Synthesis of Gold Nano- and Microplates in Hexagonal Liquid Crystals

A novel approach for the biosynthesis of silver nanoparticles using the defensive gland extracts of the beetle, Luprops tristis Fabricius

Discovering novel natural resources for the biological synthesis of metal nanoparticles is one of the two key challenges facing by the field of nanoparticle synthesis. The second challenge is a lack of information on the chemical components needed for the biological synthesis and the chemical mechanism involved in the metal nanoparticles synthesis. In the current study, microwave-assisted silver nanoparticle (AgNP) synthesis employing the defensive gland extract of Mupli beetle, Luprops tristis Fabricius (Order: Coleoptera; Family: Tenebrionidae), addresses these two challenges. This study was conducted without killing the experimental insect. Earlier studies in our laboratory showed the presence of the phenolic compounds, 2,3-dimethyl-1,4-benzoquinone, 1,3-dihydroxy-2-methylbenzene, and 2,5-dimethylhydroquinone in the defensive gland extract of L. tristis. The results of the current study show that the phenolic compounds in the defensive gland extract of the beetle has the ability to reduce silver ions into AgNPs and also acts as a good capping and stabilizing agent. A possible mechanism for the reduction of silver nitrate (AgNO3) into AgNPs is suggested. The synthesized AgNPs were characterized by Ultraviolet-Visible (UV-Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy energy-dispersive X-ray (SEM-EDX) analysis and high-resolution transmission electron microscopic (HR-TEM) techniques. The stability of biologically synthesized nanoparticles was studied by zeta potential analysis. The TEM analysis confirmed that AgNPs are well dispersed and almost round shaped. The average size of nanoparticle ranges from 10 to 20 nm. EDX analysis showed that silver is the prominent metal present in the nanomaterial solution. The AgNPs synthesized have antibacterial property against both Staphylococcus aureus and Escherichia coli. Radical scavenging (DPPH) assay was used to determine the antioxidant activity of the AgNPs. AgNPs exhibited anticancer activity in a cytotoxicity experiment against Dalton's lymphoma ascites (DLA) cell line.

Synthesis of gold nanostructures using glycine as the reducing agent

Biological synthesis of gold nanostructures could potentially offer an environmentally friendly alternative to traditional chemical synthetic methods. During the last decades, various biomolecules, including amino acids, have been successfully used as reducing and capping agents to synthesize multi-shaped gold nanostructures. A grand challenge in this field is to increase our ability to control the size and shape of gold nanostructures formed precisely by systematic synthetic approaches based on the understanding of the mechanism for structural determination. In this study, using glycine as the model amino acid and chloroaurate (AuCl₄ ^-) ions as the precursor solution, we report the finding that the shape of the gold nanostructures synthesized showed a strong correlation with the speciation of gold complexes determined by the pH, precursor concentration and chloride concentration of the solvent system. The gold chloro-hydroxy speciation [AuCl_x(OH)_4-x]^- (with x = 0-4) influenced the shape of the gold nanostructures formed, with gold nanoplatelets, nanotriangles, nanokites and nanoribbons observed at x = 4, 3, 2 and 1, respectively, and spherical nanoparticles observed at x = 0. Glycine was found to play a role as a reducing agent, but no significant effect on the morphology was observed, indicating the dominance of gold chloro-hydroxy speciation in the structural formation. These results collectively provide synthetic considerations to systematically synthesize non-spherical to spherical biosynthesized gold nanostructures by controlling the speciation of [AuCl_x(OH)_4-x]^-.

Green Synthesis of Metallic Nanoparticles and Their Potential Applications to Treat Cancer

Nanoparticle synthesis using microorganisms and plants by green synthesis technology is biologically safe, cost-effective, and environment-friendly. Plants and microorganisms have established the power to devour and accumulate inorganic metal ions from their neighboring niche. The biological entities are known to synthesize nanoparticles both extra and intracellularly. The capability of a living system to utilize its intrinsic organic chemistry processes in remodeling inorganic metal ions into nanoparticles has opened up an undiscovered area of biochemical analysis. Nanotechnology in conjunction with biology gives rise to an advanced area of nanobiotechnology that involves living entities of both prokaryotic and eukaryotic origin, such as algae, cyanobacteria, actinomycetes, bacteria, viruses, yeasts, fungi, and plants. Every biological system varies in its capabilities to supply metallic nanoparticles. However, not all biological organisms can produce nanoparticles due to their enzymatic activities and intrinsic metabolic processes. Therefore, biological entities or their extracts are used for the green synthesis of metallic nanoparticles through bio-reduction of metallic particles leading to the synthesis of nanoparticles. These biosynthesized metallic nanoparticles have a range of unlimited pharmaceutical applications including delivery of drugs or genes, detection of pathogens or proteins, and tissue engineering. The effective delivery of drugs and tissue engineering through the use of nanotechnology exhibited vital contributions in translational research related to the pharmaceutical products and their applications. Collectively, this review covers the green synthesis of nanoparticles by using various biological systems as well as their applications.

