Major objectives of my study:

1. Fabrication of low dimensional structures via template synthesis: a membrane based synthetic approach Rajesh Kumara and S.K.Chakarvarti* Department of Physics, Haryana College of Tech. & Mgmt., Kaithal, India *Department of Physics, National Institute of Technology (Deemed University), Kurukshetra, India

2. Major objectives of my study: • CONTROLLED PRODUCTION OF TRACK-ETCH MEMBRANES (TEMs) • TEMs of different diameter and shape are produced using chemical etching. • SYNTHESIS OF ZnS NANOWALLE MICROTUBULES • Nanowalled microstructures of ZnS are generated through the pores of TEMs using “Template Synthesis”. • CHARACTERIZATIONS • Morphological characterization using SEM

3. Fabrication of nano/micro structures • Two fundamental approaches have been used in fabrication and processing of nano/micro structures Top -down Bottom -up

4. Top-down – this refers to the process of scaling down bulk structures to the nano scale using etching and machining techniques – mechanical attrition (ball milling) , lithography/etching Bottom-up – this is the building up of the nano structures atom by atom, or molecules by molecules – powder/ Aerosol compaction, chemical synthesis (Template Synthesis)

5. Template synthesis (TS) • The principle of TS is producing components through use of replication. • Nano/micro structures of controlled shape, size and very LOW dimensions are fabricated. • Easy to use and very cost effective.

6. Types of template methods 1. Negative template synthesis 2. Positive template synthesis

7. Negative template methods • Such methods use prefabricated nano/micro pores or channels of pre-decided shape and size in solid materials, known as templates. • The desired material is deposited into these pores by suitable methods. • TEMs, AAM and mica sheets are negative templates.

9. Positive template methods • Use wire-like structures like DNA, Carbon nanotubes etc as templates. • materials are grown on their surfaces. • The physical dimensions like thickness are controlled by the amount of material deposited. • On removal of template, wire or tube like structures are generated.

10. Positive template method DNA Electrode Electrode Synthesized Structure

11. EXPERIMENTAL DETAILS: NTF: Polycarbonate (Makrofol-KG) Thickness: 10 micron Energy: 13.6 MeV/n (U238 ions) Flux: 106/cm2 Irradiated at GSI, Darmstadt, Germany using UNILAC facility.

12. * PC has high mechanical strength, toughness and is transparent. * Homogeneous pores can be created * It can be easily dissolved in suitable solvent (a requirement for retrieval of the synthesized wires after deposition).

13. Dissolve TEM Synthesis of nano/micro structures by Electrodeposition Place membrane in aqueous solution of metal salt copper on bottom Nanoporous TEMs M+ Apply potential - e e - M+(aq) + e- M(s)

14. Actual photograph of electrodeposition cell used in lab

15. Current–Time curve for the deposition of materials into TEMs

16. SEM photograph of ZnS Nanowalled microtubules 0.06 M ZnCl2 + 0.05 M Na2S at 600C Promising element for blue light emitting diodes Protective windows and optical element (Eg = 3.68 eV)

17. ZnS hollow tubules # Optimum time of deposition # Gases formation during deposition During etching of polymer some fixed charges are formed due to dissociation of carboxylic group on the polymer surface. Hence, TEM become anionic in nature and electrostatic attraction contribute to absorption of material on the walls of the pore.

18. Gases evolution Tubules formation mechanism t1 t=0 t2 Pore may provide an exit or out let for the gas which would push the material towards the pore wall

19. IMPORTANT CONCLUSIONS Template synthesis is a cost effective approach for the fabrication of nano/micro structures and TEM act as an ideal template. • Nanowalled microtubules of ZnS have been generated successfully using this technique.

20. THANKS FOR YOUR PATIENCE !