Fluorophores “Turned-On” by Corrosion Reactions Can Be Detected at the Single-Molecule Level

Abstract

We demonstrate that fluorogenic molecules that “turn-on” upon redox reactions can sense the corrosion of iron at the single-molecule scale. We first observe the cathodic reduction of nonfluorescent resazurin to fluorescent resorufin in the presence of iron in bulk solution. The progression of corrosion is seen as a color change that is quantified as an increase in fluorescence emission intensity. We show that the fluorescence signal is directly related to the amount of electrons that are available due to corrosion progression and can be used to quantify the catalyzed increase in the rate of corrosion by NaCl. By using modern fluorescence microscopy instrumentation we detect real-time, single-molecule “turn-on” of resazurin by corrosion, overcoming the previous limitations of microscopic fluorescence corrosion detection. Analysis of the total number of individual resorufin molecules shows heterogeneities during the progression of corrosion that are not observed in ensemble measurements. Finally, we discuss the potential for single-molecule kinetic and super-resolution localization analysis of corrosion based on our findings. Single-molecule florescence microscopy opens up a new spatiotemporal regime to study corrosion at the molecular level.

Kinetics of the Photoelectron-Transfer Process Characterized by Real-Time Single-Molecule Fluorescence Imaging on Individual Photocatalyst Particles

“…Single-molecule fluorescence experiments were performed on individual TiO 2 -tipped CNT by turning on 365 nm UV irradiation and 561 nm laser simultaneously. The unique flicker characteristics are obviously observed in the photocatalytic video (Video 1), proving that we observed single molecules . To describe clearly, an integrated fluorescence image with a low resolution (Figure b) was first obtained through outline building with Sobel edge detection.…”

“…The unique flicker characteristics are obviously observed in the photocatalytic video (Video 1), proving that we observed single molecules. 39 To describe clearly, an integrated fluorescence image with a low resolution (Figure 2b) was first obtained through outline building with Sobel edge detection. Figure 2c shows the segment of typical fluorescence bursts, which was obtained via pretreating the crude signal with 10% low-pass filtering and choosing a suitable valve of threshold (Figure S5).…”

Exploring chemistry with single-molecule and -particle fluorescence microscopy

“…This slow diffusion enables their imaging by fluorescence microscopy. Insights into fluid cracking catalysis using catalytic zeolite particle systems [13,14] and corrosion detection on iron cathodes [15,16] are example systems where unique insight has been obtained. The spatiotemporal resolution of fluorescence microscopy provides exquisite 2D and 3D reactivity maps of the location of catalytic reactions on and within these catalytic inorganic materials [11,[17][18][19][20][21][22][23].…”

“…In organic solvents [3,44] Under air-free conditions (glovebox setup and adding solid reagents during imaging) [4,5] Imaging in flow cells [9,32,52] Higher temperature imaging (diffusion at 135°C, chemical reaction at 45°C) [24,52] Types of reactions and processes imaged Hydrolysis [6] Proton-transfer [53] Epoxidation [26,33] Solubilization [4,36] Deallylation [5] Redox (nanoparticle and photocatalysis) [10,11,17,[19][20][21]54] Cross-coupling [46] Oligomerization [14] Polymerization [40][41][42]55] Hydrogenation [56] Cycloaddition [47][48][49][50] Condensation [34,57] Corrosion [15,16] Molecular metal-ligand exchange/dissociation [37][38][39]44] Oxidative addition [4,35,46] Mechanistic questions answered Identification of previously unknown organic and organometallic intermediates …”

Single Molecule Microscopic Detection of Corrosion Reactions using “Turned-on” Fluorophores

“…We demonstrate that fluorophores "turned-on" by corrosion of iron can be detected at the single-molecule scale [6]. First, we study the properties of the dye resazurin, which becomes fluorescent in the reduced form as resorufin, at the ensemble level.…”