Overcoming Downscaling Limitations in Organic Semiconductors: Strategies and Progress.

Organic semiconductors have great potential to revolutionize electronics by enabling flexible and eco-friendly manufacturing of electronic devices on plastic film substrates. Recent research and development led to the creation of printed displays, radio-frequency identification tags, smart labels, and sensors based on organic electronics. Over the last 3 decades, significant progress has been made in realizing electronic devices with unprecedented features, such as wearable sensors, disposable electronics, and foldable displays, through the exploitation of desirable characteristics in organic electronics. Neverthless, the down-scalability of organic electronic devices remains a crucial consideration. To address this, efforts are extensively explored. It is of utmost importance to further develop these alternative patterning methods to overcome the downscaling challenge. This review comprehensively discusses the efforts and strategies aimed at overcoming the limitations of downscaling in organic semiconductors, with a particular focus on four main areas: 1) lithography-compatible organic semiconductors, 2) fine patterning of printing methods, 3) organic material deposition on pre-fabricated devices, and 4) vertical-channeled organic electronics. By discussing these areas, the full potential of organic semiconductors can be unlocked, and the field of flexible and sustainable electronics can be advanced.

Self-Powered Low-Cost UVC Sensor Based on Organic-Inorganic Heterojunction for Partial Discharge Detection.

Power outages caused by the aging of high-voltage power facilities can cause significant economic and social damage. To prevent such problems, it is necessary to implement a widespread and sustainable monitoring system. Partial discharge (PD) is a preliminary symptom of power equipment aging accompanying the light, typically in the UV range. UVC (200-280 nm) is more useful than UVA and UVB because of low interference from the environment owing to its solar-blindness by the stratosphere. Therefore, to realize a wide-range and durable diagnosis system, it is necessary to develop sensors that can selectively detect UVC, while enabling mass production at low-cost and low power consumption. Here, a solution-processable photodiode sensor that is inexpensive, mass-producible, and self-powered with selective UVC detection is developed. The optoelectronic characteristics of photodiode consisting of organic p-polymer and inorganic n-ZnO nanoparticles are systematically studied to determine the optimum p-type polymer and its thickness. The device shows high-performance: fast response time (rise/fall time: 36.6/37.0 ms) and high spectral response in the UVC region (maximum responsivity of 20 mA W-1 ) under self-powered operation. Furthermore, the practical application of the device to detect PD signals with a visual alarm system under UVC release conditions is demonstrated.

Synthesis of Lead-Free CaTiO3 Oxide Perovskite Film through Solution Combustion Method and Its Thickness-Dependent Hysteresis Behaviors within 100 mV Operation.

Perovskite is attracting considerable interest because of its excellent semiconducting properties and optoelectronic performance. In particular, lead perovskites have been used extensively in photovoltaic, photodetectors, thin-film transistors, and various electronic applications. On the other hand, the elimination of lead is essential because of its strong toxicity. This paper reports the synthesis of lead-free calcium titanate perovskite (CaTiO3) using a solution-processed combustion method. The chemical and morphological properties of CaTiO3 were examined as a function of its thickness by scanning electron microscopy, X-ray diffraction (XRD), atomic force microscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible spectrophotometry. The analysis showed that thicker films formed by a cumulative coating result in larger grains and more oxygen vacancies. Furthermore, thickness-dependent hysteresis behaviors were examined by fabricating a metal-CaTiO3-metal structure. The electrical hysteresis could be controlled over an extremely low voltage operation, as low as 100 mV, by varying the grain size and oxygen vacancies.

MoS2-TiC-C Nanocomposites as New Anode Materials for High-Performance Lithium-Ion Batteries.

The MoS2-TiC-C nanocomposite was prepared by high-energy ball milling (HEBM) for application as a new anode material for lithium-ion batteries. Pure molybdenum disulfide (MoS2), Ti, and carbon black (C) were used as the starting materials for the synthesis process. Various analyses including X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) revealed that the nanosized MoS2 active materials were uniformly dispersed in a TiC-C matrix formed via the HEBM process. We investigated the cyclic performance, rate capability, and electrochemical impedance spectra using the as-prepared composite as an anode material. The results showed that the electrochemical performances of the MoS2-based nanocomposite were significantly improved compared to those of MoS2-C and MoS2 due to the presence of the TiC-C matrix in MoS2. Furthermore, we determined the optimal milling time based on the cyclic performances of the materials.

