ABSTRACT
The performance of lead sulfide (PbS) quantum-dot-based up-conversion photodetectors is greatly limited owing to a large potential barrier at the interconnection layer between the photodetecting (PD) unit and light-emitting (LED) unit. Thus, very high driving voltage is required, rendering high energy consumption and poor working stability. By introducing azetidinium iodide (AzI) at the PD/LED interface, zero-barrier interconnection was achieved for the PbS-based infrared up-conversion photodetectors. The turn-on voltage under infrared illumination was greatly reduced to 1.2 V and a high photon-to-photon conversion efficiency (ηpp) of â¼3% was obtained at 3 V, showing a 10-fold enhancement compared to those previously reported devices. The mechanism for the regulation of interface energy level alignments was related to the self-assembly of the AzI dipole molecules, resulting from the van der Waals force between the S atoms in the ligands of PbS and the protonated H atoms around N atoms in AzI.
ABSTRACT
As potential low-cost alternatives of traditional bulk HgCdTe crystals, HgTe colloidal quantum dots (CQDs) synthesized through reactions between HgCl2 and trioctylphosphine-telluride in hot oleylamine have shown promising performances in mid-wave infrared photodetectors. Tetrapodic or tetrahedral HgTe CQDs have been obtained by tuning the reaction conditions such as temperature, reaction time, concentrations, and ratios of the two precursors. However, the principles governing the growth dynamics and the mechanism behind the transitions between tetrapodic and tetrahedral HgTe CQDs have not been sufficiently understood. In this work, synthesis of HgTe CQDs through bilateral injection is introduced to study the growth mechanism. It suggests that tetrahedral HgTe CQDs usually result from the breaks of tetrapodic HgTe CQDs after their legs grow thick enough. The fundamental factor determining whether the growth makes their legs longer or thicker is the effective concentration of the Te precursor during the growth, rather than temperature, Hg-rich environment, or reactivity of precursors. A chemical model is proposed to illustrate the principles governing the growth dynamics, which provides valuable guidelines for tuning the material properties of HgTe CQDs according to the needs of applications.
ABSTRACT
Low-toxicity InP-based quantum dots (QDs) exhibit potential for replacing Cd/Pb-containing QDs in the visible and near-infrared regions. Despite advancements, further improvement relies on synthesizing homogeneous InP QDs to achieve a high color purity. In a commonly employed two-step "seed-mediated" synthetic approach, we demonstrate the high sensitivity of InP seed sizes and size distribution to the quantities of trioctylphosphine (TOP) and tris(trimethylsilyl)phosphine [(TMS)3P], attributed to the process of "self-focusing of size distribution" and enhanced reactivity of In-oleate through coordination with TOP. During growth, the processes of size focusing and defocusing are modulated by the accumulation of oleic acid and TOP molecules, as well as the amount of (TMS)3P in the growth precursor, which may relate to the dissolution process of InP magic size clusters. Through precise control, the best valley/depth ratio of InP QDs was 0.52 at the first absorption peak at 571 nm, resulting in luminescence with a full width at half-maximum of 35 at 620 nm with an absolute photoluminescence quantum yield around 90% after heteroepitaxial growth with ZnSe and ZnS shells.
ABSTRACT
Correction for 'Elaborating the interplay between the detecting unit and emitting unit in infrared quantum dot up-conversion photodetectors' by Qiulei Xu et al., Nanoscale, 2023, 15, 8197-8203, https://doi.org/10.1039/D3NR01237A.
ABSTRACT
PbS quantum dot light-emitting diodes (QLEDs) emitting around 1550 nm promise important applications in optical communications. However, due to insufficient suppression of surface traps for large-size PbS quantum dots (QDs), their performance under large driving current density was not satisfactory. In this work, octanethiol surfactant was added into a PbS QD solution and adsorbed onto the dot surface. As a result, the surface traps and the continuous oxidation of the unprotected (100) facets in PbS QDs were greatly suppressed. Therefore, the PbS QDs with octanethiol doubled their photoluminescence efficiency and showed outstanding stability. The PbS-based QLEDs with benchmark device structure showed a breakthrough high radiance of 18.3 Wâ¯sr-1â¯m-2 with >2000 mA/cm2 driving current density. The efficient passivation of surface traps with octanethiol surfactant and the suppressed coupling between excitons and surface states under large working current were the main reasons for achieving the breakthrough high radiance.
