Gallium Nitride Surface Functionalization. Matthew S. Makowski,. 1,2. Scott A. Jewett,. 1. Ben Andrews,. 3. Dmitry Zemlyanov,. 4. Michael J. Manfra,. 5,6,7.
Gallium Nitride Surface Functionalization Matthew S. Makowski,1,2 Scott A. Jewett,1 Ben Andrews,3 Dmitry Zemlyanov,4 Michael J. Manfra,5,6,7 Albena Ivanisevic8,9 1Weldon
School of Biomedical Engineering, 3Department of Biochemistry, 4Birck Nanotechnology Center, 5Department of Physics, 6School of Materials Engineering, 7School of Electrical and Computer Engineering, Purdue University; 2Indiana University School of Medicine; 8Department of Materials Science and Engineering, North Carolina State University; 9Joint Department of Biomedical Engineering NCSU/UNC-CH
GaN
1. Etch: HCl 2. Hydrogen functionalize: NH4F 3. Chlorine functionalize: PCl5 and benzoyl peroxide in chlorobenzene 4. Grignard reaction: AllylMgCl in tetrahydrofuran
Olefin cross-metathesis: Grubbs catalyst and various alkene terminated reagents in dichloromethane Figure 2. GaN Surface Functionalization Chemistry Additional Chemistry • Condensation reaction: EDC (1-Ethyl-3-[3-dimethylaminopropyl]carbodiimide) activates carboxyl groups for subsequent reaction with amine groups to form amide bonds. • Crosslinker: PMPI (p-Maleimidophenyl isocyanate) couples hydroxyl groups to thiol groups. Surface Analysis • X-ray photoelectron spectroscopy (XPS) was used to identify surface molecular species. • Atomic force microscopy measured surface roughness at the nanometer scale. GaN Stability • Oxidation inhibition: Stability of functionalized and bare surfaces was investigated by exposure to the damaging effects of oxygen plasma. • Aqueous stability: 3 mm x 3 mm GaN wafers were soaked in 1.5 mL solutions for 7 days. Ga concentration was measured by inductively coupled plasma mass spectrometry. Three replicates were tested for each solution. Cell Culture • The biocompatibility of GaN surfaces was explored by culturing PC12 cells on bare and “IKVAV” peptide functionalized GaN surfaces and using silicon surfaces as controls. PC12 cells were cultured for 6 days following treatment with nerve growth factor (NGF). • Scanning electron micrographs of cells on bare and “IKVAV” peptide functionalized surfaces were used to determine differences in cellular morphology.
References [1] Makowski, M. S.; Zemlyanov, D. Y.; Ivanisevic, A. Appl. Surf. Sci. 2011, 257, 4625. [2] Makowski, M. S.; Ivanisevic, A. Small 2011, 7, 1863. [3] Makowski, M. S.; Zemlyanov, et al. Surf. Sci. 2011, 605, 1466. [4] Jewett, S. A.; Makowski, M. S.; et al. Acta Biomaterialia 2012, 8, 728. [5] Kelsen DP, et al. Cancer 1980, 46, 2009.
C)
GaN
Ga 2p3/2
Ga2O3
Ga0
peptide
Intensity (Arbitrary Units)
Functionalization removed by Ar+ etch, exposed to O2 plasma
After binding 7-bromo-1-heptene
Before binding 7-bromo-1-heptene
N-Ga (397.00 eV)
Ga LMM 1 (400.49 eV)
Functionalized surface
Intensity (Arbitrary Units)
B)
Br 3d
Br 3d
C-NH2, N-C=O (399.51 eV)
N 1s
B)
Ga LMM 2 (395.33 eV) Ga LMM 1 (392.39 eV)
After peptide binding
Functionalized surface exposed to O2 plasma
Before peptide binding
EDC Functionalized Surface
404
402
400
398
396
394
392
390
Binding Energy (eV) 74
73
72
71
70
69
68
67
1122 1121 1120 1119 1118 1117 1116 1115 1114
66
Binding Energy (eV)
Binding Energy (eV)
Figure 3. A) 7-bromo-1-heptene was bound through olefin cross –metathesis. B) Br 3d XPS spectra for the GaN surfaces before and after binding 7-bromo-1-heptene. The bromine atom served as a label on XPS. C) The surface functionalization scheme protects the GaN surface from oxidation when exposed to an oxygen plasma.
Figure 4. A) 6-heptenoic acid was bound through olefin cross-metathesis, and the peptide was bound with a condensation reaction using EDC. The peptide sequence is NYQWVPYQGRVPYPRPGTC-NH2. B) The amide bond (blue) indicates the presence of a peptide on the surface. The peptide functionalized surface had a 63% coverage.
CSRARKQAASIKVAVSADR-NH2
A)
B)
Clean GaN "IKVAV" GaN Clean Silicon "IKVAV" Silicon
400
D)
Gallium Nitride Aqueous Stability
Clean GaN
Solution Deionized water 10% H2O2 in saline 0.1 M sodium acetate pH 5 0.1 M Tris base pH 9
300
2
Methods
A)
A)
Cells/mm
As clinical point-of-care testing systems and implantable sensing devices gain prevalence, the need is increasing for biosensor transducers that have high stability, high accuracy, label-free detection, rapid response, biocompatibility, and inexpensive fabrication. Despite the chemical and electrical stability of gallium nitride (GaN) +++ Charged + + ++ that make this semiconductor a promising + + + ++ + Analyte + material for biosensing applications, few + ID reports in the literature explore covalent Molecules biological receptor binding to GaN devices to form robust biosensor transducers. The Receptors studies described here investigated a Source Drain Gate Insulator method to covalently functionalize GaN Channel - - - - - - - - surfaces with bioreceptors and explored the n+ n+ stability and biocompatibility of the GaN surfaces. The results provide steps towards p-type Substrate the development of robust electronic devices for rapidly measuring chemical biomarkers Figure 1. Schematic of field effect transistor biosensor for disease diagnoses and management.
Results Intensity (Arbitrary Units)
Introduction
200
*
**
*
100
1. PMPI Crosslinker 2. “IKVAV” Peptide
10 µm
0 Day 1
C) Cell Culture
**
* Day 6
Day 3
** *
“IKVAV” GaN
Atomic layers of Ga released 1.1 ± 0.2 1.0 ± 0.5 1.2 ± 0.7 13.2 ± 9.1
Figure 6. Means and standard deviations are shown. The GaN wafers contained about 420,000 atomic layers of gallium. For comparison, the literature documented a total intravenous dose of 0.60 g to 0.71 g Ga in the form of gallium (III) nitrate given over 7 days in a clinical trial for tumor treatment.[5]
Surface Roughness Surface Treatment and Type
RMS Roughness (nm)
Clean GaN “IKVAV” GaN Clean Silicon “IKVAV” Silicon
0.99 ± 0.10 5.32 ± 1.32 0.68 ± 0.03 21.74 ± 1.67
10 µm
Figure 5. A) 5-hexen-1-ol was bound through olefin cross –metathesis, and the “IKVAV” peptide was bound using the PMPI crosslinker. B) PC12 cells present on GaN and silicon surfaces at 1, 3, and 6 days of nerve growth factor (NGF) treatment. Asterisks represent no statistical difference between groups (ANOVA, least squares difference, p