Effects of Various Hybrid Carbon Matrices on the ZnSe Composite Anode for Lithium-Ion Batteries.

Zinc selenide-based hybrid carbon composites were synthesized by a high-energy mechanical milling process under an Ar atmosphere. The as-synthesized ZnSe-based carbon composites were characterized by X-ray diffraction and transmission electron microscopy. First, we examined the effect of single-component carbon matrices on the electrochemical performance of ZnSe. The results showed the best performance for graphite (G), followed by carbon nanotubes (CNTs), and amorphous carbon. Based on these results, in order to further enhance the performance of ZnSe, we introduced a binary-carbon matrix consisting of graphite and CNTs at various ratios of 1:1, 1:3, and 3:1, respectively. As a result, ZnSe©G/CNT (1:3) exhibited the best performance in terms of cyclic life and rate capability. Specifically, ZnSe©G/CNT (1:3) delivered a specific capacity of 1041 mAh g-1 at a current density of 100 mA g-1 after 300 cycles with a coulombic efficiency of over 99% with high rate performance.

Facile and Scalable Preparation of a MoS2/Carbon Nanotube Nanocomposite Anode for High-Performance Lithium-Ion Batteries: Effects of Carbon Nanotube Content.

To investigate the effects of carbon nanotube content on the electrochemical performance in MoS2/CNT nanocomposite, a simple high-energy mechanical milling method was employed to prepare nanocomposites from MoS2 and CNT. Prepared with a one-step, 24-h ball-milling method, the MoS2/CNT nanocomposite showed improved performance in terms of specific capacity after 70 cycles when compared to pure MoS2. In addition, upon studying the effects of the weight ratio between MoS2 and the CNTs at (1:2), (1:1), and (2:1), we found the MoS2/CNT-(1:2) showed the highest specific capacity (~765 mAh g-1) after 70 cycles and the best rate capability due to increased conductivity. Overall, the results suggested that the addition of conductive CNTs in MoS2 not only improves the cycling stability, but also leads to an increase in the specific capacity of MoS2/CNTs, which suggests our MoS2/CNT nanocomposite as a new and promising anode material for lithium-ion batteries (LIBs).

Comparative Study of Hydrogel-Based Recyclable Photocatalysts.

A series of hydrogen-based TiO2 photocatalysts were prepared by the simple entrapment of TiO2 nanoparticles in different hydrogel matrices using gelation processes. The hydrogels, namely, agarose, alginate, and chitosan, were used as matrices for TiO2 immobilization. Morphological differences were characterized for the three different hybrid gel photocatalysts. The rate of methylene blue (MB) photodegradation increased with increasing initial TiO2 dosage in all samples. The structural properties of the hydrogels significantly affected the diffusion of MB and altered the photocatalytic activities. Among these three different hybrid gel photocatalysts, the chitosan-based TiO2 membrane showed superior activity to the agarose- and alginate-based TiO2 hybrid gels. In addition, chitosan/TiO2 still showed excellent photocatalytic activity after being reused in three cycles, suggesting that chitosan/TiO2 is a new potential eco-friendly and a cost-effective photocatalyst for wastewater treatment.

Comparative Study of Mechanically Milled MoS2 and MoSe2 in Graphite Matrix as Anode Materials for High-Performance Lithium-Ion Batteries.

Nanocomposites of MoS2/graphite and MoSe2/graphite were formed from two-dimensional materials (MoS2 and MoSe2) and graphite using a one-step ball-milling method (high energy mechanical milling, HEMM). As anode materials for lithium-ion batteries (LIBs), these nanocomposites showed higher specific capacity and greater stability during long cyclic operation compared to their pure counterparts (MoS2 and MoSe2). X-ray diffraction and transmission electron microscopy revealed that graphite nanoflakes were effectively exfoliated and covered MoS2 or MoSe2 layers to form homogeneous nanostructures via HEMM. As a result, the electrochemical performances of both MoS2/graphite and MoSe2/graphite were excellent; the specific capacities were as high as 684.8 (MoS2/graphite) and 787.3 mAh g-1 (MoSe2/graphite) after 100 cycles. Also, when compared with MoS2/graphite, the MoSe2/graphite nanocomposite showed higher specific capacity and better rate capability performance due to larger interlayer spacing, leading to fast and facile movement of Liions. Overall, we demonstrate that homogeneous nanocomposites between similar layered materials (MoS2, MoSe2 and graphite) can be easily synthesized via one-step HEMM, which can be used as excellent anode materials for LIBs.

