Novel Approach to Characterization of Rare Earth Complexation with 1, 5-Bis(2-Hydroxy-5-Chlorphenyl)-3-Cyanoformazan in Presence of Cetyltrimethylammonium Bromide

The ternary interaction of 1, 5 bis(2 hydroxy 5 chlorphenyl) 3 cyanoformazan (HCPCF) with cetyltrimethylammonium bromide (CTAB) and rare earths (RE: Yb, Dy, Er and Eu) was investigated at pH 9.84 by the microsurface adsorption spectral correction technique (MSASC). The aggregation of HCPCF on CTAB obeys the Langmuir isothermal adsorption and the interaction of RE with the HCPCF CTAB aggregate was first found to accord with the monolayer binding. The effects of temperature and ionic strength of solution on the aggregations were made. The binary aggregate and the ternary complex were characterized.

Determination of Proteins by Measuring Total Internal-reflected Resonance Light Scattering Signals on Water/Tetrachloromethane Interface with Evans Blue and Cetyltrimethylammonium Bromide

A sensitive and selective assay of proteins is proposed based on measuring the total internal-reflected resonance light scattering(TIR-RLS) signals produced on the water/tetrachloromethane(H_2O/CCl_4) interface. In an aqueous medium with pH value in the range of 3.29—3.78, electrostatic attraction occurs between the negatively charged Evans Blue(EB) and positively charged proteins, forming hydrophobic ion associates and resulting in EB-protein adsorption on H_2O/CCl_4 interface. The presence of cetyltrimethylammonium bromide prompts this adsorption, resulting in strongly enhanced TIR-RLS signals. The intensity of the enhanced TIR-RLS at 360—370 nm was found to be proportional to the concentration of proteins. For bovine serum albumin and human serum albumin, the linear range of detection is 0.07—1.2 μg/mL and the limits of detection are 6.68 and 6.30 ng/mL(3σ), respectively, while for lysozyme, the linear range of detection is 0.06—1.0 μg/mL and the limit of detection is 6.0 ng/mL(3σ). The content of the total albumin in a human urine sample could be directly determined by using the standard addition method with a percent recovery of 97.6%—104.1%, and the RSD ranging from 1.9% to 4.2%.

EFFECT OF ORTHO-METHOXYCINNAMIC ACID ON THE SOL-GEL TRANSITION OF METHYLCELLULOSE SOLUTIONS IN THE PRESENCE OF CETYLTRIMETHYLAMMONIUM BROMIDE

The sol-gel transition of methylcellulose （MC） solutions in the presence of ortho-methoxycinnamic acid （OMCA） or cetyltrimethylammonium bromide （CTAB） and in the coexistence of OMCA and CTAB was determined by the rheological measurement. It has been found that the sol-gel transition temperature of MC solutions increases linearly with the concentration of either OMCA or CTAB in solution, respectively. However, in the coexistence of OMCA and CTAB, the sol-gel transition temperature of MC solutions remains invariable, independent of the concentration of CTAB in solution. The experimental results show that OMCA has priority to adsorb on the methyl group of MC chains to form polymer-bound aggregates. In particular, these aggregates inhibit the hydrophobic interaction between CTAB and the methyl group of MC chains completely. Taking into account the fact that OMCA is almost insoluble in MC-free solutions but dissolves very well in aqueous MC solutions, we propose the formation of the core-shell architecture prompted by OMCA and the methyl group of MC chains, with the methyl group of MC chains serving as the core and the self-assembly of OMCA molecules serving as the shell. Obviously, the formation of the core-shell structure increases the solubility of OMCA, improves the stability of methyl groups of MC chains at high temperatures and inhibits the hydrophobic interaction between CTAB and the methyl group of MC chains in solution. The abnormal behavior relating to the sol-gel transition of MC solutions in the presence of OMCA or in the coexistence of OMCA and CTAB is therefore explained. Upon UV irradiation, the sol-gel transition temperature of MC solutions in the presence of OMCA, or in the coexistence of OMCA and CTAB, decreases notably. However, the dependence of the sol-gel transition temperature of MC solutions as a function of OMCA concentration, or CTAB concentration in the presence of OMCA, does not change after UV irradiation.

