Improving the EMI shielding of graphene oxide (GNO)-coated glass-fiber-GNO-MA-grafted polypropylene (PP) composites and nylon 1D-2D nanocomposite foams.

The proliferation of the latest electronic gadgets and wireless communication devices can trigger electromagnetic interference (EMI), which has a detrimental impact on electronic devices and humans. Efficient EMI shielding materials are required for EMI-SE and they should be durable in external environments, lightweight, and cost-effective. GNO-coated glass-fiber-GNO-maleic anhydride-grafted polypropylene (MAPP) composite and carbon fiber-reinforced nylon 1D-2D nanocomposite foam were successfully prepared via a cost-effective thermal process. The composites were characterized using scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The PP and nylon-based composites with ∼13% filler showed maximum electrical conductivity (EC) of 878 mS cm-1 and 1381 mS cm-1, respectively. The GNO-coated glass-fiber-GNO-MAPP foam displays a maximum EMI-SE of 120.6 dB, while the nylon graphene-carbon nanotube-metal nanoplatelet foam exhibits a maximum EMI-SE of 139.1 dB in the X-band region. The GFCFFeGMAPP composite possesses a minimum thickness of 2.56 mm and blocks most incoming radiation. These are some of the highest EMI-SE values reported so far for glass fiber and nylon-based composites, and the nylon-based composite showed excellent properties compared to the glass fiber-based composite. Thus, we believe that the developed composites can be used in a wide range of real applications, such as in military vehicles, aviation, automobiles, and the packaging of electronic circuits.

Acridine Based Small Molecular Hole Transport Type Materials for Phosphorescent OLED Application.

Two small molecular hole-transporting type materials, namely 4-(9,9-dimethylacridin-10(9H)-yl)-N-(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)-N-phenylaniline (TPA-2ACR) and 10,10'-(9-phenyl-9H-carbazole-3,6-diyl)bis(9,9-dimethyl-9,10-dihydroacridine) (PhCAR-2ACR), were designed and synthesized using a single-step Buchwald-Hartwig amination between the dimethyl acridine and triphenylamine or carbazole moieties. Both materials showed high thermal decomposition temperatures of 402 and 422 °C at 5% weight reduction for PhCAR-2ACR and TPA-2ACR, respectively. TPA-2ACR as hole-transporting material exhibited excellent current, power, and external quantum efficiencies of 55.74 cd/A, 29.28 lm/W and 21.59%, respectively. The achieved device efficiencies are much better than that of the referenced similar, 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC)-based device (32.53 cd/A, 18.58 lm/W and 10.6%). Moreover, phenyl carbazole-based PhCAR-2ACR showed good device characteristics when applied for host material in phosphorescent OLEDs.

EMI Shielding of the Hydrophobic, Flexible, Lightweight Carbonless Nano-Plate Composites.

The cost-effective spray coated composite was successfully synthesis and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction techniques. The one step synthetic strategy was used for the synthesis of nanoplates that have a crystalline nature. The composites are amorphous and hydrophobic with micron thickness (<400 m). The maximum contact angle showed by composite is 132.65° and have wetting energy of -49.32 mN m-1, spreading coefficient -122.12 mN m-1, and work of adhesion 23.48 mN m-1. The minimum thickness of synthesized nanoplate is 3 nm while the maximum sheet resistance, resistivity, and electrical conductivity of the composites are 11.890 ohm sq-1, 0.4399 Ω.cm-1, and 8.967 S.cm-1, respectively. The cobalt nanoplate coated non-woven carbon fabric (CoFC) possesses excellent sheet resistance, hydrophobic nature, and EMI shielding efficiency of 99.99964%. The composite can block above 99.9913% of incident radiation (X band). Hence, the composite can be utilized in application areas such as medical clothes, mobile phones, automobiles, aerospace, and military equipment.

Recent Advancement of Electromagnetic Interference (EMI) Shielding of Two Dimensional (2D) MXene and Graphene Aerogel Composites.

