Добірка наукової літератури з теми "Voltage sensitive nanomaterials"

A major revolution for electron microscopy in the past decade is the introduction of aberration correction, which enables one to increase both the spatial resolution and the energy resolution to the optical limit. Aberration correction has contributed significantly to the imaging at low operating voltages. This is crucial for carbon-based nanomaterials which are sensitive to electron irradiation. The research of carbon nanomaterials and nanohybrids, in particular the fundamental understanding of defects and interfaces, can now be carried out in unprecedented detail by aberration-corrected transmission electron microscopy (AC-TEM). This review discusses new possibilities and limits of AC-TEM at low voltage, including the structural imaging at atomic resolution, in three dimensions and spectroscopic investigation of chemistry and bonding. In situ TEM of carbon-based nanomaterials is discussed and illustrated through recent reports with particular emphasis on the underlying physics of interactions between electrons and carbon atoms.

Abstract Thermoelectric junctions are often made of components of different materials characterized by distinct transport properties. Single material junctions, with the same type of charge carriers, have also been considered to investigate various classical and quantum effects on the thermoelectric properties of nanostructured materials. We here introduce the concept of defect-induced thermoelectric voltage, namely, thermodefect voltage, in graphene nanoribbon (GNR) junctions under a temperature gradient. Our thermodefect junction is formed by two GNRs with identical properties except the existence of defects in one of the nanoribbons. At room temperature the thermodefect voltage is highly sensitive to the types of defects, their locations, as well as the width and edge configurations of the GNRs. We computationally demonstrate that the thermodefect voltage can be as high as 1.7 mV K−1 for 555–777 defects in semiconducting armchair GNRs. We further investigate the Seebeck coefficient, electrical conductance, and electronic thermal conductance, and also the power factor of the individual junction components to explain the thermodefect effect. Taken together, our study presents a new pathway to enhance the thermoelectric properties of nanomaterials.

A disruptive innovation in how scanning electron microscopes (SEMs) are designed and built has produced a low cost, but highperformance compact field emission SEM. By leveraging silicon processing technologies, Novelx has miniaturized the core technology inside a SEM. This miniaturization enabled the design of an all-electrostatic electron beam column that when coupled with a thermal field emission (TFE) electron source is optimized for lowvoltage imaging and sub-10nm resolution. In addition, the mySEM© has a quad-segmented microchannel plate (MCP) detector that has a topographic imaging mode that is capable of electron channeling contrast imaging (ECCI) at low imaging voltages. These capabilities were previously only available in high-end and much larger sized field emission SEMs outfitted with additional detectors. The Novelx mySEM show in Fig. 1 is now being used in material science and life science applications for characterizing a variety of energy sensitive nanomaterials, biomaterials and thin films.

A glucose meter has been developed utilizing boric acid-modified carbon dots as a fluorescence probe. Boric acid-modified carbon dots produces varying fluorescence emission with varying glucose concentration in water. Boric acid-modified carbon dots mixed with glucose addition was excited by a violet laser (405 nm), then the emission intensity was detected by a photodetector to be converted to an electrical signal that as an input signal for a microcontroller for glucose concentration measurement. The output voltage of the glucose meter is corresponding to the fluorescence emission measured by using a spectrofluorometer with glucose concentration in the boric acid-modified carbon dots. Full Text: PDF ReferencesH. Teymourian, A. Barfidokht, J. Wang, "Electrochemical glucose sensors in diabetes management: an updated review (2010–2020)", Chem. Soc. Rev. 49, 7671 (2020). CrossRef D.C. Klonoff, "Overview of Fluorescence Glucose Sensing: A Technology with a Bright Future", J Diabetes Sci. Technol. 6(6), 1242 (2012). CrossRef J.C. Pickup, F. Hussain, N.D. Evans, O.J. Rolinski, David J.S. Birch, "Fluorescence-based glucose sensors", Biosens. Bioelectron. 20, 2555 (2005). CrossRef H. Fang, G. Kaur, B. Wang, "Progress in Boronic Acid-Based Fluorescent Glucose Sensors", J. Fluoresc. 14(5), 481 (2004). CrossRef T. Kawanishi, M.A. Romey, P.C. Zhu, M.Z. Holody, S. Shinkai, "A Study of Boronic Acid Based Fluorescent Glucose Sensors", J. Fluoresc. 14(5), 499 (2004). CrossRef A.S. Krishna, P.A. Nair, C. Radhakumary, K. Sreenivasan, "Carbon dot based non enzymatic approach for the detection and estimation of glucose in blood serum", Mater. Res. Express 3(1), 055001 (2016). CrossRef G.P.C. Mello, E.F.C. Simões, D.M.A. Crista, J.M.M. Leitão, L. Pinto da Silva, J.C.G. Esteves da Silva, "Glucose Sensing by Fluorescent Nanomaterials", Crit. Rev. Anal. Chem. 49(6), 542 (2019). CrossRef X. Shan, L. Chai, J. Ma, Z. Qian, J. Chen, H. Feng, "B-doped carbon quantum dots as a sensitive fluorescence probe for hydrogen peroxide and glucose detection", Analyst 139, 2322 (2014). CrossRef J. Dong, S. Li, H. Wang, Q. Meng, L. Fan, H. Xie, C. Cao, W. Zhang, "Simple Boric Acid-Based Fluorescent Focusing for Sensing of Glucose and Glycoprotein via Multipath Moving Supramolecular Boundary Electrophoresis Chip", Anal. Chem. 85(12), 5884 (2013). CrossRef Y. Cui, F. Chen, X-B. Yin, "A ratiometric fluorescence platform based on boric-acid-functional Eu-MOF for sensitive detection of H2O2 and glucose", Biosens. Bioelectron. 135, 208 (2019). CrossRef

