Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 42
Filtrar
1.
Nature ; 579(7799): E9, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32112062

RESUMO

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

2.
Nature ; 577(7790): 346-349, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31942050

RESUMO

Highly efficient neutron detectors are critical in many sectors, including national security1,2, medicine3, crystallography4 and astronomy5. The main neutron detection technologies currently used involve 3He-gas-filled proportional counters6 and light scintillators7 for thermalized neutrons. Semiconductors could provide the next generation of neutron detectors because their advantages could make them competitive with or superior to existing detectors. In particular, solids with a high concentration of high-neutron-capture nuclides (such as 6Li, 10B) could be used to develop smaller detectors with high intrinsic efficiencies. However, no promising materials have been reported so far for the construction of direct-conversion semiconductor detectors. Here we report on the semiconductor LiInP2Se6 and demonstrate its potential as a candidate material for the direct detection of thermal neutrons at room temperature. This compound has a good thermal-neutron-capture cross-section, a suitable bandgap (2.06 electronvolts) and a favourable electronic band structure for efficient electron charge transport. We used α particles from an 241Am source as a proxy for the neutron-capture reaction and determined that the compact two-dimensional (2D) LiInP2Se6 detectors resolved the full-energy peak with an energy resolution of 13.9 per cent. Direct neutron detection from a moderated Pu-Be source was achieved using 6Li-enriched (95 per cent) LiInP2Se6 detectors with full-peak resolution. We anticipate that these results will spark interest in this field and enable the replacement of 3He counters by semiconductor-based neutron detectors.

3.
Nat Chem Biol ; 19(8): 940-950, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37055614

RESUMO

Microbial communities often display region-specific properties, which give rise to complex interactions and emergent behaviors that are critical to the homeostasis and stress response of the communities. However, systems-level understanding of these properties still remains elusive. In this study, we established RAINBOW-seq and profiled the transcriptome of Escherichia coli biofilm communities with high spatial resolution and high gene coverage. We uncovered three modes of community-level coordination, including cross-regional resource allocation, local cycling and feedback signaling, which were mediated by strengthened transmembrane transport and spatially specific activation of metabolism. As a consequence of such coordination, the nutrient-limited region of the community maintained an unexpectedly high level of metabolism, enabling it to express many signaling genes and functionally unknown genes with potential sociality functions. Our work provides an extended understanding of the metabolic interplay in biofilms and presents a new approach of investigating complex interactions in bacterial communities on the systems level.


Assuntos
Escherichia coli K12 , Escherichia coli K12/genética , Escherichia coli/genética , Transcriptoma , Biofilmes , Bactérias/genética
4.
Funct Integr Genomics ; 23(3): 225, 2023 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-37418046

RESUMO

Y box binding protein 3 (YBX3) is an indispensable factor for protein synthesis, cellular growth, and proliferation, and is intricately involved in the progression of diverse tumor types. The objective of the current study was to investigate the role of YBX3 in the prognosis, immune infiltration, and progression of clear cell renal clear cell carcinoma (ccRCC). The expression level of YBX3 in ccRCC tissues was compared using The Cancer Genome Atlas (TCGA) and analyzed using the Wilcoxon rank sum test. Logistic regression and multivariate Cox analyses were subsequently employed to scrutinize the association between YBX3 expression and the clinicopathological characteristics of patients. The TIMER 2.0 tool was also utilized to quantify the degree of immune cell infiltration of YBX3. Kaplan Meier analysis was performed to assess the correlation between YBX3 and the survival rate. A high expression level of YBX3 was significantly correlated with the tumor pathological stage, histological grade, TNM stage, and the abundance of aDC, pDC, Th1, and Treg immune cells. Higher expression of YBX3 in advanced ccRCC was found to be associated with a lower overall survival rate in the M0, N0, and T2 subgroups. In vitro, after the silencing of YBX3 in A498 cells and overexpression of YBX3 in ACHN cells, cell proliferation, colony formation, migration, invasion, cell cycle assays, and flow cytometric apoptotic analysis were performed to evaluate the role of YBX3 in the progression of ccRCC. YBX3 was found to be intricately associated with the progression and prognosis of ccRCC, and may serve as an effective treatment target for ccRCC or a biomarker for prognosis prediction.


