Tumor cells inhibit the activation of ILC2s through up-regulating PD-1 expression.

OBJECTIVE: Up-regulating programmed cell death ligand-1(PD-L1) expressed on tumor cells and tumor-infiltrating myeloid cells interacting with up-regulated programmed cell death-1 (PD-1) expressed on tumor-infiltrating lymphoid cells greatly hinder their tumor-inhibiting effect. It is necessary to explore the deep mechanism of this negative effect, so as to find the potential methods to improve the immunotherapy efficiency. METHODS AND RESULTS: In this study, we found that the PD-1 expression in lung cancer-infiltrating type II innate lymphoid cells (ILC2s) was highly up-regulated, which greatly restrained the activation and function of ILC2s. Furthermore, anti-PD-1 could restore the inhibition and effective cytokine secretion of ILC2s when co-cultured with tumor cells. In vivo studies proved that anti-PD-1 treatment promoted the activation of tumor-infiltrating ILC2s and inhibited the tumor growth of LLC-bearing nude mice. DISCUSSION: Our studies demonstrate a new PD-1/PD-L1 axis regulating mechanism on innate immune cells, which provide a useful direction to ILC2s-based immunotherapy to cancer diseases.

Synergistic Combination of Sb2Si2Te6 Additives for Enhanced Average ZT and Single-Leg Device Efficiency of Bi0.4Sb1.6Te3-based Composites.

Thermoelectric materials are highly promising for waste heat harvesting. Although thermoelectric materials research has expanded over the years, bismuth telluride-based alloys are still the best for near-room-temperature applications. In this work, a ≈38% enhancement of the average ZT (300-473 K) to 1.21 is achieved by mixing Bi0.4Sb1.6Te3 with an emerging thermoelectric material Sb2Si2Te6, which is significantly higher than that of most BiySb2-yTe3-based composites. This enhancement is facilitated by the unique interface region between the Bi0.4Sb1.6Te3 matrix and Sb2Si2Te6-based precipitates with an orderly atomic arrangement, which promotes the transport of charge carriers with minimal scattering, overcoming a common factor that is limiting ZT enhancement in such composites. At the same time, high-density dislocations in the same region can effectively scatter the phonons, decoupling the electron-phonon transport. This results in a ≈56% enhancement of the thermoelectric quality factor at 373 K, from 0.41 for the pristine sample to 0.64 for the composite sample. A single-leg device is fabricated with a high efficiency of 5.4% at ΔT = 164 K further demonstrating the efficacy of the Sb2Si2Te6 compositing strategy and the importance of the precipitate-matrix interface microstructure in improving the performance of materials for relatively low-temperature applications.

Terahertz Attenuated Total Reflection Spectral Response and Signal Enhancement via Plasmonic Enhanced Sensor for Eye Drop Detection.

With chronic ocular diseases such as glaucoma and dry eye syndrome, patients have to apply eye drops over the long term. The therapeutic effects of eye drops depend on the amount of drug contained and the stability of the solution. In addition, contamination during usage and transport can also negatively affect the quality and efficacy of eye drops. The current techniques for the characterization of eye drops are often complicated and time-consuming. Developing a fast and non-invasive way of accurately measuring eye drop quality remains an ongoing challenge. The biggest challenge and primary prerequisite for the application of this new detection technique for eye drops is the obtention of a sufficient spectral response and resolvable signal, considering the large background signal contributed by water. In this work, we use terahertz (THz) attenuated total reflection (ATR) spectroscopy combined with a sensitive hybrid graphene oxide (GO) and carbon nanotube (CNT) thin-film sensors to obtain distinct THz spectral signals in commercial eye drops. Various commercial eye drop products have been tested, and we show that they can be differentiated via their spectral signals. Our results provide a solid foundation for the future fine analysis of eye drops and the detection of their quality. Furthermore, THz spectroscopy combined with GO/CNT films has significant potential and advantages for the non-destructive characterization of aqueous pharmaceutical products.

Thermoelectric Silver-Based Chalcogenides.

