Aqueous Dispersions Research Articles

Silicon nanowire aqueous dispersions for processing into macroscopic network materials.

Nanowires and other high aspect ratio nanoparticles are building blocks to form network materials in formats such as films, sheets, fibres and electrodes that thus bridge the nano and macro scales. The assembly of nanowire network materials is enabled by a new floating catalyst chemical vapour deposition synthesis method that produces crystalline silicon nanowires (SiNW) on a scale of grams per day. Here, we produce SiNW dispersions in water by sonication through steric and electrostatic stabilisation of the negatively charged particles in basic pH or with cationic surfactants. Negative charge arises from the 1.3 nm-thin native oxide layer. Some permanent aggregates are found as a consequence of cross-links between the thin oxide at the surface of adjacent SiNWs. Removing them by centrifugation yields SiNW dispersions of 52 μg mL-1. Processing into macroscopic materials is demonstrated as transparent films and as freestanding sheets. In the sheets, the SiNWs are predominately aligned parallel to the sheet thickness, as a paper-like SiNW solid with tensile strength above 10 MPa, modulus above 1 GPa and toughness of 0.5 J g-1.

A combined experimental and DFT study of metal core/indocyanine green shell hybrid nanoparticles

Indocyanine green (ICG) is the FDA-approved fluorescent dye used for in vivo medical imaging, diagnostics, and photothermal therapy. However, this dye is easily degradable in the human vascular system, and therefore its stabilization is preferable. In this work, ICG molecules were stabilized by their adsorption on the surface of the L-methionine-capped Ag and Au nanoparticles (Ag and Au @LM NPs) in aqueous colloidal dispersions. The result is the formation of hybrid metal core/ICG shell NPs in colloidal dispersions. Additionally, colloidal dispersions were stabilized, indicating a double effect of ICG adsorption. The obtained hybrid NPs were studied experimentally (UV–Vis spectrophotometry, HRTEM, DLS, FTIR) and theoretically (DFT calculations). HRTEM revealed that the interplanar spacing between adjacent planes of NPs decreases after the dye adsorption. The results obtained from the DFT study confirmed the formation of a covalent bond between the oxygen from ICG dye SO3− group and metal NPs. Considering the characteristics of both components of the NPs/ICG hybrid system, the authors assume that this hybrid system can exhibit the synergistic effect that could lead to more successful theranostic treatment of cancer in nanomedicine.

Effect of Film Morphology on Electrical Conductivity of PEDOT:PSS.

Commercially available formulations of the popular conductive polymer, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) are aqueous dispersions that require the addition of secondary dopants such as dimethyl sulphoxide (DMSO) or ethylene glycol (EG) for fabricated films to have the desired levels of conductivity. CleviosTM F HC Solar, a formulation of PEDOT:PSS produced by Heraeus, GmbH, achieves over 500 S/cm without these secondary dopants. This work studies whether secondary dopants such as DMSO have any additional effect on this type of PEDOT:PSS. The temperature dependencies of the conductivity of F HC Solar spin-coated thin films measured using a four-probe method seem to exhibit different charge transport properties compared with secondary doped PH1000. Observations made using atomic force microscopy (AFM) show that different concentrations of DMSO affect the orientation of the PEDOT domains in the thin film. These morphological changes cause room temperature conductivity to reduce from 640 S/cm in pristine films to as low as 555 S/cm after adding 7 wt% of DMSO along the film. Such tuning may prove useful in future applications of PEDOT:PSS, such as nanoprobes, transistors and hybrid solar cells.

Lightweight ZnO/Carbonated Cotton Fiber Nanocomposites for Electromagnetic Interference Applications: Preparation and Properties.

Electromagnetic wave pollution has become a significant harm posed to human health and precision instruments. To shelter such instruments from electromagnetic radiation, high-frequency electromagnetic interference (EMI) shielding materials are extremely desirable. The focus of this research is lightweight, high-absorption EMI shielding composites. Simple aqueous dispersion and drying procedures were used to prepare cotton fiber (CF)-based sheets combined with various zinc oxide (ZnO) contents. These composites were carbonated in a high-temperature furnace at 800 °C for two hours. The obtained CF/ZnO samples have densities of 1.02-1.08 g/cm3. The EMI shielding effectiveness of CF-30% ZnO, CF-50% ZnO, and CF-70% ZnO reached 32.06, 38.08, and 34.69 dB, respectively, to which more than 80% of absorption is attributed. The synergetic effects of carbon networks and surface structures are responsible for the high EMI shielding performance; various reflections inside the interconnected networks may also help in improving their EMI shielding performance.

