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Sensitivity-Selectivity Trade-Offs in Surface Ionization Gas Detection
摘要： Surface ionization (SI) provides a simple, sensitive, and selective method for the detection of high-proton affinity substances, such as organic decay products, medical and illicit drugs as well as a range of other hazardous materials. Tests on different kinds of SI sensors showed that the sensitivity and selectivity of such devices is not only dependent on the stoichiometry and nanomorphology of the emitter materials, but also on the shape of the electrode configurations that are used to read out the SI signals. Whereas, in parallel-plate capacitor devices, different kinds of emitter materials exhibit a high level of amine-selectivity, MEMS (micro-electro-mechanical-systems) and NEMS (nanowire) versions of SI sensors employing the same kinds of emitter materials provide significantly higher sensitivity, however, at the expense of a reduced chemical selectivity. In this paper, it is argued that such sensitivity-selectivity trade-offs arise from unselective physical ionization phenomena that occur in the high-field regions immediately adjacent to the surfaces of sharply curved MEMS (NEMS) emitter and collector electrodes.
关键词： selectivity,gas detection,corona discharge,secondary electron emission,sensitivity,surface ionization
更新于2025-09-23 15:22:29
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A rhodamine-deoxylactam based fluorescent probe for fast and selective detection of nitric oxide in living cells
摘要： Nitric oxide (NO) plays vital roles in many physiological process and is closely related to many diseases. So far, a number of fluorescent probes have been constructed for the detection of NO successfully. However, the probes still suffer from long-time reaction and limited selectivity. Herein, a fluorescent probe named dRB-OPD is synthesized and used to recognize NO. The probe contains a deoxy-rhodamine B as fluorophore and o-phenylenediamino as reaction site. dRB-OPD shows fast response to NO within 40 seconds with 170-fold fluorescence enhancement. Moreover, the probe shows high selectivity towards NO over dehydroascorbic acid (DHA), ascorbic acid (AA), and methylglyoxal (MGO). Particularly, the probe can avoid the serious interference from cysteine (Cys) found in the rhodamine lactam-based fluorescent NO probes (RB-OPD). In addition, the probe is applied for the detection of exogenous and endogenous NO in the HepG2 and RAW 264.7 cells with satisfactory results.
关键词： Cell imaging,Fluorescent probe,Nitric oxide,High selectivity,Fast response
更新于2025-09-23 15:22:29
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Discovery and Characterization of a Naturally Occurring, Turn-On Yellow Fluorescent Protein Sensor for Chloride
摘要： Fluorescent proteins have been extensively engineered and applied as optical indicators for chloride in a variety of biological contexts. Surprisingly, given the biodiversity of ?uorescent proteins, a naturally occurring chloride sensor has not been reported to date. Here, we present the identi?cation and spectroscopic characterization of the yellow ?uorescent protein from the jelly?sh Phialidium sp. (phiYFP), a rare example of a naturally occurring, excitation ratiometric, and turn-on ?uorescent protein sensor for chloride. Our results show that chloride binding tunes the pKa of the chromophore Y66 and shifts the equilibrium from the ?uorescent phenolate form to the weakly ?uorescent phenol form. The latter likely undergoes excited-state proton transfer to generate a turn-on ?uorescence response that is pH-dependent. Moreover, anion selectivity and mutagenesis in the chloride binding pocket provide additional evidence for the proposed chloride sensing mechanism. Given these properties, we anticipate that phiYFP, with further engineering, could be a new tool for imaging cellular chloride dynamics.
关键词： phiYFP,mutagenesis,chloride sensor,anion selectivity,turn-on fluorescence,pH-dependent,excitation ratiometric,fluorescent proteins
更新于2025-09-23 15:21:21
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Increasing Membrane Permeability by Increasing the Polymer Crystallinity: The Unique Case of Polythiophenes
摘要： It is generally accepted in membrane technology that crystalline zones in polymeric membranes do not contribute to transport of liquids or gases. In the current study, poly(3-alkylthiophene)s (P3ATs), i.e., homopolymers and random copolymers, were synthesized to study the influence of the supramolecular organization on membrane gas separations. The monomers were polymerized via KCTCP, and GPC analysis shows that the polymers have a narrow dispersity. DSC analysis of the polymers reveals that the homopolymers, in contrast to the copolymers, crystallized, confirming their higher degree of supramolecular organization. This was supported by UV?vis absorption spectra of the polymer films, where a red-shift and a characteristic shoulder absorption peak around 600 nm were observed for the homopolymers, while absent for the copolymers. More surprisingly, the homopolymers were found to be 2 orders of magnitude more permeable to CO2 than the copolymers and also more selective.