Chemiresistors are solid state devices that change their electronic properties (more specifically, the resistance of a conductive thin film or percolation network) as a result of chemical interactions with their environment. They are a well-established and widely commercialized technology for gas or vapor sensor applications. The active layer may consist of metal oxides, polymers, nanomaterials or composites. In most cases, chemisorption or catalytic activity involving the analyte results in surface doping of the active layer, although other mechanisms (such as conductivity changes due to swelling) have also been reported. A significant part of the sensing literature is taken up by reports of ChemFETs, in which case the conductivity of the active layer can also be modulated by an applied gate voltage. Gate voltage modulation is helpful for establishing the sensing mechanism and - on occasion - for distinguishing multiple simultaneous target analytes. In most cases, however, the actual sensor operation occurs at zero gate voltage, thus reducing the ChemFET to a chemiresistor. [1] Gas sensors can be operated at high voltages and without shielding the contacts to the film from gas exposure, two simplifications that are not afforded to sensors operating in aqueous environments. Water quality sensors are a surprisingly underserved area of sensor applications.[2] Important chemical water quality parameters include pH, dissolved gases, common ions and a range of toxic trace contaminants which may be ionic or uncharged, inorganic or organic. All these water quality parameters are usually monitored using colorimetric sensors, electrochemical sensors and large lab-based instruments. None of these lend themselves to low maintenance, reagent free, low power continuous operation for online monitoring. In particular, colorimetric sensors need a resupply of reagents and electrochemical sensors require reference electrodes. Chemiresistors have the potential to eliminate all these disadvantages, but there has been slow progress in adapting them to aqueous analytes. They are simple and economical to manufacture, and can operate reagent-free and with low or no maintenance. Unlike electrochemical sensors they do not require reference electrodes. Challenges include the need to prevent electrical shorts through the aqueous medium and the need to keep the sensing voltage low enough to avoid electrochemical reactions at the sensor. We have built a chemiresistive sensing platform for aqueous media. The active sensor element consists of a percolation network of low-dimensional materials particles that form a conducting film, e.g. from carbon nanotubes, pencil trace, exfoliated graphene or MoS2. The first members of that platform were free chlorine sensors,[3-5] but we have also demonstrated pH sensitive films [6,7] and cation sensors.[8] While there are some challenges associated with expanding the range of accessible analytes,[9] we have recently expanded the applicability of our platform, in particular anions and cations that are commonly present as pollutants in surface and drinking water. Our sensors can be incorporated into a variety of systems and will also be suitable for online monitoring in remote and resource-poor locations. References: [1] A. Zubiarrain-Laserna and P. Kruse, Graphene-Based Water Quality Sensors. J. Electrochem. Soc. 167 (2020) 037539. [2] P. Kruse, Review on Water Quality Sensors. J. Phys. D 51 (2018) 203002. [3] L. H. H. Hsu, E. Hoque, P. Kruse, and P. R. Selvaganapathy, A carbon nanotube based resettable sensor for measuring free chlorine in drinking water. Appl. Phys. Lett. 106 (2015) 063102. [4] E. Hoque, L. H. H. Hsu, A. Aryasomayajula, P. R. Selvaganapathy, and P. Kruse, Pencil-Drawn Chemiresistive Sensor for Free Chlorine in Water. IEEE Sens. Lett. 1 (2017) 4500504. [5] A. Mohtasebi, A. D. Broomfield, T. Chowdhury, P. R. Selvaganapathy, and P. Kruse, Reagent-Free Quantification of Aqueous Free Chlorine via Electrical Readout of Colorimetrically Functionalized Pencil Lines. ACS Appl. Mater. Interfaces 9 (2017) 20748-20761. [6] D. Saha, P. R. Selvaganapathy and P. Kruse, Peroxide-Induced Tuning of the Conductivity of Nanometer-Thick MoS2 Films for Solid State Sensors. ACS Appl. Nano Mater. 3 (2020) 10864-10877. [7] S. Angizi, E. Y. C. Yu, J. Dalmieda, D. Saha, P. R. Selvaganapathy and P. Kruse, Defect Engineering of Graphene to Modulate pH Response of Graphene Devices. Langmuir 37 (2021) 12163-12178. [8] J. Dalmieda, A. Zubiarrain-Laserna, D. Ganepola, P. R. Selvaganapathy and P. Kruse, Chemiresistive Detection of Silver Ions in Aqueous Media. Sens. Actuators B:Chem 328 (2021) 129023. [9] J. Dalmieda, A. Zubiarrain-Laserna, D. Saha, P. R. Selvaganapathy and P. Kruse, Impact of Surface Adsorption on Metal-Ligand Binding of Phenanthrolines. J. Phys. Chem. C 125 (2021) 21112-21123. Figure 1

