Large-Scale Electrochemical synthesis of SnO2 Nanoparticles

Wei Chen, Debraj Ghosh, Shaowei Chen 2008, June

1.0 Introduction- What are nanoparticles?

• a small object that behaves as a whole unit in terms of its transport and properties

• individual molecules are usually not referred to as nanoparticles

• Nanoparticles or ultrafine particles are sized between 1 and 100 nanometers

1.1 Introduction- Preparing Nanoparticles

• may occur in nature as well• methods of creation include attrition and

pyrolysis• some methods are bottoms up, some are

called top down• Top down methods involve braking the larger

materials into nanoparticles

1.2 Introduction- Top down and Bottom down methodsNanoparticles Synthesis:

2.0 Case study 1: Electrochemical synthesis of SnO2 nanoparticles

Introduction: Why Tin oxide?• n-type semi-conductor • Wide band-gap, energy gap (Eg = 3.65 eV at

300k)• Used extensively in: Energy storage and

conversion( solar cells and lithium ion batteries), gas sensors, Transparent conducting electrodes and optoelectronic devices

2.1 Experimental set-up

2.1.1 Materials:• Tin foil (0.25 mm thick, 99.8% purity)• Ethylene glycol (99 +%)• Ammonium fluoride (98 +%, extra pure)

2.1 Experimental set-up

• 2.1.2 Procedure:i. Tin foil degreased by sonification in acetone,

ethanol and nanopure water and dried in nitrogen

ii. Two electrode cell (2 cm gap) usediii. Tin foil used as sacrificial anodeiv. Platinum (Pt) coil as the cathodev. 74 mM NH4F in ethylene glycol electrolyte

2.1.2 Procedure:

• Vi Power supply: DC, 1623 A, output voltage 0-60 v in the constant voltage mode

• Three samples at 20 v, 30 v and 40 v prepared• Centrifuging of resulting powders and washing

in nanopure water and absolute ethanol and drying at room temperature

• Annealing at 700 ˚c for 6 hours with heating and cooling rates controlled at 5˚ c /min (to convert amorphous phase to the crystalline phase)

2.1.2 Procedure:

• Powder X ray diffraction performed• High-resolution transmission electron

microscopic images were collected• Data collection and analysis was done by

Renishaw’s WiRE proprietary software • Photoluminescence studies were carried out

with a PTI flouresence spectrometer • UV=Vis spectra collected using an ATI UNICAM

UV4 spectrometer

3.0 Results • XRD Patterns

3.1 Discussionsa) JCPDS Patterns for bulk SnO2 b) as prepared SnO2 particles at 40 c) annealed particles at 20 vd) annealed particles at 30 ve) annealed particles at 40 v• diffraction peaks broadened with comparison

with those from bulk material (curve a)• Can be attributed to the small size of SnO2

particles

Discussions• Particle size can be estimated by Debye-

Scherrer equation:• D where,• D is diameter of nanoparticle• K= 0.9, • λ= 1.54059 Å and is the full width at half 𝛽

maximum of the diffraction peaks

Discussions• Particle size decrease with increasing voltages

• Therefore, voltages can be exploited in manipulation of the particle sizes

Voltage (V) Particle size (nm)

20 15.430 12.540 11.8

Conclusions• Wei Chen et al. developed an effective

electrochemical route for the preparation of SnO2 nanoparticles

• Controlling of electrode Voltages can control particles sizes

• Annealing of the amorphous particles resulted into tetragonal rutile crystalline structures with abundant [101] and [211] orientations

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