title: Sensitive SERS-pH sensing in biological media using metal carbonyl functionalized planar substrates.
abstract: Conventional nanoparticle based Surface enhanced Raman scattering (SERS) technique for pH sensing often fails due to the aggregation of particles when detecting in acidic medium or biosamples having high ionic strength. Here, We develop SERS based pH sensing using a novel Raman reporter, arene chromium tricarbonyl linked aminothiophenol (Cr(CO)3-ATP), functionalized onto a nano-roughened planar substrates coated with gold. Unlike the SERS spectrum of the ATP molecule that dominates in the 400-1700 cm(-1) region, which is highly interfered by bio-molecules signals, metal carbonyl-ATP (Cr(CO)3)-ATP) offers the advantage of monitoring the pH dependent strong CO stretching vibrations in the mid-IR (1800-2200 cm(-1)) range. Raman signal of the CO stretching vibrations at ~1820 cm(-1) has strong dependency on the pH value of the environment, where its peak undergo noticeable shift as the pH of the medium is varied from 3.0 to 9.0. The sensor showed better sensitivity in the acidic range of the pH. We also demonstrate the pH sensing in a urine sample, which has high ionic strength and our data closely correlate to the value obtained from conventional sensor. In future, this study may lead to a sensitive chip based pH sensing platform in bio-fluids for the early diagnosis of diseases.
authors.affiliation: Bio-Optical Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research (A(⁎)STAR), 11 Biopolis Way, Singapore 138667, Singapore.
authors.forename: Kien Voon
authors.initials: KV
authors.lastname: Kong
authors.affiliation: Bio-Optical Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research (A(⁎)STAR), 11 Biopolis Way, Singapore 138667, Singapore.
authors.forename: U S
authors.initials: US
authors.lastname: Dinish
authors.affiliation: Department of Urology, Singapore General Hospital, Singapore, Singapore.
authors.forename: Weber Kam On
authors.initials: WK
authors.lastname: Lau
authors.affiliation: Bio-Optical Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research (A(⁎)STAR), 11 Biopolis Way, Singapore 138667, Singapore; Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore 117543, Singapore; School of Physics, National University of Ireland Galway, Galway, Ireland. Electronic address: malini_olivo@sbic.a-star.edu.sg.
authors.forename: Malini
authors.initials: M
authors.lastname: Olivo
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry; D015374:Biosensing Techniques / Q000379:methods; D002857:Chromium / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013499:Surface Properties; D016482:Urinalysis / Q000379:methods*; D014556:Urine / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D002857:Chromium; C005464:2-aminothiophenol; D006046:Gold
keywords: Metal carbonyl reporter molecule; SERS substrates; Surface enhanced Raman scattering; Urine sample; pH Sensing