1) The document describes the synthesis of gold nanospheres and nanorods with different morphologies for use in enzyme-free electrochemical biosensors. 2) The electrocatalytic properties and stability of biosensors using different gold nanocrystal shapes were investigated. Au nanocrystals were attached to screen-printed electrodes and used to detect hydrogen peroxide. 3) Results showed that the electrocatalytic properties and sensitivity of the biosensors depended on the morphology of the gold nanocrystals used. Biosensors using different shaped gold nanocrystals were stable for over 68 days.

1. Au nanospheres and nanorods for enzyme-free electrochemical biosensor applications
By: Nur Fatihah bt Abas(154120)
Journal’s Author: Yu-Ho Won, Keon Huh, Lia A. Stanciu
OBJECTIVES:
• To prepare Au nanocrystals with different morphologies and use for enzyme-free
electrochemical biosensor applications.
• To investigate the electrocatalytic properties of Au nanocrystals as a function on their
morphologies. RESULTS AND
• To investigate the stability in time of each of the Au nanocrystal-based enzyme-free DISCUSSION
biosensors.
EXPERIMENTAL
Materials: Preparation and Preparation and
HAuCl4, NaBH4, polyvinyl characterization of characterization of
Synthesis of Au Nanocrystals: biosensor: biosensors:
pyrrolidone (PVP), tetraethyl
orthosilicate (TEOS), ammonium Au NS- decorated silica spheres
hydroxide,2-propanol, ethanol,Au were synthesized by using  Au nanocrystals-based
NRs,dispersed in deionized(DI) hydrolysis and condensation of enzyme-free biosensor
water with 0.1% ascorbic sol-gel precursor. were fabricated by
TEOS(precursor) and ammonium coating Au Au nanocrystals- Figure 1. a) Au NSs on silica, b) Au NSs, c) Au NRs(ratio 1:3) and d)
acid, <0.1% cetyl
hydroxide(catalyst) were reacted nanocrystals on SPEs. based enzyme- Au NRs (ratio 1:5).(1)-(3) are a schematic, a TEM image and UV-
trimethylammonium in 2-propanol solution.
bromide(CTAB) surfactant capping  Au nanocrystals free biosensor Vis spectrum, respectively
As-synthesized silica spheres
agents, Hydrogen peroxide dispersed in DI water
were washed several times and
(H2O2,30% w/v re-dispersed in DI water. were dropped on SPEs Stability of biosensors
solution), K4Fe(CN)6, K3Fe(CN)6, KH Au NSs were formed on silica surface and dried for
2PO4, K2HPO4 and KCl. spheres via nodified approach. 2h at 25ºC.
>HAuCl4 solution (2.5mM,100μl)  PBS solution
Apparatus and measurements: was added to the silica (0.05M,pH 7)
-Transmission electron solution(100μl) while stirred. containing KH2PO4 and
microscopy(TEM) images of Au 10μl of NaBH4 solution
K2HPO4 was prepared
nanocrystals->Tecnai 20(FEI) (0.03wt%) was added to mixed
solution for reduction of [AuCl4]- and pH values were
operating at 200kV.
 solution was washed to remove adjusted from 4-7 by
-Ultraviolet visible(UV-Vis)
unreactants. using HCl.
absorption spectra-> SpectraMax Au NSs were synthesized via  Amperometric
M5 spectrometer. method reported by Lim. HAuCl4 responses of
-Electrochemical measurements solution (0.05mM) was prepared biosensors were
of biosensor for detection of and fast injected into PVP
obtained in 3ml
hydrogen peroxide-> BASi epsilon solution(10mg in 10ml DI water) Figure 2: Schematic of enzyme-free hydrogen Figure 3: Stability test of Au nanocrystal-
at 100ºC PBS(0.05M,pH7)
C3 cell stand. peroxide biosensor and reaction on electrode based enzyme-free biosensors over 68days
Mixed solution was heated at containing 10mM
-A conventional three-electrode (SPE: screen printed electrode, WE: working in the PBS (0.05,pH5) containing 10mM
same temperature for 1h and [Fe(CN)6]³¯∕ ⁴⁻, under
system consists of screen printed electrode, CE: counter electrode, RE: reference [FE(CN)6]³⁻⁄ ⁴⁻ at 200mV to 0.33mM
cooled to 25ºC. Then, solution was magnetic stirring
electrode as a working electrode, washed to remove excessive PVP
electrode). hydrogen peroxide.
(150rpm) at applied
Pt wire as counter electrode and and re-dispersed in DI water. potential of 200mV.
Ag/AgCl electrode as reference CONCLUSION:
electrode->biosensor  Au nanocrystal-based enzyme-free biosensors for detection of hydrogen peroxide
measurements ACKNOWLEDGEMENTS: were prepared.
I would like to thank to: Electrocatalytic properties depending on morphologies of Au nanocrystals were
 Pn. Ruzniza Md Nawi for the guidance in completing this poster. prepared and characterized.
Fellow friends for guidance and also moral support . The sensitivity of biosensors was influenced by morphologies of Au nanocrystals.