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1.
Hepatology ; 2024 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-38385945

RESUMEN

BACKGROUND AND AIMS: Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses a broad and continuous spectrum of liver diseases ranging from fatty liver to steatohepatitis. The intricate interactions of genetic, epigenetic, and environmental factors in the development and progression of MASLD remain elusive. Here, we aimed to achieve an integrative understanding of the genomic and transcriptomic alterations throughout the progression of MASLD. APPROACH AND RESULTS: RNA-Seq profiling (n = 146) and whole-exome sequencing (n = 132) of MASLD liver tissue samples identified 3 transcriptomic subtypes (G1-G3) of MASLD, which were characterized by stepwise pathological and molecular progression of the disease. Macrophage-driven inflammatory activities were identified as a key feature for differentiating these subtypes. This subtype-discriminating macrophage interplay was significantly associated with both the expression and genetic variation of the dsDNA sensor IFI16 (rs6940, A>T, T779S), establishing it as a fundamental molecular factor in MASLD progression. The in vitro dsDNA-IFI16 binding experiments and structural modeling revealed that the IFI16 variant exhibited increased stability and stronger dsDNA binding affinity compared to the wild-type. Further downstream investigation suggested that the IFI16 variant exacerbated DNA sensing-mediated inflammatory signals through mitochondrial dysfunction-related signaling of the IFI16-PYCARD-CASP1 pathway. CONCLUSIONS: This study unveils a comprehensive understanding of MASLD progression through transcriptomic classification, highlighting the crucial roles of IFI16 variants. Targeting the IFI16-PYCARD-CASP1 pathway may pave the way for the development of novel diagnostics and therapeutics for MASLD.

2.
Nanomaterials (Basel) ; 13(22)2023 Nov 16.
Artículo en Inglés | MEDLINE | ID: mdl-37999315

RESUMEN

Activated carbon (AC) compounds derived from biomass precursors have garnered significant attention as electrode materials in electric double-layer capacitors (EDLCs) due to their ready availability, cost-effectiveness, and potential for mass production. However, the accessibility of their active sites in electrochemistry has not been investigated in detail. In this study, we synthesized two novel macro/micro-porous carbon structures prepared from a chitosan precursor using an acid/potassium hydroxide activation process and then examined the relationship between their textural characteristics and capacitance as EDLCs. The material characterizations showed that the ACs, prepared through different activation processes, differed in porosity, with distinctive variations in particle shape. The sample activated at 800 °C (Act-chitosan) was characterized by plate-shaped particles, a specific surface area of 4128 m2/g, and a pore volume of 1.87 cm3/g. Assessment of the electrochemical characteristics of Act-chitosan showed its remarkable capacitance of 183.5 F/g at a scan rate of 5 mV/s, and it maintained exceptional cyclic stability even after 10,000 cycles. The improved electrochemical performance of both chitosan-derived carbon structures could thus be attributed to their large, well-developed active sites within pores < 2 nm, despite the fact that interconnected macro-porous particles can enhance ion accessibility on electrodes. Our findings provide a basis for the fabrication of biomass-based materials with promising applications in electrochemical energy storage systems.

3.
Nanomaterials (Basel) ; 13(18)2023 Sep 19.
Artículo en Inglés | MEDLINE | ID: mdl-37764622

RESUMEN

Boron nitride nanotubes (BNNTs) were purified without the use of a dispersant by controlling the surface tension and steric repulsion of solvent molecules. This method effectively enhanced the difference in solubilities of impurities and BNNTs. The purification process involved optimizing the alkyl-chains of alcohol solvents and adjusting the concentration of alcohol solvent in water to regulate surface tension and steric repulsion. Among the solvents tested, a 70 wt% t-butylalcohol in water mixture exhibited the highest selective isolation of BNNTs from impurities based on differences in solubilities. This favorable outcome was attributed to the surface tension matching with BNNTs, steric repulsion from bulky alkyl chain structures, and differences in interfacial energy between BNNT-liquid and impurity-liquid interfaces. Through this optimized purification process, impurities were removed to an extent of up to 93.3%. Additionally, the purified BNNTs exhibited a distinct liquid crystal phase, which was not observed in the unpurified BNNTs.