ABSTRACT
The quantum dot up-conversion device combines an infrared photodetector (PD) and a visible quantum-dot light-emitting diode (QLED) to directly convert infrared targets to visible images. However, large efficiency loss is usually induced by the integration of the detecting unit and the emitting unit. One of the important reasons is the performances of the PD and QLED units restraining each other. We regulated the equilibrium between infrared absorption and visible emission by changing the thicknesses of infrared active layers in up-conversion devices. A good balance could be achieved between the absorption of 980 nm incident light and the out-coupling of the 634 nm emission when the active layer thickness is 140 nm, leading to the best performance of the up-conversion device. As more photogenerated carriers are produced with the increase of infrared illumination intensity, the external quantum efficiency (EQE) of the QLED unit in the up-conversion device remains little changed. This suggests the limited amount of photogenerated holes in the PD unit does not limit the EQE of the QLED unit. However, a PD unit with a high ratio of photogenerated holes trapped near the interconnection decreased the EQE in the QLED unit. This work provides new insights into the interplay between the PD and QLED units in up-conversion devices, which is crucial for their further improvements.
ABSTRACT
The development of in situ growth methods for the fabrication of high-quality perovskite single-crystal thin films (SCTFs) directly on hole-transport layers (HTLs) to boost the performance of optoelectronic devices is critically important. However, the fabrication of large-area high-quality SCTFs with thin thickness still remains a significant challenge due to the elusive growth mechanism of this process. In this work, the influence of three key factors on in situ growth of high-quality large-size MAPbBr3 SCTFs on HTLs is investigated. An optimal "sweet spot" is determined: low interface energy between the precursor solution and substrate, a slow heating rate, and a moderate precursor solution concentration. As a result, the as-obtained perovskite SCTFs with a thickness of 540 nm achieve a record area to thickness ratio of 1.94 × 104 mm, a record X-ray diffraction peak full width at half maximum of 0.017°, and an ultralong carrier lifetime of 1552 ns. These characteristics enable the as-obtained perovskite SCTFs to exhibit a record carrier mobility of 141 cm2 V-1 s-1 and good long-term structural stability over 360 days.
Subject(s)
Calcium Compounds , Oxides , Titanium , Calcium Compounds/chemistry , Oxides/chemistry , Titanium/chemistryABSTRACT
Large quantities of Triassic solid asphaltite were discovered in the Guangyuan area, northwest Sichuan. The asphaltite is formed in layers with a vertical thickness between 0.3 and 2.8 m and is stably distributed with intrusive contact with surrounding rocks. This study aims on the genesis and distribution of asphaltite through trace element, biomarker, and Re-Os isotope analyses. Trace element analysis shows the enrichment of V and Cr in the asphaltite, indicating that it is derived from relatively deep hydrocarbon sources. The carbon isotope and biomarker results suggest that the asphaltite originates from Cambrian paleo reservoir. The Re-Os isotope analysis determines a formation age of 220 ± 6 Ma, which corresponds to the late Triassic, indicating the cracking of paleo reservoirs in late Triassic. Therefore, the origin of asphaltite is epigenetic-reservoir asphaltite. The generation of oil from Cambrian source rocks began at the end of Silurian and ended after Caledonian orogeny. At the end of Permian, the fracture system was well developed due to the influence of the Hercynian movement, which provided favorable conditions for the migration of Cambrian oil. By the end of Triassic, hydrocarbons generated from Cambrian source rocks were mainly distributed in fractures and reservoirs, thus forming paleo oil reservoirs. Afterward, the paleo reservoirs were adjusted to the surface or near the surface during the Indosinian movement and thus have cracked into asphaltite. The distribution of asphaltite is closely related to the tectonic activities, and the asphaltite is preferentially stored in the anticline axes, fissures, and some interlayer fracture zones.
