Axonic Au Tips Induced Enhancement in Raman Spectra and Biomolecular Sensing

• Published in: Plasmonics (Norwell, Mass.) Vol. 10; no. 3; pp. 617 - 623
• Main Authors: Saini, Apurve, Medwal, Rohit, Bedi, Saurabh, Mehta, Bharat, Gupta, Rekha, Maurer, Thomas, Plain, Jerome, Annapoorni, S.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-06-2015; Springer Verlag
• Subjects: Biochemistry; Biochemistry, Molecular Biology; Biological and Medical Physics; Biophysics; Biotechnology; Chemistry; Chemistry and Materials Science; Disks; Dispersions; Engineering Sciences; Gold; Image transmission; Life Sciences; Micro and nanotechnologies; Microelectronics; Nanotechnology; Nucleation; Optics; Photonic; Plasmons; Stars; Tips; ATR SPR; SERS; Biosensor; Stars; Urea sensing
• ISSN: 1557-1955; 1557-1963
• DOI: 10.1007/s11468-014-9847-4

Axonic Au stars with sharp crystalline tips were synthesized via reduction of HAuCl
4
capped with cetyl trimethylammonium bromide (CTAB). A seed-mediated method was adopted in which Au seeds were used in the growth solution containing Au
+
ions, for initiating the nucleation with CTAB and with ascorbic acid acting as a mild reducing agent. Transmission Electron Microscopy image clearly reveals the synthesis of gold stars. The gold star dispersions display a well-defined optical response as observed by the presence of a sharp surface plasmon resonance centered at 525 nm. The Au stars functionalized with 11-mercaptoundecanoic acid and immobilized with urease showed improved urea-sensing behavior in comparison to pure gold disk in attenuated total reflection surface plasmon resonance (ATR SPR) mode. Surface-enhanced Raman spectroscopy performed using the functionalized Au stars showed a significant enhancement in Raman signals for a wider range of urea concentration (2–20 mg/ml).