Liquid Crystals Templating

Liquid crystal templating is a versatile technique to create novel organic and inorganic materials with nanoscale features. It exploits the self-assembled architectures of liquid crystal phases as scaffolds. This article focuses on some of the key developments in lyotropic and thermotropic liquid crystals templating. The procedures that were employed to create templated structures and the applications of these novel materials in various fields including mesoporous membranes, organic electronics, the synthesis of nanostructured materials and photonics, are described.

Selective Adsorption, Reduction, and Separation of Au(III) from Aqueous Solution with Amine-Type Non-Woven Fabric Adsorbents

Herein, adsorption, separation, and reduction of Au(III) from its aqueous solution were studied with different amine-type, non-woven fabric (NF) adsorbents fabricated with radiation-induced graft polymerization. The adsorbents exhibited different adsorption capacities of Au(III) over a concentration range of hydrochloric acid (HCl) from 5 mM to 5 M, and the diethylamine (DEA)-type adsorbent performed best under all test conditions. The DEA-type adsorbent was inert toward other metal ions, including Cu(II), Pb(II), Ni(II), Zn(II) and Li(I), within the fixed concentration range of HCl. Flow-through adsorption tests indicated DEA-type adsorbent exhibited a rapid recovery and high adsorption capacity of 3.23 mmol/g. Meanwhile, DEA-type adsorbent also exhibited high selectivity and rapid extraction for Au(III) from its mixed solution with Pt(IV) and Pd(II). After adsorption, the reduction of Au(III) was confirmed by XRD spectra, TEM, and digital micrograph images. The results indicated that nano-sized Au particles were mainly concentrated on the adsorbent in 5 mM HCl solution. In 1 M HCl solution, not only nano-sized Au particles were found, but also micro-size Au plates precipitation occurred. This study provides a novel material for selective and efficient gold uptake from aqueous solution.

Photochemical Synthesis and Catalytic Applications of Gold Nanoplates Fabricated Using Quercetin Diphosphate Macromolecules

The demand for safer design and synthesis of gold nanoparticles (AuNPs) is on the increase with the ultimate goal of producing clean nanomaterials for biological applications. We hereby present a rapid, greener, and photochemical synthesis of gold nanoplates with sizes ranging from 10 to 200 nm using water-soluble quercetin diphosphate (QDP) macromolecules. The synthesis was achieved in water without the use of surfactants, reducing agents, or polymers. The edge length of the triangular nanoplates ranged from 50 to 1200 nm. Furthermore, the reduction of methylene blue was used to investigate the catalytic activity of AuNPs. The catalytic activity of triangular AuNPs was three times higher than that of the spherical AuNPs based on kinetic rate constants (k). The rate constants were 3.44 × 10^-2 and 1.11 × 10^-2 s^-1 for triangular and spherical AuNPs, respectively. The X-ray diffraction data of gold nanoplates synthesized by this method exhibited that the nanocrystals were mainly dominated by (111) facets which are in agreement to the nanoplates synthesized by using thermal and chemical approaches. The calculated relative diffraction peak intensity of (200), (220), and (311) in comparison with (111) was found to be 0.35, 0.17, and 0.15, respectively, which were lower than the corresponding standard values (JCPDS 04-0784). For example, (200)/(111) = 0.35 compared to 0.52 obtained from the standard (JCPDS 04-0784), indicating that the gold nanoplates are dominated by (111) facets. The calculated lattice from selected area electron diffraction data of the as-synthesized and after 1 year nanoplates was 4.060 and 4.088 Å, respectively. Our calculations were found to be in agreement with 4.078 Å for face-centered cubic gold (JCPDS 04-0784) and literature values of 4.07 Å. The computed QDP-Au complex demonstrated that the reduction process took place in the B ring of QDP. This approach contributes immensely to promoting the ideals of sustainable nanotechnology by eradicating the use of hazardous and toxic organic solvents.

Supramolecular Assembly of Single-Source Metal-Chalcogenide Nanocrystal Precursors

In this feature article, we discuss our recent work in the synthesis of novel supramolecular precursors for semiconductor nanocrystals. Metal chalcogenolates that adopt liquid-crystalline phases are employed as single-source precursors that template the growth of shaped solid-state nanocrystals. Supramolecular assembly is programmed by both precursor chemical composition and molecular parameters such as the alkyl chain length, steric bulk, and the intercalation of halide ions. Here, we explore the various design principles that enable the rational synthesis of these single-source precursors, their liquid-crystalline phases, and the various semiconductor nanocrystal products that can be generated by thermolysis, ranging from highly anisotropic two-dimensional nanosheets and nanodisks to spheres.

