Interleukin-12 plasmid DNA delivery using l-thyroxine-conjugated polyethylenimine nanocarriers

The influence of the hydrophilicity and length of the cation alkyl chain in imidazolium-based ionic liquids on the dispersability of ZnO nanoparticles by ultrasound treatment was studied by dynamic light scattering and advanced rheology. ZnO nanopowder synthesized by chemical vapor synthesis was used in parallel with one commercially available material. Before preparation of the dispersion, the nanoparticles characteristics were determined by transmission electron microscopy, X-ray diffraction, nitrogen adsorption with BET analysis, and FT-IR spectroscopy. Hydrophilic ionic liquids dispersed all studied nanopowders better and in the series of hydrophilic ionic liquids, an improvement of the dispersion quality with increasing length of the alkyl chain of the cation was observed. Especially, for ionic liquids with short alkyl chain, additional factors like nanoparticle concentration in the dispersion and the period of the ultrasonic treatment had significant influence on the dispersion quality. Additionally, nanopowder characteristics (crystallite shape and size as well as the agglomeration level) influenced the dispersion quality. The results indicate that the studied ionic liquids are promising candidates for absorber media at the end of the gas phase synthesis reactor allowing the direct preparation of non-agglomerated nanoparticle dispersions without supplementary addition of dispersants and stabilizers.     

Diversity of TiO<Subscript>2</Subscript> nanopowders’ characteristics relevant to toxicity testing

In this study, the physicochemical properties of several commercial ultrafine TiO₂ powders and their behaviour in the as-received form and colloidal suspensions were analysed. Besides the particle size, the morphology and agglomeration state of the dry powders, dispersibility, ζ-potential and sedimentation in water and in phosphate-buffered saline (PBS) were studied. Also, leaching of ions from the powders during ageing in physiological solution and the ability of the photoactivated powders to decompose organic substances were evaluated. The examined TiO₂ powders revealed diversified characteristics when dispersed in water. In general, while in dry conditions the particle size appeared in the nano-range (down to 32 nm), the particles were agglomerated in aqueous suspensions at pH ~7 and only a minor amount showed dimensions below 200 nm, but none below 100 nm. The inherent pH of the 3 % suspensions varies from 3.7 to 7.5 and the surface charge at these pH values varied from highly positive to highly negative values. In PBS, the surface charge is negative and relatively low for all the samples, which resulted in agglomeration. Five out of six powders exhibited significant photocatalytic activity when exposed to UV irradiation. This also includes one cosmetic-grade powder. Furthermore, during the immersion in aqueous media at physiological temperature, the powders released foreign ions, which might also contribute to the results of cytotoxicity tests. The results revealed the major role of the particle surface charge and its impact on particle dispersion or agglomeration. Due to the high ionic strength in the liquids relevant for cell-surface interaction tests, for all the examined titania powders the nanoparticulate character was lost. However, the presence of impurities and photocatalysis might further contribute to the results of cytotoxicity tests.     

Dissolution and storage stability of nanostructured calcium carbonates and phosphates for nutrition

Rapid calcium (Ca) dissolution from nanostructured Ca phosphate and carbonate (CaCO₃) powders may allow them to be absorbed in much higher fraction in humans. Nanosized Ca phosphate and CaCO₃ made by flame-assisted spray pyrolysis were characterized by nitrogen adsorption, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. As-prepared nanopowders contained both CaCO₃ and CaO, but storing them under ambient conditions over 130 days resulted in a complete transformation into CaCO₃, with an increase in both crystal and particle sizes. The small particle size could be stabilized against such aging by cation (Mg, Zn, Sr) and anion (P) doping, with P and Mg being most effective. Calcium phosphate nanopowders made at Ca:P ≤ 1.5 were XRD amorphous and contained γ-Ca₂P₂O₇ with increasing hydroxyapatite content at higher Ca:P. Aging of powders with Ca:P = 1.0 and 1.5 for over 500 days gradually increased particle size (but less than for CaCO₃) without a change in phase composition or crystallinity. In 0.01 M H₃PO₄ calcium phosphate nanopowders dissolved ≈4 times more Ca than micronsized compounds and about twice more Ca than CaCO₃ nanopowders, confirming that nanosizing and/or amorphous structuring sharply increases Ca powder dissolution. Because higher Ca solubility in vitro generally leads to greater absorption in vivo, these novel FASP-made Ca nanostructured compounds may prove useful for nutrition applications, including supplementation and/or food fortification.     

