Synthesis of inorganic materials with complex form

Fabrication and magnetic properties of nickel dodecahedra

Here we report a one-pot route for the synthesis of nickel dodecahedra with 52.3 ± 0.1 emu g(-1) of saturation magnetization. The procedure is very simple, and only three chemicals (NiCl2·6H2O, isopropanol and polyvinylpyrrolidone) are used throughout the entire synthetic process. During the reaction, it is believed that the application of isopropanol and the amount of polyvinylpyrrolidone play an essential role in forming the dodecahedral morphology of the final product. Furthermore, a formation process of twinning and the influence of reaction kinetic factors were proposed to explain the formation of nickel dodecahedra.

Sonochemical fabrication of mesoporous TiO2 inside diatom frustules for photocatalyst

Mesoporous titanium dioxide (TiO2) has been assembled inside the macropores of diatom frustules by sonochemical condensation of titania precursor, and then thermal treated at an elevated temperature. The resulting hierarchical macro/mesoporous-structures of the TiO2 inside diatom were confirmed by characterizations of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The amount of TiO2 inside the periodic macropores of diatom was controlled by varying the sonication time. It was found that the resultant composite with only 30 wt% TiO2 loading delivered a high photocatalytic performance, even better than that of pure P25. This is attributed to its hierarchical macro/mesoporous structure as it provides a large number of accessible active sites for efficient transportations of guest species to framework binding sites. Other macro/mesoporous structures with a nearly endless variety of functional chemistries and shapes are expected to be produced, leading to a range of novel applications in remediation, molecular transportation and environmental field by using this facile strategy.

Guest-host interactions of a rigid organic molecule in porous silica frameworks

Molecular-level interactions at organic-inorganic interfaces play crucial roles in many fields including catalysis, drug delivery, and geological mineral precipitation in the presence of organic matter. To seek insights into organic-inorganic interactions in porous framework materials, we investigated the phase evolution and energetics of confinement of a rigid organic guest, N,N,N-trimethyl-1-adamantammonium iodide (TMAAI), in inorganic porous silica frameworks (SSZ-24, MCM-41, and SBA-15) as a function of pore size (0.8 nm to 20.0 nm). We used hydrofluoric acid solution calorimetry to obtain the enthalpies of interaction between silica framework materials and TMAAI, and the values range from -56 to -177 kJ per mole of TMAAI. The phase evolution as a function of pore size was investigated by X-ray diffraction, IR, thermogravimetric differential scanning calorimetry, and solid-state NMR. The results suggest the existence of three types of inclusion depending on the pore size of the framework: single-molecule confinement in a small pore, multiple-molecule confinement/adsorption of an amorphous and possibly mobile assemblage of molecules near the pore walls, and nanocrystal confinement in the pore interior. These changes in structure probably represent equilibrium and minimize the free energy of the system for each pore size, as indicated by trends in the enthalpy of interaction and differential scanning calorimetry profiles, as well as the reversible changes in structure and mobility seen by variable temperature NMR.

Bio-inspired gold microtubes based on the morphology of filamentous fungi

This communication describes a general method for templating fungal filaments with gold nanoparticles that results in a gold replica of filaments after calcination of the biological template.

Controlled synthesis of Co3O4 single-crystalline nanofilms enclosed by (111) facets and their exceptional activity for the catalytic decomposition of ammonium perchlorate

Single-crystalline, thermally stable Co₃O₄ (111) nanofilms have been successfully synthesized without any surfactant.

SERS properties of different sized and shaped gold nanoparticles biosynthesized under different environmental conditions by Neurospora crassa extract

Surface-enhanced Raman scattering (SERS) is a surface-sensitive technique that enhances Raman scattering by molecules adsorbed on rough metal surfaces. It is known that metal nanoparticles, especially gold and silver nanoparticles, exhibit great SERS properties, which make them very attractive for the development of biosensors and biocatalysts. On the other hand, the development of ecofriendly methods for the synthesis of metallic nanostructures has become the focus of research in several countries, and many microorganisms and plants have already been used to biosynthesize metallic nanostructures. However, the majority of these are pathogenic to plants or humans. Here, we report gold nanoparticles with good SERS properties, biosynthesized by Neurospora crassa extract under different environmental conditions, increasing Raman signals up to 40 times using methylene blue as a target molecule. Incubation of tetrachloroauric acid solution with the fungal extract at 60°C and a pH value of a) 3, b) 5.5, and c) 10 resulted in the formation of gold nanoparticles of a) different shapes like triangles, hexagons, pentagons etc. in a broad size range of about 10-200 nm, b) mostly quasi-spheres with some different shapes in a main size range of 6-23 nm, and c) only quasi-spheres of 3-12 nm. Analyses included TEM, HRTEM, and EDS in order to corroborate the shape and the elemental character of the gold nanoparticles, respectively. The results presented here show that these ‘green’ synthesized gold nanoparticles might have potential applicability in the field of biological sensing.

