Skip to main content

Metallic Nanoparticles, Top- Down and Bottom-Up


In metallic nanoparticles part I, the interesting and unique properties of metallic nanoparticles were mentioned and some examples for these fascinating nanoparticles such as gold and silver nanoparticles were given. Here we discover some methods for the preparation of the metallic nanoparticles.
Preparation of nanoparticles can be done by two main approaches. The first is top- down approach, in which the starting material is in the macro or micro scale and using different techniques the particles are transformed to the nano-scale. The second technique is the bottom-up approach. In this approach, which is the most used for the preparation of the nanoparticles, the nanoparticles are formed starting from atomic level to the nano-scale level. The goal of these approaches is to prepare nanoparticles with specific nano-sizes and similar sizes for all particles in which the unique properties can function.
Image retrieved from: http://nanotechnologyjd.weebly.com/
The top-down approach as its name indicate means from top (bigger) to bottom (lesser). It is similar to the manufacturing of statue from stone. The bulk or the giant stone is taken and carving plus cutting is done to the stone until the desired shape is accomplished. Similarly for metallic nanoparticles either mechanical or chemical fabrication techniques are used. Mechanical techniques include mechanical milling in which a suitable powderis placed in a high energy mill, along with a suitable milling medium. Chemical techniques can be applied by etching the metal by acids to obtain the desired particles.
The bottom-up approach starts from the atoms of the metals by chemical processes based on transformations in different mediums. It can be done in solutions such as sol-gel and colloidal methods or it can be done in gaseous medium such as, chemical vapor deposition (CVD), plasma or flame spraying synthesis, laser pyrolysis, and atomic or molecular condensation. There are also other methods that are used for the production of the metallic nanoparticles using the bottom-up approach. The details for these processes and the difference between them will be mention in the following blogs.

Posted by
https://nanografi.com/blog/metallic-nanoparticles-part-ii-top-down-and-bottomup/https://nanografi.com/blog/metallic-nanoparticles-part-ii-top-down-and-bottomup/
Labels:

Comments

Post a Comment

Popular posts from this blog

Molybdenum Trioxide Nanoparticles/Nanopowder and Applications

General Information about Molybdenum Trioxide                                                     Molybdenum trioxide is chemical compound with the formula MoO3. Its chief application is as an oxidation catalyst and as a raw material for the production of molybdenum metal.  Molybdenum Trioxide  is a very light blue powder. Molybdenum Trioxide Nanoparticles/Nanopowder and Their Applications                                                    Like many  nanoparticles/nanopowder , Molybdenum Trioxide nanoparticles/nanopowder are used as catalysts. These catalysis reactions include hydrogenation catalysis and cracking catalysis. Molybdenum Trioxide nanoparticles/  nanopowder are useful for...
Post a Comment
Read more

Rundown about Silicon Oxide Wafer

The main insulating material used in micro-technology is Silicon Dioxide, which in chemical symbols is written as SiO2. In semiconductor technology, SiO2 thin film layers are mainly used as dielectric material film in transistors, capacitors (DRAM) or flash-memories. Silicon Oxide Wafers are produced using crystallization, solid state and other ultra-high purification processes such as sublimation. This process forms a cylindrical ingot, which is then sliced and polished to form wafers. Thermal oxide is a kind of "grown" oxide layer, compared to CVD deposited oxide layer, it has a higher uniformity, and higher dielectric strength, it is an excellent dielectric layer as an insulator . In most silicon- based devices, thermal oxide layer play an important role to pacify the silicon surface to act as doping barriers and as surface dielectrics. The simplest way to produce an insulating silicon oxide layers (SiO2) on silicon wafers is to oxidize silicon with oxygen, which ...
Post a Comment
Read more

Hydroxyapatite Nanopowders and Their Applications

Hydroxyapatite, is a naturally occurring mineral form of calcium apatite with the formula Ca 5 (PO 4 ) 3 (OH). Pure hydroxyapatite powder is white. Naturally occurring apatites can, however, also have brown, yellow, or green colorations, comparable to the discolorations of dental fluorosis. Hydroxyapatite Nanopowder/Nanoparticles (50 nm, 99.95+%)  has been widely used as a biocompatible ceramic in many areas of medicine, but mainly for contact with bone tissue, due to its resemblance to mineral bone. In mammals, the skeleton presents a carbonated and partially substituted apatite, based on nanocrystal aggregates, and associated with collagen, building up 3-D structures present in various bone tissue conformations like trabecular or cancellous bone. There has been growing interest in developing bioactive synthetic ceramics that could closely mimic natural apatite characteristics. As mentioned before,  Hydroxyapatite Nanopowder  is the main inorganic constituent of bon...
Post a Comment
Read more