Assuntos
Carcinoma de Células Renais , Neoplasias Renais , Humanos , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismo , Carcinoma de Células Renais/genética , Carcinoma de Células Renais/metabolismo , Carcinoma de Células Renais/patologia , Estimativa de Kaplan-Meier , Neoplasias Renais/genética , Neoplasias Renais/metabolismo , Neoplasias Renais/patologia , Oncogenes , Proteínas de Ligação a RNA/genética
5.
Sensors (Basel) ; 23(4)2023 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-36850614

RESUMO

Perovskite CsPbBr3 semiconductors exhibit unusually high defect tolerance leading to outstanding and unique optoelectronic properties, demonstrating strong potential for γ-radiation and X-ray detection at room temperature. However, the total dose effects of the perovskite CsPbBr3 must be considered when working in a long-term radiation environment. In this work, the Schottky type of perovskite CsPbBr3 detector was fabricated. Their electrical characteristics and γ-ray response were investigated before and after 60Co γ ray irradiation with 100 and 200 krad (Si) doses. The γ-ray response of the Schottky-type planar CsPbBr3 detector degrades significantly with the increase in total dose. At the total dose of 200 krad(Si), the spectral resolving ability to γ-ray response of the CsPbBr3 detector has disappeared. However, with annealing at room temperature for one week, the device's performance was partially recovered. Therefore, these results indicate that the total dose effects strongly influence the detector performance of the perovskite CsPbBr3 semiconductor. Notably, it is concluded that the radiation-induced defects are not permanent, which could be mitigated even at room temperature. We believe this work could guide the development of perovskite detectors, especially under harsh radiation conditions.

6.
Environ Microbiol ; 24(12): 5774-5787, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36053758

RESUMO

There is a lack of appropriate methods for preparing bacterial RNA-seq library with ultra-low amount of RNA. To address this issue, we developed miniBac-seq, a strand-specific method for high-quality library construction from sub-nanogram of total RNA, which is 100-fold lower than the current benchmark kit and dramatically reduces preparation cost ($28 + $15 × samples). We further demonstrated the high sensitivity of miniBac-seq via detecting more than 500 genes from amount of total RNA equivalent to that of a single bacterial cell. Finally, we profiled the transcriptome of growth-arrested bacteria in isogenic culture of Escherichia coli. This subpopulation of bacteria is generally low in abundance but is a potent reservoir of antibiotic persistence, and their gene expression has been largely unknown due to technical limitations. Using miniBac-seq, we identified potential molecular driver towards arrested growth as well as antibiotic tolerance. Our method thus expands the capacity to quantify bacterial transcriptome in situ, which is useful to the understanding of bacterial physiology and regulation in their native contexts.


Assuntos
Perfilação da Expressão Gênica , Transcriptoma , Análise de Sequência de RNA/métodos , Perfilação da Expressão Gênica/métodos , RNA , Bactérias/genética , Antibacterianos/farmacologia , Sequenciamento de Nucleotídeos em Larga Escala/métodos
7.
J Am Chem Soc ; 143(4): 2068-2077, 2021 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-33492148

RESUMO

The detection of γ-rays at room temperature with high-energy resolution using semiconductors is one of the most challenging applications. The presence of even the smallest amount of defects is sufficient to kill the signal generated from γ-rays which makes the availability of semiconductors detectors a rarity. Lead halide perovskite semiconductors exhibit unusually high defect tolerance leading to outstanding and unique optoelectronic properties and are poised to strongly impact applications in photoelectric conversion/detection. Here we demonstrate for the first time that large size single crystals of the all-inorganic perovskite CsPbCl3 semiconductor can function as a high-performance detector for γ-ray nuclear radiation at room temperature. CsPbCl3 is a wide-gap semiconductor with a bandgap of 3.03 eV and possesses a high effective atomic number of 69.8. We identified the two distinct phase transitions in CsPbCl3, from cubic (Pm-3m) to tetragonal (P4/mbm) at 325 K and finally to orthorhombic (Pbnm) at 316 K. Despite crystal twinning induced by phase transitions, CsPbCl3 crystals in detector grade can be obtained with high electrical resistivity of ∼1.7 × 109 Ω·cm. The crystals were grown from the melt with volume over several cubic centimeters and have a low thermal conductivity of 0.6 W m-1 K-1. The mobilities for electron and hole carriers were determined to ∼30 cm2/(V s). Using photoemission yield spectroscopy in air (PYSA), we determined the valence band maximum at 5.66 ± 0.05 eV. Under γ-ray exposure, our Schottky-type planar CsPbCl3 detector achieved an excellent energy resolution (∼16% at 122 keV) accompanied by a high figure-of-merit hole mobility-lifetime product (3.2 × 10-4 cm2/V) and a long hole lifetime (16 µs). The results demonstrate considerable defect tolerance of CsPbCl3 and suggest its strong potential for γ-radiation and X-ray detection at room temperature and above.

