Fluorophore Release from a Polymethinic Photoremovable Protecting Group Through a Nonlinear Optical Process

Abstract

Triggering the release of chemical species through the use of light is crucial for modern microscopy applications, such as single‐molecule localization and, in general, in the regulation of molecular effectors. Herein, we demonstrate a nonlinear‐optical scheme for the control of photorelease. Our system consists of a two‐photon‐absorbing photoremovable protecting group (PPG) bonded to a second chromophore which undergoes photo‐induced detachment and activation upon excitation with λ=850 nm femtosecond pulses. The two‐photon PPG section consists of a cyanine‐type dye, and the releasable section is a highly fluorescent derivatized anthracene chromophore bonded to the cyanine through a photolabile etheric‐meso‐carbon bond. This method allows for the release of a fluorophore following a spatially localized two‐photon excitation event. Both the excitation energy and the long lifetime of the upper excited states of the PPG chromophore are thought to be involved in the release process.

Ultrafast Photoluminescence Kinetics from Hot Excitonic States in CdSe Nanocrystals

“…The X 1 (1S 3/2 1S) PL long lifetimes (ns) were acquired by the TCSPC technique. , The intensity-weighted average lifetimes considering triexponential fits were 36 ± 1 and 31 ± 1 ns for the D = 4.4 and 5.4 nm QDs, respectively (see Figure S2 and Tables S3 and S4 for fit parameters). These emission signals can be considered as a measurement of the average lifetime of the fully relaxed X 1 (1S 3/2 1S), which is formed in the femtosecond and picosecond time scales from the initially pumped HE states.…”

“…The intensityweighted average lifetimes ⟨τ⟩ followed eq 1 fs fluorescence lifetimes from higher singlet molecular states. 39,40,43 This pump-probe technique used an ultrashort amplified laser train pulse (800 nm, 1 kHz, 70 fs, 0.7 mJ pulse −1 ), which was divided into two. The probe consisted of 10% of the energy of the original pulse.…”

“…The nanosecond PL lifetimes were acquired in a custom-built confocal microscope coupled with a time-correlated single-photon counting (TCSPC) system. , A 405 nm pulsed laser (1 MHz) (LDH-D-C-405, PicoQuant) was focused onto a 1 cm path quartz cell with a 0.25 NA, f = 6.1 mm objective (Melles-Griot). The collected PL was filtered through a 485 nm dichroic mirror (Chroma T510lpxrxt), a 405 nm notch filter (Chroma, ZET405nf), and a 425 nm emission filter (Chroma ET425lp).…”

“…A highly sensitive up-conversion setup was used to study the ultrafast PL behavior of the different HE states. With this technique, our group has been able to follow molecular states with fluorescence quantum yields of less than 10 –5 and sub-80 fs fluorescence lifetimes from higher singlet molecular states. ,, This pump-probe technique used an ultrashort amplified laser train pulse (800 nm, 1 kHz, 70 fs, 0.7 mJ pulse –1 ), which was divided into two. The probe consisted of 10% of the energy of the original pulse.…”

Linear and Nonlinear Optical Processes Controlling S2 and S1 Dual Fluorescence in Cyanine Dyes

“…Being able to populate long-lived higher excited states is essential to enable novel photochemistry. For example, a cyanine derivative has recently been shown to undergo photodissociation following two-photon excitation to its second excited state . One may extrapolate these results and imagine that capturing energy in higher excited states may lead to more efficient solar energy capture, especially systems containing cyanine compounds, and perhaps theranostic applications whereby a compound excited to S 1 serves as fluorescent marker but when excited to S 2 serves as a therapy agent.…”