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With the rapid growth in triboelectric nanogenerator (TENG) technology, selecting appropriate tribomaterial (TM) with high electrical output performance and a cheap fabrication technique is vital f...

Introduction This report describes the treatment of an immature mandibular molar by combining vital pulp therapy (VPT) and regenerative endodontic procedures (REPs). It details the use of REP to regain functionality and continued root development of an immature root with pulp necrosis and VPT for an immature root containing vital pulpal tissues. Methods An 8-year old male presented for evaluation of a mandibular first right molar with mild buccal swelling and a nontraceable sinus tract. He recently had received a restoration. After intraoral and radiographic examination, a diagnosis of pulp necrosis and chronic apical abscess was made. After access, pulp necrosis was confirmed in the distal root; however, vital pulp tissues were present in the mesial canals. It was decided on pulpotomy (VPT) in the mesial and REP in the distal root. At the initial visit, pulpotomy was completed in the mesial root, and REP was initiated in the distal root. Three weeks later, the patient was asymptomatic and the sinus tract absent. REP was completed in the distal root, and the tooth was restored. Results At the 6-, 12-, and 18-month follow-up, the patient presented without symptoms, and the tooth responded positively to pulp sensibility tests. Radiographic examinations showed resolution of the apical radiolucency and completed root development. Conclusions Combined treatment using both VPT and REP for immature molars with different pulpal status in individual roots may be a preferable treatment option because preservation of vital pulp tissues and regeneration of new vital tissues allow for continued root development and functionality.

The relationship between the conformation of a polyelectrolyte and the performance of organic thermoelectric multilayers was studied. The conformational change of a weak polyelectrolyte via controlling assembling pH gave rise to a different thermoelectric behaviour in thin films. Organic thermoelectric multilayers were fabricated by alternately depositing bilayers (BL) of a positively-charged polyaniline (PANi) and multiwalled carbon nanotubes (MWNT), stabilized in poly(acrylic acid) (PAA), via a layer-by-layer assembly technique. The electrical conductivity and See-beck coefficient of PANi/MWNT-PAA nanocomposites were measured by varying assembly pH of PAA solutions. Altering the deposition pH of PAA resulted in different thermoelectric performances. A 40 BL thin film (∼210 nm thick) of PANi/MWNT-PAA assembled at pH 2.5/6.5 exhibited electrical conductivity of 95.2 S/cm and a Seebeck coefficient of 35 µV/K. This translates to a power factor of 11.7 µW/m·K2, which is 50 times higher than that of the same film with all components deposited at pH 2.5. Enhancement of thermoelectric behaviour in PANi/MWNT-PAA nanocomposites is attributed to a conjugated π-π network, together with a tightly packed nanostructure.

Two trimellitic anhydride-functionalized, thermally reduced graphenes with different aspect ratios, Af, and the same C/O ratio (8:1) were prepared and melt-mixed into poly(ethylene terephthalate) (PET), and the mechanical properties of the resulting nanocomposites were studied with a focus on plastic deformation behavior. A slight increase in the G′ of the melt was observed for the surface-modified low-Af graphene composites (Af = 20) below the percolation threshold, whereas a significant enhancement in G′ was observed for higher-Af graphene composites (Af = 80) at all graphene loadings, both below and above the percolation concentration. Furthermore, the use of modified low-Af graphene caused an improvement both in Young’s modulus and elongation at break of the resulting PET nanocomposites because of enhancement of interfacial adhesion between filler and matrix which resulted in the formation of a coupled network via covalent bonding and the suppression both of strain-induced orientation and strain-induced crystallization. By contrast, the use of modified higher-Af surface graphene in nanocomposites caused a drastic improvement in Young’s modulus but lower elongation-at-break than with the unmodified counterpart; the former effect is due to the formation of denser coupled networks and stronger interfacial adhesion as a result of graphene surface modification and the latter is due to the added geometrical restriction in unentangling chains from the PET matrix in the presence of higher-Af graphene. The preceding observations demonstrate the potential impacts of tuning both surface chemistry and aspect ratio of graphene in the fabrication of PET/graphene composites.

Graphene of two different aspect ratios, Af, was melt mixed with poly(ethylene terephthalate) (PET) to form amorphous PET/graphene composites with less than 5% crystallinity. The higher-order structure and mechanical properties of poly(ethylene terephthalate) (PET) in these composites were investigated using techniques such as differential scanning calorimetry and dynamic mechanical analysis, whereas transmission electron microscopy, melt rheology, and electrical conductivity were used to study the graphene dispersion. A decrease in heat capacity changes, ΔCp, of PET in nanocomposites at the glass transition temperature, Tg, without Tg change suggests that a rigid amorphous fraction (RAF) of PET was formed at the PET/graphene interface. The stiffening effect of graphene below 1 wt % loading is quite small in the glassy state region and independent of the Af of graphene. Above 2 wt %, graphene forms a mechanical percolation network with the RAF of PET and the PET chains are geometrically restricted by the incorporation of graphene with a high Af, resulting in an unexpectedly higher modulus of nanocomposites both below and above Tg.