关键词： selectivity,gas separations,permeability,membrane technology,supramolecular organization,poly(3-alkylthiophene)s,crystallinity
更新于2025-09-23 15:21:21
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[Nanostructure Science and Technology] Nanowire Electronics || One-Dimensional Nanowire-Based Heterostructures for Gas Sensors
摘要： Gas sensors with the ability to detect gaseous species in a quantitative and qualitative manner play an important role in various aspects in our daily lives. They can function as a feasible means to monitor air quality, environmental pollution, chemical detection, control of chemical processes, food quality, and medical diagnosis and so forth. One-dimensional (1D) nanostructures at least one dimension in the range of 1–100 nm (nanowires, nanorods, nanoribbons or nanobelts, nano?bers) have long been considered as promising building blocks for gas sensors [1–7]. The fascinating features of nanowires for gas sensing include high surface-to-volume ratio, sensitive surface, high crystallinity, high carrier mobility, low power consumption and ease for device integration [2, 6, 8, 9]. In 2001 nanowires were initially employed to fabricate gas sensors as proof-of-concept [2, 3]. Afterwards nanowires are drawing fast growing interest in the ?eld of gas sensing with an outcome of over 1200 publications in past 15 years from the Web of Science using the keywords nanowire and gas sensor (Fig. 7.1). It is important to note that among these publications metal oxide nanowires hold a dominant position, while other nanowires including organic polymers, metals, and other semiconductors only register a small part (12.6%). It is not strange that n-type ZnO and SnO2 nanowires are the most extensively studied materials for gas sensing because the electron mobility in ZnO and SnO2 is very high (160 and 200 cm2 V(cid:1)1 s(cid:1)1, respectively) with respect to that of other metal oxides such as In2O3, WO3 and TiO2 (100, 10 and 0.4 cm2 V(cid:1)1 s(cid:1)1, respectively).
关键词： speed,heterostructures,sensitivity,nanowires,gas sensors,metal oxide,selectivity,stability
更新于2025-09-23 15:21:21
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Synthesis and biological evaluation of phthalocyanine-peptide conjugate for EGFR-targeted photodynamic therapy and bioimaging
摘要： To improve the biocompatibility and tumor selectivity, we employed an epidermal growth factor receptor (EGFR) binding peptide (namely GE11, with a sequence of Tyr-His-Trp-Tyr-Gly-Tyr-Thr-Pro-Gln-Asn-Val-Ile) as a tumor directing vector for the delivery of zinc(II) phthalocyanine for targeted photodynamic therapy and bioimaging. The photophysical properties, cellular uptake, in vitro cytotoxicity, and in vivo biodistribution of this phthalocyanine-peptide conjugate (namely Pc-GE11) have been evaluated. Pc-GE11 exhibited higher cellular uptake on EGFR-overexpressing epidermoid carcinoma A431 cells when compared with that on human breast adenocarcinoma MCF7 cells (low EGFR expression). Moreover, pretreatment of A431 cells with GE11 peptide inhibited the cellular uptake of Pc-GE11 significantly and it exhibited exclusive light-activated cytotoxicity toward A431 cells. Furthermore, Pc-GE11 showed much higher tumor accumulation than the non-targeted control compound containing a random peptide sequence (Tyr-Trp-Gly-Pro-Asn-Ile-His-Tyr-Tyr-Thr-Gln-Val) after intravenous administration in A431-tumor bearing mice, indicating the potential application of this GE11 peptide-conjugated photosensitizer for targeted photodynamic therapy and bioimaging.