A new method for pH triggered curcumin release by applying poly(L-lysine) mediated nanoparticle-congregation

We introduce a novel method for encapsulation of curcumin by synthesizing microcapsule containing self-assembled nanoparticles using poly (L-lysine), trisodium citrate and silica sol. Such microcapsules can only be prepared in neutral and alkaline environment and unencapsulated curcumin can be effectively removed by simple centrifugation with encapsulation efficiency 57.34%. The particle sizes are in the range 0.7-3 μm with an effective diameter 1.05 μm. The structure of the microcapsules is dependent upon the solubility of curcumin in the solvent environment, the microcapsule are spherical when prepared in 10% acetone and bowl-shaped/conical when prepared in water suspension, however, the size of these curcumin encapsulated microcapsules remain similar. Fluorescence microscope images confirm that curcumin is predominantly concentrated within the shell wall of the capsules. Photophysical behavior of Micro-curcumin with respect to curcumin alone is evaluated. Release of curcumin is found to be triggered by pH where acidic environment trigger maximum release compared to basic and neutral conditions. Micro-curcumin is as stable as curcumin. Drug release efficiency is found to be 61.44% and the drug release profile of Micro-curcumin follow Higuchi model. It is also revealed that β-diketone group of curcumin responsible for scavenging activity is retained in the Micro-curcumin, thus suggesting applicability of such system as a poorly water soluble drug delivery vehicle. In contrast to other curcumin delivery systems, the presented method is easy, fast and does not need flow rate monitoring device. In addition poly (L-lysine) as a non-toxic and highly stable material that prevents metabolic degradation is used in the present preparation method.

Spontaneously amplified homochiral organic-inorganic nano-helix complexes via self-proliferation

Most spiral coiled biomaterials in nature, such as gastropod shells, are homochiral, and the favoured chiral feature can be precisely inherited. This inspired us that selected material structures, including chirality, could be specifically replicated into the self-similar populations; however, a physicochemical understanding of the material-based heritage is unknown. We study the homochirality by using calcium phosphate mineralization in the presence of racemic amphiphilic molecules and biological protein. The organic-inorganic hybrid materials with spiral coiling characteristics are produced at the nanoscale. The resulted helixes are chiral with the left- and right-handed characteristics, which are agglomerated hierarchically to from clusters and networks. It is interesting that each cluster or network is homochiral so that the enantiomorphs can be separated readily. Actually, each homochiral architecture is evolved from an original chiral helix, demonstrating the heritage of the matrix chirality during the material proliferation under a racemic condition. By using the Ginzburg-Landaue expression we find that the chiral recognition in the organic-inorganic hybrid formation may be determined by a spontaneous chiral separation and immobilization of asymmetric amphiphilic molecules on the mineral surface, which transferred the structural information from the mother matrix to the descendants by an energetic control. This study shows how biomolecules guide the selective amplification of chiral materials via spontaneous self-replication. Such a strategy can be applied generally in the design and production of artificial materials with self-similar structure characteristics.

