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Ferroelectric catalysts are known for altering surface catalytic activities by changing the direction of their electric polarizations. This study demonstrates polarization-switchable electrochemistry using layered bismuth oxyselenide (L-Bi2O2Se) bifunctional microreactors through ferroelectric modulation. A selective-area ionic liquid gating is developed with precise control over the spatial distribution of the dipole orientation of L-Bi2O2Se. On-chip microreactors with upward polarization favor the oxygen evolution reaction, whereas those with downward polarization prefer the hydrogen evolution reaction. The microscopic origin behind polarization-switchable electrochemistry primarily stems from enhanced surface adsorption and reduced energy barriers for reactions, as examined by nanoscale scanning electrochemical cell microscopy. Integrating a pair of L-Bi2O2Se microreactors consisting of upward or downward polarizations demonstrates overall water splitting in a full-cell configuration based on a bifunctional catalyst. The ability to modulate surface polarizations on a single catalyst via ferroelectric polarization switching offers a pathway for designing catalysts for water splitting.
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In contrast to the 2D organic-inorganic hybrid Ruddlesden-Popper halide perovskites (RPP), a new class of 2D all inorganic RPP (IRPP) has been recently proposed by substituting the organic spacers with an optimal inorganic alternative of cesium cations (Cs+ ). Nevertheless, the synthesis of high-membered 2D IRPPs (n > 1) has been a very challenging task because the Cs+ need to act as both spacers and A-site cations simultaneously. This work presents the successful synthesis of stable phase-pure high-membered 2D IRPPs of Csn+1 Pbn Br3n+1 nanosheets (NSs) with n = 3 and 4 by employing the strategy of using additional strong binding bidentate ligands. The structures of the 2D IRPPs (n = 3 and 4) NSs are confirmed by powder X-ray diffraction and high-resolution aberration-corrected scanning transmission electron microscope measurements. These 2D IRPPs NSs exhibit a strong quantum confinement effect with tunable absorption and emission in the visible light range by varying their n values, attributed to their inherent 2D quantum-well structure. The superior structural and optical stability of the phase-pure high-membered 2D IRPPs make them a promising candidate as photocatalysts in CO2 reduction reactions with outstanding photocatalytic performance and long-term stability.
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Organic-inorganic hybrid two-dimensional (2D) perovskites have recently attracted great attention in optical and optoelectronic applications due to their inherent natural quantum-well structure. We report the growth of high-quality millimeter-sized single crystals belonging to homologous two-dimensional (2D) hybrid organic-inorganic Ruddelsden-Popper perovskites (RPPs) of (BA)2(MA) n-1Pb nI3 n+1 ( n = 1, 2, and 3) by a slow evaporation at a constant-temperature (SECT) solution-growth strategy. The as-grown 2D hybrid perovskite single crystals exhibit excellent crystallinity, phase purity, and spectral uniformity. Low-threshold lasing behaviors with different emission wavelengths at room temperature have been observed from the homologous 2D hybrid RPP single crystals. Our result demonstrates that solution-growth homologous organic-inorganic hybrid 2D perovskite single crystals open up a new window as a promising candidate for optical gain media.
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The presence of the PbI2 passivation layers at perovskite crystal grains has been found to considerably affect the charge carrier transport behaviors and device performance of perovskite solar cells. This work demonstrates the application of a novel light-modulated scanning tunneling microscopy (LM-STM) technique to reveal the interfacial electronic structures at the heterointerfaces between CH3NH3PbI3 perovskite crystals and PbI2 passivation layers of individual perovskite grains under light illumination. Most importantly, this technique enabled the first observation of spatially resolved mapping images of photoinduced interfacial band bending of valence bands and conduction bands and the photogenerated electron and hole carriers at the heterointerfaces of perovskite crystal grains. By systematically exploring the interfacial electronic structures of individual perovskite grains, enhanced charge separation and reduced back recombination were observed when an optimal design of interfacial PbI2 passivation layers consisting of a thickness less than 20 nm at perovskite crystal grains was applied.
