This paper describes the mechanistic details of an electrochemical method to control the withdrawal of a liquid metal alloy, eutectic gallium indium (EGaIn), from microfluidic channels. EGaIn is one of several alloys of gallium that are liquid at room temperature and form a thin (nm scale) surface oxide that stabilizes the shape of the metal in microchannels. Applying a reductive potential to the metal removes the oxide in the presence of electrolyte and induces capillary behavior; we call this behavior “recapillarity” because of the importance of electrochemical reduction to the process. Recapillarity can repeatably toggle on and off capillary behavior by applying voltage, which is useful for controlling the withdrawal of metal from microchannels. This paper explores the mechanism of withdrawal and identifies the applied current as the key factor dictating the withdrawal velocity. Experimental observations suggest that this current may be necessary to reduce the oxide on the leading interface of the metal as well as the oxide sandwiched between the wall of the microchannel and the bulk liquid metal. The ability to control the shape and position of a metal using an applied voltage may prove useful for shape reconfigurable electronics, optics, transient circuits, and microfluidic components. 相似文献
The complex formation equilibrium of ethylenediaminetetramethylenephosphonic acid (EDTMP, H8L) with iron (III) has been studied potentiometrically at 25°C and an ionic strength of 0.2 M (NaCl). The successive protonation constants of ligand EDTMP and the complex formation constants were determined with the PSEQUAD program. Keeping in view the biological studies, the speciation in the system Fe (III)—EDTMP was calculated and drawn with the HySS computer program, and pFe values are compared. 相似文献
We have successfully developed a ‘turn-on’ colorimetric chemosensor for Fe3+ based on 1,10-phenanthroline. An amide derivative of 1,10-phenanthroline 4 was developed for the selective recognition of Fe3+ over Co2+, Cr3+, Cu2+, Mn2+, Ni2+, Ag+ and Zn2+ and could measure Fe3+ concentration in the range of 15–210 μM by UV–vis spectroscopy. Moreover, the addition of Fe3+ to a colourless solution of 4 turned its colour to light pink, indicating that 4 is capable of detecting Fe3+ by the naked eye. Compound 4 exhibits a major absorption band centred at 268 which shifted to 278 nm after addition of Fe3+, and a shoulder band around 514 nm was also observed. The complexation of Fe3+ with 4 was analysed at a different pH and favourable binding was observed at pH 6.2. 相似文献
Solanopubamine (3β-amino-5α, 22αH, 25βH-solanidan-23β-ol), a steroidal alkaloid was isolated from the alkaloidal fraction of Solanum schimperianum in significant yield. Its structure was established by IR, positive ESI-MS, 1D and 2D NMR. The presence of -3β-NH2 and -23β-OH groups was achieved through methylation, acetylation or coupling with octadecanoic and undec-11-enoic acids to produce six derivatives (2–7). Their structures were confirmed by spectroscopic analyses. Solanopubamine and semi-synthetic analogs are investigated for their in vitro cytotoxicity against a panel of human cancer cell lines and anti-microbial activity. Solanopubamine showed good antifungal activity only against Candida albicans and C. tenuis with MIC of 12.5 μg/mL. Semi-synthesized compounds (2–7) have failed to show anti-tumor and anti-microbial activities. 相似文献
The electrochemistry of some quinones has been focused to determine the mode of interaction in presence of polyalcohols. Three compounds of each family (benzoquinones, naphthoquinones and anthraquinones) were investigated through cyclic voltammetry in the presence of ethylene glycol (a diol)) and glycerol (a triol) in dichloromethane and acetonitrile at 25°C. The observed positive shift in both the waves of the quinone with successive addition of alcohol was attributed to hydrogen bonding in the quinone-alcohol couple. “Two electron one step” electron transfer mechanism was proposed for the increase in the first wave height at the expense of second. The depletion of the first anodic wave at higher concentration of polyalcohol was rationalized in terms of protonation-deprotonation mechanism. A prior peak observed in the presence of glycerol was ascribed to the hydrogen bonding of the alcohol with neutral quinone. The difference in basicity strength within a family as well as among the three quinone families was also addressed in view of the interaction effectiveness. 相似文献
An optimum nanoprecipitation technique for gelatin nanoparticles is established, based on aqueous gelatin solution and ethanolic solution containing stabilizer. Crosslinking with glutaraldehyde results in stable gelatine nanoparticles. Several factors such as the surfactant concentration, type of surfactant, type of nonsolvent and gelatin concentration are evaluated. Gelatin nanoparticles with 200–300 nm can be produced using 20–30 mg mL?1 of gelatin and a minimum of 7% w/v stabilizer (Poloxamer 407 or 188). Furthermore, methanol and ethanol are good nonsolvents, whereas other nonsolvents such as acetone, isopropyl alcohol, and acetonitrile, result in phase separation and visible precipitates. The entrapment efficiency of fluorescein‐isothiocyanate (FITC)‐dextran as model drug was determined to 50% with no substantial effect on particle size. 80% of the drug is only released after enzymatic digestion.
An on-line scandium preconcentration and determination method was developed with spectrophotometer associated with flow injection. Scandium from aqueous sample solution of pH 4.5 was selectively retained in the minicolumn containing XAD-4 resin impregnated with nalidixic acid at a flow rate of 11.8 mL min?1 as scandium–nalidixic acid complex. The scandium complex was desorbed from the resin by 0.1 mol L?1 HCl at a flow rate of 3.2 mL min?1 and mixed with arsenazo-III solution (0.05 % solution in 0.1 mol L?1 HCl, 3.2 mL min?1) and taken to the flow through cell of spectrophotometer where its absorbance was measured at 640 nm. The preconcentration factors obtained were 35 and 155; detection limits of 1.4 and 0.32 μg L?1 and sample throughputs of 40 and 11 were obtained for preconcentration time of 60 and 300 s, respectively. The tolerance limits of many interfering cations like Th(IV), U (VI), rare-earths and anions like tartrate, citrate, oxalate and fluoride were improved. The method was successfully applied to the determination of scandium from mock seawater samples and good recovery was obtained. The method was also validated on certified reference material IAEA-SL-1 (lake sediment) and the result was in good agreement with the reported value. 相似文献