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Photothermally Assisted Thinning of Silicon Nitride Membranes for Ultrathin Asymmetric Nanopores
摘要： Sculpting solid-state materials at the nanoscale is an important step in manufacturing of numerous types of sensor devices, in particular solid-state nanopore sensors. Here we present mechanistic insight into laser-induced thinning of low-stress silicon nitride (SiNx) membranes and films. In a recent study, we observed that focusing a visible wavelength laser beam on a SiNx membrane results in efficient localized heating, and used this effect to control temperature at a solid-state nanopore sensor. A side-effect of the observed heating was that the pores expand/degrade under prolonged high-power illumination, prompting us to study the mechanism of this etching process. We find that SiNx can be etched under exposure to light of ~107 W/cm2 average intensity, with etch rates that are influenced by the supporting electrolyte. Combining this controlled etching with dielectric breakdown, an electrokinetic process for making pores, nanopores of arbitrary dimensions as small as 1-2 nm in diameter and thickness can easily be fabricated. Evidence gathered from biomolecule-pore interactions suggests that the pore geometries obtained using this method are more funnel-like, rather than hourglass-shaped. Refined control over pore dimensions can expand the range of applications of solid-state nanopores, for example, biopolymer sequencing and detection of specific biomarkers.
关键词： photothermal heating,single-molecule,dielectric breakdown,Nanopores,nanofabrication
更新于2025-09-23 15:21:21
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Enhancement of Light Extraction from Organic Light-Emitting Diodes by SiO <sub/>2</sub> Nanoparticle-Embedded Phase Separated PAA/PI Polymer Blends
摘要： Using the phase separation of a binary immiscible polymer blend of poly(amic acid) and polyimide in combination with SiO2 nanoparticles, we have designed random nanopore and nanopillar patterns by a simple spin-coating technique. The spontaneously formed pattern structure was investigated by an atomic force microscope technique, which enhanced the external quantum efficiency of conventional green OLEDs up to a highest factor of 1.42. This enhancement is mainly attributed to the reduction of the total internal reflection at the interface of glass and air by the polymer hybrid layer on the backside of OLED devices. This work provides a new and practical approach to the development of efficient external outcoupling structures for OLEDs.
关键词： Poly(amic acid)/Polyimide (PAA/PI),phase separation,light extraction,nanoparticles,nanopores and nanopillars
更新于2025-09-19 17:13:59
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Spatially Controlled Fabrication and Mechanisms of Atomically Thin Nanowell Patterns in Bilayer WS <sub/>2</sub> Using <i>in Situ</i> High Temperature Electron Microscopy
摘要： We show controlled production of atomically thin nanowells in bilayer WS2 using an in situ heating holder combined with a focused electron beam in a scanning transmission electron microscope (STEM). We systematically study the formation and evolvement mechanism involved in removing a single layer of WS2 within a bilayer region with 2 nm accuracy in location and without punching through to the other layer to create a hole. Best results are found when using a high temperature of 800 °C, because it enables thermally activated atomic migration and eliminates the interference from surface carbon contamination. We demonstrate precise control over spatial distributions with 5 nm accuracy of patterning and the width of nanowells adjustable by dose-dependent parameters. The mechanism of removing a monolayer of WS2 within a bilayer region is different than removing equivalent sections in a monolayer film due to the van der Waals interaction of the underlying remaining layer in the bilayer system that stabilizes the excess W atom stoichiometry within the edges of the nanowell structure and facilitates expansion. This study offers insights for the nanoengineering of nanowells in two-dimensional (2D) transitional metal dichalcogenides (TMDs), which could hold potential as selective traps to localize 2D reactions in molecules and ions, underpinning the broader utilization of 2D material membranes.
