Synthesis Of Nanomaterial

SOLVOTHERMAL METHOD PHOTOCHEMICAL METHOD

ELECTROCHEMICAL METHOD

SOLVOTHERMAL METHOD

History: Solvothermal synthesis route was first proposed by YI-TAI QIAN in 1996 from university science and technology of china

This method is very similar to Hydrothermal route, the only difference in the precursor solution is usually No aqueous but this not always in the case in literature uses of the expression

SOLVO -- THERMAL

Solvant -- use of the temperature

SOLVOTHERMAL PROCESSES:A “solvothermal reaction can be defined as a chemical reaction (or a transformation) between precursor(s) in a solvent (in a close system) at a temperature higher than the boiling temperature of this solvent and under high pressure”.

auto geneous pressure or imposed pressure. Subcritical or supercritical domain. Homogeneous or heterogeneous system.

MAIN FACTORS GOVERNING THE SOLVOTHERMAL CRYSTAL GROWTH

CHEMICAL FACTORS

PHYSICAL FACTORS

KINETICAL FACTORS

- nature of the solvant,- nature of the nutrient,- nature of the seeds,- the interactions solvant/ wall of the HP. Vessel

- the Crystal growth temperature (Tgrowth),- the T value,- the pressure value,- the hydrodynamics in the crystal-growth system.

- the kinetics of dissolution,- the kinetics characterizing the diffusion of chemical species,- the crystal growth kinetics,- the duration of the crystal growth.

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New Trends in Solvothermal Crystal Growth Processes

Recently one-dimensionnal (1D) nano-structures (wires, rods, tubes…) have been the focus of intensive research owing to their applications in mesoscopic physics

and fabrication of nanoscale devices.

The formation of a 1D nanostructure depends on two steps:

- the nucleation,- the crystal growth.

In addition for generating nanostructures three main parameters must be controlled:

the dimensions, the morphology, the monodispersity (or uniformity)

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THE SOLVOTHERMAL PROCESSES ANDTHE CRYSTAL GROWTH AT THE NANOSCALE

Schematic illustrations of the different strategies for achieving 1D growth.

A) Induction of 1D morphology through the anisotropic structure,B) confinement by a liquid droplet in the liquid/solid process,C) use of templates,D) use of capping agents able to modify the growth rate in one direction,E) self assembly of OD nanostructure,F) size reduction of 1D microstructure.

Autoclave for cooking Autoclave for medical Autoclave for solovothermal

Apparatus in Solvothermal Synthesis

Apparatus in Solvothermal Synthesis – 2

whole apparatus part of chamber components of chamber

Solovothermal are usually thick walled steel cylinders with hermetic seal which must withstand high temperature and pressure for prolonged periods of times.

The autoclave material must be inert with respect to the solovent. The closure is the most important element of the autoclave.

To prevent corroding of the internal cavity of the autoclave, prodective inserts are genrally used. These may have the same shape of the autoclave and fit in the internal cavity.

Inserts may be made up of carbon free iron, glass or quarts, copper or Teflon depending on the temperature and material used.

Apparatus in Solvothermal Synthesis - 3

1.most material can be made soluble in proper solvent by heating and most material can be made soluble in proper solvent by heating and pressure in the system close to its critical point;

2.significant improvement in the chemical activity of the react and the possibility to replace the solid state synthesis and materials which may not be obtained via solid state reaction may be prepared through solvothermal synthesis.

3. Products of intermediate state metastable state and specific phase maybe easily produced, novel components of metastable state and other specific contents state may be synthesized.

4. Easy and precise to control of the size shape distribution crystallinity of the final product through ajay singh the parameters such a reaction temperature, reaction time, solvent type, surfactant type and precursor time.

5. Substances which which are low in melting point high in vapour pressure and tend to go pyrolysis will be obtained.

6. Mass production of samples solovothermal/hydrothermal.

Advantages:

Disadvantages: 1.The need to expensive autoclave.

2.safety issues during the reaction process.

3.impossibility observing the reaction process.

Applications 1.We can center size of various kind of Nano structures through solvothermal approaches including medal oxides carbonaceous Nano structures and etc.. 2.We can also produce zeolite ,nano wires, carbon nanotubes

Examples

PHOTOCHEMICAL METHOD

Photochemical method

• Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption.

• Photochemical reactions require a light source that

emits wavelengths.

Ultraviolet (wavelength from 100 to 400 nm) Visible light (400 – 750 nm) Infrared radiation (750 – 2500 nm)

Sources of Photochemical

In the early experiments sunlight was the light source.

Mercury vapor lampsLow pressure mercury vapor lamps (254 nm)

Laser beamsLEDs have a relatively narrowband Rayonet lamps

Poly chromatic sources

Monochromatic Source

The emitted light must of course reach the targeted functional group

• The solvent is an important experimental parameter.

• Chlorinated solvents are avoided because the C-Cl bond can lead to chlorination of the substrate.

• Strongly absorbing solvents prevent photons from reaching the substrate.

• Hydrocarbon solvents absorb only at short wavelengths and these preferred for Photochemical.

• Experiments requiring high energy photons.

• Solvents containing unsaturation absorb at longer wavelengths and can usefully filter out short wavelengths.

Solvents:

ELECTROCHEMICAL METHOD

It is possible to control particle size by adjusting the electrolysis

parameters and to improve homogeneity of Ag NPs by changing

the composition of the electrolytic solution.

PVP can be used to protect Ag NPs from agglomeration,

significantly reduces silver deposition rate and promotes silver

nucleation & Ag NPs formation rate.

Electrochemical method

Electrochemical method for synthesis of Ag NPs

The rate of reaction was found to increase with:

– Decrease in the distance between the electrodes (1–2 cm)

– Increase in the voltage (5–50 V DC)

– Increase in the temperature

A longer reaction time resulted in:

– Larger size of Ag NPs

– Higher concentration of Ag NPs

Alternatively, the cathode could be other metals such as

platinum.

The presence of PVA (1–100 ppm):

– Acts as supporting electrolyte

– Accelerates the NP nucleation and growth

– Produces highly concentrated suspensions of NPs

Electrochemical method for synthesis of Ag NPs

THANK YOU ByARJUN KUMAR BM.Sc. Nano science & technologyI year