Nanomaterial-based Devices Research Articles

Review on Sensing Applications of Perovskite Nanomaterials

Recently, perovskite-based nanomaterials are utilized in diverse sustainable applications. Their unique structural characteristics allow researchers to explore functionalities towards diverse directions, such as solar cells, light emitting devices, transistors, sensors, etc. Many perovskite nanomaterial-based devices have been demonstrated with extraordinary sensing performance to various chemical and biological species in both solid and solution states. In particular, perovskite nanomaterials are capable of detecting small molecules such as O2, NO2, CO2, etc. This review elaborates the sensing applications of those perovskite materials with diverse cations, dopants and composites. Moreover, the underlying mechanisms and electron transport properties, which are important for understanding those sensor performances, will be discussed. Their synthetic tactics, structural information, modifications and real time sensing applications are provided to promote such perovskite nanomaterials-based molecular designs. Lastly, we summarize the perspectives and provide feasible guidelines for future developing of novel perovskite nanostructure-based chemo- and biosensors with real time demonstration.

Perovskite Nanocrystal Fluorescence-Linked Immunosorbent Assay Methodology for Sensitive Point-of-Care Biological Test

Summary Quantitative fluorescence immunoassay is a vital and convenient method in point-of-care (POC) testing for food safety and clinical healthcare. However, current marking materials, from organic luciferin to quantum dots, still lack the requirement of increasing need for multiple targets of interest because of their too broad emission. Here, a new label material, perovskite nanocrystals (Pe-NCs), with a narrower photoluminescence spectrum is reported, and a sensitive and quantitative immunoassay method named the perovskite nanocrystal fluorescence-linked immunosorbent assay is preliminarily demonstrated. The key point of realizing water-dispersed and stable Pe-NCs was addressed by functionalizing with hydroxyl groups. The fluorescent probes (perovskite antibody) were constructed via electrostatic adsorption with narrow full-width at half-maximum (∼18 nm), laying the foundation for future study of multi-target detection. Both indirect competitive immunity and sandwich immunoassay were successfully demonstrated. This work provides a possible label material for POC tests and may open up a promising avenue of next-generation immunoassay.

Enhanced Oxygen Evolution Reaction Performance of WO3/Nb:SrTiO3 Heterostructures By Graphene Layer

Photoelectrochemical (PEC) water splitting using photo-active nanomaterials is a promising technique to generate hydrogen in a sustainable way. The charge-transfer and charge separation in photoelectrode are important factors in determining the performance of PECs. Here, we utilize single layer graphene as a photocatalyst on WO3 thin film / Nb:SrTiO3 (100) structure to enhance oxygen evolution reaction in alkaline electrolyte. The graphene-decorated photoelectrodes exhibit efficient charge transfer due to electronic and electrochemical properties of graphene edges, which leads to decreasing onset potential and increasing photo current density from 237 μA/cm2 to 763 μA/cm2 at 1.23 V vs RHE. In addition, such extremely thin layer can protect the photoelectrode from chemical corrosion without disturbing the light absorption. We discuss the role of graphene edges for photoelectrochemical water oxidation. Thus, these results can provide a new route for advanced designs of nanomaterial-based PECs devices. Acknowledgments This research was supported by next generation engineering researcher program of national research foundation of Korea (NRF) funded by the Ministry of Science, ICT (NRF-2019H1D8A2106002).

3-D Printed Multifunctional Sensor Platform for Space Applications

Nanomaterials offer a unique set of advantages as sensors for space applications. For instance, one and two dimensional materials such as carbon nanotube, graphene and molybdenum disulfide have high surface-to-volume ratio and superior electrical properties, resulting in highly sensitive environmental sensors. In addition, great mechanical, thermal, and electrical stability, as well as radiation hardness due to minute cross-sectional area, make them useful in space applications. Furthermore, lightweight, low power consumption and small size make nanomaterial-based devices suitable for targeted space missions with limited resources. Nanomaterial-based environmental sensors can be used for the in situ detection of neutrals, trace gases, volatile organics and environmental parameters in a wide range of mission architectures, including atmospheric probes, plume flybys on icy or ocean worlds such as Enceladus or Europa, and landed missions. For example, the multifunctional sensor platform can detect trace gases that can fingerprint various biological and abiotic processes on outer planetary bodies. It can be used to simultaneously detect methane, ammonia and other gases difficult to detect using mass spectrometry due to mass interference issues, and thus can be used in tandem with mass spectrometers. In addition, such a platform can be used for quick screening of samples in sample return missions without adding significantly to the mass and power of the payload. Furthermore, Human exploration missions can benefit from these highly sensitive sensors to detect leaks of toxic gases that are commonly onboard such as hydrazine, ensuring human safety and mission success. This talk will discuss the development of the multifunctional sensor platform with a suite of environmental nanosensors fabricated with additive manufacturing techniques, the performance of the sensors and their applicability to space missions.