Synthesis of Au Nanoparticles with Benzoic Acid as Reductant and Surface Stabilizer Promoted Solely by UV Light

Photoreductive synthesis of colloidal gold nanoparticles (AuNPs) from Au³⁺ is one important process for nanoprocessing. Several methods have been proposed; however, there is no report of a method capable of producing AuNPs with inexpensive reagents acting as both reductant and surface stabilizer, promoted solely under photoirradiation. We found that UV irradiation of water with Au³⁺ and benzoic acid successfully produces monodispersed AuNPs, where thermal reduction does not occur in the dark condition even at elevated temperatures. Photoexcitation of a benzoate-Au³⁺ complex reduces Au³⁺ while oxidizing benzoic acid. The benzoic acid molecules are adsorbed on the AuNPs and act as surface stabilizers. Change in light intensity and benzoic acid amount successfully creates AuNPs with controllable sizes. The obtained AuNPs can easily be redispersed in an organic solvent or loaded onto a solid support by simple treatments.

Nanofluid Types, Their Synthesis, Properties and Incorporation in Direct Solar Thermal Collectors: A Review

The global demand for energy is increasing and the detrimental consequences of rising greenhouse gas emissions, global warming and environmental degradation present major challenges. Solar energy offers a clean and viable renewable energy source with the potential to alleviate the detrimental consequences normally associated with fossil fuel-based energy generation. However, there are two inherent problems associated with conventional solar thermal energy conversion systems. The first involves low thermal conductivity values of heat transfer fluids, and the second involves the poor optical properties of many absorbers and their coating. Hence, there is an imperative need to improve both thermal and optical properties of current solar conversion systems. Direct solar thermal absorption collectors incorporating a nanofluid offers the opportunity to achieve significant improvements in both optical and thermal performance. Since nanofluids offer much greater heat absorbing and heat transfer properties compared to traditional working fluids. The review summarizes current research in this innovative field. It discusses direct solar absorber collectors and methods for improving their performance. This is followed by a discussion of the various types of nanofluids available and the synthesis techniques used to manufacture them. In closing, a brief discussion of nanofluid property modelling is also presented.

Synthesis of nanostructured alumina with ultrahigh pore volume for pH-dependent release of curcumin

Versatile new high porous alumina supports were synthesized by double templates. They gave different release state for curcumin drug. The release of (insoluble) curcumin reached to 80% in SGF. The new formulation enhanced the SH-SY5Y cells survival.

Synthesis of gold structures by gold-binding peptide governed by concentration of gold ion and peptide

Although biological synthesis methods for the production of gold structures by microorganisms, plant extracts, proteins, and peptide have recently been introduced, there have been few reports pertaining to controlling their size and morphology. The gold ion and peptide concentrations affected on the size and uniformity of gold plates by a gold-binding peptide Midas-11. The higher concentration of gold ions produced a larger size of gold structures reached 125.5 μm, but an increased amount of Midas-11 produced a smaller size of gold platelets and increased the yield percentage of polygonal gold particles rather than platelets. The mechanisms governing factors controlling the production of gold structures were primarily related to nucleation and growth. These results indicate that the synthesis of gold architectures can be controlled by newly isolated and substituted peptides under different reaction conditions.

Rapid Seedless Synthesis of Gold Nanoplates with Microscaled Edge Length in a High Yield and Their Application in SERS

We report a facile and reproducible approach toward rapid seedless synthesis of single crystalline gold nanoplates with edge length on the order of microns. The reaction is carried out by reducing gold ions with ascorbic acid in the presence of cetyltrimethylammonium bromide (CTAB). Reaction temperature and molar ratio of CTAB/Au are critical for the formation of gold nanoplates in a high yield, which are, respectively, optimized to be 85 °C and 6. The highest yield that can be achieved is 60 % at the optimized condition. The synthesis to achieve the microscaled gold nanoplates can be finished in less than 1 h under proper reaction conditions. Therefore, the reported synthesis approach is a time- and cost-effective one. The gold nanoplates were further employed as the surface-enhanced Raman scattering substrates and investigated individually. Interestingly, only those adsorbed with gold nanoparticles exhibit pronounced Raman signals of probe molecules, where a maximum enhancement factor of 1.7 × 10⁷ was obtained. The obtained Raman enhancement can be ascribed to the plasmon coupling between the gold nanoplate and the nanoparticle adsorbed onto it.

