Lateral Force Microscopy of Interfacial Nanobubbles: Friction Reduction and Novel Frictional Behavior.

Atomic force microscopy is used to conduct single-asperity friction measurements at a water-graphite interface. Local mapping of the frictional force, which is based on the degree of the cantilever twisting, shows nearly friction-free when a tip scans over a nanobubble. Surprisingly, apart from being gapless, the associated friction loop exhibits a tilt in the cantilever twisting versus the tip's lateral displacement with the slope depending on the loading force.

High-Resolution Characterization of Preferential Gas Adsorption at the Graphene-Water Interface.

The contact of water with graphene is of fundamental importance and of great interest for numerous promising applications, but how graphene interacts with water remains unclear. Here we used atomic force microscopy (AFM) to investigate hydrophilic mica substrates with some regions covered by mechanically exfoliated graphene layers in water. In water containing air gas close to the saturation concentration (within ∼40%), cap-shaped nanostructures (or interfacial nanobubbles) and ordered-stripe domains were observed on graphene-covered regions but not on pure mica regions.

Nucleation processes of nanobubbles at a solid/water interface.

Experimental investigations of hydrophobic/water interfaces often return controversial results, possibly due to the unknown role of gas accumulation at the interfaces. Here, during advanced atomic force microscopy of the initial evolution of gas-containing structures at a highly ordered pyrolytic graphite/water interface, a fluid phase first appeared as a circular wetting layer ~0.3 nm in thickness and was later transformed into a cap-shaped nanostructure (an interfacial nanobubble).

Mobile Charge-Induced Fluorescence Intermittency in Methylammonium Lead Bromide Perovskite.

Organic-inorganic halide perovskite has emerged as a very promising material for solar cells due to its excellent photovoltaic enabling properties resulting in rapid increase in device efficiency over the last 3 years. Extensive knowledge and in-depth physical understanding in the excited state carrier dynamics are urgently required. Here we investigate the fluorescence intermittency (also known as blinking) in vapor-assisted fabricated CH3NH3PbBr3 perovskite.

Interface-induced ordering of gas molecules confined in a small space.

The thermodynamic properties of gases have been understood primarily through phase diagrams of bulk gases. However, observations of gases confined in a nanometer space have posed a challenge to the principles of classical thermodynamics. Here, we investigated interfacial structures comprising either O2 or N2 between water and a hydrophobic solid surface by using advanced atomic force microscopy techniques.

Probing and controlling fluorescence blinking of single semiconductor nanoparticles.

In this review we present an overview of the experimental and theoretical development on fluorescence intermittency (blinking) and the roles of electron transfer in semiconductor crystalline nanoparticles. Blinking is a very interesting phenomenon commonly observed in single molecule/particle experiments. Under continuous laser illumination, the fluorescence time trace of these single nanoparticles exhibit random light and dark periods.