A Dynamic Graphene Oxide Network Enables Spray Printing of Colloidal Gels for High-Performance Micro-Supercapacitors.

Properly controlling the rheological properties of nanoparticle inks is crucial to their printability. Here, it is reported that colloidal gels containing a dynamic network of graphene oxide (GO) sheets can display unusual rheological properties after high-rate shearing. When mixed with polyaniline nanofiber dispersions, the GO network not only facilitates the gelation process but also serves as an effective energy-transmission network to allow fast structural recovery after the gel is deformed by high-rate shearing. This extraordinary fast recovery phenomenon has made it possible to use the conventional air-brush spray technique to print the gel with high-throughput and high fidelity on nonplanar flexible surfaces. The as-printed micro-supercapacitors exhibit an areal capacitance 4-6 times higher than traditionally spray-printed ones. This work highlights the hidden potential of 2D materials as functional yet highly efficient rheological enhancers to facilitate industrial processing of nanomaterial-based devices.

Strong and Reversible Adhesion of Interlocked 3D-Microarchitectures

Diverse physical interlocking devices have recently been developed based on one-dimensional (1D), high-aspect-ratio inorganic and organic nanomaterials. Although these 1D nanomaterial-based interlocking devices can provide reliable and repeatable shear adhesion, their adhesion in the normal direction is typically very weak. In addition, the high-aspect-ratio, slender structures are mechanically less durable. In this study, we demonstrate a highly flexible and robust interlocking system that exhibits strong and reversible adhesion based on physical interlocking between three-dimensional (3D) microscale architectures. The 3D microstructures have protruding tips on their cylindrical stems, which enable tight mechanical binding between the microstructures. Based on the unique 3D architectures, the interlocking adhesives exhibit remarkable adhesion strengths in both the normal and shear directions. In addition, their adhesion is highly reversible due to the robust mechanical and structural stability of the microstructures. An analytical model is proposed to explain the measured adhesion behavior, which is in good agreement with the experimental results.

Heterogeneous Integration of Three-Primary-Color Photoluminescent Nanoparticle Arrays with Defined Interfaces.

Minimized photoluminescent devices require both high-density fluorescent arrays and minimal cross-talk between neighboring pixels on the limited area. However, the challenges to achieve the overall integration of nanomaterial-based devices hinder the development of microscale full-color displays, including micro/nanoarray density, orientation control, multimaterial interface morphology, and uniform colors. Here, we report a heterogeneous integration approach to control the orientation, combination, and density of fluorescent micro/nanoarrays on flexible substrates. By controlling the defined interface and critical shrinkage width of liquid bridges, the width of three-primary-color micro/nanolines reached 100 nm. The interval between two parallel luminous lines is down to 40 μm, and the optical cross-talk effect is remarkably reduced. This work provides a facile approach to prepare high-performance micro-photoluminescent and imaging arrays for next-generation flexible display and lighting technology.

Nanomaterial-based devices for point-of-care diagnostic applications.

In this review, we have discussed the capabilities of nanomaterials for point-of-care (PoC) diagnostics and explained how these materials can help to strengthen, miniaturize and improve the quality of diagnostic devices. Since the optical, electrochemical and other physical properties of nanomaterials are dictated by their composition, size and shape, these factors are critical in the design and function of nanomaterial-based PoC diagnostics.

Direct-current triboelectricity generation by a sliding Schottky nanocontact on MoS2 multilayers.

The direct conversion of mechanical energy into electricity by nanomaterial-based devices offers potential for green energy harvesting 1-3 . A conventional triboelectric nanogenerator converts frictional energy into electricity by producing alternating current (a.c.) triboelectricity. However, this approach is limited by low current density and the need for rectification 2 . Here, we show that continuous direct-current (d.c.) with a maximum density of 106 A m-2 can be directly generated by a sliding Schottky nanocontact without the application of an external voltage. We demonstrate this by sliding a conductive-atomic force microscope tip on a thin film of molybdenum disulfide (MoS2). Finite element simulation reveals that the anomalously high current density can be attributed to the non-equilibrium carrier transport phenomenon enhanced by the strong local electrical field (105-106 V m-2) at the conductive nanoscale tip 4 . We hypothesize that the charge transport may be induced by electronic excitation under friction, and the nanoscale current-voltage spectra analysis indicates that the rectifying Schottky barrier at the tip-sample interface plays a critical role in efficient d.c. energy harvesting. This concept is scalable when combined with microfabricated or contact surface modified electrodes, which makes it promising for efficient d.c. triboelectricity generation.