4.
Sci Adv ; 8(23): eabn2611, 2022 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-35687678

RESUMEN

In sprouting angiogenesis, the precise mechanisms underlying how intracellular vascular endothelial growth factor receptor 2 (VEGFR2) signaling is higher in one endothelial cell (EC) compared with its neighbor and acquires the tip EC phenotype under a similar external cue are elusive. Here, we show that Merlin, encoded by the neurofibromatosis type 2 (NF2) gene, suppresses VEGFR2 internalization depending on VE-cadherin density and inhibits tip EC induction. Accordingly, endothelial Nf2 depletion promotes tip EC induction with excessive filopodia by enhancing VEGFR2 internalization in both the growing and matured vessels. Mechanistically, Merlin binds to the VEGFR2-VE-cadherin complex at cell-cell junctions and reduces VEGFR2 internalization-induced downstream signaling during tip EC induction. As a consequence, nonfunctional excessive sprouting occurs during tumor angiogenesis in EC-specific Nf2-deleted mice, leading to delayed tumor growth. Together, Nf2/Merlin is a crucial molecular gatekeeper for tip EC induction, capillary integrity, and proper tumor angiogenesis by suppressing VEGFR2 internalization.

5.
Nat Commun ; 12(1): 4405, 2021 07 20.
Artículo en Inglés | MEDLINE | ID: mdl-34285232

RESUMEN

Stimulator of interferon genes (STING) promotes anti-tumour immunity by linking innate and adaptive immunity, but it remains unclear how intratumoural treatment with STING agonists yields anti-tumour effects. Here we demonstrate that intratumoural injection of the STING agonist cGAMP induces strong, rapid, and selective apoptosis of tumour endothelial cells (ECs) in implanted LLC tumour, melanoma and breast tumour, but not in spontaneous breast cancer and melanoma. In both implanted and spontaneous tumours, cGAMP greatly increases TNFα from tumour-associated myeloid cells. However, compared to spontaneous tumour ECs, implanted tumour ECs are more vulnerable to TNFα-TNFR1 signalling-mediated apoptosis, which promotes effective anti-tumour activity. The spontaneous tumour's refractoriness to cGAMP is abolished by co-treatment with AKT 1/2 inhibitor (AKTi). Combined treatment with cGAMP and AKTi induces extensive tumour EC apoptosis, leading to extensive tumour apoptosis and marked growth suppression of the spontaneous tumour. These findings propose an advanced avenue for treating primary tumours that are refractory to single STING agonist therapy.


Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Proteínas de la Membrana/agonistas , Neoplasias/tratamiento farmacológico , Nucleótidos Cíclicos/farmacología , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Animales , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Apoptosis/efectos de los fármacos , Apoptosis/inmunología , Línea Celular Tumoral/trasplante , Modelos Animales de Enfermedad , Resistencia a Antineoplásicos/efectos de los fármacos , Femenino , Técnicas de Silenciamiento del Gen , Células Endoteliales de la Vena Umbilical Humana , Humanos , Inmunidad Innata/efectos de los fármacos , Inyecciones Intralesiones , Masculino , Proteínas de la Membrana/antagonistas & inhibidores , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones , Ratones Transgénicos , Neoplasias/irrigación sanguínea , Neoplasias/inmunología , Neoplasias/patología , Nucleótidos Cíclicos/uso terapéutico , Fosforilación/efectos de los fármacos , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptores Tipo I de Factores de Necrosis Tumoral/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/inmunología , Microambiente Tumoral/efectos de los fármacos , Microambiente Tumoral/inmunología , Factor de Necrosis Tumoral alfa/metabolismo
6.
Nanomaterials (Basel) ; 11(6)2021 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-34205908

RESUMEN

The design of photoactive materials and interface engineering between organic/inorganic layers play a critical role in achieving enhanced performance in energy-harvesting devices. Two-dimensional transitional dichalcogenides (TMDs) with excellent optical and electronic properties are promising candidates in this regard. In this study, we demonstrate the fabrication of size-controlled MoS2 quantum dots (QDs) and present fundamental studies of their optical properties and their application as a hole-transport layer (HTL) in organic solar cells (OSCs). Optical and structural analyses reveal that the as-prepared MoS2 QDs show a fluorescence mechanism with respect to the quantum confinement effect and intrinsic/extrinsic states. Moreover, when incorporated into a photovoltaic device, the MoS2 QDs exhibit a significantly enhanced performance (5/10-nanometer QDs: 8.30%/7.80% for PTB7 and 10.40%/10.17% for PTB7-Th, respectively) compared to those of the reference device (7.24% for PTB7 and 9.49% for PTB7-Th). We confirm that the MoS2 QDs clearly offer enhanced transport characteristics ascribed to higher hole-mobility and smoother root mean square (Rq) as a hole-extraction material. This approach can enable significant advances and facilitate a new avenue for realizing high-performance optoelectronic devices.

