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Hydrocalumite structured layered double hydroxides (LDHs) with various Fe3+ ratios were prepared through a coprecipitation method. In order to control the Fe3+ content in LDH, binary Ca–Fe LDHs were first synthesized with various Ca/Fe ratios. The X-ray diffraction pattern showed that only a limited Ca/Fe ratio resulted in LDH formation. The Fe3+ content in LDH was controlled by applying Al3+ while the divalent and trivalent metal ratio was set to 2. Through X-ray diffraction patterns, ternary LDHs with Ca–Al–Fe composition were successfully synthesized without significant impurities, with the Al increasing crystallinity. Quantification showed that Al moiety participated in the formation of the LDH framework more than Ca and Fe, implying a structural stabilization in the presence of Al. In order to investigate the global and local structure of Fe moiety in the LDH, both solid state UV-vis and X-ray absorption spectroscopies were carried out. Both spectroscopies revealed that the existence of Al induced slight local distortion in coordination but global crystal stabilization.

International audience; Immobilization of antimicrobial drug is one of the fascinating approach to expand the application of antibacterial property to consumer product. In order to stabilize antimicrobial agent, levofloxacin (LVX), into polymer substrate for sustained antibacterial activity, the drug molecules were immobilized in layered double hydroxide (LDH) and embedded in polyurethane substrate. As prepared MgAl-LDH was calcined at 400C and reconstructed with LVX for intercalation. The X-ray diffraction patterns and cross-sectional transmission electron microscopy images showed lattice expansion along the crystallographic c-axis upon LVX intercalation, suggesting the successful loading of the drug. Fourier-transformed infrared spectra revealed that intact structure of LVX was well preserved between LDH layers. Elemental analysis indicated that the loading capacity of LVX in the hybrid was 41.7%. Bacterial colony forming inhibitory assay of exhibited ~100% antibacterial activity for both LVX alone and LVX-LDH hybrid (LL) on Bacillus subtilis. To determine sustainability of antibacterial activity by the hybrid, either LVX alone or LL hybrid was loaded in polyurethane (PU) substrate of which antibacterial activity was evaluated before and after immersing in phosphate buffered saline for 3 days. The LVX composited PU showed dramatic decrease in antibacterial activity down to 0% after buffer treatment; however, LL composited PU still contained antibacterial activity (~34% of colony suppression) after phosphate buffered saline immersion.

Due to characteristic properties of silver (Ag), Ag nanoparticles have attracted unprecedented attention invarious scientific fields such as sensors, catalysts, antibacterial materials, and so on. To obtain tailor-made functionalities of Ag nanoparticles with desired physicochemical properties, proper fabrication process is needed to control their sizes, morphologies or arrangements by hybridization with different components,immobilization on solid struts, and etc. Herein, we suggest a facile synthetic route to obtain Ag-pillared mesoporous nanoclays through simultaneous crystal growth and arrangement of Ag nanoplates with thehelp of a 2-dimensional inorganic template. To obtain Ag-pillars, layered silver-thiolate self-assemblywas exfoliated to monolayers (Ag precursor) and then in-situ hybridized with layered double hydroxide in a layer-by-layer manner. Through reductive calcination, silver thiolate transformed to Ag-pillars which grew in nanoplate morphology with well-arrangement in confined space of nanoclays. Crystal structure,morphology, and pore structure of Ag-pillars in nanoclays were systematically characterized. Surface enhanced Raman scattering effect of arranged Ag-pillars on metal oxide substrate obtained upon calcination was also investigated with rhodamine 6 G. Refereed/Peer-reviewed

Silver metal nanostructures have gained much interest, due to their utility in various fields, based on their unique properties at nanosize. Tremendous research efforts have been made to establish synthetic methods to manipulate their shape and size. The most challenging synthesis in silver nanostructures has been known as a plate-like shape having a few nanometers size thickness and high aspect ratio. Here, we demonstrate a novel and facile synthetic route for ultrathin (≤1 nm) silver nanosheets using silver carboxylthiolate as precursor. Such silver thiolate formed single-layered colloid in aqueous basic solution, due to the electrostatic repulsion between carboxylate groups. These single layers of silver thiolates were stabilized within the interlayer space of layered double hydroxide (LDH). When silver thiolates confined in LDHs were calcined under reductive atmosphere, the LDHs effectively suppressed the vertical growth of silver crystals. Refereed/Peer-reviewed

