Subnanometer structure and function from ion beams through complex fluidics to fluorescent particles

Abstract

The vertical dimensions of complex nanostructures determine the functions of diverse nanotechnologies. In this paper, we investigate the unknown limits of such structure-function relationships at subnanometer scales. We begin with a quantitative evaluation of measurement uncertainty from atomic force microscopy, which propagates through our investigation from ion beam fabrication to fluorescent particle characterization. We use a focused beam of gallium ions to subtractively pattern silicon surfaces, and silicon nitride and silicon dioxide films. Our study of material responses quantifies the atomic limits of forming complex topographies with subnanometer resolution of vertical features over a wide range of vertical and lateral dimensions. Our results demonstrate the underutilized capability of this standard system for rapid prototyping of subnanometer structures in hard materials. We directly apply this unprecedented dimensional control to fabricate nanofluidic devices for the analytical separation of colloidal nanoparticles by size exclusion. Optical microscopy of single nanoparticles within such reference materials establishes a subnanometer limit of the fluidic manipulation of particulate matter and enables critical-dimension particle tracking with subnanometer accuracy. After calibrating for optical interference within our multifunctional devices, which also enables device metrology and integrated spectroscopy, we reveal an unexpected relationship between nanoparticle size and emission intensity for common fluorescent probes. Emission intensity increases supervolumetrically with nanoparticle diameter and then decreases as nanoparticles with different diameters photobleach to similar values of terminal intensity. We propose a simple model to empirically interpret these surprising results. Our investigation enables new control and study of structure-function relationships at subnanometer scales.

Two-Dimensional Nanochannel Arrays Based on Flexible Montmorillonite Membranes

“…When the Debye screening length (κ –1 ) of a fluid electrolyte is larger than the size of nanochannels, the formed electrical double layers near the nanochannel’s inner walls overlap, and the ions of the same charge are repelled but the counterions are attracted by the surface charges on the inner walls of the nanochannels; therefore, ion transport in nanofluids shows different and unique characteristics from that in bulk fluids. Consequently, great attention has been devoted to the research of nanofluidics, owing to its potential applications in molecule delivery, electrochemical energy conversion and storage, and ultrasensitive detection of biomolecules. − Conventional fabrication methods, including focus ion beam, mold machining, UV lithography, nanowire templating, and chemical vapor deposition, mainly involve creating a single nanopore/nanochannel/nanotube, and the fundamental mechanism of molecular/ionic transport through these nanoscale architectures has been extensively explored. − To realize real-world applications of nanofluidics, large-scale integration of such nanofluidic devices are urgently required, and thus, two-dimensional (2D) nanofluidics based on layered membranes have currently aroused considerable interest because of its unique advantages, such as facile fabrication, scalability, high flux, easy modification, highly controllable channel size, etc. − …”

Nanoparticle Manufacturing – Heterogeneity through Processes to Products

“…Magneto-optical films indicate the magnetic properties and interactions of single nanoparticles, , which are otherwise difficult to discern. Nanofluidic devices manipulate nanoparticles for optical imaging or electronic detection, enabling size and charge measurements. , Nanofluidic size exclusion can achieve sub-nanometer accuracy and elucidate optical properties of nanoparticles, but measurement devices must be sufficiently reliable and economical to produce to have broad impact …”

“…Nanofluidic devices manipulate nanoparticles for optical imaging 255 or electronic detection, 256 enabling size and charge measurements. 257,258 Nanofluidic size exclusion can achieve sub-nanometer accuracy and elucidate optical properties of nanoparticles, 259 but measurement devices must be sufficiently reliable and economical to produce to have broad impact. 260 2.7.…”

Characterization of nanoparticle size distributions using a microfluidic device with integrated optical microcavities

“…Electron microscopy or scanning probe microscopy can provide accurate information on the shape of the nanoparticles 8,9 . For example, Atomic Force Microscopy (AFM) technique can characterize nanoparticles with the size range of 1 − 20 nm in dry and liquid states 10,11 . Although AFM has high compatibility with different samples and measurement environments, it is limited due to the need for sample preparation.…”