ABSTRACT
This report demonstrates high-performance infrared phototransistors that use a broad-band absorbing organic bulk heterojunction (BHJ) layer responsive from the visible to the shortwave infrared, from 500 to 1400 nm. The device structure is based on a bilayer transistor channel that decouples charge photogeneration and transport, enabling independent optimization of each process. The organic BHJ layer is improved by incorporating camphor, a highly polarizable additive that increases carrier lifetime. An indium zinc oxide transport layer with high electron mobility is employed for rapid charge transport. As a result, the phototransistors achieve a dynamic range of 127 dB and reach a specific detectivity of 5 × 1012 Jones under a low power illumination of 20 nW/cm2, outperforming commercial germanium photodiodes in the spectral range below 1300 nm. The photodetector metrics are measured with respect to the applied voltage, incident light power, and temporal bandwidth, demonstrating operation at a video-frame rate of 50 Hz. In particular, the frequency and light dependence of the phototransistor characteristics are analyzed to understand the change in photoconductive gain under different working conditions.
ABSTRACT
Cervical cancer is the second most prevalent malignant tumor in women worldwide. Failure of successful treatment is most prevalent in patients with the metastatic disease and the chemotherapy refractory disease. Tumor necrosis factor α-induced protein 8 (TNFAIP8) serves as an anti-apoptotic and pro-oncogenic protein, and is associated with cancer progression and poor prognosis in a number of different cancer types. However, the physiological and pathophysiological roles of TNFAIP8 in cervical carcinogenesis and development remain poorly understood. In the present study, it was demonstrated that TNFAIP8 protein expression levels were significantly increased in cervical cancer tissues compared with the non-tumor adjacent tissues using immunohistochemistry. Additionally, it was demonstrated that TNFAIP8 overexpression is associated with cisplatin resistance. Furthermore, depletion of TNFAIP8 impaired HeLa cell proliferation and viability in vitro, improved cisplatin sensitivity, and promoted cisplatin-induced cellular apoptosis and death. Subsequent mechanistic analysis demonstrated that TNFAIP8 silencing promoted caspase-8/-3 activation and p38 phosphorylation in HeLa cells treated with cisplatin, whereas apoptosis regulator B-cell lymphoma-2 expression was inhibited with TNFAIP8-silenced HeLa cells following treatment with cisplatin. These data suggested that TNFAIP8 serves as an anti-apoptotic protein against cisplatin-induced cell death, which eventually leads to chemotherapeutic drug-treatment failure. Therefore, the present data suggested that TNFAIP8 may be a promising therapeutic target for the treatment of cervical cancer.
ABSTRACT
Infrared photodetectors are essential to many applications, including surveillance, communications, process monitoring, and biological imaging. The short-wave infrared (SWIR) spectral region (λ = 1-3 µm) is particularly powerful for health monitoring and medical diagnostics because biological tissues show low absorbance and minimal SWIR autofluorescence, enabling greater penetration depth and improved resolution in comparison with visible light. However, current SWIR photodetection technologies are largely based on epitaxially grown inorganic semiconductors, which are costly, require complex processing, and impose cooling requirements incompatible with wearable electronics. Solution-processable semiconductors are being developed for infrared detectors to enable low-cost direct deposition and facilitate monolithic integration and resolution not achievable using current technologies. In particular, organic semiconductors offer numerous advantages, including large-area and conformal coverage, temperature insensitivity, and biocompatibility, for enabling ubiquitous SWIR optoelectronics. This Account introduces recent efforts to advance the spectral response of organic photodetectors into the SWIR. High-performance visible to near-infrared (NIR) organic photodetectors have been demonstrated by leveraging the wealth of knowledge from organic solar cell research in the past decade. On the other hand, organic semiconductors that absorb in the SWIR are just emerging, and only a few organic materials have been reported that exhibit photocurrent past 1 µm. In this Account, we survey novel SWIR molecules and polymers and discuss the main bottlenecks associated with charge recombination