Fabrication of Self-Healable and Patternable Polypyrrole/Agarose Hybrid Hydrogels for Smart Bioelectrodes.

We present a new class of electrically conductive, mechanically moldable, and thermally self-healable hybrid hydrogels. The hybrid gels consist of polypyrrole and agarose as the conductive component and self-healable matrix, respectively. By using the appropriate oxidizing agent under conditions of mild temperature, the polymerization of pyrrole occurred along the three-dimensional network of the agarose hydrogel matrix. In contrast to most commercially available hydrogels, the physical crosslinking of agarose gel allows for reversible gelation in the case of our hybrid gel, which could be manipulated by temperature variation, which controls the electrical on/off behavior of the hybrid gel electrode. Exploiting this property, we fabricated a hybrid conductive hydrogel electrode which also self-heals thermally. The novel composite material we report here will be useful for many technological and biological applications, especially in reactive biomimetic functions and devices, artificial muscles, smart membranes, smart full organic batteries, and artificial chemical synapses.

Trehalose-Induced Variation in Mechanical Properties of Vesicles in Aqueous Solution.

The effect of the trehalose incorporation on the nanomechanical properties of dipalmitoylphosphatidylcholine vesicles was studied using atomic force microscope (AFM) on mica surface. The vesicles were prepared only with the variation in the trehalose concentration and adsorbed on the mica surface. After the morphology of the adsorbed vesicles was characterized, the behavior of an AFM tip into the vesicle was monitored using the plot of the tip displacement versus the tip deflection. It was observed that the breakthrough of the tip into the vesicles occurred two times. Each breakthrough represented each penetration of the tip into each layer. Force data prior to the first breakthrough fitted well with the Hertzian model to estimate Young's modulus and bending modulus of the vesicles. It was found that the Young's modulus and bending modulus decreased proportionally to the increase in the trehalose concentration up to 0.5 of trehalose to lipid. However, above 0.5, the moduli were a little varied with the increase. In the identical measurements at glucose, just a slight change in the moduli was observed with the increase in the glucose composition from 0 % glucose up to even 2:1 ratio of glucose:lipid. These results in the mechanical properties seem attributable to the osmotic and volumetric effects on the headgroup packing disruption.

Fabrication of Vertically Aligned Carbon Nanotube or Zinc Oxide Nanorod Arrays for Optical Diffraction Gratings.

We report on new fabrication methods for a transparent, hierarchical, and patterned electrode comprised of either carbon nanotubes or zinc oxide nanorods. Vertically aligned carbon nanotubes or zinc oxide nanorod arrays were fabricated by either chemical vapor deposition or hydrothermal growth, in combination with photolithography. A transparent conductive graphene layer or zinc oxide seed layer was employed as the transparent electrode. On the patterned surface defined using photoresist, the vertically grown carbon nanotubes or zinc oxides could produce a concentrated electric field under applied DC voltage. This periodic electric field was used to align liquid crystal molecules in localized areas within the optical cell, effectively modulating the refractive index. Depending on the material and morphology of these patterned electrodes, the diffraction efficiency presented different behavior. From this study, we established the relationship between the hierarchical structure of the different electrodes and their efficiency for modulating the refractive index. We believe that this study will pave a new path for future optoelectronic applications.

Versatile Papertronics: Photo-induced Synapse and Security Applications on Papers.

Paper is a readily available material in nature. Its recyclability, eco-friendliness, portability, flexibility, and affordability make it a favored substrate for researchers seeking cost-effective solutions. Electronic devices based on solution process were fabricated on paper and banknotes using PVK and SnO2 nanoparticles. The devices manufactured on paper substrates exhibited photosynaptic behavior under ultraviolet pulse illumination, stemming from numerous interactions on the surface of the SnO2 nanoparticles. A light-modulated artificial synapse device was realized on a paper at a low voltage bias of -0.01 V, with an average recognition rate of 91.7% based on the Yale Face Database. As a security device on a banknote, 400 devices in a 20 × 20 array configuration exhibited random electrical characteristics owing to the local morphology of the SnO2 nanoparticles and differences in the depletion layer width at the SnO2/PVK interface. The security PUF key based on the current distribution extracted at -1 V showed unpredictable reproducibility with 50% uniformity, 48.7% inter-Hamming distance, and 50.1% bit-aliasing rates. Moreover, the device maintained its properties for more than 210 d under a curvature radius of 8.75 mm and bias and UV irradiation stress conditions. This article is protected by copyright. All rights reserved.

Theragnostic pH-sensitive gold nanoparticles for the selective surface enhanced Raman scattering and photothermal cancer therapy.

We report a nanoparticle-based probe that can be used for a "turn-on" theragnostic agent for simultaneous Raman imaging/diagnosis and photothermal therapy. The agent consists of a 10 nm spherical gold nanoparticle (NP) with pH-responsive ligands and Raman probes on the surface. They are engineered to exhibit the surface with both positive and negative charges upon mildly acidic conditions, which subsequently results in rapid aggregations of the gold NPs. This aggregation simultaneously provides hot spots for the SERS probe with the enhancement factor reaching 1.3 × 10(4) and shifts the absorption to far-red and near-infrared (which is optimal for deep tissue penetration) by the coupled plasmon resonances; this shift was successfully exploited for low-threshold photothermal therapy. The theragnostic gold NPs are cancer-specific because they aggregate rapidly and accumulate selectively in cancerous cells. As the result, both Raman imaging and photothermal efficacy were turned on under a cancerous local environment. In addition, the relatively small hydrodynamic size can have the potential for better access to targeted delivery in vivo and facilitated excretion after therapy.

Superb Li-Ion Storage of Sn-Based Anode Assisted by Conductive Hybrid Buffering Matrix.

Although Sn has been intensively studied as one of the most promising anode materials to replace commercialized graphite, its cycling and rate performances are still unsatisfactory owing to the insufficient control of its large volume change during cycling and poor electrochemical kinetics. Herein, we propose a Sn-TiO2-C ternary composite as a promising anode material to overcome these limitations. The hybrid TiO2-C matrix synthesized via two-step high-energy ball milling effectively regulated the irreversible lithiation/delithiation of the active Sn electrode and facilitated Li-ion diffusion. At the appropriate C concentration, Sn-TiO2-C exhibited significantly enhanced cycling performance and rate capability compared with its counterparts (Sn-TiO2 and Sn-C). Sn-TiO2-C delivers good reversible specific capacities (669 mAh g-1 after 100 cycles at 200 mA g-1 and 651 mAh g-1 after 500 cycles at 500 mA g-1) and rate performance (446 mAh g-1 at 3000 mA g-1). The superiority of Sn-TiO2-C over Sn-TiO2 and Sn-C was corroborated with electrochemical impedance spectroscopy, which revealed faster Li-ion diffusion kinetics in the presence of the hybrid TiO2-C matrix than in the presence of TiO2 or C alone. Therefore, Sn-TiO2-C is a potential anode for next-generation Li-ion batteries.

Electron-rich hybrid matrix to enhance molybdenum oxide-based anode performance for Lithium-Ion batteries.

Although MoO2-based electrodes have been intensively studied as potential candidate anodes for lithium-ion batteries (LIBs) based on their high theoretical capacity (840 mAh g-1 and 5447 mAh cm-3), common issues such as severe volume variation, electrical conductivity loss, and low ionic conductivity, are prevalent. In this study, we demonstrate enhanced Li-ion kinetics and electrical conductivity of MoO2-based anodes with ternary MoO2-Cu-C composite materials. The MoO2-Cu-C was synthesized via two-step high energy ball milling where Mo and CuO are milled, followed by the secondary milling with C. With the introduction of the Cu-C hybrid matrix in MoO2 nanoparticles via the element transfer method using mechanochemical reactions, the sluggish Li-ion diffusion and unstable cycling behavior were significantly improved. The inactive Cu-C matrix contributes to the increase in electrical and ionic conductivity and mechanical stability of active MoO2 during cycling, as characterized by various electrochemical analyses and ex situ analysis techniques. Hence, the MoO2-Cu-C anode delivered promising cycling performance (674 mAh g-1 (at 0.1 A g-1) and 520 mAh g-1 (at 0.5 A g-1), respectively, after 100 cycles) and high-rate property (73% retention at 5 A g-1 as comparison with the specific capacity at 0.1 A g-1). The MoO2-Cu-C electrode is a propitious next-generation anode for LIBs.

Unique photothermal response and sustained photothermal effect of pH-responsive gold-nanoparticle aggregates.

