Search

Rice-shaped protein–copper oxide hybrid (RSPCO) was prepared by one-pot method in the presence of amphiphilic proteins. The enzyme-mimicking activity of RSPCO depends much on the substrate structure. RSPCO shows superior peroxidase-like activity with 3,3′,5,5′-tetramethylbenzidine (TMB) as a substrate. RSPCO exhibits both peroxidase- and oxidase-like activities with 1,2-diaminobenzene (OPD) as the substrate. RSPCO does not exhibit peroxidase-/oxidase-like activity when using 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonic acid)diammonium salt (ABTS) as the substrate. Furthermore, pyrogallol (PA)-induced activity switching effect is dependent on the type of enzyme-like activity of nanozyme and the substrate structure. The different effect of PA on the enzyme-like activity of RSPCO attributes mainly to the different affinity of substrates toward RSPCO. PA can significantly inhibit the peroxidase-like activity of RSPCO with TMB used as the substrate. Due to the efficient inhibiting effect, an excellent PA colorimetric sensor with low limit of detection being 15 nM (signal-to-noise ratio of 3) was developed based on RSPCO. With the features of simplification and low cost, protein–copper oxide hybrid nanozymes has the potential application in medial, environmental, and food areas. The present work provides new information about activity–structure relationship of copper oxide nanozyme, which is important for the applications of nanozymes in practice. [ABSTRACT FROM AUTHOR]

The individual compounds in an emulsion of tartaric acid stabilized by a commercial surfactant, Laureth 4, were brought into contact in order to estimate the deviation from equilibrium conditions during emulsion evaporation. The transfer of compounds between the phases was followed by visual observation of new phases appearing and the movement of the interfaces with time. The results revealed that, conversely to the equilibrium processes in the corresponding salicylate emulsions, in the present system the dissolution of the acid was faster than the formation of birefringent structures and the variation of different colloidal structures could be followed in the experiment. A suitable choice of initial ratio between the three compounds enabled the transfer of compounds to result in an early depletion of the solid acid and subsequently information could be obtained about the relation between the transport of surfactant and water-acid solution into the birefringent layer. A significant dependence was found between the composition of the entrants into the layer and the amount of surfactant liquid remaining. [ABSTRACT FROM AUTHOR]

Selected pairs of phases in the system, not in equilibrium, were brought into contact and the transport between them was evaluated from the changes in volumes with time. The results showed the rate determining factors to be the extremely slow absorption of compounds into the solid acid layer and of water into the surfactant inverse micellar solution. The former factor was referred to the protracted process of modifying the crystalline structure and the latter to the minute diffusion coefficient of the inverse micelles. In the same manner the contact between the lamellar phase liquid crystalline phase and a solid solution of the surfactant in the acid led to the formation of two inverse micellar solutions of different composition separated by a liquid crystalline layer instead of the expected aqueous liquid and one inverse micellar solution, which appeared first after significantly extended times. The equilibration was significantly retarded by the slow diffusion of acid molecules through one of the liquid layers. [ABSTRACT FROM AUTHOR]

The viscosity during evaporation was determined for emulsions in the system water, vegetable oil, a commercial surfactant, Tween 80R, and the results related to the phases of the emulsion according to the phase diagram. The correlation between the viscosity and the fraction of liquid crystal in the emulsion was pronounced for the emulsions with the oil as the dispersed phase. For the emulsions with oil as the major phase, the effect was significantly less. [ABSTRACT FROM AUTHOR]

The surface dilational modulus of the star-like block copolymer AP432 and linear block copolymer L64 was studied using the oscillating bubble method at an accessible frequency range of 0.05 to 2 Hz, which was compared with anionic surfactant sodium oleate (C17H33COONa) and the influence of inorganic salt NaNO3 on the surface dilational modulus of AP432 and L64 was also studied. The results indicate that for AP432 and L64 the dilational modulus varies slightly, just decrease gradually with concentrations increasing and never reaches high values with the dilational frequency increasing, but the dilational modulus of C17H33COONa increases gradually with the increase of dilational frequency and pass through the maximum values with increasing concentration. The properties of AP432, L64, and C17H33COONa at the air/water interface were also observed by surface tension measurement. Based on these experimental results, a simple possible adsorption model of these molecules at air/water interface is proposed. [ABSTRACT FROM AUTHOR]

The radical scavenging properties of puerarin are investigated in buffered hydroalcoholic media and Triton X-100 micellar solutions using the free-radical diphenylpicrylhydrazyl (DPPH•) method. The reactions, which follow the mixed second-order rate law, are investigated under pseudo-first-order condition by use of a large excess of puerarin. The rate constants (k2) observed for puerarin show notable pH dependence. These differences in reactivity of puerarin toward the oxidants at different acidity of the solution have been assumed to arise from the acid-base equilibrium of puerarin. The influence of acid-base equilibrium on bond dissociation energy for puerarin has also been investigated by means of DFT calculations. It has been concluded on the basis of these calculations that monoanionic form of puerarin is more powerful radical scavenger than the neutral molecule. When the reactions take place in Triton X-100 micelles, the radical scavenging properties of puerarin are enhanced. The results may be due to the special location of puerarin in Triton X-100 micelles. [ABSTRACT FROM AUTHOR]