Waterborne Polymer Coatings with Bright Noniridescent Structural Colors.

Structural color pigments offer an efficient, sustainable, and environmentally friendly approach to obtain waterborne polymer coatings. We developed polymer-based spherical photonic pigments to incorporate in aqueous dispersions of polymer nanoparticles used to obtain waterborne polymer films. Our spherical photonic pigments are assembled from polymer nanoparticles and are highly stable in water dispersion, maintaining their optical properties in the final polymer films. Unlike conventional dyes and pigments, which are prone to photobleaching because they are based on the absorption of light, photonic pigments rely on the selective reflection of light by their nanostructure and therefore are not photodegraded. Furthermore, different colors can be obtained from the same materials, changing only their nanostructure, in this case, the size of the polymer nanoparticles. Our novel spherical photonic pigments are noniridescent and can be incorporated in aqueous polymer nanoparticle dispersions without deteriorating their structure to produce waterborne polymer coatings with structural color. This approach for structural colored waterborne polymer coatings is efficient, simple, and environmentally friendly, offering excellent prospects for application in paints and coatings.

Stability of Nano-Sized Aqueous Dispersion of n-Heptadecane to Thermal Cycling

A stable aqueous dispersion of n-heptadecane was prepared by ultrasonification without the addition of surfactants. Using the dynamic light scattering, the characteristic size (hydrodynamic radius) of the dispersion‘s particles (100 nm) was determined. On the basis of temperature dependence measurements of scattered light intensity, the temperatures of melting, crystallization and transition to rotator phase of n-heptadecane particles in the studied dispersion were determined. The results obtained are in good agreement with literature data. It has also been experimentally shown that this aqueous dispersion can withstand up to 400 thermal cycles of heating and cooling from 3 °C to 30 °C, retaining ist colloidal stability. The results obtained allow to consider this dispersion as a promising basis for the development of Phase Change Materials.

Quantitative evaluation of adsorption behavior of carboxymethylcellulose on carbon nanotubes by time-domain NMR with the aim of obtaining stable dispersions

This study applied time domain NMR (TD‐NMR) to investigate the effect of carboxymethylcellulose (CMC) adsorption on the dispersion of carbon nanotubes (CNTs) in water. In many aqueous dispersions, the relaxation time measured by TD‐NMR is dominated by bound water on the particle surface. In contrast, since CMC molecules are adsorbed on the hydrophobic surface of CNTs, we proposed a model where relaxation times of hydration water of CMC adsorbed on CNTs, hydration water of free CMC, and bulk water are dynamically averaged in the TD‐NMR measurement. In this study, conversely, we presented the procedure to calculate the fraction of CMC adsorbed on CNTs from the measured relaxation time. Since the adsorbed layer of CMC can stabilize CNTs, the amount of adsorbed CMC is expected to be closely related to the dispersion state of CNTs. TD‐NMR measurements of CNT slurrys with different CMC concentrations showed that the adsorption ratio reached almost 100% (adsorption saturation) when the CMC concentration became larger than that of CNTs. At the adsorption saturation, it was confirmed that the CNT slurry exhibited the lowest apparent viscosity, and the model electrode showed the highest electro-conductivity. In addition, we demonstrated that the adsorption ratio is helpful to assess the dispersion state of CNTs and to optimize the dispersion process. The current study showed that TD‐NMR is very useful for quantitative evaluation of sterically stabilized dispersions because it can evaluate the adsorption rate of adsorbed polymers without dilution.

Quantum Yield of the Emission of Carbon Quantum Dots: Tricks Due to Solvent Polarity and Excitation Dynamics

