arXiv subjects

Pia Bhatia

Publications and source records attributed to Pia Bhatia.

4 recordsLinked to original sources

arXiv2025

Amino Acid Translocation Through a Dual Nanopore Platform

We demonstrate a dual nanopore platform (DNP) containing a top 2D MoS2 pore in series with a 3 to 5 nm thick SiN pore, vertically separated by 30 nm, with diameters of 1.0 and 3.0 nm, respectively. This platform enables independent probing of analytes by each pore, thereby providing complementary information. We measure translocations of single amino acids (AA) and evaluate current blockades recorded across the two pores upon applying voltage. Small diameters ensured tight passage of individual AAs through the nanopores and provided a good signal-tonoise ratio (RMS current noise of 16 pA_RMS and SNR = 6). We focus on measurements of O-Phospho-L-tyrosine at 400 mV, demonstrating single amino acid detection and a good quantitative agreement with the calculated open pore and blocked currents. Based on these results, future device performance can benefit from slightly smaller pores, specifically the SiN pore, higher voltages and electrolyte concentration, and lower system noise.

physics.app-ph↗

arXiv2025

Reversible nanopore sealing and in situ iron oxide nanoparticle synthesis on thin silicon nitride membranes

We report in-situ synthesis of iron oxide particles inside silicon nitride nanopores via a chemical reaction, monitored by current readout. Nanopores were formed by electroporation on glass chips (diameters from 1.7 to 11.3 nm), transmission electron microscopy (TEM) drilling (diameters from 6.5 to 64.6 nm), or hydrofluoric acid (HF) etching (diameters from 12.6 to 36.2 nm) in 5 to 20 nm thick membranes. Nanopores seal on timescales from ~1 ms to ~3.6 s, across a range of sizes and concentrations. We show single and ~5-pore arrays, as fabricated, after sealing, and after cleaning and pore recovery. These results are independent of fabrication method. Energy dispersive X-ray spectroscopy (EDS), aberration-corrected scanning TEM (AC-STEM), and powder X-ray diffraction (XRD) verify the synthesis of mixed magnetite and maghemite iron oxide. This work advances nanoparticle-nanopore chips for applications in biosensing, plasmonics and photonics when position and size control is required.

cond-mat.mtrl-sci↗

arXiv2024

Correlated Structural and Optical Characterization of Hexagonal Boron Nitride

Hexagonal boron nitride (hBN) plays a central role in nanoelectronics and nanophotonics. Moreover, hBN hosts room-temperature quantum emitters and optically addressable spins, making it promising for quantum sensing and quantum photonics. Despite many investigations of their optical properties, however, the emitters' chemical structure remains unclear, as does the role of contamination at surfaces and interfaces in forming the emitters or modifying their properties. We prepare hBN samples that are compatible with confocal photoluminescence (PL) microscopy, transmission electron microscopy (TEM), and atomic-force microscopy (AFM), and we use those techniques to quantitatively investigate correlations between fluorescent emission, flake morphology, and surface residue. We find that the microscopy techniques themselves induce changes in hBN's optical activity and residue morphology: PL measurements induce photobleaching, whereas TEM measurements alter surface residue and emission characteristics. We also study the effects of common treatments $\unicode{x2014}$ annealing and oxygen plasma cleaning $\unicode{x2014}$ on the structure and optical activity of hBN. The methods can be broadly applied to study two-dimensional materials, and the results illustrate the importance of correlative studies to elucidate structural factors that influence hBN's functionality as a host for quantum emitters and spin defects.

cond-mat.mtrl-sci↗

arXiv2020

Systematic Characterization of Hydrophilized Polydimethylsiloxane

Flexible microfluidics have found extensive utility in the biological and biomedical fields. A leading substrate material for compliant devices is polydimethylsiloxane (PDMS). Despite its many advantages, PDMS is inherently hydrophobic and consequently its use in passive (pumpless) microfluidics becomes problematic. To this end, many physical and chemical modifications have been introduced to render PDMS hydrophilic, ranging from amphiphilic molecule additions to surface plasma treatments. However, when transitioning from lab benchtop to realized medical devices, these modifications must exhibit long-term stability. Unfortunately, these modifications are often presented but their mechanisms and long-term stability are not studied in detail. We have investigated an array of PDMS modifications, utilizing contact angle goniometry to study surface energy over a 30-day evolution study. Samples were stored in air and water, and Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) analysis was used to confirm surface functional group uniformity. We have identified preferred modification techniques for long-lasting PDMS devices and characterized often overlooked material stability.

physics.app-ph↗