Photochemical Growth of Highly Densely Packed Gold Nanoparticle Films for Biomedical Diagnostics

Abstract

Utilizing ultraviolet photochemical reduction of gold(III) chloride trihydrate (HAuCl4), a new kind of synthesis of a highly dense gold nanoparticle film on a p-type silicon wafer was conducted. Through scanning electron microscopy and atomic force microscopy, the gold nanoparticle film was confirmed to be 90 nm thick, with an average gold nanoparticle size of 125 nm in diameter. To explore applications in surface enhanced Raman spectroscopy (SERS), a protein model of streptavidin and pegylated biotin functionalized to the surface of gold nanoparticle films was employed. Observations indicate that there was a proximity induced excitation of localized surface plasmons due to the densely packed gold nanoparticle film. Excitation of the localized surface plasmons leading to hot spots of SERS activity on the gold nanoparticle film allowing it to act as an eco-friendly and highly sensitive SERS substrate for biomedical diagnostic applications.

Nanoparticle Size Influences the Self-Assembly of Gold Nanorods Using Flexible Streptavidin–Biotin Linkages

“…As expected, as the NR size increased, signal intensity increased due to increased electronic field enhancements at the hot-spots where streptavidin was localized. − Additionally, we once more observed evidence that the mini rods were not undergoing self-assembly, as they showed no signal enhancement of streptavidin and displayed signals characteristic of gold NRs with no streptavidin present (Figure ). The lack of a SERS effect with the mini rods, as well as the trend of increasing signal strength as NR size increased, corroborates the TEM and extinction data shown earlier.…”

Accessible hotspots for single-protein SERS in DNA-origami assembled gold nanorod dimers with tip-to-tip alignment

“…3b). The additional spectra displayed characteristic streptavidin Raman modes at 1239 cm −1 (amide III/β-sheet) 43,44,46,47 , 1336 cm −1 (tryptophan W7) 43,44,46 , 1560-1580 cm −1 (tryptophan W2) 43,46 as well as 1670 cm −1 (amide I/ βsheet) 43,46,47 (Fig. 3b), which also appeared in bulk measurements of streptavidin (further examples of single dimer and bulk spectra are shown in Supplementary Fig.…”

“…The obtained spectra were dominated by a central double peak at ≈1375 cm −1 , which most likely stems from nucleobases of the docking strand or origami template (ring breathing modes of T, A, and G bases) 42 . However, weaker Raman peaks indicative of biotin were also visible, at 1270 cm −1 (methylene group wagging) 43,44 , 1470 cm −1 (stretching of CH 2 ) 43,44 , and 1565 cm −1 (C-N stretch) 43,45 .…”

Colorimetric and Label-Free Optical Detection of Pb2+ Ions via Colloidal Gold Nanoparticles

“…Changing this environment will also shift the SPR frequency [ 21 , 22 ], thus enabling us to visually detect Pb 2+ via colorimetric change. In addition to this, GNPs’ large surface areas enables them to be modified easily to become probes using thiolated or disulfide-modified ligands, electrostatic interactions, antibody–antigen associations, or streptavidin–biotin binding, as seen in many publications [ 13 , 23 , 24 ].…”