Backside absorbing layer microscopy: Watching graphene chemistry

Abstract

This new microscopy technique achieves unprecedented contrast for the study of nanomaterials and their chemical modification.

Combining Electrodeposition and Optical Microscopy for Probing Size‐Dependent Single‐Nanoparticle Electrochemistry

“…This requires in situ and real time monitoring of the deposition process and the individual behavior of many structurally different NPs.T his is afforded by optical microscopy through wide field (> 50 mm 2 ), high throughput, and nanoscale resolution imaging.Optical microscopies also carry quantitative information on NP structure (size,c omposition) or their electrochemical (EC) activity such as double layer charging,catalysis,and dissolution kinetics. [3] We propose to use arecently described nanoscale optical microscopy technique,B ALM (backside absorbing layer microscopy), [4] to quantify in situ EC processes related to the case study of Ag NPs.I ti sf irst used to explore their electrodeposition. Indeed, several in situ explorations at the single-NP level [5] have challenged the existing models relying on EC transients; [6] instead, they advocate for the continuous generation of nanoclusters (NCs,size < 2nm).…”

“…[4,8] Forametal, pseudo-antireflective conditions are met when it is deposited as an ultrathin layer (5 nm for Au)o ng lass. [4] When illuminated from the backside by an inverted microscope ( Figure 1a), such BALM substrate reflects less than 1% of the incident light toward aC CD camera. As SPR or other related reflectance-based methods, [9] sensitive to local refractive index (n)v ariations,B ALM images aw ide range of materials,f rom dielectric ( Figure 1b To afirst approximation, the BALM intensity, I BALM ,was rationalized from the predicted reflectance (Fresnel equations detailed in the Supporting Information, section S1) of two layers (Aut hin layer and the probed material) sandwiched between aglass slide and an ambient (water) medium.…”

Backside absorbing layer microscopy: a universal relationship between physical thickness and reflectivity

“…This serves as a basis for a number of label free optical techniques [1][2][3][4][5][6]. Among them, the Backside Absorbing Layer Microscopy (BALM), a recent contrast technique in wide field optical microscopy [7,8], is especially promising. This reflected light microscopy lies on the use of special antireflecting layers as sample supporting plates.…”

“…The only requirement is to image the sample supported by the ARA coating from the opposite side of a thin transparent window on which it is deposited. The performance of the technique was already demonstrated by imaging 2D flakes of various materials [8], by following in situ and in real time their evolution upon small molecules adsorption and by detecting operando the electrochemical reduction of individual sub-10nm nanoparticles [9]. However, up to now the BALM images remained mainly qualitative [10] when characterization and sensing applications demand quantitative information.…”

The promise of antireflective gold electrodes for optically monitoring the electro-deposition of single silver nanoparticles

“…Such AR layers made of gold on glass are thus ideal for opto-electrochemical studies. Their optical observation is made in the so-called Backside Absorbing Layer Microscopy (BALM) 31 and we demonstrate herein how it can be implemented to follow and analyze quantitatively the electrochemical growth/dissolution of Ag NPs at an ultramicroelectrode (UME) surface.…”