Textiles screen-printed with photochromic ethyl cellulose-spirooxazine composite nanoparticles

Photochromic compounds change colour on exposure to light, while the reversion may be attributable either to radiation or may be thermal. The use of photochromism on fabrics can provide new opportunities to develop smart textiles; for example, sensors and active protective clothes. Ethyl cellulose-1,3-dihydro-1,3,3,4,5 (and 1,3,3,5,6) -pentamethyl-spiro-[2H-indole-2,3′-(3H)naphtha(2,1-b)(1,4)oxazine] composites were prepared by an oil-in-water emulsion, solvent evaporation method in order to form easily suspendable and fatigue-resistant photochromic nanoparticles in screen-printing paste. Their size was well below 1 μm and did not change substantially over a wide range of dye concentrations. After screen-printing, a homogenous photochromic layer was built on a cotton substrate surface, which represented substantial blue colour development in CIELab colour space measurements because of ultraviolet light, even at a dye concentration of 0.045% w/w. The addition of a photodegradation inhibitor, Tinuvin 144, further increased the coloration of the printed fabric

Organic nanoparticulate photochromes

Photochromic organic dyes can be widely used in materials for optically rewritable data storage, photonic switches, memories, sensors, or actuators. In recent years photochromic materials based on nanoparticles became particularly focused, since they can be dispersed in colloidal aqueous suspensions or incorporated in thin films, avoiding problems of light scattering or shallow light penetration in bulk materials. Spiropyrans, spirooxazines and diarylethenes were by far the most researched photochromes in nanoparticulate systems. Great effort was made to investigate photochromic dyes incorporated into organic nanoparticles via self-assembly strategies, covalent linkage or dispersion of the molecular species in polymers (doping). Nanoparticles composed of solely photochromic dyes were prepared by laser ablation and reprecipitation techniques. Photochromic dyes were microencapsulated by self-assembly, soap free-, emulsion/microemulsion/miniemulsion or free radical- (co)polymerization. Sol-gel processing from silane precursors to poly(organo)siloxane matrix is a common method to synthesize doped or core-shell photochromic organogels. Coloured forms of some photochromes display fluorescence; however, a more effective strategy for fluorescence modulation with photochromic molecules is integrating them, covalently or noncovalently, with a separate fluorophore in the same nanoparticles. These photoresponsive nanoparticles may find applications particularly in biological fields such as cell labelling and bioimaging. The purpose of this review is to summarize the preparation methods of organic nanoparticles containing photochromic dyes and to investigate their typical properties derived from their nanoparticulate character

Cross-linking of horseradish peroxidase enzyme to fine particles generated by nano spray dryer B-90

Enzymatic methods can be effective tools for removal of phenolic compounds from wastewater by forming reactive radicals with polymerization mechanism. Comparing with conventional chemical ways, enzymes have advantages such as low cost and high level of catalytic efficiency. At the same time, there exist some problems, e.g. the instability of enzyme structures, sensitivity to process conditions and their purification cost is high. Fine particles have been used for enzyme stabilization due to their beneficial high surface-to-volume ratio. Enzymes immobilized on fine particles may work at a broader pH, temperature and salinity range than the native enzymes. Ethyl cellulose and poly(lactic co-glycolic acid) carrier particles were prepared by nano spray drying and used for immobilizing horseradish peroxidase enzyme (HRP) by cross-linking. The optimal condition for immobilization was investigated. Fixed enzyme showed increased activity in TRIS buffer. The activity of the immobilized enzyme was enhanced at acidic and alkaline pH

Silica nanoparticles-coated poly(glycidyl methacrylate-ethylene dimethacrylate) co-polymer beads containing organic phase change materials