7.
J Clin Invest ; 131(13)2021 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-34003804

RESUMEN

The upper respiratory tract is compromised in the early period of COVID-19, but SARS-CoV-2 tropism at the cellular level is not fully defined. Unlike recent single-cell RNA-Seq analyses indicating uniformly low mRNA expression of SARS-CoV-2 entry-related host molecules in all nasal epithelial cells, we show that the protein levels are relatively high and that their localizations are restricted to the apical side of multiciliated epithelial cells. In addition, we provide evidence in patients with COVID-19 that SARS-CoV-2 is massively detected and replicated within the multiciliated cells. We observed these findings during the early stage of COVID-19, when infected ciliated cells were rapidly replaced by differentiating precursor cells. Moreover, our analyses revealed that SARS-CoV-2 cellular tropism was restricted to the nasal ciliated versus oral squamous epithelium. These results imply that targeting ciliated cells of the nasal epithelium during the early stage of COVID-19 could be an ideal strategy to prevent SARS-CoV-2 propagation.


Asunto(s)
COVID-19/virología , Interacciones Microbiota-Huesped , Mucosa Nasal/virología , SARS-CoV-2 , Enzima Convertidora de Angiotensina 2/genética , Enzima Convertidora de Angiotensina 2/metabolismo , Animales , COVID-19/patología , COVID-19/fisiopatología , Diferenciación Celular , Cilios/patología , Cilios/fisiología , Cilios/virología , Furina/genética , Furina/metabolismo , Interacciones Microbiota-Huesped/genética , Interacciones Microbiota-Huesped/fisiología , Humanos , Macaca , Modelos Biológicos , Mucosa Nasal/patología , Mucosa Nasal/fisiopatología , Pandemias , ARN Mensajero/genética , ARN Mensajero/metabolismo , RNA-Seq , SARS-CoV-2/genética , SARS-CoV-2/patogenicidad , SARS-CoV-2/fisiología , Serina Endopeptidasas/genética , Serina Endopeptidasas/metabolismo , Células Madre/patología , Células Madre/virología , Internalización del Virus , Replicación Viral/genética , Replicación Viral/fisiología
8.
Cytometry A ; 97(5): 496-503, 2020 05.
Artículo en Inglés | MEDLINE | ID: mdl-31758756

RESUMEN

Over the last two decades, numerous advances in our understanding of bone cell biology and bone mineral homeostasis have been achieved. As a dynamic connective and supportive tissue, bone is constantly sensing and responding to both external mechanical forces and internal systemic and local signals. A variety of intravital imaging approaches have been investigated to identify molecular and cellular processes and to decipher signaling pathways involved in the cellular communication between different types of bone cells that form bone multicellular units. Furthermore, bone multicellular units interact with cells of the immune and hematopoietic system to maintain bone homeostasis. Bone-forming osteoblasts and bone-degrading osteoclasts are situated on the endosteal surface of bone influencing the dynamic remodeling and the regeneration of bone tissue. Osteocytes are found at very unique locations in the bone, closely surrounded by bone matrix, forming a cellular network through their interconnected dendritic processes. Bone marrow cells fill the numerous large cavities inside the bones with various blood cell lineages arising from hematopoietic stem and progenitor cells. A highly complex and interconnected network of arterial vessels and sinusoidal capillaries span through the bone marrow spaces forming an interface between the blood circulation and the bone marrow which allows cell trafficking between both compartments. Live imaging of animals using multiphoton microscopy represents a powerful approach to address the cellular behaviors of bone and bone marrow cells over time and space in their natural tissue microenvironment. The in vivo environment is crucial, because the dynamic behavior of cells is critically influenced by many tissue factors including extracellular components, cytokine and growth factor gradients, and fluid forces, such as blood flow. The review article focuses upon recent advances in multiphoton imaging technologies as well as novel experimental approaches in the understanding of the dynamic molecular and cellular mechanisms underlying bone tissue homeostasis, remodeling, and regeneration under physiological and pathological conditions. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.


Asunto(s)
Médula Ósea , Microscopía de Fluorescencia por Excitación Multifotónica , Animales , Médula Ósea/diagnóstico por imagen , Células de la Médula Ósea , Huesos/diagnóstico por imagen , Osteoclastos
9.
ACS Appl Mater Interfaces ; 10(43): 37507-37516, 2018 Oct 31.
Artículo en Inglés | MEDLINE | ID: mdl-30270621

RESUMEN

Graphene aerogel (GA) has shown great promise as reinforcement of polymeric composites with exceptional electrical and mechanical characteristics. Although there has been significant progress in controlling the structure of GAs, no studies have appeared on the enhanced properties of GAs by employing high-quality precursor graphene flakes (GFs). However, the assembly of high-quality GFs is particularly challenging due to their highly hydrophobic and agglomerative nature in aqueous media, and of the few methods available to synthesize high-quality GFs, most produce flakes with very small lateral sizes. Herein, we report the fabrication of highly crystalline GAs using large nonoxidized graphene flakes (NOGFs) prepared by a novel graphite intercalation compound-based method. Bidirectional freeze casting is utilized for aligning NOGFs in two orthogonal directions, vertically and laterally, where the NOGF walls individually function as effective conductive pathways. The as-prepared nonoxidized graphene aerogel (NOGA) exhibits a defect concentration as low as 1.4% of impurity oxygen with an excellent electrical conductivity of 202.9 S/m at a low density of 5.7 mg/cm3. The corresponding NOGA-epoxy composite shows a remarkable electrical conductivity of 122.6 S/m and a fracture toughness of 1.74 MPa·m1/2 at a low filler content of 0.45 vol %.

10.
Nano Lett ; 18(9): 5646-5651, 2018 09 12.
Artículo en Inglés | MEDLINE | ID: mdl-30114368

RESUMEN

Two-dimensional (2D) transitional metal oxides (TMOs) are an attractive class of materials due to the combined advantages of high active surface area, enhanced electrochemical properties, and stability. Among the 2D TMOs, 2D tungsten oxide (WO3) nanosheets possess great potential in electrochemical applications, particularly in electrochromic (EC) devices. However, feasible production of 2D WO3 nanosheets is challenging due to the innate 3D crystallographic structure of WO3. Here we report a novel solution-phase synthesis of 2D WO3 nanosheets through simple oxidation from 2D tungsten disulfide (WS2) nanosheets exfoliated from bulk WS2 powder. The complete conversion from WS2 into WO3 was confirmed through crystallographic and elemental analyses, followed by validation of the 2D WO3 nanosheets applied in the EC device. The EC device showed color modulation of 62.57% at 700 nm wavelength, which is 3.43 times higher than the value of the conventional device using bulk WO3 powder, while also showing enhancement of ∼46.62% and ∼62.71% in switching response-time (coloration and bleaching). The mechanism of enhancement was rationalized through comparative analysis based on the thickness of the WO3 components. In the future, 2D WO3 nanosheets could also be used for other promising applications such as sensors, catalysis, thermoelectric, and energy conversion.

11.
Adv Mater ; 30(38): e1802951, 2018 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-30085381

RESUMEN

Emerging graphene quantum dots (GQDs) have received much attention for use as next-generation light-emitting diodes. However, in the solid-state, π-interaction-induced aggregation-caused photoluminescence (PL) quenching (ACQ) in GQDs makes it challenging to realize high-performance devices. Herein, GQDs incorporated with boron oxynitride (GQD@BNO) are prepared from a mixture of GQDs, boric acid, and urea in water via one-step microwave heating. Due to the effective dispersion in the BNO matrix, ACQ is significantly suppressed, resulting in high PL quantum yields (PL-QYs) of up to 36.4%, eightfold higher than that of pristine GQD in water. The PL-QY enhancement results from an increase in the spontaneous emission rate of GQDs due to the surrounding BNO matrix, which provides a high-refractive-index material and fluorescence energy transfer from the larger-gap BNO donor to the smaller-gap GQD acceptor. A high solid-state PL-QY makes the GQD@BNO an ideal active material for use in AC powder electroluminescent (ACPEL) devices, with the luminance of the first working GQD-based ACPEL device exceeding 283 cd m-2 . This successful demonstration shows promise for the use of GQDs in the field of low-cost, ecofriendly electroluminescent devices.