Carbon quantum dots (CQDs) are recognized as promising fluorescent nanomaterials possessing high thermal stability, tuned photoluminescence, along with the low cost of their production. Quantum yield (QY) of photoluminescence (PL) of CQDs is known to vary largely depending on the synthetic procedures/ chemical composition of CQDs, but there is still no unique approach for explanation of the nature and QY of PL emission of CQDs. Particularly, an accompanying effect of the solvent environment on QY of the PL emission is paid less attention. In this work, we compare photophysical properties of CQDs synthesized by different methods that resulted in the different composition of CQDs. First, fluoralkylated CQDs (Fluocar® Nano) doped with F, N and O heteroatoms, were synthesized via solvothermal method using urea, anhydrous citric acid and 3-(trifluoromethyl) aniline as precursors. Second, hydrophilic CQDs were obtained by liquid-phase synthesis procedure using sucrose (“standard” CQDs). Depending on the synthesis procedure the PL emission properties were tuned according to the polarity of solvent the CQDs were dispersed in. It was found that QY of PL emission of Fluocar® Nano has a much stronger magnitude and absolute dependence on the solvent polarity compared to “standard” CQDs. Fluocar® Nano demonstrated QY of PL emission as high as 93% in dioxane and as low as 30% in aqueous dispersion, whereas QY of the “standard” CQDs varied within 0.7-2.3% when relative solvent polarities ranged from 0.164 to 1.0; however, their relative changes depending on the solvent polarity were similar (Fig.1). Dynamics of the PL emission during first minute of excitation in the form of PL relaxation to some saturated value was also strong for Fluocar® Nano dispersed in less polar solvents, while the emission was stable in a strongly polar aqueous medium. Tentative conclusion was made that the surface of CQDs plays a crucial role in tuning the PL emission, providing different concentration of surface traps that become gradually fed during excitation and different interactions of CQD and polar solvents, respectively. Figure 1

Development of Highly Active Pt/C-Based Catalysts for the ORR Using an Ordered Mesoporous Carbon with Network Structure As a Support Material: Focus on the Pt Loading Process

[Introduction]In order to improve the performance of polymer electrolyte fuel cells (PEFCs) for automobiles, ordered mesoporous carbons (OMCs) have attracted attention as supports for Pt as a cathode catalyst. Our research team has successfully synthesized a network-structured OMC (Net-OMC), in which primary OMC particles on the order of several tens of nanometers have a strong network structure, unlike conventional OMC particles, which are typically several micrometers in size. The Net-OMC consists of nanometer-order primary particles, and well-developed macropores (primary and secondary pores) derived from the network structure, which realizes both high Pt dispersion and efficient mass transport. In addition, Pt nanoparticles supported on Net-OMC should be loaded within the nanopores at an appropriate depth position. This will allow the nanopores to be accessible while preventing direct contact between the Pt surface and the ionomeric binder, with resulting poisoning, while also maintaining effective proton transport.RDE measurements revealed that the Pt/Net-OMC catalyst showed higher mass activity for the ORR and higher durability for potential-step cycling compared with a commercial Pt/CB catalyst [1]. These results suggest that the aggregation and sintering of the Pt particles were successfully suppressed due to the nanopore structure.In order to further improve the catalytic activity of the Pt/Net-OMC catalyst, it is also necessary to uniformly load Pt into the nanopores at an appropriate size and depth during catalyst preparation. However, even when using the colloidal technique, which has been established for loading Pt on carbon black, it has been difficult to achieve good Pt dispersibility with conventional protocols due to the tendency of the Pt to aggregate on the Net-OMC [2]. Therefore, in this study, the conventional colloidal technique was optimized for loading Pt on the Net-OMC support.[Experimental]Loading of PtOx on Net-OMC was carried out by mixing an aqueous solution of PtOx colloid with an aqueous dispersion of Net-OMC powder, followed by heat treatment at an appropriate temperature. During this process, the slurry pH (pH 3~11), heating temperature (40~80 °C) and heating time (10~180 min) were varied to investigate their effects. The resulting slurries were then filtered, dried and reduced at 300 °C for 3 hours in flowing hydrogen to obtain Pt/Net-OMC.The morphology of the Pt/Net-OMC was observed by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). Cyclic voltammetry and linear sweep voltammetry were carried out using the conventional rotating disk electrode (RDE) technique. Furthermore, membrane-electrode assemblies (MEAs) were prepared using Pt/Net-OMC as a cathode catalyst and evaluated for catalytic activity according to an FCCJ protocol using a Japan Automobile Research (JARI) standard cell.[Results and Discussion]The variation of Pt loading behavior with slurry pH revealed that Pt tended to aggregate when the pH was below 5, while the Pt loading amount significantly decreased when the pH was above 6 (Fig. 1, Table 1). These results indicate that the optimum slurry pH was ca. 5.5 to obtain a high dispersion of Pt. It was also found that the optimum temperature for Pt loading was ca. 50 °C; when the temperature was below 40 °C, the loading amount decreased significantly, and when the temperature was above 80 °C, some of the Pt particles formed aggregates. It was also found that the Pt particles showed continuous growth, with a linear dependence of the Pt aggregate size on the loading time at 50 °C.Based on the TEM observation, the average Pt particle size on the Pt/Net-OMC that had been heated at 50 °C for 1 hour was ca. 3 nm, and the particles exhibited good dispersion. Also, the correlation between the supported state of Pt and the catalytic activity of the Pt/Net-OMC will be discussed in detail.[1] T. Miyao, H. Nishino, H. Yamazaki, S. Sato, K. Tamoto, M. Uchida, A. Iiyama, K. Shibanuma, N. Koizumi, , the 242nd ECS Meeting, #I01D-1578.[2] M. Watanabe, M. Uchida and S. Motoo, J. Electroanal. Chem., 229, 395-406 (1987)Acknowledgement: This work was partially supported by the ECCEED’30-FC project from NEDO. Figure 1