8.
J Am Chem Soc ; 143(6): 2545-2551, 2021 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-33465309

RESUMO

Pressure processing is efficient to regulate the structural and physical properties of two-dimensional (2D) halide perovskites which have been emerging for advanced photovoltaic and light-emitting applications. Increasing numbers of studies have reported pressure-induced and/or enhanced emission properties in the 2D halide perovskites. However, no research has focused on their photoresponse properties under pressure tuning. It is also unclear how structural change affects their excitonic features, which govern the optoelectronic properties of the halide perovskites. Herein, we report significantly enhanced photocurrents in the all-inorganic 2D perovskite Cs2PbI2Cl2, achieving over 3 orders of magnitude increase at the industrially achievable level of 2 GPa in comparison with its initial photocurrent. Lattice compression effectively regulates the excitonic features of Cs2PbI2Cl2, reducing the exciton binding energy considerably from 133 meV at ambient conditions to 78 meV at 2.1 GPa. Impressively, such a reduced exciton binding energy of 2D Cs2PbI2Cl2 is comparable to the values of typical 3D perovskites (MAPbBr3 and MAPbI3), facilitating the dissociating of excitons into free carriers and enhancing the photocurrent. Further pressurization leads to a layer-sliding-induced phase transition and an anomalous negative linear compression, which has not been observed so far in other halide perovskites. Our findings reveal the dramatically enhanced photocurrents in the 2D halide perovskite by regulating its excitonic features and, more broadly, provide new insights into materials design toward extraordinary properties.

9.
J Am Chem Soc ; 143(16): 6221-6228, 2021 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-33856803

RESUMO

Chalcogenide-based phase change memory (PCM) is a key enabling technology for optical data storage and electrical nonvolatile memory. Here, we report a new phase change chalcogenide consisting of a 3D network of ionic (K···Se) and covalent bonds (Bi-Se), K2Bi8Se13 (KBS). Thin films of amorphous KBS deposited by DC sputtering are structurally and chemically homogeneous and exhibit a surface roughness of 5 nm. The KBS film crystallizes upon heating at ∼483 K. The optical bandgap of the amorphous film is about 1.25 eV, while its crystalline phase has a bandgap of ∼0.65 eV shows 2-fold difference between the two states. The bulk electrical conductivity of the amorphous and crystalline film is ∼7.5 × 10-4 and ∼2.7 × 10-2 S/cm, respectively. We have demonstrated a phase change memory effect in KBS by Joule heating in a technologically relevant vertical memory cell architecture. Upon Joule heating, the vertical device undergoes switching from its amorphous to crystalline state of KBS at 1-1.5 V (∼50 kV/cm), increasing conductivity by a factor of ∼40. Besides the large electrical and optical contrast in the crystalline and amorphous KBS, its elemental cost-effectiveness, stoichiometry, fast crystallization kinetics, as determined by the ratio of the glass transition and melting temperature, Tg/Tm ∼ 0.5, as well as the scalable synthesis of the thin film determine that KBS is a promising PC material for next general phase change memory.

10.
Exp Cell Res ; 397(1): 112335, 2020 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-33132134

RESUMO

PURPOSE: Skp2, an oncoprotein, regulates tumor proliferation, invasion and metastasis. Ku70 is a critical component of the non-homologous end-joining (NHEJ) process. Both Skp2 and Ku70 are positively associated in multiple cancers. However, there is no report about the relationship between Skp2 and Ku70 proteins. METHODS: In this study, we carried out Bioinformatics and molecular biological methods to investigate the relationship between Skp2 and Ku70 proteins. RESULTS: We first observed Skp2 and Ku70 mRNAs were significantly increased in cervical cancer tissues. And we identified Ku70 as a Skp2-binding protein and the binding site located in the C-terminal of Ku70 protein. We further found that Skp2 knockdown decreased the Ku70 protein level in cells, and increase the cellular apoptosis and DNA damage, suggesting Skp2 mediates the Ku70 protein stability and function via post-translational modification. CONCLUSION: The direct interaction between Skp2 and Ku70 proteins mediates the DNA damage repair and cellular apoptosis by regulating Ku70 stability and function via post-translational modification. The molecular mechanisms how Skp2 stabilize Ku70 would be clarified in our following research work.