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Compostos de Cálcio , Chumbo/química , Imagem Óptica/métodos , Óxidos , Energia Solar , Titânio , Eletrônica , Ouro/química , Iluminação/métodos , Microscopia de Tunelamento/instrumentação , Propriedades de SuperfícieRESUMO
Using cross-sectional scanning tunneling microscope (XSTM) with samples cleaved in situ in an ultrahigh vacuum chamber, this study demonstrates the direct visualization of high-resolution interfacial band mapping images across the film thickness in an optimized bulk heterojunction polymer solar cell consisting of nanoscale phase segregated blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). We were able to achieve the direct observation of the interfacial band alignments at the donor (P3HT)-acceptor (PCBM) interfaces and at the interfaces between the photoactive P3HT:PCBM blends and the poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) anode modification layer with an atomic-scale spatial resolution. The unique advantage of using XSTM to characterize polymer/fullerene bulk heterojunction solar cells allows us to explore simultaneously the quantitative link between the vertical morphologies and their corresponding local electronic properties. This provides an atomic insight of interfacial band alignments between the two opposite electrodes, which will be crucial for improving the efficiencies of the charge generation, transport, and collection and the corresponding device performance of polymer solar cells.
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Recently, studies have revealed that human herpesvirus 4 (HHV-4), also known as the Epstein-Barr virus, might be associated with the severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Compared to SARS-CoV-2 infection alone, patients coinfected with SARS-CoV-2 and HHV-4 had higher risks of fever, inflammation, and even death, thus, confirming that HHV-4/SARS-CoV-2 coinfection in patients could benefit from clinical investigation. Although several intelligent devices can simultaneously discern multiple genes related to SARS-CoV-2, most operate via label-based detection, which restricts them from directly measuring the product. In this study, we developed a device that can replicate and detect SARS-CoV-2 and HHV-4 DNA. This device can conduct a duplex polymerase chain reaction (PCR) in a microfluidic channel and detect replicates in a non-labeled manner through a plasmonic-based sensor. Compared to traditional instruments, this device can reduce the required PCR time by 55% while yielding a similar amount of amplicon. Moreover, our device's limit of detection (LOD) reached 100 fg/mL, while prior non-labeled sensors for SARS-CoV-2 detection were in the range of ng/mL to pg/mL. Furthermore, the device can detect desired genes by extracting cells artificially infected with HHV-4/SARS-CoV-2. We expect that this device will be able to help verify HHV-4/SARS-CoV-2 coinfected patients and assist in the evaluation of practical treatment approaches.
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The ultrathin feature of two-dimensional (2D) transition metal dichalcogenides (TMDs) has brought special performance in electronic and optoelectronic fields. When vertical and lateral heterojunctions are made using different TMD combinations, the original properties of premier TMDs can be optimized. Especially for lateral heterojunctions, their sharp interface signifies a narrow space charge region, leading to a strong in-plane built-in electric field, which may contribute to high separation efficiency of photogenerated carriers, good rectification behavior, self-powered photoelectric device construction, etc. However, due to the poor controllability over the synthesis process, obtaining a clean and sharp interface of the lateral heterojunction is still a challenge. Herein, we propose a simple chemical vapor deposition (CVD) method, which can effectively separate the growth process of different TMDs, thus resulting in good regulation of the composition change at the junction region. By this method, MoS2-WS2 lateral heterojunctions with sharp interfaces have been obtained with good rectification characteristics, â¼105 on/off ratio, 1874% external quantum efficiency, and â¼120 ms photoresponse speed, exhibiting a better photoelectric performance than that of the lateral ones with graded junctions.
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1,3-Beta-d-glucan (ß-glucan) is a component of mold cell walls and is frequently found in fungi and house dust mites. The studies of ß-glucan are inconsistent, although it has been implicated in airway adverse responses. This study was carried out to determine whether airway hyperresponsiveness was seen 24 h after airway exposure to ß-glucan in guinea pigs. Two matching guinea pigs were exposed intratracheally to either ß-glucan or its vehicle. Twenty-four hours after intratracheal instillation, there was no difference between these two groups in the baseline of the total pulmonary resistance (R L), dynamic lung compliance (C dyn), arterial blood pressure, and heart rate. In contrast, the responses of R L to capsaicin injection were significantly increased in ß-glucan animals; capsaicin at the same dose of 3.2 µg/kg increased R L by 184% in vehicle animals and by 400% in ß-glucan animals. The effective dose 200% to capsaicin injection was lower in the ß-glucan animals. Furthermore, the increases in R L were partially reduced after transient lung hyperinflation to recruit the occluding airways; however, the R L induced by capsaicin injection after lung hyperinflation was significantly larger than the baseline in ß-glucan animals; also, the lung wet-to-dry ratio in capsaicin-injected animals was augmented in the ß-glucan group. Moreover, the airway hyperresponsiveness was accompanied by increases in neutrophils in the bronchoalveolar lavage fluid in the ß-glucan animals. Furthermore, the levels of substance P and the calcitonin gene-related peptide in the bronchoalveolar lavage fluid collected after capsaicin injection were increased in ß-glucan animals. We provide definitive evidence that ß-glucan can induce airway hyperresponsiveness in guinea pigs, and the neuropeptide releases play an important role in this airway hyperresponsiveness.