The two Dimensional (2D) materials such as MXene and graphene, are most promising materials, as they have attractive properties and attract numerous application areas like sensors, supper capacitors, displays, wearable devices, batteries, and Electromagnetic Interference (EMI) shielding. The proliferation of wireless communication and smart electronic systems urge the world to develop light weight, flexible, cost effective EMI shielding materials. The MXene and graphene mixed with polymers, nanoparticles, carbon nanomaterial, nanowires, and ions are used to create materials with different structural features under different fabrication techniques. The aerogel based hybrid composites of MXene and graphene are critically reviewed and correlate with structure, role of size, thickness, effect of processing technique, and interfacial interaction in shielding efficiency. Further, freeze drying, pyrolysis and hydrothermal treatment is a powerful tool to create excellent EMI shielding aerogels. We present here a review of MXene and graphene with various polymers and nanomaterials and their EMI shielding performances. This will help to develop a more suitable composite for modern electronic systems.

An effective utilization of MXene and its effect on electromagnetic interference shielding: flexible, free-standing and thermally conductive composite from MXene-PAT-poly(p-aminophenol)-polyaniline co-polymer.

MXene and conductive polymers are attractive candidates for electromagnetic interference shielding (EMI) applications. The MXene-PAT-conductive polymer (CP) composites were fabricated by a cost-effective spray coating technique and characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. A new approach has been developed for the synthesis of exfoliated MXene. The MXene-PAT-poly(p-aminophenol)-polyaniline co-polymer composite exhibited good electric conductivity (EC) of 7.813 S cm-1. The composites revealed an excellent thermal properties, which were 0.687 W (m K)-1 thermal conductivity, 2.247 J (g K)-1 heat capacity, 0.282 mm2 s-1 thermal diffusivity and 1.330 W s1/2 m-2 K-1 thermal effusivity. The composites showed 99.99% shielding efficiency and the MXene-PAT-PANI-PpAP composite (MXPATPA) had EMI shielding effectiveness of 45.18 dB at 8.2 GHz. The reduced form of MXene (r-Ti3C2T x ) increased the shielding effectiveness (SE) by 7.26% and the absorption (SEA) was greatly enhanced by the ant farm like structure. The composites possess excellent thermal and EMI SE characteristics, thus can be applied in areas, such as mobile phones, military utensils, heat-emitting electronic devices, automobiles and radars.

Triazine-Acceptor-Based Green Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes.

High-efficiency thermally activated delayed fluorescence (TADF) is leading the third-generation technology of organic light-emitting diodes (OLEDs). TADF emitters are designed and synthesized using inexpensive organic donor and acceptor derivatives. TADF emitters are a potential candidate for next-generation display technology when compared with metal-complex-based phosphorescent dopants. Many studies are being conducted to enhance the external quantum efficiencies (EQEs) and photoluminescent quantum yield of green TADF devices. Blue TADF reached an EQE of over 35% with the support of suitable donor and acceptor moieties based on a suitable molecular design. The efficiencies of green TADF emitters can be improved when an appropriate molecular design is applied with an efficient device structure. The triazine acceptor has been identified as a worthy building block for green TADF emitters. Hence, we present here a review of triazine with various donor molecules and their device performances. This will help to design more suitable and efficient green TADF emitters for OLEDs.

Hydroxyl-PEG-Phosphonic Acid-Stabilized Superparamagnetic Manganese Oxide-Doped Iron Oxide Nanoparticles with Synergistic Effects for Dual-Mode MR Imaging.

The T1-T2 dual-mode contrast agents for magnetic resonance imaging (MRI) can generate self-complementary confirmed T2 and T1 images, hence greatly improving the reliability. Facilely synthesizing nanoparticles with the ultrasensitive contrast property remains extremely challenging in nanoscience. Moreover, uncovering the mechanism correlating the signal enhancements and chemical constituents is vital for designing novel efficient synergistically enhanced T1-T2 dual-mode MRI nanoprobes. Herein, we report a one-pot facile method to synthesize the superparamagnetic manganese oxide-doped iron oxide (Fe3O4/MnO) nanoparticles for T1-T2 dual-mode MR imaging. Under external magnetic field, the local magnetic field intensities of MnO and Fe3O4 could be simultaneously enhanced through embedding MnO into Fe3O4 nanoparticles and hence can cause synergistic T1 and T2 contrast enhancements. Moreover, a novel and facile cost-effective method for large-scale synthesis of hydroxyl-polyethylene glycol-phosphonic acid-stabilizing ligands is designed. The facile synthetic method and surface coating strategy of superparamagnetic Fe3O4/MnO nanoparticles offer an idea for the chemical design and preparation of superparamagnetic nanoparticles with ultrasensitive MRI contrast abilities for disease evaluation and treatment.