Heat is abundantly available from various sources including solar irradiation, geothermal energy, industrial processes, automobile exhausts, and from the human body and other living beings. However, these heat sources are often overlooked despite their abundance, and their potential applications remain underdeveloped. In recent years, important progress has been made in the development of high-performance thermoelectric materials, which have been extensively studied at medium and high temperatures, but less so at near room temperature. Silver-based chalcogenides have gained much attention as near room temperature thermoelectric materials, and they are anticipated to catalyze tremendous growth in energy harvesting for advancing internet of things appliances, self-powered wearable medical systems, and self-powered wearable intelligent devices. This review encompasses the recent advancements of thermoelectric silver-based chalcogenides including binary and multinary compounds, as well as their hybrids and composites. Emphasis is placed on strategic approaches which improve the value of the figure of merit for better thermoelectric performance at near room temperature via engineering material size, shape, composition, bandgap, etc. This review also describes the potential of thermoelectric materials for applications including self-powering wearable devices created by different approaches. Lastly, the underlying challenges and perspectives on the future development of thermoelectric materials are discussed.

Aqueous Synthesis, Doping, and Processing of n-Type Ag2Se for High Thermoelectric Performance at Near-Room-Temperature.

Herein, we have successfully synthesized binary Ag2Se, composite Ag0:Ag2Se, and ternary Cu+:Ag2Se through an ambient aqueous-solution-based approach in a one-pot reaction at room temperature and atmospheric pressure without involving high-temperature heating, multiple-processes treatment, and organic solvents/surfactants. Effective controllability over phases and compositions/components are demonstrated with feasibility for large-scale production through an exquisite alteration in reaction parameters especially pH for enhancing and understanding thermoelectric properties. Thermoelectric ZT reaches 0.8-1.1 at near-room-temperature for n-type Ag2Se and Cu+ doping further improves to 0.9-1.2 over a temperature range of 300-393 K, which is the largest compared to that reported by wet chemistry methods. This improvement is related to the enhanced electrical conductivity and the suppressed thermal conductivity due to the incorporation of Cu+ into the lattice of Ag2Se at very low concentrations (x%Cu+:Ag2Se, x = 1.0, 1.5, and 2.0).

Bottom-Up Engineering Strategies for High-Performance Thermoelectric Materials.

The recent advancements in thermoelectric materials are largely credited to two factors, namely established physical theories and advanced materials engineering methods. The developments in the physical theories have come a long way from the "phonon glass electron crystal" paradigm to the more recent band convergence and nanostructuring, which consequently results in drastic improvement in the thermoelectric figure of merit value. On the other hand, the progresses in materials fabrication methods and processing technologies have enabled the discovery of new physical mechanisms, hence further facilitating the emergence of high-performance thermoelectric materials. In recent years, many comprehensive review articles are focused on various aspects of thermoelectrics ranging from thermoelectric materials, physical mechanisms and materials process techniques in particular with emphasis on solid state reactions. While bottom-up approaches to obtain thermoelectric materials have widely been employed in thermoelectrics, comprehensive reviews on summarizing such methods are still rare. In this review, we will outline a variety of bottom-up strategies for preparing high-performance thermoelectric materials. In addition, state-of-art, challenges and future opportunities in this domain will be commented.

Synthesis and optical and electronic properties of one-dimensional sulfoxonium-based hybrid metal halide (CH3)3SOPbI3.

We report the synthesis and optical and electronic properties of a one-dimensional sulfoxonium-based hybrid metal halide in an orthorhombic crystal system with a Pnma space group. To provide direct insights, a method is developed to calculate tolerance factors with the ionic radii of non-spherical cations from X-ray crystallographic data.

Significant Enhancement in the Seebeck Coefficient and Power Factor of p-Type Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) through the Incorporation of n-Type MXene.

Thermoelectric (TE) materials are important for sustainable development because they can directly convert heat into electricity. Compared with inorganic TE materials, conductive polymers have demonstrated unique benefits and their irreplaceability. But their TE properties, particularly the Seebeck coefficient, must be greatly enhanced for practical application. In this work, MXene (Ti3C2Tx), an n-type two-dimensional material, is blended into p-type poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The Seebeck coefficient of the composites increases with the increasing MXene loading at the MXene loading below 33 wt % and then decreases with further increasing of the MXene loading. MXene can enhance the Seebeck coefficient from 23 up to 57.3 µV K-1 and the power factor from 44.1 up to 155 µW m-1 K-2. For the first time, enhancement in the Seebeck coefficient of a p-type TE polymer by an n-type filler has been achieved. Enhancement in the Seebeck coefficient is ascribed to energy filtering of charge carriers by the internal electric field arising from the electron transfer from MXene to PEDOT:PSS. The internal electric field can filter the charge carriers with low energy and thus enhance the Seebeck coefficient.