Precipitation of calcite induced by Synechocystis sp. PCC6803

Calcite with laminate structure was successfully prepared by culturing Synechocystis sp. PCC6803 with different concentrations of calcium chloride (CaCl₂) in BG11 media. S. PCC6803 was examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser confocal scanning microscope (LCSM) and energy dispersive spectroscopy (EDS). The effects of Ca²⁺ concentrations and pH values on calcification were investigated and the micro morphs of the CaCO₃ crystals were observed by means of SEM. These results showed that CaCO₃ crystals could be more easily formed with increasing the concentration of CaCl₂ in S. PCC6803 culture solution. S. PCC6803 could largely bind calcium ions, most of which were present in extracellular polymeric substances and on the cell wall. Inside the cells there were a lot of circular areas rich in calcium ions without the crystallization of calcium. Some cells produced a thicker gelatinous sheath outside of the translucent organic thin layer. And the cells inside also produced major changes that the original chloroplasts were almost transformed into starch grains whose sizes were from 0.5 to 1 μm with relatively uniform in sizes. At the same time the cell sizes significantly reduced to only about 8-9 μm almost changing to half of its original diameters. The calcite crystals with a highly preferred orientation induced by S. PCC6803 were observed with X-ray diffraction (XRD). A critical implication was that S. PCC6803 could induce bio-calcification and then mediate the further growth of CaCO₃ crystals in the biological system.

Self-sorting of deformable particles in an asynchronous logic microfluidic circuit

A microfluidic circuit can automatically sort deformable particles based on the hydrodynamic resistance that the particles induce in a constrained microfluidic channel while flowing through it.

Biosynthesis of silver and gold nanoparticles using Bacillus licheniformis

Owing to the wide-ranging applications of noble metal nanoparticles in diverse areas of science and technology, different methods have been proposed for their synthesis. Here, we describe the methods for the intracellular biosynthesis of silver and gold nanoparticles using the bacterium Bacillus licheniformis KK2 and this same procedure can be followed for other bacteria as well. The biological synthesis of nanoparticles is highly eco-friendly and possesses distinct advantages such as enhanced stability, better control over the size, shape, and monodispersity of the nanoparticles, when compared with the more traditional physical and chemical methods which often involves the use of hazardous chemicals creating environmental concern.

Templating effect of mesostructured surfactant-silica monolithic films on the surface structural and mechanical properties

Mesostructured surfactant-silica monolithic films were prepared using a supramolecular templating method. The effect of the templating in the monolithic films on the interfacial interactions was evaluated and elucidated using the atomic force microscope techniques combined with other surface analyses to produce different surface structures and force curves depending on the surfactants. The transparent and flexible surfactant-silica monolithic films were prepared to exhibit the ordered nanostructures. The monolithic films templated by nonionic triblock copolymers (poly(ethylene oxide (EO))--poly(propylene oxide (PO))--poly(ethylene oxide (EO))) of EO₂₀PO₇₀EO₂₀ (P123) and EO₁₀₆PO₇₀EO₁₀₆ (F127) significantly exhibited flat surfaces and the higher viscoelastic properties which were supported by surface stiffness and adhesive force, whereas the monolithic film by cationic alkylammonium surfactant indicated a rough surface and the plastic deformation property by application of force. This indicated that the higher molecular weight of the EO and PO phases enhanced the phase segregation in the silica surfaces due to the higher solubility differences between both blocks to consolidate the surfactant-silica interfacial interactions. Therefore, the different surface structural and mechanical properties attributed to the interfacial organic-inorganic interaction patterns were successfully clarified.

Cellular complexity captured in durable silica biocomposites

Tissue-derived cultured cells exhibit a remarkable range of morphological features in vitro, depending on phenotypic expression and environmental interactions. Translation of these cellular architectures into inorganic materials would provide routes to generate hierarchical nanomaterials with stabilized structures and functions. Here, we describe the fabrication of cell/silica composites (CSCs) and their conversion to silica replicas using mammalian cells as scaffolds to direct complex structure formation. Under mildly acidic solution conditions, silica deposition is restricted to the molecularly crowded cellular template. Inter- and intracellular heterogeneity from the nano- to macroscale is captured and dimensionally preserved in CSCs following drying and subjection to extreme temperatures allowing, for instance, size and shape preserving pyrolysis of cellular architectures to form conductive carbon replicas. The structural and behavioral malleability of the starting material (cultured cells) provides opportunities to develop robust and economical biocomposites with programmed structures and functions.

Hybrid nanostructures for energy storage applications

Materials engineering plays a key role in the field of energy storage. In particular, engineering materials at the nanoscale offers unique properties resulting in high performance electrodes and electrolytes in various energy storage devices. Consequently, considerable efforts have been made in recent years to fulfill the future requirements of electrochemical energy storage using these advanced materials. Various multi-functional hybrid nanostructured materials are currently being studied to improve energy and power densities of next generation storage devices. This review describes some of the recent progress in the synthesis of different types of hybrid nanostructures using template assisted and non-template based methods. The potential applications and recent research efforts to utilize these hybrid nanostructures to enhance the electrochemical energy storage properties of Li-ion battery and supercapacitor are discussed. This review also briefly outlines some of the recent progress and new approaches being explored in the techniques of fabrication of 3D battery structures using hybrid nanoarchitectures.