Preparation and characterization of magnetic microgels with linear thermosensitivity over a wide temperature range

Abstract Hybrid nanogels that are both thermosensitive and superparamagnetic, and have good biocompatibility are expected to have applications in the biomedical field. In this article, a linearly thermosensitive magnetic microgel was prepared by a radical copolymerization reaction in aqueous dispersion. In this reaction, poly(ethylene glycol) diacrylate was used as a crosslinker, polyvinylpyrrolidone was used as a stabilizer, and 2-methoxyethyl acrylate, poly(ethylene glycol)methyl ether acrylate, and 2-(methacryloyloxy)ethyl acetoacetate were used as copolymer monomers. The thermosensitive magnetic microgel displays a linear volume phase transition in water upon heating over a wide range of temperatures. Transmission electron microscopy, scanning electron microscopy, and dynamic light scattering were used to characterize the morphology and dimensions of the thermosensitive magnetic microgel. This material is expected to be used in magnetically targeted drug delivery systems that require linear drug release.

Preparation of Preformed Submicron Crosslinked Polymer Coils for Conformance Control in Low-Permeability Reservoirs.

With the increasing development of low-permeability reservoirs, the significance of conformance control treatment has risen considerably. To address the conflict between injectability and plugging performance, as well as to enhance the deep migration capacity of conformance control agents, preformed submicron crosslinked polymer coils (SCPCs) have been manufactured using aqueous solution dispersion polymerization. Fourier transform infrared and scanning electron microscopy were employed to examine the chemical structure and micromorphology, while particle size distribution, zeta potential, rheological, and filtration properties were analyzed. The effectiveness of conformance control was confirmed through the parallel core displacement. The effective particle size of SCPCs was at a submicron level (500~800 nm). SCPCs exhibit a transitional threshold concentration between gel and sol states (0.25 wt%~0.5 wt%). SCPCs can efficiently block the 1.2 μm microporous filter membrane. The filtration time is up to 67.8 min. SCPCs can improve the water absorption rate of lower permeability cores from 21.21% to 57.89% with a permeability difference of 5. Therefore, SCPCs have good injectability, plugging performance, and deep migration capacity and can be used for conformance control in low-permeability reservoirs.

Poly(acrylic acid)‐Modified SnO2 Electron Transport Layer for Perovskite Solar Cells

AbstractSnO2 is one of the most used inorganic electron transport materials for organic‐inorganic halide perovskite solar cells. However, the surface defects of SnO2 will block the electron transport at the SnO2/perovskite buried interface and limit the device performance. Here, poly(acrylic acid) (PAA) is employed to modify the SnO2 electron transport layer. Carboxyl groups can react with KOH in the commercial SnO2 aqueous colloidal dispersion to produce potassium polyacrylate, the −COO− can combine not only with oxygen and Sn4+ on SnO2, but also can chelate with uncoordinated Pb2+ defects on perovskite. Moreover, carboxyl groups can form a chemical linker between SnO2 and perovskite via the esterification reaction, leading to the reduction of surface hydroxyl group defects of SnO2. The optimal solar cells with PAA modification achieve an enhanced power conversion efficiency of 18.88 % and improved stability.

N/S-GQDs/KMnO4 hybrid as a colorimetric and fluorescent dual-signal readout probe for sensitive and selective detection of ascorbic acid

