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Vibrational Sum Frequency Generation Studies of Self Assembled Monolayers on Gold for Biological Functionalization Achani K. Yatawara Department of Chemistry.

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Presentation on theme: "Vibrational Sum Frequency Generation Studies of Self Assembled Monolayers on Gold for Biological Functionalization Achani K. Yatawara Department of Chemistry."— Presentation transcript:

1 Vibrational Sum Frequency Generation Studies of Self Assembled Monolayers on Gold for Biological Functionalization Achani K. Yatawara Department of Chemistry h 1 h 2 h 3

2 SAMs for Bio-functionalization (I ) Amino/Carboxy t-SAMs- Neuron Adhesion (II) a. Maleimide t-SAMs b. Aldehyde t-SAMs b. Aldehyde t-SAMs Surface modification Chemistry -Alkanes (thiol/amines) -Alkanes (thiol/amines) -Sugars -Sugars -Amino acids-sugars -Amino acids-sugars

3 SFG technique |v=0 |v=1 IR vis SFG 2 nd order NL susceptibility SFG 2 nd order NLO technique Specifically used to study surfaces and interfaces (no-bulk contribution) Sub-monolayer sensitivity Molecular structure, conformation and orientation SFG vis IR Surface Polarization P (2) S o P Frequency domain-BB Vibrational SFG IR vis SFG = IR + vis S( )

4 I. SAMs for Neuron Immobilization FI VSFG S. H. Scott, Nature, 2006 NH 2 COOH NH 2 Hochberg et al. Nature, 2006 AFM

5 Ra =1.918 nm Gold type A Glass 40nm Cr (0.5 nm/s) 400nm Au (1.0 nm/s) gold type A with PPP polarization Experimental approach for molecular structure determination of SAMs C-H Stretch region Carboxy t- SAM mix SAM Amino t- SAM COOH NH 2 COOH NH 2 SAM on Au Au

6 C-H Stretch region gold type B with PPP polarization Ra = nm Gold type B Glass 5 nm Cr (0.1 nm/s) 50 nm Au (0.1 nm/s) Carboxy t- SAM Amino t- SAM mix SAM COOH NH 2 COOH NH 2

7 Ra = nm Gold type C Glass C-H Stretch region gold type C with PPP polarization 20 nm Cr (0.1 nm/s) 100 nm Au (0.1 nm/s) Carboxy t- SAM Amino t- SAM mix SAM COOH NH 2 COOH

8 Significant amount of Gauche defects disordered monolayer Frequencies methylene d + (~2855 cm -1 ), d - (~2925 cm -1 ) liquid-like alkane chains V d + cm -1 Liq.2855 Solid2850 V d - cm -1 Liq.2924 Solid2918 Conclusions-C-H region Porter et. al. JACS 1987 Richter et. al. Opt. Lett. 1998

9 C=O stretch region H-bonded COOH and mix SAMs Mix SAM-no separate domains COOH and amino Conclusions-C=O region mix SAM - gold type A mix SAM - gold type B COOH SAM - gold type A COOH SAM - gold type B

10 Results After Neuron Immobilization on SAMs Fluorescent microscopic Images Overall conclusions Neutron attach & grow well on amino t-SAMs, and do not attach to COOH/Mix SAMs Neuron adhesion is not critically affected by the surface roughness or details of the molecular ordering and orientation of the terminal amino groups Neuron adhesion and growth depend mostly on the chemical functionality displayed at the surface Amino t-SAMs- gold C Amino t-SAMs- gold A Amino t-SAMs- gold B Mix SAMs Carboxy t- SAMs PDL

11 II. SAMs for Surface Chemical Modifications (a) Modifications of Maleimide t- SAMs (b) Modifications of Aldehyde t-SAMs NaBH 3 CN p H ~10 Au

12 II a. Maleimide t-SAMs Surface Modification C 11 -gluc Au Maleimide t- SAM C 16 -gluc Cys-gluc C 6 -thiol 3070 cm cm cm cm -1 BeforeAfter Maleimide t-SAM After Surface covalent attachments are successful Unsaturated C-H stretch region and C=O stretch region

13 Saturated C-H stretch region Step 1 Step 1: Preparation of maleimide t- SAMs on gold Step 2 Step 2: Modification with a) C 6 thiol Au 48 hr, RT Au Maleimide t- SAMs C 6 -thiol Au 48 hr, RT

14 Step 2 Step 2: Modification with b) C 11 -glucose c) C 16 -glucose p H ~6.5 Au C 16 -glucose gluc-C-H Maleimide t- SAMs C 11 - gluc C 16 - gluc

15 Step 2 Step 2: Modification with d) Cys -glucose p H ~6.5 Au gluc-C-H Cys-gluc Maleimide t- SAMs

16 II b. Aldehyde t-SAMs Surface Modification Saturated C-H stretch region C 6 H 15 NH 2, NaBH 3 CN p H ~10 Au 48 hr, RT Au Aldehyde t-SAM After

17 Acknowledgment Prof. Alex Benderskii Group members Dr. Andrey Bordenyuk Dr. Igor Stiopkin Himali Jayathilake Champika Weeraman Fadel Shalhout Adib Samin Collaborators Prof. Gregory W. Auner Smart Sensors and Integrated Microsystems (SSIM), Department of Electrical and Computer Engineering and Department of Biomedical Engineering -WSU Dr. Olena Palyvoda Prof. Peter Andreana, Department of Chemistry –WSU Dr.Gopinath Tiruchinapally WSU start-up grant WSU research grant ACS-PRFNSF CAREER Funding

18 Before After 2732 cm cm -1 Au

19 Normalized SFG spectra of 11-amino-1- undecanethiol SAM (a) gold type A, (b) gold type B recorded after one month of preparation of SAM. This was done with PPP polarization. No residual solvent peaks.


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