The specific surface area changes in MgAl-layered double hydroxide (LDH), which is also known as hydrotalcite, were monitored along with their changes in particle size, crystallinity and local disorder around Al. Two kinds of LDHs were prepared by hydrothermal reaction during 1 day (H1) and 3 days (H3). The lateral size and thickness of H3 was twice than those of H1; however, the crystallinity and ordering around Al was comparable for both LDHs. Upon calcination at 500 °C, the local disorder around octahedral Al in both LDHs significantly increased with migrating Al to tetrahedral coordination. The degree of disorders and the migration to tetrahedral sites was more severe in H3 than H1, and this was related to the much higher increase of specific surface area in H3 (16.5 times) than in H1 (11.1 times). During the calcination, dehydroxylation of LDH gave rise to the crystal deformation and interstratified structure of metal oxides, resulting in the development of mesopores and enhancement of specific surface area. The calcined samples could recover original LDH phase upon reconstruction reaction, while the crystallinity and ordering around Al was not completely recovered. Although the small mesopores in calcined LDHs seemed to be partially blocked upon reconstruction, the specific surface area of reconstructed LDHs was still higher than pristine LDHs, possibly due to the incomplete recovery of Al ordering in LDHs.

Layered double hydroxide (LDH) nanomaterials of uniform size and homogeneous distribution are successfully developed in agarose hydrogel through the electrical double migration method. To grow LDH ...

Polydimethylsiloxane (PDMS) based adhesives were prepared by cross-linking tetraethoxyorthosilicate (TEOS) while controlling stoichiometry with PDMS, acid catalyst, and water. Particulate additives, alginate and bentonite, were added during the cross-linking process. Cationic drug lidocaine was incorporated into the adhesive with or without additive, and the time-dependent drug release profile was evaluated in phosphate buffered saline and ethanol, respectively. According to kinetic fitting to power function and parabolic diffusion, both solvent and additive type influenced drug release. In particular, particulate additives were found to suppress or facilitate drug release in water or ethanol, respectively.

Guanosine monophosphates (GMPs) were intercalated into the interlayer space of layered double hydroxides (LDHs) and the molecular arrangement of GMP was controlled in LDHs. The intercalation conditions such as GMP/LDH molar ratio and reaction temperature were systematically adjusted. When the GMP/LDH molar ratio was 1:2, which corresponds to the charge balance between positive LDH sheets and GMP anions, GMP molecules were well-intercalated to LDH. At high temperature (100 and 80 °C), a single GMP molecule existed separately in the LDH interlayer. On the other hand, at lower temperature (20, 40 and 60 °C), GMPs tended to form ribbon-type supramolecular assemblies. Differential scanning calorimetry showed that the ribbon-type GMP assembly had an intermolecular interaction energy of ≈101 kJ/mol, which corresponds to a double hydrogen bond between guanosine molecules. Once stabilized, the interlayer GMP orientations, single molecular and ribbon phase, were successfully converted to the other phase by adjusting the external environment by stoichiometry or temperature control.

In order to control Mg/Al ratio in hydrotalcite type layered double hydroxide (LDH), LDH was prepared through coprecipitation under varied synthetic parameters such as initial Mg/Al ratio (from 1 to 20) in metal solution and coprecipitation pH (9.5, 10, 10.5 and 11). Phase evolution of hydrotalcite or impurities was examined with powder X-ray diffraction pattern and the Mg/Al ratio in final product was evaluated with inductively coupled plasma-atomic emission spectroscopy. It was found that the nominal Mg/Al ratio did not correspond to the final values, showing narrow correlation range between 1 and 3 at relatively low pH ~ 9.5. By raising coprecipitation pH upto 11, Mg/Al ratio successfully increased in final LDH product upto 15.4. Under controlled initial Mg/Al ratio and coprecipitation pH, various LDHs with Mg/Al ratio between 1 and 16, which corresponded to layer charge density between 0.5 and 6(+)/100 A 2 , were obtained. The charge density and surface charge of LDHs exhibited linear correlation, showing zeta potential value 16–40 mV at neutral pH.

We successfully synthesized a size-controlled hybrid of layered double hydroxide (LDH) platelets and Gd(OH)3 nanorods through the reverse micelle method. Under controlled synthetic conditions, the hybrid was developed to a quasi-core–shell structure, where the Gd(OH)3 nanorods were covered by the LDH platelet assembly, and this was investigated by X-ray diffraction and high-resolution transmission electron microscopy. The zeta potential measurement for the hybrid revealed that Gd(OH)3 was surrounded by LDH moieties. According to dynamic light scattering, the hydrodynamic radius of the hybrid was uniformly controlled under 150 nm, which was comparable to that of one Gd(OH)3 nanorod surrounded by an LDH moiety. Thus, the obtained hybrid exhibited a maximum Hounsfield unit of 180 at a concentration of 5 mg mL−1, implying its potential as a computed tomography contrast agent. The magnetic resonance relaxivities of the hybrid were examined at pH 5 and 7, simulating lysosomal and plasma conditions; the r1 values were 7.3 and 2.9, respectively, which were highly dependent on the physiological conditions.