Mössbauer and magnetic studies of MFe2O4(M = Co, Ni) nanoparticles

Nanocrystalline MFe₂O₄ (M?=?Co, Ni) particles are synthesized by citrate precursor technique. Mössbauer and magnetic studies are carried out with the CoFe₂O₄ samples having particle sizes of 9, 14 and 30 nm and the NiFe₂O₄ samples having particle sizes of 9, 21 and 30 nm. The intrinsic magnetic parameters are found to vary with the particle size. The magnetic interactions and cation distribution present in these systems influence the room temperature Mössbauer parameters. Ferrimagnetic sextets are observed for all the different particle sizes. The observed reduction of the magnetic hyperfine field values with the decrease in the size of MFe₂O₄ particles are attributed to the intrinsic size effect and the canted spin structure at the surface of the nanoparticles.     

Aqueous ionic liquid based ultrasonic assisted extraction of four acetophenones from the Chinese medicinal plant Cynanchum bungei Decne

In this study, an aqueous ionic liquid based ultrasonic assisted extraction (ILUAE) method for the extraction of the four acetophenones, namely 4-hydroxyacetophenone (1), 2,5-dihydroxyacetophenone (2), baishouwubenzophenone (3) and 2,4-dihydroxyacetophenone (4) from the Chinese medicinal plant Cynanchum bungei was developed. Three kinds of aqueous l-alkyl-3-methylimidazolium ionic liquids with different anion and alkyl chain were investigated. The results indicated that ionic liquids (ILs) showed remarkable effects on the extraction efficiency of acetophenones. In addition, the ILUAE, including several ultrasonic parameters, such as the ILs concentration, solvent to solid ratio, power, particle size, temperature, and extraction time have been optimized. Under these optimal conditions (e.g., with 0.6 M [C₄MIM]BF₄, solvent to solid ratio of 35:1, power of 175 W, particle size of 60–80 mesh, temperature of 25 °C and time of 50 min), this approach gained the highest extraction yields of four acetophenones 286.15, 21.65, 632.58 and 205.38 μg/g, respectively. The proposed approach has been evaluated by comparison with the conventional heat-reflux extraction (HRE) and regular UAE. The results indicated that ILUAE is an alternative method for extracting acetophenones from C. bungei.     

Structural and thermoluminescence properties of undoped and Fe-doped-TiO<Subscript>2</Subscript> nanopowders processed by sol–gel method

In this study, we report on the nanocrystalline powders of TiO₂ and Fe-doped TiO₂ (anatase and rutile phases) prepared by sol–gel method. The X-ray diffraction and Raman spectroscopy measurements indicated the presence of anatase or rutile phase in nanopowders. TEM micrographs showed 10 and 112 nm average particle sizes for anatase and rutile, respectively. Furthermore, their thermoluminescence properties were analyzed.     

Effect of variation of different nanofillers on structural,electrical, dielectric,and transport properties of blend polymer nanocomposites

In the present work, the effect of various nanofillers with different particle sizes and dielectric constants (BaTiO₃, CeO₂, Er₂O₃, or TiO₂) on blend solid polymer electrolyte comprising PEO and PVC complexed with bulky LiPF₆ has been explored. The XRD analysis confirms the polymer nanocomposite formation. FTIR provides evidence of interaction among the functional groups of the polymer with the ions and the nanofiller in terms of shifting and change of the peak profile. The highest ionic conductivity is ~?2.3?×?10^?5 S cm^?1 with a wide electrochemical stability window of ~?3.5 V for 10 wt% Er₂O₃. The real and imaginary parts of dielectric permittivity follow the identical trend of the decreasing value of dielectric permittivity and dielectric loss with increase in the frequency. The particle size and the dielectric constant show an abnormal trend with different nanofillers. The AC conductivity follows the universal Jonscher power law, and an effective mechanism has been proposed to understand the nanofiller interaction with cation coordinated polymer.     

The interactive effect of agitation condition and titania particle size in hydrothermal synthesis of titanate nanostructures

The nucleation and growth mechanisms of hydrothermal synthesized nanotitanates are proposed based on the interaction effect between agitation condition and pristine titania particle size. TEM examination and N₂ adsorption measurements revealed distinct morphology and textural properties depending on TiO₂ particle size in constant agitation condition. Regarding to the supersaturation degree, heterogeneous nucleation dominates for nanotubes formation from large particle size of raw material. On the other hand, homogeneous nucleation determines nanospheres formation from small particle size of raw material. The nanotubes have an outer diameter ranging from 8 to 10 nm and inner diameter of 2 to 3 nm. The nanospheres have diameters ranging from 50 to 100 nm.     