Origin of High Thermoelectric Performance in Earth-Abundant Phosphide-Tetrahedrite.

Phosphide-based thermoelectrics are a relatively less studied class of compounds, primarily due to the presence of light elements, which result in high thermal conductivity and inherent stability problems. In this work, we present a stable phosphide-tetrahedrite, Ag6Ge10P12, which possesses the highest zT (∼0.7) among all known phosphides at intermediate temperatures (750 K). We examine the intrinsic electronic and thermal transport properties of this compound by expressing the transport properties in terms of weighted mobility (µW), transport coefficient (σE0), and material quality factor (B), from which we are able to elucidate that the origin of its high zT can be attributed to the platelike Fermi surface and high level of band multiplicity related to its complex band structure. Finally, we discuss the origin of the low lattice thermal conductivity observed in this compound using experimental sound velocity, elastic properties, and Debye-Callaway model, thus laying the foundation for similar stable phosphides as potentially earth-abundant and nontoxic intermediate-temperature thermoelectric materials.

Modulation of the doping level of PEDOT:PSS film by treatment with hydrazine to improve the Seebeck coefficient.

As the most popular conducting polymer, poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is widely used for a variety of applications, including thermoelectrics. This paper reports the modulation of the doping level by treatment with hydrazine to improve the Seebeck coefficient of PEDOT:PSS films. PEDOT:PSS films were first treated with formic acid followed by hydrazine, leading to a significant increase in the Seebeck coefficient from 17.5 to 42.7 µV K-1, about 2.5 times higher than that of the pristine film partially at the expense of electrical conductivity. An optimum power factor of 93.5 µW K-2 m-1, being 2.4 times that of the one treated with only formic acid, was achieved. The substantial improvement in the Seebeck coefficient and the power factor is collectively attributed to the removal of the PSS, and more importantly, the reduction of the doping level of PEDOT by the hydrazine treatment, which is evidenced clearly by UV-vis-NIR spectroscopy, XPS and Raman spectroscopy.

Improved Alignment of PEDOT:PSS Induced by in-situ Crystallization of "Green" Dimethylsulfone Molecules to Enhance the Polymer Thermoelectric Performance.

Dimethylsulfone (DMSO2), a small organic molecule, was observed to induce the alignment of poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS) via in-situ crystallization in PEDOT:PSS mixture, which was verified by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). A chemically stable dopant, DMSO2, remarkably raised the electrical conductivity of the PEDOT:PSS film, which was fabricated from pre-mixed solution of PEDOT:PSS and DMSO2, up to 1080 S/cm, and more importantly, such a PEDOT:PSS film showed a long-term humidity stability and it retained near 90% electric conductivity after 60 days, suggesting DMSO2 is promising for an eco-friendly alternative to replace dimethyl sulfoxide (DMSO), ethylene glycol (EG) and various acids dopants that have been widely employed to dope and post-treat PEDOT:PSS. Pairwise interaction energies and free energy of solvation between PEDOT:PSS and DMSO2 were calculated by first-principles and molecular mechanics, respectively, revealing the mechanism of DMSO2 in enhancing the electrical conductivity.

Improved Thermoelectric Properties and Environmental Stability of Conducting PEDOT:PSS Films Post-treated With Imidazolium Ionic Liquids.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most popular conducting polymers and widely used as polymer thermoelectric materials, and its thermoelectric performance could be improved by a variety of post-treatment processes. This paper reported two series of post-treatment methods to enhance the thermoelectric performance. The first series method included pre-treatment of PEDOT:PSS film with formamide, followed by imidazolium-based ionic liquids. The second series method included pre-treatment of PEDOT:PSS film with formamide, followed by sodium formaldehyde sulfoxylate, and finally imidazolium-based ionic liquids. Two series of post-treatment methods significantly improved the power factor of PEDOT:PSS when compared to that of PEDOT:PSS treated with formamide only. For example, using the first series post-treatment method with 40 vol.% ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide, the Seebeck coefficient of the PEDOT:PSS film increased from 14.9 to 28.5 µV/K although the electrical conductivity reduced from 2,873 to 1,701 S/cm, resulting in a substantial improvement in the overall power factor from 63.6 to 137.8 µW/K2m. The electrical conductivity enhancement in the formamide-treatment process was in part ascribed to the removal of the insulating PSS component. Further treatment of PEDOT:PSS film with ionic liquid caused dedoping of PEDOT and hence increased in Seebeck coefficient. In contrast, second series post-treatment method led to the reduction in electrical conductivity from 2,873 to 641 S/cm but a big improvement in the Seebeck coefficient from 14.9 to 61.1 µV/K and thus the overall power factor reached up to ~239.2 µW/K2m. Apart from the improvement in electrical conductivity, the increase in Seebeck coefficient is on account of the substantial dedoping of PEDOT polymer to its neutral form and thus leads to the big improvement of its Seebeck coefficient. The environmental stability of ionic liquid-treated PEDOT:PSS films were examined. It was found that the ionic liquid treated PEDOT:PSS retained more than 70% Seebeck coefficient and electrical conductivity at 75% RH humidity and 70°C for 480 h. The improved long-term TE stability is attributed to the strong ionic interaction between sulfonate anions and bulky imidazolium cations that effectively block the penetration of water and lessen the tendency to take up water from the air.

