Elimination of Fluorescence and Scattering Backgrounds in Luminescence Lifetime Measurements Using Gated-Phase Fluorometry

Abstract

A new gated form of phase fluorometry for measuring lifetimes is presented. The technique uses a square-wave excitation and gates the detector on only during the off period of the excitation. Using a long-lived sample, this eliminates or reduces errors from scattered light and short-lived fluorescences. Using a square-wave modulated excitation source with a 50% duty cycle, traditional data treatment can be used after, at most, a simple pi/2 phase adjustment. A combination of theory and experimental results demonstrates the validity of this new gated method and its utility for eliminating or reducing background. The results are precise, accurate, eliminate scattering errors, and greatly reduce errors due to short-lived fluorescence impurities. Errors from fluorescence bleed-through into the detection period or a slow excitation source turn off can be mitigated by using an offset time prior to gating the detector on.

Host–guest sensing by calixarenes on the surfaces

“…The introduction of receptors onto nanoparticle surfaces has provided not only stability in various solvents, but also desirable surface functionality. 55 Following the discovery of the remarkable antitumoral, antibacterial, anti-inflammatory, and wound healing properties of silver nanoparticles (AgNPs), 56,57 these materials have been modified using different macrocycles, including crown ethers, 58 cyclodextrins, 59 cucurbiturils, 60 or calixarenes, 50 and further employed as hosts in the molecular recognition of various compounds, as well as for developing new methods in chemical and biological fields. 61,62 Generally, colloidal AgNPs are prepared using hydroxylamine hydrochloride as a reducing agent.…”

Synthesis of para-sulfonatocalix[4]arene-modified silver nanoparticles as colorimetric histidine probes

“…For example, Chan and co-workers reported 15-crown-5 functionalized Au NPs for the detection of potassium ions in water. 6 Kaifer and co-workers also synthesized thiolated g-cyclodextrin-capped Au NPs for the recognition of C 60 . 7 Calixarenes are considered as the third class of host molecules after crown ethers and cyclodextrins, and have demonstrated outstanding complexation activity towards ions, neutral molecules, etc.…”

Self-Referencing Intensity Measurements Based on Square-Wave Gated Phase-Modulation Fluorimetry

“…W hen both emission periods are used and the fundamental frequency is analyzed, the result is analogous to conventional sine-wave phasemodulation m easurements. 15 If the emission is more complex and includes scattered excitation light or a multicomponent sample with a species that is short lived compared to one component, the emission will include discontinuities at the turn-on and turn-off of the excitation source. Figure 1b shows the effect of a short-lived or scatter component to the signal of Fig.…”

“…The method of correction has been described elsewhere. 15 In an LED-based instrum ent, there would be no need for a correction of this type.…”

“…We present here an adaptation of the recently described gated phase-modulation (GPM) uorimetry that uses square-wave rather than sinusoidal excitation. 15 This purely AC technique readily lends itself to use with lowcost LEDs or diode lasers, which are now available for a variety of wavelengths (,390 nm to .1000 nm). For example, indium gallium nitride or gallium nitride LEDs with peaks around 470 and 450 nm are useful for sensor systems that include metal complexes.…”