Gradient sensitive microscopic probes prepared by gold evaporation and chemisorption on latex spheres

Langmuir

Volumn 13, Issue 7, 1997, Pages 1865-1868

  Takei, H ^a   Shimizu, N ^a  

^a HITACHI LTD   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 6244297430     PISSN: 07437463     EISSN: None     Source Type: Journal    
DOI: 10.1021/la9621067     Document Type: Article

References (25)

1. (a) Fischer, U. Ch.; Zingsheim, H. P. J. Vac. Sci. Technol. 1981, 19, 882.
2. (b) Deckman, H. W.; Dunsmuir, J. H. Appl. Phys. Lett. 1982, 41, 377.
3. (c) Hulteen, J. C.; Van Duyne, R. P. J. Vac. Sci. Technol., A 1995, 13 (3), 1553.
4. Musil, C. R.; Jeggle, D.; Lehmann, H. W.; Scandella, L.; Gobrecht, J.; Doebeli, M. J. Vac. Sci. Technol., B 1995, 13 (6), 2781.
5. Electrophoretic rotation has been studied previously with a slightly similar system of colloidal doublets consisting of two different spheres. Refer to: Velegol, D.; Anderson, J. L.; Garoff, S. Langmuir 1996, 12, 675.
6. Whitesides, G. M.; Laibinis, P. E. Langmuir 1990, 6, 87.
7. Ulman. A. An Introduction to Ultrathin Organic Films from Langmuir-Blodgett to Self-Assembly; Academic Press, Inc.: San Diego, CA, 1991.
8. (a) Weisbecker, C. S.; Merritt, M. V.; Whitesides, G. M. Langmuir 1996, 12, 3763.
9. (b) Badia, A.; Gao, W.; Singh, S.; Demers, L.; Cuccia, L.; Reven, L. Langmuir 1996, 12, 1262.
10. We describe here the procedure for attaching TG to surface bound 2-AET; attaching 2-AET first and then TG was no different. Spheres already modified by 2-AET were placed in a 1.5 mL microtube, to which 100 μL of 10 mM TG and 100 μL of 50 mM carbodiimide solution (1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide, Dojindo Laboratories, Kumamoto, Japan) were added. The tube was mounted on a rotary shaker and incubated for 24 h while rotating at 10 rpm. After 1 mL of ethanol was added, spheres were collected under centrifugation at 2000g and placed on a 5 x 5 mm Cu screen. Rinsing consisted of a gentle wash with ethanol.
11. Spheres were placed in a 1.5 mL microtube containing 0.5 mL of a 100 nm gold colloid suspension (Gold Colloid 100 nm electron microscope grade, British BioCell International, Cardiff, England) and an equal volume of ethanol. Spheres and gold colloids were cocentrifuged at 2000g for 5 min and resuspended. This process was repeated a few times, and spheres were rinsed with water on a 5 x 5 mm Cu screen. Refer to the following for an earlier study on adsorption of gold colloid particles on a chemically modified surface: Freeman, R. G.; Grabar, K. C.; Allison, K. J.; Bright, R. M.; Davis, J. A.; Guthrie, A. P.; Hommer, M. B.; Jackson, M. A.; Smith, P. C.; Walter, D. G.; Natan, M. J. Science 1995, 267, 1629.
12. After spheres were dried on a polystyrene substrate, the sample was given a 5 nm coat of Pt with a sputterer (Model E102, Hitachi, Ltd., Tokyo, Japan) and observed with a scanning electron microscope (Model S-800, Hitachi, Ltd., Tokyo, Japan).
13. A latex suspension from Dyno Particles A.S. was simply allowed to dry on a substrate; without further manipulation, spheres tended to form a regular array. Refer to ref 1a for earlier works on formation of a regular array of latex spheres.
14. This procedure required a modified centrifuge tube with a flat bottom; 0.3 g of silicone rubber was placed in a 5 mL centrifuge tube and allowed to solidify while the tube rotated at 10 000 rpm in a swing rotor (Model RPS65T, Hitachi Koki Co., Ltd., Ibaraki, Japan). The polystyrene substrate was placed at the bottom of the centrifuge tube, and 1 mL of 100 nm gold colloid suspension was added. The tube was centrifuged at 15 000 rpm for 15 min, resulting in even deposition of colloid particles on the substrate. The substrate was then rinsed with water gently but thoroughly before observation with the scanning electron microscope.
15. Spheres away from the electrodes were observed though spheres did not exhibit peculiar behavior unless in the close vicinity of the electrode (<100 μm). To determine buffering capacities, 80 μL of each buffer was placed between the electrodes, and time change in pH was monitored by taking 10 μL samples, 30, 60, 90, and 300 s after the initiation of the electric field application (10 V (peak to peak), 0.5 Hz) and measuring pH with a solid state pH meter. For basic and neutral buffers, change in pH after 5 min of electric field application was less than pH 0.2. For alkaline buffers, change was as large as pH 0.7. Because electrophoretic behavior was determined within the first minute of electric field application, buffering capacities were deemed sufficient.
