Synthesis Of Inorganic Nanoparticles Research Articles

Ferritin encapsulation and templated synthesis of inorganic nanoparticles.

Understanding how inorganic nanoparticles interact with proteins is paramount to their safe and effective use in vivo. Ordered protein-inorganic nanomaterial assemblies will also enable the creation of patterned structures with useful physical properties. Thermophilic ferritin (tF) from Archaeoglobus fulgidus has unique structural features and self-assembly properties that facilitate stable but also reversible interaction with gold nanoparticles (AuNPs). In this chapter we describe how to express and purify tF and induce its assembly around AuNPs. We also describe methods for characterizing the tF-AuNP complex as well as templating NP growth within the protein cavity.

Innovative Inorganic Synthesis

I am delighted to introduce this Special Issue of Inorganics; the first themed issue of the journal and one dedicated to Innovative Inorganic Synthesis. [...]

Shape-controlled synthesis of gold nanostructures using DNA origami molds.

We introduce a new concept that allows the synthesis of inorganic nanoparticles with programmable shape. Three-dimensional DNA origami nanostructures harboring an internal cavity are used as molds. A small gold nanoparticle within the cavity nucleates solution-based gold deposition leading to mold filling. We demonstrate the fabrication of 40 nm long rodlike gold particles with quadratic cross section and the formation of higher order assemblies of the obtained particles, which is mediated by their DNA shell.

Bottom-Up, Wet Chemical Technique for the Continuous Synthesis of Inorganic Nanoparticles

Continuous wet chemical approaches for the production of inorganic nanoparticles are important for large scale production of nanoparticles. Here we describe a bottom-up, wet chemical method applying a microjet reactor. This technique allows the separation between nucleation and growth in a continuous reactor environment. Zinc oxide (ZnO), magnetite (Fe3O4), as well as brushite (CaHPO4·2H2O), particles with a small particle size distribution can be obtained continuously by using the rapid mixing of two precursor solutions and the fast removal of the nuclei from the reaction environment. The final particles were characterized by FT-IR, TGA, DLS, XRD and SEM techniques. Systematic studies on the influence of the different process parameters, such as flow rate and process temperature, show that the particle size can be influenced. Zinc oxide was obtained with particle sizes between 44 nm and 102 nm. The obtained magnetite particles have particle sizes in the range of 46 nm to 132 nm. Brushite behaves differently; the obtained particles were shaped like small plates with edge lengths between 100 nm and 500 nm.

Formation mechanism of chalcogenide nanocrystals confined inside genetically engineered virus-like particles

Engineered virus-like particles (VLP) are attractive for fabricating nanostructured materials for applications in diverse areas such as catalysis, drug delivery, biomedicine, composites, etc. Basic understanding of the interaction between the inorganic guest and biomolecular host is thus important for the controlled synthesis of inorganic nanoparticles inside VLP and rational assembly of ordered VLP-based hierarchical nanostructures. We have investigated in detail the formation mechanism and growth kinetics of semiconducting nanocrystals confined inside genetically engineered bacteriophage P22 VLP using semiconducting CdS as a prototypical example. The selective nucleation and growth of CdS at the engineered sites is found to be uniform during the early stage, followed by a more stochastic growth process. Furthermore, kinetic studies reveal that the presence of an engineered biotemplate helps in significantly retarding the reaction rate. These findings provide guidance for the controlled synthesis of a wide range of other inorganic materials confined inside VLP, and are of practical importance for the rational design of VLP-based hierarchical nanostuctures.

Controllable synthesis and self-assembly of PbCO3 nanorods in shape-dependent nonionic w/o microemulsions

Microemulsion-based synthesis of inorganic nanoparticles is a versatile method, where many parameters can be varied to control the properties of products. In this work, solely by modifying the morphology of nonionic reverse microemulsions from spheres to cylinders, while keeping the water-to-surfactant ratio (W/S), salt concentration, volume fraction of surfactants, and temperature constant, we successfully controlled the variation of the length of PbCO3 nanorods with the same diameter. Short nanorods are formed in the spherical microemulsions, while long nanorods are produced in the cylindrical microemulsions. In addition, an amorphous-to-amorphous transformation from spherical nanoparticles to nanorods is observed and nanorods self-assemble into one-dimensional chains in the microemulsion solution.

Lactam-mediated synthesis of inorganic nanoparticles and size/surface-dependent properties: a case study on zinc oxide

Lactams have strong polarity, high boiling points, and strong coordination capacity. However they are yet to be well accepted as solvents for the synthesis of nanomaterials. This work aims at developing a facile and general lactam method to synthesize inorganic nanoparticles such as ZnO and Fe3O4 using three homologous lactams, γ-butyrolactam (BL), δ-valerolactam (VL) and e-caprolactam (CL), as solvents. The resulting nanoparticles (NPs) are uniform and spherical in shape and have good dispersion. The ZnO NPs synthesized in BL, VL and CL have average diameters of ca. 30.0, 7.3, and 8.5 nm, respectively. The average diameters of Fe3O4 NPs synthesized in BL, VL and CL are ca. 6.3, 4.0 and 4.8 nm, respectively. Moreover, their dispersion tends to deteriorate with increasing number of methylene groups in the lactam. Some explanations for the influence of lactam on the morphology of the synthesized NPs are proposed. Optical properties of ZnO NPs are investigated and are correlated with their morphologies and surface states. 6-Aminohexanoic acid (AHA), a biocompatible amino acid, is used to displace lactam capped on the surfaces of ZnO NPs.

In situ synthesis of gold nanoparticles in exponentially-growing layer-by-layer films

In situ synthesis of inorganic nanoparticles (NPs) in polyelectrolytes multilayers (PEMs) has recently gained much attention. Due to the versatility of their composition, PEMs offer a unique opportunity to synthesize a variety of NPs. So far, mostly cationic precursors have been used and only few studies have investigated the possibility of using amine groups to bind anionic precursors. Here, we use exponentially growing poly(l-lysine)/hyaluronan (PLL/HA) films as a nanoreservoir to bind and sequester aurochlorate (AuCl4-) anions thanks to the large number of free amine groups. The polypeptide–polysaccharide reactive template enabled the formation in a spatially-confined environment of gold NP at a very high yield. The synthesized gold NPs were homogenous and well-dispersed in the nanocomposite. Importantly, there was no particular effect of the film-ending layer (either PLL or HA). The largest particles of ∼9nm and the largest amount of gold were obtained at acidic pH of 3. When the pH was increased, smaller and more numerous NPs were synthesized but the total amount of gold was lower. Based on UV–visible spectrometry, FTIR and TEM data, we finally propose a scheme for the mechanism of gold NPs formation, in which several groups of PLL and HA contribute to the binding of gold ions, the nucleation and growth of NPs, and their stabilization in the “bulk” of the film.

Cobaltocenium‐Containing Block Copolymers: Ring‐Opening Metathesis Polymerization, Self‐Assembly and Precursors for Template Synthesis of Inorganic Nanoparticles

Side-chain cobaltocenium-containing block copolymers are prepared by ring-opening metathesis polymerization (ROMP). These block copolymers include one cobaltocenium-containing block, with the second block being either a nonmetal-containing segment or a cobaltocenium-containing segment with different counterions. These block copolymers are self-assembled into spherical core/shell micelles in solutions. A template strategy is used to prepare cobalt (II or III)-containing nanoparticles by treating the self-assembled micelles via UV/ozonolysis and pyrolysis. Characterization by X-ray photon spectroscopy and X-ray diffraction indicates that these nanoparticles consist of different oxidants of cobalt, depending on the chemical compositions of block copolymers.

Facile synthesis of inorganic nanoparticles by a precipitation method in molten ε-caprolactam solvent

This work reports on a general route to synthesize inorganic nanoparticles. Using molten e-caprolactam (CL, melting point = 69.2 °C) as a nonaqueous solvent and a stabilizer, various types of inorganic nanoparticles such as metal oxide, metal hydroxide and sulfide are readily synthesized via precipitation reactions of inexpensive precursors at about 100 °C for 2 h. These nanoparticles are relatively uniform in size and have relatively high crystallinity. Some of them such as ZnO and Fe3O4 have excellent optical and magnetic properties. Appropriate polarity, dielectric constant and coordinating effect are three key aspects for the formation of high-quality nanoparticles. The approach developed in this work would pave a new way for facile, low toxicity, solvent-recyclable and large-scale synthesis of inorganic nanoparticles with well-controlled dimensions and properties.

Recent progress in the synthesis of inorganic nanoparticles

Nanoparticles probably constitute the largest class of nanomaterials. Nanoparticles of several inorganic materials have been prepared by employing a variety of synthetic strategies. Besides synthesizing nanoparticles, there has been considerable effort to selectively prepare nanoparticles of different shapes. In view of the great interest in inorganic nanoparticles evinced in the last few years, we have prepared this perspective on the present status of the synthesis of inorganic nanoparticles. This article includes a brief discussion of methods followed by reports on the synthesis of nanoparticles of various classes of inorganic materials such as metals, alloys, oxides chalcogenides and pnictides. A brief section on core-shell nanoparticles is also included.

Investigation of counter-current mixing in a continuous hydrothermal flow reactor

Temperature profiles have been measured inside a counter-current mixer for the continuous hydrothermal synthesis of inorganic nanoparticles, at conditions (10–25mlmin−1 superheated water, referred to a density of 1gml−1, at 350–450°C and 24.1MPa, mixed with precursors at 10–20mlmin−1) used in work published by some of the authors and others. The superheated water cooled significantly before meeting the precursors, owing to internal transfer of heat through the wall of the inner tube to the products flowing around it. Consequently, the region immediately after the fluids had fully mixed was at a lower temperature than that determined from an overall heat balance. The flow of superheated water emerging from the inner pipe was characterised using the relevant dimensionless groups (Reynolds, Froude).

Protein-assisted synthesis route of metal nanoparticles: exploration of key chemistry of the biomolecule

Essentially, biomolecule assisted synthesis of inorganic nanoparticles can be divided into two categories. One uses multi-domain protein cages (template) and other relies on the self-assembly of the biomolecules including small peptides, DNA, and denatured protein. Protein templated synthesis of various nanomaterials is relatively well understood as the cages of the biological macromolecules and their specific interaction with inorganic ions ultimately dictate the size and crystallinity of the nanomaterials. On the other hand formation of nanoparticles using protein in the cost of the native structural integrity for the self-assembly is not well understood till date. In the present work we report a protein-assisted synthesis route to prepare highly crystalline 3–5 nm gold nanoparticles, which relies systematic thermal denaturation of a number of proteins and protein mixture from Escherichia coli in absence of any reducing agent. By using UV–vis, circular dichroism spectroscopy, and high-resolution transmission electron microscopy we have explored details of the associated biochemistry of the proteins dictating kinetics, size, and crystallinity of the nanoparticles. The kinetics of nanoparticles formation in this route, which is sigmoidal in nature, has been modelled in a simple scheme of autocatalytic process. Interestingly, the protein-capped as prepared Au nanoparticles are found to serve as effective catalyst to activate the reduction of 4-nitrophenol in the presence of NaBH4. The kinetic data obtained by monitoring the reduction of 4-nitrophenol by UV/vis-spectroscopy revealing the efficient catalytic activity of the nanoparticles have been explained in terms of the Langmuir–Hinshelwood model. The methodology and the details of the protein chemistry presented here may find relevance in the protein-assisted synthesis of inorganic nanostructures in general.

Purification and biochemical characterization of recombinant human H-ferritins from Saccharomyces cerevisiae

Recombinant human H-ferritins produced from Saccharomyces cerevisiae were purified and their molecular properties were characterized. Electrophoresis of the recombinant H-ferritins showed revealed bands with mobilities similar to those of the H-ferritins produced by Escherichia coli. The pI of H-ferritins from yeast was more basic than that of H-ferritins produced by E. coli. When the cells were treated with tunicamycin, the pI of H-ferritins was driven to a sharp band with the pI range similar to that of those produced by E. coli, implying that the H-ferritins from yeast are glycosylated. The iron uptake of H-ferritins was rapid in the initial stage, with a slight reduction when compared to ferritins from E. coli. Recombinant ferritins are commonly used during synthesis of inorganic nanoparticles in their cores for chemical and industrial purposes. Transmission electron microscopy revealed that the reconstitution yield and size distribution of the core minerals were affected depending on the protein shells. The H-ferritins with higher reconstitution yields (64.4%) showed slightly larger sizes (mean 6.52 nm) with narrower size distribution.

Facile Synthesis of PtNi Intermetallic Nanoparticles: Influence of Reducing Agent and Precursors on Electrocatalytic Activity

In this paper, a nonaqueous synthesis of PtNi nanoparticles is presented using multiple reducing agents and metal precursors. Through this investigation, it was found that all the species present in solution have an impact on the resulting nanoparticles. Metal precursor choice has a major effect on the resulting nanoparticles and their behavior. When using acetylacetonate (acac) precursors, the acac ligands bind tightly with the resulting metal particles and cannot be easily removed through washing. After annealing to nucleate the intermetallic phase, these ligands decompose into a carbonaceous coating rendering the particles inactive toward formic acid oxidation. This led to the development of a chloride precursor Li2NiCl4, not previously used for synthesis of inorganic nanoparticles, which is soluble in ether solvents unlike NiCl2 and many other metal chlorides. Using the lithium metal chloride as a precursor, the organic content of the nanoparticle products is greatly reduced as seen by lower weight lo...

Utilizing the amidation reaction to address the “cooperative effect” of carboxylic acid/amine on the size, shape, and multicolor output of fluoride upconversion nanoparticles

Here we elucidate the “cooperative effect” of carboxylic acid/amine on the size, shape, and multicolor output of fluoride upconversion nanoparticles (UCNPs) utilizing the amidation reaction. During the synthesis of NaYF4 UCNPs using oleic acid (OA) and octadecylamine (OM) as ligands, the evolution of the reaction solution was monitored by FT-IR and proton nuclear magnetic resonance (1H-NMR) spectroscopy. It is shown that N-octadecyloleamide (OOA) was formed and tightly bonded to the surface of the fluoride UCNPs. FT-IR and 1H-NMR analyses point towards a two-step OOA formation mechanism where OA initially reacted with OM to form an acid–base complex (C17H33CO2− +NH3C18H37) in reaction mixture, which further transformed into OOA before the nucleation of fluoride UCNPs at elevated temperature. Importantly, we find that the interaction of OOA with the surfaces of the fluoride UCNPs was stronger than that of OM, and that OOA could strongly quench the green-emitting levels of excited Er3+ ions. A series of control experiments and analyses demonstrate that OOA was not only responsible for the control of the size and shape of NaYF4: 20% Yb, 2% Er UCNPs, but also for the multicolor tuning of them. Those observations reveal that the “cooperative effect” between carboxylic acid and amine results from the amidation reaction and its product. This paper provides us with some new deep insights into the “cooperative effect” of carboxylic acid and amine during the synthesis of inorganic nanoparticles under thermolysis. Furthermore, other lanthanide-ion doped fluoride UCNPs with controlled size, shape and multicolor output can also be obtained in the same way.

Biomolecules in the synthesis and assembly of materials for energy applications

Biomolecules such as RNA, DNA, peptides, and proteins are emerging as powerful chemical tools for the synthesis of inorganic nanoparticles. Specific biomolecule sequences have been isolated that afford remarkable control over the size, shape, polymorph, and hierarchical assembly of nanoparticles. Such exquisite control over nanoparticle growth and integration has already produced materials with unexpected photophysical properties and battery devices with improved performance. Continued exploration of biomolecule-mediated materials synthesis portends further advances in materials for the energy sciences. This review surveys the use of biomolecules in the synthesis and assembly of materials with a primary focus on methods that allow vast landscapes of biomolecule sequence space to be sampled simultaneously to discover unique sequence codes for new materials.