A nanoscale pn junction in series with tunable Schottky barriers

PN junctions in nanoscale materials are of interest for a range of technologies including photodetectors, solar cells, and light-emitting diodes. However, Schottky barriers at the interface between metal contacts and the nanomaterial are often unavoidable. The effect of metal-semiconductor interfaces on the behavior of nanoscale diodes must be understood, both to extract the characteristics of the pn junction, and to understand the overall characteristics of the final device. Here, we study the current-voltage characteristics of diodes that are formed in fully suspended carbon nanotubes (CNTs). We utilize tunable Schottky barrier heights at the CNT-metal interface to elucidate the role of the Schottky barriers on the device characteristics. We develop a quantitative model to show how a variety of device characteristics can arise from apparently similar devices. Using our model we extract key parameters of the Schottky barriers and the pn junction, and predict the overall I-V characteristics of the device. Our equivalent circuit model is relevant to a variety of nanomaterial-based diode devices that are currently under investigation.

Temperature-induced effect on refractive index of graphene based on coated in-fiber Mach–Zehnder interferometer**Project supported by the Shandong Provincial Natural Science Foundation of China (Grant Nos. ZR2009AM017 and ZR2013FM019), the National Postdoctoral Project of China (Grant Nos. 200902574 and 20080441150), the Shandong Provincial Education Department Foundation of China (Grant No. J06P14), and the Opening Foundation of State Key Lab of Minning

The temperature-induced complex refractive index (CRI) effect of graphene is demonstrated theoretically and experimentally based on a graphene coated in-fiber MZI (Mach–Zehnder interferometer). The relationships between real and imaginary parts of the graphene CRI and temperature are obtained through investigating the dip wavelength and intensity of the MZI interference spectrum changing with temperature, respectively. The temperature effect of CRI of the graphene is also analyzed theoretically. Both experimental and theoretical studies show that the real part and imaginary part of the CRI nonlinearly decrease and increase with temperature increasing, respectively. This graphene-coated in-fiber MZI structure also possesses the advantages of easy fabrication, miniaturization, low cost and robustness. It has potential applications in nanomaterial-based optic devices for communication and sensing.

3D micro-structured arrays of Zn\u039f nanorods

The fabrication of nanostructures with controlled assembly and architecture is very important for the development of novel nanomaterial-based devices. We demonstrate that laser techniques coupled with low-temperature hydrothermal growth enable complex three-dimensional ZnO nanorod patterning on various types of substrates and geometries. This methodology is based on a procedure involving the 3D scaffold fabrication using Multi-Photon Lithography of a photosensitive material, followed by Zn seeded Aqueous Chemical Growth of ZnO nanorods. 3D, uniformly aligned ZnO nanorods are produced. The increase in active surface area, up to 4.4 times in the cases presented here, provides a dramatic increase in photocatalytic performance, while other applications are also proposed.

Self-assembled thin films of Fe3O4-Ag composite nanoparticles for spintronic applications

Controlled self-assembly of multi-component magnetic nanoparticles could lead to nanomaterial-based magnetic devices with novel structures and intriguing properties. Herein, self-assembled thin films of Fe3O4-Ag composite nanoparticles (CNPs) with hetero-dimeric shapes were fabricated using interfacial assembly method. The CNP-assembled thin films were further transferred to patterned silicon substrates followed by vacuum annealing, producing CNP-based magnetoresistive (MR) devices. Due to the presence of intra-particle interfaces and inter-particle barriers, an enhanced MR ratio and a non-linear current-voltage relation were observed in the device. The results of this work can potentially pave the way to the future exploration and development of spintronic devices built from composite nanomaterials.

Simultaneous topographical, electrical and optical microscopy of optoelectronic devices at the nanoscale.

Novel optoelectronic devices rely on complex nanomaterial systems where the nanoscale morphology and local chemical composition are critical to performance. However, the lack of analytical techniques that can directly probe these structure-property relationships at the nanoscale presents a major obstacle to device development. In this work, we present a novel method for non-destructive, simultaneous mapping of the morphology, chemical composition and photoelectrical properties with <20 nm spatial resolution by combining plasmonic optical signal enhancement with electrical-mode scanning probe microscopy. We demonstrate that this combined approach offers subsurface sensitivity that can be exploited to provide molecular information with a nanoscale resolution in all three spatial dimensions. By applying the technique to an organic solar cell device, we show that the inferred surface and subsurface composition distribution correlates strongly with the local photocurrent generation and explains macroscopic device performance. For instance, the direct measurement of fullerene phase purity can distinguish between high purity aggregates that lead to poor performance and lower purity aggregates (fullerene intercalated with polymer) that result in strong photocurrent generation and collection. We show that the reliable determination of the structure-property relationship at the nanoscale can remove ambiguity from macroscopic device data and support the identification of the best routes for device optimisation. The multi-parameter measurement approach demonstrated herein is expected to play a significant role in guiding the rational design of nanomaterial-based optoelectronic devices, by opening a new realm of possibilities for advanced investigation via the combination of nanoscale optical spectroscopy with a whole range of scanning probe microscopy modes.

