Molecularly imprinted polymer (MIP)-based electrochemical sensors for the protein α-synuclein (a marker for Parkinson's disease) were developed using a peptide epitope from the protein. MIPs doped with various concentrations and species of transition metal dichalcogenides (TMDs) to enhance conductivity were electropolymerized with and without template molecules. The current during the electropolymerization was compared with that associated with the electrochemical response (at 0.24~0.29 V vs. ref. electrode) to target peptide molecules in the finished sensor. We found that this relationship can aid in the rational design of conductive MIPs for the recognition of biomarkers in biological fluids. The sensing range and limit of detection of TMD-doped imprinted poly(AN-co-MSAN)-coated electrodes were 0.001-100 pg/mL and 0.5 fg/mL (SNR = 3), respectively. To show the potential applicability of the MIP electrochemical sensor, cell culture medium from PD patient-specific midbrain organoids generated from induced pluripotent stem cells was analyzed. α-Synuclein levels were found to be significantly reduced in the organoids from PD patients, compared to those generated from age-matched controls. The relative standard deviation and recovery are less than 5% and 95-115%, respectively. Preparation of TMD-doped α-synuclein (SNCA) peptide-imprinted poly(AN-co-MSAN)-coated electrodes.
Disulfides/chemistry , Molecularly Imprinted Polymers/chemistry , Molybdenum/chemistry , Sulfides/chemistry , Tungsten Compounds/chemistry , alpha-Synuclein/analysis , Electrochemical Techniques/methods , Humans , Limit of Detection , Mesencephalon/chemistry , Organoids/chemistry , Parkinson Disease/diagnosis , Peptide Fragments/chemistry , alpha-Synuclein/chemistry
Parkinson's disease (PD) is a progressive nervous system disorder that affects movement, whose early signs may be mild and unnoticed. α-Synuclein has been identified as the major component of Lewy bodies and Lewy neurites, which are the characteristic proteinaceous deposits that are the hallmarks of PD. In this work, three alpha-synuclein peptides were synthesized as templates for the molecular imprinting of conductive polymers to enable recognition of alpha-synuclein via ultrasensitive electrochemical measurements. The peptide sequences encompassed specific residues where mutations are known to accelerate PD (though the target sequences, in this study, were wild-type.) The different peptide targets were all successfully imprinted, but with differing imprinting effectiveness, probably owing to differences in target carboxylic acids (which can bind to the aniline (AN) m-aminobenzenesulfonic acid (MSAN) MIP polymers.) Composition of the imprinted polymer, (the mole proportions of AN and MSAN), and the concentrations and sequences of imprinted peptide templates were optimized by measuring the electrochemical responses to target peptides. The imprinted electrode can detect alpha-synuclein at fg/mL levels, and was therefore used to measure alpha-synuclein in the culture medium of human brain organoids generated from normal and idiopathic PD patients.
Biosensing Techniques , Parkinson Disease , Brain/metabolism , Epitopes , Humans , Organoids/metabolism , alpha-Synuclein
We introduce a single-grain gate-all-around (GAA) Si nanowire (NW) FET using the location-controlled-grain technique and several innovative low-thermal budget processes, including green nanosecond laser crystallization, far-infrared laser annealing, and hybrid laser-assisted salicidation, that keep the substrate temperature (Tsub) lower than 400 °C for monolithic three-dimensional integrated circuits (3D-ICs). The detailed process verification of a low-defect GAA nanowire and electrical characteristics were investigated in this article. The GAA Si NW FETs, which were intentionally fabricated within the controlled Si grain, exhibit a steeper subthreshold swing (S.S.) of about 65 mV/dec., higher driving currents of 327 µA/µm (n-type) and 297 µA/µm (p-type) @ Vth ± 0.8 V, and higher Ion/Ioff (>105 @|Vd| = 1 V) and have a narrower electrical property distribution. In addition, the proposed Si NW FETs with a GAA structure were found to be less sensitive to Vth roll-off and S.S. degradation compared to the omega(Ω)-gate Si FETs. It enables ultrahigh-density sequentially stackable integrated circuits with superior performance and low power consumption for future mobile and neuromorphic applications.
A high-quality HfGeOx interfacial layer (IL) was formed in a HfO2/Al2O3/HfO2/GeOx gate stack through thermal annealing. The diffusing of GeO into the HfO2 layer led to the mixing of the GeOx and HfO2 layers, as identified through energy-dispersive X-ray Spectroscopy (EDX). X-ray photo-electron spectroscopy (XPS) data for HfGeOx IL confirmed the formation of Ge-O-Hf bonds owing to the induced shift of the Ge3dox spectra to lower binding energies. The electrical and reliability data indicated that the capacitor with HfGeOx IL presented not only lower interface states density (Dit, approximately 7 × 1011 eV-1cm-2) but also less Dit increment (approximately 3 × 1011 eV-1cm-2) after stressing than did the capacitor without the HfGeOx IL. Moreover, the Ge p-metal-oxide-semiconductor field-effect transistor HfGeOx IL exhibited a high effective hole mobility (approximately 704 cm2/V s).
High-frequency operation with ultrathin, lightweight, and extremely flexible semiconducting electronics is highly desirable for the development of mobile devices, wearable electronic systems, and defense technologies. In this work, the experimental observation of quasi-heterojunction bipolar transistors utilizing a monolayer of the lateral WSe2-MoS2 junctions as the conducting p-n channel is demonstrated. Both lateral n-p-n and p-n-p heterojunction bipolar transistors are fabricated to exhibit the output characteristics and current gain. A maximum common-emitter current gain of around 3 is obtained in our prototype two-dimensional quasi-heterojunction bipolar transistors. Interestingly, we also observe the negative differential resistance in the electrical characteristics. A potential mechanism is that the negative differential resistance is induced by resonant tunneling phenomenon due to the formation of quantum well under applying high bias voltages. Our results open the door to two-dimensional materials for high-frequency, high-speed, high-density, and flexible electronics.
We report a low current collapse GaN-based high electron mobility transistor (HEMT) with an excellent thermal stability at 150 °C. The AlN was grown by N2-based plasma enhanced atomic layer deposition (PEALD) and shown a refractive index of 1.94 at 633 nm of wavelength. Prior to deposit AlN on III-nitrides, the H2/NH3 plasma pre-treatment led to remove the native gallium oxide. The X-ray photoelectron spectroscopy (XPS) spectroscopy confirmed that the native oxide can be effectively decomposed by hydrogen plasma. Following the in situ ALD-AlN passivation, the surface traps can be eliminated and corresponding to a 22.1% of current collapse with quiescent drain bias (V DSQ) at 40 V. Furthermore, the high temperature measurement exhibited a shift-free threshold voltage (V th), corresponding to a 40.2% of current collapse at 150 °C. The thermal stable HEMT enabled a breakdown voltage (BV) to 687 V at high temperature, promising a good thermal reliability under high power operation.
Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.
The experimental observation of band-to-band tunneling in novel tunneling field-effect transistors utilizing a monolayer of MoS2 as the conducting channel is demonstrated. Our results indicate that the strong gate-coupling efficiency enabled by two-dimensional materials, such as monolayer MoS2 , results in the direct manifestation of a band-to-band tunneling current and an ambipolar transport.