and trapping, which are more challenging to address in narrow-band-gap photodetectors in comparison with devices operating in the visible to NIR. As we call attention to discrepancies in the literature regarding performance metrics, we share our perspective on potential pitfalls that may lead to overestimated values, with particular attention to the detectivity (signal-to-noise ratio) and temporal characteristics, in order to ensure a fair comparison of device performance. As progress is made toward overcoming challenges associated with losses due to recombination and increasing noise at progressively narrower band gaps, the performance of organic SWIR photodetectors is steadily rising, with detectivity exceeding 1011 Jones, comparable to that of commercial germanium photodiodes. Organic SWIR photodetectors can be incorporated into wearable physiological monitors and SWIR spectroscopic imagers that enable compositional analysis. A wide range of potential applications include food and water quality monitoring, medical and biological studies, industrial process inspection, and environmental surveillance. There are exciting opportunities for low-cost organic SWIR technologies to be as widely deployable and affordable as today's ubiquitous cell phone cameras operating in the visible, which will serve as an empowering tool for users to discover information in the SWIR and inspire new use cases and applications.
ABSTRACT
We report our effort to unravel the origin of efficient operation of nonfullerene organic solar cells (OSCs), based on a poly[4,8-bis(5-(2-ethylhexyl) thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)](PTB7-Th):3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno [1,2-b:5,6-b']dithiophene (ITIC) blend system. The effects of buildup of space charges, charge extraction, and bimolecular recombination processes on the performance and the stability of PTB7-Th:ITIC-based regular and reverse configuration OSCs are analyzed. It is found that the high-performing inverted PTB7-Th:ITIC OSCs benefit from the combined effects of (1) suppression of bimolecular recombination enabled by an augmented effective internal electric field and (2) improvement of charge extraction by avoiding the holes passing through ITIC-rich region, which would otherwise occur in a regular configuration cell. The inverted PTB7-Th:ITIC OSCs possess a significant improvement in the cell stability and a high power conversion efficiency of â¼8.0%, which is >29% higher than that of an optimized regular configuration control cell (6.1%).
ABSTRACT
Bulk heterojunction photodiodes are fabricated using a new donor-acceptor polymer with a near-infrared absorption edge at 1.2 µm, achieving a detectivity up to 1012 Jones at a wavelength of 1 µm and an excellent linear dynamic range of 86 dB. The photodiode detectivity is maximized by operating at zero bias to suppress dark current, while a thin 175 nm active layer is used to facilitate charge collection without reverse bias. Analysis of the temperature dependence of the dark current and spectral response demonstrates a 2.8-fold increase in detectivity as the temperature was lowered from 44 to -12 °C, a relatively small change when compared to that of inorganic-based devices. The near-infrared photodiode shows a switching speed reaching up to 120 µs without an external bias. An application using our NIR photodiode to detect arterial pulses of a fingertip is demonstrated.
ABSTRACT
Organic solar cells (OSCs) with inverted structure usually exhibit higher power conversion efficiency (PCE) and are more stable than corresponding devices with regular configuration. Indium tin oxide (ITO) surface is often modified with solution-processed low work function metal oxides, such as ZnO, serving as the transparent cathode. However, the defect-induced subgap states in the ZnO interlayer hamper the efficient charge collection and the performance reproducibility of the OSCs. In this work, we demonstrate that suppression of the ZnO subgap states by modification of its surface with an ultrathin Al layer significantly improves the charge extraction and performance reproducibility, achieving PCE of 8.0%, which is â¼15% higher than that of a structurally identical control cell made with a pristine ZnO interlayer. Light intensity-dependent current density-voltage characteristic, photothermal deflection spectroscopy, and X-ray photoelectron spectroscopy measurements point out the enhancement of charge collection efficiency at the organic/cathode interface, due to the suppression of the subgap states in the ZnO interlayer.