Sonoelectrochemical Synthesis of Nano Zinc (II) Complexes with 9-Anthracenecarboxylic Acid: Effect of Current Density and Study of their Photophysical Properties

A new zinc complex, [Zn (9-AC)₂] (1) (9-AC = 9-anthracenecarboxylic acid), was prepared via conventional electrochemical method in a fast and facile process and fully characterized by ¹H NMR, ¹³C NMR, IR spectroscopy and elemental analysis. The nano structures of the same compound were successfully produced by a facile and environment-friendly sonoelectrochemical route at different current densities (0.5, 1.2, 1.8, 2.5 and 3.5 mA/cm²). The new nano-structure particles were characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analysis. Thermal stability of single crystal and nano-size samples of the prepared compound was studied by thermogravimetric and differential thermal analysis. The comparison of the effect of current density without and with ultrasonic irradiation on particle size has been investigated in convectional electrochemical and sonoelectrochemical method respectively. The results showed that using ultrasonic irradiation with increasing the current density lead to decrease the particle sizes unlike conventional electrochemical method. In other words, when the current density increase from 0.5 to 3.5 mA/cm², in sonoelectrochemical method, the particle sizes decrease from 100 to 48 nm while, in convectional electrochemical method, the particle sizes increase from 400 to 1200 nm and possible explanation offered. Photoluminescence properties of the nano-structured and crystalline bulk of the prepared complex at room temperature in the solid state have been investigated in detail. The results indicate that the size of the complex particles has an important effect on their optical properties.     

Study of SiRNA-loaded PS-mPEG/CaP nanospheres on lung cancer

The TiO₂/BiOI heterostructured nanofibers were prepared by electrospinning–solvothermal two-step process. The BiOI nanosheets, which owned a thickness of tens of nanometers and an average side length of about 300 nm, were intensive and crossed arranging on the TiO₂ nanofibers whose diameter was about 400–550 nm and length was about 15–45 μm. The absorption edge of TiO₂/BiOI heterostructured nanofibers was extended to more than 600 nm in visible-light region and the TiO₂/BiOI exhibited enhanced visible-light photocatalytic performance and excellent recyclability compared to the individual TiO₂ nanofibers and the BiOI microflowers in the photodecomposition of methylene blue, which was ascribed to nanoscale size heterostructure, narrow energy band, peculiar band gap structures, and porous surface structure.     

Catalyst-free low temperature synthesis of discrete anatase titanium dioxide nanocrystals with highly thermal stability and UVC-cut capability

A novel, facile, catalyst-free, and low temperature process for the synthesis of discrete anatase TiO₂ nanocrystals has been developed in the absence of stabilizing agent. The product was shown to be discrete anatase TiO₂ nanocrystals with a mean diameter of 4.97 ± 0.9 nm and a specific surface area of 393 m²/g. By varying the water content and precursor concentration, the particle size could be tuned. Also, the resultant colloid solution was quite stable even in the absence of stabilizing agent because of the coverage of EG molecules on the particle surface. In addition, the anatase TiO₂ nanocrystals obtained in this work had highly thermal stability even at temperatures up to 800 °C. Also, as compared to Degussa P25 TiO₂ powders, they exhibited stronger absorption at 200–350 nm and higher transmittance in the visible light region. Thus, the new approach proposed in this work was practicable for the synthesis of anatase TiO₂ nanocrystals, particularly for those requested to have highly thermal stability and UVC-cut capability.

     

Characterization of size, surface charge, and agglomeration state of nanoparticle dispersions for toxicological studies

Characterizing the state of nanoparticles (such as size, surface charge, and degree of agglomeration) in aqueous suspensions and understanding the parameters that affect this state are imperative for toxicity investigations. In this study, the role of important factors such as solution ionic strength, pH, and particle surface chemistry that control nanoparticle dispersion was examined. The size and zeta potential of four TiO₂ and three quantum dot samples dispersed in different solutions (including one physiological medium) were characterized. For 15 nm TiO₂ dispersions, the increase of ionic strength from 0.001 M to 0.1 M led to a 50-fold increase in the hydrodynamic diameter, and the variation of pH resulted in significant change of particle surface charge and the hydrodynamic size. It was shown that both adsorbing multiply charged ions (e.g., pyrophosphate ions) onto the TiO₂ nanoparticle surface and coating quantum dot nanocrystals with polymers (e.g., polyethylene glycol) suppressed agglomeration and stabilized the dispersions. DLVO theory was used to qualitatively understand nanoparticle dispersion stability. A methodology using different ultrasonication techniques (bath and probe) was developed to distinguish agglomerates from aggregates (strong bonds), and to estimate the extent of particle agglomeration. Probe ultrasonication performed better than bath ultrasonication in dispersing TiO₂ agglomerates when the stabilizing agent sodium pyrophosphate was used. Commercially available Degussa P25 and in-house synthesized TiO₂ nanoparticles were used to demonstrate identification of aggregated and agglomerated samples.     