Assuntos
Apoptose , Dano ao DNA , Reparo do DNA , Autoantígeno Ku/metabolismo , Processamento de Proteína Pós-Traducional , Proteínas Quinases Associadas a Fase S/metabolismo , Neoplasias do Colo do Útero/patologia , Feminino , Humanos , Autoantígeno Ku/genética , Proteínas Quinases Associadas a Fase S/genética , Neoplasias do Colo do Útero/genética , Neoplasias do Colo do Útero/metabolismo
11.
J Am Chem Soc ; 142(18): 8342-8351, 2020 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-32279505

RESUMO

Hybrid layered halide perovskites have achieved impressive performance in optoelectronics. New structural types in the two-dimensional (2D) halide system such as the Dion-Jacobson phases have attracted wide research attention due to the short interlayer distance and unique layer orientation that facilitate better charge-transport and higher stability in optoelectronic devices. Here, we report the first solid solution series incorporating both A and A' cations in the 2D Dion-Jacobson family, with the general formula (A')(A)Pb2Br7 ((A' = 3-(aminomethyl)piperidinium (3AMP) and 4-(aminomethyl)piperidinium) (4AMP); A = methylammonium (MA) and formamidinium (FA)). Mixing the spacing A' cations and perovskitizer A cations generates the new (3AMP)a(4AMP)1-a(FA)b(MA)1-bPb2Br7 perovskites. The crystallographically refined crystal structures using single-crystal X-ray diffraction data reveal that the distortion of the inorganic framework is heavily influenced by the degree of A' and A alloying. A rising fraction of 4AMP in the structure, decreases the Pb-Br-Pb angles, making the framework more distorted. On the contrary, higher FA fractions increase the Pb-Br-Pb angles. This structural evolution fine-tunes the optical properties where the larger the Pb-Br-Pb angle, the narrower the band gap. The photoluminescence emission energy mirrors this trend. Raman spectroscopy reveals a highly dynamical lattice similar to MAPbBr3 and consistent with the local distortion environment of the [Pb2Br7] framework. Density functional theory (DFT) calculations of the electronic structures reveal the same trend as the experimental results where (3AMP)(FA)Pb2Br7 has the smallest band gap while (4AMP)(MA)Pb2Br7 has the largest band gap. The structural effects from solely the organic cations in the 2D system highlight the importance of understanding the high sensitivity of the optoelectronic properties on the structural tuning in this broad class of materials.

12.
J Am Chem Soc ; 142(14): 6625-6637, 2020 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-32176495

RESUMO

Large organic A cations cannot stabilize the 3D perovskite AMX3 structure because they cannot be accommodated in the cubo-octhedral cage (do not follow the Goldschmidt tolerance factor rule), and they generally template low-dimensional structures. Here we report that the large dication aminomethylpyridinium (AMPY) can template novel 3D structures which resemble conventional perovskites. They have the formula (xAMPY)M2I6 (x = 3 or 4, M = Sn2+ or Pb2+) which is double of the AMX3 formula. However, because of the steric requirement of the Goldschmidt tolerance factor rule, it is impossible for (xAMPY)M2I6 to form proper perovskite structures. Instead, a combination of corner-sharing and edge-sharing connectivity is adopted in these compounds leading to the new 3D structures. DFT calculations reveal that the compounds are indirect band gap semiconductors with direct band gaps presenting at slightly higher energies and dispersive electronic bands. The indirect band gaps of the Sn and Pb compounds are ∼1.7 and 2.0 eV, respectively, which is slightly higher than the corresponding AMI3 3D perovskites. The Raman spectra for the compounds are diffuse, with a broad rising central peak at very low frequencies around 0 cm-1, a feature that is characteristic of dynamical lattices, high anharmonicity, and dissipative vibrations very similar to the 3D AMX3 perovskites. Devices of (3AMPY)Pb2I6 crystals exhibit clear photoresponse under ambient light without applied bias, reflecting a high carrier mobility (µ) and long carrier lifetime (τ). The devices also exhibit sizable X-ray generated photocurrent with a high µτ product of ∼1.2 × 10-4 cm2 /V and an X-ray sensitivity of 207 µC·Gy-1·cm-2.

