Nano Trends最新文献

Piezoelectricity or piezoelectric effect is a phenomenon by which mechanical energy is converted into electrical energy and vice versa. Piezoelectric effect has been observed in several organic materials. Therefore, in past few years organic piezoelectric materials have received significant research interests in biomedical applications and specifically for fabrication of implantable biomedical devices because of their high piezoelectric performance, excellent biocompatibility and biodegradability, superior mechanical properties, and cheap fabrication process. This article provides a comprehensive review of the recent research progress on organic piezoelectric materials. It extensively covers the piezoelectric properties and preparation methods of different organic piezoelectric materials including amino acids, peptides, proteins, polysaccharides, and polymers (such as PVDF, PLLA, PHB), as well as their representative implantable biomedical device applications namely biosensing, tissue regeneration, and drug delivery. Finally, the article discusses the challenges and future directions of this research field.

The limitations of modern CMOS technology have created a call to action for novel devices with great scalability potential. Graphene has been recognized as a suitable material for an enhanced transistor channel based on its incredibly large conductivity while also being easily scaled. Previous research has noted the importance of a top gate device structure, which is difficult to accomplish for graphene transistors due to graphene's incompatibility with oxide growth processes. A novel process flow for graphene field effect transistors with scalability is presented. The emphasis is on the growth of multilayer graphene using chemical vapor deposition and the implementation of polydimethylsiloxane as a gate dielectric. Polydimethylsiloxane gate insulator thickness of 815 nm and 570 nm were successfully developed on 4in large-scale wafers. Two devices of similar channel dimensions and different dielectric were compared and mobilities of 14.57cm²V⁻¹s⁻¹ and 0.44 cm²V⁻¹s⁻¹ were measured. Gate voltage sweeps from -20 V to 20 V also demonstrated channel current modulation with a charge neutrality point between 5 V and 8 V, indicating achievement of expected device operation.

Three-dimensional insights into the microstructure of composite materials are vital for enhancing their performance under operational conditions. Phase-sensitive methods can offer supplementary data, especially for materials with low absorption, compared to standard absorption-based techniques. This work presents the correlative X-ray imaging and computed tomography results of polymer composites reinforced with glass fibers using an inverted Hartmann mask. This method identified areas with enhanced refraction and scattering due to glass fibers and discriminated signals based on their orientation, offering an advantage in evaluating anisotropic materials. The simplicity of the setup, adding the inverted Hartmann mask, makes integration feasible in commercial CT scanners and existing radiography laboratories, enabling simultaneous phase, scattering, and absorption information extraction. Our approach, which combines refraction and scattering with absorption signals, exposes intricate structures beyond the usual spatial resolution threshold. Despite the distinct absorption coefficients of air, polymer-based, and glass fibers, the inverted Hartmann mask is crucial for examining similar absorption composites and low-absorbing materials. This research offers profound insights into the microstructures of fiber-reinforced polymer composites, laying the groundwork for studies of nanostructured functional composite materials.

Perovskite oxides have garnered significant attention as potential active materials for supercapacitor applications. Recently, metal-doped perovskite oxides have gained prominence due to their potential to provide a synergistic blend of electrical conductivity, substantial electrochemical active surface area, and robust electrochemical activity. In this study, we systematically investigate the electrochemical properties of strontium titanate oxide (SrTiO_3, STO) and chromium-doped strontium titanate oxide (Cr-STO), synthesized via the solid-state reaction method. Various material characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), are employed to examine the crystal structure, morphology, and chemical composition of these samples. Notably, Cr-STO demonstrates an approximately twentyfold increase in electrochemical surface area compared to pristine STO, resulting in enhanced anion storage capabilities when employed in alkaline 3 M KOH aqueous electrolytes. Detailed electrochemical kinetic studies reveal an augmented pseudocapacitive behavior in Cr-STO, with a more pronounced diffusive nature compared to pristine STO. Furthermore, symmetric supercapacitors fabricated with Cr-STO electrodes exhibit excellent electrochemical performance, maintaining over 93 % of their initial capacity after 10,000 charge-discharge cycles at a current density of 1 A g⁻¹. These findings highlight the significant potential of chromium-doped strontium titanate oxide as a valuable contribution to the ongoing pursuit of novel material for supercapacitors.