Influence of Low Cetyltrimethylammonium Bromide Concentration on the Interactions and Properties of Hemoglobin with Acyclovir

The effects of cetyltrimethylammonium bromide （CTAB） on the properties of hemoglobin （Hb） at low CTAB concentration were studied in Hb/acyclovir/CTAB system by the methods of UV-Vis spectrum, fluorescence, zeta potential, conductivity and negative-staining transmission electron microscope （TEM）. With the increase of CTAB concentration, the UV peak intensity at 276 nm, the intrinsic fluorescence, the zeta potential of Hb and the system conductivity were all enhanced. Hb was easily oxidized to oxyHb and hemichrome. In Hb/acyclovir/CTAB system, CTAB made the UV-Vis spectrum, fluorescence, conductivity and conformation of Hb tend to be returned to those of the original Hb but the zeta potential not to do so. The UV absorption peak of Hb-acyclovir complex disappeared and the tight structure of Hb aroused by acyclovir was refolded. When CTAB concentration was higher than 5 × 10 ^5 mol/L, the two absorption peaks at 536 and 576 nm appeared again, and the Hb structure became looser again.

Spectrofluorimetric Determination of Tetracycline Using Eu^(3+)Chelation and Cetyltrimethylammonium Bromide

The fluorescence of tetracycline was greatly enhanced by chelation with Eu 3+ in Tris HCl buffer (pH8.5). The addition of cetyltrimethylammonium bromide, a cationic surfactant, further enhanced the fluorescence of tetracycline Eu 3+ chelates.This spectrofluorimetric method for the determination of tetracycline yielded a linear responeses in the range of 10 nmol/L 10 μmol/L. The detection limit was 5 nmol/L (or 2.22 ng/mL).The recovery of tetracycline spiked in serum at levels of l and 0.09 μg/mL was 97.9% and 97.8%, respectively. This method is fast, sensitive and suitable for the determination of tetracycline in biological specimens.

Preparation and Properties of the Heteropolyoxometalates of Large Organic Cation with Molybdotungstosilicic Acids

Some new heteropolyoxometalates of large organic cations with molybdotungstosilicic acids （general formula： （CTMA）4SiMoxW12-xO40·mH2O·nDMF, x=0,2,4,6,8,10,12） were prepared by the reaction of cetyltrimethylammonium bromide （CTMAB,C16H33N（CH3）3Br） with H4SiMoxW12-xO40（x=0,2,4,6,8,10,12） in aqueous solution and recrystallization in DMF, and characterized by elemental analysis, IR spectra,TG- DTA and XRD techniques. The IR spectrum confirms the presence of Keggin structure and organic cations in these compounds, and it is indicated that the stretching vibration of the M-Od, M-Ob-M and Si-Oa becomes more red-shifted when molybdenum is gradually substituted for the tungsten atom. In particular, the thermal decomposition of the heteropolyoxometalates was studied in nitrogen atmosphere. The TG-DTA curves show that their thermal behaviors not only contain the release of water molecule, DMF molecule, CTMA and its fragments but also contains simultaneous collapse of Keggin anion. Their end products of the thermal decomposition are the mixture of WO3, MoO3 and SiO2. And from the final decomposition temperature of view, it is found that the thermal stability of these compounds gradually is decreased when the number of molybdenum atoms is increased.

Surfactant-enhanced electrochemical detection of bisphenol A based on Au on ZnO/reduced graphene oxide sensor

Bisphenol A(BPA),one of the most commonly used plastic organic monomers,is widely used in manufacturing food packaging and containers.However,the gradual emissions of BPA from manufacturing plastic products bring great potential in human health threats,which urgently need to develop a simple and rapid method for detecting BPA.Cetyltrimethylammonium bromide(CTAB),a typical surfactant,is used to enhance the electrochemical detection of trace endocrine disruptors due to the fact that it can effectively enrich and absorb hydrophobic phenolic compounds through the hydrophobicity of its long-chain alkanes.Based on these,the present study reports a ternary composite of Au on zinc oxide/reduced graphene oxide nanosheets(Au/ZnO/rGO)as electrochemical sensor for detecting BP A.With the addition of CTAB,the analytic performances toward BP A detection are significantly improved 3.8 times compared with those without CTAB.The pH,accumulation potential and time are optimized.Moreover,the electrochemical activity of CTAB/Au/ZnO/rGO sensor is also evaluated by cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS),differential pulse voltammetry(DPV)and scan rate.The sensor displays two linear range from 10to 1340 nmol·L^(-1)and 1340 to 10,000 nmol·L^(-1),and a low detection limit of 4.95 nmol·L^(-1).Lastly,the sensor also exhibits good reproducibility,selectivity and potential practical application for BPA detection in real samples.