Evaporation paths were calculated for aqueous solutions of polyethylene oxide (PEO) and polypropylene oxide (PPO) from the phase diagram. With the exception of solutions with a predominant fraction of one of the polymers the evaporation gave rise to phase separation for intermediate water contents. With similar restrictions for the fractions of the polymers the separated phase contained greater amounts of water and of PPO. In the two-phase region two consolute points were found, one at lower water content and greater PPO content; the other one with the opposite extremes. The difference in the composition of these two points was significantly greater for the polymers, approximately 0.4, than for the water content, less than 0.1. As a consequence there was a transfer of each polymer and of water between the phases during the evaporation. The evaporation of water took place preferentially from the phase with less water and more PEO, and in addition water as well as polymers was transferred from this phase to the one with less water and greater amount of PPO. The versatility of the phase diagram approach was demonstrated by displaying the variation in phase ratios and phase compositions as function of water weight fraction, water weight, and weight of the water evaporated. Another example of the same feature was a simple equation to obtain the amount of water to be added to a mutual solution of the two polymers in order to obtain the two phases in equal amounts. [ABSTRACT FROM AUTHOR]

A model is presented to provide quantitative measures to estimate the trends of the change in the penetration of the added component into the polar part of the amphiphile layer in lamellar liquid crystals of water and ethoxylated surfactants with added water (or polar solvents). The total thickness of the bi-layer is treated as composed of an aqueous layer, of a layer of the polar groups from the surfactant and of the hydrocarbon chains of the latter. A fraction α of the added water is assumed penetrating the polar group layer leading to its expansion. The evaluation is built on the fact that experimental determinations of the interlayer spacing in the overwhelming majority of cases show a first order linear dependence on the ratio of added water. In the model this linearity is obtained by variation of the degree of penetration of water. The model indicated a reduction in the degree of penetration with added water, which is a rational trend. The model demonstrates the earlier interpretation of a structure, whose interlayer spacing is invariant with water contents as nonswelling; for example, in which all added water penetrates the amhiphile layer, is not appropriate. The model demonstrates the constancy of the interlayer spacing to be a consequence of a balance between the expansion of the amphiphile layer and the increase of a "free water" layer. [ABSTRACT FROM AUTHOR]

The interphase electric properties of the SDS/ n ‐C 5 H 11 OH/L‐phenylalanine (L‐phe)/H 2 O system have been investigated by the method of AC impedance. The results show that at the constant weight ratio of n ‐C 5 H 11 OH/H 2 O=50/50 and the total L‐phe concentration, with an increase of the total concentration of sodium dodecyl sulfate (SDS) in the system, the structure of the upper phase always takes W/O (water/oil) form, whereas that of the lower phase changes from O/W (oil/water) to BI (bi‐continuous) when the total concentration of SDS reaches 3.0%. The microstructure transition of microemulsions at the SDS concentration of 3.0% makes the increase of the interphase capacitance and interphase charge‐transfer current apparently slow down with further increase of SDS concentration. In addition, L‐phe can transfer from the lower phase to the upper phase with increase of the total SDS concentration. At a constant concentration of SDS, with an increase of the total L‐phe concentration, the concentrations of L‐phe in both the upper and lower phases increase the interphase capacitance and the interphase charge‐transfer current of the system increase first rapidly and then slowly, but the interphase resistivity of the system decreases first rapidly and then slowly. [ABSTRACT FROM AUTHOR]

This article reports the lubrication of the mixed system of CdS nanoparticles and Triton X-100/C 10 H 21 OH/H 2 O lamellar liquid crystals. CdS nanoparticles could be synthesized in the lamellar liquid crystal's solvent layer, limited by its amphiphile bilayer. The CdS nanoparticles were spherical and the size was about 5 nm. The lubrication properties of the mixed system of the lamellar liquid crystal and CdS nanoparticles were determined. The results showed that the presence of CdS nanoparticles could improve the antiwear ability and extreme pressure property of Triton X-100/C 10 H 21 OH/H 2 O lamellar liquid crystals. [ABSTRACT FROM AUTHOR]

The hydrolysis of cephanone in water, cetyl trimethyl ammonium bromide(CTAB) micelle, and CTAB/n-C5H11OH/H2O O/W microemulsion was studied through UV-VIS absorption spectroscopy. The mechanism of the hydrolysis and the effects of both the acidity of the media and the composition of O/W microemulsion on the hydrolysis were studied. The results show that the hydrolysis rate of cephanone increases with the acidity. Compared with water, CTAB micelle and CTAB/n-C5H11OH/H2O O/W microemulsion suppress this hydrolysis. The inhibition of the hydrolysis of cephanone by CTAB micelle and CTAB/n-C5H11OH/H2O O/W microemulsion is related to the location of cephanone in the interphases of CTAB micelles and CTAB/n-C5H11OH/H2O O/W microemulsion droplets. [ABSTRACT FROM AUTHOR]

