scholarly journals Excitons in 2D perovskites for ultrafast terahertz photonic devices

2020 ◽  
Vol 6 (8) ◽  
pp. eaax8821 ◽  
Author(s):  
Abhishek Kumar ◽  
Ankur Solanki ◽  
Manukumara Manjappa ◽  
Sankaran Ramesh ◽  
Yogesh Kumar Srivastava ◽  
...  
Keyword(s):  
Flexible Substrate ◽  
Photonic Devices ◽  
Solution Processed ◽  
Diverse Range ◽  
Light Emitting ◽  
Free Carriers ◽  
Wide Range ◽  
Potential Applications ◽  
Self Assembled ◽  
Terahertz Fields

In recent years, two-dimensional (2D) Ruddlesden-Popper perovskites have emerged as promising candidates for environmentally stable solar cells, highly efficient light-emitting diodes, and resistive memory devices. The remarkable existence of self-assembled quantum well (QW) structures in solution-processed 2D perovskites offers a diverse range of optoelectronic properties, which remain largely unexplored. Here, we experimentally observe ultrafast relaxation of free carriers in 20 ps due to the quantum confinement of free carriers in a self-assembled QW structures that form excitons. Furthermore, hybridizing the 2D perovskites with metamaterials on a rigid and a flexible substrate enables modulation of terahertz fields at 50-GHz modulating speed, which is the fastest for a solution-processed semiconductor-based photonic device. Hence, an exciton-based ultrafast response of 2D perovskites opens up large avenues for a wide range of scalable dynamic photonic devices with potential applications in flexible photonics, ultrafast wavefront control, and short-range wireless terahertz communications.

scholarly journals A Slot-Die Technique for the Preparation of Continuous, High-Area, Chitosan-Based Thin Films

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1566
Author(s):  
Oliver J. Pemble ◽  
Maria Bardosova ◽  
Ian M. Povey ◽  
Martyn E. Pemble
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
High Volume ◽  
Mechanical Anisotropy ◽  
Diverse Range ◽  
Direction Parallel ◽  
High Area ◽  
Wide Range ◽  
Slot Die ◽  
Potential Applications

Chitosan-based films have a diverse range of potential applications but are currently limited in terms of commercial use due to a lack of methods specifically designed to produce thin films in high volumes. To address this limitation directly, hydrogels prepared from chitosan, chitosan-tetraethoxy silane, also known as tetraethyl orthosilicate (TEOS) and chitosan-glutaraldehyde have been used to prepare continuous thin films using a slot-die technique which is described in detail. By way of preliminary analysis of the resulting films for comparison purposes with films made by other methods, the mechanical strength of the films produced was assessed. It was found that as expected, the hybrid films made with TEOS and glutaraldehyde both show a higher yield strength than the films made with chitosan alone. In all cases, the mechanical properties of the films were found to compare very favorably with similar measurements reported in the literature. In order to assess the possible influence of the direction in which the hydrogel passes through the slot-die on the mechanical properties of the films, testing was performed on plain chitosan samples cut in a direction parallel to the direction of travel and perpendicular to this direction. It was found that there was no evidence of any mechanical anisotropy induced by the slot die process. The examples presented here serve to illustrate how the slot-die approach may be used to create high-volume, high-area chitosan-based films cheaply and rapidly. It is suggested that an approach of the type described here may facilitate the use of chitosan-based films for a wide range of important applications.

scholarly journals Solution-Processed OLEDs Based on Thermally Activated Delayed Fluorescence Copper(I) Complexes with Intraligand Charge-Transfer Excited State

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1125
Author(s):  
Teng Teng ◽  
Jinfan Xiong ◽  
Gang Cheng ◽  
Changjiang Zhou ◽  
Xialei Lv ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Density Functional ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Functional Theory ◽  
Solution Processed ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Wide Range

A new series of tetrahedral heteroleptic copper(I) complexes exhibiting efficient thermally-activated delayed fluorescence (TADF) in green to orange electromagnetic spectral regions has been developed by using D-A type N^N ligand and P^P ligands. Their structures, electrochemical, photophysical, and electroluminescence properties have been characterized. The complexes exhibit high photoluminescence quantum yields (PLQYs) of up to 0.71 at room temperature in doped film and the lifetimes are in a wide range of 4.3–24.1 μs. Density functional theory (DFT) calculations on the complexes reveal the lowest-lying intraligand charge-transfer excited states that are localized on the N^N ligands. Solution-processed organic light emitting diodes (OLEDs) based on one of the new emitters show a maximum external quantum efficiency (EQE) of 7.96%.

scholarly journals Biodiversity of Secondary Metabolites Compounds Isolated from Phylum Actinobacteria and Its Therapeutic Applications

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4504
Author(s):  
Muhanna Al-shaibani ◽  
Radin Maya Saphira Radin Mohamed ◽  
Nik Sidik ◽  
Hesham Enshasy ◽  
Adel Al-Gheethi ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Bioactive Compounds ◽  
Extreme Environments ◽  
Software Tool ◽  
Gene Clusters ◽  
Well Being ◽  
Bioactive Substances ◽  
Diverse Range ◽  
Wide Range ◽  
Potential Applications