Writing on superhydrophobic nanopost arrays: topographic design for bottom-up assembly

A well-known property of superhydrophobic surfaces, such as an array of hydrophobic nanoposts, is to allow only limited surface contact of a liquid to the tips of the nanoposts. Herein we demonstrate that material deposition from solution, whether solid precipitation, surface adsorption or colloidal adhesion in static system, or dynamic "writing", can be limited to these specific areas of the surface when in this nonwetting state. As an example of solid precipitation, we show that nucleation of CaCO(3) results in the growth of small, uniform, amorphous deposits (which can merge and recrystallize) instead of disordered, large crystals due to the abundance of identical, small heterogeneous nucleation sites. The growth of amorphous CaCO(3) can be used to trap molecules from solution, as a potential application for controlled drug release. To demonstrate the localized surface adsorption, we show that chemical functionalization of the post tips can make them "sticky" for specific attachment of species (such as colloidal particles) from solution. The electrostatic charge and relative size ratio of the particle/post diameters control the attachment of particles to the post tips with great specificity. Dynamic conditions have also been shown for writing using droplets translated across the nonwetting surface at controlled speeds during deposition. These methods offer unprecedented control over the heterogeneous nucleation and localized growth of crystals from solution and avoid nonspecific adsorption. There is selective control of colloidal or molecular attachment to the nanopost tips, whereby the contact area, time of contact, and tip surface chemistry for reaction are all independently tunable parameters.

Collagen for bone tissue regeneration

In the last decades, increased knowledge about the organization, structure and properties of collagen (particularly concerning interactions between cells and collagen-based materials) has inspired scientists and engineers to design innovative collagen-based biomaterials and to develop novel tissue-engineering products. The design of resorbable collagen-based medical implants requires understanding the tissue/organ anatomy and biological function as well as the role of collagen's physicochemical properties and structure in tissue/organ regeneration. Bone is a complex tissue that plays a critical role in diverse metabolic processes mediated by calcium delivery as well as in hematopoiesis whilst maintaining skeleton strength. A wide variety of collagen-based scaffolds have been proposed for different tissue engineering applications. These scaffolds are designed to promote a biological response, such as cell interaction, and to work as artificial biomimetic extracellular matrices that guide tissue regeneration. This paper critically reviews the current understanding of the complex hierarchical structure and properties of native collagen molecules, and describes the scientific challenge of manufacturing collagen-based materials with suitable properties and shapes for specific biomedical applications, with special emphasis on bone tissue engineering. The analysis of the state of the art in the field reveals the presence of innovative techniques for scaffold and material manufacturing that are currently opening the way to the preparation of biomimetic substrates that modulate cell interaction for improved substitution, restoration, retention or enhancement of bone tissue function.

Metallic silver nanoparticle: a therapeutic agent in combination with antifungal drug against human fungal pathogen

Silver nanoparticles (Ag-NPs) are known to have inhibitory and fungicidal effects. Resistance against fungal infection has emerged as a major health problem in recent years, which needs great and immediate concern. Here, we report the extracellular biological synthesis of silver nanoparticles through a simple green route approach using a marine mangrove (Rhizophora mucronata) and silver nitrate. Aqueous extract of marine mangrove helped in reduction and was used as capping agent in biological synthesis. Nanoparticles were characterized using microscopy and spectroscopy techniques such as HRTEM, UV-Vis absorption spectroscopy and FTIR spectroscopy. X-ray diffraction analysis showed that the nanoparticles had face centered cubic structure with crystalline nature. FTIR spectroscopy showed the presence of different functional groups, such as hydroxyl and carbonyl, involved in the synthesis of nanoparticles. The antifungal activity of fluconazole and itraconazole was enhanced against the tested pathogenic fungi in the presence of Ag-NP and confirmed from increase in fold area of inhibition. This environmentally friendly method of biological synthesis can be easily integrated for various medical applications.