title: Two-photon ratiometric sensing of Hg2+ by using cysteine functionalized Ag nanoparticles.
abstract: We have demonstrated a novel two-photon sensing strategy to detect mercury ions with high selectivity and sensitivity. This sensing approach is based on the observation that addition of Hg(2+) into a cysteine functionalized Ag nanoparticle solution could significantly enhance their two-photon emission. An enhancement factor of up to 100 fold was obtained when mercury was added. A detection limit of as low as 65 nM could be achieved. The sensitivity and sensing range can be easily tuned. Compared to the conventional colorimetric or extinction spectrum based methods, this scheme offers improved sensitivity, quantitative detection of Hg(2+) with a larger dynamic range, and allows detection deep into biological environments such as cells and tissues where deep penetration is required. The sensitivity could be further improved by using two-photon microscopy with the additional advantages of 3D detection and mapping.
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
authors.forename: Cuifeng
authors.initials: C
authors.lastname: Jiang
authors.forename: Zhenping
authors.initials: Z
authors.lastname: Guan
authors.forename: Siew Yin Rachel
authors.initials: SY
authors.lastname: Lim
authors.forename: Lakshminarayana
authors.initials: L
authors.lastname: Polavarapu
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Xu
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D003545:Cysteine / Q000737:chemistry*; D008628:Mercury / Q000032:analysis* / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D017785:Photons; D012680:Sensitivity and Specificity; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D012834:Silver; D008628:Mercury; D003545:Cysteine