A nanostructured Ni(OH)2/graphene oxide (GO) hybrid was fabricated via the controlled reassembly of exfoliated GO with nickel hydroxide to form a delaminated structure. To examine the effect of electron beam irradiation on the hybrid material, the obtained Ni(OH)2/GO was exposed to the electron beam, and the total doses of the electron beam were varied from 150 to 250 kGy. The electron-beam-irradiated hybrid was reduced to fabricate a new nanostructured material in which nickel nanoparticles were homogeneously deposited onto the graphene nanosheets (GNS). According to the transmission electron microscopy analysis, a large number of defect sites could be developed after the electron beam treatments. The electrochemical hydrogen storage property (approximately 170 mAh/g) of the hybrid sample after the electron beam treatment was determined to be much superior to that of the GNS (approximately 20 mAh/g), demonstrating that this synthetic methodology via electron beam bombardment could be extended to the development of new nanostructured materials with enhanced hydrogen storage properties.

We studied the physico-chemical properties of ZnO nanoparticles under physiological pH conditions (gastric, intestinal and plasma) as functions of their size (20 and 70 nm) and surface chemistry (pristine, l -serine, or citrate coating). ZnO nanoparticles were dispersed in phosphate buffered saline under physiological pH conditions and aliquots were collected at specific time points (0.5, 1, 4, 10 and 24 h) for further characterization. The pH values of the aqueous ZnO colloids at each condition were in the neutral to slightly basic range and showed different patterns depending on the original size and surface chemistry of the ZnO nanoparticles. The gastric pH condition was found to significantly dissolve ZnO nanoparticles up to 18–30 wt%, while the intestinal or plasma pH conditions resulted in much lower dissolution amounts than expected. Based on the X-ray diffraction patterns and X-ray absorption spectra, we identified partial phase transition of the ZnO nanoparticles from wurtzite to Zn(OH)2 under the intestinal and plasma pH conditions. Using scanning electron microscopy, we verified that the overall particle size and morphology of all ZnO nanoparticles were maintained regardless of the pH.

To fabricate electrochemical hydrogen storage materials with delaminated structure, the graphene oxide (GO) in the ethylene glycol solution was reassembled in the presence of the precursor of Ni nanoparticles, and then, the reassembled hybrid was reduced under hydrogen atmosphere to obtain Ni/graphene hybrid. X-ray diffraction patterns and X-ray absorption spectscopic (XAS) analysis clearly show that Ni nanoparticles in Ni/graphene hybrid maintain its nanosized nature even after hybridization with graphene nanosheet (GNS). According to the TEM analysis, the Ni nanoparticles with an average size of 5.2 nm are homogeneously distributed onto the GNS in such a way that the nanoporous structure with much amount of void spaces could be fabricated. The obtained Ni/GNS exhibits a hydrogen storage capacity of 160 mA h/g, while the specific capacity of the graphene nanosheet was only 21 mA h/g. A flexible delaminated structure of Ni/GNS nanocomposite could provide additional intercalation sites for accommodation of hydrogen, leading to the enhancement of hydrogen storage capacity.

Background In order to obtain biomaterials with controllable physicochemical properties, hybrid biomaterials composed of biocompatible biopolymers and ceramic nanoparticles have attracted interests. In this study, we prepared biopolymer/ceramic hybrids consisting of various natural biopolymers and layered double hydroxide (LDH) ceramic nanoparticles via an electrophoretic method. We studied the structures and controlled-release properties of these materials. Results and discussion X-ray diffraction (XRD) patterns and X-ray absorption spectra (XAS) showed that LDH nanoparticles were formed in a biopolymer hydrogel through electrophoretic reaction. Scanning electron microscopic (SEM) images showed that the ceramic nanoparticles were homogeneously distributed throughout the hydrogel matrix. An antioxidant agent (i.e., ferulic acid) was loaded onto agarose/LDH and gelatin/LDH hybrids, and the time-dependent release of ferulic acid was investigated via high-performance liquid chromatography (HPLC) for kinetic model fitting. Conclusions Biopolymer/LDH hybrid materials that were prepared by electrophoretic method created a homogeneous composite of two components and possessed controllable drug release properties according to the type of biopolymer.