Graphene was modified with trimellitic anhydride groups, and its polyethylene-terephthalate-based (PET-based) nanocomposites were prepared by melt-mixing. Percolation thresholds observed from chang...

UV–Vis spectrometry and quartz crystal microbalance were used to measure the growth of these films as a function of the number of bilayers deposited, while scanning electron microscopy and transmission electron microscopy were used to visualize the morphology of the thin film coatings on the cotton fabric. Nanocomposites formed of cationic starch (CS) and clay introduced fire protection properties into the pure cotton fabric by layer-by-layer (LbL) technique. The optical properties and mass of the films were precisely controlled by the number of bilayers. In this case, CS and clay multilayer thin films were used to increase the thermal stability of the fabrics and improve the anti-flammable properties through the formation of a ceramic char layer and thermally stable carbonaceous structure at a high temperature. This study demonstrates the ability of the LbL technique to produce anti-flammable starch–clay nanocomposite thin films. Cone calorimetry showed the lower total heat release and heat release capacity of the LbL-coated fabric. The LbL-coated cotton samples exhibited a reduced afterglow time in vertical flame tests. An increased amount of residue indicates that the LbL technique is a simple method which can be used to produce eco-friendly flame retardant thin film coatings.

Triboelectric nanogenerators (TENGs) are considered promising next-generation mechanical energy harvesters owing to their desirable attributes such as light weight, portability, eco-friendliness, and low cost. However, cost-effective, scalable, and facile manufacturing methods are still required for the commercialization of TENGs, especially for textile-type TENGs compatible with a variety of textile products. In this work, we report for the first time the layer-by-layer (LbL) assembly of graphene multilayers for low-cost, durable, scalable, and wearable TENGs. The LbL-based graphene multilayers are fabricated on polymer substrates with flat, undulated, and textile surfaces, where graphene multilayers play dual roles as a positive tribo-material and as an electrode. The polymer substrate here is utilized as a negative tribo-material. We identify the optimal number of layers for graphene composites and analyze this outcome using their morphological and electrical properties. Due to the hydrogen bonding-based LbL wet processes, graphene composite multilayers could be well deposited on undulated surfaces as well as on large-scale fabric textiles. These LbL-deposited graphene multilayers yield graphene based-TENGs (G-TENGs) with high durability and high performance. Finally, a graphene multilayer on a textile sample is demonstrated as a scalable and wearable textile-based G-TENG (TG-TENG) operated in a single electrode mode, thereby enabling low-cost manufacturing and high compatibility with textile products such as cloths, curtains, bags and so on. The simple, cost-effective, scalable, and versatile LbL assembly can therefore enable the fabrication of wearable energy harvesting sources for many portable personal microelectronic devices (e.g., self-powered wireless sensors).

The combination of clay and intumescent, also termed hybrid organic−inorganic coating is an attractive strategy to improve the flame retardancy of polyurethane foam (PUF). However, the fabrication of such flame retardants remains challenging as it requires the deposition of many layers to achieve the desired level of the intumescing effect. Herein, we describe a facile route to fabricate a hybrid clay−intumescent coating comprising a OnePot−deposited chitosan (CH)−phytic acid (PA) polyelectrolyte complex (PEC) intumescent stacked on top of a layer-by−layer self−assembled clay trilayer (TL) of poly− d −lysine, CH, and alginate-stabilized montmorillonite. Combustibility tests using cone calorimetry revealed that a PUF coating of CH−PA PEC intumescent on a 5 TL clay nanobrick wall (CH−PA@5 TL@PUF) can reduce the peak heat release rate (a critical flammability metric), peak rate of smoke release, and peak CO2 production rate of neat PUF by 73%, 33%, and 65%, respectively. Additionally, this hybrid coating imparted UL−94 horizontal burning rating by avoiding melt dripping and flashover, while the neat foam was completely consumed during the UL−94 flammabilty test. The proposed method is adaptable for the facile construction of other multifunctional surfaces in various application fields.