Hot gold: The photothermal response upon pulsed laser irradiation is studied for pH-responsive gold-nanoparticle aggregates and compared to that of gold nanorods. The aggregates show a slight red shift in the absorption spectrum and retain the photothermal effect, whereas the nanorods lose the photothermal effect and exhibit a stark blue shift in the absorption.

Nanomaterials for Ion Battery Applications.

Nanomaterials offer opportunities to improve battery performance in terms of energy density and electrochemical reaction kinetics owing to a significant increase in the effective surface area of electrodes and reduced ion diffusion pathways [...].

Gallium-Telluride-Based Composite as Promising Lithium Storage Material.

Various applications of gallium telluride have been investigated, such as in optoelectronic devices, radiation detectors, solar cells, and semiconductors, owing to its unique electronic, mechanical, and structural properties. Among the various forms of gallium telluride (e.g., GaTe, Ga3Te4, Ga2Te3, and Ga2Te5), we propose a gallium (III) telluride (Ga2Te3)-based composite (Ga2Te3-TiO2-C) as a prospective anode for Li-ion batteries (LIBs). The lithiation/delithiation phase change mechanism of Ga2Te3 was examined. The existence of the TiO2-C hybrid buffering matrix improved the electrical conductivity as well as mechanical integrity of the composite anode for LIBs. Furthermore, the impact of the C concentration on the performance of Ga2Te3-TiO2-C was comprehensively studied through cyclic voltammetry, differential capacity analysis, and electrochemical impedance spectroscopy. The Ga2Te3-TiO2-C electrode showed high rate capability (capacity retention of 96% at 10 A g-1 relative to 0.1 A g-1) as well as high reversible specific capacity (769 mAh g-1 after 300 cycles at 100 mA g-1). The capacity of Ga2Te3-TiO2-C was enhanced by the synergistic interaction of TiO2 and amorphous C. It thereby outperformed the majority of the most recent Ga-based LIB electrodes. Thus, Ga2Te3-TiO2-C can be thought of as a prospective anode for LIBs in the future.

Ga2Te3-Based Composite Anodes for High-Performance Sodium-Ion Batteries.

Recently, metal chalcogenides have received considerable attention as prospective anode materials for sodium-ion batteries (SIBs) because of their high theoretical capacities based on their alloying or conversion reactions. Herein, we demonstrate a gallium(III) telluride (Ga2Te3)-based ternary composite (Ga2Te3-TiO2-C) synthesized via a simple high-energy ball mill as a great candidate SIB anode material for the first time. The electrochemical performance, as well as the phase transition mechanism of Ga2Te3 during sodiation/desodiation, is investigated. Furthermore, the effect of C content on the performance of Ga2Te3-TiO2-C is studied using various electrochemical analyses. As a result, Ga2Te3-TiO2-C with an optimum carbon content of 10% (Ga2Te3-TiO2-C(10%)) exhibited a specific capacity of 437 mAh·g-1 after 300 cycles at 100 mA·g-1 and a high-rate capability (capacity retention of 96% at 10 A·g-1 relative to 0.1 A·g-1). The good electrochemical properties of Ga2Te3-TiO2-C(10%) benefited from the presence of the TiO2-C hybrid buffering matrix, which improved the mechanical integrity and electrical conductivity of the electrode. This research opens a new direction for the improvement of high-performance advanced SIB anodes with a simple synthesis process.

Photopatternable quantum dots forming quasi-ordered arrays.

We have functionalized core-shell CdSe/ZnS quantum dots (QDs) with a photosensitive monolayer, rendering them solution processable and photopatternable. Upon exposure to ultraviolet radiation, films composed of this material were found to polymerize, forming interconnected arrays of QDs. The photoluminescence properties of the nanocrystal films increased with photocuring. The material was found to be suitable for spin casting and was used as the active layer in a green electroluminescent device. The electroluminescence efficiency of devices containing a photocured active layer was found to be largely enhanced when compared to devices containing nonphotocured active layers. The material also showed excellent adhesion to both organic and inorganic substrates because of the unique combination of a siloxane and a photopatternable layer as ligands. The pristine functionalized nanocrystals could easily be used for two-dimensional patterning on organic and inorganic substrates. The photopatternable quantum dots were uniformly dispersed into a photopolymerizable resin to fabricate QD embedded three-dimensional microstructures.