Contact Angle Measurement for Dispersed Microspheres Using Scanning Confocal Microscopy

Abstract

Scanning confocal microscopy was used for contact angle measurement of individual microspheres. The measurements were carried out by using different laser‐scanned layers of the particle floating on the air–water interface. The ratio of the diameter for the cross‐section of the protruded area of the particle at the air–water interface to the actual diameter of the particle is used for contact angle measurements. Two systems, i.e., glass and polystyrene microspheres with diameters of 3–10 and 6 µm, respectively, with water were used for this investigation (this size range of particles are most relevant to inhalation applications). Using the developed methodology, contact angles of 27° and 41° were measured (with water) for glass and polystyrene particles, respectively. The theoretical error in contact angle measurement for the developed methodology is determined to be generally about 1° with a maximum of 3° for contact angle of particles ranging from 2 to 24 µm in size; the experimental error was 4–6°. The contact angles of glass and polystyrene particles were compared to those obtained from pendant drop method and confirmed.     

Salinity Controlled Vesicle Formation and Growth in Aqueous Mixture of Aerosol OT/Triton X‐100

Mixed vesicles can be formed spontaneously from aqueous mixture of the double‐tailed anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) and the nonionic surfactant octylphenoxypolyethoxyethanol (Triton X‐100) under the inducement of salt, the formation mechanism of which should be attributed to the compression of salt on the electric bilayers of the head groups. The stability and the polydispersity of the vesicles are superior to single‐component AOT vesicles, which can be proved by the TEM image and visual observation. The vesicle region was presented in a pseudo‐ternary diagram of AOT/TX‐100/brine. The size of the vesicle was measured using dynamic light scattering. It is found that the vesicle size increases with the salinity but decreases with the content of TX‐100 in the mixture at the same salinity. Especially, the vesicle size is independent of the surfactant concentration at fixed salinity.     

Clouding and Hydrodynamic Behavior of Pluronic-Surfactant Interaction in Aqueous Salt Solutions

Clouding behavior of PEO-PPO-PEO and PPO-PEO-PPO block copolymers were studied in presence of sodium dodecyl sulfate (SDS) and NaCl. Extensive study of Pluronic P84 (EO₁₉PO₄₃EO₁₉) with different salts and ionic surfactants, were carried out using cloud point, viscosity and dynamic light scattering (DLS) measurements. The change in cloud point, as well as the size of P84 micelles in aqueous salt solution obeys the Hofmeister lyotropic series. Results on P84-ionic surfactant mixture indicate stronger interaction in case of SDS compared to those in presence of dodecyl trimethylammonium chloride (DTAC); here interaction seems to diminish in the presence of salts.     

Dispersed Structure of Ethanol‐Gasoline Fuel According to Dynamic Light Scattering Method

The dispersed structures of mixtures of five different gasolines with anhydrous ethanol were investigated by the dynamic light scattering (DLS) method. The aim of the work was to find whether these blends are colloid systems. Influence of different parameters was investigated to verify the results of this research. Ethanol‐gasoline blends were found to be colloid systems with the drop size of 20–150 nm.     

Small‐Angle Neutron Scattering (SANS) Study of Magneto‐Vesicles

Small‐angle neutron scattering from magneto‐vesicles (MVs) prepared by extrusion was studied. Contrast variation allowed the determination of structure and sizes of the vesicles and the encapsulated magnetic nanoparticles, respectively. The results from MVs synthesized with a 0.3% volume fraction of citrate‐coated magnetic nanoparticles are compared to those of similarly prepared vesicles of the neutral lipid 1,2‐Dioleoyl‐sn‐Glycero‐3‐Phosphocholine (DOPC) (without magnetic particles), and magnetic particles not encapsulated in vesicles. It is observed that the bilayers of the as‐prepared MVs, and the encapsulated nanoparticles retain their structural properties, highlighting the suitability of the MVs for applications.     

Solution Behavior of Poly(n-Isopropylacrylamide) in Water: Effect of Additives

The effect of different kinds of additives (electrolytes, nonelectrolytes, hydrotropes, and surfactants) on the cloud point (CP) of low molecular weight and narrow dispersed poly(n-isopropylacrylamide) (PNIPAM) synthesized via reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization was examined. The CP showed a concentration dependent variation and it is greatly modified in the presence of additives. The size of the random polymer coil at 30°C obtained from dynamic light scattering (DLS) measurements is often influenced by the presence of additives. We have explained the effects of different additives on PNIPAM in terms of their interaction with polymer and resultant changes in the coil structure.     

钯氮共掺杂TiO2的制备与表征及其可见光催化活性

在空气气氛和N₂中热处理表面均匀分散有尿素和氯化钯的纳米管钛酸,制备了两个系列Pd/N共掺杂的TiO₂光催化剂,并对所得样品进行了X射线衍射、透射电镜、X射线光电子能谱、紫外-可见漫反射光谱、荧光光谱和电子自旋共振等表征.结果表明,焙烧气氛对样品的形貌、晶体结构、光谱吸收、生成的氧空位浓度和可见光光催化性能的影响很大,其中在空气气氛中制备的样品光催化性能优于在N₂中制备的样品.在可见光(λ≥420nm)照射下,以丙烯为模型污染物考察了样品的光催化活性,发现在空气中400℃下焙烧的样品具有最佳的可见光催化活性.另外,讨论了Pd/N共掺杂TiO₂光催化剂具有可见光响应的机理,认为掺杂的Pd/N元素和制备过程中生成的氧空位是影响可见光催化性能的重要因素.     

Polymer colloids formed by polyelectrolyte complexation of vinyl polymers and polysaccharides in aqueous solution

The polyelectrolyte complex formed from the polyanion and polycation was studied by turbidimetry, static and electrophoretic light scattering, and elementary analysis. Sodium salts of polyacrylate (PA) and heparin (Hep) were chosen as the polyanion, and hydrochloric salts of poly(vinyl amine) (PVA) and chitosan (Chts) as the polycation. Although these vinyl polymers and polysaccharides have remarkably different backbone chemical structures and linear charge densities, all the four combinations PA-PVA, PA-Chts, Hep-PVA, and Hep-Chts provide almost stoichiometric polyelectrolyte complexes which are slightly charged owing to the adsorption of the excess polyelectrolyte component onto the neutral complex. The charges stabilize the complex colloids in aqueous solution of a non-stoichiometric mixture, and the aggregation number of the complex colloids increases with approaching to the stoichiometric mixing ratio. The mixing ratio dependence of the aggregation number for the four complexes is explained by the model proposed in the previous study.     

A small-angle X-ray scattering study of nanoparticle assembly in an aligned nematic liquid crystal

The assembly of colloidal particles in a nematic liquid crystal has been investigated using small-angle X-ray scattering. The structure and orientation of nanoparticle assemblies in bulk samples of aligned nematic liquid crystal have been determined. The method offers some advantages over optical microscopy, which is usually restricted to investigations of thin cells and micron-sized particles. The scattering from chains of particles has been calculated, and comparison with experimental results has shown that suspensions of 48 and 105 nm diameter silica nanoparticles formed highly ordered structures perpendicular to the liquid crystal director, consistent with quadrupolar defect-induced assembly.