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Introduction to oxide nanoparticles

The most widespread route to fabrication of metal oxide nanoparticles involves the “bottom-up” approach involving the precipitation from aqueous solution from metal salts. Organometallic species can also be used, but due to their cost and the difficulty in manipulating these compounds, they are used less frequently. An alternative “top-down” approach has been demonstrated for aluminum and iron oxide nanoparticles; however, it is possible that this methodology could be extended to other oxides.

From molecular species to nanoparticles

Hydroxide, oxyhydroxide or hydrated oxide solid phases obtained via precipitation are made of particles whose average size may range from a few nanometers to a few microns. Particle morphology may vary depending on synthesis conditions. Moreover, aging in aqueous solution may bring about significant dimensional, morphological and structural changes.

Use of metal salts

The dissolution of metal salts in water results in the formation of solvated coordination compounds in which the chemistry of such complexes, and especially their acid behavior, provides a framework for understanding how the solid (oxide) forms via polycondensation. The binding of water molecules to the metal cation results in the increase in the acidity such that they tend to be deprotonate spontaneously according to the hydrolysis equilibrium

[M(H 2 O) n ] z+ + h H 2 O → [M(OH) h (H 2 O) n-h ] (z-h)+ + h H 3 O +

or by the neutralisation with a base,

[M(H 2 O) n ] z+ + h HO- → [M(OH) h (H 2 O) n-h ] (z-h)+ + h H 2 O

in which h is the hydroxylation ratio of the cation. The resulting hydroxylated complexes condense via two basic mechanisms of nucleophilic substitution, depending on the nature of the coordination sphere of the cations. Condensation of aquohydroxo complexes proceeds by elimination of water and formation of hydroxo bridges (olation), while for oxohydroxo complexes, condensation proceedes via the formation of oxo bridges (oxolation).

In order to understand how small particles form and what role the experimental parameters play on their characteristics and on evolution, it is useful to review the kinetic aspects of condensation reactions. The precipitation of a solid involves four kinetic steps.

  1. Formation of the zero-charge precursor. [M(OH) z (H 2 O) n-z ] 0 , which is able to condense and form a solid phase.
  2. Creation of nuclei, through condensation of zero-charge precursors.
  3. Growth of the nuclei through addition of matter, until the primary particle stage is reached.
  4. Nucleation and growth steps form particles under kinetic control following a reaction path of minimum activation energy under conditions imposed to the system (acidity, concentration, temperature), but the products are not necessarily thermodynamically stable.

Aging of the suspensions, which may take place over a long time scale (hours, days or months), allows the system to tend toward, or reach stability, and it is often associated with modifications of some physical or chemical characteristics of the particles.

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply

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Source:  OpenStax, Nanomaterials and nanotechnology. OpenStax CNX. May 07, 2014 Download for free at http://legacy.cnx.org/content/col10700/1.13
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