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This paper reports a novel micro/nanostructure co-hot embossing technique. Gold-capped nanostructures were used as localized surface plasmon resonance (SPR) sensors and were integrated into a microfluidic channel. The advantage of the co-hot embossing technique is that the SPR sensors do not need to be aligned with the microfluidic channel while bonding to it. The integrated SPR sensor and microfluidic channel were first characterized, and the sensitivity of the SPR sensor to the refractive index was found using different concentrations of glycerol solutions. The SPR sensor was also used to quantify latent membrane protein (LMP-1) when modifying anti-LMP-1 at the surface of the SPR sensor. Different concentrations of LMP-1 samples were used to build a calibration curve.
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Técnicas Biossensoriais , Ressonância de Plasmônio de Superfície , Técnicas Biossensoriais/métodos , Ouro/química , Dispositivos Lab-On-A-Chip , Proteínas de Membrana , Ressonância de Plasmônio de Superfície/métodosRESUMO
Various types of 2D organic-inorganic perovskite solar cells have been developed and investigated due to better electron transport behavior and environmental stability. Controlling the formation of phases in the 2D perovskite films has been considered to play an important role in influencing the stability of perovskite materials and their performance in optoelectronic applications. In this work, Lewis base urea was used as an effective additive for the formation of 2D Ruddlesden-Popper (RP) perovskite (BA)2(MA)n-1PbnI3n+1 thin film with mixed phases (n = 2~4). The detailed structural morphology of the 2D perovskite thin film was investigated by in situ X-ray diffraction (XRD), grazing-incidence small-angle X-ray scattering (GISAXS) and photoluminescence mapping. The results indicated that the urea additive could facilitate the formation of 2D RP perovskite thin film with larger grain size and high crystallinity. The 2D RP perovskite thin films for solar cells exhibited a power conversion efficiency (PCE) of 7.9% under AM 1.5G illumination at 100 mW/cm2.
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In this study, we investigated the interplay of three-dimensional morphologies and the photocarrier dynamics of polymer/inorganic nanocrystal hybrid photoactive layers consisting of TiO(2) nanoparticles and nanorods. Electron tomography based on scanning transmission electron microscopy using high-angle annular dark-field imaging was performed to analyze the morphological organization of TiO(2) nanocrystals in poly(3-hexylthiophene) (P3HT) in optimal solar cell devices. The Three-dimensional (3D) morphologies of these hybrid films were correlated with the photocarrier dynamics of charge separation, transport, and recombination, which were comprehensively probed by various transient techniques. Visualization of these 3D bulk heterojunction morphologies clearly reveals that elongated and anisotropic TiO(2) nanorods in P3HT not only can significantly reduce the probability of the interparticle hopping transport of electrons by providing better connectivity with respect to the TiO(2) nanoparticles, but also tend to form a large-scale donor-acceptor phase-separated morphology, which was found to enhance hole transport. The results support the establishment of a favorable morphology for polymer/inorganic hybrid solar cells due to the presence of the dimensionality of TiO(2) nanocrystals as a result of more effective mobile carrier generation and more efficient and balanced transport of carriers.
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Fontes de Energia Elétrica , Energia Solar , Tiofenos/química , Titânio/química , Nanoestruturas/química , Tamanho da Partícula , Propriedades de SuperfícieRESUMO
Perovskite α-CsPbI3 nanocrystals (NCs) with a high fluorescence quantum yield (QY) typically undergo a rapid phase transformation to a low-QY δ-CsPbI3 phase, thus limiting their optoelectronic applications. In this study, organic molecule hexamethyldisilathiane (HMS) is used as a unique surfactant to greatly enhance the stability of the cubic phase of CsPbI3 NCs (HMS-CsPbI3) under ambient conditions. The reaction kinetics of the phase transformation of CsPbI3 NCs are systemically investigated through in situ photoluminescence (PL), X-ray diffraction, and transmission electron microscope (TEM) measurements under moisture. The activation energy of HMS-CsPbI3 NCs is found to be 14 times larger than that of CsPbI3 NCs capped by olyelamine (OLA-CsPbI3 NCs). According to density functional theory calculations, the bonding between HMS and CsPbI3 NCs is stronger than that between OLA and CsPbI3 NCs, preventing the subsequent phase transformation. Our study presents a clear pathway for achieving highly stable CsPbI3 NCs for future applications.