Fabrication of Flexible, Lightweight, Magnetic Mushroom Gills and Coral-Like MXene⁻Carbon Nanotube Nanocomposites for EMI Shielding Application.

MXenes, carbon nanotubes, and nanoparticles are attractive candidates for electromagnetic interference (EMI) shielding. The composites were prepared through a filtration technique and spray coating process. The functionalization of non-woven carbon fabric is an attractive strategy. The prepared composite was characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. The MXene-oxidized carbon nanotube-sodium dodecyl sulfate composite (MXCS) exhibited 50.5 dB (99.999%), and the whole nanoparticle-based composite blocked 99.99% of the electromagnetic radiation. The functionalization increased the shielding by 15.4%. The composite possessed good thermal stability, and the maximum electric conductivity achieved was 12.5 Scm-1. Thus, the composite shows excellent potential applications towards the areas such as aeronautics, mobile phones, radars, and military.

Sunlight active U3O8@ZnO nanocomposite superfast photocatalyst: synthesis, characterization and application.

Sunlight active U3O8@ZnO nanocomposite photocatalyst has been synthesized for the first time using co-precipitation method. The synthesized composite has a particle size ranging from 18 nm to 30 nm with band gap energy of 2.9 eV. The composite photocatalyst is capable of degrading methylene blue completely within 30 min under sunlight irradiation. Therefore, this superfast efficient sunlight-active photocatalyst is very useful in industrial organic waste water treatment.

Electromagnetic Shielding by MXene-Graphene-PVDF Composite with Hydrophobic, Lightweight and Flexible Graphene Coated Fabric.

MXene and graphene based thin, flexible and low-density composite were prepared by cost effective spray coating and solvent casting method. The fabricated composite was characterized using Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX). The prepared composites showed hydrophobic nature with higher contact angle of 126°, -43 mN·m-1 wetting energy, -116 mN·m-1 spreading Coefficient and 30 mN·m-1 lowest work of adhesion. The composites displayed excellent conductivity of 13.68 S·cm-1 with 3.1 Ω·sq-1 lowest sheet resistance. All the composites showed an outstanding thermal stability and constrain highest weight lost until 400 °C. The MXene-graphene foam exhibited excellent EMI shielding of 53.8 dB (99.999%) with reflection of 13.10 dB and absorption of 43.38 dB in 8⁻12.4 GHz. The single coated carbon fabric displayed outstanding absolute shielding effectiveness of 35,369.82 dB·cm²·g-1. The above results lead perspective applications such as aeronautics, radars, air travels, mobile phones, handy electronics and military applications.

Oxadiazole-Based Highly Efficient Bipolar Fluorescent Emitters for Organic Light-Emitting Diodes.

In this study, a series of bipolar fluorescence emitters named 2DPAc-OXD, DPAc-OXD, 2PTZ-OXD and PTZ-OXD were designed and synthesized with excellent yields. The characterization of materials was investigated by using nuclear magnetic resonance (NMR) (¹H, 13C), mass spectrometry and thermogravimetric analysis (TGA). To investigate device efficiencies, two different OLED devices (Device 1, Device 2) were fabricated with two different host materials (Bepp2, DPEPO). The Device 2 with 2PTZ-OXD as fluorescent emitter exhibited excellent power and current efficiencies of 6.88 Lm/W and 10.10 cd/A, respectively. The external quantum efficiency of 2PTZ-OXD was around 3.99% for Device 2. The overall device properties of phenothiazine donor were better than acridine derivatives.

Utilizing a Spiro Core with Acridine- and Phenothiazine-Based New Hole Transporting Materials for Highly Efficient Green Phosphorescent Organic Light-Emitting Diodes.