13.
Angew Chem Int Ed Engl ; 59(29): 11856-11860, 2020 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-32270587

RESUMO

Semiconductive metal-organic frameworks (MOFs) have emerged in applications such as chemical sensors, electrocatalysts, energy storage materials, and electronic devices. However, examples of semiconductive MOFs within flexible electronics have not been reported. We present flexible X-ray detectors prepared by thermoplastic dispersal of a semiconductive MOF (SCU-13) through a commercially available polymer, poly(vinylidene fluoride). The flexible detectors exhibit efficient X-ray-to-electric current conversion with enhanced charge-carrier mobility and low trap density compared to pelleted devices. A high X-ray detection sensitivity of 65.86 µCGyair -1 cm-2 was achieved, which outperforms other pelleted devices and commercial flexible X-ray detectors. We demonstrate that the MOF-based flexible detectors can be operated at multiple bending angles without a deterioration in detection performance. As a proof-of-concept, an X-ray phase contrast under bending conditions was constructed using a 5×5 pixelated MOF-based imager.

14.
J Am Chem Soc ; 141(13): 5518-5534, 2019 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-30827098

RESUMO

The unique hybrid nature of 2D Ruddlesden-Popper (R-P) perovskites has bestowed upon them not only tunability of their electronic properties but also high-performance electronic devices with improved environmental stability as compared to their 3D analogs. However, there is limited information about their inherent heat, light, and air stability and how different parameters such as the inorganic layer number and length of organic spacer molecule affect stability. To gain deeper understanding on the matter we have expanded the family of 2D R-P perovskites, by utilizing pentylamine (PA)2(MA) n-1Pb nI3 n+1 ( n = 1-5, PA = CH3(CH2)4NH3+, C5) and hexylamine (HA)2(MA) n-1Pb nI3 n+1 ( n = 1-4, HA = CH3(CH2)5NH3+, C6) as the organic spacer molecules between the inorganic slabs, creating two new series of layered materials, for up to n = 5 and 4 layers, respectively. The resulting compounds were extensively characterized through a combination of physical and spectroscopic methods, including single crystal X-ray analysis. High resolution powder X-ray diffraction studies using synchrotron radiation shed light for the first time to the phase transitions of the higher layer 2D R-P perovskites. The increase in the length of the organic spacer molecules did not affect their optical properties; however, it has a pronounced effect on the air, heat, and light stability of the fabricated thin films. An extensive study of heat, light, and air stability with and without encapsulation revealed that specific compounds can be air stable (relative humidity (RH) = 20-80% ± 5%) for more than 450 days, while heat and light stability in air can be exponentially increased by encapsulating the corresponding films. Evaluation of the out-of-plane mechanical properties of the corresponding materials showed that their soft and flexible nature can be compared to current commercially available polymer substrates (e.g., PMMA), rendering them suitable for fabricating flexible and wearable electronic devices.

15.
J Am Chem Soc ; 141(43): 17421-17430, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31589035

RESUMO

Semiconductors possessing both magnetic and optoelectronic properties are rare and promise applications in opto-spintronics. Here we report the mixed-anion semiconductor BaFMn0.5Te with a band gap of 1.76 eV and a work function of 5.08 eV, harboring both antiferromagnetism (AFM) and strong red photoluminescence (PL). The synthesis of BaFMn0.5Te in quantitative yield was accomplished using the "panoramic synthesis" technique and synchrotron radiation to obtain the full reaction map, from which we determined that the compound forms upon heating at 850 °C via an intermediate unknown phase. The structure refinement required the use of a (3+1)-dimensional superspace group Cmme(α01/2)0ss. The material crystallizes into a ZrCuSiAs-like structure with alternating [BaF]+ and [Mn0.5Te]- layers and has a commensurately modulated structure with the q-vector of 1/6a* + 1/6b* + 1/2c* at room temperature arising from the unique ordering pattern of Mn2+ cations. Long-range AFM order emerges below 90 K, with two-dimensional short-range AFM correlations above the transition temperature. First-principles calculations indicate that BaFMn0.5Te is an indirect band gap semiconductor with the gap opening between Te 5p and Mn 3d orbitals, and the magnetic interactions between nearest-neighbor Mn2+ atoms are antiferromagnetic. Steady-state PL spectra show a broad strong emission centered at ∼700 nm, which we believe originates from the energy manifolds of the modulated Mn2+ sublattice and its defects. Time-resolved PL measurements reveal an increase in excited-state lifetimes with longer probe wavelengths, from 93 ns (at 650 nm) to 345 ns (at 800 nm), and a delayed growth (6.5 ± 0.3 ns) in the kinetics at 800 nm with a concomitant decay (4.1 ± 0.1 ns) at 675 nm. Together, these observations suggest that there are multiple emissive states, with higher energy states populating lower energy states by energy transfer.