A facile low temperature synthesis of TiO2 nanorods for high efficiency dye sensitized solar cells

Titania (TiO₂) nanorods have been synthesized with controlled size for dye-sensitized solar cells (DSSCs) via hydrothermal route at low hydrothermal temperature of 100 °C for 24 h. The titania nanorods were characterized using XRD, SEM, TEM/HRTEM, UV-vis Spectroscopy, FTIR and BET specific surface area (S _BET), as well as pore-size distribution by BJH. The results indicated that the bulk traps and the surface states within the TiO₂ nanorods films have enhanced the efficiency of DSSCs. The size of the titania nanorods was 6.7 nm in width and 22 nm in length. The high surface area can provide more sites for dye adsorption, while the fast photoelectron-transfer channel can enhance the photogenerated electron transfer to complete the circuit. The specific surface area S _BET was 77.14 m²?g^?1 at the synthesis conditions. However, the band gap energy of the obtained titania nanorods was 3.2 eV. The oriented nanorods with appropriate lengths are beneficial in improving the electron transport property and thus leading to the increase of photocurrent, together enhancing the power conversion efficiency. A nearly quantitative absorbed photon-to-electrical current conversion achieved upon excitation at wave length of 550 nm and the power efficiency was enhanced from 5.6 % for commercial TiO₂ nanoparticles Degussa (P25) cells to 7.2 % for TiO₂ nanorods cells under AM 1.5 illumination (100 mW?cm^?2). The TiO₂ cells performance was improved due to their high surface area, hierarchically mesoporous structures and fast electron-transfer rate compared with the Degussa (P25).     

Titanium dioxide nanoparticles prepared by laser pyrolysis: Synthesis and photocatalytic properties

TiO₂ nanoparticles were synthesized via the laser pyrolysis of titanium tetrachloride-based gas-phase mixtures. In the obtained nanopowders, a mixture of anatase and rutile phases with mean particle size of about 14 nm was identified. Using the thermal heated laser nanopowders, mechanically stable films were produced by immobilizing titania nanopowders on glass substrates (the doctor blading method followed by compression). The photocatalytic activity of the prepared films was tested by the degradation of 4-chlorophenol in an aqueous solution under UV-illumination. By referring to known commercial samples (Degussa P25) similarly prepared, higher photocatalytic efficiency was found for the laser-prepared samples.     

Magnetic and Mössbauer spectroscopic studies of NiZn ferrite nanoparticles synthesized by a combustion method

The properties of nanocrystalline Ni_0.5Zn_0.5Fe₂O₄ synthesized by an auto-combustion method have been investigated by magnetic measurements and Mössbauer spectroscopy. The as-synthesized single phase nanosized ferrite powder is annealed at different temperatures in the range 673–1,273 K to obtain nanoparticles of different sizes. The powders are characterized by powder X-ray diffraction, vibrating sample magnetometer, transmission electron microscopy and Mössbauer spectroscopy. The as-synthesized powder with average particle size of ~9 nm is superparamagnetic. Magnetic transition temperature increases up to 665 K for the nanosized powder as compared to the transition temperature of 548 K for the bulk ferrite. This has been confirmed as due to the abnormal cation distribution, as evidenced from room temperature Mössbauer spectroscopic studies.     

Optimized method of dispersion of titanium dioxide nanoparticles for evaluation of safety aspects in cosmetics

Nanoparticles agglomerate when in contact with biological solutions, depending on the solutions’ nature. The agglomeration state will directly influence cellular response, since free nanoparticles are prone to interact with cells and get absorbed into them. In sunscreens, titanium dioxide nanoparticles (TiO₂-NPs) form mainly aggregates between 30 and 150 nm. Until now, no toxicological study with skin cells has reached this range of size distribution. Therefore, in order to reliably evaluate their safety, it is essential to prepare suspensions with reproducibility, irrespective of the biological solution used, representing the above particle size distribution range of NPs (30–150 nm) found on sunscreens. Thus, the aim of this study was to develop a unique protocol of TiO₂ dispersion, combining these features after dilution in different skin cell culture media, for in vitro tests. This new protocol was based on physicochemical characteristics of TiO₂, which led to the choice of the optimal pH condition for ultrasonication. The next step consisted of stabilization of protein capping with acidified bovine serum albumin, followed by an adjustment of pH to 7.0. At each step, the solutions were analyzed by dynamic light scattering and transmission electron microscopy. The final concentration of NPs was determined by inductively coupled plasma-optical emission spectroscopy. Finally, when diluted in dulbecco’s modified eagle medium, melanocytes growth medium, or keratinocytes growth medium, TiO₂–NPs displayed a highly reproducible size distribution, within the desired size range and without significant differences among the media. Together, these results demonstrate the consistency achieved by this new methodology and its suitability for in vitro tests involving skin cell cultures.     

