Danmar Gloria Supervisors: Professor D Brynn Hibbert A/Prof. Grainne Moran Optical Sensors for Environmental and Food Quality Monitoring

Development of an Optical Sensor based on 7-amino-1,3-naphthalene disulfonic acid (AmNDS) for Analysis of Hexanal Arsenic Speciation by Surface Enhanced Raman Spectroscopy OPTICAL SENSORS Outline

ArseniteArsenate Methylarsenite Methylarsenate Dimethylarsenite Dimethylarsenate Arsenic Chowdhury, R., A. Dutta, et al. (2008). "In vitro and in vivo reduction of sodium arsenite induced toxicity by aqueous garlic extract." Food and Chemical Toxicology 46(2): Hung, D. Q., O. Nekrassova, et al. (2004). "Analytical methods for inorganic arsenic in water: a review." Talanta 64(2):

Laboratory Techniques Atomic Absorption Spectroscopy Atomic Fluorescence Spectroscopy Inductively Coupled Plasma Neutron Activation Analysis Electrochemical Methods Polarographic Techniques Cathodic Stripping Voltammetry Anodic Stripping Voltammetry

Recent technology AdvantageDisadvantage Ease of useWeak Correlation Contains mercury as waste Wide spectrum of metals from different samples Contains radioactive source High SensitivityDurability being questioned Interferences from Cu, Hg, Zn Colorimetric Kits XRF handheld devices Microelectrode ASV Biological Assay Laser Induced Breakdown Spectroscopy Melamed, D. (2005). "Monitoring arsenic in the environment: a review of science and technologies with the potential for field measurements." Analytica Chimica Acta 532(1): ARSENIC SPECIATION

Raman Spectroscopy Monochromatic Light (Laser) Inelastic Scattering

Surface Enhanced Raman Spectroscopy (SERS)  Electromagnetic Effect Kim, K., H. S. Lee, et al. (2007). "Silver-particle-based surface-enhanced resonance Raman scattering spectroscopy for biomolecular sensing and recognition." Analytical and Bioanalytical Chemistry 388(1): enhancement factor can be as much as Enhancement of the electric field of the surface Frequency of surface Plasmon in resonance with incident radiation Oscilation is perpendicular to surface Charge transfer complex  Chemical Effect nanoscale roughness

Aims To have a SERS active system that will be able to speciate Arsenic  Prepare a metal surface that will give a SERS response  Incorporate an Arsenic sensitive molecule in the metal surface (4-(2-Mercaptoethyl) Pyridinium)  Optimization and Characterization of the SERS system nanoscale roughness

Metal Surface Cl - (1)(2) (3) (4) Cl - Charge / C2.54E-04 Geometric Area cm E-02 Electrochemical Area cm E-01 Roughness Factor5.47 Polycrystalline Gold

Raman Shift / cm S 1308S 1170W 1062W 1015S 767S 653W SERS Spectra of Roughened Polycrystalline Gold Brolo, A. G., Z. Jiang, et al. (2003). "The orientation of 2,2'-bipyridine adsorbed at a SERS-active Au(1 1 1) electrode surface." Journal of Electroanalytical Chemistry 547(2):

Metal Surface based on μAg particle 2µm Ag particles Fluorescein Isothiocyanate SERS marker Kim, K., H. S. Lee, et al. (2007). "Silver-particle-based surface-enhanced resonance Raman scattering spectroscopy for biomolecular sensing and recognition.“ Analytical and Bioanalytical Chemistry 388(1):

SERS was observed Optimize the electrochemical technique of roughening gold (may include other instrumental techniques such as Atomic Force Microscopy to characterize the surface) Characterize the system with Arsenic Immobilize an Arsenic sensing molecule on the metal surface (4-(2-Mercaptoethyl) Pyridinium) Electochemically Roughened Gold Surface µAg particles, silver electrodes Optimize the preparation of the SERS surface Summary other possible metal surface Immobilize an Arsenic sensing molecule on the metal surface (4-(2-Mercaptoethyl) Pyridinium)

Development of an Optical Sensor based on 7-amino-1,3-naphthalene disulfonic acid (AmNDS) for Analysis of Hexanal Arsenic Speciation by Surface Enhanced Raman Spectroscopy OPTICAL SENSORS Outline

Rancidity of Oats  Hexanal one of the major oxidative products of oats rancidity.  Hexanal was correlated in rancidity of oats in several studies.  Derived from fatty acids linoleic and linolenic acids Fritsch C.W., Gale J., J. Am. Oil Chem. Soc., 1977, 38-39,

2 3 1 Objectives  One of the specific goal is to characterize an optical sensing molecule  To develop an optical nose for food quality analysis.

Sensing Molecule 7-amino-1,3-naphthalene disulfonic acid (AmNDS)  Highly Fluorescent  Solvatochromic Property  Water Soluble

Effect of Hexanal on Fluorescence of AmNDS  Imine formation  Solvatochromic effect polarity

Parameters M AmNDS pH % Propanol Dependence of AmNDS on Hexanal Measurement was done immediately after preparation* * Slow reaction was observed λ excitation = 415 nm 1. D Doran (2004) UNSW

Multi Way Analysis PARAFAC: Emission Excitation Concentration

Three Component Model

Two Component Model

Summary  AmNDS with the aid of multiway analysis can be used for the determination of Hexanal and possibly other types of Aldehydes

Time Line Activity Literature Review on Arsenic & SERS System Deveopment of the SERS system based on electrochemically roughened gold Development of other SERS metal surfaces Optimization of the SERS system Characterization of the SERS systems with Arsenic species Write up

Acknowledgement  Prof D Brynn Hibbert  A/Prof. Grainne Moran  Prof. Justin Gooding  Dr. Jason Harper  Dr. James Hook  Dr. Diako Ebrahimi  Don Barnett  All colleagues in LAB 234 & ROOM 121  UNSW for Univ. International Postgraduate Award

THANK YOU!

LogP: ACD/LogP: XLogP: ALOGPS: # of Rule of 5 Violations: 0 ACD/LogD (pH 5.5): ACD/LogD (pH 7.4): ACD/BCF (pH 5.5):1ACD/BCF (pH 7.4):1 ACD/KOC (pH 5.5):1ACD/KOC (pH 7.4):1 #H bond acceptors:7#H bond donors:4 #Freely Rotating Bonds: 3Polar Surface Area: Å 2 Index of Refraction:1.733Molar Refractivity:68.62 cm 3 Molar Volume:171.3 cm 3 Polarizability: cm 3 Surface Tension:90.1 dyne/cmDensity:1.769 g/cm 3 Flash Point:Celsius Enthalpy of Vaporization: kJ/mol Boiling Point: Celsius at 760 mmHg Vapour Pressure:mmHg at 25 Celsius