Next-generation electronics require mechanical flexibility and durability as well as electrical conductivity. In this report, few-layer graphene and polyelectrolytes were assembled into ultrathin films on flexible plastic substrates by a simple and cost-effective layer-by-layer technique. This technique integrated high electrical conductivity and excellent oxygen barrier property into a single film. These characteristics have been rarely reported for other types of thin films prepared by solution processing. The optical properties, film thickness, and mass of the films were precisely controlled by the number of bilayers. After a brief exposure to nitric acid (HNO3) vapor, the films exhibited much improved electrical conductivity while preserving their other properties. Raman, x-ray photoelectron, and FT-IR spectroscopy proved that the effects of the HNO3 treatment were due to the removal of polymeric components and restricted to the film surface, and not due to the chemical doping of graphene.

In this study, we report the crystallinity effects of submicrometer titanium dioxide (TiO2) nanotube (TNT) incorporated with silver (Ag) nanoparticles (NPs) on surface-enhanced Raman scattering (SERS) sensitivity. Furthermore, we demonstrate the SERS behaviors dependent to the plasmonic-photonic interference coupling (P-PIC) in the TNT-AgNP nanoarchitectures. Amorphous TNTs (A-TNTs) are synthesized through a two-step anodization on titanium (Ti) substrate and crystalline TNTs (C-TNTs) are then prepared by using thermal annealing process at 500 °C in air. After thermally evaporating 20-nm thick Ag on TNTs, we investigate SERS signals according to the crystallinity and P-PIC on our TNT-AgNP nanostructures. (A-TNTs)-AgNP substrates show dramatically enhanced SERS performance compared with (C-TNTs)-AgNP substrates. We attribute the high enhancement on (A-TNTs)-AgNP substrates with electron confinement at the interface between A-TNTs and AgNPs due to the high interfacial barrier resistance caused by band edge ...

In contrast to commercial piezoelectric ceramics, lead-free materials such as ZnO and a polymer matrix are proper candidates for use in ecofriendly applications. In this article, the authors represent a technique using ZnO nanowires with a polyvinylidene fluoride (PVDF) matrix in a piezoelectric polymer composite. By aligning the nanowires in the matrix in a desired direction by AC dielectrophoresis, the piezoelectric behavior was enhanced. The dielectric constant of the composite was improved by increasing the concentration of the ZnO nanowires as well. Specifically, the resulting dielectric constant shows an improvement of 400% with aligned ZnO nanowires by increasing the poling effect compared to that of a randomly oriented nanowire composite without a poling process.

Introduction Studies have shown that there is a significantly higher concentration of interleukin 6 (IL-6) in inflamed pulp tissues compared with healthy pulp tissues. The aims of this study were to investigate the baseline differences between mesenchymal stem cells (MSCs) isolated from healthy human dental pulp stem cells (H-DPSCs) and inflamed dental pulp stem cells (I-DPSCs) and their correlation to IL-6 and to determine whether IL-6 can affect the differentiation potentials of these cells. Methods MSCs isolated from healthy and inflamed pulp tissues were cultured and characterized in vitro. The levels of secreted IL-6 in the culture supernatants from H-DPSCs and I-DPSCs were measured by enzyme-linked immunosorbent assay. IL-6 and neutralizing IL-6 were added to H-DPSCs and I-DPSCs, respectively. Immunofluorescence staining, alizarin red staining, and Western blotting were performed to assess the differentiation potentials of H-DPSCs and I-DPSCs. The independent unpaired 2-tailed Student's t-test was performed after quantification analysis. Results H-DPSCs and I-DPSCs showed a similar expression of MSC-associated markers including CD44, CD73, CD90, and CD105, whereas H-DPSCs showed a lower level of IL-6, lower osteogenic differentiation potentials, and higher neurogenic differentiation potentials compared with I-DPSCs. The addition of IL-6 to H-DPSCs increased osteogenic potentials and decreased neurogenic potentials, whereas the neutralization of IL-6 for I-DPSCs led to decreased osteogenic potentials and increased neurogenic potentials. Conclusions The findings of this study indicated IL-6 has the capacity to enhance osteogenesis while hindering neurogenesis of DPSCs.

Nanogenerator-based technologies have found outstanding accomplishments in energy harvesting applications over the past two decades [...]

The use of halogen-based materials has been regulated since toxic substances are released during combustion. In this study, polyurethane foam was coated with cationic starch (CS) and montmorillonite (MMT) nano-clay using a spray-assisted layer-by-layer (LbL) assembly to develop an eco-friendly, high-performance flame-retardant coating agent. The thickness of the CS/MMT coating layer was confirmed to have increased uniformly as the layers were stacked. Likewise, a cone calorimetry test confirmed that the heat release rate and total heat release of the coated foam decreased by about 1/2, and a flame test showed improved fire retardancy based on the analysis of combustion speed, flame size, and residues of the LbL-coated foam. More importantly, an additional cone calorimeter test was performed after conducting more than 1000 compressions to assess the durability of the flame-retardant coating layer when applied in real life, confirming the durability of the LbL coating by the lasting flame retardancy.