Nanocomposites containing magnetic iron oxide (magnetite) nanoparticles and layered double hydroxide (LDH) nanosheets were prepared by two different methods, exfoliation-reassembly and coprecipitation, for aqueous chromate adsorbent. According to X-ray diffraction, scanning electron microscopy, and atomic force microscopy, both nanocomposites were determined to develop different nanostructures; LDH nanosheets well covered magnetite nanoparticles with house-of-cards-like structure in exfoliation-reassembly method, while coprecipitation resulted in LDH particle formation along with magnetite nanoparticles. Zeta-potential measurement also revealed that the magnetite surface was effectively covered by LDH moiety in exfoliation-reassembly compared with coprecipitation. Time, pH, concentration dependent chromate adsorption tests, and magnetic separation experiments exhibited that both nanocomposites effectively adsorb and easily collect chromate. However, exfoliation-reassembly nanocomposite was determined to be slightly effective in chromate removal by 10%. Chromate adsorbed nanocomposites could be regenerated by treating with bicarbonate and the regenerated nanocomposites preserved 80% of chromate adsorption efficacy after three times of recycling. Refereed/Peer-reviewed

Composite hydrogels were prepared that consisted of quasi-colloidal layered double hydroxide (LDH) nanoparticles and agarose via the electrophoretic method, starting from three different agarose concentrations of 0.5, 1, and 2 wt/v%. The composite hydrogel was identified to have a uniform distribution of LDH nanoparticles in agarose matrix. Microscopic studies revealed that the composite hydrogel had a homogeneous quasi-colloidal state of LDHs, while the simple mixture of LDH powder and agarose hydrogels did not. It was determined that agarose concentration of the starting hydrogel did not significantly influence the amount of LDH that developed in the composite. The chromate scavenging efficiency of the composite hydrogel and corresponding agarose or mixture hydrogel was evaluated with respect to time, and chromate concentration. In general, the composite hydrogels exhibited much higher chromate removal efficacy compared with agarose or mixture hydrogels. Through estimating chromate adsorption by LDH moiety in the composite or mixture hydrogel, it was suggested that the agarose component facilitated the stability and dispersibility of the quasi-colloidal state of LDH nanoparticles in the composite resulting in high adsorption efficacy. From Freundlich isotherm adsorption fitting, composites were determined to possess beneficial cooperative adsorption behavior with a high adsorption coefficient.

We have prepared organic–inorganic hybrid materials consisting of layered metal hydroxides and hydrogel polymers for potential use as a drug delivery system. The hybrid materials were synthesized by an electrophoretic method; anionic precursors, OH–/CO32–, and cationic metal Zn2+ were migrated into hydrogel by applying an electrical potential of 25 V for 20 min to form inorganic nanocrystals inside the hydrogel matrix. Hydrozincite [Zn5(OH)8(CO3)] nanoparticles, a kind of layered metal hydroxide, were determined to develop inside the hydrogel according to powder X-ray diffraction, FTIR, and X-ray absorption spectroscopy. Scanning electron microscopic images showed that the prepared hybrid materials have well-dispersed inorganic nanoparticles in the hydrogel matrix. In order to evaluate the potential of the thus prepared hybrid materials as a drug-delivery system, the well-known antioxidant ferulic acid was incorporated and their time-dependent release profile was obtained by HPLC.

We have evaluated the particle sizes, zeta potentials and hydrodynamic radii of zinc oxide (ZnO) nanoparticles in various aqueous conditions such as deionized water, phosphate buffered saline and Minimum Essential Media Eagle. In order to study the size and surface chemistry effect in colloidal behaviors, different size of 20 and 70 nm ZnO nanoparticles were selected and their surface was modified with either citrate or L-serine. It was revealed that surface modification did not strongly affect the particle size or morphology but altered the surface charge and chemistry. In various aqueous media, although the surface charge of ZnO nanoparticles are slightly affected by the existence of electrolyte, the overall particle sizes and morphologies are determined to be preserved, suggesting that their properties as nanoparticles are not significantly changed in physiological conditions.

We prepared pressure-sensitive adhesive (PSA)-containing cross-linked siloxane powders (CS) as a reservoir for a transdermal drug delivery system (TDDS) and evaluated their sustained drug-release properties. PSA, as a patch-type adhesive, was synthesized by a hydrosilylation reaction of vinyl-terminated polysiloxanes with hydrogen-terminated polydimethylsiloxanes. CS was also prepared via a hydrosilylation process with vinyl-terminated polydimethylsiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinyltetracyclosiloxane ( ), hydrogen-terminated polydimethylsiloxane, and dimethylhydrogenmethyl oligomeric siloxane copolymer. The results of release performances using ascorbic acid as a model drug showed a cumulative linear slope over a week, indicating a constant release performance. Our data suggest that this siloxane TDDS could be useful for constant drug release over a long period. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42154.