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This work presents polymer photovoltaic devices based on poly(3-hexylthiophene) (P3HT) and TiO2 nanorod hybrid bulk heterojunctions. Interface modification of a TiO2 nanorod surface is conducted to yield a very promising device performance of 2.20% with a short circuit current density (J(sc)) of 4.33 mA/cm2, an open circuit voltage (V(oc)) of 0.78 V, and a fill factor (FF) of 0.65 under simulated A.M. 1.5 illumination (100 mW/cm2). The suppression of recombination at P3HT/TiO2 nanorod interfaces by the attachment of effective ligand molecules substantially improves device performance. The correlation between surface photovoltage and hybrid morphology is revealed by scanning Kelvin probe microscopy. The proposed method provides a new route for fabricating low-cost, environmentally friendly polymer/inorganic hybrid bulk heterojunction photovoltaic devices.
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A hollow nanostructure is attractive and important in different fields of applications, for instance, solar cells, sensors, supercapacitors, electronics, and biomedical, due to their unique structure, large available interior space, low bulk density, and stable physicochemical properties. Hence, the need to prepare hollow nanotubes is more important. In this present study, we have prepared CuCrO2 hollow nanotubes by simple approach. The CuCrO2 hollow nanotubes were prepared by applying electrospun Al2O3 fibers as a template for the first time. Copper chromium ions were dip-coated on the surface of electrospun-derived Al2O3 fibers and annealed at 600 °C in vacuum to form Al2O3-CuCrO2 core-shell nanofibers. The CuCrO2 hollow nanotubes were obtained by removing Al2O3 cores by sulfuric acid wet etching while preserving the rest of original structures. The structures of the CuCrO2-coated Al2O3 core-shell nanofibers and CuCrO2 hollow nanotubes were identified side-by-side by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The CuCrO2 hollow nanotubes may find applications in electrochemistry, catalysis, and biomedical application. This hollow nanotube preparation method could be extended to the preparation of other hollow nanotubes, fibers, and spheres.
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The inherent instability of UV-induced degradation in TiO2-based perovskite solar cells was largely improved by replacing the anatase-phase compact TiO2 layer with an atomic sheet transport layer (ASTL) of two-dimensional (2D) Ti1-δO2. The vital role of microscopic carrier dynamics that govern the UV stability of perovskite solar cells was comprehensively examined in this work by performing time-resolved pump-probe spectroscopy. In conventional perovskite solar cells, the presence of a UV-active oxygen vacancy in compact TiO2 prohibits current generation by heavily trapping electrons after UV degradation. Conversely, the dominant vacancy type in the 2D Ti1-δO2 ASTL is a titanium vacancy, which is a shallow acceptor and is not UV-sensitive. Therefore, it significantly suppresses carrier recombination and extends UV stability in perovskite solar cells with a 2D Ti1-δO2 ASTL. Other carrier dynamics, such as electron diffusion, electron injection, and hot hole transfer processes, were found to be less affected by UV irradiation. Quantitative pump-probe data clearly show a correlation between the carrier dynamics and UV aging of perovskite solar cells, thus providing a profound insight into the factors driving UV-induced degradation in perovskite solar cells and the origin of its performance.
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In this study, a photoresist template with well-defined contact hole array was fabricated, to which radio frequency magnetron sputtering process was then applied to deposit an alloyed Zr55Cu30Al10Ni5 target, and finally resulted in ordered metallic glass nanotube (MGNT) arrays after removal of the photoresist template. The thickness of the MGNT walls increased from 98 to 126nm upon increasing the deposition time from 225 to 675s. The wall thickness of the MGNT arrays also increased while the dimensions of MGNT reduced under the same deposition condition. The MGNT could be filled with biomacromolecules to change the effective refractive index. The air fraction of the medium layer were evaluated through static water contact angle measurements and, thereby, the effective refractive indices the transverse magnetic (TM) and transverse electric (TE) polarized modes were calculated. A standard biotin-streptavidin affinity model was tested using the MGNT arrays and the fundamental response of the system was investigated. Results show that filling the MGNT with streptavidin altered the effective refractive index of the layer, the angle of reflectance and color changes identified by an L*a*b* color space and color circle on an a*b* chromaticity diagram. The limit of detection (LOD) of the MGNT arrays for detection of streptavidin was estimated as 25nM, with a detection time of 10min. Thus, the MGNT arrays may be used as a versatile platform for high-sensitive label-free optical biosensing.