The current review aims to summarise the biodiversity and biosynthesis of novel secondary metabolites compounds, of the phylum Actinobacteria and the diverse range of secondary metabolites produced that vary depending on its ecological environments they inhabit. Actinobacteria creates a wide range of bioactive substances that can be of great value to public health and the pharmaceutical industry. The literature analysis process for this review was conducted using the VOSviewer software tool to visualise the bibliometric networks of the most relevant databases from the Scopus database in the period between 2010 and 22 March 2021. Screening and exploring the available literature relating to the extreme environments and ecosystems that Actinobacteria inhabit aims to identify new strains of this major microorganism class, producing unique novel bioactive compounds. The knowledge gained from these studies is intended to encourage scientists in the natural product discovery field to identify and characterise novel strains containing various bioactive gene clusters with potential clinical applications. It is evident that Actinobacteria adapted to survive in extreme environments represent an important source of a wide range of bioactive compounds. Actinobacteria have a large number of secondary metabolite biosynthetic gene clusters. They can synthesise thousands of subordinate metabolites with different biological actions such as anti-bacterial, anti-parasitic, anti-fungal, anti-virus, anti-cancer and growth-promoting compounds. These are highly significant economically due to their potential applications in the food, nutrition and health industries and thus support our communities’ well-being.

scholarly journals Peptide Nanomaterials for Drug Delivery Applications

2020 ◽  
Vol 21 (4) ◽  
pp. 401-412 ◽  
Author(s):  
Sreekanth Pentlavalli ◽  
Sophie Coulter ◽  
Garry Laverty
Keyword(s):  
Drug Delivery ◽  
Self Assembly ◽  
Diverse Range ◽  
Drug Molecules ◽  
Sustained Drug Delivery ◽  
Self Assembling ◽  
Wide Range ◽  
Methods Of Synthesis ◽  
Self Assembled

Self-assembled peptides have been shown to form well-defined nanostructures which display outstanding characteristics for many biomedical applications and especially in controlled drug delivery. Such biomaterials are becoming increasingly popular due to routine, standardized methods of synthesis, high biocompatibility, biodegradability and ease of upscale. Moreover, one can modify the structure at the molecular level to form various nanostructures with a wide range of applications in the field of medicine. Through environmental modifications such as changes in pH and ionic strength and the introduction of enzymes or light, it is possible to trigger self-assembly and design a host of different self-assembled nanostructures. The resulting nanostructures include nanotubes, nanofibers, hydrogels and nanovesicles which all display a diverse range of physico-chemical and mechanical properties. Depending on their design, peptide self-assembling nanostructures can be manufactured with improved biocompatibility and in vivo stability and the ability to encapsulate drugs with the capacity for sustained drug delivery. These molecules can act as carriers for drug molecules to ferry cargo intracellularly and respond to stimuli changes for both hydrophilic and hydrophobic drugs. This review explores the types of self-assembling nanostructures, the effects of external stimuli on and the mechanisms behind the assembly process, and applications for such technology in drug delivery.

Design, Fabrication, and Testing of a Novel Design for Flexible Light-Emitting Diode Signage Modules

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Ram C. Adhikari ◽  
Dawood S. Beyragh ◽  
Majid Pahlevani
Keyword(s):  
Printed Circuit Boards ◽  
Maximum Stress ◽  
Experimental Testing ◽  
Light Emitting Diode ◽  
Flexible Substrate ◽  
Internal Stresses ◽  
Curved Surfaces ◽  
Standard Size ◽  
Light Emitting ◽  
Wide Range

Abstract This paper presents a new design architecture for mechanically flexible light-emitting diode (LED) signage modules for applications in digital advertising on curved surfaces. The new design comprises an array of commonly used rigid printed circuit boards (PCBs) but of smaller size with some spacing between them, which is encapsulated by a flexible substrate or potting material, instead of a large single rigid PCB in the entire LED module as in the case of conventional LED signage modules. Commonly used through-hole type red-green-blue (RGB) LEDs are considered. To demonstrate the design, manufacturing, and mechanical flexibility of the design, a prototype LED signage module with a typical industry standard size of 304 mm × 304 mm × 10 mm was designed and fabricated. Experimental testing and finite element simulations were conducted to analyze mechanical flexibility and internal stresses in the module. The results demonstrate that the new design provides flexible LED modules, without altering the conventional LED control system. It is shown that maximum stress occurs in the spacing between the PCBs and is small even for large module deflection. As the curvature of module deflection was decreased, the maximum stress increased, indicating an important design parameter for the module deflection. The proposed design architecture will enable both indoor and outdoor digital advertising using billboards on a wide range of curved surfaces.