Tunable in-plane torsional strength of surface functionalized two dimensional nanomaterials.

In this paper, the in-plane torsional properties of two dimensional nanomaterials are revealed to be tunable by surface functionalization using molecular dynamics simulations. The torsional strengths of both graphene and graphyne under circular shearing are found to first decrease and then increase anomalously with the increase of the hydrogenation ratio. The minimum strength of such U-shaped strength evolution appears at different hydrogenation ratios H for graphene (H = 50%) and graphyne (H = 70%), demonstrating a correlation between hydrogenation and the unit lattices of 2D nanomaterials. By studying the torsional characteristics of a graphene annulus with varying outer-to-inner boundary radius ratios, the anomalous increase of torsional strength at a high hydrogenation ratio is revealed to be the result of wrinkling deformation as well as chemical bond hybridization. Further analyses of the local stress distribution are carried out for understanding the mechanism of surface hydrogenation tuned in-plane torsional strength of graphene and graphyne. Torsional strength of the graphene annulus with an elliptical outer boundary also shows a U-shaped evolution with hydrogenation ratio, while the shape effect of the graphene annulus can smooth the change of the torsional characteristics with hydrogenation. Our results provide novel insights into the development of 2D nanomaterial-based annular devices.

Decidual Glycodelin-A regulates the phenotype and functions of human macrophages

Mycotoxins are low-molecular weight natural products produced as secondary metabolites by filamentous fungi and more than 500 mycotoxins with different physicochemical properties are currently known. Contamination by mycotoxins can result in liver and kidney diseases, nervous system damage, immunosuppression, and carcinogenicity. Consequently, the food safety authorities have set strict maximum permissible limits for mycotoxins. Over the past two decades numerous analytical techniques have been developed for mycotoxin detection in food. Recently, the application of nanotechnology in biosensors can range from transducer device to recognition ligand, label, and running systems. The application of nanomaterials in sensor development provides excellent advantages such as miniaturization of devices and signal enhancements. Such nanomaterial-based sensor devices can be sensitive, cost effective, and highly beneficial for the food industry ensuring on-site safety and preservation of food quality. This chapter reviews some recent developments on nanomaterial-based sensors developed for analysis of mycotoxin in food.

Effects of the physicochemical properties of gold nanostructures on cellular internalization.

Unique physicochemical properties of Au nanomaterials make them potential star materials in biomedical applications. However, we still know a little about the basic problem of what really matters in fabrication of Au nanomaterials which can get into biological systems, especially cells, with high efficiency. An understanding of how the physicochemical properties of Au nanomaterials affect their cell internalization is of significant interest. Studies devoted to clarify the functions of various properties of Au nanostructures such as size, shape and kinds of surface characteristics in cell internalization are under way. These fundamental investigations will give us a foundation for constructing Au nanomaterial-based biomedical devices in the future. In this review, we present the current advances and rationales in study of the relationship between the physicochemical properties of Au nanomaterials and cell uptake. We also provide a perspective on the Au nanomaterial-cell interaction research.

Focused energy field method for the localized synthesis and direct integration of 1D nanomaterials on microelectronic devices.

In the focused energy field method, localized heating, and convective mass transfer in a liquid precursor realizes selective synthesis and direct integration of 1D nanomaterials as well as their surface functionalization, all in a low-temperature, liquid environment. This allows facile fabrication of 1D nanomaterial-based nanoelectronic devices.

The ion implantation-induced properties of one-dimensional nanomaterials.

Nowadays, ion implantation is an extensively used technique for material modification. Using this method, we can tailor the properties of target materials, including morphological, mechanical, electronic, and optical properties. All of these modifications impel nanomaterials to be a more useful application to fabricate more high-performance nanomaterial-based devices. Ion implantation is an accurate and controlled doping method for one-dimensional nanomaterials. In this article, we review recent research on ion implantation-induced effects in one-dimensional nanostructure, such as nanowires, nanotubes, and nanobelts. In addition, the optical property of single cadmium sulfide nanobelt implanted by N+ ions has been researched.

Surfactant‐Free Scalable Synthesis of Bi2Te3 and Bi2Se3 Nanoflakes and Enhanced Thermoelectric Properties of Their Nanocomposites (Adv. Mater. 10/2013)

Nanomaterial-based thermoelectric devices request scalable production and compositional tolerance for reliable device performance. On page 1425 Unyong Jeong and co-workers suggest a large-quantity synthesis of surfactant-free nanoflakes of Bi2Te3 and Bi2Se3. The chemical composition of the heterostructured nanocomposites is precisely controlled by mixing the nanoflake suspensions. A maximum ZT (0.7 at 400 K) is achieved with a broad content of 10–15% Bi2Se3 in the nanocomposites.