1. Voltammetric sensing of mercury(II) ion by using bimetallic nanoparticles modified glassy carbon electrode
Samia Siddiqqui
National centre of excellence in analytical chemistry university of sindh jamshoro, sindh
3/15/2017

2. Outlines Introduction Effects of Hg (ll) sensor & modification process
Results and discussions
Conclusion

3. Sensors
A sensor is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument.
Voltammetry
Voltammetry is a category of electroanalytical methods used in analytical chemistry and various industrial processes which give information about an analyte obtained by measuring the current as the potential is varied.

4. Why Mercury is centre of attention
Hg2+ possess highly toxic effect and long lasting adverse health impacts on humans and animals therefore the assessment of mercury distribution in environmental samples is a key task for the scientists.

5. Nanosciences Bimetallic nanoparticles
A new class of material have been investigated which is composed of two different metals.
Bimetallic nanoparticles are the combination of two metals at nanoscale size.
From the scientific and technological view point BMNPs are more investigating material than monometallic nanoparticles.
BMNPs show improved eletcronic , optical stability, in electrochemical reaction and electrocatalytical performances than MMNPs due to alloy effect.

6. Wet Chemical reduction Hydero themal
Thermal reduction
Thermal decompositio
Wet Chemical reduction
Hydero themal
Chemical reduction
BMNPs
Simple & economic
easily adopted
Control size & shape
Faster & easy
green
Laser ablation
Sono chemical reduction
Polyol method

7. Objectives To develop innovative schemes for the synthesis of BMNPs.
To use green, environmental friendly and cost effective chemicals as reducing and/or capping agent.
To test different combinations of precious metals and non precious metals for their synergic effects with various compositions.
Investigate optimum conditions for synthesis of BMNPs
To investigate catalytical effeciency of synthesized BMNPs in various field of Applications.

8. Conventional techniques for determination of Hg(II)
Atomic absorption spectrometry (AAS)
Atomic fluorescence spectrometry (AFS)
Inductive coupled plasma – atomic emission spectrometry (ICP – AES)
Mass spectrometry (MS)
Chromatography and other miscellaneous methods, etc
Limitations:
These all techniques require complicated sample preparation procedures.
i.e. derivatization & complexation.
Highly Expensive in terms of running and equipments cost.
Require highly equipped laboratory.
These methods are not environment friendly 8

9. Superiority of Electroanalytical methods over other analytical methods
Voltammetry
Simpler & rapid analysis
Low running cost
Better selectivity, sensitivity, reproducibility, LOD, and LOQ
Good for organic as well as inorganic (metals) determinations
Simpler set-up
Useful for simultaneous determination
Trace Analyzer
797 Metrohm
Reference
Electrode
Counter
Working Electrode
DME GC 9

10. Application Study Potentiostat 3 electrode system
Working Electrode: GCE
Reference Electrode: Ag/AgCl
Auxilliary or Counter: Platinum Electrode
Differential pulse voltammetric measurements were carried out by Trace Analyzer model 797 Metrohm

11. Modification of glassy carbon electrode with BMNPs
BMNPs + dry + nafion + dry = modified GCE
BMNPsNps
Nafion

12. Results & discussions
Effect of different electrode on peak current of 10ppb Hg(ll) ion on nafion modified BMNPs electrodes
Effect of Bare GCE, Modified GCE, and Nafion mod: GCE 12

13. Effect of different supporting electrolyte on peak current of 10ppb Hg(ll) ion on nafion modified BMNPs with GCE
Effect of different modes on peak current of 10ppb Hg(ll) ion on nafion modified BMNPs with GCE

14. Comparison of BMNPs--GCE with monometallic Au-Nps-GCE and Ag Nps-GCE for determination of 10ppb Hg(ll) ion
Twenty successive D.P voltammogram of 10 ppb of Hg(ll) ion on nafion modified BMNP sensor

15. Linear calibration plot of Hg2+ in the range of 0
Linear calibration plot of Hg2+ in the range of 0.002–19 ppb, R2 value of with LOD value is found to be ppb and LOQ value is found to be 0.002ppb.The sensitivity of develop sensor was calculated to be 4.21x 106 µA,Mm-1Cm-2

16. Application of sensor to real samples
Determination of mercury in water samples
Samples type
Locality
Calibration method
(ppb )n
Standard addition method (ppb)n
Gajarwa lake
Nawabshah
47.49 ± 4.6
47.36 ± 0.3
Phuleli cannal
Hyderabad
38.95 ± 3.0
38.12 ± 0.7
Keenjhar lake
Thatha
36.67 ± 4.1
36.46 ± 1.0
Mancher lake
District Dadu
52.62 ± 1.4
52.87 ± 0.2
River indus
Jamshoro
48.63 ± 0.8
48.85 ± 0.6
Quantification of heavy metal ions (ppb) in various types of water samples * by current sensor; **, by official method; ±, standard deviation of triplicate sample.
±, Standard deviation ; n, No. of replications, 3 16

17. Conclusions
Au-Ag core shell nanoparticles have been synthesized by using L-cysteine as green and ecofriendly reducing as well as capping material in order to avoid the need of hazardous and non-toxic reducing/ capping agents.
Application of nafion stabilized BMNPs on GCE demonstrated the development of highly selective, sensitive sensor for estimation of Hg2+ ions at the working range of – 19ppb with LOD of 0.61ppt (3pM) and the sensitivity of develop sensor was calculated to be 4.21x 106 µA,mM Cm-2.
The as developed sensor was successfully applied for detection of Hg (II) ions in various types of real water samples of environmental concern.

18. The results of this study describes an extremely high concentration of Hg (II) among all types of waters collected from various localities of Sindh Province.