Spectral and electrochemical investigation of p-sulfonatocalix[4]arene-stabilized vitamin E aggregation

FRET-based Solid-state Luminescent Glyphosate Sensor Using Calixarene-grafted Ruthenium(II)bipyridine Doped Silica Nanoparticles

Calixarene-functionalized luminescent nanoparticles were successfully fabricated for the FRET-based selective and sensitive detection of the organophosphorus pesticide glyphosate (GP). p-Tert-butylcalix[4]arene was grafted on the surface of [Ru(bpy)₃ ]²⁺ incorporated SiNps to produce self-assembled nanosensors (RSC). FRET was switched on in the presence of GP by means of energy transfer due to binding with p-tert-butylcalix[4]arene grafted on the surface of the RSC. The FRET efficiency of the GP-RSC system was increased gradually with the addition of GP. The FRET efficiency was evaluated as 87.69 % and a high binding affinity was established by the binding constant value, 1.16×10⁷  M^-1 , using a Langmuir binding isotherm plot. The estimated limit of detection (LOD) was 7.91×10^-7  M, which was lower than the Environmental Protection Agency (EPA) recommendation. The probe also effectively responds to real sample analysis. The sensitivity and selectivity was realized due to the efficient FRET towards the fluorescence properties of the [Ru(bpy)₃ ]²⁺ complex.

Selective and sensitive fluorescent sensor for Pd2+ using coumarin 460 for real-time and biological applications

The efficient fluorescent property of coumarin 460 (C460) is utilized to sense the Pd²⁺ selectively and sensitively. Fabrication of a sensor strip using commercial adhesive tape is achieved and the detection of Pd²⁺ is attempted using a handy UV torch. The naked eye detection in solution state using UV chamber is also attempted. The calculated high binding constant values support the strong stable complex formation of Pd²⁺ with C460. The detection limit up to 2.5 × 10^-7 M is achieved using fluorescence spectrometer, which is considerably low from the WHO's recommendation. The response of coumarin 460 with various cations also studied. The quenching is further studied by the lifetime measurements. The binding mechanism is clearly explained by the ¹H NMR titration. The sensing mechanism is established as ICT. C460 strip's Pd²⁺ quenching detection is further confirmed by solid-state PL study. The in-vitro response of Pd²⁺ in a living cell is also studied using fluorescent imaging studies by means of HeLa cell lines and this probe is very compatible with biological environments. It could be applicable to sense trace amounts of a Pd²⁺ ion from various industries. Compared with previous reports, this one is very cheap, sensitive, selective and suitable for biological systems.