Insight into the activity of efficient acid–base bifunctional catalysts for the coupling reaction of CO2

The fixation of carbon dioxide with epoxide catalysed by a series of carboxylic acidic functionalised ionic liquids (ILs) catalysts is investigated by density functional theory method. Except for the catalysts reported by the experiment, the catalytic activity of a new designed catalyst (4c see Scheme 1) is also explored. These ILs are categorised into four groups according to the different cation structures and number of functional groups. The effects of different chain length, anion, and cation structure on the catalytic activity are explored. The elongation of alkyl chain length in cation will increase the product yield, while increasing the chain bulk has almost negligible effect on the enhancement of catalytic activity. Utilisation of imidazole group as the cation is better than pyridine group. And the cation with two functional groups will have a better catalytic activity than that with one functional group.     

Raman spectra of acetonitrile in imidazolium ionic liquids

Raman spectra of dilute solutions of acetonitrile in ionic liquids reveal the characteristic features of ionic liquids' polarity. This is accomplished by investigating the Raman bandshape of the ν (CN) band, corresponding to the CN stretching mode of CH₃CN, which is a very sensitive probe of the local environment. The amphiphilic nature of the CH₃CN molecule allows us to observe the effect of electron pair acceptor and electron pair donor characteristics on ionic liquids. It has been found that the overall polarity of nine different ionic liquids based on 1‐alkyl‐3‐methylimidazolium cations is more dependent on the anion than cation. The observed wavenumber shift of the ν (CN) band of CH₃CN in ionic liquids containing alkylsulfate anions agrees with the significant different values previously measured for the dielectric constant of these ionic liquids. The conclusions obtained from the analysis of the ν (CN) band were corroborated by the analysis of the symmetric ν₁ (CD₃ ) stretching mode of deuterated acetonitrile in different ionic liquids. Copyright © 2010 John Wiley & Sons, Ltd.     

Physicochemical characterization of paramagnetic ionic liquids 1‐vinyl‐3‐alkylimidazolium tetrahalogenidoferrate(III) [VRIM][FeClmBr4 − m]

Using microwave‐assisted synthesis method, a series of paramagnetic ionic liquids comprising 1‐vinyl‐3‐alkylimidazolium VRIM⁺ cation and tetrahalogenidoferrate (III) FeCl_mBr_{4 ? m}^? anion were designed and synthesized. The structure was analyzed using ¹H NMR and Raman spectroscopy. Ultraviolet–visible absorption spectra, thermal stability, magnetic susceptibility, viscosity, ionic conductivity, and solubility were characterized. Results show that elongation of the alkyl chain leads to replacement of bromides with a small amount of chlorides in the anion, shifting of UV maximum absorption peaks to shorter wavelengths, reduction of ionic conductivity, and solubility in polar solvents, as well as increase in fluidity, magnetic susceptibility, and solubility in nonpolar solvents. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of high-energy milling on the solid-state synthesis of pure nano-sized Li4Ti5O12 for high power lithium battery applications

Li₄Ti₅O₁₂ was synthesized from Li₂CO₃ and anatase TiO₂ using different degree of milling to test the hypothesis that finer starting materials can result in a smaller Li₄Ti₅O₁₂ particle size and better high-rate discharging capacities. The degree of milling was controlled using three different ZrO₂ media sizes for 3 hours of high-energy milling, whereas 5 mm balls were used for 24 hours ball milling. High-energy milling produced significantly finer starting materials and Li₄Ti₅O₁₂ particles compared to those produced by ball milling. Among the three different balls used in high-energy milling, the 0.10 mm media showed the most favorable results. Pure Li₄Ti₅O₁₂ with a mean particle size of 146 and 175 nm were synthesized by an economic solid-state reaction combined with high-energy milling using 0.05 and 0.10 mm beads, respectively. These pure nano-sized Li₄Ti₅O₁₂ exhibited a much higher specific capacity and superior rate capability than those of coarse rutile TiO₂-contained Li₄Ti₅O₁₂ particles.