Water dispersed fluorescent organic aggregates for the picomolar detection of ClO4- in water, soil and blood serum and the attogram detection of ClO4- in the solid state by a contact mode method

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 4; no. 31; pp. 7420 - 7429
• Main Authors: Kumar, Rahul, Sandhu, Sana, Singh, Prabhpreet, Kumar, Subodh
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• Subjects: Aggregates; Blood; Contact; Fluorescence; Materials selection; Serums; Soil (material); Solid state
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c6tc01891b

Fluorescent organic aggregates (FOAs) of CS-1 have been used for the fluorescence based selective estimation of ClO4- ions. CS-1 undergoes self-aggregation to form FOAs ( phi = 0.35) with a diameter of 140 plus or minus 50 nm in aqueous medium. Dynamic light scattering and field emission scanning electron microscopy studies reveal that FOAs of CS-1 undergo further aggregation to form larger particles upon addition of ClO4- (10 pM-1 nM concentration) but at higher concentrations of ClO4- ions, these FOAs undergo dis-aggregation to give finally a molecularly dissolved complex of CS-1 and ClO4-. This ClO4- induced aggregation-dis-aggregation process of FOAs of CS-1 is associated with super-amplified fluorescence quenching following two domains of non-linear complexation with Ksv values of 2.42 108 M-1 and 3.59 105 M-1 and variation in the lifetime measurements of FOAs of CS-1 at different concentrations of ClO4-. The lowest limit of detection is 10 pM in solution and 6 10-18 g cm-2 in the solid state by a contact mode method with a selectivity of similar to 10 000 over other inorganic anions and allows the quantitative measurement of ClO4- ions using front surface steady state fluorescence of paper strips coated with CS-1. FOAs of CS-1 find applications in the determination of ClO4- in tap water, soil and also blood serum. Probe CS-2, which differs from CS-1 in lacking three methyl groups on the m-phenylene spacer, shows poor sensitivity (LOD 1.6 mu M) towards ClO4-. DFT studies of CS-1 and CS-2 and their complexes with ClO4- reveal the effect of methyl substituents on their geometries.