Preparation of Mesoporous Nano-Hydroxyapatite Using a Surfactant Template Method for Protein Delivery

Mesoporous nano-hydroxyapatite （n-HA） has gained more and more attention as drug storage and release hosts. The aim of this study is to observe the effect of the ratio of surfactant to the theoretical yield of HA on the mesoporous n-HA, then to reveal the effect of the mesoporous nanostructure on protein delivery. The mesoporous n-HA was synthesized using the wet precipitation in the presence of cetyltrimethylammonium bromide （CTAB） at ambient temperature and normal atmospheric pressure. The morphology, size, crystalline phase, chemical composition and textural characteristics of the product were well characterized by X-ray Powder Diffraction （XRD）, Fourier Transform Infrared Spectroscopy （FTIR）, Scanning Electron Microscopy （SEM）, Transmission Electron Microscopy （TEM）, Dynamic Light Scattering （DLS） and N2 adsorption/desorption, respectively. The protein adsorption/release studies were also carried out by using Bovine Serum Albumin （BSA） as a model protein. The results reveal that the mesoporous n-HA synthesized with CTAB exhibits high pure phase, low crystallinity and the typical characteristics of the mesostructure. The BSA loading increases with the specific surface area and the pore volume of n-HA, and the release rates of BSA are different due to their different pore sizes and pore structures, n-HA synthesized with 0.5% CTAB has the highest BSA loading and the slowest release rate because of its highest surface area and smaller pore size. These mesoporous n-HA materials demonstrate a potential application in the field of protein delivery due to their bioactive, biocompatible and mesoporous properties.

Direct self-assembly of CTAB-capped Au nanotriangles

Densely packed and ordered ＂suprastructures＂ are new types of nanomaterials exhibiting broad applications. The direct self-assembly of cetyltrimethylammonium bromide （CTAB）-capped gold nanotriangles to form ＂suprastructures＂ was systematically investigated by varying the temperature and tilt angle of the silicon wafer used in the assembly process. Under optimal conditions, nanotriangles form into regular patterns, maintain their integrity, and form edge-to-edge, point-to-point, and face-to-face connections to form ordered ＂suprastructures＂ within an area of hundreds of square microns, achieving a high level of regularity. The formation of the ＂suprastructures＂ under optimal conditions could be mainly attributed to the complex balance between multiple temperature-dependent factors, including the atom diffusion rate, solvent evaporation rate, self-assembly rate, and the time for which the nanoparticle stays in the wet medium.

CTAB Assisted Synthesis of CuS Microcrystals:Synthesis,Mechanism,and Electrical Properties

CuS microcrystals were successfully prepared through a mild solvothermal reaction in ethylene glycol （EG） with the assistance of cationic surfactant cetyltrimethylammonium bromide （CTAB）. An interesting morphology evolution from flower-like microspheres to hollow microspheres, and finally to smooth nanoflakes was observed when increasing the amount of CTAB. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and UV-vis spectroscopy. It was found that the amount of CTAB played an important role in determining the morphology of the CuS microcrystals. Electrical measurement reveals that the as-prepared CuS microspheres were of high conductivity, which might favor their device applications. It is expected that CuS microcrystals with controlled morphologies and structures will have important applications in solar cells. This simple but effective method could also be extended to the controlled growth of other inorganic microcrystals.

A conductive anionic Co-MOF cage with zeolite framework for supercapacitors

Conductive MOFs could exhibit full potential as integrated electrode materials for supercapacitors without interference from additional conductive additives.Here we report an anionic Co-MOF cage with zeolite framework,which was balanced by the redox-active guest [Co(H2O)6]2+ and protonated[(CH3)2NH2]2+ ions.Benefit from the unique ion skeleton structure,Co-MOF exhibits a conductivity higher than most of reported MOFs with the value of 1.42 × 10^-3 S/cm,which can be directly fabricated as electrode for supercapacitors.A maximum specific capacitance of 236.2 F/g can be achieved at a current density of 1 A/g of Co-MOF.Additionally,the electric performance and morphology of this Co-MOF can be modified by cetyltrimethylammonium bromide(CTAB) and the maximum specific capacitance could increase up to 334 F/g at 1 A/g when the ratio of ligand and CTAB is 1:6(Co-MOF-6).Furthermore,the specific capacitance can retain at 64.04% and 77.92% of the initial value after 3000 cycles of Co-MOF and Co-CTAB-6,respectively.Obviously,the addition of CTAB further improves both capacitance and cycle stability.