Green Synthesis of Metallic Nanoparticles via Biological Entities

Nanotechnology is the creation, manipulation and use of materials at the nanometre size scale (1 to 100 nm). At this size scale there are significant differences in many material properties that are normally not seen in the same materials at larger scales. Although nanoscale materials can be produced using a variety of traditional physical and chemical processes, it is now possible to biologically synthesize materials via environment-friendly green chemistry based techniques. In recent years, the convergence between nanotechnology and biology has created the new field of nanobiotechnology that incorporates the use of biological entities such as actinomycetes algae, bacteria, fungi, viruses, yeasts, and plants in a number of biochemical and biophysical processes. The biological synthesis via nanobiotechnology processes have a significant potential to boost nanoparticles production without the use of harsh, toxic, and expensive chemicals commonly used in conventional physical and chemical processes. The aim of this review is to provide an overview of recent trends in synthesizing nanoparticles via biological entities and their potential applications.

Electrodeposition of Pluronic F127 assisted rod-like EMD/carbon arrays for efficient energy storage

In the traditional Duracell battery, the results obtained to date remain marginal in terms of cyclability. The development of the existing Zn-MnO2 with superior electrochemical performance for use in alkaline rechargeable batteries is reported. Electrolytic manganese dioxide (EMD) was synthesized from a conventional manganese sulphate bath but having a unique non-ionic surfactant (Pluronic F127), and activated carbon, in an electrolytic cell. The surface areas and morphologies of the as-prepared EMDs were influenced by the presence of these novel additives in the solution while the X-ray data revealed that there was no noticeable change in the crystal orientations thus all the EMDs were structurally similar. The synergistic effect of the optimal ratio of surfactant to carbon powder produced rod-like arrays exhibiting a larger surface area, which facilitates ion transport for better energy storage. It is interesting to note that EMD deposited in the presence of F127 showed better cyclability whereas in the presence of carbon, although it showed better storage capability, it was endowed with poor efficiency when compared with the surfactant added sample, nevertheless the results are better than the existing Zn-MnO2 technology (additive free EMD). Therefore, both the surfactant (50 mg dm(-3)) and the activated carbon (5 g dm(-3)) have been added together in the bath and the resultant EMD exhibits a high specific capacity and an excellent cycling stability. Moreover, the presence of surfactant and activated carbon improved the discharge capacity and its retention thus making this alkaline technology feasible for storing renewable energy for future use. The synergistic effect and the mechanism involved have been discussed.

A seed-less method for synthesis of ultra-thin gold nanosheets by using a deep eutectic solvent and gum arabic and their electrocatalytic application

Ultra-thin and large gold nanosheets were easily synthesized by using a deep eutectic solvent as a reducing and directing agent with gum arabic as a stabilizer and shape-controlling agent through a seed-less protocol.

Liquid crystalline thermotropic and lyotropic nanohybrids

This review is meant to give the reader an insight into hybrids incorporating different types of nanoparticles, e.g. metallic or metal oxides, within different types of lyotropic and thermotropic liquid crystals, from relatively small calamitic molecules to the larger discotics and polymers. In particular, this review highlights the importance of nanoparticle-liquid crystal interactions in accessing hybrid materials that exhibit synergetic properties.

Preparation and Characterization of Copper Dendrite Like Structure by Chemical Method

Abstract Copper particles are prepared at room temperature using a simple chemical method. The method used is capable of giving high yields. In this method sodium borohydride is used as a reducing agent and poly vinly pyrrolidone (PVP) as a capping reagent. The prepared copper particles are characterized by X-ray diffraction method and Energy dispersive x-ray analysis (EDX). The scanning electron microscopy (SEM) images show the formation of dendrite like structures. The transmission electron microscope (TEM) studies also conform the formation of dendrite structures.

Shape-tailoring and catalytic function of anisotropic gold nanostructures

We report a facile, one-pot, shape-selective synthesis of gold nanoparticles in high yield by the reaction of an aqueous potassium tetrachloroaurate(III) solution with a commercially available detergent. We prove that a commercial detergent can act as a reducing as well as stabilizing agent for the synthesis of differently shaped gold nanoparticles in an aqueous solution at an ambient condition. It is noteworthy that the gold nanoparticles with different shapes can be prepared by simply changing the reaction conditions. It is considered that a slow reduction of the gold ions along with shape-directed effects of the components of the detergent plays a vital function in the formation of the gold nanostructures. Further, the as-prepared gold nanoparticles showed the catalytic activity for the reduction reaction of 4-nitrophenol in the presence of sodium borohydride at room temperature.

Shape-tailoring of gold nanostructures: can a detergent act as the reducing or protecting agent?

A commercially available detergent was found to be an effective reducing as well as stabilizing agent for the synthesis of differently shaped gold nanoparticles in an aqueous solution at an ambient condition and the as-prepared gold nanoparticles behave as an efficient catalyst for the reduction reaction of 4-nitrophenol at room temperature.

Anisotropic nanomaterials: structure, growth, assembly, and functions

Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications.