Synthesis of nanoparticles

Titanium dioxide nanoparticles were produced by the controlled hydrolysis of titanium tetraisopropoxide (TTIP) in the presence of reverse micelles formed in CO2 with the two fluorinated surfactants [53]. Based on dynamic light scattering measurements, the amorphous Ti02 particles formed by injection of TTIP were larger than the reverse micelles, indicating surfactant reorganization. The size of the particles and the stability of dispersions in CO2 were affected by the molar ratio of water-to-surfactant headgroup, (iVq), the precursor concentration, and the injection rate. 

In the nanowater pools (called nano reactors), nanosized metals and metallic salts can be conveniently synthesised. In the case of synthesis of metals, metal ions from their salts are reduced by different agents like sodium borohydride, ascorbic acid etc. Metallic salts are generally prepared by exchange reactions. The addition or mixing can be done in two ways. 

The metal salts are taken in w/o microemulsion in a container. Concentrated solution of the reductant or the desired reacting salt is then injected into the solution to perform the reaction process. The produced nanoparticles of the metals, viz. Cu, Ag, Au, Pd, Pt etc., or their salts can be isolated by destabilisation of the microemulsion system and washing and cleaning the products and storing them in inert conditions as required. 

The metal salts and the reductants or two reacting salts are taken in the water pools of the same microemulsion system. They are then slowly mixed with constant stirring as per stoichiometric requirements. The process of reduction or reaction takes place in situ and the desired nanoclusters of the metals or their desired salts are formed. They can be separated, washed and stored as described above. 

In both the procedures, by varying to, the dimensions of the synthesised particles can be altered. The pictorial representations of the above protocols are illustrated in Fig. 6.2. As can be seen, the internal phenomenon of droplet fusion followed by fission takes place. The materials formed during fusion by reaction get distributed among the droplets upon fission. By probability, some droplets may remain empty which is more in dilute solution of the reactants. The occurrence of the process of fusion and fission has been established by the TRFQ (time-resolved fluorescence quenching method [ 18-20]). The internal dynamics of the disperse particles essentially guide the formation characteristics of nanoparticles. 

The above-described procedures are in use in the preparation of insoluble (truly speaking, sparingly soluble) metal salts (sulphides, selenides, halides, sulphates, carbonates, oxides etc.). Isolation, cleaning, calcination (wherever required) can be performed as required. Procedural information maybe found in recent literature [21-24]. According to experimental observations, the nature of the yield (particle size in particular) may depend on the sequence and rate of mixing. This aspect is not often tested in practice. 

Anthony M. Rush, Carrie R. James, and Nathan C Gianneschi 

Handbook of Metathesis VoL 3 Polymer Synthesis, Second Edition. 

The assembly of amphiphilic block copolymers to generate discrete nanoscale structures is primarily driven by the hydrophobic effect, with micelle size and shape governed by a set of basic principles rooted in surfactant phase-separation behavior [22-28]. Important parameters that control the size of micelles are the degree of polymerization of the polymer blocks and the Flory-Huggins interaction parameter [28]. 

Along with the hydrophobic effect, micelle formation is further guided by the volume ratio of the hydrophobic and hydrophilic polymer domains. Through these principles, it is possible to synthetically engineer soft matter to organize into various nanoscale morphologies that can be precisely tuned as a result of the chemical control provided by, in this particular discussion, a well-defined ROMP catalyst [22,26]. 

Liaosha Wang,Jianhua Li, Ruoyu Hong, and Hongzhong Li 

Nanocomposites are made from two or more solid-phase materials, with at least one dimension in nanometers (1-100 nm). The solid phase can be amorphous, semicrystalline, grain, or a combination. The solid phase can also be organic, inorganic, or a combination. According to the size of the solid phase, nanocomposites generally include the following three types nanoparticles and nanopartide compounds (0-0 composites), nanoparticles and conventional bulk composites (0-3 composites), and composite nano films (0-2 composites). In addition, the nanolayered structure material is referred to as nanomaterial, and the multilayer nanocomposite made of different materials is also known as nanocomposite. 

Composite materials exhibit excellent performance, which can be widely used in aerospace, defense, transportation, sports, and other fields. Nanocomposites are one of the most attractive parts of the composite materials. Due to the fast development in recent years, nanocomposites are widely used by the developed countries for manufacturing new materials. The research on nanocomposites indudes organic-inorganic composites, nanopolymer matrix composites, and inorganic-inorganic composites. In this chapter, combined with our research experience, we mainly introduce the nanopolymer matrix composites to the readers. The synthesis and modification of nanopartides and preparation, characterization, and applications of nanopolymer matrix composites are mainly discussed. 

Nanomaterials are solid jrartides at the intermediate state, that is, between atoms/ molecules and macroscopic objects. Owing to small size effect, large surface effect. 

Polymer Composites Volume 2, First EdMon. Edited by Sabu Thomas, Kuruvilla Joseph, Sant Kumar Malhotra, Koichi Goda, and MeyyarappaOil Sadasivan Sieekala. 

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A similar procedure was adopted for synthesis of nanoparticles of cellulose (CelNPs). The polysaccharide nanoparticles were derivatised under ambient conditions to obtain nanosized hydrophobic derivatives. The challenge here is to maintain the nanosize even after derivatisation due to which less vigorous conditions are preferred. A schematic synthesis of acetyl and isocyanate modified derivatives of starch nanoparticles (SNPs) is shown in scheme 3. The organic modification was confirmed from X-ray diffraction (XRD) pattern which revealed that A- style crystallinity of starch nanoparticles (SNPs) was destroyed and new peaks emerged on derivatisation. FT-IR spectra of acetylated derivatives however showed the presence of peak at 3400 cm- due to -OH stretching indicating that the substitution is not complete. 

Synthesis of nanoparticles can be performed at mild conditions (high temperature or very low pressure are unnecessary). 

It must be pointed out that formation and stabihzation of nanoparticles in reversed micelles are the result of a delicate equilibrium among many factors. In addition, lacking a general theory enabling the selection a priori of the optimal conditions for the synthesis of nanoparticles of a given material with the wanted properties, stable nanoparticles containing w/o microemulsions can be achieved only in some system-specific and experimentally selected conditions. 

The synthesis of nanoparticles has been intensively pursued not only for their fundamental scientific interest, but also for many technological applications [1]. For many of these applications, the synthesis of monodisperse nanoparticles (standard deviations a < 5%) with controlled particle sizes is of key importance, because the electrical, optical, and... 

The basic principle of chemical synthesis of nanoparticles is to initiate chemical reactions and control the nu-cleation and growth of the reaction products. In order to achieve monodispersity, LaMer has shown that the separation of the nucleation stage from the growth stage is an important factor to be considered (Figure 1). 

Spreader-Bar Structures as Molecular Templates for Electrochemical Synthesis of Nanoparticles... 

Thermodynamic control (Figure 1, right) is based on adsorption of substances until quasi-equilibrium stage. In this case, the surface ratio of the adsorbed species is defined by the ratio of products of their concentration and binding constant. This deposition is much less influenced by poorly controllable fluctuations of external conditions and provides much better reproducibility. The total coverage can be almost 100%. Because of these reasons, the thermodynamic control is advantageous for preparation of mixed nanostructured monolayers for electrochemical applications including a formation of spreader-bar structures for their application as molecular templates for synthesis of nanoparticles. 

Figure 2. Electrochemical template-controlled synthesis of nanoparticles on nanostructured monolayer. The size of nanoparticles depends on the reduction charge and can be adjusted easily. (Reprinted from Ref [18], 2005, with permission from Wiley-VCH.)...

Currently, nanotechnology research is propelled by the need to develop strategies for the synthesis of nanoparticles with controlled shape and size distributions. The aim of this chapter is to provide some insight into the recent advances in nanoparticle synthesis using plants and plant derived materials. 

The synthesis of nanoparticles using plant biomass has been investigated by many [24,26]. Using high resolution transmission electron microscopy (HRTEM), it has been... 

Hammer-Nprskov d-band model, 70, 272-273, 327 Heme-copper oxidase, 610 High Throughput Synthesis of Nanoparticles, 572-574 Hydrogen (underpotential) adsorption, 60-63,254, 471-484, 526 Hydrogen evolution reaction (HER), 31, 79-87... 

Saez V, Mason TJ (2009) The synthesis of nanoparticles using Sonoelectrochemistry a review. Molecules 14 4284-4299... 

Abstract This chapter discusses the effect of ultrasound propagation in water and aqueous solutions, in the atmosphere of inert and reactive gases. Sonochemical studies of aqueous solutions of divalent and trivalent metal ions and their salts have been reviewed and the precipitation behaviour of hydroxides of metal ions has been discussed. Synthesis of nanoparticles of many metals using ultrasound and in aqueous solutions has also been discussed briefly. Besides, the nephelometric and conductometric studies of sonicated solutions of these metal ions have been reported. 

The template method involves using the pores in a microporous solid as nanoscopic beakers for the synthesis of nanoparticles of the desired material [1,3,10]. A wide variety of materials are available for use as template materials [1,10,14-19]. Pore diameter sizes range from Angstroms to many p,m. Several of the more common materials used as templates are reviewed below. 

Various metal and metal oxide nanoparticles have been prepared on polymer (sacrificial) templates, with the polymers subsequently removed. Synthesis of nanoparticles inside mesoporus materials such as MCM-41 is an illustrative template synthesis route. In this method, ions adsorbed into the pores can subsequently be oxidized or reduced to nanoparticulate materials (oxides or metals). Such composite materials are particularly attractive as supported catalysts. A classical example of the technique is deposition of 10 nm particles of NiO inside the pore structure of MCM-41 by impregnating the mesoporus material with an aqueous solution of nickel citrate followed by calicination of the composite at 450°C in air [68]. Successful synthesis of nanosized perovskites (ABO3) and spinels (AB2O4), such as LaMnOs and CuMn204, of high surface area have been demonstrated using a porous silica template [69]. 

Swihart MT (2003) Vapor synthesis of nanoparticles. Curr Opin Colloid Interf Sci 8 127-133... 

Johannessen T, Jenson JR, Mosleh M, Johansen J, Quaade U, Livbjerg H (2002) Flame synthesis of nanoparticles Application in catalysis and product/process engineering. Chem Eng Res Des 82 1444-1452... 

Before we go through the organometalUc or metal organic route to the synthesis of nanoparticles, a brief description of other synthetic methods is given below. 

Jones AC (2002) Molecular design of improved precimsors for the MOCVD of electroceramic oxides. Journal of Materials Chemistry 12(9), 2576-2590 Jones AC, Chalker PR (2003) Some recent developments in the chemical vapour deposition of electroceramic oxides. Journal of Physics D-Applied Physics 36(6), R80-R95 Kammler HK, Madler L, et al (2001) Flame synthesis of nanoparticles. Chemical Engineering Technology 24(6), 583-596... 

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