16. Control refers to spheres with gold evaporation but without chemical modification. We classify response of spheres to an electric field (up to 10 V/3 mm) in the following descriptive manner: (a) strong, spheres reoriented themselves briskly, and no sample-to-sample discrepancy; (b) moderate, spheres reoriented themselves, but a minority was reoriented in the opposite direction, or some sample occasionally exhibits an opposite trend; (c) weak, spheres responded weakly to an electric field, but the direction of reorientation was not consistent even within the same sample; (d) no, no reorientation at all.
17. Holmes-Farley, S. R.; Bain, C. D.; Whitesides, G. M. Langmuir 1988, 4, 921.
18. Bain, C. D.; Whitesides, G. M. Langmuir 1989, 5, 1370.
19. In comparison to electrophoretic rotation, the direction of linear electrophoresis as dictated by the net charge of spheres was far less consistent from one preparation to the next.
20. Refer to the following articles on formation of supramolecular structure from uniform spheres: (a) Trau, M.; Saville D. A.; Aksay, I. A. Science 1996, 272, 706. (b) Andres, R. P.; Bielefeld, J. D; Henderson, J. I.; Janes, D. B.; Kolagunta, V. R.; Kubiak, C. P.; Mahoney, W. J.; Osifchin, R. G. Science 1996, 273, 1690. (c) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J. Nature 1996, 382, 607. (d) Alivisatos, A. P.; Johnson, K. P.; Peng, X.; Wilson, T. E.; Loweth, C. J.; Bruchez, M. P., Jr.; Schultz, P. G. Nature 1996, 382, 609.
21. Refer to the following articles on formation of supramolecular structure from uniform spheres: (a) Trau, M.; Saville D. A.; Aksay, I. A. Science 1996, 272, 706. (b) Andres, R. P.; Bielefeld, J. D; Henderson, J. I.; Janes, D. B.; Kolagunta, V. R.; Kubiak, C. P.; Mahoney, W. J.; Osifchin, R. G. Science 1996, 273, 1690. (c) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J. Nature 1996, 382, 607. (d) Alivisatos, A. P.; Johnson, K. P.; Peng, X.; Wilson, T. E.; Loweth, C. J.; Bruchez, M. P., Jr.; Schultz, P. G. Nature 1996, 382, 609.
22. Refer to the following articles on formation of supramolecular structure from uniform spheres: (a) Trau, M.; Saville D. A.; Aksay, I. A. Science 1996, 272, 706. (b) Andres, R. P.; Bielefeld, J. D; Henderson, J. I.; Janes, D. B.; Kolagunta, V. R.; Kubiak, C. P.; Mahoney, W. J.; Osifchin, R. G. Science 1996, 273, 1690. (c) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J. Nature 1996, 382, 607. (d) Alivisatos, A. P.; Johnson, K. P.; Peng, X.; Wilson, T. E.; Loweth, C. J.; Bruchez, M. P., Jr.; Schultz, P. G. Nature 1996, 382, 609.
23. Refer to the following articles on formation of supramolecular structure from uniform spheres: (a) Trau, M.; Saville D. A.; Aksay, I. A. Science 1996, 272, 706. (b) Andres, R. P.; Bielefeld, J. D; Henderson, J. I.; Janes, D. B.; Kolagunta, V. R.; Kubiak, C. P.; Mahoney, W. J.; Osifchin, R. G. Science 1996, 273, 1690. (c) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J. Nature 1996, 382, 607. (d) Alivisatos, A. P.; Johnson, K. P.; Peng, X.; Wilson, T. E.; Loweth, C. J.; Bruchez, M. P., Jr.; Schultz, P. G. Nature 1996, 382, 609.
24. Refer to the following for theoretical modeling of protein crystallization with nonuniform charge distribution on model spheres was taken into account: (a) Grant, M. L.; Saville, D. A. J. Phys. Chem. 1994, 98, 10358. (b) Grant, M. L.; Saville, D. A. J. Colloid Interface Sci. 1995, 171, 35. The current technique allows for preparations of two-sided spheres only, but we are investigating schemes for extending this technique to more arbitrary patterns on spheres.
25. Refer to the following for theoretical modeling of protein crystallization with nonuniform charge distribution on model spheres was taken into account: (a) Grant, M. L.; Saville, D. A. J. Phys. Chem. 1994, 98, 10358. (b) Grant, M. L.; Saville, D. A. J. Colloid Interface Sci. 1995, 171, 35. The current technique allows for preparations of two-sided spheres only, but we are investigating schemes for extending this technique to more arbitrary patterns on spheres.