Biosynthesis of Nanoparticles by Microorganisms and Their Applications

The development of eco-friendly technologies in material synthesis is of considerable importance to expand their biological applications. Nowadays, a variety of inorganic nanoparticles with well-defined chemical composition, size, and morphology have been synthesized by using different microorganisms, and their applications in many cutting-edge technological areas have been explored. This paper highlights the recent developments of the biosynthesis of inorganic nanoparticles including metallic nanoparticles, oxide nanoparticles, sulfide nanoparticles, and other typical nanoparticles. Different formation mechanisms of these nanoparticles will be discussed as well. The conditions to control the size/shape and stability of particles are summarized. The applications of these biosynthesized nanoparticles in a wide spectrum of potential areas are presented including targeted drug delivery, cancer treatment, gene therapy and DNA analysis, antibacterial agents, biosensors, enhancing reaction rates, separation science, and magnetic resonance imaging (MRI). The current limitations and future prospects for the synthesis of inorganic nanoparticles by microorganisms are discussed.

PH‐Responsive Microgel Particles Comprising Solely Basic or Acidic Residues

AbstractpH‐responsive microgel particles with a diameter between 200 and 600 nm, comprising either basic or acidic moieties, have been synthesized by emulsion polymerization. Basic microgels were prepared by the polymerization of the hydrophobic monomer 2‐(diethylamino)ethyl methacrylate (DEAEMA), while t‐butyl methacrylate (t‐BuMA) was used as the protected ester monomer to obtain methacrylic acid (MAA)‐based microgel particles following acid hydrolysis of the ester groups. These microgels exhibit reversible swelling in water in response to changes in the solution pH. Thus, when ionized, the microgel particles are swollen due to the electrostatic repulsions between the charged monomer repeating units and the osmotic pressure created within the microgel particles by the presence of the counterions to the charged monomer units. The solution properties of the polymer microgels were investigated as a function of the solution pH by potentiometric titrations, and the effective ionization constant (Kα) of the microgels was determined. Dynamic light scattering was used to characterize the swelling behavior of the microgels as a function of the degree of ionization of the monomer residues. The tertiary amine‐based microgels swell at low pH upon protonation of the amine units, while the PMAA microgels are swollen at high pH when the acid groups become neutralized. A change of the solution pH above or below a critical value (the effective pKα of the protonated monomer repeating units) leads to the formation of collapsed PDEAEMA or PMAA latex particles, respectively. Transmission electron microscopy was used to confirm the shape and size of the microgel particles while their morphology was also characterized by scanning electron microscopy. These pH‐responsive microgels can be used as colloidal templates for the in‐situ synthesis of inorganic nanoparticles at high loadings and in controlled drug delivery.

New developments in the nonaqueous and/or non-hydrolytic sol–gel synthesis of inorganic nanoparticles

The development of nonaqueous and surfactant-free sol–gel routes to metal oxides has become a very active area within the broad field of nanoparticle research, opening up great opportunities to access a wide variety of binary, ternary and doped metal oxide nanoparticles with high crystallinity and well-defined particle morphologies — important parameters towards their application in electrochemistry, (photo)catalysis or gas sensing. Extension to other classes of inorganic nanomaterials such as nitrides and sulfides and energy optimization of the processes by using dielectric heating represents two promising research directions. Remaining future challenges are not only the development of rational synthesis strategies, nanoparticle processing, assembly and patterning into functional and integrated structures, but also the optimization of the synthesis protocol with respect to energy efficiency and waste management. This review aims at giving both an overview of the current state of research as well as a discussion of the perspectives in the area of nonaqueous and/or non-hydrolytic sol–gel technology for the synthesis, processing and application of inorganic nanomaterials.