High-performance thermoelectric materials based on ternary TiO2/CNT/PANI composites.

In the present work, we report the fabrication of high-performance thermoelectric materials using TiO2/CNT/PANI ternary composites. We showed that a conductivity of ∼2730 S cm-1 can be achieved for the binary CNT (70%)/PANI (30%) composite, which is the highest recorded value for the reported CNT/PANI composites. We further demonstrated that the Seebeck coefficient of CNT/PANI composites could be enhanced by incorporating TiO2 nanoparticles into the binary CNT/PANI composites, which could be attributed to lower carrier density and the energy scattering of low-energy carriers at the interfaces of TiO2/a-CNT and TiO2/PANI. The resulting TiO2/a-CNT/PANI ternary system exhibits a higher Seebeck coefficient and enhanced thermoelectric power. Further optimization of the thermoelectric power was achieved by water treatment and by tuning the processing temperature. A high thermoelectric power factor of 114.5 µW mK-2 was obtained for the ternary composite of 30% TiO2/70% (a-CNT (70%)/PANI (30%)), which is the highest reported value among the reported PANI based ternary composites. The improvement of thermoelectric performance by incorporation of TiO2 suggests a promising approach to enhance power factor of organic thermoelectric materials by judicial tuning of the carrier concentration and electrical conductivity.

Enhancement of thermoelectric performance of PEDOT:PSS films by post-treatment with a superacid.

Several methods such as the addition of a polar solvent, an acid as well as various post-treatments have been used to improve the thermoelectric performance of conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films. This paper reports a method using a superacid, trifluoromethanesulfonic acid, in methanol to treat PEDO:PSS films to improve their thermoelectric performance. Treatment of PEDOT:PSS films with this superacid in methanol leads to a significant increase in electrical conductivity from 0.7 to 2980 S cm-1 together with a moderate increase in Seebeck coefficient from 17.6 to 21.9 µV K-1, giving a power factor of 142 µW m-1 K-2, one of the highest values reported in the literature for conductive polymers. The figure of merit (ZT) value is estimated to be 0.19 under optimized conditions. The enhancement of thermoelectric performance, particularly the increase in both electrical conductivity and Seebeck coefficient, is due to the removal of the insulating component and polymer chain realignment giving in turn a denser packing of the conductive PEDOT polymer chains. This post-treatment method would offer an alternative way to improve the thermoelectric performance.

Fully Printable Organic and Perovskite Solar Cells with Transfer-Printed Flexible Electrodes.

The perovskite solar cells (PSCs) and organic solar cells (OSCs) with high performance were fabricated with transfer-printed top metal electrodes. We have demonstrated that PSCs and OSCs with the top Au electrodes fabricated by using the transfer printing method have comparable or better performance than the devices with the top Au electrodes fabricated by using the conventional thermal evaporation method. The highest PCE of the PSCs and OSCs with the top electrodes fabricated using the transfer printing method achieved 13.72% and 2.35%, respectively. It has been investigated that fewer defects between the organic thin films and Au electrodes exist by using the transfer printing method which improved the device stability. After storing the PSCs and OSCs with the transfer-printed electrodes in a nitrogen environment for 97 and 103 days without encapsulation, the PSCs and OSCs still retained 71% and 91% of their original PCEs, respectively.