12.
ACS Appl Mater Interfaces ; 10(21): 17957-17962, 2018 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-29741082

RESUMEN

In recent years, two-dimensional black phosphorus (BP) has seen a surge of research because of its unique optical, electronic, and chemical properties. BP has also received interest as a potential thermoelectric material because of its high Seebeck coefficient and excellent charge mobility, but further development is limited by the high cost and poor scalability of traditional BP synthesis techniques. In this work, high-quality BP is synthesized using a low-cost method and utilized in a PEDOT:PSS film to create the first ever BP composite thermoelectric material. The thermoelectric properties are found to be greatly enhanced after the BP addition, with the power factor of the film, with 2 wt % BP (36.2 µW m-1 K-2) representing a 109% improvement over the pure PEDOT:PSS film (17.3 µW m-1 K-2). A simultaneous increase of mobility and decrease of the carrier concentration is found to occur with the increasing BP wt %, which allows for both Seebeck coefficient and electrical conductivity to be increased. These results show the potential of this low-cost BP for use in energy devices.

13.
Nat Commun ; 8(1): 726, 2017 09 28.
Artículo en Inglés | MEDLINE | ID: mdl-28959057

RESUMEN

Mediating the expansion of vascular beds in many physiological and pathological settings, angiogenesis requires dynamic changes in endothelial cell behavior. However, the molecular mechanisms governing endothelial cell activity during different phases of vascular growth, remodeling, maturation, and quiescence remain elusive. Here, we characterize dynamic gene expression changes during postnatal development and identify critical angiogenic factors in mouse retinal endothelial cells. Using actively translating transcriptome analysis and in silico computational analyses, we determine candidate regulators controlling endothelial cell behavior at different developmental stages. We further show that one of the identified candidates, the transcription factor MafB, controls endothelial sprouting in vitro and in vivo, and perform an integrative analysis of RNA-Seq and ChIP-Seq data to define putative direct MafB targets, which are activated or repressed by the transcriptional regulator. Together, our results identify novel cell-autonomous regulatory mechanisms controlling sprouting angiogenesis.Angiogenesis is a complex process that requires coordinated changes in endothelial cell behavior. Here the authors use Ribo-tag and RNA-Seq to determine temporal profiles of transcriptional activity during postnatal retinal angiogenesis, identifying transcriptional regulators of the process.


Asunto(s)
Células Endoteliales , Regulación del Desarrollo de la Expresión Génica , Redes Reguladoras de Genes , Factor de Transcripción MafB/genética , Neovascularización Fisiológica/genética , Vasos Retinianos/crecimiento & desarrollo , Animales , Regulación de la Expresión Génica , Técnicas In Vitro , Ratones , Ratones Noqueados , Retina/crecimiento & desarrollo
14.
ACS Appl Mater Interfaces ; 9(20): 17369-17378, 2017 May 24.
Artículo en Inglés | MEDLINE | ID: mdl-28452466

RESUMEN

The demand for wearable strain gauges that can detect dynamic human motions is growing in the area of healthcare technology. However, the realization of efficient sensing materials for effective detection of human motions in daily life is technically challenging due to the absence of the optimally designed electrode. Here, we propose a novel concept for overcoming the intrinsic limits of conventional strain sensors based on planar electrodes by developing highly periodic and three-dimensional (3D) bicontinuous nanoporous electrodes. We create a 3D bicontinuous nanoporous electrode by constructing conductive percolation networks along the surface of porous 3D nanostructured poly(dimethylsiloxane) with single-walled carbon nanotubes. The 3D structural platform allows fabrication of a strain sensor with robust properties such as a gauge factor of up to 134 at a tensile strain of 40%, a widened detection range of up to 160%, and a cyclic property of over 1000 cycles. Collectively, this study provides new design opportunities for a highly efficient sensing system that finely captures human motions, including phonations and joint movements.

15.
J Nanosci Nanotechnol ; 16(5): 5013-6, 2016 May.
Artículo en Inglés | MEDLINE | ID: mdl-27483862

RESUMEN

State-of-the-art optical trapping designs are required to enhance the light trapping capabilities of tandem thin film silicon solar cells. The wet etch process is used to texture the glass surface by dipping in diluted acidic solutions such as HNO3 (nitric acid) and HF (hydrofluoric acid). For vapor texturing, the vapor was generated by adding silicon to HF:HNO3 acidic solution. The anisotropic etching of vapor textured wafers resulted in an etching depth of about 2.78 µm with reduced reflectance of 5%. We achieved a high haze value of 74.6% at a 540 nm wavelength by increasing the etching time and HF concentration.