As promising biochemical sensors, ion-sensitive field-effect transistors (ISFETs) are used widely in the growing field of biochemical sensing applications. Recently, a new type of field-effect transistor gated by ionic electrolytes has attracted intense attention due to the extremely strong electric-double-layer (EDL) gating effect. In such devices, the carrier density of the semiconductor channel can be effectively modulated by an ion-induced EDL capacitance at the semiconductor/electrolyte interface. With advantages of large specific capacitance, low operating voltage and sensitive interfacial properties, various EDL-based transistor (EDLT) devices have been developed for ultrasensitive portable sensing applications. In this article, we will review the recent progress of EDLT-based biochemical sensors. Starting with a brief introduction of the concepts of EDL capacitance and EDLT, we describe the material compositions and the working principle of EDLT devices. Moreover, the biochemical sensing performances of several important EDLTs are discussed in detail, including organic-based EDLTs, oxide-based EDLTs, nanomaterial-based EDLTs and neuromorphic EDLTs. Finally, the main challenges and development prospects of EDLT-based biochemical sensors are listed.

The objective of this work is to model a multi-disciplinary (multi-physics) organic photovoltaic (OPV) using mathematical modeling and analyzing the behavior of a standard planar heterojunction (PHJ) or bi-layer thin-film photovoltaic device, supporting the optimization of an efficient device for future production and assisting in evaluating and choosing the materials required for the efficient device. In order to increase photodiode performance, the device structure and geometrical properties have also been optimized and evaluated. In this work, the effects of varying the device size and transport parameters on the performance parameters of a PHJ OPV structure comprised of Indium Tin Oxide as the anode (ITO), semiconducting single-wall carbon nanotube (s-SWCNT) as the donor, fullerene C70 as the acceptor, and Aluminium (Al) as the cathode have been analyzed. The conclusion suggests that a highly effective ITO/s-SWCNT/C70/Al PHJ solar cell may be fabricated if the suggested device is appropriately built with a thin layer and a high exciton diffusion length, bi-molecular recombination coefficient, and improved mobility charge carriers, in particular hole mobility in the cell’s donor layer. In addition, the displayed current–voltage (I–V) characteristics of the proposed PHJ device are clearly indicated, with the ITO/s-SWCNT/C70/Al combination having the greatest short-circuit current density (Jsc) value of 5.61 mA/cm2, open-circuit voltage (Voc) of 0.7 V, fill factor (FF) of 79% and efficiency (ɳ) of 3.1%. Results show that the electrical performance of organic solar cells is sensitive to the thickness of the photoactive substance. These results open the path for developing inexpensive and highly efficient solar cells.