Identification of catalytic sites for oxygen reduction and oxygen evolution in N-doped graphene materials: Development of highly efficient metal-free bifunctional electrocatalyst.

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to renewable energy conversion and storage technologies. Heteroatom-doped carbon nanomaterials have been reported to be efficient metal-free electrocatalysts for ORR in fuel cells for energy conversion, as well as ORR and OER in metal-air batteries for energy storage. We reported that metal-free three-dimensional (3D) graphene nanoribbon networks (N-GRW) doped with nitrogen exhibited superb bifunctional electrocatalytic activities for both ORR and OER, with an excellent stability in alkaline electrolytes (for example, KOH). For the first time, it was experimentally demonstrated that the electron-donating quaternary N sites were responsible for ORR, whereas the electron-withdrawing pyridinic N moieties in N-GRW served as active sites for OER. The unique 3D nanoarchitecture provided a high density of the ORR and OER active sites and facilitated the electrolyte and electron transports. As a result, the as-prepared N-GRW holds great potential as a low-cost, highly efficient air cathode in rechargeable metal-air batteries. Rechargeable zinc-air batteries with the N-GRW air electrode in a two-electrode configuration exhibited an open-circuit voltage of 1.46 V, a specific capacity of 873 mAh g(-1), and a peak power density of 65 mW cm(-2), which could be continuously charged and discharged with an excellent cycling stability. Our work should open up new avenues for the development of various carbon-based metal-free bifunctional electrocatalysts of practical significance.

Elimination of burn-in open-circuit voltage degradation by ZnO surface modification in organic solar cells.

Photodegradation of inverted organic solar cells based on ZnO as an electron transport layer (ETL) was studied over short time scales of 5 min and 8 h. Devices with ZnO as ETL reproducibly exhibited a steep loss of open-circuit voltage, VOC, and shunt resistance, RSH, in a matter of minutes upon illumination. Removing the UV-content of illumination minimized VOC loss and impact on the device's shunting behavior, indicating its role in the loss. Application of an ultrathin layer of Al on ZnO led to almost negligible photoinduced VOC loss up to 8 h of exposure. By applying the fundamental Shockley diode equation, we approximated the VOC loss to be caused by dramatic increases in reverse saturation current I0. We attribute the increased rate of recombination to diminished carrier selectivity at the ZnO/organic interface. Devices with Al modified ZnO ETL demonstrated remarkable RSH (1.4 kΩ cm(2) at 1 sun), rectification ratio (10(6)) and reverse saturation current density (2.1 × 10(-7) mA/cm(2)).

Pure blue-light emissive poly(oligofluorenes) with bifunctional poss in the main chain.

Emission of conjugated polymers is known to undergo bathochromic shift from solution to film formation due to π-π stacking in the solid state. In this report, a series of pearl-necklace-like hybrid polymers is designed via the hydrosilylation condensation between bifunctional polyhedral oligomeric silsesquioxanes (B-POSS) and oligofluorene segments. Optoelectronic analyses unequivocally show that the presence of these interconnecting B-POSS can effectively reduce red-shift in photoluminescence and electroluminescence during film formation. These hybrid poly(oligofluorenes) display stable blue emission with high color purity. Thermal analyses also indicate that they are vitrified polymers with high glass transition temperature (up to 125 °C). We believe that this strategy can be extended to other conjugated systems to control color purity in electroactive materials and holds promise as new emissive materials for various applications.

Cesium carbonate functionalized graphene quantum dots as stable electron-selective layer for improvement of inverted polymer solar cells.

Solution processable inverted bulk heterojunction (BHJ) polymer solar cells (PSCs) are promising alternatives to conventional silicon solar cells because of their low cost roll-to-roll production and flexible device applications. In this work, we demonstrated that Cs2CO3 functionalized graphene quantum dots (GQDs-Cs2CO3) could be used as efficient electron-selective layers in inverted PSCs. Compared with Cs2CO3 buffered devices, the GQDs-Cs2CO3 buffered devices show 56% improvement in power conversion efficiency, as well as 200% enhancement in stability, due to the better electron-extraction, suppression of leakage current, and inhibition of Cs(+) ion diffusion at the buffer/polymer interface by GQDs-Cs2CO3. This work provides a thermal-annealing-free, solution-processable method for fabricating electron-selective layer in inverted PSCs, which should be beneficial for the future development of high performance all-solution-processed or roll-to-roll processed PSCs.