16.
Small ; 12(8): 994-9, 2016 Feb 24.
Artículo en Inglés | MEDLINE | ID: mdl-26728175

RESUMEN

PEG-functionalized graphene quantum dots (GQDs) are shown to promote fast exciton dissociation in organic solar cells. Short-chain PEG promotes the most favorable interaction with other organic layers, and the overall efficiency is improved by 36% when compared to the reference devices. The mechanism of enhancement is shown to be increased absorption due to fewer charges remain-ing in the bound state.

17.
J Nanosci Nanotechnol ; 15(6): 4398-402, 2015 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-26369055

RESUMEN

Recently, the importance of solar cell research has emerged due to emerging social issues such as environmental pollution problems and rising oil prices. Accordingly, each company is studying to make solar cell of high efficiency. In order to fabricate high-efficiency solar cells, the two major techniques have to be applied on the rear. One is complete passivation of the surface using a thermal oxide and the other one is the part that comes in contact with the electrode doped partially LBSF (Local BSF) formation. In this paper, LBC technology which is usually applied for high efficiency crystalline silicon solar cell, applied to mass productive solar cell to achieve high open circuit voltage and short circuit current with low surface recombination from rear side. Thermal SiO2/SiN(x) double layer which has superior thermal stability is formed on rear surface as passivation layer, then 1% of the whole rear surface area is locally contacted with aluminum. Finally, the cell has been fired at high temperature and the cell process has complete. The fabricated LBC cells conversion efficiency was 18.0% with 625 mV of open-circuit voltage (V(oc)), 37.58 mA/cm2 of current density (J(sc)), 76.3% of fillfactor (FF) at 5% contact coverage, respectively.

18.
Small ; 11(26): 3124-9, 2015 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-25727909

RESUMEN

Graphene flakes (GFs) with minimized defects and oxidation ratios are incorporated into polyethylene (PE) to enhance the moisture barrier. GFs produced involving solvothermal intercalation show extremely low oxidation rates (3.17%), and are noncovalently functionalized in situ, inducing strong hydrophobicity. The fabricated composite possesses the best moisture barrier performance reported for a polymer-graphene composite.

19.
J Nanosci Nanotechnol ; 15(10): 7699-705, 2015 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-26726397

RESUMEN

High-efficiency Si solar cells have attracted great attention from researchers, scientists, photovoltaic (PV) industry engineers for the past few decades. With thin wafers, surface passivation becomes necessary to increase the solar cells efficiency by overcoming several induced effects due to associated crystal defects and impurities of c-Si. This paper discusses suitable passivation schemes and optimization techniques to achieve high efficiency at low cost. SiNx film was optimized with higher transmittance and reduced recombination for using as an effective antireflection and passivation layer to attain higher solar cell efficiencies. The higher band gap increased the transmittance with reduced defect states that persisted at 1.68 and 1.80 eV in SiNx films. The thermal stability of SiN (Si-rich)/SiN (N-rich) stacks was also studied. Si-rich SiN with a refractive index of 2.7 was used as a passivation layer and N-rich SiN with a refractive index of 2.1 was used for thermal stability. An implied Voc of 720 mV with a stable lifetime of 1.5 ms was obtained for the stack layer after firing. Si-N and Si-H bonding concentration was analyzed by FTIR for the correlation of thermally stable passivation mechanism. The passivation property of spin coated Al2O3 films was also investigated. An effective surface recombination velocity of 55 cm/s with a high density of negative fixed charges (Qf) on the order of 9 x 10(11) cm(-2) was detected in Al2O3 films.

20.
Nano Lett ; 14(8): 4306-13, 2014 Aug 13.
Artículo en Inglés | MEDLINE | ID: mdl-25014607

RESUMEN

The scalable preparation of graphene in control of its structure would significantly improve its commercial viability. Despite intense research in this area, the size control of defect-free graphene (df-G) without any trace of oxidation or structural damage remains a key challenge. Here, we propose a new scalable route for generating df-G with a controllable size of submicron to micron through sequential insertion of potassium and pyridine at low temperature. Structural and chemical analyses confirm that the df-G perfectly preserves the intrinsic properties of graphene. The Co3O4 (<50 nm) wrapped by ∼ 10.5 µm(2) df-G has unprecedented capacity, rate capability, and cycling stability with capacities as high as 1050 mAh g(-1) at 500 mA g(-1) and 900 mAh g(-1) at 1000 mA g(-1) even after 200 cycles, which suggests enticing potential for the use in high performance lithium ion batteries.

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