Loren Picco

This study uses contact-mode HS-AFM to probe Aβ interactions with neuronal lipid models, demonstrating oligomer-induced bilayer destabilization, especially in low-cholesterol membranes, emphasizing lipid composition and Aβ species dependent damage.

High- speed atomic force microscopy (HSAFM) can produce thousands of topographic, nanoscale images over a small area. One emerging application of this technique is the detection and sizing of single DNA molecules derived from biological experiments and genetic testing. Using HSAFM images, researchers can visually categorize healthy and mutant DNA based on size and sequence-specific labelling, leading to rapid, high precision diagnostics. However, manually sifting through large numbers of images is time consuming and labor intensive, presenting a bottleneck for sample analysis. In this paper we look at how deep learning methods like object detection and image classification can assist in streamlining the process. To instantly assess image quality on data collected from trinucleotide repeat expansion disease samples, a fully convolutional network (FCN) was compared against Laplacian of Gaussian (LOG) and fast Fourier Transform (FFT) methods. The FCN performed the best, reproducing human categorizations with an accuracy of 96% and an AUC of 0.990. Additionally, using the YOLOv8 architecture, we have developed an object detection model capable of detecting marked DNA enriched from the FMR1 gene locus, which is mutated in from patients with Fragile X syndrome, with an average precision (AP) of 0.966. The integration of machine learning techniques in HSAFM systems shows promise to enhance the data collection and analysis process for genomics-based disease diagnosis

Nanoribbons, nanometre-wide strips of a two-dimensional material, are a unique system in condensed matter. They combine the exotic electronic structures of low-dimensional materials with an enhanced number of exposed edges, where phenomena including ultralong spin coherence times^1,2, quantum confinement³ and topologically protected states^4,5 can emerge. An exciting prospect for this material concept is the potential for both a tunable semiconducting electronic structure and magnetism along the nanoribbon edge, a key property for spin-based electronics such as (low-energy) non-volatile transistors⁶. Here we report the magnetic and semiconducting properties of phosphorene nanoribbons (PNRs). We demonstrate that at room temperature, films of PNRs show macroscopic magnetic properties arising from their edge, with internal fields of roughly 240 to 850 mT. In solution, a giant magnetic anisotropy enables the alignment of PNRs at sub-1-T fields. By leveraging this alignment effect, we discover that on photoexcitation, energy is rapidly funnelled to a state that is localized to the magnetic edge and coupled to a symmetry-forbidden edge phonon mode. Our results establish PNRs as a fascinating system for studying the interplay between magnetism and semiconducting ground states at room temperature and provide a stepping-stone towards using low-dimensional nanomaterials in quantum electronics.

Nanoribbons – nanometer wide strips of a two-dimensional material – are a unique system in condensed matter. They combine the exotic electronic structures of low-dimensional materials with an enhanced number of exposed edges, where phenomena including ultralong spin coherence times^1–4, quantum confinement⁵ and topologically protected states^6–8 can emerge. An exciting prospect for this new material concept is the potential for both a tunable semiconducting electronic structure and magnetism along the nanoribbon edge. This combination of magnetism and semiconducting properties is the first step in unlocking spin-based electronics such as non-volatile transistors, a route to low-energy computing⁹, and has thus far typically only been observed in doped semiconductor systems and/or at low temperatures^10–15. Here, we report the magnetic and semiconducting properties of phosphorene nanoribbons (PNRs). Static (SQUID) and dynamic (EPR) magnetization probes demonstrate that at room temperature, films of PNRs exhibit macroscopic magnetic properties, arising from their edge, with internal fields of ~ 240 to 850 mT. In solution, a giant magnetic anisotropy enables the alignment of PNRs at modest sub-1T fields. By leveraging this alignment effect, we discover that upon photoexcitation, energy is rapidly funneled to a dark-exciton state that is localized to the magnetic edge and coupled to a symmetry-forbidden edge phonon mode. Our results establish PNRs as a fascinating system for studying the interplay of magnetism and semiconducting ground states at room temperature and provide a stepping-stone towards using low-dimensional nanomaterials in quantum electronics.

Nanoribbons - nanometer wide strips of a two-dimensional material - are a unique system in condensed matter physics. They combine the exotic electronic structures of low-dimensional materials with an enhanced number of exposed edges, where phenomena including ultralong spin coherence times, quantum confinement and topologically protected states can emerge. An exciting prospect for this new material concept is the potential for both a tunable semiconducting electronic structure and magnetism along the nanoribbon edge. This combination of magnetism and semiconducting properties is the first step in unlocking spin-based electronics such as non-volatile transistors, a route to low-energy computing, and has thus far typically only been observed in doped semiconductor systems and/or at low temperatures. Here, we report the magnetic and semiconducting properties of phosphorene nanoribbons (PNRs). Static (SQUID) and dynamic (EPR) magnetization probes demonstrate that at room temperature, films of PNRs exhibit macroscopic magnetic properties, arising from their edge, with internal fields of ~ 250 to 800 mT. In solution, a giant magnetic anisotropy enables the alignment of PNRs at modest sub-1T fields. By leveraging this alignment effect, we discover that upon photoexcitation, energy is rapidly funneled to a dark-exciton state that is localized to the magnetic edge and coupled to a symmetry-forbidden edge phonon mode. Our results establish PNRs as a unique candidate system for studying the interplay of magnetism and semiconducting ground states at room temperature and provide a stepping-stone towards using low-dimensional nanomaterials in quantum electronics.

We studied the surface evolution of polycrystalline Cu films electrodeposited from an organic additive-free acid sulphate electrolyte on to a gold microelectrode using a high-speed Atomic Force Microscope (HS-AFM) which images an area of 2 × 2 μm at 2 frames per second and a resolution of 1000 × 1000 pixels. The ability to acquire data at this rate opens even fast growth processes to in situ investigation. Real-time images from a film deposited at ∼0.5 nm s⁻¹ revealed many interesting phenomena, most significantly highly non-uniform grain growth rates with several examples of grains showing accelerated growth compared to their neighbours. Grain overgrowth was also observed in different regions of the sample. Surface roughness scaling and slope analysis provided evidence for structural coarsening of the film and an increase in the mean slope θ with increasing film thickness t. We show how both grain overgrowth and an increase in θ can contribute to the coarsening of the surface structure as deposition proceeds.

We prove that the Euler–Bernoulli elastic beam theory can be reliably used to describe the dynamics of an atomic force microscope cantilever during the far from equilibrium snap-to-contact event. In conventional atomic force microscope operation, force-separation curves are obtained by post-processing voltage versus time traces produced by measuring one point on the cantilever close to the hanging end. In this article, we assess the validity of the Euler–Bernoulli equation during the snap-to-contact event. The assessment is based on a direct comparison between experiment and theory. The experiment uses Doppler vibrometry to measure displacement versus time for many points along the long axis of the cantilever. The theoretical algorithm is based on a solution of the Euler–Bernoulli equation to obtain the full shape of the cantilever as a function of time. The algorithm uses as boundary conditions, experimentally obtained information only near the hanging end of the cantilever. The solution is obtained in a manner that takes into account non-equilibrium motion. Within experimental error, the theory agrees with experiment indicating that the Euler–Bernoulli theory is appropriate to predict the cantilever kinematics during snap-to-contact. Since forces on the tip can be obtained from the instantaneous shape of the cantilever, this work should allow for computation of tip-sample forces during the snap-to-contact event from a conventional force-distance measured input.

High-speed atomic force microscopy (HS-AFM) is a powerful emerging technique used to gain insight into real-time nanoscale dynamics and phenomena across the sciences. By performing measurements of material properties, abundancy counting and dimensional analysis, it enables a new generation of discoveries at the atomic scale. Here, we demonstrate the use of an optical pickup unit (OPU) typically found in PCs, hi-fis and games consoles worldwide, as a vertical detection system within in a HS-AFM operated in contact mode. The OPU displacement performance is compared to that of a commercially available laser Doppler vibrometer with ±15 pm resolution. Sub-nanometre sensitivity is achieved with an OPU, presented via the identification of two resonant modes of a cantilever stimulated by ambient thermal excitation. To demonstrate the large dynamic range of the sensor at fast scan-speeds, surface profiles with step heights in excess of 100 nm and surface textures less than 10 nm were collected using a custom OPU-based HS-AFM. The high-fidelity measurements are extended to visible length scales in short timescales by imaging areas of up to 200 µ m ² area at a pixel rate of 2 megapixels s ⁻¹ , tip velocity of 10 mm s ⁻¹ and area rate of 25 µ m ² s ⁻¹ .

Atomic force microscopes (AFMs) are capable of high-resolution mapping of structures and the measurement of mechanical properties on nanometre scales within gaseous, liquid and vacuum environments. The contact mode high-speed AFM (HS-AFM) developed at Bristol Nano Dynamics Ltd. operates at speeds that are orders of magnitude faster than conventional AFMs, and is capable of capturing multiple frames per second. This allows for direct observation of dynamic events in real-time, with nanometre lateral resolution and subatomic height resolution. HS-AFM is a valuable tool for the imaging of nanoscale corrosion initiation events, such as metastable pitting, grain boundary (GB) dissolution and short crack formation during stress corrosion cracking (SCC). Within this study HS-AFM was combined with SEM and FIB milling to produce a multifaceted picture of localised corrosion events occurring on thermally sensitised AISI 304 stainless steel in an aqueous solution of 1% sodium chloride (NaCl). HS-AFM measurements were performed in situ by imaging within a custom built liquid cell with parallel electrochemical control. The high resolution of the HS-AFM allowed for measurements to be performed at individual reaction sites, i.e. at specific GB carbide surfaces. Topographic maps of the sample surface allowed for accurate measurements of the dimensions of pits formed. Using these measurements it was possible to calculate, and subsequently model, the volumes of metal reacting with respect to time, and so the current densities and ionic fluxes at work. In this manner, the local electrochemistry at nanoscale reaction sites may be reconstructed.