A squaraine and Hg(2+)-based colorimetric and "turn on" fluorescent probe for cysteine.

A novel squaraine derivative (SQ-1) was synthesized and characterized for the determination of cysteine. Binding with Hg(2+) as a fluorescent quencher to SQ-1 leads to absorption and emission turn-off. More significantly, the SQ-1-Hg(2+) complex exhibits a dual-channel chromofluorogenic responses to biologically important cysteine with a high sensitivity and selectivity over other natural amino acids, along with a low detection limit of 36.7 nM.

A squaraine-based colorimetric and "turn on" fluorescent sensor for selective detection of Hg2+ in an aqueous medium.

A novel squaraine-based chemosensor SQ-1 has been synthesized, and its sensing behavior toward various metal ions was investigated by UV-vis and fluorescence spectroscopies. In AcOH-H(2)O (40:60, v/v) solution, Hg(2+) ions coordinate with SQ-1 causing a deaggregation which induces a visual color and absorption spectral changes as well as strong fluorescence. In contrast, the addition of other metals (e.g., Pb(2+), Cd(2+), Cu(2+), Zn(2+), Al(3+), Ni(2+), Co(2+), Fe(3+), Ca(2+), K(+), Mg(2+), Na(+), and Ag(+)) does not induce these changes at all. Thus SQ-1 is a specific Hg(2+) sensing agent due to the inducing deaggregation of the dye molecule by Hg(2+).

Electrogenerated chemiluminescence of bis[4-(dimethylamino)phenyl]squaraine.

For the first time, we reported the strong electrogenerated chemiluminescence of organic dye, bis[4-(dimethylamino)phenyl]squaraine (BDPSQ), a high quantum yield and light-stable species, which might find applications in ECL analysis and imaging.

Generalized sagnac effect.

Experiments were conducted to study light propagation in a light waveguide loop consisting of linearly and circularly moving segments. We found that any segment of the loop contributes to the total phase difference between two counterpropagating light beams in the loop. The contribution is proportional to a product of the moving velocity v and the projection of the segment length Delta(l) on the moving direction, Deltaphi=4piv x Delta(l)/c(lambda). It is independent of the type of motion and the refractive index of waveguides. The finding includes the Sagnac effect of rotation as a special case and suggests a new fiber optic sensor for measuring linear motion with nanoscale sensitivity.