16.
J Chem Phys ; 151(21): 214201, 2019 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-31822096

RESUMO

We use time-resolved multi-terahertz spectroscopy for the range 4-40 meV to probe coherent and incoherent ultrafast charge carrier and exciton dynamics in the low temperature orthorhombic phase of the hybrid metal halide perovskite CH3NH3PbI3. Time- and energy-resolved terahertz reflectivity maps reveal strongly damped but coherent oscillations in the 2-4 THz reststrahlen band, indicating charge coupling to a distribution of low energy phonon modes centered at 0.9 THz (3.7 meV or 30 cm-1). First-principles calculations reveal that these modes are entirely of mixed organic/inorganic sublattice character, with the power spectrum of the coherent oscillations showing a high frequency cutoff just at the onset of organic cation-only vibrations. Two anomalous reflectivity signatures are observed which are not phonon related, which we assign to a free exciton at 12 meV appearing on a 0.5 ps time scale and a defect bound exciton at 29-32 meV appearing on slower 1 ps time scale. Our measurements reveal the coherent coupling of charges to low energy vibrations of mixed sublattice character and the presence of two distinct populations of free and bound excitons at low temperatures.

17.
J Am Chem Soc ; 140(35): 11085-11090, 2018 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-30081628

RESUMO

The two-dimensional Ruddlesden-Popper (RP) phases are an important class of halide perovskites with versatile optoelectronic properties. So far, only organic-inorganic hybrid RP phases involving long organic spacers were reported in this class. Here, we report an all-inorganic RP phase lead halide perovskite, Cs2PbI2Cl2 (1, I4/ mmm space group; a = 5.6385(8) Å, c = 18.879(4) Å), synthesized by a solid-state method. The compound exhibits a band gap of Eg ∼ 3.04 eV and photoconductivity. We find an anomalous band gap evolution in Cs2Pb1- xSn xI2Cl2 solid solutions. Our combined density functional theory and experimental study supports the thermodynamically stable nature of 1 as a unique ordered phase in the Cs2PbX4 (X = Cl, Br, I) system. The calculations suggest that 1 is a direct bandgap semiconductor with relatively small effective carrier mass along the in-plane direction, consistent with the experimentally observed in-plane UV-light photoresponse. We also demonstrate that 1 is promising for radiation detection capable of α-particle counting. Moreover, 1 shows markedly ambient and thermal stability.

18.
J Am Chem Soc ; 140(5): 1894-1899, 2018 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-29332382

RESUMO

Cu2I2Se6 is a new wide-bandgap semiconductor with high stability and great potential toward hard radiation and photon detection. Cu2I2Se6 crystallizes in the rhombohedral R3̅m space group with a density of d = 5.287 g·cm-3 and a wide bandgap Eg of 1.95 eV. First-principles electronic band structure calculations at the density functional theory level indicate an indirect bandgap and a low electron effective mass me* of 0.32. The congruently melting compound was grown in centimeter-size Cu2I2Se6 single crystals using a vertical Bridgman method. A high electric resistivity of ∼1012 Ω·cm is readily achieved, and detectors made of Cu2I2Se6 single crystals demonstrate high photosensitivity to Ag Kα X-rays (22.4 keV) and show spectroscopic performance with energy resolutions under 241Am α-particles (5.5 MeV) radiation. The electron mobility is measured by a time-of-flight technique to be ∼46 cm2·V-1·s-1. This value is comparable to that of one of the leading γ-ray detector materials, TlBr, and is a factor of 30 higher than mobility values obtained for amorphous Se for X-ray detection.