A nitrogen and sulfur co-doped graphene quantum dots (N/S-GQDs) and permanganate was employed to prepare a N/S-GQDs/KMnO4 dual-signal readout colorimetric and fluorescent probe for sensitive detection of ascorbic acid (AA). In the detection system, the addition of KMnO4 quenched significantly the fluorescence (FL) of N/S-GQDs, meanwhile, the transparent aqueous dispersion of N/S-GQDs changed into yellow–brown with new absorption peak (maximum absorption at 338 nm). Interestingly, introduction of AA into the N/S-GQDs/KMnO4 system could recover the quenched fluorescence and result in a decrease in the absorbance (at 338 nm) of the test solution in a concentration dependent manner, and hence demonstrated the potential practical use of the sensing system for AA detection. Based on various spectroscopic studies, it has been concluded that the static as well as inner filter effect was the main quenching mechanisms in the detection system. The dual-response sensor showed linear response in the concentration range between 0.01 and 30 µM with the limit of detection (LOD) of 8.3 nM and 100 nM, respectively, for the fluorescent and colorimetric detections. In addition, the proposed detection system has been successfully applied to the detection of AA in vitamin C tablets. Moreover, the proposed detection strategy is convenient and fast, prevents complex and tedious probe preparation procedure, and capable of visual detection of AA.

Ground-state electron transfer in all-polymer donor:acceptor blends enables aqueous processing of water-insoluble conjugated polymers

Water-based conductive inks are vital for the sustainable manufacturing and widespread adoption of organic electronic devices. Traditional methods to produce waterborne conductive polymers involve modifying their backbone with hydrophilic side chains or using surfactants to form and stabilize aqueous nanoparticle dispersions. However, these chemical approaches are not always feasible and can lead to poor material/device performance. Here, we demonstrate that ground-state electron transfer (GSET) between donor and acceptor polymers allows the processing of water-insoluble polymers from water. This approach enables macromolecular charge-transfer salts with 10,000× higher electrical conductivities than pristine polymers, low work function, and excellent thermal/solvent stability. These waterborne conductive films have technological implications for realizing high-performance organic solar cells, with efficiency and stability superior to conventional metal oxide electron transport layers, and organic electrochemical neurons with biorealistic firing frequency. Our findings demonstrate that GSET offers a promising avenue to develop water-based conductive inks for various applications in organic electronics.

Recent Innovations of Mesoporous Silica Nanoparticles Combined with Photodynamic Therapy for Improving Cancer Treatment.

Cancer is a global health burden and is one of the leading causes of death. Photodynamic therapy (PDT) is considered an alternative approach to conventional cancer treatment. PDT utilizes a light-sensitive compound, photosensitizers (PSs), light irradiation, and molecular oxygen (O2). This generates cytotoxic reactive oxygen species (ROS), which can trigger necrosis and/ or apoptosis, leading to cancer cell death in the intended tissues. Classical photosensitizers impose limitations that hinder their clinical applications, such as long-term skin photosensitivity, hydrophobic nature, nonspecific targeting, and toxic cumulative effects. Thus, nanotechnology emerged as an unorthodox solution for improving the hydrophilicity and targeting efficiency of PSs. Among nanocarriers, mesoporous silica nanoparticles (MSNs) have gained increasing attention due to their high surface area, defined pore size and structure, ease of surface modification, stable aqueous dispersions, good biocompatibility, and optical transparency, which are vital for PDT. The advancement of integrated MSNs/PDT has led to an inspiring multimodal nanosystem for effectively treating malignancies. This review gives an overview of the main components and mechanisms of the PDT process, the effect of PDT on tumor cells, and the most recent studies that reported the benefits of incorporating PSs into silica nanoparticles and integration with PDT against different cancer cells.

Synthesis of Poly(propylene oxide)-Poly(N,N'-dimethylacrylamide) Diblock Copolymer Nanoparticles via Reverse Sequence Polymerization-Induced Self-Assembly in Aqueous Solution.

Sterically-stabilized diblock copolymer nanoparticles comprising poly(propylene oxide) (PPO) cores are prepared via reverse sequence polymerization-induced self-assembly (PISA) in aqueous solution. N,N'-Dimethylacrylamide (DMAC) acts as a cosolvent for the weakly hydrophobic trithiocarbonate-capped PPO precursor. Reversible addition-fragmentation chain transfer (RAFT) polymerization of DMAC is initially conducted at 80% w/w solids with deoxygenated water. At 30-60% DMAC conversion, the reaction mixture is diluted to 5-25% w/w solids. The PPO chains become less solvated as the DMAC monomer is consumed, which drives in situ self-assembly to form aqueous dispersions of PPO-core nanoparticles of 120-190 nm diameter at 20 °C. Such RAFT polymerizations are well-controlled (Mw/Mn ≤ 1.31), and more than 99% DMAC conversion is achieved. The resulting nanoparticles exhibit thermoresponsive character: dynamic light scattering and transmission electron microscopy studies indicate the formation of more compact spherical nanoparticles of approximately 33 nm diameter on heating to 70 °C. Furthermore, 15-25% w/w aqueous dispersions of such nanoparticles formed micellar gels that undergo thermoreversible (de)gelation on cooling to 5 °C.

