Scalable Formation of Concentrated Monodisperse Lignin Nanoparticles by Recirculation-Enhanced Flash Nanoprecipitation

A highly controllable and scalable process for fabrication of large amounts of concentrated lignin nanoparticles (LNPs) is reported. These lignin core nanoparticles are formed through flash nanoprecipitation, however, scaling up of the fabrication process requires fundamental understanding of their operational formation mechanism and surface properties. It is shown how a semicontinuous synthesis system with a recirculation loop makes it possible to produce flash precipitated lignin nanoparticles in large amounts for practical applications. The roles of the process parameters, including flow rates and lignin concentration, are investigated and analyzed. The results indicate that the LNPs are formed by a process of continuous burst nucleation at the point of mixing without diffusive growth, which yields nanoparticles of highly uniform size following a modified LaMer nucleation and growth mechanism. This mechanism makes possible facile process control and scale-up. Effective control of the resulting nanoparticle size is achieved through the initial concentration of lignin in the injected solution. The impressive capability to produce suspensions of any predesigned multimodal distribution is demonstrated. The resulting nanofabrication technique can produce large volumes of concentrated LNP suspensions of high stability and tightly controlled size distributions for biological or agricultural applications.     

Assembling carbon nanotubosomes using an emulsion-inversion technique

Novel micro-capsules (carbon nanotubosomes) have been fabricated by cross-linking shells of amine-functionalized multi-walled carbon nanotubes (MWNTs) produced by their adsorption on water-in-oil emulsion drops followed by an emulsion-inversion.     

A unified model description of mobile and localized adsorption: I. MFA with nonadditive lateral interactions — an application to disordered adsorbed monolayer on a structureless substrate

A simple model is used to treat mobile adsorption on a structureless substrate. The influence of temperature on the state of motion of adsorbed particles is described by means of an interpolation formula used earlier in the theory of hindered rotation, whereas the influence of the nearest-neighbour potential with varying degree of coverage is accounted for in terms of a “free area”, available for individual particle motion, for which a simple analytical expression, based on an harmonic oscillator approximation, is obtained. An irregularity in the long range order of the adsorbed monolayer is introduced in terms of “varying distances”, resp. of varying energy bonds between the particles in dependence of the number of nearest neighbours actually present in the first coordination sphere of each particle (nonadditivity of the bonds).     

A unified model description of mobile and localized adsorption: II. Adsorption on crystalline surfaces — a gradual transition between mobile and localized adsorption

The model used in Part I is now extended to account for the periodic potential of the substrate. The influence of the energetical structure of the substrate on the state of motion of a single particle is allowed for at varying degree of coverage so that the gradual transition from localized to mobile adsorption with growing temperature may be described. The impact of the energetical characteristics of adsorbate and adsorbent on the critical parameters of the adsorption isotherms is investigated. These parameters are also considerably influenced when non-additivity of the lateral bonds is taken into account. On a perfectly smooth substrate, as well as in the case of potential wells of the substrate coinciding in size with the diameter of the adatoms, the model predicts the impossibility of a first order phase transition between “additive” and “nonadditive” phases. The last result could be related to the problem of 2D melting, provided the degree of disorder in both adsorbate phases is adequately expressed in terms of varying nonadditivity of the energy bonds.     

Massenspektrometrische untersuchungen der kondensation von dünnen schichten auf fremden unterlagen: I. Kinetik der adsorption und der desorption von Ag auf W

The adsorption and desorption kinetics of silver on clean polycrystalline tungsten were investigated with a mass-spectrometric technique. The deposition up to about 2 monolayers occurred without two-dimensional phase transformation. The thermal accommodation coefficient was found to be unity. The desorption energy and frequency factor for different coverages were determined. The bonding of silver atoms in the first monolayer was found to be localized. Additionally, thermal desorption experiments with linear heating rate were carried out.     

Massenspektrometrische untersuchungen der kondensation von dünnen schichten auf fremden unterlagen: II. Wachstums- und desorptionskinetik von Ag auf W

The growth and desorption kinetics of silver films on clean polycrystalline tungsten were investigated with a mass-spectrometric technique. The growth of the crystal phase started in the third monolayer by nucleation. This process occurred initially with increasing supersaturation until steady-state growth conditions were established. The evaporation coefficient β for the room-temperature films was unity. For the high-temperature films β was found to be lower than 1. The light and scanning micrographs showed that the silver films consist of isolated islands with strong epitaxial orientation to the substrate. The thermal desorption spectra confirmed qualitatively the island structure of the deposit. The kinetics data were explaned by the formation of diffusion zones around the growing cluster.     

A novel gel deformation technique for fabrication of ellipsoidal and discoidal polymeric microparticles

A simple fabrication technique for anisotropic particles of ellipsoidal/discoidal shape has been developed, based on stretching/compressing of oil-in-water emulsion templates embedded into an elastic aqueous gel; a range of solid anisotropic microparticles have been fabricated by polymerising of the deformed oil drops in the elastic gel matrix and their shape and aspect ratios have been studied as a function of the gel deformation.     

Fabrication of magnetically-functionalized lens- and donut-shaped microparticles by a surface-formation technique

We report a simple method for the preparation of magnetically-functionalized lens-like and donut-shaped polymeric microparticles, based on spreading a magnetite-doped paraffin-polymer solution at the air/water interface in the presence of an external magnetic field. We examine the parameters that affect the particle morphology and interfacial aggregation behaviour.     

A Model for Hydration Interactions between Apoferritin Molecules in Solution

We have studied how non-DLVO forces between molecules of the globular protein apoferritin in solution affect its osmotic second virial coefficient. A model explaining the effects of the solution ionic strength and pH on the interprotein interaction is developed, to give a physical interpretation of recently published experimental findings showing that the second virial coefficient of the protein apoferritin, supported by acetate buffer, goes through a minimum as a function of ionic strength. At low ionic strengths, the apoferritin second virial coefficient initially decreases with increasing sodium ion concentration, as DLVO theory predicts. However, non-DLVO hydration forces due to overlapping of the Stern layers of the protein molecules increase the second virial coefficient with further increase of sodium ion concentration, again as found experimentally at higher ionic strengths. The non-DLVO effect arises from ionic exchange between hydrogen and sodium ions at the protein surface. An adsorption shell of hydrated sodium ions forms around the protein molecules with increasing buffer concentration.