparation technology can be expanded to the manufacture process and constructed a temperature-dependent tubule for microfluidic systems.
In the present work, a new para-tert-butylcalixarene-1,2-crown-4 bonded silica stationary phase (CBS4-4) was synthesized, structurally characterized, and employed to separate polycyclic aromatic hydrocarbons (PAHs), phenols, aromatic amines, benzoic acid and its derivatives. The chromatographic behaviors of the prepared stationary phase were investigated and compared with ODS. The effects of methanol concentrations on the retention index show that CBS4-4 exhibits high selectivity for the above analytes. The separation mechanisms based on the different interactions between calixarene and the analytes were discussed. With the assistance of quantum chemistry calculation, the interaction Gibbs free energy change ?G(solv) (in the mobile phase) of p, m and o-phenylenediamine positional isomers and para-tert-butylcalixarene-1,2-crown-4 were obtained. The ?G(solv) values were consistent with the retention behavior of p, m and o-phenylenediamine on the CBS4-4. According to the chromatographic data, it can be concluded that the selectivity of CBS4-4 for analytes is mainly ascribed to hydrophobic interaction, accompanied by other effects such as hydrogen bonding interaction, ?-? and inclusion interaction. The CBS4-4 column has been successfully employed for the analysis of benzoic acid in Sprite drink.
Electrospray ionization mass spectrometry (ESI-MS) was employed to monitor the heme release and the conformational changes of myoglobin (Mb) under different solvent conditions, and to observe ligand bindings of Mb. ESI-MS, complemented by circular dichroism and fluorescence spectroscopy, was used to study the mechanism of acid- and organic solvent-induced denaturation by probing the changes in the secondary and the tertiary structure of Mb. The results obtained show that complete disruption of the heme-protein interactions occurs when Mb is subjected to one of the following solution conditions: pH 3.2-3.6, or solution containing 20-30% acetonitrile or 40-50% methanol. Outside these ranges, Mb is present entirely in its native state (binding with a heme group) or as apomyoglobin (i.e. without the heme). Spectroscopic data demonstrate that the denaturation mechanism of Mb induced by acid may be significantly different from that by the organic solvent. Low pH reduces helices in Mb, whereas certain organic content level in solution results in the loss of the tertiary structure. ESI-MS conditions were established to observe the H(2)O- and CO-bound Mb complexes, respectively. H(2)O binding to metmyoglobin (17,585 Da), where the heme iron is in the ferric oxidation state, is observed in ESI-MS. CO binding to Mb (17,595 Da), on the other hand, can be only observed after the heme iron is reduced to the ferrous form. Therefore, ESI-MS combined with spectroscopic techniques provides a useful means for probing the formation of ligand-binding complexes and characterizing protein conformational changes.
Electrospray ionization mass spectrometry (ESI-MS) has been used to characterize the denaturation of porcine hemoglobin (Hb) induced by solvent changes. This work provides evidence for the symmetric nature of Hb denaturation and demonstrates that heme losses from ?- and ?-monomers occur in parallel, in response to the addition of acid and organic co-solvents in solution. When subject to one of the following solution conditions (pH 3.2-4.0 or 15-30% acetonitrile-water or 30-45% methanol-water solution), ?- and ?-globins undergo symmetric dissociation to release the heme groups, which is detected by ESI-MS. Circular dichroism (CD) and fluorescence spectroscopy (FS) data show that the acid-induced and organic solvent-induced heme release, as observed in the mass spectra, can probably be ascribed to different aspects of the conformational changes taking place in the protein. The acidity of the solvent has a significant effect on the secondary structure, whereas organic content level in solution (15-30% acetonitrile or 30-45% methanol) tends to destroy the tertiary structure of Hb globins, both leading to release of the heme from each subunit.
Fast development of micro/nanoelectromechanical systems (MEMS/NEMS) and high-density storage technology (HDT) have stimulated the development of new materials that require hydrophobic surfaces with low adhesion and friction. Micro/nanohierarchical structures and chemical modification are two useful methods for improving nanotribological properties of mechanical components. In this study, Au surfaces with micro/nanohierarchical structures were prepared by replication of micropatterened silicon surfaces using PDMS and self-assembly of alkanethiol [CH(3)(CH(2))(9)SH] to create hydrophobic micro/nanohierarchical structures and to improve nanotribological properties of MEMS/NEMS. The effects of nanoscaled roughness (including pillar height and pillar fractional surface coverage) and chemical modification on the wetting and nanotribological properties of surfaces were systemically investigated. Results show that with the increasing of nanoscale roughness and lowering of surface energy, the surface becomes more hydrophobic, and the adhesive force and friction force are reduced greatly.
Soybean hull was chemically modified with citric acid and used as a solid phase extraction adsorbent for the determination of trace amounts of Cu(2+) in food samples by flame absorption spectrometry (FAAS). The effect of pH, sample flow rate and volume, elution flow rate and volume and co-existing ions on the recovery of the analyte were investigated. The results showed that Cu(2+) could be adsorbed on the modified soybean hull at pH 8.0 and eluted by 2.0 mL of 1.0 mol L(-1) HCl. Under the optimized conditions, the adsorption capacity of modified soybean hull was found to be 18.0 mg g(-1) for Cu(2+). The detection limit of the proposed method was 0.8 ng mL(-1) for Cu(2+) with an enrichment factor of 18. The analytical result for the certified reference tea sample (GBW07605) was in a good agreement with the certified value. The proposed method has also been successfully applied to the determination of trace Cu(2+) in dried sweet potato, lake water and milk powder, the recovery of Cu(2+) for spiked samples was between 91% and 109.6%.