关键词： bilayer TMDs,nanowells,in situ STEM,nanopores,2D materials
更新于2025-09-12 10:27:22
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Bio‐Assisted Tailored Synthesis of Plasmonic Silver Nanorings and Site‐Selective Deposition on Graphene Arrays
摘要： The spontaneous interaction between noble metals and biological scaffolds enables simple and cost-effective synthesis of nanomaterials with unique features. Here, plasmonic silver nanorings are synthesized on a ring-like protein, i.e., a peroxiredoxin (PRX), and used to assemble large arrays of functional nanostructures. The PRX drives the seeding growth of metal silver under wet reducing conditions, yielding nanorings with outer and inner diameters down to 28 and 3 nm, respectively. The obtained hybrid nanostructures are selectively deposited onto a solid-state 2D membrane made of graphene in order to prepare plasmonic nanopores. In particular, the interaction between the graphene and the PRX allows for the simple preparation of ordered arrays of plasmonic nanorings on a 2D-material membrane. This fabrication process can be finalized by drilling a nanometer scale pore in the middle of the ring. Fluorescence spectroscopic measurements in combination with numerical simulations demonstrate the plasmonic effects induced in the metallic nanoring cavity. The prepared nanopores represent one of the first examples of hybrid plasmonic nanopore structures integrated on a 2D-material membrane. The diameter of the nanopore and the atomically thick substrate make this proof-of-concept approach particularly interesting for nanopore-based technologies and applications such as next-generation sequencing and single-molecule detection.
关键词： plasmonics,selective-deposition,nanopores,hybrid-nanomaterials,silver nanorings
更新于2025-09-12 10:27:22
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An apparatus based on an atomic force microscope for implementing tip-controlled local breakdown
摘要： Solid-state nanopores are powerful tools for sensing of single biomolecules in solution. Fabrication of solid-state nanopores is still challenging, however; in particular, new methods are needed to facilitate the integration of pores with larger nanofluidic and electronic device architectures. We have developed the tip-controlled local breakdown (TCLB) approach, in which an atomic force microscope (AFM) tip is brought into contact with a silicon nitride membrane that is placed onto an electrolyte reservoir. The application of a voltage bias at the AFM tip induces a dielectric breakdown that leads to the formation of a nanopore at the tip position. In this work, we report on the details of the apparatus used to fabricate nanopores using the TCLB method, and we demonstrate the formation of nanopores with smaller, more controlled diameters using a current limiting circuit that zeroes the voltage upon pore formation. Additionally, we demonstrate the capability of TCLB to fabricate pores aligned to embedded topographical features on the membranes.
关键词： dielectric breakdown,atomic force microscope,nanopore fabrication,tip-controlled local breakdown,solid-state nanopores
更新于2025-09-12 10:27:22
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Facile fabrication and optimization of bowl-like ZnO/CdS nano-composite thin films with hierarchical nanopores and nano-cracks for high-performance photoelectrochemistry
摘要： A special nano-structured composite ZnO/CdS thin film with hierarchical nanopores and nano-cracks has been synthesized by a facile two-step method for the first time, in which both loadings of ZnO and CdS are optimized. We first fabricated the hierarchical nano-porous ZnO thin film through rapid gas/liquid interface assembly and layer-by-layer transfers of bowl-like ZnO nanoparticles for thirteen times. The ZnO nanobowls are prepared by a simple solution chemical reaction without using any templates. After annealing, the assembled ZnO film is sensitized with CdS nanoparticles by successive ionic layer adsorption and reactions for six cycles. Nano-cracks form for the ZnO/CdS nano-composite film by calcination, which is due to the different thermal expansion behavior between the ZnO film and the CdS layer. The facilely optimized ZnO/CdS films can serve as a promising photoanode in a photoelectrochemical cell, and it can generate a saturated photocurrent density as high as 7.8 mA cm?2 at ?0.9 V (vs. Hg|Hg2SO4|saturated K2SO4) under visible light illumination of 100 mW cm?2 in an aqueous solution of 0.5 M Na2S, corresponding to a solar-to-electricity conversion efficiency of 6.6%.