Aqueous submicron dispersions of surfactants as wetting agents and permeability enhancers of potato leaves

For aqueous solutions and submicron dispersions of non-micelle-forming surfactants (Tween 85, Brij L4, and Silwet L-77) kinetic tensiometric dependences and isotherms of wetting of leaves of the Prime potato variety were obtained. A technique has been developed for determining the rate of penetration of the studied liquids into potato leaves. The rate of penetration rises with increasing surfactant concentration. An increase in permeability and wetting efficiency is observed as following: Tween 85 < Brij L4 < Silwet L-77. The data obtained make it possible to evaluate the prospects for using the studied aqueous surfactant dispersions as platforms for the delivery of biologically active components into the leaves of potato plants to inhibit the proliferation of pathogens.

Stability of CO2/N2 foam generated in CaCO3 nanoparticle/CTAB aqueous dispersion

In an attempt to design a thermally stable foam with carbon sink attributes, the foamability and stability of aqueous foams generated from dispersions of CaCO3 nanoparticles (NPs) and hexadecyltrimethylammonium bromide (CTAB) are investigated. Much higher foam stability is reported here relative to literature. When compared to CTAB alone, the addition of CaCO3 NPs increases foam half-life from 5–7 min to 5–6 h in the presence of pure N2 and a gas mixture of CO2 and N2, respectively. Although there is no evidence of CTAB adsorption onto the NPs, the presence of CTAB is crucial to create the initial foam structure that is later stabilized by a network of NPs. Relative to CTAB alone, CaCO3 NPs/CTAB foam displays a higher bubble density and an average bubble size reduction of 67 %. In addition, CaCO3 NPs/CTAB foam is 20-fold more stable at 80 °C.

Thermal Analysis in the Evaluation of Solid Lipid Microparticles in the Form of Aqueous Dispersion and Fine Powder

In the presented study, an attempt was made to investigate the most important attributes of solid lipid microparticles (SLM) using thermal analysis (DSC/TG) in order to determine the importance of this technique in the research and development of lipid microparticles. Particularly interesting in our studies were drug–lipid interactions and modifications of the SLM matrix structure induced by the production method (the hot emulsification method) and further processing (e.g., spray drying), as well as changes occurring during the stability studies. Cyclosporine A, indomethacin and spironolactone were used as model active substances incorporated into SLM. The conducted research demonstrated the significant potential of DSC/TG, especially for the analysis of SLM in the form of fine powder. The method of sample preparation, consisting of evaporation of water at room temperature, turned out to be crucial for the DSC/TG analysis of SLM dispersion. In the case of the tested SLM, the basic and usually the only observed thermal transformation in the DSC spectrum was the endothermic peak associated with the lipid forming a microsphere matrix. This peak is the main source of information about the properties and stability of the tested SLM. The obtained results show that glyceryl behenate (Compritol) is a significantly better lipid for forming lipid microparticles than stearic acid. Although thermal transformations of the incorporated drug substances are not directly visible in the DSC spectra, their impact on the SLM properties can be assessed indirectly, based on changes in the lipid melting point and the shape of the DSC and TG peaks and curves. DSC/TG studies confirmed the lack of an effect of the spray drying process on the properties of drug-loaded SLM with Compritol. Studies have also shown up to a 2-year stability of SLM with CsA.

Bio-Inspired Impregnations of Carbon Rovings for Tailored Bond Behavior in Carbon Fiber Reinforced Concrete

Nature provides various templates for integrating organic and inorganic materials to create high-performance composites. Biological structures such as nacre and the structural elements of the glass sponge are built up in layers, leading to remarkable fracture toughness. In this work, the brick-and-mortar and layer-by-layer structures found in these biological examples have been abstracted and implemented by using an aqueous polymer dispersion in combination with nanoclay particles and sodium water glass. These dispersions were used as impregnation of carbon rovings in order to form bio-inspired contact zones towards the concrete matrix. The bonding behavior was investigated using the Yarn Pull-Out (YPO) test, and a beneficial behavior of the layered polymer–nanoclay dispersions was observed. Thermogravimetric analysis (TGA) was used to determine the organic impregnation content of the roving. Further, light microscopy of the roving cross-sections prior to YPO and visual analyses of the fractured contact zone of split concrete specimens provided information on the quality of the impregnation and the interaction with the concrete matrix.