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Técnicas Biossensoriais/instrumentação , Vidro/química , Metais/química , Análise em Microsséries/instrumentação , Nanotubos/química , Técnicas Biossensoriais/métodos , Biotina/química , Desenho de Equipamento , Limite de Detecção , Análise em Microsséries/métodos , Nanotecnologia , Nanotubos/ultraestrutura , Refratometria , Silício/química , Estreptavidina/análiseRESUMO
We have demonstrated two novel donor-acceptor-donor (D-A-D) hole-transport material (HTM) with spiro[fluorene-9,9'-phenanthren-10'-one] as the core structure, which can be synthesized through a low-cost process in high yield. Compared to the incorporation of the conventional HTM of commonly used 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), the synthesis process is greatly simplified for the presented D-A-D materials, including a minimum number of purification processes. This results in an increased production yield (>55 %) and suppressed production cost (<30â $ g-1 ), in addition to high power conversion efficiency (PCE) in perovskite solar cells (PSCs). The PCE of a PSC using our D-A-D HTM reaches 16.06 %, similar to that of Spiro-OMeTAD (16.08 %), which is attributed to comparable hole mobility and charge-transfer efficiency. D-A-D HTMs also provide better moisture resistivity to prolong the lifetime of PSCs under ambient conditions relative to their Spiro-OMeTAD counterparts. The proposed new type of D-A-D HTM has shown promising performance as an alternative HTM for PSCs and can be synthesized with high production throughput.
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We have identified an often observed yet unresolved intermediate structure in a popular processing with dimethylformamide solutions of lead chloride and methylammonium iodide for perovskite solar cells. With subsecond time-resolved grazing-incidence X-ray scattering and X-ray photoemission spectroscopy, supplemental with ab initio calculation, the resolved intermediate structure (CH3NH3)2PbI2Cl2·CH3NH3I features two-dimensional (2D) perovskite bilayers of zigzagged lead-halide octahedra and sandwiched CH3NH3I layers. Such intermediate structure reveals a hidden correlation between the intermediate phase and the composition of the processing solution. Most importantly, the 2D perovskite lattice of the intermediate phase is largely crystallographically aligned with the [110] planes of the three-dimensional perovskite cubic phase; consequently, with sublimation of Cl ions from the organo-lead octahedral terminal corners in prolonged annealing, the zigzagged octahedral layers of the intermediate phase can merge with the intercalated methylammonium iodide layers for templated growth of perovskite crystals. Regulated by annealing temperature and the activation energies of the intermediate and perovskite, deduced from analysis of temperature-dependent structural kinetics, the intermediate phase is found to selectively mature first and then melt along the layering direction for epitaxial conversion into perovskite crystals. The unveiled epitaxial conversion under growth kinetics controls might be general for solution-processed and intermediate-templated perovskite formation.
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The design of active and stable semiconducting composites with enhanced photoresponse from visible light to near infrared (NIR) is a key to improve solar energy harvesting for photolysis of water in photoelectrochemical cell. In this study, we prepared earth abundant semiconducting composites consisting of iron pyrite and Titanium oxide as a photoanode (FeS2/TiO2 photoanode) for photoelectrochemical applications. The detailed structure and atomic compositions of FeS2/TiO2 photoanode was characterized by high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), inductively coupled plasma with atomic emission spectroscopy (ICPAES) and Raman spectroscopy. Through the proper sulfurization treatment, the FeS2/TiO2 photoanode exhibited high photoresponse from visible light extended to near infrared range (900 nm) as well as stable durability test for 4 hours. We found that the critical factors to enhance the photoresponse are on the elimination of surface defect of FeS2 and on the enhancement of interface charge transfer between FeS2 and TiO2. Our overall results open a route for the design of sulfur-based binary compounds for photoelectrochemical applications.