ABSTRACT
The hepatitis C virus (HCV) NS4B protein is known to induce the formation of a membranous web that is thought to be the site of viral RNA replication. However, the exact functions of NS4B remain poorly characterized. In this study, we found that NS4B induced apoptosis in 293T cells and Huh7 cells, as confirmed by Hoechst staining, DNA fragmentation, and annexin V/PI assays. Furthermore, protein immunoblot analysis demonstrated that NS4B triggered the cleavage of caspase 3, caspase 7, and poly(ADP-ribose) polymerase (PARP). Further studies revealed that NS4B induced the activation of caspase 9, the reduction of mitochondrial membrane potential and the release of cytochrome c from the mitochondria. However, NS4B expression did not trigger XBP1 mRNA splicing and increase the expression of binding immunoglobulin protein (BiP, or GRP78) and C/EBP homologous protein (CHOP), which serves as the indicators of ER stress. Taken together, our results suggest that HCV NS4B induces apoptosis through the mitochondrial death pathway.
Subject(s)
Apoptosis , Hepacivirus/pathogenicity , Viral Nonstructural Proteins/metabolism , Virulence Factors/metabolism , Caspase 3/metabolism , Caspase 7/metabolism , Caspase 9/metabolism , Cell Line , Cytochromes c/metabolism , Endoplasmic Reticulum Chaperone BiP , Humans , Membrane Potential, Mitochondrial/drug effects , Poly(ADP-ribose) Polymerases/metabolism , ProteolysisABSTRACT
Interleukin-18 (IL-18) has been reported to inhibit hepatitis B virus (HBV) replication in the liver of HBV transgenic mice; however, the molecular mechanism of its antiviral effect has not been fully understood. In the present study, it was shown that IL-18 and its receptors (IL-18R) were constitutively expressed in hepatoma cell lines HepG2 and HepG2.2.15 as well as normal liver cell line HL-7702. We demonstrated that IL-18 directly inhibited HBV replication in HepG2.2.15 cells via downregulating the activities of HBV core and X gene promoters. The suppressed HBV replication by IL-18 could be rescued by the administration of BAY11-7082, an inhibitor of transcription factor NF-κB. On the other hand, it was of interest that IL-18 promoted HepG2 cell metastasis and migration dose dependently in both wound-healing assays and Transwell assays. The underlying mechanism could be partially attributable to the increased activities of extracellular matrix metalloproteinase (MMP)-9, MMP-3, and MMP-2 by IL-18, which upregulated the mRNA levels of MMP-3 and MMP-9 in a NF-κB-dependent manner. Furthermore, it was confirmed that expression of IL-18/IL-18R and most MMPs were remarkably upregulated in hepatocellular carcinoma (HCC) liver cancer tissue specimens, suggesting that IL-18/IL-18R-triggered signaling pathway was closely related to HCC metastasis in vivo. Therefore, we revealed the dual effects of IL-18 in human hepatocytes: it not only inhibited HBV replication but also promoted hepatoma cells metastasis and migration. NF-κB played a critical role in both effects. Our work contributed to a deeper understanding of the biological function of IL-18 in human hepatocytes.
Subject(s)
Hepatitis B virus/drug effects , Interleukin-18/physiology , Carcinoma, Hepatocellular/pathology , Carcinoma, Hepatocellular/physiopathology , Cell Line , Cell Movement/drug effects , Hep G2 Cells , Hepatitis B virus/physiology , Humans , Liver Neoplasms/pathology , Liver Neoplasms/physiopathology , Matrix Metalloproteinase 3/biosynthesis , Matrix Metalloproteinase 9/biosynthesis , NF-kappa B/pharmacology , Neoplasm Metastasis/physiopathology , RNA, Messenger/metabolism , Receptors, Interleukin-18/biosynthesis , Up-Regulation , Virus Replication/drug effectsABSTRACT
Development of an effective vaccine may be the key in the control of hepatitis C virus (HCV) infection. Recent studies have shown that HCV envelope proteins can induce broadly neutralizing antibodies against conserved domain for HCV binding to the cellular receptors. So HCV envelope proteins are considered as the major HCV vaccine candidate. In this study, we used Pichia pastoris yeast to express truncated HCV E1E2 protein, which consists of E1 residues 187-346 and E2 residues 381-699. The yeast can produce high level of recombinant HCV E1E2 protein. The protein has complex glycosylation and can bind to CD81, the putative HCV receptor. Moreover, the purified protein can efficiently induce anti-E1E2 antibodies in rabbits, which are able to neutralize two kinds of HCV pseudotype particles derived from HCV genotype 1a and 1b, as well as HCV virions derived from HCV genotype 2a. These findings indicate that the recombinant E1E2 glycoprotein is effective in inducing broadly neutralizing antibodies, and is a potent HCV vaccine candidate.