关键词： Nano-crack,CdS,Bowl-like ZnO nanoparticle,Gas/liquid interface assembly,Hierarchical nanopores,Photoelectrochemistry
更新于2025-09-10 09:29:36
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Intelligent Quantification of Picomolar Protein Concentration in Serum by Functionalized Nanopores
摘要： Nanopores have been well established as a promising platform for real time stochastic detection of single biomolecules and have made sufficient commercial progress in terms of DNA sequencing. Amongst the various strategies for specific protein estimation in physiological analyte, aptamer functionalized nanopores have been reported to quantify proteins down to few picomolars in control solution. In this paper, we explore the quantification of target protein in serum down to picomolar concentration using aptamer functionalized nanopores. For such cases, the current settles to a new value in multiple steps due to the low dissociation constants of the receptors and the final current blockade sensitivity is the primary indicator of target protein concentration. It has been observed that the current sensitivity histograms not only have a statistical variation (due to the fluctuations in the device fabrication) but also overlap significantly between the different concentration ranges in the picomolar regime, which makes quantification challenging. Here, we introduce probabilistic fuzzy model based on Monte Carlo simulation and demonstrate its ability by quantifying thrombin down to 50-pM concentration in undiluted serum. The method has been verified with 25 test solutions and the results reveal the potential of this computational approach toward lowering the detection limit by three orders of magnitude compared with the existing status, thus enabling the functionalized glass nanopore platform makes great progress toward clinical testing.
关键词： Real time,picomolar quantification,functionalized nanopores,probabilistic fuzzy model
更新于2025-09-09 09:28:46
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Specific Biosensing Using DNA Aptamers and Nanopores
摘要： The multiplexed biosensing of target molecules with high specificity and accuracy is of fundamental importance in both biological research and medical diagnostics. In this paper, the working range of the recent nanopore-DNA carrier based method is extended by introducing a two-step assay using specific DNA aptamers. A signal translation step allows for binding of the target in physiological conditions before the nanopore measurements. Using protein encoded DNA carriers, the simultaneous detection of three targets spanning several orders of magnitude in molecular weight is demonstrated. The single-molecule method may be integrated into nanopore sensing devices for future applied research and point-of-care applications.
关键词： DNA carriers,multiplexed sensing,nanopores,physiological condition,aptamers
更新于2025-09-09 09:28:46
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Enhanced visible-light photoelectrochemical hydrogen evolution through degradation of methyl orange in a cell based on coral-like Pt-deposited TiO2 thin film with sub-2 nm pores
摘要： TiO2 nanoparticles exhibit good photocatalytic activity for hydrogen evolution through water splitting; however, they demonstrate weak activity under visible light irradiation due to the wide band gap of TiO2. Deposition with noble metals such as platinum, as cocatalyst, led to the red-shift of the absorption edge of rutile TiO2; however, its activity is not significant for the photoelectrochemical (PEC) degradation of azo dyes such as methyl orange (MO). Herein, we investigated the photoelectrocatalytic degradation reaction of MO in a PEC cell based on Pt-deposited TiO2 thin film. The performance of the cell increased through the formation of mesoporous coral-like structures with sub-2 nm pores and the formation of defect states on the electrode surface. UV–vis studies confirmed, when methanol was added, the PEC cell exhibited a much higher MO degradation efficiency (99.6% after 28 min UV irradiation) than in the absence of methanol (64.7%). GC–MS studies confirmed the oxidation of methanol to formaldehyde, reacting on the electrode surface, followed by the reduction of the protons into hydrogen over the Pt sites. Also, the conversion of formaldehyde to formic acid and formic acid to CO2 are possible mechanisms to increase the hydrogen evolution rate to 418 μmol/h under visible light irradiation. Reaction of adsorbed active species within the surface of coral-like TiO2 structures with sub-2 nm pores provides high activity of the proposed PEC cell for visible-light-driven water splitting. These research studies may be continued to the design of other efficient semiconductor photocatalysts.
关键词： Photoelectrocatalytic activity,Photoelectrochemical cell,Coral-like TiO2 nanopores,Hydrogen production,Dye degradation
更新于2025-09-04 15:30:14