Macroporous sorbent beads of large and small sizes were prepared by the AIBN-initiated suspension radical polymerization of glycidyl methacrylate and ethylene dimethacrylate monomers in the presence of an inert porogen. The large and small microspheres were loaded with paraffin and cetyl alcohol PCMs, respectively, and coated with silica nanoparticles after sol-gel synthesis of trimethoxy(methyl)silane hydrolysate. The energy storing capacity of the form-stabilized PCM containing composite particles was monitored by differential scanning calorimetry. Accelerated thermal cycling tests were carried out to determine the thermal reliability of the microencapsulated PCMs. Paraffin and cetyl alcohol content of the microcapsules was 42.9 % and 48.9 %, respectively. The microcomposites with higher PCM content showed correspondingly higher latent heat storage capacity (melting and solidification enthalpies were 96.1 J/g and 94.7 J/g). However, there was low enthalpy change observed after 1000 thermal cycles of cetyl alcohol containing capsules, which indicated that its leakage from the microcomposites was not substantial

A légköri aeroszol higroszkópos tulajdonságainak vizsgálata = Hygroscopic behavior of atmospheric aerosol particles

Az aeroszol részecskék jelentős része vízben jól oldódó vegyületekből áll, higroszkóposak, azaz a vízre vonatkoztatott túltelítettség elérése előtt oldatcseppeket alkotnak. További vízfelvétellel, az oldatcsepp hígul, és mérete jelentősen megnövekedik. Az aeroszol részecskék higroszkópos (nedvszívó) tulajdonságaik miatt olyan jelentős folyamatokat szabályoznak, mint a légkör optikai tulajdonságai és a felhőképződés. Modellkísérletekben szerves alkotók (savak) megváltoztatják az aeroszol részecskék higroszkópos tulajdonságait, csökkentik a képződő cseppek felületi feszültségét, és oldhatóságát. Aeroszol minták elemzésével közvetett módon kimutattuk, hogy vidéki levegőben a részecskék mérésekkel meghatározott higroszkópos növekedése lényegesen kisebb, mintha a részecskék kizárólag szervetlen sókból állnának. A higroszkópos részecske növekedés és a kémiai összetétel közötti összefüggést sokszoros regresszió alkalmazásával is vizsgáltuk. Vidéki levegőben a szervetlen alkotók növelik, míg az aeroszol összes szénkoncentrációja csökkenti a részecskék higroszkopicitását. Különböző mintavételi helyeken (városi, falusi és regionális háttér) az aeroszol higroszkópos tömegnövekedése függ a részecskék méretétől. Az aeroszol finom (d1?m) a kisebb mértékű a növekedés. Az aeroszol higroszkopicitása a részecskék mérete mellett optikai tulajdonságukat (törésmutatójukat) is befolyásolja. | Significant fraction of the aerosol is composed by water soluble compounds. Consequently they are hygroscopic, which means that before reaching 100% relative humidity these particles deliquesce. Further water-uptake results in dilution as well as in enlargement of the droplets. Due to hygroscopicity, particles control several important processes like optical properties of the atmosphere and precipitation formation. The results of model experiments showed that organic compounds (acids) modify the hygroscopic behavior of the particles; they decrease the surface tension and the solubility of the particles. We found that in regional background air the actual hygroscopic growth of the particles is significantly lower compared to the growth of theoretical aerosol which is composed by solely inorganic components. We also studied the relationship between the hygroscopic growth and the chemical composition by means of multilinear regression analysis. We found that in background air inorganic compounds increase, while total carbon content decreases the particle hygroscopicity. Under different environments the growth rate varied as the function the particle size. The particle enlargement was found higher in the fine mode (d1?m). The hygroscopicity of the particles changes not only the particle size, but also modifies the optical properties (refractive index) of the particles

Poloxamers for Surface Modification of Hydrophobic Drug Carriers and Their Effects on Drug Delivery

Tri-block copolymer poloxamers are successfully employed for reducing adsorption of proteinous molecules onto hydrophobic surfaces, which will protect them from quick engulfing by macrophages. For sustained systemic circulation of hydrophobic drug carriers, particle surfaces need suitable modification for avoiding phagocytosis and this can be successfully done by poloxamers. They can affect the drug release profile, which makes them a very promising agent for targeted delivery. This review discusses the structure, characteristics and advantages of poloxamers. Poloxamer adsorption onto hydrophobic surfaces and adlayer thickness, relative phagocytic uptake and drug release profiles of coated drug loaded particles have been described in detail