关键词： EGFR-targeted,tumor selectivity,phthalocyanine-peptide conjugate,photodynamic therapy,bioimaging
更新于2025-09-23 15:21:21
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Reducing Anomalous Hysteresis in Perovskite Solar Cells by Suppressing Interfacial Ferroelectric Order
摘要： Despite booming researches in organometal halide perovskite solar cells (PSCs) of recent years, considerable roadblocks remain for their large-scale deployment, ranging from undesirable current-voltage hysteresis to inferior device stability. Among various plausible origins of the hysteresis, interfacial ferroelectricity is particularly intriguing and warrants a close scrutiny. Here, we examine interfacial ferroelectricity in MAPbI3 (FAPbI3)/TiO2 and MAPbI3/PCBM heterostructures, and explore the correlations between the interfacial ferroelectricity and the hysteresis from the perspective of nonadiabatic electronic dynamics. It is found that ferroelectric order develops at the MAPbI3/TiO2 interface owing to the interaction between the polar MA ions and TiO2. The polarization switching of the MA ions under an applied gate field would result in drastically different rates in interfacial photoelectron injection and electron-hole recombination, contributing to the undesirable hysteresis. In a sharp contrast, ferroelectricity is suppressed at the FAPbI3/TiO2 and MAPbI3/PCBM interfaces, thanks to elimination of the interfacial electric field between perovskite and TiO2 via substitution of strong polar MA (dipole moment: 2.29 Debye) by weak polar FA ions (dipole moment: 0.29 Debye) and interface passivation, leading to consistent interfacial electronic dynamics and the absence of the hysteresis. The present work sheds light to the physical cause for hysteresis and points to the direction to which the hysteresis could be mitigated in PSCs.
关键词： Ferroelectricity,Hysteresis,Perovskite Solar Cells,Excited-state Electronic Dynamics,Electron-Hole Recombination,Orientation Selectivity
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Transmission Electron Microscopy Study of UV-ozone Cleaned Silicon Surfaces for Application in High Efficiency Photovoltaics
摘要： We report a 3-D-stackable 1S1R passive cross-point resistive random access memory (RRAM). The sneak (leakage) current challenge in the cross-point RRAM integration has been overcome utilizing a ?eld-assisted superlinear threshold selector. The selector offers high selectivity of >107, sharp switching slope of <5 mV/decade, ability to tune the threshold voltage, stable operation at 125 °C, and endurance of >1011. Furthermore, we demonstrate 1S1R integration in which the selector-subthreshold current is <10 pA while offering >102 memory ON/ OFF ratio and >106 selectivity during cycling. Combined with self-current-controlled RRAM, the 1S1R enables high-density and high-performance memory applications.
关键词： selectivity,cross-point memory,select device,resistive random access memory (RRAM),sneak path,1S1R
更新于2025-09-23 15:21:01
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Laser-Microstructured Copper Reveals Selectivity Patterns in the Electrocatalytic Reduction of CO2
摘要： The local (electro)chemical environment largely influences the selectivity toward, for example, olefins or alcohols in the electroreduction of CO2 over copper (Cu)-based catalysts. However, this factor is mostly qualitatively understood. Here, by combining catalytic results from a set of laser-microstructured Cu electrodes with defined geometries and accurate modeling including bulk and local effects, we map the effect of local pH and CO2 concentration for the main products. We also show how our results are useful for device engineering.
关键词： CO2 electroreduction,CO2 concentration,selectivity patterns,copper catalysts,laser-microstructured electrodes,local pH
更新于2025-09-23 15:21:01
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Synergic effect of pore size engineering and an applied electric field on the controlled permeation of alkali metal atoms and ions across pristine and defect-containing h-BN sheets
摘要： The permeation and selectivity of alkali metal atoms and ions through normal and defected hexagonal boron nitride was studied in the presence and absence of water and an electric field. The defects include one (VB & VN), two (VBN) and three atom (VN2B) vacancies. The morphology and size of the pore (defect) in the h-BN sheet significantly affect the energy barriers. These results indicate that an h-BN sheet with appropriate pore size possesses good Li/Li+ selectivity. The permeation of lithium atoms through VN2B-h-BN is almost a barrierless process (1.75 kcal mol?1). Moreover, the VBN h-BN nanosheet selectively allows the passage of Li atoms at room temperature with the highest selectivity ratio of 1.58 × 1013. The presence of water molecules increases the barrier of alkali metal atom permeation. The effect of water molecules is more pronounced for alkali metal atom permeation through a defected h-BN nanosheet as compared to alkali metal ions. An applied electric field perpendicular to the h-BN sheet further decreases the permeation barriers. For example, the energy barrier is reduced to 31 kcal mol?1 (from 34 kcal mol?1) in the presence of an electric field for the permeation of lithium through H2O–VB h-BN–H2O. These studies can be extended to investigate the separation capability of porous hexagonal boron nitride nanosheets for other metal atoms and ions.
关键词： electric field,permeation,water molecules,alkali metal atoms,hexagonal boron nitride,defects,ions,selectivity
更新于2025-09-23 15:21:01