Subject(s)
Hepacivirus/immunology , Viral Envelope Proteins/genetics , Viral Envelope Proteins/immunology , Viral Hepatitis Vaccines , Animals , Antibodies, Monoclonal/immunology , Antibodies, Neutralizing/immunology , Antigens, CD/immunology , Antigens, CD/metabolism , Enzyme-Linked Immunosorbent Assay , Gene Expression , Glycosylation , Hepacivirus/genetics , Hepatitis C/immunology , Hepatitis C Antibodies/immunology , Neutralization Tests , Pichia/genetics , Plasmids , Rabbits , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Recombinant Proteins/isolation & purification , Recombinant Proteins/metabolism , Tetraspanin 28 , Viral Envelope Proteins/isolation & purification , Viral Envelope Proteins/metabolism , Viral Hepatitis Vaccines/immunologyABSTRACT
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ABSTRACT
Chronic hepatitis C virus (HCV) infection often leads to liver cancer. NS2/3 protease is the first of two virally encoded proteases required for HCV polyprotein processing. In this report, we investigated the function of NS2/3 protease on HCV replication and translation. Cells transfected with plasmids encoding wild-type or mutant NS2/3 and a dual-luciferase reporter construct containing an HCV internal ribosome entry site (IRES) were used to examine the effect of NS2/3 protease on translation of HCV RNA. Cells transfected with plasmids encoding wild-type or mutant NS2/3, pcDNA-NS5B and a reporter plasmid were used to examine the effect of NS2/3 protease on HCV replication. The results showed that both autocleavage processing and the uncleaved form of NS2/3 protease specifically decrease HCV IRES-directed translation, while the uncleaved form of NS2/3 protease decreases HCV NS5B RdRp activity (replication), indicating that autoregulation by NS2/3 protease of HCV replication and translation may play an important role in persistent HCV infection.
Subject(s)
Cysteine Endopeptidases/metabolism , Hepacivirus/enzymology , Hepatitis C, Chronic/virology , Protein Modification, Translational , RNA-Dependent RNA Polymerase/metabolism , Viral Nonstructural Proteins/metabolism , Cell Line , Humans , RNA, Viral/metabolism , Virus ReplicationABSTRACT
Chronic hepatitis C virus (HCV) infection often leads to liver cancer. The HCV NS2 protein is a hydrophobic transmembrane protein that associates with several cellular proteins in mammalian cells. In this report, we investigated the function of NS2 protein on HCV replication and translation by using a transient cell-based expression system. Cells co-transfected with pcDNA3.1 (-)-NS2 and the dual-luciferase reporter construct containing the HCV IRES were used to detect the effect of NS2 protein on HCV translation. Cells co-transfected with pcDNA3.1(-)-NS2, pcDNA-NS5B and a reporter plasmid were used to detect the effect of NS2 protein on HCV replication. The results showed that HCV NS2 protein up-regulated HCV IRES-dependent translation in a specific and dose-dependent manner in Huh7 cells but not in HeLa and HepG2 cells, and NS2 protein inhibited NS5B RdRp activity in a dose-independent manner in all three cell lines. These findings may suggest a novel mechanism by which HCV modulates its NS5B replication and IRES-dependent translation and facilitates virus persistence.