All-solution-processed colour-tuneable tandem quantum-dot light-emitting diode driven by AC signal

Nanoscale ◽  
2020 ◽  
Vol 12 (32) ◽  
pp. 17020-17028
Author(s):  
Suk-Ho Song ◽  
Sung-Jae Park ◽  
Tae-Jun Bae ◽  
Kyung-Mo Jung ◽  
Won-Hyeok Park ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Light Emitting Diode ◽  
Solution Processing ◽  
Solution Processed ◽  
Light Emitting ◽  
Novel Structure ◽  
Wide Range ◽  
Full Solution

We demonstrate a novel structure for a quantum-dot light-emitting diode (QD-LED) with wide-range colour-tuneable pixels, fabricated via full solution processing.

scholarly journals Improving Light Extraction of Organic Light-Emitting Devices by Attaching Nanostructures with Self-Assembled Photonic Crystal Patterns

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Kai-Yu Peng ◽  
Da-Hua Wei
Keyword(s):  
Photonic Crystal ◽  
Electronic Device ◽  
Research Work ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Organic Light ◽  
Potential Applications ◽  
Self Assembled ◽  
The One ◽  
Pet Films

A single-monolayered hexagonal self-assembled photonic crystal (PC) pattern fabricated onto polyethylene terephthalate (PET) films by using simple nanosphere lithography (NSL) method has been demonstrated in this research work. The patterned nanostructures acted as a scattering medium to extract the trapped photons from substrate mode of optical-electronic device for improving the overall external quantum efficiency of the organic light-emitting diodes (OLEDs). With an optimum latex concentration, the distribution of self-assembled polystyrene (PS) nanosphere patterns on PET films can be easily controlled by adjusting the rotation speed of spin-coater. After attaching the PS nanosphere array brightness enhancement film (BEF) sheet as a photonic crystal pattern onto the device, the luminous intensity of OLEDs in the normal viewing direction is 161% higher than the one without any BEF attachment. The electroluminescent (EL) spectrum of OLEDs with PS patterned BEF attachment also showed minor color offset and superior color stabilization characteristics, and thus it possessed the potential applications in all kinds of display technology and solid-state optical-electronic devices.

Fabrication of Organic Thin Film Transistor Arrays on Plastic and Paper Substrate for Flexible Display Application

2014 ◽  
Vol 1628 ◽  
Author(s):  
Y. Fujisaki ◽  
Y. Nakajima ◽  
M. Nakata ◽  
H. Tsuji ◽  
T. Yamamoto
Keyword(s):  
Thin Film ◽  
Flexible Substrate ◽  
Cellulose Nanofibers ◽  
High Mobility ◽  
Plastic Substrate ◽  
Organic Thin Film ◽  
Short Channel ◽  
Flexible Display ◽  
Solution Processed ◽  
Wide Range

ABSTRACTOrganic thin-film transistors (OTFTs) are the most promising candidates for flexible electronics owing to their flexible structures, the simplicity of processing large-area devices, and excellent compatibility with flexible substrates. To date, many studies have been reported that have aimed at developing a wide range of plastic electronics such as flexible displays, sensors. In this paper, we discuss our recent work, focusing on OTFT arrays and their application to flexible display. An active-matrix (AM) backplane using a low-temperature cross-linkable olefin-type polymer as the gatedielectric and an air-stable DNTT as the organic semiconductor (OSC) was successfully fabricated on a plastic substrate. The short-channel TFT array exhibited a high hole mobility of over 0.5 cm2/Vs, a low subthreshold slope of 0.31, and excellent environmental and operational stability. A 5-inch flexible OLED display exhibited a high luminescence of over 300 cd/m2 by driving of the DNTT-based OTFTs. Solution-processed OTFTs are also attracting considerable attention owing to both their simple manufacturing process and excellent transistor performance. We present a simple patterning process for a solution-processable OSC that can be used to develop a high-mobility short-channel TFT array. The OSC film was directly patterned on the confined active channel region by a simple lamination coating technique and the resulting TFTs showed a high mobility of up to 1.3 cm2/Vs. In the final section, we report on eco-friendly paper-based organic TFT array. A transparent cellulose nanofibers paper was firstly applied to a flexible substrate for the TFT backplane. A solution-processed TFT on the transparent paper exhibited a high mobility exceeding 1 cm2/Vs, good air stability, and excellent mechanical stability.

Nine Centuries of Man

2017 ◽  
Keyword(s):  
Twentieth Century ◽  
Diverse Range ◽  
Gender Expectations ◽  
Court Records ◽  
The Past ◽  
Wide Range ◽  
Police Reports ◽  
Late Twentieth ◽  
Scottish History ◽  
Late Twentieth Century

What did it mean to be a man in Scotland over the past nine centuries? Scotland, with its stereotypes of the kilted warrior and the industrial ‘hard man’, has long been characterised in masculine terms, but there has been little historical exploration of masculinity in a wider context. This interdisciplinary collection examines a diverse range of the multiple and changing forms of masculinities from the late eleventh to the late twentieth century, exploring the ways in which Scottish society through the ages defined expectations for men and their behaviour. How men reacted to those expectations is examined through sources such as documentary materials, medieval seals, romances, poetry, begging letters, police reports and court records, charity records, oral histories and personal correspondence. Focusing upon the wide range of activities and roles undertaken by men – work, fatherhood and play, violence and war, sex and commerce – the book also illustrates the range of masculinities that affected or were internalised by men. Together, the chapters illustrate some of the ways Scotland’s gender expectations have changed over the centuries and how, more generally, masculinities have informed the path of Scottish history

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