Dr. Aoife Morrin. School of Chemical Sciences Dublin City University Ireland. The National Centre for Sensor Research

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1 INVESTIGATION OF NANOSTRUCTURED MATERIALS FOR NOVEL BIOSENSOR FABRICATION METHODOLOGIES Dr. Aoife Morrin National Centre for Sensor Research School of Chemical Sciences Dublin City University Ireland

2 Introduction Emergence of nanotechnology opening new horizons for electrochemical biosensing How can nanostructured conducting polymers contribute to this space? Target Analyte Explore transduction interface Transducer Electrode Polyaniline Nanoparticles

3 Overview Electrode Interface Synthetic approaches to fabricating polyaniline nanoparticles Electrode modification with nanoparticles (i) Electrodeposition Excellent control over film thickness (ii) Casting Amenable to Mass Production Sensing Applications

4 Screen printing Sensor Platform Low start up and manufacturing cost Mass production Disposability Flexible design process Platform for glucose biosensor industry

5 Electrode Modification by Conducting Polymer Highly conductive Simple doping/dedoping chemistry Good environmental stability Electrical properties modified by ox. state of main chain Applications: Sensors electrochemical optical Anti-corrosion protection of metals Supporting material for catalysts Electrochromic displays Aniline A - + N H NH 2 N H Doped Polyaniline (conductive state) n

6 Bulk Polyaniline Chemical or electrochemical synthesis Acidic conditions for deposition Insoluble in common solvents Carcinogenic monomer Nanoparticulate polyaniline Higher Processibility Aqueous Dispersions Higher Conductivity Amenable to alternate deposition techniques Nanoscale Sensor Fabrication

7 Oxidant Synthesis of Nanoparticles Rapid Mixing method* Monomer to Oxidant ratio = 4:1 Aniline Aniline Monomer DBSA Micelle DBSA added to serve as dopant & surfactant (provide micelle structure to stabilise particles) SDS present also acts as surfactant for stabilisation * Jiaxing Huang, Richard B. Kaner, Angew. Chem. Int. Ed. 2004, 43,

8 Polyaniline Nanoparticles Volume (%) Diameter (nm) No Stabiliser Present Stabiliser Present

9 (i) Electrodeposition of Nanoparticles 50 Current (µa) 0-50 Potentiodynamic method of deposition Doped with DBSA Film thickness ~350 nm Potential (V) Nanoparticles Bulk Polymer

10 SEM Imaging of Protein on Nanoparticulate Films mg ml-1 Catalytic Signal (µa) HRP BSA 0.01 mg ml mg ml-1 1 mg ml Protein concentration mg ml * Imaging done using silverenhanced gold labelled protein (Mo anti-hcgβ antibody) *Morrin, A., Ngamna, O., Moulton, S., Killard, A.J., Smyth, M.R. (2004). Electroanalysis, The National Centre for Sensor 17: mg ml-1 20 µm Research

11 (ii) Casting 2 Current (ma) Potential (mv) Note: ph adjusted to 7.0, 5.5 % w/w nanoparticles, 5 µl Morrin, A., Wilbeer, F., Ngamna, O., Moulton, S., Killard, A.J., Smyth, M.R. (2004). Electrochem. Comm., 7:

(iii) Inkjet Printing Method for casting ultra-thin

12 (iii) Inkjet Printing Method for casting ultra-thin films, (deposits microdroplets of 2-12 pl) High precision, resolution of ~ 25 µm. Amenable to simultaneous deposition of more than one ink. Non-contact Printing. (substrate and print head don t touch) Rapid method, quality of print easily monitored in real time.

13 Inkjet Printing Technologies Thermal Piezoelectric

Favoured over other more expensive single

14 Instrumentation Strategy for Ink-Jet Printing Epson desktop printer (2880 x 720 drops per inch) Uses piezo technology Drop on demand Screen- Printed electrode Favoured over other more expensive single head devices due to the four available reservoirs.

15 Electrochemistry of Inkjet Printed Polyaniline Scan Rate Study Relationship of peak current with scan rate E-03 R 2 = Current (ma) Potential (V) mv 300 mv 200 mv 50 mv 25 mv 0.2 peak Current (A) 1.00E E E E-03 peak current \A 2.00E E E E peak anodic currents peak cathodic currents scan rate (mv.s -1 ) R 2 = Relationship of peak current with (scan rate) 1/2 peak anodic currents peak cathodic currents The National Centre for Sensor -2.00E-03 Research (scan rate) 1/2 \ (mv.s -1 ) 1/2

16 Inkjet printed (50 prints) Profilometry Drop-coated (5 µl)

17 Drop-Coating vs. Inkjet Printing Current (A) Drop-Coated (2.5 µl) Ink-Jet Printed (50 Prints) prints comparable to dropcoating 2.5 µl (Equates to ~ 20 nl / mm 2 ) Difference in deposition techniques responsible for comparable CVs. Potential (mv)

18 Water-Soluble Polyaniline Poly(2-methoxyaniline-5-sulphonic acid) (PMAS) Sulphonated polyaniline PMAS must complex with a polycation (poly-l-lyseine (PLL)) to render it insoluble Need to co-deposit, i.e., print simultaneously Inkjet has that facility PMAS PLL Before Washing After Washing

19 Water-Soluble Polyaniline Inkjet Printed 0.79 V Drop-Coated 0.75 V Current (ma) Current (ma) V V V 0.34 V Potential (V) Potential (V) Demonstrates unique advantages of using inkjet printing The inkjet printed films show improved electrochemistry compared to the evaporative cast films, indicating more efficient electron transfer process This will lead to improvement of biosensor performance

20 Biosensor Application Current (A) 8e-6 6e-6 4e-6 5 ppm 3 ppm 0.5 ppm 0.1 ppm Real-Time Multi-Calibration Study Flow Cell Setup HRP & H 2 O 2 passed over together for short periods of time. 2e Time (s) Concentrations from 5 ppm to 0.1 ppm HRP with 10 mm H 2 O 2 used. Decreasing slopes

21 Ammonia Sensing Chemical & Gas Sensing Environmental, Automotive, Chemical, Medical Biosensing Measurement in biosensors is finding increasing applications as ammonium ions are a metabolic product in many enzymatic reactions. E.g., Urea and Creatinine can be detected by sensing in this way 1 s

22 Ammonium Ion Sensing Current (ua) Current (na) Time (sec) Ammonium ions (ppm) Current (na) y = 87.01x R 2 = Ammonium ions (ppm) Current (na) y = x R 2 = Ammonium ions (ppm)

23 And To Conclude.. Synthesised polyaniline nanoparticles by a rapidmixing method Applied nanoparticles for nanostructuring macroscopic electrodes. Casting by Inkjet printing: most promising approach: high quality & amenable to manufacturing Demonstrated applications for these modified electrodes, e.g., biosensing catalytic reduction of H 2 O 2 and chemical sensing of ammonium ions.

24 Acknowledgements Prof. Malcolm Smyth Dr. Tony Killard Dr. Máire O Connor, Eimer O Malley & Claire McMorrow and all the Sensors & Separations group Henry Barry (NCSR) Prof. Gordon Wallace, Dr. Simon Moulton and Dr. Orawan Ngamna (UoW) from Enterprise Ireland under the technological development plan TD/03/107

Electrochemically Synthesized Multi-block

Electrochemically Synthesized Multi-block Nanorods Sungho Park SungKyunKwan University, Department of Chemistry & SKKU Advanced Institute of Nanotechnology (SAINT) J. Am. Chem. Soc. 2003, 125, 2282-2290