Monitoring the electrical signals generated by neurons to transmit information, is central to understanding how the brain and nervous systems work. The photoluminescence (PL) of some nanomaterials, such as semiconductor quantum dots (QDs) and fluorescent nanodiamonds (NDs), has shown higher sensitivity to electrical fields than that of any previously reported probes, which may address the persistent challenge of robust optical voltage imaging. The fundamental issue for implementing voltage-sensitive nanomaterials (VSM) in live neurons is their delivery into the plasma membrane bilayer. Currently, the delivery has been demonstrated on QDs via their spontaneous insertion directly into the plasma membrane bilayer, or indirectly into the bilayer of liposomes that later fuse with the plasma membrane. In both methods, QDs are introduced from the extracellular space and implemented to image the activity of neuronal assemblies. The first part of this thesis explores the implementation of VSM in another scenario, i.e., the voltage imaging from multiple sites on single neurons. After direct intracellular delivery, amphiphilic nanomaterials are expected to spread into distal processes and insert into the plasma membrane bilayer, being able to monitor the electrical activity in the smallest neuronal structures, such as dendritic spines. Here, the intracellular delivery of nontargeted QDs as an example, has been demonstrated by microelectrophoresis technique, where electrical currents were applied to eject charged QDs through fine-tipped glass micropipettes into living cells. The amount of delivered QDs was finely controlled by tuning the ejection duration, which had a substantial impact on preserving short-term and long-term cell health. Delivered QDs were homogeneously distributed throughout the cytoplasm and presented pure Brownian diffusion without endosomal entrapment. These original and promising results lay the foundation to apply the microelectrophoresis technique to other VSM, including the protocol for preparing nanomaterials suspension and the required tip sizes of micropipettes, which are key to their successful intracellular loading. Another fundamental issue is ascertaining the PL responses of these nanomaterials to applied voltage modulations. The second part of this thesis describes the fabrication of a multilayer device that can apply a homogeneous electric field to the embedded nanomaterials (NDs as an example). By using ultrasonication, NDs were well dispersed as single particles within the device, where the PL responses of individual NDs can be examined. Other fabrication details, such as film thickness and electrode deposition, were also described. These results provide a high-throughput screening platform to characterize the voltage sensitivities of different nanomaterials, which helps to iteratively improve their design and synthesis, including composition, size, shape, and band alignment. Collectively, the findings in this thesis provide a significant contribution to the unique interface of neuroscience and nanomaterials regarding the optical visualization of neuronal activity. The pioneering work here facilitates the future use of microelectrophoresis technique to deliver various VSM for multisite voltage imaging of single neurons. The deployment of the multilayer device promotes the development and optimization of new nanomaterials with enhanced voltage sensitivity. With these fundamental challenges to be addressed in the near future, real-time in vivo voltage imaging may be attainable in relevant animal models to elucidate the complex function of brain and nervous systems.
Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2022

Single-walled carbon nanotubes (SWNTs) are expected to be a promising nanomaterial because of their outstanding electronic, mechanical, and thermal properties. For macroscopic device applications, an assembly of SWNTs is a critical issue. We propose a self-organized micro-honeycomb network structure of SWNTs obtained by water vapor treatment of as-synthesized vertically-aligned SWNTs (VA-SWNT) for solar cell devices with higher performance. The micro-honeycomb structure was realized by simply exposing VA-SWNT to water vapor and drying in ambient condition. Honeycomb cell walls consist of capillary-aggregated vertically aligned SWNTs with heavily bundled top part. Within each cell, collapsed spaghetti-like SWNTs make contact to the substrate. The SWNT/n-Si heterojunction solar cell was built by placing the micro-honeycomb SWNTs network film on top of the substrate which has a 3 mm × 3 mm bare n-type silicon contact window in the center. The contact window is surrounded by SiO2 as insulating layer and Pt as electrode. Our preliminary tests showed that optimal photovoltaic conversion efficiency (PCE) under AM1.5 was 5.91%, with the fill factor of 72%. The open-circuit voltage and short-circuit current are 0.53V and 15.5 mA/cm2, respectively. This showed a substantial improvement compared with heterojunction solar cells using spaghetti-like SWNTs. Furthermore, the superior performance of dye-sensitized solar cells with the micro-honeycomb SWNTs was demonstrated.