Lecithin liposomes were studied by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), IR, and GC-MS. Results indicate that titanium dioxide (TiO2) nanoparticles can gain access into lecithin liposomes during sonication and the lecithin liposomes can be effectively decomposed upon illumination with near-UV light. [ABSTRACT FROM AUTHOR]

Diffusion coefficients of different aggregates in aqueous solutions formed by an amphiphilic block copolymer, Pluronic F127 (F127), were determined by cyclic voltammetry, and the critical micelle concentration (CMC, 4.31 × 10[SUP-4] mol L[SUP-1]) of F127 was obtained. The added n-butanol facilitates the formation of micelles from the monomers of F127 and makes the critical micelle temperature (CMT) of F127 solutions decrease. The diffusion coefficient of the F127 micelles decreases relatively fast at first with increasing n-butanol and then the decreasing trend slows after the solubilization of n-butanol in micelles reaches maximum. [ABSTRACT FROM AUTHOR]

The interaction between malachite green (MG) and CTAB/n-C[SUBn]H[SUB2n + 1]OH /H[SUB2]O mixed micelles is studied by UV-Vis and fluorescent spectroscopy. The results show that MG can isomerize in CTAB micelles, but the isomerization effect decreases in CTAB-alcohol mixed micelles with the increase of the concentration and the chain length of alcohol. Further studies indicate that MG can be located in the outside of the palisade of CTAB-alcohol mixed micelles. The distribution coefficient K[SUBD] of MG between CTAB-alcohol mixed micelles and) the aqueous phase increases with the concentration and the chain length of alcohol. [ABSTRACT FROM AUTHOR]

In the Triton X-100/n-C[sub n]H[sub 2n+1]OH/H[sub 2]O system, the lamellar liquid crystalline region increases and the regions of O/W, W/O and bicontinuous microemulsion domains shrink, simultaneously, with the length of the chain in the unbranched aliphatic alcohol. In the O/W region, the Gibbs free energy for alcohol transfer from the water continuous phase to Triton X-100 micellar phase increases linearly with the chain length of alcohol. In the W/O region of the Triton X-100/n-C[sub n]H[sub 2n+1]OH/ n-C[sub 7]H[sub 16]/H[sub 2]O system, as the solubilized water content increases, the effective radius (R[sub e]), the inner water radius (R[sub W]), the thickness of the interfacial layer (L) and the average aggregation number (ñ) of the reverse micelles increase, whereas the total number (N[sub d]), the total interfacial area (A[sub d]) and the change of the standard free energy (Δ[sub c - i]G[sup 0]) for alcohol transfer from the oil continuous phase to the interfacial layer of the reverse micelles decrease; and with the longer chain alcohols, the values of R[sub e], R[sub W], L, and h all increase, while the Δ[sub c - i]G[sup 0] value decreases drastically with increasing chain length. In the lamellar liquid crystalline region, increasing the alcohol chain length can increase the stability of the lamellar liquid crystalline domain. All the results show that the alcohols, n-C[sub n]H[sub 2n+1]OH, can be used as cosurfactants in the nonionic surfactant system and function similarly as in ionic surfactant systems. [ABSTRACT FROM AUTHOR]

The hydrolytic kinetics of acetylsalicylic acid in different microemulsion systems have been studied. The results show that the hydrolytic rate is affected by the microemulsion structure and the type of surfactant. The break points of the hydrolytic rate are correspond to the break points in diffusion coefficient and in conductivity that we assign to the W/O, O/W, and bicontinuous structural transitions in the microemulsion single-phase regions. [ABSTRACT FROM AUTHOR]

The phase behavior and the structural properties of Triton X-100/nC[SUB8]H[SUB17]OH/PEG1000[SUBaq] system indicate that with increasing PEG1000, the partial phase diagram can be simplified, i.e. the lamellar liquid crystalline phase region (LLC) is gradually reduced. In Triton X-100 micelles and Triton X-100/n-C[SUB8]H[SUB17]OH/PEG1000[SUBaq] O/W microemulsion droplets, PEG1000 molecules can locate either in the surfactant interfacial layer or be adsorbed on this layer. In the LLC region, PEG1000 molecules exist in the aqueous layer or in the amphiphile bilayer. This collocation of the surfactant molecules results in less order and reduced stability of the LLC phase. [ABSTRACT FROM AUTHOR]

Photoinduced electron transfer reactions of anthracene with N,N-diethylaniline (DEA) and phenothiazine (PTZ) occurred in the membrane phase of the CTAB (hexadecyltrimethylammonium bromide)/n-C[SUB5]H[SUB11]OH (1-pentanol) / H[SUB2]O microemulsion. DEA and PTZ exist in the membrane phase of the microemulsion because the presence of vitamin-C (Vc) can change the quenching constant. The change of the quenching constant for the DEA-anthracene system with the presence of Vc is more obvious than that for the PTZ-anthracene system. Thus, the DEA molecules are much closer to the polar head of the microemulsion than PTZ. Compared with DEA, the distribution of PTZ in the microemulsion tends to follow Poisson statistics. [ABSTRACT FROM AUTHOR]