Ultrathin 2D nanomaterials with extremely large surface area and unique electrochemical properties are considered excellent electrocatalyst candidates for clean energy conversion and environmental applications. However, it is still challenging to prepare 2D catalysts through a scalable and sustainable process that may become suitable for industrial demands. Here, we reported a facile cyclic synthesis method of ultrathin 2D nanomaterials based on the ionic layer epitaxy. By repeatedly refreshing a surfactant monolayer on the solution surface, free-standing 2.2 nm thick hexagonal Co(OH)₂ nanosheets were obtained from the water surface at ambient conditions in multiple cycles. These nanosheets exhibited a consistently high OER performance with an average overpotential of 427.4 ± 5.3 mV at 10 mA cm⁻². Remarkably, hexagonal NSs could be obtained from a wide range of precursor concentrations which could enable over 84 cycles of synthesis on the same stock precursor solution. It will shed light on the design of autonomous and sustainable synthesis of 2D nanomaterials for advanced electrocatalysis development toward a clean future.

In recent years, concerted research efforts have been aimed at improving the electrochemical performance of Li-ion batteries (LIBs) to meet the ever-increasing demand for energy storage devices in various applications, particularly powering of portable electronic devices and electric vehicles. One such novel approach entails the materials engineering of the basic LIB components, especially the cathode, which not only dominates the battery cost, but also limits the energy density. Meanwhile, the cathode is typically made up of LiCoO₂, a layered oxide, which despite having a relatively high energy density (∼150 – 190 Wh kg⁻¹), suffers from limited practical capacity (∼140 mA h g^–1), in addition to the scarcity, toxicity and high-cost of Co. Consequently, LiFePO₄ (LFP), a polyanion oxide, has emerged as a promising alternative owing to its relatively higher practical capacity (∼165 mA h g^–1), coupled with the more abundance, less toxicity and lower cost of Fe than Co. Nevertheless, LFP has shortcomings mainly due to its low ionic and electronic conductivities, which limit the cathode rate capability and energy density (∼90 – 140 Wh kg⁻¹). As a result, highly stable and conductive carbon-based materials, particularly graphene and its derivatives, have recently been introduced to LFP to enhance electron and Li-ion transport, while also prolonging the cycle life. Herein, the research progress made over the last five-year period (2018–2023) to improve the rate performance and cyclability of LFP cathodes by utilizing graphene-based materials is highlighted. Future research directions for employing LFP/graphene-based composite cathodes to further advance the electrochemical performance of next-generation LIBs are also discussed to set the stage for commercial applications.

Highly permeable and selective membranes with long-term stability are needed to reduce operating and capital costs of industrial gas-separation units. In this study, we fabricate new membranes made of melamine (M)- and imidazolium-based ionic liquid (IL)-modified graphene oxide (GO) deposited on a porous support and buried with a polydimethylsiloxane (PDMS) layer. The CO₂/N₂ and CO₂/CH₄ ideal selectivities of the composite membranes are respectively 65 % and 70 % higher than those of the membranes containing only the IL. This significant improvement in ideal selectivity is attributed to synergic effects of nanochannels created by GO, fixed facilitated transport provided by the IL and numerous amine groups in the melamine structure, and the increased polarity of the membrane caused by the presence of the IL. The composite membrane has a pure CO₂ permeance of 47 GPU with a high CO₂/N₂ ideal selectivity of 109 and a satisfactory CO₂/CH₄ ideal selectivity of 39. The composite membrane maintains stable performance over a 60-hour operation, highlighting its long-term reliability. The outstanding performance, coupled with the ease of fabrication, underscores the potential of these composite membranes for practical and efficient CO₂ removal from both natural and flue gas streams in real-world applications.

The effects of guanidinium iodide surface treatment (GST) on CH₃NH₃PbI₃ perovskite solar cells with decaphenylcyclopentasilane (DPPS) were investigated. GST decreases the carrier trap density and improves the photovoltaic characteristics. The X-ray diffraction results showed that the lattice constants of the perovskite crystals were increased by the insertion of GST and guanidinium into the methylammonium defects. The thermal stability of the unlaminated devices was tested in the air at 85 °C. The device prepared using GST exhibited the highest conversion efficiency. First-principles calculations supported these experimental results.

In recent years, organic chemists have taken a resolute step toward green photocatalytic synthesis. In this regard, the oxidation of organic compounds with molecular oxygen is one of the most important classes of transformations, as it increases molecular complexity while avoiding the use of toxic and harmful oxidants. To this aim, the development of new and efficient photocatalysts capable of driving valuable oxidative reactions in a sustainable manner is highly desirable. These novel photocatalytic systems need to be metal-free, easy-to-prepare, and potentially recyclable. Carbon nitride (CN) fulfills all these requirements because of its outstanding physicochemical properties, thus emerging as a promising heterogeneous photocatalytic platform. The growing popularity of this material is also substantiated by its fast and facile preparation from readily available and inexpensive molecular precursors. This Review aims at highlighting the recent advances in synthesis of carbon nitride-based materials and their applications in organic photocatalysis for the oxidation of organic molecules in presence of molecular oxygen. Lastly, forward-looking opportunities within this intriguing research field are mentioned.