Two new hole transporting materials, 2,7-bis(9,9-diphenylacridin-10(9H)-yl)-9,9' spirobi[fluorene] (SP1) and 2,7-di(10H-phenothiazin-10-yl)-9,9'-spirobi[fluorene] (SP2), were designed and synthesized by using the Buchwald-Hartwig coupling reaction with a high yield percentage of over 84%. Both of the materials exhibited high glass transition temperatures of over 150 °C. In order to understand the device performances, we have fabricated green phosphorescent organic light-emitting diodes (PhOLEDs) with SP1 and SP2 as hole transporting materials. Both of the materials revealed improved device properties, in particular, the SP2-based device showed excellent power (34.47 lm/W) and current (38.41 cd/A) efficiencies when compare with the 4,4'-bis(N-phenyl-1-naphthylamino)biphenyl (NPB)-based reference device (30.33 lm/W and 32.83 cd/A). The external quantum efficiency (EQE) of SP2 was 13.43%, which was higher than SP1 (13.27%) and the reference material (11.45%) with a similar device structure. The SP2 hole transporting material provides an effective charge transporting path from anode to emission layer, which is explained by the device efficiencies.

Spirobifluorene Core-Based Novel Hole Transporting Materials for Red Phosphorescence OLEDs.

Two new hole transporting materials, named HTM 1A and HTM 1B, were designed and synthesized in significant yields using the well-known Buchwald Hartwig and Suzuki cross- coupling reactions. Both materials showed higher decomposition temperatures (over 450 °C) at 5% weight reduction and HTM 1B exhibited a higher glass transition temperature of 180 °C. Red phosphorescence-based OLED devices were fabricated to analyze the device performances compared to Spiro-NPB and NPB as reference hole transporting materials. Devices consist of hole transporting material as HTM 1B showed better maximum current and power efficiencies of 16.16 cd/A and 11.17 lm/W, at the same time it revealed an improved external quantum efficiency of 13.64%. This efficiency is considerably higher than that of Spiro-NPB and NPB-based reference devices.

A mussel-inspired chitooligosaccharide based multidentate ligand for highly stabilized nanoparticles.

Inspired by the adhesion behaviors of mussels, we synthesized a chitooligosaccharide (COS) based multidentate ligand (ML) for preparing robust biocompatible magnetic iron oxide nanoparticles (IONPs). The COS was modified with mussel adhesive protein (MAP) mimetic multiple catechol groups and branched poly(ethylene glycol) moieties, which can not only strongly bind to IONPs through multiple catechol groups, but also afford IONPs with good colloidal stability and biocompatibility due to PEG integrated into the COS coating. The resultant ML-stabilized IONPs consist of single nanoparticles coated with ML shells and exhibited high dispersion stability in aqueous solution for a wide range of pH and concentrated salt solutions. The potential of ML-stabilized IONPs as contrast agents for T2-weighted magnetic resonance imaging was demonstrated by conducting in vivo imaging and relaxivity measurements. The ML-stabilized IONPs are therefore expected to be useful for magnetic resonance imaging under physiological conditions.

Novel hole transporting materials based on 4-(9H-carbazol-9-yl)triphenylamine derivatives for OLEDs.

During the past few years, organic light emitting diodes (OLEDs) have been increasingly studied due to their emerging applicability. However, some of the properties of existing OLEDs could be improved, such as their overall efficiency and durability; these aspects have been addressed in the current study. A series of novel hole-transporting materials (HTMs) 3a-c based on 4-(9H-carbazol-9-yl)triphenylamine conjugated with different carbazole or triphenylamine derivatives have been readily synthesized by Suzuki coupling reactions. The resulting compounds showed good thermal stabilities with high glass transition temperatures between 148 and 165 °C. The introduction of HTMs 3b and 3c into the standard devices ITO/HATCN/NPB/HTMs 3 (indium tin oxide/dipyrazino(2,3-f:2',3'-h)quinoxaline 2,3,6,7,10,11-hexacarbonitrile/N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine/HTMs)/CBP (4,4'-Bis(N-carbazolyl)-1,1'-biphenyl): 5% Ir(ppy)3/Bphen/LiF/Al (tris[2-phenylpyridinato-C2,N]iridium(III)/4,7-diphenyl-1,10-phenanthroline/LiF/Al) resulted in significantly enhanced current, power, and external quantum efficiencies (EQE) as compared to the reference device without any layers of HTMs 3.

Synthesis of some green dopants for OLEDs based on arylamine 2,3-disubstituted bithiophene derivatives.

A series of green dopants based on 2,2-diphenylvinyl end-capped bithiophene and three different arylamine moieties (9-phenylcarbazole, triphenylamine, and N,N'-di-(p-tolyl)benzeneamine) were successfully synthesized by the Suzuki and Wittig coupling reactions. The photophysical properties of these compounds are reported. The strongest PL emitting compound with the 9-phenylcarbazole moiety has been used for fabricating an OLED device with good overall performance.

Synthesis of lipoic acid-peptide conjugates and their effect on collagen and melanogenesis.

We report new examples of lipoic acid (LA)-peptide conjugates, their potential as codrugs having anti-melanogenic and anti-aging properties was evaluated. These multifunctional molecules were prepared by linking lipophilic moiety (LA) to the pentapeptide KTTKS. The inhibitory effect of LA-peptide conjugates on melanin synthesis and tyrosinase activity is stronger than that of LA or the pentapeptide alone. Importantly, the conjugates display no cytotoxicity at a high concentration. LA-KTTKS and LA-PEG-KTTKS also inhibit UV-induced matrix metalloproteinase-1 expression up to 49.5% and 69.5% at 0.5 mM, respectively. LA-peptide conjugates stimulate collagen biosynthesis in fibroblasts more efficiently than their parent molecules do. These data suggest that LA-peptide conjugates may have cosmeceutical application as anti-melanogenic and anti-aging agents.

Inhibitory effect of dibutyryl chitin ester on nitric oxide and prostaglandin E2 production in LPS-stimulated RAW 264.7 cells.

Inflammation is a highly complex process that protects against foreign challenge or tissue injury. The ester derivative dibutyryl chitin (DBC) reportedly accelerates wound healing and exerts an anti-inflammatory effect. However, little is known regarding the inhibitory effect of DBC in anti-inflammation. In this study, we investigated the effect of DBC on the inducible nitric oxide synthetase (iNOS) and cyclooxygenage-2 (COX-2) pathways and pro-inflammatory cytokine production in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages. Our results demonstrate that DBC (MW 3,772) significantly inhibits overproduction of NO and PGE(2) as well as pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin-1ß, in LPS-stimulated RAW 264.7 macrophages. Inhibition of NO and PGE(2) overproduction in LPSstimulated RAW 264.7 macrophages by DBC was mediated through the down-regulation of iNOS and COX-2 expression. These results demonstrate that DBC efficiently inhibits inflammation and has potential as an effective anti-inflammatory and wound healing agent.

Effect of electrospun non-woven mats of dibutyryl chitin/poly(lactic acid) blends on wound healing in hairless mice.

The aim of this study was to examine the proliferative ability of dibutyryl chitin (DBC) on scratch wounds in HaCaT keratinocytes and to evaluate the effect of nanoporous non-woven mat (DBCNFM) on skin wound healing in hairless mice using the advantages of DBCNFM, such as high porosity and high surface area to volume. The cell spreading activity of DBC was verified through a cell spreading assay in scratched human HaCaT keratinocytes. Scratch wound experiments showed that DBC notably accelerates the spreading rate of HaCaT keratinocytes in a dose dependent manner. The molecular aspects of the healing process were also investigated by hematoxylin & eosin staining of the healed skin, displaying the degrees of reepithelialization and immunostaining on extracellular matrix synthesis and remodeling of the skin. Topical application of DBCNFM significantly reduced skin wound rank scores and increased the skin remodeling of the wounded hairless mice in a dose dependent way. Furthermore, DBCNFM notably increased the expression of the type 1 collagen and filaggrin. These results demonstrate that DBC efficiently accelerates the proliferation of HaCaT keratinocytes and DBCNFM notably increases extracellular matrix synthesis on remodeling of the skin, and these materials are a good candidate for further evaluation as an effective wound healing agent.