title: Surfactant modulated aggregation induced enhancement of emission (AIEE)--a simple demonstration to maximize sensor activity.
abstract: A new type of easily synthesized rhodamine-based chemosensor L(3), with potential NO2 donor atoms, selectively and rapidly recognizes Hg(2+) ions in the presence of all biologically relevant metal ions and toxic heavy metals. A very low detection limit (78 nM) along with cytoplasmic cell imaging applications with no or negligible cytotoxicity indicate good potential for in vitro/in vivo cell imaging studies. SEM and TEM studies reveal strongly agglomerated aggregations in the presence of 5 mM SDS which turn into isolated core shell microstructures in the presence of 9 mM SDS. The presence of SDS causes an enhanced quantum yield (φ) and stability constant (Kf) compared to those in the absence of SDS. Again, the FI of the [L(3)-Hg](2+) complex in an aqueous SDS (9 mM) medium is unprecedentedly enhanced (∼143 fold) compared to that in the absence of SDS. All of these observations clearly manifest in the enhanced rigidity of the [L(3)-Hg](2+) species in the micro-heterogeneous environment significantly restricting its dynamic movements. This phenomenon may be ascribed as an aggregation induced emission enhancement (AIEE). The fluorescence anisotropy assumes a maximum at 5 mM SDS due to strong trapping (sandwiching) of the doubly positively charged [L(3)-Hg](2+) complex between two co-facial laminar microstructures of SDS under pre-miceller conditions where there is a strong electrostatic interaction that causes an improved inhibition to dynamic movement of the probe-mercury complex. On increasing the SDS concentration there is a phase transition in the SDS microstructures and micellization starts to prevail at SDS ≥ 7.0 mM. The doubly positively charged [L(3)-Hg](2+) complex is trapped inside the hydrophobic inner core of the micelle which is apparent from the failure to quench the fluorescence of the complex on adding 10 equivalents of H2EDTA(2-) solution but in the absence of SDS it is quenched effectively.
authors.affiliation: Department of Chemistry, Jadavpur University, 188, Raja Subodh Chandra Mallick Rd, Kolkata, West Bengal 700032, India. m_ali2062@yahoo.com.
authors.forename: Rahul
authors.initials: R
authors.lastname: Bhowmick
authors.forename: Abu
authors.initials: A
authors.lastname: Saleh Musha Islam
authors.forename: Atul
authors.initials: A
authors.lastname: Katarkar
authors.forename: Keya
authors.initials: K
authors.lastname: Chaudhuri
authors.forename: Mahammad
authors.initials: M
authors.lastname: Ali
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000295:instrumentation*; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes / Q000737:chemistry*; D056945:Hep G2 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057230:Limit of Detection; D008628:Mercury / Q000032:analysis / Q000737:chemistry; D012235:Rhodamines / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D012235:Rhodamines; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; D008628:Mercury