Nano-sized textures resulted from localized electrochemical oxidation by using atomic force microscopy (AFM) were fabricated on H-passivated Si surface. In this paper, the fabrication and nanotribological properties of nanotexture by local anodic oxidation (LAO) on H-passivated Si surface are presented. A special attention is paid to find the relation between the size of oxide nanotexture and operational parameters such as tip-sample pulsed bias voltage, pulsewidth, and relative humidity to fabricate oxide nanotexture. The nanotribological properties were investigated by a colloidal probe. The results indicate that the nanotextures exhibited low adhesion and greatly reduced friction force at nanometer scale.
A rapid and sensitive method based on transient ITP and field enhancement in CE with electrochemical detection at copper disk electrode was developed for the simultaneous separation and determination of three estrogens: estrone, 17?-estradiol, and estriol. The effects of several important factors that influence the separation and detection were investigated. Under the optimum conditions, the estrogens could be separated in 0.06 mol/L sodium hydroxide solution within 14 min. With transient ITP by addition of 0.5% NaCl, a good linear response was obtained for three estrogens from 0.2 to 10 ?mol/L, with correlation coefficients higher than 0.9993. The detection limits were 8.9 × 10(-8) , 6.7 × 10(-8) , and 1.1 × 10(-7) mol/L (S/N = 3) for estriol, 17?-estradiol, and estrone, respectively. This method was successfully employed to analyze different water samples from waterworks, tap water, fishpond, and river samples with recoveries in the range of 90.8-108.9%, and RSDs < 4.69%. The satisfied results demonstrated that this method was of convenient preparation, high sensitivity, and good repeatability, which could be applied to the rapid determination of environmental water samples.
Ginseng has been widely used for hundreds of years in both China and other countries. It is well accepted that the pharmacological effects of ginseng are attributed to ginsenosides. Ginsenoside Re is one of the active ingredients in ginseng. The present study was carried out to characterize the toxicity of ginsenoside Re after repeated oral administration in Sprague-Dawley rats.
A novel multi-interaction and mixed-mode stationary phase based on tetraazacalixarenetriazine modified silica (NCS) was synthesized and characterized by infrared spectra, elemental analysis and thermogravimetric analysis. Mechanism involved in the chromatographic separation is the multi-interaction including hydrophobic, ?-?, hydrogen-bonding, inclusion and anion-exchange interactions. Based on these interactions, successful separation could be achieved among polycyclic aromatic hydrocarbons, aromatic position isomers, organic bases and phenols in reversed-phase chromatography. Inorganic anions were also shown to be individually separated in anion-exchange chromatography by using the same column. Moreover, the results here also demonstrated that NCS based stationary phase could effectively reduce the adverse effect of residual silanol in the separation process. Such stationary phase with characteristics of multi-interaction mechanism and mixed-mode separation is potential for the analysis of complex samples.
A novel composite of vinyl group functionalized multiwalled carbon nanotubes (MWCNTs) molecularly imprinted polymer (MIP) was synthesized and applied as a molecular recognition element to construct an electrochemical sensor for parathion-methyl in this paper. The special molecular recognition properties of parathion-methyl mainly dominated by ?-?, p-? interaction and hydrogen bonding formed among functional monomer, template and matrix. A series of electrochemical experiment results proved that the prepared material had good adsorption capacity and fast mass transfer rate to parathion-methyl. The good selectivity of the sensor allowed fine discrimination between parathion and paraoxon, which had similar structures to parathion-methyl. The response of the MIPs was linearly proportional to the concentration of parathion-methyl over the range of 2.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) with a lower detection limit of 6.7 × 10(-8) mol L(-1) (S/N = 3). This sensor was also applied in the detection of parathion-methyl in pear and cucumber with average recoveries of between 94.9% and 106.2% (RSD < 5%) being obtained. The results mentioned above show that the novel electrochemical sensor is an ideal device for the real-time determination of parathion-methyl in real samples.
Diosgenin is a naturally occurring steroidal saponin abundantly present in many medical plants. In this study, diosgenin could significantly inhibit the growth of sarcoma-180 tumour cells in vivo, and remarkably increase thymus and spleen weights of S-180-bearing mice and upgrade the secretion level of TNF-? in serum. Moreover, diosgenin could stimulate lymphocyte transformation and enhance phagocytic capability of macrophages in vitro, and remarkably promoted the secretion of NO and TNF-? in macrophages. These results suggested that diosgenin could improve both specific and non-specific cellular immune responses, and the anti-tumour effects of diosgenin were achieved by immunostimulating properties instead of direct cytotoxicity.
Patterned hydrophobic Ni-P alloy films consisted of orderly and regular micro-nanoscale particles were fabricated through the synergistic effect of electrochemical deposition and chemical deposition. Ni-P alloy films were deposited for different times and characterized by scanning electro microscope (SEM). It was confirmed that the addition of reducing agent induced the formation of nanoscale particles, in contrast with pure Ni film deposited by single electrochemical deposition. As "point-discharge effect", the current density was higher at the edge of the nanoscale particles, and Ni ions would be deposited at the particles through the "point-discharge effect". Then the Ni-P alloy films grew by "reducing-discharging" process. The x-ray photoelectron spectroscopy (XPS) was used to detect the composition and valence states of these alloy films. The existence of oxidation state of element P in these films corresponding to that in H2PO3-, also gave a direct evidence for the occurrence of chemical deposition, during the electrochemical deposition process. The prolongation of deposition time could provide more time for the patterned morphology to grow up. The surface roughness, evaluated by surface profilometer, increased as the deposition time extension. And these films showed gradually increased hydrophobic properties with the increase in deposition time.
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