19.
J Am Chem Soc ; 139(23): 7939-7951, 2017 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-28505443

RESUMO

The high Z chalcohalides Hg3Q2I2 (Q = S, Se, and Te) can be regarded as of antiperovskite structure with ordered vacancies and are demonstrated to be very promising candidates for X- and γ-ray semiconductor detectors. Depending on Q, the ordering of the Hg vacancies in these defect antiperovskites varies and yields a rich family of distinct crystal structures ranging from zero-dimensional to three-dimensional, with a dramatic effect on the properties of each compound. All three Hg3Q2I2 compounds show very suitable optical, electrical, and good mechanical properties required for radiation detection at room temperature. These compounds possess a high density (>7 g/cm3) and wide bandgaps (>1.9 eV), showing great stopping power for hard radiation and high intrinsic electrical resistivity, over 1011 Ω cm. Large single crystals are grown using the vapor transport method, and each material shows excellent photo sensitivity under energetic photons. Detectors made from thin Hg3Q2I2 crystals show reasonable response under a series of radiation sources, including 241Am and 57Co radiation. The dimensionality of Hg-Q motifs (in terms of ordering patterns of Hg vacancies) has a strong influence on the conduction band structure, which gives the quasi one-dimensional Hg3Se2I2 a more prominently dispersive conduction band structure and leads to a low electron effective mass (0.20 m0). For Hg3Se2I2 detectors, spectroscopic resolution is achieved for both 241Am α particles (5.49 MeV) and 241Am γ-rays (59.5 keV), with full widths at half-maximum (FWHM, in percentage) of 19% and 50%, respectively. The carrier mobility-lifetime µτ product for Hg3Q2I2 detectors is achieved as 10-5-10-6 cm2/V. The electron mobility for Hg3Se2I2 is estimated as 104 ± 12 cm2/(V·s). On the basis of these results, Hg3Se2I2 is the most promising for room-temperature radiation detection.

20.
Zhonghua Bing Li Xue Za Zhi ; 44(8): 565-70, 2015 Aug.
Artigo em Zh | MEDLINE | ID: mdl-26705180

RESUMO

OBJECTIVE: To study the role of microRNAs (miRNAs) in ALK-negative anaplastic large cell lymphoma and CD30 positive peripheral T cell lymphoma (not otherwise specified), and discuss the pathogenesis of miRNAs in ALK-negative anaplastic large cell lymphoma. METHODS: Three cases of ALK-negative anaplastic large cell lymphoma of lymph node, 3 cases of CD30-positive peripheral T cell lymphoma (not otherwise specified) of lymph node and 3 cases of reactive hyperplasia of lymph node were detected by high flow microarray of miRNAs. The method of real-time quantitative polymerase chain reaction was further applied for 7 miRNAs in 15 cases of ALK-negatie anaplastic large cell lymphomas of lymph node and 15 cases of CD30-positive peripheral T cell lymphoma (not otherwise specified) of lymph node. RESULTS: The significant difference of 13 miRNAs was found between ALK-negative anaplastic large cell lymphoma and CD30 positive peripheral T cell lymphoma (not otherwise specified) (P < 0.05), of which the result of 5 miRNAs was consistent with miRNAs expression spectrum: miR-664b-5p, miR-1275, miR-4739, miR-4736 and miR-504-5p, the difference was statistically significant (P < 0.05). Compared with reactive hyperplasia of lymph nodes, miR-664b-5p, miR-1275 and miR-4739 were significantly under-expressed (P = 0.004, P = 0.021, P = 0.031) and miR-4736 and miR-504-5p were significantly over-expressed (P = 0.009, P = 0.007) in ALK negative anaplastic large cell lymphoma. CONCLUSIONS: MiR-664b-5p, miR-1275, miR-4739, miR-4736 and miR-504-5p may become an important indicator in the differentiation ALK-negative anaplastic large cell lymphoma from CD30-positive peripheral T cell lymphoma (not otherwise specified). MiR-4739, miR-4736 and miR-1275 may play important role in pathogenesis of negative-anaplastic large cell lymphoma by target genes: TNFRSF8 and TMOD1.


Assuntos
Linfoma Anaplásico de Células Grandes/metabolismo , Linfoma de Células T Periférico/metabolismo , MicroRNAs/metabolismo , Humanos , Antígeno Ki-1/metabolismo , Linfoma Anaplásico de Células Grandes/diagnóstico , Linfoma de Células T Periférico/diagnóstico , Reação em Cadeia da Polimerase em Tempo Real
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA