Axonic Au Tips Induced Enhancement in Raman Spectra and Biomolecular Sensing

Apurve Saini (1) , Rohit Medwal (2) , Saurabh Bedi (1) , Bharat Mehta (1) , Rekha Gupta (2) , Thomas Maurer (3) , Jerome Plain (3) , S. Annapoorni (2)

1 Amity University
2 University of Delhi
3 LNIO - Laboratoire de Nanotechnologie et d'Instrumentation Optique

Axonic Au stars with sharp crystalline tips were synthesized via reduction of HAuCl4 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).

Keywords: SERS; ATR SPR; Biosensor; Stars; Urea sensing

Domains: Optics / Photonic; Micro and nanotechnologies/Microelectronics; Biochemistry, Molecular Biology

Apurve Saini, Rohit Medwal, Saurabh Bedi, Bharat Mehta, Rekha Gupta, et al.. Axonic Au Tips Induced Enhancement in Raman Spectra and Biomolecular Sensing. Plasmonics, 2015, 10 (3), pp.617-623. ⟨10.1007/s11468-014-9847-4⟩. ⟨hal-02296427⟩